Science desk
< June 9	<< May \| June \| Jul >>	June 11 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

June 10

What is it?

I took this picture while visiting the Back Bay in Newport Beach, CA. What kind of lizard is it? I looked around, and it doesn't seem very common. If someone recognizes it or can find out what kind of lizard it is, it would be very helpful. Thanks! nd2010 00:52, 10 June 2007 (UTC)[reply]

Could be a Western fence lizard. Check out the pic of Subspecies bocourtii under the taxobox. In any case, it's probably one of the spiny lizards. Matt Deres 13:13, 10 June 2007 (UTC)[reply]

AIDS (accuqired immune deficeincy syndrome)

Is it possible for an HIV infected male to conceive with a non-infected female and have neither the mother nor the baby become HIV positive? Is there ANY known medical procedure that would prevent this infection? So that the donor HIV+ male can conceive with his own sperm and not transmit the virus? —Preceding unsigned comment added by 71.198.234.210 (talk • contribs)

Just a guess, but it might be possible by intracytoplasmic sperm injection. ›mysid (☎∆) 08:37, 10 June 2007 (UTC)[reply]

"Do not request medical or legal advice. Ask a doctor or lawyer instead." This is not something to play around with. Get medical advice up front. Edison 19:54, 10 June 2007 (UTC)[reply]

I hope Edison does not mind, but I have applied strong formatting to convince the questioner to ask a doctor, instead of a group of random internet volunteers. Nimur 20:01, 10 June 2007 (UTC)[reply]

Of course it's possible. Having unprotected intercourse with someone infected with HIV does not mean you will contract it. It could be transmitted on the first encounter, a later encounter, or never. The more often intercourse occurs however odds would predict the more likely infection will occur. So it is very possible that the scenario you raise could occur. A baby will only be infected from the mother, so unless the mother becomes infected the baby will not either (and the mother being infected does not guarantee the baby will become infected either, the risk is only 25% for a natural birth with no drug treatments used, according to the article). Try reading this on HIV transmission. I'd say in vitro fertilisation could be pretty successfully used to prevent transmission, given HIV is not carried in the DNA, the virus is passed by fluid exchange. --jjron 11:27, 10 June 2007 (UTC)[reply]

Well, according to Fertility a woman under the age of 30 has a 75% chance of getting pregnant after a year of unprotected sex (the odds drop dramatically if she's older than that). If one were being smart about this - you'd only have unprotected sex when she's ovulating - since she won't get pregnant at other times. There are all sorts of ways to try to detect when she's ovulating and it would be very smart to time unprotected sex to match the correct time in her 28 day cycle. So there are just 13 times per year (every 28 days) when it's worth trying. Perhaps 26 well times unprotected attempts will give her a 75% change of he becoming pregnant. The page on HIV says that for unprotected 'normal' sex, there is a one in one thousand chance of passing on the virus through unprotected sex - that sounds small - but over a lot of tries - those odds increase alarmingly. So over (say) 26 attempts in one year - the odds of 'getting away with it' are 0.999 raised to the power 26 - which is 0.974 - so, if you were really, really careful and did things just right - then there would be about a 3% chance (1 in 33) of passing the disease on to the woman for a 75% chance of getting her pregnant. If she did get the disease then there is a 25% chance that the child will catch it from her during childbirth. However, I very much doubt that you'd catch her ovulation cycles just right - so in all likelyhood, her chances of getting pregnant would be much less than 75%. If you just risked unprotected sex all the time to increase the chances of her getting pregnant - then her odds of catching the disease after a year would go up hugely. Overall, the risk seems awfully high to me - I most definitely wouldn't want that kind of risk. Please seek medical advice - there has to be a better way. SteveBaker 14:02, 10 June 2007 (UTC)[reply]

I've heard of a sperm washing technique that can be used on the sperm of an infected male. This sepperates the virus from the rest of the semen and thus the sperm can be used for IVF. I've heard some couples have tried this and were succesful. Others however got sick of having to wait for a succesful treatment and tried it the natural way . I don't know if in these cases the women got infected. I have no direct link as reference though (and am a bit to busy to dig one up) but this website www.aidsmeds.com is a good place to look. 62.194.90.107 14:18, 10 June 2007 (UTC)[reply]

UV light from halogen lamps

I always notice mention of the danger of ultraviolet light from unfiltered halogen lamps. I would tend to think this would not be a concern, because at the temperature of the filament (3200^oK) the blackbody radiation spectrum contains very little UV. Compared to the sun's temperature (5800^oK) the amount of UV radiation, especially burning wavelengths < 320 nm, given off at the same intensity of visible light is exceedingly miniscule. Does anyone know of actually receiving sunburn from one of these lamps, or is it just an over-cautious urban myth?

