Wikipedia

Wikipedia:Reference desk/Archives/Science/2016 October 25

< Wikipedia:Reference desk | Archives | Science
Science desk
< October 24 << Sep | October | Nov >> October 26 >
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.


October 25

edit

Is that true that the brain has arteries only without veins?

edit

I've heard that the brain is exception of our body because unlike all our organ which have arteries and veins, the brain doesn't have veins but arteries only. If it's true, what is the way of the of the body or of the heart to draw the deoxygenated blood from the brain? 93.126.88.30 (talk) 02:38, 25 October 2016 (UTC)[reply]

Cerebral circulation describes the arteries AND veins of the brain. So wherever you heard that the brain does not have veins appears to be wrong. Vespine (talk) 02:51, 25 October 2016 (UTC)[reply]
There is one place in your body with an artery where there would "normally" be a vein, but that's the glomerulus, in the kidney. Maybe you heard something about the cerebrospinal fluid and misinterpreted it? There are the dural venous sinuses, which are veins, but a bit different from your "average" vein. --47.138.165.200 (talk) 03:19, 25 October 2016 (UTC)[reply]
=Thank you. I asked the professor who told it and he explained me that they are sinuses rather than veins, they function as veins but they are sinuses. 93.126.88.30 (talk) 18:55, 25 October 2016 (UTC)[reply]
Your professor might be referring to Dural venous sinuses? But there ARE other veins in the brain which are just regular old veins: Internal cerebral veins, Superior_cerebral_veins, Great cerebral vein.Vespine (talk) 21:54, 26 October 2016 (UTC)[reply]

Why are evolutionary the testis are located outside of the body?

edit

Why are evolutionary the testis are located outside of the body? Here is in such way they are exposed to the damages due to their sensitiveness. Is there any assumption or speculation about this question? 93.126.88.30 (talk) 02:44, 25 October 2016 (UTC)[reply]

Our testes article even has a section called evolution > external testes. Vespine (talk) 02:49, 25 October 2016 (UTC)[reply]
One theory they didn't list is that they are "advertising fertility", much as breasts on female humans do. StuRat (talk) 15:37, 25 October 2016 (UTC)[reply]
[citation needed] SemanticMantis (talk) 16:09, 25 October 2016 (UTC)[reply]
For the assertion that it's not listed?? —Tamfang (talk) 01:57, 26 October 2016 (UTC)[reply]
I am pretty sure the citation is needed for the "testicles as fertility ad" bit. Hofhof (talk) 02:00, 26 October 2016 (UTC)[reply]
Yes, that is what I meant. I want a citation that tells me more about that claim, and who may have made it. As it stands now with no reference, we just have yet another zany idea proposed by StuRat. SemanticMantis (talk) 15:41, 26 October 2016 (UTC)[reply]
The only claim I made is that our article doesn't list that. StuRat (talk) 16:23, 26 October 2016 (UTC)[reply]
I have not heard this theory before. Do you have references please? DrChrissy (talk) 16:30, 26 October 2016 (UTC)[reply]
Thank you for asking politely. Start here: [1]. StuRat (talk) 17:48, 26 October 2016 (UTC)[reply]
Thanks for that. It is an interesting collection of alternative theories for internal and external testes. One point I would like to make is that it does not exactly say that external testicles advertise fertility. It describes external testes in terms of being a sexual attractant. DrChrissy (talk) 18:22, 26 October 2016 (UTC)[reply]
Good, thanks. I assume that now you understand that you did make a claim above, and that this reference supports it? Now you have traced the theory that you mentioned to a hypothesis originating in 1950's and having almost no contemporary supporters ("This theory is not widely accepted because such conspicuous displays are rare (many scrotums are barely visible) and bright coloration seems to have evolved long after the original scrotum"). That's great!
It's ok to talk about hypotheses that are not well supported, but when doing so in the future, please include a reference. SemanticMantis (talk) 20:50, 26 October 2016 (UTC)[reply]
I did not claim the theory was correct. StuRat (talk) 22:03, 26 October 2016 (UTC)[reply]
StuRat, I think you are being disingenuous here. Not only did you not provide a reference initially, but you actually misrepresented the source you were following. I spent 15 minutes looking for a mainstream article supporting your contention on Google scholar and I could not find a single one. Your posting has cost me time unneccessarily and I consider that to be disruptive. Please provide RS for your answers in the future. DrChrissy (talk) 22:50, 26 October 2016 (UTC)[reply]
I'm not understanding your differentiation between "sexual attraction" and "advertising fertility". The main purpose of sexual attraction is reproduction, so obviously apparent fertility is a critical aspect of sexual attraction. StuRat (talk) 23:02, 26 October 2016 (UTC)[reply]
Fertility is the natural capability to produce offspring. However, it is only one part of an animal's fitness. Fitness (biology), is an individual's ability to propagate its genes, and so is the ultimate criterion on which females select males. Some animals advertise their fitness using an intervening variable such as dominance. For example, dominant male mandrills have bluer backsides than more subordinate individuals. This more intense blue is a sexual attractant, but to the best of my knowledge, has not been linked to fertility per se. DrChrissy (talk) 23:33, 26 October 2016 (UTC)[reply]
You posted a theory. Whose theory is it? Where can I read more about it? This is a reference desk. SemanticMantis (talk) 17:19, 26 October 2016 (UTC)[reply]


