核因子κB活性抑制剂定量构效关系

用量子化学密度泛函及分子力学方法,计算了一系列喹唑啉衍生物分子的电子结构、几何结构及分子性质(广义结构)的各种参数,用以探讨该类药物分子的结构与对核因子抑制活性的关系.通过逐步回归分析,筛选出主要因素,建立了定量构效关系方程.结果表明,化合物的环D上17位碳原子上的取代基X的疏水参数、环A中R1取代基上第一个原子的净电荷及该取代基的立体参数,以及环A上3位碳原子的净电荷与化合物的抑制活性紧密相关,它们是影响化合物抑制活性的主要因素.采用“leaveoneout”法进行预报检验,其交叉检验相关系数较大,表明所得的模型有较强的预报能力.方程入选的都是可计算参数,这有利于计算机辅助该类NFκB活性抑制剂的分子设计.     

Studies on the QSAR of ACE Inhibitory Tripeptides with Proline as C-Terminal and Determination Inhibitory Activities

A database of 38 tripeptides with C-terminal proline was constructed to study QSAR of ACE inhibitory peptides. The model was established using PLS based on the three z-scores of 20 coded amino acids. The prediction ability of tripeptides model was improved with proline as terminal. The coefficient of determination(R2) and the cross validated coefficient(Q2LOO) of the model are 0.856 and 0.782 respectively. According to the model, two potential ACE inhibitory tripeptides IIP and IVP were synthesized. Their IC50(inhibitor concentration that reduced enzyme activity by 50%) were proved to be 1.58 and 1.39 μM respectively by direct spectrophotometric measurement, and they are very close to the predicted value by the model.     

Analysis of two-torus in a new four-dimensional autonomous system

In this paper, we report the dynamical behaviours of a four-dimensional autonomous continuous dissipative system analysed when the parameter is varied in the range we are interested in. The system changes its dynamical modes between periodic motion and quasiperiodic motion. Furthermore, the existence of two-torus is investigated numerically by means of Lyapunov exponents. By taking advantage of phase portraits and Poincar\'{e} sections, two types of the two-torus are observed and proved to have the structure of ring torus and horn torus, both of which are known to be the standard tori.     

Structures and Hydrogen Bonding Interactions in Urea-water System Studied by All-atom MD Simulation and Chemical Shifts in NMR Spectrum

采用分子动力学模拟方法结合核磁共振化学位移和粘度对尿素水溶液在稀浓度范围内的结构和弱相互作用进行研究. 从径向分布函数(RDF)分析看出,尿素水溶液中存在着几种不同类型、不同氢键形成能力的传统氢键. 氢键网络分析发现尿素水溶液体系在水富集区域,水分子倾向于自身缔合形成稳定的分子簇结构,而随着尿素浓度的逐渐增加,水的有序结构受到破坏,水分子和尿素分子发生了交叉缔合作用形成氢键,尿素分子有形成自身缔合的趋势. 分子动力学统计的平均氢键数与核磁共振化学位移和粘度数据结果进行比较,发现它们的变化趋势一致,证明了实验和理论结果有很强的可靠性.     

30.4 nm波长处Mg基多层膜反射镜

太阳光谱中重要的He-Ⅱ谱线(波长30.4 nm)的观测对于研究太阳活动和日地空间环境具有重要意义,实现空间极紫外太阳观测需要采用多层膜作为反射元件.研究了工作在30.4 nm的Mg基多层膜.以反射率最高为评价函数设计了多层膜,采用直流磁控溅射技术制备了SiC/Mg,B4C/Mg和C/Mg多层膜,用X射线衍射仪测量了多层膜的结构.研究表明虽然B4C/Mg多层膜理论反射率最高,但实际制备结果显示,SiC/Mg多层膜的成膜质量最好,反射率最高.同步辐射反射率测量表明:在入射角10°时实测的SiC/Mg多层膜反射率为44.6%.     

磁控溅射材料沉积速率的定标方法的研究

介绍了一种利用磁控溅射制备多层膜速率的定标方法。用高精度磁控溅射镀膜设备在同一块基片上先后镀制了两种周期的多层膜,用X射线衍射仪对其进行掠入射衍射测量,测量数据经线性拟合,可同时求得两种多层膜的周期,进而得到镀膜速率。与常用的定标方法相比,该方法不仅可以得到与常用定标方法相同的实验结果,而且提高了工作效率。     

SN8P1907微控制器在称重系统中的应用

SN8P1907是一款8位CMOS低功耗微处理器,它内置16位A/D转换模块和4 COM、12SEGMENT液晶驱动模块.文中给出了采用SN8P1907单片机设计小型称重系统的具体方法,该方法可以节省外置A/D转换器件和外部液晶驱动器件;同时具有设计程序简单等优点,因而是一种性价比很高的设计方案.     

Analysis of two-torus in a new four-dimensional autonomous system

In this paper, we report the dynamical behaviours of a four-dimenslonal autonomous continuous dissipative system analysed when the parameter is varied in the range we are interested in. The system changes its dynamical modes between periodic motion and quasiperiodic motion. Furthermore, the existence of two-torus is investigated numerically by means of Lyapunov exponents. By taking advantage of phase portraits and Poincaré sections, two types of the two-torus are observed and proved to have the structure of ring torus and horn torus, both of which are known to be the standard tori.     

整流与滤波电路的仿真实现

设计了基于Multisim的整流滤波仿真电路,避免了实际电路更换元器件的不便及潜在危险,可以更透彻地研究整流与滤波。通过搭建仿真电路并调节相关器件参数,直观呈现了整流滤波的波形,分析了整流后电压与理论值有差异的原因,并得出电容值越大滤波效果越好的结论,且电容充放电时间常数大于1秒时,输出电压达到最大值。     

铋系化合物改性的新型三元弛豫铁电体的性能研究

钛酸钡(BaTiO₃)陶瓷作为传统的介质电容器材料,其强铁电性会导致储能密度低下,但通过掺杂可以削弱铁电性来获得弛豫铁电体,提高储能性能。利用铋系化合物可增强弛豫特性,本文设计了BiScO₃和(Sr_0.7Bi_0.2)TiO₃取代改性的BaTiO₃基三元陶瓷材料: (0.99-x)Ba(Zr_0.1Ti_0.9)O₃-x(Sr_0.7Bi_0.2)TiO₃-0.01BiScO₃(缩写为BZT-xSBT-BS)。采用传统固相法制备的BZT-xSBT-BS陶瓷,相结构没有因为掺杂发生改变,在室温下均为纯的三方相钙钛矿结构。介电和铁电的测试与分析表明,BZT-xSBT-BS陶瓷具有典型的弛豫铁电特性。由于不等价离子Sr²⁺、Bi³⁺的掺杂导致界面松弛极化,可以增大BZT-xSBT-BS陶瓷的介电常数,但是受制于其慢的响应速度,陶瓷的介电损耗也显著增加。适量(Sr_0.7Bi_0.2)TiO₃可以提升BZT-xSBT-BS陶瓷的介电、铁电、应变和储能性能,x=0.015时的BZT-xSBT-BS陶瓷的综合性能较优:ε_r~10 372,tanδ~0.019,P_max=16.42 μC/cm²,E_c=1.41 kV/cm,S⁺_max=0.12%(@40 kV/cm),W_D=0.181 J/cm³,η=80.4%(@60 kV/cm)。