Div-Curl Problems and H1\mathbf{H}^1-regular Stream Functions in 3D Lipschitz Domains

We consider the problem of recovering the divergence-free velocity field ${\mathbf U}\in\mathbf{L}^2(\Omega)$ of a given vorticity ${\mathbf F}=\mathrm{curl}\,{\mathbf U}$ on a bounded Lipschitz domain $\Omega\subset\mathbb{R}^3$. To that end, we solve the "div-curl problem" for a given ${\mathbf F}\in{\mathbf H}^{-1}(\Omega)$. The solution is expressed in terms of a vector potential (or stream function) ${\mathbf A}\in{\mathbf H}^1(\Omega)$ such that ${\mathbf U}=\mathrm{curl}\,{\mathbf A}$. After discussing existence and uniqueness of solutions and associated vector potentials, we propose a well-posed construction for the stream function. A numerical method based on this construction is presented, and experiments confirm that the resulting approximations display higher regularity than those of another common approach

Superconducting d-wave stripes in cuprates: Valence bond order coexisting with nodal quasiparticles

We point out that unidirectional bond-centered charge-density-wave states in cuprates involve electronic order in both s- and d-wave channels, with non-local Coulomb repulsion suppressing the s-wave component. The resulting bond-charge-density wave, coexisting with superconductivity, is compatible with recent photoemission and tunneling data and as well as neutron-scattering measurements, once long-range order is destroyed by slow fluctuations or glassy disorder. In particular, the real-space structure of d-wave stripes is consistent with the scanning-tunneling-microscopy measurements on both underdoped Bi2Sr2CaCu2O8+x and Ca2-xNaxCuO2Cl2 of Kohsaka et al. [Science 315, 1380 (2007), arXiv:cond-mat/0703309].Comment: 5 pages, 3 figs, (v2) final version to be published in PR

A framework for multi-tier type evolution and data migration

This paper describes a framework that supports the simultaneous evolution of objectoriented data models and relational schemas with respect to a tool- supported object-relational mapping. Thereby the proposed framework accounts for non-trivial data migration induced by type evolution from the outset. The support for data migration is offered on the level of transparent data access. The framework consists of the following integrated parts: an automatic model change detection mechanism, a generator for schema evolution code and a generator for data migration APIs. The framework has been concepted in the IMIS project. IMIS is an information system for environmental radioactivity measurements. Though the indicated domain especially demands a solution like the one discussed in the paper, the achievements are of general purpose for multi-tier system architectures with object-relational mapping

Incorporating Road Networks into Territory Design

Given a set of basic areas, the territory design problem asks to create a predefined number of territories, each containing at least one basic area, such that an objective function is optimized. Desired properties of territories often include a reasonable balance, compact form, contiguity and small average journey times which are usually encoded in the objective function or formulated as constraints. We address the territory design problem by developing graph theoretic models that also consider the underlying road network. The derived graph models enable us to tackle the territory design problem by modifying graph partitioning algorithms and mixed integer programming formulations so that the objective of the planning problem is taken into account. We test and compare the algorithms on several real world instances

Transfer of trapped atoms between two optical tweezer potentials

Trapped, laser-cooled rubidium atoms are transferred between two strongly focused, horizontal, orthogonally intersecting laser beams. The transfer efficiency is studied as a function of the vertical distance between the beam axes. Optimum transfer is found when the distance equals the beam waist radius. Numerical simulations reproduce well the experimental results

Draft Genome Sequences of Chlamydiales Bacterium STE3 and Neochlamydia sp. Strain AcF84, Endosymbionts of Acanthamoeba spp.

Chlamydiales bacterium STE3 and Neochlamydia sp. strain AcF84 are obligate intracellular symbionts of Acanthamoeba spp. isolated from the biofilm of a littoral cave wall and gills from striped tiger leaf fish, respectively. We report the draft genome sequences of these two environmental chlamydiae affiliated with the family Parachlamydiaceae

InP-quantum dots in Al0.20Ga0.80InP with different barrier configurations

Systematic ensemble photoluminescence studies have been performed on type-I InP-quantum dots in Al0.20Ga0.80InP barriers, emitting at approximately 1.85 eV at 5 K. The influence of different barrier configurations as well as the incorporation of additional tunnel barriers on the optical properties has been investigated. The confinement energy between the dot barrier and the surrounding barrier layers, which is the sum of the band discontinuities for the valence and the conduction bands, was chosen to be approximately 190 meV by using Al0.50Ga0.50InP. In combination with 2 nm thick AlInP tunnel barriers, the internal quantum efficiency of these barrier configurations can be increased by up to a factor of 20 at elevated temperatures with respect to quantum dots without such layers.Comment: physica status solidi (c) (Proceedings of QD 2008