Wikipedia:Reference desk/Archives/Science/2014 November 23

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November 23

What charges faster?

Say a power supply supplies power at 2 amps at 50 volts, and another supplies power at 5 amps at 20 volts. Which would charge a battery faster? ScienceApe (talk) 02:45, 23 November 2014 (UTC)

Charges what? A battery designed to be charged at 2 amps and 50 volts, or one designed for 5 amps and 20 volts? Mixing them up isn't going to achieve anything useful, unless you like the smell of burning, toxic fumes and the like... AndyTheGrump (talk) 03:06, 23 November 2014 (UTC)

(edit conflict) My understanding is pretty much a layman's understanding here, but the latter would supply charge faster. An amp is a coulomb per second, so by definition more amps = faster rate of charge movement. The two chargers would have the same power (100 watts), but the higher the amperage, the higher the charge movement per second, so the faster the charging. --Jayron32 03:08, 23 November 2014 (UTC)

That's not correct. A battery is not a bucket full of free charges - for every charge (electron if you want) that goes into the battery, a charge gets pooped out. The problem is, as Andy correctly points out, "charging" is ill-defined. If we simply think about the rate at which energy is stored in the battery (power), since P = IV, they are the same. However, you'd be hard pressed to find a battery that would be happy charging under both conditions. 160.39.130.178 (talk) 06:51, 23 November 2014 (UTC)

I agree, that's not correct except in a very limited set of circumstances (and preferably some extra control circuitry to avoid the smoke and fumes). A 24v truck (lorry) battery would not charge at all from the 20v power supply, and a torch battery would probably be destroyed by connecting it to either supply. Always use a charger designed for the particular battery unless you also have a voltmeter, and ammeter, a suitable rheostat, time to watch over the progress of the charging cycle, and a full understanding of the charging characteristics of the particular battery. Dbfirs 08:01, 23 November 2014 (UTC)

Or. Use a smart charger--Aspro (talk) 14:05, 23 November 2014 (UTC)

Yes, general-purpose chargers with pre-programmed general control circuitry are useful, but mine only work for a limited range of battery types, and need to be told the battery chemistry before they start. I wouldn't advise using them on lithium batteries. Dbfirs 15:30, 23 November 2014 (UTC)

Agreed. However, intelligence is a relative term. Some chargers can discover the chemistry by monitoring the voltage profile of the battery during the initial stage of the charge (break one open and you'll see a little chip inside). Hence, my general-purpose charger, charges Ni-Cd NiMH & Li-ion automatically. So in answer to the OP's question: Just because it is possible to ask a question doesn’t mean there is a proper answer.--Aspro (talk) 16:35, 23 November 2014 (UTC)

Your charger is more intelligent than mine! Dbfirs 21:34, 25 November 2014 (UTC)

Considering just one common type of battery, the lead acid cell, if we supplied 2 amps at 50 volts to a 24 cell (nominal 48 volt ) battery, it would charge more slowly than if we supplied 5 amps at 20 volts to a 9 cell (nominal 18 volt) battery. I have worked with such batteries, ranging from 24 volts to 200 volts, with each cell running about 2 volts. But the cells may vary greatly in the amp-hours they hold, I allowed the open circuit battery voltage to be a bit lower than the supply voltage, since the cell voltage fully charged will be a bit over 2 volts). This assumes each cell in either battery has the same characteristics (amp hours). If the amp-hours in the two cases were different, then the answer depends on which battery has cells of greater ampacity. I suppose a similar analysis could be made of other battery chemistries.Edison (talk) 20:10, 24 November 2014 (UTC)

... also, in that setup, your 50v supply would have to supply slightly more than 50v to be able to fully charge the 24-cell battery because 50v is insufficient to force 2 amps though the battery against the back emf once it is more than about 90% charged. Dbfirs 21:34, 25 November 2014 (UTC)

