[HN Gopher] Unexpected 'Black Swan' defect discovered in soft ma...
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Unexpected 'Black Swan' defect discovered in soft matter for first
time
Author : dnetesn
Score : 121 points
Date : 2021-05-20 10:55 UTC (12 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| pjungwir wrote:
| It reminds me of PNP & NPN transistors. Could these liquid
| "defects" have applications too?
|
| Ever since childhood I've wondered why the water behind a rowboat
| stays flat for so long. You'd think the surrounding water would
| flow in and make it as wavy as everything else. Then a few years
| ago I was on Thera and saw the same thing with the cruise ships
| coming in. Their flat glassy trails would last for hours. Why
| does it take so long for them to vanish? It is a liquid
| transition that is weirdly persistent. Does anyone have an
| answer? If not, maybe this can be someone's wobbling plate.
| hyperpallium2 wrote:
| IDK but one factor is most of the water filling the gap would
| come from underneath (it's at higher pressure), moving up to
| the surface. Its momentum carries it slightly too high, so it
| flows outward, then down and inward again, forming a vortex on
| either side. The surface looks smooth and the twin vortices
| woukd tend to persist.
| hinkley wrote:
| WAG: does it have anything to do with dissolved gases slightly
| changing the physics of the water, making it a case of the
| waves seeing it as a transition between materials.
| Enginerrrd wrote:
| If I recall correctly, I think this is usually explained as a
| thermocline effect where as deeper water gets churned up and
| mixed in the wake, it is a different temperature than the
| surrounding water outside the wake. This water has ever-so-
| slightly different fluid characteristics and so it presents a
| bit of a barrier to the usual diffusion and mixing you might
| expect.
|
| There's also the potential for a very thin layer of some type
| of hydrophobic substance (like an oil) to be left behind that
| can dramatically reduce waves in that area. There's youtube
| videos around for that effect.
| hinkley wrote:
| Probably a different amount of dissolved gasses as well.
| [deleted]
| cinquemb wrote:
| > While the researchers were not actively looking for any
| particular defect in the material, the advanced imaging technique
| uncovered a surface defect, called a twin boundary. At either
| side of the twin juncture, the molecular networks abruptly
| transformed their handedness.
|
| Reminds me of Q1D models that simulated glassy dynamics[0]:
|
| "We describe numerical simulations and analyses of a quasi-one-
| dimensional (Q1D) model of glassy dynamics. In this model, hard
| rods undergo Brownian dynamics through a series of narrow
| channels connected by $J$ intersections. We do not allow the rods
| to turn at the intersections, and thus there is a single,
| continuous route through the system. This Q1D model displays
| caging behavior, collective particle rearrangements, and rapid
| growth of the structural relaxation time, which are also found in
| supercooled liquids and glasses. "
|
| [0]: https://arxiv.org/abs/1401.0960
| phonethrowaway wrote:
| > At either side of the twin juncture, the molecular networks
| abruptly transformed their handedness.
|
| this seems rather intuitive to me, and unsurprising.
|
| for every action there is an opposite and equal reaction.
|
| a spinning cue ball changes directions when it bounces off a
| rail.
|
| it's the same reason circular polarizers let you see through
| reflections in glass.
| [deleted]
| Chris2048 wrote:
| > In biology, we know that even a single defect in DNA, a
| mutation, can cause a disease or some other observable change in
| an organism
|
| And this would relate to material science?
| sandworm101 wrote:
| A single defect can impact the entire field. One unambiguous
| result could throw the entire standard model out the window. It
| has happened in astronomy, the father of physics, multiple
| times.
| optimalsolver wrote:
| >A single defect can impact the entire field
|
| Just ask Boeing.
| thisismyswamp wrote:
| In the way that molecules are so fast that they go past each
| other frequently, making global effects possible to arise from
| small perturbations.
| acjohnson55 wrote:
| One thing that comes to mind is prions, which cause diseases
| like mad cow and CJD.
|
| "Prions are misfolded proteins with the ability to transmit
| their misfolded shape onto normal variants of the same
| protein."
|
| https://en.m.wikipedia.org/wiki/Prion
| icoder wrote:
| I think you and parent came up with a possibly better
| example than the one in the article quoted by the
| grandparent comment, more so than it being a clarification
| of how single DNA mutations ripple out to be big problems.
| gus_massa wrote:
| That's incorrect. Molecules collide when they are close
| enough. (There is a small probability of tunneling, but it's
| really small.)
|
| Small perturbations in a crystal are call "defects"
| https://en.wikipedia.org/wiki/Crystallographic_defect and
| they are quite stable, and don't move too much. The effect is
| very local.
