7,427 research outputs found

    Equianalytic and equisingular families of curves on surfaces

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    We consider flat families of reduced curves on a smooth surface S such that each member C has the same number of singularities of fixed singularity types and the corresponding (locally closed) subscheme H of the Hilbert scheme of S. We are mainly concerned with analytic resp. topological singularity types and give a sufficient condition for the smoothness of H (at C). Our results for S=P^2 seem to be quite sharp for families of cuves of small degree d.Comment: LaTeX v 2.0

    On the first Gaussian map for Prym-canonical line bundles

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    We prove by degeneration to Prym-canonical binary curves that the first Gaussian map of the Prym canonical line bundle ωC⊗A\omega_C \otimes A is surjective for the general point [C,A] of R_g if g >11, while it is injective if g < 12.Comment: To appear in Geometriae Dedicata. arXiv admin note: text overlap with arXiv:1105.447

    Lattice location and stability of implanted Cu in ZnO

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    The lattice location of copper in single-crystalline zinc oxide was studied by means of the emission channeling technique. Following 60 keV room-temperature implantation at a fluence of  2.3 ⁣× ⁣1013\,2.3\!\times\!10^{13} cm\!^{-2}, the angular distribution of \beta\!^{-}-particles emitted by the radioactive isotope 67^{67}Cu was measured by a position-sensitive detector. The ÎČ\beta - emission patterns give direct evidence that in the as-implanted state a large fraction of Cu atoms (60--70%) occupy almost ideal substitutional Zn sites with root mean square (rms) displacements of 0.16--0.17 Å. However, following annealing at 600°C and above Cu was found to be located on sites that are characterized by large rms displacements (0.3--0.5 Å) from Zn sites

    Lattice location and thermal stability of implanted Fe in ZnO

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    The emission channeling technique was applied to evaluate the lattice location of implanted 59^{59}Fe in single-crystalline ZnO. The angular distribution of ÎČ−\beta^{-}- particles emitted by 59^{59}Fe was monitored with a position-sensitive electron detector, following 60-keV low dose (2.0×10132.0 \times 10^{13} cm−2^{-2}) room-temperature implantation of the precursor isotope 59^{59}Mn. The emission patterns around the [0001], [1102], [1101] and [2113] directions revealed that following annealing at 800°C 95(8)% of the Fe atoms occupy ideal substitutional Zn sites with root mean square displacements of 0.06-0.09 Å

    State space c-reductions for concurrent systems in rewriting logic

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    We present c-reductions, a state space reduction technique. The rough idea is to exploit some equivalence relation on states (possibly capturing system regularities) that preserves behavioral properties, and explore the induced quotient system. This is done by means of a canonizer function, which maps each state into a (non necessarily unique) canonical representative of its equivalence class. The approach exploits the expressiveness of rewriting logic and its realization in Maude to enjoy several advantages over similar approaches: exibility and simplicity in the definition of the reductions (supporting not only traditional symmetry reductions, but also name reuse and name abstraction); reasoning support for checking and proving correctness of the reductions; and automatization of the reduction infrastructure via Maude's meta-programming features. The approach has been validated over a set of representative case studies, exhibiting comparable results with respect to other tools

    Direct evidence for As as a Zn-Site impurity in ZnO

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    Biologische Kontrolle von Eulenraupen im Kohl mittels Baculoviren

