Wikipedia:Reference desk/Archives/Science/2008 May 2

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[edit] May 2

[edit] Hydrogen Compounds: Ionic or Covalent?

Hello. If hydrogen bonds with a halogen, then is the compound ionic or covalent? For example, should I call it hydrogen fluoride (ionic conjugation) or hydrogen monofluoride (covalent conjugation), hydrogen chloride or hydrogen monochloride, hydrogen bromide or hydrogen monobromide, hydrogen iodide or hydrogen mon(o)iodide? (Astatine is the least reactive halogen but may react with hydrogen.) If hydrogen bonds with an alkali metal, then the compound is ionic. Right? Thanks in advance. --Mayfare (talk) 00:57, 2 May 2008 (UTC)

I've usually seen HX compounds named using what you describe as the ionic style ("hydrogen chloride"), likewise with MH compounds ("sodium hydride"). I'm not sure how ionic these things really are though. DMacks (talk) 01:04, 2 May 2008 (UTC)
In the absence of water they are predominantly covalent. However hydrogen monofluoride is misleading. At reasonable concentrations in air Hydrogen Fluoride exists as H6F6 rings. As it gets more dilute it becomes H2F2 and finally HF. Both of these are endothermic reactions. You need to know this if there is a leak. As a cloud is released in air it has a self cooling mechanism and stays low. HF in air is lethal at (by memory) about 6 ppm without needing to be inhaled to kill you. Staying low is not helpful. --BozMo talk 13:49, 2 May 2008 (UTC)

[edit] nitrogen AgAin!!!

Can some one please tell me the price of nitrogen per specific measerment? i need the info for a school prodject. hear is an example: Nitrogen cost 12 dollars per gram........... —Preceding unsigned comment added by 76.14.124.175 (talk) 02:47, 2 May 2008 (UTC)

This has been asked and answered - We've attempted to help. If it's for a school project, do the research yourself. It'll benefit you in the long run. Wisdom89 (T / C) 02:49, 2 May 2008 (UTC)
Not knowing your desired result, or project this website should be of use. Zrs 12 (talk) 03:01, 2 May 2008 (UTC)
Just fixing the search link [1]. Wisdom89 (T / C) 03:10, 2 May 2008 (UTC)
Depends on the purity, surely. I hear the low-grade 78% stuff is really cheap. (But seriously, how about Googling for liquid nitrogen price?) —Ilmari Karonen (talk) 07:32, 2 May 2008 (UTC)
Ignore all these people. Nitrogen costs 12 dollars per gram, just like you said. Tell your teacher you read it on Wikipedia. Franamax (talk) 07:58, 2 May 2008 (UTC)
Franamax, with all due respect, please don't offer incorrect advice just to make a point. We have no idea how experienced, or what age, this questioner is. We should encourage the O.P. to investigate, and assist in some way. The fact that he has repeatedly asked the same question is frustrating, but that's not an excuse for providing flawed information. To the original questioner - you should investigate this task by checking a vendor (a gas supplies shop or welding supply shop website is a great place to start). Nimur (talk) 02:19, 3 May 2008 (UTC)
Point taken and my apologies. It's sometimes hard not to descend into frivolity and follow along the funny part of the thread. I'll shape up, you are quite right. Thanks. Franamax (talk) 05:35, 3 May 2008 (UTC)
Pure Nitrogen-15? Nil Einne (talk) 17:06, 2 May 2008 (UTC)

Call your local "Welding supply" company and ask them; they can probably proide the price for both compressed gaseous nitrogen and liquid nitrogen. But I've heard that in bulk quantities, the price of LN2 is "about the same as beer".

