Context. HR4796A is surrounded by a debris disc, observed in scattered light as an inclined ring with a high surface brightness. Past observations have raised several questions. First, a strong brightness asymmetry detected in polarised reflected light has recently challenged our understanding of scattering by the dust particles in this system. Secondly, the morphology of the ring strongly suggests the presence of planets, although no planets have been detected to date. Aims. We aim here at measuring with high accuracy the morphology and photometry of the ring in scattered light, in order to derive the phase function of the dust and constrain its near-infrared spectral properties. We also want to constrain the presence of planets and set improved constraints on the origin of the observed ring morphology. Methods. We obtained high-angular resolution coronagraphic images of the circumstellar environment around HR4796A with VLT/SPHERE during the commissioning of the instrument in May 2014 and during guaranteed-time observations in February 2015. The observations reveal for the first time the entire ring of dust, including the semi-minor axis that was previously hidden either behind the coronagraphic spot or in the speckle noise. Results. We determine empirically the scattering phase function of the dust in the H band from 13.6 degrees to 166.6 degrees. It shows a prominent peak of forward scattering, never detected before, for scattering angles below 30 degrees. We analyse the reflectance spectra of the disc from the 0.95 mu m to 1.6 mu m, confirming the red colour of the dust, and derive detection limits on the presence of planetary mass objects. Conclusions. We confirm which side of the disc is inclined towards the Earth. The analysis of the phase function, especially below 45 degrees, suggests that the dust population is dominated by particles much larger than the observation wavelength, of about 20 mu m. Compact Mie grains of this size are incompatible with the spectral energy distribution of the disc, however the observed rise in scattering efficiency beyond 50 degrees points towards aggregates which could reconcile both observables. We do not detect companions orbiting the star, but our high-contrast observations provide the most stringent constraints yet on the presence of planets responsible for the morphology of the dust.

Approved for public release; distribution is unlimited / This thesis supplements and updates previous research completed in the digital analysis of rocket motor combustion chamber holographic images. In particular this thesis deals with the software code optimization of existing automatic data retrieval algorithms that are used to extract useful particle information from the holograms using a microcomputer-based imaging system. Two forms of optimization were accomplished, the application of an optimizing FORTRAN compiler to the existing FORTRAN programs and the complete rewrite of the programs in the C language using an optimizing compiler. The overall results achieved were a reduction in executable program size and a significant decrease in program execution speed. / http://archive.org/details/codeoptimization00kaes / Lieutenant Commander, United States Navy

In the coming years, high-contrast imaging surveys are expected to reveal the characteristics of the population of wide-orbit, massive, exoplanets. To date, a handful of wide planetary mass companions are known, but only one such multi-planet system has been discovered: HR 8799. For low mass planetary systems, multi-planet interactions play an important role in setting system architecture. In this paper, we explore the stability of these high mass, multi-planet systems. While empirical relationships exist that predict how system stability scales with planet spacing at low masses, we show that extrapolating to super-Jupiter masses can lead to up to an order of magnitude overestimate of stability for massive, tightly packed systems. We show that at both low and high planet masses, overlapping mean-motion resonances trigger chaotic orbital evolution, which leads to system instability. We attribute some of the difference in behavior as a function of mass to the increasing importance of second order resonances at high planet-star mass ratios. We use our tailored high mass planet results to estimate the maximum number of planets that might reside in double component debris disk systems, whose gaps may indicate the presence of massive bodies.

