Wikipedia:Reference desk/Archives/Science/2010 May 2

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May 2

Moth Help

I live in Boston, MA---my apartment is flooded with these tiny little moth type creatures.

They're incredibly easy to kill, but their numbers are becoming worrisome!

Is there a common moth that infests in this time of year, or mayhap a well known reason to be surrounded by them? We don't leave out food!209.6.54.248 (talk) 00:40, 2 May 2010 (UTC)

You may want to check your pantry, if you have one. If they are flour moths, you don't have to leave food out to have a problem. Looie496 (talk) 01:35, 2 May 2010 (UTC)

(edit conflict) Are you sure they are moths? I haven't known moths to swarm like that. Having grown up outside of Boston, swarming insects include mosquitos, gnats, and mayflys. The only one of those that may be confused for tiny moths may be mayflys. Do you live near a swampy area or wetlands like the Back Bay Fens or something like that? --Jayron32 01:40, 2 May 2010 (UTC)

Moths don't usually accumulate for food. Light is the more usual source. At university accomodation we have lots of them about where light is abundant. Regards, --—Cyclonenim | Chat  02:54, 2 May 2010 (UTC)

Make sure they aren't eating your clothes. If so, wash any clothes they've started on, with bleach. Then store them in an air-proof container (those Space Bags are a good choice). I had a problem with moths and found tiny brown worms (their larval stage) at the top my walls, adjacent to the ceiling. I went around the whole house and killed any that I found there, and they went away. StuRat (talk) 10:55, 2 May 2010 (UTC)

When I lived in an apartment, pest control was the landlord's responsibility. You might want to talk to your building superintendent or whatever that job is called these days. --Anonymous, 20:23 UTC, May 2, 2010.

Re-engineering the universe for increasing computational capacity

In "Computational capacity of the universe" (Phys Rev Lett 88 (23):237901), Seth Lloyd estimates the storage and cumulative data-processing capacity of the universe to be proportional to ρc⁵t⁴/ħ, where t is the age of the universe, ρ is its density, c is the speed of light and ħ is the reduced Planck constant.

From Moore's law#Other formulations and similar laws, I gather that human needs for data processing and storage are increasing exponentially, which means that eventually they'll outpace the polynomial growth that Lloyd's formula implies. This means that if our needs for computation are to be satisfied, the universe will eventually have to be re-engineered to accommodate them; and if that's to be done in a way that keeps the equation valid, either ρ or c has to start growing exponentially, or else ħ has to start decaying exponentially. (NB: I'm extrapolating to its logical conclusion the general observation that when reality and human needs come into conflict, it's reality that gets changed, at increasingly fundamental levels.) Has it been studied which constant would be best to manipulate, assuming equally straightforward ways are someday found to manipulate all of them? (I'd tend to favour c, given that it would have the side effects of lowering communication latency and extending the raange of interstellar travel, but I'm probably not aware of all the considerations.) NeonMerlin 03:35, 2 May 2010 (UTC)

You're not going to manipulate any of these constants; first of all there is no need given the size of the numbers involved. Humans are in no danger of exceeding the computational capacity of the universe, however defined, for any timescale measured in units smaller than billions of years. Secondly, your statement "when reality and human needs come into conflict, it's reality that gets changed, at increasingly fundamental levels" is patently rediculous. Fundemental physical constants, like the speed of light or planck's constant, can't be manipulated to magically "create" new computational capacity. Its just silliness. --Jayron32 03:51, 2 May 2010 (UTC)

I think he's trying to say that as scientists run out of technology to explain the universe they will almost be forced to make up elaborate stories to perpetuate their point of no return theories that constantly alter previous realities to compensate for the lack of human knowledge. —Preceding unsigned comment added by 98.221.254.154 (talk) 04:19, 2 May 2010 (UTC)

C is in that equation because of it's connection to energy. The amount of calculation a particle can do is related to it's energy, and the energy of a particle is related to c. The implication of this is that to change c you are also changing the energy content of every particle in the entire universe - and where would you get such energy? Ariel. (talk) 04:19, 2 May 2010 (UTC)

I don't buy this anyway - forget about the underlying technology and think only about speed-of-light issues.

What use is computational power if it's situated in the next solar system? A computer has to shuffle data around - and if it takes 4 years to ask for a number from Alpha Centauri and four more years to get the answer back, that's going to be a pretty spectacularly slow machine. In any computation, there is a trade-off between storing something for later use - and recalculating it when needed. As the size of the machine grows, the balance tilts towards recalculating rather than storing. So as your computer grows to the size of a planet (which, in effect, is what the Internet has become), you get a 'law of diminishing returns' where you have to cache information locally rather than reaching out across the network to get it. The bigger computer can store much more information - but it becomes so slow to fetch it that you have to store it locally.

When you think about a computer that's distributed between (say) here and Neptune - the round-trip time to ask for and get back some information is around 8 hours. So the result of any calculation that takes less than 8 hours is better computed locally than being distributed over the larger computer. We might want to use the storage system on neptune (for example) for storing all of the DNA sequences of long-dead people - on the grounds that we seldom need that within 8 hours of asking for it...but if Wikipedia were stored 8 hours away - it would be useless to us.

Now consider storage on Alpha Centauri. At 8 years access time, we can't even store the results of major research programs over there. If we stored the DNA sequence of some obscure plant over on that part of the system - then it would be simpler to re-sequence the DNA of the plant than it would be to fetch it from way over there. If we stored the design for an airplane over on Alpha Centauri, it would be faster to redesign it from scratch than it would be to fetch the old design from storage in memory outside of our solar system!

When you get to the scale of a galaxy - the round-trip time exceeds the duration of an entire civilisation. It's hard to envisage a question that a human might ask where the answer could still be useful to us when it gets here 100,000 years later. There would be no point in storing things in memory on the other side of the galaxy since there would be no way for any future member of your civilisation to get it back again!

When you get to the size of the universe, you have many more problems. You ask the question of a far distant galaxy - and by the time the answer gets back, we've evolved into a different species - or the sun has exploded and we've all moved someplace else. What possible storage or computational needs could we possibly have where the answer could be useful so much later? Why store something that your species could never possibly retrieve again in the future?

While we might want something with more power than we can reasonably fit into a few planets - we simply can't have that. Our present exponential growth of computing needs will ultimately be cut short. However, the amount of growth we have left with nanotech computers, quantum computers and biological computers leaves us an immense amount of headroom before we really start to hit these limits. Humans run into these kinds of resource limitations all the time...and ultimately, we cannot grow forever.

