The response of the Gulf of Alaska (GOA) circulation to large-scale North Pacific climate variability is explored using three high resolution (15 km) regional ocean model ensembles over the period 1950-2004. On interannual and decadal timescales the mean circulation is strongly modulated by changes in the large scale climate forcing associated with PDO and ENSO. Intensification of the model gyre scale circulation occurs after the 1976-1977 climate shift, as well as during 1965-1970 and 1993-1995. From the model dynamical budgets we find that when the GOA experiences stronger southeasterly winds, typical during the positive phase of the PDO and ENSO, there is net large-scale Ekman convergence in the central and eastern coastal boundary. The geostrophic adjustment to higher sea surface height (SSH) and lower isopycnals lead to stronger cyclonic gyre scale circulation. The opposite situation occurs during stronger northwesterly winds (negative phase of the PDO). Along the eastern basin, interannual changes in the surface winds also modulate the seasonal development of high amplitude anticyclonic eddies (e.g. Hada and Sitka eddies). Large interannual eddy events during winter-spring, are phase-locked with the seasonal cycle. The initial eddy dynamics are consistent with a quasi-linear Rossby wave response to positive SSH anomalies forced by stronger downwelling favorable winds (e.g. southwesterly during El Nio). However, because of the fast growth rate of baroclinic instability and the geographical focusing associated with the coastal geometry, most of the perturbation energy in the Rossby wave is locally trapped until converted into large scale nonlinear coherent eddies. Coastally trapped waves of tropical origin may also contribute to positive SSH anomalies that lead to higher amplitude eddies. However, their presence does not appear essential. The model ensembles, which do not include the effects of equatorial coastally trapped waves, capture the large Hada and Sitka eddy events observed during 1982 and 1997 and explain most of the variance of tidal gauges along the GOA coast. In the western basin, interannual eddy variability located south of the Alaskan Stream is not correlated with large scale forcing and appears to be intrinsic. A comparison of the three model ensembles forced by NCEP winds and a multi-century-long integration forced only with the seasonal cycle, shows that the internal variability alone explains most of the eddy variance. The asymmetry between the eddy forced regime in the eastern basin, and the intrinsic regime in the western basin, has important implications for predicting the GOA response to climate change. Eastern boundary eddies transport important biogeochemical quantities such as iron, oxygen and chlorophyll-a into the gyre interior, therefore having potential upscale effects on the GOA high-nutrient-low-chlorophyll region.

The complex hydroclimatic response of the Upper Colorado River Basin (UCRB) to climate circulation patterns and their descriptive indices creates significant challenges to water managers, especially given the uncertain future of the climate. This dissertation addresses fundamental questions that surround extreme flooding in the UCRB by combining paleoflood field techniques, two analytical geochronology techniques and several numerical climate data analysis techniques. The three manuscripts included in this dissertation focus on the Dolores River Basin (DRB), a sub-basin within the UCRB in order to answer theoretical questions about the timing and climate patterns associated with extreme floods.It has become widely accepted that extreme flooding in the Lower Colorado River Basin (LCRB) is linked to a period when the frequency and intensity of El Nino periods was higher. Within the UCRB, and more specifically, the DRB, the linkages are less clear. The paleoflood chronology that we developed indicates that the peak episodes of flooding in the DRB occurred between roughly 300 A.D. and 1200 A.D. This period of flooding is out of phase with many floods in the LCRB, whose peak floods dominantly clustered in the last 700 years; a period of time coincident with the termination of large floods in the DRB. The chronology that I developed utilizes accelerator mass spectrometry radiocarbon (AMS 14C) and optically stimulated luminescence (OSL) to provide a detailed flood history, highlighting the importance of utilizing independent age control. Alternative, or less accurate chronologies would have resulted had we used AMS 14C or OSL alone, suggesting that some previously studied basins may have incorrect chronologies. The detailed flood chronology of this study has subsequently allowed us to contextualize extreme floods relative to middle--late Holocene climate variability.In an effort to provide a hydroclimatic context for flooding in the DRB, numerical analyses were applied to contemporary climate and streamflow data in order to identify the possible mechanisms that modulate precipitation and streamflow in the Western U.S. and more specifically, the DRB. Results from these techniques indicate that the DRB maintains a complex response to a major North Pacific, low-frequency circulation pattern. The North Pacific circulation modulates the low-frequency component of the DRB's precipitation and flooding, although the high frequency modulation remains very poorly characterized.

No description available.

