Wikipedia:Reference desk/Archives/Science/2007 January 10

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January 10

Joinery

I once was joinery and it got my penis caught. Not funny. If joinery is about joining bits of wood, what word describes joining metals? Brazing and welding and so forth. --Username132 (talk) 00:14, 10 January 2007 (UTC)

It's really welding as far as I know. — Kieff 02:16, 10 January 2007 (UTC)

I thought welding was just one technique, along with brazing and soldering. --Username132 (talk) 03:31, 10 January 2007 (UTC)

Perhaps you want metalworking. --Anonymous, January 10, 2007, 07:46 (UTC).

Or smithing.81.153.220.80 12:59, 10 January 2007 (UTC)

fabrication?82.38.197.184 20:04, 10 January 2007 (UTC)

Corrosive gallium

Is there a material with high thermal conductivity that does not react with gallium?

Gold, perhaps? -anonymous6494 16:58, 10 January 2007 (UTC)

Healing after a spinal injury/surgery

Hi, my dad had an accident (slip and fall) a few days ago and had to have surgery on his neck (c4 - c3 area). They inserted artificial bone into his neck. We were really scared he would be paralyzed, but he has shown a lot of improvement. He can move one hand and one leg with considerable strength and the other leg just a little but it sometimes spasms. His bad arm he can move but in the fingers he has mostly just thumb and index motion. This is at about 48 hours after the surgery.

We are hopefull that he will do a lot better, and with physio be able to walk. The problem is I really have no knowledge of how rehabilitation works outside hollywood movies (where people enter totally paralyzed and go onto win championships in football). My question is, how effective is rehabilitation at making movement better for a patient? Would it be common for someone who for example has feeling and some movement in both legs go onto to be able to walk?

I know this is a hard format to answer questions in, I am just looking for your general opinions.

Some people make remarkable recoveries, while others have only limited progress. Even for the doctors who treat the patients and know all the details it is hard to make a prognosis. The signs are hope-giving, but more than that can really not be said. You should really talk to the doctors on the case. All the best with your dad.  --Lambiam^Talk 01:30, 10 January 2007 (UTC)

After I broke my back in two places, I had two years of rehab. I gained full function (though I have places on my body where if I touch it I feel it somewhere else). In rehab, I noticed that the younger people recovered much faster than the older people. I was 10 at the time, so that is probably why I did well. I do not know if this is a universal rule or just an anomoly in the hospital I was in at the time. --Kainaw ^(talk) 06:06, 10 January 2007 (UTC)

Why do Acetone and other solvents dissolve polystyrene?

Someone please answer this for me: Why do Acetone and other solvents dissolve polystyrene? I've looked all over Net Library and other sources and have so far found no answer. Thank you! 68.191.137.57 01:24, 10 January 2007 (UTC)

Acetone is a solvent, maybe that article will help you find the answer you are after. Vespine 02:09, 10 January 2007 (UTC)

A chemical rule of thumb is that "like dissolves like", so it makes sense that an organic material like polystyrene should dissolve in organic solvents such as acetone, whereas an ionic material like table salt is better soluble in polar liquids like water. -- mglg_(talk) 02:18, 10 January 2007 (UTC)

ELISA Reading

If I have to read an enzyme-linked immunosorbent assay microplate, is it ok to obtain optical densities with a spectrophotometer instead of a microplate reader? Thanks, Elizabeth 02:29, 10 January 2007 (UTC)

Yes in theory, provided that the absorbency you are looking for is within the range of the spectrophotometer. However, most spectrophotometers read from side to side on a cuvette, meaning that you often need at least 0.5mL to get an accurate reading (depending on the volume of the cuvette and the build of the spectro), whereas microplates usually don't hold that much fluid (since the microplate analyzer reads top to bottom through the plate). Remember, the precision of the experiment won't be as good if you use two different tools, so you should choose one metod for all the data in the experiment if possible, and certainly only use one machine for all data in a data set. 24.241.20.246 16:44, 10 January 2007 (UTC)

It should be noted that "Ultramicro" cuvettes are readily available from standard suppliers (reusable for ~US$300 ea), and can hold 0.05 - 0.1 mL (50-100 microliter) volumes, about the same as most microtiter plates. I'd also recommend brushing up on Beer's Law. -- 128.104.112.15 19:21, 12 January 2007 (UTC)

Corrupted page

The Thermal Conductivity page has been vandalized - various expletives see http://en.wikipedia.org/wiki/Thermal_conductivity —The preceding unsigned comment was added by Agsmyth (talk • contribs).

