Influence of the surface curvature of carbon nanotubes on their conductivity in the dirac approximation

A method of surface curvature of carbon nanotubes has been proposed for quantitative estimation of the longitudinal conductivity of nanotubes. A dispersion relation for the electron spectrum of single-walled carbon nanotubes has been obtained analytically. The change in the zone structure of nanotubes of various types and diameters caused by taking into account the surface curvature has been analyzed. The temperature dependence of the longitudinal component of conductivity with allowance for the surface curvature for a series of nanotubes has been calculated. The comparison with the conductivity of a plane graphene has been performed. It has been shown that, in zig-zag tubes, the correction of the conductivity for the surface curvature decreases with an increase in temperature as well as with an increase in the radius of curvature.     

Study of the interaction of a palladium nanocontact with a hydrogen molecule

The interaction of a palladium nanocontact with a hydrogen molecule has been studied using molecular static method. The influence of impurity on the atomic structure and mechanical properties of the palladium nanocontact has been demonstrated. The characteristic interatomic distance has been determined in this contact. It has been found that the hydrogen molecule dissociates by interaction with nanocontact atoms.     

Mean-field approximation for the potts model of a diluted magnet in the external field

The Potts model of a diluted magnet with an arbitrary number of states placed in the external field has been considered. Phase transitions of this model have been studied in the mean-field approximation, the dependence of the critical temperature on the external field and the density of magnetic atoms has been found, and the magnetic susceptibility has been calculated. An improved mean-field technique has been proposed, which provides more accurate account of the effects associated with nonmagnetic dilution. The influence of dilution on the first-order phase transition curve and the magnetization jump at the phase transition has been studied by this technique.     

Structure of organosilicon dendrimers of higher generations

The structure of organosilicon dendrimers of the ninth generation with the four-functional core and butyl terminal groups has been studied by small-angle neutron scattering. It has been demonstrated that the dendrimers are monodisperse objects with an anisometric shape. The partial volume and the average scattering density have been determined using the contrast variation technique. It has been shown that the dendrimers under study are identical in overall sizes and scattering density distribution. It has been revealed that 20% of the overall volume of the dendrimer is accessible for the penetration of the solvent. The distribution of the scattering length density in the dendrimers has been simulated and reconstructed using the Monte Carlo method, and a change in the excluded volume for different contrasts has been revealed. The specific features of the spatial structure of organosilicon dendrimers of higher generations have been discussed.     

Magnetization and transport characteristics of layered high-temperature superconductors with different anisotropy parameters

The magnetization of a layered high-temperature superconductor with different anisotropy parameters has been calculated using the Monte Carlo method in the framework of a modified three-dimensional Lawrence–Doniach model with actual boundary conditions. The penetration of a magnetic flux into a bulk sample from the boundary has been simulated, and the curves of magnetization reversal of a high-temperature superconductor by an external magnetic field have been calculated for different anisotropy parameters γ and types of defects in the sample. It has been found that there are significant differences in the magnetization curves and transport properties of superconductors with different anisotropy parameters γ. The influence of tilted columnar defects on the critical current has been analyzed. A decreasing dependence of the critical current on the tilt angle of defects with respect to the c axis has been obtained. It has been shown that, as the anisotropy parameter increases, this dependence weakens and, for a specific value of γ, disappears. An explanation of the mechanism responsible for the disappearance of the dependence has been proposed.     

Quasi-phase-matched modulation instability in birefringent fibers

The phase-sensitive nature of polarization modulation instability has been demonstrated in optical fibers whose birefringence has been manipulated to generate phase mismatches. Quasi-phase-matched modulation instability has been demonstrated, and the gain of the quasi-phase-matched sidebands has been investigated. The results are in good agreement with experiment.     