-User: Nightvid

While the blackbody spectrum at 3200 K contains relatively little UV, it's worth bearing in mind two important points. First, you're much closer to the surface of your light bulb than you are to, say, the sun. Second, the quartz envelope used to manufacture halogen bulbs is (unless specially treated) transparent to UV, unlike the glass envelope used for conventional incandescent bulbs.

This abstract from a paper that appeared in the journal Dermatology indicates that the DNA-damaging capacity of an unfiltered 50 W halogen lamp at a distance of 7 cm (about 3 inches) is roughly comparable to that of the noonday summer sun in a mid-latitude location like Michigan. They also note that "The radiation from quartz halogen light bulbs has been reported to cause erythema in humans and skin tumors in experimental animals"; erythema would be a sunburn.

The amount of damage done can be reduced through maintaining a safe distance from the bulb (the intensity of UV will fall off with the square of the distance) or by following the bulb manufacturer's directions for shielding (a layer of ordinary glass will block the bulk of the emitted UV). Some halogen bulbs incorporate a glass outer envelope or employ specially coated quartz and don't require a separate UV shield. TenOfAllTrades(talk) 17:34, 10 June 2007 (UTC)[reply]

Also, halogen torchieres bounce the light off the ceiling, where I believe the UV will be absorbed, so this will help, too. StuRat 05:02, 11 June 2007 (UTC)[reply]

That is correct. The titanium dioxide pigment that is the opaque white base for most paints absorbs strongly at wavelengths below about 400 nm: [1]. (Of course, even torchieres shield the bulbs; in addition to preventing UV exposure, a glass shield will also contain the dangerously hot shrapnel generated if a halogen bulb fails.) TenOfAllTrades(talk) 15:44, 11 June 2007 (UTC)[reply]

Height of land + sea level change

hi,

I'm looking for images showing what would be land/sea if sea level would rise/fall by 1, 5, 10, 100, -1, -5, -10, -100 and -120 metres. Also does anyone know of a website that has some sort of thing where you can input a sea level change and it would have some sort of animation or pic showing the whole world/ parts of it which would be exposed/ submerged? thanks, --Wiki999777 13:59, 10 June 2007 (UTC)[reply]

This page has some of that for the USA's Atlantic and Gulf coasts, but only for modest rises. Any contour map of the region of interest will show you what you want, though, since the coastline is always more or less at 0 meters above sea level (places like the Netherlands and New Orleans provide exceptions). --TotoBaggins 14:55, 10 June 2007 (UTC)[reply]

This map, although not perfect, shows quite dramatically what a 120 metre fall would look like; all the areas coloured in cyan would be exposed; Russia would merge into Alaska, Australia would become linked to New Guinea, and the UK and Ireland would become land-locked nations within a much larger European landmass. Laïka 15:52, 10 June 2007 (UTC)[reply]

Eh? The colour scale below that image shows that the Cyan region represents areas that all the way down to -3000 meters - so a mere -120m change wouldn't be reveal much of the cyan areas. SteveBaker 16:44, 10 June 2007 (UTC)[reply]

Sorry; that caption wasn't there when I checked the page before (it just said "This page left intentionally (almost) blank", although I can't find in the edit history; very strange...); I was going by the article Continental shelf, which states that the depth of that shelf was less than 140 metres. Laïka 18:23, 10 June 2007 (UTC)[reply]

A few website that may be of interest include this one, that one, and this other one. Pfly 04:33, 11 June 2007 (UTC)[reply]

An obliquely related question- if sea level rose due to global warming, would our measurements of land elevation change also? --Sturgeonman 21:39, 13 June 2007 (UTC)[reply]

Discontinuous

In the article on Polymorphism (biology), polymorphism is defined as a "discontinuous variation in a single population..." What does discontinuous mean in this sentence, and in what way does it differ from a continuous variation? I checked both Wikipedia and Wictionary but didn't find a satisfying explanation. Thank you! Lova Falk 14:51, 10 June 2007 (UTC)[reply]

It means that there is some characteristic that only takes discrete values, and not a continuous range of "shades" in between. In humans, for example, blood group and eye colour are polymorphic, whereas height and skin colour are not. Gandalf61 15:00, 10 June 2007 (UTC)[reply]

Thank you!! Lova Falk 15:07, 10 June 2007 (UTC)[reply]

Theists thumbing their noses at science despite the fact that they rely on it every day

Religious folk don't like science, generally because it goes a long way towards casting doubt on their beliefs. And because of that, they like to denounce it, call it "bunk" etc, especially regarding evolution. And yet this is hypocritical, because they rely on science every day to power their cities and run their cars.