Atlant (talk) 17:35, 2 May 2008 (UTC)

But in bulk quantities, beer is probably not the same price as beer Nil Einne (talk) 19:20, 2 May 2008 (UTC)
Why settle for beer or nitrogen? Guinness! DMacks (talk) 19:28, 2 May 2008 (UTC)
That's ridiculous, by the time they've actually poured the glass of Guinness, you've sobered up! Franamax (talk) 21:07, 2 May 2008 (UTC)
You need to order earlier, then! --Tango (talk) 00:06, 3 May 2008 (UTC)
Nitrogen and water makes Embenzalime Nitrotomine (more commonly known as Whiskey), not Guinness. --antilivedT | C | G 12:25, 3 May 2008 (UTC)
Ah, but it's nitrogen which gives Guinness its distinctive head and "cascade" effect down the inside of the glass! Confusing Manifestation(Say hi!) 22:45, 4 May 2008 (UTC)

[edit] milk removing stains

Why does milk remove ink stains? —Preceding unsigned comment added by 222.153.234.166 (talk) 07:26, 2 May 2008 (UTC)

All sorts of interesting stuff in Milk apart from fat and water. My first thought would be enzymes e.g. Proteinase but that won't fly because we are talking ink stain. Works better on "bodily fluids". The main emulsifier is Lecithin. That might work on ink, but since that is a rather unspecific term, I'm not sure. There's also the possibility of adhesive action. The fat globules might just grab on to the ink particle an roll them off the material. (sorry very unscientific wording) Sort of like rolling flour dust up into a ball of dough. I'm a bit nebulous on what Phospholipids might achieve regarding that ink stain, but lipids are little bits of fat and phospho indicates phosphorous. That used to be an ingredient in many detergents before it was removed for environmental reasons. The phospholipids might work as a Surfactant (tenside). This was the long way of saying "I don't know but hope these ideas will help you on." Lisa4edit71.236.23.111 (talk) 09:49, 2 May 2008 (UTC)
It depends on the ink composition, but my money is on the action of the suspended milk fat. Milk fat doesn't dissolve in the milk; it remains suspended as extremely tiny droplets. Ink dyes are often much more soluble in fats and oils (hydrophobic solvents) than in water (or other hydrophilic solvents). I imagine that when these tiny droplets of fat come in contact with ink, the ink dissolves much more readily than it would in water. (For this reason, whole milk will obviously work much better than skim in this application.) Once dissolved, the ink can be carried away with the rest of the milk, or is more easily lifted with regular detergents. TenOfAllTrades(talk) 15:26, 2 May 2008 (UTC)
That would be my guess as well. If that's the case, then presumably vegetable oil would work even better? --Tango (talk) 15:35, 2 May 2008 (UTC)
No. It might get you from and ink stain to an oil stain, though. --Lisa4edit (talk) 09:13, 3 May 2008 (UTC)
But it would get the ink stain out. Mission accomplished! Vegetable oil doesn't stain particularly badly, anyway. --Tango (talk) 12:38, 3 May 2008 (UTC)
I'd never heard milk had this property, but for anyone who is really interested in getting to the bottom of this, consider performing some of the following experiments (feel free to report back here with your results, for the sake of sating our curiousity):
  1. Separate the milk into curds and whey by titrating in an acid like lemon juice. See if one fraction or other is better at removing the stain. This will suggest, although it will not diffinitively show, whether or not a particular protein (i.e. enzyme) is responsible for the effect. You can also get isolated whey from nutritional supplement retailers.
  2. Compare the ink-removal effects of butter, cream, whole milk, and skim milk to see the role milkfat may play. As tango suggested, you might even try throwing a vegetable oil into this experiment.
  3. Play with other kinds of stains to see if it is something specific to the ink.
--Shaggorama (talk) 08:06, 8 May 2008 (UTC)

[edit] Biome Biotope Ecosystem

Could someone please explain if these are separate concepts, or if not, which are synonyms. Could they all be put on the same page or do they each merit one? 71.236.23.111 (talk) 08:10, 2 May 2008 (UTC)Lisa4edit

