Metal Additive Manufacturing (AM) provides the means to fabricate complex metallic parts with reduced time to market and material waste and improved design freedom. Industries with strict materials qualifications such as aerospace, biomedical, and automotive are increasingly looking to AM to meet their production needs. However, significant materials-related challenges impede the widespread adoption of these technologies for critical components. In particular, fatigue resistance in as-built parts has proven to be inferior and unpredictable due to the large and variable presence of porosity. This presents a challenge for the qualification of any load bearing part without extensive post-processing, such as Hot Isostatic Pressing, and thorough inspection. Improved understanding of the underlying mechanisms behind defect formation will assist in designing process improvements to minimize or eliminate defects without relying entirely on postprocessing. In this work, the effects of powder, processing parameters, and post-processing on porosity formation in powder-bed metal AM processes are investigated using X-ray microtomography and a newly developed in-situ high speed radiography technique, Dynamic Xray Radiography. High resolution X-ray computed tomography is used to characterize defect morphology, size, and spatial distribution as a function of process and material inputs. Dynamic X-ray Radiography, which enables the in-situ observation of the laser-metal interactions at frame rates on the order of 100 kHz (and faster), is utilized to understand the dynamic behavior and transitions that occur in the vapor depression across process space. Experimental validation of previously held assumptions regarding defect formation as well as new insights into the influence of the vapor cavity on defect formation are presented.

Anomaly detection requires a system that can reliably convert measurements of an object into knowledge about that object. Previously, we have shown that an information-theoretic approach to the design and analysis of such systems provides insight into system performance as it pertains to architectural variations in source fluence, view number/angle, spectral resolution, and spatial resolution.(1) However, this work was based on simulated measurements which, in turn, relied on assumptions made in our simulation models and virtual objects. In this work, we describe our experimental testbed capable of making transmission x-ray measurements. The spatial, spectral, and temporal resolution is sufficient to validate aspects of the simulation-based framework, including the forward models, bag packing techniques, and performance analysis. In our experimental CT system, designed baggage is placed on a rotation stage located between a tungsten-anode source and a spectroscopic detector array. The setup is able to measure a full 360 rotation with 18,000 views, each of which defines a 10 ms exposure of 1,536 detector elements, each with 64 spectral channels. Measurements were made of 1,000 bags that comprise 100 clutter instantiations each with 10 different target materials. Moreover, we develop a systematic way to generate bags representative of our desired clutter and target distributions. This gives the dataset a statistical significance valuable in future investigations.

Submitted by Rafael Santana (rafael.silvasantana@ufpe.br) on 2017-07-10T19:30:23Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertacao - Pedro Negrão.pdf: 2417925 bytes, checksum: 563fc37dbb3bf794487bc4e3c8fc102a (MD5) / Made available in DSpace on 2017-07-10T19:30:23Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertacao - Pedro Negrão.pdf: 2417925 bytes, checksum: 563fc37dbb3bf794487bc4e3c8fc102a (MD5) Previous issue date: 2016-03-29 / CAPES / As argilas compõem um grupo de matérias-primas muito importante devido a suas múltiplas funções industriais. Em especial o caulim, possui propriedades físicas e químicas que possibilitam a sua utilização no processo industrial de uma grande gama de produtos, desde matéria-prima para a indústria cerâmica, de carga e cobertura de papel, entre outras. Esta pesquisa objetivou descrever, através da caracterização mineralógica, análise química, análise granulométrica, ensaios tecnológicos e de plasticidade, as características do material arenocaulinítico sondado no município de Igarassu – PE, ocorrência localizada próxima ao bairro de Nova Cruz 2. O material foi coletado através de sondagem a trado, tendo as amostras passado por análise mineralógica por difração de raios X, análise química por fluorescência de raios X, análise granulométrica, ensaios de plasticidade e foram confeccionados corpos de prova para a realização de ensaios tecnológicos. Os resultados obtidos foram comparados com as características de caulins de outros jazimentos descritos na literatura e com as especificações dos caulins aproveitados industrialmente. / Clays form a group of so important raw materials due to its multiple industrial functions. In particular, the kaolin has physical and chemical properties which allow its use at the industrial process a wide range of products from a raw material for ceramic industry, filler and paper coating, among others. This research aimed to describe through mineralogical characterization, chemical analysis, particle size analysis, technological tests and plasticity characteristics of sandy-kaolinitic materials collected in the city of Igarassu - PE, occurrence located near the Nova Cruz 2. The material was got by auger boring, the samples submitted to a mineralogical analysis through X ray diffraction, chemical analysis through X ray fluorescence, particle size analysis, plasticity tests and was prepared specimens to be performed for the technological tests. The results obtained were compared with the characteristics of kaolin of other deposits described in the literature and with the specifications of kaolin exploited industrially.

