中能区~(40)Ar + ~(197)Au/~(159)Tb/~(nat)Ag反应中高激发热核性质研究

通过对中能区Ar+Au/Tb/Ag反应中高激发核的发射时标、发射次序、发射机制、核温度、集体运动等衰变特性的研究，提取了轻粒子和中等质量碎片（IMF）的发射时间，IMF发射时间随束流能的升高而变短，发射机制逐渐由相继衰变过渡至多重碎裂。研究了轻粒子和碎片间的发射次序，对高能粒子和碎片，轻粒子先于碎片发射，而低能时，则为碎片先于轻粒子发射。IMF发射成分与角度和碰撞参数有关，前角区来自于弹核碎裂，后角区来自于类靶热核的蒸发。在平面和出平面研究表明，中速粒子和碎片为在平面发射占主导，即存在类转动效应；对轻粒子，转动效应随粒子质量增加而增加；对中速产物均观测到该效应随碰撞参数饿增大而增大。采用几种不同的方法提取了热核的核温度，研究了不同方法之间的区别。

MB-97海洋放线菌在大豆田应用技术研究

MB 97海洋放线菌在大豆田应用技术研究表明 ,MB 97海洋放线菌可有效控制重迎茬大豆的减产损失 ,并总结出了相应的综合应用技术

Theoretical study on the formation mechanism of Iso-CH2I-Cl

The dissociation and isomerization reaction mechanism on the ground-state potential energy surface for CH2ClI are investigated by ab initio calculations. It is found that the isomer iso-CH2I-Cl can be produced from either the recombination of the photodissociation. fragments or the isomerization reaction of CH2ClI, rather than from isomerization reaction of iso-CH2Cl-I. Further explanations of experimental results are also presented. (C) 2003 Wiley Periodicals, Inc.

Low-temperature heat capacity and standard molar enthalpy of formation of 9-fluorenemethanol (C14H12O)

Low-temperature heat capacities of the 9-fluorenemethanol (C14H12O) have been precisely measured with a small sample automatic adiabatic calorimeter over the temperature range between T = 78 K and T = 390 K. The solid-liquid phase transition of the compound has been observed to be T-fus = (376.567 +/- 0.012) K from the heat-capacity measurements. The molar enthalpy and entropy of the melting of the substance were determined to be Delta(fus)H(m) = (26.273 +/- 0.013) kJ (.) mol(-1) and Delta(fus)S(m) = (69.770 +/- 0.035) J (.) K-1 (.) mol(-1). The experimental values of molar heat capacities in solid and liquid regions have been fitted to two polynomial equations by the least squares method. The constant-volume energy and standard molar enthalpy of combustion of the compound have been determined, Delta(c)U(C14H12O, s) = -(7125.56 +/- 4.62) kJ (.) mol(-1) and Delta(c)H(m)degrees(C14H12O, s) = -(7131.76 +/- 4.62) kJ (.) mol(-1), by means of a homemade precision oxygen-bomb combustion calorimeter at T = (298.15 +/- 0.001) K. The standard molar enthalpy of formation of the compound has been derived, Delta(f)H(m)degrees (C14H12O, s) = -(92.36 +/- 0.97) kJ (.) mol(-1), from the standard molar enthalpy of combustion of the compound in combination with other auxiliary thermodynamic quantities through a Hess thermochemical cycle. (C) 2004 Elsevier Ltd. All rights reserved.

Structure and acidity of Mo/H-MCM-22 catalysts studied by NMR spectroscopy

A comprehensive study on physical and chemical properties of Mo/MCM-22 bifunctional catalysts has been made by using combined analytic and spectroscopic techniques, such as adsorption, elemental analysis, and Xe-129 and P-31 NMR of adsorbed trialkylphosphine oxide probe molecules. Samples prepared by the impregnation method with Mo loadings ranging from 2-10 wt.% have been examined and the results are compared with that obtained from samples prepared by mechanical mixing using MoO3 or Mo2C as agents. Sample calcination treatment is essential in achieving a well-dispersed metal species in Mo/MCM-22. It was found that, upon initial incorporation, the Mo species tend to inactivate both Bronsted and Lewis sites locate predominantly in the supercages rather than the 10-membered ring channels of MCM-22. However, as the Mo loading exceeds 6 wt.%, the excessive Mo species tend to migrate toward extracrystalline surfaces of the catalyst. A consistent decrease in concentrations of acid sites with increasing Mo loading < 6 wt.% was found, especially for those with higher acid strengths. Upon loading of Mo > 6 wt.%, further decreases in both Bronsted and Lewis acidities were observed. These results provide crucial supports for interpreting the peculiar behaviors previously observed during the conversion of methane to benzene over Mo/MCM-22 catalyst under non-oxidative conditions, in which an optimal performance was achieved with a Mo loading of 6 wt.%. The effects of Mo incorporation on porosity and acidity features of the catalyst are discussed. (C) 2004 Published by Elsevier B.V.

On the reactivity of Mo species for methane partial oxidation on Mo/HMCM-22 catalysts

By characterizing fresh and used Mo/HMCM-22 catalysts with ICP-AES, XRD, NH3-TPD technique, UV - Vis DRS and UV Raman spectroscopy, the reactivity of Mo species for methane partial oxidation into formaldehyde were directly studied with a new point of view. By comparing the fresh and used catalysts, it was found that the tetrahedral Mo species bonding chemically to the support surface were practically unchanged after the reaction, while the polymolybdate octahedral Mo species, which had a rather weak interaction with the MCM-22 zeolite, leached out during the reaction, especially when the Mo loading was high. Correspondingly, it was found from the time-on-stream reaction data that the HCHO yield remained unchanged, while COx decreased with the reaction time during the reaction. By combining the characterization results and the reaction data, it can be drawn that the isolated tetrahedral molybdenum oxo-species (T-d) is responsible for HCHO formation, while the octahedral polyoxomolybdate species (O-h) will lead to the total oxidation of methane.

The effect of acidity on olefin aromatization over potassium modified ZSM-5 catalysts

The transformation of olefin to aromatics over ZSM-5 catalysts with different K-loadings has been investigated both in a continuous flow fixed-bed reactor and in a pulse microreactor. Investigation of variation of olefin aromatization activity with K-loadings shows that strong acid sites are indispensable for the converting of olefin to aromatics. As intermediates of olefin aromatization process, butadiene and cyclopentene not only show much higher aromatization activity than mono-olefins, but also can be transformed into aromatics over relatively weak acid sites of K/ZSM-5. A proposal is put forward, stating that among all the steps experienced in olefins aromatization, the formation of diene or cycloolfin from mono-olefins through hydrogen transfer is the key step and can be catalyzed by strong acid sites.

Two-dimensional capillary electrophoresis involving capillary isoelectric focusing and capillary zone electrophoresis

Capillary isoelectric focusing (cIEF) and capillary zone electrophoresis (CZE) was on-line hyphenated by a dialysis interface to achieve a 2D capillary electrophoresis (CE) system. The system was used with just one high-voltage power supply and three electrodes (one cathode shared by the two dimensions). The focused zone in the first dimension (i.e. the cIEF) was driven to the dialysis interface by electroosmotic flow (EOF), besides chemical mobilization from the first anode to the shared cathode. And then in the second dimension (i.e. the CZE), the separated zone was further separated and driven by an inverted EOF, which originated from the charged layer of a cationic surfactant adsorbed onto the inner wall of the capillary. Finally, a solution of ribonuclease was rapidly separated to assess the feasibility of the two-dimensional CE implement. (C) 2003 Elsevier B.V. All rights reserved.