Wikipedia:Reference desk/Archives/Science/2015 April 4

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April 4

Blunt trauma and delayed death

When someone suffers an accident but survives and dies 24, 48 or 72 hours after the accident, what has deteriorated during this period that caused death? If someone has not died right away, but some days after the accident, something would be deteriorating during this period, right?. --Noopolo (talk) 15:27, 4 April 2015 (UTC)

See Major trauma. Dmcq (talk) 15:46, 4 April 2015 (UTC)

It takes some time to die even if some organs are completely nonfunctional. The kidneys, for example, remove waste from the blood, and it would take several days for the waste to build up to a fatal level (assuming no dialysis is done).

Also, if slowly bleeding internally, it may take that long to die from loss of blood. Then there could be a burst intestine, which could take that long to kill the patient due to infection. So, there's lots of ways it could happen. StuRat (talk) 17:45, 4 April 2015 (UTC)

• There are probably dozens of ways to answer this but what I can think of as the major categories would be internal bleeding, especially in the brain or body cavity, massive tissue damage leading to necrosis, and specific damage to organs like the kidneys or liver as mentioned above which don't kill you right away. Add clots leading to thrombosis to that list. My sister's uncle-in-law was hit in the head by a football on a post-thanksgiving game, felt fine, then fell into a coma two days later and died just after new years without ever waking up. See a doctor is the only advice we can give. μηδείς (talk) 22:31, 4 April 2015 (UTC)

Is sexual attractiveness distinctly physiologically and phenotypically different from physical attractiveness?

Although sexual attractiveness in non-human species seems to be more predictable and observable, which contributes to the sexual dimorphism of a species, the human species seems to be less predictable and observable. How does a human being distinguish between physical attractiveness and sexual attractiveness? Is sexual attractiveness really just physical attractiveness, plus sexual arousal? There is a well-known study in the field of psychology, in which men were placed on a suspension bridge and were held there until an attractive woman came along. The conclusion was that the fear and arousal of being on the bridge triggered the misattribution of arousal. In other words, the men were afraid about being on top of the bridge, but seeing the attractive woman made them divert their arousal and fear to the woman, thinking that the woman caused sexual arousal and hence sexually attractive. Does sexual attractiveness involve the erection of the penis in men? What about women? How do women experience sexual attraction? 66.213.29.17 (talk) 15:49, 4 April 2015 (UTC)

Think your referring to the Arthur Aron and Donald Dutton experiments. There is more than one way to explain these observations. Something that they did not mention is that Birds of a feather flock together. So if the male meets a woman in this situation, it suggest she would make a good mate who will bring up confident self-assured children -who therefore have more chance of survival. One has to be careful with psychologists, as they can design experiments to ensure the results match their own peccadilloes. So explaining why someone else, does the same experiment years later and comes up with different results. --Aspro (talk) 16:14, 4 April 2015 (UTC)

Thinking about it, this came up in conversation a while ago. Sigourney Weaver in Alien and Linda Hamiltonin in Terminator came over as a bit flumpsy in the first films but then their caricature evolved in to two females mothers that would go to the ends of the earth to protect. That is what a male wants (a subconscious drive that he's gene line will continue) and that takes two. Trophy wives are two- a-penny and can be divorced as soon as a better one comes along (and their offspring often end up as drug addicts and privileged children that strayed from the path into depravity). So meeting a female on a swinging bridge or abseiling down a cliff rather than in Mac Donald's or Starbucks makes complete sense to me.--Aspro (talk) 16:56, 4 April 2015 (UTC)

I'll suggest reading the subsequent life of Matthias Rust as a counterpoint to Aspro's approval of thrill seekers. μηδείς (talk) 23:17, 4 April 2015 (UTC)

???!!! Mathias Rust didn't meet a female on the whole fight! This above post is mixing animal/human instincts/psychological problems/ and pure absolute twaddle. It is no counter point at all in that example. Counter point is – oh, let a musician explain how two tunes move in and out. Counter-point can happen in lives too. Thats why, and as to why: two people, who started out living different lives, find they can blend together into a very happy life together and make beautiful music together – in a way that science still can't define. They don't have to be adrenaline thrill seekers – they might find they a both have an instinctive insight to Claude Monet and good food. Some couples can – and some couples can't counterpoint. So me thinks that is a very wrong example above. Disclaimer: Due to a confused and misspent youth, I have ended up with an appreciation of both with a foot in both camps (and being a tripod, I appear to have an other foot in another place).--Aspro (talk) 15:45, 6 April 2015 (UTC)

Feeding variac with 240 VAC at 110 VAC point

So my variac has 2 input, one is for 240 VAC and the other is for 110 VAC. If I connect the 240 VAC power cable to the 110 VAC input, will it double the output voltage? Is it safe for me and the variac? 118.137.229.147 (talk) 15:54, 4 April 2015 (UTC)

Most people do not need 480 volts. When they need more than 240v they use three phase. So your variac probably comes with instructions to use it only in the way way that it was designed for. The insulation may brake down at higher voltages and quite apart from the smell you might find the results electrifying.--Aspro (talk) 17:09, 4 April 2015 (UTC)

