Synthesis and characterization of bismaleimide–polyurethane crosslinked copolymers

A series of novel crosslinked copolymers of bismaleimide (BMI) and polyurethanes (PU) were prepared by direct copolymerization of BMI monomer and urethane-modified bismaleimide (UBMI). The copolymers were characterized by FT-IR and solid state ¹³C-NMR. The reaction rate of the BMI monomer can be significantly increased by copolymerization with UBMI. The crosslinked copolymers show good mechanical properties and high thermal stability. Studies on glass transition temperatures and dynamic mechanical properties indicate that the copolymer is a homogeneous system as the polyester-type PU employed. The transmission electron microscopy (TEM) of the copolymer illustrated a one-phase structure of the cured resins when the polyester-type PU was incorporated. © 1995 John Wiley & Sons, Inc.     

A basic model of superconducting weak links

By using a linear superposition of gap functions and gauge invariance, we show that the Josephson effect and main features of pair dynamics in a superconducting weak link can be satisfactorily described on the basis of a simple wave function.     

Characterization of the glycosyltransferase activity of desVII: analysis of and implications for the biosynthesis of macrolide antibiotics

In vitro catalytic activity of DesVII, the glycosyltransferase involved in the biosynthesis of methymycin, neomethymycin, narbomycin, and pikromycin in Streptomyces venezuelae, is described. This is the first report of demonstrated in vitro activity of a glycosyltransferase involved in the biosynthesis of macrolide antibiotics. DesVII is unique among glycosyltransferases in that it requires an additional protein component, DesVIII, as well as basic pH for its full activity.     

Analytical ion cyclotron resonance spectrometry. Spectereochemical factors and a functional group interaction in some norbornyl systems

Ion cyclotron resonance results show that the rate of the acetylation of endo-bicyclo-[2.2.1]hept-5-en-2-ol by [(CH₃CO)₃]⁺ in the gas phase is similar to that of its exo-isomer and greater than that of endo-norborneol by the same ion. This suggests that steric interference of the 6-endo hydrogen is removed by making it vinylic. Additionally, the acetates of the isomeric norborneols and of exo- and endo-bicyclo[2.2.1]hept-5-en-2-ol have relative rates 1.0, 0.9, 1.1 and 0.5; these figures may be interpreted to indicate that acetylation may occur on the carbonyl oxygen here and that in the last compound the carbonyl function is protected by interaction with the olefinic bond.     

5-苯基-2-(5′-苯基噁唑基-2′)-1,3,4-噁二唑及其5-对位取代苯基衍生物的研究

合成了12个未知的5-苯基-2-(5′-苯基噁唑基-2′)-1,3,4-噁二唑及其5-对位取代苯基衍生物,讨论了化合物的结构与紫外光谱、荧光光谱和激光转换效率间的关系,以及两个化合物在11种溶剂中电子光谱的溶剂效应。     

Mössbauer effect study of some new intraligand substituted (dithiocyanato) bis (n-r-2-pyridinaldimine) iron (II)

A new series of spin-crossover octahedral Fe(II) complexes with the composition Fe (II) (N-R-2-pyridinaldimine)₂(NCS)₂, where, R=phenyl, naphthalenyl,cyclohexyl, anthracenyl, pyrenyl, 1,2,3,4-tetrahydro-1-naphthalenyl, 5,6,7,8,-tetrahedro-1-naphthalenyl, benzyl, 1-phenylethyl, 1-phenylpropyl, have been synthesized and their spin states of iron atom have been studied by means of Mssbauer spectrscopy.