Wikipedia:Reference desk/Archives/Science/2014 July 15

= July 15 =

Gender-Specific Pulse Checking in Traditional Chinese Medicine
I recently heard that in Traditional Chinese Medicine, there is a gender-specific rule regarding pulse checking that goes as follows: males get their pulses checked with their left hand, while females get theirs checked with their right hand. I saw it in a Chinese TV series some years ago where, during one episode, a TCM doctor, suspecting that his apprentice was a woman disguised as a man, first asked "him" to show "his" left hand for pulse checking, and the asked "him" to show "his" right hand for the same, which confirmed the doctor's suspicions about his apprentice's true gender.

Is this rule accurate? If so, where can I read more about this? 69.120.134.125 (talk) 06:04, 15 July 2014 (UTC)


 * I think this site is a pretty authoritative one and it doesn't mention gender. --TammyMoet (talk) 12:04, 15 July 2014 (UTC)

Can Dietary Fiber inhibit Dietary Fats absorption from the Colon?
If yes, how... Thx. Ben-Natan (talk) 09:52, 15 July 2014 (UTC)


 * Most fat should be absorbed by the small intestine, prior to reaching the large intestine/colon. And fiber doesn't inhibit fat absorption in either intestine, to my knowledge.  Note that if fat isn't absorbed, then it passes out of the body in feces, leading to loose stool/diarrhea.  There are products that limit fat absorption, such as Alli, which comes with an infamous warning to wear dark-colored pants. StuRat (talk) 14:57, 15 July 2014 (UTC)


 * Alli (Orlistat) Blocks the absorption much more than it Inhibits it... It seems reasonable for me that the Viscosity of Dietary fibers indeed inhibits this absorption. Ben-Natan (talk) 08:18, 17 July 2014 (UTC)

kWh Maximum Demand
Please let some one kind show me how to calculate kWh Maximum Demand — Preceding unsigned comment added by Kakema knowledge (talk • contribs) 11:40, 15 July 2014 (UTC)


 * There is no such thing as kWh maximum demand defined in physics, or in general, in electrical engineering. It seems like the sort of term one might encounter on an electric bill. Can you explain where you read about this term?


 * Also, when you make a post, add a space and ~ at the end to sign your post. Jc3s5h (talk) 11:46, 15 July 2014 (UTC)


 * Some commercial services have a demand meter as well as power factor. Their rate is determined by the demand and power factor (usually power factor has a minimum component that is required to be corrected if it's lower.). --DHeyward (talk)


 * Use a Maximum demand indicator?--86.171.5.136 (talk) 19:55, 18 July 2014 (UTC)

Wound healing process
For what duration, do bacteria and viruses have direct access to the blood stream after a wound injury? Is it only a few seconds? Why are blood infections from wounds rare? — Preceding unsigned comment added by 90.192.101.145 (talk) 12:19, 15 July 2014 (UTC)


 * It's going to vary dramatically by would type and other conditions. Some wounds don't break the skin, such as bruises.  In that case, bacteria have no access.  Other minor wounds, like a paper cut, are quickly sealed and scabbed over, so it may be only a few minutes.  A large wound could take days to scab over.  And certain medical conditions might prevent scab formation.  Also, some medical treatments require keeping a wound open during healing.


 * As for why infections are rare, that would be our immune system at work. Only when the microbes enter in too large of a quantity to handle, or are of a type your immune system can't handle, or your immune system is suppressed, will an infection occur.  The blood flowing out of the wound will also tend to push the microbes out, not in.  An example where an infection might occur is if a foreign object full of bacteria, such as a splinter from a shovel used to move manure, is left inside the body. StuRat (talk) 15:07, 15 July 2014 (UTC)


 * Being an encyclopedia, we have a nice article on wound healing. Specifically, it mentions that white blood cells "eat" infectious agents through Phagocytosis. We also have a nice article on blood infection, which talks a bit about causes, and it seems that skin wounding is not one of the main causes. SemanticMantis (talk) 15:13, 15 July 2014 (UTC)

Chemistry terminology
What terminology is used to describe a saline compound where the component ions can/do react with each other? Plasmic Physics (talk) 12:50, 15 July 2014 (UTC)
 * I'm not aware of any special terminology for describing such compounds (although I suppose they would usually be classified as explosive materials) -- the normal terminology for ionic salts applies (e.g. ammonium perchlorate, benzalkonium nitrate, etc.) 24.5.122.13 (talk) 02:19, 16 July 2014 (UTC)
 * I don't think so, the reaction(s) is not of the redox type. Plasmic Physics (talk) 05:37, 16 July 2014 (UTC)
 * Sounds like the situation is "unstable" because the components are "not at equilibrium" or their "reaction has not run to completion". What's an example of the context or a sentence where you would be using this term? DMacks (talk) 05:51, 16 July 2014 (UTC)


