642 research outputs found
Structural transformations in porous glasses under mechanical loading. I. Tension
The evolution of porous structure and mechanical properties of binary glasses
under tensile loading were examined using molecular dynamics simulations. We
consider vitreous systems obtained in the process of phase separation after a
rapid isochoric quench of a glass-forming liquid to a temperature below the
glass transition. The porous structure in undeformed samples varies from a
connected porous network to a random distribution of isolated pores upon
increasing average glass density. We find that at small strain, the elastic
modulus follows a power-law dependence on the average glass density and the
pore size distribution remains nearly the same as in quiescent samples. Upon
further loading, the pores become significantly deformed and coalesce into
larger voids that leads to formation of system-spanning empty regions
associated with breaking of the material.Comment: 27 pages, 13 figure
Distributions of pore sizes and atomic densities in binary glasses revealed by molecular dynamics simulations
We report on the results of a molecular dynamics simulation study of binodal
glassy systems, formed in the process of isochoric rapid quenching from a
high-temperature fluid phase. The transition to vitreous state occurs due to
concurrent spinodal decomposition and solidification of the matter. The study
is focused on topographies of the porous solid structures and their dependence
on temperature and average density. To quantify the pore-size distributions, we
put forth a scaling relation that provides a robust data collapse in systems
with high porosity. We also find that the local density of glassy phases is
broadly distributed, and, with increasing average glass density, a distinct
peak in the local density distribution is displaced toward higher values.Comment: 22 pages, 6 figure
Structural transformations in porous glasses under mechanical loading. II. Compression
The role of porous structure and glass density in response to compressive
deformation of amorphous materials is investigated via molecular dynamics
simulations. The disordered, porous structures were prepared by quenching a
high-temperature binary mixture below the glass transition into the phase
coexistence region. With decreasing average glass density, the pore morphology
in quiescent samples varies from a random distribution of compact voids to a
porous network embedded in a continuous glass phase. We find that during
compressive loading at constant volume, the porous structure is linearly
transformed in the elastic regime and the elastic modulus follows a power-law
increase as a function of the average glass density. Upon further compression,
pores deform significantly and coalesce into large voids leading to formation
of domains with nearly homogeneous glass phase, which provides an enhanced
resistance to deformation at high strain.Comment: 25 pages, 12 figure
Evolution of the pore size distribution in sheared binary glasses
Molecular dynamics simulations are carried out to investigate mechanical
properties and porous structure of binary glasses subjected to steady shear.
The model vitreous systems were prepared via thermal quench at constant volume
to a temperature well below the glass transition. The quiescent samples are
characterized by a relatively narrow pore size distribution whose mean size is
larger at lower glass densities. We find that in the linear regime of
deformation, the shear modulus is a strong function of porosity, and the
individual pores become slightly stretched while their structural topology
remains unaffected. By contrast, with further increasing strain, the shear
stress saturates to a density-dependent plateau value, which is accompanied by
pore coalescence and a gradual development of a broader pore size distribution
with a discrete set of peaks at large length scales.Comment: 30 pages, 16 figure
The influence of periodic shear on structural relaxation and pore redistribution in binary glasses
The evolution of porous structure, potential energy and local density in
binary glasses under oscillatory shear deformation is investigated using
molecular dynamics simulations. The porous glasses were initially prepared via
a rapid thermal quench from the liquid state across the glass transition and
allowed to phase separate and solidify at constant volume, thus producing an
extended porous network in an amorphous solid. We find that under periodic
shear, the potential energy decreases over consecutive cycles due to gradual
rearrangement of the glassy material, and the minimum of the potential energy
after thousands of shear cycles is lower at larger strain amplitudes. Moreover,
with increasing cycle number, the pore size distributions become more skewed
toward larger length scales where a distinct peak is developed and the peak
intensity is enhanced at larger strain amplitudes. The numerical analysis of
the local density distribution functions demonstrates that cyclic loading leads
to formation of higher density solid domains and homogenization of the glass
phase with reduced density.Comment: 23 pages, 10 figure
Atomic hydration potentials using a Monte Carlo Reference State (MCRS) for protein solvation modeling