^^^Whether you agree with this statement or not, I could REALLY do with a quote that backs it up. Preferably from the most reputable source possible. I need to stick it in an essay and I have Googled and Googled but just can't find anything.

I took a look at my big compilation of atheist quotes but couldn't find anything exactly on point. Here's the closest I found:

"Where it is a duty to worship the sun it is pretty sure to be a crime to examine the laws of heat." ~John Morle~

“Men think epilepsy divine, merely because they do not understand it. But if they called everything divine which they do not understand, why, there would be no end of divine things.” ~Hippocrates~

"Truth does not demand belief. Scientists do not join hands every Sunday, singing, 'Yes, gravity is real! I will have faith! I will be strong! I believe in my heart that what goes up, up, up must come down, down, down. Amen!' If they did, we would think they were pretty insecure about it." ~Dan Barker~

--Fuhghettaboutit 16:24, 10 June 2007 (UTC)[reply]

You're doing much like what you're accusing others of -- beginning with a conclusion that you like, and then looking for an argument to support it.

Oh, I'm well aware of that, but this assignment is due in twelve hours and I'm not in the mood to be fair and balanced. Thanks for the quotes though.

Anyway, probably the above statement is false. Most intelligent theists see no contradiction between the teaching of religion, and the theory of evolution by natural selection. Stephen Jay Gould gives a nice description of why, in an article called Non-overlapping magisteria. Llamabr 16:28, 10 June 2007 (UTC)[reply]

Why do scientists thumb their nose at theism when they rely on Him every day... :D But seriously, all you're doing is proselytizing the religion of science, let theists be. --⁪froth^t 17:09, 10 June 2007 (UTC)[reply]

Oh, just let him write his paper. Someguy1221 18:30, 10 June 2007 (UTC)[reply]

I like Carl Sagan's quip, "We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology." But you should realize that there is a difference between science and technology. Religious folk depend on technology more often than they depend on science. Though science and technology are related, they are not the same thing. Hypothetically, a Wankel engine might have been invented through prayer, trial-and-error, and total lack of thermodynamics understanding. Nimur 20:05, 10 June 2007 (UTC)[reply]

Which leads me to a full discussion of what science actually is. Trial-and-error, which leads to practical results, seems like a prototype of the scientific method anyway. Eventually, after enough trials, many of the underlying principles must become clearly evident, regardless of what the starting beliefs are. For this reason, I have no worries about the incessant debate between theists and scientists. In the end, truth will come through experiment. This is of course penchant on the definition of "truth" or "existence." As a scientist, I tend to equate existence with experimental verifiability. Religious scholars do not always agree with me. But they are so wrong. Nimur 20:12, 10 June 2007 (UTC)[reply]

But that's the point of debate- you believe truth will come through experiment, and basically everyone can agree that has meaning and value (if repeating an action 1000 times produces the same exact reaction then the statement "action causes reaction" is a valuable, true statement), but there are meaningful statements that are not scientifically verifiable and there experiment fails and religion/philosophy begins. That's Kant I think btw. --⁪froth^t 05:18, 11 June 2007 (UTC)[reply]

And anticipating someone will dispute the "1000 times" point, that consistent pattern of actions and reactions (or actions and otheractions since there's really no hard proof that a reaction is occuring) is really the basis of science (at least our system of physics), even if 1000 is a small figure --⁪froth^t 05:23, 11 June 2007 (UTC)[reply]

Science is a lot more than trial and error. There is a great little math example that shows why just trying something until it seems to work isn't the scientific way. Take a piece of paper and follow along with me:

