关于引力规范理论的研究

本文提出了具有某种规范对称性的时空几何性质,应当由有同样规范对称性物质的物理性质决定.由此分别提出了以Lorentz群、Poincaré群和de Sitter群作为规范群的引力规范理论方案,所有这些方案都不与现有的实验和观测相矛盾,并有可能为解决广义相对论中的奇性和不可重整的困难提供一些线索。     

Chalcogen-chalcogen bonds in edge-sharing square-planar d8 complexes. Are they possible?

A theoretical study of the formation of X-X bonds in complexes with the general formula [M(2)(mu-X)(2)L(4)] (M = group 10 and X = group 16 elements) having d(8) transition-metal atoms is presented. The existence of two energy minima for some complexes, with short and long X-X distances, is shown by density functional theory calculations, and the factors responsible for it are analyzed, including a strong influence of the nature of the metals and ligands on the relative stability of the two isomers. The influence of the bite angle of chelating terminal ligands and the nature of the donor atom on the relative stabilities of the two isomers are also discussed.     

直链淀粉手性固定相法分离利阿唑对映体

建立了利阿唑对映体的高效液相色谱拆分方法。采用Chiralpak AD-H手性柱在正相条件下直接拆分利阿唑对映体,考察了流动相中有机极性调节剂的种类和浓度、酸碱的种类和含量、柱温及流速等对利阿唑对映体分离的影响。确定了最佳的拆分条件:流动相为正己烷-乙醇(含0.3%二乙胺和0.1%冰醋酸)(体积比为80∶20),流速0.6 mL/min;检测波长254 nm;柱温20 ℃。在此条件下利阿唑对映体的分离度为3.4。该法简单快速,重现性好。     

层状结构钒磷酸盐(H2 NC4 H8 NH2)0.5[(VO)(PO4)]的水热合成及热稳定性

采用新配方水热合成了层状结构钒磷酸盐(H2 NC4 H8 NH2)0.5[(VO)(PO4)],用ICP、TG-DTA、单晶XRD和动态XRD对合成物进行了表征.结果表明,该化合物有机模板的开始分解温度,在空气气氛中为343℃,在氮气气氛中为376℃.有机模板的分解逃逸导致了结构的破坏.随着温度的升高结构发生重组,约760 ℃时形成(VO)2P2O7;温度继续升高,(VO)2P2O7进一步氧化,形成钒磷氧化物新物相.与结构相似化合物(H3 NCH2 CH2 NH3)[(VO)(PO4)]的热稳定性比较表明,有机模板的热稳定性及其与无机骨架结合的牢固性影响化合物的热行为.     

Isospin Dependence in Nuclear Multifragmentation Within Site Percolation and Nucleation Pictures

The isospin dependence, recently observed in Sn + Sn reactions at 40 MeV/nucleon, is discussed within the framework of two simple nuclear multifragmentation models, namely the site percolation and the nucleation-evaporation models. It is shown that both the models are able to discriminate between ¹¹²Sn+ ¹¹²Sn and ¹²⁴Sn+ ¹²⁴Sn reactions. The nucleation-evaporation model succeeds to reproduce nicely the experimental data, but the site percolation model fails in doing that, even if the cluster noncompactive effect is taken into account. The calculations indicate that the data are originated mainly from a single source.     

Nucleon Finite Volume Effect and Nuclear Matter Properties in a Relativistic Mean-Field Theory

Effects of excluded volume of nucleons on nuclear matter are studied, and the nuclear properties that follow from different relativistic mean-field model parametrizations are compared. We show that, for all tested parametrizations, the resulting volume energy al and the symmetry energy J are around the acceptable values of 16 MeV and 30 MeV, and the density symmetry L is around 100 MeV. On the other hand, models that consider only linear terms lead to incompressibility Ko much higher than expected. For most parameter sets there exists a critical point （pc, δc）, where the minimum and the maximum of the equation of state are coincident and the incompressibility equals zero. This critical point depends on the excluded volume parameter r. If this parameter is larger than 0.5 fm, there is no critical point and the pure neutron matter is predicted to be bound. The maximum value for neutron star mass is 1.85M⊙, which is in agreement with the mass of the heaviest observed neutron star 4U0900-40 and corresponds to r = 0.72 fm. We also show that the light neutron star mass （1.2M⊙） is obtained for r ≌ 0.9 fro.     

等离子喷涂Al2O3/TiO2陶瓷涂层在液态石蜡润滑下的摩擦磨损性能研究

利用纳米和微米结构Al2O3/TiO2喂料制备出2种陶瓷涂层,考察了这2种涂层在液体石蜡润滑下与不锈钢球摩擦副的摩擦磨损性能,并探讨了2种涂层的磨损机理.结果表明:液态石蜡润滑能有效降低纳米Al2O3/TiO2涂层与不锈钢球摩擦副的摩擦系数和磨损率,但是对微米涂层的润滑效果不明显.纳米涂层的摩擦系数仪为微米涂层的1/3,而磨损率则降低了70倍以上.纳米涂层的磨损机制在低载荷下是轻微的黏着磨损,高载荷下则是摩擦抛光,而微米涂层的磨损机制是晶粒脆性断裂.     

环已二胺铂(Ⅱ)类配合物跨人红细胞膜动力学研究

60年代未, Rosenberg和 Van Camp首先发现了顺式二氯二氨合铂 ?具有抗肿瘤活性 [1]。虽然顺铂用于抗癌药疗效很高,但它的毒副作用也较大。因此寻找高效、低毒的铂类抗癌药,进行了数千种铂配合物的合成,但目前用于临床的仅有几个。顺铂的抗癌机制已进行了大量研究。普遍认为它的靶分子是 DNA,它能抑制 DNA的合成 [2]。然而顺铂在临床上的毒副作用已经表明它作用的靶分子不仅仅是 DNA。细胞膜是铂类配合物进入细胞内的第一道屏障,因此研究不同铂类配合物与细胞膜的作用不仅对进一步认识这类抗癌药物的药理和毒性机制具有重要意义,…     

A hybrid method for bubble geometry reconstruction in two-phase microchannels

Understanding bubble dynamics is critical to the design and optimization of two-phase microchannel heat sinks. This paper presents a hybrid experimental and computational methodology that reconstructs the three-dimensional bubble geometry, as well as provides other critical information associated with nucleating bubbles in microchannels. Rectangular cross-section silicon microchannels with hydraulic diameters less than 200 μm were fabricated with integrated heaters for the flow experiments, and the working liquid used was water. Bubbles formed via heterogeneous nucleation and were observed to grow from the silicon side walls of the channels. Two-dimensional images and two-component liquid velocity field measurements during bubble growth were obtained using micron-resolution particle image velocimetry (μPIV). These measurements were combined with iterative three-dimensional numerical simulations using finite element software, FEMLAB. The three-dimensional shape and location of the bubble were quantified by identifying the geometry that provided the best match between the computed flow field and the μPIV data. The reconstructed flow field through this process reproduced the experimental data within an error of 10–20%. Other important information such as contact angles and bubble growth rates can also be estimated from this methodology. This work is an important step toward understanding the physical mechanisms behind bubble growth and departure.