 * It is a type salt that is stable as long as it is in the solid phase. However, in the liquid phase, the components proceed react with each other in a dynamic equilibrium, with various species present. Plasmic Physics (talk) 06:02, 16 July 2014 (UTC)
 * Metastability? DMacks (talk) 07:01, 16 July 2014 (UTC)


 * Hmmm, maybe... Plasmic Physics (talk) 07:55, 16 July 2014 (UTC)
 * For example, when ammonium chloride is melted under pressure, it forms a steady-state solution of ammonium chloride in a 1:1 mixture of liquid ammonia and hydrogen chloride. Plasmic Physics (talk) 10:47, 16 July 2014 (UTC)
 * Do you mean something like this? These sorts of reactions tend to be popular with chem demo shows, and are primarily used to explain non-equilibrium thermodynamics. (+)H3N-Protein\Chemist-CO2(-) 12:06, 17 July 2014 (UTC)


 * In what regard do you mean to say that they are similar? Plasmic Physics (talk) 12:23, 17 July 2014 (UTC)

Is there any cells in the human body which have electric charge?
I s there any cells in the human body -ecxept of the cells of the heart, myocardum- that have electric charge like the haert's cells have, or the heart is the only one which have electric charge? 80.246.133.38 (talk) 16:28, 15 July 2014 (UTC)


 * All nerve cells use electricity to process signals. This is why an electric charge can disrupt the nervous system, as in a taser. StuRat (talk) 18:19, 15 July 2014 (UTC)


 * Charge is essentially universal - see membrane potential. Cells also have external charge (which is different, and not directly related) due to e.g. sialic acid groups on glycoproteins on the surface, as is important for keeping red blood cells from sticking to one another.   I'm not thinking up a good reason why the membrane potential is so universal off the top of my head (i.e. whether it just happened to be that way in precursor organisms or if there's some good chemical reason why it should be this way), though of course now its presence affects the tuning of many ion gradients between the inside and outside of the cell.  Some archaea in acidic environments have weaker membrane potential (30mV) to help keep H+ (i.e. acid) out of the cell  but apparently some don't.  I ought to look into this further... Wnt (talk) 18:42, 15 July 2014 (UTC)


 * My guess is that the reason it's universal is that it functions as a power source for a variety of "molecular devices" that are inserted in the membrane. Note that even a voltage as small as 30 mV gives rise to a powerful electrical force when it is distributed across a gap as small as a cell membrane. Looie496 (talk) 15:26, 17 July 2014 (UTC)

Dubin: heart's and frog
In my book "Dubin: Rapid interpretation" is written that In 1855, Kollicker and Mueller discovered that when putting a motor nerve of a frog's leg on heart which beat, the leg kiks too according the beats of the heart. My questions are: 1. what kind of heart it's talking about? (human, animal etc.)80.246.133.80 (talk) 16:53, 15 July 2014 (UTC)


 * The answer to your first question is a frog's heart (or one of its ventricles, see, for example, Coleman + Holmes, The Investigative Enterprise: Experimental Physiology in Nineteenth-century Medicine, University of California Press, 1988, p 228). The "motor nerve of a frog's leg" was called "rheoscopic frog", by the way, a measuring device developed by Carlo Matteucci (see article). ---Sluzzelin talk  18:06, 15 July 2014 (UTC)

Complicated matrix to switch magnets on and off
I've got 49 magnets in a row. With a matrix of 7 times 7, ie 14 wires, I can connect them so each magnet can be switched on individually without accidentally switching another one on as well.

What I need is a matrix in which I can switch on any magnet as well as, -sometimes-, the one to the right of it. So each one individually, 1,2,3,.., 49 and 1 and 2, 2-3, 3-4, 4-5... 48-49.

By using 1 wire for ground and 49 for ech individual magnet this is very simple of course. With a program that uses trial and error I can also quickly find a matrix of 19 times 19, 38 wires that works ( connect magnet 1 to wire 11 and 36, 2 at 8/22, 3 at 8/24, 4 at 17/34, 5 at 15/35, 6 at 5/23, 7 at 16/26, 8 at 9/22, 9 at 1/20, 10 at 7/29, 11 at 7/34, 12 at 11/34, 13 at 4/32, 14 at 18/25, 15 at 14/38, 16 at 12/30, 17 at 13/35, 18 at 14/22, 19 at 5/37, 20 at 7/26, 21 at 17/32, 22 at 19/31, 23 at 12/20, 24 at 16/34, 25 at 12/32, 26 at 11/26, 27 at 3/27, 28 at 1/35, 29 at 19/38, 30 at 12/29, 31 at 10/23, 32 at 14/32, 33 at 11/29, 34 at 17/38, 35 at 7/35, 36 at 10/20, 37 at 8/38, 38 at 10/33, 39 at 9/28, 40 at 13/36, 41 at 12/21, 42 at 3/21, 43 at 16/33, 44 at 15/22, 45 at 3/32, 46 at 9/38, 47 at 1/31, 48 at 6/26, 49 at 4/28. )

I'm looking for a way to find the real minimum number of wires needed, and possibly for 3, 4, etc adjacent magnets as well.

