Science desk
< May 15	<< Apr \| May \| Jun >>	May 17 >

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.

May 16

Death by Medicine

Is this a legitimate peer-reviewed article[1]?

I have my doubts because the site it's hosted on is fishy, and the figures in the article sound way too high. ECS LIVA Z (talk) 00:22, 16 May 2017 (UTC)[reply]

It is NOT a legitimate peer-reviewed article. see here 64.170.21.194 (talk) 00:59, 16 May 2017 (UTC)[reply]

Just read up on Gary Null. Basically, he's a quack (or at least a promoter and defender of quackery). --jpgordon^{𝄢𝄆 𝄐𝄇} 01:10, 16 May 2017 (UTC)[reply]

(edit conflict) See also our article on Mercola.com's head quack. It is not merely "fishy," it is absolutely untrustworthy and so is anything on there. If Mercola.com says the sky is blue, get your vision checked. Ian.thomson (talk) 01:11, 16 May 2017 (UTC)[reply]

Thanks, guys. ECS LIVA Z (talk) 01:27, 16 May 2017 (UTC)[reply]

While I agree that Gary Null is a quack, iatrogenesis is a serious concern. StuRat (talk) 20:09, 16 May 2017 (UTC)[reply]

Resolved

Skin-mole color relation

Does the color of the skin influence the color of the moles appearing on it as I just started to believe? Imagine if the person's skin color is cyan, would the moles on it tend to be in darker shades of blue? If it is true, melanin is a black pigment that produce brown marks on the peach skin but blue marks on cyan skin because the colors blend like mixing paint of different colors. Planet Star 03:40, 16 May 2017 (UTC)[reply]

As you can read from that article, there are dozens of different kinds of moles, and each of them has a different mechanism; the color of one type of mole is different than, and may be controlled by different factors than, any of the other types. I'm not sure your question can be answered with any universal certitude. --Jayron 32 12:22, 16 May 2017 (UTC)[reply]

I believe you have a mistaken assumption that melanin makes skin more of whatever color it is. Melanin (specifically eumelanin) is a brown or black pigment, never blue. There are other effects on skin color, though, such as carotene, which can turn the skin orange, or excess silver consumption, which can turn it blue-grayish. Blood shows through lighter skin, too, making it more red when flushed with oxygenated blood, or more blue when lacking oxygenated blood. StuRat (talk) 20:03, 16 May 2017 (UTC)[reply]

Spiked bulletproof surface

Does a spiked (or with multiple protrusions) surface better protect from bullets than the flat surface of bulletproof vests and the like? My understanding is that a bulletproof material with several tens or hundreds spikes from the same material (each several cm long) better dissipates the bullet energy, while the flat surface receives the bulk of it. 212.180.235.46 (talk) 12:54, 16 May 2017 (UTC)[reply]

Whether or not it is the case, how cumbersome would a bulletproof vest be if it was covered with "several tens or hundreds spikes . . . each several cm long"? Also, intuitively it would seem to me that the spikes might well disperse the force of an oblique impact, but an orthogonal impact would likely pass between them and strike the base material directly. {The poster formerly known as 87.81.230.195} 2.122.60.183 (talk) 13:12, 16 May 2017 (UTC)[reply]

The article Armour describes the improvements made to armour over history. The effectiveness of passive armour in any given material is increased when the length of the path for deceleration of a penetrating projectile is increased. This may be achieved by increasing the armour thickness or, notably in the design of military Tanks, slanting exposed surfaces which increases effective penetration depth by secant(a) where a = tilt angle to normal to the projectile's trajectory. A layer of spikes each several cm long can be a lightweight way to add thickness to armour but it is not necessarily more effective than using the same weight of material in a solid layer in which energy from a point impact spreads out. The most advanced form of armour suitable for fighting vehicles is Reactive armour. Blooteuth (talk) 13:45, 16 May 2017 (UTC)[reply]

Probably spaced armour is closest to what you intend. If I was going to use spikes I'd have them with the wide part outermost and working like a shaped charge - that might form an effective form of reactive armour but that's just my thoughts. Dmcq (talk) 08:58, 17 May 2017 (UTC)[reply]

project engineering, project management, project management office, construction management, commercial management, design engineer

I've read all the above articles but so confused. Can someone in simple Laymans terms explain briefly the difference between project management, project engineering, project management office, design engineering, commercial management and construction management? Are there explicit boundaries between them academically or does it just depend on the project? 82.132.221.211 (talk) 18:30, 16 May 2017 (UTC)[reply]

Many of these terms are used interchangeably and will have different roles, educational requirements and responsibilities depending on the size and scope of the project. While some universities have programs in project management or construction management that is not always the case. During a career an engineer or project manager may often do a number of these jobs. Here's my opinion on, in general, what each of these titles mean, but remember that there are no clear, universal delimitation.

