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April 11

Electromagnetism and force?

I have read in some places and seen some examples that electro-magnetism , specifically ionised air and static electric fields can move objects of any kind of matter. and also is the radiation pressure of light [which i know can move matter as have read article in scientific american on it] electromagnetic. How does it work if it does. I think it does as have read an interesting article on it. Am looking into it as a skeptical answer to poltergeist phenomena. this is the interesting article. it is about an electrostatic wall

".7 CASE STUDY - LARGE PLASTIC WEB ELECTROSTATIC PROBLEMS, RESULTS AND CURE, D. Swenson, 3M Company Tremendous static charge generation on a plastic web causes unique physical phenomena and special problems. Solution was simple and cost effective.

---

David Swenson of 3M Corporation describes an anomaly where workers encountered a strange "invisible wall" in the area under a fast-moving sheet of electrically charged polypropelene film in a factory. This "invisible wall" was strong enough to prevent humans from passing through. A person near this "wall" was unable to turn, and so had to walk backwards to retreat from it.

This occurred in late summer in South Carolina, in extremely high humidity. Polypropelene (PP) film on 50K ft. rolls 20ft wide was being slit and transferred to multiple smaller spools. The film was taken off the main roll at high speed, flowed upwards 20ft to overhead rollers, passed horizontally 20ft and then downwards to the slitting device, where it was spooled onto shorter rolls. The whole operation formed a cubical shaped tent, with two walls and a ceiling approximately 20ft square. The spools ran at 1000ft/min, or about 10MPH. The PP film had been manufactured with dissimilar surface structure on opposing faces. Contact electrification can occur even in similar materials if the surface textures or micro-structures are significantly different. The generation of a large imbalance of electrical surface-charge during unspooling was therefor not unexpected, and is a common problem in this industry. "Static cling" in the megavolt range!

On entering the factory floor and far from the equipment, Mr. Swenson's 200KV/ft handheld electrometer was found to slam to full scale. When he attempted to walk through the corridor formed by the moving film, he was stopped about half way through by an "invisible wall." He could lean all his weight forward but was unable to pass. He observed a fly get pulled into the charged, moving plastic, and speculates that the e-fields might have been strong enough to suck in birds!

The production manager did not believe Mr. Swenson's report of the strange phenomena. When they both returned to the factory floor, they found that the "wall" was no longer there. But the production workers had noticed the effect as occurring early in the morning when humidity was lower, so they agreed to try again another day. The second attempt was successful, and early in the morning the field underneath the "tent" was strong enough to raise even the short, curly hair of the production manager. The "invisible wall" effect had returned. He commented that he "didn't know whether to fix it or sell tickets."

- Bill Beaty

It later claims that this could be ionized air? how would this work? Robin

The story was made up. -- Mac Davis] ⌇☢ ญƛ. 01:21, 11 April 2006 (UTC)

Here's the origianl onlien, it was easy to google. http://www.amasci.com/weird/unusual/e-wall.html which references http://www.esdjournal.com/articles/final/final.htm , with pictures. GangofOne 02:14, 11 April 2006 (UTC)

FYI amasci.com is the site of User:wjbeaty, mentioned above.

Uuuuuum so now we have established that i didnt make the story up and its from a competant source, exactly how would it work? or am i just gona get accused of fraud again instead of getting the answer i asked for? I thought thats what this part of the site was for. Robin

Actually, you are going to be accused of being unable to properly respond. I moved your comment from the bottom of the page to this section. --Kainaw ^(talk) 15:38, 11 April 2006 (UTC)

Those aren't authoriative sources. This Beaty character seems to be a crackpot as well. His page is linked to by crank.net. What else need I say? --BluePlatypus 16:56, 11 April 2006 (UTC)

That's interesting. I know Bill Beaty's site, and I wonder whether crank.net listed him as an "anticrank" or a "crank". Could you give me the context for the link that you found on crank.net, please? I tried the obvious Google searches like "beaty site:crank.net", but without success. I spend a lot of time battling real cranks on Wikipedia, and IMO Bill isn't one of them. --Heron 19:23, 11 April 2006 (UTC)

The answer Robin is looking for can be found in human psychology, not physics. Humans mispercieve things all the time. Humans misreport things all the time. "How would it work?" It doesn't. It can't. Wouldn't it be cool, useful, and a source of immense profit if it existed? Of course it would. The actual profit here lies in selling books and ads on sensationalistic sites. Always follow the money. WAS 4.250 17:37, 11 April 2006 (UTC)

Thank you for a civil reply. Actually if you study the evidence, and arthur c clarke did in his book "world of mysterious powers" not all poltergeists can be put down to misunderstanding, illusion and fraud. Secondly their seems to be many effects that can do things described in some poltergeist cases. I have been told electromagnetic fields, ultra and infra-sound, ionizing radiation,radiation pressure and static charging can shoot things about. But the complete expulsion of the case i mentioned as fraud without a proper incquiry bugs me. It seems like a genuine case. and remember ball lightning was thought to be non-existant by scientists at first but lo and behold http://physicsweb.org/articles/news/10/2/6 , http://www.newscientist.com/article/dn1720.html in fact one of these thinks that poltergeists and them may be completly related natural phenomena. not paranormal or magical or spiritual, just misunderstood. And the only bill beaty articles i can find on crank .net are critisms of over skeptical science, no listing of his site on either science, paranormal, electromagnetism, or antigravity pages which he should be listed under. Robin 22:45 april 11th

I toss this out as speculation. Since the fields where so high and the 2nd guy felt crackling over his skin, maybe the effect was physiological. Maybe the fields where so high they were interfering with the action potentials of his nerve-muscle synapses. He said he couldn't turn around , he had to back out. Lost control of some muscle groups. This could be new information for the biophysics journals, if it were followed up with more testing. --GangofOne 23:30, 12 April 2006 (UTC)

Hmmmm i doubt it was something like that as its gave no mention of loss of muscle control, it states he leant his full weight against the invisible barriar, he coudnt do that if he had lost muscle control. Also have done some research and i think that electromagnetic / static electric and static magnetic fields can produce force to move things, maybe this was a large, stationary static magnetic field? poltergeist explanation aside, i would like to know how this works. Robin 16:37 14th april

Speculating, I see three best possibilities: one with high probability and two with low. As mentioned above, very likely the effect was caused by "electrotetanus" where high-volt pulses of many mA applied to the skin will cause muscles to lock, as mentioned above. Since the original "e-wall" article, a company called "HSV Technologies" developed a similar phenomenon into a beam weapon; essentially a Tazer using UV laser-ionized paths rather than wires. A second possibility is far less likey: that the "e-wall" effect is genuine but was caused by perfectly normal physics, perhaps by small pressure gradients of ion clouds mentioned in the article, or perhaps it's akin to the recently-discovered "hot ice" effect, and is caused by an aerogel of water molecules stabilized by strong e-fields. Very interesting if true! A third possibility: the effect is genuine and is completely outside of current physics. Such events are rare but not unknown, as when Roentgen noticed a glowing chemical on his lab bench, or when Henri Becquerel put a piece of uranium ore against a photographic plate and accidentally founded an entire new field of physics.

But note well, all of this is pure speculation. There are no "answers" here, only unknowns and probabilities. Comments of skeptics aside, nobody can KNOW that it's mere electro-tetanic effect, any more than we can KNOW it's an earthshaking physics discovery. To banish the unknown, we're required to reproduce the original phenomenon and then verify its causes. (The first thing I asked Dave Swenson was whether he tried throwing an object at the "wall." Nope. Too bad, since the result would have told us a lot.) --Wjbeaty 20:23, 14 April 2006 (UTC)

Hmmm thank you for your input mr Beatey, but as i stated above, the acount talked about leaning his whole weight against it, that could not have been done with just a loss of muscle control, and also if this were true he would not haven been able to walk himself out. So we are stuck with the other two, i am more inclined to beleive the idea that it was normal physics, just in an unusal manifestation. But i have a question which is what kinds of electromagnetic [ or purely electric or purely magnetic] fields can have an effect on objects and people, not a wall effect per se, just moving or knocking about by concussive force etc? Robin 00:27 15th april Robin

Eusing Free Registry Cleaner

Does anybody have experience of using Eusing Registry Cleaner? My registry must be in need of serious cleaning out but I know that tinkering with one's registry is a dangerous activity, so I'd really want to know I can rely on any software that's going to effect it. Casual reviews much appreciated. --bodnotbod 01:25, 11 April 2006 (UTC)

If in doubt, always make a full backup first (open regedit, File -> Export, and make sure to select "All" as "Export range"). Then make small, incremental changes, restarting your computer between changes to ensure it still works. I have no familiarity with the program you mention, but check if it has a backup or undo option - most registry editors do. But, in any and all cases, make backups! :) — QuantumEleven | (talk) 06:16, 11 April 2006 (UTC)

This one looks OK (softpedia give it a clean rating though like Quantum I have no direct experience of it), but you're right to be cautious; the whole malware arms race has led to increasing amounts of malware masquerading as anti-malware tools. --Bth 10:12, 11 April 2006 (UTC)

The software claims to back up for you (or offer a restore point), but I shall follow your backup idea as best practice, thank you. Anyone with direct use of it? Oooh! ALternatively, can anyone recommend a highly regarded open source app for the same sorts of things? --bodnotbod 13:03, 11 April 2006 (UTC)

Constructivist learning theories

Does anyone know of exmaples of cognitive and social constructivist learning theories? i understand the concepts but need to exmaples to understand them clearly.

There is a very large selection of pedagogies (approached to teaching) that trace their origin to constructivist learning theories. At the base level an approach that uses hands on, discovery learning, can be considered constructivist in origin (students being the architects of their knowledge). There are many sophisticated examples (try doing a google search for constructivist pedagogy). One example I am familiar with is Covis. -Fermion 02:17, 11 April 2006 (UTC)

Yahoo! and computing services

The first page of the Yahoo! article states that Yahoo! is a "computing services" company. However, the provided link, computing services, seems to be a redirect to outsourcing. I was hoping to learn from the article what Yahoo! does, since I'm under the impression that they "run a website". I assume that the outsourcing link is inaccurate? -- Creidieki 02:29, 11 April 2006 (UTC)

The outsourcing link is accurate. Yahoo! hosts and maintains one of the e-commerce web sites for one of the companies that I work for. So we outsource the work to them. They do this for lots of companies. I'm not real familiar with the company and its services but they do perform at least some outsourcing. Here's the address for that service: http://smallbusiness.yahoo.com/merchant/ Dismas|^(talk) 04:17, 11 April 2006 (UTC)

I believe Yahoo! is also an internet service provider and provides it's own search engine. StuRat 22:29, 11 April 2006 (UTC)

Could you contain the current from a lightning strike

If you ionized the clouds (somehow), would it be possible to store the current from an lightning stike, given the amount of power discharged by them?

Your terminology "store the current" isn't what I think you mean. I think you mean "store the charge". While you could store some charge from a lightning strike, it would be very little of the overall charge. To date, devices that store charge require time to store up a charge. Lightning happens so quickly that there is no time to store much of the charge. However, it may be possible to steal a little charge from the clouds over time. There is a clear difference in charge between the top of tall buildings and the bottom. It isn't a huge amount, but it may be enough to trickle charge a battery. I've often considered doing an experiment with a lead on top of my offfice (13 floors) and a lead on the ground. The problem is that I don't have easy access to the roof and I'm sure someone would get upset if I hung a cable from the roof to the ground. But, you are free to try it. You may be able to do the same with a kite, using insulated wire for the 'string'. --Kainaw ^(talk) 13:37, 11 April 2006 (UTC)

Sorry, I must object. Flying a kite where there is possibility of lightning strike is potentially lethal. We all know Benjamin Franklin did it and became famous for it, but he was lucky. He was smart enough to know to use a silk thread (a nonconductor) for a distance to the cotton thread that went to the kite. The cotton , when wet, was a conductor, was connected to the famous key. He did NOT hold the cotton thread. He held the silk thread that was tied to the cotton thread, according to what I understand. I recommend some library research before messing with lightning. Trying to store the charge of lightening has been tried and done, by Franklin, but it is not practical. Read all about it first. No point in dying redoing 18th century science experiments. GangofOne 23:35, 11 April 2006 (UTC)

Thanks...and no I won't fry myself.

I did not say "fly a kite in a thunderstorm". I suggested that a kite be used to get an electrical lead off the ground to see if there is enough potential between high altitude and the ground to charge a battery ... when lightning is not present. As for storing the charge, there is much doubt that Franklin performed such an experiment. He flew a kite in the rain (after Thomas d'Alibard did a nearly identical experment with a tall iron rod). Then, there were many failed experiments around the world with lightning rods and jars of various substances. Many house fires followed. --Kainaw ^(talk) 23:46, 11 April 2006 (UTC)

Linux system keeps setting clock time wrong

I am running a Fedora Core 3 Linux system with Gnome 2.8. Every time I power up the system, its clock is at the wrong time, it's usually about 40 minutes in the past. I've tried setting the correct time with both date and hwclock but that only helps for the current session, when I reboot the computer the clock is at the wrong time again. Is it some weird service I'm running or is it a bug? I usually have fairly long uptimes, up to over a month, might this have something to do with it? How would I go about diagnosing it? JIP | Talk 06:42, 11 April 2006 (UTC)

Fedora might be synchronising the clock with an NTP time server every bootup. I haven't used Fedora on a day-to-day basis, but quite a few distros seem to do that. Check the ntpd service and if it's starting on bootup. -- Daverocks (talk) 09:07, 11 April 2006 (UTC)

Maybe try the BIOS? - mako 09:14, 11 April 2006 (UTC)

I've had (acutally, have) the same problem. It is caused by hwclock (see man hwclock). On my previous install I fixed it by rm /etc/adjtime, but I think that removing the --adjust parameters when hwclock is loaded should fix it as well. —Ruud 11:01, 11 April 2006 (UTC)

Another possibility is that the hardware clock is bad. They don't last forever. StuRat 22:16, 11 April 2006 (UTC)

But this is a fairly new system. I only bought it fresh from the store, assembled from off-the-shelf parts (new, not used) a year ago. JIP | Talk 15:36, 12 April 2006 (UTC)

The next step in diagnosis is to note exactly in what way it is bad. Is it always shifted by a fixed amount from the correct time? Is it always a particular date, like January 1970? Is there some other pattern? Notinasnaid 18:38, 12 April 2006 (UTC)

It is always shifted by a fixed amount of time (approximately 40 minutes in the past). JIP | Talk 13:27, 13 April 2006 (UTC)

Is ntpd running and if so whats its server list set to? it sounds like you may be syncronising off a bad time server. Plugwash 13:48, 13 April 2006 (UTC)

ntpd was not running. I activated it and set it to connect to ntp1.kolumbus.fi. This fixed my date and time settings. But as for rebooting, I am still not sure, because I use my company's private DNS server, which is only available through a PPTP connection, which is not started at bootup. So I fear that when I reboot the system, ntpd will not be able to find the NTP server, and will just quit, leaving my system back to the incorrect time. JIP | Talk 19:04, 13 April 2006 (UTC)

Timing Diagram

Hello,

I would like to write an article on Digital Electronics Timing Diagrams.

I have found a stub: wiki/Timing_diagram, but this relates to the new UML 2.0 Timing Diagram.

Where should I start my article.

Regards,

Mark

If there are two clearly different subjects that could fit into a title it can be handled using the diambiguation guidelines. Basically with two articles, you put links up the top of each page, explaining its context, and directing people looking for the other context, to the other page. A likely target for starting your article could be Timing diagram (electronics), as a suggestion. Ansell 09:01, 11 April 2006 (UTC)

UML Aggregation and SQL

I've been set the task of implementing a database schema given in UML as a MySQL database. In terms of design, what does the composition/aggregation relationship on the UML diagram translate to in terms of the tables required? The specific problem is the classic "library" system - there is a table Book which has the book details, then a relationship to an entity BookCopy, which has only one field listed. Is this extension, or inheritance, or neither? - does the arrow imply a foreign key? There is then another entity with the aggregation symbol - LoanedCopy. Could anyone give any advice on the structure of this, or a pointer to somewhere which has a decent tutorial covering UML -> SQL.

Cheers. QmunkE 12:54, 11 April 2006 (UTC)

It sounds like there would be a one-to-many relationship from the Book table to the BookCopy table. Perhaps each copy has a unique serial number ? In that case that would be the primary key to the BookCopy table. The ISDN would be the primary key in the Book table and also a foreign key column in the BookCopy table. The LoanedCopy table would be similar to the BookCopy table, but would also have info on who checked out the books, when they checked them out, when they returned them, etc. StuRat 22:09, 11 April 2006 (UTC)

Spacetime

Could anybody popularly explain the concept of four dimensional spacetime?

Time is just a dimension - like depth, width, and height. The best explanation I've heard is the "flatworld" example. Get a piece of paper. Put a penny (or something flat) on it. That is your flat man. He cannot see up and over anything because his world is completely flat. Draw a line on the paper. He can't see over it. It is a wall to him. You can make a box with an opening for a door and call it his house. When he is in his house, he thinke he is boxed in on all sides. But, you know different because you see in three dimensions. You know that you can pick him up and put him outside his house. The little flat man's point of view (lack of being able to see up) is similar to our point of view (inability to see forwards and backwards in time). --Kainaw ^(talk) 16:14, 11 April 2006 (UTC)

Spacetime GangofOne 23:20, 11 April 2006 (UTC)

Kainaw's example is greatly explored in the book Flatland by Edwin A. Abbott, a book I'd certainly recommend. EWS23 | (Leave me a message!) 01:10, 12 April 2006 (UTC)

Or The Planiverse for a more detailed and mind-blowing view of what life would really be like in 2D space. —Keenan Pepper 04:06, 12 April 2006 (UTC)

The allies of space and time was first perceived by the German mathematician Hermann Minkowski, when he studied his former pupil Einstein's Special Theory of Relativity and realized that their unique connection in behaviour due to the states of motion of the observed objects must be that they are ultimately one thing altogether- space- time, neither one nor the other. This idea was so radical and useful that Einstein incorporated it himself later for inclusion in General Relativity, ten years later. For a better mathematical understanding of the subject, please consult the special introductory page on the Special Relativity page and spacetime. Luthinya 18:32, 12 April 2006 (UTC)

If time is accepted as the fourth dimension, which it apparently is from the above responses, is that the limit of dimensions that "exist" in the universe? Is there speculation on what might be the fifth dimension? Loomis51 23:25, 15 April 2006 (UTC)

Size exclusion chromatography - De-salting a protein solution

I am trying to desalt a protein solution using a column of Sephadex G-25. Is there a rule of thumb for how concentrated this protein solution can be? (I know that if the solution is too concentrated, it causes problems) ike9898 17:08, 11 April 2006 (UTC)

Salt concentration or protein concentration? --BluePlatypus 18:29, 11 April 2006 (UTC)

Protein concentration. ike9898 20:51, 11 April 2006 (UTC)

Well, it all depends on the flow, eluent, the protein itself, etc. But 25 mg/ml seems to be the maximum recommended[1]. --BluePlatypus 21:42, 11 April 2006 (UTC)

If you have a concentrated, salty protein solution the best desalting choice might be dialysis. Simply put the solution inside some moistened dialysis tubing and place the whole thing into a low salt buffer, which you can replenish as necessary. You can leave it overnight or longer. The dialysis membrane traps the protein inside while the tiny salt ions will diffuse through the membrane into the low salt solution by osmosis. This is a routine technique in protein prep.

Another option may be using a centrifugation based device. This allows you to desalt and concentrate the protein in a single step. Refer to the manufacturer for more details (e.g. Centricon).

Size exclusion chromatography is a good technique for purifying one protein from a mixture of proteins and is seperates based on molecular weight. As in all chromatography, the amount you load on this column depends on how big the column is. The bigger the column, the more you can load. Refer to the manufacturer's instructions for your particular brand of packing for the recommended loading amount.

I'm desalting a protease and I get autolysis if I dialyse. SEC is very quick, and easy to set up in a cold room. But, my protein peak is spreading WAY too much. I thought it might be due to too high a protein conc (increasing viscosity). This technique should be routine, but it is new to me and it's giving me a royal pain! ike9898 17:55, 12 April 2006 (UTC)

LG L1515S monitor

I use a LG LCD monitor LG L1515S. Is it a low end, low quality monitor? This is the cheapest LCD monitor which I saw and I thought it does not matter to buy the cheapest monitor? Is there any problem buying cheap LCD? whats the problem? Comparing cheapest LCDs and mid/high quality CRTs, which is better?

LCDs tend to be dim, only give a good quality pic when viewed straight on (not at an angle), and occasionally have a few pixels which are some random color. CRTs don't have these probs, but might be harmful to your eyes, can be blurry, tend to be rather heavy, and may not last as long. A plasma screen display is the best of all, but most expensive, too. You should look at the max resolution (1280x1024, for example), screen size (15 inches, for example), and the refresh rate (60Hz, for example) to evaluate a monitor. Ideally, they should all be as high as possible. Note that the refresh rate often varies with the current resolution setting. A low refresh rate will make the screen appear to flicker, especially when a white screen is displayed. A low resolution will make it difficult to display much on the screen at once and a small screen will make you need to squint to see anything. StuRat 21:50, 11 April 2006 (UTC)

Refresh rates aren't really relevant to LCD monitors. One thing that does matter with LCDs is response times: the lower, the better. If you want to play videos or games, 8 ms (milliseconds) is great, and anything under 16 ms is good. In this day and age, the benefits of LCDs generally outweigh the benefits of CRTs: in fact, most places barely sell CRT monitors any more. Sum0 15:22, 13 April 2006 (UTC)

Also with lcds you have to be quite carefull about the resoloution. Higher ≠ better Windows at least (i can't speak for linux or mac) pretty much relies on changing resoloution to change the displayed size of text (there is a font size setting but the user interfaces or lots of app break if you dare change it). Running an LCD at any resolotion other than an exact fraction of its native means a blurry display that gets very hard on the eyes.

This means several things

• you must be happy with the size of things on your normal desktop at your lcds native resoloution
• if you run games you must be happy with them on your screen, lukilly games tend to use much bigger text than productivity apps so the blurring isn't such an issue but it still helps if you are happy with your games at the native resoloution or a fraction therof (happy with includes both framerate and detail, normally you balance theese by adjusting resolotion but LCDs put you in something of a straightjacket).
• If your vision deteriorates (or if an older relative wants to use your computer) you can't just lower the resoloution to compensate.

All in all this adds up to a lot of lost flexibility when moving from crt to lcd Plugwash 00:18, 14 April 2006 (UTC)

Call termination charge in USA

Is there call termination charge in USA? In India, telecom companies from which calls originate pay a call termination charge of Rs.0.30 to the network in which the call terminates. Is there any call termination charge in USA? If yes, what is the call temination rates? How come companies offer unlimited calling to other companies's phones when there is a termination charge which metres by the minute?

