The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
Children seem to have an endless desire to dig into the ground, in sandboxes and beaches and many other places. No doubt many mammals dig by instinct, but in humans as we mature we seem to lose interest - while adults garden for fun or for more serious reasons, I don't think many enjoy the digging for its own sake. It's kind of hard to think of a good way to find references on this. A mention is found at [1] but I don't think it's pursued. What I'm wondering is...
Is there a formal name or recognition for instinctive digging by children?
In very primitive societies, are there clearer indications of the usual purpose of the digging? (shelters, finding roots etc.)
What are the best biological correlates of the end of digging activity?
Has anyone compared fMRIs of dogs and kids digging in the same sandbox?
Ideally: Are there any specific genes, mutations, or metabolic aberrations proposed to have specific effect on this activity, which change during maturation and potentially might be revealed by the behavior continuing to adulthood?
I am thinking that somehow this instinct ought to give us insight into how human ancestors lived for some substantial period of evolutionary development. And just possibly inspire the invention of the best sandbox any kid has ever seen. :) Wnt (talk) 14:49, 14 July 2014 (UTC)[reply]
Digging gets a few mentions of digging in this book "Juvenile Primates: Life History, Development and Behavior" [2], and this book has a bit about digging tools and behaviors: "Tools, Language and Cognition in Human Evolution" [3]. I don't think there's any formal name for a digging instinct, but I could be wrong. I found those books with various combinations of /children human digging excavate behavior/ SemanticMantis (talk) 15:08, 14 July 2014 (UTC)[reply]
There are a lot of things you won't see the chairman of Goldman Sachs doing in a suit, like sitting on the floor or digging around in the park across from his office. That's cultural. Gardening, archaeology, and geology for example are productive and usually more interesting ways that adults channel those urges. Of course there's simple curiosity. Last time I was at the beach I dug for mole crabs out of curiosity, and not finding them, observed the larger meiofauna, and showed my nephews the baby clams and the polychaetes. My inlaws, however would never do anything so undignified. They haven't lost their genes, just unlearned their humanity. μηδείς (talk) 15:20, 14 July 2014 (UTC)[reply]
"dig, dig, dig until you are safe" - General Ian Hamilton, Gallipoli, 25 April 1915. (Hamilton, Ian (1930). Gallipoli Diary, 1915. Alexandria, Egypt: Library of Alexandria. ISBN1-4655-3837-2.) The instinct to dig is not presumably for the purpose of sheltering from artillery and machine-gun fire, but the instinct to construct things of all types is quite strong. Ruapekapeka is an earlier example, Minecraft a much later one.
Significant numbers of humans lived in caves at various points (see for example 1556 Shaanxi earthquake), which may have relevance to associating enclosure with safety. Children's den and Blanket fort constructions quite often come about through natural experimentation rather than tradition and design, whereas the construction of a Wendy house usually involves adults or older children.
When it comes down to it, though, if you find that you can wade into water safely, then you want to reach for things underneath it. Likewise, if you find there is earth and you can dig into it and you find things, you naturally want to dig further. --Demiurge1000 (talk) 21:55, 14 July 2014 (UTC)[reply]
Its doubtfull this phenomenon exists as such. Infants and young children grab and play with everything they can get their hands on unless it is unpleasant or painfull. The ground, or even way more interesting, an earth or sand ground, is just in their reach. Its simply an awesome toy and humans still play with it if they are full grown (for example building a sand castle at the beach)! --Kharon (talk) 01:44, 15 July 2014 (UTC)[reply]
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.
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)[reply]
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)[reply]
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?
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)
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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. [4] 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 [5] but apparently some don't. I ought to look into this further... Wnt (talk) 18:42, 15 July 2014 (UTC)[reply]
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)[reply]
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)[reply]
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). ---Sluzzelintalk18:06, 15 July 2014 (UTC)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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:
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)[reply]
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 "m=1, n>1" and "m>1, n=1".) Not sure how useful that "m>1, n>1" case is, though. - ¡Ouch! (hurt me / more pain) 08:34, 16 July 2014 (UTC)[reply]
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)[reply]
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)[reply]
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)[reply]
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.
