This study examines how the Delta-bluffs interface in the Mississippi River alluvial flood plain of western Mississippi affects the spatial variation of tornado occurrence and the characteristics of tornadoes that occur within fifty km of the interface. A t-test and Poisson distribution were used to test for clustering of tornadoes along the Delta-bluffs interface. Previous research has been used to show differing vegetation and soil types can act as focusing mechanisms for thunderstorm development and enhancement. An in-depth analysis of eight tornado events reveals the Delta-bluffs interface enhanced reflectivity and velocity values whenmseven of eight of the storms were within twenty km of the topographic boundary. It was also shown that changes in the roughness of the Earth’s surface can affect the SRH being ingested by a thunderstorm. It was found that F0-F1 tornadoes are significantly (p < 0.01) clustered along the interface but F2-F5 tornadoes were not significantly (p < 0.05) clustered along this boundary. It appears unlikely that characteristics of tornadoes within and outside of the Delta are statistically different.

This thesis used geographic information systems and remote sensing to measure expansion of aquaculture Northwest Mississippi. A feature extraction technique was used to identify aquaculture from satellite imagery. Variations in well water depth were examined in relation to the changes in aquaculture to explore its affects on the Mississippi River Valley Alluvial Aquifer (MRVA) aquifer. A soil moisture index was used to investigate preferential expansion of aquaculture onto soil moisture types. This study found that aquaculture expanded from 66,000 acres in 1984 to 142,000 acres in 2001. Total acreage of individual counties from the Feature Extraction is higher than estimates provided by the Mississippi Agriculture Statistics Service. It was found that aquaculture expansion covered more acres of wet soil classes than dry soil classes and the volumes of expansion onto moist soils depth time series were highly variable across the study area and showed no conclusive relationship to aquaculture expansion.

International Telemetering Conference Proceedings / October 17-20, 1988 / Riviera Hotel, Las Vegas, Nevada / A switched-capacitor technique for realization of one bit serial A/D converter is presented. A conversion accuracy that is higher than 15 bits can be expected from its integrated realization. Results of simulation are presented. It is shown that arithmetic operations on bit serial signals are possible. Using arithmetic operations on delta-modulated signals, it is possible to build inexpensive options necessary in instrumentation.

