Wikipedia:Reference desk/Archives/Science/2013 September 9

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September 9

6d transition metals

Has anyone ever published predictions on the melting and boiling points of the 6d transition metals? Double sharp (talk) 03:50, 9 September 2013 (UTC)

From some simple searching of each article, Rutherfordium has both a predicted melting point and a predicted boiling point although I haven't checked the sources. If you include it, Lawrencium also has a predicted melting point although I don't know where the figure came from as there's no citation in our article, may be you can work out from the history. Nil Einne (talk) 17:02, 9 September 2013 (UTC)

Anything for the others? (I can imagine the region around Sg and Bh having insanely high melting and boiling points!) Double sharp (talk) 05:34, 10 September 2013 (UTC)

To be clear, for all our articles those were the only 2 that mentioned a predicted melting or boiling (at least under the search terms 'melti' and 'boil' or something similar). One more Hassium, mentioned the relatively high melting point of other group 8 elements but that a melting point had not been precisely calculated (whatever it means by that). I think pretty much every one was mentioned as a predicted solid which isn't surprising but does suggest there's some estimation of the melting point even if it's simply that it's higher than room temperature. (I have no idea what's published outside our articles, I would guess the sources used in our articles would be a start.) Nil Einne (talk) 13:17, 11 September 2013 (UTC)

I had a look at the paper they were citing (I should know, I wrote that part!) and they only say that the elements are solids. That's not a terribly interesting estimate, especially for these transition metals, for which I can think of no reason why they should not be solid at STP! Cn would interest me more. Except that I've seen predictions for it being solid, liquid, or gaseous at STP (and never with associated melting and boiling points!) Double sharp (talk) 11:57, 13 September 2013 (UTC)

Stability of Technetium

Just a quick question: exactly why is Technetium radioactive despite its low atomic number? Based on a search I did in the Reference desk, our article on it used to have a section which explained why, but for some reason no longer does so. Could someone explain or link to an article/page which explains why Technetium is radioactive? Narutolovehinata5 ^tccsdnew 11:33, 9 September 2013 (UTC)

Isotopes of technetium#Stability of technetium isotopes, Mattauch isobar rule. Double sharp (talk) 12:09, 9 September 2013 (UTC)

But ⁹⁷Tc⁴³⁺ (fully ionized) should be stable as ⁹⁷Tc can only decay via electron capture. Double sharp (talk) 12:12, 9 September 2013 (UTC)

For a more detailed look at it, see this. Double sharp (talk) 12:35, 9 September 2013 (UTC)

Well, technically every element from niobium onwards is susceptible to at least spontaneous fission (see List of nuclides), so maybe that answers your question? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:33, 12 September 2013 (UTC)

Medication and the angle of the head

I've noticed that some people (no idea if it's common or not) when taking medication pop the pill in their mouth, take a sip of liquid and then tilt their head backwards. I assume that this is a belief that the pill will be easier to swallow. Is there any reason why tilting the head backwards would assist in taking pills? CambridgeBayWeather (talk) 12:47, 9 September 2013 (UTC)

Logic suggests that it provides a steeper slope off the tongue, and hence the pill would go down more easily 217.158.236.14 (talk) 12:51, 9 September 2013 (UTC)

This is entirely original research (well, not quite - I was given this tip by a friend when I had to take some large tablets), but I think the idea is that you want the medication to be swallowed with the liquid, not after the liquid. Tipping the head back makes a tablet sink to the back of the mouth, where it is swallowed at the same time as the bulk of the liquid. Conversely, for capsules, tipping the head forwards means they float to the back of the mouth with a similar effect. Since my friend gave me the tip I've always done it this way (tablets back, capsules forward) and found it significantly easier. I have observed that far fewer people use the head forwards trick with capsules than the head back trick with tablets - perhaps because it is slightly counterintuitive. Equisetum (talk | contributions) 14:06, 9 September 2013 (UTC)

More ObPersonal, based on experimenting with my cup of coffee and lunchtime baguette immediately on reading this question.

I, and I assume many if not most people, find it somewhat easier to swallow when my head is tilted back rather than in a normal sitting posture or looking downwards (e.g. in a keyboard-wards direction); this seems to be related to relative compression of the tongue and throat in these postures.

