Wikipedia:Reference desk/Science

March 19

CO2 recovery and reuse

How difficult would it be to create a mechanical or chemical process to take CO2 out of the exhaled breath and reuse it to make soda water? —The preceding unsigned comment was added by 71.100.1.200 (talk) 02:35, 19 March 2007 (UTC).

Bubbling CO2 through solutions will cause it to dissolve, this can be observed by exhaling through a straw into a solution of bromothymol blue in a neutral solution of water. (do not do this without the aid of someone experienced in chemistry) This process isn't very complete though, rebreathers rely on a scrubber to remove the CO2 from the breathing gas, typically soda lime. Once it's bound chemically, there is probably some path that would convert it into relatively pure HCO3 sol'n, but it would cost way more than creating soda water the ol' fashioned way. -- atropos235 ✄ (blah blah, my past) 04:39, 19 March 2007 (UTC)

Sub-Lightspeed Craft

If a spacecraft where built and had the capabilities to travel at half the speed of light how much shieling would it need? For example in the Project Daedalus article there is a link that describes how Daedalus would need an erosion shield for travelling at twelve to sixteen percent the speed of light, they go further to say it would probably be made out of Berillium. So to restate the question how thick would a berillium shield have to be for a craft traveling at 50 percent the speed of Light? —The preceding unsigned comment was added by 68.120.225.214 (talk) 04:18, 19 March 2007 (UTC).68.120.225.214 04:19, 19 March 2007 (UTC)

Simply put, Project Daedalus is a fictitious foray by a non-technical group of space enthusiasts. The engineering and scientific claims are not necessarily realistic. To give a straightforward answer like "30 cm of beryllium shield" would be silly - it would assume that somebody has gone through the difficult engineering and design process for a non-existent spacecraft, making the necessary tradeoffs and compensating for a minimum level of safety. In a practical sense, it is impossible to make engineering assessments about technologies which are so distant from the present state of the art. (Present craft do not travel at even a remote fraction of that speed, so there is no way we could compare our designs against it in a meaningful way). Nobody can possibly forsee the actual required specs for a craft which is many many generations beyond present-day space vehicles. In the mean-time, you might look at the Atmospheric reentry to learn about real shielding on actual spacecraft. On a more philosophical note, some of these scientific studies, such as SETI, are not meant to actually yield conclusive answers about anything, but are more of a way to stretch our way of thinking. They shouldn't be taken at face value - in fact, any level of scientific analysis that goes into them makes it blisteringly self-evident that such projects are impossible (in the foreseeable future). Nimur 08:53, 19 March 2007 (UTC)

Granting Nimur's comments as true for actually building such a craft, it can still be fun and informative to do back-of-the-envelope calculations for this kind of thing. For example, you could take the density of matter in the interstellar medium, and calculate the explosive power of each of those atoms hitting your craft at at 1/2 c and see how far you can get with a given shield. --TotoBaggins 13:12, 19 March 2007 (UTC)

My idea is to clamp onto an metallic asteroid or even a small moon, and keep that in front of the spacecraft both as a shield and a source of material for a linear accelerator (which would eject particles at the speed of light for propulsion). It might not be as effective per meter as beryllium, but you would have many kilometers of this material between the occupants and particles. StuRat 15:52, 19 March 2007 (UTC)

in the Discovery channel they had a episode (cant remember the name of the show) in which they show a forcefeild generator. yes its a real one however the only problem with it is that it takes a machine the size of a bedroom to generate the energy to protect a can of soda. its acctually more like a plasma shield and had a blueish green look to it it was pretty awsome. Maverick423 17:05, 19 March 2007 (UTC)

Thank You all for the answers you have given me but I think it is sad to say that Daedalus is out of our time reach. I look at the rapid progress of technology and doubt almost nothing as far as how far technology can progress.67.127.164.153 03:04, 20 March 2007 (UTC)

direction of rotation for IC engine

What is the convention for the direction of rotation for an internal combustion engine?

And is it only the direction of rotation of the starting (electric starter motor, pull start or other) that determines this?

Thanks 139.163.138.10 04:53, 19 March 2007 (UTC)

You can't spin an ICE in a different direction than it was designed for, the cams will not open and close the valves at the correct time, nor will any of the devices (alternator, coolant pump, oil pump) connected to the engine with the fan belt work correctly when spun backwards. I'm not sure if there's a convention to the direction, but my Corolla's engine spins counter-clockwise when viewing it from the flywheel side of the engine. -- atropos235 ✄ (blah blah, my past) 05:40, 19 March 2007 (UTC)

Given that there are IC engines that will run backwards perfectly well then I think you might need to qualify your answer. Almost all would rotate backwards, they just wouldn't run. In a 4 stroke the valve events would be all wrong, you'd be unlikely to get it to run backwards, unless it had special timing gear and a special oil pump.

For car engines most run anticlockwise from the flyweel end, but historically many manufacturers have ignored it, including Honda for many years. Greglocock 06:46, 19 March 2007 (UTC)

Right, there's nothing fundamental about internal combustion engines (encompassing a very broad range of machine designs) that prevents them from rotating or even operating in either direction (nor anything that requires them to have a rotating shaft, for that matter). Many specific rotating-shaft ICE designs are built to only run in one direction, but I've seen (older) diesels that will actually run in reverse, though poorly. Sometimes the reason that the engine only runs in one direction is because it is optimized for efficiency that way. Of course the reasons for choosing any ICE design feature will vary depending on the application and the specific type of engine under consideration. -- mattb @ 2007-03-19T07:09Z

It seems to me that the sorts of IC engines used in model airplanes (those engines having no valves) would probably be perfectly happy to run backwards, although they wouldn't be of much use while operating in that mode. And, BTW, with the exception that its cooling fan probably would be less efficient, the alternator on a modern car engine would work perfectly fine running backwards.

Atlant 12:50, 19 March 2007 (UTC)

More PSU Shocks

I recently reported that I received an electric shock while simultaneously touching my PSU and a radiator, even though the PC was off. Today, I touched a PSU from a completely different (and two week old) computer and another radiator in the same house, and while the PSU was unplugged from the mains no less, I received a similar shock (although slighltly lesser in intensity), to that which I received a few weeks ago. What is going on? --Seans Potato Business 06:05, 19 March 2007 (UTC)

I would guess that it was you that shocked the computer in this case, not vice versa. -- mattb @ 2007-03-19T06:08Z

Maybe it's a recurring phenomenon with you because of some behavior or environmental circumstance. What sort of shoes are you wearing when working on computers? Do you drag your feet on carpeted floors (this can build a lot of charge!) Do you properly ground yourself to the chassis (at least by discharging yourself to the case, or if you really want to be a nerd, you can actually use a ground bracelet). This might prevent shocks in the future, it seems like you are particularly susceptible. Nimur 09:00, 19 March 2007 (UTC)

Putting aside the issue of shocks from static electricity, you need to know that PSUs have substantial electrical filters to prevent the egress and ingress of radio frequency interference (RFI) from/to the computer. These filters connect substantial capacitors from the chassis of the computer (and the "ground"/"earthed" terminal of the line cord) to both the hot/live power line wire and the neutral/return power line wires. The end result is that if you don't properly ground/earth the computer, the case will be floating at about 1/2 the line voltage and yes, you'll get shocked every time you connect yourself between the computer's case and something that is earther (such as your radiator). You may also get shocks from the monitor or any other part connected to the computer's case.

Properly ground/earth your computer.

Atlant 12:55, 19 March 2007 (UTC)

Can I improvise an earth by connecting the case to the radiator with a peice of wire/jumper cable? I dont want to go through the rigmarole of trying (and failing) to get the house properly wired since it's apparently not a legal requirement where I'm living. It's apparently not uncommon in the Netherlands. I rent one room and will be out of there in a few months tops, to go to university. Thanks for the advice so far. :) Seans Potato Business 16:12, 19 March 2007 (UTC)

It's probably a bad idea to have exposed wiring (grounded or otherwise) randomly attached between your computer and the radiator. I think the safest course is to have a professional electrician (or your landlord) take a look at the problem. Barring that, you should probably close up your computer case entirely and try not to touch it. You might have a serious issue at hand, you should avoid adding stray wires. Nimur 18:54, 19 March 2007 (UTC)

The rewiring suggestion is not applicable to my situation. I don't wish to go into why. It's surely a better idea to have an exposed earth connection than none at all. Seans Potato Business 21:30, 19 March 2007 (UTC)

Do not ever test for electricity by seeing when you get a shock, since electrocution is possible. Hardware stores and Radio Shack sell inexpensive digital voltmeters. The radiator would normally be grounded (earthed) through the cold water pipe to this planet most of us inhabit. But that is not guaranteed. There can be insulating fittings in pipe connections, and water meters insulate the building pipes from the water main ground unless an electrician has properly made a substantial and solid ground jumper around the water meter. Electric water heaters often leak AC to the water pipes and water supply. I saw a case where a bathtub was electrically energized by a thermostat wire which was exposed and touching a drain pipe. So it is possible that the couputer is somehow grounded, through a modem or phone line or broadband cable ground, and the current is going from an energized radiator to the ground on the computer chassis. Or as you assume the computer could be what is energized, through the power system or from an energized signal wire ground. Have someone knowledgable about electricity test with a voltmeter. A piece of metal pipe going into the ground is a pretty good reference groung for testing purposes. I have learned to doubt the solidness of various supposed grounds you find inside a structure, since there are an infinite number of ways for homeowners and hacks to miswire things. Running a "ground wire" from a computer to a radiator is not recommended, since you have no solid assurance that the radiator is actually grounded. Edison 14:22, 20 March 2007 (UTC)

If I use my voltmeter to compare the red wire from my PSU with the radiator, and it reads 5v, then must the radiator be earthed? --Seans Potato Business 01:29, 21 March 2007 (UTC)

Perhaps, but the trouble is that it's very hard to evaluate the "quality" of the earth that the radiator is providing. A good earth connection (ground) today might turn into a poor connection as things corrode or the plumbing is modified. Another concern is that if you flow any substantial electrical current (even the leakage current from your computer's PSU) into the radiator, over time, galvanic corrosion can occur elsewhere in your plumbing. It's less of a problem with ordinary AC mains current than with DC, but it's still bad practice. Edison gave the best advice: provide a real earth ground connected to a grounding rod. Failing that, you might be able to obtain an "isolation transformer" or isolating UPS and operate your computer from that.

Atlant 12:40, 21 March 2007 (UTC)

molecular vibrations

I may be the expert you are looking for (Author "Vibrating Molecules, 1971) This is a very large field, so I will welcome any guidance that can be offered. Peter Gans e-mail as userer name at hyperquad dot co dot uk Retired lecturer, Leeds University, UK petergansPetergans 07:59, 19 March 2007 (UTC)

Welcome! I see you've created an account already. If you'd like to contribute, you can edit any page by clicking the "EDIT" tab at the top. You might want to look at Molecular vibration to start. Feel free to hang around the Reference Desk as well. I've added a standard greeting at your user talk page so you can find some quick links to introductory material (how to contribute, how to edit, etc). Nimur 09:10, 19 March 2007 (UTC)

reticular fibers

is it possible for reticular fibers to have parenchymal function?

According to the article on reticular fibers, "Networks of these fibers make up [... the] parenchyma of liver, testis and lung." I'm not a med student, so I don't have a good grasp on what that means. -- atropos235 ✄ (blah blah, my past) 16:26, 19 March 2007 (UTC)

yeah i saw that but have doubts since i haven't read anything like that elsewhere...

Quick comment, if you don't want your IP address shown (as you keep removing the automatic {unsigned} tag from each post you write), you can create an account which will hide it. -- atropos235 ✄ (blah blah, my past) 21:58, 19 March 2007 (UTC)

Liquid conversion

Many drinks on the internet are posted in CL and I was wondering what that is converted into on 1 OZ ? It certainly cannot be 1-1 can it or maybe it is? —The preceding unsigned comment was added by 70.50.185.202 (talk) 16:06, 19 March 2007 (UTC).

"CL" could mean centiliter, though it would properly appear as "cL" or "cl". According to Google:

one centiliter = 0.338140226 US fluid ounces

one US fluid ounce = 2.95735297 centiliters

-- atropos235 ✄ (blah blah, my past) 16:15, 19 March 2007 (UTC)

Yes, they mean centiliter. Conveniently, one cL is almost exactly 1/3 fl. oz.; there are three centiliters to the fluid ounce. TenOfAllTrades(talk) 16:21, 19 March 2007 (UTC)

Or of course if you mean Imperial fluid ounces (which are a bit smaller than US), it's 0.35195008 fl.oz. --Anon, March 20, 2007, 22:15 (Imperial), um, (UTC).

Ear bleeding

(NOTE: This is a medical question, but I am not asking for medical advice; merely curiosity.) A number of the more fantastic TV shows and films I've seen show bleeding ears (from the canal, not the lobe) as part of particularly gruesome death scenes. However, I've never actually heard of it being a symptom of any disease, and my fairly in depth first-aid book carries no mention of bleeding ears, while the only mention on Wikipedia is ear bleeding caused by over vigourous ear-wax removal. So, are there any diseases or accidents, other than direct damage to the ear itself, which would cause this? Laïka 16:59, 19 March 2007 (UTC)

I'm guessing some kind of trauma to the brain or a burst eardrum might cause ear-bleeding. Otherwise TV shows would be a bit strange. "What happened to him, doc?" "Vigourous ear-wax removal, the silent killer." "Dear God!" -GhostPirate 17:09, 19 March 2007 (UTC)

When I had an infected tooth I bled from my ear. Anchoress 17:23, 19 March 2007 (UTC)

Wonderful soundbite! ---Sluzzelin talk 17:26, 19 March 2007 (UTC)

Thanks. My cat's breath smells like cat food. Anchoress 21:26, 19 March 2007 (UTC)

• Our article on Bleeding states "Externalised bleeding from the ear may indicate brain trauma if there has been a serious head injury...". Bleeding from the ear is also mentioned in Cholesteatoma. Johntex\^talk 20:00, 19 March 2007 (UTC)

In most TV shows, bleeding from the ear is meant to represent a posterior basal skull fracture. Leaking CSF from the ear would represent an anterior basal skull fracture, but doesn't look as dramatic.... - Nunh-huh 03:35, 20 March 2007 (UTC)

Ok, thanks for that! Laïka 08:13, 20 March 2007 (UTC)

I suspect (without evidence) that the movie makers like it because it's easier to trickle some fake blood out of someone's ear/nose/mouth and produce the impression of serious injury than it is to have their makeup people produce a really convincing external wound and tie the actor up in makeup for hours while they apply it. SteveBaker 14:38, 20 March 2007 (UTC)

Treadmills

While in the gym yesterday, I spent a half hour on a treadmill and it very apparent that the effort (which equates, I guess, to "work done" or calories burned) running X miles on a treadmill appears to be much less than for an equal distance running on a pavement. Discounting variation in terrain on road running, what I would like to know is, what is the major contributing reason for comparative ease of running on a treadmill? I can think of four significant possibilities:

• Enforced pace maintenance when running on the treadmill
• Cushioned running surface on the treadmill
• Lack of wind resistance when running on the treadmill
• Lack of leg energy used to "push forward" on the treadmill

I would guess that these are listed in order of least to most influential, but would welcome any pointers to expert analysis, particulary regarding the actual difference in leg energy expended in running on the spot compared with running forwards. Finally, is there any data available on the total amount of calories I would burn per mile of treadmill running v road running. Thanks. Rockpocket 19:16, 19 March 2007 (UTC)

Those are good possibilities, and if you were holding the handlebars of the treadmill, I will also propose reduced arm movement on the treadmill. − Twas Now ( talk • contribs • e-mail ) 19:36, 19 March 2007 (UTC)

• I would suggest that outside, no ground is perfectly level. You are going up and down hills or at least slight gradients. Not true on a treadmill. —The preceding unsigned comment was added by 74.134.146.52 (talk) 19:54, 19 March 2007 (UTC).

Scientifically, the main reason may be the treadmill base acting as a linear spring. There has been tons of studies looking at how to make springy running shoes, but they all flopped... --Zeizmic 20:13, 19 March 2007 (UTC)

• Pure speculation on my part, but I wonder if some treadmill manufacturers deliberately miscalibrate the system to make you feel happier about how much work you have done? Johntex\^talk 20:15, 19 March 2007 (UTC)
• I think Zeizmic's explanation is the correct one. The baseboard of a treadmill (the surface underneath the moving belt) is generally a rather springy plywood board. This gives a lower-shock impact (which is easier on the tendons of the ankle and knee) and gives a bit of energy return. That lower impact is the design goal - it cuts injuries, and makes the treadmill suitable for those recovering from injury (it's common for athletes who are recovering from injury to be told to walk or run on a treadmill, but forbidden from running on an asphalt or concrete surface). The energy return (the bounce-back from that springy surface) is a side effect of that, and indeed it will lessen the effort of a given run (although by how much I'm not sure). A very similar effect (with the same underlying design-goal) will be experienced when running on a nice rubber-crumb running-track. Darryl Revok 11:22, 20 March 2007 (UTC)

Incidentally, the energy usage of a treadmill can be increased by using an inclined treadmill, or by just increasing the pace. StuRat 13:09, 20 March 2007 (UTC)

forget the treadmill grab a bike. i lost 50 pounds in one month by bike riding every day for about 5 hours (not all at once) and i still ate like a pig =) but maybe the mountains had something to do with that. so if thats the case just make your treadmill incline to its highest point and trust me you will get a pretty good work out. Maverick423 15:19, 20 March 2007 (UTC)

Speaker wiring question

This weekend I helped my friend set up a home theatre system. The reciever is a Yamaha RX-V2500 like this one. We hooked up seven Definitive Technology speakers for the main room, no problem. On the "B speaker" connections, we rigged up a pair of Infinity outrigger speakers like these out in the back-yard. They also work fine, except that they don't provide enough coverage for the whole back-yard. We would like to add a second pair of speakers to the back-yard.

The question is, can we hook up a second set of these outdoor speakers in series to the first set? Thanks for your help. Johntex\^talk 19:55, 19 March 2007 (UTC)

If you meant in parallel, then yes, you can. However, the same power will be distributed over the speakers so each one might not be as loud. --Wirbelwindヴィルヴェルヴィント (talk) 22:54, 19 March 2007 (UTC)

Thanks for your reply. I actually did mean in series. Because of the way the wiring runs, it would be convenient to run the wire from the receiver to the first set of speakers (as they are wired currently) and then to take wire from each of the first speakers to the second pair. Would that work?

