Wikipedia:Reference desk/Archives/Science/2011 July 16

= July 16 =

Papaya leaves
I have some papaya plants. Their leaves are pretty typical for a young papaya and similar to File:Carica papaya Leaf 2000px.jpg. However, one fairly young plant about 2m tall, has developed small vertically oriented irregular but mostly ovate leaves in the centre of the large flat leaves where the palmate veins meet, one small ovate leaf per large palmate leaf (see File:Leaf morphology.svg. I've not seen these before. Does anyone know what they are and what they are for ?  Sean.hoyland  - talk 07:03, 16 July 2011 (UTC)


 * Can you post a picture? Dauto (talk) 15:34, 16 July 2011 (UTC)


 * Yes, probably. I'll try tomorrow...assuming the sun rises.  Sean.hoyland  - talk 16:02, 16 July 2011 (UTC)


 * Here's a picture.  Sean.hoyland  - talk 01:39, 17 July 2011 (UTC)

Weight of water in the clouds
What volume of the earth's water is held in the clouds at any one time? (either in percentage terms or in a nice equivalent to X olympic swimming pools!)ny156uk (talk) 10:24, 16 July 2011 (UTC)
 * Around 39%, including soil moisture. See here.  Rcsprinter  (talk)  10:37, 16 July 2011 (UTC)


 * Actually, that page says it is about 39% of 1% of 3% including soil moisture which is about 0.01%. Dauto (talk) 15:30, 16 July 2011 (UTC)
 * And actually, it's even less than that. That 39% figure is the measure of soil and atmospheric moisture, and there is likely much more water in gaseous form in the atmosphere than in liquid form in clouds. This source gives a figure of 12900 km3 as the total water in the atmosphere, which is 0.001% of the total water on Earth.
 * As a very rough estimate of how much is contained in clouds, I make the following calculation: approximately 60% of the earth is covered by clouds at any given time, and the average liquid water path for clouds is approximately 0.1 kg/m2 (source). Knowing the surface area of Earth is 510,072,000 km2, with a little math we can find a rough estimate of 51000000000000 kg as the weight of water in all the world's clouds (a very rough estimate), which leads us to a volume estimate of 51 km3. So it is obvious just from these rough calculations that very little of the water in the atmosphere is actually contained as water in clouds. You can do a little math yourself if you'd like the volume in some other form, since I'm philosophically opposed to the "swimming pool" as a unit of volume. - Running On Brains (talk) 22:13, 16 July 2011 (UTC)
 * Also please note that weight and volume are completely different things. - Running On Brains (talk) 22:20, 16 July 2011 (UTC)
 * I wanted to suggest considering that the area of the sphere at the height where clouds reside is higher since the radius of this sphere will be larger than that of Earth, but I've done the math and the difference is about two tenths of a percent, so negligible. --Ouro (blah blah) 07:16, 17 July 2011 (UTC)

Thanks for the responses everyone! ny156uk (talk) 08:40, 17 July 2011 (UTC)

Neanderthal and Denisova genome findings; bearing on the age of Genetic Adam and Genetic Eve?
Two studies in the news recently concluded that Neanderthals and Denisovans are likely to have descendants among humans living today, i.e. they interbred with our ancestors.

The studies did not find that the mtDNA or Y-chromosome of either Neanderthals or Denisovans correspond to any known haplotype of modern humans. My question is, what can we say about the likelihood there is Neanderthal or Denisovan ancestry along the direct matrilineal or direct patrilineal line of modern humans, corresponding to a mtDNA or Y-chromosome haplotype in modern humans that scientists simply haven't come across (yet)? If that were the case, it would push back the dates of Y-chromosomal Adam and mitochondrial Eve to either half a million years ago (in the case of Neanderthals) or a million years ago (in the case of Denisovans), correct?

