Wikipedia:Reference desk archive/Science/2006 July 28

From Wikipedia, the free encyclopedia

Humanities Science Mathematics Computing/IT Language Miscellaneous Archives
The page you are currently viewing is an archive page. Whilst you can leave answers for any questions shown below, please ask new questions at one of the pages linked to above. This will insure that your question is answered more quickly.

< July 27 Science desk archive July 29 >


Politness in the name of vaingloriousness has no place on a Wikipedia discussion page, imho. (Pardon the puns, I couldn't help it).

Contents

[edit] Male/Male & Female/Female only fertilization?

I remember reading an article, I forget where, it was either Time, Popular Science, the newspaper, I forget, but the article said that scientists said it was theoretically possible to, say two gay men wanted a child, or a lesbian couple, that by taking dna from one of the men and stripping out an egg or whatever and inserting the genetic material, and doing the same with a womean (but an egg instead of sperm obviously and pulling a few genetic strings and flipping a few DNA swtiches there, that it would be possible for say, one part of the lesbian couple to inseminate her partner with sperm encoded with her DNA, and the two gay men, could have a surrogate mother who would carry a child whose DNA was comprised of the both of their DNA. Am I making sense? The article did not imply or say the technology was available now or even absolutely possible. It only said it had a potential. If someone knows anything about this, I've been looking everywhere and I cannot find the article, and I do not know the correct way to word such a concep so that I could search for it with a greater accuracy.

Perhaps this? I just searched google news for "homosexual fertility". Digfarenough 13:05, 28 July 2006 (UTC)
That only mentions the possibility briefly. But I see a problem. A female/female dna couple would produce a female (two x chromosomes). But a male/male couple would produce two y chromosomes and I don't think that gender exists. And I didn't sleep during biology classes because those were the among the very few I found interresting at school. DirkvdM 17:27, 28 July 2006 (UTC)
Don't forget that males being XY can produce women (XX) and normal men (XY). Whereas lesbian couples would only produce females. -Pascal
Er, actually, I think you're both a bit mistaken. I don't believe YY is compatible with embryo formation; the syndrome to which you're referring is 47,XYY. But as Pascal points out, since (most) men have the karyotype XY, they produce both X- and Y-carrying sperm. If one were to combine them randomly, I would expect 25% to be female, (Xs from both parents), 50% to be male (X from one, Y from the other), and 25% not to form (YY). — Knowledge Seeker দ 17:46, 28 July 2006 (UTC)
I wouldn't assume that the chromosomes are randomly combined, but rather selected individually, which means two males could choose either a son or daughter and would avoid the YY combo. StuRat
First off, Males are XY, so two fused sperm (or whatever) would have a liklihood of 25% XX, 50% XY & 25% YY. YY disomies are highly unlikely to survive--the only cases of living humans with YY that I've found on PubMed have translocated large amounts of X chromosomal material on the normally miniscule and gene-poor Y chromosomes (there are several vital genes on the X chromosome). XYY males certainly exist, though. -- Scientizzle 18:04, 28 July 2006 (UTC)
Damn, I first make a very stupid claim and then even draw an incorrect conclusion from that. DirkvdM 07:33, 29 July 2006 (UTC)
Another problem that researchers must overcome in fusing gametes from the same sex is chromosomal imprinting. Natural developmental processes depend on controlled gene expression in the zygote, much of which is regulated by inherited gene silencing (often via methylation) on the maternal or paternal chromosomes. -- Scientizzle 18:04, 28 July 2006 (UTC)

Note that the offspring of the two males would contain the RNA from the egg donor in their mitochondria and that two females could have a son with a single Y chromosome taken from a sperm donor. This would only be one out of 46 chromosomes, so the child would still be almost 98% genetically their son. StuRat 18:14, 28 July 2006 (UTC)

