Wikipedia:Reference desk/Archives/Science/2010 July 16

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July 16

Is there an easy way to estimate genes in genetics?

Let me explain. Say a man marries a woman and they have kids. The man has black hair and the woman has brown hair. For this we'll say black (B) is dominant over brown (b). Say the man has Bb and the woman has bb. Is there an easy way to figure out what hair color their children would have? I'm fairly new to genetics, so I need some help. Thanks! Raptor ^{Let's talk}/_{My mistakes; I mean, er, contributions} 00:43, 16 July 2010 (UTC)

From Human hair color "The genetics of hair colors are not yet firmly established." --Digrpat (talk) 01:09, 16 July 2010 (UTC)

I admit, bad example. What about Gregor Mendel's experiments on pea plants? How would you figure out the likelihood of an outcome involving monohybrid crossing? The Raptor ^{Let's talk}/_{My mistakes; I mean, er, contributions} 01:14, 16 July 2010 (UTC)

There certainly is an easy way! (Although the question is normally what colour hair their kids could have, not would have. There is usually the possibility of more than one outcome). Take a look at the article on Punnett Squares.24.150.18.30 (talk) 01:29, 16 July 2010 (UTC)

I worded it wrong. Like I said, I'm new to genetics. But thanks for the link! The Raptor ^{Let's talk}/_{My mistakes; I mean, er, contributions} 01:30, 16 July 2010 (UTC)

In your example (assuming the false genetic determination of hair colour, but that's unimportant), each of the couple's children would have a 50% chance of having black hair (Bb) and a 50% chance of having brown hair (bb). That's because all the woman's eggs will carry the b gene, while half the man's sperm will carry the b gene and the other half the B gene. So the couple could have three brown haired children or three black haired children: the probability of either of those cases happening is 12.5% (50%×50%×50%). Physchim62 (talk) 01:36, 16 July 2010 (UTC)

Any combination thereof would be possible (i.e. 2 brown haired, one black haired, two black haired, one brown haired). Falconus^{p t c} 04:20, 16 July 2010 (UTC)

Mendelian inheritance covers this pretty well. Ariel. (talk) 07:08, 16 July 2010 (UTC)

If you are new to genetics, try the introduction to genetics if you haven't already. Smartse (talk) 13:27, 16 July 2010 (UTC)

Another factor responsible for hair colour is levels of melanin. ~AH1^(TCU) 18:32, 16 July 2010 (UTC)

There's an article that introduces genetics? Wikipedia has everything....thanks for the info, everyone. The Raptor ^{Let's talk}/_{My mistakes; I mean, er, contributions} 16:44, 17 July 2010 (UTC)

Sound Waves

When you are in your car and the person in the car next to you blasts their rock music, your car vibrates in your ears. Is that sound waves? Please answer me!!Diver62 (talk) 00:49, 16 July 2010 (UTC)

Put simply, yes. Sometimes people can play music so loud you can actually feel the vibration of the sound waves. Raptor ^{Let's talk}/_{My mistakes; I mean, er, contributions} 00:51, 16 July 2010 (UTC)

Sound is not a wave as light is, but a compression wave. So when you feel it, you are basically feeling the minute waves of high and low pressure. --The High Fin Sperm Whale 01:38, 16 July 2010 (UTC)

You may find our article about sound helpful. hydnjo (talk) 02:44, 16 July 2010 (UTC)

Thanks, champs. I've always wondered what it was. —Preceding unsigned comment added by Diver62 (talk • contribs) 11:27, 16 July 2010 (UTC)

The speakers might also transmit low levels of infrasound, which would explain the vibration effect. ~AH1^(TCU) 18:30, 16 July 2010 (UTC)

Is this a blast furnace or some other sort of furnace?

Is this pictured object a blast furnace? According to sources I have on it (I'll be adding an article once I know whether it's a blast furnace), this furnace was used to produce iron, using coal and charcoal for fuel. Our article on blast furnace doesn't show any furnaces like this one, but I've found pictures of many more, such as this one. Nyttend (talk) 03:36, 16 July 2010 (UTC)

It could be some type of Bloomery. The designs of blast furnaces are VERY varied from culture to culture and time to time. Depending on the age and location, it could very well be a smelting furnace of some sort. Just about any metal-using culture would need a furnace of some sort for smelting purposes. --Jayron32 04:44, 16 July 2010 (UTC)

It was used for smelting from 1854 to 1874. Location is 39°19′55″N 82°20′25″W, within the Lake Hope State Park of the U.S. state of Ohio. Nyttend (talk) 04:54, 16 July 2010 (UTC)

Judging by some sources I've found today (couldn't find them last night), I'm guessing that it is a blast furnace. Article is now online at Hope Furnace. Nyttend (talk) 13:47, 16 July 2010 (UTC)

Nice work! --Sean 14:17, 16 July 2010 (UTC)

