At the moment, when energy and environmental issues are of concerned in our society, photovoltaic technology has received tremendous development and demand. Because carrier lifetime and diffusion coefficient are the important indicators to determine the recombination level, which influences the efficiency of solar cells to a large extent, they are regarded as key in choosing solar cell materials. A technique for effective lifetime measurement, modulated free-carrier absorption (FCA), can extract lifetime and diffusion coefficient simultaneously, which is supported by a general mathematical model that predicts the experimental signal accounting for the 3-dimensional (3D) charge-carrier transport and recombination within the semiconductor. A single mode 1064 nm laser modulated by an EO modulator is used as the pump and a 2050 nm modulated LED is used as probe in this experiment as the pump/probe parts. An IR camera detects the frequency-domain diffusion image from the tested silicon sample at the tested frequency range between 1 kHz to 200 kHz and the lifetime can be extracted by frequency-domain free-carrier concentration equation, which is a Lorentzian model. By simulating the diffusion data from the camera with the 3D free-carrier absorption model, we can extract lifetime and diffusion coefficient simultaneously. The fitted lifetime from frequency-domain free-carrier absorption equation is 33.5 ± 1.3 μs, and the fitted lifetime from this 3D FCA model is 32.8 ± 1.5 μs, which match to within the error bars. The fitted diffusion coefficient from this 3D FCA model is 15.6 ± 0.7 cm2/s, which agrees with the theoretical value of 16 cm2/s for silicon. Good quantitative agreement is found among the model, experimental data, and theory. / Thesis / Master of Applied Science (MASc)

Plants have evolved multiple surveillance mechanisms to detect the presence of disease-causing organisms. One mode of surveillance is based on dozens of constitutively expressed resistance (R) genes. R genes recognize pathogen gene products as signals of invasion. We are interested in how plants evolve R genes to keep pace with rapidly evolving pathogen populations. The mechanisms that drive the evolution of new R genes are poorly understood. There is data that supports the relevance of recombination in the evolution of resistance gene clusters in plants. However, a more comprehensive understanding of the molecular biology of recombination and the impact recombination has on R gene evolution is necessary. The objectives of this dissertation were to develop a genetic screen that models meiotic unequal crossing over at a synthetic RPP8 (synthRPP8) resistance gene cluster and to assess the effect of abiotic stress on recombination with the synthetic RBCSB gene cluster (synthRBCSB) in Arabidopsis. The genetic screen utilized in these studies specifically identifies a novel recombinant gene and a concomitant gene duplication that results from meiotic unequal crossing-over by coupling chimeric gene formation to the activation of the firefly luciferase gene. Two synthRPP8 clusters were constructed and extensive optimization of screening conditions were performed. An initial screen of ~1 million synthRPP8 transgenic plants was performed and plants that expressed the luc+ phenotype were isolated and analyzed. Unexpectedly, background bioluminescence was found to interfere with the identification of bona fide luc+ synthRPP8 recombinants. An abiotic stress response assay was performed and the data suggests activation of a putative stress response element in the promoter of RPP8 is responsible for background levels of in vivo luciferase activity. The background bioluminescence could not be sufficiently reduced. Therefore, two additional synthRPP8 constructs, synthRPP8-3 and synthRPP8-4, were constructed and are currently being examined for their utility to model meiotic unequal crossing-over. UV-C treatment was shown to stimulate somatic unequal crossing over, as well as upregulate defense/stress response genes and transcription factors. Meiotic recombination may also be affected by stress. Therefore, the effect of UV-C irradiation on the frequency of unequal meiotic recombination between paralogous RBCSB genes and on the expression of genes associated with the defense/stress response was examined. We observed a ~2-fold increase in the frequency of meiotic recombination after UV-C irradiation but this increase was not statistically significant. We did not detect a significant alteration in the steady-state MYB10, PR-1 and HSF-3 mRNA levels by semi-quantitative RT-PCR. The expression data we gathered provided minimal support for whether the UV-C treatment was an effective DNA damaging agent. / Ph. D.