SteveBaker (talk) 14:01, 2 May 2010 (UTC)

I guess you make another point in favour of raising c, as soon as a way is found to do it. NeonMerlin 15:52, 2 May 2010 (UTC)

You can't just arbitrarily alter the value of c. By what means would you go about changing the way the Universe works? What part of the word "constant" escapes your understanding! --Jayron32 00:48, 3 May 2010 (UTC)

Indeed. E=m.c². So if you change 'c' you've either got to find enough energy from somewhere to keep the mass of the universe the same - or if you're stuck with a finite amount of energy - then the mass of everything in the universe would decrease as the square of the change in 'c'. So if, for example, you decided to increase 'c' so that you could get to Alpha Centauri in a few months, you'd need to increase 'c' by (let's say) a factor of 10. That would decrease the mass of everything in the universe by a factor of 100 - which would instantly cause all of the stars to explode because they wouldn't have enough gravity to withstand the radiation pressure. You can't just tinker with fundamental constants without causing major upsets. Changing 'c' is premium-quality craziness! SteveBaker (talk) 13:46, 3 May 2010 (UTC)

NeonMerlin, you should ignore Seth Lloyd; he's silly. And when you see growth that looks exponential, you should fit a logistic curve to it, not an exponential curve. -- BenRG (talk) 17:39, 2 May 2010 (UTC)

Aztec knives

What are these Aztec knives made of? Flint? --The High Fin Sperm Whale 04:58, 2 May 2010 (UTC)

The image description says that they're made of flint. Is there some reason you don't believe this? Dismas|^(talk) 05:07, 2 May 2010 (UTC)

This site [1] has one made of chalcedony from the Ethnologisches Museum (berlin). The light coloured ones in the picture in question (rhs) to me look like quartz, but it may simply be the light shining off them. --220.101.28.25 (talk) 05:26, 2 May 2010 (UTC)

Sorry, I missed the image description. However, there is such thing as lightly-coloured flint (see this). --The High Fin Sperm Whale 20:14, 2 May 2010 (UTC)

Quartz is very difficult to knap due to its prominent grains. Quartzite is sometimes used, but even that makes for a very rough finished product. When I first saw the question, I assumed they were going to be obsidian, which the Aztecs put to good use in making weapons, but these are indeed flint or chert. Matt Deres (talk) 23:35, 2 May 2010 (UTC)

Another spider question

How many spiders does one eat while sleeping during the course of one's life? Alaphent (talk) 09:41, 2 May 2010 (UTC)

A quick Google search suggests as little as 4 but as many as 7-8. Although this page suggests the whole thing is a load of rubbish. Dismas|^(talk) 09:54, 2 May 2010 (UTC)

"For a sleeping person to swallow even one live spider would involve so many highly unlikely circumstances that for practical purposes we can rule out the possibility. No such case is on formal record anywhere in scientific or medical literature," says a spider expert at the Burke Museum: http://www.washington.edu/burkemuseum/spidermyth/myths/whileyousleep.html Rimush (talk) 10:31, 2 May 2010 (UTC)

One such case is in a Post mortem report (video): Misadventurous ingestion of Musca domestica by geriatric female was initially treated by a chelicerate arthropod taken orally, with consequent evolution of treatments until equine injestion and consequent termination. Cuddlyable3 (talk) 15:21, 2 May 2010 (UTC)

I woke up once when a spider lowered itself onto my cheek, which was a close call. StuRat (talk) 10:45, 2 May 2010 (UTC)

The Straight Dope : Does the average person consume four spiders per year in his sleep?. This article discusses it a bit. In it, he explains why the chances of swallowing a spider during your sleep is virtually zero, except in the case where an egg-sac hatches nearby. In that case you might inhale a few new-born spiders. But new-born spiders are so tiny that you wouldn't even notice if you were awake. APL (talk) 16:12, 3 May 2010 (UTC)

Stupid insects and spiders

I've had numerous times when an insect or spider walked right up to me, or even on me, and then I promptly killed it. Can't they see me ? Don't they have an instinct to avoid animals a million times their size ? StuRat (talk) 10:45, 2 May 2010 (UTC)

We're so massively beyond their scale and world-view that I doubt that they (the ones that don't seem to react to our movements, that is - it may be different for the ones that feed upon us) even see us as lifeforms, nor possess the intelligence to see us as such. --Kurt Shaped Box (talk) 12:26, 2 May 2010 (UTC)

Isn't there a story in the Odyssey or Sinbad the Sailor of a ship's crew landing on the back of a floating turtle and thinking it's an island? If a human sailor, albeit mythical, with some 100 billion neurons in his brain, can conceivably make this mistake with a turtle a few hundred times his size, I can't see a spider, with a brain of a mere 100 thousand, could make such a distinction when walking on a human a few hundred thousand times its size. Tonywalton ^Talk 00:07, 3 May 2010 (UTC)

StuRat, what is your opinion of this? Count Iblis (talk) 14:28, 2 May 2010 (UTC)

(Baker's law of website design: Large fonts, too many colors strange placement of text on page == Nut-job - you don't actually have to read the text to know this with 95% certainty) SteveBaker (talk) 14:41, 2 May 2010 (UTC)

And actually, this is no place to discuss people's opinions of such things. This is a Reference Desk. --Mr.98 (talk) 20:01, 2 May 2010 (UTC)

I think being concerned with the lives or deaths of insects and spiders is silliness, except when they are helpful to us. I also find myself saving the lives of pretty insects, like butterflies and ladybugs (ladybirds), but most creepy crawlies can join each other in the tread pattern on my shoes. I was upset to find that a magnificent praying mantis, living at the entrance to my work, was killed. StuRat (talk) 18:20, 4 May 2010 (UTC)

A spiders' brain is a very tiny thing indeed. They don't have a lot of space to store all of the kinds of behaviors that might turn out to be useful. The have to prioritize. Web building - yep, that's necessary. Mating behavior - yep. Feeding - yep. Avoiding being eaten by a bird - maybe. But the probability of an individual spider being killed by a large animal is so amazingly small that the evolutionary benefit to carrying that around doesn't make it worth-while to do so. Spiders who somehow gained that ability would have to expend more energy to support the growth & maintenance of that larger brain - and (evidently) that extra 'cost' would exceed the statistical benefit. It's worth remembering that the spider couldn't "learn" this human-avoidance behavior - because the first failure means death. It also can't be taught the behavior from it's parent because spiders lack language and they don't hang out with their parents for very long. So this would have to be an 'instinctive' behavior...and that means that it has to be contained in the spider's DNA. So we're not only talking the cost of having a brain big enough - but also the cost for every cell in the spider's body of storing the "instinct".

