气相色谱研究金属中陷阱放氢速率常数和激活能

业已知道当金属中溶有氢时,在受力条件下,氢就会向金属制件的薄弱区域扩散与富集,进而萌生微裂纹,并通过与裂纹的交互作用,最后导致氢脆事故的发生,因此,关于氢致开裂物理和化学过程的研究,一直受到人们的重视。     

以共价键相连的卟啉-酞菁化合物分子内能量传递及光诱导电子转移

合成了叶啉与酞菁以共价键连接起来的双发色团分子。测定了它们的吸收光谱,荧光光谱,荧光寿命等。计算了分子内能量传递过程的效率(φ_EnT)及速率常数(κ_EnT)。结果表明:在稀溶液中,卟啉与酞菁等克分子混合时,观察不到分子间能量传递过程现象的发生;而双发色团分子的分子内能量传递过程则明显发生了,其效率(φ_EnT=13～70%)与速率常数(κ_EnT=1.2×10⁷～2.0×10⁸s^-1)取决于分子的结构类型。电子转移与能量传递过程与介质性质有关。在极性溶剂中有利于电子转移过程的进行,而不利于能量传递过程;在非极性溶剂中,则有利于能量传递过程的进行,而不利于电子转移。 选择性激发酞菁发色团,观测到了只有电子转移发生的过程,其电子转移效率达到38%。     

ENERGY STORAGE STATES OF PHOTOSYNTHETIC MEMBRANES: ACTIVATION ENERGIES AND LIFETIMES OF ELECTRONS IN THE TRAP STATES BY THERMOLUMINESCENCE METHOD

Abstract Several methods discussed by R. Chen (1969) were used for the calculation of the activation energies ( E ), frequency factors ( s ) and mean lifetimes of electrons in trap states at glow peak temperatures ( T _m) and at room temperature ( T _r) from thermoluminescence glow peaks in spinach chloroplasts and Euglena cells. Results are presented for E calculated independently, i.e. without any assumptions regarding the frequency factors which were determined subsequently using the activation energy values thus calculated. The most reliable values for E , s, r( T _m) and ( T _r) for the well-resolved glow peaks Z(118 K), I(236 K), II(261 K), III(283 K), IV(298 K) and V(321 K) are as follows:
The present comprehensive study has been compared with the earlier ones and the significance of the observed high frequency factors is discussed. It is concluded that only peaks I and II, related to photosystem II, follow the Randall–Wilkins (RW) theory, whereas peaks IV and V, related to photosystem I, do not.     

THE NATURAL PHOSPHORESCENCE LIFETIME OF BIACETYL AND BENZIL IN FLUID SOLUTION

Abstract— The quantum yields of phosphorescence and fluorescence and the phosphorescence lifetime have been determined for biacetyl in benzene, p-xylene, n-heptane, and water, and for benzil in n-heptane at 22C. The following values for the fluorescence quantum yield and natural phosphorescence lifetime were obtained: For biacetyl in benzene, 2.7 times 10^-3 and 7.8 msec, in p-xylene, 2.5 times 10^-3 and 10.8 msec, in n-heptane, 2.9 times 10^-3 and 10.8 msec, in water, 1.1 times 10^-3 and 10.0 msec, and for benzil in n-heptane, 1.1 times 10^-3 and 10.4 msec.     

分布化能模型的理论及其在半焦气化和模拟蒸馏体系中的应用

通过对分布活化能模型所做的理论分析,给出了失重过程中活化能的解析表达式,阐明了失重实验中升温速率影响失重曲线的基本原理。按照本文给出的活化能求解方法,对大同煤半焦的空气气化动力学和煤焦油馏分的模拟蒸馏过程进行了分析,得到了半焦气化过程和模拟蒸馏过程的活化能变化曲线,与常规动力学分析结果的对比表明,新的DAEM方法能够很好地应用于简单反应体系。     

ISOTOPIC DESYMMETRIZATION IN THE STUDY OF HOMOGENEOUS CATALYSIS

NMR studies on isotopically desymmetrized ligands and substrates have been used to demonstrate and investigate an apparent “memory effect” in palladium-catalysed nucleophilic substitution at allylic centres. The explanation for this “memory effect” is shown to be the participation of both monomeric and oligomeric complexes, with different reaction rates.     

