α—h—ANF及其类似物的固相合成及活性研究

由计算机辅助设计.以Fmoc-AA-Pfp为单体,用固相法合成了a-h-ANF及其两种类似物,产率较高.兔心血管收缩试验表明,两种类似物的血管舒张活性均高于a-h-ANF.     

基于三氰基铁(Ⅲ)酸盐的FeⅢ4NiⅡ2六核配合物的合成、结构及磁性

利用三氰基铁酸盐(Bu₄N)[Fe^Ⅲ(Tp)(CN)₃](Tp=氢化三(1-吡唑基)硼酸)与配体2,9-二吡唑基-1,10-菲咯啉(dpzpen)以及高氯酸镍反应合成了一例氰根桥联的Fe^Ⅲ₄Ni^Ⅱ₂六核配合物[Fe₄Ni₂(Tp)₄(CN)₁₂(dpzpen)₂]·12H₂O·3CH₃OH(1)。结构研究表明配合物1具有近似菱形的Fe^Ⅲ₂Ni^Ⅱ₂骨架结构,另外2个Fe(Ⅲ)则通过氰根延伸在菱形的外侧。磁性研究表明在配合物1中氰根桥联的Fe(Ⅲ)和Ni(Ⅱ)表现出铁磁相互作用。更为重要的是,基于配合物1的结构模型,对它的变温磁化率数据进行拟合得到了不同Fe(Ⅲ)-Ni(Ⅱ)之间的磁耦合常数,得到的最佳磁耦合常数J_3d (15.73 cm^-1)>J_2d (3.53 cm^-1)≈J_1d (3.50 cm^-1)与Ni—N键的键长以及Ni—N≡C键角的变化趋势有关(J_3d： 0.206 5 nm,169.8°; J_2d： 0.206 2 nm,163.1°; J_1d： 0.198 7 nm,161.6°)。以上结果表明Ni—N键长越短,Ni—N≡C键角越大,Fe(Ⅲ)与Ni(Ⅱ)之间的铁磁耦合越强。     

单丝及多丝Z箍缩的X射线背光成像

基于X箍缩软X射线辐射点源对单丝及多丝Z箍缩发展过程进行了背光成像研究,实验平台为清华大学电机系研制的脉冲功率装置PPG-Ⅰ（500 kV/400 kA/100 ns）。成像光路安排为：作为X射线源的X箍缩和作为目标物的单丝或多丝（双丝）Z箍缩分别安装在装置的输出主电极阴阳极之间或回流导电杆处,成像胶片采用高分辨力、高灵敏度的X射线胶片。利用自行设计的电流传感器和罗氏线圈对目标物实际流过的电流进行监测。为了测定目标物金属细丝的质量消融率,设计了m级厚度的阶梯光楔。通过大量成像实验,获取了Z箍缩等离子体融合、先驱等离子体形成及不稳定性发展等过程的相关物理图像以及质量消融率、丝芯膨胀率等重要定量参数。     

Determining the resistance of X-pinch plasma

The current and the voltage of an X-pinch were measured. The inductance of the X-pinch was assumed to be a constant and estimated by the calculation of the magnetic field based on the well-known Biot-Savart's Law. The voltage of the inductance was calculated with L · di/dt and subtracted from the measured voltage of the X-pinch. Then, the resistance of the X-pinch was determined and the following results were obtained. At the start of the current flow the resistance of the exploding wires is several tens of Ohms, one order of magnitude, higher than the metallic resistance of the wires at room temperature, and then it falls quickly to about 1 , which reflects the physical processes occurring in the electrically exploding wires, i.e., a current transition from the highly resistive wire core to the highly conductive plasma. It was shown that the inductive contribution to the voltage of the X-pinch is less than the resistive contribution. For the wires we used, the wires' material and diameter have no strong influence on the resistance of the X-pinch, which may be explained by the fact that the current flows through the plasma rather than through the metallic wire itself. As a result, the current is almost equally divided between two parallel X-pinches even though the diameter and material of the wires used for these two X-pinches are significantly different.     

Rotational viscosity of a liquid crystal mixture: a fully atomistic molecular dynamics study

Fully atomistic molecular dynamics (MD) simulations at 293, 303 and 313~K have been performed for the four-component liquid crystal mixture, E7, using the software package Material Studio. Order parameters and orientational time correlation functions (TCFs) were calculated from MD trajectories. The rotational viscosity coefficients (RVCs) of the mixture were calculated using the Nemtsov--Zakharov and Fialkowski methods based on statistical-mechanical approaches. Temperature dependences of RVC and density were discussed in detail. Reasonable agreement between the simulated and experimental values was found.     

声学反问题的整体唯一性

It is proved that a sound-soft scatterer in R^N （N = 2, 3） is uniquely determined by a finite number of acoustic far-field measurements. The admissible scatterer possibly consists of finitely many solid obstacles and subsets of （N - 1）- dimensional hyperplanes.     

美式回望期权定价问题的有限体积法

随着金融市场的不断发展, 期权作为一种能够规避风险的金融衍生产品越来越引起投资者的青睐, 成交量呈逐年上升的趋势, 期权定价问题已经成为金融数学领域中一个重要的研究课题. 本文主要研究Black-Scholes模型下美式回望期权定价问题的数值解法. 美式回望期权定价问题是一个二维非线性抛物问题, 难以直接应用数值方法进行求解. 通过分析该问题的求解难点, 本文给出解决该困难的有效方法. 首先利用计价单位变换将定价问题转换为一维自由边值问题, 并采用Landau's变换将求解区域规范化; 而后针对问题的非线性特点,利用有限体积法和Newton法交替迭代求解期权价格和最佳实施边界, 并对数值解的非负性进行了分析. 最后, 通过与二叉树方法进行比较, 验证了本文方法的正确性和有效性, 为实际应用提供了理论基础.     

荧光法和液相色谱-质谱联用法测定司莫司汀导致λDNA交联率的比较研究

司莫司汀是重要的抗癌烷化剂,其抗癌机制与导致DNA股间交联有关.使用荧光法和高效液相色谱-电喷雾串联质谱联用(HPLC-ESI-MS/MS)法对司莫司汀导致的λDNA交联率进行了测定.结果表明:药物浓度为2,4,8和16mmol/L时,荧光方法测得的最大交联率分别为8.81%,11.17%,17.61%,和23.39%...     

箍缩背光照相

 利用PPG-Ⅰ脉冲功率装置（500 kV,400 kA,100 ns）驱动X箍缩负载,得到了μm量级的亚纳秒脉冲X射线辐射点源。在阴阳极轴线和回流柱上同时安装X箍缩负载,前者可作为背光照相的X射线点源;后者可作为被拍照的目标X箍缩。获得了X箍缩发展过程不同时刻的时间序列图像,在背光照相的图像中可以清晰观察到X箍缩交叉点处等离子体的外爆、箍缩以及最终的崩溃阶段。将阴阳极轴线上的X箍缩负载用Z箍缩丝阵负载代替,实现了对丝阵负载Z箍缩放电起始阶段的X射线背光照相,观察到了最初的各单丝电爆炸、等离子体膨胀及融合过程,同时观察到了双丝Z箍缩发展过程中的等离子体不稳定性。实验结果有助于深入理解Z箍缩发展的物理过程,同时可为有效的模拟建模分析提供基本的实验数据。