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K+Λ photoproduction provides the best possibility for a model independent extraction of the photoproduction process and contributing resonances. To do this, it is vital that cross section measurements are well understood. This thesis presents pγ K+Λ differential cross sections from the reaction threshold, to an invariant centre of mass energy of 1.87 GeV. The data was taken at MAMI-C electron microtron facility in Mainz, Germany, during July 2007 and April 2009. The 1.5 GeV MAMI-C electron beam was used to produce an energy tagged bremsstrahlung photon beam with a maximum energy of 1.4 GeV and an intensity of 105γs-1MeV-1. The beam impinged upon a liquid hydrogen target, with reaction products detected in two segmented calorimeter arrays; the Crystal Ball detector and TAPS. This work pioneers a new method of K+ detection in segmented calorimeters, in which the K+ was identified from the signature of its weak decay inside the crystals of the calorimeter. This proved to be an excellent method of isolating K+ and accessing strangeness photoproduction channels, with good agreement between experimental and Geant4 simulated data. A novel method in seperating K+Λ and K+Σ0 final states was also developed by identifying the photon from the decay: Σ0 → Λγ. The intense photon beam at the MAMI-C facility enabled differential cross section data with greater invariant mass resolution than previous measurements. The new measurement near threshold imposes important constraints to effective field theories based on the approximate chiral symmetry of QCD. At higher centre of mass energies it also addresses the current problem of discrepant data sets and will form an important constraint on partial wave analysis for the nucleon excitation spectrum. As such, this work contributes to a major world wide programme aiming to extract the excitation spectrum of the nucleon and to understand the dynamics and interactions of its constituents. The greater statistics near threshold, and particularly at backwards K+ centre of mass angles will give new valuable constraints to contributions from meson and hyperonic resonances on the reaction mechanism. The high resolution of the photon beam (approximately 2 MeV) also allows the first search for narrow resonances coupling to KΛ final states. The differential cross sections give good agreement with Kaon-MAID partial wave solutions, apart from at backward angles close to threshold, where the data is lower. Near threshold, the data agrees with calculations from the chiral unitary framework of Borasoy et al, tending to be in better accordance with the model than previous data. No strong structure from potential narrow resonance states was observed over the centre of mass energy region of 1650-1700 MeV, where narrow structure has been observed in recent η photoproduction of the neutron.

A Aproximação de Massa Efetiva para a função evnvelope multi-componente, na presença de uma interface, desenvolvida por Marques e Sham, será utilizada aqui, para materiais de gap estreito do grupo II-VI, da seguinte maneira: A) A forte interação entre bandas de condução e valência, nestes materiais, é justificada em um Hamiltoniano de Kane (6x6) modificado, contendo todas as ondas de Bloch propagantes e evanescentes. Na presença de uma interface, a função de onda eletrônica, &#936, é composta de uma onda de Bloch incidente, uma refletida e duas evanescentes, com a mesma energia E e momento paralelo k. Já que a estrutura da maioria dos isolantes utilizados são desconhecidos, a interface semicondutor-isolante por ser considerada como uma barreira infinita, de modo que, &#936, se anule na interface. Existe uma fina região de espessura &#945 na interface, onde o decaimento das ondas evanescentes é indispensável. Distante desta região, as ondas evanescentes possuem um papel insignificante e eventualmente anulam-se. O limite de &#945 &#8594 0 determina as condições de contorno para cada componente da função de onda envelope na interface. B) As condições de contorno são usadas para computar a estrutura de subbandas e o potencial auto-consistente para o Hg1-xCdxTe. A mais interessante característica é o afastamento dos estados de spin duplamente degenerados. Estes resultados serão utilizados para encontrarmos a dependência da energia das subbandas com um campo magnético perpendicular à interface. C) A magneto-condutividade longitudinal é calculada como função do campo magnético B &#8869. Efeitos das interações elétron-elétron e elétrons-impureza são levadas em conta nas aproximações de Hartee-Foch e auto-consistente de Born, respectivamente. Para uma interação elétron-impureza finita, encontram-se fatores de preenchimentos críticos dos níveis de Landau, onde transições de fase são observadas. Estes resultados explicam as descontinuidades presentes, em medidas experimentais, na magneto-resistividade longitudinal e transversal (Hall), em MISFET de Hg (Cd)Te. / The Effective Mass Approximation for multi-component envelope wave function in the presence of an interface in the MOSFET system, developed by Marques and Sham, will be used here, for II-VI narrow-gap semiconductors, in the following way: A) The strong interaction between conduction and valence bands, in these materials, is justified. The (6x6) Kane type modified Hamiltonian is used and the total wave function contains every propagating and evanescent waves. For an interface, the total function, &#936, is composed of one incident and one reflected and two evanescent Bloch waves, with energy E and parallel wave-vector k. Since the band structure of the most used insulators is usually not well known, the insulator-semiconductor interface can be assumed as an infinite barrier; therefore, the total wave-function there can set to zero. The semiconductor evanescent Bloch waves are indispensable in a thin layer, of thickness &#945, close to this region. Far away from the interface their role are insignificant and can be neglected. In the limit &#945 &#8594 0, the boundary condition for each the limit the total Bloch wave function, are derived. B) These boundary conditions are used to calculate the self-consistent electric subband and potential for MISFET of Hg1-xCdxTe. The subbands present a very important spin splitting, due to the internal electric field. C) The effect of a perpendicular magnetic field is also studied and the longitudinal magneto-conductivity are calculated. The effect of electron-electron and electron-impurity interactions are respectively accounted for in the Hartee-Fock and self-consistent Born approximations. For critical electron-impurity interaction, the Landau level filling shows a phase transition at a given fractional occupation (or magnetic field). These results are experimentally observed in both longitudinal and transverse (Hall) magneto-resistance for Hg(Cd)Te.