In the future, you can revert vandalism yourself by selecting an earlier revision and saving. Splintercellguy 07:18, 10 January 2007 (UTC)

Huntington's disease

I have read the article Huntington's disease. Some of the symptoms are Depression and Anxiety.

Another symptom is Chorea. Chorea is cused by overactivity of the Neurotransmitter Dopamine.

• Q1. Currently I believe there is no single medication to treat Huntington's disease?

Dopamine is a neurotransmitter that is involved in depression.

The treatments for Chorea are antipshycotics, which are antagonists of dopamine.

• Q2. Antagonizing Dopamine will cause further Depression, and thus it will make the Huntington's diseases symptoms worse?

--Jones2 23:59, 8 January 2007 (UTC)

You won't like my answer but, you'd have to ask a doctor;). I'm not one, but I do know that when the label says tell your doctor if you are on any of this other medication, they MEAN IT! Drugs can have surprising and NON intuitive side effects when taken with other drugs. brain chemistry is very complex, a normal person taking the medication of a schizophrenic may get completely different effects from the medication. For example, Antagonising OVERACTIVE dopamine to treat chorea may simply bring it to normal levels, not causing further depression at all. A doctor's job is to determine and weigh up all the positives and negatives of the treatments, there may be alternative treatments to chorea, partly why most people believe medical advice shouldn't be given out over the internet. Vespine 02:52, 9 January 2007 (UTC)

• I don't have Huntington's disease. My question is of scientific interest. I don't understand. --Jones2 05:31, 9 January 2007 (UTC)
• It's not the best of sources, but according to a 1990s-2000s fiction television show there is no cure for Huntington's. That means you need medication to treat the symptoms and suppress the progression of the disease. That would require at least 2 different meds. - Mgm|^(talk) 11:24, 9 January 2007 (UTC)

I didn't assume you had Huntington's, but your question is still asking for something that could vary greatly depending on each individual case and could only be answered by a doctor who has evaluated the individual. If someone gave you an answer, even if it was well educated, someone else could come across this site and read the answer to be more authoritative then it could possibly be. Vespine 21:43, 9 January 2007 (UTC)

One further thing, the article states it is a genetic disorder so there is no cure, we can't currently cure genetic disorders. It also states There are treatments available to help control the chorea, although these may have the side effect of aggravating bradykinesia or dystonia. So the mechanism is known at least to some degree. On the chorea article it further states There is no standard course of treatment for chorea so I think you are barking up the wrong tree. A doctor would take all that into account, including if depression or any other conditions are a concern and would tailor treatments and controls suitable for the individual. A doctor should not give you medication for one affliction if the side effects outweigh the benefits..Vespine 21:50, 9 January 2007 (UTC)

Q1: There is no treatment for the underlying cause of HD, but there are good treatments for relieving symptoms. Q2: An antidepressant may or may not cause problems, there is no "scientific" answer, only individualised therapy. Without going into details, the principles would be: Initially choose medications that have been shown to help the specific symptom, and then watch the person for side-effects. Then the choice is then to either treat the side-effect, or try a different drug. There are numerous ways of treating the symptoms of depression, conventional anti-depressants not necessarily being the best, or giving better results. Whatever the doctor chooses, it is really just a matter of accurate follow-up and changing medicines appropriately. It is a matter of individualised poly-pharmacy, and not working straight from a textbook about normal people, and the doctor knowing what she is doing, and the patient (or family) learning to observe and report positive and negative effects, and it being a mutual responsibility (doctor, therapist, patient and family) to find ways of improving the situation - there is no "theoretically right treatment". Clear goals and honest communication is the only way to go. --Seejyb 01:26, 10 January 2007 (UTC)

---

• I read the article Tardive dyskinesia. Tardive dyskinesia is characterized by repetitive, involuntary, purposeless movements. Tardive dyskinesia most commonly occurs in patients with psychiatric conditions who are treated with antipsychotic medications for many years.

