Wikipedia:Reference desk/Archives/Science/2017 September 29

= September 29 =

alpha particles in nucleus
I have heard that the the neutrons and protons in the nucleus are sometimes combined into alpha particles. But the article seems to imply that bosons don't feel the nuclear force, or at least not as well as fermions do. Is this why alpha decay happens, because the nucleus doesn't have the nuclear force to hang on to it?144.35.45.70 (talk) 02:50, 29 September 2017 (UTC)
 * Which article are you referring to? Looie496 (talk) 03:49, 29 September 2017 (UTC)


 * An Alpha Particle is simply an ionized helium atom. Alpha decay is the expulsion of a helium nucleus from an unstable heavy element, called "decay" for historical reasons, but not really decay into a different type of particle in the same way as lone neutron decay into a proton, an electron, an antineutrino and a gamma ray. μηδείς (talk)
 * Alpha Radiation or its main source Alpha decay would be the proper articles. Cluster decay however comes closest to answering the question tho it does not go into such detail in Quantum mechanics to mention individual particles. --Kharon (talk) 04:46, 29 September 2017 (UTC)
 * I think the OP is thinking too hard about the nucleus really looking like a cluster of colored balls all glued together, as classic pictures in most textbooks show it. The nucleus does't look like that.  Insofar as it looks like anything, it looks like a fuzzy sphere, not unlike an atom would look if you could look at it (that is, if vision at that scale has any meaning, which is a debate for another day).  The fuzziness may be denser than the fuzziness of the electron cloud, but it's still basically an impervious cloudy structure.  When we say that the nucleus undergoes alpha decay, we say that it emits a helium nucleus, which is to say that a new nucleus is formed, that of helium, and the remaining nucleus has lost a mass and charge equivalent to that helium nucleus (ignoring, for the sake of this discussion, binding energy/mass, etc)  That doesn't mean, however, that if you looked at that original nucleus, you could identify discrete neutrons and protons, or that those discrete particles "broke off" in any meaningful way.  If you think about alpha decay like that, you run into real problems using the same explanation for beta decay.  After all, where is the electron in the nucleus?  The classic lie to children explanation is that a neutron in the nucleus turns into a proton by emitting an electron.  Which is only sort-of correct, and works because it makes the picture easier to understand.  The next question you may be asking is "where in the nucleus was that electron".  Was it in the neutron?  No, classically, neutrons conists of three quarks, none of which are electrons.  Well, maybe electrons are themselves made of quarks, or gluons, or some other particle we know to be in there?  No, near as all models can tell, electrons are fundamental particles which means they don't have any finer structure, they aren't made of parts.  So, if the electron didn't exist in the nucleus, and there are no parts of electrons in a nucleus with which it could be built, what then?  By what mechanism does beta decay happen?  The answer is shut up and calculate.  By which to say, quantum mechanics does not behave by the same rules as newtonian mechanics, so stop trying to make it work that way.  To say that protons and neutrons exist in a nucleus is true, but only in the sense that they are a useful model to explain concepts like nuclear decay and atomic mass and charge and stuff like that.  When you start treating them as objects unto themselves as though they were little lego bricks you could just pluck off and build new things out of, you start to introduce things into your model which do not match reality.  If your model is that bad at matching reality, throw away the parts of the model that don't work.  And the part of the model where we expect these particles to behave like little hard balls is the part which we need to abandon.  -- Jayron 32 16:29, 29 September 2017 (UTC)
 * I think we can be a bit more generous to the OP. An alpha particle is indeed a type of boson, because it has a net spin that is an integer.  In principle bosons can be packed at arbitrary density, but as our boson article explains (or at least tries to explain), other factors may come into play that prevent that from happening.  Such is the case with alpha particles:  the strong forces that their components feel prevent them from coming too close together. Looie496 (talk) 17:00, 29 September 2017 (UTC)
 * That's true, but as you note the concept of boson has limited utility here. There are lots of nuclei one could construct which are boson; it's trivial as any even-nucleon nucleus (such as C-12 or a deuteron) is also a boson.  However, since the composite particles (protons and neutrons) that make up the nucleus are fermions, one gets the unreasonable task of deciding which is more important to consider when describing the properties of such a nucleus.  You do get wierd physics when boson nuclei interact (such as in a Bose–Einstein condensate).  -- Jayron 32 17:35, 29 September 2017 (UTC)
 * I fell in love with the Atomic orbital concept once i learned to understand it, because it also works so well in explaining molecular bindings and their resulting geometry and function aka chemistry. Id say its also a very good approach to understand nuclear physics. So i would recommend to ignore the quarks and focus on that instead to learn how matter "works". --Kharon (talk) 16:59, 29 September 2017 (UTC)
 * Pretty much this^^^^ -- Jayron 32 17:35, 29 September 2017 (UTC)

Pantothenic Acid and Biotin
Do large doses of Pantothenic Acid (say, 500mg a day) cause Biotin deficiency in humans? I've read conflicting reports that they compete for the same absorption mechanism and so an excess of either can cause a deficiency in the other. But I've also read that they require each other for the other to be absorbed and used. I'm confused and can't seem to find a straight answer to this question. Thanks for your time. OrvilleVoyager (talk) 17:20, 29 September 2017 (UTC)


