Afin d'améliorer la sûreté (dose plus faible) et la productivité (acquisition plus rapide) du système de la tomographie par rayons X (CT), nous cherchons à reconstruire une image de haute qualitée avec un faible nombre de projections. Les algorithmes classiques ne sont pas adaptés à cette situation et la reconstruction est instable et perturbée par des artefacts. L'approche "Compressed Sensing" (CS) fait l'hypothèse que l'image inconnue est "parcimonieuse" ou "compressible", et la reconstruit via un problème d'optimisation (minimisation de la norme TV/L1) en promouvant la parcimonie. Pour appliquer le CS en CT, en utilisant le pixel/voxel comme base de representation, nous avons besoin d'une transformée parcimonieuse, et nous devons la combiner avec le "projecteur du rayon X" appliqué sur une image pixelisée. Dans cette thèse, nous avons adapté une base radiale de famille Gaussienne nommée "blob" à la reconstruction CT par CS. Elle a une meilleure localisation espace-fréquentielle que le pixel, et des opérations comme la transformée en rayons-X, peuvent être évaluées analytiquement et sont facilement parallélisables (sur plateforme GPU par exemple). Comparé au blob classique de Kaisser-Bessel, la nouvelle base a une structure multi-échelle : une image est la somme des fonctions translatées et dilatées de chapeau Mexicain radiale. Les images médicales typiques sont compressibles sous cette base. Ainsi le système de representation parcimonieuse dans les algorithmes ordinaires de CS n'est plus nécessaire. Des simulations (2D) ont montré que les algorithmes TV/L1 existants sont plus efficaces et les reconstructions ont des meilleures qualités visuelles que par l'approche équivalente basée sur la base de pixel-ondelettes. Cette nouvelle approche a également été validée sur des données expérimentales (2D), où nous avons observé que le nombre de projections en général peut être réduit jusqu'à 50%, sans compromettre la qualité de l'image. / To improve the safety (lower dose) and the productivity (faster acquisition) of an X-ray CT system, we want to reconstruct a high quality image from a small number of projections. The classical reconstruction algorithms generally fail since the reconstruction procedure is unstable and the reconstruction suffers from artifacts. The "Compressed Sensing" (CS) approach supposes that the unknown image is in some sense "sparse" or "compressible", and reoncstructs it through a non linear optimization problem (TV/$llo$ minimization) by enhancing the sparsity. Using the pixel/voxel as basis, to apply CS framework in CT one usually needs a "sparsifying" transform, and combine it with the "X-ray projector" applying on the pixel image. In this thesis, we have adapted a "CT-friendly" radial basis of Gaussian family called "blob" to the CS-CT framework. It have better space-frequency localization properties than the pixel, and many operations, such as the X-ray transform, can be evaluated analytically and are highly parallelizable (on GPU platform). Compared to the classical Kaisser-Bessel blob, the new basis has a multiscale structure: an image is the sum of dilated and translated radial Mexican hat functions. The typical medical objects are compressible under this basis, so the sparse representation system used in the ordinary CS algorithms is no more needed. Simulations (2D) show that the existing TV/L1 algorithms are more efficient and the reconstructions have better visual quality than the equivalent approach based on the pixel/wavelet basis. The new approach has also been validated on experimental data (2D), where we have observed that the number of projections in general can be reduced to about 50%, without compromising the image quality.

