2,727 research outputs found

    Készülőben az új Európai Moha Vörös Könyv = The new Red Data Book of European Bryophytes in preparation

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    The new Red Data Book of European Bryophytes is the most important recent project of the European Committee for Conservation of Bryophytes, and the basis of bryophyte conservation in most European countries. The first edition, published in 1995, is now in urgent need of updating. Since its publication, our knowledge of the bryophytes of Europe has been considerably improved, especially concerning taxonomy and distribution. The work has started: a comprehensive table, listing the occurrence and Red List status of each species, in each European country, has been prepared. A short list of candidate species for IUCN threat assessment was established by eliminating species known with certainty to be of least concern. Of 2140 bryophyte species known to occur in Europe, 241 liverworts and 721 mosses were selected for further consideration. Among them, 28 liverworts and 98 mosses occur in Hungary. Examples of some species occurring in Hungary are presented below to show which criteria are used to select species for the European candidate list. With 12 fi gures

    Difficulties in Testing for Covarion-Like Properties of Sequences under the Confounding Influence of Changing Proportions of Variable Sites

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    The covarion (COV)-like properties of sequences are poorly described and their impact on phylogenetic analyses poorly understood. We demonstrate using simulations that, under an evolutionary model where the proportion of variable sites changes in nonadjacent lineages, log likelihood values for rates across site (RAS) and COV models become similar, making models difficult to distinguish. Further, although COV and RAS models provide a great improvement in likelihood scores over a homogeneous model with these simulated data, reconstruction accuracy of tree building is low, suggesting caution when it is suspected that proportions of variable sites differ in different evolutionary lineages. We study the performance of a recently developed contingency test that detects the presence of COV-type evolution modified for protein data. We report that if proportions of variable sites (pvar) change in a lineage-specific manner such that their distributions in different lineages become sufficiently nonoverlapping, then the contingency test can incorrectly suggest a homogeneous model. Also of concern is the possibility of different proportions of variable sites between the groups being studied. In a study of chloroplast proteins, interpretation of the test is found to be susceptible to different partitioning of taxon groups, making the test very subjective in its implementation. Extreme intergroup differences in the extent of divergence and difference in proportions of variable sites could be contributing to this effect

    Liver function as an engineering system

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    Process Systems Engineering has tackled a wide range of problems including manufacturing, the environment, and advanced materials design. Here we discuss how tools can be deployed to tackle medical problems which involve complex chemical transformations and spatial phenomena looking in particular at the liver system, the body's chemical factory. We show how an existing model has been developed to model distributed behavior necessary to predict the behavior of drugs for treating liver disease. The model has been used to predict the effects of suppression of de novo lipogenesis, stimulation of β-oxidation and a combination of the two. A reduced model has also been used to explore the prediction of behavior of hormones in the blood stream controlling glucose levels to ensure that levels are kept within safe bounds using interval methods. The predictions are made resulting from uncertainty in two key parameters with oscillating input resulting from regular feeding

    Electrostatic Patch Effect in Cylindrical Geometry. I. Potential and Energy between Slightly Non-Coaxial Cylinders

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    We study the effect of any uneven voltage distribution on two close cylindrical conductors with parallel axes that are slightly shifted in the radial and by any length in the axial direction. The investigation is especially motivated by certain precision measurements, such as the Satellite Test of the Equivalence Principle (STEP). By energy conservation, the force can be found as the energy gradient in the vector of the shift, which requires determining potential distribution and energy in the gap. The boundary value problem for the potential is solved, and energy is thus found to the second order in the small transverse shift, and to lowest order in the gap to cylinder radius ratio. The energy consists of three parts: the usual capacitor part due to the uniform potential difference, the one coming from the interaction between the voltage patches and the uniform voltage difference, and the energy of patch interaction, entirely independent of the uniform voltage. Patch effect forces and torques in the cylindrical configuration are derived and analyzed in the next two parts of this work.Comment: 26 pages, 1 Figure. Submitted to Classical and Quantum Gravit

    Measurement of a Sign-Changing Two-Gap Superconducting Phase in Electron-Doped Ba(Fe_{1-x}Co_x)_2As_2 Single Crystals using Scanning Tunneling Spectroscopy

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    Scanning tunneling spectroscopic studies of Ba(Fe1xCox)2As2Ba(Fe_{1-x}Co_x)_2As_2 (x = 0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap superconductivity. These gaps decrease with increasing temperature and vanish above the superconducting transition TcT_c. The two-gap nature and the slightly doping- and energy-dependent quasiparticle scattering interferences near the wave-vectors (±π,0)(\pm \pi, 0) and (0,±π)(0, \pm \pi) are consistent with sign-changing ss-wave superconductivity. The excess zero-bias conductance and the large gap-to-TcT_c ratios suggest dominant unitary impurity scattering.Comment: 4 pages, 4 figures. Paper accepted for publication in Physical Review Letters. Contact author: Nai-Chang Yeh ([email protected]

    Maximum black-hole spin from quasi-circular binary mergers

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    Black holes of mass M must have a spin angular momentum S below the Kerr limit chi = S/M^2 < 1, but whether astrophysical black holes can attain this limiting spin depends on their accretion history. Gas accretion from a thin disk limits the black-hole spin to chi_gas < 0.9980 +- 0.0002, as electromagnetic radiation from this disk with retrograde angular momentum is preferentially absorbed by the black hole. Extrapolation of numerical-relativity simulations of equal-mass binary black-hole mergers to maximum initial spins suggests these mergers yield a maximum spin chi_eq < 0.95. Here we show that for smaller mass ratios q = m/M << 1, the superradiant extraction of angular momentum from the larger black hole imposes a fundamental limit chi_lim < 0.9979 +- 0.0001 on the final black-hole spin even in the test-particle limit q -> 0 of binary black-hole mergers. The nearly equal values of chi_gas and chi_lim imply that measurement of supermassive black-hole spins cannot distinguish a black hole built by gas accretion from one assembled by the gravitational inspiral of a disk of compact stellar remnants. We also show how superradiant scattering alters the mass and spin predicted by models derived from extrapolating test-particle mergers to finite mass ratios.Comment: final version accepted in PRD, new Fig.4 and discussio

    Homogeneity, Flatness and "Large" Extra Dimensions

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    We consider a model in which the universe is the direct product of a (3+1)-dimensional Friedmann, Robertson-Walker (FRW) space and a compact hyperbolic manifold (CHM). Standard Model fields are confined to a point in the CHM (i.e. to a brane). In such a space, the decay of massive Kaluza-Klein modes leads to the injection of any initial bulk entropy into the observable (FRW) universe. Both Kolmogoro-Sinai mixing due to the non-integrability of flows on CHMs and the large statistical averaging inherent in the collapse of the initial entropy onto the brane smooth out any initial inhomogeneities in the distribution of matter and of 3-curvature on any slice of constant 3-position. If, as we assume, the initial densities and curvatures in each fundamental correlation volume are drawn from some universal underlying distributions independent of location within the space, then these smoothing mechanisms effectively reduce the density and curvature inhomogeneities projected onto the FRW. This smoothing is sufficient to account for the current homogeneity and flatness of the universe. The fundamental scale of physics can be \gsim 1TeV. All relevant mass and length scales can have natural values in fundamental units. All large dimensionless numbers, such as the entropy of the universe, are understood as consequences of the topology of spacetime which is not explained. No model for the origin of structure is proffered.Comment: minor changes, matches version published in Phys. Rev. Let

    Signal Processing

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    Contains reports on three research projects.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E
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