Generalized dependences of the reflection coefficient of ions from a relief surface

Dependences of the reflection coefficient of ions on their energy and the height and geometry of surface asperities obtained while studying ion beam interaction with targets by the Monte Carlo method have been analyzed. The dependences of the reflection coefficient on the height of asperities with a specified geometry under bombardment with ions of different energies, on the height of asperities for different angles of inclination of lateral walls at a specified energy of ions, and on the angle of inclination of walls for different ion energies at a fixed height have been considered. Generalized curves for reflection coefficients have been obtained, and analytical approximations have been calculated.     

Morphology and the Thermoelectric Properties of γ-GdxDy1 – xS1.5 – y Solid Solution Ceramics

Physics of the Solid State - The temperature dependences of the Seebeck coefficient, the electrical conductivity (T = 300–873 K) and also the heat conductivity coefficient, and the...     

Acoustic properties of multiferroic PbFe1/2Ta1/2O3

The longitudinal acoustic wave velocity and attenuation in PbFe_1/2Ta_1/2O₃ ceramics have been measured by pulse-echo technique in the temperature range from 4.2 to 530 K. The anomalies observed in the sound velocity and attenuation behavior versus temperature were correlated with Burns temperature, temperature range of the coexistence of relaxor ferroelectric and antiferromagnetic states, and a suggested second antiferromagnetic phase transition at low temperatures.     

Prebreakdown State and Its Diagnostics in Multilayer 0.55Pb–Mg1/3Nb2/3O3–0.45PbSc1/2Nb1/2O3 Compounds

Physics of the Solid State - The determination of the breakdown voltage and the diagnostics of the prebreakdown state of a material is a topical problem of studying characteristics of insulating...     

Relaxer ferroelectrics as promising materials for IR detectors

The dielectric and pyroelectric properties of a typical relaxer ferroelectric, 0.9PbMg_1/3Nb_2/3O₃-0.1PbTiO₃ (PMN-PT), are studied experimentally. Based on the results obtained, the pyroelectric constant and figure of merit of the material when used in IR detectors are calculated. These parameters are presented as a function of temperature and external electric field. The current and voltage sensitivities and the detectivity of PMN-PT-based IR detectors are evaluated. They are compared with the same properties of pyroelectric detectors and dielectric bolometers that use traditional pyroelectric materials as the active element and also of other uncooled photodetectors.     

Electron transport properties of thermoelectrics based on layered substituted transition metal dichalcogenides

Temperature dependences of the electrical conductivity are studied in the range 4.2’300 K and Seebeck coefficient at room temperature of bulk samples of tungsten dichalcogenide polycrystals with niobium substitutions for tungsten and selenium substitutions for sulfur – W_1–x Nb _x (S_1–y Se _y )₂. The two-dimensionalization of electron transport properties is detected at niobium concentrations x ≥ 0.1 in W_1–x Nb _x S₂ and x ≥ 0.05 in W_1–x Nb _x Se₂. In samples with additional partial selenium substitution for sulfur the electron transport remains three-dimensional. At room temperature the Seebeck coefficient (at equal electrical conductivities) is several times higher in the samples with quasi-two-dimensional transport than in the samples with three-dimensional transport. The calculation of the power factor at room temperature shows its nine times increase.     

Broadband emission from a relativistic electron bunch in a semi-infinite waveguide

A study is made of the excitation of a transition radiation pulse during the injection of a charged particle bunch through the end metal wall into a semi-infinite cylindrical waveguide. Exact analytic expressions for the fields of a thin ring-shaped bunch are obtained in terms of the Lommel functions of two variables. The energy efficiency, power, and spectrum of radiation emitted from a finite-size charged bunch in a vacuum waveguide are calculated numerically with allowance for the multimode nature of the excited field. It is shown that, under certain conditions, the bunch can generate a short, high-intensity electromagnetic pulse with a broad frequency spectrum. The effect of various parameters of the charged bunch-waveguide system (such as the bunch current, bunch duration, and waveguide radius) on the generation efficiency of a transition radiation pulse is investigated.     

On the nonlinear theory of current instability of short-wave drift oscillations

The paper deals with the studies of current instability in the inhomogeneous plasma resulting in excitation of short-wave drift oscillations with a frequency near the low-hybrid resonance.It is shown that the saturation of such an instability is associated with the spectral pumping of oscillations into the short-wave region that occurs due to the modulation instability; and maximum amplitudes of the electrical fields of oscillations are determined. The effective frequency of electron collisions due to current instability is calculated. It is indicated that the diffusion model of the Parker-Sweet magnetic field reconnection modified taking into account the anomalous resistance mechanism studied here leads to the estimate of the magnetopause width being in satisfactory agreement with the experiment.     

Interaction of a modulated electron beam with a plasma

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 11, pp. 1351–1357, November, 1989.     

Structure and properties of confined sodium nitrite

We study the lateral and transverse diffusion of amphiphiles in two-component bilayer membranes, using a coarse-grained model for amphiphilic molecules and combined Monte Carlo-Molecular Dynamics simulations. Membrane structural properties, such as the mean thickness, are also measured. The dependence of such properties on membrane composition, inter-molecular interactions, and amphiphile stiffness is determined. In particular, we show that addition of shorter amphiphiles drives the model membrane towards a more fluid state, with increased amphiphile lateral diffusion rates. These results can be understood in the framework of a simple free-volume model. Furthermore, we observe an increase in the trans-membrane diffusion when the interaction energy of amphiphiles with their neighboring molecules is decreased. Received: 6 December 2002 / Accepted: 17 April 2003 / Published online: 27 May 2003 RID="a" ID="a"e-mail: imparato@mpikg-golm.mpg.de RID="b" ID="b"e-mail: shillcock@mpikg-golm.mpg.de RID="c" ID="c"e-mail: lipowsky@mpikg-golm.mpg.de