Wikipedia:Reference desk/Archives/Science/2010 June 21

Science desk
< June 20	<< May | June | Jul >>	June 22 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

June 21

How the planet and why is divided to different countries; who made this? God, humans or nature?

I would like to know who has created the countries of the plant - God, humans or the nature or is it because we have different knids of humans?

Best regards Daniel daniel.sarbalavand —Preceding unsigned comment added by 213.7.13.253 (talk) 07:39, 21 June 2010 (UTC)

Countries are by definition human constructs. Some religions say their God created or ordained some countries like Isreal...I think.

Also, I would shy away from saying there are "different kinds of humans". I know you didn't mean it in a bad way but it evokes very a very negative response. Plus it doesn't make a whole lot of sense since we're all the same species... --mboverload@ 08:03, 21 June 2010 (UTC)

Some modern countries - mainly in Europe and much of Asia - originated from ethnic groups with a shared genetic and/or cultural heritage (including a shared language) which usually dates back many thousands of years. In some cases - for example, island states - their boundaries were largely shaped by natural geographical features. In the Americas and Africa, the boundaries of many modern countries were determined by colonialists in the 19th century and earlier, who divided up large areas into smaller areas that could be administered more effectively, and those boundaries have endured. Other countries are, in effect, empires or confederations, containing many different ethnicities (such as India or China). The article on Borders explains this further. Ghmyrtle (talk) 08:27, 21 June 2010 (UTC)

Shy away also from the example of Israel as a country because of its ambiguity. Israel may mean[1] 1) an ancient kingdom of the Hebrew tribes at the southeastern end of the Mediterranean Sea; founded by Saul around 1025 BC and destroyed by the Assyrians in 721 BC or 2) A Jewish republic in southwestern Asia at eastern end of Mediterranean; formerly part of Palestine, created by UN mandate in 1947. Cuddlyable3 (talk) 08:29, 21 June 2010 (UTC)

It's not ambiguous - the borders changed at varying times in history. But the basic location has not changed. Ariel. (talk) 08:59, 21 June 2010 (UTC)

The frontier between Spain and France has always been delimitated by the Pyrenees mountain range, all modifications of that frontier were in parts that are easy to cross. So, if God created mountains, then you can say that the frontier between Spain and France was created by God.

I dem for stuff like the great plains in the West part of Russia, preventing any invasion from Europe; the swamps and rought terrain in Central America, preventing contact between Maya civilization/Aztec civilization and Inca civilization.

There was this documental in TV saying how one of those precolumbian civs had discovered the wheel but they couldn't use it because it was all rough terrain and they hadn't animals big enough to pull a cart, and the other civ had big animals that could easily pull a cart (llamas?) but they hadn't discovered the wheel. Because of the bad terrain they never entered in contact and they could never discover the chariot and conquer all of the American continent and join all of it in a common culture that could unite the land in a single country and culture (kind of what Alexander the Great tried to do with Greek culture, Napoleon and Hitler with Europe, Greek with the Aegean Sea, Romans with the Mediterranean, etc).

Similar problems for Africa, with too many jungles and deserts to make it feasible to create a single African culture.

Arguibly, the European Union exists only because the European countries all have a common culture, and that culture was obtained by cultures managing to conquer all or most of the continent, then other cultures absorbing them and conquering stuff again, etc, until all countries get at least a part of the common culture that results from all the mixes. This was possible due to the mix of mountains and fertile plains in Europe, which allows for small civs to develop, conquer, and get conquered, and make it impossible to keep the terrain conquered for too long (too many connections with paths of invasion allowing Muslims, Turks, Huns, etc. to enter, too many thick forests and snow in the North, etc). So, again, if God created Europe's geography, it was God's fault that the European Union exists, and that there no things like the African Union or the Asian Union (the American Union kind of exists, but there is one for the Latin-conquered part, and another for the English/French conquered part). --Enric Naval (talk) 09:20, 21 June 2010 (UTC)

History of Belgium 81.131.52.86 (talk) 10:01, 21 June 2010 (UTC)

See country, nation, government, sovereignty, nation state, and sovereign state. These all mean slightly different things. "Country" by itself is ambiguous. "Nation" is not much better. But it seems safe to at least say that government, sovereignty, states, and nation states are all human inventions. Nations and territories are clearly influenced by geography, history, mass migrations, linguistics, and so on, but one should take care to avoid geographic determinism in explaining how nations, cultures, etc, came to exist in their current forms. Pfly (talk) 10:10, 21 June 2010 (UTC)

See Category:Territorial evolution.—Wavelength (talk) 13:24, 21 June 2010 (UTC)

Hi OP. Just so you know, science has definitively discounted "God" as the answer to any question about "who did" something. (except in fiction). In point of fact, some things humans made, the rest nature made - God made, makes, did, and does nothing, except in the fiction written or believed by humans. This is, at least in my estimation, the upshot of the enlightenment (an end to this kind of superstition), and, if you ask me, the major source of progress in the past few hundred years. The first step to everything you see around you, from the computer you're typing on, the mass produced furniture you're probably sitting at, the electricity powering your house, the first step toward all of this was realizing that the answer was not, is not, and will never be "God wanted it this way." 92.230.234.54 (talk) 15:01, 21 June 2010 (UTC)

One irrelevant wikilink hardly excuses this complacent atheist rant. Cuddlyable3 (talk) 19:18, 21 June 2010 (UTC)

Agreed. DRosenbach ^{(Talk | Contribs)} 04:26, 22 June 2010 (UTC)

Indeed we do have "different kinds of humans." That would be because culturally we are different. Bus stop (talk) 15:09, 21 June 2010 (UTC)

