Wikipedia:Reference desk/Archives/Science/2011 April 5

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April 5

Recommended Daily Intake

Hello. Food labels show nutritional content as percentages of recommended daily intake. Since the RDI differs according to age and gender, do the food labels assume an adult male to arrive to such figures? Thanks in advance. --Mayfare (talk) 01:23, 5 April 2011 (UTC)

I don't believe the variance is that significant. We have an article which explains a little Reference Daily Intake, it states the figures are considered to be sufficient to meet the requirements of 97–98% of healthy individuals in every demographic in the United States. Vespine (talk) 03:05, 5 April 2011 (UTC)

Do Tsunamis hit with force?

Do Tsunamis hit with force? Or, is all the force from the difference in height between the incoming water and the land? In other words, if I built a wall that could handle water of that hight - would that be enough to block the tsunami, or do i need extra strength to handle an impact? Or in another set of words, does the water in a tsunami travel with speed, and when it hits you have the impact of that motion? Or is all the motion just from water "spilling" from it's height? I'm asking because an ordinary wave in the ocean appears to travel, but the water is not actually moving forward - just the wave is, the water is actually only moving up and down. Ariel. (talk) 04:49, 5 April 2011 (UTC)

The energy of a tsunami travels outward from the epicenter, so yes, you would need to build a stronger wall than you are proposing. Didn't you see the news footage of boats and other objects being driven far inland? Clarityfiend (talk) 05:14, 5 April 2011 (UTC)

Of course I did, but everything moved so slowly, it seemed that it was just water spilling onto land that did all the damage (just an ordinary current of water can carry things very far with great force). I wanted to know if the water has extra energy besides that which it gains by spilling from a higher level to a lower one. The wall would prevent the water from spilling that way in the first place, so it wouldn't gain that energy. Ariel. (talk) 05:32, 5 April 2011 (UTC)

I believe it has a lot of speed and thus force on the open ocean, but slows down and "piles up" to become deeper waves, with less force, when it strikes land. So, yes it would have more force than just the weight of that much water, but not much more. StuRat (talk) 06:35, 5 April 2011 (UTC)

The energy in the wave in open ocean is a combination of the gravitational potential energy of the water in the upper part of the wave and the forward kinetic energy of the wavefront. This is gradually converted to potential (height) and kinetic energy of the surge as the wave approaches land, and the kinetic energy component reduces as the surge gains height on land, so, yes, a conventional sea wall will probably be adequate if it is well back from the shoreline because they are designed to cope with the kinetic energy of a raging sea, but you might need an enormous wall because the height and width of a tsunami can be unexpectedly huge. Dbfirs 08:23, 5 April 2011 (UTC)

I think that the distinction you make between water "just spilling from it's hight" and kinetic force of forward motion is, at best, misleading. Firstly, the water in a wave is not just moving up and down. It moves in a circular motion as it rolls up to the beach. Having lived on my sailboat for over twenty years and sailed it thousands of miles, I can assert quite definitly that when a steep (destabilising) wave , which a tsunami is when it reaches solid land, crashes into a boat or somthing else there is a distinct and audible impact. Also, as answer to you other question, I recall reading somewhere that when they are in the deep ocean tsunamis can travel at 3 - 500 miles an hour. I don't have the math to demonstrate it, that's more your area, but waves do hit with real enormous force. —Preceding unsigned comment added by 190.56.14.201 (talk) 16:36, 5 April 2011 (UTC)

A component of all ocean waves (specifically, the P wave) travels at the speed of sound, which is about 1.5 km/s in water. Whether the energy of a tsunami is concentrated in the P wave or in one of the other propagation modes depends on many factors. Our tsunami article is helpful; we also have wind wave for comparison (a conventional ocean surface wave) and a more technical article, wind wave model. The study of wave mechanics is very complicated. Nimur (talk) 17:41, 5 April 2011 (UTC)

I think I was too optimistic in my answer above because I was thinking of a solidly constructed sea wall. An ordinary wall would not withstand the force of the flow except at the very top of the tsunami's range inland. The idea of building a wall that would have protected property on the shores of Japan, where the tsunami reached a height of ten metres, is just preposterous. To withstand that onslaught, the wall would need to be many feet thick as well as 10 m high, and would be a major engineering project. (And unless the wall circled the property, the water would just flow round it, though with much less force.) It would probably be cheaper to build a hill more than 10 m high with reinforced edges on the seaward side. Dbfirs 22:06, 5 April 2011 (UTC)