Why do elephants and hyraxes have internal testes?

edit

Does anyone know about the evolutionary history which has led to elephants and hyraxes (our Testicle article also lists monotremes, armadillos, sloths and the rhinoceros) being the only land mammals to have internal testes? If they are able to produce viable sperm internally, why has this not evolved in other land mammals? DrChrissy (talk) 16:35, 26 October 2016 (UTC)[reply]

Here [2] is a review article on the evolution of external testes from a phylogenetic perspective. It has tons of good refs, and may have some passing discussion on "why" in various groups. There is a classic tradeoff between seed size and seed number in plants, mentioned briefly at Seed_predation. I'm not as familiar with how that might apply to mammals, but here is an article on sperm size vs. sperm number [3], which may fold in to the pro/con lists for internal/external testes. I strongly suspect you'll have a hard time getting a hold of it, but this article would probably get to the heart of your question:
If anyone finds a pdf, please let me know! (n.b. I restored your question after you removed it because 1. I had already typed this up 2. it is interesting 3. some of this may be useful to future searchers, hope you don't mind) SemanticMantis (talk) 17:19, 26 October 2016 (UTC)[reply]
Thanks for that information. No problems at all in reverting my deletion. The Testicle article offers several theories, but they all have their own problems. My own problem is that there is such a wide range of land animals with internal testes. So, any theory related to size or rate of heat loss seems to be problematic. Their behavioural ecology is also highly varied (e.g. compare the elephant compared to the sloth), so it's unlikely to be ecological constraints. DrChrissy (talk) 17:36, 26 October 2016 (UTC)[reply]
I have found this[4] rather interesting article which states "Furthermore, genera within mammalian families often exhibit variations in testicular position.10-12 Six mammalian orders contain species with internal testes and species with external testes (Marsupialia: kangaroo, etc.; Chiroptera: bats; Rodentia: rats, mice, porcupines, prairie dog, chinchilla, etc.; Carnivora; Perissodactyla (odd-toed ungulates): horses, rhinos, etc.; and Artiodactyla (even-toed ungulates): pigs, hippos, camels, deer, cows, etc.)". This really only adds to my confusion as I would have expected such an adaptation to be conserved at the level of order (just my speculation). The article then goes on to explain that some of these mammals have other thermoregulatory adaptations to keep internal testes cool "Thus, many ascrotal taxa like seals and Catacea have developed specific mechanisms for cooling their testis (e.g. venous plexuses carrying cool blood to the spermatic arteries), whereas others such as Monotremata need no such mechanisms due to their low core body temperatures." But, (there is always a "but" it seems) "The Hyracoidea and Proboscidea represent an exception as they lack a specific internal thermoregulation mechanism". DrChrissy (talk) 17:58, 26 October 2016 (UTC)[reply]
Quora, despite not being an WP:RS, suggests that there's an advantage in having internal testicles because they are protected from mechanical injuries, etc. But because "Some of the proteins in sperm don't fold properly at human body temperature", they became external to cool down. Btw, some rhino species also have internal testicles. Brandmeistertalk 19:52, 26 October 2016 (UTC)[reply]

