5,833 research outputs found

    Evolution of spin in the intermediate polar CC sculptoris

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    We report on spin variations in the intermediate polar and cataclysmic variable CC Scl, as seen by the Transiting Exoplanet Survey Satellite (TESS). By studying both the spin period and its harmonic, we find that the spin has varied since it was first observed in 2011. We find the latest spin value for the source to be 389.473(6) s, equivalent to 0.00450779(7) d, 0.02 s shorter than the first value measured. A linear fit to these and intermediate data give a rate of change of spin (Ṗ) ∼ −4.26(2.66)× 10−11 and a characteristic time-scale τ ∼ 2.90 × 105 yr, in line with other known intermediate polars with varying spin. The spin profile of this source also matches theoretical spin profiles of high-inclination intermediate polars, and furthermore, appears to have changed in shape over a period of three years. Such ‘spin-up’ in an intermediate polar is considered to be from mass accretion on to the white dwarf (the primary), and we note the presence of dwarf nova eruptions in this source as being a possible catalyst of the variations

    A Broadband Study of the Emission from the Composite Supernova Remnant MSH 11-62

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    MSH 11-62 (G291.1-0.9) is a composite supernova remnant for which radio and X-ray observations have identified the remnant shell as well as its central pulsar wind nebula. The observations suggest a relatively young system expanding into a low density region. Here we present a study of MSH 11-62 using observations with the Chandra, XMM-Newton, and Fermi observatories, along with radio observations from the Australia Telescope Compact Array (ATCA). We identify a compact X-ray source that appears to be the putative pulsar that powers the nebula, and show that the X-ray spectrum of the nebula bears the signature of synchrotron losses as particles diffuse into the outer nebula. Using data from the Fermi LAT, we identify gamma-ray emission originating from MSH 11-62. With density constraints from the new X-ray measurements of the remnant, we model the evolution of the composite system in order to constrain the properties of the underlying pulsar and the origin of the gamma-ray emission.Comment: 12 Pages, 12 figures. Accepted for publication in the Astrophysical Journa

    Entanglement and correlation functions following a local quench: a conformal field theory approach

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    We show that the dynamics resulting from preparing a one-dimensional quantum system in the ground state of two decoupled parts, then joined together and left to evolve unitarily with a translational invariant Hamiltonian (a local quench), can be described by means of quantum field theory. In the case when the corresponding theory is conformal, we study the evolution of the entanglement entropy for different bi-partitions of the line. We also consider the behavior of one- and two-point correlation functions. All our findings may be explained in terms of a picture, that we believe to be valid more generally, whereby quasiparticles emitted from the joining point at the initial time propagate semiclassically through the system.Comment: 19 pages, 4 figures, v2 typos corrected and refs adde

    Recommended age groups and frequency of mammography screening : a systematic review

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    Esta revisão teve por objetivo avaliar a força de evidência do atual indicador de desempenho português relativo ao rastreio do Câncer da Mama através da mamografia, de modo a determinar o grupo etário e a periodicidade recomendadas. Foram pesquisados artigos nas principais bases de dados internacionais de literatura médica. Incluímos artigos publicados entre Janeiro de 2006 e Janeiro de 2012 que correspondiam aos objetivos da revisão. Foi utilizada a taxonomia SORT para a classificação dos resultados. Dos 253 artigos encontrados foram selecionados cinco que cumpriam os critérios de inclusão. Estes incluem três revisões sistemáticas (RS), uma meta-análise (MA) e uma norma de orientação clínica (NOC) baseada numa RS. Os artigos selecionados avaliaram a redução da mortalidade por câncer da mama através do rastreio com mamografia. A realização do rastreio mamográfico entre os 50 e os 69 anos é recomendado em todos os artigos que avaliam esta faixa etária. A NOC recomenda o rastreio bienal. Em suma, a mamografia deverá ser realizada entre os 50 e os 69 anos com uma periodicidade bienal. Estes resultados vão ao encontro do atual indicador de desempenho do rastreio do câncer da mama em Portugal.The scope of this review was to assess the strength of evidence for the current Portuguese performance indicator on breast cancer screening with mammography in order to determine the recommended age group and periodicity for screening. A search for articles was conducted in the main international databases of medical literature. Articles published between January 2006 and January 2012 addressing the objectives of this review were included. The SORT taxonomy was used to classify the results. Of the 253 articles, five articles met the inclusion criteria and were selected for review. These included three systematic reviews, one meta-analysis and one clinical guideline based on a systematic review. A reduction in breast cancer mortality with mamography screening was the outcome in all articles selected. Mammography screening between 50 and 69 years was recommended in all articles that assess this age group. The clinical guidelines recommended screening every two years. In conclusion, the current literature recommends mammography for women every two years between the ages of 50 and 69 years. This is consistent with the current performance indicator for breast cancer screening in Portugal

    The unexpected resurgence of Weyl geometry in late 20-th century physics

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    Weyl's original scale geometry of 1918 ("purely infinitesimal geometry") was withdrawn by its author from physical theorizing in the early 1920s. It had a comeback in the last third of the 20th century in different contexts: scalar tensor theories of gravity, foundations of gravity, foundations of quantum mechanics, elementary particle physics, and cosmology. It seems that Weyl geometry continues to offer an open research potential for the foundations of physics even after the turn to the new millennium.Comment: Completely rewritten conference paper 'Beyond Einstein', Mainz Sep 2008. Preprint ELHC (Epistemology of the LHC) 2017-02, 92 pages, 1 figur