Large-scale circulation patterns have a significant modulating influence on local hydro-meteorological variables, and consequently on water availability. An understanding of the influence of these patterns on the hydrological cycle, and the ability to timely predict their impacts, is crucial for water resources planning and management. This dissertation focusses on the influence of two major large-scale circulation patterns, the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), on the Rio Grande basin and the state of Texas, US. Both study areas are subject to a varying climate, and are extremely vulnerable to droughts, which can have devastating socio-economic impacts. The strength and spatial correlation structure of the climate indices on gauged precipitation was first established. Precipitation is not linearly related to water availability; therefore a land surface model (LSM), with land use land cover constant, was used to create naturalized flow, as it incorporates all necessary hydro-meteorological factors. As not all ENSO events are created equal, the influence of individual El Niño and La Niña events, classified using four different metrics, on water availability was examined. A general increase (decrease) in runoff during El Niños (La Niñas) was noted, but some individual events actually caused a decrease (increase) in water availability. Long duration El Niños have more influence on water availability than short duration high intensity events. Positive PDO enhances the effect of El Niño, and dampens the negative effect of La Niña, but when it is in its neutral or transition phase, La Niña tends to dominate climatic conditions and reduce water availability. LSM derived runoffs were converted into 3-month Standardized Runoff Indices (SRI 3) from which water deficit durations and severities were extracted. Conditional probability models of duration and severity were developed and compared with that based on observed precipitations. It was found that model derived information can be used in regions having limited ground observation data, or can be used in tandem with observation driven conditional probabilities for more efficient water resources planning and management. Finally a multidimensional model was developed, using copulas, to predict precipitation based on the phase of ENSO and PDO. A bivariate model, with ENSO and precipitation, was compared to a trivariate model, which incorporates PDO, and it was found that information on the state of PDO is important for efficient precipitation predictions.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-04T11:42:51Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese Mitsue.pdf: 3532261 bytes, checksum: 2b3892ad1f6ef4e1621506010782d951 (MD5) / Made available in DSpace on 2016-07-04T11:42:51Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese Mitsue.pdf: 3532261 bytes, checksum: 2b3892ad1f6ef4e1621506010782d951 (MD5) Previous issue date: 2015-11-11 / CNPq / CAPEs / No presente estudo o aproveitamento de glicerol através de processos anaeróbios para geração de subprodutos de valor agregado foi analisado de duas maneiras. Em um primeiro momento foi avaliado o uso de glicerol bruto proveniente da produção de biodiesel como substrato para produção de biogás em um reator anaeróbio de fluxo ascendente e manta de lodo (UASB) em escala de bancada durante o período experimental de 280 dias. O reator foi operado sob cargas orgânicas volumétricas variando entre 0,50 e 8,06 kg DQO/m³·d. Como resultados, foram alcançadas eficiências médias de remoção de DQO de 89% e valores de conversão de metano (CH4) de 68%. A produção média de CH4 foi igual a 0,25 L CH4/g DQO. Os perfis das bandas de DGGE dos domínios Bacteria e Archaea sugeriram poucas mudanças na comunidade microbiana durante a operação do reator. Na segunda etapa da tese, 13 variáveis foram avaliadas através do design experimental de Plackett-Burman visando definir a composição adequada do meio de cultivo para a produção de 1,3-propanodiol (1,3-PDO) e/ou hidrogênio. Em seguida, dois reatores UASB foram operados usando-se glicerol analítico como substrato. O rendimento máximo de 0,8 mol 1,3-PDO/mol glicerol consumido foi alcançado, após a adição de bicarbonato de sódio aos reatores. Como produtos secundários foram produzidos propionato e acetato. Análises de ecologia microbiana demonstraram a baixa diversidade presente no lodo granular do inóculo e das fases operacionais finais da operação dos reatores. A partir dos resultados obtidos em ambas etapas de estudo, é possível concluir que o glicerol bruto proveniente da produção de biodiesel pode ser degradado eficientemente através de digestão anaeróbia, alcançando altos rendimentos de metano e que a produção contínua de 1,3-PDO a partir de glicerol em reatores UASB com lodo granular é viável. / En este estudio se analizó el aprovechamiento de glicerol mediante procesos anaerobios mediante dos enfoques diferentes. En una primera etapa se evaluó el uso de glicerol bruto generado en la producción de biodiesel como sustrato para la producción de biogás mediante un reactor anaerobio de manto de lodo con flujo ascendente (UASB) en escala de laboratorio durante un período de 280 días. El reactor operó con cargas orgánicas volumétricas que variaban entre 0,50 y 8,06 kg DQO/m³·d. Como resultado, la eficiencia media de remoción de DQO fue de 89% y la conversión media en metano (CH4) fue del 68%. La producción de CH4 fue igual a 0,25 L CH4/g DQO. Los perfiles de las bandas de DGGE de los dominios Bacteria y Archaea sugieren pocos cambios en la comunidad microbiana durante el funcionamiento del reactor. En la segunda etapa de la tesis, se evaluaron 13 factores mediante el diseño experimental de Plackett-Burman con el fin de definir la composición adecuada del medio de cultivo para la producción de 1,3-propanodiol (1,3-PDO) y/o hidrógeno. Con posterioridad, se operaron dos reactores UASB utilizando glicerol analítico como sustrato. El rendimiento máximo de 0,8 mol 1,3-PDO/mol glicerol consumido se logró tras la adición de bicarbonato de sodio a los reactores. Como subproductos secundarios se produjeron propionato y acetato. El análisis de la ecología microbiana de los reactores demostró baja diversidad presente en el lodo granular del inóculo y de las fases operativas finales de los reactores. De los resultados obtenidos en ambas etapas del estudio, se puede concluir que el glicerol bruto procedente de la producción de biodiesel se puede degradar de manera eficiente a través de la digestión anaerobia, alcanzando altos rendimientos de metano y que la producción continua de 1,3-PDO desde glicerol en reactores UASB con lodo granular es factible.