Chargers are regulated by the battery's specifications they are designed for. A power supply is voltage regulated or not. It is specified to maximum voltage and current. Switching power supplies (SMPS) use voltage regulators. Connecting it to a battery requires a higher voltage to charge. An automotive starter battery connected to a 2 amps PSU would shoutcut the output until it reaches the battery's voltage. Your 50 volts would tied down to 24 or 12 volts whatever the batterie has. A conventional transformer heats up due inadequate load. If not protected with thermal fuse, it may get of fire. A SMPS would shut down, due it never reaches its 50 volts, telling the controller there's a shortcut. If the battery or wires would fail, the 50 volts are connected to the vehicles supply line, damaging sensitive devices with its overvoltage. The differents btwn PSUs and chargers for lead batteries is a shunt to measure and regulate the current. 12 v lead batteries sould not exeed 14,7 volts to prevent generating hyrogen and oxigen that may case exploding the battery, avoid such. If a cell to the battery fails, all other cells may be on overvoltage while charging. AGM-lead-batteries are 14,2 volts max. If this voltage is reached, intelligent chargers drop their output to 13 to 13.5 volts to keep the starter battery charged over time. Other battery technologies require different chargers. Some LiOn battery blocks have their regulator installed, but are still specified how to supply them! In your case, check ebay or similar to find voltage converters regulatin current as well, if you think you need to use devices you own. Switching converters transform with efficieny sometimes about 90%. Your 50 volts converted to 26 volts would increase the current from 2 to about 3.5 amps. Limiting the current means to drop the voltage until the maximum current is reached. It would follow the battery's voltage, rising when feed. But note prevent overvoltage and limit the current! --Hans Haase (talk) 00:43, 26 November 2014 (UTC)

Dutch Tears to eat

I assume the question might seem weird but... Is there a chance to make an eatable prince rupert's drop? 128.72.80.175 (talk) 10:36, 23 November 2014 (UTC)

Very probably - see sugar glass and Amezaiku. However, I don't know if there's a technique for generating the appropriate internal stresses in a piece of sugar glass - some experimentation in the kitchen might yield results... Tevildo (talk) 11:21, 23 November 2014 (UTC)

Very probably not and certainly not with either of the proposed materials; sugar glass does not have anything remotely resembling the tensile properties of silica glass, nor would it react to the same thermal conditions that are utilized to create a dutch tear, nor is it as nonreactive and stable under similar conditions. Sugar glass shares very little with silica glass other than that it is clear and, for a time, brittle. Taffy is even less viable for the process. Between the demand that the material be chemically inert and also capable of traveling through the digestive tract without causing lacerations or other trauma, I think it unlikely any material which has the mechanical properties necessary to form a dutch tear is likely to suit. Snow talk 11:06, 24 November 2014 (UTC)

I'm not sure you could get candy glass to mimic silica glass in exactly the same way, but I feel the need to point out that it would likely be inedible anyway. It may seem like a neat prank, but I fancy that you could injure someone's mouth pretty badly. If you just want to try making the drops as a kind of kitchen experiment, that's one thing, but you specified they were to be eaten. Matt Deres (talk) 17:36, 23 November 2014 (UTC)

I can assure you there are no eatable Rupert's drops, but ones made of sugar that have been broken should be edible, no? μηδείς (talk) 22:32, 23 November 2014 (UTC)

Unlike glass, I don't believe sugar melts at high temperatures, it just catches fire. (I wonder if you could melt it in the absence of oxygen ?). So, unless you can get hot liquid sugar and then quench it, you're not going to get something like Prince Rupert's drops.

One edible sweet that does melt is chocolate. So, you might be able to create something like what you want using, say, a white chocolate. It's the fat in the chocolate that gives it the desired property, but that also makes it white (or off-white) instead of clear. The nature of fat also means it won't contain dangerously sharp bits, so the results should be perfectly edible.

Another approach might be some type of edible wax (carnauba wax is one type). You could dissolve enough sugar in it to make it taste good, too. StuRat (talk) 15:33, 26 November 2014 (UTC)

Is there any relation between Lupus and kidney stones?

