127,388 research outputs found
The white dwarf in dwarf nova SDSS J080434.20+510349.2: Entering the instability strip?
SDSS J080434.20+510349.2 is the WZ type binary that displayed rare outburst
in 2006 (Pavlenko et al., 2007). During the long-lasting tail of the late stage
of the outburst binary shown the two-humped or four-humped profile of the
orbital light modulation. The amplitude of orbital light curve decreased while
the mean brightness decreased, more over that occurred 10 times faster
during the fast outburst decline in respect to the late quiet state of slow
outburst fading. There were no white dwarf pulsations detected neither 1 - 1.5
months prior to the outburst nor in 1.5 - 2 months after the 2006 outburst in
this system. However the strong non-radial pulsations with period 12.6 minutes
and mean amplitude of 0.05^m were first detected in V band with 2.6-m Shajn
mirror telescope of the Crimean astrophysical observatory in ~ 8 months after
the outburst. The evolution of pulsations over two years in 2006 - 2008 is
considered. It is supposed that pulsations first appeared when the cooling
white dwarf (after the outburst) entered the instability strip although the
possibility of temporary lack of pulsations at some occasions also could not be
excluded.Comment: Submitted to Proceedings of 16th European White Dwarf Workshop
(EUROWD08
MRI and Neuropsychological Correlates of Carbon Monoxide Exposure: A Case Report
A 45-year-old woman experienced long-term, chronic exposure to carbon monoxide in the restaurant kitchen where she was employed as a cook. After returning to the restaurant after 5 days off work, she noticed that her symptoms returned immediately; she then aired out the room and called the gas company. Approximately 6 hr after a leak was detected, the patient went to the hospital, where her carboxyhemoglobin was found to be within normal limits and results of a neurologic examination were described as normal. Based on her symptoms, the patient believed she had been exposed to CO for at least 1 year before the leak was discovered. Initially, she experienced flu-like symptoms, which eventually resolved. At the time of her first neuropsychological evaluation (17 months after the exposure was identified), her persisting complaints included difficulties in reading, writing, speaking and word retrieval. The test results were consistent with secondary frontal lobe dysfunction associated with subcortical disorders such as those seen after CO exposure. Results of a subsequent neuropsychological examination (29 months postexposure) showed slight improvement in performance, but her performance was still consistent with mild frontal/subcortical dysfunction. Although the initial screening of a brain magnetic resonance image (MRI) performed 15 months after the exposure was interpreted as being within normal limits, two subsequent blind reviews of the same scans identified multiple bilateral lesions in the basal ganglia, which were consistent with chronic CO exposure. We present this case as an example of the utility of MRI and neuropsychological examinations in detecting central nervous system dysfunction secondary to CO exposure
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Building on Redundancy: Factoid Question Answering, Robust Retrieval and the "Other"
We have explored how redundancy based techniques can be used in improving factoid question answering, definitional
questions (âotherâ), and robust retrieval. For the factoids, we explored the meta approach: we submit the questions to the
several open domain question answering systems available on the Web and applied our redundancy-based triangulation
algorithm to analyze their outputs in order to identify the most promising answers. Our results support the added value of the
meta approach: the performance of the combined system surpassed the underlying performances of its components. To
answer definitional (âotherâ) questions, we were looking for the sentences containing re-occurring pairs of noun entities
containing the elements of the target. For robust retrieval, we applied our redundancy based Internet mining technique to
identify the concepts (single word terms or phrases) that were highly related to the topic (query) and expanded the queries
with them. All our results are above the mean performance in the categories in which we have participated, with one of our
robust runs being the best in its category among all 24 participants. Overall, our findings support the hypothesis that using as
much as possible textual data, specifically such as mined from the World Wide Web, is extremely promising.published_or_final_versio
Phase Mixing of Alfvén Waves Near a 2D Magnetic Null Point
The propagation of linear Alfvén wave pulses in an inhomogeneous plasma near a 2D coronal null point is investigated. When a uniform plasma density is considered, it is seen that an initially planar Alfvén wavefront remains planar, despite the varying equilibrium Alfvén speed, and that all the wave collects at the separatrices. Thus, in the non-ideal case, these Alfvénic disturbances preferentially dissipate their energy at these locations. For a non-uniform equilibrium density, it is found that the Alfvén wavefront is significantly distorted away from the initially planar geometry, inviting the possibility of dissipation due to phase mixing. Despite this however, we conclude that for the Alfvén wave, current density accumulation and preferential heating still primarily occur at the separatrices, even when an extremely non-uniform density profile is considered
Spontaneous emission of radiation by metallic electrons in the presence of electromagnetic fields of surface plasmon oscillations
The spontaneous emission of radiation of metallic electrons embedded in a
high-intensity enhanced surface plasmon field is considered analytically. The
electrons are described by exact dressed quantum states which contain the
interaction with the plasmon field non-perturbatively. Considerable deviations
from the pertubative behaviour have been found in the intensity dependence of
the emitted fundamental and the second harmonic signals, even at moderate
incoming laser intensities. The theoretical predictions deduced from the
formalism are in good qualitative agreement with the experimental results.Comment: 23 pages, 6 figure
The partition bundle of type A_{N-1} (2, 0) theory
Six-dimensional (2, 0) theory can be defined on a large class of
six-manifolds endowed with some additional topological and geometric data (i.e.
