In this thesis, the clean angular observables in the $\bar{B} \to D^{*+} \ell^- \bar{\nu}_{\ell}$ angular distribution is studied. Similar angular observables are widely studied in $B \to K^* \mu^+ \mu^-$ decays. We believed that these angular observables may have different sensitivities to different new physics structures.

In the presented work, first principle studies on electronic structure, stability, and magnetic properties of metal chalcogenide, CrnTem clusters have been carried out within a density functional framework using generalized gradient functions to incorporate the exchange and correlation effects. The energetic and electronic stability was investigated, and it was found that they are not always correlated as seen in the cluster Cr6Te8 which has smaller gap between its HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) and a high electron affinity of 3.39 eV indicating lower electronic stability whereas higher fragmentation energy indicating energetic stability. The high electron affinity shows that the stability of Cr6Te8 cluster can be enhanced by adding charge donating ligands including PEt3 to form stable Cr6Te8(PEt3)6 clusters as seen in experiments. The other cluster of interest was Cr4Te6 in which energetic stability was accompanied with electronic inertness marked by its large HOMO-LUMO gap, non-magnetic ground state and high fragmentation energy.

The conformal bootstrap method is a non-perturbative method that uses the symmetry in a conformal field theory to constrain and solve for the observables in the theory. We consider a conformal field theory with the symmetry group SU(N) and four general scalar fields as the only low dimensional operators. The four-point correlation function of a quartic interaction of four general scalar fields in a conformal field theory can be written as a sum over primary operators. In order to study the four-point correlator a large-N expansion is made, where N comes from the symmetry group SU(N). Using the conformal bootstrap method the anomalous dimension of the primary operators in the four-point correlator is calculated. Using the AdS/CFT correspondence the anomalous dimension of the primary operators is also calculated using Witten diagrams. / Konform fältteori är en kvantfältteori med konform symmetri. Konform symmetri är en symmetri som bevarar vinklar och lokalt ser ut som en kombination av en rotation och en förändring i skala. En metod för att beräkna de observerbara kvantiteterna i en konform fältteori är metoden "conformal boostrap". Denna metod går ut på att använda symmetrin i en konform fältteori för att begränsa och beräkna värdet på de observerbara kvantiteterna i teorin.En av de observerbar kvantiteterna i en fältteori är en korrelationsfunktion. Korrelationsfunktioner beskriver interaktionerna mellan partiklarna i en fältteori.  I detta arbete studerar vi en interaktion mellan fyra skalärfält genom att studera fyra-punkts korrelationsfunktionen för denna interaktion. Metoden vi använder är "conformal bootstrap" men vi testar också om AdS/CFT dualiteten håller för våra beräkningar. AdS/CFT dualiteten är en ekvivalens av två olika teorier, en strängteori i ett (d+1)-dimensionellt anti-de Sitter (AdS) rum och en konform fältteori (CFT) i den d-dimensionella gränsen av anti-de Sitter rummet. Enligt denna dualitet kan en observerbar kvantitet beräknas från båda dessa två teorier och ge samma resultat. Teorin vi studerar har symmetrigrupp SU(N) och vi arbetar i dimension två. Vi arbetar också med att N, matrisrangen i teorin, är stort då detta är den gräns där AdS/CFT dualiteten gäller. Enligt konform fältteori så kan en fyra-punkts korrelationsfunktion av fyra skalärer beskrivas som en summa över vad som kallas primära fält. Genom att använda "conformal bootstrap" metoden beräknas den anormala dimensionen, vilket är en korrektion av första icke-triviala ordning till dimensionen, av dessa primära fält. Samma kvantitet beräknas också från strängteorisidan av AdS/CFT dualiteten genom användandet av så kallade Witten diagram. Resultatet från båda sidor av dualiteten visas stämma överens.