Besides from "this looks like a bit like a knight on a chess board" I haven't found much logic yet. Any clues? Thanks! Joepnl (talk) 20:53, 15 July 2014 (UTC)


 * Your use of 'times' is confusing. Do you need 7 and 8, for example (ie last of one row plus first of next row)? This actually a math problem, not science Greglocock (talk) 22:02, 15 July 2014 (UTC)
 * Greglocock is right, "minimal" anything is a math problem. why not simply connect the magnets in a matrix and apply voltage at the intersection. or, if more than one magnet needs to be on at any point in time, one could simulate that by assigning each magnet a time slot and having some circuitry (perhaps one involving counters, line decoders and AND gates) scan across the magnets and activate those that are on Asmrulz (talk) 22:30, 15 July 2014 (UTC)
 * It is a math problem, really, and I was a bit fast asking it. After 2 days of trying I just made a tiny change to my program and I think I found the optimal solution. Thanks anyway! Joepnl (talk) 22:34, 15 July 2014 (UTC)


 * If you only wanted one magnet on at time, the answer would be 14 wires, with a switch on each. Using a pound sign to show when the magnet is on, and an x to show an open switch, we get this diagram:

0-0-0-0-0-0-0-x | | | | | | |  0-0-0-0-0-0-0-x | | | | | | |  0-0-0-0-0-0-0-x | | | | | | |  0-0-#-0-0-0-0--   | | | | | | |   0-0-0-0-0-0-0-x | | | | | | |  0-0-0-0-0-0-0-x | | | | | | |  0-0-0-0-0-0-0-x | | | | | | |  x x | x x x x


 * If you also want the magnet to the right on, you get this:

0-0-0-0-0-0-0-x | | | | | | |  0-0-0-0-0-0-0-x | | | | | | |  0-0-0-0-0-0-0-x | | | | | | |  0-0-#-#-0-0-0--   | | | | | | |   0-0-0-0-0-0-0-x | | | | | | |  0-0-0-0-0-0-0-x | | | | | | |  0-0-0-0-0-0-0-x | | | | | | |  x x | | x x x


 * With this setup you can turn any combo of magnets on, so long as they are all in the same row or column. However, trying to turn on two magnets on different rows and columns will result in a pair of extra magnets being turned on.  Also note that the electricity provided to each magnet is reduced when more are turned on, unless you increase the electricity to the system to compensate. StuRat (talk) 03:21, 16 July 2014 (UTC)
 * This can be generalized a bit further.
 * As long as you want to switch m times n magnets, where the magnets are in exactly m different rows and exactly n different columns, you can activate all of the rows and all of the columns. (StuRat mentioned the cases  and  .) Not sure how useful that   case is, though. - ¡Ouch! (hurt me / more pain) 08:34, 16 July 2014 (UTC)
 * You might be interested in multiplexing and Charlieplexing. I've built a multiplexed 3d LED matrix (8x8x8=512 RGB LEDs) and you can't tell only one layer is on at a time if the refresh is high enough, I imagine the same thing would apply to electromagnets. Multiplexing is very easy and you could drive this using just the 14 wires, Charlieplexing is more complex but you could get your wire count down to something like 8. Vespine (talk) 04:40, 16 July 2014 (UTC)
 * I'm no expert, but I'd worry with magnets the refresh rate might be limited by induction effects. Wnt (talk) 16:12, 16 July 2014 (UTC)
 * Selecting any 2 adjacent magnets in a matrix.png This is how far I got till now, which is optimal I think for selecting 1 magnet, or 2 adjacent magnets without accidentally switching magnets on that aren't supposed to. For 3 or for 4 I don't yet know how to do it optimally. Joepnl (talk) 14:34, 16 July 2014 (UTC)
 * The logic behind the layout for 2 adjacent magnets is clear now, each should "see" the next one like a rook on a chess board for 2 magnets at the same time. However, the next problem seems to be a too high amperage per line needed when switching on 2 or more magnets (the price of transistors is a major obstacle) with a single wire. Multiplexing doesn't work either because then the magnets have too little force (both at low (like 20Hz) and high frequencies (500Hz)). The bright side is that adding the restriction of 1 wire, 1 magnet turns this seemingly complicated case into a simple Greedy algorithm. Joepnl (talk) 23:13, 16 July 2014 (UTC)


 * If each element in the matrix is like this, then it should work. Sizing the capacitor is left as an exercise for the interested reader.

---*---  |  __|__  \ /            ---             |              |              *-*    |     |   |   _|_   _|_  )||  ___   / \  )||   |    ---  )||   |     |   |    *-*   |     |     |   |   |   |   *       |       |
 * CS Miller (talk) 08:55, 17 July 2014 (UTC)
 * That may solve the problem of not having a wire electrified all the time, but wouldn't solve the fact that there's a maximum of 24V/1A, if one of two solenoids gets a boost half of the time it would need at least 2A? Joepnl (talk) 22:59, 19 July 2014 (UTC)