Circadian clocks drive the daily patterns of behavior and physiology observed in most organisms. These internal clocks allow organisms to advantageously align their behavior to daily cycles in the environment such as light and temperature. The fruit fly Drosophila displays many robust, daily behavioral rhythms including discrete bouts of locomotor activity at dawn (i.e. morning activity) and dusk (i.e. evening activity). The molecular clocks that drive these daily activity bouts are found in approximately 150 circadian pacemaker neurons in the fly brain. Interestingly, the timing of the molecular clocks is synchronous between all pacemaker neurons, yet different subsets of these neurons appear to make quite different contributions to the regulation of morning vs. evening activity. It remains poorly understood how the molecular circadian clock drives daily rhythms in pacemaker neuron activity or how the activities of different groups of pacemaker neurons combine to produce complex behavioral output. The overall goal of this thesis is to characterize how different subsets of Drosophila pacemaker neurons contribute to daily behavioral regulation both individually and as a network. To examine daily patterns of neuronal activity in different groups of circadian clock neurons, we have established imaging methods using genetically encoded fluorescent sensors. For these sensors, changes in fluorescence levels correspond to changes in neuronal activity, thus allowing us to measure neuronal activity patterns in real-time and throughout the day. Using these tools, I have characterized the daily activity patterns of different groups of the clock neurons that agree with published rhythms in activity as assessed by patch-clamp electrophysiology and calcium imaging We have also used genetic and molecular approaches such as RNA interference (RNAi) to alter gene expression in a tissue-specific manner. These approaches allow us to manipulate the function of different groups of clock neurons and to determine how these manipulations affect rhythmic behavior and neuronal activity patterns. We have silenced different subsets of circadian pacemaker neurons using RNAi knockdown of the NARROW ABDOMEN (NA) sodium leak channel and identified a complex role for a subset of the posterior dorsal neurons 1 (DN1p) in regulating locomotor behavior. The DN1p are known to be involved in promoting morning behavior, and recent studies have shown that a subset of the DN1p regulate midday sleep bouts via downstream sleep regulating neurons. Our data suggest that the DN1p neurons likely suppress midday activity through inhibition of other circadian pacemaker neurons, and that this inhibitory role can be compensated for by light. Finally, we have also examined the intracellular mechanisms regulating circadian neuronal output. Rhythmic activity of the NA leak channel and its mammalian ortholog (NALCN) have been shown to contribute to daily excitability rhythms in circadian pacemaker neurons. We used temporally-restricted expression of RNAi and rescue constructs to identify a developmental requirement for the NA channel complex in Drosophila, and we demonstrate that channel complex proteins are very stable in the Drosophila brain. These data suggest that circadian regulation of the NA channel in adults may involve post-translational mechanisms that control activity and not just expression of the channel complex.

