423 research outputs found
On the electrical double layer contribution to the interfacial tension of protein crystals
We study the electrical double layer at the interface between a protein
crystal and a salt solution or a dilute solution of protein, and estimate the
double layer's contribution to the interfacial tension of this interface. This
contribution is negative and decreases in magnitude with increasing salt
concentration. We also consider briefly the interaction between a pair of
protein surfaces.Comment: 6 pages, 3 figures, revtex
Long-Lived Non-Equilibrium Interstitial-Solid-Solutions in Binary Mixtures
We perform particle resolved experimental studies on the heterogeneous
crystallisation process of two compo- nent mixtures of hard spheres. The
components have a size ratio of 0.39. We compared these with molecular dynamics
simulations of homogenous nucleation. We find for both experiments and
simulations that the final assemblies are interstitial solid solutions, where
the large particles form crystalline close-packed lattices, whereas the small
particles occupy random interstitial sites. This interstitial solution
resembles that found at equilibrium when the size ratios are 0.3 [Filion et
al., Phys. Rev. Lett. 107, 168302 (2011)] and 0.4 [Filion, PhD Thesis, Utrecht
University (2011)]. However, unlike these previous studies, for our system sim-
ulations showed that the small particles are trapped in the octahedral holes of
the ordered structure formed by the large particles, leading to long-lived
non-equilibrium structures in the time scales studied and not the equilibrium
interstitial solutions found earlier. Interestingly, the percentage of small
particles in the crystal formed by the large ones rapidly reaches a maximum of
around 14% for most of the packing fractions tested, unlike previous
predictions where the occupancy of the interstitial sites increases with the
system concentration. Finally, no further hopping of the small particles was
observed
There\u27s Something Fascinating \u27Bout The Moon
https://digitalcommons.library.umaine.edu/mmb-vp/6708/thumbnail.jp
Flory-Huggins theory for athermal mixtures of hard spheres and larger flexible polymers
A simple analytic theory for mixtures of hard spheres and larger polymers
with excluded volume interactions is developed. The mixture is shown to exhibit
extensive immiscibility. For large polymers with strong excluded volume
interactions, the density of monomers at the critical point for demixing
decreases as one over the square root of the length of the polymer, while the
density of spheres tends to a constant. This is very different to the behaviour
of mixtures of hard spheres and ideal polymers, these mixtures although even
less miscible than those with polymers with excluded volume interactions, have
a much higher polymer density at the critical point of demixing. The theory
applies to the complete range of mixtures of spheres with flexible polymers,
from those with strong excluded volume interactions to ideal polymers.Comment: 9 pages, 4 figure
Controlling bad-actor-AI activity at scale across online battlefields
We show how the looming threat of bad actors using AI/GPT to generate harms
across social media, can be addressed at scale by exploiting the intrinsic
dynamics of the social media multiverse. We combine a uniquely detailed
description of the current bad-actor-mainstream battlefield with a mathematical
description of its behavior, to show what bad-actor-AI activity will likely
dominate, where, and when. A dynamical Red Queen analysis predicts an
escalation to daily bad-actor-AI activity by early 2024, just ahead of U.S. and
other global elections. We provide a Policy Matrix that quantifies outcomes and
trade-offs mathematically for the policy options of containment vs. removal. We
give explicit plug-and-play formulae for risk measures
Phase separation in mixtures of colloids and long ideal polymer coils
Colloidal suspensions with free polymer coils which are larger than the
colloidal particles are considered. The polymer-colloid interaction is modeled
by an extension of the Asakura-Oosawa model. Phase separation occurs into
dilute and dense fluid phases of colloidal particles when polymer is added. The
critical density of this transition tends to zero as the size of the polymer
coils diverges.Comment: 5 pages, 3 figure
Instabilities in complex mixtures with a large number of components
Inside living cells are complex mixtures of thousands of components. It is
hopeless to try to characterise all the individual interactions in these
mixtures. Thus, we develop a statistical approach to approximating them, and
examine the conditions under which the mixtures phase separate. The approach
approximates the matrix of second virial coefficients of the mixture by a
random matrix, and determines the stability of the mixture from the spectrum of
such random matrices.Comment: 4 pages, uses RevTeX 4.
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Decision tools for sustainable development
Sustainable food production and improved food security are major aim of donors and developing country governments alike. Sustaining food production whilst avoiding environmental degradation require a supportive policy framework and the delivery of appropriate information to facilitate the decision making procedure. Better decision-making provides better early warning, improved judgement of risk and better timing of intervention. Decision Tools for Sustainable Development bring together up-to-date techniques for the collection and management of environmental and socio-economic information. It describes practical decision-making tools for use at all levels from local to international, for rural communities, research services, the food industry and for institutional decision-makers. The book will be essential reading for research managers, development specialists, government policy-makers, NGO staff and all those who need to make sound and effective decisions for the sustainable development of natural resources
Adaptive link dynamics drive online hate networks and their mainstream influence
Online hate is dynamic, adaptive -- and is now surging armed with AI/GPT
tools. Its consequences include personal traumas, child sex abuse and violent
mass attacks. Overcoming it will require knowing how it operates at scale. Here
we present this missing science and show that it contradicts current thinking.
Waves of adaptive links connect the hate user base over time across a sea of
smaller platforms, allowing hate networks to steadily strengthen, bypass
mitigations, and increase their direct influence on the massive neighboring
mainstream. The data suggests 1 in 10 of the global population have recently
been exposed, including children. We provide governing dynamical equations
derived from first principles. A tipping-point condition predicts more frequent
future surges in content transmission. Using the U.S. Capitol attack and a 2023
mass shooting as illustrations, we show our findings provide abiding insights
and quantitative predictions down to the hourly scale. The expected impacts of
proposed mitigations can now be reliably predicted for the first time
Long Cycles in a Perturbed Mean Field Model of a Boson Gas
In this paper we give a precise mathematical formulation of the relation
between Bose condensation and long cycles and prove its validity for the
perturbed mean field model of a Bose gas. We decompose the total density
into the number density of
particles belonging to cycles of finite length () and to
infinitely long cycles () in the thermodynamic limit. For
this model we prove that when there is Bose condensation,
is different from zero and identical to the condensate density. This is
achieved through an application of the theory of large deviations. We discuss
the possible equivalence of with off-diagonal long
range order and winding paths that occur in the path integral representation of
the Bose gas.Comment: 10 page
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