1,791 research outputs found
Detecting respiratory bacterial communities of wild dolphins: Implications for animal health
Infectious diseases contribute to the vulnerable status of marine mammals, including respiratory illnesses. This study aimed to capture exhaled breath condensate (blow) for microbial identification from wild Indo-Pacific bottlenose dolphins Tursiops aduncus. Individual dolphins were sampled by holding a funnel connected to a 50 ml centrifuge tube over the blowhole of the animal near shore in Shark Bay (SB), Western Australia. Four individuals were sampled on 2 occasions along with seawater samples. Comparative blow and pool water samples were collected from 4 individual common bottlenose dolphins Tursiops truncatus housed in the National Aquarium (NA), Baltimore, Maryland, USA. Bacteria were identified using the V4 region of the 16S rRNA gene from extracted DNA. We identified bacteria independent of seawater in SB dolphins, which included the classes Alphaproteobacteria (26.1%) and Gammaproteobacteria (25.8%); the phyla Bacteroidetes (15.6%) and Fusobacteria (7.2%); and the genera Pseudomonas (11.5%), Pedomicrobium (4.5%), Streptobacillus (3.7%), Phenylobacterium (2.2%) and Sphingomonas (2.1%). There were broad similarities in phyla between SB and NA dolphins yet there were differences between lower taxonomic groups. A number of operational taxonomic units (OTUs) were shared between dolphin individuals, which may be a result of their genetic lineage (siblings or parentage), shared living and social interactions. A number of genera were observed in SB dolphins which have species known to be infectious in marine mammals such as Pseudomonas, Mycoplasma and Streptococcus. This study successfully characterised bacteria from DNA captured in blow from wild dolphins. The ability to capture these communities from individuals in the wild provides a novel health indicator
Non-hermitean delocalization in an array of wells with variable-range widths
Nonhermitean hamiltonians of convection-diffusion type occur in the
description of vortex motion in the presence of a tilted magnetic field as well
as in models of driven population dynamics. We study such hamiltonians in the
case of rectangular barriers of variable size. We determine Lyapunov exponent
and wavenumber of the eigenfunctions within an adiabatic approach, allowing to
reduce the original d=2 phase space to a d=1 attractor. PACS
numbers:05.70.Ln,72.15Rn,74.60.GeComment: 20 pages,10 figure
Excitons and Excitonic Molecules in Mixed Crystals
Low-temperature (1.8 K) excitonic absorption, reflection and
photoluminescence spectra of mixed crystals were
studied at 0.01, 0.02, 0.03 and 0.05. Energy gap and rydbergs of
excitonic B, C and A-series decrease monotonically at the increase of .
Spectral half-widths of absorption lines of B and A-series increase
monotonically at the increase of due to fluctuations of crystal potential.
Emission lines of excitonic molecules were observed in photoluminescence
spectra of crystals. Binding energy of molecule
increases at the increase of that is due to the decrease of the
electron-hole mass ratio.Comment: 10 pages, 7 figures, paper submitted to Physica B: Condensed Matte
Symplectic Quantization of Open Strings and Noncommutativity in Branes
We show how to translate boundary conditions into constraints in the
symplectic quantization method by an appropriate choice of generalized
variables. This way the symplectic quantization of an open string attached to a
brane in the presence of an antisymmetric background field reproduces the non
commutativity of the brane coordinates.Comment: We included a comparison with previous results obtained from Dirac
quantization, emphasizing the fact that in the symplectic case the boundary
conditions, that lead to the non commutativity, show up from the direct
application of the standard method. Version to appear in Phys. Rev.
Dirac gaugino as leptophilic dark matter
We investigate the leptophilic properties of Dirac gauginos in an
R--symmetric N=2 supersymmetric model with extended gauge and Higgs sectors.
The annihilation of Dirac gauginos to leptons requires no chirality flip in the
final states so that it is not suppressed as in the Majorana case. This implies
that it can be sizable enough to explain the positron excess observed by the
PAMELA experiment with moderate or no boost factors. When squark masses are
heavy, the annihilation of Dirac gauginos to hadrons is controlled by their
Higgsino fraction and is driven by the and final states.
