This thesis presents two measurements of the top quark pair production cross section at sqrt{s} = 1.96 TeV using data from the DØ experiment. Both measurements are performed in the dilepton final state and make use of secondary vertex b-tagging. With 158 pb-1 of data in the electron-muon final state, the measured cross section is: σ(top-antitop) = 11.1 +5.8 -4.3 (stat) +- 1.4 (syst) +- 0.7 (lumi) pb. With 425 pb-1 of data in the electron+track and muon+track final states, the measured cross section is: sigma(top-antitop) = 6.3 +2.1 -1.8 (stat) +- 1.1 (syst) +- 0.4 (lumi) pb. Both measurements are in agreement with the prediction from perturbative QCD calculations. In addition, an estimate of the DØ silicon detector lifetime is presented. The radiation damage is determined by studying the depletion voltage of the silicon sensors as a function of time. Based on this data the silicon detector is estimated to remain operational up to delivered luminosities of 6-8 fb-1.

An individual’s life history is a sequence of events which eventually determine its contribution to the next generation, or fitness. These events are affected by environmental factors, genetic make-up and decisions made by an individual and its breeding partner. Recognition of these determinants helps to understand both short-term ecological changes and long-term evolutionary dynamics in a population. In this thesis long-term individual-based data on common gull (Larus canus) is used to study age-dependent reproductive success, survival, pair retention and breeding time. Collected pedigree data enabled to study genetic variation of traits and the selection on them. The reproductive success of common gulls increased steadily until very old age. This increase cannot be explained by selection effects, since individuals with lower breeding success were shown not to have lower survival. Consequently, this gain must be ascribed primarily to an age-related improvements of individual competence and/or increased reproductive effort. Annual survival of adult birds was age- and year-dependent. The latter was partly explained by winter severity. The size of the white spots on five outermost primaries predicted the bird’s future survival and divorce probabilities and hence, pair endurance capability. Gulls with larger spots enjoyed higher survival and lower divorce rates compared to birds with smaller spots. This suggests that the wing tip pattern might function as a condition dependent signal, revealing individual variation in quality. One of the advantages of persistent pair bond was the ability to start breeding early in the season. The timing of breeding of firm pairs advanced with time not only due to mates’ increasing age, but also owing to their experience together. Although both sexes had phenotypic effects on laying date, it was heritable only in females. On the phenotypic and genotypic level, early laying was under positive fecundity and survival selection in females.

Replicating the multi-hierarchical self-assembly of collagen (peptide chain to triple helix to nanofiber and, finally, to a hydrogel) has long attracted scientists, both from the fundamental science perspective of supramolecular chemistry and for the potential biomedical applications perceived in tissue engineering. In terms of triple helical formation, collagen is the most abundant protein in the human body with at least 28 types, yet research involving collagen mimetic systems has only recently began to consider the innate ability of collagen to control helix composition and register. Collagen triple helices can be homotrimeric or heterotrimeric and while some types of natural collagen form only one specific composition of helix, others can form multiple. It is critical to fully understand and, if possible, reproduce the control that native collagen has on helix composition and register. In terms of nanofiber formation, many approaches to drive the self-assembly of synthetic systems through the same steps as natural collagen have been partially successful, but none have simultaneously demonstrated all levels of structural assembly. In this work, advancements in the ability to control helix composition and replicate the multi-hierarchical assembly of collagen are described. Both positive and negative design for the assembly of AAB type collagen heterotrimers were utilized by promoting heterotrimer formation though the use of charged amino acids to form intra-helix electrostatic interactions, while simultaneously discouraging homotrimers, resulting in the identification of multiple peptide systems with full control over the composition of the resulting triple helix. Similar salt-bridged hydrogen bonds between charged residues were incorporated into nanofiber forming peptides, one of which successfully assembled into sticky-ended triple helices, nanofibers with characteristic triple helical packing visible in the solution state, and strong hydrogels that are degraded by collagenase at a similar rate to natural collagen. Together, these results provide a better understanding of the self-assembly of collagenous sequences as well as a novel design scheme for synthetic extracellular matrix mimetics with potential applications in regenerative medicine and drug delivery.

The main purpose of this work is to investigate the behavior of the recently released by Microsoft company the Kinect sensor, which contains the properties that go beyond ordinary cameras. Normally, in order to create a 3D reconstruction of the scene two cameras are required. Whereas, the Kinect device, due to the properties of the Infrared projector and sensor allows to create the same type of the reconstruction using only one device. However, the depth images, which are generated by the Infrared laser projector and monochrome sensor in Kinect can contain undefined values. Therefore, in addition to other investigations this project contains an idea how to improve the quality of the depth images. However, the base aim of this work is to perform a reconstruction of the scene based on the color images using pair of Kinects which will be compared with the results generated by using depth information from one Kinect. In addition, the report contains the information how to check that all the performed calculations were done correctly. All  the algorithms which were used in the project as well as the achieved results will be described and discussed in the separate chapters in the current report.