Venus in a small telescope

The other day I was looking at Venus with my 6.25" reflector. I was hoping to see it as a crescent. All I could see was a very bright spot, with all three eyepieces. Is Venus just too bright for that? Bubba73 ^{(You talkin' to me?)}, 04:11, 16 July 2010 (UTC)

Venus is very bright at present. Aspects of Venus shows that the next time of greatest brilliancy is on 27 September 2010, less than three months away. Venus will continue to get brighter and remain very bright from August to January, and then fade after that. Dolphin (t) 04:18, 16 July 2010 (UTC)

I know it is very bright. Is it so bright that it overpowers so I can't see the crescent? Bubba73 ^{(You talkin' to me?)}, 04:21, 16 July 2010 (UTC)

Over the next few months Venus will be visible with the naked eye during the day. It appears much less bright during the day. Try viewing Venus through your telescope during the day and you might be able to see the exact outline, crescent or whatever. Dolphin (t) 04:26, 16 July 2010 (UTC)

As of now Venus is slightly gibbous, i.e. slightly more than half full (which is harder to see clearly than when it's a crescent), but in your telescope you should be able to see the shape: it will soon (mid-August) go through 'half' phase and then become an increasingly larger but thinner crescent over the following two months. Likely the brightness will be causing you some problem; also, if you're looking when Venus is quite near the horizon, atmospheric distortion will blur the shape, so Dolphin's suggestion of daylight viewing, which reduces the contrast and places the planet further from the horizon, will help - but be very careful not to let your telescope point at the Sun - even an accidental glimpse could permanently damage your eyesight! It's also possible that your telescope may have slipped out of good collimation and not be focussing accurately - have you tried checking that it's still showing stars as good point images? How well is it showing Mars, which is only about 15 degrees to the east of Venus (but which is very near (92%) full) right now? 87.81.230.195 (talk) 06:23, 16 July 2010 (UTC)

Maybe it is just too bright right now. I may try putting in the Barlow lens and see if that helps cut down the brightness. I'll try before it gets completely dark too. Bubba73 ^{(You talkin' to me?)}, 15:58, 16 July 2010 (UTC)

The Barlow lens might indeed work, in that increasing the magnification (on the same aperture) decreases the brightness. On the other hand, it will also magnify any atmospheric distortions, telescopic aberrations and telescope/mount vibrations. Something you might also try is stopping off some of your aperture by putting a partial mask on the front end of your tube (typically, a cover with a small - say 2-inch diameter - hole, off-centre to avoid the secondary mirror of what I'm guessing is a reflecting 'scope). This also reduces the image brightness, and may reduce some optical aberrations if they're part of the problem. Good luck!87.81.230.195 (talk) 18:13, 16 July 2010 (UTC)

I saw Venus in my 4.5" telescope recently, and was able to observe the cresent quite well. My telescope also has a mask that reduces the frontal aperture to a mere 2", and this is useful for brighter objects. If your telescope doesn't have that, you can try a telescope filter that blocks most of the light so the image will be darker and easier to see, or it could be poor atmospheric seeing disrupting your view. ~AH1^(TCU) 18:27, 16 July 2010 (UTC)

How do fish drink?

The question just popped into my head. Do they every once in a while just take a gulp? Do their bodies simply absorb a certain autonomically regulated amount through their skin? their gills?--162.83.139.249 (talk) 04:34, 16 July 2010 (UTC)

Fish do not drink; they get all the moisture they need through their food, but they can also absorb water through their skin. (This applies to freshwater fish as well as to saltwater fish.)--Shantavira|^{feed me} 05:38, 16 July 2010 (UTC)

That's wrong, take a look at the diagrams at Osmoregulation#Regulators_and_conformers. Freshwater fish do not drink at all, but saltwater fish continually drink through their mouths. Smartse (talk) 13:25, 16 July 2010 (UTC)

You can also take a look at swim bladder. ~AH1^(TCU) 18:22, 16 July 2010 (UTC)

Thanks!--162.83.139.249 (talk) 07:47, 18 July 2010 (UTC)

Permanent marking LDPE

My water bottle is made from opaque low-density polyethylene. I would like to write my name on it. I've tried using a permanent marker (both a Sharpie super twintop and a PaperMate W10) and while the line holds, it quickly comes off in normal use (never mind washing). What can I use to permanently write on this surface? -- Finlay McWalter • Talk 15:06, 16 July 2010 (UTC)

You can etch it, with either conventional tools, laser etching, or a solvent. We used to CNC a lot of HDPE and we would always put in a mark or ID on each piece with the tool. A dremel will do the trick, or even a razor or screwdriver (depending on how nice you want it to look). You should be able to make a thin enough etch that it won't puncture the bottle. Nimur (talk) 15:29, 16 July 2010 (UTC)

is there something wrong in the way I've corresponded to scientists?

