Critical and multicritical behavior in the Ising–Heisenberg universality class

Critical behavior of three-dimensional classical frustrated antiferromagnets with a collinear spin ordering and with an additional twofold degeneracy of the ground state is studied. We consider two lattice models, whose continuous limit describes a single phase transition with a symmetry class differing from the class of non-frustrated magnets as well as from the classes of magnets with non-collinear spin ordering. A symmetry breaking is described by a pair of independent order parameters, which are similar to order parameters of the Ising and O(N) models correspondingly. Using the renormalization group method, it is shown that a transition is of first order for non-Ising spins. For Ising spins, a second order phase transition from the universality class of the O(2) model may be observed. The lattice models are considered by Monte Carlo simulations based on the Wang–Landau algorithm. The models are a ferromagnet on a body-centered cubic lattice with the additional antiferromagnetic exchange interaction between next-nearest-neighbor spins and an antiferromagnet on a simple cubic lattice with the additional interaction in layers. We consider the cases N = 1, 2, 3 and in all of them find a first-order transition. For the N = 1 case we exclude possibilities of the second order or pseudo-first order of a transition. An almost second order transition for large N is also discussed.     

激光等离子体X光辐射非平衡特性实验研究

在ＬＦ－１１和ＬＦ－１２高功率激光装置上进行的实验中，设计了一些特定的激光束－金腔靶－探测器条件，创造了激光直接加热、准辐射加热和激光、Ｘ光混合加热三种物理条件，采用软Ｘ光透射光栅能谱时空分辨技术，测量了腔靶、缝靶和双孔靶等高分辨Ｘ光能谱，研究了激光等离子体Ｘ光辐射非平衡特性。     

Effect of pure and mixed solvents on the solubility, crystal growth and morphology of ethyl p-dimethylamino benzoate (EDMAB): An organic nonlinear optical material

The effects of pure and mixed solvents of ethanol and acetone on solubility, nucleation and growth of ethyl p-dimethylamino benzoate (EDMAB) were investigated. It was found that solubility of EDMAB increased as the volume ratio of acetone increased in the mixed solvent. Growth experiments were performed at 32 °C using pure and mixed solvents with different volume ratios of ethanol and acetone. Bulk single crystals of EDMAB were grown-in the experiment conducted using mixed solvent of 25% acetone and 75% of ethanol, whereas thin platelet crystal of EDMAB was obtained in the experiment conducted using pure ethanol. The acetone rich system resulted in uncontrolled nucleation with large number of tiny crystals, possibly due to high vapor pressure of acetone. The grown crystals were subjected to various analytical studies such as powder X-ray diffraction, Vickers microhardness, dielectric studies as a function of frequency and optical transmission and the powder Kurtz method.     

运用量子约束动力学对具有耗散的量子位的追踪控制

在有限温度环境内，量子约束动力学及其追踪控制可使退相干系统的相干性稳定一段时间.约束方程产生的控制场能够按量子比特的动力学状态进行控制(量子动力学轨道的反馈控制)；依靠量子比特的这种反馈效应，可使量子位稳定在设定的时间内.同时，在量子位的稳定方面，温度扮演一种消极的角色. 关键词： 量子约束动力学 耗散量子位的控制 追踪控制 量子比特的反馈效应     

宽波段多步激发K_2-系统产生的钾原子高位态辐射

本文首次报道以690.0～715.0nm宽波段范围内任何波长的脉冲染料激光激发K_2—K系统,由高位钾分子与钾原子碰撞以及分子-原子的混合激发等过程而产生钾原子404.4,404.7和470.05～590.0nm波段内高位态辐射的实验结果,并对激发机制进行了探讨.     

组合发电仪的制作

仪器应用生活中常见的材料,仅仅围绕物理学科知识,通过巧妙设计,组装出一系列发电机。旨在让学生明白各种发电机的工作原理,以及能量之间是如何相互转化的,培养学生节约能源,保护环境利用清洁能源的意识。此外本仪器制作简单,便于学生亲手制作,锻炼动手能力的同时,又可提高学习兴趣。     

Mammalian-specific genomic functions: Newly acquired traits generated by genomic imprinting and LTR retrotransposon-derived genes in mammals

