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991.
992.
The synthesis,structural characterization and thermal behavior of a novel one-dimensional manganese (Ⅱ) complex of formula [Mn(1,5-nds)(Him)4]n [1,5-nds=naphthalene-1,5-disulfonate,Him=imidazole] is reported.The complex crystallizes in the triclinic system,space group P1,with a=0.835 42(13) nm,b=0.983 45(18) nm,c= 0.987 42(19) nm,α=60.523 0(10)°,β=97.748(2)°,γ=87.189(2)° and Z=2.The 1,5-nds ligand assumes the μ2 coordination mode and interlinks Mn(Ⅱ) ions into infinite one-dimensional chain structure along [111] direction,with the adjacent Mn…Mn distance being 1.144 99(12) nm.The chains are assembled into a three-dimensional supramolecular architecture via hydrogen bonds and C-H…π interactions.IR spectra and thermal analysis data are in agreement with the crystal structure. 相似文献
993.
994.
J. Hermann L. Mercadier E. Mothe G. Socol P. Alloncle 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010
We have performed spectroscopic analysis of the plasma produced by pulsed laser ablation of brass in a low pressure argon atmosphere. The intensities of several spectral lines of copper, zinc and lead were measured for succeeding laser pulses applied to the same irradiation site. The intensities and spectral shapes of the observed transitions were compared to the spectral radiance computed for plasma in local thermal equilibrium. At a delay of 600 ns after the laser pulse, the plasma is characterized by typical values of temperature and electron density of 1.1 × 104 K and 1.2 × 1017 cm− 3, respectively, and an elemental composition equal to that of the sample. Small changes of spectral line intensities were observed with increasing number of applied laser pulses. They were attributed to the alteration of the plume expansion dynamics as a consequence of crater formation on the sample surface. The results indicate that the mass transfer from the solid to the plasma is stoichiometric. 相似文献
995.
Shengang Xu Hiroto Kudo Tadatomi Nishikubo Shinya Nakamura Shunichi Numata 《Journal of polymer science. Part A, Polymer chemistry》2010,48(9):1931-1942
The acetyl esterified calixarene (CA) derivatives were prepared from calix[4]resorcinarene (CRA), and p‐tert‐butylcalixarene (BCA[n], n = 4, 6, 8), respectively. Using these CA derivatives as curing agents, the thermal curing reactions of two multifunctional epoxy resins (jER 828, 186 g/equiv., and ESCN, 193.7 g/equiv.) were investigated. The temperatures of glass transition (Tg) and decomposition (T) were measured by DSC and TGA, respectively. Based on the yields, Tgs, and Tds of the thermal cured jER 828 epoxy resin with CRA‐E100, the curing conditions were optimized to be tetrabutylphosphonium bromide (TBPB) as catalyst in NMP at 160 °C for 15 h. Under this curing condition, the cured materials of jER 828 or ESCN using various CA derivatives as curing agents were prepared. Except for BCA4 derivatives, the yields of thermal curing reaction were higher than 90%. Tgs and Ts of the resultant cured materials were in the range of 113–248 °C and 363–404 °C, respectively. These results mean that the cured epoxy resins with excellent Tgs were successfully formed by using CA derivatives as curing agents. It was also found that the Tgs of cured epoxy resins were strongly affected by the degree of esterification of CA derivatives. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1931–1942, 2010 相似文献
996.
Driving forces of in-plane chain orientation of polyimides (PIs) and their precursors were discussed and the mechanisms were proposed. A polyimide precursor, poly(amic acid) (PAA) derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) with p-phenylenediamine (PDA) showed a certain degree of in-plane orientation in its solution-casting process and clear molecular weight dependence. The results allowed us to propose the casting-induced in-plane orientation mechanism of the rigid PAA chains. The imidization-induced in-plane orientation mechanism was also discussed by investigating how residual solvent content influences the degree of in-plane orientation of resultant PI films. The results suggested that the magnitudes of the PI chain in-plane orientation are dominated by a combined effect of the initial PAA orientation, apparent stretching based on a great thickness decrease, and the molecular mobility during thermal imidization. In a system derived from s-BPDA with 2,2′-bis(trifluoromethyl)benzidine (TFMB), the effect of molecular mobility during thermal imidization was predominant when cured under usual thermal conditions owing to the presence of the trifluoromethyl groups contributing to weakened intermolecular interaction. In s-BPDA/TFMB and s-BPDA/m-TOL systems (m-TOL = m-tolidine), a melt-induced in-plane orientation phenomenon was observed at temperatures corresponding to their Tg’s when the extents of in-plane chain orientation (f values) were monitored as a function of temperature in the stepwise heating process. This behavior is very curious because there are no appreciable dimensional, morphological, and structural changes as some driving forces just above the Tg of s-BPDA/TFMB. 相似文献
997.