The US telecom industry places all sorts of goofy charges and surcharges on telephone calls. While our article doesn't enumerate many, the FCC has a sample phone bill complete with charges and explanations for a typical US monthly phone bill. As for termination charges specifically, I think that varies by plan. As I recall, such charges may exist but are frequently handled by a long-distance provider who then provides the end-user with a flat per-minute rate. — Lomn Talk 19:46, 11 April 2006 (UTC)

Difference between Google news & topix.net

What is the difference between topix.net and Google news? Both seem to aggregate news. But topix.net serves ads and no one minds while there has been lawsuits against Google news and it is not able to serve ads. Whats the reason and whats the difference between these two?

First, money. Google is a cash cow for lawyers to sue. Second, methodology. Google searches anyone they like and they post results of their search. News sites have to partner with Topix (see their 'about us' page for info on the types of partnerships they have). --Kainaw ^(talk) 23:58, 11 April 2006 (UTC)

A medical query?

Taking my place at the urinal this afternoon, I was joined by my newest coworker setting up shop at the adjacent recepticle. Somewhat contrary to my own restroom M.O., he asked how I was doing, and out of politeness I returned the question. However, despite the divider between the urinals (which really ought to be law), I was struck by that phenomenon commonly known as "stage fright." That is, even though I had a full bladder on (in) my hands, I was incapable of micturating until immediately after he left. Why/how does this occur?

The bladder is controlled by the autonomic nervous system. Parasympathetic neurons innervate the wall of the bladder (the detrusor muscle, trigone and sphincter). Parasympathetic stimulation results in contraction of the bladder muscle and relaxation of the urinary sphincter resulting in urination. This is opposed by the sympathetic division of the autonomic nervous system.

Anxiety or fear, including social anxiety, results in decreased parasympathetic stimulation and increased sympathetic stimulation of the bladder, resulting in relaxation of the bladder proper and tightening of the urinary sphincter, making it more difficult to pee. There's always the stall. - Nunh-huh 18:47, 11 April 2006 (UTC)

There is an article covering this: Paruresis --Ed (Edgar181) 20:34, 11 April 2006 (UTC)

I believe this is an evolutionary adaptation. That is, urinating or defecating in the presence of a stranger (or someone you don't fully trust) is a bad idea, as it leaves you vulnerable to attack. Thus, humans (and other animals) tend to delay elimination until they feel safe to do so. I suggest you use a stall, instead. StuRat 21:37, 11 April 2006 (UTC)

Indeed this phenomenon is contrary to the popular train of thought: that fright causes urination. As noted above, in humans, a sympathetic response to a stimulus will basically keep you from urinating, it is when you get to a safe place and the sympathetic stimulus stops that you will urinate (in a situation where your body decides you are safe again, although you still may be "scared") often uncontrollably. This reaction is actually a situation rather specific to humans: in canines, for example, sympathetic stimulation will usually cause urination when the bladder is anything but empty. Tuckerekcut 01:20, 12 April 2006 (UTC)

I believe in dogs, urinating on themselves is used as a sign of submission. StuRat 03:49, 12 April 2006 (UTC)

Urination is construed as such by other dogs, and rightly so. if a dog is scared, the sympathetic nervous system is activated, which causes urination. Thus fear causes submission. That this cascade is not under voluntary control is not particularly unusual.Tuckerekcut 03:25, 14 April 2006 (UTC)

There is also another possible explanation for this, which you may find slightly disturbing (but you shouldn't, it's quite natural). I was once at a fully packed pub where there was a lineup for the ladies' room but not the men's (as is so often the case), but this time the girls decided what the hell and started to use the men's room. There was no divider between urinals, and they were the type where the drain is at the bottom, so basically you're urinating against a wall. In any case, being out in the open (literally!) in front of all those female strangers was, to be polite, somewhat titilating. It also had the result of making it impossible to urinate. The medical explanation for this is simple: when aroused, the bladder is completely cut off from the urethra, and its impossible to urinate. (You guys know what I mean!). It's also common for heterosexual men to become involuntarally aroused in certain situations. Bottom line: Even if you're totally straight, the fact that your genitals are hanging out of your pants in the presence of another person (in this case, a male) can lead to difficulty in urinating. Loomis51 23:50, 15 April 2006 (UTC)

benefits of organic foods for immunno-compromised individuals...

I would like to know what the benefits are, if any, of organic foods are for immuno-compromised individuals, those with HIV/Hep C in particular. Thank you.

---BR.

I'm not sure that they are. You may want to check out our article on organic food. The crux of your question revolves around how organic foods differ from ordinary foods, which itself is the center of a firestorm of debate. However, the article does mention that organic foods grown in manure actually increase the risk of contamination with E. coli and other bacteria, which is not a benefit at all. Isopropyl 19:29, 11 April 2006 (UTC)

No body knows. No rigorous research has been done on this. Some doctors believe that there may be benfits, but it's highly controversial. For great justice. 01:23, 13 April 2006 (UTC)

There was some research in the UK last year sometime which found that there was no scientifically identifiable benefit in earing organic fruit & vegetables. AllanHainey 10:01, 13 April 2006 (UTC)

computer repair?

what is the best way to fix up an old computer?Cooliabeanias 19:26, 11 April 2006 (UTC)

Using old computers to run Linux is always a good choice. It runs well even with limited resources, and you can learn to use it on an expendable machine. Isopropyl 19:29, 11 April 2006 (UTC)

If you are technical enough to figure out what type of power supply and memory you have, you can look into getting an upgraded motherboard and CPU that will use the same power supply and memory. You'll benefit from extra CPU speed with little investment. The common mistake is to buy the motherboard first - then finding out that you need to buy a new power supply and new memory because the old stuff is incompatable. Then, the cost is so much that you could have bought a new computer. --Kainaw ^(talk) 19:53, 11 April 2006 (UTC)

Many "old" but workable computers get put out with the trash. It is possible to get quite usable parts from such machines. Power supplies, drives, cases, sound cards. Sometimes the machine works perfectly, just is old. This is a wasted opportunity, when so many people, mostly kids, could learn a lot from having such a machine. Out of date for the lastest stuff perhaps, but plenty good for learning. If you can put together such machines, you can just give them away, if nothing else. GangofOne 23:15, 11 April 2006 (UTC)

I've tried to give away old "refurbished" computers for email/web browsing. It is difficult. Beggers quickly become choosers. I set up four computers at the homeless shelter with a 5th providing a shared dial-up connection. The problem was that the shelter didn't want to provide a line for dial-up. So, they just became machines for playing solitaire (which was easier to do with the many decks of free cards laying around). Also - on a distantly related topic - I was with a professor doing a talk on Beowulf Clusters. A reporter at the conference asked if these clusters will make use of all the old computers out ther. The professor's response was memorable: "Sure, if you want a huge power hungry heat box with nearly as much processing speed as a standard home PC." --Kainaw ^(talk) 23:38, 11 April 2006 (UTC)

There are charities exporting refurbished computers to developing countries (see eg here). But I can't help wondering whether the economics of this really work, given that most new computers are manufactured closer to the people being sent the old ones ... (And the "it reuses them which is better than the environmentally-unfriendly components getting junked" argument has to be balanced against the fuel used, surely.)

The only really practical use I can think of for old boxes is as middleboxes if you're running a small LAN off a shared broadband connection or something. --Bth 10:29, 13 April 2006 (UTC)

Chemicals

how do chemicals reacted in diffrent ways when mixed together thanks alot tomas

They react in a predictable fashion depending upon their chemical properties, hope this helps.

• There are several good articles where you could start looking to find what you need: chemical reaction, list of reactions or the category Category:Chemical reactions. --Ed (Edgar181) 20:30, 11 April 2006 (UTC)

Well, if there was an easy answer to that question, there wouldn't be much need for chemists, would there? :) --BluePlatypus 21:31, 11 April 2006 (UTC)

Library Classification of books

I have the responsibility of classifying our monastery library. I have been able to find a conversion of Library of Congress numbers with the Dewey Decimal numbers for an annual fee of over $300. Out of the question for such a small library. Is there a conversion table or some kind of rule of thumb that would help quicken the process? I have not been too successful wiht an internet search.--216.129.236.59 19:44, 11 April 2006 (UTC)

Is the Poor Clares Monastery in Great Falls? How large a library do you have? Does the existing library have Dewey call numbers, and you want to switch over to Library of Congress? If so, and if the library is not too large, would it be useful to use the LOC website to look up the books and obtain the LOC call number? Some of the external references in the linked articles may help. - Nunh-huh 20:18, 11 April 2006 (UTC) You may also want to consider joining the "Project:Wombat" mailing list, where a lot of librarians hang out, and ask this question there. - Nunh-huh 00:31, 12 April 2006 (UTC)

I have an old book called Dewey Decimal Classification and Relative Index - published by Forest Press Inc, Lake Placid, NY. My copy is dated 1959, so whether it's still being printed or not I have no idea. Unfortunately, given its age, it has no ISBN (ironically it has a LoC Call number - 59-11569). It is designed for libraries and provides a list of all the dewey classifications both alphabetically by subject and numerically by code. Understandably, given its age, it has certainly been considerably revised since then (where would you file books on DVD recording, OCR, or even digital watches?), but if it's still out there it might be exactly what you need. Grutness...wha? 02:36, 12 April 2006 (UTC) uhh. skip that - I misread the question. Grutness...wha? 02:42, 12 April 2006 (UTC)

I am familiar with the Forest Press book. I used it in school eons ago. I don't need a detailed list as we are going with a modified Dewey Decimal classification. And, good heavens, Nunh-huh, why would you come up with Great Falls Montana and specifically a Poor Clare Monastery at that? Isn't that a little obscure and wild? Our books are unclassified at this point. So I am starting from scratch. 12:22, 12 April 2006 (UTC)

Your IP address (216.129.236.59) is listed as being in Great Falls, MT. --Kainaw ^(talk) 13:24, 12 April 2006 (UTC)

I found this site which gives the Dewey classification if you enter the ISBN. If you can get your hands on a bar-code scanner (maybe an old CueCat somewhere?), there seem to be several free utilities around to help in creating a catalog. --LarryMac 15:09, 12 April 2006 (UTC)

Not much help for any book published before 1970, though... Shimgray | talk | 15:29, 12 April 2006 (UTC)

Speaking as a cataloguer for a small-medium library, we use DDC20 at work - it's two decades old, but as long as you're willing to be creative with some sections (we have a heading which technically parses as "21st century history of the Soviet Union"!) that's not much of a problem. Anyway, the point there is that older editions of Dewey work fine, and if you try asking around it's quite possible a larger library (or library school) still has the old cataloguing manuals gathering dust on a shelf somewhere after they went to a more modern version - they're not much use after you've changed, except for training purposes, so asking nicely might well just get them as a donation.

Of course, real classifying might be more effort than you want... if all you need is a very simple "high-level" classification, OCLC do publish a list of the "thousand sections", the top-level sections of Dewey (PDF), which should give you a baseline to be going on with. For individual books, you could try running them through the Library of Congress online catalogue - they have Dewey numbers listed for most of their stock - but it's probably just as quick to give them a general classification yourself once you have the hang of it. Shimgray | talk | 15:28, 12 April 2006 (UTC)

Thank you, for all your help. With the information provided I was able to find just what I needed. Shimgray's link to OCLC.org I was able to find the summary. Now I will be able to keep our classification consistant and heave others help me do the cataloging. We want the library to be extra user friendly and so we are using a modified DDC. I checked with all our PC monasteries on-line and culled the best possible classification system for our smaller libraries whcih ae also over loaded in the 200's. And, yes, I am at the Poor Clare Monastery in Great Falls, Nunh-huh. I would like to go back and do some adding to the Poor Ladies entry as it is bare bones information. It will have to wait a while as I have my hand full right now.Judith 20:26, 12 April 2006 (UTC)

Sounds good, and glad you got to a solution. Have a good time organizing, and we await any contributions to the Poor Clare article with patient antici-----pation! (It really is a little pitiful!) - Nunh-huh 23:34, 12 April 2006 (UTC)

I suppose it depends on how many books you have but I always prefer a more idiosyncratic filing system - largest to smallest, left to right. It makes it more fun looking for something & increases the chance of finding something you never knew you were looking for.AllanHainey 10:04, 13 April 2006 (UTC)

Gasoline and styrofoam

I've always been told that styrofoam will dissolve in gasoline and therefore you shouldn't store one in the other. Does this happen? And if so, why? Dismas|^(talk) 22:17, 11 April 2006 (UTC)

Yes, gasoline does dissolve styrofoam; I know because I once tried to fashon a funnel from a styrofoam cup, to help get gas into my moped. Gasoline is a non-polar solvent, and it is good at dissolving other non-polar materials, including stryofoam. Some synthetic polymers are much more resistant to this than others. ike9898 22:21, 11 April 2006 (UTC)

Gasoline is a good solvent. Some idiots apparently use it in the washing machine to clean grease off their clothes, and then get a nice explosion when they put the clothes in the dryer. (The clothes may not have any oil stains, but you will need to pick them out of the debris to find out.) StuRat 22:34, 11 April 2006 (UTC)

Styrofoam melts easily in any number of solvents, including gasoline, turpentine, paint thinners, etc.. It can also sometimes melt from lemon juice. Ande B 00:48, 12 April 2006 (UTC)

Dissolving styrofoam and soap in gasoline is a good cheap way to jellify it, creating a napalm. :) -- Mac Davis] ⌇☢ ญƛ. 04:29, 12 April 2006 (UTC)

Thanks for the replies, everyone. I'm sure the gasoline that those people use in their washing machines does wonders for their septic systems if they happen to be on one.  :-) Dismas|^(talk) 10:29, 12 April 2006 (UTC)

Coyote/dog hybrids

I overheard a man at the pet store the other day say that his dog is half coyote. Are Dog/Coyote hybrids fertile? User:Zoe|^(talk) 23:01, 11 April 2006 (UTC)

I guess Coydog answers my question. User:Zoe|^(talk) 23:04, 11 April 2006 (UTC)

April 12

Gettin' burnt...

i accidentally burnt my finger yesterday with an iron, and little watery poxes appear on my finger, why's that? Thx --203.218.93.206 01:08, 12 April 2006 (UTC)

I'll take blisters for $400, Alex. - Nunh-huh 01:09, 12 April 2006 (UTC)

You can check out Burn (injury) as well for more information about burns. Ansell 01:11, 12 April 2006 (UTC)

You have a second-degree burn. (Please leave your OHIP number on my userpage.) - Cybergoth 04:22, 13 April 2006 (UTC)

Need Help on an Article

Can I get some help with checking the information on the Boiling Constants page and also setting up the data into tables? Ctifumdope 01:33, 12 April 2006 (UTC)

One comment, the Wikipedia naming convention is to only capitalize the first word in an article name, and make it singular, so you should rename the article accordingly to Boiling constant. StuRat 03:43, 12 April 2006 (UTC)

Help:Table is a good page that can help you with formatting your information into tables. -- Daverocks (talk) 04:35, 12 April 2006 (UTC)

I moved the page to List of boiling constants of solvents. -- Mac Davis] ⌇☢ ญƛ. 05:40, 12 April 2006 (UTC)

Sound and Balloons.

hi, i would like to know why and how does a exploding balloon produce sound? thankyou — Preceding unsigned comment added by 202.138.102.141 (talk • contribs)

Sound waves in air are composed of alternating pressure differences. The pressure inside a balloon is higher than outside (or it wouldn't be inflated in the first place). When you prick it, the pressure equalises; because the speed of propagation of pressure differences isn't infinite (it is, of course, the speed of sound), this doesn't happen instantaneously -- an expanding sphere of high pressure radiates out from the balloon, which you hear as a bang when it reaches your ear. --Bth 09:46, 12 April 2006 (UTC)

I was interested in this question, since the process is somewhat identical to earthquakes. Here is a good reference: [[2]] It has nothing to do with the air, but the speed of the fracture propagation, and the whip of the fragmented ends. These form mini sonic booms. You can experiment by interferring with the latex (tape) and showing how it muffles the sound. You can do different things to get a really loud pop. --Zeizmic 14:30, 12 April 2006 (UTC)

ElectroMagnetic Disturbance

How is it that a nuclear explosion creates an elecromagnetic pulse?How does this harm modern IC's only when they are in use?

See electromagnetic bomb for the processes involved and how they interfere with electronics. But where do you get the idea that ICs are only vulnerable when in use? Unless they're shielded (by being put in some sort of Faraday cage) they're going to be vulnerable on or off. --Bth 10:56, 12 April 2006 (UTC)

Computing Data Storage DVD

What is the difference between a DVD-RW DVD-R and DVD+RW DVD+r?

"R"s can be written to once, then the data's fixed; "RW"s are rewritable (with full erasure first for the -, random access for the +). The +/- thing is a standards mismatch between different manufacturers (like VHS/Betamax for video formats, except that we're still at the stage where the marketplace hasn't chosen a standard). Various arguments are advanced in favour of the two; you can read more at the articles in question. --Bth 10:45, 12 April 2006 (UTC)

Altitude and temperature

Why does it become cooler as we go higher?As we are nearing sun i suppose it should get hotter.-explain

Erm, no. For one thing, the heat from the Sun reaches the Earth as radiation, much of which passes through the atmosphere and heats up the ground, but the overall siutation is complicated --there are layers where temperature increases with altitude, but the processes involved are more involved than just "it's nearer the sun". See Earth's atmosphere for more. --Bth 10:35, 12 April 2006 (UTC)

The higher you go the thinner the atmosphere is, which means fewer particles to transfer the sun's radiation (or heat absorbed from surroundings) to you. Also with more room to move the particles are less energetic. Higher pressure = hotter. Lower pressure = cooler.--Anchoress 11:08, 12 April 2006 (UTC)

However, in the thermosphere the temperature is controlled by the absorption of solar radiation and the temperatures can get as high as 2000^oC. So there the questioner's original assumptions do sort of hold. --Bth 11:11, 12 April 2006 (UTC)

It's still entirely irrelevant that you're closer to the sun. The difference in solar radiation intensity between the ground and the top of the thermosphere (using 690km) is $9.2\times 10^{-6}$, which is hardly important. It is true that some high-energy radiation is available there for heating that isn't available on the ground, but it's more like the rest of the atmosphere is in the thermosphere's shadow, rather than that the thermosphere is appreciably physically closer to anything. --Tardis 17:11, 12 April 2006 (UTC)

Unfortunately your idea happens to be the common misconception. It is totally irrelevant here, as Tardis has said, whether you are close to the sun or not. The fact is that as you go up higher, the atmospheric pressure drops considerably, and with fewer air particles to transmit the sun's radiation or generate energy between themselves by bumping into each other, naturally the air temperature drops. I suppose your closer distance does mean that you would expect to feel the heat of its radiation more strongly, but even without the effects of the atmospheric pressure as I have described, considering the vast cosmic distances between the sun and the earth, even a mountaineer standing at the top of Everest will not be able to feel all that much difference to when he was upon sea- level itself. Luthinya 18:39, 12 April 2006 (UTC)

Vectors in EMW

Is there an easier practical illustration of the common terms we use in Electromagnetic Theory like Gradient,Curl,Divergence?

Which illustrations are you already familiar with? In general, they're slightly fiddly to get across in non-mathematical form, hence the amount of handwaving that generally goes on, but they work wonderfully once you get your head round the del operator.

Having said which, Feynman probably handles them wonderfully in Volume II of the Lectures on Physics; I'll look it up tonight when I get home. --Bth 10:40, 12 April 2006 (UTC)

In fact, Feynman pretty much takes the same delaying the physical meaning until you've grasped the maths approach that I was suggesting. Rather surprising. --Bth 10:22, 13 April 2006 (UTC)

Marine Engineering

How is it possible to maintain a watertight seal between the rotating propeller shaft and the hull in a submarine or ship keeping in mind the intense water pressures the submarine will face when submerged?

I'm sure this question's been asked before, but I can't find it ... --Bth 11:08, 12 April 2006 (UTC)

Stuffing box --Zeizmic 11:45, 12 April 2006 (UTC)

calcium / sugar

Is it oxalic acid, made from calcium?, that the body uses to digest sugar?? not sure if i spelling right.

m

Oxalic acid is two COOH groups bolted onto each other; it contains no calcium. Enzymes are what break foods down in digestion -- for the specifics of the digestion of sugar, see glycolysis and for what happens after that, Krebs cycle. Calcium is important in the body as a constituent of bones and teeth. --Bth 12:48, 12 April 2006 (UTC)

As a note Calcium is involved in Muscle contraction and is involved in carrying the eletrical charge down a Neuron in the Electrical synapse. Wish I had better sources for the neuron thing as it's been 9 years since my animal physiology course.--Tollwutig 13:30, 12 April 2006 (UTC)

Oxaloacetic acid is an intermediate in the breakdown of most sugars, yes. Neuronal transmission is mostly the affair of sodium and potassium. Physchim62 (talk) 13:41, 12 April 2006 (UTC)

Though calcium is involved in transmission across chemical synapses, by triggering the release of neurotransmitter vesicles. I'm guessing calcium has only a small role in typical electrical synapses because the intracellular concentration of calcium is so low in most cells. --David Iberri (talk) 22:03, 12 April 2006 (UTC)

And, yet, if the concentration of calcium ions in the extracellular fluid drops, it produces excessive and painful muscle contractions called hypocalcemic tetany. The concentration may be low, but Ca is certainly not unimportant to neurmuscular transmission. alteripse 00:43, 13 April 2006 (UTC)

MIME

Can you please explain what a "MIME TYPE" is?and can you list a few MIME types?

We have a good article on MIME. MIME helps identify what the type of content that is being sent is. Some examples are: text/plain, text/html, image/jpg (I think). -- Daverocks (talk) 12:42, 12 April 2006 (UTC)

IIRC the last one should be image/jpeg. --cesarb 19:18, 12 April 2006 (UTC)

Time series analysis

The linear regression model can be used to estimate expected value. When applied to a time series, linear regression may not be useful because it is time-neutral. If I have a scatter chart of a time series, what kind of statistics tool should I use, if I want to:

• Estimate a rope's possibility of breaking over time. The rope is under a significant load, the fibers of the rope could break any minute. So the strength of the rope may suddently decrease over time. To estimate the possibility of breaking at t₀, we may forget about past values. Let's say we have a lab and 1000 such ropes and loads.

• Estimate a rich person's tendency to buy gifts over time. Suppose the man is influenced by his ever-changing mood. If he's very happy, he can be buying gifts all the time. We don't know if he's happy at any given moment, but we can increase the weight of t₀±Δ to emphasize the influence of his mood.

