Дисертації з теми "XFM"

We present a methodology of an agile formal method named eXtreme Formal Modeling (XFM) recently developed by us, based on Extreme Programming concepts to construct abstract models from a natural language specification of a complex system. In particular, we focus on Prescriptive Formal Models (PFMs) that capture the specification of the system under design in a mathematically precise manner. Such models can be used as golden reference models for formal verification, test generation, etc. This methodology for incrementally building PFMs work by adding user stories (expressed as LTL formulae) gleaned from the natural language specifications, one by one, into the model. XFM builds the models, retaining correctness with respect to incrementally added properties by regressively model checking all the LTL properties captured theretofore in the model. We illustrate XFM with a graded set of examples including a traffic light controller, a DLX pipeline and a Smart Building control system. To make the regressive model checking steps feasible with current model checking tools, we need to keep the model size increments under control. We therefore analyze the effects of ordering LTL properties in XFM. We compare three different property-ordering methodologies: 'arbitrary ordering', 'property based ordering' and 'predicate based ordering'. We experiment on the models of the ISA bus monitor and the arbitration phase of the Pentium Pro bus. We experimentally show and mathematically reason that predicate based ordering is the best among these orderings. Finally, we present a GUI based toolbox for users to build PFMs using XFM.
Master of Science

The diagenetic and low-temperature deformation behaviour of an oolitic grainstone is examined through quantitative analysis of the rock's microfabric and trace-element distribution using state-of-the-art methods: Synchrotron X-Ray Fluorescence Microscopy, Electron Backscatter Diffraction, and high-definition Light and Electron Microscopy. The results demonstrate that microstructural and trace-element heterogeneity can cause extreme localisations of dissolution and deformation in mineralogically homogeneous limestone. This work implies that reliable estimates of chemical, hydraulic, and mechanical properties of limestones must account for microstructure and trace-element distribution.

"As information on the World Wide Web continues to proliferate at an astounding rate, the Extensible Markup Language (XML) has been emerging as a standard format for data representation on the web. In many application domains, specific document type definitions (DTDs) are designed to enforce a semantically agreed-upon structure of the XML documents. In XML context, these structural definitions serve as schemata. However, both the data and the structure (schema) of XML documents tend to change over time for a multitude of reasons, including to correct design errors in the DTD, to allow expansion of the application scope over time, or to account for the merging of several businesses into one. Most of the current software tools that enable the use of XML do not provide explicit support for such data or schema changes. Using these tools in a changing environment entails making manual edits to DTDs and XML data and reloading them from scratch. In this vein, we put forth the first solution framework, called XML Evolution Manager (XEM), to manage the evolution of DTDs and XML documents. XEM provides a minimal yet complete taxonomy of basic change primitives. These primitives, classified as either data or schema changes, are consistency-preserving. For a data change, they ensure that the modified XML document conforms to its DTD both in structure and constraints. For a schema change, they ensure that the new DTD is well-formed, and all existing XML documents are transformed also to conform to the modified DTD. We prove both the completeness of our evolution taxonomy, as well as its consistency-preserving nature. To verify the feasibility of our XEM approach we have implemented a working prototype system in Java, using the XML4J parser from IBM and PSE Pro as our backend storage system. We present an experimental study run on this system where we compare the relative efficiencies of the primitive operations in terms of their execution times. We then contrast these execution times against the time to reload the data, which would be required in a manual system. Based on the results of these experiments we conclude that our approach improves upon the previous method of making manual changes and reloading data from scratch by providing automated evolution management facilities for DTDs and XML documents."

Der Vortrag stellt zwei Filesysteme aus der kommerziellen Welt vor die derzeit auf Linux portiert werden: JFS von IBM und XFS von SGI. Es wird ein Ueberblick ueber die beiden Dateissysteme, ihre Eigenschaften und ihre Portiertung gegeben.

Foi desenvolvido o aparato experimental necessário à realização de experimentos de RMN em baixas temperaturas, com o objetivo de investigar fenômenos críticos nos sistemas antiferromagnéticos diluídos FexZn1-xF2. Estudou-se a dependência do segundo momento da linha de ressonância do F0 com a temperatura, desde T ≈ TN até T ≈ 250K, através de medidas experimentais e simulações numéricas baseadas num modelo de campo médio. Também foi estudada a dependência angular da meia largura e da forma da linha. Os resultados das simulações numéricas concordam qualitativamente, mas não quantitativamente, com os resultados experimentais. Encontramos também a indicação de uma distribuição em T2 ao longo da linha de ressonância do F0, quando H0 é orientado perpendicularmente ao eixo C. O expoente crítico da magnetização do REIM foi medido diretamente a partir do segundo momento da linha do F0, após um esfriamento da amostra sem campo aplicado (Zero Field Cooling). O resultado obtido β=0.36 ± 0.01 concorda com o valor esperado β= 0.35
The experimental apparatus required for Nuclear Magnetic Resonance low temperatures experiments was developed for the investigation of critical phenomena in the diluted antiferromagnetic FexZn1-xF2. The dependence of the second moment of the F0 resonance line with the temperature was studied from T ≈ TN to T ≈ 250K, both by experimental measurements and numerical mean field simulations. Angular dependence of the line width and line shape were also investigated. The numerically simulated results qualitatively agreed, but quantitatively didn´t agree with the experimental results. We found an indication of a distribution in T2 through the F0 resonance line, when H0 is oriented perpendicularly to the C axis. The magnetization critical exponent β of the REIM was measured directly from the second moment of the F0 resonance line, after a zero field cooling procedure. We obtained β= 0.36 ± 0.01 which is to be compared with the theoretical value β= 0.35

Le modèle généralement admis de formation hiérarchique des structures de l'univers prédit que les surdensités locales à petite échelle s'effondrent en premier puis fusionnent pour former des systèmes de plus en plus larges. Dans ce contexte, les amas de galaxies sont les structures les plus massives à avoir atteint l'équilibre et, à ce titre, fournissent de fortes contraintes cosmologiques, indépendantes et quasi-orthogonales à celles déduites du fond diffus cosmologique et des supernovae. La détection de ces systèmes via l'émission X du gaz intra-amas permet d'assembler de larges échantillons faiblement contaminés et constitue à ce jour la méthode de sélection la plus robuste. Le relevé XMM-LSS entend cartographier 64 deg2 du ciel avec XMM-Newton, le satellite X le plus sensible jamais construit, afin de constituer un échantillon sans précédent de plusieurs centaines d'amas jusqu'à z=1 et plusieurs dizaines de milliers de noyaux actifs de galaxies (AGN). Cette thèse présente un ensemble de méthodes développées afin de sélectionner les sources étendues et les AGNs dans les données XMM, ainsi que des outils d'analyse détaillée pour les amas détectés. Les résultats obtenus avec les 5 premiers degrés carrés du relevé sont ensuite retracés: d'abord les propriétés de l'échantillon d'AGNs et l'analyse de leur corrélation angulaire; puis, les implications de l'échantillon d'amas X pour l'évolution de la relation température - luminosité X du milieu intra-amas; et enfin sa modélisation cosmologique dans le cadre du modèle hiérarchique. Quelques comparaisons multi longueurs d'onde ainsi que les perspectives pour un relevé plus étendu sont également considérées
The widely acknowledged model of hierarchical structure formation of the universe, predicts that local small-scale overdensities collapse first then merge to form increasingly larger systems. In this context, galaxy clusters constitutes the most massive structures that have reached equilibrium and, as such, provide tight cosmological constraints that are independent and quasi-orthogonal to those arising from the cosmic microwave background and the supernovae. The detection of these systems through the X-ray emission of the intra-cluster medium allows the assembly of large, weakly contaminated samples and prevail to date as the most robust selection technique. For this reason, the XMM-LSS survey intends to map 64 deg2 of the sky with XMM-Newton, the most sensitive X-ray satellite ever built, so as to gather an unprecedented sample of several hundreds of clusters up to z=1 and a few tens of thousands of active galactic nuclei (AGN). This thesis presents a set of methods developed in the purpose of selecting extended sources and AGNs in XMM data, as well as detailed analysis tools for the detected clusters. The results derived from the first 5 square degrees of the survey are then depicted: first the properties of the AGN sample and the analysis of their angular correlation; then, the implications of the X-ray cluster sample on the evolution of the temperature - X-ray luminosity relation, emphasizing the impact of selection effects; and finally its cosmological modelling in the framework of hierarchical model. Some multi-wavelength comparisons as well as prospects for larger surveys are also considered

Tato práce popisuje průběh refaktoringu programu mkfs.xfs za účelem zpřehlednění jeho kódu a vyčištění technického dluhu naakumulovaného za dvacet let existence tohoto programu, a následně jeho statickou analýzu. Použité nástroje (CppCheck, Coverity, Codacy, GCC, Clang) jsou srovnány z hlediska počtu i typu nalezených chyb.

