Diffusion-controlled phase growth on dislocations

We treat the problem of diffusion of solute atoms around screw dislocations. In particular, we express and solve the diffusion equation, in radial symmetry, in an elastic field of a screw dislocation subject to the flux conservation boundary condition at the interface of a new phase. We consider an incoherent second-phase precipitate growing under the action of the stress field of a screw dislocation. The second-phase growth rate as a function of the supersaturation and a strain energy parameter is evaluated in spatial dimensions d=2 and d=3. Our calculations show that an increase in the amplitude of dislocation force, e.g. the magnitude of the Burgers vector, enhances the second-phase growth in an alloy. Moreover, a relationship linking the supersaturation to the precipitate size in the presence of the elastic field of dislocation is calculated.Comment: 10 pages, 4 figures, a revised version of the paper presented in MS&T'08, October 5-9, 2008, Pittsburg

Computational steering in realitygrid

The RealityGrid project (http://www.realitygrid.org) aims both to enable the discovery of new materials through integrated experiments and to understand the behaviour of physical systems based on the properties of their microscopic components using diverse simulation methods spanning many time and length scales. A central theme of RealityGrid is the facilitation of distributed and collaborative steering of parallel simulation codes and simultaneous on-line, high-end visualisation. In this paper, we review the motivations for computational steering and introduce the RealityGrid steering library and associated software. We then outline the capabilities of the library and describe the service-oriented architecture of the latest implementation, in which the steering controls of the application are exposed through an OGSI-compliant Grid service

Wavelet-based Image deconvolution for Wide Field CCD Imagery

We show how a wavelet-based image adaptive deconvolution algorithm can provide significant improvements in the analysis of wide-field CCD images. To illustrate it, we apply our deconvolution protocol to a set of images from a Baker-Nunn telescope. This f/1 instrument has an outstanding field of view of 4.4°x4.4° with high optical quality offering unique properties to study our deconvolution process and results. In particular, we obtain an estimated gain in limiting magnitude of ΔR∼0.6 mag and in limiting resolution of Δρ∼3.9 arcsec. These results increase the number of targets and the efficiency of the underlying scientific project

The association of sport and exercise activities with cardiovascular disease risk: The Atherosclerosis risk in Communities (ARIC) study

Background: This study assessed the independent associations between participation in self-reported sport and exercise activities and incident cardiovascular disease (CVD). Methods: Data were from 13,204 participants in the Atherosclerosis Risk in Communities Study cohort (1987–2015). Baseline sport and exercise activities were assessed via the modified Baecke questionnaire. Incident CVD included coronary heart disease, heart failure, or stroke. Multivariable-adjusted Cox proportional hazard models assessed the association of participation in specific sport and exercise activities at enrollment with risk of CVD. Results: During a median follow-up time of 25.2 years, 30% of the analytic sample (n = 3966) was diagnosed with incident CVD. In fully adjusted models, participation in racquet sports (hazard ratio [HR] 0.75; 95% confidence interval [CI], 0.61–0.93), aerobics (HR 0.75; 95% CI, 0.63–0.88), running (HR 0.68; 95% CI, 0.54–0.85), and walking (HR 0.89; 95% CI, 0.83–0.95) was significantly associated with a lower risk of CVD. There were no significant associations for bicycling, softball/baseball, gymnastics, swimming, basketball, calisthenics exercises, golfing with cart, golfing with walking, bowling, or weight training. Conclusions: Participation in specific sport and exercises may substantially reduce the risk for CVD

Fredholm Determinants, Differential Equations and Matrix Models

Orthogonal polynomial random matrix models of NxN hermitian matrices lead to Fredholm determinants of integral operators with kernel of the form (phi(x) psi(y) - psi(x) phi(y))/x-y. This paper is concerned with the Fredholm determinants of integral operators having kernel of this form and where the underlying set is a union of open intervals. The emphasis is on the determinants thought of as functions of the end-points of these intervals. We show that these Fredholm determinants with kernels of the general form described above are expressible in terms of solutions of systems of PDE's as long as phi and psi satisfy a certain type of differentiation formula. There is also an exponential variant of this analysis which includes the circular ensembles of NxN unitary matrices.Comment: 34 pages, LaTeX using RevTeX 3.0 macros; last version changes only the abstract and decreases length of typeset versio

