979 research outputs found
Towards Novel Nonparametric Statistical Methods and Bioinformatics Tools for Clinical and Translational Sciences
No full textAs the field of functional genetics and genomics is beginning to mature, we become confronted with new challenges. The constant drop in price for sequencing and gene expression profiling as well as the increasing number of genetic and genomic variables that can be measured makes it feasible to address more complex questions. The success with rare diseases caused by single loci or genes has provided us with a proof-of-concept that new therapies can be developed based on functional genomics and genetics. Common diseases, however, typically involve genetic epistasis, genomic pathways, and proteomic pattern. Moreover, to better understand the underlying biologi-cal systems, we often need to integrate information from several of these sources. Thus, as the field of clinical research moves toward complex diseases, the demand for modern data base systems and advanced statistical methods increases. The traditional statistical methods implemented in most of the bioinformatics tools currently used in the novel field of genetics and functional genomics are based on the linear model and, thus, have shortcomings when applied to nonlinear biological systems. The previous work on partially ordered data (Wittkowski 1988; 1992), when combined with theoretical results (Hoeffding 1948) and computational strategies (Deuchler 1914) has opened a new field of nonparametric statistics. With grid technology, new tools are now feasible when screening for interactions between genetics (Wittkowski, Liu 2002) and functional genomics (Wittkowski, Lee 2004). Having more complex study designs and more specific methods available increases the demand for decision support when selecting appropriate bioinformatics tools. With the advent of rapid prototyping systems for Web based database application, we have recently begun to complement previous work on knowledge based systems with graphical Web-based tools for acquisition of DESIGN and MODEL knowledge.Biostatistics Bioinformatics NIH NCRR ROADMAP
Studying travel-related individual assessments and desires by combining hierarchically structured ordinal variables
No full textSubjective mobility, Travel desires, Ordinal variables, Factor analysis, Multidimensional data,
The K-band intensity profile of R Leonis probed by VLTI/VINCI
No full textWe present near-infrared K-band interferometric measurements of the Mira star R Leonis obtained in April 2001 and January 2002 with the VLTI, the commissioning instrument VINCI, and the two test siderostats. These epochs correspond to near-maximum stellar variability phases ∼0.08 and ∼1.02 (one cycle later), respectively. The April 2001 data cover a range of spatial frequencies (31–35 cycles/arcsecond) within the first lobe of the visibility function. These measurements indicate a center-to-limb intensity variation (CLV) that is clearly different from a uniform disk (UD) intensity profile. We show that these measured visibility values are consistent with predictions from recent self-excited dynamic Mira model atmospheres that include molecular shells close to continuum-forming layers. We derive high-precision Rosseland diameters of 28.5±0.4masand 26.2±0.8 mas for the April 2001 and January 2002 data, respectively. Together with literature estimates of the distance and the bolometric flux, these values correspond to linear radii of 350+50−40 R_☉ and 320+50−40 R_☉, and to effective temperatures of 2930±270 K and 3080±310 K, respectively
WISDOM: Supporting Biomedical Research Through a System for Web-based Interactive Study Design, Operation and Management
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Étude détaillée des pulsations d'étoiles évoluées "AGB" par interférométrie au V.L.T.I.
