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951.
Quantitative characterization of low-lying excited electronic states in materials is critical for the development of solar energy conversion materials. The many-body Green's function method known as the GW approximation (GWA) directly probes states corresponding to photoemission and inverse photoemission experiments, thereby determining the associated band structure. Several versions of the GW approximation with different levels of self-consistency exist in the field. While the GWA based on density functional theory (DFT) works well for conventional semiconductors, less is known about its reliability for strongly correlated semiconducting materials. Here we present a systematic study of the GWA using hematite (α-Fe(2)O(3)) as the benchmark material. We analyze its performance in terms of the calculated photoemission/inverse photoemission band gaps, densities of states, and dielectric functions. Overall, a non-self-consistent G(0)W(0) using input from DFT+U theory produces physical observables in best agreement with experiments. 相似文献
952.
Methanol (MeOH) oxidation reaction (MOR) at Pt electrodes under potentiostatic conditions has been investigated by electrochemical in situ FTIR spectroscopy (FTIRS) in attenuated-total-reflection configuration under controlled flow conditions in 0.1 M HClO(4) with 2 M MeOH, where the mass transport effects are largely eliminated using a flow cell. Our results reveal that (i) at constant potentials, the methanol dehydrogenation rate decreases while the CO(ad) oxidation rate increases with the accumulation of CO(ad) until the maximum CO(ad) coverage (ca. 0.5 ML i.e., the steady state) is reached; (ii) at fixed CO(ad) coverage, the rates for MeOH decomposition to CO(ad) and CO(ad) oxidation increases with potential from 0.3 to 0.7 V (vs. RHE), with Tafel slopes for MeOH dehydrogenation of ca. 440 ± 30 mV/dec, which is independent of CO(ad) coverage; (iii) the current efficiency of the CO pathway in MOR at 0.6 and 0.7 V is below 20% and it decreases toward higher potentials. The mechanisms as well as the potential induced change in the kinetics of different pathways involved in MOR are briefly discussed. 相似文献
953.
Molecular dynamics (MD) and quantum mechanics (QM) were used to investigate fluorescence resonance energy transfer (FRET) between coumarin and ethidium in two Mergny's DNA hybridization systems. By combining the transition dipoles calculated by the quantum semi-empirical method and the conformations of the FRET probes collected by MD, FRET efficiencies were derived from the F?rster equation at five temperatures from 273 K to 313 K. The plotted efficiencies were compared with Mergny's experiments, and showed good agreement. The simulated orientation factor and isotropically averaged orientation factor were compared, and the results demonstrated that the assumption of isotropic orientations is invalid when FRET probes are close to each other. The first order kinetic assumptions were also used to calculate the transfer efficiencies, and the results show that this D-A FRET process approximates the first order kinetic reactions. 相似文献
954.
Ho CL Hsu KP Tseng YH Wang EI Liao PC Chou JC Lin CN Su YC 《Natural product communications》2011,6(2):267-270
The hydrodistillated leaf essential oil of Machilus kusanoi was analyzed to determine its composition and yield. Twenty-three compounds were identified, the main components being beta-caryophyllene (23.3%), beta-eudesmol (17.1%), alpha-terpineol (16.0%), n-dodecanal (14.2%), and n-decanal (10.4%). Sesquiterpene hydrocarbons (28.1%) and non-terpenoids (25.0%) were the predominant groups of compounds. The leaf oil exhibited excellent antimicrobial and anti-wood-decay fungal activities. 相似文献
955.
Gui‐Ge Hou Li‐Ying Ma Xian‐Ping Dai 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(10):m321-m323
The title compound, [Zn(C9H7N3)2(H2O)4](CF3O3S)2, contains an octahedral [ZnL2(H2O)4]2+ cationic complex with trans geometry (Zn site symmetry ), and each 5‐(3‐pyridyl)pyrimidine (L) ligand is coordinated in a monodentate fashion through the pyridine N atom. In the extended structure, these complexes, with both hydrogen‐bond acceptor (pyrimidine) and donor (H2O) functions, are linked to each other by intermolecular water–pyrimidine O—H...N hydrogen‐bonding interactions, resulting in a double chain along the crystallographic a axis. The trifluoromethanesulfonate anions are integrated into the chains via O—H...O hydrogen bonds between the coordinated water and sulfonate O atoms. These double chains are associated into a novel three‐dimensional network through interchain water–pyrimidine O—H...N hydrogen bonds. The asymmetric ligand plays an important role in constructing this unusual supramolecular structure. 相似文献
956.
