In the eye of a chicken, a new state of matter comes into view (2014) | Hacker News Reader

In the eye of a chicken, a new state of matter comes into view (2014)

princeton.edu

How is a nanoscale arrangement of molecules a new state of matter? Seems like this is all University press release puffery at its best.

That does seem like a bit of an exaggeration. But then, "state of matter" isn't particularly well-defined, as far as i know, so who's to say it isn't one?

Perhaps relevant to this is the point about band gaps:

> The Princeton scientists discovered a few years ago that hyperuniform materials can have “band gaps,” which block certain frequencies from propagating

That's a property that crystals can have, but disordered materials can't, right? So it's interesting that a non-crystalline material can have that property.

Quasicrystals and metamaterials exhibit the same phenomena. They were well known and studied in 2014. Regardless, having unique interactions with the outside world is not a new intrinsic state.

Is this not how many things in nature work? Embryological development involves cells dividing until the concentration of some substance is less than or greater than some amount. I understand it may be a discovery about chicken eyes, but why is this important to embryology let alone physics and "states of matter"?

This was written up in 2016: https://www.quantamagazine.org/hyperuniformity-found-in-bird...

In addition to the other comments, what interested me about the findings mentioned in the 2016 quantamag article was the shared problem solving required to answer Joe Corbo's sense that there was a pattern to be found in the distribution of retinal cells.

To conclusively identify the pattern, the biologists needed to contact a theoretical chemist who studied optimal object packing density. Looking at the rest of that 2016 article shows the possible shared mechanisms and mathematics behind not just the hyperuniformity found in chicken retinas, but the same packing phenomena in other systems/objects. It is exciting to find organizational principles which can be seen in many different systems.

The other elements I like are that any study of receptors and neural organization, connection, and communication is that this outside-in approach ties in with study of the whole visual system and can connect other neurophysiological and cognitive findings. Not only is this relevant for some specialists, but many people are curious about the conscious experiences and capabilities of other species so learning about this may generate popular interest depending on the findings.

As a commentator (twic) mentions below, one of his colleagues did not care about the receptor packing patterns in her data. However, what one person ignores or deems a waste of time, another can pick up and use. Somewhere out there is a graduate student who is frantically looking for a finding to publish so I bet someone would be interested in looking at the control, visualization, quantification, or prediction of receptor spacing. I don't work at the cellular level, but this sounds fundamental. Mr. Twic - any reason not hand off your observation to an undergraduate or other interested party?

This needs a (2014)

Thanks! Added.

I'm confused. How is hyper-uniformity different from a homogeneous mixture?

What is the difference between a hyper-uniform material, and a material that has had adequate time to mix through diffusion?

It's a kind of order that is regular enough to be (considered) a crystal in many way, but it has the same properties in every direction.

Some research show that it should be possible to create transparent materials out of particles that would be opaque without the particle position correlations a material with the disordered hyper-uniformity has.

In a homogeneous mixture, at some scale, you can still find clumping - after all, if the elements of the mixture are randomly distributed, why wouldn't you? Whereas, in a hyperuniform mixture, there is no clumping.

A computer-scientific analogy would be sequences of random numbers. A sequences of bits can be perfectly random and still contain a hundred zeroes in a row. Whereas if you had a sequences of a billion bits which never had a run of a hundred zeroes, you could be pretty sure that it wasn't random.

You can measure this with metrics like the Ripley K:

http://wiki.landscapetoolbox.org/doku.php/spatial_analysis_m...

Before i was a programmer, i was a cell biologist. A colleague was studying CCR5, a cell-surface receptor that is involved in HIV entry into cells. She used electron microscopy with a rather tricky "rip-off" preparation [1] to look at the spatial distribution of CCR5 in cell membranes. One of the things she observed was that the receptors were remarkably evenly spaced. Being slightly more computationally inclined than her, i did some reading, came across the Ripley K metric, and wrote some Python scripts to analyse the distribution of receptors in her images. Lo and behold, they were indeed dispersed, suggesting that there was some cellular mechanism pushing the receptors apart. It turned out that the spacing wasn't actually very interesting to her, it was just a curiosity she'd noticed, so it was a complete waste of time really. Anyway, that was back in 2005. I'm glad these chicken eyeball bods have finally caught up, but it doesn't seem like a massive revelation.

[1] https://www.ncbi.nlm.nih.gov/pubmed/1906908

So it sounds like one could summarize the distribution as being random, but constrained by a cost function which locally maximizes entropy, i.e. reduces clumping.

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