3-Dimensional Core-Collapse

In this paper, we present the results of 3-dimensional collapse simulations of rotating stars for a range of stellar progenitors. We find that for the fastest spinning stars, rotation does indeed modify the convection above the proto-neutron star, but it is not fast enough to cause core fragmentation. Similarly, although strong magnetic fields can be produced once the proto-neutron star cools and contracts, the proto-neutron star is not spinning fast enough to generate strong magnetic fields quickly after collapse and, for our simulations, magnetic fields will not dominate the supernova explosion mechanism. Even so, the resulting pulsars for our fastest rotating models may emit enough energy to dominate the total explosion energy of the supernova. However, more recent stellar models predict rotation rates that are much too slow to affect the explosion, but these models are not sophisticated enough to determine whether the most recent, or past, stellar rotation rates are most likely. Thus, we must rely upon observational constraints to determine the true rotation rates of stellar cores just before collapse. We conclude with a discussion of the possible constraints on stellar rotation which we can derive from core-collapse supernovae.Comment: 34 pages (5 of 17 figures missing), For full paper, goto http://qso.lanl.gov/~clf/papers/rot.ps.gz accepted by Ap

Tuning the superconducting and magnetic properties in Fe_ySe_0.25Te_0.75 by varying the Fe-content

The superconducting and magnetic properties of Fe$_{y}$Se$_{0.25}$Te$_{0.75}$ single crystals ($0.9\leq y \leq1.1$) were studied by means of x-ray diffraction, SQUID magnetometry, muon spin rotation, and elastic neutron diffraction. The samples with $y<1$ exhibit coexistence of bulk superconductivity and incommensurate magnetism. The magnetic order remains incommensurate for $y\geq 1$, but with increasing Fe content superconductivity is suppressed and the magnetic correlation length increases. The results show that the superconducting and the magnetic properties of the Fe$_{y}$Se$_{1-x}$Te$_{x}$ can be tuned not only by varying the Se/Te ratio but also by changing the Fe content

Critical Behaviour of the Drossel-Schwabl Forest Fire Model

We present high statistics Monte Carlo results for the Drossel-Schwabl forest fire model in 2 dimensions. They extend to much larger lattices (up to $65536\times 65536$) than previous simulations and reach much closer to the critical point (up to $\theta \equiv p/f = 256000$). They are incompatible with all previous conjectures for the (extrapolated) critical behaviour, although they in general agree well with previous simulations wherever they can be directly compared. Instead, they suggest that scaling laws observed in previous simulations are spurious, and that the density $\rho$ of trees in the critical state was grossly underestimated. While previous simulations gave $\rho\approx 0.408$, we conjecture that $\rho$ actually is equal to the critical threshold $p_c = 0.592...$ for site percolation in $d=2$. This is however still far from the densities reachable with present day computers, and we estimate that we would need many orders of magnitude higher CPU times and storage capacities to reach the true critical behaviour -- which might or might not be that of ordinary percolation.Comment: 8 pages, including 9 figures, RevTe

Avaliação preliminar de parâmetros epidemiológicos da tristeza parasitaria bovina no Mato Grosso do Sul.

Epidemiologia; Bovino; Tristeza parasitaria; Praga; Sanidade; America do Sul; Brasil; Mato Grosso do Sul.bitstream/item/137587/1/PESQ-EM-ANDAMENTO-38.pdfCNPGC

Full real-space analysis of a dodecagonal quasicrystal

The atomically resolved real-space structure of a long-range-ordered dodecagonal quasicrystal is determined based on scanning tunnelling microscopy. For the BaTiO3-derived oxide quasicrystal which spontaneously forms on a Pt(111) surface, 8100 atomic positions have been determined and are compared with an ideal Niizeki–Gähler tiling. Although the Niizeki–Gähler tiling has a complex three-element structure, the abundance of the triangle, square and rhomb tiling elements in the experimental data closely resembles the ideal frequencies. Similarly, the frequencies of all possible next-neighbour tiling combinations are, within the experimental uncertainty, identical to the ideal tiling. The angular and orientational distributions of all individual tiling elements show the characteristics of the dodecagonal quasicrystal. In contrast, the analysis of the orientation of characteristic and more complex tiling combinations indicates the partial decomposition of the quasicrystal into small patches with locally reduced symmetry. These, however, preserve the long-range quasicrystal coherence. The symmetry reduction from dodecagonal to sixfold is assigned to local interaction with the threefold substrate. It leads to atomic flips which preserve the number of quasicrystal tiling elements

Chimeric polyomavirus-derived virus-like particles: the immunogenicity of an inserted peptide applied without adjuvant to mice depends on its insertion site and its flanking linker sequence

We inserted the sequence of the carcinoembryonic antigen-derived T cell epitope CAP-1-6D (CEA) into different positions of the hamster polyomavirus major capsid protein VP1. Independently from additional flanking linkers, yeast-expressed VP1 proteins harboring the CEA insertion between VP1 amino acid residues 80 and 89 (site 1) or 288 and 295 (site 4) or simultaneously at both positions assembled to chimeric virus-like particles (VLPs). BALB/c mice immunized with adjuvant-free VLPs developed VP1- and epitope-specific antibodies. The level of the CEA-specific antibody response was determined by the insertion site, the number of inserts, and the flanking linker. The strongest CEA-specific antibody response was observed in mice immunized with VP1 proteins harboring the CEA insert at site 1. Moreover, the CEA-specific antibodies in these mice were still detectable 6 mo after the final booster immunization. Our results indicate that hamster polyomavirus-derived VLPs represent a highly immunogenic carrier for foreign insertions that might be useful for clinical and therapeutic applications