Draw a circle, put a dot somewhere on the circumpherence - the circle contains one 'region'.
Add a second dot on the circumpherence (it can go anywhere - but it's easier to draw if you space the dots out widely) - connect the two dots with a line - you now have two regions.
Add a third dot somewhere on the perimeter of the circle and connect it to both the first and second - and now you have four regions. 1,2,4... See a pattern?
OK so let's add a fourth dot - connect it to all of the previous dots (you should be looking at a circle with a quadrilateral inside - with both of it's diagonals drawn in). Count them up - now you have eight regions...oh, yeah - I see a rule emerging. 1,2,4,8... It seems like every time you add a dot, it doubles the number of regions!
Let's check that - I got 8 with four dots - so if I add a fifth, I should get 16 regions. So, go ahead, add a fifth dot - connect it to all of the others (you should have a 5 pointed star inside a pentagon inside a circle...resist the temptation to place a candle at each corner and summon a deamon!)...Wow! I got 16 regions! 1,2,4,8,16... I can write an equation for this! I think I'm getting the idea of this math stuff!

Now if you stopped and wrote that the number of regions ('R') for 'N' dots is: R=2^(N-1) - then you just showed the difference between trial and error and math and science. You didn't understand WHY that happened. So now, add a sixth dot and connect it up every way you can to the others - you'll find that you don't get 32 regions as you might have expected - you only get 30 (if your points are spaced evenly around the edge) or 31(if they weren't exactly equally spaced) - no matter what, you can't make the expected 32 regions! Urgh! 1,2,4,8,16,31?! The universe hates me! So this seemingly great rule that we 'discovered' by repeated trials isn't a rule at all - it just looked that way for a while. This kind of thing is everywhere - you never know how many trials you have to make in order to be sure that you have explored all of the phenomena. How do you ever know that you've done enough trials? The answer is that you have to have a hypothesis - you have to have a theory that you're trying to prove or disprove. You have to know why the experiment worked - or failed. The experimental technique of science is there to try to verify theories...that's a lot different from trial and error. SteveBaker 13:38, 11 June 2007 (UTC)[reply]

Certainly classical mechanics is not in any way provable- by observing a system you can predict its behavior but there's no reason for gravity to suddenly become repulsive other than that it hasn't happened yet, and no reason for the laws of thermodynamics to be infallable other than that they have never failed yet. Mathematics is obviously provable since it's all a big made-up system based on logic (probably logic specific to our minds) and it "works" by definition. When you extend classical mechanics with mathematics into quantum mechanics and all that other modern yuck that's probably not even accurate let alone provable, it still retains the uncertainty of classical mechanics. And I believe that spreads to all other forms of science as well, at least where the utterly infallable King Math isn't too involved. And in any case, on a much lower level, all we really know is colored streaks passing through our visual field and tingly sensations from our fingers, etc. If we observe patterns and make predictions that's nice but there's no making sure statements about them. Skeptical_hypothesis, Philosophical_skepticism#Motivations_for_external_world_skepticism, and all that you know. --⁪froth^t 23:47, 11 June 2007 (UTC)[reply]

Good example, SteveBaker. I'm not trying to call the scientific method "trial and error" - I'm suggesting that if you start by simple trial-error methods, you will eventually develop a full-blown scientific method as the natural end result. Theory emerges from experiment. Nimur 17:32, 11 June 2007 (UTC)[reply]

Really a beautiful example. But that means, physics is no science, if it's true what they say about how a physicist proves that all odd numbers are prime:

Physicist: "1,3,5,7,9,11,13 all are prime"

Mathematician: "But 9 isn't!"

Physicist: "Oh, that's just a statistical error! — Sebastian 23:10, 11 June 2007 (UTC)[reply]

If the first statement was about race instead of science, people would see how ignorant it is. Religious people are not against science. The Catholic church is one of the largest contributors to astronomy in the world and run a number of observatories. It's pretty obvious that those that don't understand religion, understand science even less. --Tbeatty 20:58, 10 June 2007 (UTC)[reply]

Race and religion are different. People choose their religion, nobody chooses their race (or gender, or sexuality, or height, or date of birth...) It's not ok to judge based on race, but it is ok to challenge beliefs.

Also, note that "60 percent of professors in [the] natural and social science disciplines describe themselves as either atheist or religiously agnostic. In comparison, among those in the general U.S. population, about 3 percent claim to be atheists and about 5 percent are religiously agnostic." [2] It's very ignorant of the truth to say that religious people are more prone to understand science. Lastly, read up on Galileo Galilei if you're so proud of the Catholic Church's stance on Science.