Dr. Thomas Diemant Andreas Bergbreiter Dr. Joachim Bansmann Dr. Harry E. Hoster Prof. Dr. R. Jürgen Behm 《Chemphyschem》2010,11(14):3123-3132
The correlation between structural and chemical properties of bimetallic PtRu/Ru(0001) model catalysts and their modification upon stepwise annealing of a submonolayer Pt‐covered Ru(0001) surface up to the formation of an equilibrated PtxRu1?x/Ru(0001) monolayer surface alloy was investigated by scanning tunneling microscopy and by the adsorption of CO and D2 probe molecules. Both temperature‐programmed desorption and IR measurements demonstrate the influence of the surface structure on the adsorption properties of the bimetallic surface, which can be explained by changes of the composition of the adsorption ensembles (ensemble effects) for D adsorption and by changes in the electronic interaction (ligand effects, strain effects) of the metallic constituents for CO and D adsorption upon alloy formation. 相似文献
998.
论文采用二维热模型分析了圆柱型Ni/MH电池在过充电过程中的热效应.实验提供了更为精准的数据以建立精确的热模型.利用石英频率微量热仪对电池的热容量以及电池在不同电流过充电时的发热量和散热速率进行了测量,继而将散热速率曲线拟合成线性函数和三段不同的指数函数.线性阶段之后的散热过程符合数学微分表达式,这些表达式有助于理解过渡阶段和过充电阶段散热速率的变化规律.热传导方程中产热速率采用理论计算值.最后使用FEM模拟了电池在1C,3C,5C充电过程每一阶段末时刻的电池内部温度场分布,结果相对准确. 相似文献
999.
Donatella Diana Dr. Barbara Ziaco Dr. Guido Scarabelli Dr. Carlo Pedone Prof. Giorgio Colombo Dr. Luca D. D'Andrea Dr. Roberto Fattorusso Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(18):5400-5407
The analysis of the folding mechanism in peptides adopting well‐defined secondary structure is fundamental to understand protein folding. Herein, we describe the thermal unfolding of a 15‐mer vascular endothelial growth factor mimicking α‐helical peptide (QKL10A) through the combination of spectroscopic and computational analyses. In particular, on the basis of the temperature dependencies of QKL10A Hα chemical shifts we show that the first phase of the thermal helix unfolding, ending at around 320 K, involves mainly the terminal regions. A second phase of the transition, ending at around 333 K, comprises the central helical region of the peptide. The determination of high‐resolution QKL10A conformational preferences in water at 313 K allowed us to identify, at atomic resolution, one intermediate of the folding–unfolding pathway. Molecular dynamics simulations corroborate experimental observations detecting a stable central helical turn, which represents the most probable site for the helix nucleation in the folding direction. The data presented herein allows us to draw a folding–unfolding picture for the small peptide QKL10A compatible with the nucleation–propagation model. This study, besides contributing to the basic field of peptide helix folding, is useful to gain an insight into the design of stable helical peptides, which could find applications as molecular scaffolds to target protein–protein interactions. 相似文献
1000.
以 SBA-15 为载体, 采用沉积沉淀法制备了纳米 Au 催化剂, 研究了不同预处理条件对 Au 在载体表面状态的影响, 考察了催化剂样品催化 CO 氧化性能. 以高分辨率透射电子显微镜、N2 吸附、X 射线衍射、紫外-可见漫反射吸收谱、X 射线光电子能谱和电感耦合等离子体发射光谱等手段对催化剂的结构和表面性质进行了表征. 结果表明, 经还原焙烧处理后的 Au/SBA-15 催化剂热稳定性较好, Au 在 SBA-15 孔道表面呈高分散状态, 样品在 CO 氧化反应中表现出优异的低温催化活性和高温稳定性, 同时具有优异的抗烧结性能和良好的循环稳定性. 相似文献