• Estimate a person's tendency to invest over time. Suppose all that person has is a stock ticker. At the time of decision making, he/she only has past performance. -- Toytoy 12:40, 12 April 2006 (UTC)

Did you come up with those examples yourself? 'Cos they sound awfully like homework ... --Bth 13:02, 12 April 2006 (UTC)

Yes, that's homework. And I am my own teacher. @#$% I should have taken some statistics while I was in college but I did not. -- Toytoy 13:13, 12 April 2006 (UTC)

I'm not sure how a linear regression is relevant here. In the rope example, it sounds like you're trying to statistically describe the lifetimes of ropes under stress. That's just one-dimensional data: a vector of times. You'd just be using standard things like mean, variance, and [[skewness|]] to analyze that. The other two examples don't have a clear goal to me... if you have data like "on December 11, Roger bought 2 gifts" and "on December 12, Roger bought 0 gifts", all you can usefully do is find times that seem interesting and posit that important events happened then. If you additionally had "on the evening of December 11, Roger's pet mouse caught the flu", then you might want to compute some sort of correlation between the two sets of data. With appropriate quantification of everything and some luck, you might be able to come up with a reasonable model ($d^{2}{\mbox{gifts}}/dt^{2}=k({\mbox{good news density}})$ or something), and then you could do predictions of one variable (gifts or good news) from the other. But when, say, you were trying to calibrate $k$, you'll just want to use regular statistics, since your model exists outside of time and does not need to be causal. If you do do past-only analysis, it's typically as simple as truncating your data to whatever point in time, fitting some sort of curve to it in the usual ways, then extrapolating beyond it. --Tardis 17:24, 12 April 2006 (UTC)

This is just a shot in the dark as I'm not sure I understand your question fully, but have you considered multiple regression analysis with time being the third variable? It's available on excel. Sorry if this makes no sense, it's been a while since I took stats. Loomis51 00:01, 16 April 2006 (UTC)

A problem about Live Linux CD.

Hi, just recently i got a softwares dvd, in which Tablix Live Linux CD's ".iso" file was supposed to be there. but actually it was a ".rar" file. so i extracted the whole "rar" file, and then "burned" all the extracted files onto a CD. i am using windowsXP. then i tried to run "tablix" from that cd by making default boot from cd drive, but it didnt work. after that i ran the cd on winXP, even then it didnt start, actually a ".html" file about "tablix" from the cd did start on autorunning, but the OS wouldnt start. now how to do it? even on their website they have not mentioned how to install and use it for windows user. Similarly, on the same DVD, there is an "image" of Cluster Knoppix, but when i see that file's properties, it doesnt show it to be an "iso" file. i tried to burn that knoppix image on to a cd, by using nero 7, but it showed the message that unrecongnisable format, and so i didnt go further. so wats all this going on ? i am a windows user, and if a normal user like me has to go through so much hassles for just trying Linux, is it serving good to the open source community? not at all. so could you please recommend some Live CD OS which can work directly without such hassles. Also , can u tell me any website or organisation , which could send me these Live Linux CD's or other free Linux CD stuff to me. i am from india, and internet speed at my home is not too great, and also too expensive for me to download the ".iso" files of around 600mb size. so if u could recommend some sites which would do so and send me the CD's in india at my place? thank you.

If you have WinRAR installed on Windows, it makes itself the default application to open ".iso" files. This could possibly be why you think it's a rar file, because WinRAR likes to open iso images. If you're right, though, and the images are really ".rar" files, it would probably be better to put all the extracted files into an iso of its own, rather than burning all the files manually. Also, when you say you tried to run Tablix and it "didn't work", does that mean that Windows started booting and the CD didn't? More details would be appreciated. Also, if you tried to get Nero 7 to burn an image file and it said "unrecognisable format", then what you're trying to burn definitely isn't an ISO. What format is that image in? -- Daverocks (talk) 12:51, 12 April 2006 (UTC)

More generally, you could try Linux India (that's the WP article, this is their site) or one of their affilliated LUGs (Linux User Groups) for help getting started with Linux -- it seems to be a large part of their mission to help newbies. And if you don't manage to solve your problems, apparently thanks to LI's activities, sites like this one now sell distros on cheap CD to India. --Bth 13:01, 12 April 2006 (UTC)

I think Ubuntu linux will still mail you free cd's. They send a live CD and an installation CD. And your problems seem to have to do with the configuration of your Windows system, not the linux distrobutions themselves. But I agree getting in touch with the local linux groups would be good, as you'll have lots of things that will be much easier if you have someone to help you with. - Taxman ^Talk 17:48, 12 April 2006 (UTC)

Have you set your bios to boot from cd? For great justice. 01:15, 13 April 2006 (UTC)

He noted that "i tried to run "tablix" from that cd by making default boot from cd drive". Still, maybe he didn't try to set the order through BIOS. -- Daverocks (talk) 04:02, 13 April 2006 (UTC)

Yeah, sorry, I missed that! For great justice. 15:55, 14 April 2006 (UTC)

Why are adults less able than children to tolerate dizziness?

Most kids could spin in circles for a minute or more with only mild nausea that quickly passes. Many or most adults would feel ill to the point of vomiting from such motion, and are probably more likely to get nauseous from a simple thing like swinging. Why are children generally better able to handle getting dizzy? --Jonathan Kovaciny 12:49, 12 April 2006 (UTC)

Your assumption does not sound correct to me. People that are highly active can handle motion better than people who rarely move. Children spin, tumble, and run around more than adults. So, a higher percentage of children have a tolerance for that action. Adults who continue to spin, tumble, and run around maintain the tolerance. Also, children who spend all their time sitting in front of the tv do not have a tolerance for motion. --Kainaw ^(talk) 13:11, 12 April 2006 (UTC)

I certainly can't go on as many roller-coasters as a twelve-year-old. DJ Clayworth 03:34, 15 April 2006 (UTC)

Need to buy a 'surge protector'

1:24 PM 4/12/2006 DST Need to buy a 'surge protector'

Hi all, I need to buy a 'surge protector' or I think an 'automatic voltage stabilizer' for my home computer as power cuts are becoming more

frequent. The budget is low and i don't think I need anything as fancy as a Uninterruptible Power Supply; just a Plain Old stabilizer is sufficient? I

don't know much about the impact of a hot boot on the devices in my Willamette processor or the 1.5 GHz board. All I know is there might be some

damage to the hard disk with repeated incidents of power failures. Is there anything I am missing? Thanks for your care and dedication. I have been reading this page for quite some time now and I CTRL+D ed it on my firefox. Yours truly, -- Kushal one 17:38, 12 April 2006 (UTC)

A surge protector is no use at all in a power cut. It is designed to protect against sudden increases in power ("surges"). In a power cut, the computer switches off, unless you have an Uninterruptible Power Supply. Notinasnaid 18:34, 12 April 2006 (UTC)

Don't know what a stabilizer is, but you need some form of Uninterruptible power supply --Zeizmic 19:55, 12 April 2006 (UTC)

A UPS can act as a stabilizer, in that it will maintain a steady voltage in the event of power sags or power surges. A surge protector alone might help in eliminating any surge that occurs as power is restored after a power cut. --205.143.37.68 21:25, 12 April 2006 (UTC)

I think there is a difference between a 'surge' protector and a 'spike' protector. I am not sure if that is relevant to what is being discussed here, but here goes what I think is the difference. A 'surge' protector is for things like electric motors which will overheat if too much current is pushed through them, often they have circuit breakers to protect against that. A 'spike' protector protects against brief overvoltages which often occur when powerlines are near a lightning strike, these are very hard on electronics and can cause progrsssive failure because each spike does some damage to the components.

Yes. If you are living somewhere with frequent power cuts, you likely have spikes and surges too. Get a UPS. If you can't afford one, a surge protector will help reduce damage from too much electricity, but won't help with not enough. For great justice. 01:08, 13 April 2006 (UTC)

Thanks all of you. I will need to look for a spike protector then? FGJ (if I call you that), I don't think I can afford a UPS but I will look into the prices for it too. My second question stands. I don't know much about the impact of a hot boot on the devices in my Willamette processor or the 1.5 GHz board. All I know is there might be some damage to the hard disk with repeated incidents of power failures. Is there anything I am missing? Sorry for the added trouble.

The colour of water

I recall reading once a upon a time that the colour white corresponds to the highest frequency point on the Sun's black body curve (somewhere around 6000K). This is not coincidence, but an evolutionary adaptation. Rather than saying "sunlight is white at its brightest" it is probably more accurate to say "our manner of perceiving white has been conditioned by the sun." An animal around a red dwarf might perceive our red as white and our white perhaps might be invisible in the manner of x-rays etc. OK, if that's utterly out to lunch somebody tell me.

So this got me thinking about water the other day. Again, it's obviously not coincidence that our main biotic solvent happens to be transparent. Would it be fair to say "our manner of perceiving transparency has been conditioned by water"? Another hypothetical alien basking in liquid ammonia might view H2O as an opaque poison? Any formula that describes this sort of thing? I suppose the evolutionary mechanism would be "the clearer the water the safer the drinking." Marskell 17:50, 12 April 2006 (UTC)

As I understand (part of) your question, you are asking if, given different conditions during our evolution, we could ahve evolved in a way that water was not transparent to us, but something else (that is opaque to us) might be transparent to these alterative people. Water is transparent becuase it absorbs little radiation from the 'visible' portion of the spectrum. The radiation absorbed by water wouldn't change, but we could have evolved so that our eyes were attuned to a different part of the spectrum. I believe water is fairly opaque in the UV, so if our eyes saw UV, water would indeed be opaque as well. As to whether there is some solvent that is opaque in the visible but transparent on UV or infrared, there probably is, msaybe someone could provide an example? Chapuisat 18:41, 12 April 2006 (UTC)

"the colour white corresponds to the highest frequency point on the Sun's black body curve", better to say, not highest frequency, but rather , most abundant. Which is maybe what you mean. Yes, it is natural that we are sensitive to the light frequencies that are most copious in penetrating the atmosphere. To be otherwise would be a missed opportunity. But it doesn't apply to transparency. What is transparent to light is physically determined couldn't be changed subjectively in the viewer. Anyway, why would it matter if water where opaque? What if water were silvery like mercury, why would that matter? Except for minor adjustments, like not diving into water without testing depth etc? I don't see why life couldn't evolve if that where the case. (Water in the eyes, would be a problem; probably a workaround) GangofOne 23:08, 12 April 2006 (UTC)

Transparency could be changed if we are talking about seeing with a radically different spectrum of "visible light". For example, if infrared was all we could see, we would perceive some things as being transparent which are not transparent to the radiation we call "visible light", and we would perceive some things as opaque which are currently transparent. Transparency is not quite the same sort of thing as color perception but it is not radically far off. But the "color of water" bit is misleading in this regard, I think. --Fastfission 00:02, 13 April 2006 (UTC)

"Highest" --> "most abundant", yes thank-you, that was poor word choice. So you're saying it is essentially coincidence ("couldn't be subjectively changed in the viewer")? As for why it would matter, I would guess that opacity would be something of a handicap to early marine creatures. Perhaps a transparent solvent is not required for evolution, but it certainly doesn't hurt once you develop eyes. Marskell 08:06, 13 April 2006 (UTC)

Of course the light we get from the sun is ALSO in the range of energy transitions of many chemical reactions, (many chemical reactions for chemicals our living world is made of, because it evolved under those conditions. note the circularity...) EG photosynthesis rxns, etc. Here is where in the intelligent design advocates can speculate. If the sun gave off microwaves, say, than a planet to form life would have to have a mwave transparent atmosphere, chemistry of life as we know it would be impossible, would have to be different chemistry. etc. Many techincal problems. And if you try to track down solutions, it may be that eventually all alternate scenarios won't work. Then ID might say, constants of physcics are such that nuclear rxns in the sun are such that the radiation it gives off are such that on a particular type of planet with certain gaseous atomosphere at certain temperature could form life rxns that make life possible and allow life to see and cognized that the constants of physics are such that .... (It all fits together) I mean the IDists COULD make such a claim, if they were smart enough. --GangofOne 19:40, 13 April 2006 (UTC)

If water were opaque with respect to our definition of 'white', then life evolving in oceans would presumably adapt to whatever the most abundant radiation filtering through was, and the surface of the ocean would probably become prime real estate. It could lead to some interesting results, like radically different mechanisms for photosynthesis at small variations in depth. Peter Grey 03:21, 14 April 2006 (UTC)

Water transparency is vital for terrestrial as well as aquatic organisms. If water were not transparent to humans, critical eye components such as the lens and vitreous humor would be opaque. :furthermore, since vertebrate eyes evolved in ancestors to vertebrates, we inherited our vision from aquatic creatures. — Knowledge Seeker দ 05:40, 14 April 2006 (UTC)

Even if vision could not be developed for whatever reason, there are other ways to sense one's environment. Echolocation can be an adequate substitute for vision, and an organism living in a sufficiently dense environment (such as underwater) can sense movement around itself via a pressure sense. 84.239.128.9 18:02, 14 April 2006 (UTC)

A problem about GIMP

Hi, just recently i downloaded GIMP (latest version) from sourceforge.net, and all the help files and also animation package along with the necessary GTK. it was working fine on my laptop, but when i tried to install it on my personal computer, running winXP, during installation it said that some files were already present , so it gave me option of "renaming" them. but i decided not to rename them. so it got installed with no problem.but now whenever i try to run it, a msg appears that "an error has occured and GIMP will shut down". this error just wouldnt go. i re-installed it several times, but it didnt work, now what should i do? GIMP is great , but these problems just make open source a headache. could u help me?

Why is this an open source problem? As for Gimp, did you remove it first before reinstalling it? --Kainaw ^(talk) 18:38, 12 April 2006 (UTC)

yes i did uninstall it before installing it.

For more specific help here, you'll need to be a bit more specific about the errors during installation, and whether you get the same errors each time. Also, have you tried that project's help forum? --Tardis 20:15, 12 April 2006 (UTC)

Skew Universe

What exactly are the implications of a skew universe, and what are the possiblities that we may live in one ourselves? Luthinya 18:41, 12 April 2006 (UTC)

You'll have to give a rigorous definition of "skew universe" first. It doesn't seem to be a well-established scientific term. Perhaps you'd be interested in brane cosmology? Also, skew in other fields is typically a relative description; it means nothing if you only consider one object. If that's the case here, then the question "do we live in a skew universe?" is meaningless, and the "implications of a skew universe" are null. Now, if we somehow found another universe and it was skew to ours... --Tardis 20:34, 12 April 2006 (UTC)

I think this is a follow up to the question about the perpendicular universe theory that was asked a while back--172.129.106.218 00:10, 13 April 2006 (UTC)

Unless its the same person, I think he is just asking about parallel universes. Check it out. -- Mac Davis] ⌇☢ ญƛ. 01:18, 13 April 2006 (UTC)

I know which section you were talking about vaguely, since I myself have seen it, but I am NOT the same person- since I am obviously female- and as far as I know my problem does not concern parallel universes directly, which I had taken a considerable interest in a few months earlier. My question arose from an article of a scientific journal- whose name I can't recall- discussing the various possibilities of different "models" of the universe arising from modern physics. The article only contained a brief sentence concerning the skew universe so I decided to ask here to satisfy my curiosity. I have had a vague idea now- I've checked for the word skew in a mathematics article and obtained the relevant information. LCS 08:32, 13 April 2006 (UTC)

radiology

What is the flow of electrons in an x-ray tube?

See X-ray; in particular, the history section. --Tardis 20:47, 12 April 2006 (UTC)

cells

Why do lysosomes function best in acidic environments?

Maybe you should look up lysosome? I'm sure that has the answer to your homework question. --Tardis 20:56, 12 April 2006 (UTC)

This isn't sufficiently answered on Lysosome. --David Iberri (talk) 21:17, 12 April 2006 (UTC)

(After an edit conflict, and noting that this didn't immediately strike me as a homework question...)

It's really the digestive enzymes within the lysosomes that function better in acidic environments. Each of these enzymes (like all enzymes) is a protein whose ability to function is dependent on its ability to assume the proper shape. If the enzyme is in the wrong shape, it won't be able to act efficiently on its substrate. For lysosomal enzymes, having the wrong shape means not being able to perform enzymatic digestion optimally. A protein's shape is governed by its tertiary structure, which is maintained in large part by hydrogen bonds between the protein's amino acids. And hydrogen bonds are exquisitely sensitive to pH. Change the pH enough and the hydrogen bonds will be disrupted, forcing the protein to assume an improper shape (called denaturation) and therefore become less active.

This provides some measure of protection to the cell. Consider a case in which the lysosome bursts, spilling digestive enzymes into the cytoplasm. The higher pH (less acid) of the cytoplasm would render the lysosomal enzymes less active, protecting the cell from digesting itself. Hope that helps, David Iberri (talk) 21:17, 12 April 2006 (UTC)

I thought it was -- it mentioned the pH-dependence of the digestive enzymes, and the bit about their being somewhat disabled if a lysosome leaked. But the denaturation details you gave are nice. I didn't even ask the question, but thanks. --Tardis 15:37, 13 April 2006 (UTC)

Relativity and the speed of light

My friend posed the following scenario to me earlier: Assume that you have a highly efficient solar sail attached to a ship, and that you set the ship and sail in motion in space. Assuming the ship does not pass near enough to any highly massive objects to greatly affect its speed, and that it receives a steady supply of solar energy, will the ship ever exceed or match the speed of light?

I say no. Mass increase tells us that, even given a steady source of energy, the ship's mass would increase without bound as its velocity increases, and the ship would require infinite energy to meet the speed of light.

However, my friend tells me that, given Newton's F=MA, sufficient energy would allow the sail and ship to meet and exceed the speed of light.

I am quite confident of my own thoughts on the matter. However, I would like concrete mathematical or physical evidence to show my friend the error of his ways.

--Doubleplusungood 22:46, 12 April 2006 (UTC)

You're entirely correct; in fact, it requires an infinite energy (and hence infinite time) to accelerate an object with non-0 mass to c , which will, of course, never happen. The kinetic energy of the spacecratft would be $E_{k}=mc^{2}({\frac {1}{\sqrt {1-(v/c)^{2}}}}-1)\!$ (see Kinetic_energy#In_relativistic_mechanics). As v approaches c, this number approaches infinity. Recommend a good book on relativity to your friend. --Borbrav 00:26, 13 April 2006 (UTC)

He's kind of right - sufficient energy will accelerate the ship to the speed of light. It's just that sufficient energy doesn't exist in the universe... For great justice. 01:05, 13 April 2006 (UTC)

As for concrete physical evidence, particle accelerators verify relativity all the time. You can accelerate a charged particle with changing electric fields, and as it gets closer to the speed of light, its energy grows (and therefore it acts heavier) without limit. No matter how long you keep accelerating it, it will never reach or exceed the speed of light. —Keenan Pepper 08:15, 13 April 2006 (UTC)

Hello! This is doubleplusungood again, with a few additional questions. My aforementioned friend is with me now. Here are his thoughts: 1. In the solar sail example, assume the universe is composed only of a single star and the sail device. The star is thus emitting radiation that continues constantly to hit the sail. The constant addition of energy will never reduce. Due to the absence of gravity (negligible gravity, that is), the sail will never slow down of its own right, and the continual input of energy will continue to accelerate the sail, due to conservation of energy. 2. Since light is affected by gravity (e.g. black holes), and can also be slowed down (by gravity and refraction through everyday objects, like water or diamond). Since Newton declared that only mass is affected by gravity, light must therefore have mass. In accordance with relativity, light thus cannot attain the speed of light. What is the speed of light (as light can slow down), and what is light, since it must have mass and cannot travel at a velocity of "c"? --Doubleplusungood 17:44, 13 April 2006 (UTC)

There's a very simple explanation you're overlooking: Newton was wrong. Massless particles are affected by gravity. Chuck 20:40, 13 April 2006 (UTC)

There are two types of particles: those with a rest mass and those without. Those with a rest mass cannot be accelerated to c, regardless of energy input, per above. Those without rest mass (e.g. photons) can only move at the speed of light, and have a "mass" that is related to the energy they carry. --Borbrav 22:10, 13 April 2006 (UTC)

An even simpler explanation: you have to substitute the relativistic version of F=MA. Peter Grey 03:26, 14 April 2006 (UTC)

Answering point 1) of Doubleplusungood. Let's simplify the problem: forget relativity, use only newton's mechanics. Let the Star be in point (0,0,0) and the sail moving along axis x. Newton's equation for sail, projected on axis x, will look like this:

M*a_x = -G*M*m/x^2 + C/x^2, where C is a constant

where a_x is projection of sail acceleration on axis x. C/x^2 is force, caused by star's light: as the sail moves from the star, the spacial angle, at which it's seen from the star is reduced as 1/x^2. It's just geometry. (And the light intensity is the same in the same spatial angle.) C is some constant, depending on intensity of Star's shining and surface of the sail. OK? We can rewrite the right hand of equation as Y/x^2, where Y is new constant, positive or negative. This new equation M*a_x = Y/x^2, is the same equation, as the equation of a charge in electrical field. So, the answer is this: sail will never gain infinite speed. It will gain some constant speed if Y>0, and will return to Star if Y<0.

Just, guys. Don't stop thinking and finding new problems. Currently i know better; tomorrow you'll do. :-) ellol 11:30, 14 April 2006 (UTC)

Also, as the sail approaches c relative to the light source, the light will be redshifted further and further, constantly decreasing the energy available to push the sail, even if the light was in a coherent straight beam. Tzarius 01:36, 15 April 2006 (UTC)

Another point -- the "slowing down" of light in refraction doesn't really have anything to do with relativity -- it's the result of the electromagnetic wave that makes up the light coupling to the electric fields in the material doing the refracting. The "fundamental speed limit" c, the speed of light in a vacuum, is unchanged. A particle can go faster than the "local" speed of light in a medium as long as it's still going slower than c. This creates the light equivalent of a sonic boom -- Cherenkov radiation. --Bth 05:43, 15 April 2006 (UTC)

Excretion and body temperature

Is it possible to lower one's body temperature by urinating or defecating? The answer is probably a resounding no, but I want to know for sure. Bhumiya (said/done) 22:47, 12 April 2006 (UTC)

No. Poop and pee are the same temperature as the human body as long as they're in the human body. So there's no chilling or warming effect by getting rid of either of them. - Nunh-huh 23:30, 12 April 2006 (UTC)

Not by urinating or defecation but by eating and drinking it is possible because all of that food/water has to be heated. Just look at the energy balance. Assume you take in all food and water at room temp. (25 C) for one day. Assume it comes out of your body at 98.6 F (37 C). Then, 12 C or 12 K is the difference. Now find the specific heat of the composition of urine, probably around water, which is about 4.18 J/(g*C). Approximate urine as water again and at 1 g urine / 1 mL urine

..then for every 1 mL of water you consume at room temp you're burning 50 J which is .012 food Calories (kcal). I think this is negligible. Even if you drank 10 liters of water a day that'd only be 120 Calories of heat exiting your body. That's nothing.

Because I don't have an approximation of the specific heat of feces I don't know how much energy it takes to heat it, but you can bet that based on our water approximation that the energy spent to heat up the food you take in is nothing compared to the Calories in the food (or even if the food has no Calories it would still be so small as to be negligible).

So no, I don't think it's physically possible to intake so much food and water as to decrease your body temp.