"Different kind of humans", is almost suggesting segration / apartide /. The science of countries and their boundries is often originating in battles and war. Study the deeds of you property and you will discover it depends on who won which battle/war. I haven't mentioned God, just humans and their wars. How scientific is that? MacOfJesus (talk) 00:16, 22 June 2010 (UTC)

Historically cultures coincided with national borders to a large degree, though I wouldn't include the bookstore. Bus stop (talk) 01:21, 22 June 2010 (UTC)

The idea of different races having distinct genetic patterns (the underpinning of racism) has been effectively disproven, as there is as much genetic diversity within races as there is between different ones. That being said, see mitochondrial DNA. In reply to the rant, see humanism and materialism, and the idea of the Tower of Babel. ~AH1^(TCU) 16:21, 23 June 2010 (UTC)

Exploration of the ocean bed

While mankind contonues to research outer space, water bodies, land ceaselessly and while scientists explore the deposits undergound, why have we not vigorously studied the various ocean beds/ ocean floors? recently i read a book ( which the scientists on this site would rubbish as figment of imagination) which goes on to talk about the wonders that lies below the ocean bed. even assuming whats written in the book is too fantastic to be true, why havent we the common public heard much about ocean floor/ ocean bed research? why dont we actually study and see what lies beneath? im not taking about scouting the ocean bed for fictitous treasures. Im talking about excavation of the ocean floor and studying what actually lies beyond that. do people involve in such studies?--Fragrantforever 09:05, 21 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

Natural resources on and below the ocean floors have been extensively studied and, where it is commercially feasible, extracted too. See our articles on offshore drilling and deep sea mining. Gandalf61 (talk) 09:24, 21 June 2010 (UTC)

..and, for further information, Physical oceanography and Category:Physical oceanography. Ghmyrtle (talk) 09:28, 21 June 2010 (UTC)

Three-quarters of the Earth's surface is ocean, and most of the ocean bed lies thousands of feet down. Studying it in detail is a lot of work. Looie496 (talk) 21:21, 21 June 2010 (UTC)

Exploring the ocean depths is a lot harder than exploring space. There's nothing but a thin little sheet of air between you and the heavens. Between you and Poseiden's relm, however, is quadbilliontrillionsinkwtftillion metric tons of water and everything suspended in it. Frankly, I'll stick with my 100 dollar kids telescope. I can see a lot farther. --mboverload@ 01:06, 22 June 2010 (UTC)

See deep-sea exploration, hydrothermal vents and brine pools. ~AH1^(TCU) 16:14, 23 June 2010 (UTC)

the supernova

i copied this question from above, because it`s seems that no one will answer it there, especially after it has transported to the archives. and it is better to see this before answering, thanks any way --Abbad Dira (talk) 11:13, 21 June 2010 (UTC).

quote: "The star almost certainly flares and whatnot in the buildup to the supernova, which might be characterized as explosions"

can these flares makes a notable changes in the star magnitude? --Abbad Dira (talk) 07:35, 16 June 2010 (UTC).

Sure, that's what variable stars are all about in some form or another. Luminous blue variable stars, in particular, appear relevant. Dwarf novae may also be. — Lomn 12:57, 21 June 2010 (UTC)

thank you. how much of these changes? 1 or 2 magnitudes? or more? --Abbad Dira (talk) 05:57, 23 June 2010 (UTC).

Take a look at core collapse supernova and cataclysmic variable star, which the NASA link describes. Stars may also shrink in diameter in the pre-amp to an eventual supernova, see for example Betelgeuse (it varies by as much as 0.9 magnitude on a semi-regular basis), but other stars such as Cepheid variables may do this regularly and Wolf-Rayet stars are another phenomenon where material is shed so quickly (in an explosion) that it leaves behind no trace of the core. However, if you're asking about detecting such variability as a sign that a supernova explosion will occur, it's probably not useful as an explosion could happen anywhere from say a year to a million years after the signs are first observed, but we can guess which known stars are likely to undergo a supernova in the future, see List of supernova candidates. ~AH1^(TCU) 16:02, 23 June 2010 (UTC)

thank you.

quote: "However, if you're asking about detecting such variability as a sign that a supernova explosion will occur, it's probably not useful as an explosion could happen anywhere from say a year to a million years after the signs are first observed, but we can guess which known stars are likely to undergo a supernova in the future, see List of supernova candidates.".

i don`t need to discover a supernova, i just interested in the ancient novae and supernovae records. can i understand from what is above that some of theses signs can happen in a range of 10 years before the explosion? and what`s about the GRBs, can they happen before the supernova event like what i have understand from this? the link says that the star`s magnitude increased gradually through a weak before the explosion, can it also increase before a year or 2 in a small flares/GRBs? --Abbad Dira (talk) 09:22, 24 June 2010 (UTC).

A GRB occurs at the end of a star's life, and the GRB described in the article occurred while the supernova (star explosion) was occurring, not before it. Novae are periodic and usually do not immediately precede or indicate the possibility of a supernova. However, Eta Carinae is a star that we need to watch for a possible supernova, or even hypernova explosion in the relatively near future, and there will likely by signs such as variations in brightness before the explosion but they will likely span over hundreds, or even thousands of years, but one thing that complicates this is that Eta is likely a double star (possibly 30 and 90 solar masses), or even a triple star. ~AH1^(TCU) 02:00, 26 June 2010 (UTC)

No antimony nitrate

Why doesn't antimony nitrate have an article? Is it subject to hydrolysis and therefore unstable? --Chemicalinterest (talk) 11:31, 21 June 2010 (UTC)

There's a antimony(III) nitrate CAS 20328-96-5 , it does hydrolyse in water, basic nitrates are also known.