Where can I find data on the thermal conductivity of Invar over a range of temperatures, say from 300 K to the melting point? By Googling <thermal conductivity invar> I could only find a value for 290 K and thereabouts. 144.138.223.252 (talk) 03:07, 16 July 2014 (UTC)[reply]
Black iridescent duck
I have a picture, but its resolution is so bad that there's no point of attaching it. Can anyone identify what a black, iridescent duck might be? It was seen in Hamilton, Ontario, is somewhat larger than the many mallards swimming around it, and is completely iridescent black (similar to a European starling), except for the head, which is closer to an extremely dark iridescent green. Its head resembles a mallards except for the black beak. While the swimming mallard resembles an "L" on its side, this duck's profile resembles a checkmark. The beak is black, as are the wings and feet. The closest thing I could find is the Cayuga duck, but the image on the article shows it being all green, while the sighted duck is mostly black except for the head. Brambleclawx03:30, 16 July 2014 (UTC)[reply]
Iridescence means it "appears to change color as the angle of view or the angle of illumination changes". Given that, it could well be the Cayuga duck, just viewed at a different angle or light than in the pic. And, of course, as with any species, there will be some variation on color from individual to individul. StuRat (talk) 03:38, 16 July 2014 (UTC)[reply]
Battery
Why has no one managed to design a massive battery to store electricity. I can be done on a small scale, why not a big one. I know that water can be stored to produce electricity but that is not the point.85.211.132.74 (talk) 06:16, 16 July 2014 (UTC)[reply]
You mean something with masses of poisonous and corrosive chemicals that degrade and leak into the environment? There's been enough cases of even small batteries catching fire and generating noxious smoke. What's the point of that when you can do it cleanly and efficiently otherwise? Lifting water up to a lake is very efficient. Flywheels too are very good though big ones need very strong containment for safety reasons. Even storing hydrogen produced by electrolysis or making fuels from that must be preferable to using tons of batteries. Dmcq (talk) 07:39, 16 July 2014 (UTC)[reply]
Of course that's not a massive battery but a massive array of batteries. There is no need to make really large battery - you just need to connect a lot of small ones together in parallel and you can make an array with as much storage as you like. I'm not so sure it is true to say that Pumped-storage hydroelectricity is efficient though. Our article says "Although the losses of the pumping process makes the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest". I'm sure the capital cost of building such storage is pretty high and you need a massive area to store the water too. Richerman(talk)15:20, 16 July 2014 (UTC)[reply]
It does not make sense. Batteries are either very inefficient (0.6) or only fairly efficient (0,8) but then very expensive. Additionaly a very big battery is stationary ofcourse so its anyway cheaper and more efficient to enshure electrical power supply by combining a network with some backup like a generator powered by a diesel engine. --Kharon (talk) 16:13, 16 July 2014 (UTC)[reply]
The article on you pointed at about pumped storage says 'PSH reported energy efficiency varies in practice between 70% and 80%, with some claiming up to 87%'. That's pretty good and the reason it is done so often. And unlike a good battery they don't degrade to only storing half the charge after two years. Flywheel energy storage and Power to gas describe the other options I mentioned and an overview is at Energy storage. Dmcq (talk) 16:44, 16 July 2014 (UTC)[reply]
About the only application I can see for a massive battery would be if it was connected to some technology to capture lightning strikes. However, I suspect that a massive supercapacitor would be better for this, and could then be used to either power a city or the charge could be converted to long-term energy storage, like by raising water to a higher elevation. StuRat (talk) 16:46, 16 July 2014 (UTC)[reply]
I just had a look at using batteries and my guess would be that for a large fixed site the best option would probably be to use a big array of car batteries. These are long lasting and hold their change well and are pretty efficient even if they don't have anywhere near the best power density. Dmcq (talk) 16:58, 16 July 2014 (UTC)[reply]
The electromotive force (voltage) of an electrochemical cell is determined by the choice of electrode materials and the electrolyte; not by the size of the cell. So a very large electrochemical cell would have a very modest emf - perhaps no more than 2 or 3 volts. It would perhaps be practical to assemble a very large battery consisting of a very great number of cells in both series and parallel so the resulting battery has a suitably large emf and is also capable of supplying a suitably large current. User:Dmcq and others have also implied the same thing by talking about a large array of car batteries. Dolphin(t)07:24, 17 July 2014 (UTC)[reply]
Not according to the usual meaning of 'metastable' as applied to chemical compounds. Although, technically speaking, exothermic reactions indicate that the reactants are metastable compared to the products. Note 'technically speaking'. 'Metastable' usually means that the compound has a ground-state configuration accessible by overcoming an activation energy, without decomposing explosively, or otherwise. Plasmic Physics (talk) 09:58, 16 July 2014 (UTC)[reply]
Wikipedia could use some editing on this point. We have no metastable compound and articles like magnesium oxide use it in this 'technical' sense. It strikes me that this concept can be used to describe anything from, say, a piece of paper in air that could be set on fire to a single molecule that could and eventually will break down (diamond to nitrogen triiodide). But there is a much more limited situation in which an individual molecule, without rearrangement, can go from a high energy state to a lower energy state (all-trans-retinal vs. 11-cis-retinal). What I would like to see more about though are the molecules that don't even undergo isomerization, but somehow manage to hold onto energy for some seconds within their structure. These are important and typically find use in large essentially semiconductor arrays (chlorophyll and accessory pigments) but also there's the classic photoluminescence of a fluorescent frisbee, etc. I wouldn't mind a guided tour through this batch of concepts. Wnt (talk) 16:31, 16 July 2014 (UTC)[reply]
Lacking an article on metastability in chemistry it's hard to tell, but isn't that concept just the chemical version of general bistability (with the possibility of more than two ground states)? "ground-state configuration accessible by overcoming an activation energy" looks like it would fit right in with the general dynamical systems language and diagrams in the bistability article. That article even mentions activation energy for info on the chemistry-specific case. I see a key distinction similar to what you point out though: a piece of paper in air is an excitable system, but probably wouldn't be considered metastable, in the sense of Plasmic's "without decomposing" We don't usually consider wood to be a type of ash, and vice versa... SemanticMantis (talk) 17:12, 16 July 2014 (UTC)[reply]
Metastable means one of two things in chemistry:
A system which is in a local potential energy minimum which is NOT an absolute potential energy minimum. The Wikipedia article title Metastability actually has a nice graphic that explains this type of metastability. That is, the system will remain in a state of metastability indefinitely if unperturbed, but where a small perterbation will generally set it moving to a new state spontaneously
A system which is thermodynamically unstable, but whose kinetics is so slow that it appears on human time scales to be stable. That is, the system is spontaneously changing, but doing so so slowly that for all practical purposes, it cannot be observed to be changing.
