966 research outputs found
Measuring Black Hole Spin using X-ray Reflection Spectroscopy
I review the current status of X-ray reflection (a.k.a. broad iron line)
based black hole spin measurements. This is a powerful technique that allows us
to measure robust black hole spins across the mass range, from the stellar-mass
black holes in X-ray binaries to the supermassive black holes in active
galactic nuclei. After describing the basic assumptions of this approach, I lay
out the detailed methodology focusing on "best practices" that have been found
necessary to obtain robust results. Reflecting my own biases, this review is
slanted towards a discussion of supermassive black hole (SMBH) spin in active
galactic nuclei (AGN). Pulling together all of the available XMM-Newton and
Suzaku results from the literature that satisfy objective quality control
criteria, it is clear that a large fraction of SMBHs are rapidly-spinning,
although there are tentative hints of a more slowly spinning population at high
(M>5*10^7Msun) and low (M<2*10^6Msun) mass. I also engage in a brief review of
the spins of stellar-mass black holes in X-ray binaries. In general,
reflection-based and continuum-fitting based spin measures are in agreement,
although there remain two objects (GROJ1655-40 and 4U1543-475) for which that
is not true. I end this review by discussing the exciting frontier of
relativistic reverberation, particularly the discovery of broad iron line
reverberation in XMM-Newton data for the Seyfert galaxies NGC4151, NGC7314 and
MCG-5-23-16. As well as confirming the basic paradigm of relativistic disk
reflection, this detection of reverberation demonstrates that future large-area
X-ray observatories such as LOFT will make tremendous progress in studies of
strong gravity using relativistic reverberation in AGN.Comment: 19 pages. To appear in proceedings of the ISSI-Bern workshop on "The
Physics of Accretion onto Black Holes" (8-12 Oct 2012). Revised version adds
a missing source to Table 1 and Fig.6 (IRAS13224-3809) and corrects the
referencing of the discovery of soft lags in 1H0707-495 (which were in fact
first reported in Fabian et al. 2009
Atenolol versus losartan in children and young adults with Marfan's syndrome
BACKGROUND : Aortic-root dissection is the leading cause of death in Marfan's syndrome. Studies suggest that with regard to slowing aortic-root enlargement, losartan may be more effective than beta-blockers, the current standard therapy in most centers.
METHODS : We conducted a randomized trial comparing losartan with atenolol in children and young adults with Marfan's syndrome. The primary outcome was the rate of aortic-root enlargement, expressed as the change in the maximum aortic-root-diameter z score indexed to body-surface area (hereafter, aortic-root z score) over a 3-year period. Secondary outcomes included the rate of change in the absolute diameter of the aortic root; the rate of change in aortic regurgitation; the time to aortic dissection, aortic-root surgery, or death; somatic growth; and the incidence of adverse events.
RESULTS : From January 2007 through February 2011, a total of 21 clinical centers enrolled 608 participants, 6 months to 25 years of age (mean [+/- SD] age, 11.5 +/- 6.5 years in the atenolol group and 11.0 +/- 6.2 years in the losartan group), who had an aorticroot z score greater than 3.0. The baseline-adjusted rate of change (+/- SE) in the aortic-root z score did not differ significantly between the atenolol group and the losartan group (-0.139 +/- 0.013 and -0.107 +/- 0.013 standard-deviation units per year, respectively; P = 0.08). Both slopes were significantly less than zero, indicating a decrease in the degree of aortic-root dilatation relative to body-surface area with either treatment. The 3-year rates of aortic-root surgery, aortic dissection, death, and a composite of these events did not differ significantly between the two treatment groups.