The majority of cloud storage platforms rely on a centralized structure, with the most popular being Microsoft Azure. Centralization causes consumers to rely on the provider to maintain accessibility and security of data. However, platforms such as Storj.io are based on a decentralized structure. To become decentralized, Storj.io uses blockchain technology in a means to create an automated consensus mechanism between the entities storing the data. There is however little research regarding performance and security issues on a decentralized platform based on blockchain technology. The purpose of this study is to identify the beneficial and non-beneficial aspects of using blockchain-based decentralized cloud storage as a substitute for centralized ones. The study focuses on performance and security. A comparative case study has been executed, consisting of an experiment and literature study. Quantitative data from an experiment was used in a hypothesis test to determine whether there were any performance differences between Microsoft Azure Blob Storage and Storj.io. A literature study generating qualitative data was then made to identify differences in security measures and from that also discuss potential security risks on a service like Storj.io. This study found that the performance of Storj.io was lower than Microsoft Azure’s Blob Storage. Causes of these results were identified to be due to the many more steps during resource allocation in Storj.io, compared to Blob Storage. Security risks identified in Storj.io through the literature study were generally connected to the consensus mechanism. However, research shows that it is very unlikely for the consensus mechanism to be compromised. Because Microsoft Azure’s service does not use a blockchain, these risks do not exist. For secure data transfer to Azure’s service, consumers have to implement encryption manually client-side. Therefore, this study could not conclude whether Storj.io is a safe alternative because a consumer using the Microsoft Azure service is responsible for implementing security measures. Conclusions drawn from this study are intended to act as new knowledge in the field of blockchain-based decentralized cloud storage. It is an outset to decide whether to use centralized cloud storage or blockchain-based decentralized cloud storage from a performance and security perspective. / Majoriteten av datalagringsmolntjänsterna är centraliserade, varav Microsoft Azure står som den mest använda molntjänsten. Centralisering innebär att konsumenten behöver lita på att värdföretaget hanterar tillgänglighet och säkerheten av data på bästa möjliga sätt. I kontrast mot en centraliserad molnplattform finns Storj.io som är en decentraliserad molnlagringstjänst. För att åstadkomma decentralisering använder sig Storj.io av blockkedjan som används för att uppnå den autonoma konsensusmekanismen mellan noderna som lagrar data. Syftet med denna studie är att identifiera för- respektive nackdelarna med en decentraliserad blockkedjebaserad molnplattform i jämförelse mot en centraliserad molnplattform. Specifikt fokuserar studien på prestanda och säkerhet. En komparativ fallstudie har utförts med ett experiment och en litteraturstudie som datainsamlingsmetoder. Den kvantitativa datan från experimentet användes i en hypotesprövning för att identifiera om det fanns någon skillnad i prestanda mellan Microsoft Azure och Storj.io. Litteraturstudien användes i syfte för att kunna styrka skillnader om säkerhetsåtgärder och säkerhetsrisker mellan molnplattformarna. Resultatet av denna studie visar att prestandan för Storj.io är lägre än Microsoft Azures molnplattform. De identifierade faktorerna som orsakade resultatet anses vara på grund av de flertal steg som krävs vid resursallokering för Storj.io. De säkerhetsrisker som uppstår hos Storj.io kom till i samband med konsensusmekanismen. För att en säkerhetsrisk skall uppstå mot konsensusmekanismen behöver det decentraliserade nätverket hotas med majoritet. Eftersom Microsoft Azure inte använder sig av blockkedjan uppstår inte dessa typer av säkerhetsrisker. För dataöverföring till Azures datalagringstjänst behöver konsumenten själv säkerställa en krypterad kommunikationskanal. I Storj.ios fall sköts alla typer av säkerhetsåtgärder automatiskt vilket eliminerar risken för säkerhetsattacker vid överföringar. Sammanfattningsvis tyder denna studie på att Storj.io inte är ett optimalt val vid prioritering av prestanda. Eftersom konsumenten som använder Microsoft Azures tjänst ansvarar för säkerhetsåtgärder drogs ingen direkt slutsats huruvida Storj.io är ett säkert substitut. Studien visar på att det existerar konensusrisker med en tjänst som Storj.io och det är upp till envar konsument att förlita sig på att dessa inte uppstår. De slutsatser som har dragits från denna studie är avsedda som ny kunskap inom fältet som berör decentraliserade molnplattformar baserade på blockkedjan. Studien kan användas som en utgångspunkt för val mellan en centraliserad och decentraliserad molntjänst baserad på blockkedjan med prioritet för prestanda och säkerhet.

The diploma thesis deals with the usage of integrated machine vision by B&R, Smart Sensor, for metal rectangular-shaped workpiece recognition and position determinition. The description of the usage of machine vision in the industry is made, the solution concept is created and the program and the user visualisation implemented. The main outcome of this work is the VITemplate library which can be used in combination with the model-based Blob analysis implemented in Smart Sensor to control the robotic arm to successfully grab all the workpieces on the belt.

The biological function of a protein is determined by its amino acid sequence, structure, and internal dynamics. In turn the prediction of a protein structure from its folding pathway involves the characterization of the dynamics of the polypeptide backbone. This study addresses how the internal dynamics of arborescent polypeptides are affected by increased crowding of the interior of these branched polymer molecules. Linear, comb-branched, and arborescent poly(L-glutamic acid) (PGA) samples were analyzed by 1H NMR spectroscopy to determine their chain conformation. The PGA chains of these constructs were shown to adopt α-helical and random coil conformations in N,N-dimethylformamide (DMF) and in dimethyl sulfoxide (DMSO), respectively. The hydrodynamic diameter (Dh) of the arborescent PGAs, determined using dynamic light scattering measurements, increased with increasing generation number and when the side-chains adopted random coil instead of α-helical conformations. The PGA samples were labelled with 1-pyrenemethylamine to determine how their structure affected the internal dynamics of the arborescent polymers in solution, from the analysis of their fluorescence spectra and decays. For each pyrene-labelled polymeric construct excimer formation increased with increasing pyrene content, and the efficiency of excimer formation increased with the generation number due to the increased density of the macromolecules. Comparison of the time-resolved fluorescence results acquired in DMF and in DMSO demonstrated that the helical conformation led to slower chain dynamics in DMF and that despite the higher viscosity of DMSO, the polypeptide side-chains were more mobile as a consequence of the random coil conformation of the linear PGA segments. These results suggest that the formation of structural motives inside a polypeptide slows down its internal dynamics.

This thesis describes work on building numerical models of the Earth's magnetosphere using magnetohydrodynamics (MHD) and other related modeling methods. For many years, models that solve the MHD equations have been the main tool for improving our theoretical understanding of the large-scale dynamics of the Earth's magnetosphere. While the MHD models have been very successful in capturing many large-scale features, they fail to adequately represent the important drift physics in the inner magnetosphere. Consequently, the ring current, which contains most of the particle energy in the inner magnetosphere, is not realistically represented in MHD models. In this thesis, Chapter 2 and 3 will describe in detail our effort to couple the OpenGGCM (Open Geospace General Circulation Model), one of the major MHD models, to the Rice Convection Model (RCM), an inner magnetosphere ring current model, with the goal of including energy dependent drift physics into the MHD model. In Chapter 4, we will describe an initial attempt to use a direct-integration method to calculate Birkeland currents in the MHD code. Another focus of the thesis work, presented in Chapter 5, addresses a longstanding problem on how a geomagnetic substorm can occur within the closed field line region of the tail. We find a scenario of a bubble-blob pair formation in an OpenGGCM simulation just before the expansion phase of the substorm begins and the subsequent separation of the bubble and the blob decreases the normal component of the magnetic field until finally an X-line occurs. Thus the formation of the bubble-blob pair may play an important role in changing the magnetospheric configuration from a stretched field to the X-line formation that is believed to be the major signature of a substorm.

Time-resolved fluorescence was applied to linear and branched pyrene-labelled macromolecules to study their internal dynamics. The linear macromolecules consisted of two series of pyrene-labelled poly(N-isopropylacrylamide)s where the polymer was either end-labelled (Py2-PNIPAM-Y where Y represents the molecular weight of the polymer and equals 6, 8, 14, 25, and 45 kDa) or randomly labelled (Py-PNIPAM-X% where X represents the pyrene content and is equal to 0.1, 2, 3, 4, 5, and 6 mol%) with pyrene. Four dendrimer generations based on a bis(hydroxymethyl)propionic acid backbone represented the branched macromolecules where the terminal sites were labelled with pyrene (PyX-GY-COOH where X represents the number of pyrene units incorporated into the Y`th generation dendrimer). A polystyrene-dendrimer hybrid was also synthesized (PyX-GY-PS). The fluorescence decays of the Py2-PNIPAM-Y and Py-PNIPAM-X% samples were acquired in solvents of varying viscosity and were analyzed with the Birks Scheme and the Fluorescence Blob Model (FBM) to yield the excimer formation rate constants and , respectively. The two parameters showed the same trends with varying viscosity, implying that the same information concerning chain dynamics is obtained from the randomly and end-labelled PNIPAM samples. The fluorescence decays of the Py2-PNIPAM-Y samples were acquired in ethanol and in water to determine how pyrene solubility affects the behavior of the polymers in solution, as probed by time-resolved fluorescence. It was found that the decreased pyrene solubility in water led to large amounts of intra- and intermolecular pyrene aggregation. Finally, the pyrene-labelled dendrimers were studied in tetrahydrofuran (THF) to probe the mobility of the chain ends as a function of generation number. The average rate of excimer formation, , obtained from the Model-Free analysis of the fluorescence decays in THF, increased linearly with generation number. This finding, combined with molecular mechanics optimizations, led to the conclusion that excimer formation was greatly enhanced due to the branched nature of the dendrimer molecule. Together, these studies illustrate three different applications of the use of time-resolved fluorescence to characterize the internal dynamics of pyrene-labelled macromolecules.