See, for example, the two definitions under "World English Dictionary" here.
In simplest terms, metastable means "stable-ish" or "stable enough" or "sorta stable, but not really stable-stable" or something like that. --Jayron3223:11, 16 July 2014 (UTC)[reply]
This makes sense, thanks. After some reflection, I'm confident that it's not wrong to describe chemical explosives as metastable. Confusingly, they might not fit into certain strict senses of chemical metastability (because the end products have undergone several major chemical changes compared to the original substance), but they are clearly metastable from a dynamical systems perspective, because the system is relatively inert and stable to small perturbations, until a perturbation of high enough energy initiates the explosive reactions. SemanticMantis (talk) 17:15, 17 July 2014 (UTC)[reply]
SemanticMantis, Wikipedia does not lack articles on metastability in chemistry. Metastability in electronics is an inevitable result of any attempt to map a continuous domain to a discrete one. It is demonstrated when a flip-flop receives too short setup and hold times to arrive at a bistable state. It is a probable but not essential consequence of the flip-flop's metastability that random thermal noise will eventually drive it into one of its stable states Q=0 or Q=1, unrelated to earlier inputs (data on which is lost).
The etymology of the prefix meta- shows it to have long been a catch-all for different things:
meta- word-forming element meaning 1. "after, behind," 2. "changed, altered," 3. "higher, beyond;" from Greek meta (prep.) "in the midst of, in common with, by means of, in pursuit or quest of," from PIE *me- "in the middle" ). Notion of "changing places with" probably led to senses "change of place, order, or nature," which was a principal meaning of the Greek word when used as a prefix (but also denoting "community, participation; in common with; pursuing"). The sense, "higher than, transcending, overarching, dealing with the most fundamental matters of," is due to misinterpretation of metaphysics as "science of that which transcends the physical." This has led to a prodigious erroneous extension in modern usage, with meta- affixed to the names of other sciences and disciplines, especially in the academic jargon of literary criticism, which affixes it to just about anything that moves and much that doesn't.
Metastability as a concept in chemistry offers a description of the collective behaviour of atoms but it may be misleading to consider stages in a chain of reactions as states of metastability for two reasons:
1) Reaction products are never permanently isolated. That we can speak of an ignition temperature needed to initiate burning or an explosion demonstrates that there is an irreversible route to increase the combined Entropy of the system and its environment; it just isn't happening right now. On a cosmological scale, every physical state of every thing is arguably a metastable state on the decay path to the end of everything when there will be no thermodynamic free energy to sustain processes such as computation and life. Metastability in substances thus seems exposed by way of a Reductio ad absurdum to be an oxymoron.
The term metastability is a semantic construction with necessarily time-limited scope. A Dice is in a metastable state all the time until it is rolled, but from a deterministic perspective the stable end result was never in doubt. Albert was sure that God "is not playing at dice". However there would be no Divine Comedy nor Summa Theologica if Dante and Thomas respectively had not envisioned God as player in a metastable standoff between good and evil. While a Western philosopher (Buridan) conceives man as an ass unable to save himself from a metastable dilemma, there is more common sense to hear from an Islamic source:
Suppose two similar dates in front of a man, who has a strong desire for them but who is unable to take them both. Surely he will take one of them, through a quality in him, the nature of which is to differentiate between two similar things.