Collectivity Embedded in Complex Spectra of Finite Interacting Fermi Systems: Nuclear Example

The mechanism of collectivity coexisting with chaos in a finite system of strongly interacting fermions is investigated. The complex spectra are represented in the basis of two-particle two-hole states describing the nuclear double-charge exchange modes in $^{48}$Ca. An example of $J^{\pi}=0^-$ excitations shows that the residual interaction, which generically implies chaotic behavior, under certain specific and well identified conditions may create strong transitions, even much stronger than those corresponding to a pure mean-field picture. Such an effect results from correlations among the off-diagonal matrix elements, is connected with locally reduced density of states and a local minimum in the information entropy.Comment: 16 pages, LaTeX2e, REVTeX, 8 PostScript figures, to appear in Physical Review

The TeraGyroid Experiment

The TeraGyroid experiment at SC 03 addressed a large-scale problem of genuine scientific interest at the same time as showing how intercontinental grids enable new paradigms for collaborative computational science that can dramatically reduce the time to insight. TeraGyroid used computational steering to accelerate the exploration of parameter space in condensed matter simulations. The scientific objective was to study the self-assembly, defect pathways and dynamics of liquid crystalline cubic gyroid mesophases using the largest set of lattice-Boltzmann (LB) simulations ever performed, involving in some cases lattices of over one billion sites and for highly extended simulation times. We describe the application in sufficient detail to reveal how it uses the grid to support interactions between its distributed parts, where the interfaces exist between the application and the middleware infrastructure, what grid services and capabilities are used, and why important design decisions were made. We also describe how the resources of highend computing services were federated with the UK e-Science Grid and the US TeraGrid to form the TeraGyroid testbed, and summarise the lessons learned during the experiment

Generic Business Model Types for Enterprise Mashup Intermediaries

The huge demand for situational and ad-hoc applications desired by the mass of business end users led to a new kind of Web applications, well-known as Enterprise Mashups. Users with no or limited programming skills are empowered to leverage in a collaborative manner existing Mashup components by combining and reusing company internal and external resources within minutes to new value added applications. Thereby, Enterprise Mashup environments interact as intermediaries to match the supply of providers and demand of consumers. By following the design science approach, we propose an interaction phase model artefact based on market transaction phases to structure required intermediary features. By means of five case studies, we demonstrate the application of the designed model and identify three generic business model types for Enterprise Mashups intermediaries (directory, broker, and marketplace). So far, intermediaries following a real marketplace business model don’t exist in context of Enterprise Mashups and require further research for this emerging paradigm

Galloylated proanthocyanidins from shea (Vitellaria paradoxa) meal have potent anthelmintic activity against Ascaris suum

Proanthocyanidins (PA) from shea (Vitellaria paradoxa) meal were investigated by thiolytic degradation with benzyl mercaptan and the reaction products were analysed by high performance liquid chromatography–mass spectrometry. These PA were galloylated (≈40%), contained only B-type linkages and had a high proportion of prodelphinidins (>70%). The mean degree of polymerisation was 8 (i.e. average molecular size was 2384 Da) and epigallocatechin gallate (EGCg) was the major flavan-3-ol subunit in PA. Shea meal also proved to be a potentially valuable source for extracting free flavan-3-ol-O-gallates, especially EGCg (575 mg/kg meal), which is known for its health and anti-parasitic benefits. Proanthocyanidins were isolated and tested for bioactivity against Ascaris suum, which is an important parasite of pigs. Migration and motility tests revealed that these PA have potent activity against this parasitic nematode

Magnetic Field Amplification in Galaxy Clusters and its Simulation

We review the present theoretical and numerical understanding of magnetic field amplification in cosmic large-scale structure, on length scales of galaxy clusters and beyond. Structure formation drives compression and turbulence, which amplify tiny magnetic seed fields to the microGauss values that are observed in the intracluster medium. This process is intimately connected to the properties of turbulence and the microphysics of the intra-cluster medium. Additional roles are played by merger induced shocks that sweep through the intra-cluster medium and motions induced by sloshing cool cores. The accurate simulation of magnetic field amplification in clusters still poses a serious challenge for simulations of cosmological structure formation. We review the current literature on cosmological simulations that include magnetic fields and outline theoretical as well as numerical challenges.Comment: 60 pages, 19 Figure