an orientation, a spin structure, a conformal structure, and an R-symmetry
bundle with connection). We discuss the nature of the object that generalizes
the partition function of a more conventional quantum theory. This object takes
its values in a certain complex vector space, which fits together into the
total space of a complex vector bundle (the `partition bundle') as the data on
the six-manifold is varied in its infinite-dimensional parameter space. In this
context, an important role is played by the middle-dimensional intermediate
Jacobian of the six-manifold endowed with some additional data (i.e. a
symplectic structure, a quadratic form, and a complex structure). We define a
certain hermitian vector bundle over this finite-dimensional parameter space.
The partition bundle is then given by the pullback of the latter bundle by the
map from the parameter space related to the six-manifold to the parameter space
related to the intermediate Jacobian.Comment: 15 pages. Minor changes, added reference
Probing the bulk ionic conductivity by thin film hetero-epitaxial engineering
Highly textured thin films with small grain boundary regions can be used as model systems to directly measure the bulk conductivity of oxygen ion conducting oxides. Ionic conducting thin films and epitaxial heterostructures are also widely used to probe the effect of strain on the oxygen ion migration in oxide materials. For the purpose of these investigations a good lattice matching between the film and the substrate is required to promote the ordered film growth. Moreover, the substrate should be a good electrical insulator at high temperature to allow a reliable electrical characterization of the deposited film. Here we report the fabrication of an epitaxial heterostructure made with a double buffer layer of BaZrO3 and SrTiO3 grown on MgO substrates that fulfills both requirements. Based on such template platform, highly ordered (001) epitaxially oriented thin films of 15% Sm-doped CeO2 and 8 mol% Y2O3 stabilized ZrO2 are grown. Bulk conductivities as well as activation energies are measured for both materials, confirming the success of the approach. The reported insulating template platform promises potential application also for the electrical characterization of other novel electrolyte materials that still need a thorough understanding of their ionic conductivity. © 2015 National Institute for Materials Science
Contrasting patterns of selection between MHC I and II across populations of Humboldt and Magellanic penguins
IndexaciĂłn: Web of ScienceThe evolutionary and adaptive potential of populations or species facing an emerging infectious disease depends on their genetic diversity in genes, such as the major histocompatibility complex (MHC). In birds, MHC class I deals predominantly with intracellular infections (e.g., viruses) and MHC class II with extracellular infections (e.g., bacteria). Therefore, patterns of MHC I and II diversity may differ between species and across populations of species depending on the relative effect of local and global environmental selective pressures, genetic drift, and gene flow. We hypothesize that high gene flow among populations of Humboldt and Magellanic penguins limits local adaptation in MHC I and MHC II, and signatures of selection differ between markers, locations, and species. We evaluated the MHC I and II diversity using 454 next-generation sequencing of 100 Humboldt and 75 Magellanic penguins from seven different breeding colonies. Higher genetic diversity was observed in MHC I than MHC II for both species, explained by more than one MHC I loci identified. Large population sizes, high gene flow, and/or similar selection pressures maintain diversity but limit local adaptation in MHC I. A pattern of isolation by distance was observed for MHC II for Humboldt penguin suggesting local adaptation, mainly on the northernmost studied locality. Furthermore, trans species alleles were found due to a recent speciation for the genus or convergent evolution. High MHC I and MHC II gene diversity described is extremely advantageous for the long term survival of the species.http://onlinelibrary.wiley.com/doi/10.1002/ece3.2502/epd
Strong solutions of the thin film equation in spherical geometry
We study existence and long-time behaviour of strong solutions for the thin
film equation using a priori estimates in a weighted Sobolev space. This
equation can be classified as a doubly degenerate fourth-order parabolic and it
models coating flow on the outer surface of a sphere. It is shown that the
strong solution asymptotically decays to the flat profile
Integrable models: from dynamical solutions to string theory
We review the status of integrable models from the point of view of their
dynamics and integrability conditions. Some integrable models are discussed in
detail. We comment on the use it is made of them in string theory. We also
discuss the Bethe Ansatz solution of the SO(6) symmetric Hamiltonian with SO(6)
boundary.
This work is especially prepared for the seventieth anniversaries of
Andr\'{e} Swieca (in memoriam) and Roland K\"{o}berle.Comment: 24 pages, to appear in Brazilian Journal of Physic
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