Ferromagnetic Film on a Superconducting Substrate

We study the equilibrium domain structure and magnetic flux around a ferromagnetic (FM) film with perpendicular magnetization M_0 on a superconducting (SC) substrate. At 4{\pi}M_0<H_{c1} the SC is in the Meissner state and the equilibrium domain width in the film, l, scales as (l/4{\pi}{\lambda}_{L}) = (l_{N}/4{\pi}{\lambda}_{L})^{2/3} with the domain width on a normal (non-superconducting) substrate, l_{N}/4\pi\lambda_L >> 1. Here \lambda_L is the London penetration length. For 4{\pi}M_0 > H_{c1} and l_{N} in excess of about 35 {\lambda}_{L}, the domains are connected by SC vortices. We argue that pinning of vortices by magnetic domains in FM/SC multilayers can provide high critical currents.Comment: 4 pages, 2 figures, submitted to PR

Lattice dynamics of anharmonic solids from first principles

An accurate and easily extendable method to deal with lattice dynamics of solids is offered. It is based on first-principles molecular dynamics simulations and provides a consistent way to extract the best possible harmonic - or higher order - potential energy surface at finite temperatures. It is designed to work even for strongly anharmonic systems where the traditional quasiharmonic approximation fails. The accuracy and convergence of the method are controlled in a straightforward way. Excellent agreement of the calculated phonon dispersion relations at finite temperature with experimental results for bcc Li and bcc Zr is demonstrated

Phonon quarticity induced by changes in phonon-tracked hybridization during lattice expansion and its stabilization of rutile TiO2_2

Although the rutile structure of TiO$_2$ is stable at high temperatures, the conventional quasiharmonic approximation predicts that several acoustic phonons decrease anomalously to zero frequency with thermal expansion, incorrectly predicting a structural collapse at temperatures well below 1000\,K. Inelastic neutron scattering was used to measure the temperature dependence of the phonon density of states (DOS) of rutile TiO$_2$ from 300 to 1373\,K. Surprisingly, these anomalous acoustic phonons were found to increase in frequency with temperature. First-principles calculations showed that with lattice expansion, the potentials for the anomalous acoustic phonons transform from quadratic to quartic, stabilizing the rutile phase at high temperatures. In these modes, the vibrational displacements of adjacent Ti and O atoms cause variations in hybridization of $3d$ electrons of Ti and $2p$ electrons of O atoms. With thermal expansion, the energy variation in this "phonon-tracked hybridization" flattens the bottom of the interatomic potential well between Ti and O atoms, and induces a quarticity in the phonon potential.Comment: 7 pages, 6 figures, supplemental material (3 figures

Phonon self-energy and origin of anomalous neutron scattering spectra in SnTe and PbTe thermoelectrics

The anharmonic lattice dynamics of rock-salt thermoelectric compounds SnTe and PbTe are investigated with inelastic neutron scattering (INS) and first-principles calculations. The experiments show that, surprisingly, although SnTe is closer to the ferroelectric instability, phonon spectra in PbTe exhibit a more anharmonic character. This behavior is reproduced in first-principles calculations of the temperature-dependent phonon self-energy. Our simulations reveal how the nesting of phonon dispersions induces prominent features in the self-energy, which account for the measured INS spectra and their temperature dependence. We establish that the phase-space for three-phonon scattering processes, rather than just the proximity to the lattice instability, is the mechanism determining the complex spectrum of the transverse-optical ferroelectric mode

Including lateral interactions into microkinetic models of catalytic reactions

In many catalytic reactions lateral interactions between adsorbates are believed to have a strong influence on the reaction rates. We apply a microkinetic model to explore the effect of lateral interactions and how to efficiently take them into account in a simple catalytic reaction. Three different approximations are investigated: site, mean-field, and quasichemical approximations. The obtained results are compared to accurate Monte Carlo numbers. In the end, we apply the approximations to a real catalytic reaction, namely, ammonia synthesis. (c) 2007 American Institute of Physics

Geology and Wine 13. Geographic Information System Characterization of Four Appellations in West Texas, USA