The photovoltaic properties of CdTe-based thin films depend on recombination levels formed in the CdTe layer and at the heterojunction. The localized states are resultant of structural defects (metal sublattice, chalcogen sublattice, interstitial), controlled doping, deposition process, and/or post-deposition annealing. The photoluminescence study of CdTe thin films, from both the bulk and heterojunction, can reveal radiative states due to different defects or impurities. Identification of defects allows for potential explanation of their roles and influence on solar cell performance. A thorough understanding of the material properties responsible for solar cell performance is critical in further advancing the efficiency of devices. The presented work is a systematic investigation using photoluminescence to study CdTe thin films with varying deposition processes. The thin (polycrystalline) films explored in this study were deposited by either the elemental vapor transport technique (EVT) or close spaced sublimation (CSS). Two device architectures were investigated, the typical CdTe/CdS device and the CdSeXTe1-X (CST) alloy device. Post-deposition annealing processes were either laser or thermal. The study of the CdTe thin films is grouped in three general categories: (a) EVT films: Intrinsic and Extrinsic (Group V: Sb and P), (b) CST alloys, and (c) Post-deposition Laser Annealed (LA) films. The main goal of this dissertation is to understand the influence of fabrication procedures (deposition conditions, post deposition thermal and chemical treatments, added impurities, and device architecture) on the defect structure of the CdTe thin films. The behavior of the photoluminescence (PL), studied as a function of the measurement temperature and excitation intensity, provides insight to the mechanism causing the radiative recombination levels. Analysis of the PL spectra for CdTe films with intrinsic doping demonstrated stoichiometric control of native defects for both the Cd- and Te-rich conditions. PL spectra of CdTe:Sb films showed unique Sb-related bands. Also, impurity-related defects were identified in the CdTe:P spectra. Spectral analysis support the need for optimization of dopant concentration. The effects of selenium (Se) thickness and post-deposition processing on the formation of CST alloy were demonstrated in the changing PL spectra. The native defects (and complexes) identified in films with thermal anneal processing were the same as those identified in films with laser anneal post-deposition processing. The PL data were collected and other characterization techniques were used to support the defect assignments. A repository of material properties, which include the recombination levels along with structural defect assignment for each of the CdTe deposition processes, is provided. This project will lend the solar cell community information on CdTe defects for different processing conditions, ultimately influencing the fabrication of improved solar cells.

This thesis addresses sound production in bowed-string instruments from two perspectives: the physics of the bowed string, and bow control in performance. Violin performance is characterized by an intimate connection between the player and the instrument, allowing for a continuous control of the sound via the main bowing parameters (bow velocity, bow force and bow-bridge distance), but imposing constraints as well. In the four included studies the focus is gradually shifted from the physics of bow-string interaction to the control exerted by the player. In the first two studies the available bowing parameter space was explored using a bowing machine, by systematically probing combinations of bow velocity, bow force and bow-bridge distance. This allowed for an empirical evaluation of the maximum and minimum bow force required for the production of a regular string tone, characterized by Helmholtz motion. Comparison of the found bow-force limits with theoretical predictions by Schelleng revealed a number of striking discrepancies, in particular regarding minimum bow force. The observations, in combination with bowed-string simulations, provided new insights in the mechanism of breakdown of Helmholtz motion at low bow forces. In the second study the influence of the main bowing parameters on aspects of sound quality was analyzed in detail. It was found that bow force was totally dominating the control of the spectral centroid, which is related to the perceived brightness of the tone. Pitch flattening could be clearly observed when approaching the upper bow-force limit, confirming its role as a practical limit in performance. The last two studies were focused on the measurement of bowing gestures in violin and viola performance. A method was developed for accurate and complete measurement of the main bowing parameters, as well as the bow angles skewness, inclination and tilt. The setup was used in a large performance study. The analyses revealed clear strategies in the use of the main bowing parameters, which could be related to the constraints imposed by the upper and lower bow-force limits and pitch flattening. Further, it was shown that two bow angles (skewness and tilt) were systematically used for controlling dynamic level; skewness played an important role in changing bow-bridge distance in crescendo and diminuendo notes, and tilt was used to control the gradation of bow force. Visualizations and animations of the collected bowing gestures revealed significant features of sophisticated bow control in complex bowing patterns. / QC 20100809