Project Engineering-An engineer who leads a project. They would have some responsibility for schedules and budgets, but would also spend some time working on technical problems for the project. They would lead/help lead the engineering team if there is one.

Project Management-The project administrator. They handle or lead teams that handle schedules, budgets, ordering, coordination between departments, etc. Basically they make sure the project comes in on time and under budget. They are a main point of contact between the project team and the customer.

Project management office-Group or person who standardizes how a company runs projects. They decide what software will be used for schedules, budgets, ordering etc. This saves time and expense. They make sure records are kept so that if a new project is similar to an older one, you can reuse relevant forms, studies, maps or even vendor phone numbers for the new project. They should prevent reinventing the wheel.

Construction management-A project manager who specializes in construction projects, rather than a general PM who might oversee software development, a new car design, designing a building. A Construction Manager will often be on-site day to day at a construction site.

Commercial management-A person who finds projects for the other jobs in this list. They might also be called sales, business development, etc. They find new customers, identify projects to bid on and help develop the bid or proposal. They identify sub-contractors needed for the project or bid.

Design engineer-Any type of engineer who works on developing, prototyping or improving a new product. Some may jump from concept design to concept design, while others may develop a concept, prototype it and then support it once it's in production.Tobyc75 (talk) 20:36, 17 May 2017 (UTC)[reply]

Explosive Reactive Armour

I've heard stories where an occupying army (I think it was Soviet/Russia in this case) were patrolling urban areas with main battle tanks and infantry columns. The tanks were equipped with Explosive Reactive Armour. The resistance forces figured out that they could drop rocks from the top of buildings onto the tank and it would trigger the ERA and kill any near-by infantry. The Soviet/Russia forces were forced to remove all their ERA armor, in which case the tanks became easy pickings for RPGs due to their thin side and back armor.

Is there any truth to this story? Scala Cats (talk) 19:37, 16 May 2017 (UTC)[reply]

I am skeptical. Let's look at the components of the claim:

1) Soviet tanks use ERA. This is true. See Reactive_armour#Explosive_reactive_armour.

2) Dropping rocks from buildings sets it off. I'm doubtful that this would supply the required energy, unless it's more like a boulder and/or a rather high building.

3) The ERA detonation can harm nearby infantry. This is true, per our article. However, knowing this, it would be odd to deploy infantry alongside an ERA-equipped tank.

4) Removing ERA leaves only a thin layer of armor. This contradicts our article, which states: "Their use requires that a vehicle be fairly heavily armoured to protect itself and its crew from the exploding ERA." Of course, the elimination of the ERA will make it somewhat more vulnerable to anti-tank weapons.

Note also that there are other forms of reactive armor which solve this potential issue. StuRat (talk) 19:50, 16 May 2017 (UTC)[reply]

For point 3, I think this was back in the Soviet-era when ERA was still brand new technology, so it's plausible that they just didn't know any better. Presumably the Soviet commanders learned their lesson the first few times and would no longer deploy infantry around ERA-equipped tanks. Scala Cats (talk) 20:16, 16 May 2017 (UTC)[reply]

Those who tested it certainly would have known, but I can see this info not getting down to the infantry commander who tells his troops to shadow a tank for protection from small arms fire. The infantry commander may not even know the tank was so equipped. However, once they figured it out, removing the ERA seems like an odd choice ("Throwing out the baby with the bathwater"). Bringing in armored personnel carriers would make far more sense. StuRat (talk) 20:20, 16 May 2017 (UTC)[reply]

Concurring with StuRat But there seems to be a contradiction there or at least unexplained point. Why did the Soviets remove the ERA from their tanks? Your initial scenario seemed to suggest this was due to injury to infantry deployed near the tanks, but if the better solution was simply to be more careful with the deployment of infantry it would seem this would be something the Soviet commanders would realise before removing all their armour, even if they didn't appreciate it during initial deployment. Nil Einne (talk) 05:49, 17 May 2017 (UTC) Edit: 01:41, 18 May 2017 (UTC)[reply]

Understanding ammonia

Why is ammonia written with the more electronegative element first, unlike most binary compounds?? Georgia guy (talk) 20:50, 16 May 2017 (UTC)[reply]

Carbon hydride is written that way too (CH4) Sagittarian Milky Way (talk) 22:07, 16 May 2017 (UTC)[reply]

I thought CH₄ is methane (gas at room temperature). 50.4.236.254 (talk) 23:12, 16 May 2017 (UTC)[reply]

According to IUPAC, ordering by increasing relative electronegativity is just as acceptable as ordering alphabetically, although some specific compounds, especially binary compounds, tend to only be written one way. Someguy1221 (talk) 23:21, 16 May 2017 (UTC)[reply]