|
| The defects in DNA can have a huge effect if they are in an
| (un)lucky spot, and they are completely unrelated to material
| science.
| trutannus wrote:
| Basically, insofar as the perturbation does not impact more
| than the local lattice structure (sometimes just a few NM
| across), the overall lattice (therefore properties) will be
| rather unaffected. I know pure crystals will often have
| embedded impurities (ie: precursor residues in the
| product). The impact for the DNA change is that DNA is used
| to create downstream materials, whereas materials are
| generally used because of their properties directly. As
| long as a defect does not impact to a great extent the
| general properties of the material, it is irrelevant.
|
| In terms of movement inside a lattice structure, the only
| real movement is vibrational and rotational movement, so
| global effects because of particles moving about has far
| lower influence.
| DrJokepu wrote:
| Depends on the type of defect. Dislocations can move around
| quite a bit and they do affect the structural integrity of
| the material.
|
| This is why if you bend a fork, you will never be able to
| fully unbend it (without heat treatment), there will always
| be a S-shaped bend it it.
| kragen wrote:
| an iron whisker with a single crystal defect in it has
| dramatically different macroscopic properties, especially
| tensile strength, from an iron whisker without a single
| crystal defect.
| [deleted]
| thisismyswamp wrote:
| A Black Swan is an "unknown unknown", something you don't just
| lack understanding of, but don't expect or predict. The
| statistical interpretation of the term was popularized by Nassim
| Taleb in the book of the same name:
| https://www.goodreads.com/book/show/242472.The_Black_Swan
| [deleted]
| yosito wrote:
| And what is "soft matter"?
| Cd00d wrote:
| Matter is stuff.
|
| Condensed matter is stuff that is not gas.
|
| Soft matter is shorthand for soft condensed matter, which is
| stuff that is not gas nor solid.
|
| Fluidics, liquid crystals, polymers are examples of soft
| matter.
|
| Source: I am a soft matter physics PhD that focused on liquid
| crystal phase characterization.
| dmingod666 wrote:
| The article seems is too shallow in details of their
| seemingly very important discovery. Atleast nothing I could
| decipher. What do you think is relevant in their finding?
| abledon wrote:
| from article....
|
| "Materials can be broadly classified as hard or soft matter.
| Hard materials, like metal alloys and ceramics, generally
| have a very regular and symmetric arrangement of atoms.
| Further, in hard matter, ordered groups of atoms arrange
| themselves into nanoscopic building blocks, called unit
| cells. Typically, these unit cells are comprised of only a
| few atoms and stack together to form the periodic crystal.
| Soft matter can also form crystals consisting of unit cells,
| but now the periodic pattern is not at the atomic level; it
| occurs at a much larger scale from assemblies of large
| molecules."
| jtbayly wrote:
| Apparently swans are. I'd guess most birds, especially geese,
| since their feathers make nice pillows.
| wernercd wrote:
| This has nothing to do with black swans, the birds... this
| has to do with unexpected results that are easy to explain
| in hindsight after the truth is known.
|
| https://en.wikipedia.org/wiki/Black_swan_theory
|
| "Taleb's "black swan theory" refers only to unexpected
| events of large magnitude and consequence and their
| dominant role in history. Such events, considered extreme
| outliers, collectively play vastly larger roles than
| regular occurrences.[2]:xxi"
|
| This discovery (unexpected behavior of matter) seems like
| it'll have a surprising and large magnitude.
| meepmorp wrote:
| The way they use the phrase here has nothing to do with
| Black swan theory or Taleb's book.
|
| It just means something very rare, and that's been the
| common meaning of the phrase in English for hundreds of
| years. It comes from Latin.
| jtbayly wrote:
| But no correction of my improper interpretation of "soft
| matter"? ;-)
| wernercd wrote:
| its early and the caffeine hasn't set in (still hasn't).
| I guess this is a better comment if I read it with a
| sarcastic twist?
| teachingassist wrote:
| I'm not sure I agree with anything you have said here.
|
| "Black Swan" was in use before Taleb's book, at a similar
| frequency as it is today (Google Trends scores 2 vs 3, where
| 100 is when the book was released).
|
| "Black swan" as a phrase dates at least to Roman times, often
| referring to the philosophical idea that the observation of a
| single black swan would prove their existence. (I've heard
| 'black sheep' used for this as well, although that has other
| more popular meanings).
|
| The interesting part is that this did come to pass, for black
| swans: which are only native to Australia.
|
| So, in my mind, it refers to something which is conceivable,
| but not believed to exist and not (yet) observed.