O delta do rio Tubarão, situado na costa centro-sul catarinense entre os municípios de Tubarão, Jaguaruna e Laguna, constitui raro exemplo de delta lagunar ativo no Brasil. Sua planície deltaica cobre área aproximada de 250km2, onde são encontradas evidências de migração de canais fluviais dadas por séries de truncamentos de antigos distributários, alguns ainda ativos. Dez testemunhos foram obtidos junto aos principais canais distributários do rio Tubarão, a partir dos quais foram realizadas análises de fácies, granulométrica, de minerais pesados, de teor de matéria orgânica e de relações químio-isotópicas, além de datações 14C. Também foram levantados acervos históricos de fotografias aéreas e de dados de prospecção mineral de subsuperfície. Cerca de 5000 anos atrás, na região de seu ápice, próximo ao rio tributário Capivari de Baixo, o delta do rio Tubarão ingressou numa antiga baía lagunar e ramificou-se em sete distributários principais que, desde seus momentos iniciais de migração, foram controlados por avulsões autogênicas rumo a antigas depressões do fundo da bacia receptora. Tais avulsões progradaram o delta inicialmente para SW, depois para ENE, e então para NNE, favorecendo a fragmentação da antiga baía lagunar em uma série de lagos e lagunas menores. Diante deste cenário dinâmico, sambaquis foram erigidos no entorno do sistema lagunar, constituindo importantes registros arqueológicos de interação entre evolução sedimentar e ocupação humana pré-histórica. O resultado das análises granulométricas indicou que a sedimentação deltaica, nas proximidades de encostas de morros, foi misturada com colúvio e/ou depósitos de fluxos gravitacionais, como evidenciado pela presença de intervalos texturalmente muito imaturos em alguns testemunhos. Em relação à análise de minerais pesados, o principal fator de controle nas variações da assembleia em depósitos de delta e de bacia é a proveniência sedimentar. Em termos mediatos, essa proveniência reflete fontes plutônicas e metamórficas (médio a alto grau) do Batólito de Florianópolis (e xenólitos associados) e do Complexo Granito-Gnáissico, e rochas arenáceas alteradas da Bacia do Paraná. Em termos imediatos, depósitos deltaicos destacam-se pela afinidade mineralógica com as areias do rio Tubarão, inferida sobretudo a partir da presença mútua de grãos alterados de cianita e estaurolita, enquanto que depósitos da bacia lagunar destacam-se por sua similaridade mineralógica com areias dos rios tributários Braço do Norte e Capivari de Baixo, neste caso principalmente pela presença de zircão. A matéria orgânica presente nos depósitos do delta e de sua bacia receptora resulta do aporte de fontes terrestres (fornecido pelos rios) e marinhas (trazido via desembocaduras lagunares), fato que é evidenciado pelos resultados de \'delta\'\'POT.13 C\', \'delta\'\'POT.15 N\' e razão \'C IND.ORG\'/\'N IND.TOTAL\'. Particularmente, nos sedimentos da bacia, variações entre diferentes tipos de matéria orgânica têm ocorrido ao longo do Holoceno, as quais são atribuídas tanto ao isolamento físico progressivo do sistema lagunar em relação ao mar aberto como por mudança climática regional (aumento destacado de precipitação). A análise isotópica de oxigênio (\'delta\'\'POT 18 O\') de conchas de moluscos em depósitos da bacia indicou enriquecimento relativo em \'ANTPOT.16 O\' durante o Holoceno. Este resultado, a exemplo daquele dos isótopos de carbono e de nitrogênio dos sedimentos, sugere isolamento gradual das águas lagunares em relação às de mar aberto. / The Tubarão river delta, located on the centre-south coast of Santa Catarina State, among the municipalities of Tubarão, Jaguaruna and Laguna, is rare example of active lagoonal delta in Brazil. Its delta plain covers an area of about 250km2, where there are evidences of migration of fluvial channels in a set of truncations of ancient distributaries, some of these still in activity. Ten cores were acquired adjacent to the main distributary channels of the Tubarão river, from which analyses of facies, grain size, heavy minerals, organic matter, chemistry-isotope ratios, and radiocarbon datings were performed. Also, aerial photographies and data of subsurface mining were surveyed from historical collections. Thereabout 5,000 years ago, in the region of its apex, near Capivari de Baixo tributary river, the Tubarão river delta entered an ancient lagoonal bay and branched seven main distributaries. Since the beginning of its migration, these distributaries were controlled by autogenic avulsions towards ancient depressions in the bottom of the basin. Initially, these avulsions prograded the delta towards SW, afterwards to ENE, and then to NNE, favoring the fragmentation of the ancient lagoonal bay in a set of smaller lakes and lagoons. Faced with this dynamical scenario, shellmounds were erected surrounding the lagoon system, composing important archaeological records of the interaction between sedimentary evolution and prehistoric human occupation. The results of the grain size analysis showed that the deltaic sedimentation, in the vicinity of slopes of hills, was mixed with colluvium and/or gravity flow deposits, that is evidenced by the presence of texturally very immature intervals in some cores. The analysis of heavy minerals, by its turn, showed that the main controlling factor in the variations of its assemblage in deposits of delta and basin is the sedimentary provenance. In terms of mediate sources, this provenance reflects plutonic and metamorphic (medium to high grade) rocks of the Florianópolis batholith (including its xenoliths) and of the Granite-Gneiss Complex, and weathered sedimentary sandstones of the Palaeozoic Paraná basin. Regarding immediate sources, deltaic deposits stand out by its mineralogical affinity with sands of the Tubarão river, mainly by the mutual presence of weathered grains of kyanite and staurolite, whereas deposits of the lagoon have mineralogical similarity with the sands of Braço do Norte and Capivari de Baixo tributary rivers, especially in relation to the presence of zircon. The origin of the organic matter found in the deposits of the delta and in its lagoonal basin is both from sedimentary input of terrestrial sources (provided by rivers) and marine (brought via inlets), fact evidenced by results of \'delta\'\'POT.13 C\', \'delta\'\' POT.15 N\', and \'C IND.ORG\'/\'N IND. TOTAL\' ratio. Particularly, in the sediments of the basin, variations between different types of organic matter have occurred during the Holocene, and are attributed both to the progressive physical isolament of the lagoon system from the open sea, and by local climate change (pronounced augment of precipitation). The isotope analyses of oxygen (\'delta\'\'POT.18 O\') of molluskan shells from the deposits of the basin present relative enrichment in \'ANTPOT.16 O\' during the Holocene. This result, as well as the one from isotope analyses of carbon and nitrogen of sediments, suggests gradual isolation of the lagoonal waters of influence of waters from the open sea.