We present new Hubble Space Telescope observations of three a priori known starlight-scattering circumstellar debris systems (CDSs) viewed at intermediate inclinations around nearby close-solar analog stars: HD 207129, HD 202628, and HD 202917. Each of these CDSs possesses ring-like components that are more massive analogs of our solar system's Edgeworth-Kuiper Belt. These systems were chosen for follow-up observations to provide imaging with higher fidelity and better sensitivity for the sparse sample of solar-analog CDSs that range over two decades in systemic ages, with HD 202628 and HD 207129 (both similar to 2.3 Gyr) currently the oldest CDSs imaged in visible or near-IR light. These deep (10-14 ks) observations, made with six-roll point-spread-function template visible-light coronagraphy. using the Space Telescope Imaging Spectrograph, were designed to better reveal their angularly large debris rings of diffuse/low surface brightness, and for all targets probe their exo-ring environments for starlight-scattering materials that present observational challenges for current ground-based facilities and instruments. Contemporaneously also observing with a narrower occulter position, these observations additionally probe the CDS endo-ring environments that are seen to be relatively devoid of scatterers. We discuss the morphological, geometrical, and photometric properties of these CDSs also in the context of other CDSs hosted by FGK stars that we have previously imaged as a homogeneously observed ensemble. From this combined sample we report a general decay in quiescent-disk F-disk/F-star optical brightness similar to t(-0.8), similar to what is seen at thermal IR wavelengths, and CDSs with a significant diversity in scattering phase asymmetries, and spatial distributions of their starlight-scattering grains.

We present Gemini Planet Imager polarized intensity imagery of HD 100453 in Y, J, and K1 bands that reveals an inner gap (9-18 au), an outer disk (18-39 au) with two prominent spiral arms, and two azimuthally localized dark features that are also present in Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) total intensity images. Spectral energy distribution fitting further suggests that the radial gap extends to 1 au. The narrow, wedge-like shape of the dark features appears similar to predictions of shadows cast by an inner disk that is misaligned with respect to the outer disk. Using the Monte Carlo radiative transfer code HOCHUNCK3D, we construct a model of the disk that allows us to determine its physical properties in more detail. From the angular separation of the features, we measure the difference in inclination between the disks (45 degrees) and their major axes, PA = 140 degrees east of north for the outer disk, and 100 degrees for the inner disk. We find an outer-disk inclination of 25 degrees +/- 10 degrees from face-on, in broad agreement with the Wagner et al. measurement of 34 degrees. SPHERE data in J and H bands indicate a reddish disk, which indicates that HD 100453 is evolving into a young debris disk.

La gravitation joue un rôle important dans de nombreux domaines de l'astrophysique : elle assure notamment la cohésion et la stabilité des planètes, des étoiles et des disques. Elle est aussi motrice dans le processus d'effondrement de structure et conduit, dès lors qu'un moment cinétique initial est significatif, à la formation d'un disque.Ma thèse est consacrée à l'étude des disques de gaz, et plus particulièrement à la description du potentiel et du champ de gravité qu'ils génèrent dans l'espace et sur eux-mêmes (l'auto-gravitation). Bien que la force de Newton soit connue depuis longtemps, la détermination des interactions auto-gravitantes reste difficile, en particulier lorsque l'on s'écarte significativement de la sphéricité. La principale difficulté tient dans la divergence hyperbolique du Noyau de Green 1/(r'-r) et nécessite un traitement propre. L'approche théorique est intéressante car elle fournit de nouveaux outils (techniques numériques, formules approchées, etc...) qui peuvent aider à produire des solutions de référence et à améliorer les simulations numériques.Dans une première partie, nous introduisons le sujet, les notions et les bases essentielles. Le chapitre $1$ est consacré à une présentation succinte du contexte scientifique et aux motivations de notre travail. Dans le chapitre $2$, nous reproduisons dans ces grandes lignes le cheminement conduisant au développement multipolaire, à partir de l'équation de Poisson et de la formule intégrale de Newton. Il s'agit de l'une des méthodes les plus classiques permettant d'obtenir le potentiel gravitationnel d'un corps. Les deux systèmes de coordonnées les plus utilisées sont mis en avant : sphériques et cylindriques. A travers quelques exemples, nous montrons les limites de cette approche, en particulier dans le cas de l'auto-gravité des disques.Dans une deuxième partie, nous abordons le vif du sujet. Le chapitre $3$ présente l'approche basée sur les intégrales elliptiques que nous retrouverons dans l'ensemble du manuscrit (cas général d'abord, puis cas axi-symétrique). Dans le chapitre $4$, nous établissons un premier résultat concernant le noyau de Green dans des