A series of pyrene end-labeled monodisperse poly(ethylene oxide)s (PEO(X)-Py2 where X represents the number average molecular weight (Mn) of the PEOs and equals 2, 5, 10 and 16.5 K) and one pyrene mono-labeled PEO (PEO(2K)-Py1) were synthesized and characterized in solution using fluorescence. First, the end-to-end cyclization (EEC) of PEO(X)-Py2 was investigated in seven organic solvents with viscosities (η) ranging from 0.32 to 1.92 mPa•s. The classical Birks scheme was used to globally fit the pyrene monomer and excimer fluorescence decays. The fraction of pyrenes that did not form excimer (ffree) was found to increase with increasing η and Mn. This result was contrary to the assumptions made by Birks’ scheme. To account for this, ffree was assumed to represent the fraction of PEO chains other than the monolabeled polymer impurities that cannot accomplish EEC. A fluorescence blob model (FBM) was applied to handle this assumption in the process of excimer formation for the PEO(X)-Py2 samples in solution. The radius of a blob, Rblob, in organic solvents was determined according to the results retrieved from the FBM. To quantitatively account for the existence of pyrene impurity in pyrene-labeled macromolecules, known amounts of PEO(2K)-Py1 were added into a PEO(2K)-Py2 solution and the fluorescence decays were fitted globally according to the Birks scheme and “model free” (MF) analysis to verify the validation of the MF analysis. The MF analysis was then applied to determine the amounts of 1-pyrenebutyric acid (PyBA) that had been added to a solution of pyrene end-labeled fourth generation dendritic hybrid (Py16-G4-PS). The results demonstrated that the contribution from unwanted fluorescent species could be isolated and quantitatively accounted for by fitting the fluorescence decays of the pyrene monomer and excimer globally with the MF analysis. Since the PEO(X)-Py2 samples form hydrophobic pyrene aggregates in aqueous solution, a sequential model (SM) was proposed to characterize the pyrene excimer formation of PEO(X)-Py2 in water at different polymer concentration (CP). The capture distance over which the pyrenyl end-groups experience hydrophobic forces in water was determined by assuming that the end-to-end distances of the PEO(X)-Py2 samples adopt a Gaussian distribution and that the fraction of pyrenes that are aggregated (fE0) determined by the sequential model corresponds to the fraction of PEO(X)-Py2 chains whose end-to-end distance is smaller than the hydrophobic capture distance. Since a surfactant can interact with a hydrophobically modified water-soluble polymer in aqueous solution, the interactions taking place between PEO(X)-Py2 and sodium dodecyl sulfate (SDS) were investigated at a low PEO(X)-Py2 concentration. The pyrene monomer and excimer fluorescence decays of the PEO(X)-Py2 and SDS solutions were acquired at various SDS concentrations and globally fitted according to the MF analysis to retrieve the parameters that described the kinetics of pyrene excimer formation. At high SDS concentrations above the critical micelle concentration (CMC), the pyrene end-groups of the short-chain samples (PEO(2K)-Py2 and PEO(5K)-Py2) were incorporated inside the same micelle and excimer was formed intramolecularly, while most pyrene groups of the long-chain samples (PEO(10K)-Py2 and PEO(16.5K)-Py2) were isolated into different micelles. Lastly, both the rheological properties and fluorescence behavior of a pyrene-labeled hydrophobically-modified alkali-swellable emulsion (Py-HASE) polymer in basic aqueous solution with SDS were studied. Furthermore, a joint experimental setup that combined a rheometer and a steady-state fluorometer was applied to investigate at the molecular level the effect that a shearing force had on the polymeric network. However, despite the dramatic decrease in solution viscosity with increasing shear rate, no change in the fluorescence spectra was detected, suggesting that changes in the polymeric network that affected the balance of intra- versus intermolecular pyrene associations did not impact the process of excimer formation. Together the experiments described in this thesis represent the broadest set of examples found in the scientific literature where information on the dynamics and level of association of pyrene-labeled polymers has been retrieved through the quantitative analysis of the fluorescence decays acquired with pyrene-labeled polymers in solution.

Cette thèse est consacrée à l'étude des «blobs à haute excitation»<br />(HEBs), phase caractéristique de la formation des étoiles massives,<br />encore mal connue. Ces objets sont des régions HII compactes des<br />Nuages de Magellan, observables dans le domaine optique. Par le biais d'observations à haute résolution angulaire (HST, ainsi que<br />restoration d'images de téléscopes au sol), j'ai mis en évidence les différentes populations stellaires associées aux blobs. Des<br />observations proche-IR (VLT) m'ont également permis de sonder<br />l'environnement extrêmement hétérogène de ces objets. De plus, une<br />étude spectroscopique m'a permis de définir une nouvelle catégorie de ces objets : les blobs à faible excitation (LEBs). Cet ensemble de données m'a permis de mener une étude détaillée de plusieurs<br />propriétés physiques de ces objets et souligne l'intérêt de leur étude avec les instruments en cours de réalisation (ALMA, JWST, etc.).

