On the Crystal Structure of [Cu(OH)_2(H_2O)_2(4-C_5H_4NCOOH)_2]

In their report of the crystal structure of the compound claimed to be [Cu(OH)2(H2O)2(4- C5H4NCOOH)2], the authors did not give any experimental details on the location and refinement of the water and hydroxyl hydrogen atoms[1]; they had assumed the presence of the carboxylic -CO2H unit on the basis of the infrared stretching frequency at 1700 cm-1 that is only of medium intensity. The cell constants for the compound are, in fact, identical, with those documented for tetraaquabis(isonicot…     

Parallel sparse Gaussian elimination with partial pivoting

In this article, we consider the factorization of a sparse nonsymmetric matrix using Gaussian elimination with partial pivoting on a multiprocessor having a globally-shared memory. The parallel algorithm makes use of a static data structure developed by George, Liu and Ng in [17]. Some numerical experiments on a Sequent Balance 8000 are presented to demonstrate the efficiency of the parallel implementation.Research supported in part by the Applied Mathematical Sciences Research Program, Office of Energy Research, U.S. Department of Energy under contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc.     

用宇宙线大气簇射Ne-Nμ关系研究“膝”区原初成分

用梁王山宇宙线观测站获得的宇宙线大气簇射μ子数据, 与假设原初分别为质子、氦核、中等核(Z=15)和铁核的Monte-Carlo模拟结果进行比较, 结果显示宇宙线膝区原初成分无明显变化且以轻核为主.     

Dirac current in expanding spacetime

We study the behaviour of Dirac current in expanding spacetime with Schrödinger and de Sitter form for the evolution of the scale-factor. The study is made to understand the particle-antiparticle rotation and the evolution of quantum vacuum leading to particle production in such spacetime.     

热解压力对生物质焦结构及气化反应性能的影响

利用加压固定床反应器、吸附仪、X射线衍射仪、元素分析仪、电感耦合等离子原子发射光谱仪等考察了热解压力对生物质半焦(以下简称半焦)产率、物化结构、元素组成的影响规律。同时,利用热天平对不同热解压力下所制半焦的气化行为进行了考察。结果表明,随热解压力升高,半焦产率增大,当压力升至1.0 MPa后,半焦产率基本不变;半焦中C元素含量随热解压力的升高而增加,而H元素含量和BET比表面积则减小;此外,随热解压力升高,玉米秸秆焦和锯末焦的石墨化程度增强,而稻壳焦的石墨化程度则基本不受热解压力影响。气化反应的研究表明,玉米秸秆焦及锯末焦的平均气化反应速率随热解压力的提高而减小,而稻壳焦的平均气化反应速率基本不受热解压力的影响。热解压力对半焦BET比表面积及碳微晶结构的影响规律与气化反应速率变化规律的对比研究表明,热解压力引起半焦微晶结构的变化是造成热解压力对半焦气化反应速率影响的主要原因。     

基于6-羟基-2-吡啶基膦酸配体的铜配合物的合成、结构及磁性

在水热条件下, 以6-羟基-2-吡啶基膦酸为主配体, 4, 4′-联吡啶(bpy)及1, 2-二(4-吡啶基)乙烯(bpe)为桥联配体, 合成了2个铜膦酸配位聚合物[Cu₃(L)₂(bpy)₂(H₂O)₂]· 2H₂O (1), [Cu₃(L)₂(bpy)₂(H₂O)₃]· 2H₂O (2)。配合物1中, Cu²⁺离子由膦酸配体连接成一条链, 该链由bpy桥联成二维层, 层与层之间通过氢键作用构成三维结构。配合物2与配合物1是同构的, 桥联配体是bpe。磁性研究表明, 配合物1与2中铜离子之间存在反铁磁性耦合。     

Hydrogen reactivity on highly-hydroxylated TiO2(110) surfaces prepared via carboxylic acid adsorption and photolysis

Combined scanning tunneling microscopy, temperature programmed desorption, photo stimulated desorption, and density functional theory studies have probed the formation and reactivity of highly-hydroxylated rutile TiO(2)(110) surfaces, which were prepared via a novel, photochemical route using trimethyl acetic acid (TMAA) dissociative adsorption and subsequent photolysis at 300 K. Deprotonation of TMAA molecules upon adsorption produces both surface bridging hydroxyls (OH(b)) and bidentate trimethyl acetate (TMA) species with a saturation coverage of nearly 0.5 monolayers (ML). Ultra-violet light irradiation selectively removes TMA species, producing a highly-hydroxylated surface with up to ~0.5 ML OH(b) coverage. At high coverages, the OH(b) species typically occupy second-nearest neighbor sites along the bridging oxygen row locally forming linear (2 × 1) structures of different lengths, although the surface is less ordered on a long scale. The annealing of the highly-hydroxylated surface leads to hydroxyl recombination and H(2)O desorption with ~100% yield, thus ruling out the diffusion of H into the bulk that has been suggested in the literature. In agreement with experimental data, theoretical results show that the recombinative H(2)O desorption is preferred over both H bulk diffusion and H(2) desorption processes.     

Dynamical aspects of the adsorption hysteresis phenomenon

Equilibrium and nonequilibrium transport properties of adsorbates in mesoporous Vycor porous glass have been experimentally studied using nuclear magnetic resonance techniques. With the known geometrical characteristics of porous glass and with measured self-diffusivities, transient sorption curves have been quantitatively compared to those predicted within a Fick's law model. This model correctly describes data outside a hysteresis region. In contrast, in the hysteresis region, a two-step mechanism of density relaxation is required to explain the behavior. These two mechanisms are identified as diffusion at early stages and activated density redistribution at later stages of adsorption. The latter mechanism, being intrinsically slow in nature, is anticipated to prevent the system from reaching equilibrium.     

球面上等收敛算子的有界性

设Rⁿ 是n-维欧氏空间n≥3.用Ω_n表示Rⁿ 上的单位球面,对于函数f∈L（Ω_n）,E_N^δ（f）表示其Fourier-Laplace级数的δ阶Cesaro平均所决定的等收敛算子,其中,λ:=（n-2）/2,δ是熟知的临界指标.对于0<δ≤λ,令p₀:=(2λ)/（λ+δ）,本文主要证明了如下结果: