稀土和锕系化合物中重费密子行为

本文采用周期Anderson哈密顿量研究了稀土和锕系化合物中的重费密子行为。对f电子间库仑关联项做了平均场近似并引入自能项反映多体作用的效应。对自能项采用了单格位近似,在准粒子表象中讨论了系统的性质,通过对f电子平均占据数的自洽计算,得到了准粒子有效质量,讨论了形成重费密子的条件,以及相应的磁性的变化,并做了数值计算。所得结果与最近的实验进行了比较。 关键词：     

Features of magnetic and magnetoelectric properties of rare-earth multiferroic PrFe3(BO3)4 with the singlet ground state

The features of magnetization of rare-earth multiferroic PrFe₃(BO₃)₄ with the singlet ground state have been investigated theoretically. The magnetic anisotropy of the crystal has been studied. The temperature dependences of anisotropy constants have been calculated. The phase H-T diagram has been constructed. The dependences of the behavior of magnetization vectors of magnetic sublattices on the external magnetic field have been obtained. The magnetoelectric effect has been investigated, and the dependences of polarization on the temperature and field have been found for its various orientations. The theoretical data have been compared with the experimental data and their good agreement has been established.     

Specific features of the structure of detonation nanodiamonds from results of electron microscopy investigations

The experimental results of a comprehensive investigation of the structure of detonation synthesis nanodiamonds by electron microscopy methods have been presented. The morphology of diamond nanoparticles has been investigated and the microdiffraction patterns have been analyzed. The method of characteristic fast electron energy loss spectroscopy in transmission electron microscopy has been used. The local density of structural components of a nanodiamond (diamond core and fullerene-like shell) has been obtained. The shape of the shell surrounding the nanocrystal has been determined using model calculations. A hypothesis explaining the charging of the nanodiamond surface has been proposed.     

BEPCⅡ国产500 MHz超导腔运行综述

北京正负电子对撞机二期(BEPCⅡ),国产500 MHz超导腔经过紧张的安装调试于2017年10月正式投入带束流运行。首先对此国产超导腔两次降温调试的相关参数进行了监测和对比分析;其次研究了通过高功率老练的方法改善超导腔的品质因数,并实时监测超导腔老练过程中的辐射剂量;最后对超导腔的带束流运行情况进行了介绍分析。结果表明:BEPCⅡ国产500 MHz超导腔虽然放置了6年,但是状态良好,通过高功率老练能够降低超导腔的辐射剂量,改善其性能,完全满足束流运行要求。     

Ab-initio Hartree-Fock self-consistent-field calculations—An indigenous development of computer programs

A set of indigenously developed computer programs for ab-initio Hartree-Fock calculations on both closed- and open-shell molecules have been described. These programs have been written for calculations using GTO basis sets. Integral formulae have been taken from Taketaet al [8]. Structures and functions of the programs have been discussed. These programs have been extensively tested. Molecular integrals over GTO basis sets have been chosen for tests and as numerical examples in this paper. Results of calculations using very accurate minimal bases have been given for methane. Time taken for these computations in a CDC Cyber 180/840 machine has been indicated. Trends in the calculations have also been illustrated by employing 4-gaussian expansions for the STO’s and by varying the basis size for LiH and BH⁺. An erratum to this article is available at .     

Optical methods for the generation of terahertz radiation and subterahertz acoustics of solids

Various methods to increase the efficiency of the generation of broadband terahertz radiation based on optical rectification have been analyzed. The solutions of self-consistent optical terahertz equations have been studied using the inclined front technique. The effect of symmetric and asymmetric resonant impurity centers incorporated into a crystal has been examined. Transient and asymptotic stages of generation have been considered. Attention has been focused on the evolution of the spectra of both generated terahertz and input optic signals. One- and two-frequency generation modes have been discussed. Acoustic analogs that would provide the possibility of the generation of the gigahertz acoustic supercontinuum using subterahertz elastic signals in a solid have been analyzed. The main similarities and differences between terahertz optics and subterahertz acoustics have been revealed.     