How many people can parent one child? Could one also combine the brains of one person, the musical talent of another, the looks of a third, etc? DirkvdM 07:33, 29 July 2006 (UTC)
The intelligence of George Bush, the musical talent of Roseanne Arnold (specifically, her singing of the US national anthem), and her looks, as well ? StuRat 08:10, 29 July 2006 (UTC)
One can remain otimistic, but the human oocyte would be rather a problem. At fertilisation, it is not a gamete, it is a haploid cell arrested during the second meiosis - a long and poorly understood path from when it first differentiated in the fetus. No such entity as human female "gamete" exists (unless that is what one would call a 23X sperm?). It completes meiosis and becomes haploid only after a sperm penetrates it. At what stage could one introduce foreign DNA and expect the system to still function? Would male chromosomes be capable of maintaining the arrested meiosis stage? The problems are formidable; haploid little tadpoles are simple by comparison. I sometimes think men went out hunting and fighting because their contribution to the survival of the human gene was simpler to make in quantity, and that the the psycho/phenotype lines that did not protect the finite number of these very special reproductive cells that the female carried died out from lack of oocytes, not of sperm. Selfish genes make some sense. --Seejyb 23:20, 29 July 2006 (UTC)
The article which deals with this is parthenogenesis. I'm a little surprised no-one's mentioned this already. Dysprosia 11:55, 3 August 2006 (UTC)

[edit] rotation speed of the universe?

I have been wondering the possible rotation of the universe for quite some time. The subject haven't been discussed in any literature I've come across with, altho it seems like quite non-trivial and possibly interesting.

I guess it would be notoriosly difficult - if not outright impossible - to carry out such measurements. There's no reference points, obviously - d'uh! Without reference, it's the same as standing in a closed box. We can't distinguish movement from being "stationary", nor can we distinguish gravity from acceleration.

Based on the red shift and studies on other subjects, we have an estimate on the expansion speed of the universe. However, not knowing the mass of the universe, we can't tell what kind of circular orbital speeds we should expect at any distance from the centre. If the universe is expanding, however, we can be sure that the universe is not on a circular - but perhaps on an elliptic orbit around itself at the moment.

What might matter more, is the beginning of the "orbit". If a object is throwed away from a surface of a gravitational body, it will either experience an orbit that intersects with the body, or an escape orbit. If all the parts of the universe were on such an colliding orbit, eventual collapse would be imminent. However, artificial satellites sent from the surface of the earth are able to maintain (near) circular orbits, not intersecting the surface of the planet. This is possible because the payload and the fuel are accelerated in opposite directions after leaving the surface of the earth.

Likewise, universe might be on a non-self-intersecting orbit around itself, non-collapsing, yet not infinitely expanding - if there is significant difference in orbital angular speed in different parts of the universe. Now I'm not saying anything on whether or not such different orbits would or would not intersect. However, the energy for making that difference would have come from somewhere. I'm not saying that it has, just not ruling out that it couldn't have. Total angular momentum of the universe must have been preserved since the big bang, although differences in part of it could have emerged. Anyways, I'm going too far from the real question..

What is the current status on the study of this subject? Is the universe rotating, non-rotating, or is it an open question, or is either possibility just "assumed" out of convenience? Can we only make an equation that show the dependence of expansion speed on the angular speed and the mass of the universe, or is there base for the estimation of some single parameters?

If true, this theory would put a whole new spin on the universe. :-) StuRat 04:12, 31 July 2006 (UTC)

Uh, I guess those were questions, rather than a question. Anyways, as usually, I'd just love to hear your answers (and discussion). Thank you. 193.166.173.23 12:32, 28 July 2006 (UTC) Oh, it's as if my session timed out while I wrote down this minor question, or I was never logged in. Santtus 12:34, 28 July 2006 (UTC)

Oh, and I have to add to the story before letting anyone answer. If the estimate on the mass of the universe is based on assumption of non-rotation, obviously the universe would have a larger mass should it actually be rotating, in order to give the same appearance of phenomena for us poor humans, who are doomed to wander in here without any outside physical references whatsoever. *sigh* Santtus 12:41, 28 July 2006 (UTC)