People do choose their ignorance and that statement on religion was ignorant. Also, I believe your 60% stat, if it's even true, goes way down when you only include the physical sciences. Social sciences are notoriously anti-religious but have little bearing on hard science disciplines. And I don't think sciences track record was any better during the time of Galileo than religion. Both have grown and both have had their ignorance. --Tbeatty 22:28, 10 June 2007 (UTC)[reply]

Don't forget that some religious sects do avoid using modern science and technology, like the Amish. StuRat 04:13, 11 June 2007 (UTC)[reply]

That's not untrue, but I believe they give more consideration to the effect on their lifestyle than to the level of technology. So for example, cell phones can be OK as long as they're used in a prescribed way that doesn't interrupt life at home. They avoid a modern way of life, but not necessarily all modern technology. --Reuben 04:41, 11 June 2007 (UTC)[reply]

That's probably the spirit of the thing, but I doubt all groups are so lenient --⁪froth^t 05:27, 11 June 2007 (UTC)[reply]

Pharyngula recently linked to Scientific Knowledge in the US by Religion, if it is not too late for you. --Eldereft 09:16, 11 June 2007 (UTC)[reply]

If you'd like a quote against it you could look at the writings of William Jennings Bryan, who makes it quite clear that he had no problems with technology and much of modern science but that he thinks that evolution is really more ideology than science. I'd be surprised if that is far off the mark from how these people deal with that particular "paradox". Remember that the best way to make an argument is to take the strongest, and best formulated opposition to it, and try to find a way around that. If you can beat that, then you're making a good argument. If you can't, then you're just dealing with strawmen. --24.147.86.187 11:53, 11 June 2007 (UTC)[reply]

Where the Bible most directly contradicts science is in the story of creation in Genesis, if taken literally. People existing on Earth within a few 24 hour days of the creation of the universe is contradicted not only by the theory of evolution, but by just about every field of science, including geology, astronomy, biology, archeology, anthropology, physics, etc. StuRat 15:52, 11 June 2007 (UTC)[reply]

Don't take it literally. I'm sure you used the terms "rising sun" and "when the sun goes down", which from the point of view of science are ridiculous, taken literally. There are many scientists who believe in Genesis as part of their religion, it kinda makes sense once you stop assuming "days" are equal to our regular one-earth-revolution days. After all, the protagonist of Genesis is God... who knows how long one God-day is? Maurog 08:57, 12 June 2007 (UTC)[reply]

There was day and then there was night, the end of the x day. Take it or leave it IMO, not much room for long-day theories --⁪froth^t 13:52, 12 June 2007 (UTC)[reply]

One God-day would be the time it takes for God to rotate fully about his axis... clearly. 213.48.15.234 09:29, 13 June 2007 (UTC)[reply]

Religious people are superstitious morons, whether they like it or not. That's a fact. They believe, among other nonsense, that good people will go to heaven and bad people will go to hell, that sounds so childish to me. As the literacy rate increases, religious affiliation decreases, what means that sooner or later we'll be free from them. --Taraborn 20:57, 13 June 2007 (UTC)[reply]

Brain Cells

Can stem cell research help us to grow more brain cells.

No.

A BBC report says yes. [3]. However, the report says, "Stem cells are seen as a potential way of reversing the effects of Alzheimer's, Parkinson's and other similar diseases in the brain." It says nothing of just adding in some extra grey matter for kicks. -Quasipalm 22:10, 10 June 2007 (UTC)[reply]

Olfactory sensory neurons are the cells that transfer the signal of a "smell" from your nose to your brain. These die off every 5 or 6 weeks throughout our life and have to be replaced from stem cells, a process known as neurogenesis. There is a significant amount of research into these cells, since they provide a means for us to, as you say, "grow more brain cells." Rockpocket 02:10, 11 June 2007 (UTC)[reply]

If you're thinking more brain cells = smarter, don't. Growing more brain cells, not in response to a neurological disorder that is preciptated by the die-off of neurons like Parkinson's disease, may not be necessarily a good thing... The proper development of every brain (in every animal that has a semblance of a central nervous system) includes the production of far more cells than eventually "needed" in the adult animal. The programmed die-off of specific populations, and the "trimming" of superfluous neurons as the brain orders itself is vital to the final state of the brain. There are a number of disorders (especially that result in experimental animal models with controlled mutations) in which the regulation of this process is disrupted; too many neurons provides a lot of development problems. In fact, even cell transplantation procedures in Parkinson's patients can have this effect: they may trade the symptoms of the disease caused by a massive loss of dopaminergic neurons of the substantia nigra for dyskinesia caused by, essentially, neuronal hyperactivity in the region.

