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September 19

Borde, Guth, Vilenkin and contracting universe

I remember an interview with Guth and he says that positing a contracting universe prior to expansion would be problematic due to the probable occurrence of singularities. I don't totally understand this. If the mass was contracting, I could see why it could be probable that most of the mass would form singularities, but I don't see why it could not be probable that some small amount of the mass—however little in comparison to the total—could continue on past a state of maxiumum density into an expanding stage. I don't understand these things well at all, so any simple explanation as to why I've just got this all wrong would be great. --Atethnekos (Discussion, Contributions) 05:36, 19 September 2013 (UTC)

The problem would not be that no mass would expand afterwards. The problem is with the singularities themselves. Where are they? The universe wouldn't be as smooth as we observe it to be if its initial condition (after the contraction) was that lumpy. Dauto (talk) 12:29, 19 September 2013 (UTC)

Ah, I see. That gives me much more to think about, thank you. --Atethnekos (Discussion, Contributions) 18:03, 21 September 2013 (UTC)

September 20

Weekly medicines

I'm back from the pharmacy, and the pills that I'm going to take are to be taken weekly. This surprised me a bit, as most medicines I've taken before are taken daily or twice a day. Granted, I don't know much about how these things work, but intuitively, my understandig of a drug that's taken frequently is: the drug enters the body, passes through the system and is then either 'used up' or disposed off (e.g. through urination). But how does this work for a drug that's taken weekly? I.e. how is the drug as effective a week after being taken compared to right after it's been taken? 168.120.4.239 (talk) 02:20, 20 September 2013 (UTC)

There's a trend toward taking longer acting drugs, since the patient is more medically compliant the fewer doses they take. Certain antibiotic pills like zithromax are like this now, each pill lasting for several days, with a five-day course of six pills having effect for quite a while after the last pill is taken. Metabolic half life can vary greatly. Slow acting fat-soluble hormone pills can be effective for quite a while. Exenatide for blood sugar is long lasting, and has a form that can be given weekly--good if you are perhaps senile and get home nurse visits weekly. There are myriad reasons and mechanisms. A drug may effect a condition that takes some time to reach a state that needs addressing (see IP 121's answer below on chemo and cell division). There are osteoporosis pills that are given twice a year if their effects can be tolerated, but in smaller and more frequent doses by the less tolerant. A specific explanation would need the name of a specfic drug--you should look up our articles and check the stats on their metabolism. μηδείς (talk) 02:47, 20 September 2013 (UTC)

There are also certain meications for which a high dose weekly schedule produces less side effects than a low dose daily schedule. Our article on methotrexate merely says that it is dosed weekly rather than daily, but when I was prescribed it, I was told by my doctor that this was the reason. MChesterMC (talk) 09:30, 20 September 2013 (UTC)

Why would this effect exist ? If anything, I'd expect a higher dosage at one point in the cycle from a weekly drug than a daily one (at 1/7th the dosage). StuRat (talk) 10:59, 20 September 2013 (UTC)

Chemotherapy drugs, of which methotrexate is a archtypical example and one of the oldest cancer chemo drugs, act by wrecking cell processes during division. Depending on the type of cancer, the drug is given at intervals of either two or three weeks. The idea is the a dose is given and many cells (cancerous or not, but division is a high probability in cancer cells) that are in the process of dividing are stuffed up and die. Cells that are not in the process of dividing (again, cancerous or not) are not affected. Within a few hours of receiving the drug, almost all of it is excreted in urine. The body is then left with cells that will want to divide sometime in the next 2 or 3 weeks, with the probability of cancer cells getting ready to divide rising over that 2 or 3 week period. About 2 or 3 weeks later, a maximum of remaining cancer cells are ready to divide again, so you hit them with another dose. The dividing cells then die, and you are then left with unaffected cancer cells wanting to divide 2 or 3 weeks later. So, 2 or 3 weeks later, hit them again. The cancer is driven into a cycle - just as like a boxer getting up again, you hit them hard at their worst time. Giving the drug more frequently will not be effective, as less cancer cells will be ready to divide. It would however, kill blood cell production. Giving the drug on a 3 week cycle allows the production of blood cells to continue at something somewhat less than the normal continuous rate, being interrupted for a while every 2 or 3 weeks, which the patient can tolerate. Chemo is almost always used for breast cancer, as breast cancer cells divide frequently. Chemo is not much used for prostate cancer, as prostate cancer cells (usually) divide infrequently and it is hard to drive them into "hit when they are down" cycling.

We don't know what Chester was prescribed methrotrexate for. It is used for other purposes beside chemotherapy for cancer, e.g., Crohn's, psoariasis. The approach my be different for these uses.121.215.11.211 (talk) 15:08, 20 September 2013 (UTC)

I am not sure if I read the methotrexate article correctly, but it seemed like weekly doses were safer than daily doses which might be taken too quickly together or be misadminitered if taken intravenously. Basically fewer chances for a life-threatening mistake. μηδείς (talk) 17:24, 20 September 2013 (UTC)

It's for the reasons I gave, and normally for most cancers 2 to 3 weeks, not weekly. If you attempted to give methotrexate as chemotherapy for cancer more frequently, you would reduce blood white cell count risking disease and death from infections, without killing many cancer cells, because it only kills cells that are dividing. For treating things like Crohn's, the mechanism for treatment is different (the idea is to partly cripple the immune system) and much lower dosages would be used, so safety comes with the lower dose, which can be more frequent. When methotrexate and similar drugs are used as cancer chemotherapy, hospitals use a number of special checks to ensure the dose is correct, and records kept & the whole procedure makes getting another dose too early extremely unlikely. But the risks if a high dose is given in error are not that bad. Just because you can't make any new red or white cells for a couple of days, you won't die - you should already have plenty in circulation. You might be a bit thick (so called "chemo brain") on learning new tasks or subjects as your brain won't be able to make new cells either. 124.182.5.71 (talk) 01:18, 21 September 2013 (UTC)

• For the OP. If you are interested in this topic generally, see Pharmacokinetics especially the "LADME" acronym which deals with the manner in which a drug is processed by the body. Pharmacokinetics looks, among other things, into how long it takes for a drug to enter and then pass out of the system, how long its effects last, etc. Based on the particular pharmacokinetic properties of a particular pill will determine how long between doses. --Jayron32 17:31, 20 September 2013 (UTC)

... and in addition to pharmacokinectics, one would also need to know the drug's margin of safety (redlink!), which is (roughly) the ratio of its lethal dose to its therapeutic dose. So for example, even if two drugs have the exact same pharmacokinectics, one could be prescribed a higher (and less frequent) dose of the one with the larger safety margin, since the body could tolerate the resultant higher peak concentrations. Abecedare (talk) 18:14, 20 September 2013 (UTC)

It depends on the drug, but something like Fosamax is taken weekly because it isn't circulating free in the serum but incorporated into the bone. There is a much more familiar drug that works a bit like this -- sodium fluoride, treatment with which during childhood is believed to affect dental health for many years. Wnt (talk) 18:02, 20 September 2013 (UTC)

Some drugs act in such as way that the effect doesn't change much with concentration in the body. For example, Xarelto, used to reduce the risk of strokes caused by blood clots in people with fauly heart valves or atrial fibrillation, has an effect roughly proportional to blood concentration up to a certain level, and beyond that concentration the effect levels off. This means that the effect stays roughly constant while the blood concentration is reducing over time since the last dose. So patients are told to take the next dose at the end of the plataeu time. 124.182.5.71 (talk) 01:18, 21 September 2013 (UTC)

Which is the most intelligent insect?

I'm really interested in insects with individual intelligence, not colony insects. I'd personally have assumed that the preying mantises (manti?) would be contenders for most intelligent insect. I've read pet mantis owners saying that they can learn recognise individual humans and can be trained, but I'm not 100% sure if that's true or not. --146.90.70.130 (talk) 12:24, 20 September 2013 (UTC)

It's hard to tell, because we can't get any of them to hold a pencil well enough to take the WAIS-IV. --Jayron32 13:41, 20 September 2013 (UTC)

Yes, first you'd have to define what intelligence means for an insect. I don't think anyone's bothered yet. HiLo48 (talk) 14:25, 20 September 2013 (UTC)

Please don't guess at answers. There are whole books and journals devoted to similar topics. SemanticMantis (talk) 14:35, 20 September 2013 (UTC)

It's hard to eliminate social insects in that. Honey bees have about a million neurons compared to a fruit fly's hundred thousand. There's probably a lot of that involved in social interactions. Dmcq (talk) 14:32, 20 September 2013 (UTC)

There are lots of caveats, e.g. how to define intelligence, how to compare intelligence, etc. That being said, insects can learn, and can display complex behaviors, and some can learn different things, or learn faster, than others. You aren't interested in social insects, but solitary bees and solitary wasps can generally learn quite a bit, how to navigate, find landmarks, get food from different sources, etc. Basically, many of the things you can train honey bees to do, you can train (some) solitary bees to do. As a general principle, we'd expect top predators to need more intelligent behavior than most herbivores. Mantids (plural of mantis is mantids or mantises) fit the bill, and also the dragon flies. You can google and find lots of sites describing how to care and train mantids. Dragon flies can "hover" in a breeze without flapping their wings, that takes some serious sensory feedback and brain power.