CONCLUSIONS : Among children and young adults with Marfan's syndrome who were randomly assigned to losartan or atenolol, we found no significant difference in the rate of aorticroot dilatation between the two treatment groups over a 3-year period
COVID-19 unmasked global collaboration protocol:Longitudinal cohort study examining mental health of young children and caregivers during the pandemic
Background: Early empirical data shows that school-aged children, adolescents and adults are experiencing elevated levels of anxiety and depression during the COVID-19 pandemic. Currently, there is very little research on mental health outcomes for young children. Objectives: To describe the formation of a global collaboration entitled, 'COVID-19 Unmasked'. The collaborating researchers aim to (1) describe and compare the COVID-19 related experiences within and across countries; (2) examine mental health outcomes for young children (1 to 5Â years) and caregivers over a 12-month period during the COVID-19 pandemic; (3) explore the trajectories/time course of psychological outcomes of the children and parents over this period and (4) identify the risk and protective factors for different mental health trajectories. Data will be combined from all participating countries into one large open access cross-cultural dataset to facilitate further international collaborations and joint publications. Methods: COVID-19 Unmasked is an online prospective longitudinal cohort study. An international steering committee was formed with the aim of starting a global collaboration. Currently, partnerships have been formed with 9 countries (Australia, Cyprus, Greece, the Netherlands, Poland, Spain, Turkey, the UK, and the United States of America). Research partners have started to start data collection with caregivers of young children aged 1-5Â years old at baseline, 3-months, 6-months, and 12-months. Caregivers are invited to complete an online survey about COVID-19 related exposure and experiences, child's wellbeing, their own mental health, and parenting. Data analysis: Primary study outcomes will be child mental health as assessed by scales from the Patient-Reported Outcomes Measurement Information System - Early Childhood (PROMIS-EC) and caregiver mental health as assessed by the Depression Anxiety Stress Scale (DASS-21). The trajectories/time course of mental health difficulties and the impact of risk and protective factors will be analysed using hierarchical linear models, accounting for nested effects (e.g. country) and repeated measures
Sporting embodiment: sports studies and the (continuing) promise of phenomenology
Whilst in recent years sports studies have addressed the calls âto bring the body back inâ to theorisations of sport and physical activity, the âpromise of phenomenologyâ remains largely under-realised with regard to sporting embodiment. Relatively few accounts are grounded in the âfleshâ of the lived sporting body, and phenomenology offers a powerful framework for such analysis. A wide-ranging, multi-stranded, and interpretatively contested perspective, phenomenology in general has been taken up and utilised in very different ways within different disciplinary fields. The purpose of this article is to consider some selected phenomenological threads, key qualities of the phenomenological method, and the potential for existentialist phenomenology in particular to contribute fresh perspectives to the sociological study of embodiment in sport and exercise. It offers one way to convey the âessencesâ, corporeal immediacy and textured sensuosity of the lived sporting body. The use of Interpretative Phenomenological Analysis (IPA) is also critically addressed.
Key words: phenomenology; existentialist phenomenology; interpretative phenomenological analysis (IPA); sporting embodiment; the lived-body; Merleau-Pont
Avaliação da incidĂȘncia de antracnose, do desempenho e estado nutricional de variedades de mangueira, para cultivo orgĂąnico, na regiĂŁo centro-norte do Estado de SĂŁo Paulo.
A mudança do perfil do consumidor, aliada aos riscos da contaminação por agrotĂłxicos, tem levado Ă busca de alternativas ecologicamente apropriadas para produção de frutas. Os objetivos deste trabalho foram avaliar a incidĂȘncia de antracnose, o desempenho e estado nutricional de variedades de mangueira conduzidas organicamente na regiĂŁo de Pindorama-SP. Foram utilizadas 17 variedades de mangueira. O experimento foi instalado em delineamento experimental em blocos completos ao acaso, com 17 tratamentos (variedades) e seis repetiçÔes. Foi avaliada a severidade de antracnose nas folhas, atravĂ©s de uma escala diagramĂĄtica, atribuindo-se notas aos sintomas. Foram avaliados o crescimento e o desenvolvimento (altura da planta, perĂmetro do tronco e da copa) e o estado nutricional, mediante anĂĄlise foliar, das diferentes variedades utilizadas. AtravĂ©s dos resultados obtidos, podem-se considerar como muito suscetĂveis Ă antracnose as variedades Bourbon, Rocha e Rosa; e resistentes, as variedades IAC 111, Alfa, Beta e Parvin; as variedades de manga apresentaram o mesmo padrĂŁo de crescimento; as maiores alturas da planta corresponderam aos maiores diĂąmetros do tronco e da copa; a variedade Parvin apresentou o melhor desempenho dentre as variedades estudadas, com relação Ă resistĂȘncia Ă antracnose, altura e diĂąmetro do caule e da copa, podendo ser recomendada ao cultivo orgĂąnico. As variedades Omega e Alfa tambĂ©m apresentaram bom crescimento, podendo ser indicadas para esse cultivo, pelo menos nessa fase inicial; as variedades Surpresa e Rosa nĂŁo apresentaram bom desempenho, no campo, em relação Ă s demais, nĂŁo devendo ser recomendadas para o cultivo orgĂąnico, principalmente a variedade Rosa, bastante suscetĂvel Ă antracnose. As concentraçÔes de N, P e K foram elevadas na fase vegetativa das plantas, comparadas Ă baixa concentração de Ca; houve carĂȘncia de Boro em todas as variedades estudadas. A manga Rosa, provavelmente, sofreu toxicidade ao excesso de manganĂȘs, ocasionando diminuição em seu desenvolvimento
Magnetic Interactions and Transport in (Ga,Cr)As
The magnetic, transport, and structural properties of (Ga,Cr)As are reported.