In response to the original question: eventually stem cell research should provide a means of reliably creating differentiated neurons from muilt- or totipotent cell lines. Should. — Scientizzle 05:22, 11 June 2007 (UTC)[reply]

Also, brain power is more about the density of connections between cells than the number of cells involved. SteveBaker 13:06, 11 June 2007 (UTC)[reply]

So if someone wanted to reshape their brain to make themselves cleverer, have a better memory, be able to work stuff out faster, what would they have to do?

The best is to probably spend free time reading and doing mental excercises. A little Mozart might help. Practice makes the most difference, you know, whether its playing football or solving calculus problems... — Scientizzle 19:06, 11 June 2007 (UTC)[reply]

Yep - there are no shortcuts - the more you use your brain, the more you can use your brain. Play chess, listen to classical music, do math problems, write poetry, learn quantum physics, learn to play the piano. My biggest mental workout is researching answers to questions on the help desk. SteveBaker 03:51, 12 June 2007 (UTC)[reply]

Genetic Mapping

Here it says; "Chiasma counts in human male meiosis show an average of 49 crossovers per cell (Morton et al., 1982). Since each crossover gives 50% recombinants, the chiasma count implies a total male genetic map length of 2450 cM. The current version of the Location Database (Collins et al., 1996) suggests a total male map length of 2851 cM. Chiasmata are more frequent in female meiosis (exemplifying Haldane's rule that the heterogametic sex has the lower chiasma count), and the total female map length in the Location Database is 4296 cM (excluding the X). Thus over the 3000 Mb autosomal genome, 1 male cM averages 1.05 Mb and 1 female cM averages 0.70 Mb; the sexaveraged figure is 1 cM = 0.88 Mb."

What is meant by the assertion that "each crossover gives 50% recombinants"? --83.84.74.28 21:31, 10 June 2007 (UTC)[reply]

The quote is from here. That source explains it fairly well, so I'm not sure which part you find confusing – can you be more specific? Look at its Fig. 11.2(A) when you read the text:

Consider a person who is heterozygous at two loci [A and B], and so types as A1A2 B1B2. Suppose the alleles A1 and B1 in this person came from one parent, and A2 and B2 from the other. Any of that person's children who inherit one of these parental combinations (A1B1 or A2B2) is nonrecombinant, whereas children who inherit A1B2 or A2B1 are recombinant (Figure 11.1). The proportion of children who are recombinant is the recombination fraction between the two loci A and B.

[...] If the loci are syntenic, that is if they lie on the same chromosome, then they might be expected always to segregate together, with no recombinants. However, this simple expectation ignores meiotic crossovers. During prophase of meiosis I, pairs of homologous chromosomes synapse and exchange segments (Figure 2.14). Only two of the four chromatids are involved in any particular crossover. A crossover, if it occurs between the positions of the two loci, will create two recombinant chromatids carrying A1B2 and A2B1, and leave the two noninvolved chromatids nonrecombinant. Thus one crossover generates 50% recombinants between loci flanking it.

The argument in the rest of your quote is as follows: One centiMorgan (cM) is defined as the genetic distance between two loci that causes there to be a 1% chance of a recombination event between these loci. Thus the average number of recombination events is 0.01 per cM of DNA length. The average total number of crossovers in a male cell is quoted as 49, but according to the above each crosssover has only 50% probability of generating a recombination event in a particular chromatid, so the average number of recombination events is only 49*50% = 24.5. Thus they calculate a naive estimate of the "genetic map length" of the whole male genome to be 24.5/0.01 = 2450 cM. --mglg_(talk) 22:41, 10 June 2007 (UTC)[reply]

Okay, I understand it now; thanks! But now I have another question. If two loci are one cM apart, does that mean that recombination occurs in 1% of all mieoses and therefore presents in 0.5% of individuals or that it occurs in 1% of individuals and occurs 2% of all mieoses? --83.84.74.28 18:44, 12 June 2007 (UTC)[reply]

My understanding (which is purely from your source) is that 2% of all meioses will have a crossover between the loci, and 1% of the resulting gametes will contain a recombination between the loci. To qoute: "Two loci that show 1% recombination are defined as being 1 centimorgan (cM) apart on a genetic map." --mglg_(talk) 19:38, 12 June 2007 (UTC)[reply]

"Sweating out toxins"

I keep hearing that sweating removes toxins from your body. For some reason, it sounds like nonesense to me, since I'm pretty sure that that's what the liver is for.

