907 research outputs found

    Line width distributions as evidence for axisymmetry in the broad line regions of active galaxies

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    The nuclei of a wide class of active galaxies emit broad emission lines with widths at half maximum (FWHM) in the range 103−10410^{3}-10^{4} km s−1^{-1}. This spread of widths is not solely a consequence of the range of the luminosities of these sources since a plot of width versus luminosity shows a large scatter. We propose that the broad line emission region (BLR) is axially symmetric and that this scatter in line width arises from an additional dependence on the angle of the line of sight to the axis of the emission region. Such a relation is natural in unified models of active nuclei which link a variety of observed properties to viewing angle. Adopting a simple form for the line width as a function of luminosity and angle, and convolving this with the observed luminosity function, allows us to predict a line width distribution consistent with the available data. Furthermore, we use the relation between the equivalent width of a line and the luminosity in the continuum (the `Baldwin Effect') to predict an observed correlation between line width and equivalent width. The scatter on this correlation is again provided by angular dependence. The results have applications as diagnostics of models of the broad line emission region and in cosmology.Comment: 8 pages including 4 figures. Accepted for publication in MNRAS Letter

    The luminosity dependence of opening angle in unified models of active galaxies

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    In unified models of active galaxies the direct line of sight to the nucleus is unobscured only within a certain cone of directions. An opening angle for this cone is usually estimated by methods such as the overall ratio of Seyfert 1s to Seyfert2s, the latter assumed to be obscured versions of the former. Here we shall show, as has often been suspected, that the opening angle of the cone depends on the luminosity of the central source, with higher luminosities corresponding to larger opening angles. This conclusion depends only on the assumption that the width of the broad emission lines at a given luminosity is a measure of inclination angle, an assumption that is supported by observation in radio-loud systems. On the other hand we show that the scatter in X-ray spectral index is not primarily an effect of viewing angle, in contrast to what might be expected if the scatter on the spectral index versus luminosity relation were a consequence of absorption in the obscuring material. The observed correlation between linewidth and spectral index appears to be a further consequence of the dependence of opening angle on luminosity.Comment: 8 pages, 7 figures, uses mn.sty. Accepted for publication in MNRA

    Determining the cosmological parameters from the linewidths of active galaxies

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    We have previously shown that the linewidth distribution in AGN can be accounted for by an axisymmetric broad emission line region. In this paper we show that the linewidth distribution changes with redshift and that these changes are dependent on H_0 and q_0. We show that relatively small samples of AGN at high redshift with measured linewidth at half maximum can be used to distinguish between values of H_0 and q_0. Furthermore larger low redshift samples can be used to distinguish between luminosity functions and hence different models of quasar evolution.Comment: Accepted for publication in MNRAS. 8 pages LaTeX, uses mn.st

    Estimating fuel channel bore from fuel grab load trace data

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    Detailed measurements of the graphite core fuel channels are made by specialist inspection equipment during planned outages, typically every 18 months to 3 years. The bores of the graphite fuel bricks are obtained during these inspections and are used to provide important information about the health of the core. Additionally, less detailed online monitoring data is obtained much more frequently during refuelling events, called the fuel grab load trace (FGLT), which can be also used to infer the health of the graphite core. This paper describes the process of creating a model which isolates a component of the refuelling data and maps it directly to dimensional measurements of fuel channel bore. The model is created from a combination of the theoretical understanding of the physical interactions of the fuel stringer during refuelling events and several years of refuelling and inspection data to estimate suitable model parameters. Initially the model created was a coarse estimation of FGLT to fuel bore dimension but through refinements a much more accurate model has been created. An application of this model is shown through a case study of a recent outage where estimations were made on refuelling data and were compared to previously unseen inspection data

    Volumetric Absorptive Microsampling (VAMS) for Targeted LC-MS/MS Determination of Tryptophan-Related Biomarkers