Part of the problem is just that the Infinity speakers are quieter than the Definitive Technology speakers. What my friend wants to do is to have both A + B on a once, so that the same music can be playing in the house and outside on the patio. However, the receiver does not have a seperate volume for A vs B. A volume that is good for the B speakers is deafeningly loud for the A speakers. We thought about putting a seperate volume control onto the B speakers, and we shopped for one. However, all the ones we saw at our Radio Shack would not accomodate the size wire we are using. I don't remember the gauge, but the wire itself is pretty thick and it is well protected for outdoor use. Having already purchased and run the thick wire, we are reluctant to replace it with cheaper, thinner wire that would fit into one of these volume control boxes.

So, is it possible to connect speakers in series, or is there a better solution? Johntex\^talk 23:04, 19 March 2007 (UTC)

Please check the specifications in the manual for the amp, and see if the series impedance (the sum of the individual impedances) is within the allowance for the amp. The amp is more of a concern than the speakers or the wire. Edison 04:45, 20 March 2007 (UTC)

First up, putting a second set of speakers in series is /safer/ than in parallel, so far as your amp goes. BUT you will make the original set quieter, in fact there is a very good chance that you'll end up with less noise outside than before. I wouldn't recommend putting speakers in parallel unless you understand the specs very well, or your amp has good output circuit protection. I wouldn't risk it. Really the best thing is to go and find another amp, then T the input to the first amp into the second amp, or take the line out signal from the first amp into the second one. Greglocock 07:36, 20 March 2007 (UTC)

Affordable solar panels

I'm an eco-conscious individual who rents his appartment (in Boston, MA) and whose wallet isn't too fat. I'm thinking of sticking a small solar panel on my roof to generate electricity, probably to sell it back to the grid. Is this feasable nowadays? And how much initial investment would such a thing (both the panel and hooking up to the grid, however you do that) cost?

Thanks,
Mike, 19:58, 19 March 2007 (UTC)

• It is feasible, but how feasible it is depends on many things. Climate is one, government rebates are another. The time to pay-back an investment in solar energy is typically 4-10 years, depending primarily on these fators. Our article on Solar power has a lot of info. Johntex\^talk 20:03, 19 March 2007 (UTC)

• And also see Deployment of solar power to energy grids. Johntex\^talk 20:06, 19 March 2007 (UTC)

If you're in Boston, you're probably getting energy from NSTAR, and as far as I can tell, they don't really do green energy :/ - that is, I don't think they don't have any programs to encourage or enable environmentally minded people like yourself to take initiative. Good luck though - I know you can connect solar systems into your house mains, but I wouldn't expect to get paid for it - could be wrong though. --18.214.0.135 04:14, 20 March 2007 (UTC)

Buying power back may be automatic. That is, the present meter might run backwards when you provide power. I'd aim to meet, but not exceed, the total power needs of the tenant. This means you would produce excess power on sunny days but not enough on cloudy days and at night. On the other hand, even if they don't buy back the excess, you can still provide it to your tenants as a plus ("reduced electricity bills during the day, due to solar cells on the roof") and possibly charge higher rent, as a result. This would be particularly valuable if you live in an area with insufficient power availability which has brown-outs or black-outs when all the air conditioners are on in summer. It does take quite a bit of power to run A/C, though, so you would need large solar panels. If not, at least they can run a fan when the A/C dies during a power outage. You might also want to consider passive solar heating. For example, conventional or vertical blinds, facing the Sun, which are white on one side and black on the other would allow the tenant to use the solar heating, but only when they want it. StuRat 13:03, 20 March 2007 (UTC)

Not particularly sure what the climate is like in Boston but if you use a fair amount of hot water, you may also want to consider a solar heated hot water system. Such systems tend to be more efficient then just generating electricity for obvious reasons. Of course, this would require plumbing and the like so may be too expensive for you Nil Einne 14:17, 20 March 2007 (UTC)

Electronics Express and walmart have the lowest prices on solar panels. walmart sells a panel that generates 12 volts for 9.99 and electronic express sells a 2X2 grid for 150.00 think that grid generates 240 volts. just rechecked *its been a while since i checked the site* no more 2x2 grids but they got a 18 volt panel for 16.00. however none of that wont do you any good if you got not light =P here is the link to the prices [1] and the link to the site[2] hope this helps you out with what your looking forMaverick423 15:24, 20 March 2007 (UTC)

Ok, thanks for the replies everyone! -Mike, 17:02, 20 March 2007 (UTC)

Mutation in nectariens

can someone explain how the mutation in the nectarines happens? why?—Preceding unsigned comment added by 83.135.36.133 (talk • contribs) 12:34, 2007 March 19

Well, the nectarine article says the fruit was grown in England as early as 1616, but that the history is "unclear". This source suggests they "probably originated in China over 2,000 years ago and were cultivated in ancient Persia, Greece and Rome." A few more details emerge here. -- MarcoTolo 23:10, 19 March 2007 (UTC)

The mutation is in the peach gene g (glabrous, "without hairs, smooth.") The mutation appears to be spontaneous, singular (i.e. just one mutation is all it takes), and is recessive (perhaps in Blake MA, "The JH Hale peach as a parent in peach crosses" Proc Am Soc Hortic Sci, 1933). -- MarcoTolo 23:23, 19 March 2007 (UTC)

earth and space science

fraction of difference between two fixed temperatures is called what?

${\cfrac {\Delta T}{T}}$ ? This sounds like carnot engine efficiency, but I might be misinterpreting your question fragment. Nimur 23:15, 19 March 2007 (UTC)

Or it could be just ${\Delta T}$, from ${\Delta T}={\cfrac {T_{1}}{T_{2}}}$ [Mαc Δαvιs] (How's my driving?) ❖ 05:45, 20 March 2007 (UTC)

$\Delta T$ would generally indicate a difference, not a fraction: $T_{2}-T_{1}$. -- mattb @ 2007-03-20T13:19Z

What is the complete breakdown for X55 Cr Mo V14?

I can find Cr (Chromium) and Mo (Molybdenum). These are used in selling knives as the materials the knife is made of.

Thanks,

Chris

V could be vanadium, which is used in some high-temperature stainless steels. From preliminary search, this means that the Chromium + Molybdenum + Vanadium total percentage is 14%. I can't find information on the X55. See our steel article or Stainless_steel#Types_of_stainless_steel... there's similar nomenclature in the latter article. It seems that steel standards are proprietary and expensive: this handbook costs >$500US! Nimur 23:08, 19 March 2007 (UTC)

out feet

Was wondering what may cause feet to be facing to the sides with respect to the movement of the person and what effects may this bring

—The preceding unsigned comment was added by Bastard Soap (talk • contribs) 21:39, 19 March 2007 (UTC).

No idea what causes it but my mum used to tell me off if she saw me walking at "ten to two". I happen to notice that the majority of people who walk like this have a rather 'lazy' looking posture, whereas I tend to walk a little more forest-gump like (???). ny156uk 21:56, 19 March 2007 (UTC)

Could be for stability. When I took fencing lessons, I was taught that my feet should be at 90 degrees to each other. Clarityfiend 22:35, 19 March 2007 (UTC)

This is called pronation of the feet, and may be due to flat feet. Here is a web article about it. If you are a runner, you should try to avoid this, as it has negative ergonomic effects and can adversely affect your speed. Nimur 22:55, 19 March 2007 (UTC)

(Insert standard medical disclaimer here). The illustration looks more like femoral retroversion to me. What effects this may have depends largely upon the age of the individual in question (i.e. its normal in infants, but may be somewhat concerning in adults). There is a good review of lower limb issues in children in the journal American Family Physician from August of 2003 (link). -- MarcoTolo 23:02, 19 March 2007 (UTC)

I heard an aunt describing a course to improve elderly people's balance in which they were told to walk like this for the improved stability. Aaadddaaammm 08:06, 20 March 2007 (UTC)

Also, I personally seem to have my feet attached to my legs in such a way that I either walk with my feet facing slightly outwards, or my knees facing slightly in. Seriously, if I extend my legs straight out with my knees facing up, my feet face out. Since, like Ny156uk, my mum told me off for walking with my feet facing outwards, I walk with my knees facing in. It hasn't seemed to lead to any problems, other than shoes wearing out in an uneven pattern, but I would advice anyone else in this situation to consult with an appropriate doctor to determine which manner of walking would be best before they settle into a pattern and their bones form to accomodate it! I assume this can't be too uncommon. <OT>I suppose I got a slight wiggle to my walk for my troubles, which is no bad thing, but I also got mocked by PE teachers for my running style.</OT> Skittle 17:22, 20 March 2007 (UTC)

Some martial arts and yoga often have you place your feet parallel rather than like the illustration. This always seemed unnatural to me. Any thoughts on this? —Pengo 13:28, 23 March 2007 (UTC)

science

What is the chemical symbol for sodium chloride and what is its compound's molecular weight?24.148.188.8 23:20, 19 March 2007 (UTC)

Did you look at our article on sodium chloride? --Wirbelwindヴィルヴェルヴィント (talk) 23:26, 19 March 2007 (UTC)

Focal point of an earthquake

What is the point on Earth's surface directly above the focus of an earthquake?

The epicenter. Did you check earthquake? Nimur 23:34, 19 March 2007 (UTC)

I'm not familiar with "focus," I learned it was "origin" or "hypocenter." [Mαc Δαvιs] (How's my driving?) ❖ 05:44, 20 March 2007 (UTC)

All three terms mean the same thing in this context. Note that this contrasts with the popular use of "epicenter" (of some other sort of phenomenon) to mean its origin or focus, and also with the use of "hypocenter" to mean the point on the Earth's surface directly below a nuclear explosion (otherwise called "ground zero"). --Anonymous, March 20, 2007, 22:19 (UTC).

March 20

Medical term needed

what is the equivalent Medical term for the tamil disease "Akki" —Preceding unsigned comment added by 122.164.132.63 (talk • contribs)

Herpes? [3] --David Iberri (talk) 01:52, 20 March 2007 (UTC)

(EC)This site claims that akki is Herpes simplex. -- MarcoTolo 01:54, 20 March 2007 (UTC)

Magnavox MWD2205 4 Head VCR/DVD Player Issues

I lost my manuel, and I am trying to find out if there is a tracking button on the player or the remote so that I can fix the tracking on a VHS tape. —The preceding unsigned comment was added by Andreagambler (talk • contribs) 03:28, 20 March 2007 (UTC).

• Owner's manual here; [4] --BenBurch 07:35, 20 March 2007 (UTC)

MONTREAL PROTOCOLS

By Who was the protocol developed ??

What are the major gudielines and how are they monitored ??

are there any consequences ?? —The preceding unsigned comment was added by 59.101.237.5 (talk) 10:07, 20 March 2007 (UTC).

Montreal Protocol. It is usually easier to check the article before posting here. —The preceding unsigned comment was added by 128.12.131.62 (talk) 10:27, 20 March 2007 (UTC).

Body colour changes due to diet

A while back I knew this person who had some sort of device with two metal prongs that they put in a glass of water. They claimed that it was silver and putting silver into the water. Also they claimed that if they drank too much they could turn grey. Sorry to be vage but thats all I have. Can anyone shed some light on this? I've heard they if humans drink too much carrot juce they'd turn orange but this really puzzeled me. Thanks! Think outside the box 12:19, 20 March 2007 (UTC)

That's not too vague. Both are true. Excess consumption of colloidal silver causes argyria. StuRat 12:40, 20 March 2007 (UTC)

Wow! I should warn them. Thanks for that StuRat Think outside the box 13:03, 20 March 2007 (UTC)

You're quite welcome. StuRat 00:45, 24 March 2007 (UTC)

We have a sugar + colourings + additives + orange juice drink called Sunny Delight in the UK. It was really popular amongst kids about ten years ago. I remember reading in the paper about a kid who turned orange after drinking pretty much nothing else but Sunny Delight. As for the colloidal silver, take a look at Stan Jones - probably the most notable grey/blue skinned man in the world. --Kurt Shaped Box 13:06, 20 March 2007 (UTC)

Too much carrot or carrot juice can result in an orangey tinge to the skin. It appears to be something that may occur, especially when a infant switches to solids. Do a google for orange skin or carotenemia Nil Einne 14:10, 20 March 2007 (UTC)

Carrots contain carotinoids, which are pigments, also responsible for autumn leaves and beetroots :) A lot of flamingo's food contains carotinoids, which is why they are pink :) If it works for them, it is likey to work with other animals too :) HS7 14:17, 20 March 2007 (UTC)

This isn't quite the same, but a lack of iron leads to paler skin :) HS7 14:32, 20 March 2007 (UTC)

We have Sunny Delight in the US too and everytime a girl drinks too much and becomes orange she gets a five second blurb on the news. [Mαc Δαvιs] (How's my driving?) ❖ 15:28, 20 March 2007 (UTC)

Hilariously, people here went through a phase of thinking that Sunny Delight was some sort of 'health drink'. There were a few stories in the press about it making kids' teeth fall out too... ;) --Kurt Shaped Box 16:02, 20 March 2007 (UTC)

That's the way they advertise it, sadly. Dump a bunch of corn syrup in, add 1% juice and dump seven packets of ascorbic acid into it and you have a 100% VITAMIN C SPORTS DRINK THAT'S COOL AND HEALTHY! -Wooty Woot? contribs 23:10, 20 March 2007 (UTC)

That's 'cause it is :) [Mαc Δαvιs] (How's my driving?) ❖ 18:15, 21 March 2007 (UTC)

CRO

how a cro can be used to measure L,C,and self capacitance of an inductor?

You'd really need a signal generator as well. Beyond that, all that's necessary is an impedance bridge and some simple linear algebra. -- mattb @ 2007-03-20T13:23Z

What is a cro? A raucous bird with its final consonant amputated? A (something) (something) oscillator? A cathode ray oscilloscope? Something that goes with Magnon? Edison 14:09, 20 March 2007 (UTC)

An oscilloscope could obviously measure the change in electric current over time (given a known source voltage and source resistance). This would allow you to calculate the L and R components of the inductor. (A square-wave or pulse generator might make this easier by allowing you to create a repetitive waveform.) For self-capacitance, I think you'll need to identify the resonant frequency and this means the use of an appropriate signal generator. Presumably, this is a homework question so I'll leave it to you to work out the details of test-circuit arrangement and mathematics.

Atlant 15:58, 20 March 2007 (UTC)

Yeah, you could manage without a signal generator, perhaps by generating a step function of sorts with a good switch ('twould need to have nearly no contact bounce). Even so, methinks this is less precise than methods using a signal generator. -- mattb @ 2007-03-20T21:50Z

I assume you want to measure separately, some inductance, some capacitance, and then the self capacitance of an inductor. There are some equations to help on this:

e = L di/dt

i = C dv/dt

f= 1/(2pi* sqrt LC)

So if you applied aknown di/dt to an inductor and measured the voltage, you could find the inductance.

Also, if you provided a steady current to a capacitor and measured its dv/dt you could calculate its caopacitance.

The third is a little more tricky, becuyase you have all 3 elements in the equivalent cct. Inductance, capacitance and resistance. Agree with Atlant, you need to find the inductance and then the self resonant frequency. You can then calculate the self capacitance.

8-)) —The preceding unsigned comment was added by 88.109.124.137 (talk • contribs).

Well, thinking a bit about what mattb was saying, I guess I was presuming some sort of electrical "impulse" generator, even if it was only a switch connecting the voltage source. A storage 'scope would be handy, allowing the observation of single-shot events. Otherwise, some sort of relaxation oscillator would be useful so you can have repetitive events. (In some old 'scopes, the horizontal trace signal was externally available and could be used!) Given an impulse, I guess you could evaluate the self-resonant frequency based on provoking ringing of the inductor; we used to test "flyback" transformers (television Horizontal output transformers) in that way. Then one could apply the various formulae.

Atlant 12:46, 21 March 2007 (UTC)

Yes, and I was (perhaps too presumptiously) assuming a scope with storage capabilities when I mentioned the single pulse measurement method. -- mattb @ 2007-03-23T02:45Z

Blonde Hair/Blondes

a quastion on genetics. Do pepole with blonde hair(real ones) have to posses other blonde facial hair : as eyebrows , beards and so on ? —The preceding unsigned comment was added by 82.81.145.66 (talk) 16:15, 20 March 2007 (UTC).

No. Body hair is often a different colour from head hair. Indeed, most natural blondes will have darker body hair. Rockpocket 17:23, 20 March 2007 (UTC)

Spelling note: Hair is blond, not "blonde". A blonde is a woman with blond hair. A man with blond hair is a blond (no "e"). --Trovatore 17:28, 20 March 2007 (UTC)

If anyone's curious, Blond#Etymology.2C_spelling.2C_and_grammar explains some of the spellings. -- Diletante 17:51, 20 March 2007 (UTC)

There is a illness in which a person has their whole body hairs white or blond. cant recall the name but i know its because they lack pigment in their bodys which if exposed to to much sunlight can cause some painful and sometimes deadly sideeffects. Maverick423 17:37, 20 March 2007 (UTC)

Albino. Clarityfiend 17:49, 20 March 2007 (UTC)

Interesting to hear that natural blond(e)s often have darker body hair, Rockpocket. It would be enlightening to know more about the genetics of that. For example, I know that while the genes that code for red hair on the head are generally recessive to everything other than blond hair, the linked gene(s?) for red 'Grown-up hair' appear to be dominant. How does the blond head/ dark body fit? Skittle 18:17, 20 March 2007 (UTC)

The answers to those questions aren't known, Skittle. The only gene that has a number of commonly found alleles that are strongly associated with human hair colour is the MC1R gene. Loss-of-function alleles are strongly associated with red hair. In most non-human mammals, MC1R is agonised (activated) by melanocortin hormones (proteins derived from pro-opiomelanocortin) to produce black/brown eumelanin pigments. An alternative agonist of MC1R is Agouti signalling peptide (ASP), when it binds to MC1R the protein "switches" the cascade to produce red/yellow phaeomelanin. So in non-human mammals, by controlling the production of ASP and melanocortins (either in a autocrine, paracrine or endocrine fashion), the animals can make yellow/red or black brown hair. You can see how spatial control of these proteins could result in different hair in different parts of the body. Infact, this mechanism is known to control the dark back/light belly colouration seen in many animals.

So, it was tempting for pigmentation biologists to hypothesize that the same type of system controlled variable pigmentation in humans. However, there proved to be a problem with this theory. Firstly blond hair in humans is actually a form of "light" eumelanin rather than phaeomelanin (which produces red hair in humans). Its not entirely clear why this type of eumelanin appears blond, but its thought that variation in the structure of the pigment-complex alters its pigmentary properties. But this is why both blondes and brunettes often tan well, while red-heads don't. Also, ASP doesn't appear to be involved in human pigmentation at all, instead human MC1R appears to have a level of endogenous activity which is ramped up on binding to melanocortins, but not "switched" by an alternative agonist. The production of phaeomelanin (red hair) in humans results on the reduction of the endogenous activity caused by loss-of-function mutations. So, the genetics of dark/blond hair are not known at the moment. Neither is the exact mechanism behind the difference in head hair/ body hair colour in humans, but there are clues. Its thought likely that paracrine hormone production is involved, since body hair production increases, darkens and thickens as we become sexually mature and body hair is almost always darker than head hair in blondes, never lighter.

