Roots of the affine Cremona group

Let k[x_1,...,x_n] be the polynomial algebra in n variables and let A^n=Spec k[x_1,...,x_n]. In this note we show that the root vectors of the affine Cremona group Aut(A^n) with respect to the diagonal torus are exactly the locally nilpotent derivations x^a\times d/dx_i, where x^a is any monomial not depending on x_i. This answers a question due to Popov.Comment: 4 page

Cultural context and attitudes towards genetically modified food in Greece and West Germany

'Bisherige Untersuchungen haben gezeigt, dass es innerhalb der Europäischen Union zum Teil erhebliche Unterschiede in den Einstellungen zu gentechnisch veränderten Lebensmitteln (GM food) gibt. Die Erklärungen für die gefundenen Einstellungsunterschiede basieren vor allem auf soziodemografische und Wissensvariablen als einstellungsdeterminierende Faktoren der Einstellung gegenüber GM food. Kulturelle Unterschiede werden hingegen als Erklärungsfaktoren kaum in Betracht gezogen. In dem vorliegenden Papier werden Hypothesen über den Einfluss des kulturellen Kontext auf die Ablehnung von GM food formuliert. Diese Hypothesen basieren auf Überlegungen, die sich aus der Kombination des Ansatzes von Hofstede (1997) mit dem Einstellungsmodell von Eagly und Chaiken (1993) ergeben. Die Überlegungen beziehen sich auf Griechenland und Westdeutschland als Länder mit Stellvertreterpotential für einen bestimmten kulturellen Kontext (modern vs. traditional). Als Ergebnis kann festgehalten werden, dass das Wissen über GM food nur in Westdeutschland einen Effekt hat, in Griechenland sind hingegen die negativen Beliefs über GM food von großer Bedeutung für die Einstellung gegenüber GM food. Generell lässt sich festhalten, dass in Westdeutschland eine wesentlich strukturiertere Einstellungsstruktur zu finden ist als dies in Griechenland der Fall ist.' (Autorenreferat)'Although there are strong national differences in people's rejection of in genetical modification in food production (GM food), research mainly examined sociodemographics and knowledge an GM food as general determinants of attitudes towards GM food. Cultural differences seldom are taken into account, usually there are no theoretically founded hypotheses, which can be tested empirically. In the present paper we formulate specific hypotheses an cultural context effects an rejection of GM food by combining Hofstedes (1997) approach with cultural differentiation to a general beliefattitude model as it is represented in the core of Eagly and Chaikens (1993) composite model. Specific hypotheses are formulated for Westgermany and Greece as cases of contrasting cultural contexts (modern vs. traditional pattems of orientation). We find, that knowledge an GM food has an effect an rejecting GM food only in Westgermany, whereas negative beliefs are more important in determining GM food rejection in Greece. Generally, the attitude structure in Westgermany is more differentiated than in Greece, as it is reflected in more variance explained by knowledge, beliefs and sociodemographic status in Westgermany than in Greece.' (author's abstract)

The eclipsing post-common envelope binary CSS21055: a white dwarf with a probable brown-dwarf companion

We report photometric observations of the eclipsing close binary CSS21055 (SDSS J141126+200911) that strongly suggest that the companion to the carbon-oxygen white dwarf is a brown dwarf with a mass between 0.030 and 0.074 Msun. The measured orbital period is 121.73min and the totality of the eclipse lasts 125s. If confirmed, CSS21055 would be the first detached eclipsing WD+BD binary. Spectroscopy in the eclipse could provide information about the companion's evolutionary state and atmospheric structure.Comment: 6 pages, 5 figure

Feasibility of High-Power Diode Laser Array Surrogate to Support Development of Predictive Laser Lethality Model