No full textCette thèse exploite des mesures interférométriques multi-époques d étoiles évoluées de la branche horizontale asymptotique (AGB) du diagramme HR. Il s agit d étoiles de masses petites à intermédiaires (0.6 10 Mo) en phase finale de leur évolution. Ces étoiles pulsantes subissent une perte de masse très importante via un vent stellaire dense et poussiéreux qui enrichit l environnement stellaire de gaz et de poussières. Ces processus de perte de masse sont encore mal compris et font l objet de beaucoup d investigations. Grâce à leur luminosité et diamètre très importants, ces étoiles sont des cibles privilégiées d observations à Haute Résolution Angulaire. Les étoiles AGB étudiées ici ont été mesurées pendant plusieurs cycles d oscillation au moyen des deux interféromètres AMBER et MIDI du VLTI, donc en proche et moyen infrarouge. Le but de cette investigation est la connexion entre le mécanisme de pulsation, la condensation et la chimie des poussières dans le but de mieux comprendre leur perte de masse. J ai étudié un échantillon de quatre étoiles évoluées, les variables de type Mira riches en oxygène RR Aql, S Ori, Gx Mon et R Cnc, au moyen de donnée MIDI multi-époque et de données AMBER individuelles. Ces données sont modélisées par des modèles standards de disques uniformes ou gaussiens. Les données AMBER sont modélisées par une atmosphère auto-excitée libre de poussière incluant les couches moléculaires juste supérieures responsables du continuum spectral (modèles de série P et M, Ireland et al. 2004a,b). Les données MIDI permettent de rajouter à ce modèle l enveloppe gazeuse radiative. Le transfert radiatif de l enveloppe utilise le code mcsim_mpi (Ohnaka et al., 2006) et prolonge le travail de Wittkowski et al. (2007). Deux types de poussière sont envisagés, silicate et Al O . Les modèles ont été simulés à différentes phases et avec différents paramètres de l enveloppe de poussière pour étudier la variabilité de la photométrie et de la dimension interférométrique en infrarouge moyen. Les visibilité spectrales n ont pas permis, pour aucune de nos étoiles, de mettre en évidence de variation significative intra-cycle ou d un cycle à l autre, dans nos barres d erreur de 5 à 20%. Notre étude montre que les spectres de visibilité et de photométrie des quatre étoiles sont bien décrits par le modèle d enveloppe radiative au-dessus d une source centrale décrite par un modèle d atmosphère dynamique. L enveloppe de poussière optiquement mince de RR Aql est bien modélisée par des grains de silicate. L addition de grains de Al O n améliore pas l ajustement du modèle, mais n exclut pas la présence d une enveloppe interne optiquement plus mince que celle de silicate. GX Mon est bien modélisé par une combinaison de A Al O et de silicates, alors que les enveloppes d nS Ori et R Cncn sont modélisables par des grains de Al O seul sans contribution de silicate. Les rayons inférieurs des enveloppes sont de l ordre de 2 à 2.5 rayons photosphériques pour Al O et de 4 à 5 pour le silicate. Les modélisations effectuées dans ce travail de thèse confirment que les variations inter et intra-cycle attendues ne sont pas détectables dans la précision de nos mesures. Cette étude est la première comparaison entre des mesures interférométriques couvrant plusieurs cycles d oscillation et des modèles couvrant une large gamme de phases des oscillations.This thesis presents multi-epoch interferometric observations of evolved stars on the Asymptotic Giant Branch (AGB). The Asymptotic Giant Branch is populated by low to intermediate mass stars (0.6 10 Mo) in the final stage of their stellar evolution. Pulsating AGB stars suffer from strong mass loss via a dense and dusty outflow from an extended stellar atmosphere returning gas and dust to the interstellar medium. The processes leading to the violent mass loss are not well understood and are therefore under intense investigations. Due to the AGB stars large diameters and high luminosities, evolved stars are ideal targets for high angular resolution observations. The AGB stars presented in this thesis were observed over several pulsation cycles using the near-infrared AMBER and mid-infrared MIDI instruments at the Very Large Telescope Interferometer (VLTI). The goal of this study is to investigate the connection between the pulsation mechanism, the dust chemistry of AGB stars, and the condensation sequence in order to better understand the mass loss process. The thesis studies a sample of four evolved stars, the oxygen-rich Mira variables RR Aql, S Ori, GX Mon, and R Cnc. We obtained multi-epoch MIDI observations and individual AMBER observations. The presented data are modelled using basic models of uniform disks and Gaussian profiles. The AMBER data, along with the basic models, are modelled using dust-free self-excited dynamic model atmospheres (P and M series). These modeles represent the stellar atrmosphere including the continuum forming atmosphere and overlying molecular layers (Ireland et al., 2004b,a). In addition to the basic models, the MIDI data are fitted by a radioactive transfer model of the circumstellar dust shell where the central stellar intensity profile is described by the previously mentioned series of dust-free dynamic model atmospheres, which are based on self-excited pulsation model. The radiative transfer model is computed using the radiative transfer code mcsim_mpi (Ohnaka et al., 2006). The modelling approach follows the work presented by Wittkowski et al. (2007). For all stars, two dust species of silicate and Al O grains were examined. In order to investigate the expected variability of our