Wikipedia:Reference desk/Archives/Science/2015 October 19

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October 19

Microdroplet computing

Here's an interesting rabbit hole for you to explore: the Belousov-Zhabotinsky reaction. Used to assess malignant tumors An application of "microdroplet computing" perhaps optimized for three-valued (not binary?) logic,[1] involving spherical "cells" that self-assemble that visibly flicker and seem to sync and desync with each other (see [2]).

Apart from the woozy feeling this is one of my parallel-universe dreams, I'm hampered here by a lack of citations to scientific sources, source accessibility issues with those I have, and a lack of a clue about how random floating droplets turn into a neural network that can diagnose cancer (from what data?) Can someone throw us a clue - how does this work, and how serious is it as a method of reinventing the computer? Wnt (talk) 00:18, 19 October 2015 (UTC)

Are you familiar with reaction diffusion systems in general? Basically in a thin plate, the BZ reaction has an inhibitor and a catalyzer that diffuse at different rates, and fun ensues. In the well-mixed version, the analysis isn't so terrible, see e.g. the Brusselator and the Oregonator for finite-dimensional ODE approximations. Start with the Brusselator if you just want the concepts and don't care about the details of the chemistry. The gist of it is that you get an N-shaped isocline and the path through state space goes round and round.

As for for computation - if you pour out a thin sheet of BZ in dish with a maze of barriers, the waves that take the shortest path will get to the end first, and so the autocatalytic reaction has in some sense "solved" a "hard" problem. With a normal computer, the solution time of the maze depends on the configuration of the maze, number of walls, etc. With this chemical "computer" solution time only depends on wave speed. You can play similar games with Dictyostelium amoebae - if you search google scholar you'll see tons of fun papers on Cyclic_adenosine_monophosphate exciting spiral waves and other weird stuff as part of the slug-formation phase of the slime molds. I don't know the details of how this binary classifier in the cited article is working in terms of input encoding, but I suspect this computation is just a fancy version of the maze-solving abilities of these things. SemanticMantis (talk) 15:11, 19 October 2015 (UTC)

(Fun fact not mentioned in our article: BZ reaction was discovered when trying to make a model or simplified version of the krebs cycle). SemanticMantis (talk) 15:34, 19 October 2015 (UTC)

• Here's a freely accessible and relevant journal article out computing with BZ, [3], it also mentions Physarum. Here's a whole book title "reaction-diffusion computers" [4], sharing a few coauthors with the article above. SemanticMantis (talk) 17:21, 19 October 2015 (UTC)

I don't know anything about this type of computing but I want to point out that, as a rule, things tend to be Turing-complete. Even simple automata like Conway's Life and SMETANA are Turing-complete. Probably almost any nonlinear physical system can be coerced into acting as a digital computer, though not necessarily very efficiently. I don't know anything about machine learning but I suspect that many nonlinear systems are trainable (not just neural networks), and it may not be hard to get 90% accuracy on the CANCER database images, especially if they used the same images for training and testing. -- BenRG (talk) 21:28, 19 October 2015 (UTC)

Actually that SMETANA article says it might not be Turing-complete - something about not having infinite number of cells, or else not being able to define final output? And it says the same applies to cellular automata, though our Conway's Game of Life article says that is Turing-complete. I don't claim to know myself; still, your overall point is taken. My lack of understanding of how the cancer test works is keeping me well confused about how impressive this is. Wnt (talk) 22:33, 19 October 2015 (UTC)

How does a DVD player work? Specifically, how does it manage to track the microscopic grooves?