I've written to at least a dozen different researchers concerning various inquiries or leads, often asking them if they know any suitable colleagues if they're not suitable or too busy. I was wondering if there's something wrong in the way I craft my emails. Too direct? Not distinctive enough? Do they not take emails from rising third year undergrads seriously?

For example, yesterday I was supposed to get some algae samples from another researcher, along with their species names, to do some plasmodesmata / cytoplasmic channel experiments. So on Thursday afternoon I wrote something like this:

subj: Just a small inquiry =)

Hi,

I was wondering about news if the algae samples were ready yet; or just their biological classifications. Perhaps I could come over to your lab or office when they are ready? 

Thanks so much!

-- 
John Riemann Soong Lüwen
Biochem, Cogsci UVA '12

Even people in the same national laboratory ignore me. =( What am I doing wrong? John Riemann Soong (talk) 15:59, 16 July 2010 (UTC)

Hmm... Maybe they would like more face-to-face contact. --Chemicalinterest (talk) 16:09, 16 July 2010 (UTC)

The e-mail is extremely informal to the point of rudeness for people you don't know who are professionals, and it sounds like you are an undergrad who expects them to drop everything they are doing to interpret and act upon your e-mail, which you have spent very little time working on. You are writing to them as if they are another undergraduate; it's very inappropriate for an academic setting. Here is a more appropriate e-mail:

subj: Algae samples

Dear Dr. [Name],

I am a third-year undergraduate in the biochemistry program here at [wherever]. I recently heard that your algae samples had been prepared, though there was some ambiguity for me over whether the samples themselves were ready, or just their biological classifications. Can you confirm this for me? If they are ready for pickup, would it be possible for me to pick them up at some time that was convenient to you? 

Thank you for your time,
John 

-- 
John Riemann Soong Lüwen
Biochem, Cogsci UVA '12

Notice that I have written this as if it were from one professional to another, not a kid to another kid. Smiley faces, exclamation points, lack of a name or title -- these are not appropriate for professional correspondence with people you don't know fairly well. If you look like you just dashed off the e-mail without thinking about it, they are likely to ignore it without thinking about it. --Mr.98 (talk) 16:12, 16 July 2010 (UTC)

Professional communication - we have an article on everything. Bear in mind the difference between an inquiry to somebody you don't know; a technical report / technical request to somebody you work with; and an informal communication unrelated to work with your professional colleagues. Nimur (talk) 16:30, 16 July 2010 (UTC)

Ok. I did have an enthusiastic conversation with the guy on Tuesday. I am a little more formal when it comes to emailing authors I don't know. John Riemann Soong (talk) 17:05, 16 July 2010 (UTC)

Whatever you do, don't use silly smilies when talking with "adults." Things like =) just say "this person does not take this seriously" to basically anyone older than 22, as far as I can tell. If your e-mail screams "I do not take this seriously," don't expect them to take it seriously, either. I will note, anecdotally, that this is something that many people of "current undergraduate age" seem to not understand. A lot of the older academics and so on blame it on the "kids" never learning how to write formal letters (which used to be taught about a million years ago) or being extremely used to e-mail as an informal means of communication, and not ever being taught how to modulate their formality according to circumstance. I don't know how much I buy the "these kids today" types of arguments, but there is probably some merit to it. You should generally err on the side of formality in situations where you need something from someone who has more stature than you (whether "stature" is measured by age, position, education, power, what have you). If you go too far into formality, they will say, "oh, just call me Bob," and you'll have some idea where you stand. But you won't go bad treating people with respect, as if your communication to them is important, and as if their time was valuable to you. You can go very wrong with being too informal—it is an insult and an irritation to have someone demand something of you without treating you with a modicum of respect, at least in the USA. --Mr.98 (talk) 17:50, 16 July 2010 (UTC)

Speaking as a nominal adult, I find this tragic and would much rather receive the first version with the silly smiley than the long-winded and stuffy second version, regardless of how important a person I might be. I wonder if maybe you are falling foul of heavily restrictive spam filters, the kind which put all emails in the trash if they don't come from a whitelist of addresses and domains. This has happened to me in the past when sending emails to a scientist friend at his lab address; took me a while of feeling snubbed before it became clear what was going on. 81.131.47.121 (talk) 19:30, 16 July 2010 (UTC)

I don't know about that. When emailing someone (as with any form of communication) you should use the appropriate "tone" (not sure if that's the right word.). If you were actually chatting to the guy, you wouldn't be the same way you are when you're chatting to your friend over a beer - why would you treat them the same over email? Zain Ebrahim (talk) 20:32, 16 July 2010 (UTC)

But if I did talk to him face-to-face in an informal manner, would be completely blank me and walk away? If so, well, he's a very special individual. 81.131.47.121 (talk) 20:53, 16 July 2010 (UTC)