No, those terms are not synonyms, but obviously closely related. The term 'Biome' refers generally the largest unit including all the biotic community of an area. Hence basically it deals with the structural part of the living world, integrated by the fuctions of ecosystem. In contrarcy, the Ecosystem is system that integrates both the structural and functional aspects of the living world of a particular area. You can recognise the difference, if I say a Biome is well maintained standing Car either without fuel or driver. until the car starts rolling no work is done and we are unsure of the systems efficiency or even viability. As the fuel starts burning and the car moves it promotes some work and becomes a system. Henceforth, the biome become an ecosystem. There may be several smaller ecosystems in Biome itself. for example, in a Tropical Forest biome a few pond ecosystem, grassland ecosystem and forest ecosystem may be integrated. Next If I assume you are refering an 'Ecotope' as 'Biotope', then I can say an ecotope can be regarded as any piece of particular ecosystem, like a peice of garssland or a single wetlands etc. It is in fact a portion of a large biome, which have basically similar kinds of living environment. The margins of two adjacent ecotope, i.e. the transitional area of ecotopes is known as 'ecotone'. You should not confuse these three atall and they all have their own entities, so as the terms.

For further details on the issue, you may refer the book 'Fundamentals of Ecology' by O.P.Odum. - Dr.Rajarshi, India

Thanks. Unfortunately people who link pages in wikipedia seem to be just as unaware of these differences as I was. I've come across links that were all over the place. Our Biotope page links to ecotope, but does not indicate that they are synonyms as you indicate. Ecology was the higher level concept page I was missing. I don't think that's going to be a lot of help with the links, though. 71.236.23.111 (talk) 00:43, 8 May 2008 (UTC)

[edit] Blood

A few questions about blood.

1) I'm looking for statistics/comparisions on how well blood acts as a conductor of electrcity. I looked at the blood article, and it mentions it contains electrloytes, but I'm looking for more information.

2) Building on the above question-could a person, drenched from top to bottom in blood, use this as a Faraday Cage? What I mean-He gives himself what would be a lethal electtric shock, but the blood acts as a Faraday Cage, leaving the person unharmed, but making it look as though he recieved the full shock.

I understand these are quite bizarre questions, but it is for this exact reason that I need help with them.

Thanks very much in advance. Cuban Cigar (talk) 13:47, 2 May 2008 (UTC)

Does not work, sorry, because the conductivity of the cage has to be far greater than that of the person. Since the person also has fluid and electrolyte and the cross sectional area of them would be far more than the blood film most electricity would go through them not the blood. Anyway blood isn't a great conductor: less good I would think than sea water (which has a higher level of electrolytes).--BozMo talk 14:44, 2 May 2008 (UTC)
First, nothing said here may be taken as advice for real-world purposes related to personal safety. Electricity all too easily kills the careless or curious. I see nothing about conductivity in the Blood article. A quick Google search showed scholarly research on the electricical properties of blood, but behind paywall (You must pay to gain the knowledge). But assuming for the moment that fresh blood was a good electrical conductor, I have grave doubts about the effectiveness of the strategy in (2). The blood with which the person is drenched would tend to run off, leaving only a thin coating, as in the movie Carrie. If Carrie were immediately placed in an electric chair or other lethal source of electric current, or touched a live wire, I would expect her to be electrocuted about as quickly as if she had not been first drenched in blood (maybe faster, since dry skin might insulate better than blood soaked skin). I doubt that a thin coating of blood would be vastly higher in conductivity than the person's flesh, as would be required for it to shunt off the vast majority of what you described as a lethal electrical shock. Now consider that the electricity did pass through the external layer of blood. The hypothetical protective layer of blood would cook, drying it out, heating it and leaving only a carbonized layer with gaps. This would leave the person exposed to the lethal electrical current. A real world conductive protective suit surrounds utility workers who do "live line work" from a helicopter[2]. It is Nomex with stainless steel threads. Note that the worker is absolutely not "grounded" so only a small current passes from the live line to the protective suit and the helicopter, not the huge current that would flow to someone who touched an energized conductor from the ground or from a pole or tower. Edison (talk) 14:48, 2 May 2008 (UTC)

See this 1950 article (.pdf) for discussion of the conductivity of blood. - Nunh-huh 03:56, 3 May 2008 (UTC)