• I have read the article Chorea. Chorea is characterized by brief, irregular contractions that are not repetitive or rhythmic, but appear to flow from one muscle to the next, it also adds twisting and writhing movements. Chorea is caused by overactivity of the Neurotransmitter Dopamine.

• I have read the article Antipsychotic Drugs. Antipsychotic Drugs activity is mediated primarily by antagonism at dopamine receptors.

• Now Tardive dyskinesia is caused by lack of Dopamine.

• Now Chorea is caused by excess Dopamine.

• Now Tardive dyskinesia & Chorea have similar symptoms.

• Now a person with Huntington's disease have symptoms Depression, Anxiety & Chorea.

• Now a person with Bipolar Disorder have Depression but are treated with Antipsychotic Drugs. Which leads to Tardive dyskinesia.

• I am sure you can infer my above question now. --Jones2 06:31, 10 January 2007 (UTC)

I'm not an expert at all, and this is not a definative answer, but perhaps a pointer towards an explanation. Yesterday I had the pleasure of meeting Paul Greengard, a Nobel Prize winner for work on dopamine mediated signal transduction in the nervous system. He talked at some length about his work and, what I learned from him, was how a multitude of neuro-stimuli including antipsychotic drugs, alcohol, caffiene, LSD, PCP, cocaine, marijuana, amphetamines, ritalin and prozac - many of which produce contrasting physiological effects and act through different transductions pathways - all converge at a common protein called DARPP-32. It at first seems impossible to imagine how a single protein can mediate such different neurochemical effects. But - and I couldn't do the complexity or elegance of the system justice here - an incredibly sophisticated network of positive and negative feedback loops via kinases and phosphatases interact to give the protein a remarkable scope of action. Indeed DARPP-32 itself can be phosphorylated on up to seven different serine sites. Combinations of phosphorylation at least four of them are known to regulate its activity, and thus the proteins that DARPP-32 itself phosphorylates.

Now here is how this is related your your query: these sites are phosphorylated independently by downstream cascades of different dopamine receptor classes (D1-like or D2-like receptors). Moreover, other neurotransmitter signalling pathways have a huge, and differential, influence on DARPP-32 phosphorylaytion downstream of, and at the level of, both receptors. In other words, the same "dose" of dopamine at synapse can give very different responses via DARPP-32, depending on the receptor it signals through. And the local signaling environment for a given neuron - which can change from second to second - can effect both the type of dompamine receptor that is active and the effect of either receptor's signaling at DARPP-32.

So, while I don't have a specific answer for you, I believe Greengard's body of work - coupled with the consideration of signaling through different dopamine receptors - provides a mechanism that can explain why modulation of dopaminergic signaling can result in such seemingly paradoxical effects. Rockpocket 02:47, 12 January 2007 (UTC)

Though I thought the questioner was simply trolling in a rather unsophisticated way, I liked your answer, Rocketpocket, and envy the opportunity you had. It is wonderful to see how the basic scientists are working out why real life health problems, such as drug responses, are as tricky as are. --Seejyb 15:44, 12 January 2007 (UTC)

Thank you. I was very lucky. Greengard is a remarkable character (what he did with his Nobel Prize winnings speaks volumes about the man) and his work is incredibly inspiring. I heard today that I'm going to have the opportunity to have dinner with another Nobel winner, Sydney Brenner in a few weeks. So if anyone has any good RD questions on Caenorhabditis elegans or genomics I'll put them to him. I'm hopeful that if I meet enough of these people, some of their genius will rub off! ;) Rockpocket 19:02, 12 January 2007 (UTC)

force constant

A spring of force constant 'k'is cut into 3 equal parts.What is th force constant of each

Well, imagine that your big spring is made of three identical springs. The formula for three springs connected in parallel is:

${\frac {1}{k_{big}}}={\frac {1}{k_{A}}}+{\frac {1}{k_{B}}}+{\frac {1}{k_{c}}}\,$

Where k_big is the original k and k_small is the new k. As all three ks are the same,

${\frac {1}{k_{big}}}={\frac {3}{k_{small}}}\,$

Therefore

$3k_{big}=k_{small}\,$

It should be easy to solve from here. Laïka 14:31, 10 January 2007 (UTC)