He probably wouldn't completely blank you, but he might just say "Sorry, I'm busy at the moment. Please come back later." and then walk off. With email, there isn't the same assumption that you should get some kind of immediate response. If you don't want to respond straight away you can just ignore the email until you get around to dealing with it. If you talk to someone in person, social norms require them to respond immediately in some way. --Tango (talk) 21:09, 16 July 2010 (UTC)

Writing and face-to-face are very different forms of communication and have very different social norms attached to them. Additionally, academia is a place that is based on hierarchies, hierarchies which take a lot of time and effort to get to higher rungs of. It doesn't really matter whether one likes this or not — this is how it is, and if you want to communicate with academics, much less be one, you have to learn how to navigate the system on its own terms. There are some individual academics who obviously are different about such a thing, but you never err by being overly respectful. Personally I have found this to be true in general, 81.131's sentiments to the contrary. People like to be treated as if they are important, 99% of the time. They might not always dislike being treated as a friend or an equal, but it can be jarring and often inappropriate. (One always knows when a con is going down if you are on the street and someone you don't know walks up with a friendly face and says, "My man! How are you doin'! Let me talk to you for just a second...") --Mr.98 (talk) 21:55, 16 July 2010 (UTC)

But the algae samples ... you don't ignore the serious part of a message like that just because it began "Hi!" and you didn't like it. That would be extremely petty. Perhaps he is one of those people who is averse to emails of all kinds and functions by phone calls only. 81.131.47.112 (talk) 23:53, 16 July 2010 (UTC)

Even the serious part does not reflect seriousness. The entire e-mail stinks of informality. It does not give respect, and does not recognize that there is zero reason for this person to do what they are asking (they are not, for example, selling a service). If you are asking someone to do something for you that they do not need to do, you should be respectful. The e-mail for an academic would be perceived as rude and disrespectful. --Mr.98 (talk) 20:23, 17 July 2010 (UTC)

Keep in mind that among academic scientists you will encounter a relatively high proportion of people with sub-average communication skills. You might encounter those that don't seem to understand the subtext of something that is said. Just try to be professional and explain your self as well as you can. ike9898 (talk) 17:14, 16 July 2010 (UTC)

I don't think it has anything to do with that. If you were writing to academic historians you'd have the same (lack of) response if you sent that e-mail. It is just heavily outside the norms of communication that academics are used to in a professional setting, and it confirms any doubts they might have that undergraduates don't take them seriously. (And academics are a sensitive bunch.) --Mr.98 (talk) 17:56, 16 July 2010 (UTC)

Also, in the salutation part of the email, it's a good idea to use a colon rather than a comma. ~AH1^(TCU) 18:20, 16 July 2010 (UTC)

Actually, in my experience, American academics still tend to go for commas much more often than colons, though the reverse might be the case overseas (foreign academics often communicate more formally in general). That's just my personal experience so take it with the appropriate grain of salt. Dragons flight (talk) 18:37, 16 July 2010 (UTC)

I've never heard of using a colon after a salutation in a letter or email. Where does that come from? --Tango (talk) 21:10, 16 July 2010 (UTC)

I don't know its ultimate origins, but the use of the colon is fairly common in business and legal correspondence. The comma is seen as less formal. Dragons flight (talk) 21:20, 16 July 2010 (UTC)

I don't think that kind of minor Miss Manners stuff is really what is at issue here. What matters is the overall tone and extremely colloquialisms (like smileys). Your academics in question probably don't know the Miss Manners stuff, but they do know when they are being talked to like a peer, which is inappropriate unless you have been invited to do so (either explicitly or implicitly). --Mr.98 (talk) 21:55, 16 July 2010 (UTC)

It's not really an issue of formality. You're asking somebody to take some trouble to help you, but you haven't put any effort into it, and you're not offering anything in return, not even gratitude. People are often willing to help when it is treated as a special favor, but nobody likes to be treated as though it's their job to help you. The same thing applies to people who answer questions on Wikipedia, by the way. Looie496 (talk) 23:17, 16 July 2010 (UTC)

You can also just pick up the phone and call the person who can help you. If you need to communicate some details via email, you can always do that after you've spoken to the person on the phone. Count Iblis (talk) 23:23, 16 July 2010 (UTC)

Formality aside, I would point out that even for informal communication 'just a small inquiry' is inherently a bad subject line. Just as with the RD or any forum you should generally aim for informative subjects lines in e-mails no matter who you're communicating with and how well you know them or how informal you're being Nil Einne (talk) 12:16, 17 July 2010 (UTC)

Well, it's worse than that really. To me, "just a small inquiry :-)" immediately translates as "you have promised me something and you haven't done it, so I am politely reminding you". It's informative, only in the wrong direction. Looie496 (talk) 16:50, 17 July 2010 (UTC)

Of course 'just a small inquiry - algae samples' would at least tell them what you're politely reminding them about Nil Einne (talk) 12:10, 18 July 2010 (UTC)

"Regards," is a good way to sign off. In the place of "Yours truly," or "Thank you for your time," I like the simpler "Regards." Bus stop (talk) 12:57, 18 July 2010 (UTC)

replacing and changing cell media while under a microscope

I want to change the cell media of observed human cells on a microscope slide while still on the microscope )we want to track particles at the same time so we don't want to lose our positions too much).