I'm familiar with machine tools where you can turn a dial to position a tool to the nearest thousandth of an inch, or, if you are careful and have a high quality machine, perhaps even to the nearest ten thousandth of an inch. And I've heard rumors that adjusting the voltage on a voice coil can achieve even greater accuracy. But I don't think DVD players use voice coils, and I can't imagine that the tracks on a plastic disk that is snapped onto a mechanical hub will be truely concentric. There's some kind of voodoo going on here and I haven't been able to find out just how it's being done. Dogwon. — Preceding unsigned comment added by 50.43.33.62 (talk) 01:40, 19 October 2015 (UTC)

They track the groove using feedback from the reflected beam. For (perhaps outdated) technical details see The Compact Disc Handbook by Ken C. Pohlmann, pp. 107-119. ("It is interesting to note that the movement of a CD player's pickup is similar to that of a stylus in an LP groove. With the aid of the auto-tracking system, the pit signal 'pulls' the pickup across the disc in the same way that the phono cartridge is pulled across an LP by the groove.") Seeking across the disk surface is only approximate, but CD-ROM and DVD encode the sector number along with the payload data so there's no danger of reading the wrong one. -- BenRG (talk) 02:11, 19 October 2015 (UTC)

I don't like that way of describing it. Pohlmann's "in the same way as" refers only to the motion of the component, but sounds as if it refers to the reason why it moves. --174.88.134.156 (talk) 04:04, 19 October 2015 (UTC)

There are some details given in the CD player article. I think most CD and DVD players use 2 separate movements, a screw drive for coarse movement of the whole optical assembly, and tracking coils that control the lens for fine movement. Ssscienccce (talk) 06:30, 19 October 2015 (UTC)

The CD player article does give a pretty good description, but it's still a bit vague. What I might be running into here is proprietary techniques. I would think that motion control that was this accurate and this cheap would have wider applications. — Preceding unsigned comment added by 50.43.33.62 (talk) 05:03, 21 October 2015 (UTC)

Is the opposite of the wilderness domestication?

I am not sure where do human beings fit in. Feral human children seem to belong in the wild, raised by wolves or other animals. But if children live in the greater human community raised by their own human parents, then would that be domestication or something else? 71.79.234.132 (talk) 02:24, 19 October 2015 (UTC)

The term "domestic" refers to being "attached" to home and family,[5] so by definition virtually all humans are "domesticated", even most of those who live in wilderness areas. Some adult humans isolate themselves. But the notion of children being raised by wolves is basically a myth. A child would most likely become dinner in such a situation. The opposite of "wilderness" would appear to be "inhabited" or "cultivated".[6] ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:35, 19 October 2015 (UTC)

Our article Wilderness defines it as the "most intact, undisturbed wild natural areas left on our planet—those last truly wild places that humans do not control and have not developed with roads, pipelines or other industrial infrastructure." This pretty much excludes permanent modern human habitation, although very rare modern humans such as Norman Clyde spent a large percentage of their lives in the wilderness. Even Clyde usually withdrew from the wilderness during the winter. Domestication refers to the taming and breeding of animals for human use. Undomesticated animals flourish outside wilderness areas. Near where I live, which is far from wilderness, undomesticated animals such as raccoons, rats, coyote, deer, lizards, snakes and turtles are common. Plus an abundance of undomesticated birds, including wild turkeys. Cullen³²⁸ Let's discuss it 04:36, 19 October 2015 (UTC)

The scope of our article Feral child suggests that children being "raised" by a variety of animals, including wolves, is not entirely mythical. (The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 15:03, 19 October 2015 (UTC)

I would say the opposite of "feral" is "socialized". So, a properly socialized child, or dog, knows how to get along with other people, while a feral child or dog does not.

Also note that feral children don't have to be raised by animals, they can also just be neglected. If a child is kept in a cage, never talked to, and just tossed food, they will be messed up as an adult. StuRat (talk) 18:30, 19 October 2015 (UTC)

"Higher animals"

What determines if an animal species is a higher animal or lower animal? Would humans fit under higher animals or outside the dichotomy? 71.79.234.132 (talk) 02:45, 19 October 2015 (UTC)

What is your source for the terminology? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:50, 19 October 2015 (UTC)

Everywhere. 71.79.234.132 (talk) 02:51, 19 October 2015 (UTC)

Check Evolution of biological complexity and you'll see that "higher" is not regarded as very useful scientifically. However, if you google subject, in general it means "more advanced", like being vertibrates as opposed to being worms. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:54, 19 October 2015 (UTC)