-Snpoj 02:13, 13 April 2006 (UTC)

I have no idea why Snpoj completely changed the question. The question was whether you can reduce your body temperature by urinating or defecating, and Snpoj concludes: "So no, I don't think it's physically possible to intake so much food and water as to decrease your body temp." Wha...?

In any case, I disagree. First, it must be remembered that human body temperature varies depending on the area of the body. The internal organs are generally warmer than the extremeties. For example, the torso is, under most circumstances, warmer than the fingers and toes.

Thus 98.6F is merely the mean temperature of the healthy human body. The fingers and toes are no doubt lower in temperature, and the innards, for example the bladder, is somewhat higher.

Since urine is excreted from the bladder, it goes to reason that its temperature is somewhat higher than the mean temperature of the body, and by urinating and eliminating this warmer than average liquid, the mean temperature of the body naturally decreases. (What else would create the "shiver" effect when a guy pees?) ;-) Loomis51 00:34, 16 April 2006 (UTC)

As a liquid, urine will evaporate, so the truly desperate might try urinating on themselves in order to take advantage of the enthalpy of vaporization. Isopropyl 08:24, 13 April 2006 (UTC)

Or get into watersports with a friend. JackofOz 00:00, 15 April 2006 (UTC)

April 13

Perfect Secrecy in a Cryptographic System

According to Claude Shannon's paper, perfect secrecy is obtained when |P|=|C|=|K|. Is it admissable to have |C|=|P|<|K|? i.e. if I have a cipher where Pr(y|x) = Pr(x) does the size of the key matter as long as it isn't smaller than the C or P space? This is all assuming that the keys are equally possible and unique. Any help would be greatfully appreciated, C.Meyers

Have a read of one-time pad, and consider what would happen if any part of the key longer then the plaintext is simply discarded by both sender and receiver. --Robert Merkel 07:08, 13 April 2006 (UTC)

The statement that I have in my lecture notes from the crypto module I took a year ago says that perfect secrecy exists iff $|K|\geq |C|\geq |P|$, where K, C, and P are the sets of all keys, ciphertexts, and plaintexts, respectively (and |X| is the cardinality of set X.) This is slightly different from the relation you've given, where all three sets have to be the same size. -- AJR | Talk 12:29, 13 April 2006 (UTC)

Cheese!

I assume individually packaged cheese slices solved two problems:

1. consumer demand for pre-cut cheese (i.e. not having to cut out a slice from a big block, just like sliced/unsliced bread)

2. consumer demand for cheese with a longer expiration date. Individually wrapped cheese will last much longer than cheese in a block which supposedly goes bad after about 5 days because once you open it, you've opened an manufactured air-tight seal.

Question: is assumption 2 correct? (how bout 1?)

-Snpoj 02:25, 13 April 2006 (UTC)

• 1 makes sense, 2 less so. Many of the best types of cheese last a lot longer than a few days (though pre-processed ones may not, of course). In fact, many types of cheese are far better after they've matured for a considerable length of time. Grutness...wha? 03:57, 13 April 2006 (UTC)

Assumption 2 is incorrect. My friend (who's worked with cheese professionally) tells me that cheese is pretty much good until it molds, and even then those parts can just be cut off. Also, if exposure to air was a problem, then you would want to reduce the surface area exposed. Isopropyl 08:21, 13 April 2006 (UTC)

I'll chime in with a bit of a note on this. While cheese that is exposed to air doesn't go bad itself, it will dry out. For softer cheeses with higher moisture content, this definitely affects the texture and the quality of the eating experience.

A minor caveat to the 'just cut off the moldy bits' approach—mold and toxic mold secretory products can travel a short distance into the cheese beyond the extent of visible contamination. Again, this is more of a concern in soft, moist cheeses. The bold are still welcome to cut off the mold and enjoy; just remember that you may want to cut a bit of a margin around the mold.

Finally, individually wrapped cheese slices do let you avoid the mold problem altogether. Presumably, a person will only open a slice with the intent to eat it (nearly) immediately; there is no time for mold spores to settle and grow. In a sense, I'd say that assumption 2 holds because people want to avoid the perception that their cheese has gone bad, whether or not it is still safe to eat.

The major problem with the processed, prepackaged, hermetically-sealed cheese slices is that – in my entirely subjective opinion – they don't taste very good. They're also only available in a limited number of flavors. TenOfAllTrades(talk) 12:37, 13 April 2006 (UTC)

A good cheese will last months, though its appearance will get worse and it might frighten some people. Consider (3) it allows people who don't trust their small children with knives to still have them make a cheese sandwich (4) it provides a controlled and measured amount of cheese, rather than a rather random personal slice (5) it is easier to snack on the pack outside the kitchen. Notinasnaid 09:10, 13 April 2006 (UTC)

cgi script code demands unix?

I looked at a cgi script and it's got '$mailprog = '/usr/lib/sendmail -i -t';' in it. Does that mean it can't be used on a Windows based server? Can you get unix emulators for windows like you can get Wine for unix/linux...? --Username132 (talk) 05:02, 13 April 2006 (UTC)

Don't know about the first question but I think this is a popular linux emulator for Windows -Snpoj 05:06, 13 April 2006 (UTC)

I don't think there is a version of sendmail compiled for Windows. You could try Cygwin, as Snpoj said, but I don't find that to be entirely reliable, especially if you would be planning to use it for server purposes. -- Daverocks (talk) 06:39, 13 April 2006 (UTC)

You could rewrite the script so that it uses a mail service on Windows instead (you'd have to check what mail service is available, there is no one standard). Notinasnaid 09:07, 13 April 2006 (UTC)

PC monitors on TV

Why does a monitor on TV (like in the news) have weird bands going down it over and over? --Username132 (talk) 05:24, 13 April 2006 (UTC)

• Cathode ray tubes create pictures by scanning from top to bottom. So if you point a television camera at a CRT screen, each frame [29.97 per second in NTSC, 25 per second in PAL] will see the screen at a different part in the cycle, and a different part of the screen will look bright. -- Filliam H Muffman 06:01, 13 April 2006 (UTC)

• • This is an issue that occours whenever a continuous signal is sampled too slowly with inadequate prefiltering (prefiltering visual data before sampling it is very hard because of the sheer bulk of it). A signal that the sampler is too slow to correctly capture (e.g. thats changing faster than half the sample rate) will manifest itself as a slower signal at the difference between the original frequency and the closest multiple of the sample rate. Other common examples of such effects on TV are racing car wheels (they appear to slow down and then stop again as the car accellerates) and helicopter blades (they are invisible to the naked eye but appear as black bands rotating in a semi-random way on TV) Plugwash 23:22, 16 April 2006 (UTC)

Can't ping 127.0.0.1

I run Mandriva Linux version 2006.0 and I've struggled with this problem for quite a while, namely that I can't ping 127.0.0.1 (local loopback), nor can anything make a connection to it. I can use ping to ping everything else (e.g. yahoo.com, wikipedia.org), so ping is not the problem. This is what happens when I try to ping 127.0.0.1:

[root@davidlaptop ~]# ping 127.0.0.1
connect: No buffer space available

Configuration of the loopback interface is fine:

[root@davidlaptop ~]# ifconfig lo
lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:9279 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9279 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:524961 (512.6 KiB)  TX bytes:524961 (512.6 KiB)

Some people have asked me about my /etc/hosts file, but this is also normal:

[root@davidlaptop ~]# cat /etc/hosts
127.0.0.1               davidlaptop localhost

Now here is the strangest part. After bootup, I am able to ping 127.0.0.1 with no problem. However, after about 5-10 minutes, pinging 127.0.0.1 suddenly stops working, again yielding the message "no buffer space available". And although most of the time I am unable to ping 127.0.0.1, sometimes it suddenly starts working for seemingly no reason. Usually it stops working after this as soon as I stop being active on the Internet (my Internet is through interface wlan0). This problem is extremely frustrating as it causes me to be unable to test my Apache server, my FTP server or use Tor at all. Does anyone have any idea why it might be happening? I can provide more details on request. -- Daverocks (talk) 07:02, 13 April 2006 (UTC)

These links are the closest that I could find to a solution, although there is no confirmation that the solution worked for all involved. [3] Another link is [4] they have an even longer explanation and it says solved, but I am not sure that the problem is the same. Ansell 07:54, 13 April 2006 (UTC)

Thanks, those links are quite helpful, more relevant than the ones I was able to find. Particularly the first one you provided had helpful information. I'm still not sure what's going on, and I still haven't "definitely" solved the problem. However, something seems to be happening when I disable the lisa service and stop cupsd. Thanks for your input. -- Daverocks (talk) 01:44, 14 April 2006 (UTC)

Black Holes and Gravity

If Black Holes may possess a gravitational field so great that even light cannot escape it (except under exceptional circumstances such as Quantum tunnelling), then is it implausible to assume that a same type of mass-energy may be generated within the universe that will really allow superluminal velocities? I know that the square root within the transformations of Special Relativity turns imaginary when the velocity exceeds the speed of light, and thus explained away as making no sense, but considering the implications again of a Black Hole- if the gravitational field may be generated so great that even the photon cannot escape it, then this field, being a curvature in spacetime caused by mass-energy of some sort, must similarly lead to the possiblility of an energy level capable of exceeding the speed of light. In that case, maybe the imaginary square root may be taken to mean something even more esoteric. Or is something still missing from the story? All help appreciated. LCS 08:44, 13 April 2006 (UTC)

is it implausible to assume that a same type of mass-energy may be generated within the universe that will really allow superluminal velocities?

Yes, for a mass to reach superluminal velocity, than that would require a kinetic energy as being infinity. How unlikely. Gravity and electromagnetism are separate forces. -- Mac Davis] ⌇☢ ญƛ. 10:11, 13 April 2006 (UTC)

See tachyon. There's no evidence for them. —Keenan Pepper 11:06, 13 April 2006 (UTC)

java

I sort of know that java is a program [to help you?] but do you need it on your computor? I get more updates to install on my M/C than I do from Microsoft and it's very persistant to get me to install them I have XP with service pack 2 installed 60.229.175.88 09:12, 13 April 2006 (UTC)

It is useful if you want to see Java Applets on webpages, or if you want to run Java based programs on your computer. The Java download here [5] enables this. Ansell 09:32, 13 April 2006 (UTC)

Java is often used to show you part of a web page. You probably have it already. Bear in mind that Microsoft offer you updates because you already have an older version of the software and if they are security fixes it may be very important to install them. Notinasnaid 09:33, 13 April 2006 (UTC)

Never ever accept Microsoft Updates. You'll just be putting a lot of hard-working hackers out of business. Please, someone, think of all the poor hackers. --Kainaw ^(talk) 12:02, 13 April 2006 (UTC)

Untrue, Kainaw : the old game betwen fortress and cannon must go on. If flaws are not corrected, then poo' hacker is unemployed. --DLL 18:01, 14 April 2006 (UTC)

You are correct. Let me rephrase: Never ever accept Microsoft Updates. You'll just be putting a lot lazy script-kiddies out of business. Please, someone, think of all the lazy script-kiddies. --Kainaw ^(talk) 18:14, 14 April 2006 (UTC)

snake

My daughter wants to know from which part of snake's body its eggs come out ? Not the process of mating or reproduction but somthing like from where exactly the baby comes out.

Thanks

At the risk of stating the obvious, the vagina. (Google produces some fascinating results, but you may not want your daughter to see them). Henry^Flower 09:34, 13 April 2006 (UTC)

The Snake article has a reproduction section that doesn't exactly entail where the eggs come out, however, it does explain a bit about some snakes which do not lay eggs, rather keeping them inside them and/or giving birth to live young. I assume the position that they lay eggs from would be about 2/3rds of the way down the body, however I can't seem to find any sources for that right now. Ansell 09:40, 13 April 2006 (UTC)

This page claims a video, which I have not watched: http://www.arkive.org/species/ARK/reptiles/Coronella_austriaca/more_moving_images.html. Notinasnaid 09:49, 13 April 2006 (UTC)

You can't see the whole body of the snake in the video, so it's hard to judge, but I'd say it's about 3/4 of the way down. On the bottom, of course. Interestingly our vagina article mentions that the vagina leads to the cloaca 'in some reptiles', but doesn't say which reptiles. Henry^Flower 09:59, 13 April 2006 (UTC)

The same question was asked and better answered at "Ask A Scientist" - Zoology Archive - Snake Delivery - 1/19/2004:

"most snakes lay eggs (oviparous) some of them deliver a baby, outside the eggshell ready to live (viviparous). The reproductive system of the reptiles including the snakes are simpler than the one of the mamals and resembles the birds. There are both in males and females an opening to the exterior called "cloaca". The cloaca is the passage from a internal chamber into which the digestive, urinary and reproductive systems empty. So both the baby snake or the non-hatched egg go to the exterior through the cloaca. Incidentaly, inside the female snake body there is a tract called oviduct provided with conditions for egg fertilization and embryo formation." [6] WAS 4.250 11:32, 13 April 2006 (UTC)

The human brain

I’ve was told that researches were made about our brain’s function that found that when we see things and when we imagine things, the brain uses the same parts. Meaning that our brain cannot differ between what it sees to what it remembers/imagines. Can you please guide me to those researches? Thank you

---

There was an article all about this in the February/March Scientific American Mind pages 18-23. Called "Picture This." by Thomas Grueter. It refrences:

Image and Brain: The Resolution of the Imagery Debate. Stephen M. Kosslyn. MIT Press. 1996.

Return of the Mental Image: Are There Really Pictures in the Brain? Zenon Pylyshyn in Trends in Cognitive Sciences Vol. 7. No. 3, pages 113-118; 2003.

If you can't find it on the internet, I can scan in the article for you without any trouble. See my talk page User_talk:Mac_Davis. Here is a search for zenon pylyshyn cognitive [7].

--  Mac Davis] ⌇☢ ญƛ. 10:22, 13 April 2006 (UTC)

---

A myth or a true story?

I was told that the Indians couldn’t see Columbus’s ships arriving because they didn’t have that image in the image bank in their brain. Is it a myth or a true story?

Hahahahah! It is a myth. Just because you haven't seen anything before doesn't mean you can't see it! How do you think you see things that you haven't seen before? -- Mac Davis] ⌇☢ ญƛ. 10:13, 13 April 2006 (UTC)

It's true. I kept telling 16 year old girls that I cannot see their nakedness because I do not have that image in the image bank in my brain and so if they take off all their clothes then all I can see is a blank spot where their nakedness is. Ohanian 10:33, 13 April 2006 (UTC)

Do they believe you? I would think not, but then again people may be more guillible than I think. --Bowlhover 01:53, 15 April 2006 (UTC)

I heard that story. I believe it was from a documentary on Amerigo Vespucci. In his novel about the New World, the native women were beautiful, big breasted, and extremely dumb. The men were stupid and lazy and handed over tons of gold and silver to the white men to have sex with their women for them. His story was, obviously, not written from real accounts. --Kainaw ^(talk) 12:00, 13 April 2006 (UTC)

Definitely a myth. This story has been spread a bit by the movie What The Bleep Do We Know!?, a "documentary" which is not at all scientifically accurate. rspeer / ɹəədsɹ 15:35, 13 April 2006 (UTC)

I believe "What the BLeep" got the idea from some anthropologist's writing. I am trying to track down whose. Any body know? I KNOW this story was out there before that movie came along. Plus, the movie explains it badly and exaggeratedly. --GangofOne 19:06, 13 April 2006 (UTC)

I'm not entirely sure about the truthfulness of What the bleep do we know, but a similar thing I heard about when going through the topic of evolution comes to mind, I'll try to retell the story briefly:

An explorer went to live with a jungle-dwelling people, who obviously had never left the jungle, he befriended them and decided to take one of their people to his world. On their way to a city, they crossed a savanna, the short jungle-dweller (being short is a nifty adaptation for jungle life) spotted a couple of grazing animals in the distance, he recognized them as flies, and tried to wave them away with his hand.

The reason for this is that the jungle-dwelling man had never ever seen anything so far away, and his concept of distance was limited to perhaps five metres away at most, as jungles don't really have that much open space. In a sense, he could not possibly imagine something that big being visible from that distance, and could thus not know that things look smaller with distance. -Obli (Talk)^? 21:38, 13 April 2006 (UTC)

I'd be suspicious of that one too. Most stories about the silly things "savages" do are false at best and insidious at worst. --Fastfission 01:36, 14 April 2006 (UTC)

There are many reports of pygmy tribes from the forest who have difficulty working with directions that go over long distances and gawking at wide-open plains. It is really no different than Americans failing to comprehend a kilometer and gawking at fields covered with green instead of cement. --Kainaw ^(talk) 12:50, 14 April 2006 (UTC)

Well, it's definitely false. Of course you can see things you've never seen before. When you were born, you didn't have any images in the "image bank" of your brain. Does that mean you're going to be blind for life? --Bowlhover 18:34, 14 April 2006 (UTC)

Cognitively blind. If you don't have a concept for something, you don't register it. Babies are such, until they are taught, (by which I mean interactions with reality, not in school). Concepts, that is to say, bundles of recurrent sensations that have been reified, are then defined in terms of other concepts available to the developing conscious being. However, if you have bad conceptual scheme through which you, as adult, perceive everything, then you are also insulated from the new; this is also a tragedy, for which the cure is claimed to be various spiritual/psychological processes that are available for a reasonable fee (classes now forming), but generally just substitute one conceptual scheme for another. Anyway, there are many examples from psychology experiments. They flash a playing card for a fraction of second, to be identified. Well, the trick is they make a black King of Hearts, say, but the experimentees CAN'T SEE IT, and say King of Hearts , or King of Spades , and NOT WHAT IT IS. That black K of H is like the ships of the Europeans to the indigious; doesn't fit into their conceptual schema, at first. This general state of affairs is definitely NOT a myth. Read The Social Construction of Reality for starters. --GangofOne 22:05, 14 April 2006 (UTC)

Hmm, not entirely comfortable with that exposition. Babies may be said to be cognitively blind, but only because it takes many months before "the penny drops" and the baby suddenly understands that he/she is separate from "other things". Until then, to the child there is only one all-encompassing "thing". That's not to say they can't see and desire to touch physical objects, but they still don't make any cognitive distinction between themself and the object. But when a Spanish galleon appears in the harbour, the 15th century American native definitely sees it and definitely knows it is a strange object external to themself. Whatever name they give it would simply reflect their lack of a frame of reference at that time. We refer to UFOs as "flying saucers" too, but I'd bet that's not what they are. JackofOz 23:52, 14 April 2006 (UTC)

Gangofone, are there any psychology experiments in which participants are shown something bizarre, something they haven't seen before, and the person conducting the experiment asks the participants if they can see the object? The experiment you gave as an example is irrelevant--the participants can't see the card very well if it's only flashed across their eyes, so they take whatever they managed to see and compare it with what they know about poker cards, to find the card that matches best. If the participants were given a chance to carefully look at the cards, I'm sure they could see that the king of hearts is black (for example). --Bowlhover 01:53, 15 April 2006 (UTC)

I've never seen a black king of hearts in my entire life. Does that mean that if I was shown one it would be invisible to me? Before I saw Star Wars for the first time, I had never seen a wookie before. Why wasn't Chewbacca invisible to me? The whole idea is definitely a myth, and not even a very believable one at that. Loomis51 00:55, 16 April 2006 (UTC)

"I've never seen a black king of hearts in my entire life. Does that mean that if I was shown one it would be invisible to me?" A rather strange argument, especially for a lawyer. I don't have all the details of the card experiment from Psychology 101, probably could find it somewhere. The experimentees who don't see the black king of hearts, are not asked "Did you see that?", they are asked "What did you see?" They have no difficulty identifying the red K of H or other regular cards. If they are allowed to examine the deck, and are thus clued in, THEN they have no difficulty recognizing the black K of H etc. So it's not the breifness of the exposure that is preventing them from seeing the reality, because they see reality otherwise just fine; the problem is in their concepts of reality. The story is not about optics, it's about concepts (preconceptions) and perception. --GangofOne 07:00, 16 April 2006 (UTC)

I've never read the original paper before, but here it is: http://psychclassics.yorku.ca/Bruner/Cards/ Classics in the History of Psychology "On the Perception of Incongruity: A Paradigm", Jerome S. Bruner and Leo Postman (1949) Harvard University. First published in Journal of Personality, 18, 206-223. --GangofOne 07:10, 16 April 2006 (UTC)

I see this experiment is also mentioned on p62 and 112, Kuhn ,THe Structure of Scientific Revolutions, 1962 . "Until taught by prolonged exposure that the universe contained anomalous cards, they sww only the type of cards for which previous experience had equipped them... What a man sees depends both upon what he looks at and also upon what his previous visual-conceptual experience has taught him to see..." Also mentioned in this CIA textbook for analysts: http://www.cia.gov/csi/books/19104/art5.html Chapt 2 "Perception: Why Can't We See What Is There To Be Seen?", mentions Jerome S. Bruner and Leo Postman, "On the Perception of Incongruity: A Paradigm," in Jerome S. Bruner and David Kraut, eds., Perception and Personality: A Symposium (New York: Greenwood Press, 1968).

I believe it was Columbus who wrote in his log that he saw mermaids, but they weren't as beautiful as expected. Some say he maybe saw manatee, but maybe he really saw a swimming wookie. --GangofOne 10:12, 16 April 2006 (UTC)

The original question asked was if it was true that the Indians could not see Columbus' ships arriving as they had never seen large ships before. The question seems to me to clearly have implied that the Indians saw nothing, i.e. the ships were invisible. However, if the question is whether or not the Indians recognized these large objects that they did in fact see to be ships, then the answer would possibly be no. But that doesn't seem to be what the questioner was asking. The question was whether the Indians were able to see Columbus' ships at all, which clearly they were. Loomis51 13:37, 16 April 2006 (UTC)

Computer Network Tockin Ring

Dear All,

I have some confussion related to Computer Networking below theories/terminology, If anyone can clear me below points. than I highly be thankfull.

• 01: Why saying? "Token Ring" is Local Area Network Technology
• 02: Why "Token Ring" is not inlist in Channel Access Methods?
• 03: Please tell me difference between "Network technology, Access Method and Network Protocol"

Thanks.