    Isolation and fine mapping of Rps6: An intermediate host resistance gene in barley to wheat stripe rust

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    A plant may be considered a nonhost of a pathogen if all known genotypes of a plant species are resistant to all known isolates of a pathogen species. However, if a small number of genotypes are susceptible to some known isolates of a pathogen species this plant maybe considered an intermediate host. Barley (Hordeum vulgare) is an intermediate host for Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat stripe rust. We wanted to understand the genetic architecture underlying resistance to Pst and to determine whether any overlap exists with resistance to the host pathogen, Puccinia striiformis f. sp. hordei (Psh). We mapped Pst resistance to chromosome 7H and show that host and intermediate host resistance is genetically uncoupled. Therefore, we designate this resistance locus Rps6. We used phenotypic and genotypic selection on F2:3 families to isolate Rps6 and fine mapped the locus to a 0.1 cM region. Anchoring of the Rps6 locus to the barley physical map placed the region on two adjacent fingerprinted contigs. Efforts are now underway to sequence the minimal tiling path and to delimit the physical region harbouring Rps6. This will facilitate additional marker development and permit identification of candidate genes in the region

    A standardized framework for accurate, high-throughput genotyping of recombinant and non-recombinant viral sequences

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    Human immunodeficiency virus type-1 (HIV-1), hepatitis B and C and other rapidly evolving viruses are characterized by extremely high levels of genetic diversity. To facilitate diagnosis and the development of prevention and treatment strategies that efficiently target the diversity of these viruses, and other pathogens such as human T-lymphotropic virus type-1 (HTLV-1), human herpes virus type-8 (HHV8) and human papillomavirus (HPV), we developed a rapid high-throughput-genotyping system. The method involves the alignment of a query sequence with a carefully selected set of pre-defined reference strains, followed by phylogenetic analysis of multiple overlapping segments of the alignment using a sliding window. Each segment of the query sequence is assigned the genotype and sub-genotype of the reference strain with the highest bootstrap (>70%) and bootscanning (>90%) scores. Results from all windows are combined and displayed graphically using color-coded genotypes. The new Virus-Genotyping Tools provide accurate classification of recombinant and non-recombinant viruses and are currently being assessed for their diagnostic utility. They have incorporated into several HIV drug resistance algorithms including the Stanford (http://hivdb.stanford.edu) and two European databases (http://www.umcutrecht.nl/subsite/spread-programme/ and http://www.hivrdb.org.uk/) and have been successfully used to genotype a large number of sequences in these and other databases. The tools are a PHP/JAVA web application and are freely accessible on a number of servers including

    Bio-Based Fire Retardant for Coco Lumber using Aloe barbadensis miller (Aloe Vera), Mangifera indica (Mango), or Persea americana (Avocado) and Boron Additives

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    Accidental fires are prevalent in low-income communities and one of the solutions to decrease fire risk is to apply fire retardants on combustible materials. While extensive research was available in creating fire retardants with inorganic chemicals, further studies are needed for bio-based fire retardants. The development of bio-based fire retardants involves testing organic matter for the presence of fire-retardant compounds such as nitrogen, phosphorus, and polyphenols. This study sought to determine the effectiveness of the peels of Aloe barbadensis miller (aloe vera), Mangifera indica (mangoes), and Persea americana (avocados) in creating bio-based fire retardants for coco lumber. Maceration was used to get the fruit and plant extracts. Boric acid and borax were also added as additives to boost fire retarding properties. The burning behavior of the lumber was observed in a modified horizontal flammability test and a modified flame spread test and measured in terms of mass loss, smoke density, char yield, and charring rate. The results revealed that among the fruits, the mango-based fire-retardant inhibited mass loss the most (M = 0.006, SD = 0.003), while the avocado-based fire-retardant inhibited smoke the most (M = 0.036, SD = 0.016). No significant difference was found among the groups as determined by One-way ANOVA and MANOVA (p \u3e 0.05). An indirect relationship was found between smoke density and char yield, which may be examined to improve the smoke suppressing ability of commercial fire retardants. Future studies may also refine the plant extracts and use standard flammability tests

    Set points, settling points and some alternative models: theoretical options to understand how genes and environments combine to regulate body adiposity

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    The close correspondence between energy intake and expenditure over prolonged time periods, coupled with an apparent protection of the level of body adiposity in the face of perturbations of energy balance, has led to the idea that body fatness is regulated via mechanisms that control intake and energy expenditure. Two models have dominated the discussion of how this regulation might take place. The set point model is rooted in physiology, genetics and molecular biology, and suggests that there is an active feedback mechanism linking adipose tissue (stored energy) to intake and expenditure via a set point, presumably encoded in the brain. This model is consistent with many of the biological aspects of energy balance, but struggles to explain the many significant environmental and social influences on obesity, food intake and physical activity. More importantly, the set point model does not effectively explain the ‘obesity epidemic' - the large increase in body weight and adiposity of a large proportion of individuals in many countries since the 1980s. An alternative model, called the settling point model, is based on the idea that there is passive feedback between the size of the body stores and aspects of expenditure. This model accommodates many of the social and environmental characteristics of energy balance, but struggles to explain some of the biological and genetic aspects. The shortcomings of these two models reflect their failure to address the gene-by-environment interactions that dominate the regulation of body weight. We discuss two additional models - the general intake model and the dual intervention point model - that address this issue and might offer better ways to understand how body fatness is controlled
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