基于弹性统计理论的硅橡胶纳米复合材料本构关系的建立

基于考虑了悬垂链的橡胶弹性统计模型,通过引入应变放大因子,建立了硅橡胶纳米复合材料的基于微观机制的本构关系,其中利用硅橡胶分子信息(分子量M、乙烯基含量wt_(Vi)%)、乙烯基反应程度(q)估算获得本构方程中的交联点间链段分子量(Mc),网络链(network strands)体积分数(Φ)等参数,通过拟合确定了与纳米粒子相关的部分参数(初始应变放大因子X_0,极限应变放大因子X_∞,衰减因子z),对掺杂白炭黑的单组分及长短链配合硅橡胶拉伸应力-应变数据进行拟合,在采用相同X_∞,z值情形下,拟合曲线仍能与实测值符合较好(拟合的Adj.R-Square值分别为0.99576、0.99596)。基于微观物理机制的本构关系能够成为联系微观分子结构参数与宏观应力的桥梁,本文工作有望为更有针对性地改进和优化硅橡胶的性能提供依据。     

极强激光场驱动超亮伽马辐射和正负电子对产生的研究进展

高功率超短超强激光脉冲的诞生开启了相对论非线性光学、高强场物理、新型激光聚变、实验室天体物理等前沿领域.近年来,随着数拍瓦级乃至更高峰值功率激光装置的建成,超强激光与等离子体相互作用进入到一个全新的高强场范畴.这种极强激光场与等离子体相互作用蕴含着丰富的物理过程,除了经典的波与粒子作用、相对论效应、有质动力效应等非线性物理过程外,量子电动力学(QED)效应变得格外重要,例如辐射阻尼效应、正负电子对产生、强伽马射线辐射、QED级联、真空极化等.本文主要介绍我们近年来在极端强激光场与等离子体相互作用中激发的QED效应以及伴随的超亮强伽马射线辐射和稠密正负电子对产生等方面的研究进展.     

Unequal crossover recombination - population screening for PHOX2B gene polyalanine polymorphism using CE

Congenital central hypoventilation syndrome (CCHS) is a rare neurological disorder characterized by abnormal autonomic central nervous system control of breathing during sleep. Mutations in the paired-like homeobox 2B (PHOX2B) gene, including point mutation, frameshift, and polyalanine expansion, are associated with the pathogenesis of CCHS. In this study, PHOX2B mutations were analyzed in seven CCHS patients, their family members, and 1520 healthy individuals from the general population using CE to provide high sensitivity and resolution screening for the PHOX2B polyalanine polymorphism. Seven mutations in the PHOX2B gene, including two frameshift mutations and five polyalanine expansions in the 20-residue polyalanine tract, were identified. The various phenotypes observed in CCHS patients with PHOX2B mutations suggest that the size of the expansion allele is associated with the CCHS risk. In addition, significant differences were found in allele and genotype distributions between the healthy individuals. Alleles (GCN)(20) and (GCN)(15) had the highest population incidence rates of 94.84 and 4.51%, respectively, with the remaining alleles, (GCN)(13) and (GCN)(7), accounting for 0.59 and 0.06%, respectively. Therefore, it has been demonstrated that CE can be used to improve the detection of polyalanine expansions in the PHOX2B gene. The attractive alternative method is a promising tool for the detection of disorders involving trinucleotide repeat tracts.     

华中五味子挥发性成份的研究

华中五味子有收敛、止咳、止汗、止泻、活血和健胃等作用。近年来已分离到约15种非挥发性成份,但关于它的挥发性成份迄今未见报道。我们用毛细管气相色谱法分离出     

等离子体在任意强度的直流电场中产生电流的过程

通过Fokker-Planck模拟,研究了等离子体在任意强度的直流电场中产生电流的过程以及电子分布函数的演变过程.研究发现,不同强度的电场中等离子体的行为存在着明显的差别.在弱电场中,电流与电场满足Spitzer公式,且电流产生的响应时间约等于撤销电场后电流衰减的弛豫时间;在中等强度的电场中,电子分布函数呈现为静止Maxwell分布和漂移Maxwell分布之和,而且在中等强度或者强直流电场中弛豫时间也将远远大于响应时间.根据电子分布函数的演变规律,推导了一组类似于流体力学方程的公式,这组方程像Spitzer公式一样简便地描述了等离子体中电流与电场的关系,并且对电场强度没有限制.数值模拟显示这组方程比Spitzer公式更适用于等离子体的混合粒子模拟中. 关键词： 等离子体电流 电子分布函数 Fokker-Planck模拟 Spitzer公式     