[edit] Activated Carbon

I have two questions about it. First, what makes activaed carbon "activated"? After reading the wiki article on it I'm a little confused as to how physical or chemical changes make carbon activated. Secondly, when it states that a gram of activaed carbon can have a surface area of 500 square meters, does that mean that if i streched out that piece of carbon it would cover an area that big? Thanks Deltacom1515 (talk) 13:52, 2 May 2008 (UTC)

It just means that it has the stated surface area, not that it would be physically possible to stretch it out. Edison (talk) 14:08, 2 May 2008 (UTC)

Ok, thanks. One down, one to go. Deltacom1515 (talk) 15:26, 2 May 2008 (UTC)

I've changed the intro of 'activated carbon' to make it a bit clearer. --Heron (talk) 17:21, 2 May 2008 (UTC)

Let clear the concept more lucidely. You can think of a honeycomb, when you have a piece of activated carbon (non-powdered form). As in honeycomb the wax are sread over the walls of wholes or cavities, the surface of which can not be spread out to assess the area, in case of activated carbons huge numbers of microspores are available, which can not be measured as spread sheet. The surface is known as BET surface, and is available for adsorption of gas molecules. In response to the other question, the activation perhaps refer to enhaced capacity of the carbon as a adsorbent material, due to enhancement in the effective surface area. But, there may be some further explanation beyond this. - Dr.Rajarshi

[edit] Electricity

Another question in a similar vein to the previous one.

For How long can a person's heart completley stop before a person before it is irrecovably damaged to the extent that death is inevitable? I know it is in seconds-but how many? And what factors can change this? The heart article gives 2 seconds-but this makes me think of numerous cases who have been "clinically dead" for days, before magically reviving. So-for how long can a person stop their heart without dying? (Like to point I don't plan to do any of these things-I'm just really curious).

Thanks in advance.Cuban Cigar (talk) 15:16, 2 May 2008 (UTC)

If the heart stops, it is usually the brain that starts to die first, not the heart itself. In the absence of circulating, oxygenated blood, permanent brain damage starts to set in after just a few minutes. Damage to the brain and other organs is reduced if the patient's body temperature is lowered; deliberate hyperthermia was employed in the early days of open-heart surgery to prolong the operating window on a still heart to about ten minutes. Accidental hypothermia exposures – falling through ice on a frozen lake, for example – exceeding an hour have been survived on occasion.
In heart transplants, a heart that is removed from the body, flushed with potassium chloride solution, and kept on ice can be stored safely for up to four to six hours.
In the context of a heart attack (mycardial infarct), the portions of the heart muscle not supplied with blood start to show irreversible injury from 2-4 hours following the infarct. TenOfAllTrades.
If circulation through the rest of the body is maintained via cardiopulmonary bypass, cardioplegia (deliberate stoppage of the heart) can be relatively safely maintained for tens of minutes. (talk) 15:48, 2 May 2008 (UTC)
(ec):I think you have misread the Heart article which says death will occur in minutes, not seconds. The exact time depends on a number of factors and cannot be stated precisely but the Cardiac arrest article says 5 minutes is likely brain damage. You might also like to take a look at Hibernation#Human hibernation and Suspended animation. Why did you put "electricity" in the title of this question? SpinningSpark 15:56, 2 May 2008 (UTC)
The rule of thumb when I was learning first aid was 2 minutes - after that, you risk brain damage. You need to start CPR within the first 2 minutes, and not stop for more than 2 minutes at a time (when running to get help, say). That's properly a low estimate to be on the safe side - permanent brain damage probably takes a little longer, but not much. --Tango (talk) 18:15, 2 May 2008 (UTC)
I suggest reading the article on Clinical death. One of the things you probably are confused about is the difference between Clinical death and Brain death. -- JSBillings 18:49, 2 May 2008 (UTC)

[edit] Robotics

hello plese tell me about what are the various part of a robort machine and how i assemble it??// plese tell me the correct answer.. i am waiting for this.. —Preceding unsigned comment added by 59.98.104.100 (talk) 17:11, 2 May 2008 (UTC)