Laïka, you mean connected in series, right? Springs add like capacitors, and "uncutting" a spring is certainly connecting them that way. --Tardis 16:31, 10 January 2007 (UTC)

Opps! Yes, sorry. Laïka 22:10, 10 January 2007 (UTC)

Circuit with two switches

In my kitchen there are two light switches. When one is up and the other is down, the lights turn on. When both are down or both are up, the lights turn off. Can someone show me with a simple diagram or a lucid explanation how this circuit works? I have only high school level Physics in me, so simpler is better. Thanks, J. Finkelstein 08:24, 10 January 2007 (UTC)

See light switch. Here is the circuit diagram. In your case, one of the switches is upside-down, so just imagine the central double wire having been twisted.--Shantavira 09:07, 10 January 2007 (UTC)

supply voltage to light

Just for "completeness", I'll note that there was an older way of wiring these switches called the Carter system. It was used a lot when "wiring" meant actual, individual single-conductor wires in the walls (see knob and tube wiring), but it's no longer considered acceptable because, in some switch positions, it makes the "shell" of the light bulb base carry line voltage, potentially electrocuting a person attempting to change the light bulb. But you might well encounter this scheme in an older house.

Atlant 14:21, 10 January 2007 (UTC)

That seems a weird system. Does it have any advantages over a simple SPST switch? 80.169.64.22 16:46, 10 January 2007 (UTC)

Put one switch by each of two entrances to a room so one can turn the light on or off when entering or leaving by either door. DMacks 18:03, 10 January 2007 (UTC)

Just imagine you are using a pitch black stairwell. You need to switch the light on at the bottom of the stairwell. Now, once you reach the top, how would you switch off the light? 202.168.50.40 23:59, 10 January 2007 (UTC)

A linguistic curiosity here. The two switches in the diagram are formally "single-pole double-throw" (SPDT) switches, but in everyday hardware-store vocabulary they have two other names -- which are "two-way switch" and "three-way switch"! Apparently "two-way" is because they have two active positions, and "three-way" because they have three terminals. There is also a "four-way switch", which has four terminals that it connects in pairs, either straight-through or criss-crossed depending on the switch position. (Internally it's a DPDT switch with two pairs of terminals joined up.) One or more of these can be interposed along the two wires between the two three-way switches in the diagram above, to allow the same light to be controlled from additional points. --Anonymous, January 11, 2007, 04:00 (UTC).

--Of course I wrote this before reading the following question. Oh well. --Anon, 04:01 (UTC).

Rider question 8-)

Can you tell me the wiring diagram to be able to turn a light on or off from 3 or more locations?--Light current 21:46, 10 January 2007 (UTC)

You mean the one at the end of the light switch article? DMacks 21:51, 10 January 2007 (UTC)

Yes THanks--Light current 21:57, 10 January 2007 (UTC)

I'm guessing this is rhetorical, nevertheless, interesting. Google is useful too. David D. (Talk) 22:12, 10 January 2007 (UTC)

Will there be a mass die-off of my local gulls?

I've just heard that they're planning to close down my local landfill site this year. The area will be covered with earth and landscaped. I find myself wondering what will become of the hundreds (thousands?) of gulls that feed on the landfill on a daily basis. I'm not certain but I think that the gulls that feed on the rubbish there are a different group of gulls to the ones that feed in the urban areas. In the short term, it may be the case that the gulls from the landfill descend into town in search of food - a neighbour told me that when they closed the landfill in the place he used to live, the gull population in his town tripled for a time, with some of the gulls becoming very aggressive towards humans, presumably due to hunger (they'd attack anyone carrying anything edible as there simply wasn't enough discarded food in the streets to go around). So, what will happen to the gulls in the long term? Will they have the sense to move on eventually, or will the people of my town be subjected to the sight of sickly, starving gulls and corpses in the streets? I'd be lying if I said that I wasn't concerned about this... --Kurt Shaped Box 09:09, 10 January 2007 (UTC)

It could depend on how big the gulls are. The huge aquilline gulls we get in Thanet would probably eat smaller animals if they couldn't get enough food. And they could also try to eat out of bins &c, like foxes. Gulls die all the time, but there aren't usually lots liying around the streets here.Hidden secret 7 13:54, 10 January 2007 (UTC)