Worse still, how many large animals actually go out of their way to kill spiders? Cows don't, sheep don't. I bet most large animals don't. That means that many species of spider didn't evolve with large spider-killing animals around them. Humans spread across the planet very rapidly in evolutionary terms - and many species are still playing catch-up. Even large, smart animals haven't evolved the necessary fear of humans. A large bear that might attack a human hasn't evolved to realise that we carry guns - or that if you do kill one of us, a posse of humans will come along the next day and hunt you down - or that if bears in general pose a problem for humans in general, we're going to round you all up and relocate you somewhere you don't want to be. Bears aren't stupid - they simply haven't had time to evolve to cope with the rapid pace of change on the planet.

A bigger question is why are you (an otherwise intelligent human) indiscriminantly killing spiders? All but a few species are harmless to us - and help keep the population of other insects (like flies and wasps) to a minimum. Flies and wasps are harmful to humans (flies spread diseases and wasps sting us). So we should perhaps ask instead: "How come large, super-smart animals like StuRat don't have an instinct to carefully avoid killing beneficial spiders?"

SteveBaker (talk) 14:39, 2 May 2010 (UTC)

That would be because, even if there's only a small risk of a spider bite, this risk isn't worth the even smaller benefit. Also, waking up with a spider crawling on you is just as unpleasant as an insect. StuRat (talk) 14:56, 2 May 2010 (UTC)

However here in the UK there are no harmful spiders at all, yet people still squash them, Perhaps people just don't like spiders. Tonywalton ^Talk 00:07, 3 May 2010 (UTC)

Some sources state that the factoid about eating spiders in your sleep is a myth, but while awake people eat more spiders and insects in food (example). As for killing spiders, there's a Russian superstition that killing 40 spiders brings a person good luck, and on the other hand some people eat fried spiders. ~AH1^(TCU) 23:47, 2 May 2010 (UTC)

@ StuRat so you don't ever do things with a small risk like driving, or crossing the road? These activities are way more risky than an encounter with a wee spider in the UK. Why not just say they frighten you because you've never taken the time to understand them. There must be a law somewhere that states that fear is directly proportional to the individual's ignorance of the feared object. Caesar's Daddy (talk) 07:57, 3 May 2010 (UTC)

I suppose you could call it ignorance, in that not knowing which spiders are harmful, we tend to just kill them all to be safe. As for driving, there's a huge benefit to driving, like allowing me to hold a job, while there's no such huge benefit to tolerating spiders on me. StuRat (talk) 13:48, 3 May 2010 (UTC)

Well, there are no harmful spiders in the UK - so if that's where you live, you can stop killing them without any additional risk. There is some benefit to tolerating them - so on balance, that's the rational thing to do. The main problem for the spiders, however, is not the rational - it's the irrational. Of course, here in Texas...not so much. We have quite a few nasty little buggers who certainly need to be squished on sight if found in your home. I've had one hand swell to twice it's normal size following a spider bite...it's no fun! But still, it doesn't take buy 10 minutes to dig out a list of venomous spiders and learn to recognize them. Brown Recluse and Black Widows get squished without a fair trial - but even so, some - like the pink-kneed tarantulas are quite magnificent animals and get treated to a half mile car trip in nice cosy box to someplace I can safely release them. SteveBaker (talk) 20:04, 3 May 2010 (UTC)

Steve, don't you know I'm from Detroit, by now ? Was that injury from a spider you were trying to save ? StuRat (talk) 18:25, 4 May 2010 (UTC)

Then, of course there is Cochineal - which is an insect from which red food coloring is made. Take a look at all the foods containing "E120" - 70,000 crushed insects per pound of coloring. SteveBaker (talk) 13:41, 3 May 2010 (UTC)

Burning fat without burning muscle

Hi. I've been working hard in the gym over the last few months, and I have developed quite big arms and chest muscles. Now, I would like to burn some fat which has accumulated in my belly in order to start developing a six-pack. Which kind of exercise is best to burn fat, without burning any of my hard-earned muscles? Is aerobic or anaerobic exercise better? Should I eat before the exercise, or not (so that the body burns fat faster)?

Thanks a lot! --81.44.96.96 (talk) 09:45, 2 May 2010 (UTC)

Keep excercising but eat less calories. 89.242.97.110 (talk) 11:11, 2 May 2010 (UTC)

Fewer calories is one thing, but the source of those calories is also important. For example, you wouldn't want to cut protein, as that's needed to maintain those muscles. StuRat (talk) 12:20, 2 May 2010 (UTC)

Western eat far more protein than they need anyway. 89.242.97.110 (talk) 12:26, 2 May 2010 (UTC)

On average, yes, but we still get many people on crazy diets who don't get enough. StuRat (talk) 13:09, 2 May 2010 (UTC)

The reverse is more likely. Excessive protein is bad for you, see Protein (nutrient) 89.242.97.110 (talk) 20:44, 2 May 2010 (UTC)

(ec) No, that ("Keep excercising but eat less calories") is not the answer. The answer is, be absolutely certain to eat 0.7-0.8 grams of protein per pound that you weigh to keep your muscle. For example, if you weigh 180 pounds, then 180 * 0.8 = 144 grams of protein. That's a lot! It's equivalent to the protein from 28 egg whites per day (ie two and a half cartons of eggs). Or a steak like this. If you eat less than that while continuing to exercise, you will lose muscle, period. (Of course, the easiest way to get your protein intake may be a protein powder). Now as for losing FAT while you exercise and retain MUSCLE, yes, it is true that if you eat fewer calories you will lose weight, but that is not the right way to lose weight while keeping muscle, as your body will realize you're only getting, say, 900 calories, and you will just lose fat and muscle and everything. The correct thing to do is to keep a normal intake, say 2500 calories, including, crucially the amount of protein that I listed (150 grams, say, if you weigh 180 pounds), absolutely continue to do weight training (if you don't use your muscles, they will disappear), do this weight training, say, every 3-4 days. Then, every day, get on the elliptical machine, and use it until it shows that you have expended 3500 calories. The elliptical machine, on a fair resistance setting, is a monster at burning calories. Now, you might not FEEL like you've just burned more calories than your whole daily intake (2500) but you did: the machine does not lie, as calories are a measure of physical work (ie a physics concept) and if you've done that physical work (moved resistance) by definition you have burned those calories.

