3种羧酸类基质的基质辅助激光解吸/电离质谱行为

引言基质辅助激光解吸/电离质谱(MALDI-MS)这种新的“软电离”质谱技术，能够在短短10年间，得到广泛应用与迅速发展，很大程度上要归功于基质的辅助效应。基质在样品的解吸/电离过程中，起着关键作用。对基质本身MALDI-MS的研究，不仅可以、刻认识M

Barrier property and structure of acrylonitrile/acrylic copolymers

A series of acrylonitrile (AN) copolymers with methyl acrylate (MA) or ethyl acrylate (EA) as comonomer (5-23 wt%) was prepared by free-radical copolymerisation. The permeability coefficients of the copolymers to oxygen and carbon dioxide were measured at 1.0 MPa and at 30 degrees C, and those to water vapor also measured at 100% relative humidity and at 30 degrees C. All the AN/acrylic copolymers are semicrystalline. As the acrylate content increase, the permeability coefficients of the copolymers to oxygen and carbon dioxide are increased progressively, but those to water vapor are decreased progressively. The gas permeability coefficients of the polymers were correlated with free-volume fractions or the ratio of free volume to cohesive energy.

Enzymatic degradation of poly(epsilon-caprolactone) film in phosphate buffer solution containing lipases

The enzymatic degradation of poly(epsilon-caprolactone) (PCL) films in phosphate buffer solution containing lipases has been studied by DSC, WAXD and SEM. Three lipases, pseudomonas lipase (PS), porcine pancreatic lipase (PP), and candida cylindracea lipase (AY), were used. The results showed that the degradation of PCL films in phosphate buffer solution containing PP or AY was very slow: no weight loss could be found within 1 week. However, PCL film could degrade rapidly and completely within 4 days in phosphate buffer solution containing PS lipase. (C) 1997 Elsevier Science Limited.

Gas-phase ion-molecule reactions of C-60 and theoretical studies of [C60C2H3O](+) adduct cations

Gas-phase ion-molecule reactions of buckminsterfullerene (C-60) with the acetyl cation CH3-C-+=O (m/z 43) and formylmethyl cation (CH2)-C-+-CH=O (m/z 43, or oxiranyl cation), generated from the self-chemical ionization of acetone and vinyl acetate, respectively, were studied in the ion source of a mass spectrometer. Adduct cations [C60C2H3O](+) (m/z 763) and protonated C-60, [C60H](+) (m/z 721), were observed as the major products. AM1 semiempirical molecular orbital calculations on the possible structures, stabilities and charge locations of the isomers of the adducts [C60C2H3O](+) were carried out at the restricted Hartree-Fock level. The results indicated that the sigma-addition product [C-60-COCH3](+) is the most stable adduct for the reaction of C-60 with CH3-C-+=O rather than that resulting from the [2+2] cycloaddition. The [2+3] cycloadduct and the sigma-adduct [C60CH2CHO](+) might be the most possible coexisting products for the reactions of C-60 with (CH2)-C-+-CH=O or oxiranyl cation. Other [C60C2H3O](+) isomers are also discussed. (C) 1997 by John Wiley & Sons, Ltd.

Rheological studies on the phase dissolution in a block copolymer

The microphase transition in a styrene-butadiene-styrene triblock copolymer was studied by rheometric mechanical spectroscopy. A high-temperature-melt rheological transition from the highly elastic, nonlinear viscous behavior typical of a multiphase structure to linear viscous behavior with insignificant elasticity typical of a single-phase structure was observed. The transition temperature is determined according to the discontinuity of the rheological properties across the transition region, which agrees well with the results obtained from the small angle X-ray scattering data and the expectation of the random phase approximation theory. Maybe for the first time, microphase dissolution was investigated theologically. The storage modulus (G') and the loss modulus (G '') increase with time during the process. An entanglement fluctuation model based on the segmental density fluctuations is presented to explain the rheological behavior in this dissolution process. (C) 1997 John Wiley & Sons.

Roles of oxygen vacancy and lower valence metallic ion in direct decomposition of NO over La-2-x(Sr,Th)(x)CuO4+/-lambda

Two systems of La2-xSrxCuO4+/-lambda and La2-xThxCuO4+/-lambda, mixed oxides with K2NiF4 structure were synthesized. The compositions and structures of the catalysts were characterized by means of XRD, XPS, chemical analysis and so on. The catalytic behavior for the direct decomposition of NO has been investigated. The results show that the catalytic activity is closely related to the oxygen vacancy and lower valence metallic ion in the direct decomposition of NO. The presence of oxygen vacancy is necessary for mixed oxide to have steady activity in NO decomposition.