For more refs, here's a whole book on insect learning [1], and here's a nice review article [2].

I know you said insect, but if you are interested in smart arthropods more generally, check out the Portia_(genus) of jumping spiders. They have very complex hunting behavior and spatial reasoning, they can see prey, leave visual contact, then loop around to ambush. This type of hunting is commonly associated with e.g. lions, and much bigger-brained vertebrates! You can catch salticids in most parts of the world, I highly recommend playing with some, their intelligence is (to me) almost palpable! SemanticMantis (talk) 14:35, 20 September 2013 (UTC)

"Dragon flies can "hover" in a breeze without flapping their wings" - is that possible, even in principle? I don't see how. When all of the air is moving around them, there is no frame of reference for "the ground" - so all of their motion is relative to the air flow. From that perspective, why wouldn't they just drop out of the sky? This is more a matter of thermodynamics than brain power or aerodynamics! If there were some means for this to be possible (eg if they had something to hold on to - like a kite has a string) - then it's rather trivial to orient wings at a dihedral angle and be stable in the airflow...kites do it with no brain cells at all! No, I have to call "bullshit" on that one! SteveBaker (talk) 18:06, 20 September 2013 (UTC)

Are you calling BS on dragonflies hovering in an air flow without flapping - or the ability to hover in an airflow without flapping in general? Because I'm pretty sure that gulls can do the latter. They can 'hang' in a certain spot, only by making what would appear to be minute movements of their (spread) wings, but certainly with no flapping, as such. Feed a gull somewhere like the edge of a cliff or on the end of a pier (throw bread to one that's already hovering - because they seem to like hanging out and doing that in these areas anyway) and you'll probably see what I mean. Though I may be missing something here... --Kurt Shaped Box (talk) 22:19, 20 September 2013 (UTC)

In both of those cases, the gulls are able to make use of slope-lift. In strictly aerodynamic terms, in order to create a lift force to counter gravity - you must also create a drag force - and that's going to blow you downwind - so you can't hover. In slope lift, the airflow itself has an upwards component. But in straight-line wind over a level surface - I don't think it's possible to hover without inputting some energy somewhere. SteveBaker (talk) 04:37, 21 September 2013 (UTC)

SteveBaker and Kurt Shaped Box (I ping you because this thread is a little stale) dragonflies can indeed hang nearly stationary in the air, much like gulls do, without any gross flapping motions. In both cases, they do make small adjustments to to their wings, and keep in mind that for dragonflies, very complex flows can be created with four wings that can be positioned in a wide variety of configurations. For a visual example, see e.g. this video [3]. I've seen better examples in real life, but that's the best I could find on youtube without too much hassle. I count maybe one big flap in the whole 19 seconds, the rest of the movements are just sort of "snapping" into different relatively fixed positions. I didn't really mean to debate the semantics of "flap" or "hover", and I think you'll agree this is pretty amazing, no matter what we call it :) SemanticMantis (talk) 01:01, 23 September 2013 (UTC)

One flap every 19 seconds isn't "without flapping" - it's "without flapping very often". The point is that there has to be some kind of energy input...and once every 19 seconds is quite believable. But without flapping at all, there is no possible way for a heavier-than-air insect to stay up there without some kind of a tether in a simple straight-line airflow. SteveBaker (talk) 02:31, 23 September 2013 (UTC)

Or did the dragonfly only flap because it was ready to move on? :) BTW, thanks for the reply to my point about the gulls. I've got a terrible habit of reading these things and then going to do something else and forgetting to acknowledge it... Bridges are another place where you can see floaty gulls. I'd imagine that other birds can do the same, but gulls are quite conspicuous. --Kurt Shaped Box (talk) 06:46, 23 September 2013 (UTC)

We can't really agree on what intelligence means in humans, and with animals much closer to humans than insects, dogs, our article Dog intelligence highlights some of the problems. Some argue that the easily trained, obedient dogs are most intelligent. Others point out that such traits in humans would be seen as seriously problematic. HiLo48 (talk) 14:43, 20 September 2013 (UTC)

Yes, you are right, there are problems with various definitions. But rather than say "there are problems with definitions, I cannot give any answers", I've decided to post good scientific refs, and point the OP toward the better-defined concepts of learning and behavior. You are right that "most intelligent insect" cannot be firmly established, for a variety of reasons. But there are lots of very "smart" insects out there, and lots of research into insect learning and behavior. I think that information will be helpful to the OP. SemanticMantis (talk) 14:51, 20 September 2013 (UTC)

The folk that consider that easily trained dogs, like poodles, are the most intelligent, have not experienced the truely intelligent breeds like Australian cattle dogs or German Sheperds. It is harder to train German Sheperds because they are smart enough to think "why should I sit when you say "sit" - I've done it twice for you today already - sheesh!" And they train you. I trained my Germans Sheperd to jump high in the air to retrieve a tennis ball suspended from a clothes line. She can do almost 3 metres. I have set the height at 2 m, increasing it 100 mm or so until it appeared she couldn't manage it. At 2.6 m, she looked at the ball, looked at me, looked at the ball again, made two leaps not quite making it, and howled as in frustration. Recalling that she managed greater heights a few months before, I cranked the height to 2.8 m and then gone inside the house. 10 minutes later the children who lived next door came home from school. The dog made one single leap, got the tennis ball, and took it over to the children. That is the mark of true intelligence - she tried to trick me, with her very good acting, and she nearly succeeded. 121.215.11.211 (talk) 15:35, 20 September 2013 (UTC)

It seems to me you could just use some of the brute force methods that are currently being used to study the mouse brain. You can take an insect brain, slice it up into a nanometer thin slices, scan all these slices and then reconstruct the structure of the neural network. In case of the mouse brain they will do this for only a fraction of a cubic millimeter of brain matter. Once you have the exact digital representation of such a brain, you can simulate how it behaves using a supercomputer. Count Iblis (talk) 16:51, 20 September 2013 (UTC)

Once you've sliced an insect's brain up it won't be all that smart. HiLo48 (talk) 21:48, 20 September 2013 (UTC)

Ants are widely said to have the largest brain/body ratio; however, this seems to be confined to the optic lobes as a matter of vision. (PMID 2720368) Of course, as we know from human development, changes in brain size can be subtle even when there are enormous changes in intelligence. As one of the first replies alluded, it will not be easy to evaluate insect intelligence based on behavior, due to a lack of obvious standard activities they all do that require mental effort. Wnt (talk) 17:58, 20 September 2013 (UTC)

Ants are colonial (see the OP's question), boring, and follow fixed action patterns. μηδείς (talk) 21:51, 20 September 2013 (UTC)

• My first thought on reading this was Bumblebee! and google confirms it. μηδείς (talk) 21:49, 20 September 2013 (UTC)

Well, it has to be the bumble bee, apparently it had the intelligence to outsmart aerodynamics. Aerodynamics couldn't stop it from flying. Plasmic Physics (talk) 05:36, 21 September 2013 (UTC)

There may be something to that idea - I imagine managing flight using dynamic stall at each wingbeat might take some extra brainpower? But they are also social, so if we're excluding them (rather than just not evaluating colony intelligence) we might want to look at various solitary wasps. (Yellow jackets are also said to be intelligent [4] but are also colonial) See [5], a charming naturalist narrative which singles out Ammophila (wasp). I understand the argument that insect behavior is part of a simple, inflexible pre-program, but I wonder if humans really do so much better when abducted by aliens for tests. Wnt (talk) 14:54, 22 September 2013 (UTC)

The individual bumble bee seems pretty flexible, regardless of the hive intelligence. I took the OP's prohibition as applying to the colony, not the member as members. That being said, the bumble bee article says they exhibit flower constancy, repeatedly visiting only the same plant so long as it produces, and this may indicate another fixed action pattern, rather than intelligent learning. μηδείς (talk) 15:53, 22 September 2013 (UTC)