This work is a study of complex many-body systems with non-trivial interactions. Many such systems can be described with models that are much simpler than the real thing but which can still give good insight into the behavior of realistic systems. We take a look at two such systems. The first part looks at a model that elucidates the variety of magnetic phases observed in rare-earth heterostructures at low temperatures: the six-state clock model. We use an ANNNI-like model Hamiltonian that has a three-dimensional parameter space and yields two-dimensional multiphase regions in this space. A low-temperature expansion of the free energy reveals an example of Villain's `order from disorder' [81, 60] when an infinitesimal temperature breaks the ground-state degeneracy. The next part of our work describes biological systems. Using ECIS (Electric Cell-Substrate Impedance Sensing), we are able to extract complex impedance time series from a confluent layer of live cells. We use simple statistics to characterize the behavior of cells in these experiments. We compare experiment with models of fractional Brownian motion and random walks with persistence. We next detect differences in the behavior of single cell types in a toxic environment. Finally, we develop a very simple model of micromotion that helps explain the types of interactions responsible for the long-term and short-term correlations seen in the power spectra and autocorrelation curves extracted from the times series produced from the experiments.

The development in additive manufacturing methods has cleared the path for topology optimizationby making it possible to produce complex geometries, which would not be possible to produce bytraditional manufacturing methods. Topology optimization uses iterative structural computations tond an optimal material distribution given a maximum optimization domain, load cases and/or otherstructural criteria. The relation between retained mass and structural performance of a swing armfor the vehicle BvS10 was examined for two different materials. The first material was an estimate of an additive manufactured material and the other for a high structural steel. Given the extreme load cases, the geometrical limits of the swing arm and by specifying how much mass was to be retained the stiffness was to be maximized. The optimization was performed using an elastic material model in thecommercial software ANSYS. This elastic material models was based on standard material parameters of steel. Three geometries were generated, namely OG100, OG90 and OG80, which corresponded to 101 %, 87 % and 81 % of the mass of the original swing arm, respectively. The optimization procedurewas combined with geometry modications in SpaceClaim to simplify the obtained geometries. All these geometries consisted of a hollow geometry with a greater width compared to the original geometry. The geometries were then evaluated using multilinear plastic material models based on respective material. Using the additive manufactured material model no generated geometry could perform structurally better than the original swing arm. This indicates that greater material properties must be obtainedin order to be able to reduce the weight of the swing arm. By using the material properties of the highstructural steel, it was found that at least 31.3 kg per vehicle could be reduced by using the optimizedgeometry OG80, and still not perform structurally worse than of the original swing arm. / Utvecklingen inom additiv tillverkning har öppnat vägen för topologioptimering genom att kunna producera komplexa geometrier, som inte skulle vara möjliga att tillverka med hjälp av traditionella tillverkningsmetoder. Topologioptimering använder iterativa hållfasthetsberäkningar för att finna den optimala materialfördelning givet en maximal optimeringsdomän, lastfall och/eller andra strukturella kriterier. Relationen mellan bibehållen massa och strukturella prestationer hos en pendelarm till fordonet BvS10 har undersökts för två olika material. Det ena materialet var en uppskattning av ett additivt tillverkat material och det andra materialet var ett höghållfasthetsstål. Givet dem extrema lastfall, geometriska begränsningar hos pendelarmen och genom specficera hur mycket massa som skulle behållas så skulle styvheten maximeras. Optimeringarna utfördes med en elastisk materialmodell i den kommersiellamjukvaran ANSYS. Denna elastiska materialmodell var baserad på klassiska materialparametrarfor stål. Tre geometrier genererades. Optimeringsproceduren användes i kombination med geometriska modikationer i SpaceClaim för att förenkla de optimierade geometrierna. Dessa var OG100, OG90 och OG80, vilka motsvarade 101 %, 87 % och 81 % av pendelarmens originalvikt. Alla geometrier bestod av en ihålig geometri med större bredd än originalarmens. Geometrierna utvärderades sedan med hjälp av multilinjära plastiska materialmodeller baserat på respektive material. Ingen av dessa geometrier kunde prestera bättre än originalarmen när det additivt tillverkade materialet användes. Detta indikerar att bättre materialegenskaper måste uppnås för att kunna reducera vikten hos pendelarmen. Genom attanvända höghållfasthetsstålet upptäcktes att åtminstone 31.3 kg per fordon kunde reduceras genom attanvända OG80, och fortfarande inte prestera sämre än originalarmen.