A breakwater will probably work better than a wall. In both the literal and metaphorical sense, it is impossible to "hold back the ocean" - but by constructing a strong, but diffusive, barrier, you can dissipate ocean wave energy so that it is non-destructive. A lot of times, this means scattering large, shaped stones or concrete blocks so that the waves crash through them. The intent is not to be water-proof, nor to keep a wave from going forward; instead, the objective is to dissipate the energy diffusely and minimize the damage that a wave can cause. Nimur (talk) 22:38, 5 April 2011 (UTC)

On the contrary: last week's Nova episode said that several towns in the disaster zone had 10 meter tsunami walls, and showed video of the water flowing over the top of them, not blasting through them. According to Nova, the reason the walls were not high enough was that the earthquake caused the height of the land to drop by several feet, leaving the tops of the walls well under 10 meters above sea level. Looie496 (talk) 22:38, 5 April 2011 (UTC)

Taxonomy

I thought bionomial taxonomy was organised that as name can only be used for one genus and not for two unrelated genera. Therefor I was surprised to find

• "Cinclidium leucurum" (a bird [1] commons:category:Cinclidium leucurum)
• "Cinclidium stygium" (a moss [2] commons:category:Cinclidium stygium)

Should I make a disambiguation category for commons:category:Cinclidium ? -Donar Reiskoffer (talk) 09:00, 5 April 2011 (UTC)

Since your question is about Wikimedia Commons, you might get a better or faster answer at Commons:Help desk; this page is for factual questions about science. --Colapeninsula (talk) 13:58, 5 April 2011 (UTC)

With regard to your original supposition, it's perfectly acceptable (and not uncommon) for an animal genus and a plant genus to have the same name. As our article Binomial nomenclature says, "The genus name or generic epithet must be unique inside each kingdom" (emphasis added). Deor (talk) 16:45, 5 April 2011 (UTC)

based on chemistry

if you were required to to determine whether a particular metal, or some compound, had reacted with a specific reagent, what sensory evidence could be used to argue that a chemical transformation of the substance had occurred? —Preceding unsigned comment added by 146.141.1.93 (talk) 12:55, 5 April 2011 (UTC)

The best place to look is in the first chapter of the high school chemistry textbook your teacher assigned you to read. See {{DYOH}} for more information. --Jayron32 13:01, 5 April 2011 (UTC)

Warkany syndrome 1 and 2

What's the difference? Albacore (talk) 13:30, 5 April 2011 (UTC)

Warkany syndrome 1 is "trisomy 8 mosaicism", compared with Warkany syndrome 2, or "complete trisomy 8". StuRat (talk) 15:35, 5 April 2011 (UTC)

I've now expanded Warkany syndrome to describe both diseases. StuRat (talk) 15:55, 5 April 2011 (UTC)

CORRECTION: Both the complete and mosaic forms of trisomy 8 appear to be called Warkany syndrome 2, while Warkany syndrome 1 appears to be an X-chromosome linked problem: [3]. I will correct our articles accordingly. StuRat (talk) 16:56, 5 April 2011 (UTC)

I will second what StuRat said. My reading of the very minimal literature on "Warkany syndrome 1" ([4] and [5]) is that it seems to refer to a single extended family reported by Warkany in a 1961 article on intrauterine growth retardation. The family history was consistent with X-linked recessive inheritance of intrauterine growth retardation and small head size, but these features are pretty nonspecific and no linkage to a specific gene has ever been established. Warkany syndrome 2, on the other hand, is synonymous with trisomy 8, which in the complete form (all cells of the body have an extra chromosome 8) is almost always perinatally lethal, and in the mosaic form (some cells have an extra chromosome 8 while the others have the normal two copies) individuals have a fairly characteristic and recognizable set of features. I would argue that the proper terminology should be trisomy 8 or mosaic trisomy 8 instead of "Warkany syndrome" since the eponym is not particularly widely used and actually seems to confuse the issue. In fact, I suspect that the condition once referred to as "Warkany syndrome 1" has been abandoned, given that the OMIM number ([6]) listed in the above NLM link and in an earlier review article on X-linked mental retardation ([7]) has been removed from the database and this condition is no longer mentioned in a more recent review of X-linked mental retardation ([8]). --- Medical geneticist (talk) 20:15, 5 April 2011 (UTC)