I'll leave you with an interesting finding from the human MC1R red-hair studies: it was found that there was a corrolation between being a heterozygote ("carrier") for a loss-of-function MC1R allele and having gingerish facial and/or pubic hair, when head hair was not red. I, myself, have a "touch of red" when I grow a beard (I'll spare you the details of my pubes). So I genotyped myself and, true enough, I have one allele that is associated with red-hair and one that functions normally. Why this heterzyogote effect applies only to the body is unclear, but a similar genetic heterozygosity (in yet known genes) may account for differences in blondes also. But, moral of the story: if both you and your partner do not have red hair, but do have ginger pubes, then the chances of you having a red-hair child is significantly increased. End of public service announcement (with apologies for the length of this reply). Rockpocket 19:17, 20 March 2007 (UTC)

Thanks. That was a little beyond my biology, but I got the gist, and I think I'll have to reread, looking things up. Oh, and the last bit was sort of what I was refering to above. Skittle 20:45, 20 March 2007 (UTC)

Just to make sure u are talking about facial hair. it is clear to me that the blond color don't appear on the whole body hair , but mostly blond pepole also have blond eyebrows and blonde beards , I never saw a blonde (convining enough) that has black eyebrows so I'll repeat the quastion , does blonds always have blond eyebrows and other facial hair. btw the thank you for the spelling remark , the reason for the mistake I guess is the fact that I don't live in a country where English is the native language .

Its all depends on how you define the colour "blond". True, I have never seen a natural blonde with black eye brows or beards, but there are plenty with darker eyebrows and beards than their hair colour. A lot of blond men will have reddish beards also. My wife is a natural blonde and has what I would call "light brown" eyebrows (she doesn't have a beard). That said, her eyebrows do tend to turn more blond in colour when she has been exposed to the sun for a period of time. Rockpocket 20:27, 20 March 2007 (UTC)

No, I have very blond hair and my eyebrows are quite dark. In fact, the carpet matches the drapes. On top of that, my beard is reddish brown (russet?). − Twas Now ( talk • contribs • e-mail ) 05:06, 21 March 2007 (UTC)

There's quite a lengthy article in a recent edition of Science covering this very topic.

Atlant 12:54, 21 March 2007 (UTC)

Just to complicate things- I used to have blond hair, but it has been slowly turning brown for the last 18 years, and I still have very light coloured hair on my arms, legs and moustashe, whilst the rest of my hair is much darker :) HS7 19:22, 21 March 2007 (UTC)

Splitting Hairs

I have very thick wavy hair and have the constant problem of split ends. It seems that no matter what I do, I just have a whole bunch of them. Then it got me thinking: Is there a genetic benefit for humans to have this condition? And while we are at it, was there a genetic benefit to have straight hair whereas in Africa, to have curly hair? —The preceding unsigned comment was added by Juliet5935 (talk • contribs) 18:15, 20 March 2007 (UTC).

In early humans (long long time ago when we still followed the rules of selective reproduction) hair could play two roles. It could provide a benefit, such as providing warmth is cold regions or shielding from the sun in hot regions. Also, it may be used for sexual attraction. In modern times, pretty much all humans reproduce with no regard for genetic fitness, so it doesn't matter anymore. --Kainaw ^(talk) 19:34, 20 March 2007 (UTC)

Whoa, there. Saying that "pretty much all humans reproduce with no regard for genetic fitness, so it doesn't matter anymore" is simply not true. It is true that what made one fit in previous generations no longer does so today--nearsighted people don't get eaten by the nearest tiger--but as long as there are variations among people, some will be genetically "fitter" for their environment and more likely to leave more offspring. The environment may have changed, and the rules of selection may be different, but just because they don't follow your notion of fitness doesn't mean they don't exist. grendel|khan 15:19, 21 March 2007 (UTC)

I pointed out "genetic fitness". The two primary factors that correlate to the number of children per woman are financial means and education level. Those with the most poverty and least education have the most children. Those with the least poverty and most education have the least children. It is a stretch to claim that genes are a major factor in poverty and education. --Kainaw ^(talk) 16:29, 21 March 2007 (UTC)

To get back to the original question, I'd expect split ends to lead to "frizzy" hair, which might be better at keeping cool in hot climates. I would expect blonde frizzy hair to be prevalent in Africa, but blonde hair must have some other disadvantages, like making you easy to spot by predators and prey. I'm guessing that by the time blonde hair developed, people were mostly farmers and herders, not hunter-gatherers, so this issue was less important. Straight, dark hair that mats down is probably best for retaining heat in cold climates, like Eskimo hair. StuRat 21:37, 22 March 2007 (UTC)

This is pure speculation - there is no data to back it up, nor is it even a likely scenario.

For most people, split ends are simply the result of hair trauma. Asking if there is an evolutionary advantage in that situation is like asking whether there is an evolutionary advantage to having a broken arm.

Its entirely normal for the distal ends of long hair to be damaged because each particular shaft has has been washed, brushed, and manipulated literally thousands of times. According to David de Berker et al (Clinics in Dermatology, Volume 19, Issue 2 , March-April 2001, Pages 129-134) "it is normal for hair of 1 meter in length to have split ends and damaged cuticle. When the same changes are seen in hair of 20 mm, it either means that the hairs have been exposed to excessive heat and perming processes or that there is something intrinsically wrong with the hair". That said, if you have short hair, and have not exposed it to extreme conditions, then you may have a condition such trichothiodystrophy, trichorrhexis invaginata, pili torti, monilethrix, pseudomonilethrix... the list goes on. The cause of most of these conditions are either unknown or as a result of some keratin mutations. In the latter case your hair would be the least of your worries.

As for split ends leading to frizzy hair, leading to the ability to keep cool, leading to prevelence in Africa. Total nonsense. Frizzy hair, such as those found in Africans, has nothing to do with split ends whatsoever. The curliness of hair is determined by the basal area of the follicle, with the bending process linked to a lack of axial symmetry in the lower part of the hair bulb. (See Sebastien Thibaut et al, Biology of hair shape, International Journal of Dermatology, 2005, 44, (Suppl. 1), 2–3). Finally, the only data available of pigmentation and human evolution strongly suggests positive selection due to the solar protective qualities of black, curly hair and skin, over blonde straight hair and white skin. There was no mention in that paper of the selective pressures of lions prefering the taste of easy to catch white skin over black. So the bottom line is that we don't know what advantage curly hair might provide to our African friends, but we do know that it has enhanced solar protective qualities. The most parsimonious explanantion, based on what we do know, would be that this pressure was relaxed in more northern climes and therefore curly hair was lost by genetic drift, or by sexual selection against. Rockpocket 03:04, 23 March 2007 (UTC)

You seem to be confused between frizzy hair and curly hair, they are not the same thing at all. Frizzy hair is caused by split ends, while curly hair is caused by elliptical cross sections (versus circular cross sections for straight hair). It is quite common to have straight, frizzy hair. StuRat 05:08, 25 March 2007 (UTC)

Your sexual selection theory is pure speculation with no data to back it up. Mate selection will generally favor features which are advantageous in a particular environment, as any individual which selects mates based on features which are disadvantageous to survival will be less likely to pass on their genes. There is a notable exception, in the form of "health indicators", such as the male peacock's tail feathers. While having large tail feathers is not in itself helpful for the bird's survival, the ability to grow the feathers shows the bird must be otherwise healthy, so is a good choice for a mate. StuRat 14:22, 23 March 2007 (UTC)

Once again, you are speaking total nonsense. At least two notable experts in the field have proposed that very theory with regards to hair colour. Firstly Jonathan Rees (Professor of Dermatology at Edinburgh University) has suggested sexual selection as a mechanism based on a study of the number of red and blond haired woman represented in Renaissance art (when in reality the number of woman with hair that colour would be low in the population). His theory is discussed in detail in by Marion Roach in Roots of Desire: The Myth, Meaning and Sexual Power of Red Hair, Bloomsbury USA, 2005. [ISBN 1-58234-344-6]. Secondly, and more convincingly, Peter Frost (a Canadian anthropologist) presented evidence in European hair and eye color: A case of frequency-dependent sexual selection? (Evolution and Human bahviour, Volume 27, Issue 2, Pages 85-103, 2006) that there was an operational sex ratio (OSR) in early Europeans leading towards a male shortage. He concludes that such an "OSR imbalance would have increased the pressures of sexual selection on early European women, one possible outcome being an unusual complex of color traits: hair- and eye-color diversity". The only study (PMID 10733465) that has attempted to determine whether true Darwinian selection, as you propose above, played a role in hair/skin colour in Europeans found no evidence for such pressures. Your comments above demonstrate you clearly do not understand human evolutionary genetics at any level of sophistication, perhaps you should restrict yourself to providing directions to reliable sources on this subject, rather than misleading readers with woefully innacurate theories. Rockpocket 17:28, 23 March 2007 (UTC)

Your evidence is weak. The best evidence you can find is someone saying "one possible outcome being...", which is clearly just their own speculation. One wild speculation based on another is not fact, and you should not represent it as such. Furthermore, if you are so incapable of engaging in civil debate that you need to lie about what your opponent says in an attempt to win ("lions preferring the taste...") then you have no place on the Ref Desk or in Wikipedia. Also, if you want to be taken seriously, learn how to spell or at least how to use a spell-checker. StuRat 23:08, 23 March 2007 (UTC)

The evidence isn't particularly strong and I never said it was fact, instead I phrased it as "the most parsimonious explanantion, based on what we do know". This is a perfectly accurate description it, because there is evidence, published by experts in reliable journals (you could try reading the entire article rather than making judgements from a single quote). Their analysis is of value, because it is educated; yours is not. My comment about lions was an obviously tongue-in-cheek aside. If you didn't get the inference, let me rephrase: there is no published data suggesting "blonde hair must have some other disadvantages, like making you easy to spot by predators and prey". The Ref Desk is not the place for "civil debate," it is the place for providing direction to expert information. When you start providing that instead of wild theories without any basis in reality, I'll take advice from you. Rockpocket 02:29, 24 March 2007 (UTC)

Preferring the speculation of an "expert" over the speculation of everyone else is just an argument from authority. If there is no proof, there is no proof, regardless of who makes the claim. A scientist's guess is no better "evidence" than anyone else's guess. If there were any actual facts to support his speculation, I'm sure you would have mentioned them. Incidentally, you also need to work on your grammar, as "description it" is not a valid phrase. StuRat 13:17, 24 March 2007 (UTC)

good control theory book?

I'm looking for a good book on Control theory, particularly PID controllers and their tuning. (I know the basics about these subjects, but would like to know more.) Something nicely practical, not merely abstrusely theoretical. Anyone got any recommendations? --Steve Summit (talk) 18:17, 20 March 2007 (UTC)

I was going to suggest my Control Theory textbook from a few years ago. Then I realized I couldn't remember the title, or the author. I went to get it, and realized that I left it in the last state I was in. It probably wasn't such a good Control Theory book after all, I guess. However, I do remember from that class that there was a highly-experienced industrial roboticist who was working on his degree after some ten years in the field. His anecdote is that "in practice, you tune a PID by trial and error." I had formal theoretical training before practical experience, so I beg to differ, but there is still some merit to that approach. If it's practical-knowledge you want, you might look in to a book on mechatronics instead of control-theory - the overlap is significant, but the treatment tends to be much more practical. Nimur 17:55, 22 March 2007 (UTC)

swollen legs

Hi, my mum's lower extremities(legs) ve been swollen for the past 5days now and she claims the problem is from her heart,she said her heart is not pumping well,that's why her legs are swollen.But i dont get it,please how is the swollen effect connected to the heart? couldnt it be edema nor blood cloth?please i need some clarifications on this and also the cause of the problem.(Note- is not a medical advice,is just to clarify my curiosity.) thanks

For starters, you can read up on congestive heart failure and interstitial fluid. Anchoress 18:44, 20 March 2007 (UTC)

Of course, she should definitely see a doctor in any case (I'm assuming my writing that doesn't violate the medical advice rules). $\sim$ Lenoxus " * " 19:03, 20 March 2007 (UTC)

See Eclampsia - often due to high blood pressure. Pregnant women are particularly prone to this. It's quite dangerous. But "See A Doctor" is the only advice we're allowed to give. SteveBaker 20:27, 21 March 2007 (UTC)

The eclampsia article makes it sound like it's a pregnancy-only syndrome. Anchoress 01:13, 23 March 2007 (UTC)

• If your mum hasn't seen the doctor, she should. --BenBurch 02:06, 22 March 2007 (UTC)

Daily intake of nuts

I've seen this so many times but now that I'm looking I can't find it. What's the recommendation for daily intake of nuts for health? Is it a handful, 30g, what? Anchoress 18:51, 20 March 2007 (UTC)

I can't find a simple answer from the USDA... here is information for the total meat/nut/bean consumption, but not specifically nuts. Nimur 19:32, 20 March 2007 (UTC)

Thank you very much for that link; I will bookmark it for use with other projects. What I'm looking for is the advice on nuts only (not legumes or other proteins) with regards to the beneficial qualities of nuts' omegas, other good fats, and other micronutrients. Anchoress 19:54, 20 March 2007 (UTC)

I don't recall ever having seen a campaign for "nuts". Unfortunately these days, a lot of dietary information seems commercially driven: meat, milk, eggs they all have "foundation" seem to go on about "recommended portions" but the truth is, there isn't one single food group which can't be substituted out of a diet, which may very much be the case for nuts. I personally don't eat a lot of nuts and I bet a lot of people don't ever eat nuts, in fact, there are people who are fatally allergic to nuts. So my guess is, there simply is no accurate recommended daily intake of nuts, as long as you don't exceed any other intakes such as 'oil' or 'salt' or whatever else. Vespine 21:57, 20 March 2007 (UTC)

You can get more than the recommended daily intake of nuts here at the reference desks...or were you talking about those nuts? Clarityfiend 02:16, 21 March 2007 (UTC)

Yeah I know, I think I've already OD'd today. Anchoress 02:31, 21 March 2007 (UTC)

Here is a ref from 2001:[5] that says an ounce (30g) of buts five or more times a week reduces risk of coronary artery disease by 25 to 39% (assuming you aren't allergic, of course).Edison 13:47, 21 March 2007 (UTC)

Yeah, that's exactly the kind of thing I was looking for. Thank you!!! Anchoress 18:26, 21 March 2007 (UTC)

surely it would reduce the risk even if you were allergic :] HS7 19:19, 21 March 2007 (UTC)

Correct, if you die of anaphylactic shock, that substantially reduces your future risk of heart disease. StuRat 21:27, 22 March 2007 (UTC)

Also, of all the nuts, walnuts are the best as far as omega-3. I like them in oatmeal with brown sugar and raisins (or bananas). StuRat 21:27, 22 March 2007 (UTC)

blood type and sub antibodies

I have Leukemia CML type. I was given a card that states I am:

Blood Group O  RH positive
Antibodies: anti-K-1

It is the anti-K-1 part that I do not understand the significance of.)

I am hoping some one will be able to explain to me what the importance of the anti-K-1 antibodies means.

Thank You, LL —The preceding unsigned comment was added by 74.13.56.147 (talk) 19:01, 20 March 2007 (UTC).

This appears to be medical short-hand for the Kell antigen system. You should surely verify with your doctor. You might want to get a more general idea from our blood type article. Nimur 19:35, 20 March 2007 (UTC)

I think it is the Anti-Kell₁ antibody. See Hemolytic disease of the newborn (anti-Kell). It is normally in infants. --Kainaw ^(talk) 19:41, 20 March 2007 (UTC)

METAR report

I have a METAR report that ends in RMK 6AC140 NOSIG. What does the 6AC140 mean? Thanks.

Do you mean the weather-related METAR? If so, does the article offer any useful info? Anchoress 21:59, 20 March 2007 (UTC)

Look, that answer is really not helpful. I'm asking because the article does not provide me with the answer, and I've been unable to find the exact information online. If you can point me to some information which does, that would be appreciated. —The preceding unsigned comment was added by 129.78.64.102 (talk) 23:44, 20 March 2007 (UTC).

Well now that I know that you mean the METAR I linked to, and you did read the article, I do have more info I could point you to, but I don't expend energy assisting people who don't accept my good faith efforts to help them in the spirit in which they were given. Apologies in advance for being off-topic and snarky. Undoubtedly someone else will be able to find the info I found to answer your question. Anchoress 01:03, 21 March 2007 (UTC)

May I remind you of the large block of text at the top of the page which asks users to "search first". Asking me to do the same and then claiming to have the necessary information and simultaneously withholding it from me, punishes me for actually following procedure and is contrary to WP:AGF. Do as you wish.

You're right, that was rude of me, and I'm sorry. In my defense, I have a horrible headache and probably shouldn't be posting at all. Anchoress 03:31, 21 March 2007 (UTC)

No harm, no foul.

I agree with the original comments from Anchoress. As there are certainly more than one "METAR report" in the world, you should have specified that you meant the weather-related report, provided the link, and stated that it didn't answer your question. Just because we ask people to read the article first does not mean we can assume they have all done so. In fact, there are many who fail to do so, so it was quite reasonable of Anchoress to ask if you did, since you failed to volunteer that info on your own. StuRat 19:39, 22 March 2007 (UTC)

Thanks for that, Stu. Anchoress 05:23, 24 March 2007 (UTC)

If you are referring to the difference in METAR reporting in the US and everywhere else, the RMK (remark) section is inherently nonstandard, so saying that I want detail on a portion of the METAR remark section is not ambiguous.

Secondly, I am quite confident of your abilities in going to articles yourself. There is one and only one article relating to the keyword "METAR", and it deals solely with weather reporting. I fail to see how Anchoress or yourself could have confused this with something else.

Finally, if I follow correct procedure and the METAR article answered my question, then there would be no need for me to ask the question. It is not an unreasonable assumption that Anchoress at least take a cursory examination of the article to confirm whether it might answer the question (a simple search of the article would suffice) before suggesting I read it. If she would have done so, she would have come to the independent conclusion that the article wasn't helpful either. Do you understand how unhelpful it is referring me to an article that doesn't answer the question, when she could have checked ahead and saved us all the trouble?