 * I see no studies on PubMed for humans. I do see studies on rats, mice, and bulls. The only one with a very conclusive result involved increasing both Pantothenic Acid and Biotin while reducing Folic Acid. The result was an increase in cancer risk. As of 2008, my nutrition textbook states that there have been no conclusive studies on Pantothenic Acid or Biotin supplements. Instead, B-complex vitamins are used, which include both. 209.149.113.5 (talk) 18:56, 29 September 2017 (UTC)


 * "Large doses of pantothenic acid do not cause symptoms, other than (possibly) diarrhea. There are no known toxic symptoms from biotin." Source: https://medlineplus.gov/ency/article/002410.htm


 * I am wondering why anyone would take large doses of Pantothenic Acid supplements without taking any Biotin supplements. Most people just take a B Complex supplement, which contains both. Also, large doses of either do nothing except create expensive urine. --Guy Macon (talk) 19:48, 29 September 2017 (UTC)

Design engineers
Many site and project engineers have to be reactive, for example if a problem arises on site or an incident occurs. Is design engineeeing less reactive? Or is it possible the design engineer could also be called in if something goes wrong on site? 94.10.178.193 (talk) 20:01, 29 September 2017 (UTC)
 * The work of a Design engineer is information intensive and unless (s)he takes care to deliver all necessary information and skill, (s)he remains liable to be called upon to solve problems that arise later in manufacturing and implementation of a project. The documentation accompanying a piece of technology is often the only means by which the user can fully understand said technology. Blooteuth (talk) 20:43, 29 September 2017 (UTC)


 * Both. For instance the Millennium Bridge at first swayed from side to side due to well understood resonance. It was much easier then for the design team (using real data)  to then add dampening correction. This would have been difficult and more expensive to do at the conceptual stage before the bridge had been built. Architects tend to be conservative,  even when creating something new. The counter lever roof on the original Wembly stadium was new on that scale but the principles had already been proven on a smaller scale. Even the largest domed-roof is only a cement version of an Igloo.  A sky scraper using new construction techniques on Manhater Island was found to be unsafe, but its short comings were rectified, negating the neead to demoish it.   Yet, as always some architects get is wrong... Ronan Point and Tacoma Narrows Bridge etc. Aspro (talk) 20:58, 29 September 2017 (UTC)


 * "Even the largest domed-roof is only a cement version of an Igloo." But surely the builders of the Pantheon had never seen an igloo. CodeTalker (talk) 21:56, 29 September 2017 (UTC)
 * It's not even true. An igloo is a circular cantilever.  Some domes (which are thinner, but require centring during construction) are circular arches. Andy Dingley (talk) 22:10, 29 September 2017 (UTC)


 * Design engineers are usually called in as second or third level support when a problem arises with a product after it is in use. This is nearly universal practice with software products, and also with complex or custom physical products. -Arch dude (talk) 02:46, 30 September 2017 (UTC)


 * As a design engineer in a car company I spent hours each week working on problems on the assembly line with my parts, and would also get involved in recalls and technical service bulletins. Greglocock (talk) 07:15, 30 September 2017 (UTC)

are neurons specific to a single neurotransmitter?
I've been trying to self educate myself about the brain, neurons, etc. My background is computer science and I have a decent understanding of artificial neural networks. One question I'm not sure about that seems rather important is: how specific is a neuron to a neurotransmitter? I.e., does each neuron only respond to and/or take input from a single neurotransmitter, or can neurons respond to neurotransmitters in different ways (e.g., dopamine might excite neuron x but serotonin inhibit it). This seems to me to be an important differentiator between ANNs and actual neural networks. Are there other major differences (or would that take a book to respond to)? Thanks. --MadScientistX11 (talk) 22:24, 29 September 2017 (UTC)
 * Almost every type of neuron responds to a wide variety of neurotransmitters. In fact, almost every type of neuron releases multiple neurotransmitters.  The only real restriction is Dale's principle, which says that a neuron releases the same set of neurotransmitters at all of its output synapses -- and even that has exceptions.  You're right that simple ANNs don't capture this aspect of real neurons.  There are more sophisticated types of ANNs that do, as described in our biological neuron model article, but they are of more interest to biologists than computer scientists. Looie496 (talk) 23:03, 29 September 2017 (UTC)
 * Looie's got it right, and you also have to consider that a specific neuron can accept stimuli from scores of other neurons that themselves react to different neurotransmitters. We are at the beginning of understanding the brain.  Endocannabinoids were only recognized as neurotransmitters in the last decades of the last century.
 * Look at the plethora of designer drugs that coroners can't even detect as the underground drug industry outruns them. Neuroplasticity, and positive feedback (short term) and negative feedback (long term) and refractory period are not necessarily directly related, but may be of interest, and lead to other links such as SSRI's and serotonin syndrome may be of interest. There's also neuron and action potential and synapse.
 * I won't waste your time with more links, I have to go get me some dopamine. μηδείς (talk) 03:44, 30 September 2017 (UTC)
 * and Thanks a lot. That cleared up my confusion, excellent answers!!  --MadScientistX11 (talk) 18:00, 2 October 2017 (UTC)