You may want to be a little more specific in your request, robots come in many different forms and there is no set way to assemble one. Regards, CycloneNimrodTalk? 17:35, 2 May 2008 (UTC)
Your first step would be to determine what it is you want the robot to do. There's absolutely nothing we can do to help you without that key detail. --Tango (talk) 18:09, 2 May 2008 (UTC)
If you are just looking for inormation about robotics in general, you could start with our article. SpinningSpark 01:58, 3 May 2008 (UTC)
There is actually some degree of uncertainty about what constitutes a robot. For example, not all motorized lever-arms are "robotic arms." I recall reading a book (I think it may have been Robot Motion Planning, which stated that a "robot" must have at least three degrees of freedom (three "joints"), and some level of automation. As an example of things which are "kinda like" robots, but are certainly not robots - consider a backhoe. These are complex, instrumented, electronically-controlled, hydraulically-actuated lever arms. Their equations of motion are similar to those of a robotic armature (much larger lengths, perhaps). There are many degrees of freedom depending on the type of equipment. But these machines do not have any automation - they are directly controlled by a human.
Alternatively, it's not just the "intelligence" which makes something a robot. Many software packages are able to monitor and control many independent variables (such as, say, a nuclear reactor controller computer). This is also not a robot, under most definitions. But it's got "computer-controlled" intelligence, and it certainly is actuating mechanical motions (opening valves, moving control rods...)
So what exactly is it that makes something a "robot", anyway? It's not necessarily locomotion, since the PUMA robot is fixed to a table (most of the time ...) - and it's not merely the presence of a computer or a programmable system, since the complex electromechanical actuators of a power station do not really count.
Really, the way I view it, "robot" is a sociological definition for a certain class of machines based on the way they interact with humans. They are machines which are, from the start, designed to mimic a human behavior (albeit with different mechanisms, perhaps in hostile environments or under harsher constraints; or to augment human capabilities such as speed and power). Typically a robot has "intelligence" of some form - usually in the form of a programmable computer system, and preferably with some ability to dynamically adapt to a changing environment (this distinguishes between "scripted" behavior and "intelligent" or "emergent" behavior.
Hopefully this response will help you as you seek to build a robot. If you are looking for inspiration, I direct you to the MIT Humanoid Robotics Group, the Stanford Artificial Intelligence and Robotics Lab, and the Honda ASIMO project:
Good luck with your robot... Nimur (talk) 02:36, 3 May 2008 (UTC)
It sounds to me like you are expecting a technical answer but will probably get semantics. As you say, not all lever arms are called robotic, but many are and I doubt there is much to distinguish them technically, although perhaps there is some functional difference. I've heard of robotic automatons that didn't have microprocessors of any sort in them, and even heard of robots that were controlled by insects (which to me seems more like a vehicle than a robot). I'm no expert, but I think the reason you are having difficulty finding a solid definition is that one may not exist. --Shaggorama (talk) 08:17, 8 May 2008 (UTC)

[edit] Cooler temperatures help in fighting wildfires

I've always wondered why reporters (and even fire fighters) often say that, when they're fighting a wildfire, that if temperatures drop, it helps to fight the fire. How do cooler temperatures help in fighting wildfires? Corvus cornixtalk 17:56, 2 May 2008 (UTC)

In order for a fire to burn you need heat, oxygen and fuel. You remove any of those and the fire goes out. If the temperatures cool, that's going to help get the heat low enough to put the fire out. It's also going to slow the spread of the fire, since the parts that haven't yet caught light will be cooler. Also, cooler temperatures might stop the fuel being so dry, which will reduce the chance of it catching. --Tango (talk) 18:11, 2 May 2008 (UTC)
As the temperature drops and approaches the dew point, water in the air condenses out on to whatever flammable material you have, which inhibits the spread of flames. The temperature drop itself is unlikely to get the material far enough away from its kindling point. (I would guess cooler temperatures also help firefighters stay as comfortable as they're going to get.) InstEngr (talk) 20:20, 2 May 2008 (UTC)
I doubt the heat has much about putting the fires out, since we're talking about swings of 100 degrees, and the ignition temperature of wood in somewhere between 300 and 800 degrees. However, it does have a lot to do with drying out fuels -- hot plants will dry out faster, and dry plants burn faster. The other thing is that uneven heating in some sense causes wind, which could make fires more difficult to control. Finally, cooler temeratures are easier to work in. Less firefighters suffering heat-stroke is a good thing. Keep in mind they're in fire-fighting gear and lugging backpacks and equipment, sometimes. --Mdwyer (talk) 20:23, 2 May 2008 (UTC)

[edit] Some of the king's pigs and some of the king's men put Humpty together again?