Yes / We investigated the meiotic role of Srs2, a multi-functional DNA helicase/translocase that destabilises Rad51-DNA filaments and is thought to regulate strand invasion and prevent hyper-recombination during the mitotic cell cycle. We find that Srs2 activity is required for normal meiotic progression and spore viability. A significant fraction of srs2 mutant cells progress through both meiotic divisions without separating the bulk of their chromatin, although in such cells sister centromeres often separate. Undivided nuclei contain aggregates of Rad51 colocalised with the ssDNA-binding protein RPA, suggesting the presence of persistent single-strand DNA. Rad51 aggregate formation requires Spo11-induced DSBs, Rad51 strand-invasion activity and progression past the pachytene stage of meiosis, but not the DSB end-resection or the bias towards interhomologue strand invasion characteristic of normal meiosis. srs2 mutants also display altered meiotic recombination intermediate metabolism, revealed by defects in the formation of stable joint molecules. We suggest that Srs2, by limiting Rad51 accumulation on DNA, prevents the formation of aberrant recombination intermediates that otherwise would persist and interfere with normal chromosome segregation and nuclear division. / Biotechnology and Biological Sciences Research Council (BB/K009346/1)

Mercuric Iodide is the most promising of all semiconductor materials currently under investigation for use as radiation detectors at room temperature. While substantial studies have been conducted on single crystal HgI2, polycrystalline HgI2 remains a comparatively less studied form. The HgI2 films are deposited on TEC-15 LOF glass with a Tin Oxide (SnO2) coating which acts as the growth surface and front contact. The back contact, Palladium (Pd), is deposited by sputtering through a shadow mask. The films are circular in shape with an approximate diameter of 2.5 cm and thicknesses ranging from 50-600 micro m. The film has seven contact points defined by Pd electrodes for spectral response(SR) and I-V measurements. Measurements were done on the film with a visible light source. Numerical modeling helps us understand device properties and processes that take place in operation of the device. The focus of this work was to identify loss mechanisms in photoresponse, reveal fundamental device properties, and develop a quantitative device model for MSM HgI2 thin films using the DC Device modeling simulation tool MEDICI ™. The values for input parameters were chosen from literatutheory and reasonable estimates. Comprehensive studies were performed to investigate the sensitivity of SR and light I-V characteristics to each input parameter. Surface&Bulk recombinations have been investigated in this thesis. A Single, homogeneous region with all possible combinations of carrier mobilities, surface and bulk recombination parameters was not able to explain completely the measured SR. A Two-region model with the first region (0-0.5) μ m being surface&bulk recombination dominated, and the second (0.5-300) μ m bulk recombination dominated, was able to match the complete measured SR of current devices. The key parameters determined from the simulations are the mobilities, bulk lifetimes and surface-recombination velocities at the front contact for both carriers. These are consistent with expectations based upon known single crystal properties

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 130-133).

Thesis (Ph. D.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains viii, 174 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Mercuric Iodide in its tetragonal form has received a lot of attention for many years as a prospective room temperature X-ray and y-ray detector. Its basic properties are well suited for this purpose. Its wide band gap of 2.1eV contributes to a high dark resistivity of 1012ohm-cm or higher. A high atomic number of its constituent atoms (Hg-80, I -53) and a density of 6.3g/cm3 result in its efficient interaction with incident X-ray or y-ray radiation. Single crystalline mercuric iodide has been thoroughly studied and successfully utilized in commercial radiation detectors. But with the urgent need for large area ,low cost efficient X-ray detectors, focus has now shifted towards the development and understanding of the properties of thin film Polycrystalline Mercuric iodide detectors. Such detectors also have the advantage of being most suited for direct X-ray detection i.e. a direct conversion of incident X rays into electric signals which are then used to obtain an equivalent image in digital X-ray imaging. They also can be used in applications where a scintillator intermediate is used to generate visible light from incident high energy photons.Therefore it is important to study their optical response in order to understand and evaluate their Optical Properties. The present work focuses on obtaining the Optical response of the thin film Mercuric iodide photoconductive detectors .These films were grown on TEC-15 LOF glass with a Tin Oxide (SnO2) coating on it, which acts as a growth surface for the films and also functions as the front contact of the detector.Palladium which is sputtered on top of this film acts as the back contact. There are a total of seven contacted devices on each film sample and each device has been tested for its optical response in terms of Spectral Response and I-V characteristics in both light and dark conditions.

