Needle crystals eat square crystals
What happens to organic thin film devices as they age? Will the device stop working? Will the optoelectronic properties change? Can I prevent this by keeping it in the fridge?
In this paper, we observe the evolution of a thin film of PTCDI molecules which initially contains two coexisting species: needle crystal islands and square crystal islands. As time goes on, the needle crystals grow by consuming the square crystals, which shrink, eventually to extinction. We attempt to describe this evolution mathematically, look at why it happens, and consider what we can do to change how quickly it takes place.
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LC12113
What's inside a black hole
--- an answer from superstring simulations
How can one see what's inside a black hole?
A possible theoretical answer has been given recently
by computer simulations.
In fact, inside any black hole there exists a singular point,
at which Einstein's general relativity breaks down and
a quantum theory of gravity becomes necessary.
Superstring theory is one such candidate, which is most promising
and attractive, and it provides a quantum mechanical model
which was conjectured more than 10 years ago to describe the
interior of a black hole.
In this paper we succeeded in simulating the model by a supercomputer
at the difficult low temperature regime, and obtained a relationship
between the energy and the temperature.
Surprisingly the results agreed well with Hawking's theory,
which deduces the relationship only from the exterior of the black hole.
Actually a small discrepancy grows with increasing temperature, but this
behavior has also been explained as corrections to Hawking's theory
due to thermal oscillations of strings.
This work not only enables us to understand microscopically the
mysterious thermodynamical properties of black holes that Hawking
discovered, but also suggests how they should be modified if
superstring theory is "the" quantum theory of gravity that describes
our real world. The next ambitious goal of superstring simulations
would be to understand yet another singular point that appears in
cosmology, namely the big bang.
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LZ11642
Structural Memory of Glass
Recently amorphous materials have received an increased interest in their structure, dynamics, and mechanical properties, which remain ill-understood despite a considerable research effort. Unlike the plasticity of crystalline materials, the plasticity of glasses cannot be defined unless a completely novel description is introduced. This is what we propose in our accepted PRL paper reference number LZ11642 Rountree. Our work shows how the structure of silica can be irreversibly modified by the application of an external shear stress: under shear plasticity a non-reversible anisotropy sets in and appears stable. This provides a new interpretation of the small scale plasticity of glass; it is well revealed by the fabric tensor. The fabric tensor is a commonly used tool in granular materials/soil mechanics, more recently it has been applied to foams. To my knowledge our study is the first one to propose a "fabric tensor" at the atomic scale and to make evidence for plasticity induced anisotropy for a cohesive amorphous material. This is why we believe that it deserves additional coverage.