Predictive modeling and simulation of high power laser-target interactions is sufficiently undeveloped that full-scale, field testing is required to assess lethality of military directed-energy (DE) systems. The cost and complexity of such testing programs severely limit the ability to vary and optimize parameters of the interaction. Thus development of advanced simulation tools, validated by experiments under well-controlled and diagnosed laboratory conditions that are able to provide detailed physics insight into the laser-target interaction and reduce requirements for full-scale testing will accelerate development of DE weapon systems. The ultimate goal is a comprehensive end-to-end simulation capability, from targeting and firing the laser system through laser-target interaction and dispersal of target debris; a 'Stockpile Science' - like capability for DE weapon systems. To support development of advanced modeling and simulation tools requires laboratory experiments to generate laser-target interaction data. Until now, to make relevant measurements required construction and operation of very high power and complex lasers, which are themselves costly and often unique devices, operating in dedicated facilities that don't permit experiments on targets containing energetic materials. High power diode laser arrays, pioneered by LLNL, provide a way to circumvent this limitation, as such arrays capable of delivering irradiances characteristic of De weapon requires are self-contained, compact, light weight and thus easily transportable to facilities, such as the High Explosives Applications Facility (HEAF) at Lawrence Livermore National Laboratory (LLNL) where testing with energetic materials can be performed. The purpose of this study was to establish the feasibility of using such arrays to support future development of advanced laser lethality and vulnerability simulation codes through providing data for materials characterization and laser-material interaction models and to validate the accuracy of code predictions. This project was a Feasibility Study under the LLNL Laboratory Directed Research and Development (LDRD) Program

Bolted joints in laminated composites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76154/1/AIAA-1984-917-791.pd

Black holes admitting a Freudenthal dual

The quantised charges x of four dimensional stringy black holes may be assigned to elements of an integral Freudenthal triple system whose automorphism group is the corresponding U-duality and whose U-invariant quartic norm Delta(x) determines the lowest order entropy. Here we introduce a Freudenthal duality x -> \tilde{x}, for which \tilde{\tilde{x}}=-x. Although distinct from U-duality it nevertheless leaves Delta(x) invariant. However, the requirement that \tilde{x} be integer restricts us to the subset of black holes for which Delta(x) is necessarily a perfect square. The issue of higher-order corrections remains open as some, but not all, of the discrete U-duality invariants are Freudenthal invariant. Similarly, the quantised charges A of five dimensional black holes and strings may be assigned to elements of an integral Jordan algebra, whose cubic norm N(A) determines the lowest order entropy. We introduce an analogous Jordan dual A*, with N(A) necessarily a perfect cube, for which A**=A and which leaves N(A) invariant. The two dualities are related by a 4D/5D lift.Comment: 32 pages revtex, 10 tables; minor corrections, references adde

Economic Potential of Substituting Legumes for Synthetic Nitrogen in Warm Season Perennial Grasses used for Stocker Cattle Grazing

Stocker cattle grazing warm season perennial grasses is an important economic activity in the southern Great Plains. Substantial increases in the price of nitrogen fertilizer is negatively affecting forage producers’ profitability. Two alternative nitrogen management systems that use annual and perennial legumes have been developed for bermudagrass pastures. The goal of the study is to determine if the legumes systems are more profitable than the conventional practice of applying synthetic sources of nitrogen. Results of the two-year grazing study show that the legume systems could not compete economically with the common practice.economics, grazing, legumes, bermudagrass, nitrogen fertilizer, stocker cattle, Crop Production/Industries, Farm Management, Production Economics,

The ultraviolet limit and sum rule for the shear correlator in hot Yang-Mills theory

We determine a next-to-leading order result for the correlator of the shear stress operator in high-temperature Yang-Mills theory. The computation is performed via an ultraviolet expansion, valid in the limit of small distances or large momenta, and the result is used for writing operator product expansions for the Euclidean momentum and coordinate space correlators as well as for the Minkowskian spectral density. In addition, our results enable us to confirm and refine a shear sum rule originally derived by Romatschke, Son and Meyer.Comment: 16 pages, 2 figures. v2: small clarifications, one reference added, published versio