This change seems appropriate. I've quickly tossed a variety of chromosome 8 trisomy material into the article, but of course, they're all very different conditions. It seems like the current organization has the tail wagging the dog, so to speak. Wnt (talk) 21:43, 5 April 2011 (UTC)

Perhaps they should be broken off into several articles, but, even with them all together, it's still a tiny article. Breaking them up would make each article a mere stub. StuRat (talk) 21:48, 5 April 2011 (UTC)

I went ahead and changed Trisomy 8 from a redirect to its own page. I think this makes sense as it can now cover other trisomy 8 related subjects that are not "Warkany syndrome". I subsequently reduced some of the information under Warkany syndrome which looks a little more like a disambig page but is probably more helpful than trying to have all of trisomy 8 under that title. Thanks to Albacore for stimulating this activity, which hopefully clarifies the situation a bit! --- Medical geneticist (talk) 23:44, 5 April 2011 (UTC)

Lunar dust and telescopy

What are the practical implications of lunar dust on lunar lander telescopes for the 9-10 micron infrared range? Can sweepers help? 99.2.149.161 (talk) 18:26, 5 April 2011 (UTC)

The dust will radiate infrared in that range of wavelengths and so make background glow that will desensitize the detectors, like a photo taken through sunlit haze. The weeper article suggests that magnets could attract the dust. If you can attract the dust before it gets to the optic surface, that is best. The first article suggest abrasion could be taking place too, which will not be fixed by a magnet, you would just have to stop the particles getting there in the first place. Graeme Bartlett (talk) 10:00, 6 April 2011 (UTC)

Swimming beneath the waves.

I just read the Wiki article about waves (in water) a subject that completely baffles me - as did the article - it seemingly being for wave-power engineers - unlike me - a poor Samaritan Beach Bum. I was interested to know how the recent Tsunami in Japan had developed such devastating power following the earlier geological techtonic plate shift under the ocean when I suddenly recalled a recent holiday in Southern Tenerife in the Atlantic Ocean. There, the waves were a source of great fun as they rolled up to the beach and knocked me over and over with their force. But then, I tried diving beneath the waves as they rolled up to the shore and hey presto, they rolled over me with no discernible disorientation on my part. And I am talking here about a difference of about 3 feet between standing up to meet the wave head-on - and diving below the surface as it began its approach. Anyone here able to explain in layman's terms what is happening in this scenario? Thanks. 92.4.43.217 (talk) 18:38, 5 April 2011 (UTC)

It's the quick change from being in air to being in water that's disorienting, probably due to the huge difference in density and thus weight. Since you were already under water in the 2nd case, the passing waves may be barely noticeable. StuRat (talk) 19:05, 5 April 2011 (UTC)

I was thinking it was more along the lines of being hit by a car and lying on the street while the car passes over you. In one instance, the object delivers a force directly to the person, changing their momentum, moving them suddenly and disorienting them (or even worse in the event of the car). In the other instance the force passes safely over the top of the person with no ill effects. Ks0stm ^(T•C•G) 19:14, 5 April 2011 (UTC)

To put it very simply, ordinary waves are caused by the wind disturbing the surface of the sea. They are comparatively small and mostly involve just the surface layers going up and down, or more accurately in a roughly circular motion which doesn't extend down more than roughly the waves' wavelength (crest-to-crest distance): although their shape moves forward, the actual water inside them is overall going nowhere, except at the edge of the water - the shore - where they topple over under gravity and sprawl out up the shore a little. By contrast a Tsunami wave is caused by a large area of seabed suddenly lifting (or dropping) the whole depth of the ocean. The resulting waves are thousands of times longer in wavelength (distance from crest to crest) and many millions of times greater in volume than any 'ordinary' wave.

Think of a large paddling pool with a very strong and stiff bottom. You can make small 'ordinary' waves in it just by moving your hand up and down gently at the surface by an inch or so (as the wind does to the ocean surface). Now grasp the edge of the pool and suddenly jerk it up by a foot and hold it there (assuming you have the strength) - the much larger 'slosh', which will probably spill over the edge, is like a tsunami.