On wave propagation in a random micropolar thermoelastic medium,second moments,and associated Green’s tensor

The couple stress theory developed by Eringen comprises granular materials as also composite fibrous materials. As such, micropolar materials present an inclusive model of composite materials. This article endeavors to study aspects of wave propagation in a random weakly thermal micropolar elastic medium. The smooth perturbation technique has been employed. The classical thermoelasticity has been used. Six different types of waves have been observed to propagate in the random interacting medium. Dispersion equations have been derived. The effects due to random variations of micropolar elastic and thermal parameters have been observed. Change of phase speed occurs on account of randomness. Attenuation coefficients for high-frequency waves have been computed. Second moment properties have been discussed with application to wave propagation in the random micropolar elastic medium. 36 + 1 components of the associated Green’s tensor have been computed. Integrals involving correlation functions have been transformed to radial forms. A special type of correlation function has been used to approximately measure effects of random variations of parameters.     

Temperature dependence of the cyclotron resonance in graphene

The dynamic conductivity of graphene in a magnetic field under the conditions of cyclotron resonance has been calculated. The effect of the temperature on cyclotron resonance has been analyzed. So-called multiple resonances have been considered. A dimensionless quantity determining the width and amplitude of the cyclotron peak in the conductivity has been found. Coulomb corrections to the electronic spectrum have been discussed.     

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.     

Generalized classical mechanics

Generalized classical mechanics has been introduced and developed as a classical counterpart of the fractional quantum mechanics. The Lagrangian of generalized classical mechanics has been introduced, and equation of motion has been obtained. Lagrange, Hamilton and Hamilton-Jacobi frameworks have been implemented. Oscillator model has been launched and solved in 1D case. A new equation for the period of oscillations of generalized classical oscillator has been found. The interplay between the energy dependency of the period of classical oscillations and the non-equidistant distribution of the energy levels for fractional quantum oscillator has been discussed. We discuss as well, the relationships between new equations of generalized classical mechanics and the well-known fundamental equations of classical mechanics.     

Bistability of a “chevron” smectic C* liquid crystal in an external electric field

The system of nonlinear equations describing a surface-stabilized ferroelectric smectic C* liquid crystal in the chevron geometry has been investigated by numerical methods in the framework of the continuum model of liquid crystals. Stable orientational and structural configurations have been studied, and the results obtained have been compared with those derived using simplified models. The height of the potential barrier separating two stable configurations has been determined, and the transition between them under the action of the external electric field has been examined. It has been demonstrated that this effect has a threshold character. The dependence of the threshold field on the film thickness has been analyzed.     

Calculation of the intensity of Touschek electrons in the VEPP-4M storage ring

Formulas for calculating the intensity of intrabeam scattering of electrons in the Born approximation for the one- and two-dimensional collision models have been obtained for the nonrelativistic and relativistic cases. The Baier-Katkov-Strakhovenko two-dimensional relativistic model with Coulomb corrections has been analyzed. Formulas in the ultrarelativistic limit have been obtained using this model. Different models have been compared. The intensities of Touschek electrons and the polarization contribution have been calculated under the conditions of the detection of scattered particles at the VEPP-4M storage ring. The calculations have been compared to experimental data.     

Homogeneous nucleation of dislocations

The mechanism and stochastic properties of the homogeneous nucleation of dislocations have been studied. An approach has been proposed for determining the nucleation rate based on consideration of the lifetimes of a metastable state. Primary data have been obtained using the molecular dynamics method. The dependences of the nucleation rate on the shear stresses have been determined for several temperatures. An approximation of the obtained results in terms of the Arrhenius equation has been proposed. The regions of shear stresses and temperatures in which the mechanism of homogeneous dislocation nucleation can be realized have been estimated.     

Statistical description of a paired nucleus with the inclusion of angular momentum

The effect of angular momentum on an excited paired nucleus has been studied. The BCS Hamiltonian, modified to include the z-projection of angular momentum has been diagonalized and expressed in terms of the quasiparticle occupation numbers. The grand partition function and all the relevant thermodynamical functions as well as the level-density expression have been derived for the general case of an arbitrary set of single-particle levels. Furthermore, the formalism has been applied to the uniform model and, whenever possible, analytical expressions have been derived. In particular the zero-temperature angular momentum dependence of the gap parameter, the critical angular momentum as well as the yrast line have been calculated. The critical temperature as a function of angular momentum, which defines the phase transition between paired and unpaired systems, has been calculated. A new effect called the thermally assisted pairing correlation, involving an increase of pairing with increasing temperature has been predicted. The completeness of the formalism as applied to spherical or deformed nuclei has been discussed.     