Moreover, at variance with the Majorana case, Dirac gauginos with a
non-vanishing higgsino fraction can also have a vector coupling with the
gauge boson leading to a sizable spin--independent scattering cross section off
nuclei. Saturating the current antiproton limit, we show that Dirac gauginos
can leave a signal in direct detection experiments at the level of the
sensitivity of dark matter searches at present and in the near future.Comment: 24 pages, 10 figures, typos corrected, final version published on
JCA
Electron correlation effects in a wide channel from the quantum Hall edge states
The spatial behavior of Landau levels (LLs) for the quantum Hall
regime at the edge of a wide channel is studied in a self-consistent way by
using a generalized local density approximation proposed here. Both exchange
interaction and strong electron correlations, due to edge states, are taken
into account. They essentially modify the spatial behavior of the occupied
lowest spin-up LL in comparison with that of the lowest spin-down LL, which is
totally empty. The contrast in the spatial behavior can be attributed to a
different effective one-electron lateral confining potentials for the
spin-split LLs. Many-body effects on the spatially inhomogeneous spin-splitting
are calculated within the screened Hartree-Fock approximation. It is shown
that, far from the edges, the maximum activation energy is dominated by the gap
between the Fermi level and the bottom of the spin-down LL, because the gap
between the Fermi level and the spin-up LL is much larger. In other words, the
maximum activation energy in the bulk of the channel corresponds to a highly
asymmetric position of the Fermi level within the gap between spin-down and
spin-up LLs in the bulk. We have also studied the renormalization of the
edge-state group velocity due to electron correlations. The results of the
present theory are in line with those suggested and reported by experiments on
high quality samples.Comment: 9 pages, 4 figure
The nature of slow dynamics in a minimal model of frustration-limited domains
We present simulation results for the dynamics of a schematic model based on
the frustration-limited domain picture of glass-forming liquids. These results
are compared with approximate theoretical predictions analogous to those
commonly used for supercooled liquid dynamics. Although model relaxation times
increase by several orders of magnitude in a non-Arrhenius manner as a
microphase separation transition is approached, the slow relaxation is in many
ways dissimilar to that of a liquid. In particular, structural relaxation is
nearly exponential in time at each wave vector, indicating that the mode
coupling effects dominating liquid relaxation are comparatively weak within
this model. Relaxation properties of the model are instead well reproduced by
the simplest dynamical extension of a static Hartree approximation. This
approach is qualitatively accurate even for temperatures at which the mode
coupling approximation predicts loss of ergodicity. These results suggest that
the thermodynamically disordered phase of such a minimal model poorly
caricatures the slow dynamics of a liquid near its glass transition
Sparticle masses in deflected mirage mediation
We discuss the sparticle mass patterns that can be realized in deflected
mirage mediation scenario of supersymmetry breaking, in which the moduli,
anomaly, and gauge mediations all contribute to the MSSM soft parameters.
Analytic expression of low energy soft parameters and also the sfermion mass
sum rules are derived, which can be used to interpret the experimentally
measured sparticle masses within the framework of the most general mixed
moduli-gauge-anomaly mediation. Phenomenological aspects of some specific
examples are also discussed.Comment: 43 pages, 17 figures, references adde
Ideas del alumnado de primaria y secundaria sobre aleatoriedad
En este trabajo comparamos las características de las secuencias de resultados
aleatorios y distribuciones aleatorias de puntos generadas por tres grupos de alumnos
de Educación Primaria y Secundaria con las propiedades matemáticas de las mismas.
La finalidad es describir el significado personal que dichos estudiantes asignan a la
aleatoriedad.In this paper we compare the features in random sequences and random distribution
of points produced by three groups of students in Primary and Secondary Education
with the mathematical properties of the same. The aim is to describe the meaning of
randomness for these students.Facultad de Educación y Humanidades - Campus de Melilla (Universidad de Granada)Este trabajo es parte de los proyectos SEJ2004-00789, Madrid, MCYT y FQM-126, Junta de Andalucí
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