2,994 research outputs found
Preconditioned Bi-Conjugate Gradient Method for Radiative Transfer in Spherical Media
A robust numerical method called the Preconditioned Bi-Conjugate Gradient
(Pre-BiCG)method is proposed for the solution of radiative transfer equation in
spherical geometry.A variant of this method called Stabilized Preconditioned
Bi-Conjugate Gradient (Pre-BiCG-STAB) is also presented. These are iterative
methods based on the construction of a set of bi-orthogonal vectors. The
application of Pre-BiCG method in some benchmark tests show that the method is
quite versatile, and can handle hard problems that may arise in astrophysical
radiative transfer theory.Comment: 19 pages, 12 figure
NLTE analysis of spectra: OBA stars
Methods of calculation of NLTE model atmosphere are discussed. The NLTE trace
element procedure is compared with the full NLTE model atmosphere calculation.
Differences between LTE and NLTE atmosphere modeling are evaluated. The ways of
model atom construction are discussed. Finally, modelling of expanding
atmospheres of hot stars with winds is briefly reviewed.Comment: in Determination of Atmospheric Parameters of B-, A-, F- and G-Type
Stars, E. Niemczura et al. eds., Springer, in pres
Framework synthesis to inform the ideation and design of a paper-based health information system (PHISICC)
BACKGROUND: Health information systems (HIS) are meant to support decision-making at all levels of the system, including frontline health workers. In field studies in Cote d'Ivoire, Mozambique and Nigeria, we observed health workers' interactions with the HIS and identified twelve decision-making components of HIS. The objective of this framework synthesis is to portray these components in HIS research, in order to inform the ideation of a paper-based HIS intervention (PHISICC). METHODS: We searched studies in the Cochrane Central Register of Controlled Trials (CENTRAL), Embase, Epistemonikos, Medline, in-Process on the Ovid platform, OpenGrey, PDQ Evidence ("pretty darnd quick" Evidence), the World Health Organization (WHO) Global Health Library and included studies focussing on HIS interventions, data quality, information support tools and data use for decision-making in the context of the governmental health care sector. We assessed the methodological quality of studies using the Critical Appraisal Skills Programme tool. We synthesised the findings based on the decision-making components of HIS and thematic areas. RESULTS: The search identified 6784 studies; 50 were included. Most of the 50 studies had quality concerns. All studies included at least one of the decision-making components: the most prominent were the technical aspects of 'recording' and 'reporting'. Data use for decision-making was much less represented. CONCLUSION: HIS research focuses on the more technical aspects of HIS. Further research on HIS, given the strong push towards HIS digitalisation, should consider putting at the centre the human experience of decision-making and data use, in order to make HIS relevant for quality of care
Olfactory receptor-dependent receptor repression in Drosophila.
In olfactory systems across phyla, most sensory neurons express a single olfactory receptor gene selected from a large genomic repertoire. We describe previously unknown receptor gene-dependent mechanisms that ensure singular expression of receptors encoded by a tandem gene array [Ionotropic receptor 75c (Ir75c), Ir75b, and Ir75a, organized 5' to 3'] in Drosophila melanogaster Transcription from upstream genes in the cluster runs through the coding region of downstream loci and inhibits their expression in cis, most likely via transcriptional interference. Moreover, Ir75c blocks accumulation of other receptor proteins in trans through a protein-dependent, posttranscriptional mechanism. These repression mechanisms operate in endogenous neurons, in conjunction with cell type-specific gene regulatory networks, to ensure unique receptor expression. Our data provide evidence for inter-olfactory receptor regulation in invertebrates and highlight unprecedented, but potentially widespread, mechanisms for ensuring exclusive expression of chemosensory receptors, and other protein families, encoded by tandemly arranged genes
Zoneamento climático da ferrugem do eucalipto para o Estado do Paraná.
Edição do 37º Congresso Paulista de Fitopatologia. CD-ROM. Resumo 140
Polarized Line Formation in Multi-Dimensional Media.III. Hanle Effect with Partial Frequency Redistribution
In the previous two papers, namely, \citet{anuknn11} and \citet{anuetal11} we
solved the polarized radiative transfer (RT) equation in multi-dimensional
(multi-D) geometries, with partial frequency redistribution (PRD) as the
scattering mechanism. We assumed Rayleigh scattering as the only source of
linear polarization () in both these papers. In this paper we extend
these previous works to include the effect of weak oriented magnetic fields
(Hanle effect) on line scattering. We generalize the technique of Stokes vector
decomposition in terms of the irreducible spherical tensors ,
developed in \citet{anuknn11}, to the case of RT with Hanle effect. A fast
iterative method of solution (based on the Stabilized Preconditioned
Bi-Conjugate-Gradient technique), developed in \citet{anuetal11}, is now
generalized to the case of RT in magnetized three-dimensional media. We use the
efficient short-characteristics formal solution method for multi-D media,
generalized appropriately to the present context. The main results of this
paper are the following: (1) A comparison of emergent profiles
formed in one-dimensional (1D) media, with the corresponding emergent,
spatially averaged profiles formed in multi-D media, shows that in the
spatially resolved structures, the assumption of 1D may lead to large errors in
linear polarization, especially in the line wings. (2) The multi-D RT in
semi-infinite non-magnetic media causes a strong spatial variation of the
emergent profiles, which is more pronounced in the line wings. (3)
The presence of a weak magnetic field modifies the spatial variation of the
emergent profiles in the line core, by producing significant
changes in their magnitudes.Comment: 31 pages, 14 figures, Submitted to ApJ, Under revie
Homogeneous nucleation of colloidal melts under the influence of shearing fields
We study the effect of shear flow on homogeneous crystal nucleation, using
Brownian Dynamics simulations in combination with an umbrella sampling like
technique. The symmetry breaking due to shear results in anisotropic radial
distribution functions. The homogeneous shear rate suppresses crystal
nucleation and leads to an increase of the size of the critical nucleus. These
observations can be described by a simple, phenomenological extension of
classical nucleation theory. In addition, we find that nuclei have a
preferential orientation with respect to the direction of shear. On average the
longest dimension of a nucleus is along the vorticity direction, while the
shortest dimension is preferably perpendicular to that and slightly tilted with
respect to the gradient direction.Comment: 10 pages, 8 figures, Submitted to J. Phys.: Condens. Matte
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