Wikipedia:Reference desk/Archives/Science/2016 January 14

= January 14 =

Electric motors and hybrid vehicles
Hybrid in the sense of a flying car or a car boat, something along those lines. If you were to make these things using electric motors, do you need separate electric motors to drive the wheels and the propeller/jets? Or could you in theory use a single electric motor to provide power to both the wheels and the propellers/jets? ScienceApe (talk) 04:32, 14 January 2016 (UTC)


 * Yes you could use just one motor and a complex transmission, or you could devote one motor to each wheel/prop. If your design never uses both forms of propulsion at once then you may come in cheaper/lighter with a single motor solution. Greglocock (talk) 05:13, 14 January 2016 (UTC)


 * "propeller/jets" - probably not jets. The hard part for small planes is payload weight is traded for fuel.  --DHeyward (talk) 05:35, 14 January 2016 (UTC)


 * I took "jets" to mean the boat kind, as in a Jet Ski, not the airplane kind. StuRat (talk) 05:45, 14 January 2016 (UTC)


 * Terrafugia has been pitching their "Transition" aircraft, which uses one engine: "Running on premium unleaded automotive gasoline, the same engine powers the propeller in flight or the rear wheels on the ground." Their proposed TF-X will have multiple electric engines.  They just need somebody to design it, build it, program it, test it, operate it, fund it, ...
 * Nimur (talk) 17:33, 14 January 2016 (UTC)


 * For the flying car, weight is critical, so you really don't want an electric motor to start with, because they, along with the required batteries, have a lower power-to-weight ratio than gasoline, jet fuel, etc. Also, a car can't be designed with the same lightweight components you use in a plane, or it would be too fragile for the road.  So, an electric-powered flying car is quite impractical (it might be possible, but that's not the same as practical).


 * For the amphibious vehicle, electric power would be a bit more practical, as power-to-weight ratio is less of a concern. There are basically two types I am aware of, hovercraft and ducks.  The power-to-weight ratio would be less of a concern in the second type.  StuRat (talk) 05:42, 14 January 2016 (UTC)


 * Electric engines can be split up very easily and effective down to multiple smallest size engines instead of one big because they are very simple constructions in essence. Combustion engines on the other hand are way more complicated because they need lots of additional parts like an injection system, a starter, often even additional special parts like a choke for starting cold etc.. Thus its much harder to replace one big combustion engine with multiple small ones.
 * Now in addition to that ist much easier and more effective to just lay two electric cables instead of adding a transmission to every location you want a central motor's power to be split up to. Thats why for example each of the 6 Curiosity (rover)'s wheels has its very own engine. --Kharon (talk) 00:18, 15 January 2016 (UTC)


 * There's also quite a bonus in torque if you drive the wheels and propeller of that vehicle directly with electric motors instead of using a transmission (where you get friction losses, perhaps even losses in torque owing to the gearing or teleflex cables used to transmit power).
 * Speed and torque both can be controlled by at each motor by pulse-width modulation circuitry, which is cheaper and easier than a physical transmission. If the point of the exercise is to get more motion per watt, electric motors to drive the wheels and the propeller of the vehicle could well be lighter than a transmission to do the same thing from a single motor. loupgarous (talk) 19:58, 15 January 2016 (UTC)


