18,677 research outputs found

    Binarity in Cool Asymptotic Giant Branch Stars: A Galex Search for Ultraviolet Excesse

    Get PDF
    The search for binarity in AGB stars is of critical importance for our understanding of how planetary nebulae acquire the dazzling variety of aspherical shapes which characterises this class. However, detecting binary companions in such stars has been severely hampered due to their extreme luminosities and pulsations. We have carried out a small imaging survey of AGB stars in ultraviolet light (using GALEX) where these cool objects are very faint, in order to search for hotter companions. We report the discovery of significant far-ultraviolet excesses towards nine of these stars. The far-ultraviolet excess most likely results either directly from the presence of a hot binary companion, or indirectly from a hot accretion disk around the companion.Comment: revised for Astrophysical Journa

    Reducing sample variance: halo biasing, non-linearity and stochasticity

    Get PDF
    Comparing clustering of differently biased tracers of the dark matter distribution offers the opportunity to reduce the cosmic variance error in the measurement of certain cosmological parameters. We develop a formalism that includes bias non-linearities and stochasticity. Our formalism is general enough that can be used to optimise survey design and tracers selection and optimally split (or combine) tracers to minimise the error on the cosmologically interesting quantities. Our approach generalises the one presented by McDonald & Seljak (2009) of circumventing sample variance in the measurement of fdlnD/dlnaf\equiv d \ln D/d\ln a. We analyse how the bias, the noise, the non-linearity and stochasticity affect the measurements of DfDf and explore in which signal-to-noise regime it is significantly advantageous to split a galaxy sample in two differently-biased tracers. We use N-body simulations to find realistic values for the parameters describing the bias properties of dark matter haloes of different masses and their number density. We find that, even if dark matter haloes could be used as tracers and selected in an idealised way, for realistic haloes, the sample variance limit can be reduced only by up to a factor σ2tr/σ1tr0.6\sigma_{2tr}/\sigma_{1tr}\simeq 0.6. This would still correspond to the gain from a three times larger survey volume if the two tracers were not to be split. Before any practical application one should bear in mind that these findings apply to dark matter haloes as tracers, while realistic surveys would select galaxies: the galaxy-host halo relation is likely to introduce extra stochasticity, which may reduce the gain further.Comment: 21 pages, 13 figures. Published version in MNRA

    Projeto Rondon no município de Caridade – CE: avaliação dos resultados obtidos com as feiras da saúde

    Get PDF
    Trabalho apresentado no II Congresso Nacional do PROJETO RONDON, realizado em Florianópolis, SC, no período de 23 a 25 de setembro de 2015 - Universidade Federal de Santa Catarina.A Organização Mundial de Saúde (OMS) classifica as condições de saúde em agudas e crônicas, tendo a Hipertensão Arterial Sistêmica (HAS) e o Diabetes Mellitus (DM) como condições crônico-degenerativas de saúde. Assim, tais patologias recebem atenção especial do sistema de saúde, haja vista a alta prevalência das complicações cardiovasculares, cerebrovasculares, nefrológicas e visuais oriundas dessas doenças. Nesse sentido, essas afecções e seus agravos necessitam de ações efetivas de promoção e prevenção da saúde. A Feira da Saúde foi uma das oficinas do Centro Universitário de Patos de Minas – UNIPAM durante o Projeto Rondon de Janeiro/2015 - Operação Mandacaru em Caridade - CE. As ações basearam-se na realização de um circuito de atendimento, no qual o paciente foi acolhido e devidamente identificado e a seguir, foram coletadas e registradas, em uma ficha própria desenvolvida para a feira, informações de saúde desses indivíduos. Ao final do circuito, cada pessoa atendida apresentou esse instrumento a um rondonista. Após a avaliação dos dados encontrados na ficha, o membro da equipe dialogou com o paciente, dando ênfase em orientações que, de acordo com as evidências científicas, reduzem a mortalidade, como uma alimentação saudável, a prática regular de atividade física, a redução ou abolição do consumo de bebidas alcóolicas, tabaco e outras drogas e a utilização correta de medicamentos para o controle da Hipertensão Arterial e do Diabetes Mellitus. Ao longo da realização do Projeto Rondon no município, esta oficina foi desenvolvida quatro vezes, em Caridade e nos distritos de São Domingos e Ipueira dos Gomes, ultrapassando o número de 250 indivíduos atendidos. Desses, 135 tiveram suas fichas sorteadas aleatoriamente para a avaliação do perfil dos pacientes acolhidos nas feiras de saúde. Dentre os resultados obtidos, perceberam-se nitidamente os hábitos de vida desfavoráveis para o aparecimento e a progressão das doenças crônicas, sendo relevante citar o percentual elevado de pacientes com sobrepeso e obesidade e o sedentarismo, este último observado através dos mais de 80% dos pacientes que não praticavam nenhuma atividade física. Portanto, acredita-se que as Feiras da Saúde foram de suma importância para a conscientização da população desse município para o autocuidado orientado através de hábitos de vida saudáveis