systèmes axi-symétriques et verticalement homogènes : une forme alternative et régulière du noyau, quelque soit le point de l'espace. Nous avons exploité cette nouvelle formule pour déduire une bonne approximation du potentiel des disques géométriquement minces, des anneaux et des systèmes faiblement étendus en rayon. Ceci fait l'objet du chapitre $5$.Dans une troisième partie, nous étudions les effets de bords sur la composante verticale du champ de gravité, $g_z$, causés par un disque mince axi-symétrique. Le chapitre $6$ est dédié à l'approximation de Paczynski \citep{pacz78}, qui permet traditionnellement d'exprimer le champ comme une fonction linéaire de la densité de surface locale. Cette approximation n'est en fait strictement valide que dans le cas du modèle du "plan infini", loin d'un disque réaliste. Près du bord externe des disques où la gravité décroit, l'approximation de Paczynski s'avère assez imprécise (facteur $2$ typiquement), et ne donne pas de bons résultats et doit être corrigée. Toujours dans l'hypothèse d'une homogénéité verticale de la densité, nous avons construit une expression pour $g_z$ qui tient compte de ces effets de bords. Le chapitre $7$ est consacré à ce résultat.Dans une dernière partie, nous relâchons l'hypothèse de symétrie axiale (le disque est discrétisé en cellules cylindriques homogènes). Nous nous sommes inspirés du travail d'\cite{ansorg03} afin d'exprimer, via le théorème de Green, le potentiel d'une cellule cylindrique homogène par une intégrale de contour. Ce résultat s'applique directement aux simulations de disques, où ceux-ci sont découpés en cellules cylindriques, chacune ayant sa propre densité.Une conclusion et quelques perspectives sont données en fin de manuscrit. / Gravitation plays an important role in many fields in astrophysics: it appears in the cohesion and stability of bodies such as planets, stars, disks and galaxies. In the Universe, the formation of most astrophysical objects involves disk-like configurations by a main process: the gravitational collapse. The structure and the evolution of these disks (protoplanetary disks, circumplanetary disks...), are an important stage in the process of the formation of stars, planets or satellites. It is therefore fundamental to understand their physics and develop appropriate tools. I devoted my Ph.D. to the computation of the gravitational potential and field of astrophysical disks. Although Newton's force is known for long, the determination of self-gravitating interactions inside bodies remains a difficult task. Strong deviations to sphericity require more efforts. The main difficulty is to manage properly the hyperbolic divergence of the Green kernel $\frac{1}{|r-r'|}$. In this purpose, the theoretical approach is interesting as it can provide powerful formulae and new tools, which can also help to produce reference solutions. So, I have investigated new methods able to treat this question as rigorously as possible.In a first part, chapter $1$ is devoted to the scientifc context and motivations. In the chapter $2$ we derive the well known multipole expansion in spherical and cylindrical coordinates from the Poisson equation and Newton's equation. We show the limits of these two developments in the context of astrophysical disks. In chapter $3$, we discuss the formalism based on elliptic integrals, its advantages and drawbacks, and we describe two methods which use this approach in the special case of axisymmetrical disks.In the second part, chapter $4$ is about the discovery of an alternate formula for the Green kernel, which involves regilar function. To obtain this result, we assume that the disk is vertically homogeneous (i.e., the density varies only with the radius), and that it is axially symetric. In chapter $5$, by using this new expression, we build an approximation for the potential in the special case of geometrically thin disks and rings, and another one for systems which are radially confined.In the third part, chapter $6$ is devoted to the study of edge effects on the vertical component of the gravitational field caused by a thin disk. According to Paczynski's approximation, the field is a linear function of the surface density \cite{pacz78}. This approximation is strictly valid only in the infinite slab model, while we are interested in a realistic disk. Close to the outer edges, where gravity decreases, Paczynski's approximation fails and must be corrected. By assuming again a density varying with the radius only, we have derived a new expression for the vertical component of gravitational field, which properly accounts of the presence of the edge of the disk. This is the main subject of the chapter $7$. In the last part (chapter $8$), we generalize the work by \cite{ansorg03}, valid under axial symmetry only. Using a similar approach, we built an expression for the self-gravitating potential of cylindrical cells, which is not known in closed form yet. This expression is made of a single integral over the boundary of the cell. This result can be applied in hydrodynamical simulations, where disks are usually discretised into homogeneous cylindrical cells, each cell having its own density.A conclusion and a few perspectives end the thesis.