Normal galaxies are galaxies whose emission is not dominated by active galactic nuclei (AGN). Current X-ray observatories allow X-ray studies of normal galaxies beyond the local group (≥ 1 Mpc). This thesis presents a study of normal galaxy samples drawn from serendipitous sources detected by the XMM-Newton Observatory up to a few hundred Mpc. The work begins with a pilot study in which a sample of 72 normal galaxy candidates is selected from the XMM-Newton/2dF Wide Angle Serendipitous Survey using X-ray-to-optical flux ratios, X-ray luminosities and the 2dF optical spectra. This sample is classified, based on optical emission lines, into five subsamples: AGN, star-forming (SF) galaxies, composite galaxies, unclassified narrow-emission-line galaxies (NELGs) and absorption-line galaxies (ALGs). The X-ray properties of these subsamples, shown by X-ray spectra and hardness ratios, are broadly consistent with the optical classifications. The Second XMM-Newton Serendipitous Catalogue (2XMM) is then used to cross-correlate with Sloan Digital Sky Survey (SDSS) and yields a sample 463 normal galaxy candidates (the XS sample) using the same selection criteria as in the pilot study. Using the continuum-subtracted optical emission line measurements from the Max-Planck-Institute for Astrophysics/Johns Hopkins University catalogues (the MPA/JHU catalogues), a complete subset of the XS sample is separated into five subsamples: AGN, SF galaxies, composite galaxies, unclassified NELGs and ALGs. The X-ray properties, on the basis of the X-ray spectra and hardness ratios, are largely consistent with expectations from their optical classifications. Additional parameters from the MPA/JHU catalogues, such as star-formation rates (SFRs) and stellar masses, are used for further investigation of the nature and properties of individual subsamples. The effectiveness of the normal galaxy selection criteria is investigated to show how efficient the X-ray-to-optical flux ratios are on separating AGN from truly normal galaxies.

Galaxy clusters are the largest known gravitationally bound objects, their study is important for both an intrinsic understanding of their systems and an investigation of the large scale structure of the universe. The multi- component nature of galaxy clusters offers multiple observable signals across the electromagnetic spectrum. At X-ray wavelengths, galaxy clusters are simply identified as X-ray luminous, spatially extended, and extragalactic sources. X-ray observations offer the most powerful technique for constructing cluster catalogues. The main advantages of the X-ray cluster surveys are their excellent purity and completeness and the X-ray observables are tightly correlated with mass, which is indeed the most fundamental parameter of clusters. In my thesis I have conducted the 2XMMi/SDSS galaxy cluster survey, which is a serendipitous search for galaxy clusters based on the X-ray extended sources in the XMM-Newton Serendipitous Source Catalogue (2XMMi-DR3). The main aims of the survey are to identify new X-ray galaxy clusters, investigate their X-ray scaling relations, identify distant cluster candidates, and study the correlation of the X-ray and optical properties. The survey is constrained to those extended sources that are in the footprint of the Sloan Digital Sky Survey (SDSS) in order to be able to identify the optical counterparts as well as to measure their redshifts that are mandatory to measure their physical properties. The overlap area be- tween the XMM-Newton fields and the SDSS-DR7 imaging, the latest SDSS data release at the starting of the survey, is 210 deg^2. The survey comprises 1180 X-ray cluster candidates with at least 80 background-subtracted photon counts, which passed the quality control process. To measure the optical redshifts of the X-ray cluster candidates, I used three procedures; (i) cross-matching these candidates with the recent and largest optically selected cluster catalogues in the literature, which yielded the photometric redshifts of about a quarter of the X-ray cluster candidates. (ii) I developed a finding algorithm to search for overdensities of galaxies at the positions of the X-ray cluster candidates in the photometric redshift space and to measure their redshifts from the SDSS-DR8 data, which provided the photometric redshifts of 530 groups/clusters. (iii) I developed an algorithm to identify the cluster candidates associated with spectroscopically targeted Luminous Red Galaxies (LRGs) in the SDSS-DR9 and to measure the cluster spectroscopic redshift, which provided 324 groups and clusters with spectroscopic confirmation based on spectroscopic redshift of at least one LRG. In total, the optically confirmed cluster sample comprises 574 groups and clusters with redshifts (0.03 ≤ z ≤ 0.77), which is the largest X-ray selected cluster catalogue to date based on observations from the current X-ray observatories (XMM-Newton, Chandra, Suzaku, and Swift/XRT). Among the cluster sample, about 75 percent are newly X-ray discovered groups/clusters and 40 percent are new systems to the literature. To determine the X-ray properties of the optically confirmed cluster sample, I reduced and analysed their X-ray data in an automated way following the standard pipelines of processing the XMM-Newton data. In this analysis, I extracted the cluster spectra from EPIC(PN, MOS1, MOS2) images within an optimal aperture chosen to maximise the signal-to-noise ratio. The spectral fitting procedure provided the X-ray temperatures kT (0.5 - 7.5 keV) for 345 systems that have good quality X-ray data. For all the optically confirmed cluster sample, I measured the physical properties L500 (0.5 x 10^42 – 1.2 x 10^45 erg s-1 ) and M500 (1.1 x 10^13 – 4.9 x 10^14 M⊙) from an iterative procedure using published scaling relations. The present X-ray detected groups and clusters are in the low and intermediate luminosity regimes apart from few luminous systems, thanks to the XMM-Newton sensitivity and the available XMM-Newton deep fields The optically confirmed cluster sample with measurements of redshift and X-ray properties can be used for various astrophysical applications. As a first application, I investigated the LX - T relation for the first time based on a large cluster sample of 345 systems with X-ray spectroscopic parameters drawn from a single survey. The current sample includes groups and clusters with wide ranges of redshifts, temperatures, and luminosities. The slope of the relation is consistent with the published ones of nearby clusters with higher temperatures and luminosities. The derived relation is still much steeper than that predicted by self-similar evolution. I also investigated the evolution of the slope and the scatter of the LX - T relation with the cluster redshift. After excluding the low luminosity groups, I found no significant changes of the slope and the intrinsic scatter of the relation with redshift when dividing the sample into three redshift bins. When including the low luminosity groups in the low redshift subsample, I found its LX - T relation becomes after than the relation of the intermediate and high redshift subsamples. As a second application of the optically confirmed cluster sample from our ongoing survey, I investigated the correlation between the cluster X-ray and the optical parameters that have been determined in a homogenous way. Firstly, I investigated the correlations between the BCG properties (absolute magnitude and optical luminosity) and the cluster global proper- ties (redshift and mass). Secondly, I computed the richness and the optical luminosity within R500 of a nearby subsample (z ≤ 0.42, with a complete membership detection from the SDSS data) with measured X-ray temperatures from our survey. The relation between the estimated optical luminosity and richness is also presented. Finally, the correlation between the cluster optical properties (richness and luminosity) and the cluster global properties (X-ray luminosity, temperature, mass) are investigated.
Im Rahmen dieser Arbeit habe ich die 2XMMi/SDSS Galaxienhaufendurchmusterung erstellt (2XMMi/SDSS galaxy cluster survey), eine Suche nach Galaxienhaufen welche auf der Detektion ausgedehnter Röntgenquellen im XMM-Newton Quellenkatalog (2XMMi-DR3) basiert. Die Hauptziele dieser Suche sind die Identifizierung bisher unbekannter röntgenheller Galaxienhaufen, die Erforschung ihrer Beziehungen zwischen Röntgenleuchtkraft und Temperatur (X-ray scaling relation), eine Entdeckung von möglichen weit entfernten Galaxienhaufen und die Beziehung zwischen Eigenschaften im Optischen und Röntgenbereich. Die Durchmusterung ist für alle Quellen der Himmelsregionen ausgelegt, die vom Sloan Digital Sky Survey (SDSS) erfasst werden. Das Ziel besteht darin, ihre optischen Gegenstücke zu finden und deren Rotverschiebungen zu bestimmen. Die gemeinsamen Himmelsareale zwischen XMM-Newton und dem Bildmaterial vom SDSS-DR7 umfassen 210 deg^2. Meine Durchmusterung enthält 1180 mögliche Galaxienhaufen mit wenigstens 80 vom Hintergrund bereinigten Photonen im Röntgenbereich, die einer Qualitätskontrolle erfolgreich standgehalten haben. Um die Rotverschiebungen der möglichen Galaxienhaufen im optischen Bereich zu bestimmen nutzte ich drei Vorgehensweisen: (i) Ein Abgleich jener Kandidaten mit den neuesten und umfangreichsten Katalogen optisch ausgewählter Galaxienhaufen, die in der Literatur verfügbar sind. (ii) Ich entwickelte einen Algorithmus, um Rotverschiebungen der optischen Gegenstücke aus Daten vom SDSS-DR8 zu ermitteln, welches zu photometrischen Rotverschiebungen von 530 Galaxiengruppen-/haufen führte. (iii) Ein weiterer von mir entwickelter Algorithmus nutzte die spektroskopischen Rotverschiebung von roten leuchtkräftigen Galaxien (LRGs) in den Daten des SDSS-DR9 und ergab 324 Gruppen und Haufen. Zusammengefasst enthält diese Probe 574 auch im optischen nachgewiesener Galaxiengruppen und -haufen mit bekannten Rotverschiebungen (0.03 ≤ z ≤ 0.77) - der zur Zeit umfangreichste Katalog von im Röntgenbereich ausgewählten Galaxienhaufen basierend auf aktuellen Röntgenbeobachtungen. Unter jenen Haufen waren ca. 75% im Röntgenbereich nicht bekannt und 40% fanden in der bisherigen Literatur noch keine Erwähnung. Um die Röntgeneigenschaften der im Optischen bestätigten Haufen zu bestimmen, war eine automatische Reduktion und Analyse der Röntgendaten unverzichtbar. Die Prozedur, welche Modelle an die Röntgenspektren anpasste, ergab Temperaturen kT von 0.5 – 7.5 keV für 345 Kandidaten. Für alle Haufen, die auch im optischen auffindbar waren, bestimmte ich die physikalischen Eigenschaften L500 (0.5 x 10^42 – 1.2 x 10^45 erg s^-1) und M500 (1.1 x 10^13 – 4.9 x 10^14 M⊙). Die Probe optisch bestätigter Galaxienhaufen mit gemessenen Rotverschiebungen und Röntgeneigenschaften kann für viele astrophysikalische Anwendungen genutzt werden. Als eine der ersten Anwendungen betrachtete ich die Beziehung zwischen LX - T; das erste Mal für eine so grosse Anzahl von 345 Objekten. Der aktuelle Katalog enthält Gruppen und Haufen, die einen grossen Bereich in Rotverschiebung, Temperatur und Helligkeit abdecken. Der Anstieg jener Beziehung ist im Einklang mit bereits publizierten Werten für nahegelegene Galaxienhaufen von hoher Temperatur und Helligkeit. Nach dem Ausschluss leuchtschwacher Gruppen und der Einteilung der Daten in drei nach Rotverschiebung geordneter Gruppen, waren keine signifikanten Änderungen von Anstieg und intrinsischer Streuung zu beobachten. Als zweite Anwendung unserer Durchmusterung, untersuchte ich die Haufen bezüglich deren Eigenschaften im Optischen und im Röntgenbereich. Zuerst betrachtete ich den Zusammenhang zwischen den Eigenschaften (absolute Helligkeit und optische Leuchkraft) der hellsten Haufengalaxie (BCG) mit denen des Haufens als Ganzem (Rotverschiebung und Masse). Danach berechnete ich die Reichhaltigkeit der Galaxienhaufen und deren optische Leuchtkraft innerhalb von R500 für eine Stichprobe nahegelegener Haufen (z ≤ 0.42, hier sind SDSS Daten noch empfindlich genug um den Grossteil der Haufengalaxien abzubilden) mit gemessenen Röntgentemperaturen. Schlussendlich konnten dieWechselwirkungen zwischen den optischen Eigenschaften (Reichhaltigkeit und Leuchtkraft) und den globalen Eigenschaften (Röntgenleuchtkraft, Temperatur und Masse) näher untersucht werden.