Drugs

edit

Are there any psychoactive, hormonal or psychiatric drugs that cause neither tolerance, dependence, withdrawal, paradoxical effects, severe side effects, drug effects happening long after use (like LSD) nor a rebound where whatever the drug was fighting comes back stronger than before after the effect wears off? Or do they all have one of those or another, i.e. steroids, LSD (flashbacks), and antidepressants (erection dysfunction)? Ignoring non-physical dependence unless many users get it since anything can cause that. Like a drug with no effect besides "increase persistence of vision to 2 seconds" probably wouldn't make most people psychologically addicted so would qualify. 173.46.76.152 (talk) 04:12, 25 October 2016 (UTC)[reply]

Nitrous oxide. Vespine (talk) 04:39, 25 October 2016 (UTC)[reply]
Hmm... Recreational_use_of_nitrous_oxide#Health_concerns is an unsourced passage, but I did remember a documentary-fiction on Victorian GB mentioning similar effects. Arguably those are not "severe side effects" and dependence is psychological, though.
Oh, and although the request is probably legitimate curiosity, it looks no different to the polite version of "what can I get high on?". TigraanClick here to contact me 08:57, 25 October 2016 (UTC)[reply]
I don't think it's really our business whether the OP wants to get high or not. It's legitimate to ask what euphoric substances have other enumerated effects. What people do with that information is their own lookout. We should certainly be careful not to claim that any particular substance does not have bad effects, unless we are very very certain of that indeed and can back it up. --Trovatore (talk) 09:10, 25 October 2016 (UTC)[reply]
In that exact case, I tend to agree that is not our business, but that is my own opinion. If a random IP asked which drug store products work best to dissolve a human body, I hope many would feel uncomfortable answering; similarly, some knowledgeable people might refuse to answer a question about drug use if there is a practical intent behind it. Nothing to do with the medical disclaimer. TigraanClick here to contact me 15:58, 25 October 2016 (UTC)[reply]
Fair enough. --Trovatore (talk) 23:52, 27 October 2016 (UTC) [reply]
here and here are some references to side effects of nitrous oxide. --Jayron32 11:50, 25 October 2016 (UTC)[reply]
Altering your brain waves for 3 minutes does not sound like a long term or particularly severe side effect, imho. And the webmd article is ridicolous, I don't see any good sources for the claim that severe low blood pressure or sever Methemoglobinemia are "COMMON" side effects from nitrous use. It's very widely and "incautiously" used in dentistry and during labour. Nitrous_oxide#Safety Vespine (talk) 21:46, 25 October 2016 (UTC)[reply]
Salvia divinorum may satisfy some of your criteria. SemanticMantis (talk) 14:08, 25 October 2016 (UTC)[reply]
Here and here are some sources about Salvia Divinorum. Also Salvinorin A is the active ingredient, and the Wikipedia article contains further information on its effects. --Jayron32 16:11, 25 October 2016 (UTC)[reply]
Apparently WebMD did not read or did not trust the Johnson et al. (2011) article, because they say there is "insufficient evidence" for S. divinorum "producing hallucinations", while the hallucinogenic effects are clearly reported in the latter peer-reviewed article. Its abstract concludes that S. divinorum has "a unique profile of subjective effects having similarities to classic hallucinogens, including mystical-type effects." SemanticMantis (talk) 17:04, 25 October 2016 (UTC)[reply]
I wonder what they thought the species name came from? Matt Deres (talk) 13:47, 27 October 2016 (UTC)[reply]
Oddly, our article quotes Albert Hoffman as objecting to divinorum, claiming that it means "of the ghosts". I say "oddly" because my searches for the meaning of divinus don't say anything about ghosts. They mostly say it means "divine".
So Salvia divinorum should be the sage of the divines. Our article says "diviners", but I think this is unnecessary; "divine" used as a noun already means someone who reveals that which is hidden, as in St John the Divine, a name which does not ascribe divinity to John (that would be a heresy!) but AIUI is more of a statement of his occupation. --Trovatore (talk) 02:29, 28 October 2016 (UTC)[reply]
Won't speak to unprescribed use. but Modafinil is an atypical stimulant (not euphoric as MDMA or methylamphetamine are) with few or none of the side effects of the sympathomimetic amines such as amphetamines. It's marketed as a Wakefulness promoting drug for the treatment of narcolepsy and other sleep disorders. loupgarous (talk) 04:24, 27 October 2016 (UTC)[reply]

diabetes type I and II:sugars as ?:fats as ??:salt.