I suppose that human farmers who repeatedly harvest from one or a few fields rather more fertile fields they drive past on the way are also displaying cognitive limitation. :) Seriously, I don't know, and neither do these authors [6] but I'm not convinced it proves low intelligence. Wnt (talk) 20:51, 22 September 2013 (UTC)

It doesn't prove low intelligence. But fixed action patterns are often mistaken for intelligence, which they are not. Mother wasps don't learn how to sting and bury prey for their young. They just have complex fixed action patterns that achieve that effect. Interrupt them and they will restart their actions without realizing they have already accomplished that goal. If that is the case with bumble bee nectar gathering it doesn't speak well for their intelligence. Indeed, if we define intelligence as learning, the question is very open, and if we define it as creativity, only animals like crows and apes are known to possess it in the area of creating tools. We have a large article, animal intelligence. μηδείς (talk) 21:31, 22 September 2013 (UTC)

The limiting factors on humans, generally speaking, don't have to do with intelligence, but rather with resource limitations. I do find it funny that dogs are rated intelligent if they can be easily trained to obey orders. I don't think that's regarded as the first criterion of intelligence in humans. I hope not, anyway. :( ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:08, 22 September 2013 (UTC)

Training dogs to work is more a question of our intelligence as applied to their capabilities. Hunting using trackers, pointers, flushers, and retrievers is based on the dog's natural capacities as a wolf, interrupted (the dog is capable of enough self control to point without then chasing, or retrieve without then eating) and redirected by our intelligence to our purpose. That's basically the same unskiled labor as working a cash register in humans--handling the money without pocketing it.

Training dogs to do tricks is like teaching children to do tasks like tying their shoes. There's nothing obvious about shoelaces that metaphysically directs us to want to tie them. We can learn the arbitrary (to the child) sequence of doing so if we are praised. The stimulus is external, unlike trying to eat something that smells and tastes good, which children (and dogs) will do if left to their own devices. μηδείς (talk) 22:24, 22 September 2013 (UTC)

According to this source there were "there were birds in the sky". Bus stop (talk) 23:00, 22 September 2013 (UTC)

You may be confused, Bus Stop, I think you meant to say... μηδείς (talk) 01:41, 23 September 2013 (UTC)

Well of course I am confused. I'm hoping that insects are intelligent. Why wouldn't I want an intelligent salticid? At least if this guy is called Four eyes we will know why. Bus stop (talk) 23:35, 23 September 2013 (UTC)

Training dogs to do tricks like "beg", "sit", etc is indeed just a sequence that the dog learns to get praise or food - and requires little inteligence on the part of the dog. Stupid breeds like poodles and spaniels do well at it. But there are other sorts of training. In the training of guide dogs for the blind, the more truely intelligent breeds like labradors are used - poodles and spaniels, which do simple tricks well, just can't cut it. Guidedogs are trained to look at obstacles from the point of view of the human, and make decisions. For instance, that low tree branch hanging over the foot path - from the dog's point of view it matters not a whit - he can just go under it. But the human will hit it. Dog makes a series of decisions: Is branch too low for human, need human to duck? Or is it ok - just keep walking? Go around? Stop until road traffic is safe and take human off footpath (signal human about that deep gutter) to get around obstacle? Or stop and get human to make decision? This is a severe test of intelligence, as a) it requires the dog to evaluate things form the human's point of view, not the dog's, and b) it requires on the spot decisions, not just a pre-programmed sequence. Labradors can do it well. Poodles cannot. A somewhat similar requirement mental flexibility is required of police dogs, which are usually German Shepards, which many in the dog show set regard as stupid, as they get bored with simple pre-learnt tricks. 120.145.70.130 (talk) 03:09, 23 September 2013 (UTC)

wasp and spiders

I’m not sure if this count, but this little blue wasp managed itself very well to literally kill and abduct this big spider of arguably three or four times its body weight, here in Cuba this wasps are very common. If they are not intelligent then they are really bold…

In the middle of the “fight” the spider tried to bite it several times, and I disturbed it with my flash too, but the wasp neither start over again nor leave the poor spider alone, it just keep trying different ways to engage its target… it’s funny, at first the wasp fly an land almost in front of me and stand for a moment staring at me moving its orange antennas like saying: hey! this is mine… get out!! :)

Iskánder Vigoa Pérez (talk) 04:08, 24 September 2013 (UTC)

Do we need to eat saturated fat?

Can saturated fat be left out of the diet altogether or is there a minimum amount we need to eat? Count Iblis (talk) 20:36, 20 September 2013 (UTC)

The only essential fats are those involved in child development. So the answer depends on the questioners age, and since it is impolite to ask you your age, I recommend you seek the opinion of a medical doctor or equivalently competent authority on the subject. Tim AFS (talk) 20:40, 20 September 2013 (UTC)

Essential fatty acid. μηδείς (talk) 21:46, 20 September 2013 (UTC)

I stand corrected. Thank you. Tim AFS (talk) 05:29, 21 September 2013 (UTC)

Thank you. It was not my goal personally to correct you, and I appreciate the polite response. μηδείς (talk) 01:44, 22 September 2013 (UTC)

The only known essential fatty acids are alpha-linolenic acid and linoleic acid, neither of which is saturated. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 23:16, 20 September 2013 (UTC)

There is not a minimum amount of saturated fat we need to eat. Although there are good arguments made to include some saturated fats in your diet (see references), the FDA website says to choose the foods with the lowest amount of saturated and trans fat. http://www.fda.gov/food/ingredientspackaginglabeling/labelingnutrition/ucm274590.htm, http://www.hsph.harvard.edu/nutritionsource/fats-full-story/, http://www.fourhourworkweek.com/blog/2009/06/06/saturated-fat/ Bradbchnn (talk) 01:41, 21 September 2013 (UTC)

Thanks! Count Iblis (talk) 00:44, 22 September 2013 (UTC)

I strongly doubt this question can be answered. Saturated fats are essentially universal in nature, in plants and animals - there are many things that are low in them but I can't think of a living thing you can eat that contains none at all. So in order to test the effect of omitting all saturated fats in humans you'd need to feed people a highly artificial diet, which may be viewed as an experiment that is unsafe and unethical to carry out long enough to see the long-term effects. Wnt (talk) 15:00, 22 September 2013 (UTC)

The experiment would be done if there were a person with a metabolic defect who could not metabolize such fats, and who had to have a special diet or die from such a disease, along the lines of Lorenzo's Oil. μηδείς (talk) 22:27, 22 September 2013 (UTC)

There are many extreme veganist dieters, e.g. Bill Clinton and Angelina Jolie. Count Iblis (talk) 17:24, 23 September 2013 (UTC)

Harvesting power from the oceans?

http://www.intpowertechcorp.com/ has amazing ideas (check out the ~10 minute video) but would it be more practical just to drop anchor and produce power from a http://www.makanipower.com/home/ turbine? Tim AFS (talk) 20:37, 20 September 2013 (UTC)

That depends on whether you want to use the power for ship propulsion or for electricity generation. Note, however, that both these devices create a potential hazard to aircraft. 24.23.196.85 (talk) 22:58, 20 September 2013 (UTC)

Makani says they have aircraft hazard indication transmitters and stay below 1000 feet. I'm not sure the answer depends on the ultimate use of the energy produced. Tim AFS (talk) 05:32, 21 September 2013 (UTC)

Of course it does -- if you want to generate electricity, the Makani device would be more efficient, as you correctly suspected (it converts wind power to electricity in two steps, whereas the INT device requires three steps, hence the better efficiency), but if you want ship propulsion, then the INT device will be more efficient (one-step conversion of wind to kinetic energy, whereas the Makani takes three steps). 24.23.196.85 (talk) 21:14, 21 September 2013 (UTC)

Notung vs. Excalibur

(This is tangentially related to the discussion "Sword made of precious metals") Suppose two Dark Age warriors get into a duel -- one being armed with a Celtic/Anglo-Saxon sword, and the other with a Teutonic/Viking sword. Which of them would have the advantage in the fight? 24.23.196.85 (talk) 23:11, 20 September 2013 (UTC)

Which warrior is the better swordsman in general? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:28, 21 September 2013 (UTC)

Too many unknowns really. Which is longer? Lighter? Sharper? (Each article says its sword could cut metal.) Clarityfiend (talk) 07:14, 21 September 2013 (UTC)

Nothung is better than Excalibur, Nothung. Of course, you should take that with a Gram of salt. Clarityfiend (talk) 07:10, 21 September 2013 (UTC)

