Probability measures, L\'{e}vy measures and analyticity in time

We investigate the relation of the semigroup probability density of an infinite activity L\'{e}vy process to the corresponding L\'{e}vy density. For subordinators, we provide three methods to compute the former from the latter. The first method is based on approximating compound Poisson distributions, the second method uses convolution integrals of the upper tail integral of the L\'{e}vy measure and the third method uses the analytic continuation of the L\'{e}vy density to a complex cone and contour integration. As a by-product, we investigate the smoothness of the semigroup density in time. Several concrete examples illustrate the three methods and our results.Comment: Published in at http://dx.doi.org/10.3150/07-BEJ6114 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Emergent Form from Structural Optimisation of the Voronoi Polyhedra Structure

In the course of the exploration of computational means in the architectural design process, in order to investigate more complex, adaptive geometries, the Voronoi diagram has recently gained some attention, being a three-dimensional space-filling structure which is modular but not repetitive. The project looks at the Voronoi diagram as a load-bearing structure, and whether it can be useful for structural optimisation. Hereby the edges of the Voronoi polyhedra are regarded as structural members of a statical system, which then is assessed by structural analysis software. Results seem to indicate that the Voronoi approach produces a very specific structural as well as spatial type of order. Through the dislocation of the Voronoi cells, the statical structure becomes more complex through emergent topology changes, and the initially simple spatial system becomes much more complex through emerging adjacencies and interconnections between spaces. The characteristics of the emerging form, however, lie rather in the complexity how shifted spaces and parts are fitted together, than in a radical overall emergent geometry. Spatially as well as a structurally, the form moves from a simple modular repetitive system towards a more complex adaptive one, with interconnected parts which cannot stand alone but rather form an organic whole

Reentry vehicle leading edge Patent

Leading edge design for hypersonic reentry vehicle

Studies of proteinograms in dermatophytes by disc electrophoresis. 1. Protein bands in relation to growth phase

Homogenates were prepared from various growth phases of Microsporum gypseum grown on different amino acids as the nitrogen source. When analyzed on 7.5% polyacrylamide disc gels, the water-soluble proteins in these homogenates gave essentially identical banding patterns

Phaseseparation in overdoped Y_{1-0.8}Ca_{0-0.2}Ba_2Cu_3O_{6.96-6.98}

The dimpling in the CuO_2 planes of overdoped Y_{1-y}Ca_yBa_2Cu_3 O_{6.96-6.98} (y=0.02-0.2) has been measured by x-ray absorption-fine- structure spectroscopy (Y-K EXAFS). A step-like decrease around 12% Ca indicates a percolation threshold for distorted sites of 5 cells, and thus phase segregation. We conclude the charge carriers added by substitution of Y{3+} by Ca{2+} to be trapped at the Ca sites and their nn environment.Comment: 5 pages, 2 eps figures, uses AIP 6x9 styl

Quasiparticle band structure of the almost-gapless transition-metal-based Heusler semiconductors

Transition-metal-based Heusler semiconductors are promising materials for a variety of applications ranging from spintronics to thermoelectricity. Employing the $GW$ approximation within the framework of the FLAPW method, we study the quasi-particle band structure of a number of such compounds being almost gapless semiconductors. We find that in contrast to the \textit{sp}-electron based semiconductors such as Si and GaAs, in these systems the many-body corrections have a minimal effect on the electronic band structure and the energy band gap increases by less than 0.2~eV, which makes the starting point density functional theory (DFT) a good approximation for the description of electronic and optical properties of these materials. Furthermore, the band gap can be tuned either by the variation of the lattice parameter or by the substitution of the \emph{sp}-chemical element

Nonconventional screening of the Coulomb interaction in FexOy clusters: An ab-initio study

From microscopic point-dipole model calculations of the screening of the Coulomb interaction in non-polar systems by polarizable atoms, it is known that screening strongly depends on dimensionality. For example, in one dimensional systems the short range interaction is screened, while the long range interaction is anti-screened. This anti-screening is also observed in some zero dimensional structures, i.e. molecular systems. By means of ab-initio calculations in conjunction with the random-phase approximation (RPA) within the FLAPW method we study screening of the Coulomb interaction in FexOy clusters. For completeness these results are compared with their bulk counterpart magnetite. It appears that the onsite Coulomb interaction is very well screened both in the clusters and bulk. On the other hand for the intersite Coulomb interaction the important observation is made that it is almost contant throughout the clusters, while for the bulk it is almost completely screened. More precisely and interestingly, in the clusters anti-screening is observed by means of ab-initio calculations

Effect of Local Electron-Electron Correlation in Hydrogen-like Impurities in Ge

We have studied the electronic and local magnetic structure of the hydrogen interstitial impurity at the tetrahedral site in diamond-structure Ge, using an empirical tight binding + dynamical mean field theory approach because within the local density approximation (LDA) Ge has no gap. We first establish that within LDA the 1s spectral density bifurcates due to entanglement with the four neighboring sp3 antibonding orbitals, providing an unanticipated richness of behavior in determining under what conditions a local moment hyperdeep donor or Anderson impurity will result, or on the other hand a gap state might appear. Using a supercell approach, we show that the spectrum, the occupation, and the local moment of the impurity state displays a strong dependence on the strength of the local on-site Coulomb interaction U, the H-Ge hopping amplitude, the depth of the bare 1s energy level epsilon_H, and we address to some extent the impurity concentration dependence. In the isolated impurity, strong interaction regime a local moment emerges over most of the parameter ranges indicating magnetic activity, and spectral density structure very near (or in) the gap suggests possible electrical activity in this regime.Comment: 9 pages, 5 figure