Yes, fine, but you're arguing why the word metastable should not be used because either a) the etymology of meta or b) the futility of determining between a metastable state and a truly stable state when the only stable state is the heat death of the universe. That's fun to do, and probably makes you feel superior to everyone whom you think has it wrong, and it must the make you feel really good because the whole entire world has it wrong according to you. Still, that's a useless tangent to take us on, because lots of people DO use the word to mean very specific things, and it's more useful to help the OP understand what people mean when they use the word, than to try to show the OP how smart you are because you can use your unassailable logic to prove the entire scientific world, and their use of that word, wrong... --Jayron3201:03, 18 July 2014 (UTC)[reply]
July 17
Can Magnesium or Nsaid drugs inhibit muscle Metabolism?
Someone Anaerobically exercises his Limbs... After the workout his muscles keep to contract and he start's having Doms. Can taking Magnesium or Nsaid drugs (To ease this Dom's Pain) actually damage the Anabolic process he aimed to achieve by the workout? Thx. Ben-Natan (talk) 08:26, 17 July 2014 (UTC)[reply]
Copper#Physical appears to state that Os is one of the four coloured metals (the others being Cs, Cu, and Au). Greenwood & Earnshaw on the other hand state that Cs, Cu, and Au are the only three coloured metals. So is Os coloured? If so, could anyone explain why it is coloured? Double sharp (talk) 13:30, 17 July 2014 (UTC)[reply]
There are several pictures of it on the osmium article (and another at [7]). It's variously described as "blue–white" or "blue–black". To my eye, it appears mostly like a generic meta, silvery with maybe a tint of a color, not as obviously colored like copper, gold, and highly pure cesium seem. DMacks (talk) 16:16, 17 July 2014 (UTC)[reply]
It seems to me that a type of hydroelectric power could be generated by using the gravitational potential energy of rain collected on rooftops. The most power could be generated where you have tall buildings with frequent rain. Such power generation would be intermittent, of course, so, like solar and wind energy, being able to sell it back to the electric company to reduce your bills might be the best approach. Does such a system exist ? StuRat (talk) 13:54, 17 July 2014 (UTC)[reply]
I suspect that the cost of the system would outweigh the savings. The Pumped-storage hydroelectricity article discussed a few questions above contains this calculation: "For example, 1000 kilograms of water (1 cubic meter) at the top of a 100 meter tower has a potential energy of about 0.272 kW·h (capable of raising the temperature of the same amount of water by only 0.23 Celsius = 0.42 Fahrenheit)."
Large buildings could use rooftop rain collection for Greywater collection, to prevent the need to pump water for toilet flushes to upper stories. The savings in the power bill would be higher than if it was used for generation, and the system would be much simpler. Our articles on related subjets don't have much to say about it - it would be interesting to know if any buildings are using that sort of approach. Katie R (talk) 14:14, 17 July 2014 (UTC)[reply]
I'm all but sure it does; my company captures and uses greywater captured via roof collection for warming the freezer floor and then washing out the delivery trucks. We'd probably flush the toilets with it afterwards, but it would be inconvenient to install the extra piping necessary. Matt Deres (talk) 15:09, 17 July 2014 (UTC)[reply]
It doesn't seem to be a viable method, if you do the calculations. Looking at this table, yearly precipitation is, depending on the location, at most ~3 meters/year. So one m2 of roof surface gets 3 m3/year, which is 9.5 * 10-8 m3/s. Each m3 at 1000 meters altitude has 1000 kg * 9.8 m/s2 * 1000 meter = 9.8 * 106 J of potential energy, so energy output is, on average 0.931 W/m2 at 100% efficiency at 1000 meters altitude in a very rainy location. Even the cheapest solar panels will get you a great deal more power output per m2. Buildings of more reasonable dimensions (~100 meters high), get less then 0.1 W/m2 even without any losses. - Lindert (talk) 14:41, 17 July 2014 (UTC)[reply]
Since this system wouldn't preclude other uses of the roof, such as solar panels, I'm not sure that looking at it this way is the right approach. Presumably the infrastructure to drain the water off the roof is in place in any case, with the only additional cost being that of the water turbine(s)/electrical generator(s) at the bottom of the drains. So, the cost of those units should be compared with the value of the electricity generated. StuRat (talk) 16:59, 17 July 2014 (UTC)[reply]
A two story house would generate a few cents' worth of electricity per month. It would take centuries, more likely millennia, to pay for a generator. If you factor in maintenance it's a total no go. Googling for "roof hydroelectricity" and such will find people doing it as a hobby, but for anything serious it is a few magnitudes off, cost/benefit -wise. 88.112.50.121 (talk) 23:42, 17 July 2014 (UTC)[reply]
Since the kinetic energy in the water derives from the height that the droplets are formed at (ie, where the cloud is at) - it doesn't matter how tall your building is. Collecting water into a big tank on the roof and letting it fall through a generator to ground level would waste the energy in the water at the moment of impact onto the roof. If you can collect THAT energy - then the total of energy gathered by the impact of the water on the roof PLUS the energy gained by releasing it to ground level is the same - regardless of the height of the building. That said, the speed of a falling raindrop reaches terminal velocity eventually - but still, that kinetic energy has to go somewhere - so the friction with the air is warming up the raindrop and you'd have to collect the microscopic amount of energy from the temperature of the raindrop being a fraction of a degree warmer than ambient air. But the numbers simply aren't there...there just isn't enough energy to be had to make it worth building a machine to capture it - and then have the machine sit idle all the time it's not raining hard enough to overcome the internal losses in the machine itself.
