BiMnO3的铁电铁磁机制,轨道有序和自旋有序的第一原理

为了探讨多铁材料铁电畸变的根本机制及其电子结构对于性能的影响,采用基于密度泛函理论的广义梯度近似方法,对多铁材料BiMnO3的高温顺电顺磁相、室温铁电顺磁相和低温铁电铁磁相的电子结构做了第一原理计算.对态密度、电子密度以及Mulliken电荷等计算结果的分析表明:Bi-6p轨道与O-2p轨道间的选择性共价作用增强是铁电畸变的首要引发因素,6s电子的极化也是其导致的效应之一.对与多铁现象共生的轨道有序和自旋有序的研究指出了去中心化的晶格畸变、Jahn-Teller畸变和自旋失措引发的晶格畸变三者之间的相互耦合以及耦合对铁电铁磁性的影响.     

新时期研究生挫折教育略论

加强对研究生的挫折教育,已成为新时期研究生教育的一项非常重要而迫切的任务。研究生挫折教育的途径主要有:培养研究生树立良好的挫折观;将远大志向与正确、切实的短期目标有机结合;研究生导师要将挫折教育作为自身工作的重要职责和内容;要创设挫折情境,加强实践体验;在研究生中积极开展抗挫互助活动;帮助研究生学会自我调适、自我超越、自我教育。     

The bipartite edge frustration of graphs under subdivided edges and their related sums

The bipartite edge frustration of a graph G, denoted by φ(G), is the smallest number of edges that have to be deleted from G to obtain a bipartite spanning subgraph of G. This topological index is related to the well-known Max-cut problem, and has important applications in computing stability of fullerenes. In this paper, the bipartite edge frustration of an infinite family of fullerenes is computed. Moreover, this quantity for four classes of graphs arising from a given graph under different types of edge subdivisions is investigated.     

论情势变更原则适用的有关问题

本通过对情势变更原则的概述，从基于公平与诚信对合同当事人之间的权利和义务进行调整，以消除因情势变更所造成的不公平后果，维护当事人的合法权益的实践出发，阐明了情势变更原则适用合同纠纷的条件和程序，以及该原则与不可抗力、商业风险、显失公平等法律规则的区别。     

A taxonomy of novice user perception of error on the Web

Novice users face many challenges when browsing the Web. The goal of this experiment was to learn about how users perceive error situations when using the World Wide Web. Specifically, the goal was to learn which circumstances cause users to believe that an error has occurred. An exploratory experiment took place with 78 subjects who were novice users. In the experiment the subjects were asked to identify when they perceived that an error had occurred. The subjects reported a total of 219 error situations. These error situations were then classified by the researchers into the following four categories: user error, system error, situational error, and poor Web design. Based on the collected data, suggestions are presented for improving the usability of Web browsers and Web sites.     

Magnetic and specific heat studies of the frustrated Er2Mn2O7 compound

A new Er2Mn2O7 compound was synthesized by the ceramic method and its crystal structure was characterized using powder X-ray diffraction (XRD) and observed by scanning electron microscopy (SEM). The magnetic properties were investigated using a BS2 magnetometer and the heat capacity was studied using a quantum design (PPMS). The structural study revealed that this compound was monophasic and crystallized in the monoclinic system with the P2/M space group. Magnetization measurements were carried out in the temperature range of 1.8-200 K under an applied magnetic field of 0.05 T. A crossover from a room temperature paramagnetic phase to an antiferromagnetic one at low temperature was detected from the magnetic study. The magnetic susceptibility, in the paramagnetic region above 40 K, was found to present a simple Curie-Weiss type behavior. From the specific heat (CP) measurements in magnetic fields up to 5 T, we noted the presence of a wide peak characteristic of a second order mag-neto-structural transition.     

