324 research outputs found
Equilibration, generalized equipartition, and diffusion in dynamical Lorentz gases
We prove approach to thermal equilibrium for the fully Hamiltonian dynamics
of a dynamical Lorentz gas, by which we mean an ensemble of particles moving
through a -dimensional array of fixed soft scatterers that each possess an
internal harmonic or anharmonic degree of freedom to which moving particles
locally couple. We establish that the momentum distribution of the moving
particles approaches a Maxwell-Boltzmann distribution at a certain temperature
, provided that they are initially fast and the scatterers are in a
sufficiently energetic but otherwise arbitrary stationary state of their free
dynamics--they need not be in a state of thermal equilibrium. The temperature
to which the particles equilibrate obeys a generalized equipartition
relation, in which the associated thermal energy is equal to
an appropriately defined average of the scatterers' kinetic energy. In the
equilibrated state, particle motion is diffusive
Adiabatic-Nonadiabatic Transition in the Diffusive Hamiltonian Dynamics of a Classical Holstein Polaron
We study the Hamiltonian dynamics of a free particle injected onto a chain
containing a periodic array of harmonic oscillators in thermal equilibrium. The
particle interacts locally with each oscillator, with an interaction that is
linear in the oscillator coordinate and independent of the particle's position
when it is within a finite interaction range. At long times the particle
exhibits diffusive motion, with an ensemble averaged mean-squared displacement
that is linear in time. The diffusion constant at high temperatures follows a
power law D ~ T^{5/2} for all parameter values studied. At low temperatures
particle motion changes to a hopping process in which the particle is bound for
considerable periods of time to a single oscillator before it is able to escape
and explore the rest of the chain. A different power law, D ~ T^{3/4}, emerges
in this limit. A thermal distribution of particles exhibits thermally activated
diffusion at low temperatures as a result of classically self-trapped polaronic
states.Comment: 15 pages, 4 figures Submitted to Physical Review
Classical motion in force fields with short range correlations
We study the long time motion of fast particles moving through time-dependent
random force fields with correlations that decay rapidly in space, but not
necessarily in time. The time dependence of the averaged kinetic energy and
mean-squared displacement is shown to exhibit a large degree of universality;
it depends only on whether the force is, or is not, a gradient vector field.
When it is, p^{2}(t) ~ t^{2/5} independently of the details of the potential
and of the space dimension. Motion is then superballistic in one dimension,
with q^{2}(t) ~ t^{12/5}, and ballistic in higher dimensions, with q^{2}(t) ~
t^{2}. These predictions are supported by numerical results in one and two
dimensions. For force fields not obtained from a potential field, the power
laws are different: p^{2}(t) ~ t^{2/3} and q^{2}(t) ~ t^{8/3} in all dimensions
d\geq 1
Domain Growth Kinetics in a Cell-sized Liposome
We investigated the kinetics of domain growth on liposomes consisting of a
ternary mixture (unsaturated phospholipid, saturated phospholipid, and
cholesterol) by temperature jump. The domain growth process was monitored by
fluorescence microscopy, where the growth was mediated by the fusion of domains
through the collision. It was found that an average domain size r develops with
time t as r ~ t^0.15, indicating that the power is around a half of the
theoretical expectation deduced from a model of Brownian motion on a
2-dimensional membrane. We discuss the mechanism of the experimental scaling
behavior by considering the elasticity of the membrane
Normal transport properties for a classical particle coupled to a non-Ohmic bath
We study the Hamiltonian motion of an ensemble of unconfined classical
particles driven by an external field F through a translationally-invariant,
thermal array of monochromatic Einstein oscillators. The system does not
sustain a stationary state, because the oscillators cannot effectively absorb
the energy of high speed particles. We nonetheless show that the system has at
all positive temperatures a well-defined low-field mobility over macroscopic
time scales of order exp(-c/F). The mobility is independent of F at low fields,
and related to the zero-field diffusion constant D through the Einstein
relation. The system therefore exhibits normal transport even though the bath
obviously has a discrete frequency spectrum (it is simply monochromatic) and is
therefore highly non-Ohmic. Such features are usually associated with anomalous
transport properties
Interplay of complete wetting, critical adsorption, and capillary condensation
The excess adsorption in two-dimensional Ising strips subject to identical boundary fields, at both one-dimensional
surfaces decaying in the orthogonal direction as , is studied
for various values of and along various thermodynamic paths below the
critical point by means of the density-matrix renormalization-group method. The
crossover behavior between the complete wetting and critical adsorption
regimes, occurring in semi-infinite systems, are strongly influenced by
confinement effects. Along isotherms the asymptotic power law
dependences on the external bulk field, which characterize these two regimes,
are undercut by capillary condensation. Along the pseudo first-order phase
coexistence line of the strips, which varies with temperature, we find a broad
crossover regime where both the thickness of the wetting film and
increase as function of the reduced temperature but do not follow any
power law. Above the wetting temperature the order parameter profiles are not
slab-like but exhibit wide interfacial variations and pronounced tails. Inter
alia, our explicit calculations demonstrate that, contrary to opposite claims
by Kroll and Lipowsky [Phys. Rev. B {\bf 28}, 5273 (1983)], for critical
wetting transitions do exist and we determine the corresponding wetting phase
diagram in the plane.Comment: RevTeX 23 Pages and 17 figures, submitted to Phys. Rev.