 * An electric drive does not need a transmission or gearbox. Electric motors have a high and nearly constant efficiency. Batteries can not store that much energy than fuel does. Weight and volume are limiting factors for traction batteries in a vehicle. Combustion engies have brake specific fuel consumption in load and rotational speed and less efficiency than electric engines. A transmission or gearbox transforms the ratio of rotational speed and torque of the combustion engine to keep it operating in the mode of the lowest possible fuel consumption. There are several variants of hybrid vehicles. Patents protect the use of some solutions. The one used in Japan, connects two motorgenerators (electric motors which can be used as a generator as well) over a planetary gear box, using it to sum or subtract torque between motors and drive axle. The combustion engine is attached to the smaller of the motorgenerators. A clutch is installed to protect the gears only. The combustion engine just adds torque to the system. This torque is beeing used to charge the traction battiery and drive the vehicle. The ration is controlled by the two motorgeneratos. Charging the battiery from a generator is a lost my the efficiency ratio of each of the converters. Batteries are changed with a higher voltage than the batterie output is. Driving the vericle directly from the combution enginge makes it more efficienty when the combustion engine is beeing operated in an optimal mode. The motorgenerators also keep the ratio by vehicle speed and engine operation mode. This video, shows it. The cobustion engine speeds up to its maximum power output, not to its highes rpm. Kicking the accellerator down, the vehicle still speeds up while the combustion engine is operating in constant rpm making the mechanic from the garage think the first time, there's someting wrong with the clutch, which is not true. -- Hans Haase (有问题吗) 01:52, 16 January 2016 (UTC)
 * Uhh just so you know, that video is from a video game. You can tell by the "grass". ScienceApe (talk) 20:10, 16 January 2016 (UTC)
 * Sorry ScienceApe, indeed, geat simulation, have these from real camera., This violent driving – I do not support – shows how the combustion engine reduces rotational speed when not needed. Faster than 50 km/h (~30 mph) it never turns of due to high rotational speeds in the planetary gear. -- Hans Haase (有问题吗) 12:51, 18 January 2016 (UTC)
 * Similar to the Japanese patent using motorgenerators on a planetary gear, a German patent uses hydraulic drive over planetary gear it machines for food production It also shows how the Japanese hybrid operate in reverse gear on empty battery or cold combustion engine. -- Hans Haase (有问题吗) 12:16, 16 January 2016 (UTC)

Update after the sections was moved to the archive

ScienceApe, here's an update to answer Your question: Jetplanes can use the jetengines for taxiing, but not in an efficient mode of fuel consumption, only. A tow tractor would be more efficent. A electric motors installed in a wheels of planes cause to carry this load all the flight, eating up nearly all the savings of energy it achieves to the taxiway. -- Hans Haase (有问题吗) 14:10, 25 February 2016 (UTC)

History of puberty blockers
When was the first one developed? When did they become widely available? -- Brainy J  ~ ✿ ~ ( talk ) 04:44, 14 January 2016 (UTC)


 * This article from 2006 is the earliest ref in our current article. It cites this 1983 article  describing a different treatment of precocious puberty in 1983. I do not know if that was the first puberty blocker, but it's a start. If you need access to these articles, ask at WP:REX. Sorting through the citations of the 1983 paper and our precocious puberty article (or even just reading them it carefully, which I did not) may answer you questions more conclusively. SemanticMantis (talk) 16:17, 14 January 2016 (UTC)

Platinum electrode
What electrochemical cell voltage would be considered as a safe upper limit, bellow which oxidation hence dissolution of the platinum electrode is negligible? I'm running an electrowinning setup using a complex leachate, containing multiple components. I've been using 4.0 V, but that is a complete guess. Plasmic Physics (talk) 10:53, 14 January 2016 (UTC)
 * Standard electrode potential (data page) indicates the standard reduction potential for Pt2+ --> Pt is +1.188 volts. -- Jayron 32 16:08, 14 January 2016 (UTC)


 * I don't think it works that way, besides, I've had no obvious degradation of the anode. Plasmic Physics (talk) 20:37, 14 January 2016 (UTC)

What's the difference between transvestites and transsexuals?
When you see one can you tell, this is a transvestite but not transsexual? Are transvestites just part-time transsexuals?--Scicurious (talk) 13:57, 14 January 2016 (UTC)


 * We do have articles transvestite and transsexual - the former could use some work though. It sounds from that like "transvestite" is coined not really that long ago to mean cross-dressing, but its creator used it to refer to more long term transsexuality? Wnt (talk) 14:35, 14 January 2016 (UTC)


 * I'd say transvestism is about behavior and transsexualism about gender identity. --Llaanngg (talk) 15:27, 14 January 2016 (UTC)


