Defect formation processes in structures of magnesium silicates treated by ammonium bifluoride

Authors have studied destruction and defect formation processes of magnesium silicate structures treated by ammonium bifluoride. Obtained amorphous products with uncertain chemical composition were researched by electron microscope and X-ray. High reactivity of these defective structures in solid phase reactions has been identified

Defect formation processes in structures of magnesium silicates treated by ammonium bifluoride

Authors have studied destruction and defect formation processes of magnesium silicate structures treated by ammonium bifluoride. Obtained amorphous products with uncertain chemical composition were researched by electron microscope and X-ray. High reactivity of these defective structures in solid phase reactions has been identified

Canonical quantization of macroscopic electrodynamics in a linear, inhomogeneous magneto-electric medium

We present a canonical quantization of macroscopic electrodynamics. The results apply to inhomogeneous media with a broad class of linear magneto-electric responses which are consistent with the Kramers-Kronig and Onsager relations. Through its ability to accommodate strong dispersion and loss, our theory provides a rigorous foundation for the study of quantum optical processes in structures incorporating metamaterials, provided these may be modeled as magneto-electric media. Previous canonical treatments of dielectric and magneto-dielectric media have expressed the electromagnetic field operators in either a Green function or mode expansion representation. Here we present our results in the mode expansion picture with a view to applications in guided wave and cavity quantum optics.Comment: Submitted to Physical Review A 24/07/201

Cooperative Transport of Brownian Particles

We consider the collective motion of finite-sized, overdamped Brownian particles (e.g., motor proteins) in a periodic potential. Simulations of our model have revealed a number of novel cooperative transport phenomena, including (i) the reversal of direction of the net current as the particle density is increased and (ii) a very strong and complex dependence of the average velocity on both the size and the average distance of the particles.Comment: 4 pages, 5 figure

Realistic Models of Biological Motion

The origin of biological motion can be traced back to the function of molecular motor proteins. Cytoplasmic dynein and kinesin transport organelles within our cells moving along a polymeric filament, the microtubule. The motion of the myosin molecules along the actin filaments is responsible for the contraction of our muscles. Recent experiments have been able to reveal some important features of the motion of individual motor proteins, and a new statistical physical description - often referred to as ``thermal ratchets'' - has been developed for the description of motion of these molecules. In this approach the motors are considered as Brownian particles moving along one-dimensional periodic structures due to the effect of nonequilibrium fluctuations. Assuming specific types of interaction between the particles the models can be made more realistic. We have been able to give analytic solutions for our model of kinesin with elastically coupled Brownian heads and for the motion of the myosin filament where the motors are connected through a rigid backbone. Our theoretical predictions are in a very good agreement with the various experimental results. In addition, we have considered the effects arising as a result of interaction among a large number of molecular motors, leading to a number of novel cooperative transport phenomena.Comment: 12 pages (5 figures). submitted to Elsevier Preprin

Analytical techniques and instrumentation, a compilation

Procedures for conducting materials tests and structural analyses of aerospace components are presented as a part of the NASA technology utilization program. Some of the subjects discussed are as follows: (1) failures in cryogenic tank insulation, (2) friction characteristics of graphite and graphite-metal combinations, (3) evaluation of polymeric products in thermal-vacuum environment, (4) erosion of metals by multiple impacts with water, (5) mass loading effects on vibrated ring and shell structures, (6) nonlinear damping in structures, and (7) method for estimating reliability of randomly excited structures

The temperature field for thermosensitive finite cylinder under convective heat exchange with the variable temperature surroundings

Розглянуто двовимірну нелінійну стаціонарну задачу теплопровідності для термочутливого циліндра скінченої довжини. Враховано теплообмін на усіх поверхнях циліндра із зовнішніми середовищами різних функційно-змінних температур. Розв’язок задачі побудовано з використанням методу лінеаризувальних параметрів щодо визначення температурних полів у термочутливих елементах конструкцій та скінчених інтегральних перетворень.A lot of structural elements of modern technology take the form of a finite cylinder and in the manufacture and operation are often subjected to significant temperatures (high and low level temperatures). To ensure their reliable operation already at the design stage the detailed analysis of the temperature field and flow conditions of heat exchange processes should be carried out taking full account of heterogeneity (due to the fact that the physical and mechanical properties of materials depend on temperature changes) and actual operating condition also (taking into account heat exchange on all surfaces the surrounding temperatures of which are not constant). The method of construction the solutions to two-dimensional nonlinear stationary heat conduction problems on the example of thermosensitive cylinder with convective heat exchange is proposed. The convective heat exchange with varying (on the coordinates) surroundings temperature through all cylinder surfaces is considered. The two-step linearization (partial - by introducing the Kirchhoff variable and final - by using the linearizing parameters method) is realized for solving the corresponding nonlinear heat conduction problem. This method is effective for constructing analytical and numerical solutions of heat conduction problems for thermosensitive bodies, if they have convective heat transfer conditions at their surfaces. This method involves the construction of solution to the equation for Kirchhoff variable with a linear condition that includes certain "linearizing parameters". The resulting linear problem for the Kirchhoff variable is solved by finite integral transformation method. The distribution of temperature field of cylinder and also the influence of material temperature-sensitivity on it taking into account linear dependence of heat conduction factor is determined. The comparison of the obtained solutions with solutions of similar problems for the permanent characteristics of the material and the mid-integral characteristics values for a given temperature range is made

Influence of infrared radiation on the electrical characteristics of the surface-barrier nanostructures based on MBE HgCdTe

Impact of illumination on the admittance of the MIS structures based on MBE Hg1-xCdxTe with graded-gap layers and single quantum wells was investigated. It is shown that for HgCdTe-based nanostructures the illumination greatly affects the capacitance and conductance dependencies. The capacitance-voltage characteristics exhibit a low-frequency behavior, which is associated with a decrease in the differential resistance of the space charge region. Especially informative illumination exposure is in the study of deep traps in n-HgCdTe (x=0.21-0.23) without graded-gap layer. Illumination leads to the low-frequency behavior of capacitance-voltage characteristics of MIS structures based on p-HgCdTe with HgTe single quantum well in the active region, and maximums in the voltage dependences do not appear