Hi, user 129: Just to let you know, I did check the METAR article, but I didn't (at the time) know enough about the topic to know for certain that it didn't answer your question. And I asked if you had checked the article because, as StuRat stated, many (most) questioners on the RDs don't check the relevant articles before posting their ?s, and so it is the habit of most regular respondents to assume that - unless the ?er informs us otherwise - the ?er hasn't checked the article. In fact, many ?ers don't even know there are relevant articles on WP. And, because there are so many possible avenues of research to follow in answering your question, I just wanted to confirm what you had done yourself before pursuing any of them. Anyways, sorry for any upset or consternation my usual question answering MO has caused, and best wishes! Anchoress 05:23, 24 March 2007 (UTC)

I understand completely that some people "don't get it"; but it isn't that hard: if the keyword or part of the keyword that I was interested in wasn't present in the article, then the article is most likely not useful or helpful. There really wasn't any harm done in you asking, I just felt that the suggestion wasn't helpful. I didn't mean my original responses in an irritated fashion either, but I just wanted to make my points regarding your response clear.

To explain in more detail why we ask people if they have read the article and found the info there, consider it from the POV of efficiency. There is only one question asker, so it only takes X amount of time for them to read the relevant article(s) and report if they found the answer there. On the other hand, there may well be 10 responders, and 100 readers of the question. If each of those must independently read the relevant article(s) to confirm that they are not helpful, that will take 10X or 100X the effort, and for no good reason. If the original poster simply states that they read the relevant article(s) and didn't find the answer, the time of all those responders and potential responders can be better spent researching elsewhere. I understand that the implication that you aren't smart enough to read the relevant articles on your own may be insulting, just like when you call for computer support because you have a blank screen and they ask if the computer is plugged in. However, there are indeed people who call with unplugged computers, so they do have a legit reason to ask. Those of us smart enough to check such things on our own first just need to bear with them until they get past the "computers for dummies" part of their script. StuRat 16:29, 24 March 2007 (UTC)

The problem I have, StuRat, is that one should check whether the article is worth being referred to before referring it to others. Granted the respondent can't be expected to know everything about every article, but in this case, it wasn't extremely difficult to see whether the keyword in question was contained in the article.

What's the full METAR? I think there are some sites that can translate. Splintercellguy 00:02, 21 March 2007 (UTC)

Yes, but they do not necessarily translate everything, and its likely that not all remarks will be translated either. —The preceding unsigned comment was added by 129.78.64.102 (talk) 00:06, 21 March 2007 (UTC).

Hmm, I'm no expert, but googling "6AC140" yields METARs with similar string portion as yours. Splintercellguy 01:24, 21 March 2007 (UTC)

You don't get it. I want to know what 6AC140 translates to, not just METARS with that reported. For example, NOSIG in the above example means that no significant change is expected. What does 6AC140 mean? —The preceding unsigned comment was added by 129.78.64.102 (talk) 02:15, 21 March 2007 (UTC).

Okay, trying here. From this page, it has this line in the table for remarks:

6pppp - 6 hour precipitation in .01 inches

Perhaps this is what you want? I try to please :). Splintercellguy 04:20, 21 March 2007 (UTC)

Thanks, but I don't think that's it. The pppp signifies four similar characters, (eg VVVVSM is designates four characters for visibility plus an SM to denote statute miles) -- it's not very good syntax, but it's what they use. It still doesn't explain what the AC is and AC140 is five characters.

The only reference so far I can find to AC in METAR syntax is a reference to the could genus (ie alto cumulus). I'm still looking, though. --Cody.Pope 04:58, 21 March 2007 (UTC)

Thanks. I noticed that too, but it doesn't seem to fit.

Aight, I can't be totally sure, but is you look at this list of METARs and cross reference it with this list of cloud types, you'll notice that whenever a block of #XX### appears, as a remark, the XX matches to some type of cloud type. I can't tell you what the numbers mean, however. Hope that helps, it sure was interesting learning about METAR cause until right now, I knew NOTHING about it. So if you're about to fly a plane, don't trust what I just said (if I find more, I'll post it). --Cody.Pope 05:20, 21 March 2007 (UTC)

Actually, I think you're on to something. I think the last three characters are the flight level of the cloud. I still don't know what the first digit is for, though.

Ok, so if we buy the cloud type and flight level argument, you'll also notice that when multiple #₁XX#₂#₃#₄ blocks appear, #₁ of the first block is always smaller than #₁ of the next block -- so perhaps it's a distance in some-unit(?) till you encounter that cloud type along the flight path? --Cody.Pope 05:36, 21 March 2007 (UTC)

There could be multiple flight paths, could there not?

Ah yes, there could be. Some kind of directional marker? --Cody.Pope 06:12, 21 March 2007 (UTC)

6AC140 is very strange. AC is not in FAR/AIM handbook in METAR section. Could it be a plain language remark? I don't see AC as a weather code because it's too similiar to aircraft. That said, could it mean 6 aircraft 14,000 ft? I;ve never seen that in a METAR but it could indicate weather baloons or something related to the metar station. What was the METAR station that issued it and what was the full line? --Tbeatty 06:00, 21 March 2007 (UTC)

Perhaps, but I think we've narrowed down the XX portion as a cloud type, I've now found a bunch of METAR reports (from multiple locations) with the aforementioned patterns (ie #₁XX###, with #₁ increasing in each progressive block). --Cody.Pope 06:11, 21 March 2007 (UTC)

6 = Second lowest broken cloud layer. AC = altocumulus 140 = 14,000 ft. Closest I can find. Here is a good source. --Tbeatty 06:42, 21 March 2007 (UTC)

Yes, I thought that it may have been the cloud overage in oktas on the way home. Thanks to all!

Body heat - How's it done?

I'm curious as to the process by which warm-blooded animals actually create internal heat. I guess it's a chemical system of some kind but I'd like to know how it's done.Cuzzi 22:16, 20 March 2007 (UTC)

Read up on the process in the homeothermic article. Anchoress 22:24, 20 March 2007 (UTC)

You might also want to read up on the citric acid cycle and electron transport--VectorPotential^Talk 00:47, 21 March 2007 (UTC)

Thanks, folks. So - would the quick answer be that heat is a bi-product of the conversion of nutrients into energy?Cuzzi 01:18, 21 March 2007 (UTC)

Yeah. :-) That was going to be my answer but I thought you wanted something more detailed. Internal combustion engine. Anchoress 01:22, 21 March 2007 (UTC)

(EC) Well, "by-product" generally implies that something is an peripheral process, where as homeothermic (warm-blooded) metabolism depends on the elevated temperature to a large degree. If you said "body heat is a function of the conversion of nutrients into energy" you'd be pretty safe. -- MarcoTolo 01:25, 21 March 2007 (UTC)

One of the byproducts is carbon dioxide, amongst other things. For example.Vespine 04:09, 21 March 2007 (UTC)

I think the more important aspect, is that metabolism is the primary function, and that when the production of ATP(ie metabolism) stops, *that* is when you release heat by dissipating the energy built up by electron transport, that would otherwise be used to synthesize ATP--VectorPotential^Talk 21:40, 21 March 2007 (UTC) Thanks, folks - that was all very informative and enlightening :-)Cuzzi 11:30, 24 March 2007 (UTC)

March 21

Bullet velocities and wound types

This question has been bugging me for some time, and I could never find the answer, so I'll ask here:

When a human is shot in the torso with a 9mm bullet from a handgun, what causes more damage to the body; the laceration of the bullet passing through the tissue, or the blunt trauma which creates internal bleeding, bruising, etc.? And does this change with other types of ammo, eg. 5.56, 7.62, .50 Cal? Thanks guys, --71.197.149.164 00:17, 21 March 2007 (UTC)

See the article on stopping power. There is also have a stub at wound ballistics, but it's not very thorough yet. Nimur 01:28, 21 March 2007 (UTC)

The subject you are dealing with here is terminal ballistics, that and the above articles seem to have a lot of overlap. Bullets in the 9mm range generally don't cause a lot of 'blunt force' or mechanical type damage unless they are hollow point. People under the influence of drugs like pcp, and even just very strongly willed people, such as those with special forces training can function quite normally with several bullet wound, as long as you can 'block out the pain'. Unless the bullet actually hits your spine, brain or heart, it's generally the bleeding and 'shock' and stuff that eventually kills you. Apparently it isn't actually that uncommon for someone to faint from shock when they are being shot at, even if they aren't hit by a bullet. Vespine 02:40, 21 March 2007 (UTC)

As for the second part, yes of course, bullet type, speed and mass has a massive impact of what happens if a person is hit. Typically the more mass in the bullet the more damage it will cause. Continuing from my post above, a 9mm bullet is considered survivable if you get treatment and you are not hit in the spine, heart or brain, definitely that is not true for a .50 Cal, I imagine anything but a hit to the extremities would be fatal. Vespine 04:13, 21 March 2007 (UTC)

It depends on a lot of things. Mainly, damage is related to how much energy can be imparted from the moving bullet to the body in the quickest amount of time. Hollow points are designed to expand when they hit fluid. This tends to slow them down very rapidly and the energy is transferred very rapidly from the bullet to the body. This limits how far it penetrates, though, so there is a tradeoff. The ideal self protection round would be a very heavy bullet that expanded when it entered the body and stopped with 0 velocity in the spine. Military rounds such as the 5.56mm NATO ball and 9mm ball round are designed to wound consistent with the goals of warfare. Police in the U.S. usually use a .40 cal hollow point which is designed to rapidly stop (i.e. very lethal) someone without overpenetration. --Tbeatty 07:11, 21 March 2007 (UTC)

Thank you very much, I am quite satisfied. 71.197.149.164 16:40, 21 March 2007 (UTC)

lisps(speech impediments)

I would like to know if the lisp (speech impediment) is hereditary? — Preceding unsigned comment added by 69.112.118.126 (talk • contribs) 01:48, 21 March 2007 (UTC)

Physical lisps (as opposed to learned behaviour) are normally caused by physical issues. Thumb-sucking and missing teeth are usually attirbuted, but so can hereditary facial features. So, for the most part, it is not hereditary, but can be. --Kainaw ^(talk) 02:19, 21 March 2007 (UTC)

Travel to the Asteroid Belt

How long would it take to travel to the asteroid belt using minimal energy and current means? Say, the inner edge. I can't find a good distance for it anywhere.-- ×××jijin+machina | Chat Me!××× -- 06:56, 21 March 2007 (UTC)

• I think here is got it at about 4 months going 32,400mph http://www.spacetoday.org/SolSys/ThePioneers.html -- ×××jijin+machina | Chat Me!××× -- 07:02, 21 March 2007 (UTC)

That would be if you were just passing by. If you wanted to stop there, you'd have to decelerate, so it would take a good deal longer. Clarityfiend 08:19, 21 March 2007 (UTC)

You could decelerate once you got there, but that use much more fuel. Think outside the box 11:01, 21 March 2007 (UTC)

Our article on Hohmann transfer orbit says that it is "almost always the most economical way to get from one circular orbit to another". It also gives a formula for the time taken for the transfer. Plugging in the numbers, and assuming that the inner edge of the astreoid belt is at about 2 AU, I get a transfer time from earth orbit to the asteroid belt of about 340 days - say 11 months. Gandalf61 11:29, 21 March 2007 (UTC)

Enzymes

Does anyone know who discovered enzymes? Mattyatty 13:45, 21 March 2007 (UTC)

From Enzyme: As early as the late 1700s and early 1800s, the digestion of meat by stomach secretions[2] and the conversion of starch to sugars by plant extracts and saliva were known. However, the mechanism by which this occurred had not been identified.[3] [...] In the 19th century, when studying the fermentation of sugar to alcohol by yeast, Louis Pasteur came to the conclusion that this fermentation was catalyzed by a vital force contained within the yeast cells called "ferments" [...] In 1878 German physiologist Wilhelm Kühne (1837–1900) coined the term enzyme, which comes from Greek ενζυμον "in leaven", to describe this process. The word enzyme was used later to refer to nonliving substances such as pepsin, and the word ferment used to refer to chemical activity produced by living organisms. Does that answer your question? grendel|khan 15:15, 21 March 2007 (UTC)

Permanent magnets drain

is it true that if a permanent magnet held against another permanent magnet with the same poles facing for a long period of time they will lose their charge ? is there any exception to this ? and would this ocur in a system where both poles face each other very often but then move away from each other? clockwork fromage —The preceding unsigned comment was added by 216.113.96.124 (talk) 15:00, 21 March 2007 (UTC).

Permanent magnets vary in how "hard" they are. "Soft" magnetic materials can be easily depolarized/repolarized by an external magnetic field whereas "hard" materials are harder to depolarize/repolarize. Essentially, there's a minimum magnetic field needed to change the polarization of any given permanent magnet. Some things help cause repolarization: Heat (see Curie point) and ordinary mechanical shock and vibration (which jostel the individual atoms and allows them to flip to conform to the new magnetic field).

It's unlikely that two identical magnets unvibrated and at ambient temperature would depolarize each other.

Atlant 16:04, 21 March 2007 (UTC)

so theoricaly, if a device relied on magnetic as its source of power it would never run out right? clockwork fromage

The problem with that, assuming you want to use electricity, is that an electric generator has to rotate, whereas a magnet will only move things one way by itself :( HS7 19:18, 21 March 2007 (UTC)

Energy must be conserved. If you tried to extract a meaningful amount of power from the apparatus as you described, the magnets would rapidly demagnetize. They are not an infinite source of energy. In simple problems, they can be treated as constant sources of magnetic flux but in reality they will run out of energy if you extract it. Nimur 19:50, 21 March 2007 (UTC)

Normal permanent magnets could not be "drained" in such a fashion; they are in a lower energy state when they are magnetized than otherwise. I think you would just never find a way to extract anything from them. --Tardis 21:34, 21 March 2007 (UTC)

Magnets are not like batteries - they don't store or produce energy - so they don't "run down" in the sense that a battery might. However, they can get demagnitised under various complicated situations. The idea that you could build a motor that used the 'power' of magnets is an old one - but this won't work - magnets simply aren't like that. However, that doesn't stop various 'nut jobs' from imagining that this is possible. SteveBaker 20:22, 21 March 2007 (UTC)

In spite of everything written above, magnets really do get weaker if you store them with an open magnetic circuit (or, worse, with a closed-the-wrong-way magnetic circuit, like the original poster was describing). This effect can be practically significant. Many types of permanent magnet motor cannot be disassembled without ruining the magnet. (When the motor is assembled, other parts of the motor short out the magnetic field.) This is also the reason why permanent magnets are sometimes stored with an iron "keeper" across the poles.

And yes, conservation of energy holds. No perpetual motion. —The preceding unsigned comment was added by 24.91.135.162 (talk) 20:42, 21 March 2007 (UTC).

It would be possible to make something "move" using magnets for a seemingly perpetual period of time, but a condition of perpetual motion machine is that energy must be extracted from it, trying to extract energy from the system would cause it to slow and eventually stop. Similarly someone asked a while ago why the moon, if in perfect balance, couldn't be considered a perpetual motion machine (forgetting the sun exploding etc.) the answer was that if you tried to extract any energy from the moon's orbit, it would slow down and eventually fall to earth. So I think the rule is similar here, I saw one of those desk toys that would almost convince you perpetual motion was possible with magnets, but if you tried to extract any energy from it, it would slow down very quickly. Vespine 01:19, 22 March 2007 (UTC)

Refrigerators

How do the doors on refrigerators seal? Most modern fridges have that rubber gasket and when you close the door there is that signature "thoop" sound. But there doesn't seem to be a mechanism of any sort for a physical lock. Do the gaskets have magnets in them to hold the door shut? Dismas|^(talk) 16:26, 21 March 2007 (UTC)

Try it...take a piece of metal that sticks to a magnet and see if it sticks to the seal. DMacks 17:56, 21 March 2007 (UTC)

I'm fairly sure that most of these have a magnetic strip that runs the length of the seal. I've seen some high-end refrigerators that maintain negative pressure in the cabinet, but your home fridge probably isn't doing this. Note that in days past, mechanical latches were used to hold the door shut. -- mattb @ 2007-03-21T17:58Z

It's ferromagnetic [Mαc Δαvιs] (How's my driving?) ❖ 18:10, 21 March 2007 (UTC)

There should be a rubber strip around the edge of the inside of the door (as seen in this photo). If you cut it open (not a good idea unless you're throwing out the fridge anyway!), you can the magnet; it looks and feels like a long piece of smooth, flexible black rubber. The magnet serves two purposes: not only does it keep the fridge door shut, but it keeps the rubber strip pressed right up against the frame of the fridge, ensuring an airtight seal which increases efficiency and hygiene and keeps smells inside the fridge. Laïka 18:18, 21 March 2007 (UTC)

It works all by itself. Warm air from the room gets inside your refrigerator while it is open. When you close the door the air is rapidly cooled down by the surrounding refrigerator walls, which causes its pressure to decrease and seals the door. The effect increases for a few seconds, while the air is cooled down, then it diminishes over a longer time, due to leackage. Try pulling at a refrigerator door, when it has been closed about 5-10 seconds ago. You will notice a significantly higher resistance than usual. The effect also causes a notable sound. I have no idea, whether it is your "thoop".

—The preceding unsigned comment was added by 84.187.7.58 (talk) 06:00, 23 March 2007 (UTC).

Cooking wine & spoilage

How long can a (large) bottle of red wine with screw-top last (with the top on) once opened? Would there be any valued added in putting some salt in it, as is done with commercial cooking wine? Thanks --64.56.107.126 16:49, 21 March 2007 (UTC)

Depends how much air is in the bottle, and how much you shook it up and what the wine was like originally. Assuming it is a robust young red I'd stick it in the fridge, and if only a glass or so is missing it'll probably last a week quite happily, might even improve. Worst case, if it is half empty, and was an old wine, it would probably start to taste a bit 'thin' on the third day, and the temperature shock from the fridge might not do it any good either. Salt won't have much effect at a guess. I have had white wines that went from good-ish to undrinkable in 1/2 an hour, but they were very old and on their last legs. I keep a bottle in the fridge that started as a bottle of sherry, it gets topped up with anything that is too good to pour away, it is fine after a year (I'm not bothered about colour when I use wine in cooking). I would be a bit careful with red wine in food - I'm not convinced that it is always a good thing, certainly cheap red wine can create some pretty odd tastes and smells in stews Greglocock 07:18, 22 March 2007 (UTC)

I have read that the salt is put in cooking wine not so much to preserve it as to make it undrinkable. The salt makes it taste bad and might cause vomiting, but usual;ly tastes ok in a cooked dish. Edison 14:28, 22 March 2007 (UTC)

genetic epidemiology questions

Hello, I was asked a question in the exams regarding genetic epidemiology please verify if my attempted solution is correct. please pardon if the question itself is incomplete , im quoting them from memory

• question1:

how many affected individuals with gene DD? given P(DD)= 1 P(Dd)=P(dd)= 0,0001.

couldn't solve this. perhaps this question is incomplete and it would be nice if you could insert the missing parameters and give a sample solution.

