Biconical critical dynamics

A complete two loop renormalization group calculation of the multicritical dynamics at a tetracritical or bicritical point in anisotropic antiferromagnets in an external magnetic field is performed. Although strong scaling for the two order parameters (OPs) perpendicular and parallel to the field is restored as found earlier, in the experimentally accessible region the effective dynamical exponents for the relaxation of the OPs remain different since their equal asymptotic values are not reached.Comment: 6 pages, 2 figures; some additions, corrected typo

Polymeric compositions and their method of manufacture

Filled polymer compositions are made by dissolving the polymer binder in a suitable sublimable solvent, mixing the filler material with the polymer and its solvent, freezing the resultant mixture, and subliming the frozen solvent from the mixture from which it is then removed. The remaining composition is suitable for conventional processing such as compression molding or extruding. A particular feature of the method of manufacture is pouring the mixed solution slowly in a continuous stream into a cryogenic bath wherein frozen particles of the mixture result. The frozen individual particles are then subjected to the sublimation

Critical slowing down in random anisotropy magnets

We study the purely relaxational critical dynamics with non-conserved order parameter (model A critical dynamics) for three-dimensional magnets with disorder in a form of the random anisotropy axis. For the random axis anisotropic distribution, the static asymptotic critical behaviour coincides with that of random site Ising systems. Therefore the asymptotic critical dynamics is governed by the dynamical exponent of the random Ising model. However, the disorder influences considerably the dynamical behaviour in the non-asymptotic regime. We perform a field-theoretical renormalization group analysis within the minimal subtraction scheme in two-loop approximation to investigate asymptotic and effective critical dynamics of random anisotropy systems. The results demonstrate the non-monotonic behaviour of the dynamical effective critical exponent $z_{\rm eff}$.Comment: 11 pages, 4 figures, style file include

Der Einfluss von Feld- und Landschaftsparameter auf die Abundanzen wichtiger Rapsschädlinge

In agroecological research it has been appreciated only fairly recently that plant-insect interactions and other ecological processes depend on scales much larger than a single habitat (Wiens et al. 1997). Crop-pest interactions have mainly been studied on single pest species by focusing either on the impact of field parameters or on landscape structure but only rarely included both factors (Östman et al. 2001). Here we investigated how the abundances of three major insect pest species in oilseed rape (OSR) responded to field parameters and landscape characteristics at various spatial scales. Pest species considered in the current study include (i) ceutorhynchid stem weevils that lay eggs in leaf petioles or midribs of OSR plants while the larvae tunnel in the stems; (ii) pollen beetles that feed on pollen and destroy flower buds and (iii) brassica pod midge that lay eggs into OSR pods where the hatched larvae consume the seeds as well as tissue of the pod walls and cause the pods to split prematurely (Alford et al. 2003). Studying these different groups of pests is especially important because they attack different parts of the crop, use different habitats as overwintering sites and also differ in their mobility; with the exception of pollen beetles these pest species have never been studied in a landscape context. The specific objectives of this study were to determine (i) whether the major OSR pest species differ in their relation to field and landscape characteristics and (ii) at which spatial scales landscape variables are effective.Der Einfluss von Feld- und Landschaftsparameter auf die Abundanzen wichtiger Rapsschädlinge (Rapsglanzkäfer - Meligethes aeneus und M. viridescens, Nitidulidae, Coleoptera; Gefleckter Kohltriebrüssler und Großer Rapsstängelrüssler - Ceutorhynchus pallidactylus und C. napi, Curculionidae, Coleoptera; Kohlschotenmücke - Dasineura brassicae, Cecidomyiidae, Diptera) wurde untersucht. In Raps-Untersuchungsfeldern wurden die Beziehungen zwischen Schädlingsabundanzen und Feld-/Landschaftsparametern in 29 von strukturarm bis komplex reichenden Landschaftssektoren auf acht räumlichen Skalen (Radien 250 - 2000 m) untersucht. Die Abundanzen der Stängelrüssler waren signifikant positiv korreliert mit der Bestandesdichte des Raps und der Bodenqualität. Die Abundanzen der Rapsglanzkäfer reagierten auf allen Radien signifikant negativ mit dem Anteil an Rapsfläche und positiv mit der Bestandesdichte. Die Dichte der Kohlschotenmücke war jeweils auf dem kleinsten Radius signifikant positiv mit dem Anteil an Gehölzen korreliert, negativ mit dem Anteil an Rapsfläch

Opportunity cost and prudentiality : a representative-agent model of futures clearinghouse behavior

Includes bibliographic references (p. 31-38)

Skalenabhängiger Einfluss der Landschaft auf die Diversität epigäischer Spinnen in Winterrapsfeldern

