排序方式: 共有29条查询结果,搜索用时 15 毫秒
1.
A monodendron that over a broad temperature range self-assembles in quasi-spherical supramolecular aggregates organized on a thermotropic cubic Pm3n lattice was examined by TEM. Grain boundaries were found parallel to the (1 0 0) and (3 2 0) planes. In well annealed specimens, in which grain boundaries are rare, two types of stacking fault were numerous, suggesting their relatively low energy. In the original Pm 3n lattice and in the two stacking fault arrangements, the supramolecular aggregates are distorted to an oblate shape, which is likely to be favoured by a crowded microscopic interface between core and tail moieties. Symmetry and phase selection for the ordered arrangement of amphiphilic molecules is discussed. 相似文献
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The purpose of this article is to characterize symplectic and Hamiltonian circle actions on symplectic manifolds in terms of symplectic embeddings of Riemann surfaces.More precisely, it is shown that(1) if(M, ω) admits a Hamiltonian S~1-action, then there exists a two-sphere S in M with positive symplectic area satisfying c1(M, ω), [S] 0,and(2) if the action is non-Hamiltonian, then there exists an S~1-invariant symplectic2-torus T in(M, ω) such that c1(M, ω), [T] = 0. As applications, the authors give a very simple proof of the following well-known theorem which was proved by Atiyah-Bott,Lupton-Oprea, and Ono: Suppose that(M, ω) is a smooth closed symplectic manifold satisfying c1(M, ω) = λ· [ω] for some λ∈ R and G is a compact connected Lie group acting effectively on M preserving ω. Then(1) if λ 0, then G must be trivial,(2) if λ = 0, then the G-action is non-Hamiltonian, and(3) if λ 0, then the G-action is Hamiltonian. 相似文献
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STABILITY ANALYSIS OF A TURBINE ROTOR SYSTEM WITH ALFORD FORCES 总被引:1,自引:0,他引:1
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A new method for measuring and exploiting the magnetic field dependence of chemically induced dynamic nuclear polarization (CIDNP) is described. A solution of an amino acid or protein together with a flavin photosensitizer is irradiated with laser light at a position in the bore of a superconducting NMR magnet where the field is between 0.1 T and 7.0 T. The polarized sample is then transferred by rapid injection into an NMR tube at the centre of the magnet (at 9.4 T), where the spectrum is recorded. The observed 1H CIDNP field dependence of tyrosine agrees well with the diffusion model of the radical pair mechanism. The field dependence of histidine, tryptophan and methionine CIDNP allows the g values of the transient radicals responsible for the polarization to be determined. Experiments in which amino acids compete for the photoexcited flavin indicate that methionine residues could be used as probes of surface accessibility, especially if the polarization is generated in low fields (~ 0.7 T) and detected in high fields (≥ 9.4 T). Possible extensions of the technique to study protein folding and the structures of partially denatured states of proteins are discussed. 相似文献
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In recent years certain new technologies demand optically transparent high Tgpolymer materials.Some aliphatic polymers containing cyclic structure are in the marketalready and have been applied to manufacture various devices in optics industry.However,these polymers are usually of nonpolar character and their difficulties inadhesion and solubility in solvents limited their applicability in many technologies[1 ,2 ] .The polymerization of polar group-containing internal cyclic olefins by transit… 相似文献
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EFFECT OF FORESTLAND AVAILABILITY BY OWNERSHIP TYPE ON LICENSE SALES FOR HUNTING: A SPATIAL APPROACH
SEONG‐HOON CHO J.M. BOWKER ROLAND K. ROBERTS SEUNG GYU KIM DAYTON M. LAMBERT NEELAM C. POUDYAL 《Natural Resource Modeling》2012,25(4):549-573
Abstract The effect of forestland availability under different ownership types on license sales for hunting in nine Southeastern states is empirically evaluated. An equation that represents license sales for hunting is estimated assuming the sale of hunting licenses in a particular county is related to the characteristics of that county as well as the characteristics and license sales for hunting in its neighboring counties. The positive effects of the amounts of both national and private forestland on license sales reaffirm the potential benefits of maintaining forestland to stimulate hunting. The positive spillover effect of national forests on license sales for hunting suggests that availability and close access to hunting in national forests within neighboring counties are important in supporting hunting license sales in a county. This study contributes to the general understanding of the drivers affecting individuals’ decisions to use natural resources for hunting. Advances in natural resource modeling, specifically the spatial process model and geospatial data used in this research, make it possible to examine the interactions between the spatial dynamics and ownership attributes of the natural system, allowing policy makers to design natural resource management practices that respond to a system characterized by these interactions. 相似文献
7.
设λ,μ是两个序列空间并有符号弱滑脊性,(λ,μ)是变换λ进入μ的无穷矩阵算子所成的无穷矩阵代数,本文研究了这类代数的强,Mackey、弱乘法序列连续性问题。 相似文献
8.
By using the sequential effect algebra theory, we establish the partitions and refinements of quantum logics and study their entropies. 相似文献
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最强Orlicz-Pettis拓扑 总被引:4,自引:0,他引:4
引进了lp(p≥1)空间的子集是本性紧概念,借此给出了抽象对偶系统(E,F)中最强Orlicz-Petits拓扑SOP(E,F)以及产生该拓扑的最大映射集族的表示.利用此结果搞清楚了现有两种Orlicz-Petits拓扑即Dierolf拓扑(M)和Twed-dle拓扑(E,T’)的确切意义以及它们之间的相互关系.指出了的最大性所蕴涵的理论意义和应用价值.证实了σ(F,E)-条件紧集和σ(F,E)-可数紧集都含于中。进而实质性地改进了矢位测度论中的Graves-Rness定理、抽象函数论中的Thomas定理等重要结果. 相似文献
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