Miscibility of linear low density polyethylene (LLDPE)-graft-poly(methyl methacrylate) with poly(vinylidene fluoride) (PVF2) and its application as compatibilizer LLDPE/PVF2 blends

Differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used to study the miscibility of blends of a graft copolymer of poly(methyl methacrylate) on linear low density polyethylene (LLDPE-g-PMMA, G-3) with poly(vinylidene fluoride)(b) (PVF2) and the compatibilization of blends of LLDPE/PVF2. The specific interaction between PMMA side chains and PVF2 in G-3/PVF2 binary blends is weaker than that between the homopolymers PMMA and PVF2. There are two states of PVF2 in the melt of a G-3/PVF2 (60/40, w/w) blend, one as pure PVF2 and the other interacting with PMMA side chains. The miscibility between PMMA side chains and PVF2 affects the crystallization of PVF2. LLDPE-g-PMMA was demonstrated to be a good compatibilizer in LLDPE/PVF2 blends, improving the interfacial adhesion and dispersion in the latter. Diffusion of PMMA side chains into PVF2 in the interfacial region reduces the crystallization rate and lowers the melting point (T-m) and the crystallization temperature (T-c) of PVF2 in the blends.

The application of the MPB4 theory to the interface between between two immiscible electrolyte solutions .4. The differential capacitance of the water/nitrobenzene interface in the presence of 2:2 electrolyte

We have developed a new theoretical model based on the MPB4 theory to calculate the differential capacitance of the interface of 0.05mol/L MgSO4 in water and 0.1mol/L TBATPB in nitrobenzene. Our results coincide with the experimental values very well. It indicates that our model may describe well the structure of ITIES not only in the presence of 1:1 electrolyte but also in the presence of 2:2 electrolyte.

Relationship between the structure and catalytic activity of La2-xSrxNiO4-lambda(0<=x<=1) mixed oxides for NH3 oxidation

A series of samples having the composition of La2-xSrxNiO4(0 less than or equal to x less than or equal to 1) were prepared and used as catalysts for NH3 oxidation. It was found that the La and oxygen vacancies exist in the La2-xSrxNiO4-lambda(0 less than or equal to x less than or equal to 1). The unit cell volume decreases with the increase of x. For bath c and a parameters there appeared a turning point at x = 0.5. Doping with a lower valence cation Sr2+ in the case of La2NiO4 resulted in an increase of Ni3+, consequently the formation of oxygen vacancies, the increase of reducing ability and the increase of catalytic activity. In the oxygen TPD of La2-xSrxNiO4(0 less than or equal to x less than or equal to 1) appeared three peaks, the alpha' peak at about 400K was attributed to the surplus oxygen desorption, the a peak at 700K which approaches to a maxium at x = 0.6 was attributed to the oxygen adsorbed at oxygen vacancies. The beta peak at about 1000K which depends closely on the x and favors the catalytic activity was attributed to the reduction of Ni3+. The catalytic activity of La-2-x SrxNiO4 mixed oxides in the NH3 oxidation in general could be attributed to the extent of the redox reaction: 2Ni(2+) + O-2 + V-0(..) reversible arrow 2Ni(3+) + 20(-) where V-0(..) representes the oxygen vacancies and O- the oxygen species adsorbed at the vacancies.

La_(2-x)Sr_xNiO_(4-λ)系列催化剂结构与氨氧化活性的关系

本文报道了La_(2-x)Sr_xNiO_(4-λ)(O≤x≤1)系列复合氧化物的固体结构性质和用于氨的氧化制硝酸的催化性能.La_(2-x)Sr_xNiO_(4-λ)的晶胞体积Ⅴ随x的增大而逐渐减小;c轴在x≤0.5前逐渐增大,在x≥0.5后逐渐减小.a轴在x≤0.5前逐渐减小,在x≥0.5后基本保持恒定.在x≤0.5前,La_(2-x)Sr_xNiO_(4-λ)中存在氧过剩,在x≥0.5后存在氧缺陷.TPD表明,a氧(吸附在氧缺陷上的氧)在x=0.6时出现极大,β氧(晶格氧)随x增大而逐渐增大.La_(2-x)Sr_xNiO_(4-λ)的氧化还原能力,Ni~(3+)的量,氨氧化的NO选择性都随x增大而增加.由此得出,Ni~(3+)是催化剂的活性离子,β氧是氨的氧化的活性氧种,在La_(2-x)Sr_xNiO_(4-λ)上的氨的氧化遵循氧化还原(Redox)机理.