Mammals, including human beings, have evolved a unique viviparous reproductive system and a highly developed central nervous system. How did these unique characteristics emerge in mammalian evolution, and what kinds of changes did occur in the mammalian genomes as evolution proceeded? A key conceptual term in approaching these issues is “mammalian-specific genomic functions”, a concept covering both mammalian-specific epigenetics and genetics. Genomic imprinting and LTR retrotransposon-derived genes are reviewed as the representative, mammalian-specific genomic functions that are essential not only for the current mammalian developmental system, but also mammalian evolution itself. First, the essential roles of genomic imprinting in mammalian development, especially related to viviparous reproduction via placental function, as well as the emergence of genomic imprinting in mammalian evolution, are discussed. Second, we introduce the novel concept of “mammalian-specific traits generated by mammalian-specific genes from LTR retrotransposons”, based on the finding that LTR retrotransposons served as a critical driving force in the mammalian evolution via generating mammalian-specific genes.     

湖南砂矿金刚石中石墨包裹体拉曼光谱原位测定：形成条件及成因指示

石墨是天然金刚石中最常见的包裹体之一,按其形成顺序可分为原生、同生、次生,原生/同生与次生石墨包裹体的存在指示了金刚石形成的环境及形成后可能经历的变化。对湖南沅水流域产出的13粒宝石级-半宝石级砂矿金刚石中的原生/同生石墨包裹体及次生石墨包裹体进行显微激光拉曼光谱的原位测试。测试显示,湖南沅水流域金刚石中原生/同生石墨包裹体与次生石墨包裹体的G带与D带拉曼位移均存在漂移,其中原生/同生石墨包裹体G带的漂移范围为1 591～1 600 cm-1,次生石墨的漂移范围为1 575～1 588 cm-1,显示其形成压力较低,结晶压力变化范围大。原生/同生石墨漂移程度估算出该区域压力范围为4.01～5.88 GPa,估算结果与利用橄榄石包裹体拉曼位移估算的源区压力范围基本一致。该区域内金刚石中原生/同生石墨包裹体的D带拉曼位移在1 350～1 368 cm-1之间,D带与G带的强度比(I_D/I_G值)值位于0.36～0.82之间,具有较低有序度结构/结晶程度与橄榄岩型金刚石的高结晶度石墨明显不同指示该区域部分砂矿来源的金刚石的形成深度较浅,成因与榴辉岩关系更为密切,形成过程极可能曾位于石墨-金刚石稳定域附近。研究结果表明,金刚石石墨包裹体拉曼位移的漂移程度可成为探索金刚石原生源区形成环境的有效方法之一。     

CRT显示器稳定性实验研究

用屏幕色度计对一台SONY-G520显示器的显色特性进行了测量,研究了其开机稳定性和短、中、长期内的色差及色度偏差。实验结果表明,开机后,显示器的亮度Y和色度x,y分别可在2h,30min和1h达到相对稳定状态,且在达到相对稳定后,在短、中、长期内的平均色差分别为0.0611,0.1469和1.2536CIELAB色差单位;在中期内,Y,x,y,L,a,b的平均偏差分别为0.0663,0.0008,0.0015,0.0695,0.4740和0.1766。通过对显示器稳定性的测量,为在对比度敏感测量和色貌模型、图像质量、图像感知模型评价等研究领域中用显示器进行实验研究奠定了基础。     

Energy transfer in hyperthermal Xe-graphite surface scattering

The scattering of a hyperthermal Xe from a graphite (0001) surface has been studied using a molecular beam-surface scattering technique and molecular dynamics (MD) simulations. The angular and velocity distributions of scattered Xe atoms were measured at incidence energies from 0.45 to 3.5 eV, three incidence angles of 15°, 35° and 60° and the surface temperatures of 300 K and 550 K. The observed time-of-flight spectra exhibit a sharp velocity distribution with only one velocity component, which is ascribed to the direct inelastic scattering process. The angle-resolved energy ratios of the mean final translational energy over the mean incidence energy E_f/E_i agree well with those predicted based on the assumption of the conservation of the momentum parallel to the surface. The Hard-Cube model, where the mass of the cube is approximately 310 u, has reproduced the angle-resolved flux distributions of scattered Xe atoms. In the Hard-Cube model almost 80% of the normal component of the incidence translational energy is found to be lost in collision. The MD simulations reproduce well the experimental results by using the Brenner potential for intralayer C atoms and a Lennard-Jones potential for interlayer C–C pair interactions.