Agricultural intensification is a major threat to biological diversity worldwide. Land management activities enhancing landscape diversity are therefore regarded as a key strategy to halt species loss in cultural landscapes. Diverse and abundant communities of predatory arthropods, e.g. spiders (Araneae), have a high potential to suppress pest populations (Symondson et al. 2002) and could therefore contribute to allow reductions of pesticide use. Crop fields alone are usually not able to sustain diverse and individual-rich populations of predatory arthropods, because agricultural management results in disturbances and habitat deteriorations (harvest, soil cultivation, pesticide application) that kill or drive away large parts of the populations. Therefore semi-natural and perennial habitats in agricultural landscapes are considered to be of great importance for beneficial arthropods. On the one hand they offer refuge habitats in times when arable fields are hostile, e.g. fields with bare grounds during winter (Schmidt & Tscharntke 2005). On the other hand, viable populations of predatory arthropods in semi-natural habitats can serve as sources for (re-) colonisation of arable fields (Schmidt & Tscharntke 2005). Because of these exchanges between crop and non-crop areas it is important to include the surrounding landscape when investigating field-scale processes. We investigated the relations between spider assemblages in arable fields and the surrounding landscape in 29 fields of winter oilseed rape (OSR) in an agricultural landscape in eastern Austria. The objectives of this study were to estimate (1) how much spider assemblages in oilseed rape fields are influenced by the surrounding landscape, (2) the relative influence of landscape variables compared to field-scale variables and (3) at which spatial scales landscape variables are effective.Die Intensivierung der Landwirtschaft stellt weltweit eine der bedeutendsten Bedrohungen der Biodiversität dar. Maßnahmen, die die Diversität der Landschaft erhöhen werden daher als eine zentrale Möglichkeit gesehen, den Verlust von Arten in Kulturlandschaften zu stoppen und durch die Förderung von Nützlingen einen Betrag zu einer Reduktion des Pestizideinsatzes zu leisten. Wir untersuchten den Einfluss der Landschaft auf epigäische Spinnen (Araneae) in 29 Winterrapsfelder in einer durch landwirtschaftliche Nutzung dominierten Region östlich von Wien (Österreich). Spinnen – generalistische Prädatoren, die ein bedeutsames Potenzial in der natürlichen Schädlingskontrolle aufweisen – wurden während der Feldsaison 2005 mit Barberfallen erfasst. Die umgebenden Landschaften wurden hinsichtlich Zusammensetzung, Diversität und Komplexität charakterisiert (Landschaftsausschnitte mit 250 bis 2000 m Radius). Zusätzlich wurden Feldparameter, vor allem die Bewirtschaftung betreffend, in die Analyse einbezogen. Die Datenanalyse erfolgte mit Generalized Linear Models. Unsere Ergebnisse zeigten, dass die Spinnengemeinschaften hinsichtlich Diversität und Individuenzahlen auf unterschiedliche Landschaftvariablen auf unterschiedlichen Skalenebenen reagieren. Für die Gesamtartenzahl war der Anteil an gehölzdominierten Habitaten in der näheren Umgebung der Felder der wichtigste, fördernde Faktor. Die Anzahl der häufigen Arten und die Gesamtindividuenzahlen hingegen nahmen mit dem Anteil an Brachen bzw. der Lauflänge an Wegrainen in größerem Umkreis der Felder zu. Diese Ergebnisse unterstreichen die Bedeutung von naturnahe Landschaftselementen, v.a. Brachen, für epigäische Spinnen als eine Gruppe von räuberischen Arthropoden in Agrarsystemen

Development of a Gd Loaded Liquid Scintillator for Electron Anti-Neutrino Spectroscopy

We report on the development and deployment of 11.3 tons of 0.1% Gd loaded liquid scintillator used in the Palo Verde reactor neutrino oscillation experiment. We discuss the chemical composition, properties, and stability of the scintillator elaborating on the details of the scintillator preparation crucial for obtaining a good scintillator quality and stability.Comment: 9 pages, 4 figures, submitted to NIM

Time dependent Bs mixing from lepton-kaon correlations with the ALEPH detector

Searches for $B_s$ oscillations were made using data taken with the ALEPH detector in the years 1991--1994. Inclusive methods use leptons to tag the $B_s$ state at decay and to reconstruct the $B_s$ decay time. The $B_s$ state at production time is tagged either with a second lepton in the opposite hemisphere or a jet-charge algorithm. Also kaons from the fragmentation process were used to determine the initial state. Exclusive methods use $D_s$ or $D_s$-lepton events to reconstruct the $B_s$ at decay time. The initial state is inferred using leptons, jet charge or fragmentation kaons. No oscillations are observed and lower limits for the $B_s$ mass difference are obtained. A combined limit will be presented taking the correlations between the different analyses into account

The non-integrability of the Zipoy-Voorhees metric

The low frequency gravitational wave detectors like eLISA/NGO will give us the opportunity to test whether the supermassive compact objects lying at the centers of galaxies are indeed Kerr black holes. A way to do such a test is to compare the gravitational wave signals with templates of perturbed black hole spacetimes, the so-called bumpy black hole spacetimes. The Zipoy-Voorhees (ZV) spacetime (known also as the $\gamma$ spacetime) can be included in the bumpy black hole family, because it can be considered as a perturbation of the Schwarzschild spacetime background. Several authors have suggested that the ZV metric corresponds to an integrable system. Contrary to this integrability conjecture, in the present article it is shown by numerical examples that in general ZV belongs to the family of non-integrable systems.Comment: 10 pages, 13 figure