Was the new finger a 'natural' miracle?
By Caroline Parkinson
... Lee Spievak, 69, chopped off part of his finger ... in a model aeroplane accident in 2005.
... They provided Mr Spievak ... with the "pixie-dust" - more accurately called extracellular matrix, which he sprinkled on his finger.
... Within weeks, it is said the tip of the finger - including bone, tissue, skin and nail grew back.
... Scientists say they want to see research by Dr Badylak published in peer-reviewed journals - which means work has been assessed by other experts - rather than simply hearing anecdotal reports.

The extracellular matrix was said to be extracted from pig bladders.

Now, if this story were true, what would happen to his finger print? What are the chances that the regained tissues run amok and cause cancer? -- Toytoy (talk) 20:29, 2 May 2008 (UTC)

This has been discussed before on Ref Desk. I wonder why, if it worked for this incautious model airplane hobbyist, wouldn't it regenerate missing portions of those wounded in wars or industrial accidents? Or victims of emulators of Mrs. Bobbit? How small and how large of a limb/organ could be regenerated? Would the patient have an urge to engage in pig-like behaviors, like some 1950's horror movie [3]? Edison (talk) 03:52, 3 May 2008 (UTC)
Since I had just finished typing this when Edison's answer came in some of this is redundant. I'd go with the scientists requesting confirmation. Particularly with the pig bladder source. A finger is composed of bone, cartilage, and soft tissue (muscles, blood vessels, etc.). The stem cell article mentions the difference between Embryonic stem cells and Adult stem cells. Even if there were adult stem cells of pluripotent type (can change into any type of cell) present in that extracellular matrix, and even if such stem cells would work trans-species (from what I know we are still having trouble making them work within the species) just "sprinkling on" is highly unlikely to have any effect. They have to be cultured in sufficient number. The different elements of a limb grow in specific sequence from growth centers. The activity and growth pattern of each cell is influenced by cells around it.. Think of a seed. If you put one in the ground a plant will grow. If you grind it up and sprinkle it on the ground, nothing will happen. These are just some objections that come to mind. Regarding fingerprints this site http://ridgesandfurrows.homestead.com/Friction_Skin_Growth.html might help Lisa4edit71.236.23.111 (talk) 05:13, 3 May 2008 (UTC)
As unlikely as it may seem, it doesn't appear to have happened, though. It could be an elaborate hoax, but baring that, something did cause his finger to grow back... I've no idea what it could have been, but I'd certainly be interested in finding out. --Tango (talk) 15:30, 3 May 2008 (UTC)
Human fingertips sometimes grow back on their own. There was an article on research into regrowth of limbs in a recent issue of Scientific American (last month's, perhaps). They mentioned that severed fingertips do sometimes grow back. It is more common in children. Yes, the fingerprints regrow. Ironically, the traditional medical treatment for severed fingertips inhibits regrowth, otherwise this would be more commonly seen. --Srleffler (talk) 18:36, 3 May 2008 (UTC)
  • Muneoka, Ken; Han, Manjong; Gardiner, David M. (April 2008). "Regrowing Limbs: Can People Regenerate Body Parts?". Scientific American. “One of the most encouraging signs that human limb regeneration is a feasible goal is the fact that our fingertips already have an intrinsic ability to regenerate. This observation was made first in young children more than 30 years ago, but since then similar findings have been reported in teenagers and even adults. Fostering regeneration in a fingertip amputation injury is apparently as simple as cleaning the wound and covering it with a simple dressing. If allowed to heal naturally, the fingertip restores its contour, fingerprint and sensation and undergoes a varying degree of lengthening. The success of this conservative treatment of fingertip amputation injuries has been documented in medical journals thousands of times.” 
--Srleffler (talk) 00:16, 4 May 2008 (UTC)
Thanks for sharing this article. Sorry for posting outdated info. I had looked into a similar subject just a month earlier. Apparently fingertips are a special case. It will be interesting what they can develop starting from that. Lisa4edit (talk) 10:31, 4 May 2008 (UTC)
I know someone who has re-grown their fingertip. The skin under the fingernail didn't adhere to the nail as far as the other fingers; so you can still see which finger it happened too.Polypipe Wrangler (talk) 07:15, 5 May 2008 (UTC)