Photometry of eclipsing dwarf-nova EX Draconis was performed at the observatory of Astronomical Institute of the Academy of Sciences of the Czech Republic in Ondřejov and at the Astronomical Observatory on Kolonické sedlo during 63 nights. I calculated times of minimum light by two methods - the mirror method and the derivative method. The mirror method is more precise for these measurements with longer exposure time and smaller coverage of the light curve of eclipse. 53 new times of minima calculated by the mirror method and times of minima obtained from the older articles about EX Dra were included in the O-C diagram and fitted by the sine function and theoretical curve of LITE caused by an unseen third body. Period of cyclic changes for the sine function is 25 years, instead of 4 or 5 years period given in older papers.Period of the third body orbit is aproximately 17 years and its minimum mass is 53.5 Jupiter's mass. The sum of squared deviations is 5 times smaller for the LITE, which means that the LITE ilustrates the O-C diagram better. I determined the average outburst period for three observational seasons and I drew the phase curve of outburst. Finally, I calculated the short period of the light changes outside eclipse.

Le procédé industriel d’extraction d'inuline consiste en une diffusion de longue durée et à température élevée. Ce procédé induit l’extraction des sucres mais également des impuretés. Les étapes de purification de jus deviennent alors plus complexes. Pour pallier à ces problèmes, il est essentiel de réduire la température de diffusion pour limiter l’extraction des impuretés. Récemment, la technique de champs électriques pulsés (CEP) a démonté ses avantages dans le domaine sucrier et également dans d’autres applications agro-alimentaires. L’objectif de ce travail de thèse est de d’optimiser et valider la faisabilité de cette techniques dans le cas de la chicorée. Une purification par filtration dynamique est envisagée et proposée pour remplacer la purification classique. Les résultats de l’extraction montrent qu’il est possible d’intensifier l’extraction de l’inuline par application de CEP. Le prétraitement des cossettes de chicorées à 600 V/cm et 50 ms, réduit de 20°C la température de diffusion (60°C au lieu de 80°C actuellement). Une économie d’énergie importante est réalisée (gain 90 kJ/kg chicory juice). La combinaison innovante d’un prétraitement électrique et un traitement thermique (chauffage ohmique) provoque une perméabilisation importante des cellules et permet de réaliser des diffusions « à froid ». Les analyses qualitatives de jus de diffusion classique et jus CEP montrent que la pureté des extraits CEP est plus élevée (87.2% vs 86.7%). Les essais de filtration sur membrane montrent que les performances de la filtration (pureté, flux, colmatage,…) dépendent énormément de l’origine de l’extrait. Le jus CEP contient moins d’impureté que le jus thermique, est donc plus facile à filtré. Cependant, col matage de membrane restent dans les deux cas important. Un module de filtration dynamique avec disque rotatif a été utilisé pour améliorer les performances de la filtration. Ce module a permit de réduire le colmatage des membranes, améliorer la pureté des extraits et atteindre des facteurs de réduction volumique important (10). / Industrial inulin extraction requires high temperature and long duration to ensure inulin productivity. In addition complex steps are necessary to purify extracted chicory juice and to obtain inulin with desirable purity. In order to avoid the extracting of inulin at high temperature, to obtain chicory juice with better quality and to purify chicory juice with more simple operation, pulsed electric fields (PEF) and membrane filtration were applied to this study : PEF was used to intensify inulin extraction from chicory roots. By pre-treatment of chicory slices at 600 V/cm, diffusion temperature at pilot scale can be decreased to 60oC from about 80oC (industrial extraction condition) to obtain comparable juice inulin concentration. Moreover, this moderate temperature diffusion brought out interesting energy savings compared to that of conventional diffusion. For the goal of extracting inulin at “cold” condition (for example 30oC) PEF induced combined electroporation/ohmic heating pretreatment was applied for chicory tissue denaturation. Better solute extraction was observed after effective damage of chicory tissue diffusivity.Juice extracted from PEF assisted diffusion (PEF juice) was confirmed had higher inulin purity and less impurity in