Bi-annual report on the activities at the ROssendorf BeamLine (ROBL) at the ESRF in Grenoble. The report contains selected contributions on actual research topics, a list of all scheduled experiments, and short experimental reports.

Galaxies are astronomically large systems that consist of vast amounts of stars, and in between there exists the interstellar medium. This medium consists of clouds of gas which play an important role in a galaxy’s history and formation. With the right conditions a region can experience a period of star formation which we measure with a Star Formation Rate (SFR). The lifecycle of stars can create outbursts of hot gas which collapse back into the galaxy over time to contribute more to the interstellar medium. The gas is hot enough to release X-rays which we can detect with orbiting space observatories such as NASA’s Chandra Telescope. By studying these hot, high energy regions we can relate them to other known properties of galaxies to give us insight on the processes of merging systems. Using archival data from Chandra we measured the spatial extent of the soft diffuse X-ray-emitting hot interstellar gas in a sample of 49 local merging galaxies. The galaxies or galaxy pairs are classified by merger stage based on their morphology. The stages range from post-merger remnants to premerger pairs in which two separate regions could be identified. After processing the data, we made initial estimates of the regions based on their optical extent. X-ray counts were extracted and background counts from the nearby sky were subtracted for calibration. An iterative procedure was used to produce and modify elliptical radial profiles by size and position angle until a good fit was found. The best fit radius was defined as the point where the background subtracted counts decreased to less than twice the uncertainty. With an accurate estimate of the region sizes, we infer a third dimension to find the volumes of the regions. The inferred volumes were used to calculate electron densities and total masses of the hot interstellar gas. Relationships among hot, molecular, and atomic gas were investigated and plotted to determine any trends. Our results show a strong correlation between the volume of hot gas and SFR. Another strong trend was between volume and X-ray luminosity. The SFR is correlated with the ratio of hot to cold gas. Galaxies with higher SFRs have proportionally more hot gas relative to the cold gas. These relationships show that major mergers have regions of starbursts which expel hot gas, and the more numerous the young stars, the larger the volume of hot gas. Future research in this area can reveal more about the process of merging and the evolution of galaxies.

The main focus of this thesis is on the phase retrieval problem. This problem has a broad range of applications in advanced imaging systems, such as X-ray crystallography, coherent diffraction imaging, and astrophotography. Thanks to its broad applications and its mathematical elegance and sophistication, phase retrieval has attracted researchers with diverse backgrounds. Formally, phase retrieval is the problem of recovering a signal 𝔁 ∈ ℂⁿ from its phaseless linear measurements of the form |𝛼ᵢ∗𝔁| + 𝜖ᵢ where sensing vectors 𝛼ᵢ, 𝑖 = 1, 2, ..., 𝓶, are in the same vector space as 𝔁 and 𝜖ᵢ denotes the measurement noise. Finding an effective recovery method in a practical setup, analyzing the required sample complexity and convergence rate of a solution, and discussing the optimality of a proposed solution are some of the major mathematical challenges that researchers have tried to address in the last few years. In this thesis, our aim is to shed some light on some of these challenges and propose new ways to improve the imaging systems that have this problem at their core. Toward this goal, we focus on the high-dimensional setting where the ratio of the number of measurements to the ambient dimension of the signal remains bounded. This regime differs from the classical asymptotic regime in which the signal's dimension is fixed and the number of measurements is increasing. We obtain sharp results regarding the performance of the existing algorithms and the algorithms that are introduced in this thesis. To achieve this goal, we first develop a few sharp concentration inequalities. These inequalities enable us to obtain sharp bounds on the performance of our algorithms. We believe such results can be useful for researchers who work in other research areas as well. Second, we study the spectrum of some of the random matrices that play important roles in the phase retrieval problem, and use our tools to study the performance of some of the popular phase retrieval recovery schemes. Finally, we revisit the problem of structured signal recovery from phaseless measurements. We propose an iterative recovery method that can take advantage of any prior knowledge about the signal that is given as a compression code to efficiently solve the problem. We rigorously analyze the performance of our proposed method and provide extensive simulations to demonstrate its state-of-the-art performance.

