928 research outputs found
Roche tomography of cataclysmic variables - V. A high-latitude star-spot on RU Pegasi
We present Roche tomograms of the secondary star in the dwarf nova system RU
Pegasi derived from blue and red arm ISIS data taken on the 4.2-m William
Herschel Telescope. We have applied the entropy landscape technique to
determine the system parameters and obtained component masses of M1 = 1.06
Msun, M2 = 0.96 Msun, an orbital inclination angle of i = 43 degrees, and an
optimal systemic velocity of gamma = 7 km/s. These are in good agreement with
previously published values. Our Roche tomograms of the secondary star show
prominent irradiation of the inner Lagrangian point due to illumination by the
disc and/or bright spot, which may have been enhanced as RU Peg was in outburst
at the time of our observations.We find that this irradiation pattern is
axi-symmetric and confined to regions of the star which have a direct view of
the accretion regions. This is in contrast to previous attempts to map RU Peg
which suggested that the irradiation pattern was non-symmetric and extended
beyond the terminator. We also detect additional inhomogeneities in the surface
distribution of stellar atomic absorption that we ascribe to the presence of a
large star-spot. This spot is centred at a latitude of about 82 degrees and
covers approximately 4 per cent of the total surface area of the secondary. In
keeping with the high latitude spots mapped on the cataclysmic variables AE Aqr
and BV Cen, the spot on RU Peg also appears slightly shifted towards the
trailing hemisphere of the star. Finally, we speculate that early mapping
attempts which indicated non-symmetric irradiation patterns which extended
beyond the terminator of CV donors could possibly be explained by a
superposition of symmetric heating and a large spot.Comment: 14 pages, 10 figures, 3 tables Accepted for publication in Monthly
Notices of the Royal Astronomical Societ
Multivariate sensitivity analysis for a large-scale climate impact and adaptation model
We develop a new efficient methodology for Bayesian global sensitivity analysis for large-scale multivariate data. The focus is on computationally demanding models with correlated variables. A multivariate Gaussian process is used as a surrogate model to replace the expensive computer model. To improve the computational efficiency and performance of the model, compactly supported correlation functions are used. The goal is to generate sparse matrices, which give crucial advantages when dealing with large datasets, where we use cross-validation to determine the optimal degree of sparsity. This method was combined with a robust adaptive Metropolis algorithm coupled with a parallel implementation to speed up the convergence to the target distribution. The method was applied to a multivariate dataset from the IMPRESSIONS Integrated Assessment Platform (IAP2), an extension of the CLIMSAVE IAP, which has been widely applied in climate change impact, adaptation and vulnerability assessments. Our empirical results on synthetic and IAP2 data show that the proposed methods are efficient and accurate for global sensitivity analysis of complex models
The isomorphism problem for some universal operator algebras
This paper addresses the isomorphism problem for the universal
(nonself-adjoint) operator algebras generated by a row contraction subject to
homogeneous polynomial relations. We find that two such algebras are
isometrically isomorphic if and only if the defining polynomial relations are
the same up to a unitary change of variables, and that this happens if and only
if the associated subproduct systems are isomorphic. The proof makes use of the
complex analytic structure of the character space, together with some recent
results on subproduct systems. Restricting attention to commutative operator
algebras defined by radical relations yields strong resemblances with classical
algebraic geometry. These commutative operator algebras turn out to be algebras
of analytic functions on algebraic varieties. We prove a projective
Nullstellensatz connecting closed ideals and their zero sets. Under some
technical assumptions, we find that two such algebras are isomorphic as
algebras if and only if they are similar, and we obtain a clear geometrical
picture of when this happens. This result is obtained with tools from algebraic
geometry, reproducing kernel Hilbert spaces, and some new complex-geometric
rigidity results of independent interest. The C*-envelopes of these algebras
are also determined. The Banach-algebraic and the algebraic classification
results are shown to hold for the weak-operator closures of these algebras as
well.Comment: 46 pages. Final version, to appear in Advances in Mathematic
Published findings from the spouse assault replication program: A critical review
Published reports from seven jointly developed experiments have addressed whether or not arrest is an effective deterrent to misdemeanor spouse assault. Findings supporting a deterrent effect, no effect, and an escalation effect have been reported by the original authors and in interpretations of the published findings by other authors. This review found many methodologically defensible approaches used in these reports but not one of these approaches was used consistently in all published reports. Tables reporting the raw data on the prevalence and incidence of repeat incidents are presented to provide a more consistent comparison across all seven experiments. This review concludes that the available information is incomplete and inadequate for a definitive statement about the results of these experiments. Researchers and policy makers are urged to use caution in interpreting the findings available to date.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45108/1/10940_2005_Article_BF02221298.pd
Somatic mutations affect key pathways in lung adenocarcinoma
Determining the genetic basis of cancer requires comprehensive analyses of large collections of histopathologically well- classified primary tumours. Here we report the results of a collaborative study to discover somatic mutations in 188 human lung adenocarcinomas. DNA sequencing of 623 genes with known or potential relationships to cancer revealed more than 1,000 somatic mutations across the samples. Our analysis identified 26 genes that are mutated at significantly high frequencies and thus are probably involved in carcinogenesis. The frequently mutated genes include tyrosine kinases, among them the EGFR homologue ERBB4; multiple ephrin receptor genes, notably EPHA3; vascular endothelial growth factor receptor KDR; and NTRK genes. These data provide evidence of somatic mutations in primary lung adenocarcinoma for several tumour suppressor genes involved in other cancers - including NF1, APC, RB1 and ATM - and for sequence changes in PTPRD as well as the frequently deleted gene LRP1B. The observed mutational profiles correlate with clinical features, smoking status and DNA repair defects. These results are reinforced by data integration including single nucleotide polymorphism array and gene expression array. Our findings shed further light on several important signalling pathways involved in lung adenocarcinoma, and suggest new molecular targets for treatment.National Human Genome Research InstituteWe thank A. Lash, M.F. Zakowski, M.G. Kris and V. Rusch for intellectual contributions, and many members of the Baylor Human Genome Sequencing Center, the Broad Institute of Harvard and MIT, and the Genome Center at Washington University for support. This work was funded by grants from the National Human Genome Research Institute to E.S.L., R.A.G. and R.K.W.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62885/1/nature07423.pd
Integrated genomic characterization of oesophageal carcinoma
Oesophageal cancers are prominent worldwide; however, there are few targeted therapies and survival rates for these cancers remain dismal. Here we performed a comprehensive molecular analysis of 164 carcinomas of the oesophagus derived from Western and Eastern populations. Beyond known histopathological and epidemiologic distinctions, molecular features differentiated oesophageal squamous cell carcinomas from oesophageal adenocarcinomas. Oesophageal squamous cell carcinomas resembled squamous carcinomas of other organs more than they did oesophageal adenocarcinomas. Our analyses identified three molecular subclasses of oesophageal squamous cell carcinomas, but none showed evidence for an aetiological role of human papillomavirus. Squamous cell carcinomas showed frequent genomic amplifications of CCND1 and SOX2 and/or TP63, whereas ERBB2, VEGFA and GATA4 and GATA6 were more commonly amplified in adenocarcinomas. Oesophageal adenocarcinomas strongly resembled the chromosomally unstable variant of gastric adenocarcinoma, suggesting that these cancers could be considered a single disease entity. However, some molecular features, including DNA hypermethylation, occurred disproportionally in oesophageal adenocarcinomas. These data provide a framework to facilitate more rational categorization of these tumours and a foundation for new therapies
Study of ordered hadron chains with the ATLAS detector
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Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector
A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements
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