There was a recent article in New Scientist relating to the universe rotating. The online version (which you have to pay for) is here [1]. JMiall 13:04, 28 July 2006 (UTC)
Blah, I subscribed to the magazine, but apparently I'd have to wait for the first issue to be delivered and use a printed code in the postal delivery to enable my online content. So you nice folks at Wikipedia have still a good 3-4 weeks of time to discuss this before I recieve my "spoilers" from the postal service ;) Eh, this might be of interest to a wider audience than those willing to subscribe to a premium service.. Santtus 14:13, 28 July 2006 (UTC)
I would have thought the question was meaningless (considering no point of reference outside the universe), so I await sight of the New Scientist article with interest.--Shantavira 14:47, 28 July 2006 (UTC)
It would be meaningful, even though no outside reference could be established. Given the lack of other meaningful explanations, the disparity between calculated mass and the observed gravity could be properly attributed to non-zero rotation of the measured body. Santtus 15:37, 28 July 2006 (UTC)
Rotational speed can be measured. Rotation imparts a centrifugal force on the object being rotated. This force is greater the faster the rotation and can be measured. So align such an object with an object on both sides of the universe and measure how fast it rotates. Thus the rotational speed of the object can be determined, and how fast it is moving closer or futher away can also be measured by red shift. Thus the speed and direction of the object can be determined.
Yeah, why not joggle with the universe while we're at it. It would just be much more convenient not to extend a measurement device for such a great distance. So obviously we'll have to contend with earth-bound measurements.. or anyways, measurements on distances insignificant compared to that of the diameter of the observable universe. The problem is that we have no solid medium in the universe where we would attach those measurement devices into ;P Santtus 15:32, 28 July 2006 (UTC)
Basically, you are saying that outward momentum from a central point is due to centrifugal force and therefore evidence of rotation. Right?? If something like a big bang sent everything outward in a straight line with no spinning, you would still have outward momentum. --Kainaw (talk) 15:30, 28 July 2006 (UTC)
Obviously he would have the universe-long measurement device free-floating in universe, not "attached" to anything like planets that would be moving fast away from the centre ;) Yes it would take quite a bit time to set up such a device, and even more so to get any readings from the device. Maybe it didn't even have to be very long. Still, I believe we're gonna get results faster by using what we have on earth and in vicinity. Santtus 15:43, 28 July 2006 (UTC)
If you ment that, I dont think that expanding is by itself any indication of rotation. Santtus 15:46, 28 July 2006 (UTC)
I'm not entirely sure what you are getting at, but if the basic issue is: "Does the total angular momentum of the observable universe = 0?", then that is at least an approachable question. One obvious observation is that any large scale rotation would give rise to anisotropy in the universe, with a natural direction defined by the axis of rotation, just as the equator and poles of the Earth move differently with respect to the Earth's rotation. Such anisotropy might have observable implications that could been sought for in WMAP or SDSS. Also, if we are just talking about angular momentum conservation from some initial non-zero value, then that would have to be accomplished by ordinary gravitational forces, when would tend to concentrate mass in a plane perpendicular to the axis of rotation, just as galaxies collapse into rotating disks. Dragons flight 15:53, 28 July 2006 (UTC)
I believe the idea that the Universe is rotating was originally put forward by Godel. It is a meaningful question as a reference point is only required for uniform motion. The current thinking is that the Universe is not rotating as (it is thought) the rotation would produce observable change in the cosmic microwave background. This has not been seen.
The suggestion by Dragons flight that the angular momentum be zero is I think a reference to the intrinsic angular momentum (spin). The net spin of all the individual particles in the Universe is zero.
Another reason cosmologists find the idea of a rotating Universe distasteful is that it would mean there would be a 'special place' in the Universe and therefore contravene the cosmological principle.

Thank you everybody for the answers! There's lot to think about this that I can't put into words right now, but thank you for your answers. Santtus 22:28, 2 August 2006 (UTC)

[edit] herniated disc

Are there any proven scientific cures or treatments for people who have herniated discs?

