A collective extension of relational grammar

Relational grammar was proposed in Suppes (1976) as a semantical grammar for natural language. Fragments considered so far are restricted to distributive notions. In this article, relational grammar is extended to collective notions

Manifestly N=3 supersymmetric Euler-Heisenberg action in light-cone superspace

We find a manifestly N=3 supersymmetric generalization of the four-dimensional Euler-Heisenberg (four-derivative, or F^4) part of the Born-Infeld action in light-cone gauge, by using N=3 light-cone superspace.Comment: 9 pages, LaTeX, no figures, macros include

Fabrication and electrical transport properties of embedded graphite microwires in a diamond matrix

Micrometer width and nanometer thick wires with different shapes were produced \approx 3~\upmum below the surface of a diamond crystal using a microbeam of He$^+$ ions with 1.8~MeV energy. Initial samples are amorphous and after annealing at $T\approx 1475$~K, the wires crystallized into a graphite-like structures, according to confocal Raman spectroscopy measurements. The electrical resistivity at room temperature is only one order of magnitude larger than the in-plane resistivity of highly oriented pyrolytic bulk graphite and shows a small resistivity ratio($\rho(2{\rm K})/\rho(315{\rm K}) \approx 1.275$). A small negative magnetoresistance below $T=200$~K was measured and can be well understood taking spin-dependent scattering processes into account. The used method provides the means to design and produce millimeter to micrometer sized conducting circuits with arbitrary shape embedded in a diamond matrix.Comment: 12 pages, 5 figures, to be published in Journal of Physics D: Applied Physics (Feb. 2017

A Multi-wavelength MOCASSIN Model of the Magellanic-type Galaxy NGC 4449

We use the photoionisation and dust radiative transfer code MOCASSIN to create a model of the dwarf irregular galaxy NGC 4449. The best-matching model reproduces the global optical emission line fluxes and the observed spectral energy distribution (SED) spanning wavelengths from the UV to sub-mm, and requires the bolometric luminosity of 6.25e9 Lsolar for the underlying stellar component, M_d/M_g of 1/680 and M_d of 2.2e6 Msolar.Comment: 4 pages, 4 figures, submitted to Proceedings of the IAU Symposium 284: The Spectral Energy Distribution of Galaxies (SED2011

A semiconductor laser system for the production of antihydrogen

Laser-controlled charge exchange is a promising method for producing cold antihydrogen. Caesium atoms in Rydberg states collide with positrons and create positronium. These positronium atoms then interact with antiprotons, forming antihydrogen. Laser excitation of the caesium atoms is essential to increase the cross section of the charge-exchange collisions. This method was demonstrated in 2004 by the ATRAP collaboration by using an available copper vapour laser. For a second generation of charge-exchange experiments we have designed a new semiconductor laser system that features several improvements compared to the copper vapour laser. We describe this new laser system and show the results from the excitation of caesium atoms to Rydberg states within the strong magnetic fields in the ATRAP apparatus

Black hole solutions in Euler-Heisenberg theory

We construct static and spherically symmetric black hole solutions in the Einstein-Euler-Heisenberg (EEH) system which is considered as an effective action of a superstring theory. We considered electrically charged, magnetically charged and dyon solutions. We can solve analytically for the magnetically charged case. We find that they have some remarkable properties about causality and black hole thermodynamics depending on the coupling constant of the EH theory $a$ and $b$, though they have central singularity as in the Schwarzschild black hole.Comment: 8 pages, 13 figures, figures corrected and some comments adde

Pockmarks in the Witch Ground Basin, central north sea

Marine sediments host large amounts of methane (CH4), which is a potent greenhouse gas. Quantitative estimates for methane release from marine sediments are scarce, and a poorly constrained temporal variability leads to large uncertainties in methane emission scenarios. Here, we use 2‐D and 3‐D seismic reflection, multibeam bathymetric, geochemical, and sedimentological data to (I) map and describe pockmarks in the Witch Ground Basin (central North Sea), (II) characterize associated sedimentological and fluid migration structures, and (III) analyze the related methane release. More than 1,500 pockmarks of two distinct morphological classes spread over an area of 225 km2. The two classes form independently from another and are corresponding to at least two different sources of fluids. Class 1 pockmarks are large in size (>6 m deep, >250 m long, and >75 m wide), show active venting, and are located above vertical fluid conduits that hydraulically connect the seafloor with deep methane sources. Class 2 pockmarks, which comprise 99.5% of all pockmarks, are smaller (0.9–3.1 m deep, 26–140 m long, and 14–57 m wide) and are limited to the soft, fine‐grained sediments of the Witch Ground Formation and possibly sourced by compaction‐related dewatering. Buried pockmarks within the Witch Ground Formation document distinct phases of pockmark formation, likely triggered by external forces related to environmental changes after deglaciation. Thus, greenhouse gas emissions from pockmark fields cannot be based on pockmark numbers and present‐day fluxes but require an analysis of the pockmark forming processes through geological time

Lorenz function of Bi2_{2}Te3_{3}/Sb2_{2}Te3_{3} superlattices

Combining first principles density functional theory and semi-classical Boltzmann transport, the anisotropic Lorenz function was studied for thermoelectric Bi$_{2}$Te$_{3}$/Sb$_{2}$Te$_{3}$ superlattices and their bulk constituents. It was found that already for the bulk materials Bi$_{2}$Te$_{3}$ and Sb$_{2}$Te$_{3}$, the Lorenz function is not a pellucid function on charge carrier concentration and temperature. For electron-doped Bi$_{2}$Te$_{3}$/Sb$_{2}$Te$_{3}$ superlattices large oscillatory deviations for the Lorenz function from the metallic limit were found even at high charge carrier concentrations. The latter can be referred to quantum well effects, which occur at distinct superlattice periods

Thermoelectric transport in Bi2Te3/Sb2Te3\text{Bi}_2\text{Te}_3/\text{Sb}_2\text{Te}_3 superlattices

The thermoelectric transport properties of $\text{Bi}_2\text{Te}_3/\text{Sb}_2\text{Te}_3$superlattices are analyzed on the basis of first-principles calculations and semi-classical Boltzmann theory. The anisotropy of the thermoelectric transport under electron and hole-doping was studied in detail for different superlattice periods at changing temperature and charge carrier concentrations. A clear preference for thermoelectric transport under hole-doping, as well as for the in-plane transport direction was found for all superlattice periods. At hole-doping the electrical transport anisotropies remain bulk-like for all investigated systems, while under electron-doping quantum confinement leads to strong suppression of the cross-plane thermoelectric transport at several superlattice periods. In addition, insights on the Lorenz function, the electronic contribution to the thermal conductivity and the resulting figure of merit are given

A semiconductor laser system for the production of antihydrogen

Laser-controlled charge exchange is a promising method for producing cold antihydrogen. Caesium atoms in Rydberg states collide with positrons and create positronium. These positronium atoms then interact with antiprotons, forming antihydrogen. Las er excitation of the caesium atoms is essential to increase the cross section of the charge-exchange collisions. This method was demonstrated in 2004 by the ATRAP collaboration by using an available copper vapour laser. For a second generation of charge-e xchange experiments we have designed a new semiconductor laser system that features several improvements compared to the copper vapour laser. We describe this new laser system and show the results from the excitation of caesium atoms to Rydberg states wit hin the strong magnetic fields in the ATRAP apparatus