Where can I find an scientific essay about the topic. It's only for the general knowledge, not for medical advice. 213.57.99.239 (talk) 12:07, 23 November 2014 (UTC)

One could try Google Scholar. Click on More at top left of Google search window. Then on Even More at the bottom of drop down window. It is in the section Specialized Searches. Un-click patent search box. Thats what my doctor does. I kiddle you not.--Aspro (talk) 14:15, 23 November 2014 (UTC)

I didn't say that I tried there and I didn't saw something about. Maybe I don't know to search by?/: 213.57.99.239 (talk) 16:24, 23 November 2014 (UTC)

The fact that you can not find anything, may indicate that there is no known connection. For a casual interest inquiry (which is what your appears to be) I personally would be satisfied with that conclusion. --Aspro (talk) 21:16, 23 November 2014 (UTC)

I found something but without references. (answer No.7 here)213.57.99.239 (talk) 02:44, 24 November 2014 (UTC)

Why no three legged animals and the such?

Why is nature not producing three legged animals, or three eyed mammals (with an eye to check your back)?--Senteni (talk) 19:18, 23 November 2014 (UTC)

It's easier for a growing organism to copy and paste one genetic code when the cell splits, rather than have two different ones. See Symmetry in biology. Three legs wouldn't be very stable, anyway, and an eye in the back would screw up binocular vision. So even if some individuals were built that way, natural selection would weed them out. Not sure why we have one heart. InedibleHulk (talk) 19:51, 23 November 2014 (UTC)

I can imagine that getting two hearts to beat in synchrony would be an issue, assuming that there weren't two separate circulatory systems. Agree about the eyes though; the brain only really looks through one eye and uses limited information from the other - see ocular dominance. Alansplodge (talk) 20:30, 23 November 2014 (UTC)

Ocular dominance is hardly a universal trait, though, however common it seems to be in Mammalia. And even in those species where it is present, it is still necessary for the eyes to have rough parity in overall health and robustness, since the dependence upon one eye over the other is highly contextual and hardly invariable between circumstances and individuals. Further, addressing Hulk's point, a third eye would not necessarily disrupt binocular vision; it could in fact be neurophysically isolated into a somewhat separate stream of visual cognition that none-the-less integrates into a great sense of spatial awareness as with any other pair of sensory modalities, or it could conceivably be incorporated into a form trinocular vision. Point in fact, there are countless species which incorporate visual information from more than two eyes with overlapping fields of vision, albeit in pairs. The absence of such a feature probably has more to do with the types of selective pressures that have been touched upon below than with possibility of interfering with depth perception, since a third eye would provide more comparative redundancy, not less. Snow talk 10:33, 24 November 2014 (UTC)

I once knew a somewhat three-eyed iguana, and he was never stepped on, so I suppose there's no harm in having a different sort of odd eye. I can't envision something living comfortably looking three or five ways, the same way, at once. That might just be my human limits at work, though. InedibleHulk (talk) 02:08, 25 November 2014 (UTC)

I don't think there is any reason other than three limbed creatures didn't evolve because it provided no evolutionary advantage over five limb (echinoderms), eight limbed molluscs, anthropoids etc. and four limbed tetrapods. I don't see what copy and pasting genetic code has to do with it. Cellular differentiation works for five limbed starfish as it does for humans. Also, not all creatures need binocular vision and spiders have up to four pairs of eyes, and a neural system to make sense of the information. --Aspro (talk) 21:08, 23 November 2014 (UTC)

I suspect you mean arthropods not anthropoids. —Tamfang (talk) 07:37, 25 November 2014 (UTC)

• Vertebrates do have three eyes, the third one has evolved into the pineal gland in Humans, but it is visible in some reptiles and fossil fish. Three legs would require a huge change in a whole lot of genes at once. It is simply a case of you can't get there from here, although certain perciform fish approximate a three-point stance, like frogfish and mudskippers. See also, hopeful monster. μηδείς (talk) 22:30, 23 November 2014 (UTC)

“a huge change in a whole lot of genes at once” is not necessary if the creature evolved its first three legs from an ancestral linage that had not yet developed any legs. I've already given examples of starfish, octopus and, four legged animals, all of which develop limbs independently from each other. It would be having a homologous ancestor where such a fundamental change in locomotion would be very surprising.--Aspro (talk) 00:22, 24 November 2014 (UTC)

I don't see why a four-legged mammal couldn't evolve to lose one leg. The symmetry argument is a strong one - but not impossible to overcome.