Comparing the waves that you played in to a tsunami is like comparing being hit in the face by a cup of water to being hit in the face by an entire full-size swimming pool. {The poster formerly known as 87.81.230.195} 90.197.66.111 (talk) 20:40, 5 April 2011 (UTC)

Thanks each for those easier to understand explanations. So if the body of ordinary non-tsunami water is relatively stable beneath the waves, am I to understand that underwater entities such as fish, submarines, and plantlife are unaffected by the waves above? I ask this because when I see underwater natural history documentaries, plantlife such as grows on the seabed and on rock formations does sway to and fro. 92.4.36.124 (talk) 11:29, 6 April 2011 (UTC)

Wave effects would be less the further below them you are. A person on a submarine at 500 feet below the surface might not be very aware of heavy seas on the surface, where if it was 100 feet down, he probably would, so how far below the surface you are plays a huge roll. On those nature shows, in order to have good lighting, they are probably within 100 feet of the surface (water eventually blocks out the sunlight). Also, currents exist that are only vaguely related to the wave action above that would cause plants to sway.

OK. Case explained and understood. Thanks to all who responded. By the way - how come your last reply didn't leave an IP? 92.4.43.109 (talk) 18:14, 6 April 2011 (UTC)

He must have forgot, and apparently the SignBot isn't working. I will mark this Q as resolved. StuRat (talk) 18:19, 8 April 2011 (UTC)

Resolved

Guitar tuning

More often than not when I pick up my guitar I find it's gone sharp and I need to slacken the strings. I would have expected the opposite. Any explanations? Thanks 109.125.10.211 (talk) 20:09, 5 April 2011 (UTC)

It depends on the environment the guitar is in. In fact, if you have been playing a lot, your fingers will tend to warm the strings, slackening them. If you leave the guitar for a while, as the stings cool they will tighten, which is likely the source of the sharpening. --Jayron32 20:20, 5 April 2011 (UTC)

That makes sense- thanks 109.125.13.60 (talk) 19:08, 6 April 2011 (UTC)

Monkeys and bananas

The image, sometimes a cartoon one, of monkeys (and apes, being that many people think that they're the same thing anyway) sitting around eating bananas all day is really common, to the point of being almost ubiquitous.

In the real world however, be it in the wild, or in captivity - how often do monkeys and apes actually eat bananas? Do bananas in fact even form a significant part of their regular diets? --Kurt Shaped Box (talk) 20:28, 5 April 2011 (UTC)

Not sure how often they get them, but they do appear to be one of their favorite things to eat. Being a fellow primate, and seeing some of the other things they eat, I'm not surprised that bananas look good by comparison. StuRat (talk) 21:32, 5 April 2011 (UTC)

In captivity, of course, diet is controlled by humans. Many commercial monkey foods feature banana as an ingredient, and zoos/monkey owners do commonly feed bananas. As StuRat points out, humans enjoy bananas, and monkeys do seem to like the flavor too. So yes, many captive primates eat bananas on a daily basis. As for wild primates, they are generally frugivores, and bananas can be a large source of resources. Note that bananas are an old-world species, so of course no New_World_monkey could eat them in the wild. Wild Old_world_monkeys and apes likely feast on wild bananas when they can, but (to the best of my knowledge) ripe bananas will only be available for a few months a year. So in 'natural' conditions, bananas would probably constitute a large portion of a (some) primates' diets, but only for part of the year. SemanticMantis (talk) 21:55, 5 April 2011 (UTC)

Bananas might have been Old World originally, but a lot of bananas are grown on plantations in Central and South America that could be accessible to clever New World monkeys in the wild. Googlemeister (talk) 13:18, 6 April 2011 (UTC)

I wonder, do bananas now grow wild in the Americas, as an invasive species ? StuRat (talk) 22:55, 6 April 2011 (UTC)

No. They are becoming increasingly hard to cultivate on purpose, due to a lack of genetic variation, various pathogens, etc. I'm not saying there are no 'feral' bananas in the new world, but they are not an 'invasive species' (note invasive != exotic) SemanticMantis (talk) 18:09, 8 April 2011 (UTC)

It should be noted that wild bananas more difficult to peel. Imagine Reason (talk) 13:37, 6 April 2011 (UTC)