Cheng-Kang Wu · Hai-Xing Wang · Xian Meng · Xi Chen · Wen-Xia PanInstitute of Mechanics Chinese Academy of Sciences Beijing China School of Astronautics Beijing University of Aeronautics Astronautics Beijing China Department of Engineering Mechanics Tsinghua University Beijing China 《Acta Mechanica Sinica》2011,27(2):152-163
The aerodynamic aspects of indirect thrust measurement by the impulse method have been studied both experimentally and numerically. The underlying basic aerodynamic principle is outlined, the phenomena in subsonic, supersonic and arc-heated jets are explored, and factors affecting the accuracy of the method are studied and discussed. Results show that the impulse method is reliable for indirect thrust measurement if certain basic requirements are met, and a simple guideline for its proper application is given. 相似文献
957.
In this paper,a class of discrete time non-autonomous competing system with feedback controls is considered. With the help of differential equations with piecewise constant arguments,we first propose a discrete model of a continuous non-autonomous competing system with feedback controls. Then,using the coincidence degree and the related continuation theorem as well as some priori estimations,a suficient condition for the existence of positive solutions to difference equations is obtained. 相似文献
958.
959.
Xian Zu Lin 《数学学报(英文版)》2011,27(5):863-870
Let G/P be a homogenous space with G a compact connected Lie group and P a connected subgroup of G of equal rank. As the rational cohomology ring of G/P is concentrated in even dimensions, for an integer k we can define the Adams map of type k to be l
k
: H*(G/P, ℚ) → H*(G/P, ℚ), l
k
(u) = k
i
u, u ∈ H
2i
(G/P, ℚ). We show that if k is prime to the order of the Weyl group of G, then l
k
can be induced by a self map of G/P. We also obtain results which imply the condition that k is prime to the order of the Weyl group of G is necessary. 相似文献
960.
The single 2 dilation wavelet multipliers in one-dimensional case and single A-dilation (where A is any expansive matrix with integer entries and |detA| = 2) wavelet multipliers in twodimensional case were completely characterized by Wutam Consortium (1998) and Li Z., et al.
(2010). But there exist no results on multivariate wavelet multipliers corresponding to integer expansive dilation matrix
with the absolute value of determinant not 2 in L
2(ℝ2). In this paper, we choose $2I_2 = \left( {{*{20}c}
2 & 0 \\
0 & 2 \\
} \right)$2I_2 = \left( {\begin{array}{*{20}c}
2 & 0 \\
0 & 2 \\
\end{array} } \right) as the dilation matrix and consider the 2I
2-dilation multivariate wavelet Φ = {ψ
1, ψ
2, ψ
3}(which is called a dyadic bivariate wavelet) multipliers. Here we call a measurable function family f = {f
1, f
2, f
3} a dyadic bivariate wavelet multiplier if Y1 = { F - 1 ( f1 [^(y1 )] ),F - 1 ( f2 [^(y2 )] ),F - 1 ( f3 [^(y3 )] ) }\Psi _1 = \left\{ {\mathcal{F}^{ - 1} \left( {f_1 \widehat{\psi _1 }} \right),\mathcal{F}^{ - 1} \left( {f_2 \widehat{\psi _2 }} \right),\mathcal{F}^{ - 1} \left( {f_3 \widehat{\psi _3 }} \right)} \right\} is a dyadic bivariate wavelet for any dyadic bivariate wavelet Φ = {ψ
1, ψ
2, ψ
3}, where [^(f)]\hat f and F
−1 denote the Fourier transform and the inverse transform of function f respectively. We study dyadic bivariate wavelet multipliers, and give some conditions for dyadic bivariate wavelet multipliers.
We also give concrete forms of linear phases of dyadic MRA bivariate wavelets. 相似文献