But let's consider just the flow of water off the roof of a 400 meter tall building (the Empire State Building, for example)...it has a roof area of 10,000 square meters. The rainfall in New York is around 1.2 meters per year. So 12,000 cubic meters of water per year fall through 400 meters. A cubic meter of water weighs 1000 kg. The total gravitational potential energy gathered by having that water flow through a frictionless pipe to a generator at ground level would be m.g.h which is 12,000,000 . 9.8 . 400 = 48,000 MJ...which is the amount of energy used by a typical US automobile in a year. So adding all of this stuff to the Empire State Building would allow ONE occupant to charge his electric car...assuming the system is 100% efficient and extracts ALL of the energy from the falling water regardless of it's speed and volume. Even a light mist of rain would have to generate energy. More likely, it would be not even half that efficient.
So it's not tremendous amounts of energy. But the real problem is that the energy comes all at once during a heavy rainstorm - then nothing for weeks more. You'd probably find that almost all of the usable water flow would come in a handful of big storms during the year - and your machine would have to have the capacity to work in the heaviest deluges. So you'd need a water turbine capable of generating all the energy that a typical car uses over several months over a period of a few hours. An incredibly rough estimate suggests that this machine would probably be a hundred times more expensive than a car engine - and can't really power a car - and that's using the rain energy from the fourth tallest building in the USA.
RE: "Since the kinetic energy in the water derives from the height that the droplets are formed at (ie, where the cloud is at) - it doesn't matter how tall your building is." I have to disagree with your conclusion here. When it hits the roof it will lose any kinetic energy it had at that point, and I can't think of any good way to capture that energy, except maybe hanging some dirty laundry out and using the raindrops to wash them. So, at that point all that's left is the gravitational potential energy, which is dependent on the height of the roof. Note that it's not necessary to build a tank on the roof, it can flow down the downspouts as it always does. And cars are rather energy intensive devices, how about if we instead use the energy to power the adjacent apartments, or sell it back to the energy company, as I suggested ? A nice benefit of powering apartments is that they might be able to disconnect from the grid during storms, when power spikes are a risk. Also, you might not want to use equipment large enough to handle the maximum flow rate at the downspouts, just have a bypass for the excess, when the flow rate is too high.
Also, at my Mom's house, I installed a system to collect rainwater in a rain barrel, then slowly release it. This is to prevent a flooding problem whenever it rains. (Her drainage system just can't keep up with the rainfall.) Now this is at ground level, where the pressure is too low to be useful, but I could imagine a similar system in use atop tall buildings, where water is currently collected in tanks to prevent overtaxing the sewers during storms, then slowly drained. If such a system exists, then we could add a very small device to convert that gravitational potential energy to electricity, at a steady rate, at the bottom of the downspouts. StuRat (talk) 16:51, 18 July 2014 (UTC)[reply]
Using your Empire State Building calcs, I get 13333 Kwh, and I pay about $0.15 per Kwh, so that's $2000 a year. If we want the device to pay for itself in 5 years, we could thus spend around $10,000 for the device. Is that enough to pay for such a device ? StuRat (talk) 17:08, 18 July 2014 (UTC)[reply]
That's using the relatively low pressure of a municipal water supply, not quite the same as the pressure from a high building. StuRat (talk) 16:36, 18 July 2014 (UTC)[reply]
What technically quest been bestly?