Gulls are pretty resourceful. Like most birds, their natural food supplies vary throughout the year so they will be happy to look elsewhere. In fact, they will probably find a healthier supply than scraps of plastic and rotting food, so the closure will probably be good for them in the long term. Whether they invade the town will depend what other resources are available to them.--Shantavira 14:01, 10 January 2007 (UTC)

Do you live near the coast? If so, I'd imagine that the gulls could still get more than enough by trailing the trawlers, but you'd see less of them, as they would spend more time at sea. This document states that the North Sea alone could support over 2,000,000 seabirds on fishing wastes alone. Given that this fascinating RSPB document about seabirds states that there are fewer than 2,000,000 birds in British waters, my guess is that there is more than enough fish waste out there to sustain a few thousand extra gulls. Laïka 14:08, 10 January 2007 (UTC)

(edit conflicted) Incidently, where I live, gulls have learned that the most profitable way to survive is to hang around schools around break and lunchtimes, and then swoop in to pick up all the dropped crisps and sandwiches as soon as the playground clears. It's always amusing to watch them (and also squirrels) perching on the rims of bins to try and retrieve leftovers, only to fall in themselves! Laïka 14:16, 10 January 2007 (UTC)

Yeah, they used to do that when I was at school too. They'd start hanging around on the roof of the kitchens when they started cooking the dinners in the mid-morning - and wait. All the waste food went into a big skip thing for pigswill and the gulls would climb inside to eat - some kids thought it was funny to try and knock the lid down when there were gulls inside. When the bin was next opened, they would attack the dinner ladies. --Kurt Shaped Box 21:30, 10 January 2007 (UTC)

I think your fears are justified. Unless a new source of food exists nearby, which can feed as many gulls, their future is bleak. The particular concern is that they only know how to get food that's lying on the ground, not having any experience in hunting. This type of dependency should not have been allowed to be created in the first place, perhaps ultrasonic speakers could have kept them away from the dump all those years ? StuRat 14:14, 10 January 2007 (UTC)

Apparently (I was told this when we visited the landfill on a school trip) they've been trying for years to find a way to keep the gulls away. AFAIK, ultrasound doesn't work on them, they ignore fireworks and flares after they've seen them a few times and they seem to understand the concept of 'shotgun' and 'rifle' once they've seen them in action (they apparently know the difference too - they fly high, out of the range of the pellets when the men have shotguns and stay low to the ground and fly away at top speed when they see rifles). On the other hand, I was told by someone else who used to work there that the local council don't actually mind the gulls being there too much because they eat quite a few rats and are good at locating the nests and eating the babies. --Kurt Shaped Box 17:43, 10 January 2007 (UTC)

Judging from this article their aggressiveness is probably nothing to do with their hunger and more to do with their proximity to humans. David D. (Talk) 21:40, 10 January 2007 (UTC)

They attacked people at my school too :( Lots of people I knew were late to lessons as seagulls wouldn't let them close enough to the nest to get a football &c back :)Hidden secret 7 19:05, 11 January 2007 (UTC)

Ah. That's your typical 'angry mother gull' response. Pound for pound, I'd say that a sitting hen gull is the most dangerous creature on the planet. :) --Kurt Shaped Box 23:26, 11 January 2007 (UTC)

geophysics

application of geophysical survey to the solution of a geofeatures eg salt dome.

Exploration geophysics is not a great article, but it does have some links. --Zeizmic 12:50, 10 January 2007 (UTC)

Frozen Corona

How does this work? Dismas|^(talk) 13:40, 10 January 2007 (UTC)

The beer was first cooled to well below the freezing temp, without actually freezing, due to a lack of nucleation sites. This is called a supercooled liquid. In such a state, almost any disturbance can allow nucleation sites to be created, in this case air bubbles (note how it freezes from the top, where the air bubbles are). Other methods are to add small particles or release pressure. StuRat 13:59, 10 January 2007 (UTC)

It's also related to a topic we were discussing here about a week ago. In a closed, inelastic container (like a beer bottle), the freezing of water would imply expansion (and therefore, massive pressure increases). Carried far enough, it might rupture the bottle explosively, but up to that point, the rise in pressure just inhibits further freezing (thus providing another mechanism to allow the supercooling that StuRat mentioned). But uncap the bottle (and remove the excess pressure) and suddenly... - Atlant 14:26, 10 January 2007 (UTC)

work done by frictional force

Please give me a hint to solve this problem: a uniform chain of length L and mass M overhangs a horizontal table with two-thirds part on the table.The friction coefficient between the table and chain is 'u'.Find the work done by friction during the period the chain slips off the table.