77.86.115.161 (talk) 12:33, 21 June 2010 (UTC)

Just because something has a CAS number (and plenty of suppliers pretending to sell it) doesn't mean that it actually exists! This paper from 1996 says that only a basic nitrate is known for antimony. Physchim62 (talk) 13:00, 21 June 2010 (UTC)

We'd better tell the CRC press - they list in in [2] ! (there's more info here [3]) 77.86.115.161 (talk) 13:12, 21 June 2010 (UTC)

It probably is only stable in nitric acid. --Chemicalinterest (talk) 13:03, 21 June 2010 (UTC)

Why I asked was because Physchim62 posted a response at WP:RD/S#Oxidation of antimony that nitric acid oxidizes antimony to antimony pentoxide. I was wondering whether the Sb₂O₅ would react with additional nitric acid to produce antimony nitrate. --Chemicalinterest (talk) 13:07, 21 June 2010 (UTC)

No it doesn't seem to - there's a possibility of covalent Antimony(v) nitrate compounds being made under extreme conditions such as using sources of Nitronium ion, or other very reactive compounds.

eg SbF(NO₃)₄ is mentioned here [4], more closer to a pure nitrate is SbO(NO₃)₃.DMSO [5]

I can't find a Sb(NO₃)₅ made under any conditions. It might exist - but not via nitric acid.77.86.115.161 (talk) 13:41, 21 June 2010 (UTC)

Looking at periodic properties, you might be interested in this 1877 account of an attempted preparation of anhydrous Sn(NO₃)₂! From the description given, it is clear than the Sn(II) was oxidized to Sn(IV) before the anhydrous salt could be prepared. Simple Sn(NO₃)₂ is still unknown, although basic nitrates are known. Tin tetranitrate is covalent. Physchim62 (talk) 14:29, 21 June 2010 (UTC)

Wouldn't iron(II) nitrate be unstable too because the iron(II) would be oxidized to iron(III)? --Chemicalinterest (talk) 15:00, 21 June 2010 (UTC)

Often.. Using nitric acid plus iron or 'iron(II) hydroxide' would oxidise iron to iron(III) though a preparation exists using cold dilute nitric acid, but , nitrate is not an effective oxidising agent in neutral solutions (ie it's a slow reaction)- so iron(II) nitrate can be prepared eg type of reaction that might make it _{unfortunately Ag+ is an oxidant..}

ferrous nitrate can be expected to be unstable in acid solutions.

It does exist though but in solution "..is very unstable and decomposes when heated even slightly, forming basic ferric nitrate and liberating nitric oxide. To prepare a pure ferrous nitrate, decomposition of a ferrous sulphate solution by barium or lead nitrate is employed" [6]87.102.11.212 (talk) 15:11, 21 June 2010 (UTC)

Indeed. In practice, the oxidation of iron(II) to iron(III) is quite slow compared to the time it takes you to do the necessary reactions. Also, [Fe(H₂O)₆]²⁺ is not very acidic (unlike the iron(III) equivalent), so there is no particular tendency to form basic salts. Physchim62 (talk) 15:24, 21 June 2010 (UTC)

animal tool use

Obviously humans use tools, and a few other animals can make and use tools, but are humans unique in that they are the only animals that use tools to make other (better) tools? Googlemeister (talk) 14:21, 21 June 2010 (UTC)

That is the distinction that I've heard many times before. Animals (and early humans) had tools that just happened to be fit for the job when they were found. Humans figured out how to make tools that can increase the effectiveness of other tools and then learned to manufacture tools from raw materials. -- kainaw™ 14:29, 21 June 2010 (UTC)

Wild chimps have been observed stripping the leaves from a stick, and chewing on the end to make a better termite-grabbing stick. Captive chimps can use a small stick to grab a larger stick to grab some food.

However, I don't know if they've used a tool to make/improve another tool. CS Miller (talk) 18:03, 21 June 2010 (UTC)

Tool making (as opposed to just tool use) has been observed in several species (primarily primates, but others too). I've never heard of other animals using tools to make tools, though. Past experience suggests we'll find animals that do sooner or later - that's what's happened every other time we've come up with something we think only humans do. --Tango (talk) 18:29, 21 June 2010 (UTC)

Oh, I should give a link to: Tool use by animals. --Tango (talk) 18:30, 21 June 2010 (UTC)

if I sterilise my kitchen knife with the flame from my gas stove, will I ruin it?

I have a big stainless steel kitchen knife. As far as I know, it doesn't have a means of being sharpened. The knife has been in some pretty disgusting situations (due to people putting it in the same part of the sink where food gets stuck and sits for days and I had no time to wipe it down with bleach and wait 20 minutes, so I just took the range support off the stove and lit up a gas flame (there's a hole underneath the burner) and ran the knife through the base of the flame.

I didn't run it through until it was red hot but I had some water droplets on the side of the knife and I basically watched the droplets boil off as my "diagnostic". The thing I'm wondering is whether I can ruin my blade if I heat it up too long? And I noticed particles coming off as I washed it -- I hope I didn't melt any temperature-sensitive protective coatings or anything. John Riemann Soong (talk) 15:18, 21 June 2010 (UTC)

You definately can ruin it - see Tempering - I don't know what sort of knife it is and is can depend on that, but the cutting edge will probably dis-benefit from any tempering (lose hardness).

Cleaning the knive is the best way to sterilise it - eg hot water + washing up liquid. If the blade is attached to a separate handle the join is one place to watch out for for build up of gunk.

See also Sterilization (microbiology) - boiling water after properly cleaning it is a better bet. As is alcohol. Also hydrogen peroxide, bleach, or steam (from a kettle) are good ideas.