Des molécules sont présentées aux T Vγ9Vδ2 par une protéine de co-stimulation immune BTN3A.Le membre BTN3A2 est surexprimé dans 4 cancers, et pourrait agir comme récepteur leurre.Récemment, l’isoforme BTN3A2 a été décrite comme régulant la localisation membranaire du BTN3A1 grâce à une hétérodimérisation.L’objectif de mon projet était d’identifier le ligand de BTN3A2 pour une immunothérapie.Ainsi, nous avons tout d’abord sélectionné, par des études de liaison utilisant la cytométrie en flux, quelques lignées cellulaires T exprimant le ligand de BTN3A2. Puis basé sur notre sélection, la comparaison du profil d’expression génique a été effectuée, nous permettant d’établir une liste de protéines membranaires candidats du ligand de BTN3A2,les molécules HLA de classe II. Après génération de lignées cellulaires surexprimant les candidats potentiels de la méthode transcriptomique, ces cellules ont été utilisées pour des tests de liaison avec le BTN3A2-Fc qui se sont révélés négatifs dans les différentes conditions.De plus, la technologie de transfections transitoires puis tests de liaison, a été utilisée pour identifier les récepteurs partenaires potentiels de BTN3A2.Les quatre produits géniques restants ont été sélectionnés, PLPP3, SEMA6A, SEMA6C et MSR1 mais non validés.Finalement, nous avons utilisé un agent de capture avec trois bras, permettant une liaison covalente, qui a montré que BTN3A1 était le candidat potentiel. Dans notre projet, nous avons confirmé l’hétérodimérisation de BTN3A1/A2 et nous avons démontré la forme existante d’hétérodimérisation pour former une voie de signalisation activant les cellules T Vγ9Vδ2. / Molecules are presented to Vγ9Vδ2 T cells by immune costimulatory protein BTN3A.BTN3A2 which is devoid of a functional intracellular domain, is overexpressed in 4 cancers. Recently, BTN3A2 was described as regulator of subcellular localization of BTN3A1 thanks to heterodimerization. The aim of our project, was to identify the ligand of BTN3A2 for immunotherapy. Therefore, we have first selected by binding studies using flow cytometry, few T cell lines expressing BTN3A2 ligand.Based on the selection, a gene expression profile comparison was performed and allowed us to establish a list of membrane proteins expressed only in positive cell lines, BTN3A2 ligand candidates. The highest FC were found for HLA class II molecules. Cell lines overexpressing potential candidates of transcriptomic method were used for binding assays using BTN3A2-Fc, but were negative in all conditions. Then cell microarray technology was used to identify potential receptor partners of BTN3A2. 4 remaining gene products were selected, PLPP3, SEMA6A, SEMA6C and MSR1. The validation of these candidates was not done after transient transfection and binding test with BTN3A2-Fc (using flow cytrometry). Moreover, chemoproteomic experiments were performed to isolate and identify by mass spectrometry (MS) BTN3A2 ligand. Therefore, we used an original capture reagent (TFR) with three moieties, allowing covalent binding, which showed clearly BTN3A1 as a potential candidate. In our project, we have confirmed the heterodimerization of BTN3A1/A2 and we have demonstrated an existing form of heterodimerization that could interact with other proteins, to form a signaling pathway activating Vγ9Vδ2 T cells.