Start with the definitional functions - what is work, and the equation for it? What is friction and the equation for it? Hipocrite - «Talk» 15:46, 10 January 2007 (UTC)

It presumably involves an integral over time or (more cleverly) over the length of the chain, because different parts of the chain will experience different amounts of force over different distances. (Using the length of the chain is my hint.) --Tardis 16:42, 10 January 2007 (UTC)

Images with eyes closed

When you press against your eyes while there closed, how come after 3-4 seconds you "see" colors and patterns? nicholassayshi216.253.128.27 16:40, 10 January 2007 (UTC)

See phosphene and closed-eye hallucinations. X [Mac Davis] (DESK|How's my driving?) 17:38, 10 January 2007 (UTC)

Hey I get that too. :( I can see stage 1 CEV, but to me they seem mostly pink and yellow. And if I close my eyes really tightly there is a very bright yellow patch that moves and pulsates randomly. I think this is stage 3 CEV. Once it was blue instead, and much smaller. :) I think I read somewhere that pressure on someones eyes appears as light, as the eyes can only detect things as images. Also could the first one be caused by the less sensitive cells of the retina? :?Hidden secret 7 19:00, 10 January 2007 (UTC)

Phosphenes from pressure come from mechanical stimulation of the retina—the eyeball is pressed against it. Pink and yellow! For me it is green and shades of black when I close my eyes. In the dark it is like television static, but I also see phosphenes (but not the hallucinations) in the center of vision appearing and disappearing in the same way as the static, like bacteria in an optimal environment reproducing. X [Mac Davis] (DESK|How's my driving?) 20:24, 10 January 2007 (UTC)

At high altitude / in space, you can get noticable sparkles from cosmic rays passing through your eye. Dragons flight 19:59, 10 January 2007 (UTC)

Sometimes when taking marijuana one encounters effects like this even though this is not written in the article. --helohe (talk) 00:16, 11 January 2007 (UTC)

Another one I forgot, sometimes I can see pages of writing floating past, but I can't see what any of the words are, possibly as they don't really exist :(Hidden secret 7 19:02, 11 January 2007 (UTC)

Ink

How do you separate two colours in ink--82.19.94.30 16:50, 10 January 2007 (UTC)

There are many ways, however I expect what you are looking for is Paper chromatography. --Neo 16:58, 10 January 2007 (UTC)

Blonde haired blue-eyed cavemen

As a person with brown eyes and hair, I am fed up with seeing cavemen always depicted with those characteristics, as though blue-eyed blondes were a more advanced form of life. Surely there must have been blue-eyed blonde cavemen especially as I understand blue eyes are determined by a regressive gene? Also, am I correct in thinking that when the mummy of Pharoah Rameses the Second was taken to Paris for 'repairs'the hair-dye experts from Loreal found that he had naturally red/ginger/auburn hair? Or is this just a tale? Thank you.

Depending on what you mean by cavemen, the answer may largely be no. Our article on blonde hair suggests it became prevalent only ~10,000 years ago. The near total absense of blonde hair and blue eyes outside of European populations suggests that the prevalance of both are likely to be relatively recent quirks of evolution. Dragons flight 19:57, 10 January 2007 (UTC)

Also that guy you see in the commercials... it's not makeup ...that's what he really looks like. Barringa 20:13, 10 January 2007 (UTC)

However the effect of presenting blonde-haired blue-eyed as the "advanced" group in film is interesting. See the Clan of the Cave Bear; neaderthals were all dark hair, the modern human (played by Daryl Hannah) was blonde and blue eyed. --TeaDrinker 21:51, 10 January 2007 (UTC)

In The Complete Valley of the Kings, New York, Thames & Hudson, 1997, it is mentioned that a study done in 1975 in Paris where Ramses II was taken, the mummy's hair was not just dyed red from henna but had originally been red. It would appear the white nationalist community likes this idea, as they have written about him, and other "white" Pharoahs [http://www.stormfront.org/whitehistory/hwr8a.htm here].

