Studies on solid state reactions of coordination compounds. LXIII. Solid state synthesis of a series of tetranuclear Mo(W)—Ag mixed-metal clusters. Crystal structures of [(n-Bu)4N]3[MoOS3Ag3Br4] and [(n-Bu)4N]3[WS4Ag3Cl4]

A series of tetranuclear Mo(W)-Ag mixed-metal clusters have been synthesized by making use of the solid state reactions of [NH₄]₂[MYS₃](M= Mo, W; Y= O, S), AgX(X= Cl, Br, I) and (n-Bu)₄NX' (X' =Cl, Br), two of which [(n-Bu)₄N]₃[MoOS₃Ag₃Br₄] (1) and [(n-Bu)₄N]₃[WS₄Ag₃Cl₄] ( 2 ) have been structurally characterized by X-ray analysis. The crystal data: 1 , cubic, P4 3m, αequals;12.093(4) Å, Z=1, R =0.076; 2 , cubic, P4 3m, αequals;12.059(2) Å, Z =1, R =0.075. The cluster anion core [Ag₃MS₃X'] of the two compounds can be viewed as a cube in which the four metal atoms and the four non-metal atoms are statistically distributed, respectively. Substitution reaction with PPh₃ ligand is also discussed for this type of tetranuclear clusters.     

Multivariate classification based on metal contents in human senile cataract lenses

Multivariate classification methods were used to evaluate data on the concentrations of eight metals in human senile lenses measured by atomic absorption spectrometry. Principal components analysis and hierarchical clustering separated senile cataract lenses, nuclei from cataract lenses, and normal lenses into three classes on the basis of the eight elements. Stepwise discriminant analysis was applied to give discriminant functions with five selected variables. Results provided by the linear learning machine method were also satisfactory; the k-nearest neighbour method was less useful.     

Determination of tripolyphosphate in frozen cod and scallop adductor by ion chromatography

We introduce a method for the determination of tripolyphosphate in frozen cod and scallop adductor by using ion chromatography. The tripolyphosphate was extracted from minced cod and scallop adductor with deionized water by ultrasonic leaching, and then the proteins soluble in water were precipitated with trichloroacetic acid and removed by filtering. An ion chromatograph with an ionpac AS11-HC anion-exchange column, an ASRS (Anion Self Regenerating Suppression), a conductivity detector and a gradient pump (sodium hydroxide gradient) was used. The detection limit was below 5 mg tripolyphosphate/kg cod or scallop adductor. This method is applicable to the determination of polyphosphates in aquatic products and the procedures are easy to implement.     

Solid state synthesis of copper(I) thiotungstate cluster compounds at low heating temperatures. Crystal structures of [(n-Bu)4N]3-[WS4Cu3Cl3Br] and [Et4N]4[WS4Cu4I6]

Summary Reaction of [NH₄]₂[WS₄] with CuX (X = Cl or I) and R₄NX (R = Et or n-Bu) in the solid state gave two new bimetallic compounds with W:Cu compositions from 1:3 to 1:4. Compound (1), [(n-Bu)₄N]₃[WS₄Cu₃Cl₃Br], crystallizes in the hexagonal space group R3c with a = 17.051(5), c = 38.372(5) Å, V = 9661.8 ų, Z = 6. The cluster anion of (1) comprises a cubane-like cluster core [WS₃Cu₃Br] of C₃ symmetry with a Cl atom attached to each of the three Cu atoms and one terminal sulphido ligand attached to the W atom. Compound (2), [Et₄N]₄[WS₄Cu₄I₆], crystallizes in the monoclinic space group C2/m with a = 29.702(6), b = 12.7887(5), c = 15.327(3)Å, = 99.69(2), V = 5738.1 ų, Z = 4. In the cluster anion of (2), four edges of the WS₄ core are coordinated by four Cu atoms, giving a WS₄Cu₄ aggregate of approximate C_2V symmetry.     