So, that is where the fat-burning comes in. Now you must keep very strictly to a 2500 calorie diet, and every day burn 3500 on the elliptical machine on a fair resistance level. At that rate, you will lose 1000 calories per day. 1 pound of fat is 3500 calories, so every three and a half days you will lose a pound of pure fat. If you continue doing this, while not stopping with either the weight training, the proper amount of protein, and the 2500 calories of real good food, you can have a real six-pack, totally toned and defined everything, etc. I have personally developed a six-pack using the above methodology and can attest to it. Hope this helps. 84.153.248.35 (talk) 12:31, 2 May 2010 (UTC)

Even for a body-builder, I don't think your protein requirements would be as high as that. Exessive protein is just used as calories. Do you have any quality independant scientific sources for the above please? I imagine the sellers of high-protein supplements are going to try to convince you that you need a lot of it. 89.242.97.110 (talk) 13:03, 2 May 2010 (UTC)

Please refer to this [2] Science Desk question regarding protein intake and "strength training", from ≈4 days ago. It has references that look "quality independant scientific". (I must admit that I answered this question!). 89.242.97.110 is quite right to ask for references, they should always be provided. Ref.Weight_lifting_and_training
♥ Recommended 'normal protein' RDA (Recommended Dietary Allowance) is 0.8 grams per kilogram of lean bodyweight (1 kilogram=2.2 pounds) ie. Higher than what you thought was a high figure! exactly the same as I provided - see below.
♥ For muscle building an intake of 1.6-2.2 grams per kilogram of bodyweight is recommended.
Aerobic exercise would be best for 'fat burning' as it can be carried on far longer than anaerobic exercise. Short, high intensity exercise is not as good at calorie burning as moderate 'long term' exercise. See also Weight Loss/Dieting--220.101.28.25 (talk) 13:38, 2 May 2010 (UTC)

Particularly see the "Fat loss versus muscle loss" Section--220.101.28.25 (talk) 13:46, 2 May 2010 (UTC)

hey, we're saying the exact same thing! You just said "For muscle building an intake of 1.6-2.2 grams per kilogram of bodyweight is recommended" and your figure of 1.6 grams per kilogram is exactly the same 0.72 grams per pound that I listed!! So my number is the same as your number, 1.6 (in per kg). Now, your range goes higher, it goes up to 2.2. grams per kilogram you weigh. That is 0.99g per pound that you weigh. Even while you are trying to really body-build and gain muscle mass, I think that is just a teeny bit too much. You won't have any use of the extra amount over 0.8 grams per pound you weigh. But the low end of your range is 0.72, just like I said (0.7-0.8), and the high end of your range, 0.99, is just a little bit over what I said. So basically we are in total agreement. The original poster can go ahead and "play it safe" and take 0.99g per pound he weighs daily, or he can follow my advice and take 0.7g-0.8g per pound that he weighs. But we both agree that any more than that and he will not benefit, and any more than that and he will lose protein. 84.153.248.35 (talk) 14:23, 2 May 2010 (UTC)

Burning 3500 kcal on the elliptical each day is absolutely insane. That would take about 5.5 hours at normal resistance. And advising our OP to sustain a deficit of 1000 kcal a day without first talking to a doctor is NOT appropriate. This is why we have the no-professional-advice rule. Btw, the RDA for protein is (as 220 says) 0.8g per kg of lean body mass. Also, a lot of the energy your body burns is through normal metabolism - see Basal metabolic rate. Zain Ebrahim (talk) 14:59, 2 May 2010 (UTC)

To the OP: to get a handle on what 84 is talking about I recommend you read Basal metabolic rate and the article on Harris-Benedict equation might also be interesting. As for your question, I suggest talking to the personal trainers at your gym. Zain Ebrahim (talk) 15:06, 2 May 2010 (UTC)

← ← @84 No real need to whisper! ;-) I think here I have seen 0.8 gm and read it as per Kg not per pound. Perhaps not a good idea to mix 'imperial' and 'Metric' quantities ie 0.8 grams per pound is not as 'scientific' as we should try to be. I was actually answering 89.242.97.110s' comment that they thought the protein requirement was too high. So yes we are basically in agreement, with the references!. Throw a few conversions in here, 800 grams (1.8 lb), 1,600 to 2,200 grams (3.5 to 4.9 lb), the upper figure does seem high! But, everyones metabolism is different. Arnie Schwarzenegger could probably, once, have done that easily. And if it's not 'used' it will just be er, 'excreted'. Wasteful.

I was mainly trying to provide references, very important here. Doesn't matter what you know/believe to be true, must be wp:verifiable! Has been some real turmoil caused by editors, in all Good Faith, giving rather wp:POV opinions.

As Zain says (beating me to it) talk to a 'pro', though I'd suggest a nutritionist/ dietician or similar. We can't give specific advice for a person, we can't even see them! Guten Nacht! 84 and all. :-) --220.101.28.25 (talk) 15:53, 2 May 2010 (UTC)

Protein (nutrient) suggests 0.8g per kg for a mature adult, and the relevant reference from there also says that extreme amounts of protein is harmful. 0.8g per kg for a person weighing 180lbs is about 65g of protein. 100g of raw peanuts contains nearly this amount according to High protein diet, but many foods in the everyday diet already contain some protein so there may be no point in deliberately eating protein-rich food as the excess is just used as calories by the body. 89.242.97.110 (talk) 20:49, 2 May 2010 (UTC)

@81.44.96.96: This Men's Health article (entitled "how to lose muscle") has some very sensible suggestions. It amounts to eat, sleep, rest, and exercise sensibly; to break any of these you'd have to be behaving fairly immoderately . Unfortunately every gym has a few people who think progress is made only by suffering. -- Finlay McWalter • Talk 17:22, 2 May 2010 (UTC)

Good advice there, Finlay McWalter. Moderation in all things. This seems a good reference for Protein intake:"Contemporary Issues in Protein Requirements and Consumption for Resistance Trained Athletes", Journal of the International Society of Sports Nutrition. 2006; 3(1): 7–27. Published online 2006 June 5. doi: 10.1186/1550-2783-3-1-7. Retrieved 3 May 2010. --220.101.28.25 (talk) 15:05, 3 May 2010 (UTC)

Take your finger out of my butt, please...