Texas produces approximately 90 000 hl of wine annually from more than 200 wineries and 1214 ha of vineyards. Eight wine grape production regions are officially recognized as American Viticultural Areas (AVAs) in Texas. Improved understanding of the growing conditions within each AVA facilitates selection of well-adapted cultivars that is critical for continued success and expansion of the wine industry. A geographic information system (GIS) was developed to enable enhanced characterization of the climatic, geologic and edaphic conditions of Texas AVAs. The GIS contains datasets describing climatic variables, geology, soils, elevation and topography, all of significance to grape production. This paper characterizes the four viticultural areas (AVAs) of west Texas: Texas High Plains AVA, Escondido Valley AVA, Texas Davis Mountains AVA, and Mesilla Valley AVA. Common features of the four AVAs are relatively high elevation, warm to very warm growing-season temperatures, mild winter temperatures, and low annual precipitation. Local differences in elevation and topography modify climatic conditions among AVAs, providing variations in growing degree-days and ripening-period mean temperatures that influence the performance of grape cultivars. The Texas High Plains and Texas Davis Mountains AVAs have the lowest growing degree-days and coolest ripening-period mean temperatures; Escondido Valley and Mesilla Valley AVAs are drier and warmer, resulting in fruit ripening earlier than in the High Plains and Davis Mountains AVAs. Variable underlying geology leads to differing soil types planted to vineyards in each AVA; predominantly loamy fine sands and fine sandy loam in Texas High Plains, silty clay loam and loam in Escondido Valley, loam and clay loam in Texas Davis Mountains, and clay loam and sandy loam in Mesilla Valley. West Texas produces red wines from Cabernet Sauvignon and Merlot cultivars, which are notable for good tannin and excellent colour; recent planting trends to warm-climate cultivars, including Tempranillo, Sangiovese, Mourvèdre, and Grenache, are producing blended wines of great promise. Similarly, a solid reputation for white wines from Chenin blanc and Chardonnay is being enhanced by increased production of Viognier, Vermentino, and other warm-climate varietal wines. Sommaire Texas produit environ 90 000 hectolitres de vin par année provenant de plus de 200 établissements vinicoles et 1214 ha de vignes. Huit régions de productions de raisins de cuve sont officiellement reconnues comme zones viticoles américaines (AVA) en Texas. Une meilleure compréhension des conditions de croissance au sein de chacune AVA facilite le choix des variétés, (cultivars) adaptées pour le succès et l’expansion continue de l’industrie viticole. Un système d’information géographique (SIG) a été développé pour permettre la caractérisation améliorée des conditions climatiques, géologiques et édaphiques de l’AVA de Texas. Le SIG contient les ensembles de données décrivant les variables climatiques, la géologie, les sols, l’altitude, et topographie d’importances pour la production viticole. Ce document caractérise les quatre Zones viticoles de l’Ouest Texas: Texas High Plains, Escondido Valley, Texas Davis Mountains, et Mesilla Valley. Les caractéristiques communes entre des quatre AVA sont relativement haute altitude, très chaudes températures de saison de croissance, les températures de l’hiver doux et faibles précipitations annuelles. Les variations locales en altitude et topographie modifient les conditions climatiques entre les zones viticoles américaines et entraînent des variations des degrés-jour de croissance (GDD) et la température moyenne de mûrissement (RPMT), ce qui exercent une influence sur rendement des cultivars de raisin. Le Texas High Plains et le Texas Davis Mountains zones viticoles ont les GDD les plus bas et une RPMT froide; le Escondido Valley et Mesilla Valley zones viticoles sont plus secs et plus chauds, ce qui entraine le mûrissement de fruit plus tôt que dans le High Plains et Davis Mountains AVAs. Variable géologie sous-jacente conduit à une variation des types de sol plantés aux vignobles dans chaque AVA ; principalement loam sableux et le loam sablo-argileux dans Texas High Plains, loam limoneux et loam dans Escondido Valley, loam et loam argileux dans Texas Davis Mountains, et loam argileux et loam sableux dans Mesilla Valley. Ouest Texas produit des vins rouges de Cabernet Sauvignon et le Merlot qui se distinguent par le tanin et une couleur excellente, les tendances récentes à la plantation de climat chaud cultivars, y compris le Tempranillo, le Sangiovese, Mourvèdre, et Grenache, produisent des vins d’assemblages de grandes promesses. De même, une solide réputation pour les vins blancs de Chenin blanc et le Chardonnay est améliorer par l’augmentation de la production de Viognier, Vermentino, et d’autres vins de climat chaud cépages

Extensive sequence-influenced DNA methylation polymorphism in the human genome

Background: Epigenetic polymorphisms are a potential source of human diversity, but their frequency and relationship to genetic polymorphisms are unclear. DNA methylation, an epigenetic mark that is a covalent modification of the DNA itself, plays an important role in the regulation of gene expression. Most studies of DNA methylation in mammalian cells have focused on CpG methylation present in CpG islands (areas of concentrated CpGs often found near promoters), but there are also interesting patterns of CpG methylation found outside of CpG islands. Results: We compared DNA methylation patterns on both alleles between many pairs (and larger groups) of related and unrelated individuals. Direct observation and simulation experiments revealed that around 10% of common single nucleotide polymorphisms (SNPs) reside in regions with differences in the propensity for local DNA methylation between the two alleles. We further showed that for the most common form of SNP, a polymorphism at a CpG dinucleotide, the presence of the CpG at the SNP positively affected local DNA methylation in cis. Conclusions: Taken together with the known effect of DNA methylation on mutation rate, our results suggest an interesting interdependence between genetics and epigenetics underlying diversity in the human genome

Interactions of Heavy Hadrons using Regge Phenomenology and the Quark Gluon String Model

The search for stable heavy exotic hadrons is a promising way to observe new physics processes at collider experiments. The discovery potential for such particles can be enhanced or suppressed by their interactions with detector material. This paper describes a model for the interactions in matter of stable hadrons containing an exotic quark of charges $\pm {1/3}e$ or $\pm {2/3}e$ using Regge phenomenology and the Quark Gluon String Model. The influence of such interactions on searches at the LHC is also discussed

Parties, promiscuity and politicisation: business-political networks in Poland

Research on post-communist political economy has begun to focus on the interface between business and politics. It is widely agreed that informal networks rather than business associations dominate this interface, but there has been very little systematic research in this area. The literature tends to assume that a politicised economy entails business-political networks that are structured by parties. Theoretically, this article distinguishes politicisation from party politicisation and argues that the two are unlikely to be found together in a post-communist context. Empirically, elite survey data and qualitative interviews are used to explore networks of businesspeople and politicians in Poland. Substantial evidence is found against the popular idea that Polish politicians have business clienteles clearly separated from each other according to party loyalties. Instead, it is argued that these politicians and businesspeople are promiscuous. Since there seems to be little that is unusual about the Polish case, this conclusion has theoretical, methodological, substantive and policy implications for other post-communist countries