Pills/capsules are generally harder and sometimes larger and more angular than typical (masticated) food boluses (boli?) or particles that are swallowed, and combined with one's heightened consciousness in swallowing pills (as opposed to the semi-unconscious actions of normal feeding) are in any case harder than normal to swallow: tilting the head back therefore helps to counteract this added difficulty. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 14:49, 9 September 2013 (UTC)

Thanks. I find, to my annoyance, that I am now doing it as well. CambridgeBayWeather (talk) 00:10, 10 September 2013 (UTC)

On rare occasions I find I have not taken enough water for a large or set of pills, and rather than gag while pouring more water, I will tilt my head back and swallow. This happened only last week taking a C supplement. I don't think it's necessary with small pills or sufficient water, I very rarely find I need to do it. μηδείς (talk) 00:26, 10 September 2013 (UTC)

Unless you're using a straw, you're pretty much compelled to tilt your head backward when drinking something. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:28, 10 September 2013 (UTC)

That's blatently, obviously, CLEARLY false! Do you even think a tiny bit before answering questions here?

It depends entirely on the vessel you're drinking from. Suppose we take an idealized situation, a hemispherical bowl that's utterly full of some liquid. When you tilt the bowl in any direction, by even the tiniest amount - liquid spills out. So long as you can place one edge of the bowl to your lips and tilt it even a tiny fraction - you can easily drink without tilting your head. The same is true of a cylindrical container - which has most normal drinking vessels covered.

Moreover, by creating some suction and using the flexibility of one's lips, it's easily possible to drink from a flat liquid surface without even tilting either head or container.

Only if the container is very small - and far from full, might you may be unable to tilt it sufficiently to get liquid out without the opposite rim hitting your face and then you'll have to tilt your head backwards - or if the container flares outwards (like a conical flask) then you might have to tilt your head forwards to avoid your chin hitting the bottom part of the container. But for something like a glass, it's very easy to drink without tilting your head so long as it's reasonably full.

Just try something once before making such ridiculous pronouncements. SteveBaker (talk) 15:02, 10 September 2013 (UTC)

Just take your personal attacks and stick 'em where the moonshine don't shine. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:37, 10 September 2013 (UTC)

And when you're finished with that task, go to google images and search [chugging], and then send notes to all those folks tilting their heads back and inform them that they're drinking the wrong way. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:53, 10 September 2013 (UTC)

Well, if you search for "chugging" I'd expect that - it means "drinking rapidly" - and to do that, you need to tip your head back. But that's not what you said. You said: "...pretty much compelled to tilt your head backward when drinking..." - so if I search Google images for pictures using the more reasonable search term "drinking" - then I see a good mix of people tilting their heads back and not tilting their heads back. So, it doesn't appear that people are in any way "compelled" to do that - and I'm sure you now realize that which is why you try to deflect the criticism by searching other terms to find one that might somehow support your ridiculous claim. Indeed if you look closely at the "drinking" photos where people are tilting their heads back while drinking, you'll see that most (but admittedly not all) are drinking from bottles and cans and other narrow-mouthed containers - or are emptying the last drops from something - exactly as I said above. The ones who are merely taking a mouthful of water (as one would to swallow a pill) are much less likely to be tipping their heads back. So what you said was incorrect. You can't have even stopped for a moment to think about what happens when someone drinks before you answered because even a 10 second test of your claim shows that it's bullshit. So just man-up and admit that you were wrong...it happens all the time to all of us here - there is no shame in it. SteveBaker (talk) 14:03, 11 September 2013 (UTC)

Surely SB was being ironic? His comment must have been a joke. No sane person uses five apostrophes around allcaps. μηδείς (talk) 18:04, 10 September 2013 (UTC)

Let's hope so, for his sake. And I must remind you that we don't do medical diagnoses here. If there are concerns about his mental health, he needs to see an appropriate professional. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:06, 10 September 2013 (UTC)

Here's a little something I found by googling the subject.[1] It's evident that tilting the head back is pretty common. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:00, 10 September 2013 (UTC)

So if that link you provided is correct then what I originally thought was right. Look at #7 which says don't tilt your head back. By the way I use #10 and have done since I was a kid. It ensures that you don't get to taste the pill which is what happens if you put it in your mouth first. CambridgeBayWeather (talk) 00:30, 11 September 2013 (UTC)

So I think we have an answer now. It's evident that some people do tilt their heads back when swallowing pills - and other don't. It's neither necessary to do that - nor advised - and some advice says not to because there is some scant evidence that it may actually make the "gag response" worse. SteveBaker (talk) 14:03, 11 September 2013 (UTC)

wasp 2

What time of the year do queen wasps hibernate in the UK? I had one in my house today flying around and now and it seems to have gone somewhere and hidden. Would this be the right time of year for such behavior? I had one last year as well which emerged in May after sleeping the winter in a cupboard, could it be the same one? Waspgirl03 (talk) 15:03, 9 September 2013 (UTC)

Queen wasps normally come out of hibernation in the middle of April. However, due to abnormal temperatures in the UK in 2012, wasps in 2013 came out of hibernation later than normal. Up until July population rates of wasps were below normal however the UK is now being plagued by wasps due to the long hibernation.Jenn859 (talk) 20:19, 11 September 2013 (UTC)

Three-masted merchantman tonnage discrepancy

According to this painting by Samuel Walters, the Thames, of 454 tons, was built in London in 1829 for the West India trade. Originally owned by Hibberts of London, she later passed into the ownership of Thompson of London and was in service for over thirty years.