 * When you just see anyone, you can't necessarily tell that much about them. Sexual orientation and gender identity are not inherently visible. Note also that trans people can be homosexual or heterosexual or bisexual or even asexual. Gender identity and sexual orientation and other factors combine to a lot of different sorts of people. You may also enjoy background reading on notions of gender and sex, as well as cisgender, transgender, genderqueer, or attraction to transgender people.
 * Some people choose to present a visual image that helps signal their status to others, while other people do not. The general notion of this in biology is Signalling_theory. Depending on where you live, you may have seen many transsexual or transgender people and not known it, e.g. Passing_(gender).
 * To answer your question directly - If you see someone who you think is cross-dressing or transsexual, the only way to know for sure if they identify as either is to ask them. But that is very rude. If I were to meet you as a stranger in public, I wouldn't ask who you like to fuck or why you wear the clothes you wear, and I'd think you'd prefer it that way :) In the USA at least, the polite thing to do is to reserve questions of this nature for people with whom we already closely familiar. SemanticMantis (talk) 15:59, 14 January 2016 (UTC)
 * Our article on Transvestism says that it is, regardless of its underlying motivation, a behavior, dressing as a member of the opposite sex. Our article Transsexual defines the term as referring to those who identify with a gender inconsistent with their physiological sex, and wish to physically change to the gender with which they identify.
 * How to tell the two apart? You can't.  Transsexuals at some point often are transvestites - especially after sex reassignment therapy or other medical interventions aimed changing the patient's ostensible sex to what the patient identifies with.
 * Transvestites are not "part-time" transsexuals. A transsexual is always a transsexual, never "part-time."  Now, the reverse is possible - a transsexual may cross-dress only part of the time.  Or, like the movie director Ed Wood, a transvestite may be heterosexual but have comfort issues which compel him or her to dress as the opposite sex.  It's worth mentioning that women in Western countries often wear male attire without being called "transvestites."   In some other countries today, this is not only transvestism, but culturally deprecated and even illegal. loupgarous (talk) 21:54, 14 January 2016 (UTC)


 * I wouldn't say that after sex reassignment transsexual are often transvestites. Quite in contrary. They are physically, mentally and legally a member of their target sex, who will very probably dress like a typical member of this sex.
 * I also would not say that Western woman wear male attire. Attire worn by men became unisex or with no gender mark. Women in trousers, box shorts, shirts, suits are all wearing these unisex clothes. Denidi (talk) 01:55, 15 January 2016 (UTC)
 * Well, pantaloons weren't always considered unisex - see women and trousers. Which brings us to an important point that since the definition is cultural, it changes, and there may be varying motives, pragmatism ranking very high on the list.  Even non-transvestites might be affected when the other sex clothing is simply unpleasant. Wnt (talk) 17:10, 15 January 2016 (UTC)

popping zits
In nature are zits supposed to be popped or left alone? Which is most beneficial from an evolutionary standpoint? — Preceding unsigned comment added by 62.37.237.15 (talk) 20:15, 14 January 2016 (UTC)


 * Check out danger triangle of the face. It is rare, but popping acne or furuncles in that area can lead to infections that spread to other areas, causing Cavernous_sinus_thrombosis, or to the brain, causing meningitis. SemanticMantis (talk) 20:41, 14 January 2016 (UTC)


