Wikipedia

Wikipedia:Reference desk/Archives/Science/2012 November 19

< Wikipedia:Reference desk | Archives | Science
Science desk
< November 18 << Oct | November | Dec >> November 20 >
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.


November 19

edit

manual lenses in bridge cameras

edit
Besides Fujifilm what others brands make super-zooms cameras with a lens capable of doing manual zoom and manual focus??
recently a friend was looking for a super-zoom, and showed me a canon SX – something, and it felt like a toy in my hands, and he don’t like the Fuji’s IQ,
are any Sony, Canon, or Nikon camera bridge (with a zoom around 18~30x) like the hs line of fuji??

Iskánder Vigoa Pérez (talk) 00:24, 19 November 2012 (UTC)[reply]

From bridge camera "With zoom ranges and sales rapidly increasing in the early 21st century, every major camera manufacturer has at least one 'super zoom' in their lineup." So, just wait and see. Or try one like the Sony NEX-some # or one of its concurrents. [1] is a good source of such information. Philoknow (talk) 16:35, 19 November 2012 (UTC)[reply]
Yes, sure, but talking about now?? There isn’t any 15-30x camera capable of manual zoom and focus… or at least manual focus?
the canon sx40 looks just like a toy wat side of my mom’s fuji hs20
my friend has family that will come to Cuba next week and he wants to exploit this opportunity
Iskánder Vigoa Pérez (talk) 19:39, 19 November 2012 (UTC)[reply]
It may help if you further explain your question. I assume many bridge cameras probably even most bridge cameras have manual focusing at lead thats what our article and many other discussions seem to suggest. Heck I think even some higher end P&S or those at the crossover point have manual focusing (I seem to recall using at least camera with it and a search also finds mention of manual focus in some P&S cameras) although it may be very hard to use due the difficult focusing on the LCD (our article mentions many bridge cameras provide a zoomed in focus square), it's ultimately primarily a software issue. But your original question makes me think you want more then simple manual focusing. Do you want manual focusing using some sort of focus ring or similar rather then adjusting a slider on screen with cursors? (Your second question also seems to reaffirm this point. Surely nearly even single non fixed zoom camera offers some sort of manual zoom even the vast majority of P&S ones. i guess some may have some sort of point to zoom or try to zoom in faces when set to potrait mode but manually zooming must be the way most people use zoom cameras. Even cameras without a zooming lens will often provide zooing controls due to 'digital zoom'. Of course the controls will often be a simple cursor or with modern touch screen controls perhaps an on screen slider.)
In any case a simple search for 'bridge camera manual focus' finds this review [2] which discussess manual focus methods in various recent bridge cameras most of which appear to have fairly high zooming levels. There are also lots of other older discussions from the same search, while many of the models may now be old you should be able to find their replacements and see what they do. Of course if you can't find anything fulfilling your requirements your best bet may be to consider a DSLR, its not clear why your focused on bridge cameras. Pricewise it's often not clear cut nowadays so I assume its a size issue but if you have special requirements you may have no choice.
Nil Einne (talk) 01:44, 20 November 2012 (UTC)[reply]
Yes, I meant a bridge camera with two rings, a focus ring and a zoom ring… (just like the Fujifilm’s HS)I recommended him to buy a d3200 and a cheap tamron18-200 (he can afford it) but he wants something larger, 20x or more…
I guess the IQ of a picture taken whit this camera/lens, at 200mm and cropped to the half will still be better than the IQ of a picture of any bridge… and making math that’s 22x or so, I told him but he wants a bridge camera with 20 x or more…
Do you know any model available right now (from canon, nikon, sony or pentax), or are the fujis the only choice?
Thanks for the answer!
Iskánder Vigoa Pérez (talk) 03:19, 20 November 2012 (UTC)[reply]

pneumonia survival rates

edit

what was the pneumonia survival rate before antibiotics, and what is it now?--Wrk678 (talk) 01:40, 19 November 2012 (UTC)[reply]