Someone on Wikipedia even says as much; from Sauna:

"Steambaths and saunas induce perspiring to provide a comprehensive cleansing of the skin and sweat glands. Skin is the largest organ in the body. 30% of body wastes are passed through the skin. Profuse sweating enhances the detoxifying capacity of the skin by opening pores and flushing impurities from the body."

Is there any truth to this? --Quasipalm 22:03, 10 June 2007 (UTC)[reply]

According to the Eccrine sweat glands page, part of the secretions of the sweat glands is waste. -- JSBillings 23:12, 10 June 2007 (UTC)[reply]

I don't have a reference, but I've always assumed anyone talking about sweating out toxins is a quack. Friday (talk) 23:13, 10 June 2007 (UTC)[reply]

Is it possible to sweat out alcohol? I know of people who use saunas after a heavy night of drinking in order to sober up... --Kurt Shaped Box 23:15, 10 June 2007 (UTC)[reply]

No toxins, alcohol, or foreign substances are excreted in sweat in enough volume to make a difference to body concentrations. Quackery pure and simple. Take no health advice and do not pay a dollar for any health-related services to anyone who claims this. alteripse 00:19, 11 June 2007 (UTC)[reply]

Sweat is certainly one way in which some toxins are excreted, but the amount pales in comparison to the work of the kidneys & liver. Here's an interesting link. The sweat glands are not filtering organs. What comes out is essentially what's in the blood, modestly concentrated by the controlled reuptake of water. One thing that's important to note: inducing excessive sweating to remove alcohol or other toxins could make things worse by causing dehydration. That "30% of body wastes are passed through the skin" sounds like a steaming load to me...I'll have to check that out. — Scientizzle 00:40, 11 June 2007 (UTC)[reply]

Isn't the composition of urine and sweat about 97 or 99% identical? Surely there's some waste excreted with sweat, but it couldn't possibly be as efficient as urinating. --Wirbelwindヴィルヴェルヴィント (talk) 02:24, 11 June 2007 (UTC)[reply]

So, the guy I used to flat-share with who'd cocoon his thighs and midriff with cling film before he went to work in the morning in order to sweat the booze out was just wrapping himself in plastic for no good reason? Hehehe. --Kurt Shaped Box 09:42, 11 June 2007 (UTC)[reply]

Perhaps if you included sloughed skin cells, hair, and sebum, the portion of human waste material leaving via the skin might be brought closer to 30%. Vranak

That's a possibility if you're considering all possible waste that could possibly leave via the skin. Definitely. (Although if you include CO2 as "waste", that number would drop considerably. Including H2O as waste makes it more confusing and environment-dependent.) But there's just no way that 30% of metabolic waste (which would include most "toxins", something dead skin cells generally aren't considered) is excreted in sweat (in humans). I guess the context of the quote needs to be properly framed and clarified, to say the least.

I took a cursory look at PubMed to see if there was much acadmemic literature on sweating out toxin and came up fairly empty...I'll keep looking. — Scientizzle 18:45, 11 June 2007 (UTC)[reply]

This source suggests that humans lose 0.5-10L/day in H2O (as roughly isotonic sweat). — Scientizzle 20:06, 11 June 2007 (UTC)[reply]

If you consider salt to be "waste", then a substantial amount of waste is in sweat. If you don't, then only minor quantities of other substances are present. Since most people consume way more salt than they need, it isn't unreasonable to consider it to be waste to be disposed of, I suppose. StuRat 04:06, 11 June 2007 (UTC)[reply]

Is there anything that my doctor can proscribe me...

Is there anything that my doctor can proscribe me that can increase the volume and potency of my semen ejaculations, as well as reduce the recharge time between ejaculations of semen?