A significant challenge in the surgical resection of tumors is accurate identification of tumor margins. Current methods for margin detection are time-intensive and often result in incomplete tumor excision and recurrence of disease. The objective of this project was to develop a near-infrared narrowband imaging (NIR NBI) system to image tumor and its margins in real-time during surgery utilizing the contrast provided by gold nanoparticles (GNPs). NIR NBI images narrow wavelength bands to enhance contrast from plasmonic particles in a widefield, portable and non-contact device that is clinically compatible for real-time tumor margin demarcation. GNPs have recently gained significant traction as nanovectors for combined imaging and photothermal therapy of tumors. Delivered systemically, GNPs preferentially accumulate at the tumor site via the enhanced permeability and retention effect, and when irradiated with NIR light, produce sufficient heat to treat tumor tissue. The NIR NBI system consists of 1) two LED's: green (530 nm) and NIR (780 nm) LED for illuminating the blood vessels and GNP, respectively, 2) a filter wheel for wavelength selection, and 3) a CCD to collect reflected light from the sample. The NIR NBI system acquires and processes images at a rate of at least 6 frames per second. We have developed custom control software with a graphical user interface that handles both image acquisition and processing/display in real-time. We used mice with a subcutaneous tumor xenograft model that received intravenous administration and topical administration of gold nanoshells and gold nanorods. We determined the GNP's distribution and accumulation pattern within tumors using NIR NBI. Ex vivo NIR NBI of tumor xenografts accumulated with GNPs delivered systemically, demonstrated a highly heterogeneous distribution of GNP within the tumor with higher accumulation at the cortex. GNPs were observed in unique patterns surrounding the perivascular region. The GNPs clearly defined the tumor while surrounding normal tissue did not indicate the presence of particles. In addition, we present results from NBI of tumors that received topical delivery of conjugated GNPs. We determined that tumor labeling using topical delivery approach resulted in a more homogenous distribution of GNPs compared to the systemic delivery approach. Finally, we present results from the on-going in vivo tumor margin imaging studies using NIR NBI. Our results demonstrate the feasibility of NIR NBI in demarcating tumor margins during surgical resection and potentially guiding photo-thermal ablation of tumors. / text

Ultra-narrow row (UNR) cotton (Gossypium hirsutum L.) is a production system using high plant populations in reduced row spacings. The responses of this production system to nitrogen fertilizer have not been fully investigated. Evaluations of yield and earliness of harvest are also important. A three-year study was conducted at the Texas Agricultural Experiment Station farm, Burleson County, TX, on a Ships clay (very-fine, mixed, active, thermic Chromic Hapluderts) and a Weswood silty clay loam (fine-silty, mixed, superactive, thermic Udifluventic Haplustepts). A split plot design was used. Nitrogen fertilizer rates of 0, 50, 101, and 151 kg N ha-1 were applied as the whole plots and row spacings of 19, 38, and 76 cm were established as the split plots. Data included lint yield and yield components, as well as earliness of crop maturity and earliness-related parameters such as boll distribution. Lint yield was increased by higher nitrogen rate. There was no nitrogen rate by row spacing interaction on lint yield, implying fertilizer rates do not need to be changed for UNR systems. Reductions in row spacing did not significantly affect lint yield in any year. Responses such as reduced bolls per plant, increased plant populations, increased ginout, and decreased boll size were often significant and combined to allow the crop to maintain equivalent yields as row spacings were reduced. The slight UNR earliness advantages were probably due to changes in boll distribution. Based on these results, increases in lint yield and earliness may not reliably contribute to the profitability of UNR cotton.

Temporal and wavelet characteristics of initial breakdown pulses are meticulously studied especially during the earliest moment of lightning events. Any possible features during the earliest moment that may exist which lead to either negative cloud-to-ground (CG), positive cloud-to-ground, cloud or isolated breakdown flashes in Sweden are investigated. Moreover, the occurrence of narrow bipolar pulses (NBPs) as part of a CG event that has been recorded from tropical thunderstorms are also included in the investigation. Electric field signatures selected from a collection of waveforms recorded using fast electric field broadband antenna system installed in Uppsala, Sweden and Skudai, South Malaysia are then carefully analyzed in order to observe any similarities or/and differences of their features. Temporal analysis reveals that there are significant distinctions within the first 1 ms among different types of lightning flashes. It is found that a negative CG flash tends to radiate pulses more frequently than other flashes and a cloud flash tends to radiate shorter pulses than other flashes but less frequently when compared to negative CG and isolated breakdown flashes. Perhaps, the ionization process during the earliest moment of negative CG flashes is more rapid than other discharges. Using a wavelet transformation, it can be suggested that the first electric field pulse of both negative CG and cloud flashes experiences a more rapid and extensive ionization process compared to positive CG and isolated breakdown flashes. Further temporal analysis on NBPs found to occur as part of CG flashes show the disparity of the normalized electric field amplitude between the NBPs prior to and after the first return stroke. This indicates that the NBPs intensities were influenced by the return stroke events and they occurred in the same thundercloud. The similarity between the temporal characteristics of NBPs as part of CG flashes and isolated NBPs suggests that their breakdown mechanisms might be similar.