分子束研究GaAs和InP与氯的激光化学反应动态学

本文采用CW超声分子束和时间分辨质谱技术,研究了在紫外和可见(355nm和560nm)脉冲激光辐照下GaAs(100)和InP(100)表面与氯的激光化学反应动态学。由质谱和飞行时间谱测得反应的主要产物为GaCl_x和InCl_x(x=1,2),研究了激光波长和能量密度对产物飞行时间谱的影响,首次发现提高入射Cl₂分子的平动能对上述激光诱导气-固相反应有明显的增强作用。     

Stereoselective synthesis of an advanced taxusin intermediate: an application of the type 2 intramolecular Diels–Alder reaction

Stereoselective synthesis of an advanced taxusin intermediate is described. The key step is the successful application of the type 2 intramolecular Diels–Alder (IMDA) reaction for the assembly of the tricyclic core of this natural product.     

A Study of Synthesis, Immobilization and Catalytic Capability of Metalloporphyrin

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The Preparation,Characterization and X-ray Structural Analysis of Tetrakis[1,3-dimethyl-2(3H)-imidazoleselone]cadmium(II) Hexafluorophosphate

Abstract A new compound, [Cd(dmise)₄][PF₆]₂, has been synthesized and characterized via standard solid and solution state methods including single crystal X-ray crystallography (dmise = 1,3-dimethyl-2(3H)-imidazoleselone). The title compounds crystallizes in orthorhombic space group P bcn with a = 12.783(3), b = 22.206(4), c = 13.153(3) ?, V = 3733.8(13) ?³, Z = 4. The complex is a high melting, yellow water soluble 2:1 electrolyte solid that state has a flattened tetrahedral CdSe₄ coordination geometry. To date this is the only structural study reported for a homoleptic selenourea complex of cadmium. Graphical abstract The Preparation, characterization and X-ray structural analysis of Tetrakis[1,3-dimethyl-2(3H)-imidazoleselone]cadmium(II) hexafluorophosphate Daniel J. Williams, Bradley J. McKinney, Ben Baker, Kevin P. Gwaltney and Donald VanDerveer Tetrakis[1,3-dimethyl-2(3H)-imidazoleselone][PF₆]₂ is prepared in 82% yield by direct combination of cadmium acetate dihydrate, ammonium hexafluorophosphate, and the ligand in boiling acetonitrile. X-ray crystallography shows a structure with a distorted tetrahedral coordination sphere around the cadmium. This is the first report of a structural characterization of a homoleptic cadmium selenourea complex. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

非结构网格上一种新型的高分辨率高精度无波动的有限元格式

在非结构网格上构造出无波动无自由参数耗散性有限元格式 ,即NND有限元格式 .通过若干个典型二维跨音速和超音速可压缩无粘定常流动的算例证明这确是一个高精度的 ,对激波具有高分辨率的无波动的新型有限元格式 .特别与网格自适应相结合 ,可得到十分满意的结果     

Renormalization of the inverse square potential

The quantum-mechanical D-dimensional inverse square potential is analyzed using field-theoretic renormalization techniques. A solution is presented for both the bound-state and scattering sectors of the theory using cutoff and dimensional regularization. In the renormalized version of the theory, there is a strong-coupling regime where quantum-mechanical breaking of scale symmetry takes place through dimensional transmutation, with the creation of a single bound state and of an energy-dependent s-wave scattering matrix element.     

Monosyllabic word recognition at higher-than-normal speech and noise levels

The effects of intensity on monosyllabic word recognition were studied in adults with normal hearing and mild-to-moderate sensorineural hearing loss. The stimuli were bandlimited NU#6 word lists presented in quiet and talker-spectrum-matched noise. Speech levels ranged from 64 to 99 dB SPL and S/N ratios from 28 to -4 dB. In quiet, the performance of normal-hearing subjects remained essentially constant in noise, at a fixed S/N ratio, it decreased as a linear function of speech level. Hearing-impaired subjects performed like normal-hearing subjects tested in noise when the data were corrected for the effects of audibility loss. From these and other results, it was concluded that: (1) speech intelligibility in noise decreases when speech levels exceed 69 dB SPL and the S/N ratio remains constant; (2) the effects of speech and noise level are synergistic; (3) the deterioration in intelligibility can be modeled as a relative increase in the effective masking level; (4) normal-hearing and hearing-impaired subjects are affected similarly by increased signal level when differences in speech audibility are considered; (5) the negative effects of increasing speech and noise levels on speech recognition are similar for all adult subjects, at least up to 80 years; and (6) the effective dynamic range of speech may be larger than the commonly assumed value of 30 dB.     

分子内结构环境对解离能的影响

为了理解化学键的这一结构效应, 本文对具有相同化学键而分子内结构环境不同的系列分子进行了计算研究, 讨论了化学键结构环境对解离能的影响.