    The redshift and broad band spectral energy distribution of NRAO 150

    Full text link
    Context. NRAO 150 is one of the brightest radio and mm AGN sources on the northern sky. It has been revealed as an interesting source where to study extreme relativistic jet phenomena. However, its cosmological distance has not been reported so far, because of its optical faintness produced by strong Galactic extinction. Aims. Aiming at measuring the redshift of NRAO 150, and hence to start making possible quantitative studies from the source. Methods. We have conducted spectroscopic and photometric observations of the source in the near-IR, as well as in the optical. Results. All such observations have been successful in detecting the source. The near-IR spectroscopic observations reveal strong Hα\alpha and Hβ\beta emission lines from which the cosmological redshift of NRAO 150 (z=1.517±0.002z=1.517\pm0.002) has been determined for the first time. We classify the source as a flat-spectrum radio-loud quasar, for which we estimate a large super-massive black-hole mass 5×109M\sim5\times 10^{9} \mathrm{M_\odot}. After extinction correction, the new near-IR and optical data have revealed a high-luminosity continuum-emission excess in the optical (peaking at 2000\sim2000\,\AA, rest frame) that we attribute to thermal emission from the accretion disk for which we estimate a high accretion rate, 30\sim30\,% of the Eddington limit. Conclusions. Comparison of these source properties, and its broad-band spectral-energy distribution, with those of Fermi blazars allow us to predict that NRAO 150 is among the most powerful blazars, and hence a high luminosity -although not detected yet- γ\gamma-ray emitter.Comment: 8 pages, 4 figure

    Biomimetic cork-based CeO2 ecoceramics for hydrogen generation using concentrated solar energy

    Get PDF
    Naturally occurring and sustainable materials can be used as a template to create biomimetic/biomorphic ceramics, known as Ecoceramics (environmentally conscious ceramics). In this work, cork was chosen as template to produce novel ceria (CeO2) ecoceramics, for applications in water splitting for H2 production via direct concentrated solar thermochemical fuel production (TCFP). The cork powder was pyrolised at 900 °C and the resulting carbon skeleton was infiltrated with an aqueous CeO2 precursor, and then heated at 1000 °C for 2 h to produce the ecoceramic. The cellular structure of the cork was maintained, with hexagonal cell dimensions of 20-30 μm in diameter, but the grains were nanoscale at ≤100 nm. XRD data confirmed that CeO2 was the only crystalline phase obtained. An important feature was that, while the rectangular side walls were maintained to hold the three-dimensionally ordered macroporous (3DOM) cellular cork structure, the rear hexagonal walls were pierced repeatedly through the structure, unlike in the original cork structure, which will allow gasses such as H2 to permeate well into the structure, greatly increasing the reactive area available for catalysis. The next step will be to test the capabilities of both the regular, porous 3DOM structure and the nanoscale grains for thermochemical water splitting to produce hydrogen under direct concentrated solar energy

    Determining the regimes of cold and warm inflation in the susy hybrid model

    Full text link
    The SUSY hybrid inflation model is found to dissipate radiation during the inflationary period. Analysis is made of parameter regimes in which these dissipative effects are significant. The scalar spectral index, its running, and the tensor-scalar ratio are computed in the entire parameter range of the model. A clear prediction for strong dissipative warm inflation is found for n_S-1 \simeq 0.98 and a low tensor-scalar ratio much below 10^{-6}. The strong dissipative warm inflation regime also is found to have no \eta-problem and with the field amplitude much below the Planck scale. As will be discussed, this has important theoretical implications in permitting a much wider variety of SUGRA extensions to the basic model.Comment: paragraph added at the end of section V; references added; accepted for publication in Phys. Rev.