With MRI and other technologies, are we getting any closer to eliminating the highly invasive digital rectal exam and colonoscopy ? The MRI seems to carry far less risk, so that would be another advantage. What's the current limitation preventing replacement, a lack of resolution in the MRI images ? StuRat (talk) 12:25, 2 May 2010 (UTC)

If you know another way of removing prostate fluid for microcellular examination post it here! MRI doesn't resolve down to cellular level AFAIK. --TammyMoet (talk) 13:00, 2 May 2010 (UTC)

I can think of one more enjoyable way to produce prostate fluid... However, I don't believe "removal of prostate fluid" is a normal part of either of the procedures I listed as candidates for elimination. StuRat (talk) 13:12, 2 May 2010 (UTC)

DRE is obviously cheaper and easier than any kind of other technique—it takes five minutes and a greased finger, and the analysis happens "in real time" without any money spent on fancy machines or their operators. So I doubt that's going away anytime soon, even if it isn't the most fun medical procedure in the world (it's hardly the worst, though—I don't find it as bad as getting blood drawn, personally). Colonoscopy is a different thing altogether. I suspect the problem is that current MRI tech doesn't allow the fine-grained manipulation of the colon itself, or resolve in color, that makes a big difference. The colonoscopy can also remove polyps in realtime as well during the procedure, and the tissue can be analyzed in the lab later—that's handy. An MRI is going to maybe tell you there are things in there, but still require you to go in and get them. So that's not as useful. --Mr.98 (talk) 13:48, 2 May 2010 (UTC)

Is the OP's dislike of the colonoscopy procedure based on imagined or actually experienced discomforts? I tolerated the examination easily and found the experience interesting. I was able to watch my inside view on a TV screen and discuss what was going on with the nurses. I was surprised to see that the colon bore is more triangular than round, and of course am reassured that nothing untoward was discovered. The only significant discomfort came as flatulence on my way home after the colonoscopy. MRI is slow to give a result, needs a major expensive installation, and this video may persuade the OP that it has its own risks: "There are obvious potential hazards to people and equipment in the area (of the MRI)...The magnet environment under certain circumstances can be a dangerous place...Complacency can be fatal." Cuddlyable3 (talk) 14:54, 2 May 2010 (UTC)

The other thing about a colonoscopy is that you can remove tissue samples at the same time, thus removing the need for two procedures. I had an MRI scan last year, and the procedure itself wasn't unpleasant. However, the recovery took days: I was disoriented and dizzy immediately, I couldn't drive home, and I couldn't sleep properly. Comparing it with the gastroscopy I had a few years previously, of the two procedures I prefer the gastroscopy! --TammyMoet (talk) 15:36, 2 May 2010 (UTC)

TammyMoet your account is interesting because there seems to be no reliable information about persisting aftereffects of MRI. If yours was not a (rare) reaction to the contrast agent you may have been given, I would ask whether you suffer from claustrophobia. Cuddlyable3 (talk) 17:18, 2 May 2010 (UTC)

No it wasn't a reaction to gadolinum, and as I had some free time after the procedure I spent some of it on the internet looking for the cause of my reaction. It doesn't appear to be that rare, and I left my experiences on a particular website which was set up by a radiologist in the UK collecting such experiences. I don't suffer from claustrophobia. I have my own explanation as to what happened, which as it falls into an area called by some "pseudo-science" or "woo woo" doesn't belong here. --TammyMoet (talk) 18:25, 2 May 2010 (UTC)

This is NOT MEDICAL ADVICE but you might find this article by Harriet Hall over at SBM interesting. Vespine (talk) 22:39, 2 May 2010 (UTC)

According to a couple of web links I dug up on the spur of the moment, the cost of an MRI ranges from $400 to over $2500 depending on the details of the procedure. Enough said, I think. Looie496 (talk) 22:52, 2 May 2010 (UTC)

That makes it more expensive than DRE, but I don't know about colonoscopy. Googling around seems to indicate that colonoscopies range from $1K to much more depending on what is done (assuming uninsured, in the US). --Mr.98 (talk) 23:38, 2 May 2010 (UTC)

CT and MRI are being evaluated as alternatives to colonoscopy (see virtual colonoscopy). There several significant limitations, however. For one, they're newer technologies, so we don't have studies showing that they are good screening methods (do people undergoing CT colonography have a lower mortality rate after 20 years? 30 years?). Also, the resolution is not nearly as good as direct visualization. CT involves ionizing radiation. MRI is quite expensive and wouldn't really afford a cost savings over colonoscopy. One of the major drawbacks is that the patient still must drink the preparation the night before (and in my experience, the part about colonoscopies that patients usually dislike is taking the preparation, not the procedure itself), so the virtual colonoscopy isn't necessarily more comfortable than actual colonoscopy. And then, finally, imaging studies have no way to obtain samples (until we develop a Star Trek–style transporter), so if there is any abnormality seen, the next step is to to a full colonoscopy (and another round with the preparation). Since polyps are seen on a fair number of colonoscopies, this would mean that a number of people would have to undergo two preparations and twice the expense. Regarding the digital rectal examination, it's fast, cheap, and safe. It's going to be very difficult to develop a replacement procedure. — Knowledge Seeker দ 00:17, 3 May 2010 (UTC)

The above answer is quite good. To add to it, virtual colonoscopy (VC) may also have a higher occurrences of false positives in polyp detection. The inside of the colon has to be reconstructed digitally from 3D scans and thus depend greatly on the quality of the "raw" image (image contrast, patient movement, image artifects, distribution of contrast media, etc.) and also what computer algorithm was used do the digital reconstruction. Since the digital image cannot definitively tell you if you have something "bad" and quite often tells you that you "may have" something, it is likely that you will STILL get something stuck up your rectum after a VC session. My cynical side thinks that currently VC is just another wayfor clinics (who plaster ads everywhere) to generate revenue based on patient fear ($ from VC then onwards to possible $$ from follow-up exams), however I think that with continued development in more reliable VC techniques a tool like this could be of great benefit to patients in the future.Sjschen (talk) 15:32, 5 May 2010 (UTC)

soy

it seems overnight every fast food place in America switched to soybean oil and soy flour ect. im allergic to soy. what am i supposed to do? —Preceding unsigned comment added by Tom12350 (talk • contribs) 13:30, 2 May 2010 (UTC)