Trying to insert even a tiny syringe needle underneath the slip lifts it. And its an inverted microscope, so this makes it even more difficult.

Does anyone know how I could drill a hole in the cover slip or the glass slide maybe? Or how to work with extremely narrow capillary tubes? (They are so thin they are like 100 microns thick.) I don't know how to draw or pump fluid up or down them. John Riemann Soong (talk) 16:03, 16 July 2010 (UTC)

You'll probably need some type of microscrope flow chamber, which are specially made to allow you to mount a coverslip with your cells and apply different solutions. Some of these set-ups get quite fancy, with multiple ports, stage heaters, etc. You can buy them commercially or DIY. --- Medical geneticist (talk) 16:26, 16 July 2010 (UTC)

Depending on what type of experiment you're doing (and your budget), you can readily purchase virtually any type of fluid-handling slide you might need. If you don't need a coverslip above the cells, then you can use a chambered coverslip product like these ones. It's a slide-sized piece of coverslip glass (#1 or #1.5) with plastic wells sealed to the top, and a removable plastic lid. They come in a number of chamber sizes, and you grow the cells in the chambers right on the coverslip glass. Since it's a coverslip on the bottom, you can observe the live cells at an inverted microscope while they're still bathed in medium. In a similar vein, this company sells small petri dishes (35 and 50 mm diameter) with a small circular hole cut in the bottom. The hole is sealed with a coverslip glued to the bottom of the plate; again, you can image living cells (and add and remove medium!) right at the inverted microscope. In a pinch (if your funding doesn't allow you to purchase these dishes) then it should be possible to construct workable substitutes using your own petri dishes, coverslips, and waterproof non-toxic adhesive.

Now, if you're doing some sort of more complex fluidics, or you need the liquid to be confined to a narrow space, then those chambers I've described won't work. I've seen premanufactured coverslips with all sorts of interesting fluidics on them, but my mind is blanking on the names of manufacturers. TenOfAllTrades(talk) 21:06, 16 July 2010 (UTC)

Following up on my previous comment, I finally recalled the name of the company I was thinking of. Ibidi makes a number of different chamber and channel slides which may meet your needs. Good luck! TenOfAllTrades(talk) 02:01, 21 July 2010 (UTC)

A friendly grad student drilled two small holes each, in several glass slides for me, that would fit within the cover slip. I might use them today and tell you guys how it goes. but thanks for all the links -- they are interesting should I ever proceed beyond hacks -- to something more intense for example. John Riemann Soong (talk) 16:21, 19 July 2010 (UTC)

DOLPHINS

How can dolphins dive so deep? Some dive even deeper than the photic zone and dolphins withstand all that pressure upon them. Why aren't people like them? Is their skin tougher or their body denser or what? I know dolphins are friendly and one of the most intelligent. I love dolphins!!!!!!!:) —Preceding unsigned comment added by Diver62 (talk • contribs) 16:37, 16 July 2010 (UTC)

It seems that with your overt obsession with dolphins :), you've overlooked that a number of organisms can dive much deeper and much longer -- such as the sperm whale. I'd suggest reading up on the sperm whale, as you might find more info relating to them on this topic, as it seems it's a much bigger deal regarding these organisms. DRosenbach ^{(Talk | Contribs)} 16:43, 16 July 2010 (UTC)

You may also be interested in the Mammalian diving reflex which explains why the lungs of the animals are not crushed (Blood plasma filled lungs). -- Sjschen (talk) 16:51, 16 July 2010 (UTC)

Shame on you,DRosenbach. I know the sperm whale is a wonder, but i decided to ask about dolphins. Please answer my original question. You know, I love marine biology and cetolgy. that is everything in the sea.Diver62 (talk) 16:49, 16 July 2010 (UTC)

Shame on me?! What does that even mean? Being somehwhat similar creatures, it is exceedingly likely that whatever permits the sperm whale to accomplish such tasks similarly permit dolphins. Now cut being a clown. DRosenbach ^{(Talk | Contribs)} 19:06, 16 July 2010 (UTC)

Thanks Sjschen, but it doesn't say anything about dolphins? Only penguins!Diver62 (talk) 16:56, 16 July 2010 (UTC)

Umm, the MDR applies to all aquatic mammals. And it only gives a few words about penguins. -- Sjschen (talk) 17:10, 16 July 2010 (UTC)

Thanks champ.Diver62 (talk) 17:36, 16 July 2010 (UTC)