Recrystallisation is an important topic in the metal industry since the process may drastically alter the properties of the materials subjected to it. By controlling the recrystallisation process, the material properties can be adjusted as desired, which could lead to stronger materials and hence lighter constructions, decreasing our material consumption. This is currently regulated using softening curves complied from tensile tests, a method which does not show the degree of recrystallisation of a metal. This thesis work therefore explores the possibility to characterise the recrystallisation process using in situ X-ray diffraction, XRD, during heating.The method proposed is using in situ heat treatments of aluminium samples combined with XRD measurements. The results show that it is possible to follow the recrystallisation process of rolled aluminium alloy AA3003 by using in situ XRD during heating, a discovery that could facilitate development and understanding of new materials. Nevertheless, further investigations of the subject is required before the method will be profitable. / Rekristallisation är ett viktigt ämne inom metallindustrin, detta eftersom materialegenskaper drastiskt kan förändras under rekristallisationsprocessen. Genom att kontrollera rekristallisationsprocessen kan materialegenskaper skräddarsys efter applikation. Även starkare material kan tillverkas och därav kan lättare strukturer konstrueras och på så vis minskar även materialåtgången. Idag regleras rekristallisation med hjälp av mjukningskurvor sammanställda genom dragprov, en metod som inte kan visa rekristallisationsgraden av en metall. Detta examensarbete utforskar möjligheten att karaktärisera rekristallisationsprocessen genom att använda in situ röntgendiffraktion, XRD, under värmningsprocessen.Den framtagna metoden inkluderar in situ värmebehandlingar av aluminiumprover i kombination med XRD-mätningar. De erhållna resultaten från experimenten visar på att det är fullt möjligt att följa rekristallisationsprocessen av aluminiumlegering AA3003 med in situ XRD, en upptäckt som kan komma att underlätta vid utveckling och förståelse av legeringar och nya material. Dock krävs fortsatta studier i ämnet innan metoden kan anses vara lönsam.

Background: It is well known that pediatric patients are different from adult patients. Not only are children of a smaller physical size, but their anatomy differs as well. They are also more vulnerable to ionizing radiation than adults are, since their larger attributable life-time risk for cancer. This entitles children as extra radiosensitive patients, and special concern should be taken regarding their radiosensitive organs. Computed tomography (CT) examinations inevitably involve exposure of all skin-deep organs although rarely being objects for the diagnostic task. For example, multiple CT head examinations increase the risk of radiation induced cataract in eye lenses. Absorbed dose to these radiosensitive skin-deep organs should therefore be decreased by available optimization strategies in accordance withthe ALARA principle -as low as reasonably achievable- which guides the process of optimization anddose reduction. Two optimization strategies to decrease absorbed dose to skin-deep organs are Bismuth (Bi) shielding and organ-based tube current modulation (organ-based TCM). Aim: The aim of this work was to assess two dose optimization strategies for decreasing absorbed dose to skin-deep organs in pediatric CT imaging: Bi shielding and organ-based TCM. The specific patient categories chosen were newborn, one year old and five year old. Materials and Methods: Three anthropomorphic phantoms representing newborn, one year old and five year old were scanned with CT protocol parameters selected in accordance with clinical routine for pediatric CT examinations at Karolinska University Hospital in Stockholm. Dose differences from introducing the optimization strategies were obtained by using thermoluminescence dosimeters (TLDs) and metal oxide semiconductor feld effect transistor dosimeters (MOSFETs). Monte Carlo estimated dose values were introduced as a comparison to further establish the validity of the obtained measured values. Results: The benefit in decreased radiation dose to anterior skin-deep organs - when applying the optimization strategies - depended on both body region and body size. Bi shielding was more advantageous the smaller and less attenuating the body was. Organ-based TCM was more advantageous, if an increased dose to posterior organs could be accepted. A less attenuating and smaller phantom did not benefit by organ-based TCM due to increased posterior irradiation. Conclusions: The general conclusion is that the optimal choice of optimization strategy will depend on both body region being scanned and age. Regarding CT head examinations, pediatric patients of ages between newborn and five year old will benefit most by application of organ-based TCM, if an increased dose to backside head can be justified. Regarding CT thorax examinations, newborn and one year old patients will benefit most by application of Bi shielding, while organ-based TCM is preferable for five year old patients.