From the article Pnemonia#Management: 10% mortality now vs 50% before antibiotics for patients who end up in the hospital. RudolfRed (talk) 02:47, 19 November 2012 (UTC)[reply]

yes but not everyone ended up is hospital back then either, so I need rates for those that died at home.--Wrk678 (talk) 03:31, 19 November 2012 (UTC)[reply]

I found this page: http://www.jci.org/articles/view/29920, which says 30-40% fatality rate. RudolfRed (talk) 04:28, 19 November 2012 (UTC)[reply]
Also note that the fatality rate may be different for different strains. StuRat (talk) 03:43, 20 November 2012 (UTC)[reply]

Element transmutation

edit

Can iron transmute to silver?--Almuhammedi (talk) 13:40, 19 November 2012 (UTC)[reply]

Probably not. Iron is at the apex of the nuclear binding energy graph, which means that it is the hardest element to transmute out of. To put it another way, given a long enough time frame, thermodynamically the entire universe should be transmuting into iron. Nuclear fusion of smaller elements in stars produces iron as the ultimate end product, and spontaneous fission shouldn't produce any element smaller than iron. --Jayron32 13:47, 19 November 2012 (UTC)[reply]
Well sure, but that's not really the question being asked. (Strictly speaking, because of activation energy barriers associated with nuclear fusion, what you would actually get if you wait long enough is a cold, near-perfect vacuum contaminated ever-so-slightly with hydrogen, helium, and an elemental assortment enriched in stuff around the iron peak. Further, most grand unified theories predict that all 'stable' nuclei and even bare protons will eventually decay, with a half life on the rough order of 1036 years. See, for instance, proton decay, ultimate fate of the universe, and future of an expanding universe.)
Energetically-unfavorable transmutation is certainly possible, and happens on a regular basis in laboratories all over the world. It also occurs in nature; on the largest scale supernova nucleosynthesis is responsible for virtually all of the heavier-than-iron elements in the universe. (One could argue on that basis, not entirely speciously, that much of the silver we have already is the result of transmutation of iron.) Whether the multiple steps required to get from iron (atomic weight around 56) up to silver (atomic weight around 107) could be carried out industrially with meaningful yields is questionable, and whether it could be done economically is doubtful in the extreme. TenOfAllTrades(talk) 15:49, 19 November 2012 (UTC)[reply]
This does not answer your question, but it is Quite Interesting. See also Synthesis of precious metals. Trio The Punch (talk) 13:53, 19 November 2012 (UTC)[reply]
It used to be that a nuclear engineer learned how to read the periodic table, suitably modified for radiochemistry. Here are some educational decay charts from Lawrence Berkeley National Lab. I know of no direct transition from iron to silver: but you can sum over the known probabilities of all possible intermediate transition probabilities and determine exactly how unlikely the transition is. Like many processes in nuclear physics, the probability of iron-to-silver transmutation is probably tiny but non-zero. For perspective, consider how much silver we have on earth, and how much hydrogen we started with in the original phase of stellar nucleosynthesis. That ought to give you a sort of intuitive idea about the scale of the probability. Start with a sun-sized blob of hydrogen, and after a few billion years, you end up with a tiny amount - maybe a few thousand tons - of silver. The probability of hydrogen transmuting to silver is very small, and yet, on a cosmological scale, even very rare events can occur. Nimur (talk) 13:59, 19 November 2012 (UTC)[reply]
Given you have a nice neutron source like a nuclear reactor you will transmute 1g of iron into a few mg of silver and a lot of other elements over time (most likely years). The whole thing will be radioactive like hell but if you wait 10 half-lifes you are save.--Stone (talk) 14:19, 19 November 2012 (UTC)[reply]
  • My feeling is that most silver has originated by transmutation from iron (supernova nucleosynthesis) - but it turns out your workbench has to include the right kind of supernova, an "r-process-rich star". A second r process, to be precise. This is apparently explained in [3], but that is not an easy read! Found via [4] which is far too simple. Still... if you can do it in a supernova, then this is just a matter of engineering. :) Wnt (talk) 17:00, 19 November 2012 (UTC)[reply]