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    L-Tryptophan (TRP) metabolites and related biomarkers play crucial roles in physiological functions, and their imbalances are implicated in central nervous system pathologies and neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease, Parkinson's disease, schizophrenia and depression. The measurement of TRP metabolites and related biomarkers possesses great potential to elucidate the disease mechanisms, aid preclinical drug development, highlight potential therapeutic targets and evaluate the outcomes of therapeutic interventions. An effective, straightforward, sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous determination of 24 TRP-related compounds in miniaturised murine whole blood samples. Sampling and sample pretreatment miniaturisation were achieved thanks to the development of a volumetric dried blood microsampling approach. Volumetric absorptive microsampling (VAMS) allows the accurate sampling of microvolumes of blood with advantages including, but not limited to, minimal sampling invasiveness, logistical improvements, method sustainability in terms of solvents and energy consumption, and improvement of animal studies in the framework of the 3Rs (Replacement, Reduction and Refinement) principles on animal welfare. The VAMS-LC-MS/MS method exhibited good selectivity, and correlation coefficient values for the calibration curves of each analyte were >0.9987. The limits of quantitation ranged from 0.1 to 25 ng/mL. The intra- and inter-day precisions in terms of RSD were <9.6%. All analytes were stable in whole blood VAMS samples stored at room temperature for at least 30 days with analyte losses < 14%. The developed method was successfully applied to the analysis of biological samples from mice, leading to the unambiguous determination of all the considered target analytes. This method can therefore be applied to analyse TRP metabolites and related biomarkers levels to monitor disease states, perform mechanistic studies and investigate the outcomes of therapeutic interventions

    Effect of physiological overload on pregnancy in women with mitral regurgitation

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    OBJECTIVES: to evaluate the structural and functional heart abnormalities in women with mitral regurgitation during pregnancy.INTRODUCTION: Women with mitral regurgitation progress well during pregnancy. However, the effects on the heart of the association between pregnancy and mitral regurgitation are not well established.METHODS: This is a case-control, longitudinal prospective study. Echocardiograms were performed in 18 women with mitral regurgitation at the 12th and 36th week of pregnancy and on the 45th day of the puerperium. Twelve age-matched healthy and pregnant women were included as controls and underwent the same evaluation as the study group.RESULTS: Compared with controls, women with mitral regurgitation presented increased left cardiac chambers in all evaluations. Increasing left atrium during pregnancy occurred only in the mitral regurgitation group. At the end of the puerperium, women with mitral regurgitation showed persistent enlargement of the left atrium compared with the beginning of pregnancy (5.0 +/- 1.1 cm vs 4.6 +/- 0.9 cm; p < 0.05). Reduced left ventricular relative wall thickness (0.13 +/- 0.02 vs 0.16 +/- 0.02; p < 0.05) and an increased peak of afterload (278 +/- 55 g/cm(2) vs 207 +/- 28 g/cm(2); p < 0.05) was still observed on the 45th day after delivery in the mitral regurgitation group compared with controls.CONCLUSIONS: Pregnancy causes unfavorable structural alterations in women with mitral regurgitation that are associated with an aggravation of the hemodynamic overload

    A Pair Polarimeter for Linearly Polarized High Energy Photons

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    A high quality beam of linearly polarized photons of several GeV will become available with the coherent bremsstrahlung technique at JLab. We have developed a polarimeter which requires about two meters of the beam line, has an analyzing power of 20% and an efficiency of 0.02%. The layout and first results of a polarimeter test on the laser back-scattering photon beam at SPring-8/LEPS are presented

    Operation of Faddeev-Kernel in Configuration Space

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    We present a practical method to solve Faddeev three-body equations at energies above three-body breakup threshold as integral equations in coordinate space. This is an extension of previously used method for bound states and scattering states below three-body breakup threshold energy. We show that breakup components in three-body reactions produce long-range effects on Faddeev integral kernels in coordinate space, and propose numerical procedures to treat these effects. Using these techniques, we solve Faddeev equations for neutron-deuteron scattering to compare with benchmark solutions.Comment: 20 pages, 8 figures, to be published in Few-Body System

    Ethics, space, and somatic sensibilities: comparing relationships between scientific researchers and their human and animal experimental subjects

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    Drawing on geographies of affect and nature-society relations, we propose a radical rethinking of how scientists, social scientists, and regulatory agencies conceptualise human and animal participants in scientif ic research. The scientific rationale for using animal bodies to simulate what could be done in human bodies emphasises shared somatic capacities that generate comparable responses to clinical interventions. At the same time, regulatory guidelines and care practices stress the differences between human and animal subjects. In this paper we consider the implications of this differentiation between human and animal bodies in ethical and welfare protocols and practices. We show how the bioethical debates around the use of human subjects tend to focus on issues of consent and language, while recent work in animal welfare reflects an increasing focus on the affectual dimensions of ethical practice. We argue that this attention to the more-than-representational dimensions of ethics and welfare might be equally important for human subjects. We assert that paying attention to these somatic sensibilities can offer insights into how experimental environments can both facilitate and restrict the development of more care-full and response-able relations between researchers and their experimental subjects. <br/
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