To predict the performance of an electro-optical sensor system (EO-system) requires taking the weather situation into consideration. The possibility to use weather data from satellites instead of ground – and flight stations has been investigated. Nearly 170 satellites (about 10% of the functional satellites in orbit) were found to have atmosphere and weather monitoring. A method to select satellite data has been created based on three criteria: (1) the satellite should have a least one payload that measure a weather parameter for EO-system, (2) it should be possible to download data, free of charge, from the specified payload and (3) the satellite should cover geographical areas of interest for a potential user. The investigated performance property is the range, which is affected by many weather parameters, and focus has been on aerosols. The mean value for the aerosol extinction coefficient, for day- and nighttime conditions in December 2016, from the satellite CALIPSO’s lidar instrument Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) has been downloaded from www.earthdata.nasa.gov and implemented in a new developed application to predict the range for an EO-system. In the satellite data, from December 2016, it could be seen that the presence of aerosols, on a global scale, appears below 5 km and that the concentration of aerosols for nighttime condition is higher in local areas. For the test wavelength band of 0.9–2.5 µm, the application showed that the aerosol impact reduced the range by nearly 87%, if the EO-system was in a layer with aerosols. The application for the range prediction of EO-systems is on an early stage and need further development, especially its weather and scene parameters, to become a successful tool for a potential user in the future. / Att förutsäga prestandan hos ett elektro-optiskt sensorsystem (EO-system) kräver att man tar hänsyn till bland annat förhållandet i atmosfären. Möjligheten att använda väderdata från satelliter istället för mark- och flygstationer har undersökts. Det hittades nästan 170 satelliter (cirka 10% av de fungerande satelliterna i omloppsbana) med inriktning på atmosfär- och väderövervakning. En metod för att välja ut satellitdata har skapats som baseras på tre kriterier: (1) satelliten ska ha minst ett instrument som mäter en väderparameter för EO-system, (2) man ska, från internet, kunna ladda ner mätdata från det specifika instrumentet och (3) satelliten ska passera över ett område som är av intresse för en potentiell användare. Den prestandaegenskap som har undersökts är räckvidden, som påverkas av flera väderparametrar, där fokus har legat på inverkan från aerosoler. Medelvärdet för extinktionskoefficienten av aerosoler, för dag och natt i december 2016, från satelliten CALIPSO’s lidarinstrument Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) laddades ner från www.earthdata.nasa.gov och användes i en nyutvecklad applikation för att förutsäga räckvidden hos ett EO-system. Från satellitens mätningar i december 2016 kunde man se att förekomsten av aerosoler mestadels befann sig, globalt sett, uppdelat i olika lager under 5 km höjd och att koncentrationen av aerosoler är högre på natten i lokala områden. Applikationens beräkningar visade att förekomsten av aerosoler påverkade räckvidden för exempel våglängdsbandet 0.9–2.5 µm med en försämring upp till 87% när EO-systemet befann sig i ett skikt av aerosoler. Applikationen för att förutsäga räckvidden hos EO-system är i dess begynnelse och kräver vidareutveckling av både väder- och scenparametrar för att det ska bli ett framgångsrikt verktyg.