I modify the quasilocal energy formalism of Brown and York into a purely Hamiltonian form. As part of the reformulation, I remove their restriction that the time evolution of the boundary of the spacetime be orthogonal to the leaves of the time foliation. Thus the new formulation allows an arbitrary evolution of the boundary which physically corresponds to allowing general motions of the set of observers making up that boundary. I calculate the rate of change of the quasilocal energy in such situations, show how it transforms with respect to boosts of the boundaries, and use the Lanczos-Israel thin shell formalism to reformulate it from an operational point of view. These steps are performed both for pure gravity and gravity with attendant matter fields. I then apply the formalism to characterize naked black holes and study their properties, investigate gravitational tidal heating, and combine it with the path integral formulation of quantum gravity to analyze the creation of pairs of charged and rotating black holes. I show that one must use complex instantons to study this process though the probabilities of creation remain real and consistent with the view that the entropy of a black hole is the logarithm of the number of its quantum states.

Three-dimensional large-eddy simulations (LES) of single and multiple jets in cross-flow (JICF) were conducted using the 19-bit Lattice Boltzmann Equation (LBE) method coupled with a conventional Navier-Stokes (NS) finite-volume scheme. In this coupled LBE-NS approach, the LBE-LES was employed to simulate the flow inside jet nozzles, while the NS-LES was used to simulate the cross-flow. The key application area was to study the micro-blowing technique (MBT) for drag control similar to recent experiments at NASA/GRC. A single jet in the cross-flow case was used for validation purposes, and results were compared with experimental data and full LBE-LES simulation. Good agreement with data was obtained. Transient analysis of flow structures was performed to investigate the contribution of flow structures to the counter-rotating vortex pair (CRVP) formation. It was found that both spanwise roller (at the lee side of the jet) and streamwise vortices (at the jet-side) contribute to the generation of the CRVP. Span-wise roller at the corner of the jet experiences high spanwise vortex compression as well as high streamwise vortex stretch. As a result, they get realigned, mix with the jet-side streamwise vortices, and eventually generate the CRVP. Furthermore, acoustic pulses were used to test the proper information exchange from the LBE domain to the NS domain, and vice-versa. Subsequently, MBT over a flat plate with porosity of 25 percent was simulated using nine jets in a compressible cross-flow at a Mach number of 0.4. Three cases with injection ratios of 0.003, 0.02 and 0.07 were conducted to investigate how the blowing rate impacts skin friction. It is shown that MBT suppressed the near-wall vortices and reduced the skin friction by up to 50 percent. This is in good agreement with experimental data.

In this study, a new approach for the matching and reconstruction of line features from multispectral stereo aerial images is presented. The advantages of the existing multispectral information in aerial images are fully taken into account all over the steps of pre-processing and edge detection. To accurately describe the straight line segments, a principal component analysis technique is adapted. The initial correspondences between the stereo images are generated using a new pair-wise stereo matching approach which involves a total of seven relational constraints. The final line to line correspondences between the stereo images are established in a precise matching stage in which the final line matches are assigned by means of three novel measures and a final similarity voting scheme. Once the line matches are established, the stereo reconstruction of those matches is performed by an innovative reconstruction approach that manipulates the redundancy inherent in line pair-relations. By this way, the reconstruction of the stereo matches that are observed in a nearly-parallel geometry with the epipolar lines can also be performed accurately. The proposed approach is tested over two different urban test sites with various built-up characteristics, and as a result, very successful and promising stereo line matching and reconstruction performances are reached. Besides, the comparison of the results of the proposed approach with the results of one of the state-of-the-art stereo matching approaches proves the superiority and the potential of proposed approach.

<p>In this thesis I have theoretically studied electron recombination processes with small molecular ions.</p><p>In these kind of processes resonant states are involved. To calculate the potential energy for these states as a function of internuclear distance, structure calculations and scattering calculations have to be performed.</p><p>So far I have been studying the ion-pair formation with in electron recombination with H₃⁺. The cross section for this process has been calculated using different kind of models, both a time dependent quantum mechanical and a semiclassical.</p><p>I have also studied the direct process of dissociative recombination of HF⁺. To calculate the total cross section for this process, we have performed wave packet propagation on thirty resonant states and summed up the individual cross sections for these states.</p><p>The cross sections for both these processes have a similar appearance to those measured experimentally in the ion storage ring CRYRING in Stockholm.</p>

