4,176 research outputs found
Geometry of the extreme Kerr black holes
Geometrical properties of the extreme Kerr black holes in the topological
sectors of nonextreme and extreme configurations are studied. We find that the
Euler characteristic plays an essential role to distinguish these two kinds of
extreme black holes. The relationship between the geometrical properties and
the intrinsic thermodynamics are investigated.Comment: Latex version, 10 page
Diversity in the structures and ligand binding sites of nematode fatty acid and retinol binding proteins revealed by Na-FAR-1 from Necator americanus
Fatty acid and retinol binding proteins (FARs) comprise a family of unusual α-helix rich lipid binding proteins found exclusively in nematodes. They are secreted into host tissues by parasites of plants, animals and humans. The structure of a FAR protein from the free-living nematode Caenorhabditis elegans is available, but this protein (Ce-FAR-7) is from a subfamily of FARs that does not appear to be important at the host-parasite interface. We have therefore examined Na-FAR-1 from the blood-feeding intestinal parasite of humans, Necator americanus . The three dimensional structure of Na-FAR-1 in its ligand-free and ligand-bound forms, determined by nuclear magnetic resonance spectroscopy (NMR) and X-ray crystallography, respectively, reveals an a-helical fold similar to Ce-FAR-7, but Na-FAR-1 possesses a larger and more complex internal ligand binding cavity and an additional C-terminal a-helix. Titration of apo -Na-FAR-1 with oleic acid, analysed by NMR chemical shift perturbation, reveals that at least four distinct protein:ligand complexes can be formed. Na-FAR-1, and possibly other FARs, may have a wider repertoire for hydrophobic ligand binding, as confirmed here by our finding that a range of neutral and polar lipids co-purify with the bacterial recombinant protein. Finally, we show by immunohistochemistry that Na-FAR-1 is present in adult worms with a tissue distribution indicative of possible roles in nutrient acquisition by the parasite and in reproduction in the male
Geometry and topology of two kinds of extreme Reissner-Nordstrm-anti-de Sitter black holes
Different geometrical and topological properties have been shown for two
kinds of extreme Reissner-Nordstrm-anti-de Sitter black holes. The
relationship between the geometrical properties and the intrinsic
thermodynamical properties has been made explicit.Comment: Latex, 12 pages, 4 figure
Local observables for entanglement witnesses
We present an explicit construction of entanglement witnesses for depolarized
states in arbitrary finite dimension. For infinite dimension we generalize the
construction to twin-beams perturbed by Gaussian noises in the phase and in the
amplitude of the field. We show that entanglement detection for all these
families of states requires only three local measurements. The explicit form of
the corresponding set of local observables (quorom) needed for entanglement
witness is derived.Comment: minor corrections, title change
Influence of Lorentz violation on Dirac quasinormal modes in the Schwarzschild black hole spacetime
Using the third-order WKB approximation and monodromy methods, we investigate
the influence of Lorentz violating coefficient (associated with a special
axial-vector field) on Dirac quasinormal modes in the Schwarzschild
black hole spacetime. At fundamental overtone, the real part decreases linearly
as the parameter increases. But the variation of the imaginary part with
becomes more complex. For the larger multiple moment , the magnitude of
imaginary part increases with the increase of , which means that presence of
Lorentz violation makes Dirac field damps more rapidly. At high overtones, it
is found that the real part of high-damped quasinormal frequency does not tend
to zero, which is quite a different from the symptotic Dirac quasinormal modes
without Lorentz violation.Comment: 10 pages, 4 figur
Applying consumer responsibility principle in evaluating environmental load of carbon emissions
There is a need for a proper indicator in order to assess the environmental impact of international
trade, therefore using the carbon footprint as an indicator can be relevant and useful. The aim of this
study is to show from a methodological perspective how the carbon footprint, combined with input-
output models can be used for analysing the impacts of international trade on the sustainable use
of national resources in a country. The use of the input-output approach has the essential advantage
of being able to track the transformation of goods through the economy. The study examines the environmental
impact of consumption related to international trade, using the consumer responsibility
principle. In this study the use of the carbon footprint and input-output methodology is shown on the
example of the Hungarian consumption and the impact of international trade. Moving from a production-
based approach in climate policy to a consumption-perspective principle and allocation,
would also help to increase the efficiency of emission reduction targets and the evaluation of the
ecological impacts of international trade
Extreme black hole entropy obtained in an operational approach
The entropy of anti-de Sitter Reissner-Nordstrom black hole is found to be
stored in the material which gathers to form it and equals to regardless
of material states. Extending the study to two kinds of extreme black holes, we
find different entropy results for the first kind of extreme black hole due to
different material states. However for the second kind of extreme black hole
the results of entropy are uniform independently of the material states.
Relations between these results and the stability of two kinds of extreme black
holes have been addressed.Comment: latex, 10 pages, to appear in Int. J. Mod. Phys.
Merger Dynamics of the Pair of Galaxy Clusters -- A399 and A401
Convincing evidence of a past interaction between two rich clusters A399 and
A401 was recently found by the X-ray imaging observations. In this paper we
examine the structure and dynamics of this pair of galaxy clusters. A
mixture-modeling algorithm has been applied to obtain a robust partition into
two clusters, which allows us to discuss the virial mass and velocity
distribution for each cluster. Assuming that these two clusters follow a linear
orbit and they have once experienced a close encounter, we model the binary
cluster as a two-body system. As a result, four gravitationally bound solutions
are obtained. The recent X-ray observations seem to favor a scenario in which
the two clusters with a true separation of Mpc are currently
expanding at 583 km/s along the direction with a projection angle of 67.5
degree, and they will reach a maximum extent of Mpc in about
Gyr.Comment: 11 pages, including 6 EPS figures and 4 tables, uses chjaa.cls,
Accepted by the ChJA
Dirac Cosmology and the Acceleration of the Contemporary Universe
A model is suggested to unify the Einstein GR and Dirac Cosmology. There is
one adjusted parameter in our model. After adjusting the parameter
in the model by using the supernova data, we have calculated the gravitational
constant and the physical quantities of , and by using the present day quantities as the initial conditions and
found that the equation of state parameter equals to -0.83, the
ratio of the density of the addition creation and the
ratio of the density of the matter including multiplication creation, radiation
and normal matter at present. The results are self-consistent
and in good agreement with present knowledge in cosmology. These results
suggest that the addition creation and multiplication creation in Dirac
cosmology play the role of the dark energy and dark matter.Comment: 13 pages, 8 figure
Phenomenological Understanding of a Transport Regime with Reflection Symmetry in the Quantum Hall System in a Composite Fermion Picture
In this paper, we present a phenomenological picture based on the composite
fermion theory, in responding to the recent discovery by Shahar et al. of a new
transport regime near the transition from a quantum Hall liquid to a
Hall insulator(ref[8]). In this picture, the seemingly unexpected reflection
symmetry in the longitudinal resistivity can be understood clearly
as due to the symmetry of the gapful excitations which dominate
across the transition, and the abrupt change in at the
transition. The parameter in the linear fit of in ref[8] is
also given a simple physical meaning and the effective mass can be calculated
from , which gives a reasonable value of several electron band mass.
When taking into account the result of network model, the almost invariant Hall
resistivity across the transition is also well-understood.Comment: 4 pages, RevTex, final version to appear in Phys.Rev.
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