This thesis presents an X-ray and optical analysis of the Subaru XMM-Newton Deep Survey (SXDS), focusing on the analysis of the combined XMM-Newton and INT-WFC data. The SXDS has an unprecedented combination of depth and area coverage, covering 1.3 square degrees, making this survey the largest ultra-deep survey to date. The vast majority of the ≈ 1000 X-ray sources within the survey are found to be active galactic nuclei (AGN), making this an excellent resources for investigating the distribution of unobscured and obscured sources.;Concentrating on the AGN population, cross-correlation of X-ray, optical and spectroscopic data have enabled investigation into optical and X-ray colours, optical morphologies, redshift distribution and X-ray and optical obscuration. This thesis, utilizing underlying X-ray and optical properties of AGN such as central nucleus luminosity and obscuration also introduces a simple toy model with the aim of understanding the SXDS AGN X-ray-to-optical flux ratio distribution.;XMM-Newton's large field of view and SXDS field depth has also enabled investigations into the X-ray spectral properties of the brightest 130 sources (> 300 total EPIC counts) within the SXDS. These sources are shown to mainly comprise of unobscured and obscured AGN with a range of intrinsic absorptions and best filling photon indices of ? ≈ 1.8 -- 2.0, consistent with other X-ray surveys.;To illustrate the capabilities of XMM-Newton the X-ray source properties of two powerful, high redshift (z = 2.48) narrow line radio-loud type-2 quasars B3 0731+438 and 3C 257, observed separately from the SXDS are also presented.;The combined optical and X-ray analysis presented in this thesis reveals the SXDS AGN population comprise of a large population of unobscured and obscured AGN. These sources have a range of absorption columns, redshifts and luminosities, encompassing low luminosity AGN through to luminous quasars and demonstrate a strong relationship between optical and X-ray obscuration.

We aim to characterise the X-ray binary population as a function of the local stellar population (in terms of age, metallicity, and stellar density) in the Magellanic Bridge, the interconnecting region between the Small and Large Magellanic Cloud. Gardiner and Noguchi (1996) suggest that closest approach between Small and Large Magellanic Cloud, as evidenced by dramatic phase shift in star formation, occurred approximately 200 Myr ago. During the approach, gas had been tidally stripped (most likely from the Small Magellanic Cloud) into the interconnecting Bridge. According to models of star formation history (Harris, 2007), alongside optical surveys of the Bridge (Skowron et al., 2014), there is strong evidence to suggest that the young, low metallicity stellar population formed in situ, rather than being tidally stripped from either Magellanic Cloud. Three fields located near the Western Bridge observed by Harris (2007) were also observed with the XMMNewton. Cross-matching between optical and X-ray sources was performed, and any interesting matches were followed up with spectroscopic analysis, using the 1.9 m telescope located in Sutherland. A Be/X-ray Binary (BeXRB) candidate is discussed, and if confirmed, will be the furthest known BeXRB from the SMC.

Cette thèse présente les travaux sur les amas de galaxies réalisés dans le cadre d'un relevé des grandes structures de l'univers avec le télescope XMM: le XMM Large-Scale Structure Survey (XMM-LSS). Dans ce relevé de 64 degrés carrés, les amas de galaxies sont l'ingrédient le plus important - ce sont des sondes cosmologiques qui donnent des contraintes sur la cosmologie, complémentaires de celles du rayonnement cosmologique fossile (CMB) et des supernovae de type la (SN-la). En plus leur importance cosmologique, les études multi-longueur d'onde d'amas particuliers sont importantes sur le plan de la dynamique interne et de la croissance des structures. J'illustre ce point avec des exemples d'études d'amas de l'ère pré-XMM et Chandra. Ensuite je présente le XMM-LSS qui va tendre nos connaissances sur les grandes structures traces par les amas à des distances de l'ordre de z~1. Dans le cadre du XMM-LSS, j'aborde d'abord le problème de la détection des sources dans des images en rayons X avec XMM -- ces sources (amas et quasars) seront la base de tous les suivis associés. La comparaison des procédures de détection l'aide d'images XMM simules nous a permis de choisir la mieux adaptée: un filtrage d'image brute avec des ondelettes en utilisant le modèle du bruit de Poisson, suivi par une détection avec SExtractor. Une fois la procédure de détection établie, j'ai estimé la fonction de sélection qui nous permet de prédire les contraintes cosmologique drives des amas du XMM-LSS. J'ai ensuite étudié les premiers candidats amas des observations du XMM-LSS. Leur nombre d'environ 15 par degrés carrés est en bon accord avec nos prédictions. A l'aide d'une procédure de visualisation des donnes multi-lamda, les premiers candidats amas ont été programmés pour un suivi spectroscopique. Je présente les résultats d'analyse des premiers amas à z >0. 6 du XMM-LSS observés au VLT. Pour la première fois, grâce à la sensibilité d'XMM, nous commençons à détecter des amas à grand redshift dans divers états dynamiques et d'une masse moyenne. L'efficacité et la faisabilité du programme XMM-LSS sont ainsi démontrées d'une manière décisive
This thesis presents my work on the clusters of galaxies realized in the framework of a survey of the large-scale structure of the Universe with the XMM observatory: the XMM Large-Scale Structure-Survey (XMM-LSS). In this 64 square degrees survey, the clusters of galaxies are the most important ingredient - these are the cosmological probes that give constraints on the cosmology, complementary to those from the cosmic microwave background (CMB) and type la supernovae (SN-la). In addition to their importance for the cosmology, the multi-wavelength studies of single clusters are also important from the viewpoint of the internal dynamics that is linked to the structure formation. I illustrate this point with examples of analysis of clusters from the epoch pre-XMM and Chandra. Next I present the XMM-LSS that will be a major step forward for our knowledge on the large-scale structures as traced by the clusters at distances of the order of z~1. In the framework of the XMM-LSS, I begin first with attacking the problem of detecting sources in X-ray images with XMM, which is extremely important because these sources (clusters and quasars) will be the basis of all the associated follow-ups. The comparison of the detection procedures, with the help of an efficient procedure for XMM image simulations, allowed us to choose the best adapted one: wavelet filtering of the input raw photon image by using Poisson noise model, followed by detection with SExtractor. Once the detection procedure established, I estimate the selection function that is used to predict the cosmological constraints from the clusters in the XMM-LSS. Next I study the candidate clusters from the first XMM-LSS observations. Their number of about 15 per square degree is in a good agreement with our predictions. With the help of a multi-wavelength visualization procedure, the first candidate clusters were programmed for a spectroscopic follow-up. I present the results for the first z > 0. 6 clusters spectroscopically observed at the VLT. For the first time, thanks to sensitivity of the XMM, we start to detect high redshift and intermediate mass clusters in various dynamical states. The performance and the feasibility of ,the XMM-LSS program are thus fully demonstrated