DEER

The deer in our back yard come out of the woods even in the day and eat up all the pansies outside the vegetable garden in the back. If you put human hair on the ground will they not come by or eat anything, or is that just an old wives tale?? Answer requested immediately?'Bold text' —Preceding unsigned comment added by Diver62 (talk • contribs) 16:46, 16 July 2010 (UTC)

No

This is not a science question, and the Reference Desk is not a chat room for opinions like this. --Sean 17:00, 16 July 2010 (UTC)

I'm sorry. I deleted it. I'm stupid, right? Just started Wikipedia and didn't know. THanks anyway.Diver62 (talk) 17:02, 16 July 2010 (UTC)

I think the Science desk is as good a place as any for this question, as it deals with animal behavior. This site claims that the only guaranteed way to keep deer out is to build an 8 foot high (!) fence. It has other suggestions that sound like less work (although "get a dog" is actually probably more work). Comet Tuttle (talk) 17:43, 16 July 2010 (UTC)

The question I was responding to was "What is your opinion on police?", by the same user as this one, who later deleted part of that section. --Sean 17:58, 16 July 2010 (UTC)

thanks, Thanks, THANKS, TANKS!!!!!!!!!!!Diver62 (talk) 18:25, 16 July 2010 (UTC)

(It's really pointless to say things like "Answer requested immediately" and "PLEASE, I NEED AN ANSWER!!!!!!!!!!!!!!!!". This service is supported by volunteers - we answer when we have time, when we feel like it, when we have a good answer, when there's nothing good on TV, when the question is particularly interesting, whenever. Demanding answers on particular timescales or in particular ways (eg saying "Shame on you,DRosenbach" - when this was actually a highly relevant answer) just pisses people off and results in worse service - not better! You might also want to ration yourself to the number of questions you ask - you've been asking a lot recently, and that upsets people: particularly when the answer can easily be found with just a couple of minutes searching. Your questions below about sea snakes and jellyfish could easily have been answered just by typing those words into the Wikipedia search box and reading what comes up as a result. This service is really here for answering questions that are too difficult to answer that way - or which require tricky interpretation of hard-to-understand articles. Either way, being overly demanding and upsetting the volunteers never ends well!) SteveBaker (talk) 19:04, 16 July 2010 (UTC)

How does cactus retain water? --75.83.211.75 (talk) 04:21, 21 January 2011 (UTC)--75.83.211.75 (talk) 04:21, 21 January 2011 (UTC)

How long does it take for a cactus to mature? I know some of them can live 300 years. I wondered since i have a cactus garden!!Diver62 (talk) 17:23, 16 July 2010 (UTC)

It depends on what type of cactus. A small cactus may take a few months to mature, whereas a large Saguaro takes 75 years just to grow a side arm. --The High Fin Sperm Whale 17:49, 16 July 2010 (UTC)

Wow! Does cactus still look the same even when its dead? because i think part of my cactus is dead, but it looks alive.Diver62 (talk) 18:21, 16 July 2010 (UTC)

It depends on what type of cactus. Green ones will generally turn brown. The more succulent the cactus, the more obvious it will be when it loses moisture. -- kainaw™ 18:30, 16 July 2010 (UTC)

it is green on the top of the plant, and brown on the bottom! it gets fertilized once a month in the summer, and water once a month the rest of the year. Help!Diver62 (talk) 18:33, 16 July 2010 (UTC)

That's not a good sign. I had a cactus that died on the bottom, but the top stayed alive for a very long time. The roots were dead and it fell out of the soil, but it stayed green on top for quite a while (since they can live without water for a long time). Are you sure water once a month is the right plan for them? You should check. Ariel. (talk) 23:24, 16 July 2010 (UTC)

Snakes

Do saltwater snakes bite divers underwater? —Preceding unsigned comment added by Diver62 (talk • contribs) 17:24, 16 July 2010 (UTC)

See Sea snake#Behavior and Sea snake#Venom. Comet Tuttle (talk) 17:39, 16 July 2010 (UTC)

THanks. sometimes i just don't know what to look up. silly me.Diver62 (talk) 18:22, 16 July 2010 (UTC)

DNA construct naming/nomenclature?

