大学无机化学实验课程内容的优化

对大学无机化学实验的编排顺序进行调整,使无机化学实验和无机化学理论课程衔接更加紧密。另外,从3个方面对实验课程的内容进行优化：删减无机化学实验课本中的陈旧内容,增添前沿领域实验;补充设计研究型实验,培养学生的创新精神;引入现代化手段,实现实验课程教学信息化。     

金属有机物气相外延生长InAIGaN薄膜及其性能表征

在不同的生长温度和载气的条件下，采用低压金属有机物气相外延方法生长了系列的InAlGaN薄膜，通过能量色散谱(EDS)，高分辨X射线衍射(mixRD)和光致发光谱(PL)对样品进行表征与分析，研究了生长工艺对InAlGaN外延层结构和光学性能的影响。发现当以氮气做载气时，样品的发光很弱并且在550nto附近存在一个很宽的深能级发光峰；当采用氮气和氢气的混合气做载气时，样品中的深能级发光峰消失且发光强度明显提高。以混合气做载气，InAlGaN薄膜中铟的组分随生长温度的升高而降低，而薄膜的结构和光学性能却提高。结合PL和HRXRD的测试结果得到了较佳的生长参数：即载气为氢气和氮气的混合气以及生长温度在850℃到870℃。     

Structural Insight into the Binding of Hypoxanthine with Purine Nucleoside Phosphorylase from Streptococcus mutants

Purine nucleoside phosphorylase is a key enzyme in the purine-salvage pathway and an attractive target for drug design. The crystal structure of Streptococcus mutants purine nucleoside phosphorylase(Smu PNP) has been solved by molecular replacement at 1.80  resolution and refined to R factors of 19.9%/23.7%(Rcryst/Rfree) . Sequence alignment and structural comparison show that Smu PNP has more similarity with PNPs isolated from human and malarial sources than the bacterial PNPs. The structure complexed with hypoxanthine(HPA) and sulfate ion was solved at 2.24  resolution and refined to R factors of 21.6%/24.1%(Rcryst/Rfree) . It is interesting to note that the resulting electron density indicated the product,HPA,presents in the active site although inosine was included in the crystallization mixture with Smu PNP. Asn233 and Glu191 are the important residues for ligand binding and recognition. Comparison with PNPs from different species gives detailed information about binding of small molecules on the active site,which is important for the studies of enzymatic mechanism and rational design of specific inhibitors for PNPs.     

＂Final all possible steps＂ approach for accelerating stochastic simulation of coupled chemical reactions

In this paper, we develop a modified accelerated stochastic simulation method for chemically reacting systems, called the ＂final all possible steps＂ （FAPS） method, which obtains the reliable statistics of all species in any time during the time course with fewer simulation times. Moreover, the FAPS method can be incorporated into the leap methods, which makes the simulation of larger systems more efficient. Numerical results indicate that the proposed methods can be applied to a wide range of chemically reacting systems with a high-precision level and obtain a significant improvement on efficiency over the existing methods.     

人体-结构系统的水平振动实验

针对静止状态人对结构水平振动特性的影响,建立实验平台,分别测试并分析了质量块-结构系统、单人-结构系统、多人-结构系统水平自振频率与阻尼比变化规律.给出了两种人-结构系统静态水平耦合模型的比较分析以及人体的水平振动频率估计.结果表明：在分析静止状态下人对结构水平振动特性的影响时,人体不可简单作为质量块或质量-弹簧-阻尼系统,而应看作带人体刚性质量的质量-弹簧-阻尼系统.结合实验测试数据和人-结构系统水平耦合模型,得到人体水平前后向频率范围为0.236~3.748 Hz,人体水平左右向频率范围为0.194~5.32 Hz.     

转糖苷法合成烷基糖苷

用转糖苷法合成了新型表面活性剂——烷基糖苷。对影响得率的因素如反应物配比、催化剂量、反应时间和温度分别进行了讨论。实验结果用非线性回归的方法得到数学模型,求解非线性规划得到反应的最佳条件:葡萄糖、正丁醇、十二醇、催化剂的摩尔比为1720.008,反应温度为120,反应时间为1 h。测定了不同浓度下溶液的表面张力,得到其临界胶束质量浓度为0.006%。实验证明,烷基糖苷具有较好的泡沫力和泡沫稳定性。     

Verwey相变处Fe3O4的结构、磁性和电输运特性

作为典型的金属–绝缘体转变,Fe3O4的Verwey相变蕴涵的丰富物理现象与微观机制,因而受到了人们的广泛关注.在Verwey相变处,Fe3O4的晶体结构、电子结构以及磁各向异性等均发生转变,但其磁基态并未发生改变.与其他强关联体系相比,Fe3O4的Verwey相变不需要考虑磁交换耦合作用的变化,有利于揭示强关联体系中金属–绝缘体转变的物理本质.本文从晶体结构、电荷有序、电输运特性、磁性和铁电特性等方面简要地介绍了Fe3O4的Verwey相变的研究历史和现状.     

Photoluminescence Investigation of Two-Dimensional Electron Gas in an Undoped AlxGa1-xN／GaN Heterostructure

Low-temperature photoluminescence measurement is performed on an undoped AlxGa1-xN/GaN heterostructure. Temperature-dependent Hall mobility confirms the formation of two-dimensional electron gas (2DEG) near the heterointerface. A weak photoluminescence (PL) peak with the energy of - 79meV lower than the free exciton (FE) emission of bulk GaN is related to the radiative recombination between electrons confined in the triangular well and the holes near the fiat-band region of GaN. Its identification is supported by the solution of coupled one-dimensional Poisson and Schr6dinger equations. When the temperature increases, the red shift of the 2DEG related emission peak is slower than that of the FE peak. The enhanced screening effect coming from the increasing 2DEG concentration and the varying electron distribution at two lowest subbands as a function of temperature account for such behaviour.