X-ray observations of the Galactic Centre (GC) can provide invaluable insight into the physical processes within this unique region. In this thesis we investigate the nature of the GC diffuse X-ray emission. We have utilised archival XMM-Newton data to create image mosaics of the central 100 pc region in both continuum bands spanning the 2–10 keV energy range and in a set of narrow bands encompassing various emission lines. We use these mosaics, along with complementary X-ray spectral information, to show that the bulk of the very-hot thermal emission (kT ~ 7:5 keV) can be explained in terms of a population of unresolved point sources, most likely magnetic CVs. Our analysis argues against the requirement for significant amounts of very-hot diffuse plasma. We also investigate a number of soft thermal features. We propose that the putative outflow from Sgr A* may result from the collimated winds of massive stars in the Central Cluster, or alternatively from outbursts on the central supermassive black hole. We show that the characteristics of the soft thermal emission to the north-east of Sgr A* are consistent with those of a mixed- morphology supernova remnant. The final feature considered is a looped structure to the south of the Galactic Plane. Our analysis supports the hypothesis that this is a superbubble deriving from the interaction of supernova shocks with the surrounding ISM. We also investigate the nature and properties of the intermediate-to-faint Galactic Bulge point source population based on a sample of 3610 X-ray source detections from the 2XMMi-DR3 catalogue. We conclude that the spectrally-soft sources are largely coronally-active systems, whereas the spectrally-hard sources are a more heterogeneous set, albeit the majority of which are accreting binaries.

I present an investigation into the X-ray properties of galaxy clusters, consisting of a principal component analysis of ROSAT data and studies of three clusters observed with the XMM-Newton satellite. The principal component analysis provides an investigation into similarities between cluster surface brightness profiles. Initial results for 42 clusters are presented and compared to existing models. The cluster profiles are reproduced to good accuracy using three principal components. Correlation of the principal components to physical properties is investigated but the results are inconclusive. Observations of Abell 1413, Abell 665 and Abell 2163 made with XMM-Newton were investigated spectrally and spatially to determine cluster properties. Global temperatures were found to be 7.08 +/- 0.140.13 keV for Abell 665 and 11.98 +/- 1.2 keV for Abell 2163. The temperature and abundance profiles of the clusters are very different, with some differences attributed to the recent merging of subclusters in Abell 665 and Abell 2163. Spatial analysis of the cluster surface brightness profiles is undertaken with beta and NFW models. The profiles produced for the three clusters are used to estimate the variation of gas, gravitational and iron mass with radius. These are used to draw general conclusions, such supernovae numbers (NSNII 109--11). The cosmological density and matter density parameters are found; &OHgr;0 = 0.22 -- 0.33 +/- 0.1 and &OHgr; m ? 0.12+/-0.060.04. This suggests a low density universe, but is subject to uncertainty due to extrapolation to larger radii.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Este trabalho focaliza o fluxo do conhecimento xam?nico nos centros urbanos, que ? sustentado por uma rede de intera??o a que intitulo de circuito neoxam?nico. Os grupos praticantes do denominado xamanismo urbano, ou neoxamanismo, constituem um segmento do fen?meno Nova Era. N?o o considero um trabalho de religi?o, mas, uma pesquisa sobre um caso peculiar, sobre tradu??o de rituais ind?genas e seus atores no meio urbano. Focalizo as redes globais que os ligam a ind?genas da aldeia e o interc?mbio de saberes pr?ticos e simb?licos, formando uma linhagem de modeladores, alimentada pela centralidade do conhecimento e na tradu??o de rituais e pr?ticas de cura. A cosmologia ind?gena ? vivenciada na metr?pole como modo de vida atrav?s de viv?ncias em rituais tornando global o local. A partir da atua??o desses atores evidencio quest?es como tradu??o, modelagem e poder pessoal. O trabalho de pesquisa, a aprendizagem e o fluxo de rela??es que formam um jogo de constitui??o de poder das autoridades neoxam?nicas. Busquei principalmente situa??es nos eventos de xamanismo urbano organizados por Sthan Xanni?, no Rio de Janeiro, S?o Paulo e Minas Gerais principalmente

Mestrado em Engenharia Electrónica e Telecomunicações
Neste trabalho é apresentado um estudo teórico sobre alguns dos efeitos não lineares que ocorrem nas fibras que suportam as redes ópticas, com especial incidência sobre a modulação cruzada de fase (XPM). Com o objectivo de usar estes mesmos efeitos para monitorizar essas mesmas redes, é também feita uma introdução sobre alguns dos sistemas de monitorização óptica existentes. Uma técnica de monitoria em redes ópticas com base nos efeitos de XPM é apresentada e estudada. A metodologia assenta na caracterização dos efeitos sofridos por um canal de teste (variância de fase e amplitude) na presença de várias condições de rede. Esta análise confirma que os efeitos da XPM variam com a alteração de alguns parâmetros importantes do sistema, sendo por isso um bom mecanismo de caracterização. ABSTRACT: This work presents a theoretical study about some of the nonlinear effects that occur in the fibers that support the optical networks. Particular attention will be given to cross-phase modulation (XPM). In order to use these effects to monitor these networks, introductions to some of the existing monitoring systems are also presented. One monitoring technique in optical networks based on XPM effects is presented and studied. The methodology rests on the characterization of the effects suffered by a probe channel (phase and intensity variance), under several network conditions. This analysis confirms that the XPM effects depend on some of the important system parameters, thus being a good characterization mechanism.