If I recall correctly, Nothung was forged by Siegfried, while Excalibur was forged by the gods (presumably) and its caretaker was the Lady of the Lake. I would go with the one made by the hands of superior beings. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:11, 21 September 2013 (UTC)

And if I recall correctly, Nothung was originally forged by the gods and given to Siegmund by Wotan, and then reforged by Siegfried after it shattered on Wotan's spear. So in fact, both these swords were made by superior beings. 24.23.196.85 (talk) 20:34, 21 September 2013 (UTC)

• A lot depends on the quality of the swords. Smiths in those days had great difficulty forging swords that were not brittle and hence easily breakable -- that's why really high-quality swords were such notable objects. The best material at that time was probably Damascus steel, but it wasn't available in Europe. Looie496 (talk) 15:38, 21 September 2013 (UTC)

The Varangians (Vikings) had access to Constantinople, a major trading hub. Damascus steel was likely available there.--Auric talk 16:00, 21 September 2013 (UTC)

In the Dark Ages (5th century AD), it's unlikely that the Vikings already had access to Damascus steel -- so the more likely material for their swords would be plain high-carbon steel (most likely high-quality 1090 or 1095 steel). But they did have access to advanced (for their time) bladesmithing techniques, including differential tempering and pattern welding, which would have allowed them to make their swords ultra-strong without sacrificing toughness. 24.23.196.85 (talk) 20:34, 21 September 2013 (UTC)

Does eating chlorophyll help the production of hemoglobin?

chlorophyll a

Heme b

Just read a newspaper ad says "Chlorophyll's structure is similar to that of a hemoglobin, and hemoglobin is used to make red blood cells, which delivers oxygen in the body; so chlorophyll helps increasing red blood cells, and is beneficial to human body".Is this accurate?--朝鲜的轮子 (talk) 23:41, 20 September 2013 (UTC)

Heme molecule, to start with. Interesting question. μηδείς (talk) 23:51, 20 September 2013 (UTC)

Prob'ly not more than eating any other protein -- the chlorophyll molecule will have to be digested before it can be absorbed by the body. However, foods that contain lots of iron DO help make more hemoglobin, because iron is an essential part of it. 24.23.196.85 (talk) 00:00, 21 September 2013 (UTC)

The heme molecule is not a protein, it's a hydrocarbon porphyrin ring surrounding an associated iron ion then associetd with a protein globin molecule. Chlorophyll has a porphyrin chlorin ring surrounding a magnesium ion and attached to a phytol tail. Our articles discuss the breakdown of used heme molecules by the liver and their creation in the same system that deals with cholesterol and steroids. See porphyrin for its synthesis. A search for articles on chlorophyll digestion does not make it likely that chlorophyll is reused for hemoglobin synthesis. μηδείς (talk) 00:39, 21 September 2013 (UTC)

I don't see much since [7] which says:

"After release from the plant food matrix, natural chlorophyll (CHL) derivatives are exposed to the acidity of the gastric digestion resulting in conversion to respective metal-free pheophytins (PHE). Within the upper small intestine, PHE derivatives partition into bile salt lipid micelles resulting in solubilization of PHE and movement across the unstirred water layer and ultimately into the enterocyte presumably by passive diffusion [49]. The extent to which natural chlorophyll derivatives are metabolized and/or secreted into circulation is currently unknown. Chlorophyllin: After digestive release of water-soluble SCC derivatives, significant degradation of Cu-chlorin e6 derivatives occurs, leaving primarily Cu-chlorin e4 and potentially residual amounts of Cu-chlorin e4 ethyl ester [50]. Uptake of SCC derivatives by intestinal cells seems to proceed predominantly by a facilitated process, with absorbed SCC derivatives efficiently effluxed back to the luminal compartment [50] by unidentified efflux system (potentially BCRP/ABCG2 55, 56 and 57). A portion of the internalized SCC derivatives is passed from the enterocyte into circulation as noted by Egner et al [38]. The extent to which SCC derivatives are metabolized and the extent to which the metabolites may be transported out of the enterocyte are currently unknown."

I should point out, however, that despite the superficial similarity you can notice a number of little variations around the edges between the heme and chlorophyll. As a rule, removing or changing this sort of carbon-carbon bond at the edge of an aromatic ring complex is not easy to do - my gut feeling is that biology is going to deal with that sort of problem either by doing nothing to the structure and excreting the remnants at some point, or else by adding lots of oxygen, completely opening up the rings and splitting it to small compounds, when then would be part of general metabolism. Wnt (talk) 14:33, 22 September 2013 (UTC)

That's your gut feeling about digestion? DMacks (talk) 07:39, 23 September 2013 (UTC)

September 21

Camera lens for fast-paced sports

A friend has a choice of two lenses for her Nikon camera: Nikon 70-200mm f/4 or 70-200mm f/2.8. Which should she buy (price is not the issue) and why? She will be taking photos of professional hockey games. Bielle (talk) 20:21, 21 September 2013 (UTC)

Homework? The "which" and "why" will be well explained in any basics of photography book; she should buy the book before investing in the glass. 88.112.41.6 (talk) 20:34, 21 September 2013 (UTC)

No, not homework. Bielle (talk) 20:46, 21 September 2013 (UTC)

For taking pictures of fast-moving objects, f/2.8 would prob'ly be a better choice, because it will gather more light and thus allow shorter exposure times (which, in turn, will reduce motion blurring). The tradeoff, however, is a shallower depth of field. 24.23.196.85 (talk) 21:04, 21 September 2013 (UTC)

To avoid confusion, in case anyone should interpret 24's answer as indicating that there is a tradeoff in choosing the f/2.8 lens, there isn't (and I'm sure that 24 didn't intend to say there was). F/4 and f/2.8 indicate the maximum apertures of the two lenses. See F-number for a somewhat technical explanation of what these numbers mean. The lower the number, the more light is allowed to pass through the diaphragm. Going from f/4 to f/2.8 doubles the amount of light, allowing you to halve the exposure time, with the advantages in sports photography that 24 explained. It is correct that the depth of field is shallower with the f/2.8 setting. But if you use both lenses at f/4, the depth of field will be the same. Another factor to consider with a telephoto lens, is that you'll easily get a blurred picture because of not holding the camera steadily enough. Is she planning on using a tripod? If not, an f/4 lens with built-in image stabilization might be a better choice than an f/2.8 lens without image stabilization. You said "Nikon lenses", but you are probably aware that there are other manufacturers such as Sigma and Tamron who produce lenses for Nikon cameras. I'd definitely recommend doing some research and reading reviews of the lenses under consideration before buying. --NorwegianBlue ^talk 23:00, 21 September 2013 (UTC)

It also has to be mentioned that in practice you can crank up the ISO value to get the exposure time you need, so what the f/2.8 will allow you to do is to work with lower ISO values which means that you'll have less noise. You do have noise reduction options, but that will affect image sharpness.

Perhaps a moot issue because of motion blurring mentioned above by the IP and NorwegianBlue and also the limitations of the lock on autofocus (you won't be able to use the best autofocus points when using the "lock on mode" to keep a moving target in focus), but in theory a perfect lens with higher aperture has a higher absolute sharpness (the part that is perfectly in focus should be sharper). This is because the angular resolution is of the order of the wavelength divided by the aperture. But I think that even for the best commercially available lenses, the quality of the lens will lead to the maximum image sharpness being quite a bit less than the theoretical limit. The higher quality f/2.8 lens at that diaphragm of f/2.8 will have a similar quality as that other lens at f/4, so I don't think that the maximum image sharpness will be better for that f/2.8 lens. But you would expect that when both lenses are used at the same diaphragm that the higher quality f/2.8 lens should have a better sharpness. Count Iblis (talk) 00:25, 22 September 2013 (UTC)

I shoot the Tamron 70-300mm f/4-f/5.6 lens on my Nikon camera. I recommend it over the 70-200mm and even over the Nikon 70-300mm, and I have done side-by-side comparisons with all of the above. Why would I choose the lower aperture and the off-brand lens?

Truthfully, the super-huge apertures degrade image quality more than they improve it. They defocus - because they have shallower depth of field; but they also defocus because it's harder to build perfect glass at that size. Off-angle lighting and geometric distortion are easily noticeable to me on the f/2.8 70-200mm lens. Chromatic aberration is quite a bit worse than the 70-300mm model.