Plankton imaging systems such as SIPPER produce a large quantity of data in the form of plankton images from a variety of classes. A system known as PICES was developed to quickly extract, classify and manage the millions of images produced from a single one-week research cruise. A new fast technique for parameter tuning and feature selection for Support Vector Machines using Wrappers was created. This technique allows for faster feature selection, while at the same time maintaining and sometimes improving classification accuracy. It also gives the user greater flexibility in the management of class contents in existing training libraries. Support vector machines are binary classifiers that can implement multi-class classifiers by creating a classifier for each possible combination of classes or for each class using a one class versus all strategy. Feature selection searches for a single set of features to be used by each of the binary classifiers. This ignores the fact that features that may be good discriminators for two particular classes might not do well for other class combinations. As a result, the feature selection process may not include these features in the common set to be used by all support vector machines. It is shown through experimentation that by selecting features for each binary class combination, overall classification accuracy can be improved and the time required for training a multi-class support vector machine can be reduced. Another benefit of this approach is that significantly less time is required for feature selection when additional classes are added to the training data. This is because the features selected for the existing class combinations are still valid, so that feature selection only needs to be run for the new combination added. This work resulted in a system called PICES, a GUI based user friendly system, which aids in the classification management of over 55 million images of plankton split amongst 180 classes. PICES embodies an improved means of performing Wrapper based feature selection that creates classifiers that train faster and are just as accurate and sometimes more accurate, while reducing the feature selection time.

As a potential solution to the global energy and environmental pollution, design and synthesis of artificial photocatalysts with high activities have attracted increasing scientific interests worldwide. In recent years, the graphitic carbon nitride (g-C3N4) has shown new possible applications in the photocatalytic field due to its unique properties. However, the photocatalytic efficiency of the pristine g-C3N4 is greatly limited by the high recombination rate of the photo-induced electron-hole pairs. In this thesis, the aim is to design and fabricate efficient g-C3N4 based photocatalysts with enhanced photocatalytic activities under a visible light irradiation. In order to achieve this goal, two strategies have been employed in the present thesis. First, the as-obtained g-C3N4 was used as the host material to construct staggered-aligned composite photocatalysts by selecting semiconductors with suitable band positions. By this method, three kinds of g-C3N4-based composite photocatalysts such as g-C3N4/ZnS nanocage, g-C3N4/m-Ag2Mo2O7 and g-C3N4/MIL-88A were successfully fabricated. Second, the microstructure of the g-C3N4 was modified by the H2O2-treatment at an elevated temperature and ambient pressure. In this study, the g-C3N4 was prepared by a simple pyrolysis of urea. As for all the as-synthesized phtocatalysts, the structures, morphologies and the optical properties were carefully characterized by the following techniques: XRD, SEM, TEM, FT-IR and DRS. Also, the band edge positions of m-Ag2Mo2O7 and MIL-88A were studied by the Mott-Schottky methods. Thereafter, the photocatalytic activities were evaluated by using a solution of rhodamine B (RhB) as a target pollutant for the photodegradation experiments performed under a visible light irradiation. The results showed that all the aforementioned g-C3N4-based photocatalysts exhibited enhanced photocatalytic activities in comparison with the pristine g-C3N4. For the case of the g-C3N4-based composite photocatalysts, the enhancement factor over the pristine g-C3N4 can achieve values ranging from 2.6 to 3.4. As for the H2O2-treated g-C3N4, the degradation rate constant can be 4.6 times higher than that of the pristine g-C3N4. To understand the key factors in new materials design, we also devote a lot of efforts to elucidate the basic mechanisms during the photocatalytic degradation of organic pollutant. Based on the results of the active species trapping (AST) experiments, the main active species in each photocatalytic system were determined. In the g-C3N4/m-Ag2Mo2O7 and the g-C3N4/MIL-88A system, three kinds of active species of ·O2-, h+ and ·OH were found to be involved in the photocatalytic reaction. Among them, the ·O2- and h+ were the main active species. In the g-C3N4/ZnS and H2O2-treated g-C3N4 photocatalytic systems, the main active species was determined as the ·O2-. The reaction pathways of these active species were also demonstrated by comparing the band edge positions with the potentials of the redox couple. In addition, the relationship between the active species and the photocatalytic behaviors of N-de-ethylation and conjugated structure cleavage were studied. Finally, possible mechanisms to explain the enhanced photocatalytic activities were proposed for each photocatalytic system. The results in this thesis clearly confirm that the photocatalytic activity of the g-C3N4 based photocatalyst can efficiently be enhanced by constructions of staggered-aligned composites and by modification of the microstructure of the g-C3N4. The enhanced photocatalytic performance can mainly be ascribed to the efficient separation of the photo-induced electron-hole pairs and the increase of the active sites for the photocatalytic reaction. / <p>QC 20150909</p>