Section 1 in this information about the convict ship Thames gives the tonnage as 366.

I suspect both links are about the same ship. Are they? If they are about the same ship, what, if anything, is the difference between the term tons and tonnage? Why is the apparently same ship given a different value (454 and 366 respectively) for something I suspect should be the same?

--Senra (talk) 16:24, 9 September 2013 (UTC)

See Ship measurements. The tonnage of a ship is a measure of the _volume_ (not weight) of cargo it can carry. Describing a ship as "450 tons" might be expressing its maximum cargo volume using a different metric, or it might be expressing its maximum cargo weight, _or_ it might be expressing the displacement of the ship. The numbers you give (without any more precise definition) aren't inconsistent, and probably do refer to the same ship. Tevildo (talk) 17:33, 9 September 2013 (UTC)

It's possible that the ship was refitted for these different kinds of service - that could easily affect the tonnage. Of course there are many measures of tonnage too. Read Displacement (ship) for a few possibilities. SteveBaker (talk) 17:34, 9 September 2013 (UTC)

Thank you both. Useful input. Yes indeed. She could have been refitted between the two dates. The first link suggests the painting was completed in 1839, ten years after she was built. The second link indicates a voyage (the maiden voyage?) occurred between London and Van Diemen's Land (now Tasmania) between 31 July 1829 and 21 November 1829. --Senra (talk) 18:52, 9 September 2013 (UTC)

Religious people and Alzheimer's disease

Is there a correlation between actively religious people (people who attend weekly religious services and mingle with fellow congregants) and occurrence of Alzheimer's disease? 164.107.103.9 (talk) 20:54, 9 September 2013 (UTC)

Our article says: "At present, there is no definitive evidence to support that any particular measure is effective in preventing AD" - so going to church doesn't prevent the disease. It also says "People who engage in intellectual activities such as reading, playing board games, completing crossword puzzles, playing musical instruments, or regular social interaction show a reduced risk for Alzheimer's disease." - so if attending religious services counts as "regular social interaction" - then maybe, but it's not specifically being religious that does it - doing intellectually difficult things in a social environment is good - so you could join a musical group, take a degree course in particle physics or play Dungeons and Dragons (heretical!) and get the same kinds of benefits. SteveBaker (talk) 21:06, 9 September 2013 (UTC)

I once heard a story about the correlation between Alzheimer's disease and the occurrence of it in American nuns. 164.107.103.9 (talk) 21:20, 9 September 2013 (UTC)

I would also add that physical activity and education may also contribute to Alzheimer's. It's not just intellectual stimulation. So, going to church - if a person enjoys the experience of going to church, meeting new people, and thinking about thought-provoking biblical topics and verses - may not be so bad, after all. 164.107.103.9 (talk) 21:45, 9 September 2013 (UTC)

You may be thinking of the famous Nun Study, which was a study of which nuns developed Alzheimer's, rather than a finding that nuns are generally susceptible. You may find the article enlightening. Someguy1221 (talk) 21:38, 9 September 2013 (UTC)

The only relevant academic study I could find is PMID 17470754, which found that the rate of cognitive decline in Alzheimer's patients tends to be slower if they are high in religiosity or spirituality. Looie496 (talk) 23:01, 9 September 2013 (UTC)

Similar to Looie496 source, there's PMID 20088813, which also found a slower rate of decline in Alzheimer's patients with high religiosity. Unfortunately, both studies deal with patients who have already been diagnosed with Alzheimer's. They don't address the question of whether religiosity is correlated (positively or negatively) with an Alzheimer's diagnosis in the first place. (The latter study is much more difficult to do.)

