Wikipedia:Reference desk/Archives/Science/2014 December 31

= December 31 =

Proper name for a wrench that works on smooth shafts and how it works
I came across this tool called a "feathering shaft wrench". Here's a video of how it works. It's called a "feathering shaft wrench" in this particular scenario because it's a wrench used to grip the feathering shaft on RC helicopters, but the same mechanism is in use in other fields as well, e.g. in milling chunks. I'm looking for the general name of this mechanism that's capable of griping smooth shafts.

Also, how does this thing work? (Normally I would just Google it to find out, but I can't find the name of this mechanism, hence my first question.) The shaft is perfectly smooth and contains no gripped flats, and there doesn't appear to be any gripping "teeth" on the wrench itself. If anything, the inside of the wrench looks exactly like a needle roller bearing. How does the wrench manage to grip the shaft? WinterWall (talk) 02:03, 31 December 2014 (UTC)


 * The wrench probably uses something like this: (click on the 'How it works' tab). It uses needle rollers in tapered recesses - turning one way, the roller moves freely, but going the other way the taper forces the roller against the shaft. The manufacturer describes it as a 'roller clutch', though it may also have other names. AndyTheGrump (talk) 02:15, 31 December 2014 (UTC)


 * Thank you very much, Andy. WinterWall (talk) 02:25, 31 December 2014 (UTC)


 * See also Sprag clutch. Dolphin  ( t ) 00:00, 1 January 2015 (UTC)


 * See also, strap wrench. μηδείς (talk) 02:00, 1 January 2015 (UTC)

Implantable Fuel-Cell
Does anyone know of research that has been done into fuel cells that run on blood, and which could then be implanted for (obviously fairly small-scale) electricity generation? GoldenRing (talk) 02:20, 31 December 2014 (UTC)


 * Neither having burnt plasma nor burnt bloodcells would be worth the metabolic cost and likelihood of toxemia and liver and kidney failure. Is there some reason heel pumps in your shoes or a bicycle hooked to a generator wouldn't be preferable? μηδείς (talk) 03:02, 31 December 2014 (UTC)


 * Pure curiosity. It seems to me the mechanism ought to be able to eg extract glucose direct from the bloodstream and convert it to water+CO2.  I'm not sure why that might induce toxemia or liver or kidney failure, though an auto-immune reaction might be a risk, I guess.  GoldenRing (talk) 03:31, 31 December 2014 (UTC)


 * They do have a device that runs a watch based on body movements, so that might be a more practical way to power some kind of monitor device, if that's what you had in mind. StuRat (talk) 05:44, 31 December 2014 (UTC)


 * Alternatives would seem to be a better choice. Inductive charging and the technology for pacemakers would seem to be a better fit for small scale electrical generation.  Pedometers and other motion related activity would be a second choice if it wasn't life safety.  I doubt anyone would use blood as a primary source of energy for anything that was life safety.  I personally would love to see a something that consumed calories and built muscle without exercise.  --DHeyward (talk) 05:57, 31 December 2014 (UTC)


 * I'm with you there. We need to find a way to convince our bodies we aren't on the verge of starvation, and that all muscle doesn't need to be converted to fat the moment we stop moving.  Besides us lazy folks, there's also weightless astronauts and the crippled/bedridden to consider. StuRat (talk) 06:04, 31 December 2014 (UTC)


 * I confess there was a certain amount of this, combined with the post-Christmas bloat, that set me thinking this way. GoldenRing (talk) 10:07, 31 December 2014 (UTC)
 * This has indeed been looked at intensively, usually using the glucose present in blood/CSF etc as fuel, just the first link I found: http://www.extremetech.com/extreme/130923-mit-creates-glucose-fuel-cell-to-power-implanted-brain-computer-interfaces. And Medeis, I don't know why you're talking about burnt stuff, you do realise fuel cells don't have to always run at elevated temperatures? Also, it is blatantly obvious why you would want to do this, rather than hell pumps or a bike, limitless power for implants. Fgf10 (talk) 10:50, 31 December 2014 (UTC)