M.Sadiq Qadri [enough with the personal info]

Why do you care whether a "token ring" is a LAN or not. As long as it's implemented correctly it will work. The only time, I care about the definition of "token ring" is when I need to hand in my computer science assignment at University. Ohanian 10:29, 13 April 2006 (UTC)

Token ring is it's own access method. Think about it, terminals can *only* speak when they have the token. The Token Ring article does quite a good job at describing it. --Jmeden2000 13:16, 13 April 2006 (UTC)

Token Ring is a LAN technology, it just uses a different structure for determining which system is transmitting data. In fact modern Token Ring systems use the same physical infrastructure as Ethernet. The reason Token Ring is not commonly used is 1) Originally IBM propriatary technology. 2) More expensive due to 1. You may want to look up Local Area Network, Token Ring. If you want more detailed information on Networking I would suggest you by a used copy (new is $65+) of a Comptia Network+ exam. As these guides cover the basics of Networking and a lot of the terminology of Networking.--Tollwutig 15:00, 13 April 2006 (UTC)

Fundamental forces, "weak charge"

Electromagnetism is the coupling of photons to electric charge. Gravity is the coupling of hypothetical gravitons to all energy. The strong force is the coupling of gluons to color charge. The weak force the coupling of W and Z bosons to... what? My physics book mentions "weak charge", but doesn't go into any detail and doesn't say what kinds of particles have it. I notice we don't have an article on it either. Is there really such a thing as "weak charge"? —Keenan Pepper 11:21, 13 April 2006 (UTC)

No fundamental weak charge exists. "Originally, weak interactions were thought to be separate from electromagnetic forces. Eventually, three fairly massive particles were discovered: W+, W-, Z. The weak force is an electromagnetic interaction producing one of these particles. The particle travels then is absorbed through electromagnetic interactions with another particle. Although the Z-particle has no electric charge, it does have a spin. It can interact with magnetic force. Standard electromagnetic force is transmitted by photons of light. Weak force is transmitted by these "weak" particles. Still the actual interactions are the based on the same force." [8] WAS 4.250 11:47, 13 April 2006 (UTC)

All leptons and quarks with left-handed chirality are susceptible to the weak force. Notably, as a result it's the only force to affect neutrinos, and the only force that can cause flavour changing processes (thus it's responsible for beta decay, though note that the Z boson cannot cause flavour changing -- there are no flavour changing neutral currents). See weak interaction for lots more. But as per WAS's quote there isn't an identifiable "weak charge" as such. --Bth 12:00, 13 April 2006 (UTC)

See Weak hypercharge. I'm guessing that that corresponds to the weak coupling constant, or maybe it's weak isospin. Cedders 00:30, 14 April 2006 (UTC)

Well, I still don't understand it, so I guess I'll just have to wait until I take... Particle physics? Quantum field theory? What? —Keenan Pepper 01:04, 14 April 2006 (UTC)

The thing is that the weak force comes out the other side of the spontaneous symmetry breaking of the electroweak interaction. At "high" energies, the electroweak force couples to weak hypercharge. At low energies, the EM force couples to electric charge and the weak interaction is the mess that's left over when you separate that out from the electroweak interaction. As such the thing it couples to is rather complicated and messy (it doesn't couple to weak isospin, really: weak isospin is a symmetry of the weak interaction the way isospin is for the strong). We could really do with a page on Wikipedia that serves as an introduction to the all the gauge stuff, though -- you could argue that all these articles need more context for the non-specialist than they currently have.

Just for the record, though, I took a few particle physics courses, and I never really got a good sense of the weak force coupling to some specific property (though maybe I wasn't paying enough attention); it was always taught primarily in terms of what it did. --Bth 09:30, 14 April 2006 (UTC)

CDMA 2000

Qualcomm says CDMA 2000 provides an always-on Internet connection. What does it mean and how does it work? How is always-on different from other type, that is not always one in previous cell phone technologies?

I presume it means it is always connected, like broadband, rather than only connected when you connect it, like dial-up. For great justice. 15:40, 13 April 2006 (UTC)

Cross border complexities related to the IT industry in India

What cultural bias exists towards western economic philosophies as thsy relate to the IT and Software industry in India?

Did the homework question also misspell the word they? hydnjo talk 14:56, 13 April 2006 (UTC)

The instructions above for answering questions specifically states to be nice. Spelling flames and assumptions about the origin of the question (without even answering the question) isn't very nice. As to the question, googling '"western economic philosophy" india software' got nothing, but '"western economic" india outsourcing' got lots of interesting hits, including:

• [9]
• [10]
• [11]

and lots of others. I didn't find anything on Wikipedia, but maybe someone else will.--Anchoress 21:24, 13 April 2006 (UTC)

Width of the United States

How many miles wide is the United States? I could not find this statistic in United States nor Geography of the United States. Thanks. -- Reinyday, 17:35, 13 April 2006 (UTC)

This question is not very well-defined. First we must specify what portion of the Earth we designate as "the United States". But it's not very interesting to say that the US is typified by the distance between Hawaii and Maine, as that's certainly not representative. So let's suppose you mean the contiguous United States. Obviously even that is not a rectangle (even disregarding the curvature of the Earth), and so does not have a single "width" or "height". But presuming that by "width" we mean "east-west extent", we can talk about the lengths of various lines of latitude running through the country (these will be of many different lengths). As a very rough approximation, using the Extreme points of the United States article, I see Lubec, Maine at 66°59′5″ W, and Cape Alava at 124°43′59″ W. They're not at the same latitude -- about 3° different -- but it's close. The portion of the latitude line midway between theirs (about 46°25′ N) between their longitude lines is (using the quadratic mean radius of $Q_{r}=3,959.871{\mbox{ mi}}$)

$Q_{r}\cos(46^{\circ }25')(124^{\circ }43'59''-66^{\circ }59'5'')=2751.5{\mbox{ mi.}}$

A similar expression using San Diego, California and Miami, Florida (though they are 7° apart in latitude, so this is a poorer approximation) gives 2237.4 mi. The best one can really say from these figures is that the "width of the US" is $2500\pm 250{\mbox{ mi}}$. (Remember that these are not great-circle distances; the shortest route from (40°N,90°W) to (40°N,80°W) is not to go due east. But the differences at these latitudes are on the order of a percent or so; the errors in averaging the latitudes are larger.) --Tardis 18:20, 13 April 2006 (UTC)

If you define the US in terms of effective control, we control land and water all across the globe, and indeed into space. If you define US as legal sovereign teritory by law, our embasseys are technically our sovereign territory, and again we are global. If you define US as States and territories we entend from at least Maine to Guam and probably further, but I'm not gonna look up every island the UN assigns us control over. The distance of the two points in Alaska that are furthest from each other is interesting and similar to Canada and Russia useless distances. It is all about definition. Something to ponder: When you find the right way to ask a question, the question is the answer to itself. WAS 4.250 20:43, 13 April 2006 (UTC)

Or you could go from Hawaii to Florida, or Hawaii to Alaska, or Florida to Alaska for even longer distances. -- Mac Davis] ⌇☢ ญƛ. 23:58, 13 April 2006 (UTC)

This is the cousin of a question I asked about a year ago and never got much of a response. It's about crows flying within the borders of a country. How would one go about accurately determining the greatest "straight-line" distance between any two points within a contiguous area? E.g. a glance at a map suggests the longest line within the 48 contiguous US states might be from somewhere on the west coast near Seattle to somewhere on the east coast in Florida, but that's very rough. Is there a more accurate measurement? Does a list of longest crow-flights by country exist anywhere? JackofOz 23:22, 14 April 2006 (UTC)

Protiens and Sugars

Where might I find a list of the important protiens and sugars that build the human body? Specifically, something that will help me in understanding how humans decompose at teh chemical level. 64.198.112.210 20:20, 13 April 2006 (UTC)

List of proteins WAS 4.250 20:30, 13 April 2006 (UTC)

A list of proteins and sugars won't give you what you need. Try decomposition, though it's not too detailed, it may get you started. There was a book called something like Corpse that discussed this, too, but I can't quite think of the exact title. - Nunh-huh 20:57, 13 April 2006 (UTC)

Ah, but they didn't discuss it chemically. Corpse was lovely, but it was more about corpse fauna and time-of-death determination than anything else. DuctapeDaredevil 03:19, 14 April 2006 (UTC)

I agree that a list won't be much help. What happens chemically will depend on what's causing the decomposition - bacteria or microorganisms will be quite different to what happens in cremation. You might take a look at Amino acid, Denaturation_(biochemistry), Glycoprotein, and Chemical_makeup_of_the_human_body. There's also decomposition Putrefaction and rancidification. Looking from the point of view of preventing decomposition there's the Mummy article. Richard Taylor 04:13, 15 April 2006 (UTC)

Bomb defusal

I was watching a certain movie over the weekend, and it contained a scene where a bomb is being defused Hollywood-style: a guy with wirecutters clipping the red wire. Does this have any factual basis? Is there a history of bombs being defused in this fashion? Isopropyl 22:50, 13 April 2006 (UTC)

It's the correct way to defuse a Hollywood-style bomb: one with a half-dozen sticks of dynamite wired to an alarm clock. Our bomb disposal article covers how real-world bombs are taken care of. --Serie 23:55, 13 April 2006 (UTC)

Thanks! Isopropyl 02:42, 14 April 2006 (UTC)

I don't know, but I'd like to add a similar question. What is the big, red LED readout for on such Hollywood-style bombs? Is it there for the convenience of those who just may be standing by the bomb, so they'll know when they'll be blown up? If so, that's very considerate of the bomb designer, don't you think? Erik the Rude 23:20, 13 April 2006 (UTC)

Unless it's a trap; #15. Melchoir 00:06, 14 April 2006 (UTC)

I have another question: why do bombs on TV often beep (they also have a red LED that flashes) before exploding? I'm guessing that it's for the same reason as what Erik the Rude said--so that people who happen to be near the bomb have time to escape. --Bowlhover 17:41, 14 April 2006 (UTC)

Tradition. The first design for a clock-based time bomb consisted of a mechanical alarm clock with a percussion cap or other impact-based explosive attached to one of the bells as a detonator. Because of this, if the detonator took a few hits to trigger, you'd hear the alarm ringing before the bomb went off. --Serie 20:16, 14 April 2006 (UTC)

April 14

Ramjet

I was wondering if anyone could give me a few really nice links on how to build Ramjets? Patrick Kreidt

Ramjet -- Mac Davis] ⌇☢ ญƛ. 00:58, 14 April 2006 (UTC)

Dermatographic urticaria

Is this disorder genetically inherited? --218.102.207.71 00:55, 14 April 2006 (UTC)

In general, Urticaria (also known as hives) is not something that can be passed to others, be it either genetically or through contact. However, if there is something causing this reaction, that stimulus may be transmissible. For the most part, hives are caused by allergic reactions, and the propensity for allergies can be passed on genetically. Therefore, in a situation where two individuals both are allergic to a substance, if that substance is transfered via physical contact from one to the other it may appear that the urticaria was transferred.

There is another type of urticaria that is not a syptom of an allergic reaction. These hives can be brought on by periods of extreme emotions. This type of urticaria tends to be more prevalent in certain populations, suggesting that it can be passed on genetically. Emotionally induced urticaria, however, usually do not last more than a few minutes and very rarely require treatment of any kind, prophylactic or otherwise.Tuckerekcut 03:12, 14 April 2006 (UTC)

I don't think anyone knows for certain if dermatographic urticaria is genetically inherited. It may be due to the development of one's particular immune system which is a product of one's environment and genetics. - Cybergoth 04:45, 14 April 2006 (UTC)

Combining CC-BY-SA

I wanted to combine a CC-BY-SA 2.0 and CC-BY-SA-2.5 image. Is there any changes between the two licenses that would make this impossible? I assume this is doable, but I wanted to make sure, as not to create a copyright violation. Thanks in advance, Linuxerist L/T 01:14, 14 April 2006 (UTC)

CC-BY-SA 2.0 says that you can use later versions of the same license (CC-BY-SA), so it shouldn't be a problem as long as you license the resulting image as CC-BY-SA 2.5. --Fastfission 04:11, 15 April 2006 (UTC)

Darn search engines

What is the name of the theory that the act of observing changes the behaviour of the subject being observed? -- Francs2000 01:27, 14 April 2006 (UTC)

I think this is what you mean: Uncertainty_principle but according to that page "The uncertainty principle is frequently, but incorrectly, confused with the "observer effect", wherein the observation of an event changes the event. The observer effect is an important effect in many fields, from electronics to psychology and social science.". Not sure if I completely agree with that statement but there you have it. -Snpoj 01:46, 14 April 2006 (UTC)

Thanks for that. What I was actually looking for was the Hawthorne effect because it applies to social sciences, but your link led me to it. -- Francs2000 01:51, 14 April 2006 (UTC)

male midwives

how many men are there in midwifery in UK? thanks.robyn

This doesn't look like an especially reliable source, but according to menstuff.org there were 87 male midwives out of 35,000 or so practicing midwives. That's data from ten years ago, though. Isopropyl 03:00, 14 April 2006 (UTC)

Hmm, this site says 10.73% in 2005. Isopropyl 03:02, 14 April 2006 (UTC)

• How many men in midwifery are there in the other countries of Europe except in UK?thanks a lot.robyn

• How many men are there in midwifery in some other european countries (except in UK).thanks.robyn

• How many men are there in midwifery in some european countries, except in UK?thank a lot.robyn

• How many men are there in midwifery in Finland?in Netherlands? thanks a lot.rob

I'm afraid I know nothing about the subject, but I'd just like to say that 'midwifery' is one of my favourite words. Thank you. Phileas 05:43, 14 April 2006 (UTC)

Invision power board

Is it possible to export/move an invision power board to another host, either by condensing it to a core file somehow, or using some sort of util? Any response is appreciated. -Tim Rhymeless (Er...let's shimmy) 05:27, 14 April 2006 (UTC)

Please could you clarify your question? It is possible to export the post data from an Invision Power Board to another forum (say phpBB for instance) But to point you towards the appropriate utility you would need to say what forum software you are hoping to resolve your data onto. --Limeyuk 19:43, 14 April 2006 (UTC)

Well, I've been looking at either setting up a new Invision Power Board, or going to phpBB. There's a bit of a constraint on time. I don't know what I'm doing, but I can relay any complicated info onto people that do. -Tim Rhymeless (Er...let's shimmy) 05:02, 15 April 2006 (UTC)

Is this a hoax?

Has anyone heard of the term isodiasphere (according to the article, describing two nuclides with the same neutron excess) before?

I came across the article while rooting through Wikipedia:Cleanup and am tempted to prod it as an OR neologism (or a subtle hoax, assuming less good faith). The phenomenon it describes seems real if obvious enough, but the term doesn't appear anywhere I can find except Wikipedia and its mirrors. It's not known to Google Scholar, it appears nowhere in the nuclear physics preprint servers, it's not in the index of Krane (ISBN 047180553X), and it doesn't even appear on the site listed as an "external source" by the article.

It's not linked anywhere in Wikipedia except from Chart of Nuclides, and that link was added by the originator of the article (User:Esotericv2), who has no other contributions. But I just thought I'd check with all the knowledgeable people here first. --Bth 07:57, 14 April 2006 (UTC)

I did a search for this term in Chemical Abstracts which contains the abstracts of nearly every publication in the world covering chemistry and the major journals covering physics. It did not locate any mention of that term. --Ed (Edgar181) 12:48, 14 April 2006 (UTC)

Based upon the link for this, I expect it would not be a chemistry term, but one for Nuclear Physics. I did find this link

http://sun.folk.en.ogarnij.info/en/Isodiasphere

Chem Abstracts covers the major journals in the area of nuclear physics, so that shouldn't be an issue. The link you provide is also just a copy of the English Wikipedia article. So still, as far as I can tell, there is no use of this term apart from the article here. --Ed (Edgar181) 14:46, 14 April 2006 (UTC)

I nominated this for deletion. I think it's nonsense. --BluePlatypus 17:42, 14 April 2006 (UTC)

Space-Time Curvature under General Relativity

stereotypical relativity diagram

This is a question about how non-scientific explanations of the Theory of General Relativity are supposed to explain gravitation. Layman explanations of space-time curvature usually have a diagram (apparently always the same one) which shows a two-dimensional surface streched (downwards) into a third dimension at the location of a body having mass. The story goes that a second body going by with no acceleration will follow a curved path because space-time is curved by the first body.

What I don't understand is why this would cause one body to curve towards another rather than away. When I try to figure out what the curved path will actually be (from the diagram), it looks like the it should curve away. Apparently, it is implied that the second body would fall into the 'depression' in the original two-dimensional surface because of.... what? the influence of gravity? It's apparently using gravity to explain gravitation. How is this explanation supposed to work? The Wikipedia article hints it's not a simplistic as the picture, but doesn't seem to go beyond that.

If someone is able to post a complete and thorough reply to this question, please forward it to the Nobel Prize committee. Seriously, though, the curved sheet model just takes advantage of the fact that objects rolling around on a big sheet in a 1 G field happen to move in a way similar to what general relativity predicts for objects moving past planets and the like. It's meant to show you how things move, not why things move. To really understand why things move, you will have to understand nasty things like metric tensors and the Einstein field equations. -- Filliam H Muffman 07:24, 7 April 2006 (UTC)

Well.. I don't quite see why you'd think it would curve away. If you have a downward "dimple" in a tablecloth or similar and roll a ball towards it, moving in a straight line, it will go around the rim in a curved path once it hits the dimple and continue away in a straight line in a different direction, having been deflected somewhat inwards. That analogy is the point of the picture. If the dimple was raised instead of lowered, then it would be deflected in the opposite, outwards, direction. But gravity doesn't act in that direction, which is why you've got a lowered dimple and not a raised one in the picture. --BluePlatypus 07:54, 7 April 2006 (UTC)

The diagram also gives a nice visual analogy for the inverse square law, since the gradiant of the curve is much steeper near the object than far away. But like the others have said, this is a way of visualizing how the objects would move so, not why. — Asbestos | Talk (RFC) 13:36, 7 April 2006 (UTC)

• In other words, it's just a cool picture? It's describing the exactly the same behaviour as Newtonian gravitation. Peter Grey

• Pretty much. It's also meant to give an idea that general relativity deals in spacetime curvature, which, among other things, predicts that light is also affected by gravitation. That makes gravitational lensing possible. Newtonian gravity claimed that light doesn't bend because it's massless. -- Filliam H Muffman 03:03, 10 April 2006 (UTC)

One of the byproducts of Special Relativity has been the famous equation, E= mc², that first stated the fact of mass and energy being only two sides of the same coin, instead of what previous physicists have conceived. While Newton had previously thought light to be massless and thus insupsceptible to gravitation, nonetheless certain details within the mathematical framework he had produced for gravity as a force did predict a certain amount of bending occuring when light approaches gravitational bodies (a third less than what Einstein later proposed), which, although he knew was true, was never able to explain away with his theory. The new definition in modern physics, now, for the word massless, also meant something different. It refers only to those particles with no rest mass, but not necessarily no remaining kinetic energy whatsoever. Due to Einstein's equation, as previously indicated, you may say that light does have mass if you wish to, since its energy could be easily converted to mass via the constant of c². However, the energy of the photon is constantly changing during its flight, so the records for mass you will be able to obtain will never be invariant, thus referred to as the relativistic masss. In modern physics, however, it is no longer considered appropriate to define the particle on terms of its relativistic mass for obvious reasons, and thus it suffices to say that light is massless in the fact that it has no rest mass. Nonetheless, as long as the photon still possessed the kinetic energy/relativistic mass necessary for its existence, then it shall be supsceptible to curvatures in space- time like other particles with rest mass. Luthinya 10:21, 10 April 2006 (UTC)

Erm, where have you got that "third less" from? The Newtonian prediction for the deflection of light around a point mass is half the value given by GR. --Bth 10:34, 10 April 2006 (UTC)

Sorry, got my figures wrong. Thanks for correction. Luthinya 10:45, 10 April 2006 (UTC)

This kind of picture is indeed confusing, but there is another reason for it that hasn't been addressed fully above. The key is the mechanism by which "curved spacetime" affects the motion of objects (particles, satellites, light, whatever). General relativity says that an object moving only under the influence of gravity follows a geodesic in spacetime, which is the analogue of a straight line in Euclidean geometry. Since the spacetime itself is curved, these "straight lines" have properties we do not expect, but they are, in a precise sense, the "least curved" lines you can have within curved spacetime.

Roughly speaking (see below), one of the important properties they share with Euclidean straight lines is that they are the shortest distance between two points. This means you can picture a geodesic in the following way. Take a curved surface, such as the dimpled fabric surrounding the ball in the relativity diagram asked about above, and fix two points, one to be the "pitcher" and one to be the "catcher." We then want to draw the geodesic on the curved surface connecting the two points, representing the path of an object from the pitcher to the catcher. We do this by using a rubber band, stretched taut: this automatically follows the shortest path between the points.

Now suppose we look at the result as viewed from above. If there were no curvature, the rubber band would be a straight line between the two points. Since the ball is there, dimpling the surface downward, the rubber band will not take a path that appears straight as viewed from above, since that path will be rather long due to the dimpling. Instead, the rubber band will curve around the ball slightly, to avoid the trip into the depths of the dimple. When seen from above, it appears that the ball is affecting the path of the object with some "force", when in fact the object is trying to follow the best approximation to a "straight line" that it can in the circumstances.

All that is rather hard to say without additional pictures, hope it comes across. Anyway, very little of that is usually included with the usual picture, which is why it is easy to come to very inaccurate conclusions about what the picture is trying to say. If you want a better version of all this, look at Taylor and Wheeler, Spacetime Physics.

Note for experts: in spacetime, with its Lorentz metric, geodesics are actually local maximizers of proper time; but part of the point of the kind of picture we're discussing is to give a Riemannian picture. --Spireguy 20:12, 11 April 2006 (UTC)

Still, for most layemen beginners, it does offer a much more approcheable beginning for the subject, even if much of the important details have been left out. As far as the geodesic problem is concerned, since we as humans possess four dimensions (including Time), and yet space- time may curve in a way that is impossible for us to conceive or imagine- only "talk about", it immediately shows that space- time curves into at least one more dimension than that to which we are accustomed of in our daily life, i.e. the 4D bodies. And just as the 2D figures upon cardboard cannot stand up vertically upon it, since they have no motion or conception of 'depth', we as 4D people cannot cross the barriers of dimension and traverse into the 5th or other higher dimension freely, as we now have the ability to in our 4D world. We therefore have to kind of traverse with the curvatures of the surface of higher- dimensional space- time, which is to us expressed in a 4D fashion like differently laid card boards are to the 2D beings. Thus, for us, the easiest way between two places in space- time may not necessarily be a straight line, but more usually a curved 4D geodesic adapted from the curvatures of space- time from gravity. Luthinya 20:34, 11 April 2006 (UTC)

That's what I'm getting at. Isn't a path curving away from the point mass shorter? What we would need to visualize would be a contraction of space, not a stretching, right? Peter Grey 04:25, 12 April 2006 (UTC)

Bear in mind that we're measuring "shortest" in the coordinate system defined by the grid drawn on the sheet. The deformations of the sheet deform the coordinate system itself -- that's the whole point of the analogy. What looks longer to us from outside the sheet is shorter, when measured in a system where the side of a "square" on the sheet is a constant however stretched it looks to us. --Bth 11:12, 12 April 2006 (UTC)

The shortest path "in the coordinate system" is the straight line. Or is something still missing in the story? Peter Grey 16:13, 12 April 2006 (UTC)

Um, no. In order to walk the "straight line" in which you are depicting, we must abandon the 4th dimensioned (including Time) curvature of the "surface" of the grid (space- time), and seek to traverse into extra dimensions in order to ignore the curved influences of gravitational objects. However as 4D beings this is pratically impossible for us, so instead of this the shortest route for us will have to be the the curved surface of the grid, which at least is 4D and possible to traverse. Therefore, instead of what Newton has previously proposed, the shortest route between two things is not a 'straight line' in the usual sense of the word, but a geodesic varying according to the shape of surrounding space-time influenced by gravitational fields. At least a longer way is shorter than the impossible, so to speak. The thing is that on the diagram you cannot see the grid curving into extra dimensions the way it should, which is what makes the analogy slightly hard to come to mind. Remember the analogy is only a start to understanding; try eventually to draw away from the picture and just let the ideas flow accross your head- aided by some mathematics, you'll find this much easier.