comparison to juice from conventional thermal diffusion process. The juice was purified by membrane filtration in order to investigate a simple chicory juice purification method. Since it contains less impurity, dead-end filtration performance of PEF juice was significantly improved, with less membrane fouling and higher inulin purity in filtrate. However, permeate flux of membrane filtration was seriously restricted by the membrane fouling. In order to improve filtration flux, rotating disk module was introduced in this study for clarification and purification of chicory juice. Elevated shear rate of rotating disk (1500–2000 rpm) could effectively control or even eliminate membrane fouling and lead to satisfying carbohydrate transmission (98%) and desirable permeate flux even at high volume reduction ratio (10). In view of energy saving, optimization of RDM assisted chicory juice filtration was carried out and yielded optimal operation conditions to maximize average flux and minimize specific energy consumption.

Neste trabalho foi desenvolvido um novo m´etodo de s´ntese espectral para modelar o disco de acres¸cao de vari´aveis catacl´smicas (VCs) nao magn´eticas. O principal objetivo deste trabalho ´e analisar a emissao do cont´nuo e das linhas em uma ampla faixa espectral no ultravioleta (UV). O disco ´e separado em an´eis concentricos e, para cada anel uma atmosfera de disco com vento ´e calculada. Na base, as atmosferas sao calculadas consistemente com o vento, tendo a distribui¸cao de densidade dos modelos de atmosferas de disco de Wade e Hubeny. A estrutura ´e calculada no sistema co-m´ovel com um perfil de velocidade vertical obtido da solu¸cao da equa¸cao de Euler para um disco de acres¸cao. O comportamento das linhas e do cont´nuo como fun¸cao da inclina¸cao orbital ´e consistente com as observa¸coes. Tamb´em foi verificado que a taxa de acres¸cao influi sobre a temperatura do vento levando `as mudan¸cas correspondentes nas intensidades relativas das linhas. Foi encontrado que a massa da prim´aria tem uma forte influencia na profundidade dos perfis de absor¸cao. Tamb´em, encontramos que a os perfis de linha sao fortemente sens´veis ao incremento da taxa de perda de massa, aumentado a intensidade das linhas de emissao. Foram escolhidos dados espectrosc´opicos no UV de duas VCs Nova-like (NL) de baixa inclina¸cao, RW Sex e V3885 Sgr e dois sistemas de alta inclina¸cao, RW Tri e V347 Pup. Uma concordancia dos perfis em emissao dos modelos foi encontrada quando confrontados com os dados no caso de sistemas de alta inclina¸cao. Uma falta de fluxo nas linhas de alta ioniza¸cao Civ ¸¸1548,1551 and Nv ¸¸1238,1242, pode ser o sinal da influencia da boundary layer (BL) ou da influencia da irradia¸cao das regioes externas do vento pelo disco interno. Estas influencias seriam cruciais no caso de sistemas baixa inclina¸cao, mas sao menores no caso de sistemas de alta inclina¸cao. / We have developed a new spectral synthesis method for modeling the accretion disk of non-magnetic cataclysmic variables (CVs). The aim of this work is to analyze the continuum and line emission of disks in a wide ultraviolet (UV) spectral range. The disk is separated in concentric rings, and for each ring a wind plus disk atmosphere are calculated. The wind atmospheres are calculated consistently with a density given by Wade and Hubeny disk-atmosphere models at their base. The structure is calculated in the co-moving frame with a vertical velocity profile defined by the Eulers equation solution for the disk wind. We found that the resulting line and continuum behavior as a function of the orbital inclination is consistent with the observations. We also verify that the accretion rate changes the wind temperature, leading to corresponding trends in the intensity of lines. We found that the primary mass has a strong effect on the absorption profiles depth. It was verified that the lines profiles are strongly sensitive to the wind temperature structure and a rise of mass loss rate increases the line intensity. Selected UV data for two high orbital inclination nova-like (NL) CVs, RW Tri and V347 Pup, were confronted with synthetic spectra. The line widths and profiles are reasonably well reproduced by the models. A lack of flux in some high ionization lines (C iv ¸¸1548,1551 and Nv ¸¸1238,1242) may be the signature of the boundary layer (BL) effect and/or the irradiation of outer wind by inner disk. We also found that for high inclination systems the vertical wind structure is less important than for low inclination system models.