 * This is definitely one of those "No Medical Advice" questions. We aren't allowed to offer advice on diagnosis, prognosis or treatment of medical conditions...so we can't advise you on how to treat pimples - even if the treatment is something as seemingly mundane as popping/not-popping them.  Beware of arguments from an evolutionary standpoint - evolution may not care whether you wind up with smooth skin or something that looks like the surface of the moon.  These things tend to be cultural in nature. SteveBaker (talk) 20:57, 14 January 2016 (UTC)
 * I'm not asking for medical advice, I just asking what nature intended. How is this any more medical advice than asking if nature intended broken bones to heal or not? I don't have zits, I'm not asking this for myself. I'm asking generally as a scientific question. 62.37.237.15 (talk) 21:08, 14 January 2016 (UTC)
 * Or to put it a different way; have the millions of years of human evolution favored popping or not popping zits, from a purely evolutionary (therefore survival) standpoint. No cultural issues needed. 62.37.237.15 (talk) 21:12, 14 January 2016 (UTC)
 * Nature does not intend anything.
 * And apparently both zit-poppers and zit-non-poppers managed to survive. So, evolution did not made up her mind about this. But as said above, this is a bad perspective, you can be in a social environment that strongly prefers the one or the other. In the same way as people might have their preferences toward deformed/normal feet, or tanned/fair skin, thin/fat bodies. --Scicurious (talk) 21:52, 14 January 2016 (UTC)
 * Quick and dirty answer? Pop your zits in the presence of a potential mate, and your chances of passing your genes on through sex drop precipitously.  This answers your question regarding evolution.  Popping zits would seem to reduce the popper's chances of transmitting his or her genes to future generations.  That being said, previous posters' remarks about "zit-poppers and zit-non-poppers" managing to survive imply a genetic basis for the behavior which hasn't, as far as I'm aware, been investigated, much less proven.  It's just a gross habit that would only get you laid if you found someone who thought it was attractive and was aroused somehow by it.  Think that's ever going to happen? loupgarous (talk) 22:03, 14 January 2016 (UTC)
 * lol, I'm pretty sure that I could pop my zits (I rarely have them, yay yay for testosterone blockers!) in front of most of my mates (male or female) and they wouldn't really care. My ex-girlfriend didn't really have zits either, but I'm sure that she would have popped them in front of me, and we would still have great sex afterwards. Yanping Nora Soong (talk) 22:21, 14 January 2016 (UTC)
 * De gustibus non disputandam... loupgarous (talk) 23:50, 14 January 2016 (UTC)


 * Regarding the claim that "Pop your zits in the presence of a potential mate, and your chances of passing your genes on through sex drop precipitously. [...] Popping zits would seem to reduce the popper's chances of transmitting his or her genes to future generations": the second statement does not follow from the first, because the smart zit-popper doesn't pop zits in the presence of a potential mate, but before meeting a potential mate, thereby accomplishing the zit-popping purpose of minimizing the zit's appearance, thus increasing the popper's chance of transmitting genes. —SeekingAnswers (reply) 05:26, 16 January 2016 (UTC)


 * From an evolutionary standpoint, nothing is "supposed" to do anything. Nature is not a conscious agent. The only question that makes sense is, "How does this behavior affect the fitness of the organism?" I suspect popping pimples might slightly decrease an organism's fitness, because it can lead to infection, but the risk is not that great, so I imagine the overall selection pressure is pretty tiny. --71.119.131.184 (talk) 22:16, 14 January 2016 (UTC)


 * I doubt that popping zits can lead to an non-treatable infection nowadays. Scicurious (talk) 22:32, 14 January 2016 (UTC)
 * This is a ref desk, what you doubt or don't doubt is completely irrelevant. Vespine (talk) 23:23, 14 January 2016 (UTC)
 * That's just an expression. I could have said: I don't have any ref at hand right now, but I don't believe popping zits can lead to an non-treatable infection nowadays. Scicurious (talk) 23:40, 14 January 2016 (UTC)
 * That's exactly the problem. Not having any references but an opinion. A reference like [www.webmd.com/skin-problems-and-treatments/teen-acne-13/pop-a-zit Before You Pop a Pimple] from WDMed, a web-site I normally trust, collides with your assumptions. Denidi (talk) 23:54, 14 January 2016 (UTC)
 * I have myself on occasion offered a "I doubt something", but ONLY if the thread had not already had some relevant replies leading towards an opposite conclusion AND even more critically was not related to something that could have serious negative health repercussions. Vespine (talk) 00:51, 15 January 2016 (UTC)

