Wikipedia:Reference desk/Archives/Science/2014 March 9

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.

March 9

Likely Error in Microphyte Page

The microphyte/microalgae page had an illustration of Spirulina, a cynobacteria. Microalgae are algae, which are eukaryotic while cynobacteria are prokaryotic. The caption for spirulina also included dubious unsourced information about its health benefits. Aslo the algae page listed cynobacteria as both an "included group" and an "excluded group". These errors have all been corrected, but please let me know if I was mistaken. Greg Comlish (talk) 04:32, 9 March 2014 (UTC)

Note the second paragraph of algae, which begins "There is no clear consensus definition of algae." Many sources do include cyanobacteria in "algae," and these claims are sourced in the article. This is in old problem, and the best we can do on WP is acknowledge some of the issues of nomenclature. Still, it doesn't make sense to have a disputed member as an example, when there are plenty of unequivocal mycrophyta that could be pictured - So your edit to microphyte does seem to be an improvement.

I'm not feeling WP:BOLD at the moment, but expect your edit to algae to be reverted once enough people catch wind of it. The truth of the matter is, cyanobacteria are included as algae in some sources, and excluded in others. The list format did make it a bit confusing though. Perhaps the ideal compromise is to have cyanobacteria listed in both "included" and "excluded" sections, with both instances having a footnote that says "some sources include cyanobacteria as an algae, while others do not." -- but the place for this kind of discussion is Talk:Algae, where there is already a whole thread about "prokaryotic algae".

There's a reason why systematics and cladistics are used when biologists want to be careful about describing relationships and group memberships. "Algae" doesn't even have a taxonomic rank, it's just a "group", and a highly polyphyletic one at that. So -- I wouldn't lose too much sleep over trying to nail down a strict scientific definition of this known-to-be-problematic grouping. This is all basically covered in the first three paragraphs of algae, before you made any changes. SemanticMantis (talk) 05:41, 9 March 2014 (UTC)

sinuses and eyes

Recently when I was having an eye test the optician said casually, 'Of course you have sinus problems.' As a result I now wonder whether problems with sinuses affect eyes and/or eyesight. If so, how please? And if not, how did she know? Thank you in advance. — Preceding unsigned comment added by 78.127.60.178 (talk) 08:12, 9 March 2014 (UTC)

It need not have been anything to do with your eyes at all; people with sinus problems have a distinct nasally quality to their voice. It could be that your hair dresser would make the same remark. That said, there are obviously connections between eyes / nose / sinuses (see, for example, photic sneeze reflex) and irritated sinuses can lead to weepy or red eyes. I try not to go to my optometrist deep in hay fever season as I know I'll get weird results. Matt Deres (talk) 13:21, 9 March 2014 (UTC)

If a person's nose/sinuses are plugged up, their tear ducts may no longer drain properly, resulting in watery eyes, and they may also be suffering from a general allergic reaction or cold, either of which can cause red, itchy, watery eyes. StuRat (talk) 17:43, 9 March 2014 (UTC)

Thank you for your responses. They both adopt a commonsense approach but I must admit I was hoping for something more scientific. For instance, years ago, women taking the contraceptive pill experienced difficulties using contact lenses. It transpired that pregnant woman (which to their bodies, women taking the pill appear to be) produce a film over the eyes. This phenomenon was previously unknown. I wondered if there might be a more direct connection between the eyes and sinuses than normally supposed. — Preceding unsigned comment added by 78.127.60.178 (talk) 10:12, 11 March 2014 (UTC)

A point well-taken. Some PDE5 inhibitors (notably, Viagra) have the uncommon side effect of triggering rare anterior optic neuropathies, in some cases irreversibly causing loss of vision. It turns out eyes are linked to treatments for dysfunction of much more distant parts of the body than the sinuses. loupgarous (talk) 05:08, 12 March 2014 (UTC)

Education : Blacksmithing, Goldsmithing, Gem-cutting

Hey, I asked a question here on the reference-desk yesterday regarding metals and railways and I got such good response that I was thinking I should ask another question related to metal. Something I have been thinking about for a while.

If one is thinking about taking up Blacksmithing, Goldsmithing or even Gem-cutting as a profession, what education would be needed? Chemistry and metallurgy seem obvious, but what else, and where would be a natural place to start?

By the way, for any Wiki-modders out there who might read this, There doesn't seem to be an own reference page for questions related to 'Education'. If there is, then I must have missed it. Perhaps there should be? So science seemed the most natural place to ask this question.

Krikkert7 (talk) 16:29, 9 March 2014 (UTC)

Metallurgy is the general topic for metals, but that deals more with smelting, etc., whereas a blacksmith or goldsmith shapes existing metals, for the most part. Lapidary is the topic of dealing with gems. However, smithing and gem-cutting don't require advanced degrees, but rather you would look for an apprenticeship where you could learn from a master.