Cook yourself, or don't eat fried food, or eat at a restaurant where they use different ingredients. Or perhaps you can desensitize yourself. Graeme Bartlett (talk) 13:41, 2 May 2010 (UTC)

Might this constitute medical advice? Consult with a physician to determine what would happen if you eat soy from a fast-food restaurant. If the consequences are serious (and we aren't qualified or able to tell you), then you should not eat at fast food restaurants (or anywhere that you can't verify soy-free ingredient lists). Nimur (talk) 13:43, 2 May 2010 (UTC)

not just fast food places use soy every restaurant does including places like chilies tgf Fridays, moes ect. they also put it it hot pockets. —Preceding unsigned comment added by Tom12350 (talk • contribs) 13:47, 2 May 2010 (UTC)

Yes, eating prepackaged foods will require reading the label carefully for soy/soya. Making foods from scratch, like cutting up potatoes and frying them yourself, using an oil you choose, is a lot safer. StuRat (talk) 15:03, 2 May 2010 (UTC)

They will have made a decision based on profit margins. What you can do is write to them and explain that this means you can no longer eat there, since they do not offer a safe option for you. You can alert friends and family to your inability to eat at these places, so social events are held elsewhere (maybe someone's house): any enthusiastic friends might be encouraged to write to these places and explain that they are no longer able to hold their social events there, since they do not offer a safe option for you. Essentially, you make it clear to the companies that this decision has lost them custom. They might still consider it a good decision (who knows how this affects their profits), but you are adding weight to the other side.

I do sympathise: I've lived most of my life with someone extremely allergic to peanuts, and this sort of thing can accumulate. Luckily, things have changed over the years so that companies consider it in their interests to warn for nuts and peanuts, and some companies work hard to offer safe options precisely because there is a market for them. But eating out is still difficult, and always subject to change.

And, I hope it doesn't need saying, but absolutely do not follow Graeme's advice to attempt desensitizing yourself: people have died doing that. Any attempt at exposing yourself to something you are allergic to should be carried out under medical supervision, as advised by a doctor, so that you can be treated and even resuscitated if needed. 86.178.225.111 (talk) 15:08, 2 May 2010 (UTC)

My daughter has a sensitivity to both soy protein and cow milk protein, so I can sympathize. Who knew that virtually all brands of hot dog weiners have milk in them? Not I, until I had to start reading the labels on frigging everything. We have an article on soy allergy which helpfully contains a list of additives that do or may contain soy. Hope that helps. Some fast food places list ingredients and nutritional information on their websites, but beware of corporations that just don't give a crap about your health and lie to you. Matt Deres (talk) 01:24, 3 May 2010 (UTC)

I thought that desensitization was a medical procedure rather than something to try on your own. From examples I have heard, it is not very successful. Graeme Bartlett (talk) 21:39, 3 May 2010 (UTC)

It is: Allergen immunotherapy. Buddy431 (talk) 00:16, 4 May 2010 (UTC)

Indeed, but that's not the same as "desensitize yourself". That is "talk to your doctor about the possibility of being desensitized, and hear them explain whether that is typically successful for people your age with your allergy, and consider whether the procedure (carried out under medical supervision) is a good idea in your case". It's the difference between the babysitter feeding a toddler a peanut butter sandwich because she'd heard that a little bit of peanuts helped, and a medical procedure carried out starting with minuscule amounts of allergen under controlled conditions. The person I know with peanut allergies had to abort a similar procedure under medical supervision, because they reacted too much to skin contact with peanuts: the medical staff didn't consider it safe to proceed. Forgive the jumping in, but people thinking it's a good idea to try desensitizing themselves instead of as a medical procedure is a really bad thing. 86.178.228.18 (talk) 22:23, 4 May 2010 (UTC)

Deepest part of ocean

Mariana Trench says that "[it] is the deepest known part of the world's oceans". I would like to know:

1. What are the odds that there is a deeper part? (I admit that this can be seen as inviting wild speculation, but perhaps it can be quantified based on the percentage of as yet unsurveyed area.)
2. I understand that the entire World Ocean has been measured from space using gravity-based algorithms, but would this be accurate enough to detect narrow trenches?
3. If not, would finding a deeper part be down to essentially luck or are there ongoing efforts to systematically measure the entire World Ocean? (I believe various navies were quite active in this respect in the 1960s but they probably have better things to do now.)

Thank you in advance. 83.81.60.233 (talk) 15:35, 2 May 2010 (UTC)

Trenches are formed by subduction zones, hence they are very special parts of the sea floor. Common sea floor is much shallower. Given that we know pretty well where all the subduction zones on this planet are and that there is great interest in studying them in detail, I would guess that it is pretty certain that the Mariana trench is the deepest part of the ocean without actually knowing what fraction of the general sea floor has been measured. --Wrongfilter (talk) 16:31, 2 May 2010 (UTC)

We have actually had quite accurate maps of the sea floor for fifty years, after the advent of Side-scan sonar. Widespread seafloor mapping was what led to our modern understanding of plate tectonics. It is highly unlikely that a large seafloor feature on scale with the Mariana Trench would have been missed by this point. --Jayron32 00:42, 3 May 2010 (UTC)

All the trenches are known, e.g. Oceanic trench#Major oceanic trenches. They are hundreds or thousands of kilometers long, and not easy to miss given even cursory surveys of the ocean floor. However, finding the specific deepest point in a given trench requires detailed mapping. I wouldn't be shocked if there happened to be a spot in one of them that was a little deeper than Challenger Deep (the deepest known part of Mariana), but the longer that record stands the less likely it becomes that we will find anything deeper. Dragons flight (talk) 05:19, 3 May 2010 (UTC)

More to the point, the size of such a place would have to be very small in order to evade our surveys - there comes a point where you'd have to be talking about a narrow crack or hole smaller than the precision with which we're surveying the ocean bottom.