| brobdingnagians wrote:
| The Roman writer Juvenal is the origin of the phrase [1].
| Neat to see pictures of them. [2] And humbling to think it
| took almost two thousand years for them to find out that the
| proverbial phrase was wrong.
|
| [1] https://www.etymonline.com/word/black%20swan
|
| [2] https://en.wikipedia.org/wiki/Black_swan
| gumby wrote:
| > "Black Swan" was in use before Taleb's book
|
| In fact he likely used the term for his title because it's a
| well-known metaphor.
| tmptmp123 wrote:
| The term black swan as it appears on the book actually comes
| from a philosopher. I think it is from David Hume. Does anyone
| here on HN knows? Its basically the concept in science that the
| connection between cause and effect is an ilusion. I remember
| reading the thought experiment from a philosopher in that
| context. Since google stopped working finding these things has
| proven more difficult.
| meepmorp wrote:
| A black swan is not "an unknown unknown." It's something very
| rare, possibly non-existent - the phrase has been part of the
| English language for centuries (from Latin), and is clearly not
| being used in reference to Taleb's book:
|
| > "This defect is like a black swan--something special going on
| that isn't typical," said Dr. Edwin Thomas, professor in the
| Department of Materials Science and Engineering
| devy wrote:
| Yep. Even though related but the phrase "black swan" is
| different from the "Black Swan Theory".
|
| The wikipedia entry[1] has the explanation of both. And the
| usage by Dr. Thomas certain refers to the phrase not the
| theory.
|
| [1]: https://en.wikipedia.org/wiki/Black_swan_theory
| peheje wrote:
| Rather "Outside context problem"?
| SAI_Peregrinus wrote:
| Related, but that's a subset of "black swan". Not every
| "black swan" is a problem.
| rozab wrote:
| The meaning of the phrase changed completely once black swans
| were actually discovered in Australia.
| waheoo wrote:
| Did it though?
| RosanaAnaDana wrote:
| Right..
| blacksmith_tb wrote:
| Isn't that the point? Before English-speakers had seen
| one, 'black swan' was a nonsense impossibility, like
| water flowing uphill. After Brits saw them in Australia,
| the phrase changed from 'total impossibility' to
| 'extremely unlikely but what do you know, actually true!'
| amelius wrote:
| What is the relevance of the term here?
| mohanmcgeek wrote:
| That it's in the title?
|
| GP is pointing out that it's being used incorrectly
| meepmorp wrote:
| The term isn't used incorrectly
| gumby wrote:
| except that, this being the Internet, the observation is
| not in fact correct.
|
| (I think we've all been "guilty" of this at one point or
| another)
| dkarl wrote:
| This subthread is an illustration of the HN tendency to seize
| on whatever aspect of the article we think we can sound smart
| about, which, despite seemingly being an isolated comment
| that the scientist did not clarify or expand on at all, the
| journalist cleverly elevated to the headline.
| arkitaip wrote:
| You've just summarized the beauty that is n-gate.
| agilob wrote:
| Black Swan event is always unexpected, unpredictable, with no
| prior recorded history of such event, so no one could prepare
| for such event. It's always catastrophic as a system couldn't
| be possibly ready for it.
| booleandilemma wrote:
| Black swan is one of those terms no one can quite seem to agree
| on and people correct others corrections.
|
| Kind of like np-completeness.
| atq2119 wrote:
| NP-completeness has a rigorous mathematical definition.
| People who know the field definitely agree on it, there's
| nothing fuzzy about it.
| GuB-42 wrote:
| ... and AI
| harshbutfair wrote:
| I still think it's a strange phrase. To me a black swan is a
| normal swan.
| robbiep wrote:
| But until Europeans had come to Australia, no Europeans had
| ever seen a black swan
| domano wrote:
| So if i see a black swan here in germany, this means it is
| a a descendant of an australian swan?
| robbiep wrote:
| apparently so
|
| [0] https://en.wikipedia.org/wiki/Black_swan_emblems_and_
| popular...
| inopinatus wrote:
| Grey geese though.
| cleansy wrote:
| However, in this article it's referred to as an actual black
| swan, not the concept in the book.
| [deleted]
| wernercd wrote:
| "actual black swan, not the concept"
|
| 2nd paragraph of article, first sentence: "This defect is
| like a black swan--something special going on that isn't
| typical,"
|
| So how is this an actual black swan - a bird with wings...
| and not a "black swan" - an unkown unknown (as described
| eslewhere)?
| CositaS wrote:
| The actual article this story is about:
| https://www.pnas.org/content/118/12/e2018977118
|
| (the link was there but buried at the bottom of the page)
| [deleted]
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