<p>An important component in many communication system is the digital to analog converter. The component is needed in order to convert real world analog quantities to digital quantities which are easier to process. As the market for hand held devices with wireless communication with the outer world has increased new approaches for sharing the frequency spectrum are needed. Therefore it would be interesting to look at the possibility to design an analog to digital converter that, in runtime, can change the frequency band converted, and hence the used standard. This thesis study one of the possibilities to design such an ADC, as a Σ∆ modulator, and more precise the structure called Cascade of resonators with distributed feedback and input (CRFB). The order of the modulator in this study is two.</p>

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

Groundwater is now being considered as an alternative water supply in the Pearl River Delta (PRD) because of the increasing demand for fresh water coupled with deterioration in river water quality as a result of rapid urbanization and industrialization. There are thick aquitards in the PRD as a result of several times transgression and regression in the Holocene. This study considers this aquitards as a research object because it has a significant impact on the underneath confined aquifer. It is necessary to analyze the hydraulic properties of the aquitards. A slug-test is a reasonable method to determine the hydraulic conductivity and specific storage of the low-permeability aquitards of silt and clay in the PRD. In this study, several slug-test methods were used to determine the hydraulic parameters of aquitards in several piezometers at the key site MZ04in the PRD. The results from these methods were compared to obtain the most reasonable group of hydraulic parameters. A reasonable equivalent numerical method is applied at the key site MZ04 site after the calibration with the C-B-P solution and the KGS model. The natural groundwater regime is obtained, which is helpful for the further research. A three-dimensional numerical model using MODFLOW is carried out under some assumptions and the simplification for the sediments structure. The characteristics of regional groundwater flow and the influence of hydraulic properties of the aquifer-aquitard system on groundwater flow were analyzed. The simulated groundwater level both in the unconfined aquifer and confined aquifer agree reasonably well with the observed data. Study on the water budget of the groundwater showed that the quantity of ground water discharged from participation to participate the water exchange is very small. In the groundwater participated water exchange, 97% of them flow into rivers, while only 3% of them flow into the sea. Moreover, the vertical flow is more important than the horizontal flow to the regional ground water balance in aquitards according to the water budget obtained from the model. The research of the PRD needs numerous data due to the complicated deposition and evolution process of the sediments and the intensive river network. The modeling results are preliminary because of the complexity of the geological and hydrogeological conditions in the PRD and the limitation of the observed water level data. The hydraulic parameters calculated for this study and the model results can provide a basis for further research on groundwater in the PRD. / published_or_final_version / Earth Sciences / Master / Master of Philosophy