• question2:

given p(A)=.7 ,and there are 100 individuals what is fAa? (fAa is the conditional probability that an individual is affected given he has the genotype Aa)

attempting to solve: p(a) =1-.7= .3 assuming hardy weinberg equilibirium: p(Aa)= 2*.3*.7=.42

p(affected|Aa)= P(affected and Aa)/p(Aa) = .001/.42 =.0024

• question3:

given p(AA and affected)=.08, p(A)=.2 calculate p(affected and AA)?

attempting to solve: perhaps the question is wrong, maybe one needs to calculate p(affected|AA).

p(AA)= .2*.2=.04

p(affected|AA)= P(affected and AA)/p(AA)= .08/.04 = 2

probably a wrong answer, how can conditional probability greater than 1? -

Thank you very much for patiently reading through this list of questions. Iam perplexed, lecture notes are of little use, any help would be wonderful.

Thanks in advance.

212.201.73.208 17:05, 21 March 2007 (UTC)

i think the answer to question 1 is that only 1 individual is affected and that its puff daddy =)

Vasopressin and caffeine

i ave just read articles on Vasopressin and i was wondering if there might be a relation between long term caffeine intake and the brain chemical fonction of Vasopressin like agressivity to other males and bonding to sexual partners clockwork fromage —The preceding unsigned comment was added by 216.113.99.149 (talk) 17:48, 21 March 2007 (UTC).

I think you're a little ahead of the game. I don't believe such a link has been established, which doesn't mean it doesn't exist. However, the caffeine article states the over use and intoxication effects of caffeine, which has been around for a long time, and none of it seems to mention aggression or relationship issues. Vespine 21:58, 21 March 2007 (UTC)

There is known to be cross-talk between caffiene induced and vasopressin induced release of intracellular Ca2+ stores, somewhere at, or upstream of, an endoplasmic reticular Ca2+-ATPase. However, knowing there is a molecular interaction between the two signalling pathways is very different from knowing their behavioural consequences. Rockpocket 22:05, 21 March 2007 (UTC)

Nuclear bombs

Hello,

On the British Vanguard am i right in thinking that there are 48 warheads on each sub and that each warhead in 100x more powerful than the bomb dropped on Hiroshima?

If so what would happen if they were all targeted in the middle of, say, London. What would be the scale of damage?

Thanks, --12345 wiki 20:29, 21 March 2007 (UTC)

Submarines of the Vanguard class can each carry 16 missiles, each missile can have up to 8 warheads, each warhead is either 100 kilotons or 475 kilotons - depending on which type of warhead is selected. The Hiroshima bomb was between 13 and 16 kilotons. So the sub carries 128 wardheads - each of which could be around 30 times the power of the Hiroshima bomb. Just one of those warheads would be more than enough to reduce the whole of central London to rubble. SteveBaker 21:34, 21 March 2007 (UTC)

I always wonder about threats to drop a zillion nukes on some specific site...like here, would 127 more do much more damage other than a deeper hole and more fallout? DMacks 21:40, 21 March 2007 (UTC)

(afer edit conflict)According to the article, it had 12 missile tubes capable of firing the trident missile which has a maximum payload of 3.8 megatons, the bomb dropped on Hiroshima was 13 kilotons.. It's hard to speculate the extent of the damage caused by a weapon like this and a description is probably impossible for a human to even fathom. Imagine this, a circle in the middle of London maybe 3 kilometres in radius is a crater in the ground, a circle 8 km in radius most buildings are levelled and even 20km windows are blown out, there is moderate damage to buildings and there are still fatalities. The nuclear explosion article is quite good. Now I am become death, the destroyer of worlds. As for the multiple nuke scenario, I don't think the "blasts" would add up, but there would definitely be an effect on fall out. The radioactive material comes from the blast it self, so more blasts, more radioactive material. I'm sure the big glass crater in the ground would reduce the amount of material gicked up in each subsequent blast but it would still add. Vespine 21:47, 21 March 2007 (UTC)

You're right about the 48 warheads (that's what Nuclear weapons and the United Kingdom says), but not about their yield. That article indicates the British bombs are similar to (or perhaps derivatives of) the US W76 warhead, which has a yield of 100 kilotons. The Fat Man (Nagasaki) bomb was around 21 kilotons, and Little Boy (Hiroshima) 16 kilotons (max). So Vanguard's warheads are maybe six times as powerful as Hiroshima. There's really no military need to make ones larger than that: you'd just end up digging a deeper hole. Atomic bombings of Hiroshima and Nagasaki says the area of total destruction at Hiroshima was about 2 miles across - lets guess that a 100kt bomb maybe destroys 3 miles across (like anything, more power gives diminishing returns) - that's around 9 square miles. That's per warhead. Now you wouldn't just launch all your warheads to one location, or all at one time - they'd all blast one another (what the nice nuclear men call "fratricide"). So you'd launch them over a space of a couple of hours, and you'd spread out their targetting so their effects would be maximised. 48x9 is about 400 square miles, or around 2/3s of Greater London would (in some evil-optimal scenario) be entirely destroyed. But really this is total overkill - five or six explosions, spread across the central section of the city, would be enough to horribly devastate it and kill maybe a million people. That's why Britain feels it needs only one sub at sea at a time - even accounting for losses due to (largely non-existent) missile defenses, those 48 warheads around enough to kill at least ten million people in any enemy country. I really cant for the life of me figure out why the US thinks it need 14 Ohio class subs (each with more tridents and far more warheads than the Vanguard boats) and why the Russians think they need 10 Borei class submarines. Darryl Revok 21:51, 21 March 2007 (UTC)

It is also worth remembering as well that blast effects were not the cause of the majority of deaths at Hiroshima — fire was. Many nuclear planners during the Cold War vastly underestimated the effects of nuclear weapons by ignoring fire effects (which are harder to calculate in any case) and as such vastly overestimated how many weapons would be needed to take out a city. (Lynn Eden's Whole World On Fire is my source for this, btw). (As for why the US and Russia employ so much overkill, it is because they aren't really committed to exclusively second-strike forces. Which is scary as hell. China and the UK, by comparison, have purely second-strike forces — they could never expect to launch a nuclear attack that could take out the nuclear weapons of an enemy country, but they could counter any attack launched against them.) --24.147.86.187 23:12, 21 March 2007 (UTC)

Keep in mind that there are maybe three countries in the world that could survive a nuclear strike to the largest city: the US, the Soviet Union, and China. That's a large part of why the US and the USSR had so many nuclear weapons of all sorts. --Carnildo 20:03, 22 March 2007 (UTC)

One of the other not-so-nice parts of the madness that goes into planning nuclear attacks is that you really can't use nuclear weapons on tiny small towns and villages away from the big cities - but you can more effectively crush resistance by deliberately wounding and otherwise incapacitating people in the big cities without conveniently vaporizing them. Thaking care of these casualties then completely overwhelms whatever rural resources remain - spreading despair, uncontrolled infections and consuming valuable food, water and medical care facilities. So it's not a great idea to turn major cities into smoking craters - you want a small smoking crater and then a vast area of lesser damage. Using lots of tiny warheads achieves that far more effectively than one large one. It's a nasty business. SteveBaker 04:02, 23 March 2007 (UTC)

March 22

Cyclops evolution

Did one-eyed creatures evolve first and then mutated to create two-eyed species, or did the very first proto-eyes always come in pairs? -- LukeSurl 00:18, 22 March 2007 (UTC)

It probably depends on how you define eyes, but the short answer is one-eyed creatures came first. Check out the evolution of the eye article. --Cody.Pope 00:35, 22 March 2007 (UTC)

Two eyes is pretty common in our large predator/prey domain, but that's because we benefit greatly from good depth perception. There are many other animals with more eyes, spiders have eight and bees for example have FIVE eyes! Which I think is amazing, it's one of the few cases where such an organ does not come in one or pairs!! This doesn't seem to be mentioned in our bee article:( Vespine 01:07, 22 March 2007 (UTC)

Hmm, if one eye allows you to see a 2D view of the world, and two eyes allows a 3D view of the world, do 8 eyes allow you to see into the ninth dimension ? :-) StuRat 19:20, 22 March 2007 (UTC)

If it were big enough to be seen, yes. 222.158.162.242 09:05, 23 March 2007 (UTC)

Euglena have a single eyespot, and protista are pretty far down on the evolutionary ladder, so I'm going to second the statement that one-eyed species came first--VectorPotential^Talk 01:14, 22 March 2007 (UTC)

But no one suggests that the human eye has its origins in Euglenia. Eyes (and eye-like spots) have evolved more than once. - Nunh-huh 03:46, 22 March 2007 (UTC)

Well, the wiki article I pointed to actually disagrees: "The development of the eye is considered by most experts to be monophyletic; that is, all modern eyes, varied as they are, have their origins in a proto-eye believed to have evolved some 540 million years ago." --Cody.Pope 05:25, 22 March 2007 (UTC)

That's not a disagreement. The article overstates the degree of agreement on the monophyletic theory, but even if all modern eyes did have a common origin, that doesn't mean that no other eyes have evolved (and become extinct). - Nunh-huh 05:52, 22 March 2007 (UTC)

Well, what about the article about the pineal gland? Some biologists think that it evolved as a proto-eye in land animals before binocular eyes evolved. The article on the pineal gland says: Some evolutionary biologists believe that the vertebrate pineal gland can be evolutionarily traced to a proto-eye structure in early vertebrate organisms. Interestingly, the tuatara's pineal gland functions as a third eye. Jolb 05:33, 22 March 2007 (UTC)

I didn't say that the eyespot evolved into the human eye, just that it came first (: VectorPotential^Talk 17:58, 22 March 2007 (UTC)

As a brief aside, I've been vandalism-patrolling at pineal gland for more than a year now (in fact, the miserable state of that article was a primary motivator in my early Wikipedia contributions - I couldn't bear to see scientific facts so grossly misrepresented). A lot of nuts and new-agers have distorted, mythology-based views about the human pineal gland as a "third eye." At best, it might maybe have had some photo-sensitive properties in some link way back in the evolutionary chain, possibly. (See the article and talk page for more details of the citations, studies, etc). There is no scientific evidence that the current human pineal gland has photosensitive behavior - for one thing, it is deep inside the interior of the head and does not have exposure to light. Any metaphysical/spiritual vision attributed to this endocrine gland is incorrect; it does not participate in the physiological process of sight. This doesn't stop people from CONSTANTLY ADDING THIS INFORMATION TO THE ARTICLE. Even worse, they can even come up with piles of disreputable web-links to support their claim. Sigh. I think I should mark my WikiStress level to Red, and call it a night / week / month. Nimur 07:52, 22 March 2007 (UTC)

The confusion around the pineal gland is due to not understanding that all one needs for a so-called "third-eye" is the presence of an opsin paralogue, such as melanopsin or pinopsin, to detect light. Plenty of fish and frogs express such a gene not only in pineal-like structures but also in their skin, permitting them to detect light without using their eyes. Yet, oddly enough, no-one suggests that skin is a proto-eye. Rockpocket 02:02, 23 March 2007 (UTC)

This isn't exactly what you asked, but I think it may be relevant: bilateral symmetry means that we don't have two copies of "how to make an eye" in our genes. We have elements for "how to make an eye", and for "put an eye here"--more accurately, we have elements for "how to make an eye", "put an eye here" and "duplicate everything across this axis". I'm simplifying greatly, and any evo-devo biologist reading this will be rolling their eyes, but the point is that we only needed to evolve a single copy of the eye gene; the mechanisms that make us symmetrical duplicate it. There's also a good explanation of this over at the Index to Creationist Claims: CB751: Bilateral symmetry is improbable under evolution. Read the link from there as well; it's useful. grendel|khan 19:48, 22 March 2007 (UTC)

Eyes

Do glasses improve vision or ruin it and give you headaches only? Also does eating carrots actually improve vision or is it a myth. 70.48.254.161 02:21, 22 March 2007 (UTC)

Glasses have been around for hundreds of years and they have improved the vision of countless millions of people. There would certainly be people who get head aches from wearing glasses and people who's vision degrades even though they wear glasses, but that may not be the fault of the glasses, and even if it is, there is complete universal and unilateral consensus that the benefit outweighs the risks. As for the second question, the carrot article states it is actually somewhat of an urban myth that carrots are good for your vision. Lack of vitamin A can lead to problems with vision and carrots have vitamin A, so it would be safer to say carrots may help prevent vision problems if you have a vitamin a deficiency, but to say they are good for your vision is misleading. Vespine 03:13, 22 March 2007 (UTC)

Only glasses with bad prescription should give you headaches. It doesn't really improve vision; it just changes the angle of light to compensate for less than 20/20 vision. --Wirbelwindヴィルヴェルヴィント (talk) 03:29, 22 March 2007 (UTC)

Actually, if I'm remembering correctly, it is not that the angle of light is changing, it is that the focal point of your vision is being moved forward or backward, depending on whether you or far or nearsighted. It is basically the same thing that one does when one is focusing the lens on a camera or a pair of binoculars--you move the lens backward or forward until things come into focus. This is discussed in Glasses. There is also a good image of what is happening with corrective lenses in the Hyperopia (farsightedness) topic. Lkusz 09:16, 23 March 2007 (UTC)

• When your vision is imperfect, it is because images aren't precisely projected on your . Glasses can correct this. It doesn't improve your vision - in fact, it's probably still going to degrade - but it makes looking a whole lot easier. How they affect your eyes, is disputed. Headaches can have a variety of reasons:

1. Wrong prescription.
2. Eyes need to get used to glasses because they're new.
3. Wearer doesn't consistently wear the glasses so their eyes have to get used to them again each time they use them.
4. The glasses are too old and you're in need of a new prescription. (Typically replacement should occur every 3 years if there's a significant change)

Talk to an eye specialist to see if the prescription is correct. - Mgm|^(talk) 11:36, 22 March 2007 (UTC)

Carotene, which is found in high abundance in carrots, most certainly does help with vision. In the eye, beta-carotene is converted into a form of vitamin A called retinal. That binds to a protein called opsin in the eye. When light strikes a photoreceptor, the retinal is converted from the cis form to the trans form, which in turn causes an action potential to travel along the optic nerve. The electrical signal is processed into what we perceive as vision. People with vitamin A deficiency experience night blindness. As the depletion of beta-carotene increases, the quality of vision decreases, in extreme cases resulting in blindness. That is why carrots help you see in the dark. Rockpocket 17:40, 22 March 2007 (UTC)

It's true, but most people misunderstand the phrase "good for your vision" to mean that it can actually revert defects in the eye like myopia (i.e. "fix" your eyes or "improve" your vision). —LestatdeLioncourt 06:19, 23 March 2007 (UTC)

One fact I can attest to is that your vision can improve of it's own accord, but not if you wear glasses. Vranak

In what sense and by what mechanism can your vision improve of its own accord, and how do you attest to this? Also, how does wearing glasses prevent this mechanism from working? grendel|khan 19:28, 22 March 2007 (UTC)

The muscles that point your eyes in different directions can also change the shape of your eyeballs to correct for minor defects in vision. If you're wearing glasses, this doesn't happen. --Carnildo 20:08, 22 March 2007 (UTC)

This is a common but unproven theory. A recent literature review found "...no clear scientific evidence published in the mainstream literature supporting the use of eye exercises..." (Rawstron J, Burley C, Elder M (2005). "A systematic review of the applicability and efficacy of eye exercises". J Pediatr Ophthalmol Strabismus. 42 (2): 82–8. PMID 15825744.{{cite journal}}: CS1 maint: multiple names: authors list (link)) -- MarcoTolo 00:03, 23 March 2007 (UTC)

I think the theory is true myself, haven known two people who were like this. But neither of them had remotely bad vision in the first place, so I think it's like teeth; it can repair itself, but if you have a cavity, there's no way it'll repair that. --Wirbelwindヴィルヴェルヴィント (talk) 01:12, 23 March 2007 (UTC)

Perhaps some people's vision may correct itself, but not others. One thing that I have heard from my own optometrist is that as one ages, one starts to become more farsighted. So if one starts out nearsighted, it is true that one's vision could actually improve as one gets older. That is, of course, until one starts to need bifocals.

As far as the comment on the improvement of vision being caused by the muscles of the eye changing the shape of the eyes, what is being referred to here is astigmatism. This is an entirely separate issue from near or far-sightedness. While I am unaware of whether it is possible to improve astigmatism by not wearing one's glasses, even if one was able to remove astigmatism entirely, one would not change near or farsightedness. I know this, as I once had a pair of glasses made to correct just for astigmatism to wear over contacts, so that I could wear them while driving or reading in the days before they made contacts that would correct for astigmatism. Lkusz 09:16, 23 March 2007 (UTC)

Women inventors, inventors of colour

I'm working with Grade 4 American students. They are of both genders and appear to be white, black, hispanic, and asian. We will be building circuits to make a game matching inventors to their inventions.

I'd like to make sure the game has some broad representation in terms of gender and race. I was hoping there would be a Category:Women inventors as a starting point, but that doesn't seem to exist. The first person I thought of was Grace Hopper but I'm not sure kids of that age even know what a compiler is.

