Wikipedia:Reference desk/Archives/Science/2011 February 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.

February 22

checks

is there a way to do a free background check on someone? most sites want money example http://www.publicbackgroundchecks.com --Tomjohnson357 (talk) 01:23, 22 February 2011 (UTC)

yes, if you put quotation marks around the peron's name "like this" then only people with that exact name will be returned. if it's a common name, try adding, one at a time, anything you know about the person, such as a city he or she has lived in, a school they have gone to, etc. If you really want to go into detective mode, add them as a friend on facebook. 109.128.213.73 (talk) 01:43, 22 February 2011 (UTC)

This is a terrible answer. APL (talk) 05:47, 22 February 2011 (UTC)

im referring to a criminal background check — Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 04:52, 22 February 2011 (UTC)

Why is this on the science desk? I thought that Nimur had deleted it by mistake when removing something else, but now I'm not so sure. --Trovatore (talk) 05:18, 22 February 2011 (UTC)

I have to say that I doubt it. Doing a background check is not a purely automated process, so at some point a human will be involved. I don't know, but I assume that's got to cost something. APL (talk) 05:47, 22 February 2011 (UTC)

SourceWatch (article) has backgrounds for some scientists, groups and politicians. ~AH1^(TCU) 21:08, 26 February 2011 (UTC)

Convolutor worm?

I was just watching a documentary which mentioned an unusual worm (I think they called it a "convolutor worm") that lives in symbiosis with algae and whose nutrition is provided by the algae's photosynthetic activities rather than by digestion.

I can't find an article on such a species, nor google hits. Any hints? FT2 ^{(Talk | email)} 14:17, 22 February 2011 (UTC)

Try Convolutriloba in Google, I think you'll be pleased! Richard Avery (talk) 14:30, 22 February 2011 (UTC)

Symsagittifera roscoffensis perhaps? Nanonic (talk) 14:40, 22 February 2011 (UTC)

Running an ordinary gasoline powered car on ethanol

My car runs on normal unleaded gasoline. The gas station near by house sells gas pretty cheap, but it has 10% ethanol in it. Is this safe for my car? Would it be alright if my car ran on 100% ethanol fuel? ScienceApe (talk) 15:18, 22 February 2011 (UTC)

Here's a Popular Mechanics article that answers your questions. The specific quotes: "The engineers at [Ricardo] also disassembled some old fuel systems to examine them for the effects of prolonged E10 exposure. They didn't see any." and "Pure ethanol can damage cars that aren't designed to handle it. On its own, the grain alcohol can cause galvanic corrosion, swelling of rubber components and rust or corrosion on certain metals, because of its ability to hold water." Andrew Jameson (talk) 15:40, 22 February 2011 (UTC)

Yes, 10% ethanol is safe. That's why most gas include some ethanol. No you could not use 100% ethanol in your car. 100% ethanol would require an engine with a different compression ratio.Dauto (talk) 15:42, 22 February 2011 (UTC)

That's incorrect. Using 100% ethanol in a spark-ignited does not require a different compression ratio. Ethanol has a higher octane rating than gasoline, so you could run a higher compression ratio if you desired to, but it's in no way required. Andrew Jameson (talk) 16:25, 22 February 2011 (UTC)

That's right. It's not strictly required. But without a change of compression ratio and/or adjustment of spark timing it would run very inefficiently and with low power. Dauto (talk) 02:21, 23 February 2011 (UTC)

As I understand it, the key differences in flexible-fuel vehicles is the seals, gaskets, tubing, etc. Ethanol has a different reactivity profile than gasoline, so plastics and rubbers that are perfectly stable in contact with gasoline can become brittle/break down in contact with ethanol (and vice versa). Vehicles designed with only gasoline in mind may have components which aren't stable to high ethanol concentrations. My understanding is that all modern cars can handle ethanol up to about 10%, it's E85 and the like which require special attention to materials. My understanding is that the reports you sometimes see of people having problems with 10% ethanol is due to fouling - since ethanol can dissolve different compounds than gasoline can, "gunk" that has accumulated in the fuel lines/fuel filter might be solubilized and brought to the cylinders; it's not that 10% ethanol is bad for the car, it's more that the fuel lines were dirty. -- 174.21.250.120 (talk) 17:01, 22 February 2011 (UTC)

