386 research outputs found
Electrostatic interactions in critical solvents
The subtle interplay between critical phenomena and electrostatics is
investigated by considering the effective force acting on two parallel walls
confining a near-critical binary liquid mixture with added salt. The
ion-solvent coupling can turn a non-critical repulsive electrostatic force into
an attractive one upon approaching the critical point. However, the effective
force is eventually dominated by the critical Casimir effect, the universal
properties of which are not altered by the presence of salt. This observation
allows a consistent interpretation of recent experimental data.Comment: Submitte
Self-similarity and non-Markovian behavior in traded stock volumes
The volume traded daily for 17 stocks is followed over a period of about half a century. We look at
the volume of stocks traded in a certain time interval (day, week, month) and analyze how long that traded
volume keeps monotonically increasing or decreasing. On all three times scales we find that the sequence
of traded volumes behaves neither like a sequence of independent and identically distributed variables,
nor like a Markov sequence. A compressed exponential survival function with the same parameters at all
timescales is firmly established. A day with an increase (decrease) of traded volume is most likely followed
by a day with a decrease (increase) of traded volume. We show how the apparent self-similarity results
because the small day-to-day anticorrelation carries over when larger time intervals are considered. The
observed small anticorrelation can be explained as a consequence of market forces and trader reactions
Entropy Production Associated with Aggregation into Granules in a Subdiffusive Environment
We study the entropy production that is associated with the growing or shrinking of a small granule in, for instance, a colloidal suspension or in an aggregating polymer chain. A granule will fluctuate in size when the energy of binding is comparable to kBT , which is the “quantum� of Brownian energy. Especially for polymers, the conformational energy landscape is often rough and has been commonly modeled as being self-similar in its structure. The subdiffusion that emerges in such a high-dimensional, fractal environment leads to a Fokker–Planck Equation with a fractional time derivative. We set up such a so-called fractional Fokker–Planck Equation for the aggregation into granules. From that Fokker–Planck Equation, we derive an expression for the entropy production of a growing granul
Ion-channel-like behavior in lipid bilayer membranes at the melting transition
It is well known that at the gel-liquid phase transition temperature a lipid
bilayer membrane exhibits an increased ion permeability. We analyze the
quantized currents in which the increased permeability presents itself. The
open time histogram shows a "-3/2" power law which implies an open-closed
transition rate that decreases like as time evolves. We
propose a "pore freezing" model to explain the observations. We discuss how
this model also leads to the noise that is commonly observed in
currents across biological and artificial membranes.Comment: 5 pages, 4 figure
Accumulation of Particles and Formation of a Dissipative Structure in a Nonequilibrium Bath
The standard textbooks contain good explanations of how and why equilibrium thermodynamics emerges in a reservoir with particles that are subjected to Gaussian noise. However, in systems that convert or transport energy, the noise is often not Gaussian. Instead, displacements exhibit an [Formula: see text]-stable distribution. Such noise is commonly called Lévy noise. With such noise, we see a thermodynamics that deviates from what traditional equilibrium theory stipulates. In addition, with particles that can propel themselves, so-called active particles, we find that the rules of equilibrium thermodynamics no longer apply. No general nonequilibrium thermodynamic theory is available and understanding is often ad hoc. We study a system with overdamped particles that are subjected to Lévy noise. We pick a system with a geometry that leads to concise formulae to describe the accumulation of particles in a cavity. The nonhomogeneous distribution of particles can be seen as a dissipative structure, i.e., a lower-entropy steady state that allows for throughput of energy and concurrent production of entropy. After the mechanism that maintains nonequilibrium is switched off, the relaxation back to homogeneity represents an increase in entropy and a decrease of free energy. For our setup we can analytically connect the nonequilibrium noise and active particle behavior to entropy decrease and energy buildup with simple and intuitive formulae
Motional diminishing of optical activity: a novel method for studying molecular dynamics in liquids and plastic crystals
Molecular dynamics calculations and optical spectroscopy measurements of
weakly active infrared modes are reported. The results are qualitatively
understood in terms of the "motional diminishing" of IR lines, a process
analogous to the motional narrowing of a nuclear magnetic resonance (NMR)
signal. In molecular solids or liquids where the appropriate intramolecular
resonances are observable, motional diminishing can be used to study the
fluctuations of the intermolecular interactions having time scales of 1psec to
100psec.Comment: RevTeX in LaTeX file, 12 preprint pages, 4 ps figures included. Also
available from http://insti.physics.sunysb.edu/~mmartin/pubs.html Accepted
for publication in Chem. Phys. Let
The checkpointkinase 2 (CHK2) 1100delC germ line mutation is not associated with the development of squamous cell carcinoma of the head and neck (SCCHN)
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