If we found a five centimeter wide crack that went down deeper than Challenger Deep - would we count that? What about a one meter wide cave that wiggled down deeper - would that count? Assuming the answer to that is "No" then it's safe to say that Challenger Deep is the deepest spot of any reasonable size - and that we won't find anything that big and that deep in the future. Of course, these ocean trenches are extremely geologically active (that's why they are the way they are) - so it's quite possible that some future submarine earthquake could open up a deeper spot - or perhaps even fill the deepest bit with lava or an avalanche and thereby make some not-so-deep place become the new record holder. On balance though - I think it's pretty safe to say that Challenger Deep is truely the deepest spot within reasonable criteria. SteveBaker (talk) 13:35, 3 May 2010 (UTC)

Also, it's not clear whether it would be possible to have a tiny (e.g., 5 cm wide) crack that extended several kilometers in depth. Material properties of rock and sediments don't favor such an unstable structure. (If it existed, it would soon cave or deform and fill in). This is another reason why we don't expect such features except in large-scale subduction zones. Nimur (talk) 14:39, 3 May 2010 (UTC)

The important points have been touch on, but to add one thing, space gravity surveys can and do resolve trenches - they are still several tens of kilometers wide, much larger than the resolution of the free-air gravity maps. Awickert (talk) 17:14, 3 May 2010 (UTC)

5 cm? We don't even have maps of most of the Earth's dry surface that are that well resolved. The best available maps of most of the deep ocean are about 1-5 square km per pixel. As high priority targets, the trenches may be better mapped than that (though extreme depth also makes it harder to get good resolution). However, in general I think you are being overly optimistic about how well surveyed the oceans are. Could a canyon or fissure be hiding down there? Certainly. Are any deep enough to matter? Perhaps not. Dragons flight (talk) 18:45, 3 May 2010 (UTC)

The best worldwide maps are probably the digital elevation model from the Shuttle Radar Topography Mission, which has resolution of about 30 meters per pixel worldwide (although I don't believe it actually has any ocean coverage - I'll have to check). It is available for free. I have also worked with airborne LIDAR data for small regions (e.g., an entire county) which has 1-cm accuracy per pixel. At this scale of map detail, we have to design optimization algorithms to determine whether we're looking at laser returns from plant-leaves, stems, or ground, etc. You can imagine the difficulties and the data volumes involved! I am not aware of any LIDAR technology that works underwater; but you can create very high-resolution SONAR, seismic, or bathymetry imagery; such data tends to be proprietary and there is definitely not full coverage of the Earth's entire seafloor. Again, if you can resolve to 5 cm, you have to worry about 5-cm-sized interference - like sediments swishing around on the seafloor, plant and animal life, and so on. The bottom of Challenger Deep is probably fairly rocky, and the water is probably fairly still, which might help, but there could still be time-variations of the sea bed. Nimur (talk) 11:11, 4 May 2010 (UTC)

Incidentally, I also work with SRTM and LiDAR :-). Neither are usable for bathymetry because of attenuation in water. Global bathymetry is from free air gravity anomalies, and goes down to 1 arc minute (a little under 2 km). More precise bathymetry is given from ship tracks, and I imagine that this is used to ground-truth the free air gravity maps, but as others have said, this is not anywhere near global in extent. Awickert (talk) 02:03, 5 May 2010 (UTC)

Activating the Deepwater Horizon blowout preventer

Is there some intrinsic reason why this has been so difficult so far? Couldn't a blowout preventer be designed for wireless activation -- just press a button on a command ship and it stops flow? Or is there some fundamental reason that this is not an option when designing these things? Vranak (talk) 17:20, 2 May 2010 (UTC)

Wireless signals (radio) does not work under water. Radio waves are pretty much totally blocked by seawater. But take a look here - there are acoustically activated devices, since sound travels pretty well. Ariel. (talk) 18:39, 2 May 2010 (UTC)

Wireless signals do work under water, but not well. They are used to communicate with submarines: [3]. --Phil Holmes (talk) 10:26, 3 May 2010 (UTC)

My understanding of this event is that any such equipment on the rig itself would have been destroyed in the initial large explosion, subsequent fires, and the sinking of the rig's wreckage, and that no such intact and working equipment is still in place on the seabed, even if it was there in the first place, bearing in mind that at the time of the blowout the well was being modified rather than being in routine production. 87.81.230.195 (talk) 21:39, 2 May 2010 (UTC)

When the rig blew up, that did sever the communications with the preventer, but within the first 48 hours there were remotely operated subs at the site trying to trigger it. Apparently, the preventer isn't closing even when told to do so. Failure to activate, even when told to do so, indicates a more fundamental problem than just a communications issue. Dragons flight (talk) 22:11, 2 May 2010 (UTC)

I think that the valve itself may have been wrecked by the explosion. FWiW 67.170.215.166 (talk) 02:17, 4 May 2010 (UTC)

Thanks very much guys. Vranak (talk)

Bacon curling

Why does bacon curl up when you cook it on a grill? I presume it'd be due to drying out, so there's less hydrolysed protein and thus curling would occur (the opposite to when your hair gets straighter when you shower) but I'm not sure if that's the actual reason. Regards, --—Cyclonenim | Chat  20:39, 2 May 2010 (UTC)

I don't know chemically what's happening but I've cooked a LOT of bacon I have thought about it so I'll tell you what I've observed:) I believe it is not the "meat", not the fat and not the rind that causes the curling, I think it is the sinewy connective tissue between the fat and the meat. I think it shrinks when it cooks and this is what causes the curling. I bake my bacon now because I like it really crispy and it's much easier IMHO in the oven and curling doesn't matter so much. But when I used to fry it, there was 3 spots on the bacon, where the fat "meets the meat" that I would cut through to stop it from curling. Vespine (talk) 22:29, 2 May 2010 (UTC)

I am pretty sure the curling comes from differential heating of the bacon. As noted, bacon consists of at least 3 different tissues: fat, meat, and connective tissue. All three of these will cook at different rates, and as they cook will contract or expand at different rates. Also, when you fry bacon, you set up a LARGE temperature differential, as the part of the rasher in contact with the pan is a LOT hotter than the rest of the bacon. Since baking bacon tends to evenly distribute the heat over all parts of the rasher, there is less curling. They make a device called "bacon press" designed to counteract this curling; you see them alot at diners where they make a lot of bacon on a griddle. See this Google Image search which shows you the many different styles of bacon press. The ones I have seen most often look like heavy rectangular trowels, but they come round and pig shaped as well. --Jayron32 23:56, 2 May 2010 (UTC)

I agree with Jayron; it's the temperature difference. And forget using a "bacon press" - cook your bacon on a cookie sheet with a rack. Place the bacon in a cold oven, set the thermostat for 400F, and cook until done (time will depend on thickness). Yum! Matt Deres (talk) 01:30, 3 May 2010 (UTC)

I endorse the oven method, and I'll add that the oven temperature is not at all critical... anything from 325–425 F works (at least), so if you're baking something else, you can probably throw the bacon in and it will be fine. The cooking time will, of course, vary with temperature. I've read that higher temperatures result in more bitter-tasting compounds, so I tend to use the lower end of the range, but I'm not sure it actually makes much difference. -- Coneslayer (talk) 13:11, 3 May 2010 (UTC)

To be honest the actual curling has never caused me any bother :P I tend to just grill mine plain and simple -- comes out curled but very tasty. Thanks for all the interesting answers. Regards, --—Cyclonenim | Chat  14:49, 3 May 2010 (UTC)

Electron excitation - discrete?