I'd also argue that seals and sealions represent functionally three legged animals. SteveBaker (talk) 01:34, 24 November 2014 (UTC)

We had the Trilobozoa but they didn't last past the Triassic age. Nanonic (talk) 01:44, 24 November 2014 (UTC)

"I don't see why not" is never a good argument in science, it amounts to conspiracy theorizing, look at cui bono, and Ockham's Razor just as a start. If one wants to call seals three-limbed (or whales) that's fine, but it's obvious they've got two leg bones on either side of the spine, not one leg coming out of the end of the spine, and the development of the cloaca and hindlimbs are entwined. There's the Alien Planet DVD with a two-limbed sprinter and various three legged scifinimals and the Pierson's Puppeteer. That's sci-fi. μηδείς (talk) 01:53, 24 November 2014 (UTC)

You had claimed that it would take a lot of genetic change...and if you're talking about ADDING a functional leg to a biped, then I agree, 100% - I'm merely pointing out that LOSING a leg from a quadruped is much more plausible because it only requires the failure of a relatively small number of genes. SteveBaker (talk) 04:02, 24 November 2014 (UTC)

But in fact, that's not the case. The legs, left and right, develop from the same genes being expressed slightly differently in various cells as a mechanism of morphogenesis. That is, generally speaking, most bilateral physiological structures are not the result of different genes but rather the same genes being expressed in cells that have "figured out" that they are on the left or right. Or more accurately, determining from the chemical ques of its neighbors and other contextual markers how it is meant to grow, proliferate, or differentiate in order to serve its role in the overall structure. So, the loss of a limb would, at least in-so-far as that factor is concerned, be just as unlikely as the development of a new limb -- and both highly unlikely to a mutation that could be propagated, for a variety of reasons. Those passingly familiar with the mechanisms of evolution are often prone to lay the weight of "rejected" features at the feet selective pressures but in fact in most of these cases they are largely secondary to why the feature cannot be formed to begin with; that is, the issue of reproductive fitness never gets raised. None-the-less those pressures are worth noting, and are perhaps not trivial in this case: not only is an extra limb or a missing one likely to be cumbersome to the established biomechanics of the resultant creature, decreasing its capacity to thrive and pass on the change, in higher organisms it is also likely to hinder it in terms of sexual selection, to the same effect. Vastly more influential than these selective forces, however, is the afore-mentioned fact that such a change would require a degree of genetic change that is unlikely to result in an organism viable beyond the earliest stages of development -- and that even if they do survive to the point of producing offspring, the trait is not necessarily likely to be replicated in exactly the same fashion, in diploid organisms in particular (though it might lead to an offspring with a partially aberrant limb which would in turn lead to another a recursion of the selective pressures and mechanisms above, weeding the possibility to propagation further. It's worth noting that organisms with odd numbers of limbs do from time to time occur, but they are not always true mutants, in that their malformations are often developmental rather than purely genetic. Snow talk 10:33, 24 November 2014 (UTC)

Kangaroos and wallabies use their tails as a limb in certain gaits, making them functionally three-limbed or even five limbed [1]. Acroterion (talk) 03:26, 24 November 2014 (UTC)

Incidentally, Frank Lentini was born with a somewhat functional third leg - but it's evident that this was not a genetic change - but instead the result of having a partially absorbed conjoined twin. SteveBaker (talk) 04:02, 24 November 2014 (UTC)

It also seems that the third leg, regardless of how he got it, was of no particular advantage and was more of a hindrance. Although it wasn't a terrible genetic disadvantage, as he did reproduce. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:04, 24 November 2014 (UTC)