So I'd like some inventors, especially women and people of colour, who have invented things the typical grade 4 student would be aware of. Thanks. moink 02:29, 22 March 2007 (UTC)

A few women inventors of things someone that age might know:

• Mary Anderson — windshield wiper
• Josephine Cochrane — dishwasher
• Bette Nesmith Graham — Liquid Paper

Unfortunately those are all a little anti-climactic. The difficulty of course is that non-Europeans and women did not invent at a proportional rate to European men for fairly obvious and well-documented historical reasons until relatively recently when things like educational options and economic situations become more balanced, but things invented relatively recently are going to be so complicated that most grade 4 students aren't going to know what they are (i.e. the Grace Hopper example). --24.147.86.187 03:09, 22 March 2007 (UTC)

Honestly, I feel that if you're teaching children about inventors, teach them about the most important inventors, regardless of their sex or race. If they all happen to be white european males, why try and misrepresent that fact? If you feel they're being brainwashed, you could teach them separately about gender roles and racism. Jolb 03:36, 22 March 2007 (UTC)

"Important" is a tad subjective. Don't worry; I won't be leaving out Thomas Edison. But really, can we order inventions in order of importance? What's more important? Paper or the lightbulb or the car or the dishwasher or the compiler? Who knows? I used all but the dishwasher today. moink 03:52, 22 March 2007 (UTC)

The answer in order of importance of the five you listed is 1) paper (not liquid paper) 2) lightbulb 3) car 4) compiler 5) dishwasher. --Tbeatty 07:42, 22 March 2007 (UTC)

Some inventions change the world. Other don't. The lightbulb is clearly a more important invention than the Johnny Mop or Liquid Paper. Of course we can order inventions by their importance, and though there may be quibbles and debates about that order, it's a far better representation of reality than pretending all inventions are of equal significance. - Nunh-huh 04:58, 22 March 2007 (UTC)

We have Category:Inventors_by_nationality and of course you can peruse Category:Inventors. However, I agree strongly with Jolb - why should race even be an issue? If it were a history class, you might talk about racial segregation, or educational opportunities (lack thereof, for minorities); and how this impacted the trend of inventor social and racial categorization. You could go into great depth about social injustices; and/or about how some great people managed to overcome societal barriers to achieve great accomplishments. But your project is about inventors, not the history of gender and race. As Jolb said, why misrepresent history to pretend that it has always been very inclusive? You might be doing a disservice by pretending that the history of science and technology was conducted according to modern standards and social norms. Nimur 03:49, 22 March 2007 (UTC)

Race and gender are issues when you are trying to motivate young students to feel that people like them have accomplished things. The actual facts hardly matter at that age — no matter what you teach them will be half false anyway, because the fact is that ALL of history is too complicated to be turned into something that a 9 year old can easily grasp and still be factually accurate. (speaking of which, Edison didn't actually invent the lightbulb.) Going out of your way to mix in a few people of color and a few women into a unit about important inventors is neither intellectual travesty nor incoherent — it is a pedagogical exercise, like most things at that educational level. --24.147.86.187 04:19, 22 March 2007 (UTC)

People like them? That hardly sounds enlightened! Surely you are well-meaning. But in honesty, can you tell me that a black child can not identify with Isaac Newton just because he was a white man? That is the core of the problem! A Hispanic, black, white, orange, purple... child should see the science for what it is - an equal platform on which the only important merit is the mind. I am not an Englishman or a German, but I never have any problem respecting the work of great English or German inventors and scientists. We are all "people like us." I think you will be doing great harm to your students if you teach them that they should be like their own kind. Nimur 04:38, 22 March 2007 (UTC)

"People like them." It's a perfectly innoculous phrase. People like me. People like you. It isn't meant in any pejorative sense, and isn't used in a generalizing or stereotyping sense, so don't get huffy and insert it where it isn't implied. And science has not been an equal platform for the mind, and science has not been fully international, and science has not been ignorant of the class, skin color, or gender of the participant. Giving people of all shapes, sizes, colors, etc., good role models is always positive, and counteracts the effects of a harmful media which only tells the stories of white males, IMO. --140.247.249.241 15:54, 22 March 2007 (UTC)

My point is that we should identify people based on their accomplishments, not on their race. There are ten million ways to "categorize" people - racial traits are one of the most useless categories. They don't necessarily reflect anything about the person, their personality, or even their culture. What does it mean to be "like" somebody else? Maybe a black child's mind is more like Isaac Newton than George Washington Carver. Maybe a white child has more in common with a black inventor. Why should there be any lumping of role-models? Each student should not have a personal role-model of matching color, they should match personalities and goals and mental traits. That should be the important characteristic, not the skin color. Nimur 18:41, 22 March 2007 (UTC)

no matter what you teach them will be half false anyway, because the fact is that ALL of history is too complicated to be turned into something that a 9 year old can easily grasp and still be factually accurate.

I disagree. It's wrong to treat children like idiots, and it's wrong to give them misinformation. The fact that kids are taught a lot of misinformation is not because they're incapable of understanding real information, it's because teachers are too politically motivated to give straightforward, accurate information.

Also, I agree with Nimur. By subtly sliding in things specifically on the basis of race and sex, you're subliminally inserting racial and sexual biases. It's also subliminally demeaning to women and (to use your politically incorrect terminology) "coloured people" to be like Man:Lightbulb, Man:Automobile, Man:Modern Physics, Man:Electric Circuits, Black Man:Peanut Butter, Woman:Liquid Paper. Children aren't stupid enough to be fooled into believing that they're all equally important inventors, and without adressing race and sex issues, they might draw the conclusion that women and "coloured" people might not be capable of making important inventions. Jolb 05:23, 22 March 2007 (UTC)

I don't treat children like idiots, but the fact is that history is complicated and messy. I have enough trouble trying to teach undergraduates at an Ivy League institution that history is complicated; 9 year olds can barely remember the simple stuff. Most adults can barely grasp the complexity of history in the end and have silly myths about what type of person Albert Einstein or Thomas Edison was; half of the articles on Wikipedia on these figures reflect these myths entirely. That doesn't bother me — people get things out of history other than strict historical truth, and in fact strictly accurate history is often totally useless for the sorts of things people want to use history for (to teach lessons on how to be a good citizen, on how we all got to where we are today, on how to appreciate change over time, etc.). I say this as an academic historian and as an educator, one who cares very much about teaching as well. --140.247.249.241 15:54, 22 March 2007 (UTC)

the sorts of things people want to use history for (to teach lessons on how to be a good citizen, on how we all got to where we are today, on how to appreciate change over time, etc.) You're plainly revealing that you're inserting a political motivation into teaching history. You're doing something unethical, and it's in the best intrest of future generations for you to not slant your information for political reasons. Jolb 17:29, 22 March 2007 (UTC)

Could you describe some of these silly myths that are in the articles Albert Einstein and Thomas Edison? It would be helpful if you could point them out, as they sound like the sort of thing that could be considered NPOV. grendel|khan 19:27, 22 March 2007 (UTC)

Marie Curie, List of black inventors and scientists Category:African American inventors, Category:African American engineers, Category:Women scientists. That said, I hope your lesson is to show that science is blind to both color and gender. --Tbeatty 07:56, 22 March 2007 (UTC)

Is it? It hasn't been. In fact contributions of women and people of color were systematically de-valued up until very recently, and even today the number of women and people of color in engineering and science is vastly disproportional to their abilities. That's part of the conundrum of teaching this sort of thing; you want to showcase that there was struggle, but that even in struggle there were individuals who were successful, but not make them out to be so exceptional as to be exceptions to a hypothetical rule. Professional and intellectual opinions vary quite considerably on how to best to talk about this, and I certainly don't presume to have an answer. --140.247.249.241 15:54, 22 March 2007 (UTC)

Stephanie Kwolek - Kevlar − Twas Now ( talk • contribs • e-mail ) 08:27, 22 March 2007 (UTC)

If you are including scientists as well as inventors then Rosalind Franklin deserves a mention. Gandalf61 12:00, 22 March 2007 (UTC)

Per most reference books, Thomas Edison actually did invent the light bulb. Ira Flatow, a science writer, listed 23 prior failed attempts, which may be what you refer to. See Jill Jonnes, "Empires of Light, Random House, 2003 for a recent history of the 19th century electrical developments. One could always find a prioir attempt which was unsuccessful and claim that was the "true invention" of something. See also "Edison's Electric Light: Biography of an Invention" (1986) by Paul Israel, Robert Friedel and Bernard S. Finn. Edison 14:26, 22 March 2007 (UTC)

Edison didn't invent the lightbulb, he just came up with one particular model which worked well-enough for mass-market use (specifically because of an innovation in the filament, not the bulb idea as a whole) and managed to sell along an infrastructure to go along with it. See i.e. Thomas P. Hughes, American Genesis: A Century of Invention and Technological Enthusiasm, 1870-1970 (1989). I find it ironic you cite a Paul Israel book as he is one of the bigger debunkers of the Edison myth these days (and an excellent scholar), but in any case it doesn't matter. My essential point is that the history of invention can be terribly, terribly complicated (ergo our Wikipedia encyclopedia page on the light bulb, itself meant to be a condensed summary, still has to devote a lengthy discussion to the question of whether there is a single inventor of the incandescent bulb), and to be strictly accurate one ends up a mire of questions about what it means to "invent" something in the first place. Too complicated for most adults to have any grasp on, clearly too complicated for most kids. --140.247.249.241 15:54, 22 March 2007 (UTC)

Gotta put a word in for Ada Lovelace - generally accepted to be the world's first computer programmer! SteveBaker 23:34, 22 March 2007 (UTC)

Oooh! And Hypatia - who invented a bunch of useful gadgets in about 450AD. SteveBaker 23:39, 22 March 2007 (UTC)

This [6] is a useful list. SteveBaker 23:41, 22 March 2007 (UTC)

Accretion disks

Why does matter orbiting a center of mass always accrete into a disk? Why does matter in oribt all tend to form into a plane instead of into a 3-dimensional sphere? And why is this disk-shaped accretion universal for everything from the rings of planets to galaxies? Jolb 03:28, 22 March 2007 (UTC)

First, angular momentum must be conserved; this explains why the objects are orbiting at a particular radius (elliptical or otherwise), instead of collapsing in to the massive body in the center. Next, I think that the disc forms because the average total angular momentum lies along a single axis (it must, because the total average is a single vector); this axis in turn defines the normal plane of the accreted system. Over time, each individual particle moves towards the system's net (average) angular momentum via collision, gravitation, etc. This is all due to conservation of (angular) momentum. Nimur 03:55, 22 March 2007 (UTC)

PS - See Formation and evolution of the Solar System and planetary formation for further details. Nimur 03:56, 22 March 2007 (UTC)

PPS, this ensemble article goes into brief detail about my statement about individual particles approaching the system's average. If the system is 'well behaved' (i.e. following classical gravitation, to reasonable approximation), then each individual particle approaches the system average with some spread. It's not entirely unlike temperature - each particle's energy is closely spread around the system average. Nimur 04:02, 22 March 2007 (UTC)

Visualization from University of Arizona. Nimur 04:09, 22 March 2007 (UTC)

As an extension of this, let me point out that the rotational inertia of a disk of a given radius and mass (rotating in its own plane) is 25% larger than that of a sphere with the same shape, and the inertia increases as $mr^{2}$ in either (in any!) case. That means that a disk can have a smaller radius and still preserve the total angular momentum, which means that the mass can be closer together; the disk thus has lower energy than the sphere and is more stable. (The fact that such disks tend to be denser/thicker in the middle represents a compromise between reducing the moment (by turning it into a sphere/disk hybrid) and reducing the energy further.) --Tardis 04:59, 22 March 2007 (UTC)

So, to summarize, this is all due to the object's spinning. If the object didn't have any spin at all, it would indeed collapse in a spherical fashion. StuRat 19:14, 22 March 2007 (UTC)

slotted arrays

list the properties of slotted arrays? —The preceding unsigned comment was added by Ambuj0542 (talk • contribs) 05:29, 22 March 2007 (UTC).

1. Slotted
2. Array

You probably mean antennas, though: see slotted waveguide article.

Nimur 05:34, 22 March 2007 (UTC)

what is to thrive?

what is to thrive? (not the album) —The preceding unsigned comment was added by 60.242.218.72 (talk) 06:50, 22 March 2007 (UTC).

[7] : To grow or increase in bulk or stature; to grow vigorously or luxuriantly, to flourish. Nimur 07:11, 22 March 2007 (UTC)

Try typing it in Wiktionary next time. [Mαc Δαvιs] (How's my driving?) ❖ 18:58, 22 March 2007 (UTC)

This answers the question 'What does it mean to thrive?', but the question asked what is to thrive technically means 'what is meant to thrive?' :] To find the answer to this you want to look up 'Survival of the fittest' in Wikipeda :] You may also want to look under 'Selective breeding' and 'religeon' :] HS7 20:00, 22 March 2007 (UTC)

Also see failure to thrive. --David Iberri (talk) 21:57, 22 March 2007 (UTC)

Too much sodium in the diet

I've tried washing and soaking canned goods and other foods high in sodium but to little avail. Is it possible to compensate and overcome and balance the effect on the heart of the extra high amount of sodium intake from these foods despite the precaution of washing them by adding potassium in the form of salt substitute to your foods? Nebraska bob 07:27, 22 March 2007 (UTC)

I think potassium will be just as bad for your blood pressure as sodium. You should drink more water, reduce your total salt intake, and consult a medical doctor if you have severe nutritional problems. Nimur 07:31, 22 March 2007 (UTC)

This isn't really an answer, more just advice, but the less-processed a food is the less sodium it is likely to contain. So rather than washing processed foods to remove sodium, is it possible to prepare more food from scratch yourself? Then you'll have complete control over the sodium content. Anchoress 07:35, 22 March 2007 (UTC)

Unfortunately fresh meat, vegetables and fruits instead of canned are not always available either because food is purchased in bulk and stored long term where refrigerated storage is not available or the convenience of fast foods is a necessity rather than an option. Drinking more water means urinating more but if that is the only solution for dealing with the extra sodium in highly processed foods then as long as the kidneys can handle it, it is the solution that will have to be used. Nebraska bob 09:36, 22 March 2007 (UTC)

Yeah, soaking those Whoppers must really eat up a lot of time. ;-) I kid. On another note, I wonder if MSG has the same effect on the cardio-pulmonary system that table salt does? Anchoress 20:09, 22 March 2007 (UTC)

Read this article (prepared by a rather brilliant author): [8]. :-) StuRat 18:44, 22 March 2007 (UTC)

Nice work, Stu. But I have a beef; you threw a bitch fit a few months ago when I included potatoes on a list of healthy foods, but I've seen you recommend them several times since. So are you anti-potato or just anti-me? :-( Anchoress 20:13, 22 March 2007 (UTC)

I don't recall "throwing a bitch fit". Whether they are good or bad depends largely on what form they take and what they are compared with. If you compare chili-cheese fries, potato chips, hash browns, or tater tots to steamed broccoli with lemon juice, the spud choices are abysmal. On the other hand, adding some boiled taters to canned soup almost always improves it's nutritional content. A baked potato can be good, but not if you smother it with bacon and cheese, and then toss out the skin (the most nutritious part). Taters always have a high glycemic index, so that is a negative. As for me being "anti-Anchoress", you'll note I came to your defense above on the "METAR report" question. I've generally been on your side most times since we had our tampon fight when we first met. StuRat 21:50, 22 March 2007 (UTC)

Yuck! Too much information! Get a room! --Zeizmic 22:03, 22 March 2007 (UTC)

Sorry Zeizmic, I replied on StuRat's talk page. Anchoress 01:04, 23 March 2007 (UTC)

molectronics

I am currently in my second year of a 5 year Ph.D. program at the U. of Washington (Seattle) (the primary focus being superpartners). Recently, I submitted an article dealing with the field of molectronics. An editor of this website decided that such an entry was doubious, at best. Essentially, I am writing in an attempt to verify the possibility that I know "what the fuck I am talking about."

That possibility has been verified. Of course, the article currently sitting at molectronics is extremely inadequate. Perhaps you could flesh it out on your userpage first, and then move it over into an article. − Twas Now ( talk • contribs • e-mail ) 08:30, 22 March 2007 (UTC)

Maybe it is a better idea to redirect Molectronics to Quantum ComputingMolecular computer, and add a sub-section there with the new content. Nimur 08:34, 22 March 2007 (UTC)

Yeah, if you could put some information or write a bit of an article, or some references or links on your userpage I and we would much like it. [Mαc Δαvιs] (How's my driving?) ❖ 19:00, 22 March 2007 (UTC)

Viagra

This is a question that has been in my mind for weeks... what happens when women take Viagra as an aphrodisiac?--Orthologist 15:34, 22 March 2007 (UTC)

Similar effects: increased turgidity of those structures that respond to sexual excitement with hydraulic events.

Atlant 16:07, 22 March 2007 (UTC)

Increased vasocongestion in the corpus cavernosum clitoridis and vestibular bulbs, just to, you know, use more sciencey words. [Mαc Δαvιs] (How's my driving?) ❖ 18:57, 22 March 2007 (UTC)

This isn't about the aphrodisiacal properties of Viagra, but is certainly a related topic! I wrote a paper last term on the effects of nitric oxide, a secondary messenger that is key for Viagra to function. Viagra causes vasodilation, which improves blood flow, and increases the thickness of the endometrium (uterine lining). There was a study on a small group of women (only four), all of whom had recurring spontaneous abortions (three or more per woman), and all of whom had uterine lining that was thinner than the uterine lining of the average woman (at least 8 mm is typical, yet these women had lining less than 4 mm). It was posited that the reason these women were having spontaneous abortions is that the embryo could not properly implant in the uterine lining. The use of Viagra resulted in successful pregnancies in three of the four women. − Twas Now ( talk • contribs • e-mail ) 21:20, 22 March 2007 (UTC)

Saying about acceptance of an idea

Not sure if this is really the right desk for this, but thought the Science Desk would be more likely to be patrolled by people who'd recognise this.

Ages ago, I remember reading some writer (possibly a sci-fi writer, but I wouldn't bet on it) talk about the stages of acceptance of a problem. It was something like initially claiming there was no problem, then claiming there might be a problem, but there was nothing that could be done about it, then claiming there was a problem, and something could have been done about it, but now it was too late. Obviously, some people's comments on global warming have made me think of this, but I can't remember what it actually said, or who wrote it, or where I read it. Anyone remember this one? Skittle 16:35, 22 March 2007 (UTC)

I might be way off, but I think this is in one of Douglas Adams's later books. Nimur 17:38, 22 March 2007 (UTC)

Could be. But it's also just the sort of thing that Sir Humphrey Appleby would have said on Yes, Minister. --Anonymous, March 22, 2007, 23:20 (UTC).

I think it's either from Hitchhiker's or Discworld. Probably the former. 80.169.64.22 17:16, 23 March 2007 (UTC)

Video Out on graphics card > Broken TV?

My friend hooked up his television to the video out on his graphics card via a scart adapter. The picture was fine at first but after a couple of minutes went black and white and then eventually started jumping around and bluring etc. Now when trying to watch television normally, there is disruption of the picture with it jumping, going black and white, giving a 'no signal' message etc. What could be causing this? --Seans Potato Business 17:06, 22 March 2007 (UTC)

Sounds like a TV is in NTSC mode when it should be in PAL, or vice-versa. Is there a way to restore factory-defaults via a menu or button? If not, try "rebooting" (unplug/replug the television). It is possible, but not likely that the television is permanently damaged; it is probably just in the incorrect mode. Nimur 17:40, 22 March 2007 (UTC)

Picture of the Day

Richard's Pipit

What are the dots on their tongue?