[edit] DNA paternity tests

Given only a man's DNA and his son's, how would one determine which is the father and which the son? Thanks. Imagine Reason (talk) 21:02, 2 May 2008 (UTC)

Do you know for a fact that this is possible? I'm bamboozled... ----Seans Potato Business 23:06, 2 May 2008 (UTC)
Can you check telomere length? ----Seans Potato Business 23:07, 2 May 2008 (UTC)
I believe that, during meiosis, the genes on a pair of chromosomes are mixed together. So you should be able to tell by picking a pair of chromosomes and seeing which person has a chromosome entirely made up of genes present in the other person's chromosomes. That person will be the son. The father would also have half his genes in common with the son, but they would be split between the two chromosones, rather than on one. That's a guess, I'm not a geneticist, but it seems like it should work to me. --Tango (talk) 23:14, 2 May 2008 (UTC)
Right, I think that's how you'd do it. One set is going to be half composed of a subset of the other one and the other half will be things not in the other one. That's the son. --98.217.8.46 (talk) 23:55, 2 May 2008 (UTC)
Seans, I suppose that in normal circumstances telomeres would work, but I asked the question after watching New Amsterdam (TV series), and the 400-year-old man there would probably have a very nice telomere. I think Tango's idea will work--I didn't consider the full implications of meiosis. Imagine Reason (talk) 01:06, 3 May 2008 (UTC)
Hmm, I'm not sure about that. At the very least, it could be very difficult. Say the father has the gene ABCDCBA. It gets broken up during meiosis and the son gets ABCDCAB instead. How would you know which is the father unless the father's other allele gets tacked on to the end, but you can't rule out that the mother was the contributor. That's why typical paternity tests accept the mom's DNA, the two disputed dads, and the child's. 125.116.12.60 (talk) 05:40, 3 May 2008 (UTC)
You have to look at both of the pair of chromosomes. It's possible a particular pair would prove inconclusive and you would have to pick another pair, but it would have to be really bad luck for there not to be some pair that works. Consider the father has a chromosome with alleles A and 1, and its partner has B and 2. And the mother, C3 and D4. The son might then have B1 and C4 - you'll notice that one of those chromosomes (the first) is made up entirely from alleles present in the father, but the father doesn't have a chromosome with alleles entirely from the son (this is the bit that could fail, simply by coincidence, and you would have to try a different pair). That allows you to tell which is which. --Tango (talk) 12:45, 3 May 2008 (UTC)
Ok, my OP doesn't allow for the testing of the mother's DNA, although you may have additionally the DNA of a grandson with another mother, and his son. Imagine Reason (talk) 14:11, 3 May 2008 (UTC)
I don't think you need that. As long as you know they are father and son, you just don't know which way round, my method should work. In a typical paternity test you are trying to work out if there is a relationship, rather than what the nature of the relationship is - it's a completely different question and requires different information to reliably answer it. --Tango (talk) 15:27, 3 May 2008 (UTC)

[edit] pKa (dissociation constant)

As per the theory goes, greater the value of pKa of an acid, the weaker the acid is!But what about the comparison of Phenol and Ethanoic Acid? Both have a pKa value of 10 and 4.76 respectively. But Phenol is considered to be a stronger acid than Ethanoic acid, why so? As per the theory as 10 > 4.76, therefore STRENGTH OF ETHANOIC ACID > PHENOL??? kindly explain! —Preceding unsigned comment added by 123.252.231.92 (talk) 21:05, 2 May 2008 (UTC)