I have a minor molecular biology dilemma. I've created a mutant construct based on the HPV type 16 genome with specific point mutations (two silent mutations that create restriction sites, and a non-sense+frameshift in the L1 major capsid open reading frame that renders the virus non-infectious). Here's the problem: what do I name this thing? I can't seem to find any documented nomenclature for DNA constructs that are minor modifications of naturally existing episomes, so I figured I would try to tap the collective wiki-wisdom. – ClockworkSoul 18:06, 16 July 2010 (UTC)

I don't think there is any specific nomenclature. An example that came to my mind was the "synthetic genome" that the J. Craig Venter Institute created (covered here). They named one of their genomes JCVI-1.0, so perhaps you should just name your construct with initials and a number? Something like HPV16-CwS1.0. For smaller constructs, most people try to make up a name that is short but includes some important information. Maybe you could convey that L1 is disrupted: HPV16-L1X. --- Medical geneticist (talk) 11:47, 17 July 2010 (UTC)

That works. Thanks! – ClockworkSoul 15:34, 17 July 2010 (UTC)

This site is semi-official, but doesn't even come close to your nomenclature problem. After all, "HPV type 16" is only a conventional name, not one that the powers-that-be have got around to approving. Physchim62 (talk) 15:39, 17 July 2010 (UTC)

Thanks for the response, Physchim62. You're right though: that site is more appropriate for naming at the chemical level, which I certainly wouldn't want to use for an 8000 nucleotide molecule! I did manage to to find a set of recommendations for descriptions of sequence variations, but they also weren't quite what I was looking for (but are useful nonetheless). Regarding the "HPV type 16" name being "only a conventional name", the International Committee on Taxonomy of Viruses might disagree with you! – ClockworkSoul 21:30, 18 July 2010 (UTC)

Jellyfish

Do jellyfish sting divers when they are swimming underwater, thinking they're a fish?Diver62 (talk) 18:34, 16 July 2010 (UTC)

Jelly fish are not active predators - they will sting anything that swims into their tendrils, but don't go seeking prey out. --Ludwigs2 18:38, 16 July 2010 (UTC)

i didn't know that.It isn't tendrils. That's reserved for plants. It's tentacles. what if everything avoids them and doesn't swim into their tentacles? Diver62 (talk) 18:44, 16 July 2010 (UTC)

Lacking either brain or central nervous systems, jellyfish don't "think". When their tentacles contact something, it acts by itself - the stinging cells (nematocysts) will automatically sting anything they touch - but they aren't "thinking" about it. Furthermore, not all jellyfish can sting. Many that can sting produce toxins that humans are completely immune to. On the other hand, some produce toxins so powerful that they can easily kill us. Our jellyfish article is really good - you should read it. SteveBaker (talk) 18:54, 16 July 2010 (UTC)

Box jellyfish and especially Irukandji jellyfish can be very dangerous. Their tenticles can activate venom that attacks every system in the body and even ruptures the blood cells it comes into contact with. Also, research shows that jellyfish do have "eyes" that can see, but no central nervous system to process the information. ~AH1^(TCU) 18:57, 16 July 2010 (UTC)

I wouldn't want to be in the path of those jellyfish.thanks for the jelly infoDiver62 (talk) 19:07, 16 July 2010 (UTC)

Building making it's own weather?

When I went on a tour of Boeing's Everett, Washington facility, the tour guide at one point mentioned that one warm and humid summer day before the ventilation system was installed, somehow enough heat and moisture rose to the top of the 11-story tall factory (which is many, many acres as well...I believe the tour guide also said you could fit all of Disneyland inside the building) that clouds formed and it actually rained inside the facility. Is this even possible, and if so, what goes into making the building create it's own weather system? I was under the impression that it took more depth to an atmosphere than that to create clouds/rain, but I could be mistaken. Ks0stm ^(T•C•G) 18:58, 16 July 2010 (UTC)

It has been reported that NASA's Vehicle Assembly Building (originally called the "Vertical Assembly Building") is tall enough to develop internal weather, as you will see at that article. But the Boeing Everett Factory, although huge, is not so high, and they didn't say anything like that about it when I took the tour. I think you're right to be skeptical. --Anonymous, 19:29 UTC, July 16, 2010.

I could imagine that some activities created hot humid air that condensed on a colder roof. That could have an effect similar to rain but wouldn't involve any clouds. I could easily imagine something like that happening and then being exaggerated in the retelling over the years. It does seem unlikely that one would see clouds after only 11 stories. Dragons flight (talk) 19:52, 16 July 2010 (UTC)

I saw clouds on the ground this morning. Googlemeister (talk) 20:05, 16 July 2010 (UTC)

It would merely require the right temperature, humidity and air movements, which might well arise in such an unusual structure. It's entirely possible to do this deliberately in even a small enclosed space: for example, at the interactive science centre INTECH I visited a few months ago an open-fronted cabinet no more than a couple of metres square and maybe three high with these parameters actively controlled is used to create a mini-cyclone made visible by a mini-cloud*. Ordinarily, of course, buildings are designed to requirements that, deliberately or as a by-product, preclude the necessary conditions, but with the VAB other requirements, particularly a very large and high open space, are overriding so it might just stray across the boundaries permitting them. Given NASA's scientific ethos, it would be regrettable if such a long-standing claim was baseless. I do however agree that a reliable source statement should be sought for citation. 87.81.230.195 (talk) 22:37, 16 July 2010 (UTC)

[* Addendum: the cabinet is partly visible behind the giant Newton's cradle near the centre of the second photo in our INTECH article. 87.81.230.195 (talk) 00:48, 17 July 2010 (UTC)]