Magnetic properties of porous glass-CuO nanocomposites

The magnetization of the porous glass nanocomposite with CuO nanoparticles embedded in the pores has been studied in the temperature range from 1.8 to 350 K for different pore fillings. It has been shown that the magnetic properties of these nanocomposites depend significantly on pore filling. It has been found that, in the low-temperature range for the nanocomposite with a pore filling of 55% and for pressed CuO, the ZFC and FC susceptibilities diverge, a feature which has been almost absent in the nanocomposite with 21% filling. It has been demonstrated that the kink in the temperature dependence of magnetization, which corresponds to the paramagnetic-multiferroic phase transition, does not shift in the sample with a larger pore filling as compared to that observed in the bulk sample.     

Application of CsI(T1) Scintillator With Photodiode Readout Detector in Heavy Ion Reaction Experiments

The applications of CsI(T1) scintillator with photodiode read out in heavy ion-induced reaction experiment are reported.This kind of detector has been used as E detector in a ΔE-E telescope with silicon as ΔE detector,and has been used to measure the light charged particles.Time of crossing zero point method has been employed in the experiment with a new kind of electronics,and has been used to indentify the light charged particles.     

Evaporation waves in a metastable single-component liquid

In this paper, evaporation waves appearing at rapid depressurization of a vessel filled with liquid Freon R11 have been investigated experimentally. Regimes with a high-speed evaporation front have been revealed. It has been shown that the disintegration of a metastable liquid takes place in the form of a surface evaporation wave with a cellular structure of the front and anomalously high values of the coefficient of heat transfer from the liquid. The dependence of the evaporation front velocity on the initial temperature of the liquid has been obtained. A critical temperature value below which evaporation waves are not observed has been determined. Visualization of the evaporation front structure and dynamics with the use of a high-speed video camera has been performed. It has been found that the evaporation front motion has a pulsatory character. A method to calculate the surface evaporation wave with a quasi-plane interphase boundary has been developed. It is based on a model of nonequilibrium evaporation of the liquid and experimentally measured coefficients of the heat transfer from the liquid.     

Character of variation in the microhardness of the (0001) plane of Zn single crystals under the action of electrostatic field and the possible reason for this effect

The influence of electric potential on the microhardness of the crystallographic plane (0001) of zinc single crystals has been studied. It has been established that the microhardness decreases with an increase in the supplied potential and, at the value of 0.05 V, reaches saturation. The total decrease in the microhardness is 8%. It has been shown that the variation of the microhardness is statistically significant. The observed effect has been explained by a reduction in the surface energy density due to electrization of the surface. The reduction in the surface energy with allowance for the existing single layer of adsorbed water has been estimated.     

Flicker Noise in a Locally Nonequilibrium Medium

A model implying that particles of a medium are subjected to external forces with a flicker noise spectrum has been proposed to describe fluctuations in locally nonequilibrium physical media. The Langevin equation with additional integral terms describing the action of the locally nonequilibrium medium has been derived. The spectral density of fluctuations of an electric current flowing in the locally nonequilibrium medium has been calculated. It has been found that this density in the low-frequency spectral range is flicker noise.     

激光聚变空心玻璃微球靶丸充氖工艺

 叙述了空心玻璃微球用渗透法进行高温充氖诊断气体工艺研究。分析了影响球内气体压力的一些因素；获得了向不同类型的玻璃微球中充氖诊断气体的最佳充气条件。利用该法在空心玻璃微球中充入了0.02～3MPa的氖诊断气体。     

Quantum model of the prolate spheroidal Thomson hydrogen atom

In a uniformly charged prolate spheroidal Thomson hydrogen atom the electron states have been investigated. It has been shown from the mathematical point of view that the problem is equivalent to a spheroidal hydrogen atom in a parabolic potential with the cylindrical symmetry. In the framework of adiabatic approximation, the energy of ground state has been calculated. Comparison with the case of uncharged spheroidal quantum dot has been made, and the analytical form of wave function of electron has been also obtained.     