Characteristic parameters from a human of electromagnetic signals heart system

The electromagnetic field of a human heart system is a bioelectromagnetic field. Electrocardiography （ECG） and magnetocardiography （MCG） are both carriers of electromagnetic information about the cardiac system, and they are nonstationary signals. In this study, ECG and MCG data from healthy subjects are acquired; the MCG data are captured using a high-Tc radio frequency superconducting quantum interference device （HTc rf SQUIDs） and the QRS complexes in these data are analysed by the evolutionary spectrum analysis method. The results show that the quality factor Q and the central frequency fz of the QRS complex evolutionary spectrum are the characteristic parameters （CHPs） of ECG and MCG in the time-frequency domain. The confidence intervals of the mean values of the CHPs are estimated by the Student t distribution method in mathematical statistics. We believe that there are threshold ranges of the mean values of Q and fz for healthy subjects. We have postulated the following criterion： if the mean values of CHPs are in the proper ranges, the cardiac system is in a normal condition and it possesses the capability of homeostasis. In contrast, if the mean values of the CHPs do not lie in the proper ranges, the homeostasis of the cardiac system is lacking and some cardiac disease may follow. The results and procedure of MCG CHPs in the study afford a technological route for the application of HTc rf SQUIDs in cardiology.     

自拟试题在物理化学课程学习中的实践探索*

为了促进学生对物理化学知识的掌握与理解,在物理化学教学中设计自拟试题环节,给学生布置“自己拟定一套物理化学试题(含答案)”的任务并对学生的反馈进行总结和点评。旨在让学生通过此项训练,将所学知识点系统的总结与梳理,并且更全面深入的加强对知识的理解,达到融会贯通的效果,最终有望促进物理化学的学习。     

Establishment of Constitutive Model of Silicone Rubber Foams Based on Statistical Theory of Rubber Elasticity

In this study, a constitutive model based on microscopic physical mechanism of silicone rubber foams was established. A theoretical statistical model of rubber elasticity considering the effect of dangling chains was modified to build this model. When a strain amplification factor(X) was introduced, the theoretical model could fit the tensile stress-strain data of mono-and bi-modal foam matrix well(Adj. R-Square = 0.9989, 0.9983). Parameters related to the polymer network, namely, average molecular weight(Mc) and volume fraction(ф) of chain segments between adjacent cross-linking points(network strands), were calculated by probabilistic method from the number-average molecular weight(Mn), vinyl content(w Vi) of the primary polysiloxanes and percent conversion(q) of vinyl groups. The primary and infinite strain amplification factors(X0, X∞) and decay exponent(z), introduced by X and related to the nanoparticles, were obtained by fitting. Inspired by the fact that the actual strain of matrix was lower than that of the foams', we introduced another item, strain hysteresis item(H, related with the foam porosity and cell structure), into the statistical model as well. With the same above values of Mc,ф, X0 and X∞, the model could also fit the compressive stress-strain data of mono-and bi-modal foams well(Adj. R-Square = 0.9948,0.9985). Interestingly, the strain hysteresis items of the mono-and bi-modal foams almost completely coincided under all experimental strains, which may be attributed to the almost equal porosity and similar cell structure of the two foams. This constitutive model may connect the macroscopic stress-strain behaviour to the parameters of microscopic molecular structures, promisingly providing a basis for the performance improvement and optimization of silicone rubber foams.     

聚乳酸-聚乙二醇嵌段共聚物晶行为研究

用1H NMR, SEC, XRD和DSC对聚乳酸(PLLA)-聚乙二醇(PEG)二嵌段共聚物进行了表征. 由于共聚物中两种组分比例的不同, 表现出某组分单独结晶或两种组分共同结晶. 用DSC和POM方法, 对两组分含量相当的共聚物进行了熔体结晶行为研究, 并采用Avrami方程进行了结晶动力学计算. 用Lauritzen-Hoffmann理论对PLLA-PEG结晶机理进行了分析. 在70~94 ℃范围内, 得到成核参数Kg(POM)=5.23×105 K2. 共聚物的Kg和链折叠自由能σe都比均聚物的文献报道值高, 表明PEG链段的存在影响了PLLA的结晶, 使得其成核较均聚物困难.