In A level physics, we are taught that an electron can be excited to a higher energy level by means of absorbing a photon, on condition that its energy exactly matches the energy difference between the levels. This makes sense, there doesn't seem to be a mechanism for where the "excess" energy goes. However, this can't really be correct, surely? I mean, you could never get it exactly the same. And this sort of thing happens all the time in the real world (e.g. in fluorescent tubes' outer coating). What actually happens? (Unusually, excited state seems to be written for the layperson, and hence fails to approach the issue.) 92.23.14.145 (talk) 20:43, 2 May 2010 (UTC)

I'm by no means a trained physcist so I'll let others rip apart my answer in due course, but this seems to me like just a fallacy in human logic rather than questioning whether it's actually true or not. "...get it exactly the same" - There is no "getting", there are stupidly large numbers of photons (and electrons) around, the chance of some being of the same energy is, I imagine, pretty high. Also, because energy is distributed in packets (quanta), the possibilities are slightly limited as the energy values have to be a certain factor of some constant (someone remind me which?). Regards, --—Cyclonenim | Chat  00:20, 3 May 2010 (UTC)

Ok, so in A level physics you have learned that atoms have precisely defined energy levels and that transitions between these levels are possible by absorpion/emission of photons which in this picture would ahve to have exactly the energy difference between the energy levels. You have correctly noted that this picture cannot be exactly correct.

What is wrong with this picture is the idea that an atom can both have an infinitely precisely defined energy level and be in a state that changes as a function of time. The precisely defined energy levels only appear if you ignore the coupling of the atom to the electromagnetic field. If you take this approximation serious then the atom cannot make any transitions as no interaction with the electromagnetic field means that it will not interact with photons at all.

The moment you take into account the fact that atoms do in fact couple to the electromagnetic field, then what you see is that the "energy levels" are no longer states with a precisely defined energy. The spread in energy of a state is inversely proportional to the spontaneous decay time of that state. One can heuristically unbderstand this using the time-energy uncertainty relation.

In practice this means that atoms can absorb photons that are within the the energy spread. Now this energy spread is quite small, but then each atom will have some random velocity causing its energy levels to appear to shift due to the doppler effect. This causes a gas of atoms to be able to absorp photons of a larger range of energies. This is called doppler broadening. Count Iblis (talk) 01:29, 3 May 2010 (UTC)

It's also worth pointing out that it is quite possible for photons of exactly the right energy to exist. Where the electromagnetic radiation (typically light) is created by an incandescent source (i.e. one that uses heat to produce the light), then the light produced is a broadband of every wavelength within the band. So the atoms only absorb the light whose wavelength exactly matches their energy gap. Hence Spectral line. --Phil Holmes (talk) 09:39, 3 May 2010 (UTC)

Spectral broadening is the article that should help see Spectral_line#Spectral_line_broadening_and_shift - the lines in practice are non-zero width.Sf5xeplus (talk) 10:46, 4 May 2010 (UTC)

hot water

recently my hot water tastes and smells like scouring powder. my cold water is fine. can someone explain this? —Preceding unsigned comment added by Tom12350 (talk • contribs) 20:57, 2 May 2010 (UTC)

It might help someone to answer if you give some details about how your particular hot water system works: mains-fed instant gas heater, electrically heated hot water cylinder, hot rocks in a leather cauldron? (OK, the last isn't very common these days.) 87.81.230.195 (talk) 21:26, 2 May 2010 (UTC)

its a hot water heater tank. heated by either gas or electricity. —Preceding unsigned comment added by Tom12350 (talk • contribs) 22:12, 2 May 2010 (UTC)

The hot tap water in your tank may contain extra chemicals to treat the water. ~AH1^(TCU) 23:35, 2 May 2010 (UTC)

It may be water softeners? --Jayron32 23:43, 2 May 2010 (UTC)

That would be my guess, particularly if they just added a new batch of salt to the water softener or if it's been sitting for a while unused. Under those conditions you can get excess salt in your water. If the water softener is hooked up after the water heater, try bleeding some water directly off the hot water heater to see if it's good. If so, that would seem to implicate the water softener. It could just be a bad batch of salt in there, which isn't sufficient compacted, and thus dissolves too readily in the water. StuRat (talk) 01:53, 3 May 2010 (UTC)

"The magnesium corrosion control rod present in many hot water heaters can chemically reduce naturally occurring sulfates to hydrogen sulfide." [4]. You can change the rod to aluminium (they just unscrew out, although it might be hard to do in an old tank), or add a carbon filter before the water. If you choose a filter make sure you get one designed for it - otherwise it will clog up very fast. Ariel. (talk) 02:18, 3 May 2010 (UTC)

Infrared rainbow

Yesterday I took a near-infrared picture of a double rainbow. As expected, the two arcs are displaced towards each other relative to a visible-light rainbow. Is there a frequency at which the two arcs merge, and if so, what is it? --Carnildo (talk) 21:21, 2 May 2010 (UTC)

This region is called Alexander's band, and is discussed in both that article, and in the article Rainbow. Presumably, there will be some point at which the wavelengths of light from the two bows are identical as they pass one another; however I see no reason why this overlap point would be identical for every rainbow; it may be unique for each observer. --Jayron32 23:42, 2 May 2010 (UTC)

I can't see any reason why the overlap point wouldn't be the identical for every rainbow. The critical angles for total internal reflection are determined by the properties of water and air, I believe, which are essentially constant (on Earth, at least - other planets, eg. Titan, have different angles). --Tango (talk) 01:28, 3 May 2010 (UTC)

The two rainbows may very well never meet since the refractive index of water is not a monotonic function of the light's wavelength. Dauto (talk) 04:48, 3 May 2010 (UTC)