An aquitard is not only a confining layer in the aquifer-aquitard system, but also a functional complex for nutrient reservation and microorganism inhabitation. Geochemical characteristics and geomicrobial processes in aquitards play an important role in groundwater quality, and should be well studied. The Pearl River Delta is dominated by clay-rich aquitards and was intensively influenced by Holocene transgression. In this thesis, the aquifer-aquitard system in the PRD was studied from various perspectives including geophysics, geochemistry and geomicrobiology. Sediment and groundwater samples were taken from representative locations in the PRD at different lithological units. Particle size distribution, computed axial tomography, optically stimulated luminescence dating and scanning electron microscopy were analyzed to understand the geophysical properties. Concentrations of major ions and abundances of environmental isotopes were measured for geochemical analysis. Bacterial 16S rRNA gene clone libraries were constructed to analyze microbial identifications and community structures in different strata. Gene abundances of anammox 16S and bacteria amoA in both sediment and groundwater samples were quantitatively analyzed with 15N isotope at the same depth. The mixing process of seawater and river water was the dominant factor controlling the isotopic and chemical characterizes of groundwater in the system. Isotopic fractionation in the aquitards was majorly controlled by chemical and biological reactions other than diffusion. Chemical pattern in this system was mainly controlled by topography and sea level in the Holocene. Independent sedimentary centers of strong reducing environment were located in the depressions controlled by fault zones, and generated massive amount of pyrite minerals in the sediment and NH4+ in the groundwater. The sea level and depositional environment in the Holocene determined the physical structures of the sediment and seawater/river-water ratio in the estuary. Isotopic research also demonstrated that South Asia Monsoon was the major source of atmospheric precipitation in the PRD. Bacterial species in the PRD sediment were identified. Canonical correspondence analysis between bacterial linages and environment factors showed that community structures were significantly modified by geological conditions. High bacterial diversity was observed in samples from the Holocene aquitard M1 and aquifer T1, while in the older aquitard M2 and basal aquifer T2, the bacterial diversity was much lower. Chloroflexi, γ-proteobacteria and δ-proteobacteria were the dominant phyla in the aquitard sediment. β-proteobacteria was the dominant phylum in sediment which was strongly influenced by fresh water. Anammox was the controlling biochemical process in microbial-derived ammonium loss, as demonstrated by gene abundance coupling with 15N isotope and ammonium concentration. The 16S gene abundance of anammox bacteria ranged from approximately 105 to 106 copies/g in the aquitard sediment, and ranged from 104 to 105 copies/g in aquifers. amoA gene abundance was 1-2 orders lower than anammox bacteria 16S in aquitard sediment, but in aquifers, the gene abundances of amoA and anammox 16S were similar. Interface between aquifer and aquitard was demonstrated as biochemically enhanced zone. The results of this study significantly benefited the understanding of geochemistry and microbiology in the aquifer-aquitard system, and showed directions for future work on geomicrobiology in aquitards. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

The Okavango Delta, an internationally recognized wetland, is undergoing natural and anthropogenic change at a variety of spatio-temporal scales. The objective of this research was to utilize remotely sensed imagery to assess the spatio-temporal distribution of flooding and fire and their subsequent influences on vegetation as represented by vegetation index trajectories in the Okavango Delta. The characterization of the spatiotemporal dynamics of vegetation spectral response via a time-series of remotely sensed data not only informs ecosystem and disturbance theory but also presents new methodological applications for multi-temporal change analysis. Disentangling these components from a signal is critical for better assessing the interrelationships among climatic oscillations, disturbance regimes, and human management on ecosystem response. This research tested six hypotheses regarding flooding and fire, and found that the largest number of fires occurred either within 5 km of the border to the Wildlife Management Areas or within the active (flooded a minimum of every two years) floodplains. These hypotheses indicate that burning is highest where people have accessinto the management areas and where the natural resources are plentiful. Periodicities from vegetation signal time-series did not confirm published climate-driven periodicities of 3, 8, and 18-years but did reveal seasonal (6 month) and quasi-decadal periodicities. Vegetation trajectories were more predictable with increasing flood frequency and duration, but were less predictable with increased fire frequency. The fact that increased burning resulted in less predictable behavior indicates the potential of quantifying the anthropogenic influence on the landscape using remotely sensed imagery. Flooding and fire were not statistically correlated to the residual dynamics, refuting the conceptualization of flooding and fire as disturbance and supporting the interpretation of flooding and fire as disturbance regimes. This research thus contributes methodologically and theoretically to the ecology literature by operationalizing tests for disturbance versus disturbance regimes via spatio-temporal characterization. Further, this work extends change detection techniques typically implemented with coarser spatial resolution but more frequently acquired imagery by using harmonic regression and wavelet analysis with Landsat data. Lastly, this work provides a temporally rich assessment of recent vegetation, flooding, and fire trends for improving management efforts of the Okavango Delta.