The objective of this work is the synthesis of highly functionalized hybrid organic/inorganic materials by the polycondensation of bis[3-(trimethoxysilyl) propyl]amine in the presence of surfactants. High contents of amine groups were achieved by carrying out the syntheses without an inorganic cross-linker. The silsesquioxanes obtained had a mesoporous structure. The stability of their porous system in the absence of an inorganic cross-linker was enhanced by the precursor's bridged structure. The material structures were studied by FT-IR spectroscopy, Porosimetry, X-Ray Diffraction and Small Angle X-Ray Scattering methods. A material prepared in the presence of dodecylamine as a template had a higher surface area and narrower pore size distribution while the use of sodium dodecyl sulfate resulted in the formation of mesopores with a wide size distribution. Surface amine groups in silsesquioxanes were accessible for adsorption of small molecules of acidic nature.

Les systèmes neuronaux et vasculaires nécessitent un réseau complexe pour exécuter correctement leurs fonctions. Les processus impliqués dans la création de ce réseau s'appuient sur des voies coordonnées, souvent activées par des systèmes protéine/récepteur communs, qui conduisent au remodelage du cytosquelette.En général, les cellules neuronales et vasculaires répondent aux stimuli extracellulaires sous forme de protéines solubles sécrétées, qui interagissent avec les récepteurs de surface pour favoriser l'attraction ou la répulsion vers la source des protéines sécrétées. Ce processus, appelé guidage, est régulé par sept familles de récepteurs et leurs ligands respectifs, qui s'influencent les uns sur les autres et peuvent agir sur le système neuronal, le système vasculaire ou les deux ensembles.Cette étude est centrée sur deux récepteurs transmembranaires à passage unique, les membres des familles de protéines Roundabout et UNC5 qui sont principalement impliquées dans l'angiogenèse: Robo4 et UNC5B.L'information structurelle sur la région extracellulaire de plusieurs de ces récepteurs, et comment le signal est relayé à travers la membrane, fait défaut.La déglycosylation enzymatique a confirmé que les domaines extracellulaires de Robo4 et UNC5B sont largement glycosylés avec des glycanes liés en azote du complexe type. La mutagenèse dirigée des sites de glycosylation prédits de Robo4 perturbe son expression, indiquant que ces résidus sont nécessaires pour la stabilité de la protéine et que leur glycosylation, ou leur passage dans la voie de glycosylation, pourrait être nécessaire pour un repliement correct. Les données MALS et SAXS montrent qu'en solution, Robo4 ecto est un monomère flexible de forme allongée. Les domaines ne présentent pas des caractéristiques distinctes dans le modèle construit à partir des données SAXS. Plusieurs Fabs se liant au domaine extracellulaire de Robo4 ont été caractérisés, avec l'espoir d'identifier les Fab qui pourraient inhiber l'interaction Robo4 / UNC5B rapportée pour une caractérisation plus poussée. La formation du complexe a été vérifiée par SEC-MALS et SAXS, et les constantes d'interaction ont été déterminées en utilisant SPR. Des cristaux de certains complexes domaine Fab / domaine extracellulaire Robo4 ont été produits, bien que la structure du complexe n'ait pas pu être résolue à l'heure actuelle.Les expériences de pull-down, SEC-MALS et SPR montrent que Robo4 ecto et UNC5B ecto n'interagissent pas entre elles, malgré une étude par un autre groupe montrant le contraire. Étant donné que différentes lignées cellulaires ont été utilisées, des modèles de glycosylation spécifiques, ou une tierce partie non détectée, pourraient être nécessaires pour l'interaction. En raison de leur implication avec les récepteurs extracellulaires, les héparanes sulfates sont un candidat probable, mais d'autres partenaires devraient être envisagés.La structure cristallographique de l'UNC5B ecto est similaire aux structures existantes de UNC5A et UNC5D. Le haut degré de conservation des domaines del’Ig pourrait être une indication de l'importance de cette région, qui est responsable de la liaison à Netrin. Bien que la région de liaison de Netrin soit connue pour être dans les domaines Ig, le site de liaison précis n'a pas encore été déterminé, mais il pourrait être situé à proximité ou à l'intérieur des surfaces chargées négativement présentes sur les domaines Ig observées dans la structure d’UNC5B.Le travail présenté ici devrait servir de base à une meilleure caractérisation biochimique et structurale des récepteurs extracellulaires Robo4 et UNC5B. / Neuronal and vascular systems require a complex network to properly perform their functions. The processes involved in creating this network rely on coordinated pathways, often activated through common protein/receptor systems, which lead to cytoskeletal remodelling. In general, neuronal and vascular cells respond to extracellular stimuli in the form of soluble secreted proteins, which interact with surface receptors to mediate attraction or repulsion towards the source of the secreted proteins. This process, called guidance, is regulated by seven families of receptors and their respective ligands, which influence each other and can act on the neuronal system, the vascular system or both.Structural