Try our article on spinal disc herniation. TenOfAllTrades(talk) 13:05, 28 July 2006 (UTC)

[edit] Energy density of alcohol

The food energy of ethanol is usually given as 7kcal/g. The energy of carbohydrates is just 4kcal/g. But alcohol is a metabolic byproduct of glucose - it can be produced exothermically from it by fermentation. How can the product have a higher energy density than the original? --199.89.64.178 15:11, 28 July 2006 (UTC)

Fermentation: C6H12O6 (glucose) -> 2 C2H6O (ethanol) + 2 CO2 (carbon dioxide) + 2 ATP (energy).
I assume the issue is with calculating energy per gram rather than energy per reaction. Reducing glucose to ethanol reduces the weight almost in half by removing CO2, but releases only 2 ATP. By contrast, full aerobic respiration can produce 36 ATP of energy per glucose molecule, so evidentally very little energy is lost converted in converting glucose to ethanol, while the weight is reduced considerably by removing CO2. Dragons flight 15:38, 28 July 2006 (UTC)

I don't know if it applies to your calculations, but in terms of human metabolism, alcohol is a calorie free "food". It is only when the body (alcohol dehydrogenase, then acetaldehyde dehydrogenase) converts ethanol to acetaldehyde and then to acetic acid, which can be used as "food", that the energy is avaliable to the body.Tuckerekcut 18:40, 28 July 2006 (UTC)

Sorry, this is like saying "starch is a calorie free food; only when it is converted to glucose is the energy available". All caloric food gets metabolically converted. alteripse 12:59, 29 July 2006 (UTC)
"All caloric food gets metabolically converted" is misleading for two reasons. First, there is caloric food which is simple enough to be broken down directly (namely, simple carbohydrates) without metabolic conversion. Second, of those foods which much be converted to offer food energy, a non-trivial fraction often passes through the body without conversion (or with incomplete conversion). That is, when one drinks ethanol, there will be a little ethanol in that person's urine later on (or in their breath right now). It is important to take these things into account when comparing the actual free energy to the food energy.Tuckerekcut 15:24, 29 July 2006 (UTC)
You are either playing semantic games or misusing words. Name a caloric food substance that isn't metabolically converted. Even most glucose molecules are metabolically converted as they are distributed throughout the body and used. alteripse 22:47, 29 July 2006 (UTC)
Dragon flight's reasoning is sound and seems to me appropriate to the question: per gram of substance, the calorific value of ethanol is 1.75x that of glucose.
I believe that calling alcohol a calorie free "food" may be a dangerous statement for persons reading this forum who may need to watch their energy intake. Tuckerekcut's point seems to be that when alcohol enters the calculation, one cannot simply convert from grams of substance to effective dietary kcal. In the intact human being this can be (but is not always) less than expected from simple calorific measurements of the substance itself. This is true. What other sources of calories the person takes in seems to make a difference. I cannot, however, make sense of the idea of energy-giving foods being calorie free "food". Nor that conversion has anything to do with it. In following the metabolic pathway of energy-giving foods down to the common acetyl-CoA molecule, and on to the electron transport chain, there seems to be a whole lot of converting going on. No energy yielding "food" that I have ever heard of, other than intravenous ATP, does not get converted (and even that gets converted to ADP to deliver energy). Alcohol is usually referred to as "nutrition free" calories, implying supply of energy without any other nutrient value - like eating pure glucose. But here calorie free food seems to be defined as food which first needs to be "converted", thereby qualifying as being calorie free. We know that loss of the energy available in food occurs on the way from the mouth to the mitochondrion, caused by processes both normal and pathological. That does not change the calculation of the laboratory determination of the potential calorific value of food. Or does it? Should we refer to fat eaten by a person with a short bowel syndrome and absent colon (or maybe severe chronic pancreatitis), now as calorie free food? Does glucose for a diabetic with too little insulin suddenly become a calorie free food? When is the term used? Is there some reference to the concept available? --Seejyb 22:23, 29 July 2006 (UTC)
I suppose I was getting into the semantics a little there, and that other than intercellular ATP injections everything needs to be converted to yield useable energy. What I would stress, then, is that there really are three measures of the amount of energy in food. One measure is the total free energy of the chemicals which make up the food, that is, the amount of energy required to assemble the food from individual atoms. You might find this in a reference text like the Merck Index. The second measure is the caloric potential of the food (I'm making this term up, if it is previously coined, disregard any other definitions in this context), being the amount of energy which can be extracted from the food by the (human) body under ideal circumstances. This is likely to be close to the number given in the nutrition information on the packaging of most foods (be it in kJ or Cal). The third measure is the actual amount of energy extracted, which is dependent on such things as individual metabolism, pathology, and peristalsis.Tuckerekcut 19:22, 30 July 2006 (UTC)

[edit] Portable X Server for Windows?