热重分析测定脱附活化能分布研究

以脱附过程本征动力学模型为基础,提出了一种采用热重分析技术测定脱附活化能随吸附质分子表面覆盖率分布的方法。该方法通过一条热重分析曲线就可以得到清晰的脱附活化能关于覆盖率的函数表达式。采用所提出的方法,通过不同升温速率下的热重分析实验测定了芴和蒽在活性炭上脱附活化能的线性分布,结果表明覆盖率越高,脱附活化能越低。对芴和蒽,由于覆盖率上升,脱附活化能最大降幅达18.5%和15.1%。     

ENERGY CONVERSION IN THE DECAY OF TRIPLET LUMIFLAVIN IN THE PRESENCE OF FERRI- AND FERROCYANIDE

Abstract— Flash photolysis at 450 nm has been used to study the quenching of the excited triplet state of lumiflavin and the transient species formed in subsequent reactions in deaerated phosphate buffer (pH 6.9).
The effect of the presence of ferricyanide on the life time of triplet lumiflavin has been studied. The results suggest an energy transfer reaction without concurrent electron transfer reactions. The rate constant for the process was 2.8 times 10⁹ M ^-1 s^-1. The analogous reaction with ferrocyanide could not be observed because of the efficient electron transfer reaction (δG = -20.6 kcal mol^-1) leading to the formation of the semireduced lumiflavin and ferricyanide. The rate constant for this reaction was 3.3 times 10⁹ M ^-1 s^-1. The semireduced lumiflavin radical was found to disappear in a second order reaction with a rate constant of 1.7 times 10⁹ M ^-1 s^-1. It was found to react with ferricyanide with a rate constant of 0.7 times 10⁹ M ^-1 s^-1.
A model for the various photochemical and photophysical processes involved in the decay and quenching of the lumiflavin triplet state is suggested and discussed.     

对在乙丙共聚反应中添加活化剂时活化机理的探讨

本文研究了对-甲苯磺酰氯、偶氮苯和四氢呋喃三种添加剂。对乙丙共聚反应的活化作用,实验结果表明,偶氮苯的活化作用最显著,能提高催化效率10倍左右,对-甲苯磺酰氯提高3-6倍,四氢呋喃提高1-2倍。 本文对活化机理作了较详细的探讨,讨论了各种活化剂对聚合反应的影响、活化剂对聚合反应动力学行为的影响,并研究了活化剂与催化剂各组分之间的反应。对上述三种活化剂提出了两种可能的活化途径。对-甲苯磺酰氯和偶氮苯的作用主要是使失去活性的V²⁺氧化成有活性的V³⁺化合物,从而增加了活性中心浓度使催化效率提高。而四氢呋喃主要是使V³⁺化合物稳定而延长活性寿命来提高催化效率。最后还提出了前两种活化剂氧化V²⁺化合物可能的反应历程。     

PHOTOINDUCED GENERATION OF HYDROGEN PEROXIDE AND HYDROXYL RADICALS IN MELANINS

The hydrogen peroxide produced during photolysis of melanin pigments has been measured using an oxidase electrode. The photooxidation has been shown to occur via the superoxide intermediate. In the presence of superoxide dismutase the rate of photo-induced production of hydrogen peroxide is increased, reflecting the ability of melanin to scavenge superoxide radicals. Evidence for metal-ion dependent formation of hydroxyl radicals during photooxidation of melanin pigments was obtained using electron spin resonance-spin trapping procedures. Superoxide dismutase increased the rate of formation of hydroxyl radicals in the system. Mechanisms of metal ion-induced production of hydroxyl radicals during photolysis of melanin pigments are discussed.     