Besides, you bought a Nikon for its superb image noise performance, right? The sensor and the digital processing on Nikon cameras outperform all the competition - you can verify by checking side-by-side image comparisons at a website like Digital Photography Review. In conventional wisdom, you shoot at lower ISO and wider aperture to reduce noise; but I challenge you you notice noise on a Nikon D90 at ISO400; and I challenge you to do it double-blind at ISO1600 vs. ISO400. So, the supposed rule-of-thumb is less relevant. I've shot plenty of outdoor sports games - night football, even where the lighting is worse than a hockey game - at f/5.6 at 300mm, and never had to slow my shots or worry about noise.

So, why would I recommend the Tamron variant? Most of the time, I would strongly recommend the on-brand lens, because most of the time, the glass and mechanicall quality makes a difference. But on the 70-300mm f/4-f/5.6, I happened to compare the Tamron and Nikkor side-by-side, and found the Tamron vibration reduction mechanism to be quicker and steadier than its on-brand competition, and its image quality was indistinguishable. The extra zoom, vs. a 200mm lens, is nothing to scoff at: you get 50% better control of the framing or your shot, in exhange for a little extra noise that nobody else will ever notice. You get detail and optical sharpness, which you can later trade off in post-production for even lower noise than your f/2.8 can provide.

Ultimately, you should probably rent these lenses and try both. The f/2.8 Nikkor (and many others mentioned) are quite expensive, and if you aren't sure you want it, you should spend the $50 or so to rent it for a weekend from a high quality photography store. Nimur (talk) 13:58, 22 September 2013 (UTC)

Do batteries contain a clear, harmless liquid?

Today I was changing an AA battery, and it was stuck rather hard. I felt it give a little, but some colourless liquid suddenly squirted onto my hands. Terrified that I'd gotten acid on my hands, I immediately (within about 3-5 seconds) I ran to the sink and ran my hands under cold water for about 30 seconds. When I realized I wasn't feeling any pain or burning I stopped, and removed the battery while wearing gloves. What could that liquid have been? Pokajanje|Talk 20:26, 21 September 2013 (UTC)

We don't give medical advice. You should see a doctor if there is evidence of a burn, but the liquid is more likely to be an alkaline than an acid. You did the right thing by running your hands under cold water. I've done exactly the same without any harmful effects. Dbfirs 20:55, 21 September 2013 (UTC)

This is not medical advice. I'm asking what the liquid was. Pokajanje|Talk 21:01, 21 September 2013 (UTC)

The electrolyte in a standard alkaline battery is potassium hydroxide. For KOH's material safety data sheet, see here. Red Act (talk) 21:05, 21 September 2013 (UTC)

The liquid was a suspension of zinc in potassium hydroxide. 24.23.196.85 (talk) 21:07, 21 September 2013 (UTC)

If it was a cheap battery, then the liquid was probably Zinc chloride which is an irritant and can harm skin when in concentrated form (the leaks are often diluted). Dbfirs 21:09, 21 September 2013 (UTC)

Our article on zinc-carbon battery says that they generally contain a "layer of NH4Cl or ZnCl2 aqueous paste". I don't think there's a guarantee about what it is though. I doubt it was potassium hydroxide because when you get that on your fingers and wash they seem really slippery. Wnt (talk) 14:13, 22 September 2013 (UTC)

Your fingers feel slippery with potassium hydroxide because it saponifies the oils on your skin (I realise you probably know that Wnt, but I just wanted to add it for the OP and others). For some reason I have always really liked that fact. Equisetum (talk | contributions) 17:29, 22 September 2013 (UTC)

September 22

NSaid and Ulcers

Why would the interaction between Alcohol & NSaid's substances may contribute to the development of Ulcers in Humans?, And, if it will be Capsaicinoids instead (together with the NSaid's), could that also initiate Ulcers in Humans?

Thanks for your replays. this could be very enlightening Ben-Natan (talk) 02:36, 22 September 2013 (UTC)

Ulcers are believed to be caused by Helicobacter pylori. Nsaids and drinking alcohol probably exacerbate them. μηδείς (talk) 02:44, 22 September 2013 (UTC)

What about Capsaicinoids? Ben-Natan (talk) 14:58, 22 September 2013 (UTC)

Our article says nsaids will also cause ulcers, but doesn't mention capsaicinoids. See Peptic_ulcer#Cause. μηδείς (talk) 17:31, 22 September 2013 (UTC)

Outhouses, sheds, and barns

Why are sheds smaller than outhouses? I would expect "outhouse" to be smallest, "shed" in the middle, and "barns" to be biggest. Nyttend (talk) 07:11, 22 September 2013 (UTC)

Given the irony of choosing "barn" as the term for such a tiny unit, they probably decided to go in reverse order. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:12, 22 September 2013 (UTC)

Looking at the disparity in sizes between the outhouse and the shed, my guess is that those labels were proposed by two different groups, with little regard for internal consistency. As the article mentioned, the two units are rarely used - likely the proposals for the units were primarily as an ad hoc or nonce joke, without any sort of consideration of how they would be used in long term practice. -- 67.40.209.200 (talk) 16:35, 23 September 2013 (UTC)

the effect of a working propeller on a plane

The propeller is known to produce thrust moving the plane forward. What side-effects does it have on the plane besides the main one ? In particular, a) does it tend to shift the plane off its main direction due to sense of which the blades turn ? b) is it responsible for raising the plane's tail while running on the runway, and if it isn't, what physical cause does raises it ? BentzyCo (talk) 15:01, 22 September 2013 (UTC)

The article propeller doesn't have much if anything to say about it, so either the editor didn't find anything or it's not a problem. As for what raises the tail, it's lift. Basically, once sufficient speed has been attained, the tail is going to rise. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:37, 22 September 2013 (UTC)

Besides thrust, the propellor in being turned by the engine imparts a twisting effect on the aeroplane. In high performance aircraft with single engines, this makes the plane easier/harder to turn in one dirrection than the other. It was aserious limitation of the Japanese Zero fighter. It can also make for some tricky handling on takeoff, as the plane tries to tip over, requiring the pilot to initially correct strongly for it, then taper off as speed builds up and the aircraft control surfaces begin to work more effectively. The WW2 Spitfire fighter was noted for this. The spinning propellor also acts a gyroscope, causing precession forces, making the plane try to climb or dive when turning to right or left. Pilots soon learn to correct for this. In twin engine planes, the props usually turn in opposite directions to cancel out these effects.

Because the spinning propellor casues a corkscrew motion of the air, power is wasted and as the air tries to goes past the fuselage and wings on an angle instead of parallel, drag is increased. Contra-rotating propellors eliminate these propblems.

The tail rising as the plane builds up speed down the runway is essentially a design feature or good pilot practice for tail dragger aircraft - so the pilot can see the runway ahead. Until you get enough speed to lift the tail, slewing the plane right and left alternately is sometimes practiced so you can see where you are going and avoid unexpected obstacles. The tail lift is achieved by a suitably designed tail aerofoil. In aircraft with a tricycle undercarriage, tail lift before takeoff is not done, as with the plane more or less level, the pilot can see the runway ahead anyway.

121.215.0.157 (talk) 15:43, 22 September 2013 (UTC)

"In twin engine planes, the props usually turn in opposite directions to cancel out these effects." Nope - only true for a small minority of twin-engined propeller-driven aircraft. AndyTheGrump (talk) 16:41, 22 September 2013 (UTC)

And cost makes it obvious why. In off-axis, twin-engines, rotation direction also defines which engine determines the minimum controllable airspeed and designates a critical engine (losing one engine is worse than losing the other). P-Factor and yaw combine for one side and counteract on the other side. Because of this, even twins with counterrotating propellers put the clockwise-rotating engine on the right. Symmetry still has a preference. --DHeyward (talk) 18:57, 22 September 2013 (UTC)

Well, you haven't given an data to backup your claim on cost. Cost is not an obvious factor to me at any rate. I have been involved in selling marine engines >800 kW. In boats with twin engines, the two engines and props turn in opposite directions to improve handling. The only difference between a CW-rotating 4-stroke engine and a CCW-rotating one is: 1) the camshaft, 2) the oil pump, 3) the coolant pump, and 4) the starter motor. In some engines, the arrangement of the oil filters is different so they are easily accessable on the opposite rotating engine in cramped engine rooms. As the manufacturers mass-produce many 1000's of engines in both configurations, the price of an opposite rotation engine is little different and is often the same. 120.145.70.130 (talk) 01:35, 23 September 2013 (UTC)

An interesting example of a twin-engined prop-driven aircraft is the Lockheed P-38 Lightning

