
In the eye of a chicken, a new state of matter comes into view (2014) - bryanrasmussen
https://www.princeton.edu/news/2014/02/24/eye-chicken-new-state-matter-comes-view
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kevin_thibedeau
How is a nanoscale arrangement of molecules a new state of matter? Seems like
this is all University press release puffery at its best.

~~~
twic
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.

~~~
kevin_thibedeau
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.

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my_eye
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"?

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digital55
This was written up in 2016: [https://www.quantamagazine.org/hyperuniformity-
found-in-bird...](https://www.quantamagazine.org/hyperuniformity-found-in-
birds-math-and-physics-20160712/)

~~~
2020-3030
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?

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rurban
This needs a (2014)

~~~
dang
Thanks! Added.

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allthenews
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?

~~~
twic
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...](http://wiki.landscapetoolbox.org/doku.php/spatial_analysis_methods:ripley_s_k_and_pair_correlation_function)

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](https://www.ncbi.nlm.nih.gov/pubmed/1906908)

~~~
allthenews
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.