    A systematic review of breast milk microbiota composition and the evidence for transfer to and colonisation of the infant gut

    Get PDF
    The intestinal microbiota plays a major role in infant health and development. However, the role of the breastmilk microbiota in infant gut colonisation remains unclear. A systematic review was performed to evaluate the composition of the breastmilk microbiota and evidence for transfer to/colonisation of the infant gut. Searches were performed using PUBMED, OVID, LILACS and PROQUEST from inception until 18th March 2020 with a PUBMED update to December 2021. 88 full texts were evaluated before final critique based on study power, sample contamination avoidance, storage, purification process, DNA extraction/analysis, and consideration of maternal health and other potential confounders. Risk of skin contamination was reduced mainly by breast cleaning and rejecting the first milk drops. Sample storage, DNA extraction and bioinformatics varied. Several studies stored samples under conditions that may selectively impact bacterial DNA preservation, others used preculture reducing reliability. Only 15 studies, with acceptable sample size, handling, extraction, and bacterial analysis, considered transfer of bacteria to the infant. Three reported bacterial transfer from infant to breastmilk. Despite consistent evidence for the breastmilk microbiota, and recent studies using improved methods to investigate factors affecting its composition, few studies adequately considered transfer to the infant gut providing very little evidence for effective impact on gut colonisation

    Diversidad genética de Pinus pinaster en la Península Ibérica: correlación entre isoenzimas y caracteres cuantitativos

    Get PDF
    The estimation of genetic diversity using molecular markers is a major component of genetic conservation programs. However, molecular data are only weakly correlated with adaptive variation, which seriously limits the value of molecular information for guiding conservation policies. In this paper, we used allozyme markers to analyse the distribution of gene diversity in the native range of Pinus pinaster Ait. in the Iberian Peninsula, including seven marginal populations close to the Mediterranean Basin. Then, the variability of three quantitative traits (total height, stem form and survival) was computed using data from a multisite provenance test in central Spain and the two data sets were compared. Within the general pattern of variation, marginal populations presented levels of diversity closely related to those of nearby central populations, clearly suggesting that historical factors were more important than actual population sizes in determining levels of observed diversity. A weak but nevertheless significant correlation between allozymes and quantitative variability was found in maritime pine. Environmental gradients, as measured by geographic variables, are suggested to have selective effects on quantitative traits and to influence effective population size, which might explain the weak correlation found between allozyme and adaptive variability.Uno de los principales componentes de los programas de conservación genética es el uso de marcadores moleculares para la estimación de la diversidad genética. A pesar de ello, la variación observada en marcadores moleculares está débilmente correlacionada con la variación adaptativa, lo que limita seriamente la aplicación de estos estudios en el desarrollo de políticas de conservación. En este trabajo, se compara la distribución de la diversidad genética de Pinus pinaster Ait. en la Península Ibérica obtenida con marcadores moleculares (isoenzimas) y caracteres cuantitativos (altura, forma del fuste y supervivencia). El estudio incluye siete poblaciones marginales. Éstas, muestran valores de diversidad similares a los de poblaciones centrales próximas lo que sugiere una gran importancia de los procesos históricos regionales frente a efectos relacionados con el tamaño efectivo poblacional. La correlación de los marcadores moleculares utilizados con los caracteres cuantitativos medidos en los ensayos de campo es débil, aunque significativa. Esta correlación podría explicarse considerando efectos selectivos en respuesta a gradientes ambientales que afectan a su vez el tamaño efectivo de las poblaciones
    corecore