A avaliação completa do sistema estomatognático é essencial para o diagnóstico e plano de tratamento ortodôntico. Não se devem apenas avaliar aspectos estáticos da oclusão, mas também os funcionais, pois estes últimos podem mostrar-se alterados e envolver um ou mais componentes do sistema estomatognático, entre eles, a articulação temporomandibular (ATM). Uma das alterações encontradas com freqüência é o deslocamento de disco articular, o que pode interferir no prognóstico e, eventualmente, comprometer o resultado do tratamento ortodôntico. Na tentativa de contribuir para o reconhecimento dessas alterações, este estudo teve como finalidade avaliar a concordância entre dois examinadores calibrados em relação ao diagnóstico de deslocamento de disco articular, comparar a percepção dos pacientes aos ruídos com os dados do exame clínico e eletrovibratografia, além de checar a possível equivalência entre o exame clínico e eletrovibratografia, como métodos de detecção do deslocamento de disco articular. A amostra foi composta por 60 voluntários, divididos igualmente em 4 grupos com 15 participantes cada, definidos por meio do exame clínico e agrupados segundo o gênero e a presença ou ausência de estalo. O exame clínico foi realizado por dois examinadores treinados. A eletrovibratografia foi realizada por um único operador treinado, e empregou-se o programa SonoPAK (Bioresearch Inc.). Para análise dos resultados de concordância entre ambas as técnicas e entre os examinadores, foi utilizado o coeficiente kappa. Os resultados mostraram excelente concordância inter examinadores na realização do exame clínico, concordância satisfatória entre os relatos de ruídos referidos pelos pacientes quando comparados ao exame clínico e eletrovibratografia e concordância também satisfatória entre os dois métodos estudados. / The complete evaluation of the stomatognathic system is essential to the diagnostic and orthodontic treatment plan. It should not evaluate only the occlusal static aspects, but the functional aspects, because the latter could be altered and one or more components of the stomatognathic system could be involved, including the Temporomandibular Joint (TMJ). One of the frequently found alterations founded frequently is the articular disc displacement, which could affect in the prognostic, and, eventually the result of the orthodontic treatment. Trying to contribute to recognize these alterations, the purpose of this study was to evaluate the findings of two calibrated examiners on disk displacement diagnosis, to compare the patients joint sounds perception to the to the results found by the clinical examination and electrovibratography, and beyond that check the possible matching between the clinical examination and the electrovibratography as methods of disc displacement detection. The sample was composed of 60 patients, divided equally into 4 groups of 15 participants each, defined by clinical examination and grouped according to gender and to the presence or absence of the sound (click). The clinical examination was made by two trained examiners. The electrovibratography was made by only one only operator and the SonoPAK software was used (Bioresearch Inc.). The kappas coefficient was used to analyze of the results. They showed that the examiners findings were very close in the clinical examination, partially close on the joint sounds report told by the patients when compared to the clinical examination and eletrovibratography and reasonable equivalence between the two methods studied.