Mestrado em Engenharia Mecânica
The Finite Element Method (FEM) is one of the most efficient tools used, in computational solid mechanics, for the numerical solution of Partial Differential Equations (PDE). This numerical technique has been extensively used in the past decades for finding approximate solutions to PDE in both engineering and science fields. A main feature of the FEM is the subdivision of a continuum into a discrete set of elements, being these elements connected by a topological map, usually referred to as the finite element mesh. The FEM can generally be used to model and predict the behaviour of continuous structures. However, problems arise when FEM is used on a domain with a discontinuity (like a crack). In this case, it is usual to use adaptive mesh refinement around the discontinuity. This process works ne, but has a very high computational cost. Alternatively, the eXtended Finite Element Method (XFEM) is a numerical method for modelling strong and weak discontinuities using local enrichment. It is a FEM generalization that enables the incorporation of local enrichment of approximation spaces. This enrichment is done through the partition of unity concept by adding special functions to the finite element approximation. For crack modelling in isotropic linear elasticity, the Heaviside function is used to enrich the completely cut elements and an asymptotic function is used to enrich the crack tip elements. This enrichment creates new degrees of freedom that must be integrated into the analysis during a post-processing step. This enables the domain to be modelled without explicitly meshing the crack surfaces and without a remeshing process for the crack propagation. In this context, this work addresses the main concepts of FEM and XFEM, the creation of a pedagogical XFEM software (with its numerical implementation process and software manual) and the differences between a standard FEM implementation and a XFEM program. Finally, some numerical results of the XFEM application are presented.
O Método dos Elementos Finitos (Finite Element Method - FEM) é uma das ferramentas mais eficientes para a obtenção de soluções numéricas de Equações Diferenciais Parciais (EDP) em mecânica dos sólidos computacional. Esta técnica numérica tem vindo a ser utilizada extensivamente durante as últimas décadas para a obtenção de soluções aproximadas de EDP, tanto a nível de engenharia como a nível científico. Uma das principais características do FEM é a subdivisão de um meio contínuo numa série de elementos discretos, estando esses elementos ligados por um mapa topológico, normalmente referido como malha dos elementos finitos. O FEM é utilizado geralmente para modelar e prever o comportamento de estruturas contínuas. Contudo, surgem problemas quando o FEM é utilizado em domínios que contenham descontinuidades (tais como fendas). Neste caso, é normalmente utilizado um refinamento de malha adaptativo em torno da descontinuidade. Este processo funciona perfeitamente, mas acarreta um enorme custo computacional. Alternativamente, o Método dos Elementos Finitos Estendidos (eXtended Finite Element Method - XFEM) é um método numérico utilizado para modelar descontinuidades fortes e fracas, utilizando enriquecimento local. É uma generalização do FEM que permite a incorporação de enriquecimento local de aproximação de espaços. Este enriquecimento é feito através do conceito de partição de unidade, ao adicionar funções especiais à aproximação por elementos finitos. Para a modelação de uma fenda em regime linear elástico isotrópico, é utilizada a função de Heaviside para enriquecer os elementos que são completamente cortados pela fenda, e a função assimptótica para enriquecer os elementos que contenham a ponta de fenda. Este processo de enriquecimento cria novos graus de liberdade que têm de ser incorporados no sistema, através de uma etapa de pós-processamento. Isto permite que o domínio possa ser modelado, sem que exista a preocupação de fazer coincidir a malha com a localização da fenda, e que seja preciso recorrer a um processo de remalhamento caso exista propagação da fenda. Neste contexto, o presente trabalho aborda os principais conceitos de FEM e XFEM, a criação de um software pedagógico de XFEM (com o seu processo de implementação numérica e manual do software) e as principais diferenças entre a implementação padrão do FEM e um programa de XFEM. Finalmente, são apresentados alguns resultados numéricos da aplicação do XFEM.

This work describes a software engine which works with textual documents containing historical information. The purpose of this work three-fold: firstly to show the validity of the developed engine to correctly identify and label the entities of the universe of discourse with a labelled-combined XTM-DITA model. Secondly to analyze the improvements achieved in the interaction between people (users) and computers with a practical application of the designed methodology to a real-world problem in the semantic web area and thirdly to plan its future integration into a traceability system.

Ce travail a pour objectif principal la détermination des paramètres d’Arrhenius caractérisant la réaction d'arrachement d'un atome d'hydrogène par les atomes de chlore pour sept composes halogènes: chcl#3, chcl#2f (hcfc-21), chclf#2 (hcfc-22), ch#3ccl#3, ch#3ccl#2f (hcfc-141b), ch#3cclf#2 (hcfc-142b) et ch#2fcf#3 (hfc-134a). Il est motivé par la nécessité de mieux maitriser en laboratoire l'emploi de ces réactions comme sources de radicaux halogenoalcoyle et par ailleurs, d'évaluer l'impact atmosphérique de ces réactions en tant que processus d'amorçage des mécanismes de photo-oxydation troposphérique des hydro chlorofluorocarbures (hcfc) et hydrofluorocarbures (hfc) susceptibles de remplacer les freons (chlorofluorocarbures: cfc). L'étude des séries de composes chcl#3#-#xf#x et ch#3ccl#3#-#xf#x permet également d'interpréter l'évolution de la réactivité en fonction des changements apportés dans leur structure. La détermination des paramètres cinétiques a été réalisée au moyen de la technique du réacteur a écoulement et a décharge micro-ondes couplée a une technique de prélèvement par faisceau moléculaire et d'analyse par spectrométrie de masse. Les expériences ont été conduites dans des conditions de pseudo-premier ordre par rapport à l'halogenoalcane. Les constantes de vitesse des réactions de recombinaison homogène et hétérogène des atomes de chlore ont été mesurées afin de les prendre en compte dans le traitement des données cinétiques. Les lois de dépendance avec la température des constantes de vitesse régissant la réaction des atomes de chlore avec les halogenomethanes et les halogenoethanes ont été déterminées dans le domaine de température de 298-430 k environ et discutées. L'influence de la substitution du chlore par le fluor le long des deux séries de réaction cl + chcl#3#-#xf#x et cl + ch#3ccl#3#-#xf#x sur les paramètres cinétiques et les grandeurs thermodynamiques les caractérisant a été examinée et interprétée sur la base de données théoriques récentes. Bien que du même ordre de grandeur que la réaction d'attaque des hcfc et hfc par les radicaux oh, les réactions des hcfc et hfc avec les atomes cl ne peuvent jouer qu'un rôle mineur dans l'amorçage des processus de photo-oxydation troposphérique de ces composes, la concentration moyenne des atomes de chlore étant environ 1000 fois plus faible que celle des radicaux hydroxyle dans la troposphère.

La prévision de la tenue des structures fissurées nécessite le calcul du taux de restitution d'énergie ou des facteurs d'intensité de contrainte (FIC) en pointe de fissure. Ces quantités sont généralement évaluées après une analyse éléments finis. Plus récemment l'apparition de la XFEM a permis d'améliorer la description des champs en pointe fissure et de s'affranchir des remaillages successifs après chaque pas de propagation. Néanmoins, la solution ainsi calculée demeure une solution approchée de la solution du problème de référence. Il est donc important de pouvoir évaluer la pertinence de ces calculs. Ces travaux de thèse proposent une technique à même de fournir un encadrement conservatif des FIC évalués par une méthode éléments finis classique et par la XFEM. L'utilisation des techniques d'évaluation d'erreur sur les quantités d'intérêt et de l'erreur en relation de comportement permet dans un premier temps de fournir des bornes de bonne qualité pour les FIC. On propose ensuite une méthode permettant d'évaluer l'erreur globale commise lors d'une analyse XFEM. Elle fait intervenir l'erreur en relation de comportement et des techniques de construction de champs de contrainte adéquates. On est alors en mesure de proposer un encadrement assez fin des FIC pour un coût numérique très raisonnable. L'estimation d'erreur peut finalement être envisagée comme un moyen de déterminer les quantités d'intérêt avec précision.

We present the first release of the XMM Cluster Survey (XCS), a serendipitous survey of clusters of galaxies using archival XMM-Newton data. In this thesis we describe in detail the automated pipeline used to search the XMM images for extended sources. We also discuss techniques for the identification of clusters which are already known. We perform a rigorous set of tests designed to validate and quantify the effectiveness of the algorithms. Furthermore, we have developed a methodology for describing quantitatively the survey selection function and include the implications for the XCS constraints on the cosmological parameters σ₈ and Ω_m. We compile three main catalogues from the set of 63327 detected sources. The first is a statistically well-defined sample of 142 known clusters and 1622 new candidates. The second is a smaller list of 90 XCS cluster candidates identified in the non-statistical sample. Finally, we include for completeness the point sources detected in the survey. We also describe the database used to store and access the survey data and source lists. Strategies for the long-term follow-up of the catalogues in the low, medium and high redshift regimes are investigated. We have measured photometric redshifts for 219 new candidate clusters out to z ~ 0.3. We conclude with the discoveries in the XCS of the most distant X-ray cluster currently known, at z = 1.5, and a likely supercluster at z = 0.9.

Public history has become a dynamic new field of study in South African historiography during the post-apartheid period. As a field of applied history, it has been engaged with analysing the highly contested nature of knowledge production across a wide range of public sites. These include museums, art galleries, archaeological digs, theme-parks, shopping malls, tourist attractions and heritage sites. The wider national cultural and political challenge has been that of working towards restoration, healing, and reparation in the wake of a colonial and apartheid history marked by particularly acute brutality and dispossession. This thesis analyses the attempts of one public institution, the Iziko South African Museum, to negotiate the remaking of public history in the post-apartheid period. Unlike some of the newer sites of cultural production, such as the Cape Town Waterfront and the West Coast cultural village of !Kwa-ttu, the South African Museum has a century-long history of complicity in generating images of racial and cultural others, notably Khoisan communities. The thesis begins by exploring this history and the ways in which the South African Museum has tried to come to terms with this legacy in its post-apartheid policies: firstly, in the discussions and debates around the closing of the Bushman diorama (2001), and secondly, in the creation of a new exhibition on San rock art which draws extensively on the Bleek-Lloyd Collection (/Qe: The Power of Rock Art. Ancestors, Rain-making and Healing, 2003 to the present). The Iziko South African Museum has not been successful in its attempts to meet the challenge of coming to terms with its history of collecting human remains and creating body casts and putting them on display. I argue that the measures it has introduced over the last twenty two years, including the &lsquo
revision of the Bushman diorama exhibition&rsquo
(1988-89), to Miscast (1996), and the 
closure 
of the diorama (2001), are little more than window-dressing and staged productions, with lip-service being paid to transformation. In the place of the effective opening out of debate and discussion about the Museum&rsquo
s history of racial scientific research, we have seen the presentation of a new framework of knowledge about Khoisan communities through the &lsquo
lens of rock art 
research&rsquo
and the Bleek-Lloyd-/Xam records. I see these as a way of sanitising the story about colonialism and apartheid. In making these arguments I draw upon a number of scholarly works by academics involved in public and visual history
recent literature on trauma narratives
Foucauldian discourse
and newspaper.