Why can't "lower" mean more advanced? 71.79.234.132 (talk) 03:00, 19 October 2015 (UTC)

Because it means "less advanced". ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:06, 19 October 2015 (UTC)

Yeah but you cant get any lower than a Wabbit. Wabbits are the lowest form of life--31.55.64.161 (talk) 03:46, 19 October 2015 (UTC)

With the exception of trolls. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:17, 19 October 2015 (UTC)

Carrots are a lower form of life than wabbits, because wabbits eat carrots. Most of the trolls I have known have showed behavioral evidence of being H. sapiens. Robert McClenon (talk) 21:26, 19 October 2015 (UTC)

And for clarity, "less advanced" (or "more advanced") is a confusing term in evolution, whatever you call it. Nil Einne (talk) 05:18, 19 October 2015 (UTC)

The irony is that "lower" organisms, being typically smaller, tend to reproduce more quickly, which means that they are the most evolved. Humans have genes scattered all over the genome like a bachelor's underwear, interspersed by piles of junk that our genomes don't throw away "because there might be something valuable in there." Bacteria have their genes neatly sorted out into operons, with scarcely a letter of code that doesn't need to be there. Wnt (talk) 14:47, 19 October 2015 (UTC)

The common ancestor of mice and men was morphologically closer to mice. In this sence, we are more advanced Asmrulz (talk) 14:51, 19 October 2015 (UTC)

Have you read our article on Anthropocentrism to see how scholars have come to understand, deconstruct, and contextualize a world-view that emphasizes human superiority? If we look objectively at certain parameters, like total biomass, humans are not anywhere close to the most prolific species, let alone the "most" "advanced" or "evolved." Biologists do not normally compare organisms based on subjective criteria that judges the magnitude of "advancement." That would be capricious and subjective. Nimur (talk) 14:58, 19 October 2015 (UTC)

We actually have an article Higher vertebrates which states "Older sources, particularly prior to the 20th century, may refer to amniotes as "higher vertebrates" and anamniotes as "lower vertebrates", based on the discredited idea of the Great Chain of Being." I'm glad this states "older sources" as I think most biologists would think of the terms "higher" or "lower" is being very outdated, similar to terms like "primitive fish" and "living fossils".DrChrissy ^(talk) 15:05, 19 October 2015 (UTC)

We also have an article on the great chain of being. Also worth noting that basal groups are sometimes called "primitive", and derived traits are sometimes called "advanced." In both cases, the terms that don't impose value judgements are increasingly preferred. SemanticMantis (talk) 15:31, 19 October 2015 (UTC)

If you want an objective way to distinguish "higher" from "lower", how about exclusively putting single-celled organisms in the "lower" category ? StuRat (talk) 19:16, 19 October 2015 (UTC)

User:StuRat has a reasonable suggestion to put single-celled organisms in the "lower" category and multi-cellular organisms in the "higher" category". However, this has already been implicitly done by late twentieth-century and early twenty-first century taxonomy so that the phrase "higher animals" is redundant or meaningless. The phrase "higher animals" is simply an anglicization of metazoa, but with the identification of Protista, including protozoa, as a distinct kingdom consisting of single-celled eukaryotes, there are no "lower animals" in the sense of single-celled animals, because Animalia consists of the multi-cellular animals. In modern taxonomy, if it is an animal, it is a higher animal, because amoebae, paramecia, et cetera, are no longer considered animals (thus eliminating a lot of useless argument among earlier taxonomists as to what single-celled organisms were animals and what were plants). Robert McClenon (talk) 21:20, 19 October 2015 (UTC)

No, it's not a reasonable suggestion. What's the benefit of introducing invalid and loaded terms to duplicate the already existing distinction of "unicellular" and multicellular"? 64.235.97.146 (talk) 19:43, 19 October 2015 (UTC)