However, beware that much of this work is now either done in third-world nations paying minimal wages, or by machine. So, there are only a few jobs left in those fields that pay well. For example, you could own a jewelry shop that repairs wedding rings and such. (It would probably be cheaper for them to just buy a new ring, or send the current one overseas to repair, but the sentimental value prevents them from doing either of those.) StuRat (talk) 17:35, 9 March 2014 (UTC)

In the UK there are university courses in silver and gold smithing, but the normal route to black, white, tin, silver and gold smithing is via an apprenticeship. No formal qualifications may be needed, just an aptitude. --TammyMoet (talk) 19:23, 9 March 2014 (UTC)

Things that used to be industrial necessities are now done mainly as "artisan" crafts for fairly limited markets like decorations and people trying to do authentic restoration of historical objects. Modern steel plants and machine shops are about as far from blacksmithing as you can get. There are professional societies dedicated to keeping the old trades alive like the Artists Blacksmiths’ Association of North America and Society of North American Goldsmiths. Their websites will probably have links to educational options. Colleges with studio art programs will probably offer lapidary and basic metalworking classes. Some also offer glassblowing, probably fewer offer blacksmithing. Probably the only modern metallurgy class that will be particularly useful for a blacksmith would be a class on steel microstructures and phase transformations. The strength of steel is generally determined less by the alloying elements and more by the heat treatment. For working with gems, classes in geology would be more relevant - learning how to identify minerals, what causes color/shape. Mr.Z-man 19:33, 9 March 2014 (UTC)

Blacksmithing is more of an informal trade. I remember in high school, the only future career listed that didn't require a high school diploma was blacksmith.--Auric talk 19:42, 9 March 2014 (UTC)

I know that these professions, at least blacksmithing, isn't the same as it used to be. In a way, I think it's a shame. But thanks for your answers. They were helpful. Krikkert7 (talk) 22:31, 9 March 2014 (UTC)

MSG and obesity

See sources #26 and #27 in the MSG link in the title. One study showed it doesn't cause obesity in Chinese subjects, while another study shows that it does cause obesity in a similar group of Chinese subjects. So, if we assume both studies to be factually correct, does anybody know why there would be a difference in the conclusions ?

Also, has a study been done on the effect of MSG on Europeans or Americans ? My two thoughts are that they may react differently, due to genetic differences (with Orientals having been exposed to it longer and adapted better to it) or perhaps differences in diets. StuRat (talk) 18:16, 9 March 2014 (UTC)

What mechanism is offered? MSG is the salt of glutamic acid, certainly not a huge source or calrories, nor known to be medically active. Yes, it makes plain foods less plain. But so does salt and pepper. The two cuisines that use it most, Eastern and Italian (from Parmesan cheese and tomato sauce) do't seem particularly fat. I'd look instead at the influence of affluenza. μηδείς (talk) 21:07, 9 March 2014 (UTC)

Not sure about those studies, but previously I'd heard it stimulates the appetite, hence people being hungry again an hour after eating Chinese food. StuRat (talk) 21:16, 9 March 2014 (UTC)

Yes, you'll want to look at umami. But the notion is like saying that salt causes obesity. It simply makes less palatable foods more palatable, in this case signalling to the brain the presence (whether it exists or not) of proteins. μηδείς (talk) 21:53, 9 March 2014 (UTC)

At least for me, salt limits how much of an item I can eat. I get dry mouth and my lips start to crack. Drinking lots of water helps, but that fills me up a lot sooner. And knowing my blood pressure will spike as a result and I will feel veins throbbing in my head also makes me stop. StuRat (talk) 20:39, 11 March 2014 (UTC)

The study that did find a link looked at BMI vs MSG intake at a single point in time. The study that did not find a link looked at change in BMI over a 5 year period (as well as the baseline BMI). The study that did find a link surveyed 752 people from rural areas age 40-59. The other study looked at 1282 people ages 20+ from a mix of rural and urban areas, but only from one province. The second study also points out a potential issue with the first one: "A major criticism of the present study was that the total free glutamate (specified as glutamic acid) intake of the non-users compared with of the users of MSG was the same, possibly due to the fairly homogenous dietary patterns among the predominantly rural community, or it may have resulted from inaccuracy in the assessment of MSG intake."

In general, it seems like the main reason they choose China is convenience. Chinese people cook with MSG at home, so it's easier to measure how much they're actually eating. Westerners get most of their MSG in processed and restaurant foods. Mr.Z-man 00:08, 10 March 2014 (UTC)

Acceleration of human evolution during Holocene

This paper claims that human evolution accelerated during the last 40,000 years. Unfortunately the paper is too technical for me. I was hoping someone could briefly summarize exactly how the researchers reach this conclusion ie how it is even possible to measure the rate of evolution. 65.92.5.74 (talk) 21:07, 9 March 2014 (UTC)

Well, if they can get DNA from fossils of various ages, they can determine how much of a change took place between each sample. StuRat (talk) 21:12, 9 March 2014 (UTC)

You might like to look at adaptive evolution in the human genome.--Shantavira|^{feed me} 21:18, 9 March 2014 (UTC)

• They measured the long-term rate of evolution by calculating the difference between human and chimpanzee DNA. They measured the rate of recent evolution by measuring the differences between the DNA of various modern human populations, assuming that all of them diverged from a relatively small unified African population around 40,000 years ago. I should note that the recent discovery of Neanderthal and Denisovan contributions to the DNA of some populations raises doubts about the validity of their analysis. (Their paper was published in 2007.) Looie496 (talk) 05:21, 10 March 2014 (UTC)