: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)."
: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)."
:Itwouldbe interesting to see large buildingsusing 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. [[User:Katie Ryan A|<span style="border-bottom:solid #88F">K</span><span style="border-bottom:solid #d5f">ati</span><span style="border-bottom:solid #faa">e R</span>]] ([[User_talk:Katie Ryan A|talk]]) 14:14, 17 July 2014 (UTC)
: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. [[User:Katie Ryan A|<span style="border-bottom:solid #88F">K</span><span style="border-bottom:solid #d5f">ati</span><span style="border-bottom:solid #faa">e R</span>]] ([[User_talk:Katie Ryan A|talk]]) 14:14, 17 July 2014 (UTC)
Revision as of 14:15, 17 July 2014
Welcome to the science section of the Wikipedia reference desk.
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.
Did someone here herad of any Insulin-Antagonistical foods (Or effective Supplements for that matter) documented in some "serious" Scientific literature? Thanks. Ben-Natan (talk) 01:27, 13 July 2014 (UTC)[reply]
Of all the words you thought people would need to read a Wikipedia article about because they wouldn't understand it, why would "food" be the one you choose to direct them too? --Jayron3204:56, 13 July 2014 (UTC)[reply]
To clarify, are you asking about foods that destroy insulin in the blood, or that prevent the release of insulin into the blood ? StuRat (talk) 05:03, 13 July 2014 (UTC)[reply]
I'm asking what foods can interfere with the Biosynthesis of Insulin (another good question will be what are it's precursors - One can avoid them to achieve this goal too). Ben-Natan (talk) 11:47, 13 July 2014 (UTC)[reply]
Insulin is a protein, and as such its precursors are basically the same as those of all proteins, namely, the level of protein in the diet. Because it is a large molecule, substances that act as agonists or antagonists to it are rare. A few have been synthesized in the laboratory, but as far as I can tell none have been found that occur naturally. Looie496 (talk) 16:06, 13 July 2014 (UTC)[reply]
You can look up the amino acid sequence, but any such effect would be very subtle and hard to exploit. As our Insulin article explains, there are lots of factors that influence insulin release, and I'm sure you'll get a lot more mileage working with them. I can't see any sign of a usable way of altering insulin synthesis. Looie496 (talk) 01:04, 14 July 2014 (UTC)[reply]
As far as proteins go, insulin is quite tiny. In fact the monomer is a little under 6kDa in molecular weight, which means even the hexamer (the inactive/storage form) is a mere 36kDa which is still small-to-medium in size for a globular protein. Small side point, the active form of the monomer is actually a heterodimer formed from cleavage of a single precursor. Another confounding variable here is that insulin is sometimes referred to as a "peptide hormone" which is misleading, as it has a very well defined tertiary structure. To make a true insulin antagonist you'd need something with the same structure and surface properties as insulin, but incapable of eliciting a pharmacological response. I don't think it would be that difficult to do recombinantly, in fact given the huge number of synthetic insulin analogs already in existence it's likely someone already has. Although these certainly wouldn't be considered GRAS, so it's doubtful you'd ever encounter them in food. (+)H3N-Protein\Chemist-CO2(-)14:44, 14 July 2014 (UTC)[reply]
Solar roadways
is this for real or just some well-connected people bilking the public out of its money? can they keep the money? and how to pull off something like this oneself (I really, really hate my current job)? I mean, they did their homework, by securing a grant from DOT and getting a has-been scifi actor plug them to his 8M Twitter followers Asmrulz (talk) 09:33, 13 July 2014 (UTC)[reply]
Any citeable info, especially third-party analysis such as you seek, might be suitable to add to the Solar Roadways article. But see also its talkpage, where there are strong opinions about various such analyses and other material in that article (you might find useful commentary to answer your question, but you also might find it doesn't meet wikipedia's standard to include). DMacks (talk) 09:49, 13 July 2014 (UTC)[reply]
The project has many *many* problems. It's fairly clear that it doesn't make logical/scientific/economic sense. However, a $100,000 DOT grant isn't really very much - they give small businesses grants to develop all sorts of "out there" ideas in the hope that one day one of them will make it big. The idea of using them for in-road LED signals doesn't work because the density of LED's required to do that would make the panels unaffordable. Having to heat them to remove snow and ice in order to get enough solar power to heat them...is kinda circular - and besides, if there was enough sunlight hitting the surface to generate that much heat, it would already have melted the snow and ice! The concept is totally full of holes. BUT with crowdfunding, you don't have to have an idea that actually works - only one that enough people THINK will work...and for that, this works just fine.