Conformational Flexibility and Local Frustration in the Functional States of the SARS-CoV-2 Spike B.1.1.7 and B.1.351 Variants: Mutation-Induced Allosteric Modulation Mechanism of Functional Dynamics and Protein Stability

Structural and functional studies of the SARS-CoV-2 spike proteins have recently determined distinct functional states of the B.1.1.7 and B.1.351 spike variants, providing a molecular framework for understanding the mechanisms that link the effect of mutations with the enhanced virus infectivity and transmissibility. A detailed dynamic and energetic analysis of these variants was undertaken in the present work to quantify the effects of different mutations on functional conformational changes and stability of the SARS-CoV-2 spike protein. We employed the efficient and accurate coarse-grained (CG) simulations of multiple functional states of the D614G mutant, B.1.1.7 and B.1.351 spike variants to characterize conformational dynamics of the SARS-CoV-2 spike proteins and identify dynamic signatures of the functional regions that regulate transitions between the closed and open forms. By combining molecular simulations with full atomistic reconstruction of the trajectories and the ensemble-based mutational frustration analysis, we characterized how the intrinsic flexibility of specific spike regions can control functional conformational changes required for binding with the host-cell receptor. Using the residue-based mutational scanning of protein stability, we determined protein stability hotspots and identified potential energetic drivers favoring the receptor-accessible open spike states for the B.1.1.7 and B.1.351 spike variants. The results suggested that modulation of the energetic frustration at the inter-protomer interfaces can serve as a mechanism for allosteric couplings between mutational sites and the inter-protomer hinges of functional motions. The proposed mechanism of mutation-induced energetic frustration may result in greater adaptability and the emergence of multiple conformational states in the open form. This study suggested that SARS-CoV-2 B.1.1.7 and B.1.351 variants may leverage the intrinsic plasticity of functional regions in the spike protein for mutation-induced modulation of protein dynamics and allosteric regulation to control binding with the host cell receptor.     

The effects of threat and frustration on group cohesiveness.

A field experiment concerned with the effects of threat and frustration upon cohesiveness seemed to justify several conclusions. (a) A reduction in threat seems to increase cohesiveness. (b) A reduction in frustration does not increase cohesiveness. (c) A catharsis of hostility may increase the attractiveness of teams toward which hostility is directed. (d) Strong frustration may produce "a withdrawal symptom consisting of reduced interteam competition and increased intrateam cooperation." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cooperation in social dilemmas and the need to belong: The moderating effect of group size.

The present research examined the effects of the need to belong and group size on cooperation in a public goods dilemma. On the basis of previous research (R. F. Baumeister & M. R. Leary, 1995), it was expected that those high in the need to belong would cooperate most. In addition, it was expected that the need to belong would predict cooperation for large-group members but not for small-group members. Analyses supported both hypotheses. Furthermore, individual differences in the need to belong were positively correlated with frustration about individuals' (cooperative) decision, a feeling believed to emerge from the felt uncertainty over whether cooperation would be reciprocated by others, the conflicting motivations of the need to belong and personal self-interest, or both. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In memoriam: The idioverse of Saul Rosenzweig (1907-2004).

Saul Rosenzweig (1907-2004), who founded the "common factors" approach to psychotherapy integration, and who published original and influential work during each of eight consecutive decades, died of pneumonia in St. Louis on August 9, 2004, at the age of 97. His most influential academic contributions can be placed into five categories. First, his 1933 article, "The Experimental Situation as a Psychological Problem," helped usher in the field of experimental social psychology. A second field to which Rosenzweig made enormous contributions is that of psychotherapy integration. A third field to which Rosenzweig contributed significantly is experimental psychoanalysis. Fourth, Rosenzweig played a central role in developing frustration theory, including the concept of frustration tolerance. Fifth, Rosenzweig developed the idiodynamic approach to personality assessment in the late 1940s and elaborated on it until the end of his career. Rosenzweig had been a faculty member continuously since 1949 in the Department of Psychology at Washington University in St. Louis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)