Eka-, dvi-, tri-, and chatur-
"Eka-" is sometimes used as a prefix meaning "one row below in the periodic table". For example "ununtrium" is sometimes called "eka-thallium". Have "Dvi-", "Tri-", and "Chatur-" been used in similar ways?? These are the corresponding prefixes for 2, 3, and 4. Georgia guy (talk) 22:07, 14 January 2016 (UTC)
 * See Mendeleev's predicted elements. At least rhenium was called dvi-manganese (because eka-manganese, i.e. technetium, wasn't known either). Icek~enwiki (talk) 00:22, 15 January 2016 (UTC)
 * There is and was no reason to use the higher numbers when the lower number could be used; hence you might see element 115 called eka-bismuth today, but certainly not dvi-antimony. The only cases where they were ever used AFAIK was exactly as Icek suggests: e.g. dvi-manganese, since eka-manganese was not known either. Given the rows of blanks in Mendeleyev's 1871 table where the rare earths should go, though, it's conceivable that rhenium would have become tri-manganese instead until the rare earths were separated out of the main body of the 8-group table. But there is no reason at all AFAICS to go to "chatur-" and beyond. Double sharp (talk) 08:03, 16 January 2016 (UTC)

solubility of zwitterions in organic or lipophilic solvents
What are the guidelines for whether a zwitterion (especially an alpha amino acid -- but not necessarily one of the 20) will be soluble in solvents like dichloromethane or cyclohexanol? (Chloroform or ether is also fine, I guess, since solubilities in them are tested more often.) For example, L-DOPA at its isoelectric point is weakly soluble in water, but insoluble in ether or chloroform. Which puzzles me -- how are you supposed to do acid-base extraction of an amino acid into an organic solvent if an amino acid at its pI is weakly soluble in water but even less soluble in an organic phase? Would adding a phase transfer catalyst like tetrabutylammonium bromide increase the solubility of AAs in organic solvents at the pI -- or would it reverse as soon as you tried to separate the two phases? Yanping Nora Soong (talk) 22:27, 14 January 2016 (UTC)
 * This article refers to the use of lanthanide complexes to not only extract zwitterionic amino acids, but to do so by chirality of the desired amino acid.
 * And this article discusses reverse micellar extraction of zwitterionic amino acids.
 * The Google search term I used to locate these articles is "extraction of amino acids zwitterions," and many articles came up which you may want to look at for more information. loupgarous (talk) 00:05, 15 January 2016 (UTC)
 * Thanks! That's a more useful keyword. I'm not sure if I'm understanding these "ion exchange" methods correctly (especially since I don't have any ion exchange resins at the moment). I'm looking at patents such as this one. Does this patent imply I can dissolve zwitterionic amino acids in most weakly polar or non-polar organic solvents by dissolving 2M (or 1% w/w) quartenary ammonium salts (like TBAB) into the organic solvent? Then I add the sodium salt of my amino acid (whether in the aqueous layer or as a dry salt) -- sodium bromide precipitates and I get a solution of the tetrabutylammonium salt of my amino acid in cyclohexanol or dichloromethane? I'm trying to make sure I'm understanding these procedures correctly. Yanping Nora Soong (talk) 01:14, 15 January 2016 (UTC)
 * The patent specifies "a substantially immiscible extractant phase comprising an amine and an acid, both of which are substantially water immiscible in both free and salt forms." Now, you're proposing (if I understand you correctly), to use  quaternary ammonium salts, which are generally cationic detergents and very miscible in water.  So you've already departed from the procedure defined in the patent, I think.
 * I'd encourage you to read the sources the Google search "extraction of amino acids zwitterions" turns up for ideas that fit your specific requirements more closely. loupgarous (talk) 05:29, 15 January 2016 (UTC)
 * In the "previous art" section they discussed the use of trioctylmethylammonium chloride. There is also mention of others using Aliquat 336, which AFAIK is often interchangeable with TBAB for phase transfer catalysis reactions. I have tetrabutylammonium bromide (TBAB). AFAIK, TBAB has a high critical micelle concentration, so it's pretty inaccurate to call it a detergent and also why it's favored for PTC. They actually mention the use of quats in that patent (as well as their organophosphate anionic counterparts), and I think they actually use them, they just combine quats, lipophilic anions and other surfactant stabilizers in the same organic phase. Yanping Nora Soong (talk) 08:48, 15 January 2016 (UTC)