Can you pull something like this off yourself? Maybe. Can you think of something sufficiently plausible - can you make a reasonable prototype - do you have the interpersonal skills to convince other people that your idea is good - and are your moral standards low enough that you don't give a damn that it obviously won't work? There are plenty of people like that - they'll happily sell you a magnetic bracelet to cure your arthritis or a set of pads you stick onto the soles of your feet to 'draw out toxins'....claim to have a car that runs on water (that's always a popular one!). Hardly any of them go to jail for doing it.
As for the LEDs not working when the road is covered with snow, note that the alternative, reflective signs, often doesn't work either, when the signs are covered with snow. And during a blizzard, you aren't likely to be able to see either, in any case. Then there's information painted on the road itself, such as indicating a left turn lane. I hate those. No only are they unreadable when covered by snow, but also when the car in front is idling on top of one. And then the paint inevitable starts to wear off. (Lane markers are OK, as cars rarely drive on those, but painting within the lane where it will be run over by every set of passing wheels is impractical.) StuRat (talk) 23:30, 16 July 2014 (UTC)[reply]
Can you identify this yellow moth, seen in Yorkshire, UK, Yesterday
unidentified yellow mothunidentified yellow moth
It looked very like a yellow leaf, which seems odd for this time of year. It must be unusual in the UK as I have not seen one before. -- Q Chris (talk) 15:27, 13 July 2014 (UTC)[reply]
Our brimstone moth article says that sometimes they have 3 broods per 2 year period, resulting in adults at odd times of the year, where their presumably fall camo doesn't work well. I wonder why this happens, though, as they would seem to be "sitting ducks" for predators, as a result. If they also aren't native to the UK, I wonder how that one got there or if they are an introduced species. StuRat (talk) 15:37, 13 July 2014 (UTC)[reply]
I'd looked at the Brimstone moth article, but the shape of the one in my picture is much more of a delta than that in the article. I suppose it could just be holding its wings in a different position. -- Q Chris (talk) 15:40, 13 July 2014 (UTC)[reply]
The delta shape is more apparent in the photo here, which is very like yours. It shows the distinctive reddish markings near the "leading edge" of the wing, and the less obvious greyish "dots" across the wings. AndrewWTaylor (talk) 18:43, 13 July 2014 (UTC)[reply]
Hiv transmission
How is HIV transmitted in those very few cases where people claimed to have caught it despite having protected sex? The only thing I can think of is that the condom broke or failed in some way so that fluid leaked from it. Are there any other ways? — Preceding unsigned comment added by 90.192.101.145 (talk) 17:20, 13 July 2014 (UTC)[reply]
(ec) It seems that the mouth can transmit HIV, although not from saliva, but from blood, due to small injuries. (You might get blood when using dental floss, for example.) See [4] (same as 2nd source above.) StuRat (talk) 19:32, 13 July 2014 (UTC)[reply]
Actually, our article indicates that the bulk of HIV transmission is through sexual contact. While direct blood-to-blood contact (as with shared needles) is a much more effective route to infection on a per-incident basis, there are a lot more people having sex than sharing dirty needles. TenOfAllTrades(talk) 12:34, 15 July 2014 (UTC)[reply]
In addition, while our article on hepatitis C doesn't seem to have an overall picture of transmission, the info it does have suggests the bulk of hepatitis C is not via intravenous drug users sharing needles. In particular, it notes that in developing countries, blood transfusion and unsafe medical practices generally represent the bulk of transmissions. Since it's likely a big percentage of transmissions are in the developing world (both because of their higher population and their more limited control over transmission), probably enough that regardless of how the higher rate of IDU in developed countries compares with the lower rate in developing ones, it' likely most transmissions are not IDU. For example Egypt evidentally has the highest rate of infection in the world and the majority of their cases comes from such health care transmission. And our article notes, with a 2007 source [5] that some countries don't screen blood transfusions for HCV. While the rates among IDU users are very higher in many countries (as noted by our article), somewhat similar to the sexual intercourse-HIV case, there is often a lot more people receiving medical treatments. (Hepatitis C doesn't appear to significantly spread by sexual intercourse, so it's not a major risk factor.) Nil Einne (talk) 13:45, 15 July 2014 (UTC)[reply]
July 14
Digging instinct in children?
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 [6] 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" [7], and this book has a bit about digging tools and behaviors: "Tools, Language and Cognition in Human Evolution" [8]. 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]
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.
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. [9] 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 [10] but apparently some don't. I ought to look into this further... Wnt (talk) 18:42, 15 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]
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]
Rain power ?
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]