information about the extracellular region of many of these receptors, and how signal is relayed across the membrane, is lacking.This study is focused around the extracellular domain of two single-pass transmembrane receptors of the Roundabout and UNC5 protein families that are majorly involved in angiogenesis: Robo4 and UNC5B.Based on the findings of this study, the Robo4 and UNC5B extracellular domains are extensively glycosylated with N-linked glycans of the complex type. Site-directed mutagenesis of the predicted Robo4 glycosylation sites disrupts protein expression, indicating that they are necessary for protein stability and passage through the glycosylation pathway might be necessary for correct folding. MALS and SAXS data show that in solution the Robo4 extracellular domain is a flexible monomer with extended shape. Several Fabs binding to the extracellular domain of Robo4 were characterised, with the expectation to identify those Fabs that could inhibit the reported Robo4/UNC5B interaction for further characterisation. Complex formation was verified by SEC-MALS and SAXS, and interaction constants were determined using SPR. Crystals of some Robo4 extracellular domain/Fab complexes were produced, although the structure of the complex could not be solved at the present time.Despite a study by another group showing otherwise, pull-down, SEC-MALS and SPR experiments show that the Robo4 and UNC5B extracellular domains do not interact with each other. It is proposed that the difference may be caused by different glycosylation patterns specific to the cell lines used for each study, or by an undetected third party necessary for interaction. This, however, still requires further study. SEC-MALS analysis showed that the UNC5B extracellular domain is a monomer in solution and its crystal structure was solved at 3.4 Å resolution. Comparison to the existing structures of human UNC5A and rat UNC5D shows striking similarities and a high degree of evolutionary conservation of the Ig domains might be indication of the importance of this region, which is responsible for binding to the guidance cue Netrin. Although the Netrin binding region is known to be within the Ig domains, the precise binding site has not yet been determined, but it might be located in proximity, or within, the negatively charged surfaces present on the Ig domains which are observed in the UNC5B structure.It is hoped that the work presented here will give the basis for better biochemical and structural characterisation of these two receptors.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20912号 / 理博第4364号 / 新制||理||1626(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 井岡 邦仁, 教授 川合 光, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The science and technology of X-rays has only been part of human achievement for the past 100 years, while the study of image formation in general has endured for as long as 1000 years. The ability to conceive, design, and fabricate X-ray imagers, moreover, has existed for only the past 70 years, and X-ray astronomical telescopes have been in use for a mere 35 years. Considering that aplanatic, normal incidence telescope designs required more than 400 years to perfect, it is most interesting to note that the development of ‘aplanatic’ grazing incidence telescopes has taken only about 40 years. In order to improve and expand the field of X-ray astronomy, and imaging in general, we find that these days a comprehensive systems engineering approach to X-ray image formation must be undertaken. While some industrial interests have taken steps in this direction, any academic approach is lacking from within the archival literature to date, and there are virtually no established university courses. Indeed, it would seem that top level, optical-systems-engineering is exclusively reserved for those seasoned professionals who have accumulated (though somewhat artistically) the “know-how” to efficiently conceive and implement excellent optical designs. Such expert knowledge is not and should not be mysterious. To this end, we attempt to formulate a highly comprehensive approach to X-ray optical systems engineering and implement it within the context of the Wolter Type-I and Type-II (grazing incidence) telescopes currently utilized for practical X-ray/EUV astronomy. In addition, we will transform the classical paraboloid-hyperboloid designs into ‘aplanatic’ and ‘isoplanatic’, hyperboloid-hyperboloid systems, where certain coma conditions are minimized. As will be shown, one gains little improvement in performance when choosing a quasi-aplanatic mirror design over a classical one, owing to scatter and other image degradation effects. Next we will show that a generalized hyperboloid-hyperboloid design can be comprehensively optimized for any imaging requirement, where the operational field-of-view is weighted according to spatial information content. Our H-H design has been optimized for the GOES Solar X-ray Imager mission and adopted by NASA and NOAA. It is currently undergoing fabrication by Raytheon Optical Systems Inc. who is under subcontract to the Lockheed-Martin Solar and Astrophysics Laboratory. Our design is expected to result in an 80% increase in optical system performance over the original SXI baseline design.