SBIRS-HIGH对导弹上升段位置测量精度及中末段位置预报精度的分析

根据目前的技术水平分析了高空天基红外系统(SBIRS-HIGH)的技术参数;理论上计算了SBIRS-HIGH对导弹上升段的位置测量精度以及中末段任意时刻飞行位置的预报精度;研究了SBIRS-HIGH对中段和末端导弹拦截系统的导引能力。     

阻抗谱法确定扩散系数

给出了阻抗谱法确定扩散系数的理论和方法;以钒酸盐阴极材料Na_(1+x)V_3O_(?)(L.T.)为例,应用本方法计算给出了Li~+在阴极中的扩散系数为10~(?)-10~(-9)cm~2·s~(-1);最后还对误差来源进行了讨论. 关键词：     

Characterization of partially transesterified poly(beta-hydroxyalkanoate)s using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used for the characterization of a partially transesterified poly(beta-hydroxyalkanoate), PHA, polymer produced by the bacterial strain Alcaligenes eutrophus using saponified vegetable oils as the sole carbon sources. The transesterification was carried out separately under acidic and basic conditions to obtain PHA oligomers weighing less than 10 kDa. The intact oligomers were detected in their cationized [M + Na](+) and [M + K](+) forms by MALDI-TOFMS. A composition analysis, using the MALDI-TOF spectra, indicate that the oligomers obtained via acid catalysis were terminated with a methyl 3-hydroxybutyrate end group, and those obtained by base catalysis had a methyl crotonate (olefinic) termination. In addition to HB (hydroxy butyrate), the oligomers were found to contain a small percentage of HV (hydroxy valerate). This was independently confirmed using gas chromatography/mass spectrometry (GC/MS). In comparison, the analysis of a commercial PHA polymer, transesterified under identical conditions, only showed the presence of HB, i.e. a pure PHB homopolymer. Copyright 1999 John Wiley & Sons, Ltd.     

Molecular distribution of some commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Nonylphenol ethoxylates (NPEs) belong to a group of nonionic surfactants that are collectively referred to as alkylphenol ethoxylates (APEs). APEs find widespread use in heavy-duty commercial and household cleaning formulations, shampoos, and industrial processing, i.e. textile manufacture. Their environmental impact depends on the molecular distribution and the extent of their biodegradation in municipal sewage systems, waterways and rivers. We have established two sample preparation methods that have enabled the determination of the molecular distributions of six commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS). In both methods, alpha-cyano-4-hydroxycinnamic acid, dissolved in acetonitrile/tetrahydrofuran, was used as the matrix. In one set of experiments, the NPEs were dissolved in an acetonitrile/tetrahydrofuran solvent system prior to mixing with the matrix solution, and the resulting MALDI-TOF mass spectra produced mostly sodiated molecules [M + Na](+). The NPEs, all having the formula 4-(C(9)H(19))-C(6)H(4)-(OCH(2)CH(2))(n)-OH, are Surfonic (R)N-95, N-100, N-102, N-120, N-150 and N-300. Surfonic N-95 and N-100 gave n values of 5-20; Surfonic N-102, N-120, N-150, and N-300 gave n values of 5-21, 5-22, 8-25 and 15-40, respectively. In order to develop a sample preparation method that could be used with less polar NPEs, we dissolved the NPEs (except N-300) in pentane prior to mixing with the matrix solution, and found that the MALDI spectral quality was unaffected by the solvent systems. Copyright 1999 John Wiley & Sons, Ltd.     

Atomic volumes and polarizabilities in density-functional theory

Becke and Johnson introduced an ad hoc definition of atomic volume [J. Chem. Phys. 124, 014204 (2006)] in order to obtain atom-in-molecule polarizabilities from free-atom polarizabilities in their nonempirical exchange-hole dipole moment model of dispersion interactions. Here we explore the dependence of Becke-Johnson atomic volumes on basis sets and density-functional approximations and provide reference data for all atoms H-Lr. A persuasive theoretical foundation for the Becke-Johnson definition is also provided.     

Probing mesitylborane and mesitylborate ligation within the coordination sphere of Cp*Ru(P(i)Pr3)+: a combined synthetic, X-ray crystallographic, and computational study

The reaction of Cp*Ru(P(i)Pr(3))Cl (1) with MesBH(2) (Mes = 2,4,6-trimethylphenyl) afforded the mesitylborate complex Cp*Ru(P(i)Pr(3))(BH(2)MesCl) (2, 66%). Exposure of 2 to the chloride abstracting agent LiB(C(6)F(5))(4)·2.5OEt(2) provided [Cp*Ru(P(i)Pr(3))(BH(2)Mes)](+)B(C(6)F(5))(4)(-) (3, 54%), which features an unusual η(2)-B-H monoborane ligand. The related borate complex Cp*Ru(P(i)Pr(3))(BH(3)Mes) (5, 65%) was prepared from 1 and LiH(3)BMes. Attempts to effect the insertion of unsaturated organic substrates into the B-H bonds of 3 were unsuccessful, and efforts to dehydrohalogenate 2 using KO(t)Bu instead afforded the mesitylborate complex Cp*(P(i)Pr(3))Ru(BH(2)MesOH) (6, 48%). Treatment of 1 with benzyl potassium generated an intermediate hydridoruthenium complex (7) resulting from dehydrogenation of a P(i)Pr fragment, which in turn was observed to react with MesBH(2) to afford the mesitylborate complex Cp*(P((i)Pr)(2)(CH(3)CCH(2)))Ru(BH(3)Mes) (8, 47%). Crystallographic characterization data are provided for 2, 3, 5, 6, and 8. A combined X-ray crystallographic and density functional theory (DFT) investigation of 3 and 5, using Natural Bond Orbital (NBO) and Atoms in Molecules (AIM) analysis, revealed that 3 and 5 are best described as donor-acceptor complexes between a Cp*(P(i)Pr(3))Ru(+) fragment and a bis(η(2)-B-H) coordinating mesitylborane(borate) ligand. Significant σ-donation from the B-H bonds into the Ru(II) center exists as evidenced by the NBO populations, bond orders, and AIM delocalization indices. In the case of 3, the vacant p orbital on boron is stabilized by Ru→B π back-donation as well as by resonance with the mesityl group.