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981.
The coherent flow of a Bose-Einstein condensate through a quantum dot in a magnetic waveguide is studied. By the numerical integration of the time-dependent Gross-Pitaevskii equation in the presence of a source term, we simulate the propagation process of the condensate through a double barrier potential in the waveguide. We find that resonant transport is suppressed in interaction-induced regimes of bistability, where multiple scattering states exist at the same chemical potential and the same incident current. We demonstrate, however, that a temporal control of the external potential can be used to circumvent this limitation and to obtain enhanced transmission near the resonance on experimentally realistic time scales. 相似文献
982.
We experimentally observed a counterpropagating dipole-mode vector soliton in a photorefractive SBN:60Ce crystal. We investigated the transient formation dynamics and show that the formation process differs significantly from the copropagating geometry. The experimental results are compared with fully anisotropic numerical simulations and show good qualitative agreement. 相似文献
983.
984.
Richter AG Yu C Datta A Kmetko J Dutta P 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(1):607-615
We have examined the self-assembly process of octadecyltrichlorosilane on silicon using x-ray reflectivity. By comparing the commonly used "interrupted-growth" characterization technique with results obtained in situ, we have determined that quenching the growth and then rinsing and drying the sample introduces free area into the film, presumably by removal of non-cross-linked (physisorbed) molecules. Reintroduction of a quenched and rinsed film to solvent does not restore the thickness of the film to its previous value. We have also performed in situ growth studies over a range of concentrations. For all concentrations, we observe growth of islands of vertical molecules. The growth follows Langmuir kinetics, except at short times for low concentration solutions. 相似文献
985.
Janusz Januszewski 《Geometriae Dedicata》2000,81(1-3):13-18
Every sequence of rectangles of side lengths not greater than 1, whose total area is smaller than or equal to
can be packed into the unit square. 相似文献
986.
Barbier A Mocuta C Kuhlenbeck H Peters KF Richter B Renaud G 《Physical review letters》2000,84(13):2897-2900
Using grazing-incidence x-ray diffraction, the p(2x2) surface structures of the single crystal NiO(111) and a 5 monolayer thick NiO(111) film on Au(111) were both shown to exhibit locally the theoretically predicted octopolar reconstruction, with some important differences. The single crystal exhibits a single Ni termination with double steps. The thin film exhibits both possible terminations (O and Ni) and single steps. These surfaces were found to be nonreactive with respect to hydroxylation. 相似文献
987.
Günther Richter 《Applied Categorical Structures》2000,8(1-2):161-173
Let Xbe a category with a given(E,M)-factorization structure for morphisms, M Mono
X. In general, an arbitrary endofunctor T of X fails badly to preserve the E-class. If T carries a monad structure, then T(E) E implies that the corresponding category of Eilenberg–Moore-algebras admits (E,M)-factorizations and vice versa. In order to get T as close as possible to this nice algebraic behaviour, a couniversal modification T T with (E) E is constructed in two different ways using mild and natural assumptions on E and M, respectively. T inherits its monad structure from T. In case of T = U F, F U, the Eilenberg–Moore-category of T contains a universal (E,M-algebraic hull (completion) of U [2, 3]. There are further applications to varietal hulls [4] and to function spaces. 相似文献
988.
Strauch S von Neumann-Cosel P Rangacharyulu C Richter A Schrieder G Schweda K Wambach J 《Physical review letters》2000,85(14):2913-2916
The 48Ca(e,e(')n) reaction has been investigated for excitation energies 11-25 MeV and momentum transfers 0.22-0.43 fm(-1) at the superconducting Darmstadt electron linear accelerator S-DALINAC. Electric dipole and quadrupole plus monopole strength distributions are extracted from a multipole decomposition of the spectra. Their fragmented structure is described by microscopic calculations allowing for coupling of the basic particle-hole excitations to more complex configurations. Comparison of the excitation spectrum of the residual nucleus 47Ca with statistical model calculations reveals a 39(5)% contribution of direct decay to the damping of the giant dipole resonance. 相似文献
989.
Janusz J. Charatonik Patricia Pellicer Covarrubias 《Proceedings of the American Mathematical Society》2002,130(7):2145-2154
Covering mappings on the dyadic solenoid are studied. Some results stated by Zhou Youcheng (2000) are discussed in a more detailed way by indicating certain inaccuracies in their proofs. These are either corrected or supplemented, or else suitable counterexamples are constructed. Some open questions are asked and connections with related results are considered.
990.
A fluctuation analysis technique and the comparison of experimentally deduced strength distributions with a statistical one have been used to extract level densities as a function of excitation energy from high-resolution inelastic electron scattering spectra. Both methods yield for the Jπ = 2? states around mean level spacings 〈D〉 = 6.5±1.6 keV and 〈D〉 = 5.5 ± 1.5 keV, respectively. Those level densities are then employed to estimate the magnetic quadrupole strength that is hidden in the background and escaped direct experimental detection. 相似文献