6β-Acetoxy-7 α-Hydroxyroyleanone,A New Compound from Taiwania Cryptomerioides Hayata

Two crystalline compounds from the bark of Taiwania cryptomerioides Hayata were isolated. One of them was identified as 6,7-dehydroroyleanone and the other was shown to be a new derivative of royleanone having a structure of 6β-acetoxy-7α-hydroxyroyleanone.     

Electron Paramagnetic Resonance Study of Radical Pairs and Isolated Radicals Trapped in Irradiated Long-Chain Hydrocarbons at Low Temperatures

The intrinsic characteristics of radical pairs produced in squalane and in cetane receiving high gamma-dose are extensively studied with the EPR technique at temperatures from 77°K up to 150°K. The spectra of the paired radicals occur at g=4 with a very low transition probability in contrast to that of isolated radicals which appear at g=2 A well-resolved hyperfine spectrum corresponding to the species (CH₃CH₂.CH₂CH₃) is observed in cetane. The isothermal decay rates of radical pairs in cetane below 100°K are significantly slow; however, the decay kinetics at 150°K is first order with rate constant=1.86 min^?1. A relatively slower decay rate is obtained for isolated radicals suggesting that the decay mechanism of paired radicals is through geminate recombination. The relative inter-radical distance in radical pairs is known from a decay curve as a function of temperature. The yields of radical pairs are low in both matrices, only few percents of those of isolated radicals. The formation mechanisms of paired radicals with direct radiolytic bond scission process are discussed in connection with the experimental observations.     

Kinetics of polyesterification: Adipic acid with ethylene glycol, 1,4-butanediol,and 1,6-hexanediol

Polyesterifications of adipic acid with ethylene glycol, 1,4-butanediol, and 1,6-hexanediol in the absence and presence of the foreign acid (p-toluene sulfonic acid) as catalyst were carried out under constant reaction temperatures of 140–180°C (rather than at constant oil-bath temperatures) and at ratios of diol to diacid of 0.9867–3.5880. The experimental data fit the rate equations proposed by Chen and Wu: d(RCOOR′)/dt = k_ae^αp(RCOOH)²(R′OH) – k_h(H₂O)(RCOOR′) and d(RCOOR′)/dt = k_ac(AH)e^αp(RCOOH)(RO′H) – k_h(H₂O)(RCOOR′) for self-catalyzed and acid-catalyzed reactions, respectively; the data did not fit the other equations appearing in the literature. Here p is the conversion of acid, and α is the constant related to dielectric constants. The reaction rate constants and activation energies for self-catalyzed and acid-catalyzed reactions are calculated. The activation energy is found to decrease with chain length of the alkyl group of the diol. This result is consistent with that observed by Brauman and Blair using ion cyclotron resonance spectroscopy for the variation of acidity of alcohols with chain length of the alkyl group.     

Numerical solution of minimax problems of optimal control,part 1

This paper contains general transformation techniques useful to convert minimax problems of optimal control into the Mayer-Bolza problem of the calculus of variations [Problem (P)]. We consider two types of minimax problems: minimax problems of Type (Q), in which the minimax function depends on the state and does not depend on the control; and minimax problems of Type (R), in which the minimax function depends on both the state and the control. Both Problem (Q) and Problem (R) can be reduced to Problem (P).For Problem (Q), we exploit the analogy with a bounded-state problem in combination with a transformation of the Jacobson type. This requires the proper augmentation of the state vectorx(t), the control vectoru(t), and the parameter vector , as well as the proper augmentation of the constraining relations. As a result of the transformation, the unknown minimax value of the performance index becomes a component of the parameter vector being optimized.For Problem (R), we exploit the analogy with a bounded-control problem in combination with a transformation of the Valentine type. This requires the proper augmentation of the control vectoru(t) and the parameter vector , as well as the proper augmentation of the constraining relations. As a result of the transformation, the unknown minimax value of the performance index becomes a component of the parameter vector being optimized.In a subsequent paper (Part 2), the transformation techniques presented here are employed in conjunction with the sequential gradient-restoration algorithm for solving optimal control problems on a digital computer; both the single-subarc approach and the multiple-subarc approach are discussed.This research was supported by the National Science Foundation, Grant No. ENG-79-18667, and by Wright-Patterson Air Force Base, Contract No. F33615-80-C3000. This paper is a condensation of the investigations reported in Refs. 1–7. The authors are indebted to E. M. Coker and E. M. Sims for analytical and computational assistance.     

应力对La0.83Sr0.17MnO3薄膜输运性能的影响

采用溶胶-凝胶方法在Si(111)上制备了LSMO(x=0.17)薄膜.研究了块体材料和不同厚度薄膜R -T曲线、红外光谱和X射线衍射.结果表明，LSMO薄膜属于正交晶体结构，薄膜取向与膜厚度 有关，当膜厚度为450nm或680nm时，主要取向〈200〉，而膜厚度为900nm时取向为〈020〉 ：根据离子对相互作用能和谐振子模型，得到了红外吸收与Mn—O—Mn键长和键角关系式，6 00cm^-1附近红外吸收与晶格常数b的变化有关；块体与薄膜的金属—绝缘体转变 温度(T_MI)存在较大差别，薄膜转变温度显著低于块体，并与厚度有一定关系. 认为是LSMO薄膜中的应力诱导了晶格常数变化，引起键角改变及JT效应是转变温度变化的主 要原因. 关键词： 单晶硅 晶格常数 金属—绝缘体转变温度 应力诱导