There is very little known about he evolution of blonde hair because the genetics of it are not understood, however red hair (and the strongly associated blue/green eyes, pale skin and freckles) has been studied. Variation in the gene MC1R accounts for a large proportion of redhair (in humans and pretty much every red coloured animal). A group of scientists analyzed the evolution of MC1R variants in human populations (primarly to determine how and why red-hair appeared in European populations) however, in their study they note:

Our estimates of 80,000 years for the red hair–associated Arg151Cys and Arg160Trp variants [of MC1R] likewise suggest a distant ancestral contribution from Paleolithic Eurasians to the western European populations of today.

In other words, the earliest modern humans in Europe had the genetic variants that we know cause red-hair, but certainly not fixed in the population at any great proportion, and since the alleles are recessive, it would have taken a long time until red hair began to appear with any frequency in Northern Europe. The same scientists estimate that it was another 40,000 - 60,000 years before red-heads became commonplace (sometime between 20,000 and 40,000 years ago). This would mean that late Cro-Magnon "cavemen" may have had red-heads among them, through probably not Neanderthals. Rockpocket 07:28, 11 January 2007 (UTC)

Interaction and placement of magnetic fields in a DC permanent magnet motor...?

In a 3 phase DC permanent magnet motor where magnet poles in the rotor are in alternating sequence per pole and the number of stator teeth are greater than the number of rotor poles does the magnetic field in the stator alternate sequentially from tooth to tooth and is the stator magnetic field designed to race ahead of the magnetic field in the rotor? 71.100.10.48 20:08, 10 January 2007 (UTC)

Is there such a thing as a 3 phase DC motor? I'm only aware of 3 phase AC motors, have you read electric motor?Vespine 09:46, 11 January 2007 (UTC)

I do not believe there is any 3-phase DC motor. DC or Direct Current means that the electrons flow in one direction, opposed to Alternating Current or AC. By definition, DC does not have phases, which are the opposing wave forms in high-voltage AC. DC has positive and a negative conductors with a unidirectional flow of electrons with a flat-line wave-form, while AC has 'hot' and neutral (or ground (neutral wires are grounded in the main electrical panels of buildings and at transformers at most telephone poles)) leads that alternate the directional flow of electrons in a wave (60Hz American and 50Hz European). Consequentially, AC electricity is more efficient and 'cooler' because the current of electricity alternates and heats the wire less than DC, therefore allowing for smaller conductor sizes. This concept can be visualized with sand and a tube or straw. Tilt the straw and pouring sand down the tube would be like DC electrons flowing through a wire, in one direction only, creating constant friction and heat. For AC, Cap the ends of the tube while half full of sand and slightly tilt it in an alternating fashion and the sand moves back-and-forth over itself, which gives less friction and dissipates heat better. Electricity is mostly compared to water flowing in a pipe, with pressure and mass-movement used to represent voltage and current. In AC, the Phases are opposing wave-forms of the frequency (Hz) in the ‘hot’ leads of high-voltage systems. Most homes use single-phase (but really the home has 2 phases, giving 220volts together or 110volts separately when used with neutral or ground). 3-phase means that there are different wave-forms in each of 3 leads, which add-together to increase voltage for high-voltage applications. High-voltage DC is uncommon, as it generates tremendous heat in conductors which have to be larger than if it were an AC system. Edison liked DC, Westinghouse like AC; Westinghouse won. DC is mostly used in automobiles (at 12v) and electronic equipment, which have adapters that plug into the wall or have built-in circuitry that drop the voltage and convert the AC to DC. 68.193.190.48 03:38, 8 June 2007 (UTC) by MrBi8b0 68.193.190.48 03:38, 8 June 2007 (UTC)

Further, in any PERMANENT magnet motor, the stator magnetic field does nothing, it's permanent. Vespine 09:53, 11 January 2007 (UTC)

medical term for eye crust

What is the medical term for eye crust (aka: eye gunk, eye booger, sleep, schmutz...) Whatever it is, the common terms should redirect to the proper article name. --Kainaw ^(talk) 20:31, 10 January 2007 (UTC)