If the particle where little grey or dark flakes then you might have oxidised it - in the long term this reduces the polish on the blade which is a bad thing. It could have been carbonised dirt, or burnt lacquer too...

If it was me and I had to clean it quickly I would have scrubbed it, then poured boiling water on it.

Was it stainless steel or carbon steel knife? 87.102.11.212 (talk) 15:29, 21 June 2010 (UTC)it.87.102.11.212 (talk) 15:29, 21 June 2010 (UTC)

Stainless steel. I had too much of a microbio reflex... then I realised a knife is meant to be sharp. John Riemann Soong (talk) 15:55, 21 June 2010 (UTC)

Heating it until the water is gone should get it hot enough on the surface; once it starts changing colors it has reached around 400F. --Chemicalinterest (talk) 15:37, 21 June 2010 (UTC)

But the edge might be hotter than 100 C even if some water hasn't bolied off.Sjö (talk) 10:35, 24 June 2010 (UTC)

Tin(II) hydroxide and related compounds

After adding more ammonia, I got a grayish precipitate

I reacted tin(II) sulfate (probably some of it oxidized to tin(IV) sulfate) with some ammonium hydroxide to get a tan precipitate. I reacted it with more and I got a gray precipitate. Tin(II) oxide states that it is black, so is it a mixture of tin(II) oxide and tin(IV) oxide? Thank you. --Chemicalinterest (talk) 15:40, 21 June 2010 (UTC)

No, well maybe a little ;) what you have is hydrated form of the oxide, that is a precipitate which is somewhere between tin(II) oxide and tin(II) hydroxide. Now filter it off, let it dry and then heat it – you might have a surprise... Physchim62 (talk) 16:05, 21 June 2010 (UTC)

"This hydrate is white, burns like tinder when suddenly heated" ! Are you trying to burn chemicalinterest's house down ?!

(ec repeat info) Hydrated tin(ii) oxide is white too. see p345 - if it's the hydrated oxide heating (boiling) should turn it black.87.102.11.212 (talk) 16:09, 21 June 2010 (UTC)

Will it turn red... I'll try it.--Chemicalinterest (talk) 16:16, 21 June 2010 (UTC)

is it possible to fool a plant cell into thinking a gold nanoparticle is a starch particle?

Racking for ideas... my group has lots of experience with animal cells, but not plant cells. This afternoon we are going to see how plant cells with their cell walls digested are going to behave around gold nanoparticles treated with TAT and other membrane-penetrating proteins (normally used on animal cells). At the same time I am brainstorming for other ideas. It will be very exciting if plant cells have vestigial endocytosis capabilities that get activated.

I'm also wondering how plant cells take in starch. Do they? After all, when sugar is transported up and down stems through the phloem, it's through the form of starches and not simple sugars, right?

Basically anything that would get relatively large nanoparticles (20-60 nm) into cells. (Excitingly, we may soon have a means of using much smaller particles -- 2-10 nm without suffering aggregation problems usually associated with them, if we probe the right ligands.) We know animal cells endocytose particles that large -- up to a limit of 100 nm, but they get stuck in endosomes and usually remain unprocessed for hours (by that time, since we are using particle tracking the cells have apoptosed on our microscopes). Is it crazy perhaps to try to maybe enter through plasmodesmata machinery? (If that's how starches are transported?) Very few people in my group are plant specialists.

I was thinking of coating the particle with various carbohydrate-like polymers (or even just lots of monomer ligands) that would make the particle look like useful food for a plant cell. Despite being quite large. Normally I know plants rely on bacteria, protists or fungi to digest nutrients for them. John Riemann Soong (talk) 16:11, 21 June 2010 (UTC)

erm Plant sap says sugars in sap not starch .. it's a fascinating idea of coating gold like a sugar coated pill to confuse the plant though. I'm not a biologist - maybe the bigger picture includes starch transportation.87.102.11.212 (talk) 16:15, 21 June 2010 (UTC)

Agreed, plant sap is a mixture of sugars (usually sucrose), water, hormones and minerals. No sugar polymerism I'm afraid. Plasmodesma are about 60nm in size so you might just be able to squeeze large nanoparticles through, but I have absolutely no idea how you'd go about it. Regards, --—Cyclonenim | Chat  16:21, 21 June 2010 (UTC)

Hmm. I'm thinking of culturing some plant cells on a microscope slide, then selectively rupturing the cell wall of the cells on one end of the slide. We then treat the slide with nanoparticle buffer -- the nanoparticles will be treated with movement protein? The particles will enter through the ruptured end and spread the rest of the cells through plasmodesmata and there hopefully will be no endosomes trapping them.

We could also go the whole hog and basically digest the cell wall of most of the cells, but since plant viruses usually enter through mechanically ruptured cells -- does the cell membrane need to be broken too? I don't know if chemical digestion will work. Of course selectively and mechanically rupturing plant cells sounds a little difficult -- but then so is injecting probes directly into cells, and plant cells are kinda big anyway. Anyone have tips? One thing I do NOT want to do is trigger mass apoptosis -- do I have to worry about ruptured cells releasing apoptotic factors?