No, it is not safe, it will probably burn it out, and it is not safe to try this out. The power drawn might be more than four times that for which it was designed (because the current might be more than doubled, as well as the voltage). Dbfirs 17:11, 4 April 2015 (UTC)

This equipment was not designed for this use. It is dangerous! If it is automatically regulated, never feed the output. It will cause a damage due unable to control this output. If it is a transformer only, never operate it out of specified voltage range. Transformers have a energy conversion efficiency, causing in reverse operation, the voltage output unregulated is higher without load, dropping under load due unregulated less than expected and dangerous due circuit brakers, fuses, thermal fuses and other savety equipment, if installed, are locaded on the other coil and will have no functionality when neccessary! The reverse operation, even in range of specified voltages is dangerous if not clear specified for such use! --Hans Haase (有问题吗) 19:11, 4 April 2015 (UTC)

There goes my plan for overvolting stuff to get more power from it. So is it safer to put a step up transformer after the variac? 118.137.229.147 (talk) 23:46, 4 April 2015 (UTC)

Yes, and remember that if you double the voltage, you can draw only half the current to avoid overloading your variac. Unless you really know what you are doing, "overvolting stuff" is more likely to produce burnout than more power for any length of time. Dbfirs 07:46, 5 April 2015 (UTC)

The Rotation of the Voyager Space Probe

www.youtube.com/watch?v=jGD4i1oNoyo at 00:30

How did she rotate the Voyager spacecraft?

It's very unlikely that she ignites the spacecraft's rocket engine which has very limited supply of propellents.

Did they use the spaceprobe's gyroscopes to control its rotation? -- Toytoy (talk) 16:10, 4 April 2015 (UTC)

Both Voyagers have hydrazine thrusters. They didn't have gyro orientation. The Jet Propulsion Laboratory use this fuel very sparingly. Which is why it has lasted so long. Brilliant work for a probe that was originally just going to Jupiter. --Aspro (talk) 17:21, 4 April 2015 (UTC)

An article from a couple of years back says one such maneuver uses 100 grams of hydrazine, with around 250 maneuvers left until the spacecraft runs out, minus whatever is needed for routine attitude control operations. The two Voyagers should run out of electrical power before they run out of hydrazine. 88.112.50.121 (talk) 18:40, 4 April 2015 (UTC)

Thank you guys. I knew that Voyagers have hydrazine thrusters. I just could not believe that they only use the thrusters to rotate the probes. I thought they probably have a gyro hidden inside so the parts don't show on the illustrations. Do they use compressed gas to propel the hydrazine in the zero-g tank?

This is guess: helium [1] is probably used as top pressure for the fuel tank (too cold out there for nitrogen). A stirrer [2] in the tank is also probably need to ensure liquid hydrazine only is sent to the thrusters in zero-g. Although it was designed in the 1970's they were the bees knees in current technology and is a very complex probe so it would have do doubt need these, in order to function in deep space. The thrusters primary use were for navigation not orientation. Having gyros would have added another layer of complexity and it only needs to re-orientate now and then (unlike say the Hubble). Since its launch, its software has been update too. Value for money wise, I think the two Voyagers have turned out to be one of the most successful probes, considering all the science data that they have sent back – far, far beyond all expectations. Yet their cameras only had a 80 by 80 pixel view ( OK 'pels' for the pedantic) and what do our cheap cameras in 2015 have now – yet these two probes keep sending back really useful data.--Aspro (talk) 20:33, 6 April 2015 (UTC)

I still don't understand why they did not use a gyroscope or just a motor and a spinning weight to rotate the Voyager. They have a nuclear power generater. An electrical rotating system may save them much fuel. -- Toytoy (talk) 15:22, 5 April 2015 (UTC)

What you describe is a reaction wheel. Some reasons Voyager's engineering team may have elected not to use them include:

• they didn't want to incur the mass cost of three of these systems
• they needed faster pointing (on close approach events) than reaction wheels could do
• they were worried the reaction wheels would fail, given the very long timeframe and very cold environment
• note the article says "over time, reaction wheels may build up stored momentum that needs to be cancelled" (by some other attitude control system)

146.200.157.224 (talk) 21:41, 5 April 2015 (UTC)

The difference between mutation of gene and genome

до свиданья ←Baseball Bugs What's up, Doc? carrots→ 22:19, 4 April 2015 (UTC)
The following discussion has been closed. Please do not modify it.
If gene and genome are always been a simple biological cells, so did it could a gene to mutate into a genome and genome to mutate into a gene?--83.237.192.63 (talk) 17:47, 4 April 2015 (UTC) Note: I’m suppose that the basis of life in the natural nature could not did it been complicated, it did been always simple, so gene and genome are always been a simple biological cells with similar as basis of viruses and bacteria.--83.237.199.127 (talk) 19:06, 4 April 2015 (UTC) I’m believe that the basis of the natural nature of the Lord God - the Spirit of Lord God it did been always simple, so the basis of life of natural nature as also it did been always simple too.--83.237.199.127 (talk) 19:35, 4 April 2015 (UTC)