Oddly, all the Notes & Queriesesque things I've read say that doesn't have a medical name; I can't find any sources right now, but they seemed to agree that since neither it nor its absense is a sign of disease, the medical community ignored it. Incidently, if the eye does become infected, the discharge is known as Mucopurulent discharge, due to the charming combination of mucous and pus that it hence contains. Laïka 22:21, 10 January 2007 (UTC)

A similar question has been asked twice previously without any satisfying answers. Perhaps we should make up a name! BenC7 01:19, 11 January 2007 (UTC)

I believe its salt. But thats only my opinion. OTOH see Tears--Light current 01:42, 11 January 2007 (UTC)

Some people have already done this! See here. It's "Mucopurulent mattering in the punctum." Also, interestingly, Spanish has a perfectly good word for this: lagañas, which the Oxford Spanish Dictionary translates as "sleep" or, in a British familiarity, "sleepy-dust." zafiroblue05 | Talk 21:51, 11 January 2007 (UTC)

Parts of an automobile

In my technology class, we've learned about the engine block, the transmission, and the differential. Is that the order in which the energy flows, so to speak? Thanks, anon.

I would tend to replace 'engine block' with 'crankshaft' in the above list, but otherwise that is correct. (The engine block is arguably just a stationary lump in which the pistons move. The pistons are tied to the crankshaft, which converts the reciprocating (up-and-down) motion of the pistons into smooth rotation.) TenOfAllTrades(talk) 21:24, 10 January 2007 (UTC)

And you can add wheels then road to the end, and foot -> accelerator pedal at the start. Vespine 21:33, 10 January 2007 (UTC)

Well, no, the power comes from the fuel burned, not from the foot of the driver. The gas pedal is just a control. Friday (talk) 22:13, 10 January 2007 (UTC)

Sorry, should have added a ';)'. Vespine 23:11, 10 January 2007 (UTC)

Unless you're Fred Flintstone. anonymous6494 06:45, 12 January 2007 (UTC)

Furniture materials and health effects

With out getting into too much chemestry, how can I tell if a piece of furniture has a material or finish that is off-gassing or creating other potentially harmful effects in my home? 67.94.101.67 21:55, 10 January 2007 (UTC)

Good question... you could try smelling it. Benzene and those sorts of chemicals will not smell very nice. Vranak

Water Displacement in Ferries

Could you please explain in language understandable for a 10 year old, why a ferry does not sink when cars are loaded onto it and why the cars must be balanced when they load? Thank you so much for taking the time to answer this. Linda Battler216.183.133.181 23:26, 10 January 2007 (UTC)

Does it make sense to you why boats float at all? See the "Why boats float" section of our boat article if it's not clear. Now, even with all the extra weight of the cars, the whole thing is still lighter than the water it displaces, so it still floats. One could make a boat of any weight simply by making it very large...a ferry is just a boat that is large enough to float with the cars. As for even loading, if there's more weight on one side than another, the boat will tilt that way. Tilt too far and the boat could capsize. DMacks 00:03, 11 January 2007 (UTC)

There have to be enough air-filled compartments low in the ship to keep the ship riding high enough in the water that when the cargo doors are opened, they are above the waterline. Ferries aren't unique in that if enough water gets inside (as has happened when cargo doors were either: left open, not completely closed or opened en route and either rough water or a rogue wave allowed ingress) the vessel will capsize. Ship designers and builders carefully calculate the maximum acceptable load to keep the cargo doors a safe distance above the waterline, that's fairly basic load tolerance mathematics. When empty, the ferries ride high in the water (like other cargo vessels), and they are filled to a carefully-calculated capacity to ensure that (under normal conditions) the ferry doesn't risk being swamped. Anchoress 01:38, 11 January 2007 (UTC)

You can even make ships and boats from concrete - see concrete ship and concrete canoe. Gandalf61 13:05, 11 January 2007 (UTC)

The physics of exactly when a boat will tip over are complicated (because of the effects of the hull shape), but it's related to the idea of center of mass. --Robert Merkel 02:12, 12 January 2007 (UTC)