Ancillary question - has User:Kurt Shaped Box or any member of his family eaten this? Nimur 18:11, 22 March 2007 (UTC)

I may have eaten the soup. --Kurt Shaped Box 22:04, 22 March 2007 (UTC)

Most of the time these dots indicate feed this mouth -- sort of like an offspring identification system. Sometimes where there's brood parasitism these marks help the parents figure out which babies are theirs. In Vidua for example, the species that does the parasitism actual has evolved markings to look more like the host species. --Cody.Pope 22:03, 22 March 2007 (UTC)

There's a similar thing in a species of gull (which unfortunately escapes me at the moment), where the adults have a red spot on their beaks, when prodded instinctively by the chicks, a regurgitating reflex will be induced, and Voila! Dinner for small birdies :) -Obli (Talk)^? 01:59, 23 March 2007 (UTC)

Quite a few gull species exhibit that. In the UK, Herring gulls and both Lesser and Greater black-backed gulls have the red spot on their beaks for this purpose. I can't even begin to suggest how/why that evolved... :) --Kurt Shaped Box 07:56, 23 March 2007 (UTC)

There's a number of theories: it may be because the high constrast black-on-yellow makes the bird easier to see in a dark nest, it may trigger an automatic feeding reflex in young birds, or it may be to make it easier for birds to identify parasites as Cody.pope suggested. Albino birds without the markings are often fed less than their young, implying that the markings do have a purpose. They also help bird-keepers: young chicks of different species often look similar, and the markings allow ornithologists to tell chicks apart.[9] Laïka 10:10, 23 March 2007 (UTC)

I was referring to the red spot on the beaks of the adults of certain gull species. Somehow the baby gull knows to peck at this when hungry, whilst at the same time the adult knows to regurgitate food when the spot is pecked. It seems like a very complex system to me - needlessly so, in fact. I just can't think of a single reason why gulls would evolve this. In the species that don't exhibit the red spot, the parent birds just feed each chick in turn (they don't produce large broods and AFAIK, the parent gulls work hard to ensure that each chick gets an equal share) when they return to the nest. --Kurt Shaped Box 17:33, 23 March 2007 (UTC)

What kind of squirrel is this?

I took a picture of this squirrel in New York City (Queens, near the river); it looks like an Eastern Gray Squirrel, but I wanted to confirm before I uploaded it to Commons. Is that what it is? Is this one also an Eastern Gray Squirrel? (The second was taken in eastern Connecticut.) grendel|khan 19:04, 22 March 2007 (UTC)

Great pictures!! I wish I knew which species it is.--Sonjaaa 00:19, 23 March 2007 (UTC)

weight and gravity

If three men, weighing 180, 180, and 170 pounds respectively jump six inches in the air, how much pressure (in pounds) would they put on the surface they were standing on? —The preceding unsigned comment was added by 167.206.19.12 (talk) 15:09, 22 March 2007 (UTC).

Pressure = Force / SurfaceArea

Force = G M1 M2 / r^2

Get the values for G , M1 (earth) , M2 (human) ,r (distance to centre of earth)

Get a pencil and draw out the surface area of the shoes on a big piece of paper

Measure the drawn surface area on the big piece of paper.

210.49.121.183 15:12, 22 March 2007 (UTC)

Easiest way to get the area of an irregular shape like that is to cut out and WEIGH the paper, and divide that weight by the weight of a unit square of the same paper. --BenBurch 15:20, 22 March 2007 (UTC)

I think you guys are missing the question. As the jumpers lift off towards their ultimate altitude of six inches, they impose an impulse on the surface of the Earth. I think the question is asking about this impulse. (The question doesn't ask about pounds per square inch.)

Atlant 16:05, 22 March 2007 (UTC)

Atlant, the question didn't ask about psi per se, but did ask about pressure. Pressure is not measured in pounds; this is likely the source of confusion. Force is measured in pounds (or newtons). Pressure is measured in pounds per square inch, or newtons per meter squared. — Knowledge Seeker দ 18:19, 22 March 2007 (UTC)

The force needed to lift them 6 inches is equal to their mass (in kg)*the distance (im m)*9.81, which is 240.91*0.15*9.81 :) You might be able to work out the pressure from that, but I don't know how :( HS7 16:36, 22 March 2007 (UTC)

That is the kinetic energy that they must acquire to lift themselves 6 inches above the ground, not the force. Energy = force x distance, so they could acquire this energy by exerting a large force over a small distance or by exerting a smaller force over a larger distance. Gandalf61 17:24, 22 March 2007 (UTC)

Impulse is Force x time = $\Delta$ Momentum . Pressure is Force / Area. So, Pressure = ${\frac {1}{A}}{\frac {dp}{dt}}$ and depends on the mechanics of their shoe, the contact time, the time-varying area of contact, etc. It is not an easy question to answer without sophistated, time-varying models of the points of contact. Nimur 18:20, 22 March 2007 (UTC)

Okay, sorry to move this down--I posted the question and I'll be more specific: Three men, 180, 170, 150, pounds (I know I changed the weights, this is more accurate) jump 6 inches off the floor of an elevator. The elevator has a 13 person / 2000 pound weight limit. Would the three men overload the elevator on their landing?

It depends on how they land. If you dropped a large block of metal, it would stop more quickly (its center of mass would move less from the time it hit to the time it stopped moving) than a ninja landing with bent knees, cat-like tread and all that. Consider that for the same amount of work, you'd be, in the first case, dealing with a small d and large F, and in the latter, a large d and a small F. Remember, $W=F\times d$; work equals force applied over a distance. The people are descending with a given kinetic energy, which is the amount of work done in stopping them. This can be done with a large force over a short distance (metal block), or a small force over a large distance (ninja). There's no simple yes-or-no answer to your question. grendel|khan 19:20, 22 March 2007 (UTC)

Really? So it is possible for those three men to overload the elevator? I don't have to know definatively, but it seems like it's a question that some one who knows a bit of physics would be able to fairly surely say "probably yes" or "probably not." Not to nag for an answer, but would you say it's likely the elevator would overload or unlikely that 500 pounds could come down with four times the force off a six inch hop.

Since you insist, I'll do some back-of-the-envelope calculations. Take a 500 pound (227kg) lead brick, and drop it on the elevator's floor. From a six-inch (0.15m) drop, it's got to release (227kg*9.8m/s^2*0.15m) = 334 J of energy. So, given that W=Fd, so d=W/F, then it will break if it deforms less than d = 334 J/(2000lb * 9.8m/s^2) = 334 J/8888 N = about 3.75cm, or an inch and a half. So, if a five hundred-pound lead weight is dropped from six inches' height, and if its center of mass travels less than an inch and a half between the time it hits the elevator floor and the time it stops moving, and it exerts a uniform force on the floor, then that force will be of magnitude two thousand pounds, which will break the elevator. Bear in mind that if you hit that hard, even from only six inches' drop, you'd run a risk of hurting yourself. If you try jumping on a hard surface, locking your knees and hitting on your heels, it'll feel bone-jarring. grendel|khan 21:50, 22 March 2007 (UTC)

I think the answer is almost certainly no, as long as it's just one jump, because the objects involved are men, not rigid objects like metal blocks. The natural way to land is on the balls of one's feet, with slightly bent knees, not on one's heels with straight knees (ouch!). To go over the 2000 pound limit, there would have to be an instant when the men are applying an average of 667 pounds of force each to the floor of the elevator. Given that the men are landing on the balls of their feet, how much force they are capable of applying is limited by the strength of their calf muscles. Going over the average of 667 pounds each would require a strength roughly similar to the strength required by each man getting an extra 500 pounds of weights strapped to their waist, and then rising up onto the balls of their feet. I know I don't have the strength to do that, and I think it's unlikely that any of the three men in question do, either.

If, however, instead of just one jump, the men instead are jumping up and down repeatedly, then the analysis would get more complicated. If the men jump up and down at the same frequency as the resonant frequency of the elevator, then it would be possible to break the elevator without ever appying more than 2000 pounds of force instantaneously, if the elevator damped such oscillations insufficiently. MrRedact 21:47, 22 March 2007 (UTC)

It is possible for a flea to overload the elevator, it just needs really really sturdy legs. —The preceding unsigned comment was added by 84.187.7.58 (talk) 06:15, 23 March 2007 (UTC).

Not really, of course, and the reason why is related to a significant effect that hasn't been taken into consideration above, but perhaps should be: The 2000 pound limit is about the amount of force it would take to damage the elevator cable (assuming there isn't any leeway in the rated limit, which isn't really the case), if the force is applied continuously. But there won't necessarily be any damage just because the instantaneous force applied exceeds 2000 pounds briefly, because the steel cable supporting the elevator is somewhat elastic. For a while after a force over 2000 pounds is applied, the cable will deform elastically, with a relationship between stress and strain governed by Hooke's law. The cable will only be damaged by undergoing a plastic deformation after the excessive force has been applied long enough that the resulting strain on the cable exceeds the cable's yield strength. During the time that the cable is deforming elastically, the cable is absorbing kinetic energy from the object that fell in the elevator car, converting it into potential energy in the cable. Once all of the kinetic energy is absorbed, the only remaining force on the cable is just the gravity on the stationary object, which is way under the rated limit in any case considered above. In the worst case of 100% of the kinetic energy of the object upon landing being transferred to the elevator car (in reality it will be less), the energy the cable needs to absorb is equal to the potential energy of the object before it falls, which is mgd, where g is the accelleration of gravity, m is the mass of the object, and d is the object's initial height above the elevator floor. In the case of a flea, since the mass of a flea is negligible, the maximum kinetic energy a flea can impart on the floor of the elevator car is also negligible, no matter how sturdy the flea's legs are. MrRedact 18:29, 23 March 2007 (UTC)

Indeed; you usually have to take into account a coefficient of safety (as you would are dealing with $\sigma _{allowed}$, not $\sigma _{maximum}$, and $CoS={\frac {\sigma _{maximum}}{\sigma _{allowed}}}$) and even then, $\sigma _{maximum}$ is usually the yield strength of the cable, not the fracture stress. If the high stress is short-lived, then I doubt you would have much of a permanent deformation. Titoxd^{(?!? - cool stuff)} 18:39, 23 March 2007 (UTC)

Helping a friend study physics

Unfortunately, I haven't studied it myself in a few years, so a few equations are a bit fuzzy, especially since my friend's teacher uses notation that at the very least I am not used to (e.g. capital 'W' for both weight and work). I've managed to figure out most of the equations on the list of equations to study, but a few still elude me:

1. GPE=mgh (it's potential energy, since it's mgh, right? Then what's with the G? Potential energy due to gravity?)
2. P=P_atm+Dgh (it's supposed to be pressure due to fluid, I think, but from which direction is 'height' measured?)
3. Q=mL_f and Q=mL_v (enthalpies of fusion/vaporization with some strange notation)
4. Q=ne
5. E=F/q
6. E=kq/r²
7. W=ΔEPE and V=EPE/q (Alas, I'm not so hot on electrical physics)

So if anyone could help explain these or send me in the right direction, I would most appreciate it. And no, it actually is my friend, not me ;-)

137.99.165.83 21:03, 22 March 2007 (UTC)

First things first: Potential energy is dirctly proportional to acceleration of gravity. After all, the bodies fall faster when g is larger, and initial potential energy is equal to the kinetic energy when the body is touching the ground. Secondly, total pressure is the sum of pressure due to atmosphere plus atmosphere due to fluid. The height is measured from the surface of the fluid. As for the rest, wait for someone else, because I'm not familiar with English physics terms.--Orthologist 21:31, 22 March 2007 (UTC)

I've numbered your equations for ease of reference:

1. GPE is indeed gravitational potential energy.
2. D is density (more commonly denoted by ρ), and "height" there really means "depth" -- distance from the air/fluid interface (at the top) to the point in question.
3. Q here is an amount of heat released or absorbed; m in these equations is just mass. The L_? are the specific enthalpies; "specific" means "per mass" (as opposed to "per mole" or "per volume").
4. Q here is instead an amount of electric charge; n is a number of charged particles, and e is the charge on each one ($\pm$elementary charge for protons or electrons (or electron holes)).
5. E here is the electric field, and F is force; q is the charge on which the force is applied.
6. E here is the same; k is Coulomb's constant, and r is the distance from a charge.
7. W here is work done on a charge; EPE is the electric potential energy. V is voltage, and q here is the charge on a proton.

(Whew, that was a workout trying to guess what all the equations were!) Does that help? --Tardis 21:32, 22 March 2007 (UTC)

The L's in part 3, stand for latent heat of fusion/vapourisation. Latent means hidden as energy goes into changing state, not temperature, so is hidden. And they are specific latent heats as said above (are they also enthalpies? I can't remember my chemistry now!)137.138.46.155 14:47, 23 March 2007 (UTC)

Vasopressin and caffeine (again)

i ave just read articles on Vasopressin and i was wondering if there might be a relation between long term caffeine intake and the brain chemical fonction of Vasopressin like agressivity to other males and bonding to sexual partners clockwork fromage —The preceding unsigned comment was added by 216.113.99.149 (talk) 17:48, 21 March 2007 (UTC).

I think you're a little ahead of the game. I don't believe such a link has been established, which doesn't mean it doesn't exist. However, the caffeine article states the over use and intoxication effects of caffeine, which has been around for a long time, and none of it seems to mention aggression or relationship issues. Vespine 21:58, 21 March 2007 (UTC)

There is known to be cross-talk between caffiene induced and vasopressin induced release of intracellular Ca2+ stores, somewhere at, or upstream of, an endoplasmic reticular Ca2+-ATPase. However, knowing there is a molecular interaction between the two signalling pathways is very different from knowing their behavioural consequences. Rockpocket 22:05, 21 March 2007 (UTC)

i would like to know if (assuming cafeine affects vasopressin in the brain) since caffeine would decrese vasopressin related beaviours it woudnt be as noticable as , for exemple a increase in agression and might not ave been noticed yet in studies on caffeines clockwork fromage

sorry the first paragraph was suposed to be a quote from a previous article

Its entirely possible. A large scale, controlled study on the long-term effects of caffeine on human behaviour would be an expensive and time-consuming experiment. There would be so many confounding factors that an extremely large sample size would be required to identify any significant associations. Nevertheless, caffeine is a psychoactive substance, therefore it would be naive to assume it couldn't effect long term human behaviour, though proving it does would be difficult. Rockpocket 01:47, 23 March 2007 (UTC)

atomic physics

In the atom what keeps an electron from just emiting all its energy until it finally goes and collapses into the nucleus?---- —The preceding unsigned comment was added by 71.116.166.117 (talk) 22:59, 22 March 2007 (UTC).

In atomic physics, electrons don't behave like simple point particles, like they are modelled in classical electrodynamics. Rather, it becomes neccessary to model the electron according to quantum mechanics. In quantum mechanics, an electron being attracted to an atomic nucleus can't just release an arbitrary amount of energy. Instead, the electron can only give off energy in discrete quanta. An electron near a nucleus can only exist in a finite number of possible states, each of which has a particular amount of energy associated with it. An electron can only get "closer" to the nucleus by moving to a state with lower energy, in the process releasing an amount of energy equal to the difference of the energies associated with the two states. Since there are only a finite number of possible states, there exists a state with the lowest energy level (the ground state), from which the electron can no longer lose any more energy, because there do not exist any possible states with a lower energy level that the electron can move to.

I quoted "closer" above because in quantum mechanics, electrons are no longer modelled as being at a precise location, but instead are modelled with a wave function. So at a given point in time, the "distance" between the electron and the nucleus is only meaningful in a statistical sense.

To really understand this answer, you'll have to study quantum mechanics. A good textbook I'd recommend is Principles of Quantum Mechanics, by R. Shankar. Introductory Quantum Mechanics by Richard Liboff is at a little more introductory level, but Shankar explains things better and more thoroughly. MrRedact 02:05, 23 March 2007 (UTC)

Quantum Mechanics. I'm not making fun of you - it's a good question; classically, accelerating charged particles emit radiation. The fact that this is not the case for a trapped electron in an atom was one of the important clues that led physicists to the idea of a wavefunction. Basically, the electron is a wavefunction, not a particle whizzing around the nucleus. --Bmk 02:01, 23 March 2007 (UTC)

This, by the way, was exactly the question that made the Rutherford model impractical, and is what led Niels Bohr to the Bohr model of the atom. Bohr could postulate an atom which would not lose all its energy this way, but he couldn't explain why there were stable states. The first bit of an answer came from Louis de Broglie's understanding of the wave nature of the electron; the more comprehensive answer then came from quantum mechanics. --24.147.86.187 02:51, 23 March 2007 (UTC)

Ideal gas

My roommate and I cannot agree on the solution to the following problem:

A sealed and flexible container of gas has its pressure doubled, and then its temperature doubled. What is the new volume?

My roommate believes it to be 'remains constant' (halved, then doubled), while I claim that the answer needs more information (not automatically clear what the doubled temperature has on V, only on PV). Which one of us is correct, and why?

(geez, this is like one of those retarded 'discussion' questions, heh)

137.99.77.171 00:27, 23 March 2007 (UTC)

How flexible is the container? Since PV = nRT, if you double the pressure, and double the temperature... Yea, I think the new volume should be the same as the original volume. --Wirbelwindヴィルヴェルヴィント (talk) 00:45, 23 March 2007 (UTC)

Consider the equation V = nRT/P → What happens to this equation when you double both the temperature and the pressure? − Twas Now ( talk • contribs • e-mail ) 03:21, 23 March 2007 (UTC)

I think the confusion arises from the vagueness in the question. How, exactly, did you double the pressure of the gas? The only way would be to either: double the amount of gas (that is, add more gas), to double the temperature, or halve the volume. So you're right; more information is needed. — Knowledge Seeker দ 03:49, 23 March 2007 (UTC)

Doubling the amount of gas in a flexible container will usually not double the pressure. That depends entirely on the container and the surrounding pressure. —The preceding unsigned comment was added by 84.187.7.58 (talk) 06:20, 23 March 2007 (UTC).

Yes, the problem is ill-posed unless you make some additional assumptions which are not stated as part of the problem. The first step is to double the pressure of the gas in the container. The assumption that your roommate and Wirbelwind are making is that this step is performed as an isothermal process, i.e., performed such that the temperature of the gas is the same at the end of this step as at the beginning. Note that doubling the pressure on the gas will cause the gas to heat up, even though no heat source has been applied to the gas, so for this step to be an isothermal process, you’d need to wait for the gas to cool back down to its original temperature (possibly applying refrigeration for a while to speed up the process), before considering this step to be completed.

The second step of the experiment is to double the gas’ temperature. The assumption that your roommate and Wirbelwind are making about this step is that this is done as an isobaric process, i.e., performed such that the gas’ pressure during this step remains constant. This step, too, could be tricky, depending on the nature of the “flexible container”. For example, if the “flexible container” is a balloon, assuming the external pressure on the balloon is held constant, doubling the temperature of the gas in the balloon will cause a combination of increasing the gas’ volume and increasing the gas’ pressure, so the volume of the gas will less than double during this step.