Lockheed P-38 Lightning

The engines/propellers are counter-rotating, but the 'wrong' way. With the downgoing propeller blades on the outside, the P-factor makes both engines 'critical'. Apparently it was done like this as it made the aircraft a more stable gun platform. AndyTheGrump (talk) 01:53, 23 September 2013 (UTC)

I think you guys have misunderstood P-factor. P-Factor is the shift of the centre of thrust up or down according to the aircrafts' angle of attack wrt the airspeed. If (say) the aircraft is being rotated into a climb, the prop blades are cutting air slightly slower at the top of the rotation than they are at teh bottom of rotation - so the centre of thrust moves upward away from the prop centre line, increasing the climb. This effect is the same regardless of which engine is the one rotating clockwise. However, which way round the engines are installed still affects handling and performance, as one way the props pull air away from the fueselage and toward the wing tips above the wing, and the other way around they'll do it below the wing, amking for diffrent lift, drag, and climb/dive tendency. If the fuselage, wings, tail, and engines are completely symmetrical, there cannot be any turning or yaw effect, only an up/down or pitching effect. 120.145.70.130 (talk) 02:45, 23 September 2013 (UTC)

That is nonsense. See the FAA handbook linked below: "P-FACTOR — A tendency for an aircraft to yaw to the left due to the descending propeller blade on the right producing more thrust than the ascending blade on the left. This occurs when the aircraft’s longitudinal axis is in a climbing attitude in relation to the relative wind. The P-factor would be to the right if the aircraft had a counterclockwise rotating propeller". AndyTheGrump (talk) 03:22, 23 September 2013 (UTC)

Please explain then why an aircraft, symmetrical about its longitudinal centre, and having oppositely rotating engines symmetrically constructed and installed on the wings, can have an assymetrical effect on flying. If the right engine somehow causes a turning force to the right, then the left engine must cause the same turning force to the left, and the two will cancel. What doesn't cancel are the forces producing a climbing or diving effect. The tendency to yaw left or right occurs in single engine aircraft, or twin engine aircraft with both props rotating in the same direction. 120.145.70.130 (talk) 04:24, 23 September 2013 (UTC)

Obviously, if everything is symmetrical, there is no tendency to yaw - but that doesn't make your definition of p-factor right. P-factor is the movement of the centre of thrust relative to the centre of a propeller as a result of it meeting the incoming airflow at an angle. With two propellers rotating in opposite directions, the displacement of forces cancel out - but it is still there, and it has nothing whatsoever to do with propellers supposedly "cutting air slightly slower at the top of the rotation than they are at the bottom of rotation", which is what you were claiming. AndyTheGrump (talk) 04:46, 23 September 2013 (UTC)

Glad you agree it cancels - not what you implied before. Seeing that we agree that a symmetrical counter-rotating arrangment cancels P-forces out as far as uncommanded yaw is concerned, it would seem that your claim above that making the counter rotating props the "wrong" way round makes both engines critical is incorrect. Both engines will be critical in any case. Only with both props rotating the same (either normal or counter-normal) will one engine be critical. And that is as much, if not more, due to assymetric airflow arising from corkscrewing air than due to centre of thrust shift. Now, how would the prop blades (more correctly the propellor rotation plane) be meeting the airflow at an angle? Three possibilities: They have been installed wrong (not likelly), the pilot has not trimmed correctly (he won't last long then - too much fuel usage), or the pilot is making a yaw or pitch movement. 120.145.70.130 (talk) 05:45, 23 September 2013 (UTC)

This is a science reference desk. It is not a platform for uninformed speculation. A source has been provided which explains what aircraft designers mean by 'P-factor'. Your apparent inability to understand it does not give you license to redefine it as something else. And yes, when I wrote that both engines on the P-38 were 'critical', I was correct - in both cases, a single engine failure will result in P-factor shifting the centre of thrust outboard of the centre of the remaining engine at low speed/high angles of attack - which is what 'critical' means in this context. I suggest that before responding again, you actually read the reference material provided - or even read our article on P-factor, which states the same thing. AndyTheGrump (talk) 12:13, 23 September 2013 (UTC)

I haven't redefined anything. I have said more than once that P-factor/forces arise from the propellor centre of thrust moving away from the rotation centre. That's exactly what it is about. It can move sideways and, it seems unrealised by you Andy, that it can/will move up or down as well, if the aircraft is pitched. About the P-38, you wrote The engines/propellors are counter-rotating, but the 'wrong way'. With the downgoing propellor blades on the outside, the P-factor makes both engines critical. That's nonsense. It matters not whether the outside blades are going up or down, both engines are critical in either case, due to aircraft & engine symmetry. Perhaps you need to read the sources, and your own writings, before making incourteous remarks. Instead, if you think a posting is wrong, try and explain logically why it's wrong, rather than attack the person. In doing so you might find that you are wrong. If not, great, you've taught us something. 120.145.70.130 (talk) 16:05, 23 September 2013 (UTC)

P-factor! It's that difficult-to-explain, easy-to-feel tendency to swing (yaw) the airplane to the left, and it has been the death of many a novice pilot who jumped into a more powerful aircraft without adequate training! As expressed above, there are many other non-ideal effects of the propeller: slipstream, prop wash, drag, and so on. The Airplane Flying Handbook goes over all of these details, and the full text is available online from the FAA. Nimur (talk) 16:33, 22 September 2013 (UTC)

We have a very slim article called Torque effect which describes the issue in a single sentence. A better article is at Understanding Propeller Torque and P-Factor on FlightGear wiki - there are some links at the bottom of the page. Alansplodge (talk) 16:48, 22 September 2013 (UTC)

Another effect in single engine planes is the air movement over the tail can effect rudder and elevator/aileron which can change the feeling for T-tail vs. cruciform aircraft. Specifically airspeed of the airplance is more important for T-Tail while propeller rotation can generate more airflow for cruciform tails. Balked landings are where this difference is felt most (full power, landing speed at first). --DHeyward (talk) 18:52, 22 September 2013 (UTC)

Event horizon

I would have two questions about black holes: a photon that on event horizon is radially directed outward black hole would remain stuck at horizon or would fall to singularity (and if yes, in how much time?)? And, hypothetically, if I could surpass c (the speed of light) into a black hole I could escape or I howewer would fall to singularity because there aren't ways to escape? Thanks for answering, 80.181.57.86 (talk) 22:15, 22 September 2013 (UTC)

Sounds similar to above a few days ago. Was this a homework question? --DHeyward (talk) 00:27, 23 September 2013 (UTC)

No, this isn't a homework. It's just a curiosity. 95.247.219.235 (talk) 11:13, 23 September 2013 (UTC)

aren't all heaters perfect?

Isn't a hair drier just as perfect a source of heating as anything else that uses the same number of watts? I came across this answer,

http://answers.yahoo.com/question/index?qid=20110131212343AA1MZBy

But find this response insanely bizarre: "I think its in-effiecient. Hair dryer using filament as its heater. It converts elecrical energy to internal energy, thus transfered as heat. This process generates high entropy. So using heater with refrigeration system is more efficient. "

What can that possibly mean? It sounds completely crank. Other than possibly 'melting' from overuse, i.e. in the first few minutes isn't a hair drier just as perfect in an enclosed small room as anything else (including a computer or anything else) that uses the same number of watts? Thanks. 178.48.114.143 (talk) 22:37, 22 September 2013 (UTC) — Preceding unsigned comment added by 178.48.114.143 (talk)

If you concentrate on what proportion of the energy registered on a premises electric meter is changed into heat at the desired location by a hair drier, then the hair drier is very efficient. But an electric heat pump can use energy to move heat from outdoors to indoors, and the total amount of heat put into the desired location is greater than the energy used to operate the heat pump. Jc3s5h (talk) 23:59, 22 September 2013 (UTC)

True, but of the many direct non heatpump forms of electrical heating, they are all practically 100% efficient at turning electricity into heat. That's not to say they are all equally good at a particular task.Greglocock (talk) 00:28, 23 September 2013 (UTC)

Your body heating the hair naturally while evaporation cools it vs. trying to raise the temperature of your hair beyond body temperature to improve the rate. That creates sink points for the heat the hair dryer generates: the water in the hair and the body as well as loss in transfer to the water. Energy from your body is more efficient at transfer to the water in your hair as a net change in energy from having wet hair vs. not. How much more energy (i.e. calories) do you have to eat to dry your naturally? Since the body is inefficient to begin with basically the only energy difference is going directly to supporting evaporation. Time to dry is dependent on difference between body temperature, water mass and dew point. Everything increases entropy bet some are more efficient in net entropy increase vs. useful work done. You can do the calculation for energy to naturally dry hair estimating water volume, temperature difference between body and room temperature and dew point of ambient. Then calculate the amount of time your dryer is on to dry your hair. --DHeyward (talk) 01:36, 23 September 2013 (UTC)