Instead of asking us to guess what your doctor would say, why not ask him? Friday (talk) 23:15, 10 June 2007 (UTC)[reply]

Or her (of course). Llamabr 00:48, 11 June 2007 (UTC)[reply]

Me, I'd proscribe posting frivolous questions at the Reference Desks. —Steve Summit (talk) 03:37, 11 June 2007 (UTC)[reply]

Before resorting to meds, try eating lots of protein, that may make a diff. StuRat 03:59, 11 June 2007 (UTC)[reply]

Citations, please? If you're going to give medical advice, it's useful to have a source.... TenOfAllTrades(talk) 14:37, 11 June 2007 (UTC)[reply]

It's not medical advice, it's diet advice. StuRat 15:45, 11 June 2007 (UTC)[reply]

Also, the human body is adaptive. The more often you ejaculate, the more often the body will be prepared to ejaculate. --Kainaw ^(talk) 12:40, 11 June 2007 (UTC)[reply]

Citations, please? If you're going to give medical advice, it's useful to have a source.... TenOfAllTrades(talk) 14:37, 11 June 2007 (UTC)[reply]

I believe it may have been personal research :o --⁪froth^t 23:57, 11 June 2007 (UTC)[reply]

Actually, I work in a hospital. It is general knowledge (no citation needed) that "If you (insert an action here) more often, your body will adapt to allow you to (insert same action here) more often." So, if you run more often, you body will adapt to allow to run more often. If you sleep more often, your body will adapt to allow you to sleep more often. If you eat more often, your body will adapt to allow you to eat more often. If you smoke crack more often, your body will adapt to allow you to smoke crack more often (until you die of course). --Kainaw ^(talk) 15:13, 12 June 2007 (UTC)[reply]

If you are concerned about the volume or potency of your ejaculations, see your doctor, or seek a referral to a qualified specialist. The Ref Desk isn't qualified to answer your question, and we're not an appropriate venue for providing medical advice. TenOfAllTrades(talk) 14:37, 11 June 2007 (UTC)[reply]

As others have said, rather then asking us what your doctor may be able to do, ask him/her. But medical issues aside, I have to question why you want to increase the volume and recharge time of your semen ejaculations. If you and your partner and trying to get pregnant, what matters is your sperm count and quality. I don't know for sure, but I strongly suspect you could easily increase the volume of your semen ejaculation yet reduce the sperm count (perhaps effectively maintaining the number of sperm released per ejaculation). In any case, if you have fertility concerns, you and your partner should see a professional help rather then trying random stuff which may be just making things worse. (This will also help to determine if there is a problem and if there is, what's causing it) If you concerns are not fertility related and presuming your not trying to be a porn star, then I suggest you at least speak to your partner/s first. You'll likely find that they may not be particularly interested in the volume of your ejaculations and indeed may even prefer smaller ejaculations since it's less messy. You'll probably find you and your partner/s can have a more enjoyable experience by being more creative and worrying less about the volume of your ejaculation. In any case, although this is OT, I would hope you've both/all taken adequet precautions including being tested for STDs before engaging in unprotected sex. Of course, in the end what you do is up to you. Nil Einne 17:12, 11 June 2007 (UTC)[reply]

Same old questions, same old answers. Rockpocket 00:55, 12 June 2007 (UTC)[reply]

Hehehe. I was just deciding whether to mention asparagus or not (at risk of being kicked about by the 'no stuff you heard somewhere' people). I thought that the discussion was familiar. --Kurt Shaped Box 01:41, 12 June 2007 (UTC)[reply]

Paleontology question

I recently visited the dinosaur exhibit at the American Museum of Natural History and wrote down the evolutionary relationship, in a dendrogram, between the maniraptors (I believe) Ornitholestes, Deinonychus, and Archaeopteryx, and also modern birds. Unfortunately, I will not have with me the museum map on which I wrote down this information. Can anyone clarify it for me? Is it

I. Maniraptora
 A. Ornitholestes
 B. Deinonychus
  1. Archaeopteryx
  2. modern birds?

Thanks, anon.

Hi there. You might want to post future questions here, but in the meantime I've taken the liberty of forwarding your question there. Check on the talk page there & you'll probably get an answer sooner or later. Cheers, Spawn Man 11:19, 11 June 2007 (UTC)[reply]

The big cladogram they have up at the most awesome museum ever (I'm not biased or anything ;) ) is 15 years old now and a little out of date, but from what I can tell that part is correct, except it leaves a lot of stuff out (for example, oviraptors are also maniraptorans, and are more closely related to Deinonychus and birds than to Ornitholestes, and Ornitholestes' classification as a maniraptor is still a little controversial. See the article on Maniraptora for a more complete, up to date family tree. Dinoguy2 15:25, 11 June 2007 (UTC)[reply]