(We're going to all this trouble over gold because nanorods are excellent optical rotational probes that respond differentially to polarised light depending on their orientation. And they're less toxic than quantum dots and they don't bleach like fluorophores. We want to see the rods interact with the cytosol and not just stay in a confined endosome.) John Riemann Soong (talk) 17:03, 21 June 2010 (UTC)

This is well beyond my level so I can't comment specifically on techniques, but there are numerous journal entries out there showing gold particles within plant cells ( here's one ), maybe it's worth collaborating with these people to see how they introduced the particles into the cells? They could have just been injected, but they may have used other methods too. Regards, --—Cyclonenim | Chat  17:45, 21 June 2010 (UTC)

effect of color of iris on image formation

Ever noticed black outline around the eye of tiger! know its reason? that black outline minimizes light's intensity, so tiger is able to see its prey in glare also..

willn't the color of iris in human eye (or in any other animal) have any effect on image formation ? isn't it so that person with black iris could see thing more clearly than a person with light-colored iris, in too much light? And vice versa?

and i believe that every thing that happens or is in the world is/was for some reason, so do the iris of human. Thanx .....--Myownid420 (talk) 17:49, 21 June 2010 (UTC)

See our article Iris (anatomy), specifically the section Genetic and physical factors determining iris color, for what causes the color of the human iris. On your last point, it is doubtless true that everything in the world exists for some reason, but it doesn't have to be for a good reason. Comet Tuttle (talk) 18:40, 21 June 2010 (UTC)

There are many, many different human iris colorations, which would suggest that any evolutionary effect is minimal. Physchim62 (talk) 19:23, 21 June 2010 (UTC)

Two things occur to me (pardon the personal research), light does not pass through the iris, only through the 'hole' (pupil) in the centre so it is difficult to see how the colour of the iris can affect the received light. Why not ask someone who wears coloured contact lenses. Coloured in the sense that the iris part is a distinctly different colour from their normal iris colour. Here [7] is what I mean. Richard Avery (talk) 06:35, 22 June 2010 (UTC)

wood

I have noticed that when wiping off an unfinished solid wood stool with a clean wet paper towel that a yellowish stain comes off onto the paper towel. What is the yellowish stain since the wood is unfinished? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 18:27, 21 June 2010 (UTC)

Among other things, wood contains tannins. This could be part of your yellowish stain. Pro bug catcher (talk • contribs). 19:27, 21 June 2010 (UTC)

If it's a bar stool, or used to be, there's a couple of other things I can think it could be, lol. :) Vespine (talk) 00:23, 22 June 2010 (UTC)

Cell disruption, movement proteins and apoptosis

My grad student sort of likes the plasmodesmata idea; we're now looking at particular movement protein papers to see if anything like this has been attempted before. But I want to ask -- do plant cells have responses against movement proteins? I don't know which viral proteins are particularly targeted. I want to know how much nanoparticles treated with movement protein can be added before I start eliciting defence responses.

Also anyone have tips for controlled cell disruption on one end of a plant cell culture (on a microscope slide) while leaving most of the cells alive and not in the process of apoptosis? In particular I'm thinking of using our glass-washing sonicator. I could dip the slide in a solution with mild surfactant while in the sonicator. I know the part that is not exposed to the sonicator solution will still feel sound waves, but they will be much less damaging, right? John Riemann Soong (talk) 18:38, 21 June 2010 (UTC)

Anyone have suggestions on surfactant? I don't want to completely dissolve the cell membrane of the targeted cells -- I need to leave the gap junctions intact. John Riemann Soong (talk) 20:06, 21 June 2010 (UTC)

Erm, I think this is getting to be a particularly specialized homework question! Physchim62 (talk) 21:22, 21 June 2010 (UTC)

It's not going to be marked (unless this is specifically the OP's students PhD work!) so I'd see it more of a problem solving question. Regards, --—Cyclonenim | Chat  21:34, 21 June 2010 (UTC)

I just want some quick and dirty immunology tips. Having to deal with plant defences is relatively new to us. I had to think up this idea all by myself, which probably means I'll probably have a good chance of going somewhere wrong. I just only finished my 2nd year of undergrad, so I don't want to slow down the greater project too much but I want to still be able to conduct my experiment. I want to pull it off so that way I can get my group to look at plants more often. John Riemann Soong (talk) 21:50, 21 June 2010 (UTC)

Amount of water that "sticks" to dipped object.

I would like to determine the (theoretical or real) amount of water that stays on a surface that has been dipped in water (or a water based solution). For the real value, I suppose I could weight the object before and after it has been dipped (and before the water/solution dries). Can anyone point to the theory behind this? Other methods? Or perhaps point to known answers for different objects? I want to determine this for sugar maple and aspen leaves, dipped in a sucrose solution. Ideally to figure the amount of sucrose per unit of leaf surface added by dipping. Pro bug catcher (talk • contribs). 19:24, 21 June 2010 (UTC)

The relevant property is probably surface tension. --Tango (talk) 20:58, 21 June 2010 (UTC)

We have a good article on wetting, which is the phenomenon you are asking about. My understanding is that you can't calculate it from theory (except in idealized textbook cases), you have to find a way to measure it. Physchim62 (talk) 21:13, 21 June 2010 (UTC)

Thanks. Wetting is a good article I wasn't aware of. Pro bug catcher (talk • contribs). 01:44, 25 June 2010 (UTC)

Operating of Transverse flux motor

I'm trying to understand what makes a transverse flux motor move.. for example [8] which seems typical - I can understand figures 4 and 5 ie with current applied causes magnetic field goes through the rotor... But the only way I can understand this working is on a reluctance motor principle (with more than one set of current windings) - operating on a sort of stepper principle - ie a synchronous type motor. (or maybe AC drive with sets of magnets in alternating pole direction where current reversal causes alternate rotor poles to allign , again by the reluctance principle..) Can shed more light on this? 87.102.11.212 (talk) 20:46, 21 June 2010 (UTC)

CALORIE BURN RATE FOR EXERCISE

In starting a new exercise program, I'm trying to determine how many calories are burned per each push-up I do.