edit

Are there some analogues with diabetes, where the body is having trouble with sugar, to some problem where the body is having trouble with fats or salt? thanks144.35.45.83 (talk) 16:59, 25 October 2016 (UTC)[reply]

Salt is a major factor involved in blood pressure. Some people are more salt sensitive than others. Also, people don't necessarily know what their salt intake is because they don't closely read the ingredients of everything they eat. So, it is hard to tell exactly how salt sensitive a person might be. Measuring salt sensitivity is rather simple. A common test is to go four days with a little salt as possible. Measure blood pressure each day. Then, go four days with high salt intake. Measure blood pressure day. A 5% increase in blood pressure is often diagnosed as salt sensitivity, which is what I assume you mean as having trouble with salt.
As for fat, the pancreas (which produces insulin for sugars) produces pancreatic lipase, which breaks down fats. If the pancreas doesn't produce enough pancreatic lipase, the fats will not be broken down and they will pass through the digestive system. That commonly results in bowel issues. 209.149.113.4 (talk) 19:11, 25 October 2016 (UTC)[reply]
Separate note... Salt sensitivity (above) is a term used in medicine. You will likely find an abundance of "fat sensitivity" articles on the internet. I've never personally seen "fat sensitivity" used in the medical field. The internet articles discuss how some people are more prone to increasing fat than others. They term this to be fat sensitivity. It doesn't really indicate how a person's digestive system is sensitive to fat intake. 209.149.113.4 (talk) 19:14, 25 October 2016 (UTC)[reply]
Hyperlipidemia is an overstatement for fats. Hyperlipidemia is an abundance of any of the lipids, not just the triglycerides (fats). A person can have high LDL and low triglycerides. There is no accepted term for "hypertriglyceremia." Therefore, a more complete (pedantic) answer would be that hyperlipidemia is a condition that includes excess fat in the blood stream. I would also shy away from claiming a cause-and-effect relationship between diabetes and hyperlipidemia. The "four pillars of poor health" are hypertension, hyperlipiedmia, diabetes, and obesity. They show up together very often, but it is difficult to claim that one creates the other. All we can be certain of is that increased caloric intake and lack of movement causes all four. 209.149.113.4 (talk) 17:33, 27 October 2016 (UTC)[reply]

Final element?

edit

Is there a final possible element? For example, we might have 499 (atomic number 499, symbol 499), which has a known atomic weight. 108.65.83.125 (talk) 22:05, 25 October 2016 (UTC)[reply]

Also, what would the name for an element greater than 999 be? 108.65.83.125 (talk) 22:05, 25 October 2016 (UTC)[reply]

