Thermal decomposition kinetics of titanium hydride and Al alloy melt foaming process

Metal foams, now one of research foci, are a newclass of materials with low densities and novel physi-cal, mechanical, thermal, electrical and acoustic prop-erties[1—8]. Demands from high-tech make Al alloyfoam, which has much higher specific strength than ofpure Al foam, the new development focus[9—11]. Melt foaming process is one of the approaches tofabricate Al foam and Al alloy foam and their porestructure (pore diameter and porosity) has close rela-tionship with the thermal decompo…     

电子计算机在高聚物相分析中的应用

<正> 前言高聚物的物理化学性能与其组成和相态有密切的关系,因此在高聚物特别是高分子复合材料的生产和研究中经常需要进行组分和相态的分析。本文用电子计算机对高聚物的X射线衍射图谱进行分解,建立了一种定量分析高分子复合材料的相态和组成的方法,同时可得到结晶度和晶区宽度等超分子结构参数。     

Studies on the Total Synthesis of Hainanolide (VII) - Analysis of the Relative Stereochemistry of key Intermediate 2

The natural product, hainanolide 1, also under the name harringtonolide2 demonstrated antitumor and antiviral activities in preliminary test. Its structure was determined by X-ray diffraction. The total synthesis of 1 was reported recently by Mander3. A different scheme of its synthesis has been studied in our laboratory4. Here the determination of the stereochemical structure of the key intermediate 2 in the synthesis was reported. HMBC and HMQC spectra identified the skeleton and H,…     

Nanjiols D and E, Two New Uncommon Steroids from the Chinese Soft Coral Nephthea bayeri

Marine organisms have been found to be a storehouse of steroids, particularly in term ofunique side-chain structures and unusual functionalization. Marine steroids are oftenfound in highly oxygenated forms and possessing various biological activities1.Previously, we reported the isolation and structural elucidation of three new marinesteroids, nanjiols A-C, which showed cytotoxicity against HL-60 and BEL 7402 celllines, from a soft coral Nephthea bayeri in East China Sea2. In continuation …     

聚硅氧烷聚脲多嵌段共聚物中氢键的研究

采用多种手段研究了聚硅氧烷与聚脲嵌段共聚物中所存在的各类氢键．特别探讨在聚硅氧烷软段中引入极性氰丙基对体系成氢键能力的影响和两相间相互作用力的情况结果表明，在软段分子中引入极性氰丙基有利于增加聚硅氧烷分子与聚脲链段的相互作用，这一相间作用力使两相间界面层厚度随着硬段分子量的增加而加宽，并发现在聚硅氧烷聚脲嵌段共聚物中硬段的聚集形态随溶液浓度改变变化不大，其中氢键随着温度升高而下降．     

Structural Features of a Polysaccharide from Centella asiatica

Centella asiatica has been used as remedy for sodation, stabilization and against lepra, anabrosis1 in the oriental countries. The low-molecular-weight constituents in Centella asiatica have been investigated1. However, no polysaccharides have been reported. 1BI was the first polysaccharide isolated from C. asiatica, which had immunostimulating activity in vitro. In present study, we report the structural features of 1BI. Experimental Extraction, isolation and purification Dried C.…     

对MDTA中测样品热容量的准恒温法的评述

对用调制差热分析（ＭＤＴＡ）准恒温法测样品热容量的情形进行了讨论。通过结合最基本的热传导定律和ＭＤＴＡ模型，指出了目前国际上测量样品热容量的准恒温法只能得到在所测温度范围内的物质热容量平均值，调制温度的幅度越大或调制频率越高，所得到的热容量数据越平滑。在所测温度范围内样品热容量基本不变时，用ＭＤＴＡ准恒温法较好；但当样品热容量在所测温度范围内有明显变化时，用传统差热分析法（ＤＴＡ）更好一些。     

First Total Synthesis of (±)-Aiphanol

Aiphanol was isolated from the seeds of Aiphanes aculeate Willd. (Arecaceae) collected in Peru and was reported to exhibit significant inhibitory activities against cyclooxyge- nases-1 and -2. The structure of aiphanol was elucidated by spectroscopic methods as an unprecedented stilbenolignan skeleton in which a stilbene moiety is linked to a phenylpropane unit through a dioxane bridge1. In our previous works the synthetic approach to 1,4-benzodioxane lignans were achieved2. Since aiphanol…     

NO2气相硝化金刚烷的计算研究

运用密度泛函理论(DFT)和半经验MO-PM3方法研究了NO₂气相硝化金刚烷反应机理. 计算结果表明, NO₂不能直接取代金刚烷H; 在B3LYP/6-311＋＋G(3df,2pd)//B3LYP/6-31G* 较高水平下, 对三个可能机理的反应势垒(E_a)的精确计算表明, 该反应的决速步骤为NO₂中O和N进攻1-H的竞争过程, 且1-硝基金刚烷为主要产物. NO₂中O进攻1-H决速反应过程中, 分子几何、原子自然电荷及IR光谱变化表明, C—H键的断裂和N—H键的形成是一个协同过程; 参与新键形成和旧键断裂原子C(1), H(11), O(28), O(29)和N(27)的原子自然电荷及与其相关的键长、键角有明显的变化. 反应过程中体系偶极矩的变化表明, 极性溶剂能降低反应势垒, 有利于反应的进行.     

新型大分子席夫碱配合物的合成和表征

本文用胺基封端聚四氢呋喃(Mn=862)与水杨醛反应，生成新型席夫碱遥爪配体，再与金属离子(Fe³⁺, Co²⁺, Cu²⁺)反应，得到新型大分子席夫碱配合物。用IR、ESR、UV、循环伏安法、拉伸和动态粘弹谱等表征手段对配合物进行了研究。证明所得配合物的配位结构与血红蛋白分子的功能片段的配位结构相似，钴配合物具有与血红蛋白分子相近的可逆化学吸附功能。