A three legged creature which loses the use of a leg through injury falls over whereas a four legged one just limps a bit. That's a fairly hefty evolutionary advantage.--2A01:E34:EF5E:4640:C0D9:6BB3:E3EA:FF6B (talk) 18:38, 24 November 2014 (UTC)

Yes. It has to compensate for the loss of the fourth limb. And since it takes at least three points to ensure reasonable stability on a surface, the four-legged creature can use the "extra" front paw for various purposes while still maintaining balance - obviously a significant advantage. And if it's a hind leg that's lost, it has to compensate even more, as it makes running more difficult. The flukes of a whale, etc., may appear to be a single limb, but it is actually a highly specialized pair of legs. Whales need to swim, not walk. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:58, 24 November 2014 (UTC)

Effectively, a human car driver is a three-eyed mammal, as the rear view mirror provides the functionality of the third eye. If you are asking why we did not evolve the third eye de-novo, or why our pineal gland did not migrate to the occipital bone and did not form the third functional eyeball and orbit, the answer is most likey that there was not enough evolutionary pressure to do that. Hominidae tend to live in family groups, and the function of watching someone's back falls to other group members and not to the third eye. More generally, the cranial real estate is really, really expensive, and is best allocated to either the brain or the chewing muscles; the third eyeball just doesn't get as high a priority. If anything, it seems like the number of eyes has converged to two in the process of evolution across most extant clades. All vertebrates and cephalopods have two image-forming eyes. Insects have two image-forming eyes and three ocelli, while some earlier arthropods (such as Opabinia) may have had five image-forming eyes. Arachnids - those with good eyesight at least (lycosidae, salticidae, etc.) - have one or two pairs of eyes that do most of the imaging work and another one or two pairs that are little more than light detectors. By contrast, some animals in Cnidaria, Ophiuroidea, Bivalvia, etc., with less complex and/or less centralized nervous systems, have a large number of relatively much simpler eyes. Dr Dima (talk) 21:09, 24 November 2014 (UTC)

There is all manner of tools humans have developed to extend their senses, but you still have to alternate your focus between the rear-view mirror and the front view. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:19, 25 November 2014 (UTC)

Centipedes are interesting. Bus stop (talk) 21:22, 24 November 2014 (UTC)

What are the odds of getting oral cancer from oral sex

What are the odds of getting oral cancer from oral sex? — Preceding unsigned comment added by Whereismylunch (talk • contribs) 21:35, 23 November 2014

Hard to tell about "odds", but Oral cancer discusses causes. The predominant cause is tobacco products. Warning: Illustrations not for the squeamish. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:42, 23 November 2014 (UTC)

I mean hpv induced oral cancerWhereismylunch (talk) 00:53, 24 November 2014 (UTC)

What have you found in Google so far? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:20, 24 November 2014 (UTC)

Here is two sources: [2] [3] Rmhermen (talk) 02:47, 24 November 2014 (UTC)

Contradicts what wikipedia says about hpv positive oropharyngeal cancer being 3.2 per 100000 malesWhereismylunch (talk) 20:10, 24 November 2014 (UTC)

Which appears more reliable: The links posted by Rmhermen? Or the linked sources in the article? ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:26, 24 November 2014 (UTC)

Not sure.Whereismylunch (talk) 20:50, 24 November 2014 (UTC)

The two links both note their guesses are based on more guesswork about types of cancer which HPV is "more likely" to cause. These are associated (even potentially associated) with HPV, not necessarily induced by it.

As for risk in general, this may help you understand any numbers you see. InedibleHulk (talk) 23:22, 24 November 2014 (UTC)

• This is rather simple. The odds of cancer from oral sex = (odds of HPV from oral sex)(odds of oral cancer from HPV). μηδείς (talk) 00:05, 25 November 2014 (UTC)

What are the odds of hpv from oral sex and odds of oral cancer from hpv?Whereismylunch (talk) 01:29, 28 November 2014 (UTC)