It would be more economically feasible to get to Ag from Cd, by irradiating stable 106Cd with neutrons (producing 107Cd, which undergoes electron capture to 107mAg, which decays by IT to stable 107Ag). Double sharp (talk) 06:22, 20 November 2012 (UTC)[reply]

Technically, 106Cd is only observationally stable, and can theoretically decay by β+β+ to 106Pd with a half-life of over 4.1×1020 a, but that doesn't make any difference as the half-life is so long that the decay has never actually been observed. Double sharp (talk) 06:26, 20 November 2012 (UTC)[reply]

Is this a fallacy? Classifying people from a psychological perspective

edit

If you classify people, mothers for example, into angry, controlling, narcissistic, envious, emotionally unavailable mothers, aren't you forcing reality into your categories, ignoring that anyone, any person, can have one of the typical behavior of each and every category above? Wouldn't that be a series of categories without typical specimen, since you'll end up pushing mothers into the category that better fits yours feelings? Philoknow (talk) 16:52, 19 November 2012 (UTC)[reply]

Hmmm... now there's an interesting psych experiment. Given well trained actors with detailed and well-selected instructions, who assemble an artificial research community (e.g. a supposed Mars mission psych test) can you induce any individual to fall into one of these types regardless of their previous personality? Wnt (talk) 17:03, 19 November 2012 (UTC)[reply]
Is that an allusion to a thought experiment that really happened or just the creation of one? Philoknow (talk) 17:04, 19 November 2012 (UTC)[reply]
Just me piggybacking on your question, sorry. Wnt (talk) 19:15, 19 November 2012 (UTC)[reply]
The mother issue is just an example I came across. But there are alternative categories for co-workers, partners, and whatever you want. How to you call this kind of errors in thinking? If you have too little evidence for them, isn't there a too-little-evidence-for-the conclusion fallacy? Philoknow (talk) 17:14, 19 November 2012 (UTC)[reply]
It would be the drawing of conclusions from application of invalid categories that might be fallacious, again, see the list and look for one that seems to cover what you are thinking of. (That's just a matter of what fallacy means--not all mistakes in reasoning are fallacies.) Perhaps you could give a more detailed example of the sort of thing you have in mind. Perhaps you mean someone who forms an immediate judgment of a person as a type of "x" and then interprets all that persons actions as being due to their being an "x" regardless of evidence? That would be stereotyping, which literally means solid (as in the sense of unchangeable) categorizing. μηδείς (talk) 17:58, 19 November 2012 (UTC)[reply]
I'd say it's a misconception, but not an error in the reasoning. For more on this check Scientific misconceptions and list of common misconceptions. OsmanRF34 (talk) 18:10, 19 November 2012 (UTC)[reply]
What is this fallacy?: Report says that college students who talk to parents at least once a week are less likely to have trouble with abusing alchohol/drugs, therefore parents should call child at least once a week. Logically I would say that the student who talks to parents once a week is already more responsible, etc. which is why they call/ talk to parents regularly.165.212.189.187 (talk) 19:11, 19 November 2012 (UTC)[reply]
To me, this seems like making a correlation equal to causation. What the name for this fallacy is, I don't know, but correlation=/= causation.128.227.105.163 (talk) 20:14, 19 November 2012 (UTC)[reply]
It would be correlation does not imply causation. --140.180.252.13 (talk) 20:14, 19 November 2012 (UTC)[reply]

The following is what Carl Jung wrote in a letter to Sigmund Freud dated 12th June 1911 : "My evenings are taken up largely with astrology. I make up horoscopic calculations in oder to find a clue to the core of psychological truth. Some remarkable things have turned up which will certainly appear incredible to you . . . . . . I dare say we will one day discover in astrology a good deal of knowledge that has been intuitively projected into the heavens". Cinquefoil (talk) 19:08, 19 November 2012 (UTC)[reply]