The oxidation of Pd single crystals: Pd(111), Pd(100) and Pd(110) was studied using Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), Low Electron Energy Diffraction (LEED) and Scanning Tunneling Microscopy (STM) as they were subjected to O2 in the pressure range between 1 and 150 Torr at temperatures 600-900 K. The oxygen species formed during oxidation, the oxygen uptake dependence on the sample history, the Pd single crystal surface morphology transformations, and the catalytic methane combustion over Pd single crystals were investigated in detail. The Pd single crystal oxidation proceeded through a three-step mechanism. Namely, (1) oxygen dissociatively adsorbed on Pd surface, forming chemisorbed oxygen and then surface oxide; (2) atomic oxygen diffused through a thin surface oxide layer into Pd metal, forming near surface and bulk oxygen; (3) bulk PdO formed when a critical oxygen concentration was reached in the near surface region. The diffusion of oxygen through thin surface oxide layer into Pd metal decreased in the order: Pd(110)>Pd(100)>Pd(111). The oxygen diffusion coefficient was estimated to be around 10-16 cm2 s-1 at 600 K, with an activation energy of 80 kJ mol-1. Once bulk PdO was formed, the diffusion of oxygen through the bulk oxide layer was the rate-determining step for the palladium oxidation. The diffusion coefficient was equal to 10-18 cm2 s-1 at 600 K and the activation energy was approximately 120 kJ mol-1. The oxygen diffusion through thin surface oxide layer and bulk PdO followed the Mott-Cabrera parabolic diffusion law. The oxygen uptake on Pd single crystals depended on the sample history. The uptake amount increased with the population of the bulk oxygen species, which was achieved by high oxygen exposure at elevated temperatures, for example in 1 Torr O2 at above 820 K. Ar+ sputtering or annealing in vacuum at 1300 K depleted the bulk oxygen. The Pd single crystal surface morphology was determined by the oxidation conditions: O2 pressure, treatment temperature and exposure time. When bulk PdO was formed, the single crystal surface was covered with semi-spherical agglomerates 2-4 nm in size, which tended to aggregate to form a“cauliflower-like" superstructure. The single crystal surface area during oxidation, determined by integrating the STM image, experienced three major expansions in consistent with a three-step oxidation mechanism. The surface area on the oxidized single crystals increased in the order: Pd(110)

Master of Science / Department of Agricultural Economics / Michael A. Boland / The purpose of this research was to analyze the impact of supply control variables such as market share; DO/PGI cheese hedonic quality attributes such as country of origin, type of milk, and age; and the price of a substitute artesian or farmstead cheese on the price of imported cheeses. The literature review found that the EU has been a leader in developing a process for verifying foods produced in a local geographic area. It also revealed that the ability to control supply of a differentiated product transferred consumer surplus to producer surplus. The economic theory suggests that PDO/PGI certification results in the ability of the group of producers and / or processor to control supply by effectively causing a vertical kink in the supply curve and sufficiently differentiated products have a relatively inelastic demand curve. Data was collected on 83 PDO cheeses manufactured in the EU and sold in the US. This data included market share defined as the total tons of that PDO cheese produced in that geographic region divided by the total hectares of land. Hedonic variables characterize the PDO cheeses based on aging time, type of input and country of production. The price of a competing artisan cheese similar to the PDO cheese was identified. All of these variables were used in an ordinary least squares regression model to explain the variation in the price of the imported cheese. The regression results founded that market share, country of origin (Italy and Spain), and the price of a substitute were significant in explaining the variability in imported PDO cheese prices. Market share had a greater magnitude of change suggesting that, at the margin, a small change in supply can cause a larger change in supply which was not surprising given an inelastic demand curve and a fixed supply curve. Substitutes were actually complements which at first glance appears surprising. Finally, as one might suspect, a cheese that is more mature, like wine, has a greater value.