It depends on the definition of "run". I ran a normal car engine on diesel fuel once. It would "run" if you mean "it made the car move forward when pressing on the accelerator". However, it didn't "run" if you mean "made the car travel at a reasonable speed without causing damage to the car and passengers". I expect running on ethanol without conversion to result in very very poor miles per gallon and low speeds. -- kainaw™ 17:05, 22 February 2011 (UTC)

"Diesel fuel" and "ethanol" are two different things. Diesel fuel has a lower octane rating than gasoline, while ethanol has a higher octane rating than gasoline. Diesel is also much harder to vaporize, which is why putting diesel into a gasoline engine will make it run poorly or not at all. Andrew Jameson (talk) 17:39, 22 February 2011 (UTC)

Complementing the above. I think it is also possible to get around the different compression ratio requirements by changing the timing and the behavior of the electronic injection system. Either way, you car wouldn't be able to deal with ethanol unless it is a flex-fuel design. Dauto (talk) 16:12, 22 February 2011 (UTC)

At least E10 scrounges up bits of water out of your fuel ... though apparently those using boats have many nasty things to say about it! [1]

E10 is not supposed to be used on boats or planes. Graeme Bartlett (talk) 04:12, 23 February 2011 (UTC)

Tinkerers in the 1970s (or earlier) modified automobile carbs to allow the vehicles to run on ethanol. Thee wee some limitations, but I do not recall exactly what. Low temperature operation, perhaps? Edison (talk) 05:20, 23 February 2011 (UTC)

World oil consumption

How much oil is burned in the world every day? This does count plastics, lubricants, asphalts etc. If you answer, can you please give a reference? --T H F S W (T · C · E) 18:22, 22 February 2011 (UTC)

According to Peak oil#Worldwide_production_trends (which references this report by the International Energy Agency), production has been 85.24 million barrels/day for the average of 2005-2008. Since we don't build or deplete large artificial oceans of oil, production and consumption are about equal over the medium term. --Stephan Schulz (talk) 18:38, 22 February 2011 (UTC)

I already know how much is consumed. I'm asking how much is burned. --T H F S W (T · C · E) 18:42, 22 February 2011 (UTC)

Sorry, I was confused because you listed all the other uses of oil (that only eventually may be burned). As a rough estimate, I'd still say that nearly all produced oil is burned eventually. Only a small part is made into plastics, and even those are often burned in thermal recycling. According to the US EIA, in 2009 about 94% of oil ended up in products for immediate burning. --Stephan Schulz (talk) 18:56, 22 February 2011 (UTC)

Oh, whoops, I forgot the "not". Thanks though. --T H F S W (T · C · E) 19:25, 22 February 2011 (UTC)

masonary

1.what are the composite wall?

2.please draw me 1 if any bricks in english bond with a turning corner as the blocks — Preceding unsigned comment added by Bruce sarinke (talk • contribs) 18:43, 22 February 2011 (UTC)

Here's a pic of English Bond, but there's no turning corner: [2]. StuRat (talk) 20:00, 22 February 2011 (UTC)

There's a corner on this page. Alansplodge (talk) 13:33, 25 February 2011 (UTC)

atom

In a previous post it was stated that an electron in an atom can be a kilometer from the nucleus of the atom but still be "part" of that atom. What force is maintaining that "connection?" —Preceding unsigned comment added by 165.212.189.187 (talk) 18:47, 22 February 2011 (UTC)

This is true only in the sense that there is nothing else perturbing the system - if you have miles and miles of perfect vacuum, and nothing affects the movement of the electron but its ever so gradual revolution about one proton. Otherwise this doesn't happen, and the atom is just plain ionized. (Though I suppose that there is probably some way you can analyze the interactions of non-bonded atoms as if each electron is also considered as trying to 'orbit' the other nucleus at great range, maybe under the rubric of "Van der Waals forces"?) Wnt (talk) 19:18, 22 February 2011 (UTC)