I don't remember where I read that 2,600 calories equals one pound and that one calorie equals 4.184 joules. That doesn't help me in converting push-ups to calories burned. I also remember reading, but don't remember where, that there is a conversion of weight lifted to horsepower used, where the horsepower equals a calorie equivalent.

Basically, what I want to know is; for a man weighing 255 pounds, approximately how many calories would he burn doing a correct form push-up? Buzz27 (talk) 21:00, 21 June 2010 (UTC)

You can get a lower bound by figuring out how much the man's center of gravity goes up during the push up, in feet; multiply that by 255, and you have a figure in foot-pounds, a unit of energy, which you can convert to calories in Google or something. (Be careful that there are two units called the calorie that differ by a factor of a thousand.)

But remember that the body is not perfectly efficient, so this figure is really just a lower bound. Also there are important secondary effects that are not necessarily linear in the number of push-ups — to the extent that the exerciser gets his heart rate and metabolism up, they may remain elevated for a number of hours. Also, if he builds muscle, that will increase his basal metabolism (but also possibly make him hungrier). --Trovatore (talk) 21:08, 21 June 2010 (UTC)

(expand) I'm willing to try in metric.. If your arms are A meters long, and you weigh K kilograms, each push up need AKg/2 (centre of bodies mass is ~1/2 along between shoulders and feet) (g~10) = 5AK. So if arms =0.6m and weight = 100kg thats 0.6x100x5=60x5=300Joules (or 0.3kJ) (or ~1/14 calories)

That's just for a push-up I get hot when doing push ups so I'm not 100% efficient. Anyone know how to guess human efficiency?87.102.114.9 (talk) 21:17, 21 June 2010 (UTC)

A pound of fat is about 4000 Calories. A push-up burns somewhere in the neighborhood of 1 Calorie. Unless you have incredibly strong arms, doing push-ups is not useful for burning calories -- their value is in improving your muscle strength in the arms, pectorals, and core. Looie496 (talk) 21:11, 21 June 2010 (UTC)

If you are saying that one pushup burns one food calorie, then pushups would be a great way to burn fat since someone in shape can do 100 pushups in less then 5 minutes, which is approximately the same calorie burn rate that someone running a 7 minute mile would get. If you mean the non-food calorie, then pushups are pretty worthless way to burn fat in the short term. Googlemeister (talk) 21:23, 21 June 2010 (UTC)

Pushups, and other upper-body exercises, are always going to be lousy ways of burning calories. The muscles involved in a pushup (chiefly pectoralis major and the triceps muscle) really aren't very big, and so aren't up to the job of doing lots of work and burning lots of energy. This is all because you're a biped, several million years divorced from swinging through the trees. If you want to burn calories, you need to use the big muscles of the body - chiefly the gluteus maximus, the hamstring and quadriceps groups in the thigh, the muscles of the lower abdomen, and the heart. Running, walking, cycling, skiing, and dancing use these, as do common gym machines like a stair climber or cross trainer. Even exercises like swimming and rowing, which recruit the arms and upper body too, are still heavily leg/ab/gleut biased. There's an easy (well...) way to verify this - go to the gym and use two machines - the stationary bike and the stationary hand bike. Do 100 calories-worth of exercise on each (per the little meter thing, which is sufficiently accurate for our purposes here). The 100 calories on the (leg) bike is pretty straightforward; the 100 calories on the hand bike is (even if you're pretty fit) a soul-destroying slog. I don't believe anyone ever got fit, or lost significant weight, doing pushups. My advice instead would be to check with your doctor that you're healthy to exercise, then visit a gym and have the (usually pretty well trained) exercise coach people there design a balanced program for you, that matches your fitness and meets your goals. -- Finlay McWalter • Talk 22:02, 21 June 2010 (UTC)

My personal experience (obviously OR) is that the exercises most suited for weight loss are the ones that work the whole body. In the gym, try one of the elliptical cross-trainers where you push and pull on the handlebars at the same time as you run on the foot pedals. Those burn 100 calories (as measured by the self-reporting LED display; who knows how accurate those are) with considerably less sensation of effort than a treadmill or a leg-only elliptical.

Swimming is (again in my personal anecdotal experience) a truly excellent weight-loss exercise. I think one of the reasons is that, for many exercises, the limiting factor to how hard you can work is thermal stress. In the pool, the water carries that right away, assuming they keep it at a good temperature for lap swimmers (somewhere around 70 degrees F). --Trovatore (talk) 22:09, 21 June 2010 (UTC)

Well, you should theoretically burn more calories than the physics would say since some types of exercise will up your metabolism for the rest of the day as the body repairs itself. Also, as you build muscle your resting metabolism will be higher. I'd recommend you do body weight squats instead of pushup since you'll be using bigger muscles and moving more weight. Personally, if you do decide to do body weight exercises (nothing wrong with that), then you may want to look into HIIT - that should ramp up your metabolism if you can handle it. Consult your doctor before starting any exercise program...blah...blah...blah....TheGoodLocust (talk) 22:16, 21 June 2010 (UTC)

I've read that what TheGoodLocust wrote: "as you build muscle your resting metabolism will be higher" is actually the dominant way you lose weight by exercising. The calories you burn during exercise are completely irrelevant. You can't reason in the naive way, assuming that the body has a contant metabolic rate and then say that if you burn X alories, you'll lose Y grams of fat. A few years ago this theory was put to the test in a BBC Horizon documentary. Students were given a diet containing twice the amount of calories they normally ate (about 5000 Kcal/day for most of them). The weight gain after a month was minimal, ranging from a few kg to 10 kg. After a few weeks all the weight gain was lost as the students returned to their normal diet.