The X-ray spectra of active galaxies are, to a first approximation, power-law-like. Upon more detailed investigation, however, features become apparent: in particular, an emission line corresponding to iron, around 6.4 keV, and the so-called 'soft-excess' below ~ 2 keV, whereby an extrapolation of a power-law fit to the 2-10 keV energy band under-predicts the observed counts. In this thesis, the soft X-ray excesses in samples of both low- and high-luminosity Active Galactic Nuclei (Seyfert galaxies and QSOs respectively) are analysed. This allows the parameters of the soft excess, such as strength and temperature, to be compared with X-ray luminosity. It is found, however, that there are very few differences between Seyfert galaxies and QSOs, leading to the idea that the soft excess is not strongly linked to the luminosity of the object. Time variability of the soft excess is studied, by investigating three objects (3C 273, PKS 0558-504 and 1H 0419-577) which have each been observed a number of times in the X-ray band. The soft excess is found to vary in each, with the changes possibly due to the Compton cooling of the corona above the accretion disc, brought on by an increase in accretion rate. Another sample, of high-redshift objects, is also discussed, finding that there is no evidence for spectral evolution or intrinsic absorption in these radio-quiet QSOs. When considering this sample as a whole, there is an indication of spectral flattening at higher energies, suggesting the presence of a Compton reflection hump. Finally, the existence and strength of the neutral, narrow iron line is investigated, finding that, in the more luminous objects, the equivalent width is much lower, this is the X-ray equivalent of the Baldwin effect found in the optical and UV emission lines.

In this thesis we investigate the accuracy of high-order Extended Finite Element Methods (XFEMs) for the solution of discontinuous problems, with a view to computing high-order solutions to a two-phase flow problem. We start by demonstrating optimal exponential rates of convergence for a spectral/hp element method applied to a smooth problem. We then consider an immersed method on a fixed background mesh that uses level sets to capture the location of a discontinuity and the XFEM to characterise this discontinuity on element interiors. We present an improvement to the modified XFEM of [Moes et. al., 2003] and then use it to solve both a Poisson problem and a linear elasticity problem with discontinuities modelled independently of the mesh. Very close to optimal rates of convergence are recovered for the Poisson problem with both straight and quadratically curved interfaces for approximations up to order p=4. These rates are better than those published in the literature for the XFEM with a curved weak discontinuity, and they are also the first optimally convergent results achieved using the modified XFEM for any problem with approximations of order p>1. Almost optimal rates of convergence are then also recovered for an elastic problem with a circular discontinuity for approximations up to order p=4.The use of the XFEM for time-dependent problems is investigated, and a novel level set update method that retains the signed distance property without need for reinitialisation is also presented. Finally we apply these methods to the time-dependent simulation of a two-phase flow problem. We validate the method against both an analytic dispersion relation for relaxation under small interface perturbations and an existing implementation for large interface perturbations. We then present a proof-of-concept implementation of a high-order immersed method for an oscillating tank flow problem and demonstrate the ability of our implementation to simulate problems with large amplitude interface deformations.

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A globalização é hoje uma realidade irreversível e vem provocando significativas modificações no cenário mundial, notadamente no mundo das relações econômicas. Estas, por sua vez, tornam-se ainda mais complexas e abrangentes, não podendo ser entendidas de forma minimalista. Neste contexto, torna-se premente que as Administrações Aduaneiras (Aduanas) dos países-membros do Mercosul sejam capazes de se adaptar, num processo contínuo, a este e novos cenários insurgentes, caso contrário não serão capazes de cumprir de maneira satisfatória as suas funções. A tendência da economia mundial conduz à necessidade de se ter uma visão sistêmica deste universo e um conhecimento globalizado dos perfis de contribuintes, os quais poderão se apresentar com constantes mutações . Neste panorama, far-se-á necessária uma integração sistematizada das Aduanas como pré-condição para que possam atingir níveis satisfatórios de eficácia e eficiência, viabilizando com isto a minoração dos problemas e irregularidades existentes na área aduaneira. Adicionalmente, as Aduanas modernas têm adotado um regime de parceria com os setores da iniciativa privada relacionados ao comércio exterior através do estabelecimento de um relacionamento com base em confiança mútua e objetivos comuns, com vistas a alcançar o almejado ponto de equilíbrio entre a celeridade no despacho aduaneiro facilitação - e o controle a ser exercido sobre o mesmo fiscalização - de forma a dar uma maior competitividade para o país. Diante do exposto, é notório que atualmente as nações têm procurado estabelecer Acordos cuja finalidade é o estabelecimento de intercâmbio de informações, o que corrobora a necessidade crescente de as Aduanas buscarem meios para eficientemente enfrentarem os novos cenários que, imprevisivelmente, poderão surgir. Logo, inserida neste contexto, a proposição deste tem por finalidade precípua, a partir da pesquisa e identificação dos dados de interesse mútuo dos países do Mercosul, a elaboração de um vocabulário XML XFAM - baseado em padrões e tecnologias estabelecidas, no qual são definidos, principalmente, esquemas-documentos que definem a estrutura das instâncias de documentos empregadas nos intercâmbios de informações entre as Aduanas do Mercosul e destas com as empresas nacionais. Neste processo é utilizada a internet como principal meio de comunicação e os Web Services como tecnologia viabilizadora da interoperabilidade entre sistemas

The primary motivation for writing the thesis Modern Object Oriented XML API for PHP was absence of PHP API which would be easy to use, correct and complete. This thesis analyzes the flaws of current PHP APIs and describes how they are solved in modern APIs in other programming languages. It also presents an in-depth description of XML language and its associated standards. Using the knowledge gained from the analysis, the thesis proposes a new API called phpxom based on Java API XOM. The API is then implemented according to the proposal. The resulting PHP library has all the required features -- easiness of use, correctness and completeness. Finally, the thesis analyzes the possibility to implement phpxom as a PHP extension written in C language, which would make it faster and lower its memory requirements.

A bactéria Xylella fastidiosa causa a clorose variegada dos citros, também conhecida como amarelinho. Em 2000, foi concluído o seqüenciamento do genoma deste organismo, o primeiro de uma bactéria fitopatogênica, um fato que estimulou o estudo dos possíveis mecanismos de patogenicidade empregados pela bactéria para causar a doença em citros. X. fastidiosa é uma bactéria limitada ao xilema, sendo transmitida de planta a planta através de insetos vetores. Especula-se que a bactéria produza enzimas que degradem a membrana da pontuação, permitindo a colonização de novos vasos do xilema. A identificação de genes com similaridade de seqüência a genes de celulases, xilanases, pectinases e proteases, fomentou o presente estudo visando caracterizar os genes Xf – 810, Xf – 818 e Xf – 2708, similares a endoglicanases. Estes genes foram clonados em vetores de expressão e as respectivas proteínas foram produzidas em Escherichia coli. Através de ensaios enzimáticos as proteínas foram caracterizadas como endoglicanases (EC 3.2.1.4), que são celulases com mecanismo endoglicolítico de ataque às moléculas de celulose. Estas celulases hidrolisam carboximetil celulose, Avicel e xilana, enquanto as enzimas Xf – 810 e Xf – 818 hidrolisam a celulose amolecida com ácido. Estas celulases degradam mais eficientemente a carboximetil celulose em pH ácido (entre 5,2 e 5,6) e na temperatura de 65 °C. Coletivamente, estas celulases são capazes de degradar polímeros solúveis e insolúveis, enquanto a enzima Xf – 818, é capaz de degradar oligossacarídeos derivados da celulose, como celotetraose e celopentaose, apresentando ampla variação catalítica. Esta celulase possui capacidade de ligação à celulose microcristalina, denotando a funcionalidade de seu domínio ligador de celulose. Desenvolvemos um protocolo, empregando cromatografia de troca aniônica, afinidade por metal (níquel) e filtração em gel, eficiente na purificação da proteína Xf – 818 expressa heterologamente em E. coli com fusão hexahistidina à extremidade N–terminal. A caracterização enzimática destas proteínas, com a confirmação da atividade celulásica, fornece subsídios para uma eventual função das celulases durante a colonização do hospedeiro pela bactéria, pois são cataliticamente funcionais. Ademais, corrobora a similaridade destes genes, verificada durante o seqüenciamento do genoma de X. fastidiosa.
Xylella fastidiosa is the causal agent of citrus variegated chlorosis, also known as "amarelinho". The recent sequencing of its genome, achieved in 2000, was the first of a plant pathogen, a fact that stimulated the search for putative pathogenicity factors employed by this bacterium while infecting citrus trees. X. fastidiosa inhabits exclusively the xylem vessels, being transmitted by sharpshooter vectors. Several authors argue that the bacterium produces enzymes to degrade plant cell, as a way to colonize new xylem vessels through pit membrane degradation. The identification of putative cellulases, xylanases, pectinases and proteases on X. fastidiosa genome, led us to carry out the present work to characterize the putative products of the endoglucanase genes Xf – 810, Xf – 818 and Xf – 2708. These genes were cloned into expression vectors and the proteins were produced in Escherichia coli. Based upon enzymatic assays, those proteins were characterized as endoglucanases (EC 3.2.1.4), which are cellulases able to promote the endo-hydrolysis of cellulose chains. These cellulases degraded carboxymethylcellulose, Avicel and xylan, while only Xf – 810 and Xf – 818 degraded acid swollen cellulose. The hydrolysis of carboxymethylcellulose was higher at acidic pH between 5.2 and 5.6) and at a temperature of 65 °C. As a group, these enzymes were able to degrade soluble and insoluble cellulose derivatives, while only the cellulase Xf – 818 could hydrolyze the cello-oligosaccharides cellotetrose and cellopentose, thus showing a high catalytic diversity. This protein also has the capacity to bind microcristalline cellulose, confirming the presence of a functional cellulose-binding domain. We set a protocol, employing anion exchange, metal affinity and gel filtration chromatography, to purify the Xf – 818 enzyme expressed in E. coli as a N-hexahistine fusion tag. The endoglucanase activity studied gives support for an eventual role of such cellulases during host colonization by the bacterium. Besides that, it agrees with similarities searches observed on the sequencing of X. fastidiosa genome.