PS May I add that my above language is extremely inaccurate in depiction, especially without the mathematics to compensate for it. Hope it comes through anyway. Luthinya 18:17, 12 April 2006 (UTC)

• The point I'm trying to underline is that, unless gravity is assumed (as part of the illustration of gravity), then there is no 'up' or 'down', and the diagram should demonstrate the same behaviour whether the deformation is 'down' or 'up'. Peter Grey

I'm afraid I cannot quite catch your point. What exactly do you mean by down or up? The deformation is curved into extra dimensions for which we may only talk of, yet never be able to obtain direct conceptions of for which we will understand properly since, as I said before, we cannot cross the barriers of dimensions. One should also be careful between the shortest path and the easiest path. Traditionally, we tend to think that the shortest path between two things, usually a "straight line", is also the easiest path to traverse between the two objects in question. However, because of this simultaneous involvement in meaning our brain has got accustomed to thinking that the shortest journey must necessarily be the easiest one to achieve, taking seemingly the smallest period of Time (if you can put it like that). Unfortunately, this stops being true as soon as we step out of the world of the Greek Geometres- the flat world of 2Ds where the curvatures made we can entirely ignore, since we are one dimension (in Space) higher. Already in the 3D world we are encountering trouble. When a tourguide shows you the fastest way to cross a mountain, he shows you the curved path just by the foot of the mountain and fitted to its topological curvatures. However, who would not agree that the shortest way is actually to tunnel through the mountain centre itself, and come upon the other side? True, this may be the shortest way, but it is by no means the easiest. Far easier it is to adapt to the geodesic of the landscape than to delve in it.

Space- time itself possesses more dimensions than our race, so delving becomes completely impossible. All we can do now is follow, once again, the geodesics of the landscape, and trust them to be our easiest way. (or trust maths- whichever)There will be no talk of picking or choosing either- all objects follow intuitively the easiest way to traverse between two points. When there is a stone that curves a rubber sheet downwards the ant naturally walk as close to the stone as possible in getting its way round to the other side, not even waste time climbing or delving into the stone. The same it is for us- we naturally follow the curvatures already made in the fabric of space- time. When a gigantic gravitational body curves space-time into extra dimensions unreacheable, the easiest way to cross to the other side is to the follow the geodesics and walk as close to the body as possible, giving the effect of being "gravitated towards it", rather than away from it where the journey will naturally be harder. Luthinya 09:55, 14 April 2006 (UTC)

• There seem to be two different answers emerging:

1. The picture is simply hinting at the connection with geometry. The illustration assumes a vertical force of gravity, and shows geometry causing the attraction to a point mass. That's interesting because it is bridging our intuition about gravity (basically one-dimensional) and attraction to a point mass in two dimensions, but it's also 'cheating' since one force of gravity is being explained using another force of gravity.
2. The more sophisticated version is that the curvature causes acceleration of a point moving along a geodesic. However, if this is a behaviour due only to the geometry, and there is no assumption of Newtonian gravitation, then there is no up or down, and it's not immediately obvious if a particle in motion would be deflected away from the point mass, or towards it. Peter Grey 19:48, 14 April 2006 (UTC)

• It seems that we're all talking at cross purposes to one another. Gravity is not explaining gravity; it's illustrating it. These are two very different things, at least to me. -- Filliam H Muffman 00:17, 15 April 2006 (UTC)

Excel problem

The default settings for the general format has changed into a percentage. When I start a new excel spreadsheet and type a number (eg 5), and press enter, the number appears as '0.05'. When I go to format cells, it says that the catergory is 'General'. Any idea on how to fix it? It's Office 2003. Thanks all. - Akamad 12:19, 14 April 2006 (UTC)

Go to Tools/Options, Edit tab. Uncheck the "Fixed Decimal" box. --LarryMac 15:15, 14 April 2006 (UTC)

Thank you very much. - Akamad 23:54, 14 April 2006 (UTC)

pepper pad

Have anyone used the pepper pad? (no, I am not going to buy it, but just want to know about it) I just want to know whether we must have to use the scroll button most often to move left and right? because the screen is just 6 inches wide? or is it enough since we keep the screen horizontally and read? Is the font size small and is a small font size enough since we keep it near our eyes compared to computer monitor?

Life expectancy of LCD vs Plasma HDTV operating 24 hours a day

I'm looking to upgrade a large scale video surveillance setup with a high definition video wall consisting of 12 - 50" monitors capable of displaying any number of cameras simultaneously, yet have the ability to display one camera streatched across all 12 monitors if I so choose. I cannot justify spending large chunks of budget money replacing LCD or plasma screen TV's every 6 months because either they can't handle being on 24 hours a day, or images have been burned into the phosphorous (LCD) thereby ghosting out the display.

I can hold out for the next generation if need be but I'd buy them now if they could last 2 years (17,500 hours) in that type of environment. I cannot seem to find a spec sheet outlining continuous use...I hope you can

[12] seems to say the industry promises around 20,000 hours of life out of a plasma screen. But it also says that burn in may be an issue. Anecdotally, at work we have LCD screens that are on 24/7 I know of one that has been in place for two and a half years will no ill affects. The image changes regularly though. --Chapuisat 19:25, 14 April 2006 (UTC)

Tree Height - Why Is the Sky Not the Limit?

Given species and environment, trees reach a peek height. What is it that prevents trees to grow ever taller?

The same reason why humans dont go on growing tall forever... The height depends on the strenght of the tree and a tall tree is no use if it cant stand on its own properly. Jayant,17 Years, India • contribs 16:40, 14 April 2006 (UTC)

No that's not it. Humans are genetically designed to grow up to a certain height, and stop growing at a certain age of maturity. Trees don't work that way at all. A tree tends to continue growing until it dies, which leads to another interesting question: Do trees have lifespans? or do they only die of disease or other pathologies?Loomis51 16:40, 16 April 2006 (UTC)

The main reason is not structural consideration but water. You have to get water to the top of the tree. See the cohesion-tension theory. I notice that this article is not that great in wikipedia so you should probably do a google search. In summary, there are a couple of factors that limit the ability of a tree to pull water from the soil to the top. 1) The strength of xylem vessels to with stand the negative pressure creating by "sucking" the water up. 2) the amount of force available from transpiration to pull water to the top of a tree. This is limited by the maximum tension that can be exerted on the water column (determined by the cohesion between water molecules and the adhesion between the water molecules and the inside of the xylem vessel).David D. (Talk) 16:43, 14 April 2006 (UTC)

This is all interesting, and admittedly, much of it I don't understand. Nonetheless, the explanation seems lacking in one main respect: scale. It would seem to me, the larger the tree, the stronger the xylem vessels would be, the stronger the force available from transpiration etc... The only answer I can think of as to why trees don't continue growing forever is that the eventually die, which leads me back to my above question concerning whether or not trees have natural lifespans. Loomis51 16:40, 16 April 2006 (UTC)

Why would it not be a structural consideration as well? (in the evolutionary context) A tall tree has a higher center of gravity and may topple more easily. I don't think there are a lot of evolutionary advantages to being extremely tall. --BluePlatypus 17:33, 14 April 2006 (UTC)

Once again, this argument ignores the relevance of scale. Of course the taller the tree, the higher the center of gravity, but then again, the taller and older a tree is, the thicker its trunk is, thus compensating for the higher center of gravity.Loomis51 16:46, 16 April 2006 (UTC)

Evolutionary advantages 1) Tall trees get access to unlimited sun. 2) Shade out the competition. The reason it is not a structural issue is that the load bearing forces on the wood of trees could with stand much taller trees. Clearly there are structural limitations but in most cases it is the transport of water that is the limiting factor with respect to height. Obviously we could also discuss root architecture (shallow vs deep) and susceptability to wind since this would be more important for some species. Another issue might be if a tree is in a forest or standing alone and soil conditions could make a difference too but i think this is beyond the scope of the original question. David D. (Talk) 18:02, 14 April 2006 (UTC)

Water transport can be accomplished by active molecular pumping at the level of individual cells. If need be, there could be chains of cells passing the water from cell to cell all the way up a tree. Plants do not need to depend on long single columns of water from roots to leaves. However, transport of molecules requires energy. When a tree gets very tall, a large percentage of its energy will be used for transport of molecules. Growth will slow and eventually something will destroy the tree before it reaches "the sky".....structural weakness if nothing else. --JWSchmidt 16:56, 16 April 2006 (UTC)

Telephone problems

There are 2 telephones using my phone line. About 13 hours ago, I picked up the telephone in my room, and instead of hearing the dial tone, I heard "Please hang up immediately and try your call again. This is a recording." I hung up the phone, waited for a few seconds, and picked it up again. I heard the hang-up beeps. I again hung up, waited for several seconds, and picked the phone up. I heard loud beeps, the same beeps that are heard when you don't hang up but the person on the other end did a long time ago.

It seems that a telephone using my phone line is not hanging up. But there are only 2 telephones connected to the phone line, and nobody was using the telephone not in my room.

As of now, when I pick up either phone, there is no dial tone but only a low buzzing noise. This noise is similar, though a bit louder, than the sound you hear during a successful call but when nobody is speaking.

What is likely the cause of these problems? Why did another phone line, used by the family sharing my house, fail too? I'm guessing that the problem is with the place where all the phone lines meet (in a "control panel" in the basement), since both lines failed nearly simultaneously (but the other one works now--my line still doesn't). --Bowlhover 18:17, 14 April 2006 (UTC)

I suggest there may be a problem with one of the phones. Disconnect them both, take a nap then connect one and see if it works. If it does, connect the other one and see if both work now. Your comment that the other phone line also failed suggests the problem may be the control panel in the basement like you thought.

Oh, Bowlhover, what have you been doing to draw the CIA's attention to yourself? (heads off in search of tinfoil hat) --Bth 18:41, 14 April 2006 (UTC)

LOL, I also suspected the problems might be because of a wiretap. But which wiretapper leaves their device on for hours, preventing their "victim" from making phone calls? Anyways, my phone line works now--I don't know why, and I don't know when it started working. --Bowlhover 23:42, 14 April 2006 (UTC)

This is not very common with phones. It is an old modem problem - the modems can connect, but they fail to disconnect. By chance, do you have a computer also plugged into the line? As for the sounds, they are common. The first message is a pre-recorded message that tells you to hang up. The next is a loud beep to get your attention. Then, the line is disconnected at the phone company's end and you get nothing by static. --Kainaw ^(talk) 18:48, 14 April 2006 (UTC)

No, none of the computers in my house are connected to a phone line. Also, it's not a loud beep I hear after the recorded message--it's a series of beeps that you get every time the person on the other end hangs up, followed by another louder series of beeps telling you to hang up immediately. --Bowlhover 23:42, 14 April 2006 (UTC)

Your lines are buggered. Time to haul out the old phone and call the phone company. I had a problem with my phone broadband. Turns out that when the house was renovated, the bell wires had been folded over from one end of the house to the other. We had to put in a new straight line, since DSL hates folds.--Zeizmic 13:15, 15 April 2006 (UTC)

Is Oxygen poisonous?

O^2, more precisely. I've been told that it is actually poisonous and the information about oxygen poisoning here on Wikipedia doesn't explain how it occurs very well so I'm rather confused about it. Also, is it possible to live on pure oxygen or are the other elements of air necessary for a human to respirate?

Everything is poisonous in large enough quantities. The concept of 'poison' is basically to do with the quantity. People need it, but can have too much of it. Do you have some specific questions about the oxygen poisoning article? For great justice. 20:48, 14 April 2006 (UTC)

You can live in an atmosphere of pure oxygen, but bad things can happen -- Apollo 1

The 'poison' concept means that free oxygen is poisonous within the body. That is why great pains are taken to encapsulate oxygen with iron - Hemoglobin. --Zeizmic 20:52, 14 April 2006 (UTC)

• "Poison" means "too much" more than "this is poison and that isn't". Vitamin A in tiny quantities will kill you and in even tinier quanties is necessary. Everything if taken in sufficient quantity is poisonous.
• At low pressure, like is used at high altitudes and in space, 100% oxygen is fine. No other gas is needed by the body
• The higher the pressure (the deeper in the ocean of air or water you are) the less time one can breath a given percent of oxygen. To not be poisoned by oxygen when deep sea diving the time must be short or the oxygen reduced in percentage. WAS 4.250 21:15, 14 April 2006 (UTC)

Oxygen is poisonous to certain bacteria that evolved before there was oxygen in the atmosphere. This group of bacteria is called, for obvious reasons, "anaerobic bacteria". They only live in closed spaces, like in deep wounds. For them, hydorgen peroxide, which releases oxygen, is poison, ie a "disinfectant". So what is poisonous to a given species , like possible extraterrestial species, depends on the paritcular biochemistry of that species. GangofOne 21:26, 14 April 2006 (UTC)

My understanding is a small quantity of carbon dioxide is necessary to keep a person breathing. Buildup of CO2 is what triggers respiration. In an atmosphere of pure oxygen this does not happen and a person will pass out.

No, the body creates it own CO2. WAS 4.250 21:33, 14 April 2006 (UTC)

My understanding was the CO2 in the body would be liberated in a non-CO2 atmosphere so fast the respiration would slow down and thus, less CO2 would be generated. This would result in a vicious circle sort of situation.

CO2 in the atmosphere (compared to your lungs) is already very low, removing it completely would not increase the concentration gradient by that much. Also, the CO2 is a result of metabolism in the cells so its production would not slow down if there was less CO2 in the lungs.David D. (Talk) 22:16, 14 April 2006 (UTC)

Breathing oxygen can be poisonous to humans.

This is probably caused by the excess production of superoxide, a highly reactive molecule with a free electron which can interact with other cellular molecules and distort or destroy them. One site where these superoxides are formed is in the mitochondria, the power production plants of eukaryotic cells. It is estimated that, in normal cicumstances, up to 5% of oxygen flowing through a mitochondrion can end up as superoxide, instead of being incorporated into the the normal end products of glucose metabolism, carbon dioxide and water (aerobic cellular respiration).

Superoxide combines with other cellular molecules to form reactive oxygen species or free radicals (these two are not necessarily the same), which are also highly reactive.

The problem with free radicals is that they typically cause chain reactions, i.e. superoxide damages molecule A, which becomes a free radical and damages molecule B, which becomes a free radical and damages molecule C, and so on. Fortunately, these harmful free radicals would normally be inactivated by enzymes such as superoxide dismutase and catalase, and any damage done is usually repaired before the body suffers. They are never the less implicated in the process of ageing.

In the case of oxygen toxicity, or poisoning, an increased flow of oxygen through the mitochondria leads to an increase in superoxide. A high enough increase for long enough, can cause superoxide levels to become so high that the free radicals and the resulting chain reactions cannot be held in check by the normal cellular countermeasures. The proteins, fats and even the genetic molecules (DNA and RNA) of the cell are damaged, and the cell loses its normal function, or even dies.

Two effects are most prominent:

1. The lungs become stiff, congested with fluid and inflammatory exudate, and eventually scarred, so that it becomes difficult to breathe and oxygen cannot get through to the to the blood in the pulmonary capillaries (respiratory distress syndrome). This is caused by direct cell damage and cell death, as well as changes in production of surfactant. It can be permanent and cause death.

2. The person develops fits, identical to grand mal epileptic fits. This could be due to damage to cells as such, with swelling and generalised disfunction, or to alterations in nerve transmission – either changes in neurotransmitter release or changes in the receptors for those substances. As in epilepsy, fits can cause further brain damage, physical injuries or breathing problems associated with loss of consciousness.

In humans, symptoms and signs of oxygen toxicity usually occur only after breathing oxygen with a partial pressure of greater than 60 kPa for 24 hours or longer (lower concentration are probably safe for very long periods). The higher the partial pressure, and the longer the exposure, the more the damage done.

Damage to the lungs can occur with ordinary supplementary oxygen use in hospitals, when more than 60% concentration is used for extended periods, while fits are more commonly seen under hyperbaric (high pressure) conditions, such as is encountered in deep diving or in hyperbaric chambers.

In premature babies, high oxygen concentrations are associated with damage to the eyes (retinopathy of prematurity), which can lead to blindness. There are probably more risks to the babies’ health, such as protracted lung problems and even an increased incidence of leukemia, but these have to date not been precisely defined.

Note that free radicals and reactive oxygen species are essential for normal functions. They are for instance used by the body to destroy bacteria, or for cellular signalling, so that they are in themselves not “bad”. It is the excess that harms.

Humans do not need any gas other than ogygen to respirate. Specifically, we do not need to inhale any carbon dioxide. However, if one breathes completely dry gas, especially if the gas bypasses the nose, respiratory secretions tend to dry out and thicken, increasing the risk of infection or plugging of airways in the lungs.

Seejyb 20:00, 15 April 2006 (UTC)

April 15

Animals and Babies

Do animals think like we do? Is it possible that back long ago animals used to talk? Do babies think like we do? I mean like if they are eating bananas at the age of one and don't know how to talk might they be thinking about how they hate the banana?

Category:Animal communication? Melchoir 02:00, 15 April 2006 (UTC)

Oh, and Category:Developmental psychology. Melchoir 02:07, 15 April 2006 (UTC)

Humans don't even think like one another. WAS 4.250 03:13, 15 April 2006 (UTC)

Most animals would definitely not think like we do. In fact it was recently proven lobsters are not evolutionarily developed enough to nocicept. However, animal lovers are frequently completely sure that their dog is feeling lonely, happy, or confused. It is a common tendency for people to think of inanimate objects as having human-like characteristics, in fact it is inherent, and one of the most basic ways of learning. A baby copies what its parents do. I can't find the link, but there is an article on here somewhere about different levels of emotion. Primary emotions are like fear, and contentness, the most basic. Secondary emotions are more complicated, and include confusion, and depression. -- Mac Davis] ⌇☢ ญƛ. 05:11, 15 April 2006 (UTC)

I sort of feel compelled to point out that animals aren't "inanimate objects", and that it's well-known that animals have emotions. It's also quite clear that lobsters are capable of nociception: the question that remains open to debate is to what extent that nociception is accompanied by emotional distress. The idea that humans have emotions and animals don't is, frankly, rather silly from an evolutionary standpoint. Our emotions didn't spring from nowhere, and emotions have been quite clearly described in various animals. - Nunh-huh 09:07, 15 April 2006 (UTC)

I think the word 'emotion' is not helping us here: to me it implies things like love, or anger, which I very much doubt (other) animals experience. If we can agree that my cat is not as emotionally developed as me, but that it does have some form of consciousness, then the only uncertainty is as to the degree of difference. My best guess is that my cat can experience distress, contentment and pleasure, all of which I think are induced by physical stimuli of one sort or another, rather by feelings of love for me or hate for the neighbour's cat. I doubt that animals get much more emotionally developed than that, though I haven't met many gorillas or whales. I'm quite sure that some animals are less developed. Henry^Flower 11:22, 15 April 2006 (UTC)

Linguists don't have a definite consensus, but one theory holds that the language faculty is principal difference between humans and other animals, and language is the fundamental medium of human thought. Animals, even those with communication, do not have the language faculty, and infants less than two years have only a rudimentary language ability. So although they might learn an association between a food and negative emotions, they could not be thinking about how they hate in the normal sense of 'thinking'. Peter Grey 11:39, 15 April 2006 (UTC)

• Francis Galton once wrote an article about why dogs were so great as pets -- they seem to have very similar emotional faculties as humans, and as such we can understand them pretty easily (it is easy to tell when a dog is happy, sad, angry, excited, hungry, bored), and they can understand us pretty easily (they understand tone of voice, facial expressions, they can tell when we are unhappy, etc.). He then, quite humorously, alluded to the fact at how rare this is, with a line something along the lines of "Who ever imagined shooing away a mosquito with a disapproving look, or pacifying an angry wasp with a winning smile?" In any case, with emotions in man and aninmals, I don't think one can draw too many really hard-and-fast difference between the two as categories go, with the only potential instance being language, but even then I am not sure the verdict is in on whether or not certain forms of communication amongst animals don't involve some sort of language faculty or not. --Fastfission 18:30, 15 April 2006 (UTC)

I would say that some animals exhibit all the emotional range of humans, with other primates being the closest. Even some single celled animals appear to exhibit fear and aggression. However, symbolic logic seems to be almost exclusively human. That is, the ability to think in words is not shared by animals. Some people with delayed language skills can likely recall what it's like to think without words. A series of pictures is sometimes how it's described. For example, Helen Keller didn't learn to speak sign language until later in childhood so would have recalled thinking without words, as animals do. StuRat 22:01, 15 April 2006 (UTC)

I agree with that. The ability to describe or express a feeling is what turns a feeling into an emotion. I would say that only humans have emotions, because only humans have language, but most sensate beings (including plants) are known to have feelings (which we tend to refer as 'instincts' in the case of animals). JackofOz 02:11, 16 April 2006 (UTC)

Drug Ratings

I work at a pharmacy and sometimes when I read pharmacutical magazines, I notice it say "AB rated" on some of the drug advertisements. I think there are other ratings also, but I can't remember. What does it mean? — Preceding unsigned comment added by 68.171.53.125 (talk • contribs)

Those are Therapeutic Equivalent Evaluation Codes that are used by the FDA to denote therapeutic equivalence to other pharmaceutically equivalent drug products. A drug which is AA-rated or AB-rated to another indicated that they are considered interchangeable by FDA standards and can be substituted unless the physician designates otherwise. Sometimes a number is appended (AB1, AB2, AB3, etc). Another designation, BN-rated, means "not equivatlent". see [13] - Nunh-huh 04:54, 15 April 2006 (UTC)

Organ

Which of our organ, distributes the nutrients which we(humans) gain from the digested food, to different parts of our body according to their needs?