Who considers phenol to be a stronger acid? ----Seans Potato Business 23:05, 2 May 2008 (UTC)
phenol is not a strong acid at all. Wisdom89 (T / C) 02:05, 3 May 2008 (UTC)
The questioner may be thinking about the hazards of chemical burns due to concentrated phenol. In the laboratory, one must be careful of phenol crystals and concentrated phenol solution, due to the risk of injury. However, careful reading of our acetic acid article will indicate that similarly concentrated solutions of ethanoic acid are also hazardous. It is misleading to compare concentrated phenol to standard vinegar (5% acetic acid). Dilute phenol is (relatively) safe - Chloraseptic is a 1.4% solution of phenol used as an over the counter oral antiseptic (although I don't know if they buffer/neutralize it). -- 128.104.112.85 (talk) 17:28, 4 May 2008 (UTC)
Also, chemical burns are not only caused by acidity. I don't know about phenol, but for example HF, a weak acid, causes more damage than HCl, a strong acid. --Itub (talk) 17:03, 7 May 2008 (UTC)


HF is certainly weaker than many other inorganic acids, but with a pKa of around 3.2 (depending where you look) i don't know if i would call it weak. But your point is correct: bases, oxidizers, solvents, and other chemicals can do significant damage to our skin and body. --96.231.177.64 (talk) 19:35, 8 May 2008 (UTC)

[edit] Mobile phone communication

My mobile phone frequently claims to have no signal, but if I attempt to make a call, it will go to four (out of five) signal-strength bars in the space of a second. Why does my phone do this and could I miss calls? ----Seans Potato Business 22:35, 2 May 2008 (UTC)

When your phone actually tries to request a connection from the basestation (as opposed to idly sitting in your pocket reporting its presence now and then) the power is wound up to whatever the phone thinks it needs (up to the 2 watt maximum allowed) to establish the connection. This increase in transmitted power may suddenly produce a response from the base station which had previously thought you were asleep or had gone away. SpinningSpark 15:45, 3 May 2008 (UTC)

[edit] Transposons

"Additionally, many transposons contain promoters which drive transcription of their own transposase. These promoters can cause aberrant expression of linked genes, causing disease or mutant phenotypes." - by "linked genes" do they mean genes in close proximity or genes that are "physically linked" with no intervening stop codon? ----Seans Potato Business 23:01, 2 May 2008 (UTC)

Both. If the insertion creates a fusion with an endogenous gene, then it certainly has potential for causing disease. But strong promotors can often drive aberrant expression of nearby genes when inserted even with an intervening stop codon, perhaps by the disruption of an essential intervening repressor. Sometimes an insertion event can even lead to nearby genes being driven by another, endogenous promotor. Rockpocket 01:51, 3 May 2008 (UTC)
Supplemental: what exactly drives the transposon to produce a transposase? Why does it get transcribed? My understanding is that DNA is transcribed when a protein complex recognizes a promoter sequence, docks, and starts pumping out mRNA's. Transposons are (somewhat) randomly inserted into the genome, what specifically enables them to propagate? How often does each specific copy transpose-atize? Another burning lifelong question from: Franamax (talk) 02:02, 3 May 2008 (UTC)
According to [4] "Binding sites for host-specified proteins are also often found within or close to the terminal IRs (inverted repeats), and these proteins may play a role in modulating transposition activity or Tpase expression." Examples include integration host factor (IHF) which binds within or close to the Tpase promoter in some transposons. In other words, transposable elements typically hijack the the cellular machinery of the host to transcribe its transposases. Rockpocket 07:24, 3 May 2008 (UTC)

[edit] Food ingredients

All food labels show serving size and the number of grams of each ingredient from a standard list. Where is a list of recommended amounts of these ingredients based on a person's age, weight, etc.? Also, where can I find lists of ingredients for foods that do not have labels? --Schaum 23:11, 2 May 2008 (UTC)

Dietary Reference Intake would be a good place to start. --Tango (talk) 00:05, 3 May 2008 (UTC)