If you make the above two assumptions, then yes, the volume at the end of the experiment will be the same as at the beginning. MrRedact 04:12, 23 March 2007 (UTC)

If you cannot make those two assumptions, it would be better to assume the process is adiabatic; since the ideal gas law is an approximation anyway, we may as well approach the problem as an adiabatic and internally-reversible process - that is, an isentropic process. From there, you can use ${PV}^{\gamma }=constant$, and go from there. Titoxd^{(?!? - cool stuff)} 04:47, 23 March 2007 (UTC)

But if you assume that both steps of the experiment are adiabatic, then the final volume is less than the initial volume. In particular, the only way to double the gas' temperature in the second step adiabatically would be to double the gas' pressure (again) without use of an external heat source, which would shrink the volume even further than it was already shrunk to in the first step. MrRedact 13:50, 23 March 2007 (UTC)

Snakeboards and non-holonomic locomotion

So I have been honing my snakeboard skills and I am wondering, how does the blasted thing work? I don't mean how does one make it go, I have that figured out, I just cannot for the life of me understand how my feet moving translates into the board taking off in a somewhat straight line. The snakeboard article describes it as non-holonomic locomotion. I read the pertinent article and if I understand correctly the system in non-holonomic because the board moves forward even though there is no "control" that directly allows for it, unlike a regular skateboard. All of the info I have found off-wiki is more technical/mathematical than I am presently able to grasp. I guess what I am looking for is a description of the force vectors that I can visualize. Thank you in advance for any help you can provide. 161.222.160.8 01:36, 23 March 2007 (UTC)

Bottle Rockets

A friend of mine is planning a competition in which teams would design and launch bottle rockets which are powered by a chemical reaction. My question is this: what kind of reaction would give enough thrust and impulse to allow a rocket a modest flight (~30ft), while still remaining marginally safe. Are there safe reactants that could produce this result? Would the bottles stand up to the pressure stresses? (I'm assuming the thrust would largely be a product of pressure) —The preceding unsigned comment was added by 138.29.51.251 (talk) 02:35, 23 March 2007 (UTC).

For such a short distance you could launch a cork from a bottle of carbonated water shaken vigorously. An ultrasonic device can provide the shaking. This would eliminate the possibility of causing a fire, which is perhaps the greatest risk of bottle rockets. StuRat 02:58, 23 March 2007 (UTC)

Or, instead of shaking you do the Mentos and Diet Coke reaction with a cork as the projectile. I do not know if sufficient pressure would build fast enough though. Sounds like a project for this weekend! 161.222.160.8 03:03, 23 March 2007 (UTC)

With a small nozzle, the Mythbusters were able to get Diet Coke to shoot up over 30'. But the altitude depends on the initial powered accelleration - and the amount of time for which it is applied. The accelleration is determined by the Force divided by the Mass. So the trick to getting something to go high SAFELY is to shoot something of very small mass using relatively less force - presumably requiring a less dangerous energy source. SteveBaker 03:53, 23 March 2007 (UTC)

StuRat I think the OP is using an alternate meaning of bottle rocket disambiguation) as in a water rocket which is made out of a bottle, as opposed to what you are reffering to as supposedly the more common use of the term bottle rocket.. No fire hazard with a water rocket. Rereading the post, I could still be wrong, it could be taken either way. Vespine 05:26, 23 March 2007 (UTC)

Sinus tachycardia

Apart from stress, trauma etc, are there any other causes of this condition?

I have linked the title for you, there is a list there that should answer your question.161.222.160.8 03:06, 23 March 2007 (UTC)

Verizon credit approval

i have been attempting to get a two year contract with verizon wireless however it asks for for my SSN for credit approval. the next day i get an email saying i have to do a $400 security deposit. I have good credit i am wondering why that is happening. are there any ways to bypass that.--logger 04:34, 23 March 2007 (UTC)

1) wrong place to ask. 2) get a prepaid phone or try another provider161.222.160.8 04:37, 23 March 2007 (UTC)

Where are you located? In the states, a security deposit is almost unheard for cell phone contracts. Are you dealing exclusively with email, because you may have gotten involved in a scam (never email your SSN to anyone). I would suggest going to a Verizon store in your area, and try setting up the contract in person. --Cody.Pope 04:37, 23 March 2007 (UTC)

i am in the states i got the order VIA wirefly. and i get only email for the order confirmation--logger 04:42, 23 March 2007 (UTC)

I agree with Cody. It's almost certainly a scam. What reputable company asks for $400 by email? Contact Verizon directly. Clarityfiend 04:45, 23 March 2007 (UTC)

And even if it isn't a scam, who needs to do business with a company that requires a $400 deposit ? Get a prepaid phone, like TracFone, they don't stick their noses into your credit report. In fact, you never have to give them your name (if you buy with cash). StuRat 05:46, 23 March 2007 (UTC)

I think phone companies give back the deposit after a few months though. --Wirbelwindヴィルヴェルヴィント (talk) 06:46, 23 March 2007 (UTC)

You should think of the money as gone once you give it as a deposit. You would have to sue to get it back if they decide to keep it for whatever reason, and it might very well cost you more in time off work, etc., to get your money back than you actually get. They know this, so will feel free to keep it. StuRat 15:07, 23 March 2007 (UTC)

I'm not so sure about this. You might want to find out if the security deposit is returned without any other conditions as long as you make the first few months' payments on time. At least, I think that's how cellphone deposits work. --Wirbelwindヴィルヴェルヴィント (talk) 19:13, 23 March 2007 (UTC)

Maybe your credit is no longer good because of identity theft. Get a copy of your credit reports from the credit reporting agencies. Qaz 19:43, 23 March 2007 (UTC)

Dream recall and masturbation

Ok, I know there are probably quite a few people here that have differing opinions on Lucid dreaming, but while this question does have something to do with LD, it isn't part of the question itself so give me a break, OK : ).

I am one of those people who has a lot of difficulty remembering dreams (at least since I was 16), and I've recently been making attempts to increase my dream recall (my ability to remember dreams), with some success.

Though I myself initially passed off any connection as mere coincidence, there are many antecdotes on increasing dream recall that hint that masturbation may inhibit the process, and if I trace back my most vivid dreams in the last 5 years (which is about 3 or 4 dreams), they just happen to be smack in the middle (or end) of my longest bouts of celibacy (reasons vary), so I instinctively start to wonder "why?".

Could there be any explanation for this? The Wikipedia is vehement on pushing the fact that masturbation has no known psychiological side-effects, but due to the large amounts of hormonal release involved in ejaculation, I find that surprising, almost hard to believe. 222.158.162.242 05:45, 23 March 2007 (UTC)

I've personally done plenty of experiments on masturbation and checking for correlations with things and found none. With dream recall, which is my only problem with lucid dreaming, I have found no correlation. Dream recall I have found works best for me if I wake up many times. When I wake up I try and remember (absolutely best thing to do is write them down) and then I fall asleep, have another dream, wake up, and remember. [Mαc Δαvιs] (How's my driving?) ❖ 05:57, 23 March 2007 (UTC)

Plenty of experiments, eh? =P --Wirbelwindヴィルヴェルヴィント (talk) 06:46, 23 March 2007 (UTC)

Can't help with the original question, but I'm fascinated at why one would choose to see of masturbation correlated with anything. Would you mind telling what sort of things did you checked and on what basis you hypothesized there might be a correlation? Rockpocket 07:31, 23 March 2007 (UTC)

Think of it like this: We have things like candy, money, fast food, and video games. Human beings in general are pleasured by such commodities, but bad effects emerge when large amounts of the said commodities are involved. A sceptic is driven to assume the same must be possible for something like masturbation, and a good sceptic will do his best to prove or disprove the notion. 222.158.162.242 08:47, 23 March 2007 (UTC)

I'm curious if the correlation is meant to be just for masturbation or if it is the same for sex as well? —Pengo 13:33, 23 March 2007 (UTC)

Question on the chemical composition of "crocodile" tears

Just caught an airing of an episode of CSI:NY, and one of the CSIs checked the chemical composition of the tears shed by one of the suspects and determined that they were not true "emotional" tears because they did not have certain levels of chemicals found in those kind of tears.

Presuming that you are not introducing an irritant into the eye to induce crying, aren't "crocodile tears" basically just emotional ones? What I'm thinking is that when an actor is actually able to make themselves cry, most, I believe, are inducing the emotions in themselves that would cause them to weep, and thence, the tears would be emotional tears, and not basal or reflex.

That is assuming, of course, that the person is not simply squeezing their eyes a great deal to produce more basal tears, but I wonder if enough basal tears could be produced that way for one to actually have the tears leave the eye as when one is weeping.Lkusz 08:35, 23 March 2007 (UTC)lkusz

• I'm not sure, but the only thing I can think of is that real tears would secrete certain hormones that aren't present in fake ones. But to be honest, I agree with you. It sounds like the writers took some artistic license with it. - Mgm|^(talk) 09:28, 23 March 2007 (UTC)

• • In fact, there is a difference, if the tears were artificially induced. According to the paper Effect of stimulus on the chemical composition of human tears, the protein concentration of emotional tears from women exceeded that of irritant-induced tears by 24%. If there were tears brought about by fake emotion though, it would be impossible to tell the difference (the process works by artificially inducing the same hormonal channels that normal tears do). Laïka 09:58, 23 March 2007 (UTC)

• Also, I'd expect there to be an overlap. That is, while on average "emotional tears" might contain 24% more protein, some people's "emotional tears" probably contain less protein than some people's "crocodile tears". One of the biggest failings of CSI-like shows is that they portray all evidence as 100% certain, when almost nothing is. Even a DNA test is not 100%, as the samples are often contaminated. The murderers rarely draw blood samples of themselves with a sterile needle and leave the syringe for the CSI team. The funniest one I saw was where they found a human hair in the room of the murder, so concluded the person who matched that hair must be the murderer. There are probably hairs and skin flakes from every person who has ever been in your house still there, no matter how meticulously you clean your house. StuRat 15:01, 23 March 2007 (UTC)

A new reward!

Yep! I said I'd place more, so here I am again letting you know that there is a task for you here. It involves some simple formatting, but don't attempt it if you are not familiar with footnotes. As per the reward specifications, you'll recieve an award if you can complete the task. Not much more I can say really - go forth & footnote! :) Thanks, Spawn Man 11:02, 23 March 2007 (UTC)

All done! SteveBaker 17:09, 23 March 2007 (UTC)

Hydraulic transformer

We know that pistons convert hydraulic pressure into linear motion. Any idea how conversion of hydraulic pressure to rotational motion is done?59.92.240.176

One way is to have a piston connected, via an articulated rod, to a bearing on the circumference of a wheel. You pump the cylinder and the rod pushes the wheel around, which turns its axle. We have a great animation at Steam engine which shows just this method. Darryl Revok 12:46, 23 March 2007 (UTC)

Or you can use a turbine of some kind. SteveBaker 12:52, 23 March 2007 (UTC)

CO2 recovery method

Why can we mutate a gene in any particular species of plant that causes the leaves to grow to a bigger size and photosynthesize at a faster rate so as to control gobal warming???59.92.240.176

Plants are pretty much doing the best they can already. They have evolved leaf patterns, branch angles and trunk rotation so as to optimise the surface area facing the prevailing sunlight. If plants had bigger leaves (but no other structural changes), all that would happen would be that more of the leaves would be in shadow from other leaves - and since photosynthesis is driven by sunlight, that could be strongly counterproductive. At night (and when in deep shadow), plants actually produce CO2 - so plants with larger leaves than they need could actually add to global warming - not remediate it. For this approach to work, we would need more of the earth's surface covered in natural plants - not genetically modified plants. So if (for example) we could somehow turn the Sahara desert into a rain forest - that would have a major effect. But all of these kinds of solutions are too long-term - and they are risky - they might well have unforseen consequences for the environment that we do not yet understand. Maybe the Sahara forms an important part of the world's weather systems and covering it with trees might do something terrible to the oceanic heat cycles or something. What we do know is that reversing the production of CO2 gets us back to a more natural situation that we know works. It also reduces our dependancy on fossil fuels - which we have long known are being consumed at a rate that is perhaps a million times faster than they are being renewed - and must therefore run out some day. We need to do something fairly drastic and have it take effect in a couple of decades at most. There are a bunch of things we KNOW we can do - we just have to do them. My car does 35miles per (US) gallon. It's a great car - it's not even a hybrid - it'll go 140mph and does 0-60 in 7 seconds...yeah it's a fast car too. This year's model does over 40 mpg. Why is the average US car's gas consumption 12 miles per gallon? If everyone switched from their present monsterous gas guzzler to a fuel efficient car we would produce ONE THIRD the amount of CO2 from cars. No new technology, no serious 'quality of life' issues. The fact that people aren't doing that means that there is insufficient incentive. We need a gasoline tax that BY LAW starts at 50 cents per gallon and goes up by 25 cents per gallon every year until the average US fuel consumption is over 30mpg. That money should go into research and development in the car industry. Do the same thing with commercial vehicles...but adjust the slowly ratchetting tax increases to better fit economic needs - which probably means starting with a lower tax rate - but increasing it more rapidly to give them more time to adapt. 12:51, 23 March 2007 (UTC)

Average fuel economy in the US is about 21 miles/gallon, not 12: [10]. I agree with the need for a fuel tax, but it shouldn't go up so quickly as to cause people to junk their current vehicles before they wear out, that would be even worse for the environment (and our wallets). I'd increase gasoline taxes a cent a month, for 50 years. That would be $1.20 in 10 years, $2.40 in 20 years, $3.60 in 30 years, $4.80 in 40 years, and $6.00 in 50 years. Knowing that the rate will continue to climb would convince people to buy fuel efficient vehicles the next time they buy a new car. StuRat 14:36, 23 March 2007 (UTC)

That figure of 21 mpg is the average mpg rating of US cars - ie if they were all new and well-maintained and driven as per EPA test track rules - then they would get 21 mpg. But the average of actual running cars is 12 mpg...because older cars use steeply more gas than they did when they were new, many are poorly maintained, and almost everyone drives more agressively than the EPA tests assume they do - and the EPA run cars with the A/C turned off. SteveBaker 17:45, 23 March 2007 (UTC)

As for increasing the amount of photosynthesis to convert CO₂ into oxygen and carbon, the oceans have the most potential for this. While we could increase the amount of algae or other sea plants in some areas by providing missing nutrients, like iron, there could be side-effects, as described above. For example, there was a concerted effort a generation ago to create artificial reefs by sinking used tires, but many of those tires broke loose and damaged natural reefs and the project was a disaster. We don't want to repeat mistakes like that. StuRat 14:47, 23 March 2007 (UTC)

Many would argue we don't want to repeat the mistakes of trying to manage an environment far more complex than we can comprehend. [Mαc Δαvιs] (How's my driving?) ❖ 16:03, 23 March 2007 (UTC)

Actually, since we use stomata density on fossilized plant leaves as a proxy for CO₂ ppm reconstruction, the best way to do this would be to put out a higher CO₂ ppm. Right now I recall it as being around 435 for the Earth, but when it is 1000 ppm plants are known to grow about 50% faster, with photosynthesis also working on turbo. Plant's aren't doing the best they can do, they just adapt to the parameters of the moment the best they can.

I think one of the most pernicious aspects of the modern environmental movement is the romanticization of peasant life and the idea that western society is the destroyer of the world. The environmental movement has evolved into the strongest force there is for preventing development in the developing countries. I think it is legitimate for me to call them anti-human. Ok you don't have to think that humans are better than whales or owls, but I think it is not ok to think of humans as scum. That's it's ok to have millions of them go blind or die. I just can't relate to that"

— Patrick Moore, Co-founder, Greenpace

The Sahara Desert used to be a much more luscious land. The region's desiccation is thought to be a major force in the forward movement of humans as a species—it forced humans to migrate to the Nile riverbanks and Northward they moved up to the Fertile Crescent. [Mαc Δαvιs] (How's my driving?) ❖ 15:58, 23 March 2007 (UTC)

de broglie's wavelength

assuming we have aparticle have charge (q) and mass of (m) moving with speed according to potintial diffreance (Δv) what its de broglie wave length exprission? —The preceding unsigned comment was added by 196.20.48.41 (talk) 16:34, 23 March 2007 (UTC).

It's unclear to me what you mean by "moving with speed according to potential difference Δv". For example, perhaps you're talking about a one-dimensional scattering problem, where the potential function is a step function with height Δv? If not, please describe in more detail the experiment you have a question about. MrRedact 19:09, 23 March 2007 (UTC)

MINALK GASOLINE SWEETENING

in the MINALK gasoline sweetening reactor what happens to the hydrogen di-sulphide in the gasoline, and why do we vent the reactor. and whiles venting what do we vent? —The preceding unsigned comment was added by 41.204.33.199 (talk) 17:09, 23 March 2007 (UTC).

There doesn't appear to be a Minalk article, but there is one on Merox which is relevant. It links to this[11] external PDF, which has more details of Minalk. I think the venting is excess air, probably containing hydrogen sulfide, mercaptans, and other waste product. Nimur 17:32, 23 March 2007 (UTC)

Juvenile gulls

I can understand that the mottled brown colouration of gull chicks and newly-fledged birds helps to camouflage them when in and about the nest in their natural cliff/beach/coastal scrubland habitats. I'm curious however as to why juvenile gulls maintain this plumage for so long, once independent of their parents (it can take four years for the bird to fully attain its adult plumage) and fully versed in the ways of the gull. Is there any real advantage to be had for (for example) a 2-y.o. gull to still be a predominantly dull dirty-brown bird? As far as I've seen when watching them, adult birds don't treat the juveniles any differently to any other gull in their general, daily interactions and once past the fledgeling stage, juveniles are in no way submissive to adults. --Kurt Shaped Box 17:47, 23 March 2007 (UTC)

Cracking open my animal behavior textbook, it says that not all current traits are adaptations, in other words it is not possible to explain all traits as beneficial in the evolutionary sense. Maladaptive or benign traits can develop as side-effects of otherwise beneficial adaptations. Apparently Stephen_Jay_Gould is a major critic of explaining every characterstic of living things as a beneficial adaptation. Who knows, in a few thousand years, juveniles may be white.-- Diletante

How little sodium intake is too little?

I calculated the mineral content in my diet the other day and found, to my great joy, that it contained only 431mg of sodium. This seemed so little that I thought maybe it's little enough to cause hyponatremia, yet there's no mention of hyponatremia from inadequate sodium intake at eMedicine. Anyone who knows how little is too little? Thanks in advance, Jack Daw 19:02, 23 March 2007 (UTC)

It depends on who you are (do you run marathons regularly?), and who you listen to. The lowest Adequate Intake level that I've seen for sodium is New Zealand's, which recommends at least 460 mg/day. See Edible salt. MrRedact 19:37, 23 March 2007 (UTC)

My anaerobic exercise is highly limited ;) I might do well in sipping some Gatorade during the day. Thanks for the info, Jack Daw 20:33, 23 March 2007 (UTC)