The obvious choice for element 1000 would be "Millenium". ←Baseball Bugs What's up, Doc? carrots→ 22:47, 25 October 2016 (UTC)[reply]
You might be interested in reading about the proposed island of stability. SemanticMantis (talk) 22:36, 25 October 2016 (UTC)[reply]
ec :All isotopes of all elements beyond Uranium are unstable with half-life of less than a billion years. The general trend is: the larger the mass, the shorter the half-life; but this is not always the case. See island of stability for more details. This being said, you can think of monstrously large nuclei where gravity becomes an additional stabilizing factor. There is a mass range in which the nuclei of this size -- essentially neutron stars -- will be stable both against alpha-decay and against gravitational collapse to a black hole. Dr Dima (talk) 22:42, 25 October 2016 (UTC)[reply]
I strongly believe that the final element that will ever get an official name is element 120. Georgia guy (talk) 00:25, 26 October 2016 (UTC)[reply]
I wouldn't be quite so pessimistic. I'm willing to bet that we'll get to the superactinides within a decade, looking at previous trends. Double sharp (talk) 10:26, 26 October 2016 (UTC)[reply]
See Systematic element name which only officially goes to Element 999. Try unnilnilnilium Unnn for element 1000.[5] But this reference is not so serious as it finds element symbols for element 2882 and 5885. Graeme Bartlett (talk) 02:19, 26 October 2016 (UTC)[reply]
As to final element see [6] which said 137. But at element 173 the electric field near a nucleus should be strong enough to generate a positron electron pair, so a bare nucleus would be unstable. Graeme Bartlett (talk) 02:41, 26 October 2016 (UTC)[reply]
Other references [7] which is readable here: https://arxiv.org/abs/1207.5946. Graeme Bartlett (talk) 02:54, 26 October 2016 (UTC)[reply]
The Extended_periodic_table article is worth a read, especially the End of the periodic table section of it. That article hints that element 172 or 173 might be the last element. LongHairedFop (talk) 09:53, 26 October 2016 (UTC)[reply]

This editor has been trolling the extended-periodic-table articles for some time now. The final possible element under current theories is 173. Double sharp (talk) 10:23, 26 October 2016 (UTC)[reply]

A proposed name for the "last element" is feynmanium, but last time I read these articles there was an understandable degree of uncertainty and disagreement. I mean, speculating on what happens in nuclei you've never seen before surely takes a lot of balls (I mean, 173 white ones for the protons and even more black ones for the neutrons. :) ) Wnt (talk) 19:51, 27 October 2016 (UTC)[reply]
There was a real dispute some years ago, but now there does not seem to be much doubt that the limit is somewhere around 170. (That's why the article looks a lot surer now! ^_-☆) Double sharp (talk) 06:48, 28 October 2016 (UTC)[reply]
@Double sharp: I just looked at it again and it doesn't sound surer to me. It talks about a hypothetical calculation that shows that relativistic effects influence how the 1s orbital works ... somehow. Then it talks about a Bohr model that obviously is not real. Then it briefly mentions some Dirac equation I admittedly don't understand, and cites [8] which is from 2012 that ends by saying elements over 173 may be possible. So far I'm relatively convinced that 173Ust173+ might not be possible, but as for the rest, I don't know. Wnt (talk) 19:08, 28 October 2016 (UTC)[reply]
Indelicato (which I added) is very clear about this: "the most likely 'end' of the periodic table [occurs] when the 1s electron binding energy dives below −2mc2." However, we also do not yet "understand what would an atom do when the 1s shell has dived into the negative energy continuum." Doubtless the results would not support keeping the atom that way, since this is so widely considered an "end" (only Greiner among experts disputes that). (Which is actually an interesting stopping point because 172 is expected to be the next noble gas completing the eighth period.) Double sharp (talk) 01:54, 29 October 2016 (UTC)[reply]

Kow (1972) suggested element 243 would be the last hypothetical periodic table element and that it be called zunzenium (Zz) after a Chinese idiom: "The name stands behind Zun Zen, who came last on the list of successful candidates in a royal examination." Karol (2002) suggested the previously mentioned neutron star element would have an atomic number on the order of 1021 and that the heaviest of these could perhaps be called zettium after the zetta- SI prefix for 1021, while his preference would be godzillium. Sandbh (talk) 01:28, 28 October 2016 (UTC)[reply]