Moved to the Computing referece desk

[edit] EPR spectra have three peaks, why?

Why do "rhombic" epr spectra have three peaks, I would have thought that these signals would be averaged out because of the random orientation of the molecules? Or stated differently, I would expect to see an infinite number of peaks, one for each orientation of that paramagnetic molecule in the magnetic field. Thank you,--130.126.228.60 16:12, 28 July 2006 (UTC)

Electron Spin Resonance (a synonym for Electron Paramagnetic Resonance) could help you, as well as Nuclear Magnetic Resonance, a technique which employs virtually identical physical concepts, except for nucleons, instead of electrons. The paramagnetic elements in a sample undergoing EPR are subjected to a constant magnetic field, which orients most of the samples to have an angular momentum in the direction of the field (the angular momenta are quantized, and they actually form a boltzmann distribution with a peak in the orientation of the magnetic field). The sample is then subjected to EM waves, which cause the parts of the samples for which the frequency is a resonant frequency to strongly absorb the waves. Usually in EPR the frequency is held constant while the magnetic field strength is varied to create different resonant frequencies in the sample. In short, the static magnetic field polarizes the samples and causes all similar samples to resonate at the same frequency. --Bmk 04:26, 29 July 2006 (UTC)

[edit] About vision

Always wondered, how with science view can we explain that when in the dark, if we don't look directly on the subject, we can see it clear? and vice versa: if in the dark we directly look at the subject, we see nothing. Why is that? Thank you.

Probably your peripheral vision is better at seeing in the dark because of where the rods and cones are in your eye but possibly the subject is very bright and you are getting blinded by it if you look at it directly. JMiall 17:01, 28 July 2006 (UTC)
Looking directly at something lets you see more detail, while the peripheral vision is just enough to catch your attention when you see movement and then look at the object in question. I suspect you may have looked directly at something bright in the past, and fried some of the receptors in that area, leaving an insufficient amount to see well in the dark. Your peripheral vision, remaining undamaged, is therefore better able to see at night. StuRat 17:54, 28 July 2006 (UTC)
Rod cells are located throughout the retina, but at very low number at the fovea, the center of the field of vision; Cone cells are highly concentrated at the fovea. This allows greater color vision & detail when looking directly at an object and very sensitive, but largely color-blind, vision in the periphery. In very low light, cones are largely useless, but rods can respond to a single photon of light. It's probably most effective, until one gets completely acclimated to low-light conditions, to look at objects a few degrees off to maximize sensitivity. -- Scientizzle 18:20, 28 July 2006 (UTC)
Any astronomer can tell you that dim/faraway stars are best seen peripherally—more rods. — The Mac Davis] ญƛ. 18:27, 28 July 2006 (UTC)
No no no no... this is an effect called averted vision. http://vegas.astronomynv.org/Tutorials/avertedvision.htm It's a commonly used technique in optical astronomy and is caused because the optical nerve (where there are no rods or cones) is right in the center of your vision. --35.9.66.37 14:46, 3 August 2006 (UTC)

[edit] Plant Pathology

Hi! Will anyone please explain : What is the basic difference between an Incitant and a Pathogen? Does the term 'causal organism' apply to both ? Thanks,Pupunwiki 16:29, 28 July 2006 (UTC)

According to this site, incitant is "a term used commonly, but incorrectly, to describe the causal agent of a disease. Properly, the term should refer to some other factor which promotes the pathogenic action of the causal agent". So, maybe your answer lies in that? -- Scientizzle 18:24, 28 July 2006 (UTC)