The force is electrostatic attraction, though in the case of an electron orbiting an atomic nucleus, the force must be described using quantum mechanics. When an electron's effective radius is very large, it requires very little energy to totally ionize it - in other words, the electrostatic potential energy well is much smaller than, say, the average thermal energy of a random collision with another object. So, to be stable, you have to find a way to thermally isolate the electron - which is pretty impossible in a real set-up; but hypothetically, in a perfectly isolated vacuum, with no incident energy or particles of any kind, an energized electron can stably orbit indefinitely at macroscopic radii. Nimur (talk) 21:29, 22 February 2011 (UTC)

The orbit wouldn't be stable. The electron is accelerated and would emit soft photons and cascade down to a low orbit. Dauto (talk) 02:12, 23 February 2011 (UTC)

For a thorough introduction to these highly-excited-but-not-quite-fully-ionized creatures, Rydberg atom is worth a read. TenOfAllTrades(talk) 23:42, 22 February 2011 (UTC)

An interesting feature is that these expanded atoms have a longer lifetime than the smaller excited atoms. Graeme Bartlett (talk) 04:10, 23 February 2011 (UTC)

I think you're missing the point of the question. The original question was about the atom in the ground (or indeed any other) state. And yes, even in the ground state there is a small but finite probability that the electron can be found at arbitrarily large distances from the nucleus. This is the result of the quantum mechanical treatment of the atom, with electrostatic potential/forces holding the thing together. This has no effect on the energy needed to ionize the atom (barring lots of tricky questions of how to measure or observe any of this). --Wrongfilter (talk) 09:00, 23 February 2011 (UTC)

What would be the volume of this atom? —Preceding unsigned comment added by 165.212.189.187 (talk) 15:40, 23 February 2011 (UTC)

That was actually part of the point I was trying to make with the comment "simultaneously infinitesimally close to the nucleus and infinitely far from the nucleus" [3], you can't give a definitive radius or volume to the electron density of an atom, because the electron density never really ends, it just sort of tapers off. You can set arbitrary cutoffs (say, "the radius within which 95% of the electron density is contained") but those are just that: arbitrary. - However, if you're looking for the radius/volume of the atom rather than that of the electron density, you can resort to phenomenological definitions. For example, the van der Waals radius can be defined by the the behavior of gasses, or by one half the minimal non-bonded atom-atom distances in crystals. That's the radius of a solid sphere that the atom "behaves like" under the conditions where you measured it. This tends to be rather consistent between different types of measurements for each element, somewhere in the 1-2 Å range for the common elements. The van der Waals volume is then defined as just the volume of the hard sphere with the van der Waals radius. -- 174.21.231.113 (talk) 17:53, 23 February 2011 (UTC)

Is there any evidence of atoms like this existing in the vacuum of space? —Preceding unsigned comment added by 165.212.189.187 (talk) 18:14, 23 February 2011 (UTC)

We say the electron has a certain probability of being very far from the nucleus. If you check a billion hydrogen atoms you'll maybe find one where the electron is very far from the nucleus. If you watch a single hydrogen atom, the electron will be close to the nucleus most of the time but might be very far for short periods of time. This is how nature works on the atomic level: we can only talk about probabilities of finding an electron here or there. In fact, it is impossible (by Heisenberg's uncertainty principle) to observe a trajectory of the electron. Quantum mechanics is weird and it requires quite a bit of effort to get one's head around it. There are also atoms in a special, highly excited state where the electron is even on average rather far from the nucleus (most of the responses here were about these Rydberg atoms), and yes, these have been observed. --Wrongfilter (talk) 20:19, 23 February 2011 (UTC)

Internal state

http://books.google.com/books?id=OAsQ_hFjhrAC&pg=PA216&hl=en#v=onepage&q&f=false

At the bottom of page 216, the author says that the internal state of a body will be the same regardless of whether it is moving or not. But if the internal state takes into consideration the relative positions of the particles in the body, wouldn't (by Lorentz contraction) it be different in two inertial frames? 74.15.137.130 (talk) 19:32, 22 February 2011 (UTC)