What I am curious about is, if we assume for the moment that the conclusions of these two recent articles are correct, i.e. that between 1% and 4% of the genomes of people in Eurasia is derived from Neanderthals and something like 6% of the genome of Melanesians is derived from Denisovans, then is it reasonably possible that either (or both) originated extant mtDNA or Y-chromosome haplotypes? Or would that be highly unlikely on the basis that such haplotypes in living humans would already have been documented? Mathew5000 (talk) 10:54, 16 July 2011 (UTC)


 * An extremely small Neanderthal/Denisovan haplotype population cannot be ruled out. Dauto (talk) 15:25, 16 July 2011 (UTC)


 * It would be interesting to know how much more quickly sex-limited haplotypes go to fixation than autosomal genes. I found no helpful links on that.  You could probably also predict the likelihood of finding new haplotypes given the increase in the number of haplotypes found under broader sampling conditions--something else for which I would have no idea where to look.μηδείς (talk) 23:28, 17 July 2011 (UTC)
 * In a really simplistic scenario, if a population has 1-8 % archaic human admixture then the population should also have 1-8% of mitochondrial and y-chromosome archaic human lineages. So far, after more than 25 years of sampling, an archaic lineage in modern human populations has yet to be found. The more time passes, the less likely the chance of finding one. Even samples from prehistoric human samples dating to the Upper Paleolithic period show no signs of archaic introgression. Wapondaponda (talk) 06:47, 18 July 2011 (UTC)
 * The problem with your really simplistic scenario is that it is too simplistic. Dauto (talk) 15:49, 18 July 2011 (UTC)
 * To see why, read gambler's ruin second bullet. Dauto (talk) 15:52, 18 July 2011 (UTC)
 * It is simplistic, but it is close to reality, especially for recently admixed populations. If two populations admix, then we expect that the resultant admixed population will have a mix of autosomal, y-chromosomal and mitochondrial DNA in proportions that reflect the proportions of the ancestral sources of admixture. This is what we see in contemporary admixed populations all over the world today. Over time drift, selection can change these proportions. Gambler's ruin applies, but if it applies to the y-chromosome and mitochondrial DNA, then it should apply to the autosomes as well. But in this case 1-8% of the autosomes from a neanderthal or a Denisovan have persisted, so there is good reason to expect the persistance of a y-chromosome or mitochondrial DNA from either hominids. Wapondaponda (talk) 06:59, 19 July 2011 (UTC)
 * Another thing I was wondering about is whether cultural or biological conditions would likely be a factor. One basic question is, considering that the progeny of hybridization became part of Homo sapiens groups, can we infer that it was male Neanderthals copulating with female H. sapiens? If it happened that way exclusively, then obviously there would be no mitochondrial haplotypes from the Neanderthals in today's human populations. Then you also would have to wonder, maybe only one sex of the hybrids was fertile. Or maybe there were cultural taboos so maybe boy-hybrids were rejected from the community but not girl-hybrids. Some kind of combined effects like that might result in the absence of sex-limited haplotypes originating with Neanderthals despite the persistence of Neanderthal autosomal DNA in some human populations today. Mathew5000 (talk) 08:50, 19 July 2011 (UTC)
 * What was proposed by Green et al. was that there was gene flow from Neanderthals to humans but not the other way round. There was nothing mentioned about whether the gene flow was primarily from females or males. I should point out, that the presence of Neanderthal or Denisovan admixture in humans is still a preliminary and controversial finding. The authors themselves have provided an alternative explanation. They state that the presence of "Neanderthal-like" genes in Non-African populations may be because the African population which non-Africans emerged from, may have had these "Neanderthal like" genetic variants before the out of Africa migration. This would explain why the Chinese and the Japanese both have the same Neanderthal admixture as Europeans even though Neanderthals were not known to have lived in East Asia. Wapondaponda (talk) 15:25, 19 July 2011 (UTC)

Healing of throat after radiotheraphy
how long does it normally take for a throat to heal after radiotheraphy for throat cancer? — Preceding unsigned comment added by 121.210.236.13 (talk) 12:21, 16 July 2011 (UTC)
 * Consult a qualified doctor. As stated at the top of this page we cannot give you medical advice. Cuddlyable3 (talk) 13:14, 16 July 2011 (UTC)


 * And it really isn't even about "advice" in this situation. It's just an "it depends" type of question that requires one to know about a whole host of specific variables, and even then may not be amenable to answering.  We have articles on head and neck cancer and radiation therapy for general information, but I don't think you are going to find a simple answer to your question. --- Medical geneticist (talk) 15:13, 16 July 2011 (UTC)
 * Yeah, this has got to be dependent on the dose and resultant tissue damage. 157.22.42.3 (talk) 01:49, 17 July 2011 (UTC)

haloperidol--long term effects on children?
Does anyone know of studies or have information on the long term effects of Halperidol on children? What about if the child stops taking it--do the effects wear off quickly? Thanks, Rich Peterson24.7.28.186 (talk) 16:59, 16 July 2011 (UTC)
 * The article you linked says this: ''Children and adolescents are particularly sensitive to the early and late extrapyramidal side effects of haloperidol. It is not recommended to treat pediatric patients. Use is indicated only if the psychiatric or neurologic disorder is so substantial as to be completely intractable by all other means.