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    Baculoviren sind als hoch selektive biologische Kontrollagenzien fĂŒr Kohleulenraupen (Mamestra brassicae) seit lĂ€ngerem bekannt und ihre gute Wirksamkeit wurde schon in verschiedenen GewĂ€chshaus- und Freilandversuchen nachgewiesen. Um die Kontrollsituation von Kohleulenraupen im ökologischen GemĂŒseanbau insbesondere bei niedrigen Temperaturen zu verbessern, wurden die eulenpathogenen Mamestra brassicae Nukelopolyhedrovirus (MbMNPV) und Mamestra configurata Nukleopolyhedrovirus (MacoNPV-A) als mögliche Kontrollagentien geprĂŒft. Es konnte gezeigt werden, dass auch MacoNPV-A fĂŒr M.brassicae pathogen ist. In vergleichenden Bioassays bei 24°C zeigten MbMNPV und MacoNPV-A keinen signifikanten Unterschied hinsichtlich ihrer biologischen AktivitĂ€t gegenĂŒber M.brassicae. In weiteren Bioassays wurden die konzentrationsabhĂ€ngige MortalitĂ€t von M.brassicae im 2. Larvenstadium sowie die gefressene BlattflĂ€che bei 24, 20, 16 und 12°C bestimmt. Im Vergleich zu 24 und 20°C waren die mittleren Letalkonzentrationen bei 16 und 12°C 100 bzw. 1000fach höher. FĂŒr eine mittlere Reduktion der konsumierten BlattflĂ€che waren hingegen bei Temperaturen unter 20°C 10 bis 100fach höhere Konzentrationen notwendig. Durch die Neuformulierung von MbMNPV (Probis GmbH, Wiernsheim) konnte eine Wirkungssteigerung im Vergleich zu der nicht formulierten Virussuspension im Bioassay erzielt werden. In einem Freilandtest mit kĂŒnstlicher Infestation in Kohlrabi konnte eine weitere Steigerung des Wirkungsgrades durch die Kombination mit dem Bacillus thuringiensis PrĂ€parat XenTariÂź im Vergleich zur Einzelapplikation der beiden PrĂ€parate erreicht werden. Eine breite Freilandtestung der Baculoviren-PrĂ€paraten gegen Kohlraupen bei kĂŒhler Witterung als EinzelprĂ€parat und in Kombination mit Bacillus thuringiensis PrĂ€paraten sowie neuester Applikationstechnik fĂŒr Ober- und Unterblattbehandlung wird empfohlen

    Lattice sites of implanted Cu and Ag in ZnO

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    The group I\textrm{I}b impurities Cu and Ag on substitutional Zn sites are among possible candidates for p-type doping of ZnO. In order to explore possible lattice sites of Cu and Ag in ZnO the radioactive impurities 67 ⁣^{67}\!Cu and 111 ⁣^{111}\!Ag were implanted at doses of 4 ⁣× ⁣10124\!\times\!10^{12}cm−2→1 ⁣× ⁣1014^{-2}\to1\!\times\!10^{14}cm−2^{-2} at 60 keV into ZnO single crystals. The emission channeling effects of \beta\!^{-} -particles from the decay were studied by means of position-sensitive electron detectors, giving direct evidence that in the as-implanted state large fractions of Cu and Ag atoms (60--70% for Cu and 30% for Ag) occupy almost ideal substitutional Zn sites with root mean square (rms) displacements of 0.014--0.017 nm. However, following vacuum annealing at 600 °C and above both Cu and Ag were found to be located increasingly on sites that are characterized by large rms displacements (0.03--0.05 nm) from Zn sites. We conclude that in high-temperature treated ZnO Cu and Ag are most likely not simply replacing Zn atoms but are incorporated in complexes with other crystal defects or as clusters

    Cooperation and Self-Regulation in a Model of Agents Playing Different Games

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    A simple model for cooperation between "selfish" agents, which play an extended version of the Prisoner's Dilemma(PD) game, in which they use arbitrary payoffs, is presented and studied. A continuous variable, representing the probability of cooperation, pk(t)∈p_k(t) \in [0,1], is assigned to each agent kk at time tt. At each time step tt a pair of agents, chosen at random, interact by playing the game. The players update their pk(t)p_k(t) using a criteria based on the comparison of their utilities with the simplest estimate for expected income. The agents have no memory and use strategies not based on direct reciprocity nor 'tags'. Depending on the payoff matrix, the systems self-organizes - after a transient - into stationary states characterized by their average probability of cooperation pˉeq\bar{p}_{eq} and average equilibrium per-capita-income pˉeq,Uˉ∞\bar{p}_{eq},\bar{U}_\infty. It turns out that the model exhibit some results that contradict the intuition. In particular, some games which - {\it a priory}- seems to favor defection most, may produce a relatively high degree of cooperation. Conversely, other games, which one would bet that lead to maximum cooperation, indeed are not the optimal for producing cooperation.Comment: 11 pages, 3 figures, keybords: Complex adaptive systems, Agent-based models, Social system

    Deformed two center shell model

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    A highly specialized two-center shell model has been developed accounting for the splitting of a deformed parent nucleus into two ellipsoidaly deformed fragments. The potential is based on deformed oscillator wells in direct correspondance with the shape change of the nuclear system. For the first time a potential responsible for the necking part between the fragments is introduced on potential theory basis. As a direct consequence, spin-orbit {\bf ls} and {\bf l2^2} operators are calculated as shape dependent. Level scheme evolution along the fission path for pairs of ellipsoidaly deformed fragments is calculated. The Strutinsky method yields the shell corrections for different mass asymmetries from the superheavy nucleus 306^{306}122 and 252^{252}Cf all along the splitting process.Comment: 32 pages, 8 figure
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