排序方式: 共有73条查询结果,搜索用时 31 毫秒
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Dr. Iryna Antonyshyn Dipl.-Eng. Ana M. Barrios Jiménez Dr. Olga Sichevych Dr. Ulrich Burkhardt Dr. Igor Veremchuk Dr. Marcus Schmidt Dr. Alim Ormeci Dr. Ioannis Spanos Dr. Andrey Tarasov Dr. Detre Teschner Dr. Gerardo Algara-Siller Prof. Dr. Robert Schlögl Prof. Yuri Grin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16913-16919
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The shape of semiflexible polymer rings is studied over their whole range of flexibility. Investigating the joint distribution of asphericity and the nature of asphericity as well as their respective averages, we find two distinct shape regimes depending on the flexibility of the polymer. For a small perimeter to persistence length the fluctuating rings exhibit only planar, elliptical configurations. At higher flexibilities three-dimensional, crumpled structures arise. Analytic calculations confirm the qualitative behavior of the averaged shape parameters and the elliptical shape in the stiff regime. 相似文献
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Twist stiffness and an asymmetric bending stiffness of a polymer or a polymer bundle is captured by the elastic ribbon model.
We investigate the effects a ring geometry induces to a thermally fluctuating ribbon, finding bend-bend coupling in addition
to twist-bend coupling. Furthermore, due to the geometric constraint the polymer's effective bending stiffness increases.
A new parameter for experimental investigations of polymer bundles is proposed: the mean square diameter of a ribbonlike ring,
which is determined analytically in the semiflexible limit. Monte Carlo simulations are performed which affirm the model's
prediction up to high flexibility. 相似文献
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We study the spectrum of Schrödinger operators with matrixvalued potentials, utilizing tools from infinite-dimensional symplectic geometry. Using the spaces of abstract boundary values, we derive relations between the Morse and Maslov indices for a family of operators on a Hilbert space obtained by perturbing a given self-adjoint operator by a smooth family of bounded self-adjoint operators. The abstract results are applied to the Schrödinger operators with θ-periodic, Dirichlet, and Neumann boundary conditions. In particular, we derive an analogue of the Morse-Smale Index Theorem for multi-dimensional Schrödinger operators with periodic potentials. For quasi-convex domains in Rn, we recast the results, connecting the Morse and Maslov indices using the Dirichlet and Neumann traces on the boundary of the domain. 相似文献
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The representation of the AC electrical data in the complex plane reveal two major classifications of the relaxation processes known as ideal (Debye) and non-ideal (non-Debye) types. The non-Debye relaxation has been empirically observed via Cole-Cole (C-C), Davidson-Cole (D-C), and Havriliak-Negami (H-N) responses. Each of these non-Debye relaxations is visualized with an equivalent circuit similar to the ideal relaxation. Both ideal and C-C relaxations reveal semicircular behavior in the complex plane while D-C and H-N relaxations deviate from the usual semicircular loci known as skewed behavior. The extracted equivalent circuit elements are essentially non-Debye for both D-C and H-N relaxations possessing complexity in the relaxation time. The analytical method of extracting these elements in conjunction with the empirical parameters of the D-C relaxation is described using conventional (real) domain and complex domain. The curve fitting procedure provided extremely small error for the complex domain analysis. The behavior of the D-C relaxation function and the depression parameter β are also discussed using ωτ=1 and ωτ≠1 corresponding to the maximum of the imaginary part of the impedance (Z*) or permittivity (ε*). 相似文献
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We use the polynomial formulation of the holomorphic anomaly equations governing perturbative topological string theory to derive the free energies in a scaling limit to all orders in perturbation theory for any Calabi–Yau threefold. The partition function in this limit satisfies an Airy differential equation in a rescaled topological string coupling. One of the two solutions of this equation gives the perturbative expansion and the other solution provides geometric hints of the non-perturbative structure of topological string theory. Both solutions can be expanded naturally around strong coupling. 相似文献
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Gelmboldt VO Ganin EV Fonari MS Simonov YA Koroeva LV Ennan AA Basok SS Shova S Kählig H Arion VB Keppler BK 《Dalton transactions (Cambridge, England : 2003)》2007,(27):2915-2924
Two novel compounds, (L(1)H)(2)[SiF(6)] x 2H(2)O (1) and (L(2)H)(2)[SiF(5)(H(2)O)](2) x 3H(2)O (2), resulting from the reactions of H(2)SiF(6) with 4'-aminobenzo-12-crown-4 (L(1)) and monoaza-12-crown-4 (L(2)), respectively, were studied by X-ray diffraction and characterised by IR and (19)F NMR spectroscopic methods. Both complexes have ionic structures due to the proton transfer from the fluorosilicic acid to the primary amine group in L(1) and secondary amine group incorporated into the macrocycle L(2). The structure of 1 is composed of [SiF(6)](2-) centrosymmetric anions, N-protonated cations (L(1)H)(+), and two water molecules, all components being bound in the layer through a system of NH[...]F, NH[...]O and OH[...]F hydrogen bonds. The [SiF(6)](2-) anions and water molecules are assembled into inorganic negatively-charged layers via OH[dot dot dot]F hydrogen bonds. The structure of 2 is a rare example of stabilisation of the complex anion [SiF(5)(H(2)O)](-), the labile product of hydrolytic transformations of the [SiF(6)](2-) anion in an aqueous solution. The components of 2, i.e., [SiF(5)(H(2)O)](-), (L(2)H)(+), and water molecules, are linked by a system of NH[...]F, NH[...]O, OH[...]F, OH[dot dot dot]O hydrogen bonds. In a way similar to 1, the [SiF(5)(H(2)O)](-) anions and water molecules in 2 are combined into an inorganic negatively-charged layer through OH[...]F and OH[...]O interactions. 相似文献
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目的:试验研究维医沙疗对骨关节炎动物模型骨质层转移的影响.方法:采用CT扫描的手段分别四次(建立实验对象OA模型前后各一次、进沙疗第14天和第28天各一次)采集两个实验对象股骨数据.将数据导入MIMICS软件分离实验对象股骨,根据CT值范围不同把股骨分为六个骨质层并读取各层体积.分析了各骨质层的体积在股骨总骨量中所占比例的变化和股骨平均CT值的变化.结果:分析四次CT数据的变化,发现沙疗对象股骨总骨量增长,而对照对象之下降.与此同时沙疗对象股骨平均CT值上升,相比之下对照对象平均CT值下降.结论:沙疗对关节炎对象有促进骨代谢作用,使骨质从低CT值的骨质层转移至高CT值骨质层. 相似文献