I like the first name, even though I think I've once said (IRL, not here) that one of the first signs of senility or crankiness in a chemist is the urge to reformulate the periodic system. I'm not sure I can buy neutron stars as elements. Where is their electron cloud, that would give them a chemistry? Double sharp (talk) 06:48, 28 October 2016 (UTC)[reply]
Well, yes, quite so. Karol says, "Neutron stars exist. They have traces of protons and electrons and are stable toward beta decay and to breakup by fission. Neutron stars have been around for a long time, arguably representing our heaviest elements…already in nature." He concludes by saying, "Regarding how far the [periodic] table might be extended, the question of nuclear stability for larger and larger systems and the role of fission, which predict an end to stability and ordinary chemical expectations, was discussed from a purposely simplified perspective. Eventually the role of gravity grows in significance, leading to the viability of astronomically large stable nuclei, [italics added] already present in nature as neutron stars." I gather he was engaging in a bit of academic whimsey. Sandbh (talk) 09:24, 28 October 2016 (UTC)[reply]
I must confess that the more I read this paper the less inclined I am to trust it without 1021 moles of highly radioactive salt. He suggests continuing the spdf-style blocks even though the chemistries of those elements are unlikely to follow suit (Z = 168 is almost certainly not a noble gas, but a post-transition metal similar to lead). He also completely neglects shell effects in the superheavy elements that create barriers against spontaneous fission, so that we actually do have hopes of going somewhat beyond Z = 125 and seeing the mythical second island of stability around Z = 164. (Admittedly he says that in a footnote, but would it have hurt so much to put it in the main text, especially since it would have helped his point about a neverending periodic system?) Though it seems that the n:p+:e− ratio in neutron stars is usually around 10:1:1, these electrons are not exactly available for chemistry and so I would not really consider these chemical elements. In any case, neutron stars are not really single elements: near the crust you can actually find discrete Fe nuclei. (As well, who wants to have a disconnected periodic table?) His citations range from the reliable to the laughable (e.g. C-X. Jiang, really? That guy is still confirming my statement about crankiness on viXra with his periodic table model.) Double sharp (talk) 11:06, 28 October 2016 (UTC)[reply]
I see what you mean about C-X. Jiang; one article in Physics Letters A which appears to have then been cited (exclusively) by Jiang eight times in various preprint server papers, none of which appear to have made it into journals. As for Karol, his abstract seems to anticipate your observations:

"Since the mid-18th century, a new element has been discovered on the average of every two-and-a-half years. Hypothetically extending the periodic table beyond its current seventh row is discussed from several perspectives. For heavier elements, relativistic effects confound anticipated electron configurations. Nevertheless, it is suggested that the shell-partitioned display format (spdf) following Mendeleev and Seaborg be continued. Second, the tendency of higher atomic number elements to not survive long enough to be meaningful is addressed with the liquid drop model, including simplified discussions of binding energy and fissionability that for simplicity's sake neglect shell effects. The model provocatively suggests that astronomically large "nuclei" would be stable."

"Provocative" indeed. I see Karol is described as a retired nuclear chemist who chaired the Joint Working Party for the Discovery of New Elements since its inception in 1999 and that this JWP approved elements 113, 115, 117 and 118 for inclusion in the periodic table. Sandbh (talk) 03:16, 29 October 2016 (UTC)[reply]
The thing is, though, these simplifying assumptions might be useful in the lower reaches in the periodic table, but in the areas he is speculating about they are emphatically not helping his case. I do like his graph on the average element-discovery time, though whether his predictions are applicable now: after three elements in 1994 and 1996, we've had three in 2004, one in 2006, another two in 2010, and nothing since then. So, we've been stuck at completing the seventh period with E115 and E117 for over six years now. Then again, we had an even longer gap between Hs and Ds of ten years, so we can wait a bit longer for the beginning of the eighth row. Nevertheless, Karol's credentials are impeccable and I am quite all right with overlooking the article's flaws, appealing to its nature as a little diversion. Double sharp (talk) 04:58, 29 October 2016 (UTC)[reply]

Over a year later, but there seems to be a significant amount of uncertainty about what happens after Z = 173; most people seem to expect this to be an end to the periodic table, but those who have actually done calculations on what happens when 1s dives into the negative continuum (e.g. Greiner) have come up with results suggesting that the atom remains stable, but that you cannot fully ionise it (because the inner subshells will get filled by electrons coming out of spontaneously generated electron–positron pairs if they happen to be empty, with the corresponding positrons being emitted). There have been experimental attempts to verify this by creating "nuclear molecules", bashing together two uranium atoms or something like that to make something that effectively has Z = 184 or some other supercritical figure, but the expected positron emission has not yet been observed. Double sharp (talk) 15:05, 25 February 2018 (UTC)[reply]

Retrieved from "https://en.wiki.x.io/w/index.php?title=Wikipedia:Reference_desk/Archives/Science/2016_October_25&oldid=827578352"