• The majority of digestion and absorption takes place in the small intestine - where the acidic broth from stomach is completely digested. Polymers such as proteins, polysaccharides, nucleic acids, and lipids are broken down into their monomer components by hydrolytic enzymes. These monomers are then absorbed through the lining of the small intestine into capillaries. These capillaries drain into the hepatic portal vessel, which drains into the liver. The liver has the metabolic versatility to interconvert various organic molecules, so the blood that leaves the liver has a very different composition than the blood that enters the liver. Wapatista 08:52, 16 April 2006 (UTC)

But the thing about the question that struck me was that the questioner seems to think there might be an organ overseeing appropriate distribution of nutrients, and there isn't. To some extent, the body has an ability to preferentially "feed" the brain on the basis of producing fuel preferentially used by the brain, but otherwise it's pretty much a case of every organ for itself. - Nunh-huh 09:01, 15 April 2006 (UTC)

Per Dalembert's comment below, the body does have at least some ability to regulate the delivery of nutrients and oxygen to different tissues and organs through manipulation of the cardiovascular system. Certain triggers (a shortage of oxygen, a spurt of epinephrine (adrenaline), heat or cold, etc.) can trigger the constriction or relaxation of blood vessels and changes in heart rate, regulating the amount of blood reaching particular parts of the body. There's no single organ that controls the cardiovascular system, however; it's a complex system that responds to a lot of different inputs. To name a couple, blood pressure is regulated by baroreceptors mostly in the aorta and the carotid arteries; epineprine comes from the adrenal glands that sit on top of the kidneys. TenOfAllTrades(talk) 15:57, 15 April 2006 (UTC)

So the body parts control delivery of nutrients by consensus :) WAS 4.250 16:22, 15 April 2006 (UTC)

• In a sense it is the liver, as it alters blood composition to what it is standard and therefore utilised in the body. It is also the circulatory system, as this distributes nutrients throughout the body. And in some sense it is the various organs of the endocrine system, as this releases hormones throughout the body responsible for regulating metabolism and uptake of materials by cells. Wapatista 08:52, 16 April 2006 (UTC)

The literal answer to the question, though, is simple: it is the cardiovascular system that distributes nutrients to all the parts of the body. Dalembert 14:26, 15 April 2006 (UTC)

People, look at the question. Which organ distributes nutrients to different parts of the body? Not "allocate" or "regulate" or "parse out", but simply "distribute". No debate here. Nutrients get from one organ to another in the blood, propelled by the heart. Period. Cardiovascular system is the only, literal, single correct answer. As much as I respect the liver, brain, and endocrine system, the blood flows for a purpose, and transport of nutrients, gases, and signals is that purpose. alteripse 12:16, 16 April 2006 (UTC)

"According to their needs" - the cardiovascular system isn't involved in regulation, so it's worth mentioning the other organs that do this, and also helpful to build up the "bigger picture". Although you are right. Wapatista 13:07, 16 April 2006 (UTC)

Physiological differences between white and red muscle

What are the differences between white muscle, for example, fish and bird muscle, and red muscle, for example mammal muscle? i've never come across a satisfactory answer for this question. My basic assumption is that it has something to do with blood supply to the muscles, and if so, how does this relate to function of the muscle? Wapatista 07:38, 15 April 2006 (UTC)

Muscle fibers come in different varieties. One, called the fast fibre, fast twitch fiber, Type II fiber, fast-twitch glycolytic fiber, or white muscle fiber, contracts quickly after nerve stimulation. They result in powerful contractions, but they fatigue rapidly because they contain few mitochondria. Another, called the slow fibre, Type I ffiber, slow-twitch glycolytic fibre, or red muscle fiber, contracts three times more slowly, but they fatigue less easily because they contain more plentiful mitochondria, and extensive capillary supply, and myoglobin.

Most muscle contain both types of fiber, but they are in different proportions. In animals that have "white meat", the type I fiber predominates; in those that have "red meat", the type II fibers do. - Nunh-huh 08:57, 15 April 2006 (UTC)

The article corresponding to what Nunh-huh is saying is muscle fiber.-gadfium 09:13, 15 April 2006 (UTC)

Thanks a lot. Wapatista 08:54, 16 April 2006 (UTC)

Properties of PVC

I am looking for a (simple) table/explenation of the physical properties of PVC (PolyvinylChloride). Thanks. —The preceding unsigned comment was added by 203.122.88.32 (talk • contribs) .

Polyvinyl chloride. You see, there's this search box on the page, and there's somewhere else on the page that says ... oh, forget it. Confusing Manifestation 11:01, 15 April 2006 (UTC)

Maybe someone could make a template to automatically suggest a search so it doesn't need to be typed it out manually in the future? --Username132 (talk) 01:53, 16 April 2006 (UTC)

embedded systems

what is the ato —The preceding unsigned comment was added by 202.65.149.74 (talk • contribs) .

Which tablet PC?

I am buying a tablet PC. I use the computer all the time to surf the net and also read news. I prefer to use the tablet like a slate and read because that is comfortable for me compared to using it like a laptop. What size tablet should I buy? If I buy a 10.4" tablet, will it be too small to browse the web? (Note here that I plan to use it in the slate format and not like a laptop). Or will a 10.4" be good enough size to browse websites? Should I scroll frequently in a 10.4" tablet to read pages? Or should I try 12 inches?

I would say you need excellent eyesight to make out a reasonable amount of text at 10.4 inches. I suggest you test it out on a few of your favorite websites before buying it. StuRat 19:12, 15 April 2006 (UTC)

Convert HTML to JPEG or GIF

Can I Change The Whole Internet Page (HTML) To Picture Format (JPEG or GIF ) ?

Well, you can certainly take a screenshot or your browser window. I suppose, if the page is too long, you can scroll down and take more screenshots and stitch them together in a paint program. There may well be programs that can automate this process, but if you only want to do this for one or two pages, this might be the simplest solution. —Ilmari Karonen (talk) 20:01, 15 April 2006 (UTC)

Another solution might be to print the page to a file, open the file in a paint program, and save it in whatever format you like. Of course, this assumes your paint program can read whatever format the "print to file" option produces on your computer; if you're lucky, it's PostScript, if you're not it's some proprietary printer-specific format. —Ilmari Karonen (talk) 20:05, 15 April 2006 (UTC)

You can do this easily with Ulead Photoimpact. Just open the page and then export it to an image file. -Halidecyphon 20:49, 16 April 2006 (UTC)

C++ cin stream failure

Imagine I write the following as part of main():

int n = 0; cout << "enter a number please: "; cin >> n;

And compile and run the program. Everything works great unless the user types in a letter, in which case the cin stream fails and the program ignores any further attempt to use cin.

How do I get around this problem? Thanks, JD --128.248.77.71 21:14, 15 April 2006 (UTC)

There are several things you can do, depending on whether you just want to detect the condition or recover from it. Take a look at [[14]].-gadfium 00:19, 16 April 2006 (UTC)

cin is an istream, it is reading input up until white space. Once it reads a letter, it is in an error state; you clear it with cin.clear(). But what you probably need is more sophisticated input parsing. Peter Grey 12:17, 16 April 2006 (UTC)

Simply using cin.clear() is not enough, as the letter typed is still in the input buffer and the problem just reoccurs with the next attempt to read a number. You therefore need to both clear the error condition and read the unwanted characters into a throwaway buffer, or else use cin.ignore(...) to get rid of the letter(s). The link I gave above explains this much more clearly than I could do.-gadfium 20:20, 16 April 2006 (UTC)

eMule causes DNS failure

Can anyone tell me any hint of why this is happening? It only happens in Windows, in Linux it's fine.

Specifically, I bet you have a Netgear ADSL router. I've seen several cases where eMule seems to "fill up" the DNS tables inside a Netgear router, which can only be fixed by rebooting the router. -- Finlay McWalter | Talk 23:59, 15 April 2006 (UTC)

Thanks ;)

learning Computer language

I am not trolling. I need to learn a 'computer langage' by August or I am vegetable. Please help me!

Situation: I have no previous experience with computer language. (And pleae don't tell me to learn QBasic, my sister does not count it as a computer language.) I need to learn a new language from scratch and I have heard about Python, Perl, FORTRAN (my dad used it but I don't want to nag him all the time) but I have not used any of these. Please also recommend me some free good pdf books online. Thank you.

Yours sincerely, Kushal Hada [Four tildes] Kushal one 23:41, 15 April 2006 (UTC)

Bruce Eckel has freely downloadable books teaching programming in C++, Java and Python. His books on the first two are probably not suitable for someone who has absolutely no programming experience, but I haven't looked at the last. Your choice of language should depend on what you need to use it for; if you explain why you need to learn one we may be able to help more.-gadfium 00:29, 16 April 2006 (UTC)

This issue has been discussed here before, see Wikipedia:Reference_desk_archive/Science/March_2006#Learning Computer Programming. I might add, that despite what your sister might say, QBasic is a completely valid programming language. In fact, any program that can be written in a particular language, can also be written in any other language, as long as they're Turing complete (most are, including QBasic). In fact, I would recommend starting with QBasic or C, then move on to an object-oriented language, such as C++ or Java. Of course, you can also choose the path of functional programming, and learn Scheme. It really depends on what you need to use the language for, if you're going to be writing simple things for an embedded system that you created, you might as well just start with an Assembly language, and not bother with any higher-level ones. --Aramգուտանգ 00:37, 16 April 2006 (UTC)

A pretty simple language which is also quite powerful is PHP. You can learn the basics of it in a few hours if you run through a few tutorials. It is pretty straightforward as far as scripting languages go. --Fastfission 17:09, 16 April 2006 (UTC)

Start with Pascal programming language. It was designed as the language to use to learn how to program. After you read the just mentioned wikipedia article on Pascal, read [15] and use [16]. WAS 4.250 17:21, 16 April 2006 (UTC)

April 16

Ice age

Here it says how the three main causes of ice ages are: The earth's orbit around the sun changing; the atmosphere changing; and the "arrangment of the continents". I heard how scientists say there will be another ice age in about five million years from now. How do they know that? Jonathan ^talk File:Canada flag 300.png 00:40, 16 April 2006 (UTC)

They are estimating based on the past. They find evidence of changes in Ice cores and from those changes they try to predict what is likely to happen. Admittedly, the "arrangement of the continents" reason sounds suspicious. I will have a look at that one. The orbit around the sun can be predicted with a very high degree of accuracy, and its effect on the amount of heat the earth receives, and the rates at which it receives the heat will affect when the next ice age will occur. Ansell 00:58, 16 April 2006 (UTC)

The arrangement of the continents is very important. The arrangement of land is relevant as it affects the circulation of the oceans, which has a strong modifying effect on climate - ice ages are far more likely in some continental arrangements than others. It only sounds like an odd reason because we normally think of "The Ice ages" as occurring only in the last few million years, during which time the continents have been roughly in the same places - but they've actually been going on intermittently for hundreds of millions of years. Sometimes there are long periods with no ice ages or long periods with many ice ages - the reason for these two distinct climatic histories is the positions of the land masses. Grutness...wha? 01:32, 16 April 2006 (UTC)

black people

Do they tan or is their skin always the same color? A Clown in the Dark 01:47, 16 April 2006 (UTC)

Sun tanning is simply the skin activating chemicals that are already in our skin. People who have those compounds activated because of their genes, may get slightly more tanned, however, I am not sure it would be easy to tell the difference as their extra level of activation may be very minor. Ansell 02:48, 16 April 2006 (UTC)

Black skin is not, however, immune to burning, and more to the point, it's not immune to skin cancer (though it less prone to certain types of skin cancer than lighter skin.) --jpgordon∇∆∇∆ 02:58, 16 April 2006 (UTC)

Yes, black people tan. WAS 4.250 17:32, 16 April 2006 (UTC)

They are susceptible to tanning and burning, and the effect can be just as dramatic as in whites. Bhumiya (said/done) 21:22, 16 April 2006 (UTC)

Though, as one would expect, it's much easier to notice the difference in a 1% shade to 11% shade change than a 30% shade to 40% shade change. In other words, your big fat white Uncle Al would look quite a bit more rediculous with a light burn than your dark muscular Aunt Franco.  freshgavinΓΛĿЌ  05:20, 17 April 2006 (UTC)

Drive Arrays In Proliant 3000

Since linux doesn't treat my HD very separately and treats them as one big 'hda', what does that mean if one drive fails on start up?

Similarly, if I erase my server and treat the drives as one big "logical drive" does that enhance risk of data loss in the event that one drive fails? Would they be better all as separate logical drives? Also, what is the meaning of a an array - why are my logical drives arranged under the umbrella of an 'array'?

I would like to make use of the maximum amount of space with the minimum risk of failure which I think is RAID 0, all HDs treated separately. Also, why if one drive fails, should the server demand that it is replaced before starting up? Even if it is replaced, the data isn't going to be there...? --Username132 (talk) 01:50, 16 April 2006 (UTC)

Maximum space doesn't go with minimum failure. You choose which one you are more worried about and go with that. I would personally choose RAID 0 for speed, but with the knowledge that because it is one logical drive, if one fails, there is no backup. However, if you want minimum failure, look at RAID 1, where you get everything put down twice on separate hard drives so if one fails you can still use the other one.

Linux only treats them as one big hda if they are all put together in RAID, or if you are using Logical Volume Management, or any of the alternatives. If you put two non-RAID hard drives in Linux is likely to assign one the hda and one the hdb, unless they are SCSI in which case they will be sda and sdb.

If one drive in a RAID 1 array fails on startup nothing bad happens, your computer will boot as normal. However, if you have RAID 0, you have just lost half of the data on your computer. Ansell 02:44, 16 April 2006 (UTC)

Well I want to use 8 (18.2 GB) drives. I figure I could split this into two logical arrays - one consisting of a single HD for the OS(es) and another for storage. But if 7 drives are in one logical drive does that mean that they're all one partition? I the logical drive entry doesn't explain what would happen if one drive failed? Would I be better off having 8 logical drives or the two like I just mentioned?

When did RAID come into existence? The computer I'm referring to is about 8 years old and uses hot-pluggable SCSI drives in their own little caddies. When I use Compaq SmartStart to configure 'the array', it invariably wants to put them all into one big logical drive and the "array condiguration utility" gives me a graphic kind of like this;

Controller
    |
   Array
       |
       Logical drive 1
       Logical drive 2

What's this array nonsense? I don't want any arrays... :( --Username132 (talk) 03:43, 16 April 2006 (UTC)

See Redundant array of independent disks for history and more. Servers such as yours have had RAID controllers for long, it seems, but common PCs/Desktops generally only for the past 3-4 years. Max space / Min failure would seem at it simplest to correspond to a RAID 1 setup, 2 logical drives of 4 identical physical disks each = 100% duplication. --Seejyb 14:06, 16 April 2006 (UTC)

P2P Malware

If you download a linux distro from a p2p network, couldn't someone have altered the code to add some malware and control your computer remotely? --Username132 (talk) 02:16, 16 April 2006 (UTC)

Depends on where you got the source from. If you get the link from the distro's website, then no it's fine.

You can run md5sum on the downloaded file and compare this to the sum that is given on the distro's website to confirm that your copy has not been tampered with. They may even have digitally signed the file and you can confirm it that way as well. Ansell 02:38, 16 April 2006 (UTC)

Thanks :) --Username132 (talk) 03:28, 16 April 2006 (UTC)

Forum on IMDB working?

Here is a link to the [Chinatown (1974) entry on IMDB. The forum links aren't working for me. How are they for you? -Username132 (talk) 03:44, 16 April 2006 (UTC)

Did you register? Going to the message board came up with a "Free Registration" window for me, but I don't see the need to give away my details, so i didn't proceed. The user comments were working for me. Is that what you meant? Ansell 04:47, 16 April 2006 (UTC)

Yeah, I'm registered. It even gives my login name in the top right, but when I click on the link to go to a forum (not comments), the browser load bar appears and then makes no progress... indefinately. Thanks for trying anyway. --Username132 (talk) 04:57, 16 April 2006 (UTC)

I'm having no trouble with the link. I'm registered with IMDb, and I went to the main movie page, the main forums page for the movie, and the top topic in the forums list with no problems. Was it perhaps a particular thread that you were having trouble with?--Anchoress 11:38, 16 April 2006 (UTC)

It was a whole forum that wouldn't work. Couldn't get to the forum, or the selected threads on the main movie page. It's spontaneously resolved now, but I don't know why. --Username132 (talk) 18:29, 16 April 2006 (UTC)

I frequently have problems with imdb where it loads a blank page and stops, and I have to refresh to get the info to show up. User:Zoe|^(talk) 21:31, 16 April 2006 (UTC)

Statistics - type 2 error (oh noes!)

According to false negative;

"In statistics, a false negative, also called a Type II error or miss, exists when a test incorrectly reports that a result was not detected, when it was really present. (Alternatively, a Type 2 error can be thought of as a failure by accepting the alternative hypothesis when the null hypothesis was truly false.)"

So what it says at first is that a type 2 error is accepting the null hypothesis when the alternative hypothesis was correct? And then it contradicts itself by saying alternatively, a type 2 error is accepting the alternative hypothesis EVEN THOUGH the null hypothesis is actually wrong? Putting the word 'truly' before false is also stupid. I'm changing it to 'actually'... -Username132 (talk) 04:54, 16 April 2006 (UTC)

The "clarification" inside parentheses is wrong! A type 2 error is an erroneous rejection of the alternative hypothesis. (In other word, the null hypothesis is false but one fails to reject it.) --68.238.254.236 15:20, 16 April 2006 (UTC)

How long before a feral animal becomes a native?

Hey people. I was wondering if there was a hard and fast rule in place about how long a species of feral animal has existed before it is referred to as a native. For example, the dingo was introduced to Australia about 15000 - 30000 years ago and today is generally considered a native animal to Australia. Meanwhile, the feral cats that one sees in outback Australia are as different to domesticated cats that one would consider them a different species (my mother, who used to work in rural Australia, saw examples of feral cats that looked twice as big as a domesticated cat and whose faces looked considerably different). Some of these cats can trace their ancestory in Australia back 400 or so years, leaving one to ask the question, "how long until feral cats are considered native to Australia?"

Cheers --Roisterer 06:12, 16 April 2006 (UTC)

I'm not sure that dingoes can be considered native to Australia. See introduced species for clarification; since the feral cats were introduced, by definition they cannot be native. As far as species is concerned, if these feral cats can still breed with their domestic counterparts and produce fertile offspring, they'll probably be considered the same species. Hope this helps. Isopropyl 06:32, 16 April 2006 (UTC)

You realize that you are asking a question about semantics, not natural fact? Native is an especially slippery word, but in this type of context native usually means only that things or people of its kind were already present in that place when people speaking a European language first arrived. Much evidence suggests that nearly all people and animals and plants have not existed forever in a particular place but arrived at that place at some time in the past. There is no precise answer to "how long should x have existed there before we can call it "native". alteripse 12:09, 16 April 2006 (UTC)

Eyes and sunlight

Why are eyes so heavily affected by sunlight? All it is is just a bunch of photons, it shouldn't be all that harmful.

Gamma radiation is "just a bunch of photons", too. --BluePlatypus 06:34, 16 April 2006 (UTC)

See Sun#Sun observation and eye damage. —Keenan Pepper 07:45, 16 April 2006 (UTC)

The problem is the photons are at too high of an intensity in number that the eye is built to handle... not that the eye was built. -- Mac Davis] ⌇☢ ญƛ. 11:29, 16 April 2006 (UTC)

A photon is pure energy. The eye is a delicate instrument that aquires, measures, and organizes information on that pure energy. If that pure energy is too much energy, then it damages the sensitive parts of that delicate instrumnet. WAS 4.250 17:38, 16 April 2006 (UTC)

Its just like cooking something....as long as the flame is under control the food gets cooked properly....but if you increase the flame or the heat given to it, it gets over cooked and in extreme cases, burnt... our eye is like the food....we dont want it to get burnt..... Jayant,17 Years, India • contribs 17:51, 16 April 2006 (UTC)

As our article says our eyes have evolved to stand directly looking at the sun by accident with little chance of permanent damage. Light concentrating optics and partial solar eclipses are where the real danger lies. The former can hardly be called part of our natural environment and the later is a pretty rare event. Plugwash 17:59, 16 April 2006 (UTC)

The human brain is also probably part of the reason. Just like pain receptors reacting though no damage is being done, the brain has probably evolved to make it seem that our eyes are very sensitive to the sun, in order to teach our less intelligent ancestors a lesson before they started making hobbies of looking at bright yellow balls.  freshgavinΓΛĿЌ  05:12, 17 April 2006 (UTC)

Squiggly shapes in the eyes

In certain lighting conditions I can discern small transparent shapes in my eyes. i guess they are suspended in the sclera, as any attempt to look directly at them results in them moving away in relation to the movement of the eye (a rather comical situation). The shapes are varied, but range from small spots to squiggly-amoeboid shapes, all very small.

Other people seem to have them as well. I looked but couldn't find what I was looking for under disorders of the eye.

What are they, are they bad, and is there any way to remove them? Cheers, Wapatista 09:01, 16 April 2006 (UTC)

See Floater. — Knowledge Seeker দ 09:08, 16 April 2006 (UTC)

They are normal, don't worry about it. Also see Phosphene -- Mac Davis] ⌇☢ ญƛ. 11:28, 16 April 2006 (UTC)

I've been seeing them for more than 10 years now... if they are really bugging you, try not to concentrate on them and look at some dark area... Jayant,17 Years, India • contribs 14:36, 16 April 2006 (UTC)

Center of Mass & Center of Gravity

I have a conceptual question about a roll of toilet tissue. Are its center of mass and center of gravity the same? Also, could they located in the hollow inside of the roll?Patchouli 14:16, 16 April 2006 (UTC)

Assuming that the roll is in a uniform gravitational field, the center of mass equals the center of gravity, and they are at the center of the roll, in the hollow inside of it. --Andreas Rejbrand 14:22, 16 April 2006 (UTC)

Evolution-based explanation for physical differences among races

Native inhabitants of difference parts of the world have different physical features. For example, Europeans tend to have lighter skin/eye/hair colors and "pointier" nose shapes etc. Africans, on the other hand, tend to have darker skin/eye/hair colors, bigger and rounder noses, and hair with very small curls. From the standpoint of evolution, these differences should be explainable in terms of adaptations to the environment and evolutionary advantages. I've tried to come up with an evolution-based explanation for the differences in nose shapes and hair texture, but I couldn't tie these differences to evolutionary advantages. Is there a consensus among scientists as to how nose shapes and hair texture affect survival in different geographic regions?

There is a process called genetic drift by which traits can become common in a population by "chance" without there being a "reason". You can speculate about "reasons" for traits that might lead to active selection, but it is often hard to know if you have found the real cause of a trait being selected in a population. --JWSchmidt 17:09, 16 April 2006 (UTC)

There is no consensus. There are a lot of "just-so" stories ;some are nonsense; some are probably true. Current genetic studies are being done that are beginning to provide scientific evidence that address these issues. We are a long way from having it all figured out. WAS 4.250 17:46, 16 April 2006 (UTC)

EMF (or WMF) to SVG converter

Does anyone know any free software able to convert EMF (or WMF) images to SVG files? --Andreas Rejbrand 14:17, 16 April 2006 (UTC)

You mean, apart from the programs listed by typing "wmf to svg converter" into Google? --Heron 16:32, 16 April 2006 (UTC)

Well, I thought most of them weren't free (it isn't the first time I'm looking for a free converter app.), but I'll have a more carefull look at them. --Andreas Rejbrand 17:01, 16 April 2006 (UTC)

JPEG thumbnail

After installing some software, my computer (Windows ME) no longer shows a thumbnails for jpegs in Explorer. Is there a registry class I should edit to bring it back again.--Bjwebb (talk) 14:37, 16 April 2006 (UTC)

Rapyrox

In a book I was reading, a old lady held an injection of 'rapyrox' against some guy's leg and held him hostage that way. What is rapyrox? I've done google searches, and I get nothing. Recon0. (talk) 14:47, 16 April 2006 (UTC)

I have tried to search for 'rapyrox' using several search engines but havn't found anything. Hence, it is most likely that the word has no real meaning, but is only a "invention" of the author. --Andreas Rejbrand 14:52, 16 April 2006 (UTC)

An Unusual Error in Matlab Program.