Geometric Mechanics of Curved Crease Origami

Folding a sheet of paper along a curve can lead to structures seen in decorative art and utilitarian packing boxes. Here we present a theory for the simplest such structure: an annular circular strip that is folded along a central circular curve to form a three-dimensional buckled structure driven by geometrical frustration. We quantify this shape in terms of the radius of the circle, the dihedral angle of the fold and the mechanical properties of the sheet of paper and the fold itself. When the sheet is isometrically deformed everywhere except along the fold itself, stiff folds result in creases with constant curvature and oscillatory torsion. However, relatively softer folds inherit the broken symmetry of the buckled shape with oscillatory curvature and torsion. Our asymptotic analysis of the isometrically deformed state is corroborated by numerical simulations which allow us to generalize our analysis to study multiply folded structures

Two-dimensional wetting layer structures of reduced ternary oxides on Ru(0001) and Pt(111)

Long-range ordered structures of reduced oxide films with monolayer thickness derived from BaTiO3 and SrTiO3 on Ru(0001) and Pt(111) are investigated by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Upon ultrahigh vacuum annealing at 1100 K, a hexagonal phase is observed for BaTiO3 on Ru(0001), which forms similarly from SrTiO3 on Pt(111). At higher temperatures, a triangle–square tiling called σ-phase develops in the BaTiO3/Ru(0001) system, with a unit cell rotation of 15° against the Ru(0001) substrate. Furthermore, it is shown that this 15° rotated σ-phase also forms in the BaTiO3/Pt(111) system in addition to the already known 8° rotated σ-phase. The results emphasize a strong flexibility in the structural parameters of the reduced oxide wetting layers in response to the substrate interaction strength

De bijdrage van toevoeging van cacao aan tabak aan rookverslaving

In this report the effect of these compounds on the addiction to cigarette smoking was assessed, using currently available information in the literature on psychoactive compounds of cocoa. The investigated psychoactive cocoa compounds were theobromine, caffeine, serotonin, histamine, tryptophan, tryptamine, tyramine, phenylethylamine, octopamine and anandamide. The general conclusion is that the level of these compounds in added cocoa in cigarettes is not sufficient to increase the addiction to cigarette smoking.In dit rapport wordt de mogelijke bijdrage van cacao aan rookverslaving beschreven. Cacao wordt aan tabak toegevoegd om de smaak te verbeteren. Daarnaast bevat cacao tal van psychoactieve stoffen die mogelijk bijdragen aan rookverslaving Dit literatuuronderzoek beschrijft de blootstelling, farmacologie, farmacokinetiek, toxicologie, interacties en verslavende eigenschappen van de tien meest bekende stoffen in cacao. De onderzochte stoffen zijn theobromine, caffeine, serotonine, histamine, tryptofaan, tryptamine, tyramine, fenylethylamine, octopamine en anandamide. Deze stoffen komen ook via dranken en voedsel het lichaam binnen of worden door het lichaam zelf aangemaakt. Dit rapport laat zien dat de aan roken gerelateerde blootstelling aan de psychoactieve stoffen uit cacao gering is ten opzichte van de inname via voeding en dranken en/of de lichaamseigen productie van deze stoffen. Een systemisch effect lijkt derhalve onwaarschijnlijk ook al omdat lichaamseigen stoffen snel worden afgebroken. Daarnaast kunnen deze stoffen, omdat ze geinhaleerd worden, een direct effect op de luchtwegen hebben. Daarmee zou de opname van nicotine beinvloed kunnen worden. De nicotine opname zou bijvoorbeeld kunnen toenemen via luchtwegverwijding door theobromine en cafe6ne of kunnen afnemen door luchtwegvernauwing door histamine. Dit rapport laat zien dat de aan roken gerelateerde blootstelling aan deze stoffen waarschijnlijk te gering is voor een direct effect op de luchtwegen. Verder dient te worden opgemerkt dat de hoeveelheid tryptamine, tyramine en fenylethylamine die via cacao wordt toegevoegd verwaarloosbaar is ten opzichte van de hoeveelheid die in tabak zelf aanwezig is. Tot slot is aandacht besteed aan de verbrandingsproducten van cacao. Amine verbindingen als serotonin, tryptofaan, tyramine, tryptamine en fenylethylamine vormen tijdens het roken stoffen die het enzym mono amine oxidase (MAO) remmen. MAO-remmers hebben een anti-depressieve werking en kunnen op die manier bijdragen aan rookverslaving. De conclusie van dit literatuur onderzoek is dat de afzonderlijke psychoactieve stoffen in tabak als gevolg van toevoeging van cacao niet direct bijdragen aan rookverslaving. De verbrandingsproducten van cacao doen dit, via remming van het enzym mono amine oxidase, mogelijk wel. Ook de smaak van cacao wordt geassocieerd met verslaving. De literatuur biedt geen inzicht in het effect op gezondheid en verslaving van het inhaleren van de combinatie van de 10 onderzochte stoffen uit cacao