mid-infrared photometric and interferometric data, model simulations using variations of model phase and dust shell parameters were performed. The observed visibility spectra for all studied stars do not show indications of variations as a function of pulsation phase and cycle within our investigated phases and uncertainties (5%-20%). The observed photometry spectra may indicate intra-cycle and cycle-to-cycle variations with a significance of 1-5 . However, the photometry variations cannot be confirmed within our uncertainties. Our study shows that the photometric and visibility spectra for all stars can be well described by the radiative transfer model of the dust shell that uses a dynamic model atmosphere describing the central source. For all epochs, we found the best fitting models consisting of a dynamic model atmosphere, and dust shells parameters including the optical depth of the dust shell, the inner radii, the power-law index of the density distribution, and the photospheric aangular diameter. The optically thin dust shell did not improve the model fit. However, the model simulations indicate that the presence of an inner Al O dust shell with low optical depth compared to the silicate dust shell can not be excluded. GX Mon can be modelled with a combination of Al O and silicate grains. The dust shell of S Ori and R Cnc can be well modelled using only Al O dust grains without a contribution of silicates. The inner boundary radii of Al O appears around 2-2.5 photospheric radii and the inner moundary radii of silicate appears around 4-5 photospheric radii. The modelling simulations performed in this thesis confirmed that significant intra-cycle and cycle-to-cycle visibility variations are not expected at mid-infrared flux and visibility values are expected to be less that 25% and 20% respectively, and are too low to be detected within the measurement uncertainties. The study represents the first comparison between interferometric observation and a combination of a radiative transfer modelling with dynamic atmosphere models over and extended range of pulsation phases covering several cycles.NICE-BU Sciences (060882101) / SudocSudocFranceF
Steuerliche Betriebsprüfung Handbuch für d. Prüfungspraxis ; Prüfungstechnik d. Betriebsprüfers
No full textUnderstanding consumer buying process in collaborative consumption
No full textCollaborative consumption (CC) is a form of exchange which occurs within three actors: a platform provider, a peer service provider, and a customer. CC has gained broad attention among researchers in recent years. How consumers make buying decisions in CC has gained less attention. Drawing on a review of relevant academic research author offers insights on (1) how the five-stage model of consumer buying process can help us to understand consumer buying behavior in collaborative consumption and (2) how consumer buying process differs in CC compared to other modes of exchange. With an enhanced understanding of the consumer buying process the author introduces a framework called the five-stage buying process in CC. Finally, author gives recommendations for platform providers and peer service providers
The structure of the protoplanetary disk surrounding three young intermediate mass stars II. Spatially resolved dust and gas distribution
No full textAims: We present the first direct comparison of the distribution of the gas, as traced by the [O I] 6300 Å emission, and the dust, as traced by the 10 μm emission, in the planet-forming region of proto-planetary disks around three intermediate-mass stars: HD 101412, HD 135344 B and HD 179218.
Methods: N-band visibilities were obtained with VLTI/MIDI. Simple geometrical models are used to compare the dust emission to high-resolution optical spectra in the 6300 Å [O I] line of the same targets.
Results: HD 101412 and HD 135344 B show compact (<2 AU) 10 μm emission while the [O I] brightness profile shows a double peaked structure. The inner peak is strongest and is consistent with the location of the dust, the outer peak is fainter and is located at 5-10 AU. In both systems, spatially extended PAH emission is found. HD 179218 shows a double ring-like 10 μm emission with the first ring peaking at ~1 AU and the second at ~20 AU. The [O I] emitting region is more compact, peaking between 3-6 AU.
Conclusions: The disks around HD 101412 and HD 135344 B appear strongly flared in the gas, but self-shadowed in the dust beyond ~2 AU. The difference in the gas and dust vertical structure beyond 2 AU might be the first observational evidence of gas-dust decoupling in protoplanetary disks. The disk around HD 179218 is flared in the dust. The 10 μm emission emerges from the inner rim and from the flared surface of the disk at larger radii. No dust emission is detected between ~3-15 AU. The oxygen emission seems also to come from a flared structure, however, the bulk of this emission is produced between ~1-10 AU. This could indicate a lack of gas in the outer disk or could be due to chemical effects which reduce the abundance of OH - the parent molecule of the observed [O I] emission - further away from the star. It may also be a contrast effect if the [O I] emission is much stronger in the inner disk. We suggest that the three systems, HD 179218, HD 135344 B and HD 101412, may form an evolutionary sequence: the disk initially flared becomes flat under the combined action of gas-dust decoupling, grain growth and dust settling.
Based on observations collected at
the European Southern Observatory, Paranal, Chile (Proposal ID:
077.C-0521, 077.C-0263)
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