Do amino acids sometimes combine in water?
I mean without all the hardware that a cell has, that allows to combine them into proteins, do amino acids sometimes combine by chance just by bumping into each other if you shake the water they float in for long enough? --Lgriot (talk) 22:32, 14 January 2016 (UTC)
 * If you ask whether that happens at all: Definitely, even if you don't shake. The molecules are in thermal motion anyway. And conversely, peptides sometimes break apart (i.e. are hydrolyzed) without enzymes catalyzing this reaction.
 * Maybe more interesting is the question of what fraction of amino acid molecules can be expected to be free amino acids and which fraction will be in peptides. See chemical equilibrium for a general introduction. For a dilute solution of amino acids, the equilibrium state has far more free amino acid molecules than peptide-bound ones. In a very concentrated solution, water for hydrolysis is not so abundant, and you'll find a higher fraction of peptides at the equilibrium.
 * Icek~enwiki (talk) 00:31, 15 January 2016 (UTC)
 * Short-answer: they don't. Peptide bond formation is much harder than just simple Fischer esterification-- for the issue that if you try to catalyze the reaction by deprotonating the amino group (activating the nucleophile), you deactivate the carboxylic acid as an electrophile (it becomes a carboxylate), and if you try to catalyze the reaction by acid (activating the carboxylic acid group), you deactivate the nucleophile (the amino group gets protonated, losing its lone pair). You can create an amide or peptide bond by heating your reagents at 250C, but the problem is that these harsh conditions often cause a lot of side reactions to occur, at a risk of degradation or oxidation of the sidechain. Yanping Nora Soong (talk) 00:57, 15 January 2016 (UTC)
 * Selective peptide coupling is an expensive task and an entire industry of its own: see peptide synthesis. Yanping Nora Soong (talk) 00:59, 15 January 2016 (UTC)
 * I'm reminded of the Urey-Miller experiment. If there were a simple way to string those amino acids into peptides, that would be very exciting, but it's not really so.  Now by contrast, I remember hearing that polymerizing hydrogen cyanide gives rise to actual polypeptides (once water is added) - here's a source  but I'm not sure it's the definitive one.  Now as peptide bond says, water will spontaneously hydrolyze the bond on a very slow time scale, liberating substantial energy; and this implies that the reverse of the reaction does occur, but because of the energy difference, it would occur in a very, very small proportion of the total molecules (I'm afraid I'd have to reread Gibbs free energy, at least, to try to guesstimate what proportion that is....  but AFAIR 8 kJ/mol is a biological way to say "fuggedaboudit") Wnt (talk) 01:26, 15 January 2016 (UTC)
 * Polyaspartic acid can be accomplished by simple pyrolysis of aspartic acid followed by hydrolysis (easy undergrad lab experiment). The pathway for this polypeptide is not general for all the encoded amino acids, requiring at least some aspartic acid- or glutamic acid-like component (see also that proposes this sort of reaction as relevant to prebiotic processes). DMacks (talk) 04:29, 15 January 2016 (UTC)


 * Remember, thermodynamic energy release is different from the kinetic activation barrier.
 * But if dG = -RT ln K = -8 kJ/mol, then K = e^(-dG/RT) = e^(8 kJ/mol / (298 K * molar gas constant)) = e^(3.22) = ~25
 * So the equilibrium constant for hydrolysis is around 25. The equilibrium constant for the reverse reaction would thus be around ~4%. This is actually kind of impressive, but the energy barrier is much higher -- I would guesstimate around 20-30 kcal/mol -- or around 80-120 kJ/mol. Yanping Nora Soong (talk) 08:56, 15 January 2016 (UTC)
 * If you want to understand the equilibrium dynamics of solutions of amino acids, perhaps our article on Michaelis-Menten kinetics would be helpful. loupgarous (talk) 20:31, 15 January 2016 (UTC)
 * This was a quick and dirty calculation. I'm well-aware of MMK. Of course, polymerization beyond forming more than just 1 peptide bond would be a different story... Yanping Nora Soong (talk) 00:57, 16 January 2016 (UTC)
 * The OP said "long enough", which is a pretty broad license to ignore kinetics altogether for purposes of the answer. Wnt (talk) 03:02, 17 January 2016 (UTC)