Low-energy relation for the trace of the energy–momentum tensor in QCD and the gluon condensate in a magnetic field

The nonperturbative QCD vacuum in a magnetic field has been studied. A low-energy relation for the trace of the energy–momentum tensor in the magnetic field has been obtained. It has been shown that the derivatives of the quark and gluon contributions to the trace of the energy–momentum tensor with respect to the magnetic field coincide with each other. The magnetic field dependence of the gluon condensate has been calculated in the limits of strong and weak fields.     

Synthesis and Growth Mechanism of Ultralong ZnO Nanocombs and Nanobelts on Cu Substrate

In the two-dimensional electron systems with strong coupling in MgZnO/ZnO heterostructures, the thermal behavior of Ising quantum Hall ferromagnets at the filling factor ν = 2 has been studied. The spin polarization of Hall ferromagnets has been detected by measuring the signal related to the inelastic light scattering by intrasubband spin excitons. A stepwise change in the spin polarization at the phase transition at the filling factors ν = 2,3, and 4 in the heterostructures with different electron densities has been observed. The thermal stability of the Hall ferromagnetic phases at ν = 2 has been studied and the Curie temperature has been estimated. It has been shown that the Curie temperature is determined by the formation energy for domain walls in the Ising quantum Hall ferromagnets.     

Family of graphene-based superconducting devices

A family of highly sensitive devices based on a graphene nanobridge and superconducting electrodes has been developed, manufactured, and examined. These devices can be used to create a graphene-based integral receiver. A cold-electron bolometer prototype with superconductor-insulator-normal metal tunnel junctions has been studied. Its response to a change in the temperature and external microwave radiation has been measured. A superconducting quantum interferometer with a graphene strip as a weak coupling between superconducting electrodes has been examined. The corresponding modulation of the voltage by a magnetic field at a given current has been measured. The effect of the gate voltage on the resistance of graphene has been analyzed for these samples. To confirm that graphene is single-layer, measurements with the reference samples were performed in high magnetic fields, displaying the half-integer quantum Hall effect.     

Low-temperature vibrational properties of tin nanoparticles in porous glass

The heat capacity has been studied in the temperature range 2.2–40 K and in magnetic fields up to 2 T in tin, which has been embedded in nanometer-size pores in glass having diameter ∼7 nm, in bulk tin and in glass with empty pores. Comparison of the properties of tin nanoparticles and bulk tin has been performed. An increase in the coefficient of electronic heat capacity has been found in nanostructured tin as compared with the bulk tin, and also a considerable deviation of the low-temperature lattice heat capacity from the Debye law in the temperature region T > 3 K has been found. The fact that the density of thermal vibrations in nanocrystalline tin for low energies is higher than in bulk tin has been established using low-temperature heat capacity data.     

The study of anharmonic properties and s-p-d hybridization in barium at extreme environment

Theory of pseudopotential has been used in the present study to carry out computation of various thermodynamic parameters of barium. The role of anharmonic effect due to vibrations of lattice ions has been accounted by coupling local pseudopotential with mean field potential which has been computed using second-order perturbation theory. Contribution due to thermally excited electrons has been accounted by Mermin functional. The excellent agreement of presently computed pressure with experimental result has also been observed at which body centered cubic to hexagonal close packed structure phase transition occurs. Such success leads to conclude that the s-p-d hybridization and anharmonic effects are included properly in the presently used conjunction scheme with additional advantage of its computational simplicity.     

表面电荷密度法的应用研究

本文介绍了一种边界积分方程法——表面电荷密度法。它可用于处理轴对称电场和三维电场,特别是包含介质和开放边界的系统;还可用来精确确定各种形状电极间的电容。本文对应用此法所遇到的各种奇异性问题进行了讨论,在理论推导的基础上,编制了通用程序,它可处理包含圆形、直线形电极和介质的轴对称系统,可处理矩形平面电极的三维场。利用这个程序,对尖端发射体外的电位分布及快速变像管中一种常用的聚焦系统的空间电位分布进行了计算,与差分法作了比较,还计算了考虑介质边界后的影响;计算了单球体的空间电位分布,并与解析值进行了比较,计算了几种模型的电容,并与解析值和极限值进行了比较。