Wikipedia:Reference desk/Archives/Science/2015 January 31

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.

January 31

Fiber-spinning machine for carbon nanotubes

Hi there!
What's a fiber-spinning machine and how is it like which is used for creating carbon fibers with carbon nanotubes?
Thank you very much for your help!
Calviin 19 (talk) 11:15, 31 January 2015 (UTC)

Here's a link that I think that you'll find useful, more generally look at spinning (textiles). Mikenorton (talk) 11:22, 31 January 2015 (UTC)

But is it self-assembly?--Calviin 19 (talk) 11:31, 31 January 2015 (UTC)

I have that from this paragraph: In 2003, Rice University researchers led by Richard Smalley made the first carbon nanotube fibers by running a liquid suspension of nanotubes through a fiber-spinning machine of the same type used to make commercial polymer fibers like DuPont’s Kevlar and Twaron, which is made by Teijin Aramid. The rationale was that the nanotubes would flow through the liquid and line up with one another like logs floating on a river. This alignment should make the fiber stronger and more conductive. However, the properties of these early fibers were not very good, says Matteo Pasquali, who now leads the nanotube fiber project at Rice. While other groups turned to making nanotube sheets and fibers from dry materials, the Rice group stuck with its method.--Calviin 19 (talk) 11:45, 31 January 2015 (UTC)

I'm not sure that I've understood the whole paragraph (I'm not an english speaker, I've only started to learn it with the age of twelfe and I'm eighteen years old now.).--Calviin 19 (talk) 11:51, 31 January 2015 (UTC)

This link doesn't exist.--Calviin 19 (talk) 12:57, 31 January 2015 (UTC)

See Spinning (polymers), synthetic fibre, and Carbon (fibre) for the relevant articles, although our coverage of this subject isn't as good as it could be. Mikenorton's link seems to work here, and gives a reasonable introduction to the subject - are you behind a firewall? Tevildo (talk) 16:26, 31 January 2015 (UTC)

When I click the link, the error 404 appears and it's said that the page isn't found.--Calviin 19 (talk) 16:49, 31 January 2015 (UTC)

I take it you're referring to Mikenorth's original link, not your link which is a 404 link and so it always likely to show a 404. Anyway perhaps try this Webcitation archive of the CSIRO link [1]. Nil Einne (talk) 17:22, 31 January 2015 (UTC)

The last link of the page still doesn't work.--Calviin 19 (talk) 17:25, 31 January 2015 (UTC)

Try this direct link. There isn't much useful content on that page, I'm afraid. Tevildo (talk) 20:28, 31 January 2015 (UTC)

About Binding antibody

Hi all,
This article is up for speedy deletion. Many G-hits. The science is all number-y (I will refrain from linking "Dyscalculia") and thus beyond my understanding.
What should be done with this article? Delete? Redirect? Keep and improve?
--Shirt58 (talk) 11:31, 31 January 2015 (UTC)

See WP:DICDEF for a deletion rationale, although this is more appropriate for any subsequent AfD - redirecting to Antibody seems like a reasonable course to take. Blocking antibody probably should go, as well. Tevildo (talk) 18:25, 31 January 2015 (UTC)

What is a good algebra textbook with lots of real-life examples?

I want a linear algebra book, which is rigorous but with lots of scientific or applied science examples .--Senteni (talk) 14:44, 31 January 2015 (UTC)

If you're looking for beginner texts, I'd take a look at the Schaum's Outline series of books: they're generally clearly written and well presented, and have lots of examples. While I can't recommend a specific book, they seem to have lots of books on linear algebra, one of which might fit your needs, and sellers like Google Books and Amazon often have book previews that might let you check this before buying.

If you're looking for much deeper insight, I'd definitely recommend Theodore Frankel's The Geometry of Physics (ISBN 9781107602601, publisher's website with preview), which discusses linear algebra (eg. tensors, differential forms) as a tiny subset of its overall treatment of geometric matters in physics, with lots of examples of the relevance of the maths to physics. But it's much more hardcore than the Schaum books, and I don't recommend reading it if you're not already quite comfortable with the topic at an informal level. -- The Anome (talk) 14:51, 31 January 2015 (UTC)

Also, perhaps you should take this to Wikipedia:Reference desk/Mathematics, where the real mathematicians live... -- The Anome (talk) 16:53, 31 January 2015 (UTC)

The real mathematicians seem to prefer unreal examples, the more abstract the better, not really caring if something describes a real-world phenomenon, or is just a beautiful structure. — Preceding unsigned comment added by Senteni (talk • contribs)

Then Frankel's the book for you: but I should let you know it's quite hard going, presupposes at least undergraduate applied mathematics, takes you into a lot of quite advanced modern mathematical physics, and linear algebra is only a tiny part of it. It's also quite costly, so I'd check it out at the library, or at least read the sample chapter online at the publisher's website, before considering buying it. -- The Anome (talk) 04:46, 1 February 2015 (UTC)

Infertility and safe sex

I'm honestly not seeking a medical advice, nor I was asked for, just curious: if a man and/or a woman is infertile, can they reject safe sex (assuming both are healthy, i.e. with no sexually transmitted diseases)? 93.174.25.12 (talk) 14:45, 31 January 2015 (UTC)

Safe sex is about avoiding disease transmission. Contraception is about preventing pregnancy. Guettarda (talk) 15:12, 31 January 2015 (UTC)

(EC) Your questions is fairly unclear or you seem to be confusing seperate issues.