If world university science of humankind been began at simple to implex in all, what technically quest been bestly, which start at first from implex to simple technical or around another?--Alex Sazonov (talk) 16:51, 17 July 2014 (UTC)[reply]
That question is hard to understand. I'm guessing you meant "What are some examples of technology which has changed from simple to complex and from complex to simple". If that's what you meant, then almost all technology progresses from simple to complex. But we can probably find a few examples that moved in the reverse direction. One thought is space ships, sent to the Moon and other planets, which, when they carried humans, had to be more complex than later ones carrying a robotic cargo. One of my favorite examples of a simple technology which is still in use after thousands of years, despite far more technical solutions existing, is the plumb bob used to create a vertical chalk line. StuRat (talk) 17:02, 17 July 2014 (UTC)[reply]
Thank you StuRat! In Holly Bible always been sad that God been do all at implexly miracle materia to simplely miracle material, but human mind always been do as human think as from simple to implex. Why human always do around another that God? I seen, that all technically quests always been implex that they always must been do at decide God. As I know a science always been start at implex to simple if a science quest been implex, is it’s right?--Alex Sazonov (talk) 17:55, 17 July 2014 (UTC)[reply]
As I know well the USA always decide now that simple technically decides always been bestly because the simple always been infective, is it right?--Alex Sazonov (talk) 18:11, 17 July 2014 (UTC)[reply]
I don't know if it's true or not, but there was a story that the US space program spent a lot of money to develop a pen that would work in zero gravity, while the Russians used a pencil instead. StuRat (talk) 18:19, 17 July 2014 (UTC)[reply]
Thank you StuRat. The USSR always been give a simple story technology for world. I been think, what is been always clever, the cognizing the world from implex to simple or around another?--Alex Sazonov (talk) 18:34, 17 July 2014 (UTC)[reply]
False-ish. NASA didn't develop the Space Pen - but it did cost a private company quite a bit to develop. NASA actually paid an entirely reasonable price for a bunch of them. Moreover, the Russians didn't use normal pencils because the graphite they produce when you write with them floats around in zero-g and gets into the various switches and potentiometers in the controls causing potentially lethal problems. The shavings produced when sharpening a pencil would also be a nightmare to deal with. It's believed that they actually used a form of grease pencil - but those don't write very well on paper. So this is a really bad piece of mis-information, it makes NASA seem like they spent a fortune for something that wasn't needed - when in fact, they spent very little on something that truly WAS needed. SteveBaker (talk) 19:43, 17 July 2014 (UTC)[reply]
To make a long story short, the USSR used regular air while the USA used pure oxygen, in which carbon dust is extremely explosive. Even the solid graphite of the pencil and the wood could catch fire. There is only a minor issue in air (with 21% oxygen), and we're talking about the USSR after all (overstatement, though).
One could say, "The USA threw tax money at it and used the Space Pen and pure oxygen, while the USSR threw cosmonauts at it and used a pencil and ordinary air." (Both ended up with fatalities BTW; the Groeningesque cliché of "wave after wave of cosmonauts" is a huge overstatement.) - ¡Ouch! (hurt me / more pain) 10:31, 18 July 2014 (UTC)[reply]
Simple-to-complex-to-simple is a little tough to define. For example, consider something like a boat hull. Originally, early boat-makers probably just hollowed out a log to make a canoe or lashed together logs to make a raft...really very simple. Then, as time progressed we got those amazing pieces of carpentry that made 500 ton warships out of interlocking planks, beams, etc during the age of sail - the complexity in the design and implementation was immense. Nowadays, most small boats have a hull formed from a single piece of fibreglass. Arguably, the fibreglass hull is simpler even than a hollowed out log or a log raft...but "simplicity" here depends on the assumption that you don't include all of the work it took to make the glass into thin strands and weave it into cloth - and the chemistry needed to make the epoxy that turns that in to sheets of a solid material. The entire process is vastly complex - but the resulting boat hull is simplicity itself.
It's very easy to come up with things that have become very simple if you don't include all of the infrastructure it took to get you there.
A more extreme example of that would be that I can write a command on my computer, using the smallest movements of my fingertips that will search a repository containing the whole of human knowledge (well, more or less) to find out a piece of information that our ancestors could have spent a lifetime searching dusty old libraries to discover. Is that "simpler"? It's certainly simpler for me! But include everything about computers, the Internet and so forth - and you have the most complex thing that humans have ever produced.
Thank you SteveBaker, do you mean that a science knowledge is been always simple but not implex, is it been mean that not never been implex quests in a science, they always been simple?--Alex Sazonov (talk) 20:37, 17 July 2014 (UTC)[reply]
Science is often able to swing back and forth between simple and complex. Take the ideas of how the stars and planets move:
Early astronomers (who believed that the Earth was at the center of the universe) thought that the planets went around the earth in simple, circular orbits - riding around us on crystal spheres.
But as more careful observations were made, they had to change that idea to have the planets move on wheels mounted inside those spheres - circles around circles...but these ideas had to get more and more complicated to try to fit ever more complicated observed motion to their original simple idea.
When the really simple idea that the sun is really at the center of the universe was explored, suddenly everything got incredibly simple again - planets moving in circles around the sun makes the explanation very simple again.
But they don't move in exact circles - the motion is really elliptical...so new math, new equations and more complexity was needed to explain that.
Newton's theory of gravitation provides an explanation for why the motion is elliptical - and reduced all of the motion of all of the planets known at that time to simplest imaginable gravitational equation.
But sadly, that isn't quite correct - and the way that the orbit of the planet Mercury gradually shifts can't be explained by those simple equations. It wasn't until the more complex theory of relativity came along that Mercury's orbit could be fully explained.
Sadly, even relativity doesn't completely explain the motion of stars orbiting distant galaxies - or the motion of the galaxies themselves. For that we needed to invent the concepts of Dark Matter and Dark Energy...so things are getting more complicated right now.
