20,257 research outputs found
A unique X-ray unabsorbed Seyfert 2 galaxy IRAS F01475-0740
X-ray unabsorbed Seyfert 2 galaxies appear to have X-ray absorption column
densities that are too low (NH < 10^22 cm-2) to explain the absence of broad
emission lines in their optical spectra, challenging the standard AGN
unification model. In this paper we report Suzaku exposure on the X-ray
unabsorbed Seyfert 2 galaxy IRAS F01475-0740, in which a hidden broad line
region was detected through spectropolarimetric observation. The X-ray data
show rapid and significant variations on time scales down to 5 ks, indicating
that we are viewing its central engine directly. A newly obtained optical
spectrum and previous optical/X-ray data suggest that state transition is
unlikely in this source. These make IRAS F01475-0740 a very peculiar X-ray
unabsorbed Seyfert 2 galaxy which can only be explained by absorption from
materials with abnormally high dust-to-gas ratio (by a factor of > 4 larger
than Galactic). This is in contrast to most AGNs, which typically show
dust-to-gas ratios 3 - 100 times lower than the Galactic.Comment: 13 pages, 3 figures, 1 table, accepted to the Astrophysical Journal
Letter
Resource savings by urban mining : the case of desktop and laptop computers in Belgium
Waste electrical and electronic equipment (WEEE) has become increasingly important over the last years. Additionally, the European Union recognizes the growing importance of raw materials, and the crucial role of recycling. In this study the performance of WEEE recycling was assessed for the case of desktop and laptop computers in Belgium in 2013. The analysis was performed in four steps. First, the recycling chain is analyzed through material flow analysis (MFA) at the level of specific materials. Second, an indicator is calculated, which quantifies the effectively recycled weight ratios of the specific materials. Third, a second indicator expresses the recycling efficiency of so-called critical raw materials. Finally, the natural resource consumption of the recycling scheme in a life cycle perspective is calculated using the Cumulative Exergy Extraction from the Natural Environment (CEENE) method, and is benchmarked with a landfill scenario. Overall, the results show that base metals such as ferrous metals, aluminium and copper are recycled to a large extent, but that for precious metals improvements still can be made. The input of criticality (arising from the incoming mass, as well as the individual criticality value of the assessed material) mainly comes from base metals, resulting in a high recovery performance of raw materials criticality. Finally, the natural resource consumption of the recycling scenario is much smaller than in case of landfilling the WEEE: 80 and 87% less resource consumption is achieved for desktops and laptops respectively, hence saving significant primary raw materials
HIV with contact-tracing: a case study in Approximate Bayesian Computation
Missing data is a recurrent issue in epidemiology where the infection process
may be partially observed. Approximate Bayesian Computation, an alternative to
data imputation methods such as Markov Chain Monte Carlo integration, is
proposed for making inference in epidemiological models. It is a
likelihood-free method that relies exclusively on numerical simulations. ABC
consists in computing a distance between simulated and observed summary
statistics and weighting the simulations according to this distance. We propose
an original extension of ABC to path-valued summary statistics, corresponding
to the cumulated number of detections as a function of time. For a standard
compartmental model with Suceptible, Infectious and Recovered individuals
(SIR), we show that the posterior distributions obtained with ABC and MCMC are
similar. In a refined SIR model well-suited to the HIV contact-tracing data in
Cuba, we perform a comparison between ABC with full and binned detection times.
For the Cuban data, we evaluate the efficiency of the detection system and
predict the evolution of the HIV-AIDS disease. In particular, the percentage of
undetected infectious individuals is found to be of the order of 40%
Interplay of plasma-induced and fast thermal nonlinearities in a GaAs-based photonic crystal nanocavity
We investigate the nonlinear response of GaAs-based photonic crystal cavities
at time scales which are much faster than the typical thermal relaxation rate
in photonic devices. We demonstrate a strong interplay between thermal and
carrier induced nonlinear effects. We have introduced a dynamical model
entailing two thermal relaxation constants which is in very good agreement with
experiments. These results will be very important for Photonic Crystal-based
nonlinear devices intended to deal with practical high repetition rate optical
signals.Comment: 10 pages, 8 figures, Phys Rev A (accepted
Large-scale albuminuria screen for nephropathy models in chemically induced mouse mutants
Background/Aim: Phenotype-driven screening of a great pool of randomly mutant mice and subsequent selection of animals showing symptoms equivalent to human kidney diseases may result in the generation of novel suitable models for the study of the pathomechanisms and the identification of genes involved in kidney dysfunction. Methods: We carried out a large-scale analysis of ethylnitrosourea (ENU)-induced mouse mutants for albuminuria by using qualitative SDS-polyacrylamide gel electrophoresis. Results: The primary albuminuria screen preceded the comprehensive phenotypic mutation analysis in a part of the mice of the Munich ENU project to avoid loss of mutant animals as a consequence of prolonged suffering from severe nephropathy. The primary screen detected six confirmed phenotypic variants in 2,011 G1 animals screened for dominant mutations and no variant in 48 G3 pedigrees screened for recessive mutations. Further breeding experiments resulted in two lines showing a low phenotypic penetrance of albuminuria. The secondary albuminuria screen was carried out in mutant lines which were established in the Munich ENU project without preceding primary albuminuria analysis. Two lines showing increased plasma urea levels were chosen to clarify if severe kidney lesions are involved in the abnormal phenotype. This analysis revealed severe albuminuria in mice which are affected by a recessive mutation leading to increased plasma urea and cholesterol levels. Conclusion: Thus, the phenotypic selection of ENU-induced mutants according to the parameter proteinuria in principle demonstrates the feasibility to identify nephropathy phenotypes in ENU-mutagenized mice. Copyright (C) 2005 S. Karger AG, Basel
Five-dimensional N=4, SU(2) X U(1) Gauged Supergravity from Type IIB
We construct the complete and explicit non-linear Kaluza-Klein ansatz for
deriving the bosonic sector of N=4 SU(2)\times U(1) gauged five-dimensional
supergravity from the reduction of type IIB supergravity on S^5. This provides
the first complete example of such an S^5 reduction that includes non-abelian
gauge fields, and it allows any bosonic solution of the five-dimensional N=4
gauged theory to be embedded in D=10.Comment: latex, 12 page
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