Characteristics associated with polypharmacy in people with type 2 diabetes:the Dutch Diabetes Pearl cohort
Contains fulltext :
232027.pdf (Publisher’s version ) (Open Access)AIM: To describe the prevalence and characteristics of polypharmacy in a Dutch cohort of individuals with type 2 diabetes. METHODS: We included people with type 2 diabetes from the Diabetes Pearl cohort, of whom 3886 were treated in primary care and 2873 in academic care (secondary/tertiary). With multivariable multinomial logistic regression analyses stratified for line of care, we assessed which sociodemographic, lifestyle and cardiometabolic characteristics were associated with moderate (5-9 medications) and severe polypharmacy (≥10 medications) compared with no polypharmacy (0-4 medications). RESULTS: Mean age was 63 ± 10 years, and 40% were women. The median number of daily medications was 5 (IQR 3-7) in primary care and 7 (IQR 5-10) in academic care. The prevalence of moderate and severe polypharmacy was 44% and 10% in primary care, and 53% and 29% in academic care respectively. Glucose-lowering and lipid-modifying medications were most prevalent. People with severe polypharmacy used a relatively large amount of other (i.e. non-cardiovascular and non-glucose-lowering) medication. Moderate and severe polypharmacy across all lines of care were associated with higher age, low educational level, more smoking, longer diabetes duration, higher BMI and more cardiovascular disease. CONCLUSIONS: Severe and moderate polypharmacy are prevalent in over half of people with type 2 diabetes in primary care, and even more in academic care. People with polypharmacy are characterized by poorer cardiometabolic status. These results highlight the significance of polypharmacy in type 2 diabetes
Spontaneous charged lipid transfer between lipid vesicles
An assay to study the spontaneous charged lipid transfer between lipid vesicles is described. A donor/acceptor vesicle system is employed, where neutrally charged acceptor vesicles are fluorescently labelled with the electrostatic membrane probe Fluoresceinphosphatidylethanolamine (FPE). Upon addition of charged donor vesicles, transfer of negatively charged lipid occurs, resulting in a fluorescently detectable change in the membrane potential of the acceptor vesicles. Using this approach we have studied the transfer properties of a range of lipids, varying both the headgroup and the chain length. At the low vesicle concentrations chosen, the transfer follows a first-order process where lipid monomers are transferred presumably through the aqueous solution phase from donor to acceptor vesicle. The rate of transfer decreases with increasing chain length which is consistent with energy models previously reported for lipid monomer vesicle interactions. Our assay improves on existing methods allowing the study of a range of unmodified lipids, continuous monitoring of transfer and simplified experimental procedures
Farnesylated Nuclear Proteins Kugelkern and Lamin Dm0 Affect Nuclear Morphology by Directly Interacting with the Nuclear Membrane
Nuclear shape changes are observed during a variety of developmental processes, pathological conditions and ageing. Here, the molecular mechanism is analyzed how the farnesylated nuclear proteins interact with the nuclear envelope and deform the phospholipid bilayer
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