[edit] Banks of south-flowing rivers in Europe

Battle of Smolensk contains the following intriguing sentence: "like many south-flowing rivers in Europe, the Dnieper's western bank... was higher and steeper than the eastern." Assuming that 'many' means 'more than one would expect by chance', why? HenryFlower 22:27, 28 July 2006 (UTC)

  • This is just a thought, but quite a bit of Europe is slowly rising both because of Africa's drift north and rise from the end of glaciation after the last ice age. It would only be a very small difference, but maybe it would be enough to affect the river's course, thus producing this effect in some way? Grutness...wha? 07:21, 29 July 2006 (UTC)
Another wild guess. The prevailing winds in Europe are from the west. The wind picks up more speed over water, so the east bank gets a stronger wind an as a result more erosion. But I doubt the effect (if any) will be strong enough. DirkvdM 07:41, 29 July 2006 (UTC)
perhaps Coriolis Effect? -- 84.160.196.152 14:05, 29 July 2006 (UTC)
It is indeed the Coriolis Effect. All other things being equal (including laminar flow of the river, which is impossible) the river will tend to want to flow east. This means that the river will erode more to the east, and deposit to the west, leaving river cliffs on the east and river beaches in the west.
If so, won't the river then move further and further east until it hits higher ground, which initially stops the move, but then starts eating away the base of the higher ground, resulting in an even steeper slope on the east side? DirkvdM 08:57, 31 July 2006 (UTC)
Don't the last two responses predict the opposite of what the original question stated? -- Avenue 11:00, 4 August 2006 (UTC)

[edit] Energy

Is there a metal or any substance that converts heat into electricity?

Yup. See Thermocouple.
Also pyroelectricity and piezoelectricity.

[edit] Help Me Identify This Plant

Hi guys, it would seem that this is the latest installment in Help Me Identify This Plant. I humbly ask of the Wikipedians to identify this plant for me. It's a house plant of mine that I've had for maybe two years now.

My Plant
My Plant

Also, why is it becoming discolored at its top? Also, I suspect it's crowded in there, because it looks like it has seperated into multiple plants. Thanks alot for any help! M@$+@ Ju ~ ♠ 23:48, 28 July 2006 (UTC)

I found a picture of Haworthia fasciata on google images, and that kind of looks like it. Any opinions? M@$+@ Ju ~ ♠ 23:57, 28 July 2006 (UTC)
I'd say aloe. More specifically, going by the pictures, aloe variegata. Black Carrot 02:10, 29 July 2006 (UTC)
I've had aloe before, Black Carrot, and this is somewhat different. Yes it is a succulent, but these leaves are rounder with raised white spots. I don't think it can be aloe. Of course I can always snap a piece off... M@$+@ Ju ~ ♠ 02:19, 29 July 2006 (UTC)
I'm inclined to agree with you (Mattman). Haworthia have little raised bumps/spots, whereas the aloe variegata (which is similar in appearance) is smooth. TenOfAllTrades(talk) 02:59, 29 July 2006 (UTC)
Thanks for the second opinions, Black and Ten, I think I'll go ahead and label it as the Hawthoria. M@$+@ Ju ~ ♠ 05:28, 29 July 2006 (UTC)
If it has grown like that in 2 years it likes you, Matt, but please return the compliment and call it Haworthia (Hawthoria, the succulent hawthor(n)?). Your photo looks like H. attenuata fa. caespitosa, and should have little bumps on the inside of the leaves too. The major risk of overcrowding is that the roots block the pot's drainage holes (I can't see how deep the pot is). You can safely separate all those pups. Take the whole lot out of the pot, wash off the soil, gently separate the roots and plant each one in its own pot of sandy well-drained soil. Rememember to cut out any dead leaves (the overcrowding does that) while you are at it - like any succulent the leaves seal off well where you cut them. The "discoloration" (as opposed to drying / dying leaves) is normal, and depends on light conditions. In the wild one can see the same variety growing in an area close together, with those more exposed to sun having more of a reddish-brown tip. --Seejyb 11:48, 29 July 2006 (UTC)
Thank you for your advice, I will certainly get right on the repotting! M@$+@ Ju ~ ♠ 17:16, 1 August 2006 (UTC)