I don't understand DHeyward's point at all. Nor do I understand the comparison with heat pump. My real question is simple: if there's no electric radiator in a small room, then isn't a hairdrier exactly strictly equivalent to an electric radiator drawing the same number of watts? (i.e. the ancillary action of blowing air around doesn't matter at all whatsoever). 178.48.114.143 (talk) 01:56, 23 September 2013 (UTC)

DHeywood's explanation is affected by poor english - and I don't see how it is relavent to your question either. However the comment about heat pumps is valid. If you you an electric bar radiator, electric hairdryer (which contains a heating element), using light glodes to heat, is all teh same - for every kilowatt of electric power consumed, exactly one kilowatt of heat is imparted to the inside of a closed room. However, heat pumps (reverse cycling airconditioners) work a different way. The electricity is used to run a mechanical process that moves heat energy from the outside of the room to the inside. Typically in domestic airconditioning, only about 400 watts of electric power is needed to move a kilowat of heat from outside the room to the inside. Thus in that sense a heat pump is more energy efficient than a hair dryer, because the heat energy does not come for the electricity supply, it comes from the air outside the room. 120.145.70.130 (talk) 02:30, 23 September 2013 (UTC)

I still don't get it - outside, it's even colder. What is there to 'pump'? The whole point of this question is that it's frikkin cold out. 178.48.114.143 (talk) 03:30, 23 September 2013 (UTC)

It only seems cold to humans, as they are accustomed to keeping themselves at a certain temperature. There's actually not much less heat outside than inside. Absolute zero temperature, 0 Kelvin or -273.15 K (or 0 Rankin or -459.67 F if you are non metric) is the notional temperature at which there is no heat residing in any substance. You may feel cold at 0 C (32 F), but at this temperature, the difference between feeling darn cold and nice and warm is the difference between 273 K and 300 K - not a lot in real terms. The heat in air at 0 C is not zero, it is the heat you have at 273 celcius degrees above absolute zero. 120.145.70.130 (talk) 04:13, 23 September 2013 (UTC)

Look up heat pump and coefficient of performance. IBE (talk) 04:21, 23 September 2013 (UTC)

I haven't done so but I suspect that is cruel advice. A heat pump is a device that can extract the heat energy from one place and pump it into another place, thereby heating the second place. It can do this even if the first place is cooler than the second. This is exactly how a fridge works. You could use it to heat your house using less electricity, that's what a reverse cycle air conditioner does.Greglocock (talk) 06:12, 23 September 2013 (UTC)

What? Judged as an electric heater, a fridge uses less electricity than a normal electric heater?? (To heat a room)? This is amazing news, and 2) in this case why aren't electric radiators mini fridges instead... 178.48.114.143 (talk) 07:41, 23 September 2013 (UTC)

GregLocock was just trying to get you to look at heat in the proper way - as something that can be moved from one place to another, irrespective of the temperatures. He's 100% correct in what he said, but using a fridge in this way is not practical, unless you regard continually loading it with warm things as convenient. Once the frige has moved the heat out of the food and into the room, there is no more it can do until you reload it. 120.145.70.130 (talk) 11:43, 23 September 2013 (UTC)

Viewed as a simple, idealized, thermodynamics problem, the room is (in effect) a system into which electricity flows and heat leaks back out. As you add electricity into the room, the energy content of the room will rise until the energy entering as electricity equals the energy leaving as heat leaving the room. That description is true no matter how you use the electricity. However, energy can be stored inside the room in ways other than as heat. So, for example, you might have a bizarre machine in the room that lifts heavy weights from the floor and hangs them from the ceiling. It would consume electricity and convert it into gravitational potential energy without increasing the temperature of the room. So it's not true that all devices are equally efficient at producing heat from electricity.

The hair dryer starts air moving - giving it kinetic energy without increasing the temperature in the room. But it's likely that over time, those air currents will break up into eddies and eventually friction will convert all of that kinetic energy into heat. So EVENTUALLY, the hair dryer will have converted 100% of the electricity it consumes into heat and could therefore be considered a 100% efficient heater. In general, that will be true of most consumers of electricity...but not all of them. Consider a battery charger. It takes in electricity and uses some of it to effect a chemical change in the battery. Unless you go on to discharge the battery somewhere inside the room, it isn't a 100% efficient heater.

Of course most of these kinds of thing have a finite limit to the amount of energy they can "hide" in the form of chemical change, kinetic, gravitational, etc. If you leave the battery charger plugged in after the battery is 100% charged, then it'll either reduce the amount of electricity it consumes to zero - or it'll start to get warm...and at that point, it too is an 100% efficient heater.

A refrigerator also moves energy within the room from one form to another - and for a brief period between when you plug it in and when the inside is as cold as it can be, the refrigerator will appear to generate more heat than the electricity you pump into it...but once the insides are at the preset temperature, it'll return to being merely 100% efficient.

However, there is a "real-world gotcha". Sound and electromagnetic radiation can leave the room as well as heat. So if your hairdrier makes a noise (which I'm sure it must because it's moving air around) - then some of that sound will leave the room (eg by vibrating the windows) - and that vibration won't turn into heat until AFTER it leaves the room - and since the sound took electrical energy to make - that loss of sound energy will mean that not quite ALL of the electrical energy will turn to heat. Similarly, it's likely that the motor and any electronics inside will produce some small amount of radio frequency emissions - some of which will leak out of the room before turning to heat. Light from the red-hot heating element will somewhat light up the room - and some of that light will escape through windows and under the doors...so again, it's not 100% efficient.

To be sure, the losses incurred by the hair dryer because of those things will be very tiny - but it's enough to ensure that no machine is every going to be exactly 100% efficient - although most will be very close.

The bottom line is that you can't make a perpetual motion machine this way - the energy sum has to stay the same within the room - and no practical machine will be a 100% efficient heater. That said, almost every machine you have is very close to being 100% efficient - and there is probably very little to choose between a space heater, a refrigerator and a TV set at converting electricity into heat. SteveBaker (talk) 14:02, 23 September 2013 (UTC)

Air conditioning units are routinely reversed to warm homes during winter with typical coefficient of performance above 500%, so yes, the good electric heaters are mini fridges. Electric space heaters are designed to be cheap and safe to use, but they are never gonna be a cost effective way to warm a home. Dauto (talk) 14:20, 23 September 2013 (UTC)

Yes, heat pumps (reverse air-conditioners) are really popular here in Texas. They are able to either cool the house in summer or heat it in winter. When in "heat" mode, they are effectively air-conditioning the outside world and dumping the waste heat into the house. Since that waste heat contains both heat extracted from the outside and the waste from it's own internal operation, they are more than 100% efficient in terms of the heat they deliver to the house. Of course overall, they are also chilling the already cold outside world - so overall, they don't produce more heat than they generate. I'm surprised to hear that they can be as much as 500% efficient - but they are certainly very good in situations where you need an airconditioner for summer use anyway. SteveBaker (talk) 14:44, 23 September 2013 (UTC)

The 500% coefficient of performance can only be achieved for mild winter conditions. For instance, here where I live (Central Florida) the low temperature is rarely below freezing. The colder the outdoors the smaller the coefficient of performance will be. a 300% coefficient is more typical for most of the south unless you use ground source heat pump because the underground water remains quite warm even during bitter cold nights. Further north the coefficient becomes too small and heat pumps aren't a wise choice any more. You will do better if you burn fuel locally (Natural gas or heating oil) instead of burning it at a power plant with a typical efficiency of about 40% and than using that electricity to warm the home. Dauto (talk) 15:10, 23 September 2013 (UTC)

September 23

Biology - Genus: Hepatocystis - conflict - Who described it?

Article Hepatocystis mentioned 'Miller 1908' was the first to describe the genus. According to Taxonomicon the genus Hepatozoon was described by Miller 1908, not Hepatocystis. Unfortunately I can't verify the information in Taxonomicon from a second source. Who could verify it and - if necessary - edit the article? -- from de.wikipedia.org Temdor (talk) 00:33, 23 September 2013 (UTC)

What does the letter V of ECG stand for?

