1,793 research outputs found
Adsorption preference reversal phenomenon from multisite-occupancy theory fortwo-dimensional lattices
The statistical thermodynamics of polyatomic species mixtures adsorbed on
two-dimensional substrates was developed on a generalization in the spirit of
the lattice-gas model and the classical Guggenheim-DiMarzio approximation. In
this scheme, the coverage and temperature dependence of the Helmholtz free
energy and chemical potential are given. The formalism leads to the exact
statistical thermodynamics of binary mixtures adsorbed in one dimension,
provides a close approximation for two-dimensional systems accounting multisite
occupancy and allows to discuss the dimensionality and lattice structure
effects on the known phenomenon of adsorption preference reversal.Comment: 13 pages, 4 figure
Critical behavior of long straight rigid rods on two-dimensional lattices: Theory and Monte Carlo simulations
The critical behavior of long straight rigid rods of length (-mers) on
square and triangular lattices at intermediate density has been studied. A
nematic phase, characterized by a big domain of parallel -mers, was found.
This ordered phase is separated from the isotropic state by a continuous
transition occurring at a intermediate density . Two analytical
techniques were combined with Monte Carlo simulations to predict the dependence
of on , being . The first involves
simple geometrical arguments, while the second is based on entropy
considerations. Our analysis allowed us also to determine the minimum value of
(), which allows the formation of a nematic phase on a
triangular lattice.Comment: 23 pages, 5 figures, to appear in The Journal of Chemical Physic
Quasi-chemical approximation for polyatomic mixtures
The statistical thermodynamics of binary mixtures of polyatomic species was
developed on a generalization in the spirit of the lattice-gas model and the
quasi-chemical approximation (QCA). The new theoretical framework is obtained
by combining: (i) the exact analytical expression for the partition function of
non-interacting mixtures of linear -mers and -mers (species occupying
sites and sites, respectively) adsorbed in one dimension, and its extension
to higher dimensions; and (ii) a generalization of the classical QCA for
multicomponent adsorbates and multisite-occupancy adsorption. The process is
analyzed through the partial adsorption isotherms corresponding to both species
of the mixture. Comparisons with analytical data from Bragg-Williams
approximation (BWA) and Monte Carlo simulations are performed in order to test
the validity of the theoretical model. Even though a good fitting is obtained
from BWA, it is found that QCA provides a more accurate description of the
phenomenon of adsorption of interacting polyatomic mixtures.Comment: 27 pages, 8 figure
PI3Kα inhibition reduces obesity in mice
Partial inhibition of PI3K is one of the best-validated and evolutionary conserved manipulations to extend longevity. The best known health beneficial effects of reduced PI3K are related to metabolism and include increased energy expenditure, reduced nutrient storage, and protection from obesity. We have previously shown that a dual chemical inhibitor of the alpha and delta PI3K isoforms (CNIO-PI3Ki) reduces obesity in mice and monkeys, without evident toxic effects after long-term treatment. Here, we dissect the role of the alpha and delta PI3K isoforms by making use of selective inhibitors against PI3Kα (BYL-719 also known as alpelisib) or PI3Kδ (GS-9820 also known as acalisib). Treatment of mice with the above mentioned inhibitors indicated that BYL-719 increases energy expenditure in normal mice and efficiently reduces body weight in obese (ob/ob) mice, whereas these effects were not observed with GS-9820. Of note, the dose of BYL-719 required to reduce obesity was 10x higher than the equivalent dose of CNIO-PI3Ki, which could suggest that simultaneous inhibition of PI3K alpha and delta is more beneficial than single inhibition of the alpha isoform. In summary, we conclude that inhibition of PI3Kα is sufficient to increase energy expenditure and reduce obesity, and suggest that concomitant PI3Kα inhibition could play an auxiliary role
Determination of the Critical Exponents for the Isotropic-Nematic Phase Transition in a System of Long Rods on Two-dimensional Lattices: Universality of the Transition
Monte Carlo simulations and finite-size scaling analysis have been carried
out to study the critical behavior and universality for the isotropic-nematic
phase transition in a system of long straight rigid rods of length
(-mers) on two-dimensional lattices. The nematic phase, characterized by a
big domain of parallel -mers, is separated from the isotropic state by a
continuous transition occurring at a finite density. The determination of the
critical exponents, along with the behavior of Binder cumulants, indicate that
the transition belongs to the 2D Ising universality class for square lattices
and the three-state Potts universality class for triangular lattices.Comment: 7 pages, 8 figures, uses epl2.cls, to appear in Europhysics Letter
055 HYPOXIA CONDITIONS DIFFERENTIALLY MODULATE NORMAL AND OSTEOARTHRITIC HUMAN ARTICULAR CHONDROCYTE PROTEOMES
Jamming and percolation in random sequential adsorption of straight rigid rods on a two-dimensional triangular lattice
Monte Carlo simulations and finite-size scaling analysis have been performed
to study the jamming and percolation behavior of linear -mers (also known as
rods or needles) on the two-dimensional triangular lattice, considering an
isotropic RSA process on a lattice of linear dimension and periodic
boundary conditions. Extensive numerical work has been done to extend previous
studies to larger system sizes and longer -mers, which enables the
confirmation of a nonmonotonic size dependence of the percolation threshold and
the estimation of a maximum value of from which percolation would no longer
occurs. Finally, a complete analysis of critical exponents and universality
have been done, showing that the percolation phase transition involved in the
system is not affected, having the same universality class of the ordinary
random percolation.Comment: 6 figure
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