Mechanism of lamellar spacing adjustment in directionally frozen agar gels

A theory is presented for predicting the size of ice crystals which result from steady-state, unidirectional growth within aqueous agar gels. Cellular arrays of adjacent ice crystals were separated by an amorphous water-agar membrane at a composition near the vitrification point. Using this vitrification composition and both a steady-state condition and a minimum free energy criterion, the size of ice crystals was predicted for a given solidification velocity and diffusion condition. It was found, however, that this simple model could not predict the trend towards larger crystal sizes that was observed when the initial agar concentration in the gels increased from 3% to 10% by weight agar.     

Facile Total Synthesis of (±)‐Nimbiol

A facile total synthesis of (±)‐nimbiol 1 has been achieved. In order to decrease the dioxo byproduct 2a , an improved oxidation system of CrO₃/H₂O/HOAc/NaOAc was used.     

Studies on Chemical Constituents of Polygonum Ciliinerve Ohwi

Three new apianen lactones Maomailiaoine I ( 1 ), Maomailiaoine II ( 2 ) and Maoimaliaoine III ( 3 ), together with one known apianen lactone, five known flavonoids and three other known compounds were isolated from Polgonum ciliinerve Ohwi. Their structures were deduced from spectroscopic methods and 2D NMR techniques.     

亲脂类分子增溶剂单2－氧一（2一羟基丙基）一β一环糊精（单2一HP一β一CD）的制备及其NMR表征

文中就亲脂类分子增溶剂单２－ＨＰ－β－ＣＤ的合成作了研究，产率从文献报道的５％提高到２８％。文中还给出了产物的ＮＭＲ数据。     

Interference by neutron induced second order nuclear reaction in activation analysis of platinum group elements after a nickel sulphide fire assay preconcentration

In determining the trace platinum group elements and gold in rocks and ores by the neutron activation analysis after a nickel sulphide fire assay preconcentration, there are interferences due to nuclides produced from second order nuclear reactions. This paper presents the degree of interference calculated over the ranges of long irradiation times and of reactor neutron flux from 1·10¹³ to 1·10¹⁵ n·cm^–2·s^–1. According to the results of these calculations, every one of the second order interfering reactions on the PGE+Au, except the¹⁹⁷Au(n, )¹⁹⁸Au(n, )¹⁹⁹Au reaction, can be neglected under the long irradiation time or high reactor neutron flux. Special attention is given to the interference from gold in the determining platinum.     

Synthesis and Characterization of Novel Organosoluble Methyl Substituted Poly(aryl Ether Ketone)s Containing Sulfone Linkage

Several new methyl substituted poly(aryl ether ketone)s containing sulfone linkage with inherent viscosities of 0.62–0.84 dL/g have been prepared from 4,4′‐bis(2‐methylphenoxy)diphenylsulfone and 4,4′‐bis(3‐methylphenoxy)diphenylsulfone with terephthaloyl chloride and isophthaloyl chloride by electrophilic Friedel‐Crafts acylation in the presence of DMF with anhydrous AlCl₃ as a catalyst in 1,2‐dichloroethane, respectively. These polymers having weight‐average molecular weight in the range of 71,000–49,000 are all amorphous and show high glass transition temperatures ranging from 167 °C to 191 °C, excellent thermal stability at temperatures over 400 °C in air or nitrogen, high char yields of 51–58% in nitrogen and good solubility in CHCl₃ and polar solvents such as DMF, DMSO and NMP at room temperature.     

阴阳离子型表面活性剂双水相萃取色氨酸衍生物和牛血清白蛋白

溴化十二烷基三乙胺（Ｃ１２ＮＥ）和十二烷基硫酸钠（ＳＤＳ）在一定条件下混合可以形成具有清晰界面的两个水相，称为阴阳离子型表面活性剂双水相。作者研究了利用该双水相萃取３种色氨酸衍生物和牛血清白蛋白的可能性．文中采用工作曲线校正扣除表面活性剂背景的影响，萃取结果准确可信。     

Design of Supramolecular Cyclodextrin Complex Sensors for Ion and Molecule Recognition in Water

The design and function of novel supramolecular fluoroionophore/cyclodextrin (CyD) complex sensors for ion and molecule recognition in water are reviewed. For the crown ether fluoroionophore/-CyD complex, the dimerization of the fluoroionophore inside the -CyD is found to be selectively promoted by alkali metal ion binding, thereby resulting in metal-ion-selective pyrene dimer emission in water. This supramolecular function is successfully utilized in the design of a podand fluoroionophore/-CyD complex for sensing toxic lead ion in water. The boronic acid fluoroionophore/-CyD complex binds sugars and produces increased fluorescence emission in water. The response mechanism appears to be due to the suppression of the photoinduced electron transfer (PET) from pyrene donor to trigonal phenylboronic acid acceptor. This is a novel emission function provided by the boronic acid fluoroionophore/-CyD complex sensors in water.     

Synthesis of a new PET/layered niobate hybrid material

A new organic/inorganic hybrid material was prepared by the polymerization of bis(hydroxyethyl) terephthalate (BHET) with a layered niobate compound, H₄Nb₆O₁₇, modified by 11-aminoundecanoic acid (AUA). The hybrid polymer films of BHET with H₄Nb₆O₁₇/AUA exhibited favorable characteristics, particularly of being optically clear, indicating the exfoliation and homogeneous dispersion of H₄Nb₆O₁₇ into the PET/niobate hybrid.     

Theory of helicenic hydrocarbons. Part 1: Invariants and symmetry

Helicenes form a subclass of polyhexes and correspond to hydrocarbons of considerable chemical interest. This paper is the first part of a general graph-theoretical treatment of helicenes. The invariants are studied: the relations between them, their possible values, and their upper and lower bounds in helicenes. Extremal helicenes and circular helicenes are useful definitions of subclasses of the systems under consideration. Finally an account of symmetry of helicenes is given.On leave from: Department of Mathematics, Xinjiang University, Wulumuqi Xinjiang 830046, People's Republic of China.