In ECG there is 12 leads, every one of them called V. In example V1 and V2 and V3 and so on... so, what does the letter V stand for? Thank you 95.35.220.182 (talk) 08:43, 23 September 2013 (UTC)

I always assumed it was for "Voltage" as these are points at which electric potential difference (voltage) is measured. This is just an assumption though. -- Q Chris (talk) 08:57, 23 September 2013 (UTC)

The 6 "V" leads are the precordial or "chest leads" (the other leads go on the arms or legs), and they get numbered from 1 to 6 as they are placed across the chest from right to left. I'm not certain why the chest leads are designated with "V", but perhaps it's from "ventrum", the Latin for chest. Actually, the "V" does stand for voltage: The use of chest leads was first described in 1932: Wolferth CC, Wood FC. The electrocardiographic diagnosis of coronary occlusion by the use of chest leads. Am J Med Sci 1932;183:30-35, and the positions were standardized in 1938: Barnes AR, Pardee HEB, White PD. et al. Standardization of precordial leads. Am Heart J 1938;15:235-239. It's in this latter paper that we can find that the "V" stands for voltage. - Nunh-huh 09:45, 23 September 2013 (UTC)

Thank you a lot for the help! 95.35.220.182 (talk) 10:45, 23 September 2013 (UTC)

article of CC

I'm looking for the article for the question what does the letters CC of measurement stand for? I mean about 1CC of medicine for example. 95.35.220.182 (talk) 11:34, 23 September 2013 (UTC)

cubic centimeter. -- Staecker (talk) 11:37, 23 September 2013 (UTC)

Yes, and it is equivalent to 1 ml. 1 table spoon is roughly 14.8 cc. Dauto (talk) 13:52, 23 September 2013 (UTC)

Garden Spider doing a spot of trawling?

So i'm in Britain and i've got some Zantedeschia aethiopica (Calla Lillies) sitting outside in a pot inside a washing up bowl. This washing up bowl has a few inches of water in and has many what i assume to be Mosquito larvae swimming round the water inside.

I have noticed that there is what i believe to be a rather large European Garden spider sitting on the water with its mouth submerged (and mouth-pincers(?) moving) and it seems to be slowly moving around the bowl.

What i'm wondering is, is it hunting and also is this usual behaviour? I've also noticed a small clump of soil attached to one of its rear legs and was wondering if it is possible for it to use its web to trawl like a fishing vessel?

I've considered the possibility that it is stuck but it seems to be rather happy on the water surface tension and looks large enough to pull itself out. (Cesdeva (talk) 12:04, 23 September 2013 (UTC))

Depends on the size of the spider, but Raft spiders are semi-aquatic and may exhibit such behaviour. (I don't want to look...) --TammyMoet (talk) 13:32, 23 September 2013 (UTC)

I think you're right. After re-observing, the Spider does look more like it resembles those species within Dolomedes. Now to find out which one... (Cesdeva (talk) 13:53, 23 September 2013 (UTC))

Dehumidifiers >100% efficient have a COP > 1 as heaters.

I read on a forum comment that dehumidifiers have a secondary effect of warming the room, and the amount of heat added to the air is more than 100% of the energy consumed (COP > 1). The reason given was that the latent energy from the water vapour is also emitted into the room. The system was likened to a giant heat pump where the dehumidifier takes the place of the compression side and the sun on the oceans as the evaporator?

Is this correct? If so what percentage extra heating would you get, is it significant or marginal? -- Q Chris (talk) 12:08, 23 September 2013 (UTC)

Note as our article mentions (Heat pump#Efficiency), the word 'efficiency' is generally avoided when talking about such things as efficiency is generally taken to a have a specific thermodynamic definition, instead the Coefficient of performance is normally discussed. Nil Einne (talk) 13:04, 23 September 2013 (UTC)

Noted, I have corrected the question -- Q Chris (talk) 13:31, 23 September 2013 (UTC)

It will generate more heat than the electricity it consumes (by a very tiny amount) only until the room is as dry as it can make it be. At that point, it'll be no more than 100% efficient. You might argue that you can put some water in the room to evaporate and replenish the humidity - but that evaporation would cool the room by exactly as much as the humidifier is more than 100% efficient...so the net benefit in terms of heating drops to zero. SteveBaker (talk) 14:15, 23 September 2013 (UTC)

• At a practical level, the most common way of dehumidifying air is to use an air conditioner, which causes water vapor to condense on the chilling elements. Air conditioners obviously don't warm a room -- rather the dehumidifying effect shows up as a reduction in cooling efficacy. Looie496 (talk) 14:37, 23 September 2013 (UTC)

  But they do heat the outside. If you kept the condenser of the AC unit inside the room with you, and then just drained the water outside, you'd have a dehumidifier that heated the room rather than cooled it. --Jayron32 14:47, 23 September 2013 (UTC)

Microwave attacks?

When I was at grammar school in the '60', there was a girl in my class with a birth deformity, which impaired her walking. She was the daughter of diplomats who had been located in Moscow, prior to her birth. There was talk at the time that the Russians were bombarding diplomatic staff with microwaves. Was this ever proved, and have there been instances since of people being damaged by microwave or other forms of electromagnetic or focused radiation? — Preceding unsigned comment added by 31.25.4.14 (talk) 13:20, 23 September 2013 (UTC)

People have certainly been killed accidentally by microwaves, but it's unlikely that they would cause birth defects. Generally speaking it takes ionizing radiation to do that -- microwave photons don't have enough energy to break apart a DNA molecule. Looie496 (talk) 14:32, 23 September 2013 (UTC)

Articles such as this one suggest that the microwave bombardment of the embassy building was done from the late 1950's all the way into the early 1970's. The girl you knew must have been between 11 years old and 17 years (because she was "at grammar school") and you say it was "in the 1960's" - which means that she was conceived sometime between 1943 (17 years old in 1960) and 1958 (11 years old in 1969). We know (eg from this) that the radiation started around 1956 or 57. So if you knew her in your first year at grammar school and it was the late 1960's - then it's just about numerically possible that she was irradiated before birth. Mostly, that seems to have caused cancers in the embassy staff at some unreasonably high rates. The daughter of Franz Misch (who was born in 1968) seems to have suffered mental defects - which might be attributable to the microwave bombardment - and if it was indeed the cause of that - then other deformities are certainly possible.

It would help to know what year you were born (because this girl was in your class - and therefore, presumably, within a year or so of your age) - that would tell us whether she was conceived before all of the microwave business started - which would efficiently disprove your theory.

Obviously there is no possible way to prove it. Children are born with deformities all the time - and microwave bombardment isn't often the cause - so even if she was there during the worst of the attacks, the microwaves might still have had no effect on her.

SteveBaker (talk) 14:35, 23 September 2013 (UTC)

Hmmmm - further down this article, it says: "It turned out that the Soviets had been bombarding us with microwaves, beginning in about 1964 or 1965." - which would totally bust this theory since the girl would have had to be at least 5 years old when the attack started. However, the first reference I found said: "Two retired US Secret service agents who accompanied then Vice-President Richard Nixon to Moscow in 1959 said in 1976 that the embassy was bombarded with such heavy radiation that one radiation detection device was damaged". That report seems a bit suspect to me - I mean, what kind of radiation detector would be damaged in that way? Also, if they had detectors installed in 1959, then you'd presume that the bombardment must have gone on for a while before the attack was noticed and the detectors had to be installed. Then this says that "Washington had known what was going on since the 1960's" - which doesn't fit with a destroyed radiation detector in 1959. Then this says that "US officials noticed that the Soviets had begun directing microwaves at the embassy in 1962, perhaps starting as early as 1953"...so that also confirms that the radiation detector couldn't have been destroyed in 1959 - but throws this new curve ball in by saying it might have started MUCH earlier.

So I guess the start date is a bit "fuzzy". SteveBaker (talk) 15:00, 23 September 2013 (UTC)

And more...this suggests that the microwave bombardment was actually a kind of power source for their system of hidden microphones in the embassy...interesting! SteveBaker (talk) 15:22, 23 September 2013 (UTC)

• Who'da thunk the Soviets were such evil bastards? In any case, Looie496's got it right. Microwaves cause heating, not mutations. The Soviets might as well have been pricking voodoo dolls. μηδείς (talk) 15:36, 23 September 2013 (UTC)

In 1971 the Australian magazine Electronics Today published a full technical explanation, with diagrams and a photo, of the Soviet seal microwave eavsdropping system. Based on the operating principle (passive detection & re-radistion) and the distances involved, only around a few watts from the microwave source are required. Nobody would be hurt by that. 120.145.70.130 (talk) 15:43, 23 September 2013 (UTC)

Surgical treatments for Tibialis (Anterior) Tendinitis?

How could Surgery help to solve such a problem? interesting, Thanks. Ben-Natan (talk) 16:34, 23 September 2013 (UTC)