11,835 research outputs found
Balancing Local Order and Long-Ranged Interactions in the Molecular Theory of Liquid Water
A molecular theory of liquid water is identified and studied on the basis of
computer simulation of the TIP3P model of liquid water. This theory would be
exact for models of liquid water in which the intermolecular interactions
vanish outside a finite spatial range, and therefore provides a precise
analysis tool for investigating the effects of longer-ranged intermolecular
interactions. We show how local order can be introduced through quasi-chemical
theory. Long-ranged interactions are characterized generally by a conditional
distribution of binding energies, and this formulation is interpreted as a
regularization of the primitive statistical thermodynamic problem. These
binding-energy distributions for liquid water are observed to be unimodal. The
gaussian approximation proposed is remarkably successful in predicting the
Gibbs free energy and the molar entropy of liquid water, as judged by
comparison with numerically exact results. The remaining discrepancies are
subtle quantitative problems that do have significant consequences for the
thermodynamic properties that distinguish water from many other liquids. The
basic subtlety of liquid water is found then in the competition of several
effects which must be quantitatively balanced for realistic results.Comment: 8 pages, 6 figure
Research in LMSS propagation
The Virginia Tech Satellite Communications Group has participated in the Land Mobile Satellite System (LMSS) program through JPL sponsorship since 1985. Involvement has mainly been in modeling and simulation of propagation characteristics and effects. Models developed to predict cummulative fade distributions for fading LMSS signals include LMSSMOD and the Simple Models which approximate LMSSMOD. Models to predict the mean and standard deviation of signal attenuation through roadside vegetation, namely the Average Path Model, were developed. In the area of simulation, efforts have centered around the development of a software simulator that uses data bases derived from experimental data to generate simulated data with arbitrary statistical behavior. This work has progressed to the development of an integrated analysis and simulation package, LIPS. The basic theory and results for the models and simulator have been previously documented in reports and papers. All LMSS activities are summarized and details of this year's efforts are given
Molecular Realism in Default Models for Information Theories of Hydrophobic Effects
This letter considers several physical arguments about contributions to
hydrophobic hydration of inert gases, constructs default models to test them
within information theories, and gives information theory predictions using
those default models with moment information drawn from simulation of liquid
water. Tested physical features include: packing or steric effects, the role of
attractive forces that lower the solvent pressure, and the roughly tetrahedral
coordination of water molecules in liquid water. Packing effects (hard sphere
default model) and packing effects plus attractive forces (Lennard-Jones
default model) are ineffective in improving the prediction of hydrophobic
hydration free energies of inert gases over the previously used Gibbs and flat
default models. However, a conceptually simple cluster Poisson model that
incorporates tetrahedral coordination structure in the default model is one of
the better performers for these predictions. These results provide a partial
rationalization of the remarkable performance of the flat default model with
two moments in previous applications. The cluster Poisson default model thus
will be the subject of further refinement.Comment: 5 pages including 3 figure
Getting Sexual and Gender Minority Health Into the Brick and Mortar : A Mixed Methods Implementation Study
What predicts medical student knowlege, attitudes, beliefs and behaviors about LGBTQ+ patient care? What lessons have been learned about implementing LGBTQ+ health curricular change?
Students with LGBTQ+ friends or family were 7% more likely to have relevant LGBTQ+ knowledge and 12% more likely to have affirming beliefs about LGBTQ+ patients than students who did not.
More training hours focused on LGBTQI+ health led to more clinically prepared medical students who were more likely to exhibit affirming clinical behaviors for LGBTQ patients. LGBTQ-specific training explained about 15% of the difference between people who felt prepared and those who did not.https://jdc.jefferson.edu/sexandgenderhealth/1021/thumbnail.jp
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