Time-resolved fluorescence was applied to linear and branched pyrene-labelled macromolecules to study their internal dynamics. The linear macromolecules consisted of two series of pyrene-labelled poly(N-isopropylacrylamide)s where the polymer was either end-labelled (Py2-PNIPAM-Y where Y represents the molecular weight of the polymer and equals 6, 8, 14, 25, and 45 kDa) or randomly labelled (Py-PNIPAM-X% where X represents the pyrene content and is equal to 0.1, 2, 3, 4, 5, and 6 mol%) with pyrene. Four dendrimer generations based on a bis(hydroxymethyl)propionic acid backbone represented the branched macromolecules where the terminal sites were labelled with pyrene (PyX-GY-COOH where X represents the number of pyrene units incorporated into the Y`th generation dendrimer). A polystyrene-dendrimer hybrid was also synthesized (PyX-GY-PS). The fluorescence decays of the Py2-PNIPAM-Y and Py-PNIPAM-X% samples were acquired in solvents of varying viscosity and were analyzed with the Birks Scheme and the Fluorescence Blob Model (FBM) to yield the excimer formation rate constants and , respectively. The two parameters showed the same trends with varying viscosity, implying that the same information concerning chain dynamics is obtained from the randomly and end-labelled PNIPAM samples. The fluorescence decays of the Py2-PNIPAM-Y samples were acquired in ethanol and in water to determine how pyrene solubility affects the behavior of the polymers in solution, as probed by time-resolved fluorescence. It was found that the decreased pyrene solubility in water led to large amounts of intra- and intermolecular pyrene aggregation. Finally, the pyrene-labelled dendrimers were studied in tetrahydrofuran (THF) to probe the mobility of the chain ends as a function of generation number. The average rate of excimer formation, , obtained from the Model-Free analysis of the fluorescence decays in THF, increased linearly with generation number. This finding, combined with molecular mechanics optimizations, led to the conclusion that excimer formation was greatly enhanced due to the branched nature of the dendrimer molecule. Together, these studies illustrate three different applications of the use of time-resolved fluorescence to characterize the internal dynamics of pyrene-labelled macromolecules.

During the undertaken research and development, two major systems were designed. These were; a prototype force sensor, and a movement measurement system. Both the developed systems were designed for the intended field of insect research, but were developed using very different underlying principles. The force measurement system uses the piezo-electric effect induced in piezo-electric bimorph elements to produce a measure of force exerted on the sensor. The movement measurement system on the other hand uses computer vision (CV) techniques to find and track the three dimensional (3D) position of markers on the insect, and thereby record the pose of the insect. To further increase the usefulness of the two measurement systems, a prototype graphical user interface (GUI) was produced to encapsulate the functionality of the systems and provide an end user with a more complete and functional research tool. The GUI allows a user to easily define the parameters required for the CV operations and presents the results of these operations to the user in an easily understood visual format. The GUI is also intended to display force measurements in a graphical means to make them easily interpreted. The GUI has been named Weta Evaluation Tracking and Analysis (WETA). Testing on the developed prototype force sensor shows that the piezo-electric bimorph elements provide an adequate measure of force exerted on them, when the voltage signal produced by an element is integrated. Furthermore, the testing showed that the developed force sensor layout produces an adequate measure of forces in the two horizontal linear degrees of freedom (DOF), but the prototype did not produce a good measure of forces in the vertical linear DOF. Development and testing of the movement measurement system showed that stereo vision techniques have the ability to produce accurate measurements of 3D position using two cameras. Although, when testing these techniques with one of the cameras replaced by a mirror, the system produced less than satisfactory results. Further testing on the feature detection and tracking portions of the movement system showed that even though these systems were implemented in a relatively simple way, they were still adequate in their associated operations. However, it was found that with some simple changes in colour spaces used during feature detection, the performance of the feature detection system in varying illumination was greatly improved. The tracking system on the other hand, operated adequately using just its associated basic principles. During the development of both prototype measurement systems, a number of conclusions were formulated that indicated areas of future development. These areas include; advanced force sensor configurations, force sensor miniaturisation, design of a force plate, improvement of feature detection and tracking, and refining of the stereo vision equipment.