A moving body would appear different in two different inertial frames, yes. But in the frame containing the body, the internal state when in motion isn't any different from when at rest, if the motion is uniform. If it was different, then you'd be able to tell when the body is in motion. That's what I gather from that page. ~Amatulić (talk) 21:13, 22 February 2011 (UTC)

... and remember that the Lorentz contraction is symmetric i.e. the moving observer measures the "stationary" body's dimensions as contracted. (so, in one sense, the contraction is not "real" but just a feature of the observation, though in other senses it is measurably real) Dbfirs 23:44, 22 February 2011 (UTC)

Etymologies of methane, ethane, propane, and butane

What are the name origins for methane, ethane, propane, and butane? Unlike the later pentane, hexane, etc., they don't derive from the Greek or Latin words for their number. --75.15.161.185 (talk) 22:10, 22 February 2011 (UTC)

Methane comes from Methyl, and see the bottom of that article for where that came from. Ethane is from Ethyl, and butane is from Butter. See this site for any others you have an interest in. Ariel. (talk) 00:32, 23 February 2011 (UTC)

This says that methyl was defined as "univalent hydrocarbon radical" by Jöns Jakob Berzelius in 1844. Ethyl apparently comes from ether, which itself was coined in c.1730. Here's propane and butane for your perusal as well. In reality, it looks like we should ask why pentane etc. have got such boring names. SmartSE (talk)

from etymonline

1873, from ethyl + -ane.

1868, coined from meth(yl) + chemical suffix -ane.

1866, with chemical suffix -ane, from prop(ionic acid) (1850)

1875, from but(yl),

Vespine (talk) 00:35, 23 February 2011 (UTC)

Methane from methyl from methylene: spirit of wood

Ethane from aether: ether

Propane from propionic: of first fat

Butane from butyric: of butter

Plasmic Physics (talk) 03:07, 23 February 2011 (UTC)

I guess you could call pentane either valerane or amylane, and hexane may be called caprane. Plasmic Physics (talk) 08:32, 26 February 2011 (UTC)

Bacillus cereus and alcohol prep pad contamination

I went to the Wikipedia article on Bacillus cereus when I learned that widely used alcohol prep pads(70% Isopropyl alcohol) made by the Triad Group and sold under many store names have been recalled in the US by the FDA due to contamination with Bacillus cereus. See [4]. Parents whose 2 year old died from meningitis have sued the company with the claim that the contamination caused the fatal infection: [5].

• 1)I am puzzled by the Wikipedia article on the bacillus, because it talks about it as a common inhabitant of the human intestine, and says little about it being dangerous when it enters broken skin, where a contaminated alcohol prep might introduce it, or a noncontaminated one might fail to kill it, such as before an injection or other skin penetration. There are only 2 brief sentences about its effect in skin infections,and nothing about systemic infection such as meningitis. The article actually says some positive things about it: "It recommended as pathogenic microflora in pharmaceutical oral products in Brazilian Phamacopaeia." Could someone add a bit about the risk from it being on the skin when alcohol preps are used before an injection or incision?
• 2)Also, if the purpose of an alcohol wipe is to kill off harmful bacteria, why doesn't it kill the b. cereus? Is it becasue the b. cereus as a spore is resistant to alcohol? The Wikipedia article only discusses the bacillus's sensitivity to heat. Some expert editing of the article is badly needed. In addition, the article on Alcohol says almost nothing about its use as a skin prep before injections, or for cleaning medicine vials before a hypo is introduced.