''
 * I suggest that it is not appropriate for the Ref Desk to say more and that you should indeed consult a medical professional. Bielle (talk) 17:12, 16 July 2011 (UTC)
 * Asking for primary sources is definitely within our purview, he's not asking for medical advice he's asking if anyone has studied the problem. If there was ever a clinical trial done on juvenile applications of the drug the study should have been published.  From the above quote it appears as if they have investigated its use, so I'm guessing that is available. HominidMachinae (talk) 18:58, 16 July 2011 (UTC)
 * Thanks to both of you for your thoughtful responses.-Rich Peterson199.33.32.40 (talk) 17:43, 26 July 2011 (UTC)

Turning up the music volume
This one may be in the archives, but if so I couldn't find it...why do people often feel the urge to turn up the volume when a song they like is playing even if they're able to hear it fine before they turn up the volume? Is there some psychological or biological effect that causes this behavior? Thanks, --Ks1stm (talk) [alternative account of Ks0stm] 23:23, 16 July 2011 (UTC)


 * you mean other than the obvious reason? (like moving closer to a tv when something you like comes on, even though you've seen the tv "fine" from across the room?  or bringing a newspaper closer if you're actually interested in a particular article, as opposed to glancing through headlines? ) 188.222.102.201 (talk) 23:39, 16 July 2011 (UTC)


 * That's just another description of the behaviour, rather than a reason for it. I've wondered the same thing. HiLo48 (talk) 00:45, 17 July 2011 (UTC)


 * To help concentrate on the song and block out other sounds? Dismas |(talk) 10:58, 17 July 2011 (UTC)


 * Since powerful audio amps and big speakers became common in the 1960's part of the rock music experience has been for the listener to feel his/her clothes and body vibrating from the blast of the music, and if it is loud enough it also blocks any possibility of conversation as opposed to appreciation of the music. Thus a generation or two with significant hearing loss. Edison (talk) 12:47, 17 July 2011 (UTC)

Being able to identify the song that happens to be playing on the radio and have it serve as background noise at a low volume which doesn't block out conversation and environmental warnings is different from intentionally choosing to fully immerse yourself in the subtle details of a more emotionally salient experience. If I intentionally choose a selection of songs I really like for that sole experience while doing nothing else I will automatically set the volume as loud as possible without discomfort and harm. If I simply have turned on the radio I do not expect each new song to merit the radio having been preset at that high level. At an underlying level, consciousness is a harmonic relation between the brain and its environment. Thus the power of music to hack the brain emotionally. See Entrainment (biomusicology) Harmonic Resonance theory of consciousness, and Music and emotion as well as Brainwave entrainment.


 * Please sign your posts by typing four Tildes (~). Cuddlyable3 (talk) 14:57, 18 July 2011 (UTC) I am not an IP-if you care, read the history.  Putting your remark simply stops the autsignbot.  And don't append your comments to mine.

Another thing: at lower volumes the sound appears "thinner" in that the bass frequencies seem to drop out faster than the midrange; turning up the music makes it sound "fuller". see Fletcher-Munson_curves Gzuckier (talk) 05:54, 20 July 2011 (UTC)

What kind of bug is this?
Sorry for the less-than-perfect picture. I used my cell phone camera. It's about 2-3cm long and was seen in northern Virginia. Peter Michner (talk) 23:46, 16 July 2011 (UTC)


 * Looks like a cicada skin to me. --- Medical geneticist (talk) 00:05, 17 July 2011 (UTC)

compare these images: μηδείς (talk) 00:10, 17 July 2011 (UTC)


 * Good call and absolutely correct. Once I looked up at its dorsal side, I saw the big crack down the middle. Peter Michner (talk) 16:22, 17 July 2011 (UTC)
 * The reason you haven't seen these before is that this kind of cicada only comes from underground once every 13 years. Look for them again in 2024.  i kan reed (talk) 16:34, 19 July 2011 (UTC)