High-throughput technologies in biological sciences have led to an exponential growth in the amount of data generated over the past several years. This data explosion is forcing scientists to search for innovative computational designs to reduce the time-scale of biological system simulations, and enable rapid study of larger and more complex biological systems. In the field of immunobiology, one such simulation is known as DNA recombination. It is a critical process for investigating the correlation between disease and immune system responses, and discovering the immunological changes that occur during aging through T-cell repertoire analysis. In this project we design and develop a massively parallel method tailored for Graphics Processing Unit (GPU) processors by identifying novel ways of restructuring the flow of the repertoire analysis. The DNA recombination process is the central mechanism for generating diversity among antigen receptors such as T-cell receptors (TCRs). This diversity is crucial for the development of the adaptive immune system. However, modeling of all the α β TCR sequences is encumbered by the enormity of the potential repertoire, which has been predicted to exceed 10¹⁵ sequences. Prior modeling efforts have, therefore, been limited to extrapolations based on the analysis of minor subsets of the overall TCR β repertoire. In this study, we map the recombination process completely onto the GPU hardware architecture using the CUDA programming environment to circumvent prior limitations. For the first time, a model of the mouse TCRβ is presented to an extent which enabled the evaluation of the Convergent Recombination Hypothesis (CRH) comprehensively at a peta-scale level on a single GPU. Understanding the recombination process will allow scientists to better determine the likelihood of transplant rejections, immune system responses to foreign antigens and cancers, and plan treatments based on the genetic makeup of a given patient.

The quantum impulse approximation theory has been extended to the inelastic collision. The total inelastic cross sections for the degenerated states with different angular momenta was calculated. It was proved that summing over the transitions from nl to n' and from nl to n'l' would give us the total cross section of transition from n to n'. Rate coefficients were calculated for the common gases in the atmosphere being the third particle. The resonant effect of the rate coefficients had been observed. Recombination coefficients were then calculated in terms of rate coefficients. Previous calculations were carried out in compare with the net rate flow through certain excited levels, which were found to be more stable and reflected a clearer picture of the whole process. Results have been compared with the elastic collision. A dramatic decreasing of rates when temperature increased was also observed. More thermal energy increases the probability of electrons for being re-ionized. Similar calculations had been carried out for the upper atmosphere gases, such as N₂, O₂, CO, CO₂, and H₂O. The recombination coefficients for electron combining with metallic ion Na+ were also calculated.

Title: Recombination study of ions with electrons at temperatures below 300 K Author: Tomáš Kotrík Department: Department of Surface and Plasma Science Supervisor of the doctoral thesis: Prof. RNDr. Juraj Glosík, DrSc. Department of Surface and Plasma Science Abstract: Presented is the study of recombination of ions with electrons performed at low temperatures using the Flowing afterglow with Langmuir probe experimental technique. Studied was the dissociative recombination of H and D ions at temperatures 77 - 300 K. Apart from a two-body also a three-body recombination channel assisted by neutral He atoms was identified and studied. The obtained temperature dependence of the two-body recombination rate coefficient is in a good agreement with findings of other experimental and theoretical works. The dissociative recombination of HCO and DCO ions with electrons was studied in the temperature range 150 - 300 K. The observed temperature dependence of measured recombination rate coefficient for HCO and DCO ions (~T -1.3 and ~T -1.1 , respectively) is in agreement with the majority of previous experimental works and evokes that indirect mechanism governs the recombination process. The electron- assisted collisional-radiative recombination of Ar ions was for the first time studied at temperatures 50 - 300 K. The...