<p>Members of the thioredoxin superfamily of proteins catalyze disulfide bond reduction and oxidation using the active site C-X-X-C sequence. In hyperthermophilic organisms, cysteine side chains were expected in low abundance since they were not believed to endure the high temperatures under which they grow. Recently it has been found that disulfide bonds in hyperthermophiles are more frequent, the higher the growth temperature of the organism. This is perhaps used as an adaptation to high temperature in order to stabilize proteins under harsh conditions. A protein with sequence and structural similarities to mesophilic members of the thioredoxin superfamily, called protein disulfide oxidoreductases (PDO), has been found in the genomes of recently sequenced hyperthermophilic genomes. In this study PDOs from the hyperthermophiles Aquifex aeolicus (AaPDO) and Pyrococcus furiosus (PfPDO) have been investigated. The molecular weight is about 26 kDa and their structures are comprised of two homologous thioredoxin folds, referred to as the N-unit and the C-unit, each containing a C-X-X-C motif. The sequence identity between the two units and the two proteins is low, but they are still structurally very similar. The function of these proteins in vivo is unknown. As a first step in characterizing the activity of these proteins, the redox characteristics of these domains will be investigated. During this project, the genes for AaPDO and PfPDO have been cloned into overexpression vectors, expressed in E. coli and purified to homogeneity. To allow for individual study of the activities of two units, mutated proteins were prepared in which the cysteine residues of the N-unit (AaPDOnm and PfPDOnm) and of the C-unit (AaPDOcm and PfPDOcm) and purified. Circular dichroism spectra recorded of the wild type and mutants indicate that all purified proteins are folded and that the N- and C-unit active site mutants are structurally similar to the corresponding wild type proteins.</p>

Water managers throughout the world are challenged with managing scarce resources and therefore rely heavily on forecasts to allocate and meet various water demands. The need for improved streamflow and snowpack forecast models is of the utmost importance. In this research, the use of oceanic and atmospheric variables as predictors was investigated to improve the long lead-time (three to nine months) forecast of streamflow and snowpack. Singular Value Decomposition (SVD) analysis was used to identify a region of Pacific and Atlantic Ocean SSTs and a region of 500 mbar geopotential height (Z500mb) that were teleconnected with streamflow and snowpack. The resulting Pacific and Atlantic Ocean SSTs and Z500mb regions were used to create indices that were then used as predictors in a non-parametric forecasting model. The majority of forecasts resulted in positive statistical skill, which indicated an improvement of the forecast over the climatology or no-skill forecast. The results indicated that derived indices from SSTs were better suited for long lead-time (six to nine month) forecasts of streamflow and snowpack while the indices derived from Z500mb improved short lead-time (3 month) forecasts. In all, the results of the forecast model indicated that incorporating oceanic-atmospheric climatic variability in forecast models can lead to improved forecasts for both streamflow and snowpack.

Members of the thioredoxin superfamily of proteins catalyze disulfide bond reduction and oxidation using the active site C-X-X-C sequence. In hyperthermophilic organisms, cysteine side chains were expected in low abundance since they were not believed to endure the high temperatures under which they grow. Recently it has been found that disulfide bonds in hyperthermophiles are more frequent, the higher the growth temperature of the organism. This is perhaps used as an adaptation to high temperature in order to stabilize proteins under harsh conditions. A protein with sequence and structural similarities to mesophilic members of the thioredoxin superfamily, called protein disulfide oxidoreductases (PDO), has been found in the genomes of recently sequenced hyperthermophilic genomes. In this study PDOs from the hyperthermophiles Aquifex aeolicus (AaPDO) and Pyrococcus furiosus (PfPDO) have been investigated. The molecular weight is about 26 kDa and their structures are comprised of two homologous thioredoxin folds, referred to as the N-unit and the C-unit, each containing a C-X-X-C motif. The sequence identity between the two units and the two proteins is low, but they are still structurally very similar. The function of these proteins in vivo is unknown. As a first step in characterizing the activity of these proteins, the redox characteristics of these domains will be investigated. During this project, the genes for AaPDO and PfPDO have been cloned into overexpression vectors, expressed in E. coli and purified to homogeneity. To allow for individual study of the activities of two units, mutated proteins were prepared in which the cysteine residues of the N-unit (AaPDOnm and PfPDOnm) and of the C-unit (AaPDOcm and PfPDOcm) and purified. Circular dichroism spectra recorded of the wild type and mutants indicate that all purified proteins are folded and that the N- and C-unit active site mutants are structurally similar to the corresponding wild type proteins.