BACKGROUND: Accurate description of protein interaction with aqueous solvent is crucial for modeling of protein folding, protein-protein interaction, and drug design. Efforts to build a working description of solvation, both by continuous models and by molecular dynamics, yield controversial results. Specifically constructed knowledge-based potentials appear to be promising for accounting for the solvation at the molecular level, yet have not been used for this purpose. RESULTS: We developed original knowledge-based potentials to study protein hydration at the level of atom contacts. The potentials were obtained using a new Monte Carlo reference state (MCRS), which simulates the expected probability density of atom-atom contacts via exhaustive sampling of structure space with random probes. Using the MCRS allowed us to calculate the expected atom contact densities with high resolution over a broad distance range including very short distances. Knowledge-based potentials for hydration of protein atoms of different types were obtained based on frequencies of their contacts at different distances with protein-bound water molecules, in a non-redundant training data base of 1776 proteins with known 3D structures. Protein hydration sites were predicted in a test set of 12 proteins with experimentally determined water locations. The MCRS greatly improves prediction of water locations over existing methods. In addition, the contribution of the energy of macromolecular solvation into total folding free energy was estimated, and tested in fold recognition experiments. The correct folds were preferred over all the misfolded decoys for the majority of proteins from the improved Rosetta decoy set based on the structure hydration energy alone. CONCLUSION: MCRS atomic hydration potentials provide a detailed distance-dependent description of hydropathies of individual protein atoms. This allows placement of water molecules on the surface of proteins and in protein interfaces with much higher precision. The potentials provide a means to estimate the total solvation energy for a protein structure, in many cases achieving a successful fold recognition. Possible applications of atomic hydration potentials to structure verification, protein folding and stability, and protein-protein interactions are discussed
Formation of an integrated financial regulation system of transport corporations’ economic development
Scientific findings of this article correspond with the fact that the development of interacting business entities is quite diverse. This affects the efficiency of corporations’ budget management. So, a need arises to adjust the financial assets applied to the development of integrated enterprises, basing on their economic compatibility evaluation.
Authors suggest using the companies’ development intensity determined by the increasing qualitative business activity indicators compared to the increasing quantitative ones.
Theoretical economics gives no clear definition of compatibility of developing companies. Economic practices do not pay proper attention to the development of effective financial regulation of economic development of companies integrated into a corporation.
The article suggests original definitions of economic compatibility as well as the model of forming the integrated system of transport companies’ economic development on the basis of morphological approach. Theoretical and methodological findings are approved in the business activity of transport corporationspeer-reviewe
PROSECUTOR’S SUPERVISION OVER THE ACTIVITIES OF THE BODIES OF PRELIMINARY INVESTIGATION ON COMPENSATION FOR DAMAGE CAUSED BY A CRIME AT THE STAGE OF INITIATING A CRIMINAL CASE
Aim: The article is devoted to the consideration of the essence and main directions of prosecutorial supervision over the activities of officials of the preliminary investigation bodies for compensation for harm caused by a crime at the stage of initiating a criminal case. According to the deep conviction of the authors, one of the directions for ensuring the rights and legitimate interests of victims of crimes is to ensure compensation for property and physical damage, as well as compensation for moral damage and damage to business reputation. This area of activity of the preliminary investigation bodies is no less important than bringing the perpetrators to justice in order to assign them a fair punishment. Results: The author identified some reasons that negatively affect the implementation of prosecutorial supervision over the activities of these participants in criminal proceedings to ensure compensation for harm caused by a crime at the stage of pre-investigation verification. Conclusion: In conclusion, the authors substantiate the conclusion that at present, prosecutorial supervision over the activities of officials of the bodies of preliminary investigation is relevant and especially in demand to ensure the principle of competitiveness of the parties, the creation of legal guarantees for the realization by persons who have become victims of criminal acts, the right to full compensation for the harm caused. Prosecutorial supervision is proposed to be regarded as an important dominant of the procedural function of prosecutors, aimed at preventing violations in the activities of the preliminary investigation and inquiry bodies to compensate for harm caused by criminal acts, starting from the stage of initiating a criminal case
- …