Many physicists expect that future work will eventually come up with a Theory of everything that will again reduce everything we know about absolutely everything into a single, simple equation. This may be the final end to this cycle - but it may not happen, there is some evidence that the universe simply isn't that simple.
Science is very often a cycle of coming up with a pretty good explanation for what we see in experiments - then finding situations that our explanation doesn't cover - then figuring out a more complicated explanation to cover those exceptions - then realizing that if you think about things in a slightly different way, it gets very simple again.
Thank you for you SteveBaker. What was been, in all means a science always been given a implex or a simple decisions, but why in a science always been a implex method of knowledge which always been a science example at all?--Alex Sazonov (talk) 08:08, 18 July 2014 (UTC)[reply]
May be a science is been so simple, that a implex method of knowledge not been. May be a God is been a simple miracle and mind of human is been simple too, I’m don’t know what is been better a simple or implex!--Alex Sazonov (talk) 10:07, 18 July 2014 (UTC)[reply]
Electricity is the flow of electrons...not the electrons themselves - but their movement. So the concept of color doesn't apply. It's a bit like asking "What color is speed?" or "What color is the wind?". The depiction as blue probably comes about because sparks that are made by electricity jumping a gap through air are blue. A spark is the most obvious visual image of electricity - so that presumably explains this idea. But no, electricity has no color. SteveBaker (talk) 19:46, 17 July 2014 (UTC)[reply]
Just to clarify a bit based on Red Act's provided references. The blue or purple color we associate with electric sparks is NOT the color of electricity. It is the color we get from what is called the "emission spectrum" of the specific mix of gases in the air. What happens is that, in a spark across air, electrons in the molecules of air (mostly nitrogen and oxygen) are "excited"; that means they absorb energy (from collisions between the molecules and the free electrons in the "spark"). These electrons are in unstable states, so they have to release the energy they absorbed as a result of those collisions. When the release that energy back to the universe, they do so in the form of photons (light), and these photons are the blue glow. The exact color of the glow depends on the specific material being excited... air produces that characteristic blue glow, but neon gives a red glow, argon is purple, sodium vapor is yellow, etc. For more of a discussion about the mechanics of this "absorb energy-->get excited-->relax-->release photon process, see Bohr model. --Jayron3221:54, 17 July 2014 (UTC)[reply]
The electron is assumed to be a dimensionless point particle since the electric repulsion between the parts of a finite-sized electron is supposed to be so strong that it would disintegrate.
If so, then the electron is a tiny black hole: how long does it take for such electron-black-hole to evaporate due to Hawking radiation ?
Antonquery (talk) 02:03, 18 July 2014 (UTC)[reply]
There's an article on this, black hole electron, but it's rather awful at the moment so don't read it.
Black holes in GR must satisfy q² + a² ≤ m², where q is the electric charge, a is the angular momentum, and m is the mass (all in natural units). Electrons violate this inequality by a factor of (from memory) about 1021. Therefore either they are naked singularities (no event horizon) or the GR calculation is wrong somehow. The simplest way it could be wrong is if there are large extra dimensions, but the LHC hasn't found any evidence for that.
Black hole evaporation conserves mass-energy and electric charge. There are (for unknown reasons) no charged particles lighter than the electron. Therefore electrons can't decay by Hawking radiation even if they are black holes.
It's not impossible for the electron to be a composite particle; it could be made of preons bound by a force like the strong force. It's hard to understand why its mass is so low in that case, but that's hard to understand anyway. Many preon models have been proposed over the years, but there's no experimental support for any of them. Elementary particles are not pointlike in string theory either. -- BenRG (talk) 02:54, 18 July 2014 (UTC)[reply]
An electron is not really a point particle. It's not really a finite-sized particle either. It does not necessarily have a precisely defined position in space, or size. You can describe an electron as a particle and use that model to talk about some aspects of its behavior. You can also just as well describe it as a wave and describe some of its properties that way. Both models are fully correct and equivalent. See Wave-particle duality.--Srleffler (talk) 16:16, 18 July 2014 (UTC)[reply]
Experimental evidence for muscle microtrauma in exercise?