差分电化学质谱方法（DEMS）的回顾 Ⅰ．DEMS原理和发展

差分电化学质谱（ＤＥＭＳ）是将电化学和质谱技术相结合而发展起来的一种现代电化学现场测试手段。它可现场检测电化学反应中的挥发性气体产物及动力学参数，中间体及其结构的性质等。当电极反应产物为共析出时，ＤＥＭＳ技术可同时确定每种产物的法拉第电流随电极电位或时间的变化．全文分两部分，第一部分回顾ＤＥＭＳ方法的原理与发展；第二部分介绍ＤＥＭＳ方法的应用．本文为其中之第一部分．

THE APPLICATION OF THE MPB4 THEORY TO THE INTERFACE BETWEEN 2 IMMISCIBLE ELECTROLYTE-SOLUTIONS .2. THE DIFFERENTIAL CAPACITANCE OF THE WATER 1,2-DICHLOROETHANE INTERFACE

The MPB4 theory is used to calculate the differential capacitance of the interface between LiCl in water and TBATPB in 1,2-dichloroethane at electrolyte concentrations of 0.005, 0.01 and 0.02 M. The effects of the ion size and the image force, and the influence of the electrolyte concentration, the surface charge density and the solvent effect on the inner layer potential drop are considered simultaneously. These effects can be ascribed to the ionic penetration into the opposite solution and ion-ion correlations across the interface. Our results are in better agreement with experimental data than those obtained using Gouy-Chapman theory. This indicates that the MPB4 theory may also describe the structure of the water \1,2-dichloroethane interface provided that the influence of the electrolyte concentration, the surface charge density and the solvent effect on the inner layer potential distribution are included in the calculation. Comparison of the theoretical results with those of the water \nitrobenzene interface shows that the structure of the water \1,2-dichloroethane interface is similar to that of the water \nitrobenzene interface, except that in the former case the inner-layer potential drop is much higher and the effects of the image force and the ion size are more pronounced.

THE APPLICATION OF THE MPB4 THEORY TO THE INTERFACE BETWEEN 2 IMMISCIBLE ELECTROLYTE-SOLUTIONS .1. THE DIFFERENTIAL CAPACITANCE OF THE WATER NITROBENZENE INTERFACE

We use the MPB4 theory to calculate the differential capacitance of the interface between NaBr + water and tetrabutylammoniumtetraphenyl borate (TBATPB) + nitrobenzene at electrolyte concentrations of 0.01 M, 0.02 M and 0.05 M. In addition to the effects

LIFETIME MEASUREMENTS OF SOME TMI ODD PARITY LEVELS

Eleven new lifetimes of odd parity excited energy levels in four configurations: 4f12 5d 6s 6p, 4f12 6S2 6p, 4f13 5d 6s and 4f13 6s 7s of atomic thulium have been mesured with atomic-beam laser spectrocopy. Two pulsed dye lasers are used for stepwise excitation and the time-resolved fluorescence decay was used to determine lifetime values. The accuracy of the measurements is about 10%.

(η~5-C_9H_7)_2Yb(THF)_2的晶体结构

双(茚基)镱(Ⅱ)四氢呋喃配合物(η~5-C_9H_7)_2Yb(THF)_2的晶体属单斜晶系,C_c空间群,晶体学参数a=13.506(4),b=11.081(2),c=15.577(5),β=92.68(3)°,V=2329(1),D_c=1.56g/cm~3,Z=4,μ=42.4cm~(-1),F(000)=1088,最终编离因子R=0.029,R_w=0.031。中心离子Yb~(2+)与两个茚基以η~5形式成键且与两个四氢呋喃中的氧成键,茚基的两个质心和四氢呋喃中的两个氧形成扭曲的四面体,Yb~(2+)在四面体的中心。Yb~(2+)的配位数为8。Yb~(2+)到质心In1的距离为2.52,到质心In2的距离为2.40。Yb~(2+)到O(1)的键长为2.356(7),到O(2)的键长为2.417(5)。