La caratterizzazione dell'AGN feedback è ancora un problema aperto. Uno dei possibili modi in cui l'AGN potrebbe influire sull'evoluzione della galassia ospite è attraverso la generazione di potenti venti dalle zone più interne del disco (Ultra Fast Outflows, UFOs), visti nel ~50% degli AGN vicini. Per quanto riguarda le sorgenti ad alto redshift, si hanno ancora poche detezioni di questi venti, anche se si pensa che siano altrettanto comuni. Come lavoro di tesi, ho analizzato tutti i dati in banda X disponibili per l'Einstein Cross, un quasar a z~1.7 lensato in quattro immagini da una galassia a spirale a z~0.04. Questo lavoro rappresenta la prima analisi spettrale di questa sorgente per la quale si utilizzano sia dati Chandra (35 obs., immagini risolte) che dati XMM (tre obs.) combinando le peculiarità  di entrambi i telescopi. Utilizzando un semplice modello di legge di potenza più assorbimento galattico, i dati Chandra hanno permesso di scoprire che la sorgente mostra variabilità  spettrale tra i vari puntamenti. Ho investigato limitando l'analisi agli spettri a più alta statistica, 14 spettri Chandra, 2 XMM (2002, 2018). Dai dati Chandra è stato possibile osservare che la sorgente presenta un assorbitore a densità  di colonna variabile. Detectiamo per la prima volta caratteristiche feature di Ultra Fast Outflows (UFOs) in 9 di questi 16 spettri, da cui ricaviamo una grezza stima del wind duty cycle, il cui limite inferiore è pari a ~50%. I dati XMM del 2002 sono meglio riprodotti da un assorbitore spesso, molto ionizzato e in outflow a ~0.1c, di potenza cinetica ~1.3dex della luminosità  bolometrica. Dati i modelli attuali, questo vento sembrerebbe abbastanza energetico da incidere sensibilmente sull'evoluzione della galassia ospite. I dati XMM del 2018 invece non mostrano segni caratteristici di una componente di outflow molte veloce, ma son meglio riprodotti da un assorbitore freddo, abbastanza spesso, consistente con le zone più interne del toro molecolare.

X-ray astronomers currently have access to two major X-ray observatories, XMM-Newton and Chandra. While targeted observations are likely to continue for the next few years, this will not be the case forever. Archival data will thus become an increasingly important resource. X-ray observations produce large samples of active galaxies with fewer biases than at other wavelengths. In this thesis, techniques for archival survey work are developed and applied to small 'pilot' samples of AGN from the XMM-Newton archive. A photometric redshift method for use with X-ray selected AGN is developed and tested with both faint and bright samples (from the Lockman Hole region and 2XMM serendipitous catalogue respectively). A level of accuracy surpassing other X-ray photometric redshift methods is found. A deep look at the 3C 273 field from multiple XMM-Newton observations is used to investigate continuum X-ray variability in serendipitous AGN in the field. The photometric redshift method developed is used to determine X-ray luminosities for the serendipitous sources and the commonly found anti-correlation between excess variance and X-ray luminosity is reproduced. The connection between continuum variability in the X-ray and optical/UV bands is investigated using a sample of Seyfert 1 galaxies from the XMM-Newton Science Archive. Cross correlation analysis of the light curves on timescales of ≈1000s finds no significant evidence for correlation between the bands. A larger sample of sources is taken from the serendipitous source catalogue 2XMMp to investigate cosmic variance and bias of X-ray selected sources. For full band (0.2 - 12 keV) sources above a flux limit of l x 10-14 erg cm-2 S-1, AGN bias, which characterises how AGN mass traces the underlying mass, is found to be in agreement (within the error bounds) with the bias factor determined from much larger optical surveys.

In this thesis, we present the optical to X-ray scaling relations from the XMM Cluster Survey (XCS) and the red-sequence Matched-filter Probabilistic Percolation cluster finding algorithm (redMaPPer) cluster catalogs. XCS finds galaxy clusters in the XMM-Newton public archive and redMaPPer uses optical data from the Sloan Digital Sky Survey eighth data release (SDSS-DR8) and the Dark Energy Survey first year data release (DES Y1). redMaPPer catalogs provide reliable photometric redshift estimations that have been calibrated with spectroscopic redshifts. The XCS temperature and luminosity pipelines need redshift information to calculate the X-ray observables. We introduced third generation of the XCS Post Processing Pipeline (XCS3P). A description of the previous versions is given, highlighting the modifications made for XCS3P-v3. This methodology was validated by comparing the LX - TX relation obtained from XCS3Pv1, XCS3P-v2 and the current version, the results are similar to XCS3P-v2 finding a self similar evolution. Samples of clusters are defined after several control filters, each cluster has optical and X-ray follow up, the sample has 327 unique clusters that span a redshift range of 0:08 < z < 0:8. Optical to X-ray scaling relations are obtained for the samples XCS-RM (SDSS DR8), XCS-RM (DES Y1) and XCS-RM (SDSS+DES Y1). Obtaining as a result, the most comprehensive examination of the TX - λ and LX - λ relations up to date, showing a clear correlation between the observables. This work confirms that it is possible to relate optical properties with the underlying mass. Cluster observables like the X-ray temperature, X-ray luminosity and the optical richness are well known mass tracers. The XCS3P-v3 methodology and the process followed to obtain the scaling relations are validated using four non-redMaPPer cluster catalogs, two from the optical (CAMIRA and GMBCG) and two from the millimiter (SPT and Planck). The results show a clear correlation between X-ray and optical and millimeter observables. This analysis is not a robust as for redMaPPer, thus further work is needed to present this results to the scientific community.

In this thesis, we present the XMM Cluster Survey Second Data Release (XCS-DR2) and use it to test possible spectroscopic biases, fit scaling relations, and find massive, relaxed galaxy clusters. XCS finds clusters in the XMM public archive. The new cluster candidate list includes 15,642 objects found in the 688 square degrees of sky suitable for cluster detection. XCS-DR2 is the largest X-ray selected cluster catalogue to date. It contains 7,129 unique preliminary cluster identifications and 1,177 unique firm cluster identifications. Where redshifts were available, a spectral fitting was made leading to 4,987 unique cluster temperature and luminosity measurements. XCS-DR2 is more than an order of magnitude larger than XCS-DR1. As XCS-DR2 is a catalogue of homogeneously processed galaxy clusters, it is an ideal dataset to test possible spectroscopic biases during X-ray spectral fitting. This thesis answers seven questions related to the combining and fitting of multi-observational data and the instrumental calibration of XMM. Notably we present strong evidence that spectral selection must take place before any final X-ray spectral fitting takes place. XCS-DR1 clusters have been used to fit a luminosity temperature scaling relation. This thesis presents new spectral fitting pipelines, so the previous scaling relations work was revisited to ascertain how the results have changed. Additionally, by using the latest SPT cluster catalogue, a scaling relation was fit between the X-ray and the SunyaevZel'dovich effect properties of XCS-DR2 clusters. Massive, relaxed galaxy clusters have been used to fit cosmological parameters through measurements of their baryon fractions. XCS-DR2 contains 342 clusters observed on-axis with temperature, TX ≥ 4:5 keV. A morphological analysis of these clusters shows that 20 of them appear to be relaxed. When added to the latest analysis, a subsample of six relaxed clusters, can improve ΩM and w estimates by 18% and 12% respectively.