Bacillus cereus endospores are highly resistant to ethanol, although it does have some activity against them.[6] Also, according to a cute little wiki (alas, "noncommercial use only" and not snarfable) [7] the bacillus creates ethanol by fermentation, perhaps explaining some of its resistance. Wnt (talk) 23:00, 22 February 2011 (UTC)

• 3)Rubbing alcohol only vaguely says "good against vegetative bacteria and fair against fungi and viruses, but is ineffective against spores" without any links to see what is included in "vegetative bacteria." What is and is it not effective against? Strep? Staph? Pseudomonas? Anthrax? The article on Bacterial infection lists many common infectious bacteria, but again there is no mention of what antiseptics are effective against them. The article Antiseptic says that alcohol is "commonly used" but again with no note as to its failings such as the apparent one in the case of b. cereus.
• 4)Betadine (Povidone-iodine is a more modern antiseptic. Is it a more effective prep than alcohol pads, and if so why isn't it or Tincture of iodine used instead of alcohol (if the skin discoloration due to Betadine is not a problem)? Edison (talk) 22:24, 22 February 2011 (UTC)

You make excellent points about our articles. Regarding point #4, though, povidone-iodine can cause significant reactions (e.g. PMID 17064209), and one can sometimes grow pathogenic organisms from povidone-iodine (e.g. PMID 19815282) illustrating its slow antiseptic action when in liquid form (it's activated by drying); in fact, there have been infection outbreaks associated with povidone-iodine (PMID 1376156). So, no antiseptic is perfect. -- Scray (talk) 23:34, 22 February 2011 (UTC)

So how about tincture of iodine as an alternative to practically useless 70% isopropyl alcohol prep pads?Edison (talk) 05:16, 23 February 2011 (UTC)

Tincture of iodine (elemental iodine solubilized by the presence of iodide through formation of triiodide ion) is far more prone to hypersensitivity reaction than is povidone-iodine, due to the large amount of free iodine (this is discussed in the povidone-iodine article, I believe). Thus, it is used when rapid killing is particularly important and a reactions are not (i.e. its use is relatively limited). This episode of contamination of alcohol prep pads should not, IMHO, overshadow their demonstrated utility (when used appropriately and not contaminated). Anything can be contaminated, even adhesive bandages and tongue depressors (PMID 19754749). This is why we need effective regulation of the manufacture of medical equipment, and each outbreak teaches new lessons. -- Scray (talk) 13:03, 23 February 2011 (UTC)

This news coverage was the first mention I had seen of "nonsterilized alcohol pads." I had assumed that the alcohol was an effecetive antiseptic. There is a contrast between an antiseptic which contains dangerous microbes, and their presence on things not expected to kill germs, such as gauze, cotton pads, tongue depressors, or adhesive tape. The bottle of tincture of iodine in the medicine cabinet has a little glass applicator which is applied to the cut or scrape. Presumably the iodine is supposed to kill any pathogens picked up by the applicator. An weakly effective antiseptic or antibiotic ointment applicator/dispensor seems like a route for spreading microbes from one wound or person to another. Edison (talk) 17:14, 23 February 2011 (UTC)

Agreed. Medical practice is complex, so in addition to good equipment it requires common sense, beneficence, excellent training, adherence to proper technique, and vigilance. -- Scray (talk) 18:30, 23 February 2011 (UTC)

is there a link between gender orientation to sexual orientation?

ya know, in a superficial way it seems that indeed there is, i myself don't agree and i think that even if there is, it ain't that robust...

but, what does the research shows to us?, is there a link?, and if there is, how significant it is by this stage of the research?

thanks and blessings,

beni. —Preceding unsigned comment added by 79.176.18.237 (talk) 23:16, 22 February 2011 (UTC)

What do you mean by "gender orientation"? Are you possibly referring to gender identity, or simply to which gender a person prefers the non-sexual company of? Or maybe something else entirely? Someguy1221 (talk) 00:18, 23 February 2011 (UTC)

I was going to ask the same. The term "gender" tends to be used in terms of the gender one is, or perceives oneself to be. The term orientation tends to be used to mean what one is attracted to. So you wouldn't usually talk about gender orientation. You might talk about the gender a person is or the gender they believe themselves to be, and the gender they are sexually attracted to, but you probably need to clarify the question before it can be responded any better. FT2 ^{(Talk | email)} 03:18, 23 February 2011 (UTC)

Hey, indeed, i speak about Gender Identity.

thanks! —Preceding unsigned comment added by 79.176.18.237 (talk) 11:33, 23 February 2011 (UTC)