Reversed spin polarization at the Co(001)-HfO2(001) interface

Ab initio electronic-structure calculations on the Co(001)-HfO2(001) interface are reported. The spin polarization of conduction electrons is positive at the interface, i.e., it is reversed with respect to the spin polarization in bulk Co. The electronic structure is very sensitive to the interface structure; without atomic relaxations the reversed spin polarization is not found. The possible relation with spin-polarized tunneling and magnetoresistance is discussed

Anomalous behavior of the semiconducting gap in WO3 from first-principles calculations

Several crystal structures of tungsten trioxide have been studied with a first-principles pseudopotential method. The electronic band gap increases significantly with the distortion of the octahedra that are the building blocks of the various crystal structures. Moreover, the tilting of the octahedra in the more complex structures leads to a strong increase of the gap upon compression

A Musical instrument in MEMS

In this work we describe a MEMS instrument that resonates at audible frequencies, and with which music can be made. The sounds are generated by mechanical resonators and capacitive displacement sensors. Damping by air scales unfavourably for generating audible frequencies with small devices. Therefore a vacuum of 1.5 mbar is used to increase the quality factor and consequently the duration of the sounds to around 0.25 s. The instrument will be demonstrated during the MME 2010 conference opening, in a musical composition especially made for the occasion

Double transverse spin asymmetries in vector boson production

We investigate a helicity non-flip double transverse spin asymmetry in vector boson production in hadron-hadron scattering, which was first considered by Ralston and Soper at the tree level. It does not involve transversity functions and in principle also arises in W-boson production for which we present the expressions. The asymmetry requires observing the transverse momentum of the vector boson, but it is not suppressed by explicit inverse powers of a large energy scale. However, as we will show, inclusion of Sudakov factors causes suppression of the asymmetry, which increases with energy. Moreover, the asymmetry is shown to be approximately proportional to x_1 g_1(x_1) x_2 \bar g_1(x_2), which gives rise to additional suppression at small values of the light cone momentum fractions. This implies that it is negligible for Z or W production and is mainly of interest for \gamma^* at low energies. We also compare the asymmetry with other types of double transverse spin asymmetries and discuss how to disentangle them.Comment: 12 pages, Revtex, 2 Postscript figures, uses aps.sty, epsf.sty; figures replaced, a few minor other correction

Tailoring the Implementation of New Biomarkers Based on Their Added Predictive Value in Subgroups of Individuals

Background\ud The value of new biomarkers or imaging tests, when added to a prediction model, is currently evaluated using reclassification measures, such as the net reclassification improvement (NRI). However, these measures only provide an estimate of improved reclassification at population level. We present a straightforward approach to characterize subgroups of reclassified individuals in order to tailor implementation of a new prediction model to individuals expected to benefit from it.\ud \ud Methods\ud In a large Dutch population cohort (n = 21,992) we classified individuals to low (<5%) and high (≥5%) fatal cardiovascular disease risk by the Framingham risk score (FRS) and reclassified them based on the systematic coronary risk evaluation (SCORE). Subsequently, we characterized the reclassified individuals and, in case of heterogeneity, applied cluster analysis to identify and characterize subgroups. These characterizations were used to select individuals expected to benefit from implementation of SCORE.\ud \ud Results\ud Reclassification after applying SCORE in all individuals resulted in an NRI of 5.00% (95% CI [-0.53%; 11.50%]) within the events, 0.06% (95% CI [-0.08%; 0.22%]) within the nonevents, and a total NRI of 0.051 (95% CI [-0.004; 0.116]). Among the correctly downward reclassified individuals cluster analysis identified three subgroups. Using the characterizations of the typically correctly reclassified individuals, implementing SCORE only in individuals expected to benefit (n = 2,707,12.3%) improved the NRI to 5.32% (95% CI [-0.13%; 12.06%]) within the events, 0.24% (95% CI [0.10%; 0.36%]) within the nonevents, and a total NRI of 0.055 (95% CI [0.001; 0.123]). Overall, the risk levels for individuals reclassified by tailored implementation of SCORE were more accurate.\ud \ud Discussion\ud In our empirical example the presented approach successfully characterized subgroups of reclassified individuals that could be used to improve reclassification and reduce implementation burden. In particular when newly added biomarkers or imaging tests are costly or burdensome such a tailored implementation strategy may save resources and improve (cost-)effectivenes

Studies on Wild House Mice. VII. Prenatal Maternal Environment and Aggression

The effect of the maternal environment on intermale aggression was studied by means of embryo transfer of genetically selected aggressive (SAL) and nonaggressive wild house mice (LAL), and their reciprocal F1's, to standard (NMRI) females. No effect was found on the attack latency scores (ALS), i.e., aggression: all genotypes born and raised under natural conditions showed an ALS similar that of genotypes born and raised by NMRI females. Since previous studies on wild house mice failed to demonstrate postnatal effects on aggression, and the present results indicate the absence of prenatal maternal environmental effects on aggression, the primacy of genetic over maternal variance in the development of adult intermale aggression in wild house mice is indicated

Praktijkproef Pseudomonas tegen Pythium. Toepassing van Pseudomonas fluorescens tegen Pythium in hyacint en krokus in praktijkpercelen in 2004-2005