Synthesis,experimental and theoretical analysis,and antiproliferative activity of 2-(4-methoxyphenylamino)-2-oxoethyl methacrylate

In this study 2-(4-methoxyphenylamino)-2-oxoethyl methacrylate (MPAEMA) has been synthesized and characterized experimentally (FTIR, NMR). Theoretically, physical, electronic and vibrational properties of MPAEMA molecule have been investigated using density functional theory (DFT) calculations at B3LYP/6-311++G(d,p) basis set. Bond distance, FTIR spectrum, NMR spectra and vibrational frequencies have been carried out. The calculated FTIR and NMR spectra of the headline molecule from the DFT have been compared with the measured ones, and good results have been obtained. UV spectrum characteristics and the electronic properties, like frontier orbitals, and band gap energy of MPAEMA have also been recorded by time-dependent (TD-DFT) method based on optimized structure with different solvent. The experimental results have been compared with theoretical values. Both experimental and theoretical methods have shown that the compound has successfully been synthesized. Cytotoxicity of MPAEMA has been investigated by XTT cell proliferation assay. IC50 values of MPAEMA have been identified as 1.8 mM on HeLa cell line.     

Magnetic structure of the compensated ferromagnet-multiferroic interface

The magnetic structure of the compensated ferromagnet-multiferroic interface has been considered. The law governing the decrease of distortions of magnetic order parameters with increasing distance from the interface has been found. An expression for the energy of interlayer interaction of magnetic order parameters has been derived, and it has been shown that its magnitude is determined by the exchange interaction. The condition for magnetization switching of the ferromagnetic layer by an electric field applied to the multiferroic layer has been formulated. It has been demonstrated that the magnetoelectric effect and weak ferromagnetism are not prerequisites to the development of electric field-switchable magnetoresistive memory.     

Raman Scattering by Crystals of Rare-Earth Hexaborides with Different Isotopes of Boron

Monocrystals of lanthanum hexaboride LaB₆ containing both natural boron and its isotopes ¹⁰B and ¹¹B have been produced using the solution-melt method. Polyelement hexaboride rare-earths have been grown and the corresponding ceramics have been synthesized for the first time. All these crystals have been studied by means of various techniques, generally using Raman scattering. The Raman spectra attributed to various spectral lines corresponding to nonanalyzable representations have been obtained and interpreted. Frequencies and half-widths of spectral lines have been obtained, the removal of degeneracy and the development of respective splitting of degenerate oscillations induced by defects, mainly by boron isotope inclusions, have been identified. The influence of defects on the Raman spectra has been determined.     

AC-driven bilayer graphene: quasienergy spectrum of electrons and generation of soliton-like electromagnetic pulse

Quasienergy spectrum of electrons in biased bigraphene subjected to the linear polarized high-frequency electromagnetic radiation has been derived. Quasienergy bands of ac-driven bigraphene have been investigated. Dynamical appearing of the saddle points in band structure of biased bigraphene and energy gap modification have been predicted. Electromagnetic field equation has been written using obtained quasienergy spectrum. The solution corresponding to the soliton-like electromagnetic wave has been obtained. The conditions of soliton-like wave generation in ac-driven bigraphene have been discussed.     

Modifying a graphene layer by a thymine or a uracil nucleobase: DFT studies

The hybridizations of a graphene layer by a thymine and a uracil nucleobase have been investigated by performing density functional theory (DFT) calculations. The isolated and hybrid structures have been firstly stabilized to reach the minimum energy and the electronic properties have been subsequently evaluated for the optimized structures. The structural and atomic scale parameters indicated that the tip of graphene is important in determining the properties of new hybrids. Moreover, different effects of thymine and uracil nucleobases have been identified in the hybrid structures. Quadrupole coupling constants have been evaluated to characterize the atomic scale properties, in which the most notable effects of hybridizations have been observed for the atoms close to the linking regions whereas negligible effects have been seen for other atoms.     

实验室黑白肖像艺术照的拍摄及制作方法的改进

本文对实验室条件下拍摄黑白艺术肖像的方法作了探讨,对放大相片的方法作了改进,给出了实验数据,并对拍摄结果作了分析和讨论。实验获得了放大尺寸的人物肖像艺术照片。