Zincblende GaCrAs was grown by low-temperature molecular beam
epitaxy (MBE). At low concentrations, x0.1, the materials exhibit unusual
magnetic properties associated with the random magnetism of the alloy. At low
temperatures the magnetization M(B) increases rapidly with increasing field due
to the alignment of ferromagnetic units (polarons or clusters) having large
dipole moments of order 10-10. A standard model of
superparamagnetism is inadequate for describing both the field and temperature
dependence of the magnetization M(B,T). In order to explain M(B) at low
temperatures we employ a distributed magnetic moment (DMM) model in which
polarons or clusters of ions have a distribution of moments. It is also found
that the magnetic susceptibility increases for decreasing temperature but
saturates below T=4 K. The inverse susceptibility follows a linear-T
Curie-Weiss law and extrapolates to a magnetic transition temperature
=10 K. In magnetotransport measurements, a room temperature resistivity
of =0.1 cm and a hole concentration of cm
are found, indicating that Cr can also act as a acceptor similar to Mn. The
resistivity increases rapidly for decreasing temperature below room
temperature, and becomes strongly insulating at low temperatures. The
conductivity follows exp[-(T/T)] over a large range of
conductivity, possible evidence of tunneling between polarons or clusters.Comment: To appear in PRB 15 Mar 200
Characterization of Generalized Young Measures Generated by Symmetric Gradients
This work establishes a characterization theorem for (generalized) Young measures generated by symmetric derivatives of functions of bounded deformation (BD) in the spirit of the classical Kinderlehrer\ue2\u80\u93Pedregal theorem. Our result places such Young measures in duality with symmetric-quasiconvex functions with linear growth. The \ue2\u80\u9clocal\ue2\u80\u9d proof strategy combines blow-up arguments with the singular structure theorem in BD (the analogue of Alberti\ue2\u80\u99s rank-one theorem in BV), which was recently proved by the authors. As an application of our characterization theorem we show how an atomic part in a BD-Young measure can be split off in generating sequences
Extragalactic jets on subpc and large scales
Jets can be probed in their innermost regions (d~0.1 pc) through the study of
the relativistically-boosted emission of blazars. On the other extreme of
spatial scales, the study of structure and dynamics of extragalactic
relativistic jets received renewed impulse after the discovery, made by
Chandra, of bright X-ray emission from regions at distances larger than
hundreds of kpc from the central engine. At both scales it is thus possible to
infer some of the basic parameters of the flow (speed, density, magnetic field
intensity, power). After a brief review of the available observational
evidence, I discuss how the comparison between the physical quantities
independently derived at the two scales can be used to shed light on the global
dynamics of the jet, from the innermost regions to the hundreds of kpc scale.Comment: Proceedings of the 5th Stromlo Symposium: Disks, Winds, and Jets -
from Planets to Quasars. Accepted, to be published in Astrophysics & Space
Scienc
Metal enrichment processes
There are many processes that can transport gas from the galaxies to their
environment and enrich the environment in this way with metals. These metal
enrichment processes have a large influence on the evolution of both the
galaxies and their environment. Various processes can contribute to the gas
transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy
interactions and others. We review their observational evidence, corresponding
simulations, their efficiencies, and their time scales as far as they are known
to date. It seems that all processes can contribute to the enrichment. There is
not a single process that always dominates the enrichment, because the
efficiencies of the processes vary strongly with galaxy and environmental
properties.Comment: 18 pages, 8 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 17; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
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