It is true that the terms "unicellular" and "multicellular" are preferred to "lower" and "higher". I can see an argument about "loaded" terms, but not "invalid" terms, because "higher animals" is simply a translation of the long-used term metazoa. If you mean that it is clearer in modern terminology to just name the kingdom, that is true. Animalia are multi-cellular animals. Therefore, there are no "lower animals". Robert McClenon (talk) 21:24, 19 October 2015 (UTC)

just to throw another monkey wrench in, parasites tend to become simpler, the more they evolve. how do you classify that in terms of higher/lower? Gzuckier (talk) 05:48, 20 October 2015 (UTC)

• Really, the problem with the "higher" and "lower" terminology, is that it is based on a thoroughly discredited (but still widely felt and held among the unscientifically-minded people of the world) that humanity represents the pinnacle of creation, and that all other life can be compared to humans; thus "higher" life forms are more "human like" and "lower" life forms are more different from humans. While one could devise any number of systems which use "higher" and "lower" in more appropriate ways which actually connect to the way evolution works, doing so would be confusing in that we cannot divorce the terms from the emotional baggage of "humanity is the highest form of life" concept, which is why modern biologists and taxonomists avoid those words (and related words like "primative" and "advanced" or similar pairings), not because they are automatically wrong, but because there's no way to separate the words from the incorrect understanding of them. Best to just avoid them altogether. --Jayron32 15:12, 20 October 2015 (UTC)

applications of complex numbers and argand diagrams

i need to know how complex numbers and argand diagram concepts can be useful in drawing a plan for building and its construction 14.97.34.190 (talk) 13:12, 19 October 2015 (UTC)

Do you have any reason to think that complex numbers and Argand diagrams are used in construction ? StuRat (talk) 19:11, 19 October 2015 (UTC)

This article describes the Argand plane which is just a way to show complex numbers as points on a flat plane. A simple description of a complex number is that it is made up of two numbers which can represent distances measured from an origin in two directions at 90 degrees to each other. So if we call the south-west corner of a house plan the origin, we could call a location that is 4 steps East and 3 steps North from the origin a "complex location" defined as 4+3i steps. A mathematician might describe the same location by a vector of magnitude 5 steps. However the higher mathematics that are possible using complex numbers may not be useful in drawing building plans. Bestfaith (talk) 21:57, 19 October 2015 (UTC)

Yes, what possible advantage would that have over conventional building plans ? StuRat (talk) 23:51, 19 October 2015 (UTC)

Analysis of dynamic behaviour and stability of structures (oscillations, damping), for example a bridge in the wind, or buildings during seismic events. Specific example: "Argand diagrams are used to explain why in some instances it is observed that adding viscous dampers to strongly inelastic systems can result in increases in floor acceleration rather than the intended decreases". Argand diagrams (s-plane) are used to analyse stability of feedback systems (electronic amplifier etc..), this is comparable. Ssscienccce (talk) 20:38, 20 October 2015 (UTC)

The programs of a floor Robotic vacuum cleaner and of an X–Y plotter used to draw building plans could both treat their movement coordinates as complex numbers. Bestfaith (talk) 23:16, 20 October 2015 (UTC)

Yes, and there may be some advantages in the case of the plotter. But the problem is that we have no idea what the OP wants, and he hasn't answered StuRat's question for more information. If it refers to some specific application, you'd expect google to give some results. Ssscienccce (talk) 01:31, 21 October 2015 (UTC)

This branch of mathematics would have been a lot simpler if "complex numbers" were instead called "two-dimensional numbers"...which is what they really are.

Normal numbers like -3, 5, 148, pi and 123.4546 are "one-dimensional" but the square root of -42 is a two-dimensional number. Writing those numbers as a "real" and "imaginary" part and sticking the letter 'i' in there to denote the imaginary part is horribly confusing - it would be far, far better if mathematicians had used a vector notation (real,imaginary) - this is what is called a 'tuple' - and it makes much more sense when you look at things that way. All of the stuff you were taught about complex arithmetic, argand diagrams and all that horse-shit would simply be the standard vector operations that you use for everything else where multiple numbers need to be grouped together. Whole chapters of math books could be discarded and life would be very much easier for all concerned!