If we didn't "force reality into our own categories", there'd be no way to reason or talk about anything (try it.) Psychologizing as a form of argument, however (speculating about the motives/psychological causes etc as to why one's opponent hold the views they hold, and attacking the former instead of the latter) is a bad thing Asmrulz (talk) 09:17, 20 November 2012 (UTC)[reply]

Impact depth

edit

This article gives the formula for the impact depth as derived by Newton. How can it be derived? The article gives a sketch but doesn't have the details. 65.92.7.202 (talk) 16:59, 19 November 2012 (UTC)[reply]

The key criteria from it are "impactor carries a given momentum. To stop the impactor, this momentum must be transferred [...] to the material (mass) directly in front of the impactor, which will be pushed at the impactor's speed. If the impactor has pushed a mass equal to its own mass at this speed, its whole momentum has been transferred to the mass in front of it and the impactor will be stopped." Write the equation for the momentum of the projectile; substitute a function of the the projectile's density and length for the mass term. Do the same for the target material. Set them equal to each other (conservation of momentum) and solve for...whatever. DMacks (talk) 18:39, 19 November 2012 (UTC)[reply]
Simply put, tensile strength is assumed to be negligible, and both the impactor and its target are treated as the balls of Newton's cradle.
Quite a hack IMO, but that's why it's only an approximation, which falls down if the speed is not hypersonic (in relation to the speed of sound within the projectile and the target, which is much higher than in air) or if the impactor is aerodynamic. - ¡Ouch! (hurt me / more pain) 15:52, 22 November 2012 (UTC)[reply]

Iron Dome

edit

Is the Patriot missile much worse or expensive than the Iron dome? If the Israelis find the rockets from the Palestinians so disturbing, why didn't they have lots of Iron Domes? According to the article they are not prohibitively expensive. If you compare them to a land incursion they are quite cheap. Philoknow (talk) 17:24, 19 November 2012 (UTC)[reply]

It's a different job. Patriot defends against long range missiles which descend on the target at very high speeds. Iron dome defends against short range threats, which approach at relatively low speeds. Israel's equivalent of Patriot is Arrow (Israeli missile). -- Finlay McWalterჷTalk 17:40, 19 November 2012 (UTC)[reply]
According to the article, some Israelis do think Iron Dome systems are too expensive. --Demiurge1000 (talk) 17:51, 19 November 2012 (UTC)[reply]
"too expensive" comparing to a Palestinian Quassam rocket. OsmanRF34 (talk) 18:13, 19 November 2012 (UTC)[reply]
Iron Dome is a new system. It still has some problems and is still in development. In the future they will likely have many more of them. Ruslik_Zero 18:54, 19 November 2012 (UTC)[reply]
It already successfully intercepts at least 70% of the rockets launched against populated areas (as much as 90% according to the Jerusalem Post). 24.23.196.85 (talk) 07:01, 20 November 2012 (UTC)[reply]

sderot is too close to gaza to use the iron dome. also just relying on the iron dome without taking efforts to curb rocket attacks will mean that rocket attacks will increase till it will be prohibitively expensive to use the iron dome.

Universal milling machine or turret milling machine....

edit

Hi I want to know which type of milling machine has better accuracy universal or turret milling machine. — Preceding unsigned comment added by 117.219.148.78 (talk) 19:31, 19 November 2012 (UTC)[reply]

A turret mill is generally less rigid. However, how accurately you machine any workpiece is dependent on so many factors I would not like to make a claim either way. If the job is done with the correct approach, the machines are adequately looked after, correct speeds and tools used, there is no reason why any properly designed machine tool should not be used at an accuracy determined by the machinist's available measuring instruments. Wickwack 120.145.142.95 (talk) 01:29, 20 November 2012 (UTC)[reply]
Retrieved from "https://en.wikipedia.org/w/index.php?title=Wikipedia:Reference_desk/Archives/Science/2012_November_19&oldid=1073536337"