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1.
Using first principles density functional theory, we predict a monolayer B2Si structure with space group Pmm2 in the present work. This structure is confirmed to be dynamically stable. Based on the plane wave pseudopotential approach, the charge density, electron localization function, density of states, energy band, phonon property and thermal conductivity of Pmm2-B2Si are systematically studied. It is interesting that the sp2 hybridization and coordination bond of Si are found in Pmm2-B2Si, which is the most important factor for its structural stability. The density of states and energy band analysis reveals that Pmm2-B2Si is metallic because of the partial occupied Si 3pz and B 2pz states. Moreover, the acoustic-optical coupling is important for phonon transport in Pmm2-B2Si, and the contribution of optical modes to the lattice thermal conductivity along the [100] and [010] directions is 13% and 12%, respectively. This study gives a fundamental understanding of the structural, electronic and phonon properties in Pmm2-B2Si. 相似文献
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We present a construction of permutation polynomials over finite fields by using some piecewise permutations. Based on a matrix approach and an interpolation approach, several classes of piecewise permutation polynomials are obtained. 相似文献
4.
A new mononuclear complex Mn(bbbi)2(H2O)4(ClO4)2·(bbbi)2·(H2O)2 1 (bbbi = 1,4-bis(benzimidazol-1-yl)-2-butene) is synthesized under hydrothermal conditions and characterized by IR spectroscopy, elemental analysis, and single crystal X-ray structural analysis. Crystal data for 1: triclinic, , a = 8.8478(7) ?, b = 15.0550(11) ?, c = 16.4310(12) ?, α = 108.657(7)°, β = 104.044(7)°, Γ = 99.317(7)°, V = 1942.2(3) ?3, Z = 1, final R = 0.0621. Each manganese atom is octahedrally coordinated by four aqua ligands and two nitrogen atoms of two distinct bbbi ligands. The molecule is stabilized by hydrogen bonding and π…π interactions. 相似文献
5.
Changes in the cell envelope composition of bacteria Zymomonas mobilis 113S which resulted in varied cell surface hydrophobicity (CSH) were examined using FT-IR-spectroscopy and conventional methods of biochemical analysis. Significant differences in all analyses were detected between hydrophilic and hydrophobic compounds in the envelopes of Z. mobilis. A significant positive linear relationship (P < 0.01) was observed between CSH values of Z. mobilis and the ratio of absorbance band intensities assigned to the CH2 and CH3 vibrations from lipids as well as the asymmetric and symmetric stretching vibrations of these methylene and methyl groups. Differences were also seen between the ratio of band absorbances arising from Amide I and Amide II. In addition, the ratio of absorbance intensities assigned to carbohydrates was found to correlate with the CSH of Z. mobilis. Furthermore, a significant inverse relationship (P < 0.01) was detected between CSH of Z. mobilis and the band position (frequency) shift of asymmetric and symmetric stretching of methylene groups, alkyl esters (>CO str) and Amide I, as well as a positive linear relationship (P < 0.05) between the band position shift of Amide II and carbohydrates and CSH of Z. mobilis. Qualitative and quantitative composition of the cell envelopes was found to correlate with both the CSH of Z. mobilis and the spectral data. The observed multiple correlations between the concentration of proteins, carbohydrates and lipids of cell envelopes and selected indices of FT-IR spectra indicate the complex relationship of Z. mobilis cell envelope constituents. The results of present study suggest that FT-IR spectroscopy can be used as a convenient method to evaluate the properties of cell envelopes from Gram-negative bacteria. 相似文献
6.
通过水热法合成了两种锌配位聚合物{[Zn(ic)(bip)]·2H2O}n (1)和[Zn(ic)(bpe)]n (2)(H2ic=衣康酸,bip=3,5-二(1-咪唑基)吡啶,bpe=1,2-二(4-吡啶基)乙烯),并通过X射线单晶衍射和元素分析对其结构进行了表征.配合物1和2均为含有一维金属-羧酸链的二维(4,4)格子层结构.此外,对它们的热重、粉末X射线衍射和固体荧光性能进行了考察.与配体bip相比,1的发射光谱发生了明显的蓝移(~78 nm),可能归因于配体到金属的电荷转移;2显示与游离的bpe配体相似的荧光性质,轻微的红移可能是因为与金属离子之间的配位作用导致的. 相似文献
7.
Jin-Qiang Liu Xin-Zhi Chen Baoming Ji Bang-Tun Zhao 《Research on Chemical Intermediates》2013,39(3):1143-1152
(S)-Indoline-2-carboxylic acid was synthesized by use of a nitro amination approach with l-phenylalanine as chiral pool. The first step of the synthesis was nitration of l-phenylalanine, with urea nitrate (UN)/H2SO4 as nitrating reagent, to give 2,4-dinitro-l-phenylalanine in 75.7 % yield in one-pot synthesis and 69.1 % yield by step-wise nitration. Intramolecular nitro amination of 2,4-dinitro-l-phenylalanine gave (S)-6-nitro-indoline-2-carboxylic acid in 65.7 % yield and more than 99.5 % enantiomeric excess (ee). The title compound, (S)-indoline-2-carboxylic acid, was obtained in 85.9 % yield and high ee by one-pot transformation of (S)-6-nitroindoline-2-carboxylic acid. The total synthesis consisted of three operations and gave the title compound in 42 % yield and more than 99.5 % ee. 相似文献
8.
The concept of the degree of cross-polarization is extended from stochastic electromagnetic stationary beams to stochastic electromagnetic pulsed beams, and the propagation properties of the degree of cross-polarization of stochastic spatially and spectrally partially coherent electromagnetic pulsed beams is studied. The influence of pulse duration and temporal coherence length on the degree of cross-polarization P is emphasized. It is shown that P exhibits an oscillatory behavior in free-space propagation. An increase in the pulse duration or a decrease in the temporal coherence length can weaken the oscillation of P. The validity of the results is interpreted physically. 相似文献
9.
Zhong-Li Liu Xiao-Feng LiXiu-Lu Zhang Ling-Cang CaiFu-Qian Jing 《Physica B: Condensed Matter》2011,406(23):4518-4522
We have performed the first-principles and classical molecular dynamics simulations to investigate the phase diagram and thermodynamic properties of Sr under high pressure and temperature. The obtained solid phase diagram of Sr, based on the quasi-harmonic approximation (QHA), is greatly supported by the available experimental data under low pressure. From the coexistence-phase molecular dynamics simulations, we also obtained the high-pressure melting curve of Sr which shows good agreement with the experiment. While, the experimentally observed β-Sn structure of Sr-III was found to be mechanically unstable according to our phonon dispersion calculations and evolutionary algorithm structure searches. We find that α-U phase (space group Cmcm) is energetically favorable and is the good candidate of Sr-III. 相似文献
10.
A facile synthesis of benzofuro[2,3‐c]pyridines has been achieved under mild conditions by using ammonium acetate as the nitrogen source through intramolecular cascade annulation. This reaction could efficiently construct pyridine ring and furan ring in one step. Moreover, the key annulation step was demonstrated through dihydrobenzofuran intermediates. 相似文献