Hi, i was trying to create a program to find out the sum of the digits of a given number until the sum was a single digit. For example, if i find sum of digits of the number "15", then it would be 1+5=6. But for "47", it should be 4+7=11 and 1+1=2. so i just wanted to write such a program. First i tried in C, but there handling of floating point variables would have posed problems, so i tried in Matlab. The following is the code which i wrote in Matlab. Please note that in the following code, "type" is the variable whose sum of digits i want to find out. And the variable "sumfinal" stores the final value of sum of digits.

THERE IS A PROBLEM WITH WIKIPEDIA'S CODE DISPLAYING METHODS, I HAVE MODIFIED THIS CODE ON THIS PAGE SO THAT IT SEEMS EXACTLY AS IT IS, BUT WIKIPEDIA ITSELF CREATES NEW INDENTS AND MAKES IT QUITE CLUMSY.

%%%%%%%%%%%%%%BEGINNING OF CODE%%%%%%%%%%%%%%%%
clear
format long
sum=0;
temp=0;
num=2222222222222222222;  % this is the number
while temp==0
    while num~=0        
        digit=mod(num,10);
        sum=sum+digit;
        num=(num-digit)/10;
        sum
    end
    
    
    if sum>9
        num=sum;
        sum=0;
        
    else
        break
    end
    
    
end

sumfinal=sum;
sumfinal
%%%%%%%%%%%%%%%%%%%% END OF CODE %%%%%%%%%%%%%%%%%%%%%

Now, the problem is that i tried out various combinations of numbers and all of them worked out well, but suddenly i found out that whenever i was entering numbers in multiples of "19", the results were not correct. For example, when i entered "1" nineteen times, the correct result displayed by "sumfinal" should be "1", but it shows "9". So i tried it with "2" nineteen times, even then the result was "9", though the correct result should be "2". And surprisingly for "3" nineteen times the result was "-456". So could anyone please help me with this problem. And could you also provide with the bug-free code for this problem of summation of digits. PS: I have been programming in matlab since last 8 months or so, so i am quite experienced in that. secondly, if anyone says that "2" repeated nineteen times is large number , and will not be handled correctly by matlab, then its incorrect to say so, because for simple calculations also, extremely large numbers beyond imagination can be handled. So the "range" is not a problem. I use Matlab 7.

To show code in html enclose it within <pre>...</pre> elements. Can't help you with matlab, but here's some C code that i think does what you want.

void add_digit(char* a,int c) {

  if(!*a) *a = '0';

  c += *a - '0';
  *a = '0' + c % 10;

  c = (c - (c%10))/10;
  if(c>0) add_digit(++a,c);
}

void sum_digits(char* a) {

  char* sum = a++;
  while(*a) {
    int c = *a - '0';
    *a++ = '\0';
    add_digit(sum,c);
  }
}

int main() {
  char num[256] = "2222222222222222222";
  do {
    sum_digits(num);
    printf("sum digits: %s\n",num);
  }while(num[1]);
  return 0;
}

This works, as long as you don't mind reading the interim sums right to left.EricR 17:23, 16 April 2006 (UTC)

Good evening! I happen to believe that the sum of the digits of any number (base 10) is mod(num,9) where mod is the modulo function. If you have it, use it. --DLL 18:49, 16 April 2006 (UTC)

A simple one-line solution would be: "while(number > 9) { number = (number % 10) + (number / 10) }" This assume integer division on "number / 10". If you don't have that, use "floor(number/10)". In the end, "number" will be the one-digit sum. I didn't check this with a lot of numbers, but it worked for a handfull of them. --Kainaw ^(talk) 19:11, 16 April 2006 (UTC)

Well, if you've got arbitrary sized integers that works great. Try a few > 2^32 or 2^64. EricR 20:12, 16 April 2006 (UTC)

Face-to-face intercourse in animals

What animals, if any, engage in sexual intercourse face-to-face other than humans? (Subquestion: Does it even make sense to consider non-mammals?) Off the top of my head, it seems like most mammals go with a rear mounting, 'doggy style' if you will. Seems like whales and dolphins would have to go face-to-face, or belly-to-belly as it were. Seems like the other primates might be the only other animals capable of face-to-face intercourse, but I think they don't. Any information out there? --Ananda

• Bonobos face each other when copulating and are rather famous for it. --Fastfission 17:08, 16 April 2006 (UTC)
• From Missionary position, there's also armadillos. I could swear there was also an insect that uses the position; I thought it was aphids but Google isn't helping me there. Melchoir 04:31, 17 April 2006 (UTC)

SSL CRT

What is the difference between a CRT that I generate using Cpanel and one that I can buy from Verisign (and others) and later insert into Cpanel? — Ilyanep (Talk) 16:45, 16 April 2006 (UTC)

A certificate Cpanel generates is a self-signed certificate, which means a client program connecting to a server using such a certificate has absolutely no assurance the server is not an impostor (sure, I'm amazon.com, trust me, I say so myself, now, what was your credit card number?). Verisign is one of a number of certificate authorities that issue X.509 certificates. To get a certificate authority to issue a certificate you have to prove you're the owner of the IP address the server will run on, so if you trust the CA you can trust that you're not talking to an impostor - for more on this please see the articles on X.509 certificates and certificate authorities. -- Rick Block (talk) 22:56, 16 April 2006 (UTC)

Simple Javascript question

I'm trying to do some simple Javascript and I seem to have forgotten how to do use the DOM correctly. All I want is a function which will cycle through all of the checkbox elements with an id of "record" and set their "checked" property to "true". What's the best way to cycle through them all? I'm frustrated and not finding easy answers Googling around. --Fastfission 16:54, 16 April 2006 (UTC)

Could you just traverse the DOM tree?

function topDownTraverse(n) {

  // do something w/ the node

  for(var m = n.firstChild; m != null; m = m.nextSibling) {
    topDownTraverse(m);
  }
}

EricR 22:16, 16 April 2006 (UTC)

Solar Power

I'm wondering if anybody out there is very experienced with solar power.

I'm not very familiar with the terms involved with electricity and magnetism, so please bear with with me.

Approximately how large would a solar panel have to be, given the approximate average amount of sunlight available in North America, to keep a recharchable battery powerful enough to power a five watt light bulb, sufficiently charged to constantly have power available to turn the light on whenever needed?

If my question is confusing, if I'm using the term "watt" incorrectly or if I'm leaving out some other variable I'll gladly clarify it to the best of my ability. Thanks to anyone who can help me with this. Loomis51 17:06, 16 April 2006 (UTC)

Your question is perfectly alright...:-D ....and from the solar cell article:

When exposed to direct sunlight, a 6-centimeter diameter silicon cell can produce a current of about 0.5 ampere at 0.5 volt (equivalent to about 90 W/m² average, range is usually between 50-150 W/m², depending on sun brightness and solar cell efficiency).

So..i'd guess that'd give you a good idea of how big the panel has to be... Jayant,17 Years, India • contribs 17:45, 16 April 2006 (UTC)

Thanks for the link, but as I said, my knowledge of electricity and magnetism is very poor, so I can't really make sense of all the terminology. Could you tell me how all of that translates into the actual size necessary for the panel? And if I can ask a further question, would you have a rough estimate of what the cost of the panel and the battery would be? (Nevermind the bulb) Thanks! Loomis51 18:13, 16 April 2006 (UTC)

You are welcome... The terminology (90W/m^2) means that for every square meter of a silicon solar cell it produces about 90 W.... so..if you want to recharge a 5 watt bulb..... the area should be 0.055 square meters..... so the area should be around 60-100 square centimeters.... and as for the cost, i dont know about the price in North America since i dont live there...i'll try to search for the price on the internet and put it over here... Jayant,17 Years, India • contribs 21:09, 16 April 2006 (UTC)

Yeah...here we go... that site gives a lot of information on solar panels...and gives you some models for sale..... hope you find them useful...try calling up some of the phone numbers on the website and talk to them...... if you want more information, just ask...:-D ..Jayant,17 Years, India • contribs 21:18, 16 April 2006 (UTC)

Thanks Jayant, you've been a great help! If only all Wikipedians were as courteous and helpful as you. I'm sure I'll have a few more questions in the near future, but for now I'll check out the sites you mentioned. Thanks again! Loomis51 00:22, 17 April 2006 (UTC)

This is a very easy question. All you have to do is think in terms of ENERGY. A 5 watt light bulb comsumes 5 joules of energy per second. Assume that you need the bulb to be on 24 hours per day. 1 day = 24 * 60 * 60 seconds or 86400 seconds.

Therefore a 5 watt bulb requires 5 * 86400 or 432000 joules per day. So all you need to do is to calculate the (area) amount of solar panels to generate as least 432000 joules of electrical energy per day.

Solar panels tells you how much power (in watts) they generate in the "best case senario" so you need to account for the "worse case senario". Also remember that there is no sun light at night. So multiple the "watts" of the solar panel by the amount of sunlight in seconds and make sure you includes some redundancy for cloudy periods to get the amount of energy stored per day.Ohanian 04:43, 17 April 2006 (UTC)

Which Test To Find P-value And How Many Freedom Degrees?

I've done an experiment where we took ONE SAMPLE of neurones, extracted something from them, split it into two samples and measured the quantity of a chemical in the solution, comparing it to a control set of neurones which were treated more nicely during incubation. Do I have one or zero degrees freedom? Although a repeat was performed, it was using the same sample extracted from one set of neurones? How do I know which is the appropriate statistical test to find a p-value? -Username132 (talk) 17:54, 16 April 2006 (UTC)

Chronology / Inability to locate events in time or to remember dates

I stumbled across an interesting phenomenon: While I was trying to locate a painting to a particular epoch, I asked a friend. This friend told me that she cannot remember dates and does not have the ability to juxtapose events in for example political history with events in art history. In other words, a poem written in 1917 in England would not remind her of WWI and a possible connection, although she has had several curriculi in which WWI was a topic. She coined it - amusingly - date dyslexia. Now I am asking myself if there is an official expression for this "condition". Please do not propose laziness. Thank you! Don420 19:10, 16 April 2006 (UTC)

I don't know, I am inclined to think laziness, or at least an inattentiveness to context. ;-) --Fastfission 21:35, 16 April 2006 (UTC)

I'm a little confused. Would she be able to recognize a painting as one of WWI, from the style and content (no dates involved)?  freshgavinΓΛĿЌ  05:02, 17 April 2006 (UTC)

One Line C Program Signatures

Hey There

I've seen around a lot some seriously funky 1 line C/C++ programs that are commonly found in signatures that when compiled produce a really nice pattern or shape, such as:

main(c,r){for(r=32;r;) printf(++c>31?c=!r--,"\n":c<r?" ":~c&r?" `":" #");}

Is there a name for these, and if so, does Wikipedia have an article on them, or does anyone know of a place that lists them? I'd really like to know as i find them extremely interesting and astonishing how one loop can produce such amazing results. Thanks :) -Benbread 21:46, 16 April 2006 (UTC)

These are called signature programs, and there is no Wikipedia article on them (yet). One place with a list is http://www.iwriteiam.nl/SigProg.html. -- Rick Block (talk) 22:36, 16 April 2006 (UTC)

What a headbangingly obvious name. Thanks very much - I think i'll start working on that wikipedia article tomorrow (well, today, after i go to bed) -Benbread 23:13, 16 April 2006 (UTC)

Microsoft Excel

Is there a way so that I can write something in a cell without it continuing into next cell. It just stays in the cell you are typing in.

I don't have a copy of Excel available to me right now as I'm on a Linux system, but you should be able to choose Cell properties->Text format (or text alignment?)->wrap text, or something very similar, and any text which is too long for the cell will display over multiple lines. If the row height is standard, then you won't be able to see these lines, but you can adjust the row height should you wish. In OpenOffice.org, it's Format cells->alignment->Wrap text automatically, and you also have to choose Format cells->alignment->Vertical->top to get exactly the same result.

An alternative way of stopping long text in one cell from extending over the next (blank) one is to put a space in the next cell.

Is this what you wanted, or am I misunderstanding the question?-gadfium 23:20, 16 April 2006 (UTC)

It's under 'format cells', 'alignment' to wrap text. The other suggestion, putting invisible content in subsequent cells, will also work but is not recommended (most notably because excel deems any edited cell to be part of the: print area, edited area (for when you use the home/end keys to navigate, etc) and also for formula-related issues.--Anchoress 05:11, 17 April 2006 (UTC)

Thanks, I learned something too!-gadfium 05:30, 17 April 2006 (UTC)

April 17

Ramjet Project

I have been for three days attempting to build and test a stationary ramjet with no luck, I have read the ramjet article twice but I am still confused on the construction of the ramjet. So I was wondering if anyone could point me in the right direction or give me a link that explains the construction of a ramjet? I am looking for things like types of fuel ignition methods and just bassically anything on ramjets. Thank You. Patrick Kreidt

For one thing, I thought "stationary ramjet" was an oxymoron. The design requires it to be moving very fast through some medium. —Keenan Pepper 00:43, 17 April 2006 (UTC)

I agree with Keenan Pepper. A ramjet is probably not what you want. The external links on pulse jet engines might be useful to you.-gadfium 01:52, 17 April 2006 (UTC)

Well it can be stationary if you have a constant airflow, but that isnt my problem.

Not to be useless, but I'd imagine it would be pretty difficult to find any specific instructions for building a ramjet, simply because it's not the kind of thing people build from kits and most of the plans would be either highly top-secret or simply confidential.  freshgavinΓΛĿЌ  04:54, 17 April 2006 (UTC)

Can a substance conduct heat well but not eletricity (and vice versa)

Title says it all, but if it is true could you explain how. It's not hw and any help would be apprecaited.

I believe epoxy was designed for just that. I just can't remember whether it's excellent at conducting heat but not electricity or the other way around. Loomis51 01:24, 17 April 2006 (UTC)

A material is electrically conductive if it contains charged particles that are free to move around, like electrons in a metal or ions in a salt solution. A material is thermally conductive if mechanical vibrations (heat) are quickly transferred. Diamond and deionized water are both thermal conductors but electrical insulators, because their particles are strongly attracted to each other and spread vibrations quickly, but there are no mobile charged particles to conduct electricity. I can't think of a good electrical conductor that is also a thermal insulator, but I can't say for sure there aren't any. It might be because the charged carriers also conduct heat... —Keenan Pepper 01:29, 17 April 2006 (UTC)

Thanks.

Possible. One of the best examples would be the mica used as electrical insulator but thermal conductor in the electric irons - Wikicheng 06:11, 17 April 2006 (UTC)

Physics Problem

You place a 7.50 kg television set on a spring scale. if the scale read 78.4 N, what ist he acceleration of gravity at that location? Seems easy enough, I get an answer butr that isn't what the answer key "says". I went F = ma, F/m = a.... a = 10.45m/s/s.

The answer I'm given is 9.973m/s/s, and I have no idea how that's derived. Anyone know if I missed something or if I'm right? Thanks.

00:58, 17 April 2006 (UTC)

Perhaps a dyslexic teacher? As far as I can tell if the answer is 9.973 the scale should say 74.8N. -- Rick Block (talk) 01:22, 17 April 2006 (UTC)

Haha very nice. I have another question where I inexplicably get 312 instead of 321.....I'll assume it's right. Thanks.

01:30, 17 April 2006 (UTC)

Electromagnetic spectrum upside down?

Usually on a vertical scale the smallest number is on the bottom and the largest number is on the top or if the scale is horizontal the smallest number is on the left and the largest is on the right. The electromagnetic spectrum is always shown with the longest wavelengths (long electric waves, radio waves) on the bottom/left and the shortest wavelengths (X-rays, Gamma rays) on the top/right. I am wondering what is the scientific reason for doing this. Llarsson 01:20, 17 April 2006 (UTC)

I think it's probably due to increasing frequency (and therefore, energy) as you go up the scale. — Knowledge Seeker দ 01:24, 17 April 2006 (UTC)

It really doesn't matter. Frequency goes down as wavelength goes up, so either way you put it, one of the scales would go the "wrong" way. —Keenan Pepper 01:31, 17 April 2006 (UTC)

I understand that as wavelength increases, frequency decreases so one scale would go the "wrong" way. It seems to me though that since the electromagnetic spectrum shows waves and not frequency that one would lay out the scale to show wavelength increasing. Since it does not I wonder if it is more than just a 50-50 chance that it is laid out that way. Llarsson 01:50, 17 April 2006 (UTC)

BitTorrent

I need help with BitTorrent.

I downloaded a file from a search and then downloaded BitTorrent and opened the file with the program. It's finished downloading and I don't know where to go now so that I can view the video.

Thanks.

When you opened the Torrent file, you told it where to download the file to. Remember where you saved it, and use that location to open the file. Simple. Here7ic 04:16, 17 April 2006 (UTC)

Never lose porno, especially not when it is on a computer that other people also use. Open your downloads window and click the button that reveals the file location that you downloaded. Assuming that you haven't cleared the list, or do not use internet explorer. -- Mac Davis] ⌇☢ ญƛ. 06:11, 17 April 2006 (UTC)

is there a name for the tendency to see patterns?

I seem to remember at some point learning a name for the principle that humans tend to see patterns in random data where there are no patterns. Constellations, inkblot tests, that sort of thing. I seem to think there is someone's name associated to it, like "someone's law" or "someone's principle". Searching on the internet for a while provided nothing, and I'm starting to think that maybe I'm imagining it. Is there such a name? -lethe ^{talk +} 03:35, 17 April 2006 (UTC)

Gestalt psychology? —Keenan Pepper 03:57, 17 April 2006 (UTC)

Ink blots are the Rorshasch test. Probably not what you seek. GangofOne 05:15, 17 April 2006 (UTC)

Temperature of innerstellar or innerplanetary space.

I'm probably missing something here, but I can't find the temperature of either spaces. Help? Here7ic 04:14, 17 April 2006 (UTC)

The space itself has no temperature, though you can measure it by placing objects into the space. Google says that the temperature of a perfectly conducting object at the distance of Earth from the sun will reach about 280K/7C, and you can expect objects at interstellar distances to experience near zero-K temperatures, though I'm not sure how near.  freshgavinΓΛĿЌ  04:45, 17 April 2006 (UTC)

Edit: Google also says that an object very far from galaxies and stars will probably reach a temperature of about 2.7K. Cold!  freshgavinΓΛĿЌ  04:46, 17 April 2006 (UTC)

The thing about temperature is that there has to be some matter for which you're measuring the temperature of. Temperature, at the molecular level, is basically the speed at which the molecules within matter move. Space, by definition, is a vacuum. It's devoid of matter. Therefore, no matter = no temperature. It's true, some will tell you that there may be fine dust particles in space, but then you'd be measuring the temperature of the dust particles, not the space itself. Others will say that the temperature of space is absolute zero, absolute zero (theoretically) being the state where the molecules within matter are absolutely motionless. But still, there must be matter to be measured. Space being a vacuum, there is no matter within which molecules are motionless, so absolute zero is not the answer either. Bottom line: difficult as it may be to explain or comprehend, space has no temperature. Loomis51 05:08, 17 April 2006 (UTC)

Have to disagree about the neccessity for the presence of matter. What you say seems plausible, but not true. Even matterless space is filled with electromagnetic radiation that has a characteristic spectrum, (Black body spectrum). This is what's left of the big bang, when things were hotter and closer together. After expansion, the temperature of space is now, as was said above, 2.7K. It is literally, "the echo of the Big Bang". The discoverers of this b.b. radiation got the Nobel prize. It shows up most prominently in the microwave frequecies. B.B. radiation is a fetish object for cosmologists, a lot can be determined cosmologically from studing it; the exact spectrum is known to be identical to a standard black body spectrum. Some recent satellites that study it are COBE and WMAP. If the space in question HAS a gas in it as well, the gas molecules will have a range of velocites in a certain distribution. It is computed that the e.m. radiation (better spoken of as photons) with a black body spectrum would hit gas molecules in just the right proportions to give them the velocity distribution that they indeed have. If you like, you can think of so-called "empty space" as a "photon gas"; this is not an eccentric concept in physics terminology, but a conventional one. The explanation of b.b. radiation started with Max Planck, and was the start of quantum theory, so it's a big deal, not a minor detail. (Of course if you happen to be near a star, then the photon stream is larger and you have a higher T, as Google says.) GangofOne 05:41, 17 April 2006 (UTC)

You're wrong. The definition of temperature is the average molecular kinetic energy of the matter within a given volume. No matter means no temperature, by definition.

Nor, for the record, has anyone pointed out the fact that space is not, in fact, a pure vacuum; space is actually a rather bad vacuum - there's all kinds of particulate matter there. (See here for the various measures of the density of space). We can produce much better vacuums on earth with relatively simple vacuum pumps. If space were a perfect vacuum, space-craft would not need heating systems (because there would be nothing to conduct heat from the aircraft into space). So, getting back to the question at hand, the 2.7 degree kelvin measurement is almost certainly a reference to the temperature of this interspacial matter. Raul654 06:08, 17 April 2006 (UTC)

[Edit conflict, didn't read Raul's comment] You obviously know a lot more about what we're talking about than I do, so I'm sticking my foot out by saying that I find it hard to agree with you. I'm getting everything except the fact that you say the radiation left over from the big bang makes space itself 2.7K. It may be a semantic argument ... to experience or measure temperature (sense heat) requires absorption (loss) of heat in some way, and since space doesn't absorb heat or energy (as far as I know), I find it difficult to think that it could possibly have any, as you imply when you say the temperature of space is 2.7K. I'm having trouble finding the words but I feel like I'm dealing with a tree falling in the woods with nobody there to hear it.  freshgavinΓΛĿЌ  06:16, 17 April 2006 (UTC)

Here is a link [17]. The temperatures of space differ greatly. Space near a star is a lot hotter than space far away from any galaxy. -- Mac Davis] ⌇☢ ญƛ. 06:15, 17 April 2006 (UTC)

Street Lights

Would anyone know how bright a basic street light is in lumens? Not a traffic light but one of those lights that illuminate streets and highways after dark. I'm sure they're not all the same, so a reasonable range would do quite fine. Thanks! Loomis51 04:43, 17 April 2006 (UTC)