Our article on this[1] building says it can produce internal fog; I've heard of, but can't document, showers as well. PhGustaf (talk) 22:44, 16 July 2010 (UTC)

Warm, moist air entering a cold building could condense on the structure and then drip, possibly in large amounts. It wouldn't be rain, exactly, but its effects would be the same. Acroterion _(talk) 19:24, 17 July 2010 (UTC)

fundamental forces

i have read the most basic of the standard model. i understood it well. the only doubt i have is that why does the effect of all the fundamental forces decrease over distance if force carrying particles like photons are involved? someone please throw some light. --Lightfreak (talk) 19:49, 16 July 2010 (UTC)

First of all, they don't all decrease over distance. Electromagnetism and gravity both decrease by an inverse square law. The strong force has constant strength at all distances, although it always cancels out over any distance larger than an atomic nucleus - if you have two strongly interacting particles a larger distance apart the potential energy is great enough that two more particles will be created inbetween them and they'll cancel out the force. The weak force does something odd that I don't really understand (see fundamental force for some details). The reason electromagnetism, when considered in terms of photons, decays over distance is because you can think of it like lots of photons being emitted in all directions at all times. The number of photons at each distance will be the same, but they'll be more spread out at greater distances. That's exactly what happens for electromagnetic radiation. For electric or magnetic forces it's a little different, since you are dealing with virtual photons, but the principle is the same. --Tango (talk) 21:17, 16 July 2010 (UTC)

For the inverse square laws, consider the surface area of an expanding sphere, which increases proportional to the square of the radius. Bubba73 ^{(You talkin' to me?)}, 03:16, 17 July 2010 (UTC)

I don't think that argument can be made to work. An expanding shell of W or Z bosons or pions would fall off as 1/r² in density for the same reason as light (conservation of energy), but the forces mediated by those bosons don't fall off as 1/r².

Mathematically, the electric potential satisfies the Laplace equation, ∇²Φ = 0, and the spherically symmetric static solutions to that in three dimensions look like Φ(r) ∝ 1/r. Taking the gradient of that gives a 1/r² central force. Massive fields instead satisfy ∇²Φ = m²Φ where m is a nonzero constant, and the solutions to that look like Φ(r) ∝ (1/r) e^−mr (a Yukawa potential). Taking the gradient gives a central force that dies off like 1/r² for small r but exponentially for large r. The quantity (ħ/c)m has units of mass, and is called the mass of the field. That interpretation doesn't work classically because of the ħ in there, but the rest of what I just said does work classically. Classically m has length units and can be thought of as an intrinsic curvature of the field, kind of like the cosmological constant in general relativity. (I'm not sure how close that analogy is, but it's not too far.)

The Laplace equation can be interpreted as "conservation of field lines": field lines can only start or end on charges, so as you get farther from the charge they thin out like 1/r², and the field line density is proportional to the strength of the force. Probably that picture can be extended to massive fields somehow. But I'm not sure whether to count it as an "explanation". -- BenRG (talk) 00:54, 18 July 2010 (UTC)

shellac

I have a bathroom sink with a wood cabinet below it. I am not sure what type of wood it is. There are certain small sections where the stain has come off. Can I touch these up with shellac? I do not want to use petroleum based stain. Can the shellac be applied to these sections? I can only assume the existing stain is polyurethane. If the shellac gets on areas of existing stain, will the shellac adhere to the existing stain or will it not adhere? I do not want to have to sand off any existing finish or use paint stripper. Will the shallac work? How long does shellac take to dry? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 20:30, 16 July 2010 (UTC)

Shellac will almost certainly look different, and it will not stick on polyurethane. It is not very waterproof either and so not so good for a kitchen or on something you might want to wash. Dissolve the shellac in ethyl alcohol, I hope you do not mind using that. Graeme Bartlett (talk) 22:01, 16 July 2010 (UTC)

Wax crayons work surprisingly well in that situation. --TammyMoet (talk) 06:56, 17 July 2010 (UTC)

human body aging - what's happening when things begin to sag/stretch downwards?

A particularly old woman sat next to me on the bus yesterday who was not wearing a bra. She had the classic waistline breasts which had stretched and sagged over time far, far down her chest. Thinking about the internal anatomy of the breast, it occurred to me that this process was actually rather fascinating. How, exactly, does the body cope with this sort of thing? Clearly many things must get gradually longer over time, yes? Blood vessels, connective tissue, etc. Or are the cell counts remaining the same and the cells themselves actually lengthening? 61.189.63.171 (talk) 22:39, 16 July 2010 (UTC)

Senescence covers the basics. The extracellular matrix changes; elastin and other elastic fibers wear out, etc. You might also find wrinkling a related topic. Nimur (talk) 00:11, 17 July 2010 (UTC)