This gets especially silly when complex numbers are used in electrical circuit theory - where there are no actual square-root-of-a-negative-number "complex numbers" involved, just a reason to carry two numbers around together and do operations on them that just happen to fit with the way that complex numbers are manipulated. (Worse still, those people conventionally use 'j' instead of 'i' to denote the imaginary part...which is endlessly confusing!) I know a lot of circuit designers who have consciously dumped "complex numbers" and just use standard vector notation.

So, I suppose, you can go the opposite way and express the (x,y) coordinates of the rooms of a house (which are "two-dimensional" numbers) using the X+Yi notation of complex numbers and plot the floor plan as an "argand" diagram - but it's really all rather silly and retrograde. There are absolutely no benefits to doing that - and if you *do* work that way, then you're going to be in a total and utter mess when you realize that a house is a three-dimensional object and mathematicians don't routinely have use for more-complex-numbers that have real, imaginary and some-other-thing. However, if you started off by considering everything to be a point in 2D space - then moving into 3D space when you start to care about the heights of things becomes far more natural.

Yes, you can do this - but please don't - it's just ridiculous. SteveBaker (talk) 13:24, 21 October 2015 (UTC)

This totally isn't my field, but I'm thinking there must be some kind of application of complex numbers to a phased vibration, comparable to their use in alternating current electrical diagrams. I won't say more because I surely don't know this much. Wnt (talk) 15:43, 21 October 2015 (UTC)

Yep, those were the only actual examples I found, see links above: Argand diagrams used to analyze a bridge in the wind, or seismic movement and damping in buildings. Ssscienccce (talk) 20:39, 22 October 2015 (UTC)

So, to summarize, using an Argand diagram for construction plans is excessively complex, with benefits that are purely imaginary, and i don't recommend it. StuRat (talk) 14:51, 22 October 2015 (UTC)

Pine cone?

Is this actually the umbrella pine cone in the hands of that figurine? The same alleged pineapple in the Pompeian mosaic was identified as umbrella pine cone in this book, so I wonder whether the figurine also holds it. Image search wasn't helpful. Thanks. Brandmeister^talk 19:00, 19 October 2015 (UTC)

Unlikely to be that umbrella pine as it "was first introduced to Europe by John Gould Veitch in September 1860" from Japan, according to our article. The same name is sometimes given to the stone pine whose seeds are indeed eaten in the Mediterranean region, see pine nut. Even if the Romans had discovered America, getting a pineapple back to Italy in an edible condition would have been an achievement. Alansplodge (talk) 21:24, 19 October 2015 (UTC)

How many foramens are in the skull - in total?

How many foramens are in a human body skull - in total, and by the way what are they used for? 78.111.186.18 (talk) 19:25, 19 October 2015 (UTC)

We have an article you might like to read. I found it by putting "foramen" in the search bar. 64.235.97.146 (talk) 19:38, 19 October 2015 (UTC)

Thank you very much! 78.111.186.18 (talk) 20:44, 19 October 2015 (UTC)

The human skull has numerous holes (foramina) through which cranial nerves, arteries, veins and other structures pass. This table lists 22 foramina. Bestfaith (talk) 22:06, 19 October 2015 (UTC)

So how can I now that this table shows us the real number and not less? or maybey it's just a partial list. Thank you 78.111.186.251 (talk) 20:13, 20 October 2015 (UTC)

I think you are looking for one specific number, and there really can't be one. There is significant variation in anatomy, and not every person will have the same number of foramina. Our list seems to be mostly named foramina. Add them up and that's a good estimate. But there may be unnamed accessory foramina in mandibles, bones which you could or could not include in your definition of skull; there also may be unnamed emissary venous foramina in the skull base, and others elsewhere. An exact number is not an acheivable goal, as the number will vary from person to person. - Nunh-huh 04:16, 22 October 2015 (UTC)