 * By burnt I meant oxidized, not charred, and the OP specified blood, not glucose. Blood consists mainly of plasma and red blood cells. Since a cyclist burns glucose, I don't see what's wrong with pedalling a generator rather than risk having artificial implants that besides their mechanical disruption of the body might easily kill you by hypoglycemia if they malfunction. μηδείς (talk) 16:39, 31 December 2014 (UTC)
 * Well, why did you say burnt then? Anyway, where do you think the glucose comes from? The blood of course. The OP stated exactly that in their second post. Or where you thinking you can run something off plasma? You don't see what the advantage is of having an internal inexhaustible fuel supply rather than a vulnerable external supply with skin penetrations? Don't know what to say to that! Not sure if you're grasping what this is about. Fgf10 (talk) 17:25, 31 December 2014 (UTC)
 * I made the obvious mistake of assuming you were a high school graduate. Sorry.  Nor does glucose "come" from blood, so I've obviously made multiple gross overestimations in regard to your education level.  Terribly sorry. μηδείς (talk) 01:56, 1 January 2015 (UTC)
 * Ah what a charming inability to admit being wrong, topped off with a personal attack. Lovely behaviour we've come to expect form you. For the record, active biomedical researcher with a PhD in neuroscience. Fgf10 (talk) 22:17, 1 January 2015 (UTC)
 * Techically you're right the proposed fuel cell in the paper proposes getting glucose from cerebrospinal fluid rather than directly from the blood, for various reasons mentioned in the paper. However as may be obvious the idea of getting glucose directly from the blood (as well as from interstitial fluid) is mentioned in the paper (otherwise they couldn't discuss the advantages of the CSF) so I'm fairly confused about your complaint even if I'm not Fgf10. Yes, in the linked paper the glucose for the fuel cell wasn't coming directly from the blood, but the idea of getting it directly from the blood is clearly there (although I personally wonder if getting it from interstitial fluid instead of direct may be better). In case there's still some confusion, it's worth noting that in both interstitial fluid and cerebospinal fluid, in most cases a very high percentage of the glucose will have been originated from transport via the blood (much more so in the later of course). P.S. In the case of brain implants, even if these won't use glucose directly from the blood in any case, it's probably even more significant whether you want an internal battery that needs to be replaced potentially with brain surgery, an external battery with the associated cabling etc (may also be used for a brain implant depending on internal battery location, inductive charging and any potential risks (which realisticly will also need a battery which may need replacement anyway), or these highly hypothetical but still researched ideas of a probably glucse fuel cell. Nil Einne (talk) 07:02, 1 January 2015 (UTC)


 * Yeah it's worth noting that even with pacemakers, the battery lifespan  is 4-12 years. The surgery is more minor than implanting the pacemarker, still as you may guess from the earlier sources or, as surgery it's not without risks. Of course as sorted of hinted in the earlier sources, some people may welcome the battery running out  . Still it would seem that for some, not having to run the risk of the replacement may be better, presuming that such powering methods could ever be as reliable and safe (which may be a big if). It may be that by the time such methods become available (if ever), there are batteries which can last long enough, say 50 years, that battery replacement is unlikely to be a concern for pacemakers. And there are other alternatives for some other implants . Still it's easy to imagine even these may not be enough, particularly for recreational or perhaps non essential monitoring implants (as mentioned by StuRat). Worth remembering if having the latest iPlant (or maybe Apple Imp/Apple Implant) if the current CEO stays around) isn't appealing to you (as it isn't for me), you're probably not the best source for what people find acceptable if they are quite interested. Nil Einne (talk) 19:15, 31 December 2014 (UTC)

What is the reason for the changes between the right and left valves in the heart?
Why is there in the right side triquspid valve (made of three) while in the left there is biquspid valve (made of 2)? Is there any explanation for that? 5.28.189.173 (talk) 15:36, 31 December 2014 (UTC)
 * The correct spelling is tricuspid valve and bicuspid valve (which is more commonly called the mitral valve). I'm not sure of the reason, but the mechanical factors affecting each valve are different, because the right side of the heart only pumps blood to the lungs (for oxygenation), whereas the left side pumps it to every other part of the body. Looie496 (talk) 16:27, 31 December 2014 (UTC)

Why dont things stay floating in the air
Why do things fall to the floor? If I put a piece of metal into a pool with plastic balls with much lower density it remains on the top of the balls, so, what is happening here? Lower density does not explain it completely. — Preceding unsigned comment added by Nntt21 (talk • contribs) 19:37, 31 December 2014 (UTC)


 * Buoyancy, or more specifically negative buoyancy. Short Brigade Harvester Boris (talk) 19:46, 31 December 2014 (UTC)


 * As for why a heavy object can balance on lighter objects, that has to do with the heavier object's center of mass being between the lighter supports, which makes it stable. However, the situation you described sounds like the lighter balls will eventually find their way past the edge of the metal and it will sink, unless the metal is shaped like an inverted bowl, to prevent this.  In this case it might also trap some air, unless a hole is present at the highest point. StuRat (talk) 19:55, 31 December 2014 (UTC)


