15,969 research outputs found

    Compact steep-spectrum sources from the S4 sample

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    We present the results of 5-GHz observations with the VLA A-array of a sample of candidate Compact Steep Spectrum sources (CSSs) selected from the S4 survey. We also estimate the symmetry parameters of high-luminosity CSSs selected from different samples of radio sources, and compare these with the larger sources of similar luminosity to understand their evolution and the consistency of the CSSs with the unified scheme for radio galaxies and quasars. The majority of CSSs are likely to be young sources advancing outwards through a dense asymmetric environment. The radio properties of CSSs are found to be consistent with the unified scheme, in which the axes of the quasars are observed close to the line of sight, while radio galaxies are observed close to the plane of the sky.Comment: accepted for publication in mnras; 8 pages, figure 1 with 21 images, and two additional figures; 2 table

    Preparação de dados para análise das relações entre 'Grupos de pesquisa x Projetos x Áreas de atuação' da Embrapa Informática Agropecuária.

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    A Embrapa Informática Agropecuária, buscando o aperfeiçoamento de seus instrumentos de gestão e a ampliação da integração entre os nove Grupos de Pesquisa (GPs), está desenvolvendo um instrumento gerencial que organiza de forma sistematizada as Áreas do Conhecimento e as Áreas de Aplicação dos trabalhos realizados pelos GPs, por meio da parceria entre o Núcleo de Desenvolvimento Institucional (NDI) e a Chefia de Pesquisa e Desenvolvimento (P&D). Desde outubro de 2011, ações para desenvolvimento do instrumento vêm sendo realizadas junto à área de P&D e, dentre elas, o mapeamento pelos GPs dos projetos em que atuam e projetos/áreas os quais pretendem atuar nos próximos anos, por área do conhecimento (Computação, áreas específicas ou complementares à pesquisa Agropecuária) e áreas de aplicação/atuação. A partir desse mapeamento foi desenvolvida a atividade de preparação de dados para análise das relações entre ?Grupos de Pesquisa x Projetos x Áreas de Atuação? da Embrapa Informática Agropecuária, discutida neste trabalho

    Radio polarimetry of compact steep spectrum sources at sub-arcsecond resolution

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    Aims - We report new Very Large Array polarimetric observations of Compact Steep-Spectrum (CSS) sources at 8.4, 15, and 23GHz. Methods - Using multi-frequency VLA observations we have derived sub-arcsecond resolution images of the total intensity, polarisation, and rotation measure (RM) distributions. Results heading - We present multi-frequency VLA polarisation observations of CSS sources. About half of the sources are point-like even at the resolution of about 0.1x0.1 arcseconds. The remaining sources have double or triple structure. Low values for the percentage of polarised emission in CSS sources is confirmed. On the average, quasars are more polarised than galaxies. A wide range of RM values have been measured. There are clear indications of very large RMs up to 5\,585 rad m**(-2). CSS galaxies are characterized by RM values that are larger than CSS quasars. The majority of the objects show very large values of RM. Conclusions - The available data on sub-arcsecond-scale rest-frame RM estimates for CSS sources show that these have a wide range of values extending up to about 36,000 rad m**(-2). RM estimates indicate an overall density of the magneto-ionic medium larger than classical radio sources.Comment: Accepted for publication by Astronomy & Astrophysic

    Maternal hemodynamics in normal pregnancy: reference ranges and role of maternal characteristics

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    Objectives The main aim of this study was to construct reference ranges of maternal central hemodynamic parameters during pregnancy. The second aim was to determine the maternal and pregnancy characteristics that influence these hemodynamic parameters. Methods This was a prospective cohort study of low‐risk pregnant women attending for routine antenatal care at St George's Hospital, London, UK. Exclusion criteria included any medical disorder present at the time of study recruitment, or development of hypertension or intrauterine fetal growth restriction following study recruitment. Stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) were obtained using non‐invasive cardiac output monitoring (USCOM‐1A®). USCOM‐1A utilizes a non‐imaging probe in the suprasternal notch to obtain velocity‐time integrals of transaortic blood flow at the left ventricular outflow tract. Once the distribution of the data with respect to gestational age had been determined, maternal characteristics were added to the model to test whether they provided a significant improvement in the prediction of the median value. Results The study included 627 women with a singleton pregnancy. The estimated median CO was constant for a maternal age above 32 years, but was around 0.5 L/min higher for women aged ≤ 25 years (P < 0.001). Maternal weight (P < 0.001) and height (P < 0.001) significantly affected CO values and there was a significant interaction (P = 0.002) between them. In women with a height of less than 1.60 m, there was no association between median CO and weight; however, in those with a height exceeding 1.60 m, an increase in weight was associated with an increase in CO. SV was primarily associated with height (P < 0.001), although some positive association with weight (P < 0.001) could also be observed within the normal body‐mass‐index range. Greater height (P < 0.001) was associated with lower median values of SVR, with an estimated difference of around 120 dynes × s/cm5 between 1.60 m and 1.80 m. Advancing maternal age was associated with higher median SVR, with an estimated difference of around 50 dynes × s/cm5 between 25 and 35 years. Smokers had a lower SVR by 73.5 (95% CI, 8.6–138.4) dynes × s/cm5. Conclusion Maternal hemodynamics are influenced significantly by maternal age, height and weight. We provide USCOM‐1A‐specific reference ranges and a calculator for SV, CO and SVR in uncomplicated pregnancies that correct for maternal age, height and weight. This should enable clinical application and comparison in both uncomplicated and pathological pregnancies

    VLBA polarimetric observations of the CSS quasar 3C147

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    Aims. We report new VLBA polarimetric observations of the compact steep-spectrum (CSS) quasar 3C147 (B0538+498) at 5 and 8.4GHz. Methods. By using multifrequency VLBA observations, we derived milliarcsecond-resolution images of the total intensity, polarisation, and rotation measure distributions, by combining our new observations with archival data. Results. The source shows a one-sided structure, with a compact region, and a component extending about 200 mas to the south-west. The compact region is resolved into two main components with polarised emission, a complex rotation measure distribution, and a magnetic field dominated by components perpendicular to the source axis. Conclusions. By considering all the available data, we examine the possible location of the core component, and discuss two possible interpretations of the observed structure of this source: core-jet and lobe-hot spot. Further observations to unambiguously determine the location of the core would help distinguish between the two possibilities discussed here.Comment: 11 pages, 12 figure
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