What happened was that the students with the lowest weight gain increased their metabolic rate, partially due to growing more muscles (without exercising, simply as a respons to increased calory intake). So, this experiments confirmed that the weight does not respond strongly to any attempt to change your energy balance, because your body will counteract that by adjusting your metabolic rate. You have to go to extremes like eating 5000 kcal per day without doing any exercise to see even a modest weight gain of a few kg.

This is not that surprising as without such a mechanism, you could starve to death by eating one slice of bread less every day in a few years time. To lose weight by dieting, you really must eat significantly less calories; the body then cannot compensate for that. In the Horizon documentary, it was mentioned that any weight loss by dieting is temporary. The number of fat cells more or less sets your weight. Your body regulates the metabolic rate such that the fat cells are filled to some fixed degree. If you have lost a huge amount of weight by dieting, then your fat cells are still there, but they are empty. If you then eat a normal diet, say 2000 kcal per day, your body will then slowly start to fill your fat cells; it won't take long before you're be back at your old weight.

My personal experience corroborates this picture. Since about 2 years ago, I've doubled my exercise time. I now run for about half a hour, five times per week. On the two resting days I do brisk walking. I also eat a little less than I did two years ago. But my weight was 63 kg two years ago and now it is 62 kg. The only thing that has significantly changed is my fitness. I can jog for more than an hour without getting tired (I really need to do fast running for more than 15 minutes to feel that I'm exercising at all). My resting heart rate has dropped to 40 bpm (in fact yesterday evening it was 37 bpm). It was around 48 bpm two years ago. Count Iblis (talk) 02:20, 22 June 2010 (UTC)

Yes, that was part of my point, the other idea I was trying to communicate was that certain high intensity exercise programs (e.g. HIIT) will cause your metabolism to spike for 24-48 (?) hours as your body repairs itself from the damage (e.g. microtears). TheGoodLocust (talk) 05:54, 22 June 2010 (UTC)

Well, it's very individual. At some points in my life I have been very successful at losing weight via exercise, at other times not so much. I really don't think it's mainly about muscle gain, partly because my experience is that when I have more muscles I'm also hungrier.

I'm sure Iblis is right that it's not as simple as just subtracting two numbers (not that you can accurately calculate them anyway). But in my experience is nevertheless that exercise can be effective, even if I can't be sure of the exact mechanism.

I recall that there is some research that indicates that exercise actually changes your "set point", the weight that your body tries to maintain. Alternatively, it may reduce low-level anxiety that would otherwise induce you to eat, and it also shouldn't be forgotten that time you spend exercising is time that you're not snacking. --Trovatore (talk) 06:05, 22 June 2010 (UTC)

I've also read that sleeping more helps to lose weight. It has been known for a long time that people with sleeping disorders tend to be fatter. But recently it was reported that people who simply ecide to sleep less tend to be fatter. There is a link with sleeping enough and getting enough exercise that works both ways. I have noted that I sleep a little more too now that I'm exercising more.

The following is my own speculation on this :). It could be that sleeping time counts as "virtual fat" for your body. The whole point of having a fat reserve is that you could survive for a certain amount of time on your fat reserve. What matters to your body is that amount of time, not the amount of fat. Now, your body will respond to eating less by adjusting the metabolic rate; if you eat too little then the body cannot compensate for that and you'll lose weight.

The rate at which you lose weight is then determined by what the minimum average metabolic rate over a day can be. During sleep the body can throttle down the metabolic rate more than during daytime without compromizing on how well you can function. So, the longer you sleep, the longer you can last on the same fat reserve, so you would need less fat reserves to survive for the same amount of time. The body can gauge how well it sleeps uder normal circumstances and use that to control the amount of fat reserves via complicated feedback processes.

What may enter in the calculation here is that if you were to eat far less than you need, you would become very tired and sleepy; your body will want to sleep a lot more to save energy. But if you sleep bad under normal circumstances, you may not respond to this by actually sleeping a lot more than someone who sleeps well under normal circumstances. If the body takes this into account under normal circumstances as well, then the amount of virtual fat your body calclates you have if you sleep well will be larger, so you would lose/gain more weight by sleeping more/less. Count Iblis (talk) 15:28, 22 June 2010 (UTC)

Interesting theory, I'd always assumed it was similar to a Beggars in Spain scenario and that the more people are awake the more they are going to snack. Also, being sleep deprived probably produces stress hormones which cause weight gain/hunger. TheGoodLocust (talk) 17:24, 22 June 2010 (UTC)

Faraday cage from water?

Is water/salt water conductive enough to be used as an effective faraday cage? How much protection would it provide against emp/super-emp weapons? If not what could be added to it to increase conductivity enough to provide adequate protection? I suppose I could put my cell phone in some tupperware, submerge it, and try to call it, but I think that'd be an apples to oranges comparison. Cheers. TheGoodLocust (talk) 22:10, 21 June 2010 (UTC)

Well if you dropped the device 100 meters deep in the sea water it would protect against EMP. You could reduce the skin depth by adding more salt, upto 30% should increase conductivity. Graeme Bartlett (talk) 01:39, 22 June 2010 (UTC)

Well, I figured the sea would do a good job at that, seems to keep Cthulu in check after all, and I'm assuming would work on the super emps too (plus submarines seem like faraday cages in their own right), but I was actually more curious about smaller scale applications - how many inches of salt/sea water would be required to provide emp and/or super emp protection? TheGoodLocust (talk) 03:52, 22 June 2010 (UTC)

The skin depth for a typical metal will be about 1/3000th the typical value for sea water, so 1 mm of aluminum shielding will be about the same as 3 m of sea water. I'm not sure how much shielding one needs for a nuclear EMP, but that ratio suggests it would probably be better to stick with metal shielding for most applications. Dragons flight (talk) 07:53, 22 June 2010 (UTC)

Thank you, very helpful. TheGoodLocust (talk) 08:23, 22 June 2010 (UTC)

Lots of water would be needed, although you're looking at a different effect. Water attenuates the signal so essentially absorbs the energy, a faraday cage routes the signal around the space inside it, through mutual interference.