 * Personally, I like to think of it as displacement. If the object displaces more water weight than it weighs, it floats.  A rigid gallon container van hold about 8 pounds of water.  So an empty container can float an 8 pound object (less the weight of the container.  Ships are often listed as displacement for weight.  The plimsoll line accounts for density.  --DHeyward (talk) 04:26, 1 January 2015 (UTC)

try filling them with plastic balls in a liquid or a gaseous state. If you freeze air, you can comfortably sit on top of it. (provided you bring enough insulation.) 212.96.61.236 (talk) 00:41, 2 January 2015 (UTC)


 * I think the answer you're looking for is that air is a fluid and thus can flow away from underneath an object. The plastic balls in the pool (I'm envisioning a ball pit here) aren't very fluid-like in their behavior, so even though it would be more energetically favorable for the piece of metal to be underneath the lower-density balls, there isn't a low-energy path from the current condition to that more favorable condition. See metastable state and local minimum for more information about the topic. Note that a collection of plastic balls can act like a fluid, although there typically needs to be some energy input (e.g. vibration) in order for them to flow. If your piece of metal was vibrating every so slightly, and the metal/ball size ratio was appropriate, you'd find that the piece of metal would slowly sink into pool - much like if the pool was filled with a thick sugar syrup (molasses, honey, corn syrup). Note that the slower decent in sugar syrup isn't due to the slightly higher density of the sugar syrup compared to water. You can show experimentally that it's due instead to the viscosity of the liquid - that is fluids which can't move out from under the object as fast slow the descent down more. -- 160.129.138.186 (talk) 16:47, 2 January 2015 (UTC)


 * You might want to consider just the combined effect of Brownian motion, random walks, and the Casimir effect. Brownian motion prevents small objects from staying still in a fluid, due to the chaotic effects of random walks, those items will eventually come close to a surface, such as the floor, and the Casimir effect is a virtual force that will tend to hold a somewhat flat object like a small piece of paper against another smooth surface once they touch.  With no randomly jiggling particles between the falt surfaces pushing them apart there will be a net pressure holding the two flat items together. μηδείς (talk) 00:43, 4 January 2015 (UTC)

Bumper cars security when obtaining power just from the floor
By these new bumper cars, where the power is draw completely from the floor, without a roof connection, how do they avoid people getting burned  if they step out of the car?--Nntt21 (talk) 19:43, 31 December 2014 (UTC)


 * Sounds like they work by electromagnetic induction. That requires a metal coil to pick up the electricity. StuRat (talk) 19:50, 31 December 2014 (UTC)


 * See our article on Bumper cars - it's explained there. Richerman    (talk) 20:03, 31 December 2014 (UTC)


 * No it isn't. The article just explains how the floor works: there are alternating strips of opposite polarity, and the car has enough contacts to pick up both polarities and some sort of automatic switching power supply to deal with not "knowing" which contacts are which.  Nntt's question is, if there are strips with opposite polarity on the floor where a person could step on both of them, why isn't that a hazard?  (Suppose the customer's shoes are electrically conductive, for example because it's raining or they stepped in a fountain pool or something.)  --65.94.50.4 (talk) 09:26, 1 January 2015 (UTC)
 * It would only be a potential (ha!) problem if someone got out of the car while the ride is running, which is pretty dangerous for reasons unrelated to electricity as well. Whoever is running the ride can easily and quickly turn off the power, just like when the ride ends normally. So it's only a problem for as long as someone is out of the ride and on the floor before the carnie notices it and pushes the red button.


 * Is it really a serious safety problem unless there is also some other contact in addition to the shoes (like lying down across the floor)? Having "just the sole of the shoe" completing the circuit wouldn't send current through anything except the shoe.


 * For interest, I googled a few suppliers...looks like floor pickup systems run in the vicinity of 45 volts. DMacks (talk) 10:08, 1 January 2015 (UTC)


 * According to the answer by Tinselworm here, who claims to have worked on bumper cars using this system, they are powered by 54v at 800 amps and the cars are protected by a Curtis controller that cuts off the power in 60ms in the event of a short. S/he says that touching the contacts with dry hands is "essentially safe"- which I can't say fills me with confidence. However, I'm sure that a system that is used all over the world is unlikely to be inherently unsafe, so I would imagine that the strips are far enough apart that you couldn't easily touch both a positive and negative strip with bare skin at the same time. Richerman    (talk) 15:41, 1 January 2015 (UTC)


 * You can probably find a source that warns of such low voltage being potentially deadly. As a telephone worker I frequently touched live 50 VDC wires and didn't jump much. 130 VDC made my arm muscles pull pretty hard. Skinned my knuckles once that way. Jim.henderson (talk) 15:52, 1 January 2015 (UTC)
 * See Electric shock, and remember "It's volts that jolts, but mils that kills." With wet skin, 45 V DC might give a shock of about 50 mA, which is _unlikely_ to be fatal, but you'll certainly feel it.  With dry skin, there _probably_ won't be any noticeable sensation.  Tevildo (talk) 01:43, 2 January 2015 (UTC)