Firstly safe sex is all to do with STIs. When a man and woman are involved, safe/r sex will also generally provide a fair level of contraception in cases where it matter, but that's more a side effect and isn't actually part of the safer sex component.

If a couple are in a monogamous relationship, don't have STIs considered worth worrying about and don't have behaviour which may risk transmiting STIs via other means (like intravenous drug use), then safer sex may not be needed, although some would recommend it anyway since there is always the risk the other partner may violate the expectations of the relationship (whether it's having sex or other risky behaviour). Note it's also important that there is some confidence in the belief they don't have STIs (i.e. an STI check sufficiently after the person stopped any risky behaviour), the easily noticable effects of STIs (particularly HIV) will often only show up long after the person is infectious. So saying someone is 'healthy' is confusing, a person with HIV even without any treatement may be 'healthy' for a fair while.

Whether that couple want to use contraception will depend on personal factors i.e. how much they want to avoid the possibility of pregnancy. As said, it's seperate from the safer sex issue. When safer sex is recommended, it's recommend in cases even where the risk of pregnancy is low (like male-female anal sex or oral sex) or non existant (like any form of same sex contact). In fact, it's particularly recommended for anal sex (although the risk is high enough for vaginal sex that it's universally recommended there too in cases where you can't have sufficient confidence neither partner has an STI).

While as stated, safer sex will function as a form of contraception (in the case of vaginal intercourse, condoms would be the normal), the failure rate with imperfect use is high enough that many would recommend an additional form if it really matters. Note also a couple may choose forms of contraception which provide little protection against STIs (so aren't a part of safer sex) but are sufficient for their contraptive goals, perhaps higher than condoms alone.

Finally even with professionally confirmed infertility, it's possible contraception may still be recommended (if the couple really want to avoid pregnancy), as infertility isn't a binary. Okay technically it may be more accurate to call it subfertility, but a lot of time when people mention infertility they may mean subfertility. (It may be the infertility combined with condoms is likely to give a low enough chance of pregnancy that additional contraception isn't needed.)

TLDR; whether or not a couple want to use contraception is a seperate issue from whether or not they should practice safer sex even if the social issues which give rise to one may often also give rise to the other, and one of them (safer sex) gives some level of the other (contraception). If pregnancy isn't desired, the chance of pregnancy may still be high enough when there is some level infertility or subfertility that contraception would be recommended.

Nil Einne (talk) 15:33, 31 January 2015 (UTC)

I don't really think there's anything to answer here. I mean, any couple can reject safe sex, and many do who oughtn't. Can a couple safely reject safe sex if both are disease free and pregnancy isn't an issue? Well, depending on how much each one trusts their doctor ... and their partner ... and that there aren't other unknown diseases still to be discovered ... well, in the end it's all a judgment call, and we can't make judgment calls for other people. Wnt (talk) 13:20, 1 February 2015 (UTC)

Electrolyte problems and constipation

1. Is constipation in mammals linked to any mineral deficiencies (except Magnesium)?
2. can excessive amounts of salts also cause constipation?

Ben-Natan (talk) 18:29, 31 January 2015 (UTC)

Constipation. I don't particularly feel like pouring over this article, i'm sure there must be a "causes" section, is any part of your question still left not addressed? Vespine (talk) 00:06, 2 February 2015 (UTC)

Idea of space elevator

Hi there!
Who were the first people who have thought about the space elevator? Jules Verne has mentioned it in one of his books, but in which one? Constantin Tsiolkovski has definitely not been the first person (in 1895) of having thought about the space elevator.
Thank you very much for your help!
Calviin 19 (talk) 18:23, 31 January 2015 (UTC)

I don't recall any space elevators in any Jules Verne book I ever read... the most plausible candidate would be From the Earth to the Moon, but in that work of fiction, the Gun Club spaceflight used a large piece of artillery to fire a hollow shell with people inside - not an elevator! Nimur (talk) 20:28, 31 January 2015 (UTC)

Note that a space elevator is under tension. A space tower is compression structure. What Verne book are you referring to? -- ToE 20:31, 31 January 2015 (UTC)

From the Earth to the Moon is (arguably) the first SF story to propose a plausible method of travelling to the moon, without using magic or cavorite or similar dei ex machina. See History of science fiction and Moon in fiction#Science fiction. Tevildo (talk) 20:37, 31 January 2015 (UTC)

Surely you've forgotten the very plausible Adventures of Domingo Gonsales (c. 1638), in which our astronaut ties himself to several very large migratory geese who summer in Saint Helena and winter on the moon? Nimur (talk) 20:47, 31 January 2015 (UTC)

Term for an F2-only heterozygous phenotype?

Is there any term for a heterozygous phenotype of two codominant alleles which cannot be produced as a monohybrid cross, but can arise in a dihybrid cross with a third allele on each side? In other words, is there a term for the type AB in a situation where AA × BB is impossible, and AA × BC either is impossible or is always AC, but AC × BC and/or AC × BD is sometimes AB? (The inspiration for this question, in case anyone's wondering, is the breeding mechanic in the Social Point game Monster Legends.NeonMerlin 21:52, 31 January 2015 (UTC)

Balanced lethal. D'oh, can't believe that's a redlink but it's mentioned here. It's really important for routine Drosophila stock maintenance. Wnt (talk) 22:20, 31 January 2015 (UTC)