I've been hearing for a few decades that the reason muscle strengthening exercise works is that it causes small tears in muscles, and the resulting healed muscles are stronger than the original (roughly speaking). Has anyone actually observed these tears in exercised muscles and counted more tears than exist in unexercised muscles? Failing that, what other experimental evidence exists?--Wikimedes (talk) 03:59, 18 July 2014 (UTC)[reply]
As I understand it, before there was oxygen in the air, micro-organisms released oxygen into the oceans, which reacted with iron which was then dissolved in large quantities in the water, to form rust (iron oxide), which then precipitated out. So, did this happen at a fast enough rate to visibly make the oceans rust-colored, if anyone had been around to see them ? StuRat (talk) 04:36, 18 July 2014 (UTC)[reply]
At modern rates of net primary productivity there would have been more than enough rust created to make the ocean surface appear visibly discolored. However, I don't think we can make anything other than wild ass guesses about what the rate of oxygen formation was during that early epoch. Dragons flight (talk) 10:42, 18 July 2014 (UTC)[reply]
I should think we could get a good estimate, based on the rate of iron oxide deposition on the sea floor, which can determined by taking core samples. StuRat (talk) 15:36, 18 July 2014 (UTC)[reply]
(edit conflict) Well, I'd say that the name is pretty transparently from Greek εὖ ("well") and πλήρης ("full" or "filled up"). It's based on Eupleres, the genus name of the falanouc, which is just the two Greek words stuck together. I'm not, however, finding any indication of why the falanouc was considered "well filled" by some taxonomist (maybe he saw a particulary fat one?). Perhaps someone here can turn up the scientific paper in which the species was originally described. Deor (talk) 12:09, 18 July 2014 (UTC)[reply]
Whoah, wrong track! See wikt:eu- - the first part generally means "true" in taxonomies, as opposed to say "pseudo". To begin with, here's a reference to the creation of the name from Eupleres in 2005.[9] Hmmm, except actually the word "Eupleridae" at least (no idea if it's a similar grouping) apparently dates to 1850. The name Eupleres was nonetheless first (as you'd expect) from Doyère, 1835.[10] That's Louis Michel Français Doyère. From [11] I came to [12] which at least might be the actual source text, but in classic early 1800s style I'm not finding table of contents and it's all in... French. At this point I may take a break in hope that beneficent fairy folk will stop by and wave a magic healing wand at it to make it something other than... French. :) Wnt (talk) 12:57, 18 July 2014 (UTC)[reply]
In French books, tables of contents most often appear at the end, Wnt (at least nowadays; I'm not sure about the early 19th century). In this instance, there's a "Table Méthodique" back there, but I'm not seeing any mention of Eupleres in it, nor does the name seem to be mentioned in the book's section on viverrids (p. 183 ff.), where one might expect to find it. In any case, that book's just an overview of mammalian systematics that lacks any etymological information at all, from what I can see. The initial description of Eupleres must lie elsewhere. Deor (talk) 14:45, 18 July 2014 (UTC)[reply]
Help identifying a feather
I recently found this feather in a wooded area of southeastern Pennsylvania. I am unable to identify the bird that it comes from. The feather is a very bright yellow (more so than the photo may suggest) and is about 6 inches long. I am not aware of any yellow birds in the area that are large enough to have such a feather. (Though the bird may not appear as yellow as some parts of the feather itself, because it is the underside that is the yellowest, and the presumably more exposed top side has more brown.) Can anyone help identify this? Thank you. 108.52.245.122 (talk) 12:03, 18 July 2014 (UTC)[reply]
I think you might be right. They live in this area, they are about the right size, and a Google images search finds plenty of pictures of the undersides of their wings which look bright yellow. Thanks. 108.52.245.122 (talk) 14:43, 18 July 2014 (UTC)[reply]
Disabling MANPADS
Since some countries cannot keep track of all their MANPADS (MAN Portable Air Defense Systems, i.e. Stinger missles), I am wondering if they could be made with an expiration date, much like landmines. However, since some will no doubt be stored along with other equipment or munitions, it would not be a good idea to simply detonate the warhead when the expiration date arrives. So I'm wondering if there is some chemical reaction that would render the explosive part of the warhead inert without causing an explosion or starting a fire. Yes, I know, there is a huge amount of energy stored in the warhead, but to me chemistry is mostly black magic, so maybe there is a way to do this. — Preceding unsigned comment added by 50.43.11.252 (talk) 16:13, 18 July 2014 (UTC)[reply]
Another approach would be to make the electronics fail after some period of time. A timer could go off after the designated time period, and detonate a micro-charge that would be just enough to burn through some wires or critical electronic components. Of course, the terrorists might be able to repair this or remove the charge before it detonates, if they are sophisticated enough. Using components that just naturally fail with age is another approach, and would be more difficult to prevent or repair, but there the timing would be less exact. In any case, the explosives and fuel could still be removed and used for some nefarious purpose, but probably won't kill as many people as if a plane is shot down.
I believe there is a great need for this, for example in Syria, where any weapons given to the rebels may well end up being used against civilians. StuRat (talk) 16:24, 18 July 2014 (UTC)[reply]
Identify a plant
Can anybody identify this plant, which is next to the hothouse in the Walled Kitchen Garden at Clumber Park? It is probably an exotic: the same bed contains specimens of Paulownia tomentosa and Echium wildpretii. I asked one of the gardeners (in another part of the garden, so it wasn't in sight at the time) and she thought it might be Tetrataxis, but she wasn't sure, and I haven't found a picture of that anywhere, so I don't know if that identification is even plausible.
