A comparison of a statistical-mechanics based plasticity model with discrete dislocation plasticity calculations

A two-dimensional nonlocal version of continuum crystal plasticity theory is proposed, which is based on a statistical-mechanics description of the collective behavior of dislocations coupled to standard small-strain crystal continuum kinematics for single slip. It involves a set of transport equations for the total dislocation density field and for the net-Burgers vector density field, which include a slip system back stress associated to the gradient of the net-Burgers vector density. The theory is applied to the problem of shearing of a two-dimensional composite material with elastic reinforcements in a crystalline matrix. The results are compared to those of discrete dislocation simulations of the same problem. The continuum theory is shown to be able to pick up the distinct dependence on the size of the reinforcing particles for one of the morphologies being studied. Also, its predictions are consistent with the discrete dislocation results during unloading, showing a pronounced Bauschinger effect. None of these features are captured by standard local plasticity theories. (C) 2003 Elsevier Ltd. All rights reserved

Vibrational Spectra of a Mechanosensitive Channel

We report the simulated vibrational spectra of a mechanosensitive membrane channel in different gating states. Our results show that while linear absorption is insensitive to structural differences, linear dichroism and sum-frequency generation spectroscopies are sensitive to the orientation of the transmembrane helices, which is changing during the opening process. Linear dichroism cannot distinguish an intermediate structure from the closed structure, but sum-frequency generation can. In addition, we find that two-dimensional infrared spectroscopy can be used to distinguish all three investigated gating states of the mechanosensitive membrane channel.

Межгодовая изменчивость продолжительности безледного периода в юго-западной части Карского моря

In the coming years, exploration drilling in the geological structures in the Kara Sea is planned. It will be carried out during the ice-free period using floating drilling facilities of a different ice class. The aim of the work is analysis of the interannual variability of duration of the ice-free period in the area of the geological structures the results of which are necessary for planning operational activity of the drilling platforms and optimization of expenses for exploration drilling on the Arctic shelf. For an assessment of interannual variability of the ice-free period duration in the area of the geological structures there were used data on the dates of water area clearance from ice and beginning of ice formation in the southwestern part of the Kara Sea for the period of 30 years on the basis of the AARI weekly ice charts. An analysis of interannual variability of the ice-free period duration showed that a 20-year summer (1989–2008) and a 10-year (2009–2018) intervals could be identified. It is shown that in the last decade as a result of combination of favorable hydrometeorological conditions the ice-free period duration has increased by more than 1 month. An analysis of the main hydrometeorological factors determining the ice-free period duration indicated that it is possible to perform an assessment of duration of exploration drilling operations in the water area of the East-Prinovozemelsky license blocks with a period in advance of several months. Drilling with the use of ice-resistant drilling platform allows us to extend the operation period, as drilling could be started after disappearance of close ice and finished after the ice thickness growth up to 30 cm.Рассмотрена межгодовая изменчивость сроков очищения акватории ото льда, начала ледообразования и продолжительность безледного периода в районе геологических структур в юго-западной части Карского моря. Показано, что в последнее десятилетие в результате сочетания благоприятных гидрометеорологических условий продолжительность безледного периода увеличилась более чем на месяц. Анализ основных гидрометеорологических факторов, определяющих продолжительность безледного периода, показал, что возможно выполнять оценку продолжительности операционного периода поисково-разведочного бурения на акватории Восточно-Приновоземельских лицензионных участков с заблаговременностью в несколько месяцев

PIP2-Binding Site in Kir Channels: Definition by Multiscale Biomolecular Simulations†

Phosphatidylinositol bisphosphate (PIP(2)) is an activator of mammalian inwardly rectifying potassium (Kir) channels. Multiscale simulations, via a sequential combination of coarse-grained and atomistic molecular dynamics, enabled exploration of the interactions of PIP(2) molecules within the inner leaflet of a lipid bilayer membrane with possible binding sites on Kir channels. Three Kir channel structures were investigated: X-ray structures of KirBac1.1 and of a Kir3.1-KirBac1.3 chimera and a homology model of Kir6.2. Coarse-grained simulations of the Kir channels in PIP(2)-containing lipid bilayers identified the PIP(2)-binding site on each channel. These models of the PIP(2)-channel complexes were refined by conversion to an atomistic representation followed by molecular dynamics simulation in a lipid bilayer. All three channels were revealed to contain a conserved binding site at the N-terminal end of the slide (M0) helix, at the interface between adjacent subunits of the channel. This binding site agrees with mutagenesis data and is in the proximity of the site occupied by a detergent molecule in the Kir chimera channel crystal. Polar contacts in the coarse-grained simulations corresponded to long-lived electrostatic and H-bonding interactions between the channel and PIP(2) in the atomistic simulations, enabling identification of key side chains

Matter Outflows from AGN: A Unifying Model

We discuss a self-consistent unified model of the matter outflows from AGNs based on a theoretical approach and involving data on AGN evolution and structure. The model includes a unified geometry, two-phase gas dynamics, radiation transfer, and absorption spectrum calculations in the UV and X-ray bands. We briefly discuss several questions about the mass sources of the flows, the covering factors, and the stability of the narrow absorption details.Comment: 6 figures, accepted for publication in Astrophysics and Space Scienc

Исследования ледового режима на акватории Хатангского залива в море Лаптевых

The study was carried out to reveal characteristics of the ice regime of poorly explored water area of the Khatanga Bay in the South-Western part of the Laptev Sea. Actuality of the research is due to the high potential of hydrocarbon reserves in the license area «Khatangsky» of the PAO «NK «Rosneft Currently available methods of monitoring ice cover and hydrometeorological conditions throughout the year were used. The main features of the hydrological regime of the region in the ice-free period, reflected in the spatial distribution of thermohaline characteristics and sea level fluctuations, are shown. The area under investigation has specific features of the conditions for the formation of ice cover: the entire area is covered with the fast ice; the winter fresh water infl w from Khatanga and Anabar rivers results in the desalination of sea water, and this promotes formation of ice cover, which differs in crystal structure and texture from both fresh and sea ices. These factors do influence on the mechanical properties of ice, including its strength. It was found that the average and maximum values of strength of the smooth and deformed ice of the Khatanga Gulf are approximately twice as high as the similar values of the sea ice strength in the southern part of the Laptev Sea. The basic features of the spatial distribution of different types of deformations of the ice cover such as lines of ice hummocks, zones of homogeneous ice hummocking, and stamukhas had been determined.Цель исследований – выявить особенности ледового режима малоизученной акватории Хатангского залива в море Лаптевых. На основе круглогодичных исследований на стационаре «Хастыр» и весенних исследований с использованием вертолёта обнаружены новые особенности формирования ледяного покрова, связанные с притоком пресных вод и большого количества примесей, которые приводят к повышенной прочности льда. Установлено пространственное распределение различных видов деформированного льда

Thermal conductivity of high- T c superconductors

This paper reviews existing data on the thermal conductivity of high- T c superconductors. Included are discussions of pristine polycrystalline high- T c ceramics, single crystal specimens, and high- T c materials structurally modified by substitution or by radiation damage. The thermal conductivity of high- T c superconductors is compared with that of conventional superconductors, and dramatic differences are found between the two families. Mechanisms of thermal conductivity applicable to high- T c perovskites are discussed and implications for theories of high- T c superconductivity are noted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45121/1/10948_2004_Article_BF00617463.pd