新型双发色团染料荧光光谱及其寿命的研究

有效的染料激光操作需要较高的荧光量子效率,若丹明是在500~700 nm光谱区中一类最重要的激光染料.然而,染料的基态分子和三线态对辐射能量的吸收将会大大降低激光输出效率,再者,由于若丹明类染料在紫外区的吸收系数较小,为了有效吸收泵浦能量(如用XeCI准分子激光,308 nm),就必须使用高浓度染料溶液,在这种情况下,若丹明类染料较小的Stokes位移就势必造成基态分子更大的重复吸收,即造成更大的谐振腔损耗^[1].     

PHOTOINDUCED REDUCTION OF CYTOCHROME c IN THE PRESENCE OF HYDROPEROXIDE DERIVATIVE OF BIPHENYL

Abstract The photosensitive hydroperoxide derivative of biphenyl (BPP) was synthesized by the ozonolysis of phenanthrene in methanol. When cytochrome c (cyt c ) was illuminated by UVB light in the presence of BPP (BPPUV), it was reduced both under aerobic and anaerobic conditions. The action spectrum of the reduction was consistent with that of photolytic decomposition of BPP. Both gave maximum reactions at wavelengths around 300–310 nm. Electron spin resonance studies, using 5,5-dimethyl-1-pyrroline N -oxide as a spin-trapping reagent, revealed the generation of hydroxyl radicals in the BPPUV system. Product analysis of adamantane oxidation by BPPW also suggested the generation of hydroxyl radicals rather than singlet oxygen. However, the effects of scavengers were complicated. Singlet oxygen scavengers significantly inhibit the reaction while none of the hydroxyl radical scavengers tested was effective in inhibiting the BPPUV-mediated cyt c reduction. Deuterium oxide, which extends the lifetime of singlet oxygen, inhibited rather than enhanced the reaction. Reduction of cyt c was inhibited by salts, and their activities were correlated to the electron-donating nature of the anions. These results suggest that reduction of cyt c is mediated by electron transfer from a light-induced product of BPP, rather than by free hydroxyl radicals or singlet oxygen.     

EVIDENCE FOR BRANCHING IN THE PHOTOCYCLE OF BACTERIORHODOPSIN AND CONCENTRATION CHANGES OF LATE INTERMEDIATE FORMS

Abstract— Flash photolysis transients of bacteriorhodopsin were recorded with a spectrograph -multielement photodiode array combination and the recordings were analyzed to determine the concentrations of bacteriorhodopsin intermediates "M" and "O" relative to the amount of "bR" cycling (pH 7.1,10–40°C). Estimated concentration time courses were simulated with solutions to two kinetic decay models which could account for photocycle temperature dependence. A unidirectional unbranched decay model overpredicts our estimated levels of [O(r)], whereas a model branched at the "M" intermediate describes each of the later intermediate levels well (with no evidence for an independent "N" form). Our results are consistent with "M" decay regulating the level and rates of change of [bR (t)] and (bR(f)]- and also suggest that two temperature-dependent pathways form "bR" from "M", one directly, and the other indirectly through "O".     

Pt/HM和Pd/HM催化剂表面氧的恢复与供出活化能测定

催化氧化是最重要的工业催化反应之一。七十年代以来,关于氧化催化剂的基础研究取得了长足的进步,采用各种手段对氧化催化剂的表面及体相氧种进行了考察。本文作者根据研究实用氧化催化剂的经验,结合控制论方法,亦提出了多相催化氧化反应的集团结构适应性规律。近年来,作者用TPD和吸附平衡法研究了V_2O_5/SiO_2催化剂表面氧的种类、数目和供出活性,较好地关联了催化氧化的一些事实,使以上规律更趋于半定量化。在多相氧化反应中,催化剂表面活性氧不断处于供出和恢复的循环之中,催化剂表面氧中心的供     