Influenza vaccine allergy
While administering my flu shot today, the pharmacist gave me a routine warning document (I want to call it an MSDS!) and noted that something like 1 in 1,000,000 patients will experience a serious reaction. A US government webpage makes me guess that he was referring to an allergic reaction, but the only thing in Influenza vaccine with comparable numbers is Guillain-Barré, not an allergy. What kinds of allergic reactions is the government discussing? No medical advice requested; I'm one of the 999,999 patients who didn't have a reaction. Nyttend (talk) 20:36, 31 December 2014 (UTC)


 * Don't concern yourself about it. What supposed reactions your paranoid pharmacist gave you   doesn't matter. The UK government let it slip-out recently, that swine flue vaccine could cause  narcolepsy in children.   But the vaccine industry earns billions and so a few unsubstantiated cases  should not stand in the way 'of the greater good'  (and profits) which 'you' are employed to deliver. You have a job remember – many others don't - just be thankful for that and stop asking difficult questions. --Aspro (talk) 21:28, 31 December 2014 (UTC)
 * Huh? I'm not concerned: as I said, I'm one of the 999,999 who didn't have a reaction.  I'm just trying to understand what reactions occur in 0.0001% of the vaccinated public upon getting this vaccine.  Nyttend (talk) 23:00, 31 December 2014 (UTC)


 * Pharmacovigilance and the Yellow Card Scheme etc are supposed to be a an alerting tool for theses things. Yet the reporting level is so low that 1 in 1,000,000 is make-believe. The don't have the statistics. So as I intermated. Don't try to think – that is dangerous to your career.  Just do -and remeber -you swallowed  the blue pill. You should not be asking these questions unless the red pill looks appetizing and you are willing to both suffer and enjoy reality. --Aspro (talk) 00:30, 1 January 2015 (UTC)


 * I think we need to be suspicious of this sort of advice from anyone using the name "Aspro"! For this who don't know, Aspro is or used to be a brand name of aspirin in Britain.  At one time Bayer, the original brand of aspirin, used to advertise that their product "DOES NOT DEPRESS THE HEART".  (Which is true, but neither did anyone else's brand.  Eventually they were made to stop saying that.)  And I remember my mother telling me in the 1970s that when she was younger and living in England, people used to say that Aspro was bad for your heart&mdash;obviously the result of these Bayer ads.  So we must be careful! --65.94.50.4 (talk) 09:36, 1 January 2015 (UTC)
 * Oh, For heavens sakes, “For this who don't know (sic),” Aspro is the name of a fish. , so stop reading into to things that are not there. OK--Aspro (talk) 16:45, 2 January 2015 (UTC)

Serious answer please
Trolling or joking aside, does anyone have an answer here? Nyttend (talk) 02:20, 1 January 2015 (UTC)
 * Who above is Trolling or Joking? Read Bad Pharma. Medical science has brought about miracles, where we live in a world today, where life is no longer solitary, poor, nasty, brutish, and short. Yet, modernization,  has created a world were, if  any of the  pharmaceutical CEO's  don't  satisfy their  shareholders  -his out. So the CEO's  make sure that your heath professional   (the guy that you see)  is overwhelmed by pseudo – science. Ignorance may be bliss, but then again  ignorance may be . --Aspro (talk) 03:38, 1 January 2015 (UTC)
 * I googled "reactions to flu shot" and a bunch of entries came up, including this one: Where that "1 in a million comes from" might be anybody's guess. It sounds like a suspiciously round number. ←Baseball Bugs What's up, Doc? carrots→ 02:47, 1 January 2015 (UTC)
 * It should be a suspiciously round number. There's no way anyone has the data quality to give say you have a 1/706,897 risk. Nil Einne (talk) 06:35, 1 January 2015 (UTC)

In 2009-2010, 82 million doses of influenza vaccine where administered in the US. That year, the Vaccine Adverse Event Reporting System recorded 116 instances of anaphylaxis (a potentially life-threatening allergic reaction), 98 cases of Guillain-Barré Syndrome, and 48 deaths (about half from heart problems and nearly all from people with identifiable preexisting conditions). Anaphylaxis, when it occurs, is pretty immediate so there is little doubt that it is caused by an allergic reaction to vaccine components (typically the eggs used in its production). The GBS association has been studied in detail for a long time and is plausible, though the overall risk is small and the reason for the connection is not well understood. Most of the other severe adverse events are likely to be coincidental. Of course the existence of mild averse events, e.g. aches, pains, and fever, are not uncommon, but I don't think those are the kind of events you are talking about. Dragons flight (talk) 03:21, 1 January 2015 (UTC)