Wikipedia:Reference desk/Archives/Science/2017 February 2

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February 2

What keeps the shiny side of aluminum foil from getting dull?

Is the shiny side of common aluminum foil treated in some way to make it keep its shine? Why doesn't it lose it luster from the formation of aluminum oxide? --100.34.204.4 (talk) 12:45, 2 February 2017 (UTC)

No, but see Passivation (chemistry). A very thin layer of the oxide forms quickly and stops any further oxidation. The layer is thin enough that the surface remains very shiny. Dmcq (talk) 13:32, 2 February 2017 (UTC)

• Two factors are different between aluminium and steel. Aluminium self-passivates quickly, forming an oxide film. Once formed, this film is also impermeable. So the film forms, but then protects the metal beneath from further oxidation. The effect is even more pronounced if the aluminium is deliberately anodised, so as to form a more robust and even less permeable film. In steel though, a rust layer has little protective effect as it's permeable and the steel continues to rust beneath. Titanium is similar to aluminium in its behaviour - perhaps surprisingly, it's often the more reactive metals that form these impermeable films.Andy Dingley (talk) 14:05, 2 February 2017 (UTC)

  ...though stainless steel exists, of course. "Steel" can cover quite a lot of metallurgical compositions. Tigraan^{Click here to contact me} 14:20, 2 February 2017 (UTC)

  • Stainless steel contains chromium, which makes the oxide film impermeable, thus "stainless". It doesn't form as readily though, so stainless is usually passivated deliberately after manufacture, using a solution of citric acid. Forming a film immediately and deliberately avoids the slower random formation of a self-forming film, which can give a blotchy appearance. Andy Dingley (talk) 15:12, 2 February 2017 (UTC)

  I am no expert in the glitcheriness of things. I just wanted to precise that "steel" in general does not rust - particular kinds of steel, especially low-alloy, low-carbon ones do - as a reader could have been misled. Tigraan^{Click here to contact me} 16:43, 2 February 2017 (UTC)

The shininess of aluminium foil is not due to the surface chemistry, but due to the surface roughness. To get the required thinness of foil, two separate rolls of foils are pressed together, to get them thinner. Roller side is shiny, foil side is matte. See Aluminium foil#Manufacture. Fgf10 (talk) 14:23, 2 February 2017 (UTC)

This might be interesting: "How It`s Made Aluminum Foil". Bus stop (talk) 07:36, 3 February 2017 (UTC)

Ejection Fraction

I am reading a paper on left ventricular ejection fractions. It never describes them as anything more than just LVEF. When I look at ejection fraction data, each patient has three values, such as 2C=59%, 4C=56%, BP=58%. Which of those is the ejection fraction? 209.149.113.5 (talk) 15:36, 2 February 2017 (UTC)

Can you please link the paper in question? SemanticMantis (talk) 17:11, 2 February 2017 (UTC)

To whomever asked this (the room is empty now)... 2C and 4C are linear two-chamber and four-chamber measures. Sometimes, you will get a 3C as well. BP is biplane. It is an estimated 3D value from the two linear values. You should use the BP value as the single measure, but it is also common to report the range from the lowest to the highest value. 209.149.113.5 (talk) 17:43, 2 February 2017 (UTC)

(care to explain what's going on here?) SemanticMantis (talk) 18:26, 2 February 2017 (UTC)

This computer is in the staff room of a hospital. One of the nurses here is a huge fan of Wikipedia Reference Desk and is always pushing people to use it. It looks like one person asked about LVEF and another recognized the IP address and answered the question. 209.149.113.5 (talk) 18:41, 2 February 2017 (UTC)

And a third party explained just now? Ok, thanks. I've been seeing the 209...5 IP around more recently, I thought it was one person but a collection of medical staff also makes sense. BTW if any of you have a good reference that explains the given answer, that would be great! SemanticMantis (talk) 19:28, 2 February 2017 (UTC)

See [1]. 4C (four chamber) is a monoplane measurement. Using 2C (two chamber) along with 4C, a BP (biplane) measurement may be calculated that is more accurate than the monoplane measurement. The reference describes the Simpson method for calculating ejection fraction. 209.149.113.5 (talk) 16:26, 3 February 2017 (UTC)

Trying to link the image with Harry Potter

What specific message is being conveyed by the following image? Here is some clue "Its a thing. You obtain this on doing as directed in the picture, reading it from outside to inside." The answer is of two or three words. Thanks. http://visionmanit.in/Eureka/que/pyasadilmera.png — Preceding unsigned comment added by 110.224.32.57 (talk) 20:28, 2 February 2017 (UTC)

How about "quenching thirst"? — Preceding unsigned comment added by Baseball Bugs (talk • contribs) 21:58, 2 February 2017 (UTC)

Beats me. I looked for letters in the ice cubes and managed to hallucinate "A1O" but nothing in the last. I looked up the link and got nothing. I looked up the end and got [2], which makes me wonder if somebody in India has managed to make salutary progress against the worst of their awful censorship. Based on this, my guess is hepatitis C, though there are some other possibilities. :) Wnt (talk) 22:03, 2 February 2017 (UTC)

Call a spade a spade: it's a "glass of water", (or other beverage) obviously. ~Anachronist (talk) 05:45, 3 February 2017 (UTC)

HINT: The answer lies in here:

It is pretty hard. Lets call out for Harry Potter References. Half-Blood Prince,Rupert Grint, Drops and potions

Where are you seeing these hints? Do you already know the answer? ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:49, 3 February 2017 (UTC)

No, I don't have the answer. Someone has given me the hint. — Preceding unsigned comment added by 110.224.42.244 (talk) 08:07, 3 February 2017 (UTC)