Wikipedia:Reference desk/Archives/Science/2015 June 27

= June 27 =

Possible to stop eyes from watering?
Tevildo (talk) 23:12, 28 June 2015 (UTC)

Capillary refill in newborns
In the article capillary refill is written that "The upper normal limit for capillary refill in newborns is 2 seconds." But who look at the source of this sentence (source No. 3) will find that the upper normal limit is 3 seconds rather than 2 sec. 5.28.181.99 (talk) 11:37, 27 June 2015 (UTC)


 * Fixed. (You could have done that yourself.) --70.49.171.136 (talk) 22:04, 27 June 2015 (UTC)

Chimpanzee


I don’t know how to put this politely. As I view films of chimpanzees, I notice that their rears look very unusual. One particular documentary that I saw on YouTube (I can link to it if necessary) included a chimpanzee with a disturbing growth on its bottom. At first, I assumed that it was a sign of poor health, but the narrator said that it’s attractive to male chimpanzees. The article above doesn’t mention anything about their arses. So, may I please know what this weird thing is? --Romanophile (talk) 14:29, 27 June 2015 (UTC)
 * Maybe you could do the research and edit the article. ←Baseball Bugs What's up, Doc? carrots→ 15:08, 27 June 2015 (UTC)


 * Uhh… doesn’t asking here constitute research? I’m confused. But perhaps I was foolish to ask this awkward question here. --Romanophile (talk) 17:01, 27 June 2015 (UTC)
 * If the article doesn't have the info, then someone needs to research it. There's no reason you couldn't do that work, unless someone turns out to be willing to do it for you. ←Baseball Bugs What's up, Doc? carrots→ 21:14, 27 June 2015 (UTC)


 * E.C. Hey Romanophile. Welcome to Wikipedia and thank you for asking such an interesting question; I look forward to reading the answers.  I don't believe that BB intended his remark to sound quite as harsh as it does, and I assume that he is simply saying that if you don't get an answer here, but do eventually find out elsewhere, then please either be bold and add that referenced material to our article, or if you are concerned that the material may not belong, then add it to that article's discussion page at Talk:Chimpanzee where other editors can help decide where it belongs.  Also, we appreciate follow up posts here on the reference desks providing answers to previously unanswered questions.  We have several well informed biologists who frequent this desk, so I suspect that you will soon receive both an answer and, most likely, a link to a relevant Wikipedia article.  Thank you for looking for the answer in our articles first and for pointing out that you didn't find it where you expected to.  Such information helps us improve our encyclopedia. -- ToE 21:34, 27 June 2015 (UTC)


 * This document [docx] from the Maryland Zoo states that the swelling is associated with estrus, and that "Females have an estrus cycle which lasts approximately 36 days. During the course of this cycle, as her hormone levels change, a female experiences changes in the size, shape, and color of her genital skin. As circulating estrogens increase during the follicular phase of the cycle, the size of the swelling increases.  When the anogenital skin is fully engorged, it is typically bright pink, and can measure from 938 to 1400 cc.  The state of maximal tumescence (swelling) is of variable length in different individuals and at different stages of maturity, but lasts an average of 6.5 days. It is during this time that females are sexually receptive and that the bulk of copulations with mature males occur."  It also states that "Every day the chimp keeper is responsible for scoring the females stage of the cycle." and includes the following scoring chart:
 * Complete Detumescence: Minimum size, extensive wrinkling
 * Partial Tumescence: Slightly enlarged labia
 * Labial Occlusion: Medial surfaces of labia pressed tightly together
 * Significant Tumescence: Slight wrinkling, tissues raised significantly above anus
 * Maximum Tumescence: All tissues taut and pink, no wrinkling, anus deeply recessed
 * though there seems to be some confusion in that document whether the scoring range is 0-4 or 1-5. -- ToE 22:20, 27 June 2015 (UTC)


 * Aha! I finally found our article, though it is but a stub: Sexual swelling.  There is some related material in the lede of our Concealed ovulation article, which starts:
 * Concealed ovulation or hidden estrus in a species is the lack of any perceptible change in an adult female (for instance, a change in appearance or scent) when she is "in heat" and near ovulation. Some examples of such changes are swelling and redness of the genitalia in baboons and bonobos Pan paniscus, and pheromone release in the feline family. In contrast, the females of humans and a few other species have few external signs of fecundity, making it difficult for a mate to consciously deduce, by means of external signs only, whether or not a female is near ovulation.
 * The photo you linked is of a bonobo, and our Bonobo does say, "During oestrus, females undergo a swelling of the perineal tissue lasting 10 to 20 days. Most matings occur during the maximum swelling." Bonobos are closely related to common chimpanzees, being the other extant species of the genus Pan; Our article Chimpanzee is for that genus.  Our species specific article Common chimpanzee says, "Estrous females exhibit sexual swellings." -- ToE 22:46, 27 June 2015 (UTC)

Life expectancy, what difference requires an explanation?
Given a list of countries ordered by life expectancy like here https://en.wikipedia.org/wiki/List_of_countries_by_life_expectancy, you can see the gap between Japan (84), Canada (82), Denmark (80), and so on, until you reach Sierra Leone (46) at the bottom.

It's clear that a difference like Japan to Sierra Leone would prompt a question and be worth an explanation.

However, how small does a difference in years need to be to NOT require an explanation? — Preceding unsigned comment added by Scicurious (talk • contribs) 15:47, 27 June 2015 (UTC)


 * That's actually a statistics question, essentially, given the distributions of life expectancy in each country, what is the minimum difference in means between two countries that is significant, statistically, at your chosen level of significance. Boring eh? Greglocock (talk) 01:53, 28 June 2015 (UTC)


 * The article states that the differences are primarily due to the quality of health care, and refers to some other factors, such as HIV rate. As the previous poster said, a detailed answer about a comparison between any two countries is a statistics question, rejection of the null hypothesis that the underlying distribution is the same.  Given that the number of people in each mean is large, the null hypothesis can very likely be rejected with high confidence, but statistics sometimes only states that there is causation without saying what causes what.  Robert McClenon (talk) 02:12, 28 June 2015 (UTC)


 * When you get down to the 40's, that's a sign of some rather basic problems, like a lack of clean drinking water. More subtle differences could be due to differences in diets, genetics, activity level, etc. StuRat (talk) 03:49, 28 June 2015 (UTC)


 * The best way to compare countries and where there are differences is in actuarial tables that measure "average remaining years" for each age. Life expectancy from birth sufferes from many anomalies that include the definition of infant mortality as well as chilghood mortality.  For example, I believe Japan excludes deaths that occur after birth but in the first X number of days.  That makes a huge difference when comparing to the a country like the U.S. where death after live birth is counted.  Third world countries also have a mortality in childhood that is much higher than first world countries.  The interesting metrics to look at are remaining years at age 40, 50, 60, 70, etc.  That comparison takes out a lot of factors unrelated to elderly care/diet/lifestyle/etc.  The U.S. publishes these tables and breaks them down by race, gender, etc.  Infant mortality is what seperates most demographics.  There is very little variance in remaining years past age 60 in the U.S. but infant mortality makes overall variance larger.  --DHeyward (talk) 09:48, 28 June 2015 (UTC)
 * In this specific case, see Sierra Leone Civil War, which previously had a massive effect on the life expectancy, an effect that's not completely over yet. Nyttend (talk) 12:25, 30 June 2015 (UTC)