9,831 research outputs found
On the nature of the AGILE galactic transient sources
The Italian gamma-ray satellite AGILE has recently reported the detection of
some variable high-energy sources likely of galactic origin. These sources do
not have any obvious counterpart at lower energies. We propose that these
sources are produced in proton-dominated jets of galactic microquasars. We
develop a model for microquasar jets that takes into account both primary
leptons and protons and all relevant radiative processes, including secondary
particle emission and gamma-ray attenuation due to pair creation in the jet. We
obtain spectral energy distributions that correspond to what is observed by
AGILE, with most of the power concentrated between 100 MeV and 10 GeV and
reaching luminosities of erg s. We make detailed spectral
predictions that can be tested by the Fermi gamma-ray telescope in the
immediate future. We conclude that hadronic jets in galactic accreting sources
can be responsible for the variable unidentified gamma-ray sources detected by
AGILE.Comment: 4 pages, 2 figures. Accepted for publication in Astronomy &
Astrophysics (Letters
Ab initio analysis of the x-ray absorption spectrum of the myoglobin-carbon monoxide complex: Structure and vibrations
We present a comparison between Fe K-edge x-ray absorption spectra of
carbonmonoxy-myoglobin and its simulation based on density-functional theory
determination of the structure and vibrations and spectral simulation with
multiple-scattering theory. An excellent comparison is obtained for the main
part of the molecular structure without any structural fitting parameters. The
geometry of the CO ligand is reliably determined using a synergic approach to
data analysis. The methodology underlying this approach is expected to be
especially useful in similar situations in which high-resolution data for
structure and vibrations are available.Comment: 13 pages, 3 figure
Models for gamma-ray production in low-mass microquasars
Unlike high-mass gamma-ray binaries, low-mass microquasars lack external
sources of radiation and matter that could produce high-energy emission through
interactions with relativistic particles. In this work we consider the
synchrotron emission of protons and leptons that populate the jet of a low-mass
microquasar. In our model photohadronic and inverse Compton (IC) interactions
with synchrotron photons produced by both protons and leptons result in a
high-energy tail of the spectrum. We also estimate the contribution from
secondary pairs injected through photopair production. The high-energy emission
is dominated by radiation of hadronic origin, so we can call these objects
proton microquasars.Comment: 4 pages, 2 figures, accepted for publication in the International
Journal of Modern Physics D, proceedings of HEPRO meeting, held in Dublin, in
September 200
Basis set effects on the hyperpolarizability of CHCl_3: Gaussian-type orbitals, numerical basis sets and real-space grids
Calculations of the hyperpolarizability are typically much more difficult to
converge with basis set size than the linear polarizability. In order to
understand these convergence issues and hence obtain accurate ab initio values,
we compare calculations of the static hyperpolarizability of the gas-phase
chloroform molecule (CHCl_3) using three different kinds of basis sets:
Gaussian-type orbitals, numerical basis sets, and real-space grids. Although
all of these methods can yield similar results, surprisingly large, diffuse
basis sets are needed to achieve convergence to comparable values. These
results are interpreted in terms of local polarizability and
hyperpolarizability densities. We find that the hyperpolarizability is very
sensitive to the molecular structure, and we also assess the significance of
vibrational contributions and frequency dispersion
Oral health status of patients over 18 years. Preventive Clinic Practicum I, UNNE School of Dentistry, Argentina, 2010
Introducción: con el propósito de conocer la situación de salud bucal de pacientes que asisten a la Cátedra Práctica Clínica Preventiva I de la Facultad de Odontología de la Universidad Nacional del Nordeste (UNNE), se realizó un estudio de corte transversal en septiembre y octubre del año 2010. Métodos: Las variables consideradas fueron: datos socio-demográficos, nivel de conocimientos en salud buco-dental, hábitos de higiene buco-dental y de consumo de hidratos de carbono, estado gingival, higiene bucal, estado de los dientes y acceso a la atención odontológica. Para la recolección de datos se utilizaron encuestas estructuradas auto-administradas y las historias clínicas de cada paciente. Se analizaron los datos con los programas estadísticos SPSS 15.0 y Epidat 3.1. Resultados y Conclusiones: si bien predomina un nivel de conocimientos de salud buco-dental bueno, esto no se refleja en los hábitos de higiene oral y en la periodicidad de búsqueda de atención odontológica preventiva. El examen clínico buco-dental reveló higiene buco-dental deficiente, alta prevalencia de gingivitis leve y elevada prevalencia de caries dental y de dientes obturados y perdidos como consecuencia de la misma. Es necesaria la búsqueda de estrategias programadas que permitan optimizar la educación sanitaria y mejorar los comportamientos preventivos de la población de estudio.Introduction: with the intention of identifying the oral health status of patients attending the Preventive Clinic Practicum I at the School of Dentistry, Universidad Nacional del Nordeste (UNNE), Argentina, a cross-sectional study was conducted between September and October 2010. Methods: the variables taken into account were: socio-demographic data, level of oral health knowledge, oral hygiene habits and carbohydrate consumption, gingival status, oral hygiene, teeth status, and access to dental care. The data were collected by means of structured self-administered surveys and the medical records of each patient, and they were analyzed with the statistical software SPSS® 15.0 and Epidat® 3.1. Results: although a good level of oral health knowledge is predominant, it is not reflected in oral hygiene habits or in the frequency in which individuals seek preventive dental care. The clinical examination revealed poor oral hygiene habits, high prevalence of mild gingivitis and high prevalence of dental caries as well as filled and missing teeth as a result of it. Conclusions: it is necessary to search for strategies to optimize health education and to improve preventive behaviors within the study population.Fil: Dho, María Silvina. Universidad Nacional del Nordeste. Facultad de Odontologia. Secretaria de Investigacion. Gabinete de Inv.interd.de Prevencion Salud y Epidemologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vila, Vilma G.. Universidad Nacional del Nordeste. Facultad de Odontologia. Departamento de Clinicas Integradas; ArgentinaFil: Palladino, Alberto C.. Universidad Nacional del Nordeste. Facultad de Medicina; Argentin
First record of Oligochoerus limnophilus (Acoela, Acoelomorpha) from British waters
Primer registro de Oligochoerus limnophilus (Acoela, Acoelomorpha) en aguas británicas
Informamos de la existencia de poblaciones del acelo Oligochoerus limnophilus (Acoelomorpha) en la islas Británicas sobre la base de los especímenes capturados en el río Támesis (también conocido localmente como río Isis) a su paso por Oxford, Inglaterra, ampliando así considerablemente el área de distribución de la especie, restringida hasta ahora al continente europeo. La información gráfica que aportamos, imágenes de especímenes vivos y proyecciones CLSM de estructuras informativas seleccionadas por su valor sistemático, corrobora su estrecha relación con el género Convoluta Ørsted, 1843.We report the occurrence of the acoel Oligochoerus limnophilus (Acoelomorpha) from the British Islands, based on specimens captured in the river Thames (locally known as the river Isis) in Oxford, England, thereby considerably widening the distributional range of the species that had formerly been reported only from continental Europe. We further present live images and CLSM-projections of systematically informative structures that corroborate a close relationship with the genus Convoluta Ørsted, 1843.Primer registre d'Oligochoerus limnophilus (Acoela, Acoelomorpha) en aigües britàniques
Informem de l'existència de poblacions de l'acel Oligochoerus limnophilus (Acoelomorpha) a les illes Britàniques sobre la base dels espècimens capturats al riu Tàmesi (també conegut localment com a riu Isis) al pas per Oxford, Anglaterra, amb la qual cosa ampliem considerablement l'àrea de distribució de l'espècie, restringida fins ara al continent europeu. La informació gràfica que aportem, imatges d'espècimens vius i projeccions CLSM d'estructures informatives seleccionades pel seu valor sistemàtic, corrobora l'estreta relació amb el gènere Convoluta Ørsted, 1843
Myristic acid potentiates palmitic acid-induced lipotoxicity and steatohepatitis associated with lipodystrophy by sustaning de novo ceramide synthesis.
Palmitic acid (PA) induces hepatocyte apoptosis and fuels de novo ceramide synthesis in the endoplasmic reticulum (ER). Myristic acid (MA), a free fatty acid highly abundant in copra/palmist oils, is a predictor of nonalcoholic steatohepatitis (NASH) and stimulates ceramide synthesis. Here we investigated the synergism between MA and PA in ceramide synthesis, ER stress, lipotoxicity and NASH. Unlike PA, MA is not lipotoxic but potentiated PA-mediated lipoapoptosis, ER stress, caspase-3 activation and cytochrome c release in primary mouse hepatocytes (PMH). Moreover, MA kinetically sustained PA-induced total ceramide content by stimulating dehydroceramide desaturase and switched the ceramide profile from decreased to increased ceramide 14:0/ceramide16:0, without changing medium and long-chain ceramide species. PMH were more sensitive to equimolar ceramide14:0/ceramide16:0 exposure, which mimics the outcome of PA plus MA treatment on ceramide homeostasis, than to either ceramide alone. Treatment with myriocin to inhibit ceramide synthesis and tauroursodeoxycholic acid to prevent ER stress ameliorated PA plus MA induced apoptosis, similar to the protection afforded by the antioxidant BHA, the pan-caspase inhibitor z-VAD-Fmk and JNK inhibition. Moreover, ruthenium red protected PMH against PA and MA-induced cell death. Recapitulating in vitro findings, mice fed a diet enriched in PA plus MA exhibited lipodystrophy, hepatosplenomegaly, increased liver ceramide content and cholesterol levels, ER stress, liver damage, inflammation and fibrosis compared to mice fed diets enriched in PA or MA alone. The deleterious effects of PA plus MA-enriched diet were largely prevented by in vivo myriocin treatment. These findings indicate a causal link between ceramide synthesis and ER stress in lipotoxicity, and imply that the consumption of diets enriched in MA and PA can cause NASH associated with lipodystrophy
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