The extended finite element method (XFEM) is found promising in approximating solutions to locally non-smooth features such as jumps, kinks, high gradients, inclusions, or cracks in solid mechanics problems. The XFEM uses the properties of the partition of unity finite element method (PUFEM) to represent the discontinuities without the corresponding finite element mesh requirements. In the present thesis numerical simulations of statically and dynamically loaded heterogeneous beams, heterogeneous plates and two-dimensional cracked media of isotropic and orthotropic constitutive behaviour are performed using XFEM. The examples are chosen such that they represent strong and weak discontinuities, static and dynamic loading conditions, anisotropy and isotropy and strain-rate dependent and independent behaviours. At first, the Timoshenko beam element is studied by adopting the Hellinger-Reissner (HR) functional with the out-of-plane displacement and through-thickness shear strain as degrees of freedom. Heterogeneous beams are considered and the mixed formulation has been combined with XFEM thus mixed enrichment functions are used. The results from the proposed mixed formulation of XFEM correlate well with analytical solutions and Finite Element Method (FEM) and show higher rates of convergence. Thus the proposed method is shear-locking free and computationally more efficient compared to its conventional counterparts. The study is then extended to a heterogeneous Mindlin-Reissner plate with out-of-plane shear assumed constant through length of the element and with a quadratic distribution through the thickness. In all cases the zero shear on traction-free surfaces at the top and bottom are satisfied. These cases involve weak discontinuity. Then a two-dimensional orthotropic medium with an edge crack is considered and the static and dynamic J-integrals and stress intensity factors (SIF's) are calculated. This is achieved by fully (reproducing elements) or partially (blending elements) enriching the elements in the vicinity of the crack tip or body. The enrichment type is restricted to extrinsic mesh-based topological local enrichment in the current work. A constitutive model for strain-rate dependent moduli and Poisson ratios (viscoelasticity) is formulated. The same problem is studied using the viscoelastic constitutive material model implemented in ABAQUS through an implicit user defined material subroutine (UMAT). The results from XFEM correlate well with those of the finite element method (FEM). It is shown that there is an increase in the value of maximum J-integral when the material exhibits strain rate sensitivity.

In Chapter I, I introduce the framework of observational and theoretical evidence that has been constructed to understand the vast range of X-ray characteristics exhibited by late-type stars on the basis of the magnetic dynamo that is thought to power the Sun's own modest X-ray activity, and describe the spectral analysis techniques and X-ray instruments used in this work. In Chapter 2 I present a catalogue-based classification of X-ray sources detected in the ROSAT PSPC Galactic Plane Survey in the Third Quadrant (3QGPS) and use the results to infer a denser spatial distribution of young, X-ray active stars in the local Galaxy than has been traditionally assumed. In Chapter 3 I exploit the high coronal activity of young stars to search for unrecognised members of the Hyades-age open clusters NGC 6633 and IC 4756 in deep ROSAT HRI images, and make a novel comparison of the X-ray activity levels of these clusters with that of the Hyades. In Chapter 4 I explore the X-ray emission from very low mass stars in an XMM-Newton EPIC pointing in the Pleides, finding marginal support for a decline in X-ray activity for stars with spectral types later than " M4 that may be a signature of the changeover to a non-solar-like dynamo in fully-convective stars. I also undertake spectral and variability studies of the X-ray-bright members in the field, and present evidence that the detection of early-type stars in the cluster are fully consistent with emission from late-type companions. In Chapter 5 I perform a time-resolved spectroscopic study of the nearby active K0 star AB Dor using the XMM-Newton EPIC pn, with comparison to a study using the higher-resolution XMM-Newton RGS, investigating the temperature structure and elemental adundance changes during the course of a moderate flare.

La modélisation de la cryolite, utilisée dans la fabrication de l’aluminium, implique plusieurs défis, notament la présence de discontinuités dans la solution et l’inclusion de la difference de densité entre les phases solide et liquide. Pour surmonter ces défis, plusieurs éléments novateurs ont été développés dans cette thèse. En premier lieu, le problème du changement de phase, communément appelé problème de Stefan, a été résolu en deux dimensions en utilisant la méthode des éléments finis étendue. Une formulation utilisant un multiplicateur de Lagrange stable spécialement développée et une interpolation enrichie a été utilisée pour imposer la température de fusion à l’interface. La vitesse de l’interface est déterminée par le saut dans le flux de chaleur à travers l’interface et a été calculée en utilisant la solution du multiplicateur de Lagrange. En second lieu, les effets convectifs ont été inclus par la résolution des équations de Stokes dans la phase liquide en utilisant la méthode des éléments finis étendue aussi. Troisièmement, le changement de densité entre les phases solide et liquide, généralement négligé dans la littérature, a été pris en compte par l’ajout d’une condition aux limites de vitesse non nulle à l’interface solide-liquide pour respecter la conservation de la masse dans le système. Des problèmes analytiques et numériques ont été résolus pour valider les divers composants du modèle et le système d’équations couplés. Les solutions aux problèmes numériques ont été comparées aux solutions obtenues avec l’algorithme de déplacement de maillage de Comsol. Ces comparaisons démontrent que le modèle par éléments finis étendue reproduit correctement le problème de changement phase avec densités variables.
The modelling of the cryolite bath, used in the smelting of aluminum, offers multiple challenges, particularly the presence of discontinuities in the solution and a difference in density between the solid and liquid phases. To over come these challenges, several novel elements were developed in this thesis. First of all, the phase change problem, commonly named the Stefan problem, was solved in two dimensions using the extended finite element method. A specially designed Lagrange multiplier formulation, using an enriched Lagrange multiplier solution, was implemented to impose the melting temperature on the interface. The interface velocity is determined by the jump in the heat flux across the interface and was calculated using the Lagrange multiplier values. Secondly, convection was included by solving the Stokes equations in the liquid phase using the extended finite element method as well. Thirdly, the density change between solid and liquid phases, usually neglected in the literature, was taken into account by the addition of a non-zero velocity boundary condition at the solid-liquid interface to maintain mass conservation in the system. Benchmark analytical and numerical problems were solved to validated the various components of the model and the coupled system of equations. The solutions to the numerical problems were compared to the solutions obtained using Comsol’s moving mesh algorithm. Theses comparisons show that the extended finite element method correctly solves the phase change problem with non-constant densities.

M-type red dwarfs are among the most active stars. Their light curves display random variability of rapid increase and gradual decrease in emission. It is believed that these large energy events, or flares, are the manifestation of the permanently reforming magnetic field of the stellar atmosphere. Stellar coronal flares are observed in the radio, optical, ultraviolet and X-rays. With the new generation of X-ray telescopes, XMM-Newton and Chandra, it has become possible to study these flares in much greater detail than ever before. This thesis focuses on three core issues about flares: (i) how their X-ray emission is correlated with the ultraviolet, (ii) using an oscillation to determine the loop length and the magnetic field strength of a particular flare, and (iii) investigating the change of density sensitive lines during flares using high-resolution X-ray spectra, (i) It is known that flare emission in different wavebands often correlate in time. However, here is the first time where data is presented which shows a correlation between emission from two different wavebands (soft X-rays and ultraviolet) over various sized flares and from five stars, which supports that the flare process is governed by common physical parameters scaling over a large range. (ii) As it is impossible to spatially resolve any but a very few giant stars, the only information on spatial dimensions as well as the magnetic field strength of stellar coronae has to come from indirect measurements. Using wavelet analysis, I isolated the first stellar X-ray flare oscillation. Interpreting it as a standing coronal flare loop oscillation, I derived a flare loop length as well as the magnetic field strength for this X-ray flare. (iii) The high-resolution soft X-ray spectra of Chandra and XMM-Newton allow us to determine temperatures, densities and abundances of the stellar coronae. De spite a low signal-to-noise ratio because of the relatively short duration of a flare, we find that, if adding up the photons of several flares, certain density sensitive spectral lines change significantly between quiescent and flaring states. This project led on to investigate the flaring spectrum further, and it is found that the plasma is no longer in collisional ionisation equilibrium, but that it is dominated by recombinations.