Boyle et al. have carried out a number of what appear to be good-quality prospective studies that found a correlation between between greater "purpose in life" and significantly reduced risk of developing Alzheimer's (PMID 20194831), as well as greater resistance to the effects of physical, pathological changes in the brain (PMID 22566582) among individuals who do have the disease. Note that "purpose in life" is not the same thing as "religiosity" or "theism", however. (There's a good summary of these types of tests at [2].) Boiled down, there seems to be less cognitive decline in individuals who feel useful, who feel their lives have meaning, and who feel that they still have worthwhile things to do. Commenting purely out of my own opinions, I can see how spirituality or religiosity might be avenues that encourage those types of feelings, but would be far from the only ones. TenOfAllTrades(talk) 15:00, 10 September 2013 (UTC)

Stoichiometry for explosion of Nitroguanidine

I recently expanded Nitroguanidine, a popular explosive that is apparently being introduced into air bags. Anyone have a suggestion for a balanced equation for the gas forming reaction?

(NH₂)₂CNNO₂ → ??? CO₂, NH₃, N₂...

Thanks, --Smokefoot (talk) 22:51, 9 September 2013 (UTC)

That would depend on whether the N-N bond cleaves first in the nitroaminodiyl group. If it does, then you'd not get dinitrogen, but nitrogen dioxide which nitric oxide and oxygen which then oxidises the guanidinyl radical to carbon dioxide and ammonia. Plasmic Physics (talk) 00:49, 10 September 2013 (UTC)

[3] — Preceding unsigned comment added by 128.226.130.145 (talk) 16:59, 10 September 2013 (UTC)

why do knots weaken ropes?

Our article, Rope_splicing, says "Splices are preferred to knotted rope, since while a knot typically reduces the strength by 20-40%,[1] a splice is capable of attaining a rope's full strength." Why is it that a knot reduces the strength of the rope to such a significant degree? 178.48.114.143 (talk) 22:57, 9 September 2013 (UTC)

My guess (and it's only a guess) is that when a large diameter rope goes around a tight (compared to the diameter) curve - as it does in a knot - the fibers on the outside of the curve are in tension and the fibers on the inside are in compression. When you pull on the knot, all of the force goes on the outside fibers and none whatever on the inside ones. It makes sense that with all of the force being applied to only a few of the fibers will cause them to break before the entire rope could have done if it was straight. As a few fibers snap, the tension transfers to the layer beneath - they get all of the force - so they break. And so on, and so on until the entire rope snaps. A classic cascade failure.

Think of it like the trick of tearing a phone book in half. You can't possibly do it when you try to rip the whole thing - the trick is to bend the book into a U-shape and then you're effectively only tearing one page at a time.

But this is just a guess - I'm sure someone here will come along with an "official" answer. SteveBaker (talk) 23:45, 9 September 2013 (UTC)

So is there some special knot that does not require untwisting or braiding/splicing per that article, and instead, while treating each rope as a single strand, 'knots' them together end-to-end but without very tight curves? 178.48.114.143 (talk) 00:18, 10 September 2013 (UTC)

Very strong bends include the Carrick bend, the Flemish bend and the blood knot. Tight curves are not the problem, it's about where the curves are, and how they are loaded. E.g. the blood knot has very tight curves, but they are not loaded much, and it is one of the strongest known bends. Hitches can generally be stronger than bends. The "dressing" of the knot also affects its strength. SemanticMantis (talk) 15:55, 10 September 2013 (UTC)

Knot#Strength has some details and cites. And bend knot has lots of styles for joining ropes end-to-end, including some especially suited for single-strand (though lots for multistrand that retain strength. DMacks (talk) 05:32, 10 September 2013 (UTC)

In addition to the above, I've noticed that certain types of knots become hard and brittle before the remainder of the rope. I have the think the uneven stresses on the knots cause this result. StuRat (talk) 08:53, 10 September 2013 (UTC)

• The weakening effect of knots in ropes is well known, but the details are still poorly understood. Steve's basic guess above covers it generally: it is all about the non-uniform stresses and strains introduced by knot geometry. However, translating that into specific mechanisms is quite difficult, and different mechanisms are involved for different knot types and rope types. See e.g. this well-referenced blog post [4]. Take special note of the several intuitive descriptions that that author rejects. This science article has some pretty good analysis, but is limited to monofilament line [5]. Any given cord is strongest under uniform tension. Note also that the failure mode of knots will depend on the rope type. Sheathed climbing rope will break differently than 3-ply twisted rope, which will break differently than monofilament. The US coast guard takes a more empirical approach, and simply loads and breaks several ropes with knots. They have a classic study on the topiuc, but right now I cannot find it, only references to it. Finally, a great resource for all-things-knot is the International Guild of Knot Tyers, igkt.net. One of their threads discusses the issue here [6]. SemanticMantis (talk) 15:48, 10 September 2013 (UTC)