Fertility of volcanic ash

Hi, and I am trying to figure out exactly what it is in volcanic ash that makes it so fertile to plants. I just read our article on it, and it didn't really help. As far as I can tell, volcanic ash from stratovolcanoes such as Pinatubo and Mt. St. Helens is mostly silicates, which are not known for being great for life. So what is in volcanic ash that plants love? --T H F S W (T · C · E) 21:35, 5 April 2011 (UTC)

This article says nutrients and absorbency are beneficial. --Sean 21:55, 5 April 2011 (UTC)

FYI many types of ash are considered very fertile, comparing their chemical make up to fertilizers might solve mystery ~~Xil (talk) 22:25, 5 April 2011 (UTC)

The main things that plants need are fixed nitrogen, phosphorus, and potassium. All of these are present in volcanic ash (to varying degrees, depending on the type of ash), as well as a variety of other minerals such as magnesium that are needed in lesser quantities. Looie496 (talk) 22:29, 5 April 2011 (UTC)

Beyond chemical makeup is a factor known as soil texture, which has a lot to do with suitibility of planting. Soils which have an incorrect texture have poor water retention; too much clay and the water just sits on top without sinking in at all; too much sand and gravel and the water just runs through the soil without being retained. Certain soil textures, such as loam and loess are known for high fertilities not merely for their chemical makeup, but more importantly for the way that the soils retain water and the stuff dissolved in the water. You can fertilize soil of the wrong texture all you want and you still won't get anything to grow in it; if the soil does not retain the fertilizer correctly. Perhaps ash is of the correct texture to be suitible for planting... --Jayron32 02:49, 6 April 2011 (UTC)

Laptop adapter malfunctioning

My laptop adapter is driving me nuts. It just turns off all by itself, repluging it mostly makes it switch on again, usually dosen't happen all that often, but tonight it is doing it almost every two minutes. Pretty sure it is not a broken wire. What else could be the cause? ~~Xil (talk) 22:19, 5 April 2011 (UTC)

Well, the DC jack is apparently a major failure point. See [9][10][11] etc. Oh, and consider asking the Computing Refdesk. Wnt (talk) 23:21, 5 April 2011 (UTC)

I think this is problem with the adapter itself, I kind of wish to understand better how it works to figure out what could be wrong, thus not realy a computer issue. I forgot to mention - the brick part has a activity light which is on when it is pluged in (I mean in wall), if the problem was at the other end, the light would still be on and it is not. It does though appear to happen more frequently when the laptop is on and charging, especialy if the battery is empty at the begining ~~Xil (talk) 02:20, 6 April 2011 (UTC)

Cause might be failing capacitors. I had a similar problem (device was not able to power a laptop, but was able to charge battery). Also, rarely it failed to start up, when plugging in. After replacing obviously failed capacitors, it kind of works. Other potentially failing components might be power semiconductors, but if they died, device would not work at all (probably). -Yyy (talk) 12:32, 6 April 2011 (UTC)

And how exactly do you changed them? If working, it can power the laptop without battery, occasionaly does indeed fail to turn on after being pluged in. BTW, it makes a buzzing sound, but it's been like that since I bought it (key issue here - it is expensive). Also it is working perfectly fine today, now that battery has been charged full over the night ~~Xil (talk) 13:34, 6 April 2011 (UTC)

Are you sure the activity light was on whenever the adapter was plugged in, even if the computer wasn't attached? It is not impossible to design a circuit so that the light would be on only when the power was being taken from it. Wnt (talk) 21:27, 8 April 2011 (UTC)

My laptop has a problem where the cord plugs into the laptop. The connector came loose and had to be resoldered. Perhaps you have the same prob ? StuRat (talk) 22:45, 6 April 2011 (UTC)

No, pretty sure it is within or before adapter itself (see above, light would be on if it was the laptop) ~~Xil (talk) 07:23, 7 April 2011 (UTC)

If you search popular online shopping sites, you may find knockoff adaptors suitable for your model laptop for much less than what the manufacturer charges for a brand-name replacement. The last time I bought a laptop power supply it cost less than five dollars.--Srleffler (talk) 06:20, 8 April 2011 (UTC)

I did allready buy new adapter last year, it was bloody expensive and, as you see ineffective, I couldn't find anything cheaper and my country now charges costum tax for importing even pure air so I can't order it online either ~~Xil (talk) 12:37, 9 April 2011 (UTC)

How much did it cost? -Yyy (talk) 17:57, 9 April 2011 (UTC)