Errors involved in the activation energy calculated by integral methods when the frequency factor depends on the temperature ( A = A 0 T m)

The dependence of the frequency factor on the temperature (A=A ₀ T ^m) has been examined and the errors involved in the activation energy calculated from some integral methods without considering such dependence have been estimated. Investigated integral methods are the Coats-Redfern method, the Gorbachev-Lee-Beck method, the Wanjun-Yuwen method and the Junmeng-Fusheng method. The results have shown that the error in the determination of the activation energy calculated ignoring the dependence of the frequency factor on the temperature can be rather large and it is dependent on x=E/RT and the exponent m.     

简法合成甲地孕酮

本文报道了合成甲地孕酮的简便方法,即以17α-乙酰氧基-黄体酮(3)为原料,将其烯醇醚(4)经Mannich反应,或将△~(3,5)-3,17α-二乙酰氧基-黄体酮(2)与二乙氧基甲烷反应,生成6-次甲基-17α-乙酰氧基-黄体酮(5),然后将5用钯/碳酸钙作催化剂转位得目的物甲地孕酮(6b),总收率分别为56%和50%(均以17α-羟基-黄体酮(1)为起始物)。     

用TMS—2型热机分析仪测量热释蠕变

对已经商品化的Perkin-Elmer TMS-2型热机分析仪进行改进,用来测量聚合物材料的热释蠕变行为。按照7SCr分步加载的程序,用弯曲法测量了-83～300℃温度范围内低密度聚乙烯的玻璃化转变松弛过程,并从TSCr谱上计算其相应的分子参数,实验结果与用扭转的TSCr方法所得结果相等,因此这是一种研究聚合物材料松弛行为的方便可行的技术。     

前列环素(PGI2)及其类似物的合成

本文综述了前列环素及其类似物的合成。类似物包括有7-羰基—、10,10-二氟—、5-氯—,4-羰基—、6,9-硫—、6,9-氮—,6 a-碳—前列环素以及苯前列环素等。前列环素及其类似物是一类具有抑制血小板聚集的生物活性化合物。     

聚乙二醇在高真空条件下的单链弹性

在过去二十年间，高分子的单链弹性已经得到了广泛的研究.然而由于环境和高分子之间往往有着复杂的相互作用，实验中很难得到高分子在严格无扰状态下的单链弹性（即本征弹性）.为此，利用单分子力谱技术研究了高真空条件下聚乙二醇（PEG）的单链弹性.结果表明，由于高真空条件下溶剂分子的干扰被消除，PEG在这一准无扰状态下呈现其本征弹性.在非极性有机溶剂中，由于溶剂分子和PEG之间只有微弱的范德华力作用，PEG表现出和高真空中基本一致的弹性.然而，在不同环境中，力曲线的低力区（F<100 pN）存在着细微的差异.这一现象可归因于不同条件下基底与PEG链之间的吸附力不同.采用的高真空力谱可用于研究其他高分子单链在准无扰状态下的本征弹性.     

Adsorption, desorption and activities of acid phosphatase on various colloidal particles from an Ultisol

Adsorption, desorption and activity of acid phosphatase on various soil colloidal particles and pure clay minerals were studied. Higher adsorption amounts and low percentage of desorption of acid phosphatase were found on fine soil clays (<0.2 μm). Electrostatic force and ligand exchange are the major driving forces that are involved in the adsorption of enzymes on soil clays. More enzyme molecules were adsorbed on soil clays in the presence of organic components. However, enzymes on organic clays were more easily released. One-third of the enzyme on goethite was adsorbed via ligand exchange process. Some other interactions, such as van der Waals force, hydrophobic force and hydrogen bonding may be more important in the adsorption of enzyme on kaolinite and the enzyme in this system cannot be easily removed. Coarse clays (0.2–2 μm) and inorganic soil clays had higher affinities for enzyme molecules than fine clays and organic clays, respectively. The activity of enzyme bound on soil clays was inhibited and the thermal stability was increased in the presence of organic matter. Data obtained in this study are helpful for a better understanding of the interactions of enzymes with inorganic and organic constituents in soil and associated environments.