ACTIVATION ENERGY OF DESORPTION OF DIBENZOFURAN ON ACTIVATED CARBONS

Three kinds of commercial activated carbons, such as Norit RBI, Monolith and Chemviron activated carbons, were used as adsorbents for adsorption of dibenzofiuran. The average pore size and specific surface area of these activated carbons were measured Temperature Programmed Desorption (‘TPD) experiments were conducted to measure the TPD curves of dibenzofuran on the activated carbons, and then the activation energy for desorption of dibenzofuran on the activated carbons was estimated. The results showed that the Chemviron and the Norit RB1 activated carbon maintained higher specific surface area and larger micropore pore volume in comparison with the Monolith activated carbon, and the activation energy for the desorption of dibencofuran on these two activated carbons was higher than that on the Monolith activated carbon. The smaller the pore of the activated carbon was, the higher the activated energy of dibenzofiuran desorption was.     

RESOLUTION OF SPECTRAL AND LIFETIME HETEROGENEITY OF TRYPTOPHAN FLUORESCENCE IN BACTERIORHODOPSIN

Abstract— The picosecond time-resolved fluorescence decay of bacteriorhodopsin (BR) was analyzed by the maximum entropy method. Results showed five distributions of lifetimes indicating at least five decay components. A wavelength-dependent study of emission decay of BR was carried out in the wavelength region from 310 to 390 nm. The decay at each wavelength was resolvable into four decay components by the discrete exponential analysis. The three short lifetime components (100 ± 20 ps, 400 ± 50 ps and 1.0 ± 0.1 ns) were independent of wavelength, whereas the longest lifetime component was wavelength dependent (varying from 4.1 ns at 310 nm to 5.7 ns at 390 nm). These results are inconsistent with the existing model of associating the fluorescence of bacteriorhodopsin with two or four lifetime components. An attempt is made to associate the five decay components with the emitting tryptophans of BR.     

ACTIVATION ENERGY OF DESORPTION OF DIBENZOFURAN ON ACTIVATED CARBONS

1. INTRODUCTION With the development of municipalization in China, more and more cities are challenged by the problem of how to dispose of the dramatically increased municipal waste. Generally, most of municipal solid waste is landfilled or dumped openly in the suburbs. It causes not only land waste, but also serious environment pollution. In order to solve efficiently the environment pollution caused by municipal solid waste, incineration technique was introduced in some big cities such…     

KINETICS AND MECHANISM OF CATALYSIS BY FERRIHAEMS IN THE CHEMILUMINOGENIC OXIDATION OF LUMINOL BY HYDROGEN PEROXIDE

The kinetics of catalysis by deuteroferrihaem (deuterohaemin) were studied in the chemiluminogenic oxidation of luminol by hydrogen peroxide. The results imply that two distinct catalytic mechanisms operate to yield chemiluminescence from excited aminophthalate emitter in this system. The first mechanism involves initial one-electron oxidation of luminol by an oxidised derivative of deuteroferrihaem with well-established peroxidatic oxidant properties. The second mechanism involves a concerted pathway very similar to that which has been proposed [Olsson, T., L. Ewetz and A. Thore (1983), Photochem. Photobiol. 38 , 223–229] to explain protoferrihaem (haemin) catalysis in luminol oxidation. Deuteroferrihaem is a much more effective catalyst than protoferrihaem on a mole-for-mole basis and could be used with advantage in chemiluminescence analyses.     

CO-OPERATION OF PERIPHERAL AND INTEGRAL MEMBRANE PROTEINS IN THE LIGHT DEPENDENT ACTIVATION OF ROD GTPase AND PHOSPHODIESTERASE

Abstract— During the purification of light activated GTPase, we have observed that the GTPase activity is suddenly lost because of the separation of two components which are both needed for enzymatic activity. The G fraction or protein (apparent mol. wt 55000) can selectively bind GTP and is necessary for PDE activation by illuminated rhodopsin. However, the G fraction shows no GTPase activity unless it is supplemented by illuminated rhodopsin and the H fraction, a heat labile, trypsin resistant macro-molecule with an apparent mol. wt of 53 000. The G and H fractions (and GTPase activity) show a significant increase in binding to bleached as compared with unbleached disc membranes.