11,624 research outputs found
AfrOBIS: a marine biogeographic information system for sub-Saharan Africa
AfrOBIS is one of 11 global nodes of the Ocean Biogeographic Information System (OBIS), a freely accessible network of databases collating marine data in support of the Census of Marine Life.Versatile graphic products, provided by OBIS, can be used to display the data. To date, AfrOBIS has loaded about 3.2 million records of more than 23 000 species located mainly in the seas around southern Africa. This forms part of the 13.2 million records of more than 80 000 species currently stored in OBIS. Scouting for South African data has been successful, whereas locating records in other African countries has been much less so
Vanishing largest Lyapunov exponent and Tsallis entropy
We present a geometric argument that explains why some systems having
vanishing largest Lyapunov exponent have underlying dynamics aspects of which
can be effectively described by the Tsallis entropy. We rely on a comparison of
the generalised additivity of the Tsallis entropy versus the ordinary
additivity of the BGS entropy. We translate this comparison in metric terms by
using an effective hyperbolic metric on the configuration/phase space for the
Tsallis entropy versus the Euclidean one in the case of the BGS entropy.
Solving the Jacobi equation for such hyperbolic metrics effectively sets the
largest Lyapunov exponent computed with respect to the corresponding Euclidean
metric to zero. This conclusion is in agreement with all currently known
results about systems that have a simple asymptotic behaviour and are described
by the Tsallis entropy.Comment: 15 pages, No figures. LaTex2e. Some overlap with arXiv:1104.4869
Additional references and clarifications in this version. To be published in
QScience Connec
Charmed meson decay constants in three-flavor lattice QCD
We present the first lattice QCD calculation with realistic sea quark content
of the D^+ meson decay constant f_{D^+}. We use the MILC Collaboration's
publicly available ensembles of lattice gauge fields, which have a quark sea
with two flavors (up and down) much lighter than a third (strange). We obtain
f_{D^+} = 201 +/- 3 +/- 17 MeV, where the errors are statistical and a
combination of systematic errors. We also obtain f_{D_s} = 249 +/- 3 +/- 16 MeV
for the D_s meson.Comment: note added on recent CLEO measurement; PRL versio
Hybrid-Entanglement in Continuous Variable Systems
Entanglement is one of the most fascinating features arising from
quantum-mechanics and of great importance for quantum information science. Of
particular interest are so-called hybrid-entangled states which have the
intriguing property that they contain entanglement between different degrees of
freedom (DOFs). However, most of the current continuous variable systems only
exploit one DOF and therefore do not involve such highly complex states. We
break this barrier and demonstrate that one can exploit squeezed cylindrically
polarized optical modes to generate continuous variable states exhibiting
entanglement between the spatial and polarization DOF. We show an experimental
realization of these novel kind of states by quantum squeezing an azimuthally
polarized mode with the help of a specially tailored photonic crystal fiber
Light Lepton Number Violating Sneutrinos and the Baryon Number of the Universe
Recent results of neutrino oscillation experiments point to a nonvanishing
neutrino mass. Neutrino mass models favour Majorana-type neutrinos. In such
circumstances it is natural that the supersymmetric counterpart of the
neutrino, the sneutrino, bears also lepton number violating properties. On the
other hand, the fact that the universe exhibits an asymmetry in the baryon and
antibaryon numbers poses constraints on the extent of lepton number violation
in the light sneutrino sector if the electroweak phase transition is second or
weak first order. From the requirement that the Baryon Asymmetry of the
Universe should not be washed out by sneutrino induced lepton number violating
interactions and sphalerons below the critical temperature of the electroweak
phase transition we find that the mass splitting of the light sneutrino mass
states is compatible with the sneutrino Cold Dark Matter hypothesis only for
heavy gauginos and opposite sign gaugino mass parameters.Comment: 13 pages, 4 figure
A Measurement of Newton's Gravitational Constant
A precision measurement of the gravitational constant has been made using
a beam balance. Special attention has been given to determining the
calibration, the effect of a possible nonlinearity of the balance and the
zero-point variation of the balance. The equipment, the measurements and the
analysis are described in detail. The value obtained for G is 6.674252(109)(54)
10^{-11} m3 kg-1 s-2. The relative statistical and systematic uncertainties of
this result are 16.3 10^{-6} and 8.1 10^{-6}, respectively.Comment: 26 pages, 20 figures, Accepted for publication by Phys. Rev.
Kinetic equation for gluons at the early stage
We derive the kinetic equation for pure gluon QCD plasma in a general way,
applying the background field method. We show that the quantum kinetic equation
contains a term as in the classical case, that describes a color charge
precession of partons moving in the gauge field. We emphasize that this new
term is necessary for the gauge covariance of the resulting equation.Comment: 6 pages, no figure, to appear in the proceedings of the 6th
international conference on strange quarks in matter, Frankfurt, Germany,
25-29 september 200
The Phylogeography of Rabies in Grenada, West Indies, and Implications for Control
In Grenada, West Indies, rabies is endemic, and is thought to be maintained in a wildlife host, the small Indian mongoose (Herpestes auropunctatus) with occasional spillover into other hosts. Therefore, the present study was undertaken to improve understanding of rabies epidemiology in Grenada and to inform rabies control policy. Mongooses were trapped island-wide between April 2011 and March 2013 and examined for the presence of Rabies virus (RABV) antigen using the direct fluorescent antibody test (dFAT) and PCR, and for serum neutralizing antibodies (SNA) using the fluorescent antibody virus neutralization test (FAVN). An additional cohort of brain samples from clinical rabies suspects submitted between April 2011 and March 2014 were also investigated for the presence of virus. Two of the 171 (1.7%) live-trapped mongooses were RABV positive by FAT and PCR, and 20 (11.7%) had SNAs. Rabies was diagnosed in 31 of the submitted animals with suspicious clinical signs: 16 mongooses, 12 dogs, 2 cats and 1 goat. Our investigation has revealed that rabies infection spread from the northeast to the southwest of Grenada within the study period. Phylogenetic analysis revealed that the viruses from Grenada formed a monophyletic clade within the cosmopolitan lineage with a common ancestor predicted to have occurred recently (6–23 years ago), and are distinct from those found in Cuba and Puerto Rico, where mongoose rabies is also endemic. These data suggest that it is likely that this specific strain of RABV was imported from European regions rather than the Americas. These data contribute essential information for any potential rabies control program in Grenada and demonstrate the importance of a sound evidence base for planning interventions
Muon anomalous magnetic moment in string inspired extended family models
We propose a standard model minimal extension with two lepton weak SU(2)
doublets and a scalar singlet to explain the deviation of the measured
anomalous magnetic moment of the muon from the standard model expectation. This
scheme can be naturally motivated in string inspired models such as E_6 and
AdS/CFT.Comment: 9 pages, RevTeX, 2 figures, version to be published in Phys. Rev.
Long range transport of ultra cold atoms in a far-detuned 1D optical lattice
We present a novel method to transport ultra cold atoms in a focused optical
lattice over macroscopic distances of many Rayleigh ranges. With this method
ultra cold atoms were transported over 5 cm in 250 ms without significant atom
loss or heating. By translating the interference pattern together with the beam
geometry the trap parameters are maintained over the full transport range.
Thus, the presented method is well suited for tightly focused optical lattices
that have sufficient trap depth only close to the focus. Tight focusing is
usually required for far-detuned optical traps or traps that require high laser
intensity for other reasons. The transport time is short and thus compatible
with the operation of an optical lattice clock in which atoms are probed in a
well designed environment spatially separated from the preparation and
detection region.Comment: 14 pages, 6 figure
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