Bij PPO bloembollen in Lisse is een aantal jaar onderzoek gedaan naar de biologische bestrijding van Pythium met de bacterie Pseudomonas fluorescens. Op basis van onderzoeksresultaten die behaald zijn in eerdere proeven, is in opdracht van het Productschap Tuinbouw (projectnrs 320728 en 321091) in een aantal praktijkpercelen een proef met de bacterie aangelegd, al dan niet in combinatie met de fungicide Ridomil Gold. De resultaten uit de praktijkproef onderschrijven nog eens de eerdere resultaten. Indien er verschil in stand van het gewas of in de bolopbrengst was ten opzichte van de onbehandelde controle was deze over het algemeen hoger in de met Pseudomonas behandelde veldjes. De werking van de biologische bestrijder is wisselend maar verschilt niet of nauwelijks van de werking van Ridomil Gold. Op percelen waar de combinatiebehandeling Ridomil Gold samen met Pseudomonas werd toegepast, werd geen verschil geconstateerd met de enkele behandelingen. De soms wisselvallige werking bij de Pythium bestrijding over de jaren heen geeft aan dat ondanks het potentieel de toepassing nog geen totaaloplossing is en er nog gewerkt moet worden aan een meer betrouwbare en consistentere werking, eventueel door de bacterie toe te passen in combinatie met chemische bestrijding of ander beheersmaatregelen. Een juiste formulering van de biologische bestrijder zou hier een goede bijdrage aan kunnen leveren en de toepassing vereenvoudigen

Impact of Matric Potential and Pore Size Distribution on Growth Dynamics of Filamentous and Non-Filamentous Soil Bacteria

The filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to what extent, filamentous bacteria may also display similar advantages over non-filamentous bacteria in soils with low hydraulic connectivity. In addition to allowing for microbial interactions and competition across connected micro-sites, water films also facilitate the motility of non-filamentous bacteria. To examine these issues, we constructed and characterized a series of quartz sand microcosms differing in matric potential and pore size distribution and, consequently, in connection of micro-habitats via water films. Our sand microcosms were used to examine the individual and competitive responses of a filamentous bacterium (Streptomyces atratus) and a motile rod-shaped bacterium (Bacillus weihenstephanensis) to differences in pore sizes and matric potential. The Bacillus strain had an initial advantage in all sand microcosms, which could be attributed to its faster growth rate. At later stages of the incubation, Streptomyces became dominant in microcosms with low connectivity (coarse pores and dry conditions). These data, combined with information on bacterial motility (expansion potential) across a range of pore-size and moisture conditions, suggest that, like their much larger fungal counterparts, filamentous bacteria also use this growth form to facilitate growth and expansion under conditions of low hydraulic conductivity. The sand microcosm system developed and used in this study allowed for precise manipulation of hydraulic properties and pore size distribution, thereby providing a useful approach for future examinations of how these properties influence the composition, diversity and function of soil-borne microbial communities

Massless BTZ black holes in minisuperspace

We study aspects of the propagation of strings on BTZ black holes. After performing a careful analysis of the global spacetime structure of generic BTZ black holes, and its relation to the geometry of the SL(2,R) group manifold, we focus on the simplest case of the massless BTZ black hole. We study the SL(2,R) Wess-Zumino-Witten model in the worldsheet minisuperspace limit, taking into account special features associated to the Lorentzian signature of spacetime. We analyse the two- and three-point functions in the pointparticle limit. To lay bare the underlying group structure of the correlation functions, we derive new results on Clebsch-Gordan coefficients for SL(2,R) in a parabolic basis. We comment on the application of our results to string theory in singular time-dependent orbifolds, and to a Lorentzian version of the AdS/CFT correspondence.Comment: 28 pages, v2: reference adde

The mid-Cretaceous North Atlantic nutrient trap: Black shales and OAEs

Organic-rich sediments are the salient marine sedimentation product in the mid-Cretaceous of the ocean basins formed in the Mesozoic. Oceanic anoxic events (OAEs) are discrete and particularly organic-rich intervals within these mid-Cretaceous organic-rich sequences and are defined by pronounced carbon isotope excursions. Marine productivity during OAEs appears to have been enhanced by the increased availability of biolimiting nutrients in seawater due to hydrothermal alteration of submarine basalts in the Pacific and proto-Indian oceans. The exact mechanisms behind the deposition of organic-rich sediments in the mid-Cretaceous are still a matter of discussion, but a hypothesis which is often put forward is that their deposition was a consequence of the coupling of a particular paleogeography with changes in ocean circulation and nutrient supply. In this study, we used a global coupled climate model to investigate oceanic processes that affect the interbasinal exchange of nutrients as well as their spatial distribution and bioavailability. We conclude that the mid-Cretaceous North Atlantic was a nutrient trap as a consequence of an estuarine circulation with respect to the Pacific. Organic-rich sediments in the North Atlantic were deposited below regions of intense upwelling. We suggest that enhanced productivity during OAEs was a consequence of upwelling of Pacific-derived nutrient-rich seawater associated with submarine igneous events