It's important to at least be consistent, or know the context for a chemical, or at least know the scope and audience of the situation. NaH and HNa both exist as distinct and very different chemicals, depending which atom is cationin vs anionic. DMacks (talk) 21:53, 18 May 2017 (UTC)[reply]

Great point, although I feel obligated to point out that it's not really HNa per se, because the proton needs to be locked away in an organic cage to stop it from being reduced by sodide. ^_^ Double sharp (talk) 23:34, 18 May 2017 (UTC)[reply]

Methane would be the special name for "carbon hydride", as ammonia for "nitrogen hydride". These two are the only exceptions I could think of looking at electronegativity on the right side of the table -- note that water and hydrogen sulfide and hydrogen selenide are H2O and H2S and H2Se. But an exception also exists at least in the first document I looked at for tungsten hydride [2] -- note that its electronegativity in our table is slightly greater than hydrogen! -- and also gold hydride [3] -- gold has even higher electronegativity. (But only in the Pauling scale, not the Allen scale)

If I were to take an absolutely wild guess, I would speculate that at some point people gave in to the temptation to keep the formulas the same going up and down a row of the periodic table, and made some compromises against the actual electronegativity numbers. Or maybe those were just wrong long ago and the formula became too ingrained to change -- I don't know. This is a historical question really. Wnt (talk) 23:24, 16 May 2017 (UTC)[reply]

Indeed the group similarities are important here, and honestly the precise order is not so important. "Electronegativity" as construed here is not actual electronegativity (then where would He, Ne, Ar, and the superheavy elements be?); rather it is a sort of idealised order starting at group 17 and going down to group 0. The order goes down each group with H inserted between groups 16 and 15; the lanthanides follow after La and the actinides after Ac in atomic-number order breaking up group 3, so the "idealised electronegativity order" for labelling compounds according to IUPAC is F, Cl, Br, I, At, Ts; O, S, Se, Te, Po, Lv; H; N, P, As, Sb, Bi, Mc; ...; Li, Na, K, Rb, Cs, Fr; He, Ne, Ar, Kr, Xe, Rn, Og. Mind you, it is quite common to break these when making a point about trends, to talk about "PoH₂" or "F₂O". Double sharp (talk) 00:06, 17 May 2017 (UTC)[reply]

I tried to source this ... your phrase above got me better results. I came across this which points me to the Hill system (which is not used/relevant here), and this about the pseudo-electronegativity order. So it can indeed be blamed on IUPAC. Wnt (talk) 14:48, 17 May 2017 (UTC)[reply]

The convention at work with hydrogens works a bit different. Usually (but not always; there are exceptions) acid hydrogens are commonly written first in a formula, while strongly bound hydrogens are written later in the formula. Since neither CH4 nor NH3 has any acid hydrogens, their hydrogen atoms are written later. Examples like acetic acid (H2C2H3O2) and water vs. hydroxide (H2O vs. OH-) are instructive here as well. --Jayron 32 11:19, 17 May 2017 (UTC)[reply]

And "acidic hydrogen first" is in keeping with the idea that the less-electronegative atom in a simple ionic formula would likely be the cation vs the other part the anion. Jayron32, that acetic acid formula looks incorrect...regardless of order, you're missing one hydrogen atom overall. DMacks (talk) 21:49, 18 May 2017 (UTC)[reply]

Ammonia is actually a very weak acid as well; the alkali metals will dissolve in it to form metal amides with the evolution of hydrogen. (Ca, Sr, Ba, Eu, and Yb do the same.) You might not be able to deprotonate methane in solution, but again K⁺Me⁻ (methylpotassium) is a thing, with rather discrete cations and anions.

P.S. I'd tend to write acetic acid as CH₃COOH or just AcOH, with the acidic proton left to the very end. Double sharp (talk) 23:42, 18 May 2017 (UTC)[reply]

The ammonia/active-metal mixture seems like it's actually a reduction, so you get the conjugate base (NH₂^–) of ammonia (NH₃) but not directly by having ammonia itself act directly as an acid. You actually usually need a catalyst too (ferric nitrate or the hydrate thereof), which is a Lewis acid but I'm not sure the full mechanism is known to see if the ammonia acts as anything like an "acid" rather than simply a redox partner. But simply treating ammonia with butyllithium as base does do by appearances a classic acid/base reaction. DMacks (talk) 00:40, 19 May 2017 (UTC)[reply]

True: I tend to mentally "abuse the nomenclature" and think of the electropositive metal as a base in such cases, which gets you the right answer quickly for the wrong reasons, but you are of course absolutely right. ^_^ Double sharp (talk) 02:57, 19 May 2017 (UTC)[reply]