ALR (talk) 08:17, 22 June 2010 (UTC)

Ah, well, I meant submerge a non-conductive container into sea water (e.g. tupperware), and which should conduct the signal around it. TheGoodLocust (talk) 08:23, 22 June 2010 (UTC)

Yes, I appreciate that you meant you had some way to provide watertight integrity, although a non conductive container will just allow EM waves to pass through it, so you're dependent on the mass of water to attenuate. Part of how a faraday cage works is that the metal thickness allows the cage to act as an antenna, the weight of water would be too much to achieve that.

Deep enough to protect the device the container would be crushed.

ALR (talk) 08:41, 22 June 2010 (UTC)

ALR (talk) 08:41, 22 June 2010 (UTC)

Sorry, this doesn't make sense to me. If the sea water can conduct electromagnetic energy, then that energy will take the path of least resistance, and will conduct around the plastic container. Feel free to explain further though since I may be missing/not understanding some fundamental principle. TheGoodLocust (talk) 21:44, 22 June 2010 (UTC)

This might get involved. Water does act as a conductor, but when you're talking about EMP you've got a mix of the higher frequencies that affect ICT equipment, and the lower frequencies that affect power generation and distribution equipment. The conductivity of water really isn't that important because what you're thinking about is the ability to pass a signal through it.

I've assumed that you're discussing ICT equipment; mobile phone, radio etc, because that's what a faraday cage protects.

A faraday cage works by creating a hole in the signal, the signal interacts with the shell and creates the mutual interference. You won't get that from cladding in water.

What you will get from cladding in water is a depletion of the energy in the signal, and it'll be quite quick. Submarines can only use UHF or VHF within a few metres of the surface, and to get even adequate services do need to break the surface with the antenna, the signal is depleted very quickly. HF does work to a few tens of metres, but it needs to be into the LF or VLF range to get traffic to a dived boat.

But the power is still conveyed somewhat deeper, so what you'll get is a power spike as the signal passes through.

The two different characteristics will affect the device in different ways. Hitting ICT with a higher frequency range pulse will trash the electronics, hitting it with a more general power spike will trash the electrics.

Is that any clearer?

ALR (talk) 22:27, 22 June 2010 (UTC)

I think I understand. You are saying it works on a principal similar to active noise control? If so, is it possible to generate a field beforehand to suppress an EMP or would that not be feasible due to power requirements or some other factor like not being able to calculate the correct frequency? TheGoodLocust (talk) 23:39, 22 June 2010 (UTC)

Not as such, active noise control is more of an injection of noise to counteract, whereas a faraday cage just does it by virtue of how the wave interacts with the material. It's passive in that sense.

So with respect to your latter point, not really. I also don't really see much of a need for it, an EMP is a by-product of an explosion, it's not something that one would use intentionally. Lower effects are also generated by transients in machinery, predominantly around power distribution and generation. That's why generators would normally be inside some form of shielding as well.

ALR (talk) 08:15, 23 June 2010 (UTC)

Firstly. Sea water conducts by movement of ions, which is totally different to the way metals conduct; that will make a difference in the effectiveness.

Secondly - does a faraday cage actually protect against EMP ? see http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2010_June_17#EMP maybe not.. 87.102.66.101 (talk) 21:50, 22 June 2010 (UTC)

Yes, that's why almost all military equipment is in varying qualities of faraday cage. Partly it keeps crypto signals in, but largely it keeps mutual interference and generated pulses out.

ALR (talk) 22:27, 22 June 2010 (UTC)

Bacteria in Spoiled Milk

Foodborne illness mentions a number of the most common offending pathogens—which, if any, is most likely to be contracted from drinking spoiled milk?

Alfonse Stompanato (talk) 23:33, 21 June 2010 (UTC)

I suspect the mind would be the most "common offending pathogen" you could get from drinking spoiled milk. In other words, I think people would worry themselves sick over nothing - the human digestive system is truly an amazing thing and with modern pasteurization methods I don't think you could get botulism from it and, I believe, with botulism you are actually getting sick from the waste products of the bacteria, which might not qualify as a "pathogen." TheGoodLocust (talk) 00:30, 22 June 2010 (UTC)

Soured milk is apparently an ingredient in many recipes, thus I doubt it is bad for you in any direct way. I'm not exactly sure the difference between "soured" and "spoiled" milk; it seems the terms are used inter-changeably.-RunningOnBrains^(talk) 03:38, 22 June 2010 (UTC)

It all depends on what gets into the milk. For example, S. aureus is a major cause of mastitis in cows, humans, and other mammals, and an important cause of foodborne illness, primarily as a source of a pre-formed toxin that causes self-limited form of gastroenteritis (example: PMID 327532). Unpasteurized milk can be a source of brucellosis and other pathogens in some parts of the world. That being said, commercially-pasteurized milk is extremely safe when stored and consumed according to its labeling. -- Scray (talk) 04:01, 22 June 2010 (UTC)

Yeah, there's a big difference between soured milk and spoiled milk. Leave a quart of milk sitting on a warm counter for a few days and there's a good chance you'll be able to smell the difference: butyric acid, which is a marker of spoiled milk, is one of the most obnoxious odors known to man. Looie496 (talk) 04:08, 22 June 2010 (UTC)