Thesis (M.S.)--Humboldt State University, 2007. / Includes bibliographical references (leaves 24-28). Also available via Humboldt Digital Scholar.

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Evaporation ponds that dispose of agricultural drainwater provide attractive habitat for waterbirds but may result in contaminant exposure that impairs reproduction. I estimated post-hatching survival and evaluated productivity estimates for American avocets (Recurvirostra americana) nesting at evaporation ponds in the Tulare Basin, California from 1991 to 1993. Avocets and Black-necked stilts (Himantopus mexicanus) comprised the majority of 5,969 nests found. Nest success and embryo mortality varied among ponds and between species. Embryo deformity and mortality rates associated with selenium were higher in stilts. The majority of reproductive losses were attributed to predation, especially at ponds without islands. Post-hatch survival of radiomarked avocets after 5 weeks ranged from 0.375-0.729 and differed among ponds (log-rank X²=7.12, 2 df, P=0.028). Predation accounted for 55.4% (36/65) of known mortalities. Depredated chicks ranged from 1-30 days of age with a median age of 6 days. Arsenic concentrations in avocet livers were below detection limits while boron concentrations were below detection limits at Westlake-South (WLS) and Tulare Lake Drainage District-South (TLDD-S) in 1993. Mean boron concentration in livers was 3.7 ppm at TLDD-S in 1992 and 22.9 ppm at Lost Hills Water District (LHWD). Liver selenium concentrations increased with age and differed among ponds (P=0.0001). Mercury concentrations differed among ponds (P=0.0001), but were similar to background. Growth, survival and selenium exposure were consistent to support post-hatching effects of selenium. Mortality in avocet chicks was highest at LHWD, intermediate at TLDD-S and lowest at WLS, consistent with selenium exposures. I observed lower survival, histologic lesions, lower hatchling weights, slower growth, and elevated selenium and boron in tissue at LHWD. I used capture-recapture analysis also to estimate post-hatching survival and calculated avocet productivity. Survival estimates for the first 4 weeks post-hatching, based on model averaging, ranged from 0.572 to 0.751. Productivity at some ponds was insufficient to offset adult mortality. Estimates of average annual productivity were 0.49 and 0.45 in 1992 and 1993, respectively. Juvenile survival rates necessary for recruitment to offset 10% and 20% adult mortality ranged from 0.204 to 0.408 and 0.222 to 0.444, respectively. / Graduation date: 2004

Primary objectives of this study were: (1) to compare the food habits of healthy and botulism intoxicated American avocets and blacknecked stilts for qualitative and quantitative differences, (2) to determine .which invertebrates found in the tracts of intoxicated and healthy birds contained type C toxin, and (3) to explain apparent susceptibilities among different sexes, ages and species of birds. Based on percent utilization and occurrence of food items in the esophagus , the diets of healthy and intoxicated birds were similar. However, intoxicated avocets consumed higher proportions of Gastropoda and intoxicated stilts more Hydrophilidae larvae than did healthy birds. Because of similarities in diets of healthy and intoxicated birds, birds probably became intoxicated from eating randomly toxic foods and not because of differences in diet or food preference. Examinations of esophageal contents of avocets and stilts better described recently consumed food items than did examinations of gizzard contents. Soft-bodied invertebrates were rendered unidentifiable in the gizzard. The esophageal contents of juvenile avocets and stilts contained greater proportions of animal matter than did those of adults. Only three of 86 food samples analyzed were definitely positive for type C botulism toxin. These were: one sample of Tendipedidae larvae and two of pooled gizzard contents which included fragments of Corixidae, Hydrophilidae adults, seeds and vegetative fibers. Only three of 86 food samples analyzed were definitely positive for type C botulism toxin. These were: one sample of Tendipedidae larvae and two of pooled gizzard contents which included fragments of Corixidae, Hydrophilidae adults, seeds and vegetative fibers.

It is important to understand the underlying plant defense mechanisms in order to establish best strategies to reduce losses due to diseases in cereals. The current available information is mostly on model organisms and their plant-pathogen interactions. However, this study is focused on the identification of genes involved in the resistance mechanism of one of the most devastating diseases of wheat, yellow rust. The strategy undertaken was to use differential display method (DD) together with microarray technology, on yellow rust differential lines of wheat (Avocet-Yr1 and Avocet-Yr10) infected with the virulent and avirulent Puccinia striiformis f. sp. tritici races (Pst: PST17, PST45, 169E136 and 232E137) together with appropriate control infections. DD primer combinations of ninety allowed the detection of fourteen differentially expressed genes which were also confirmed by real-time QRT-PCR analysis. All of but one were found to be novel sequences in wheat genome. Among those, two very important genes were identified as full ORF including 5&rsquo / and 3&rsquo / end untranslated regions (UTR) / namely cyclophilin like protein (putative antifungal activity) and ubiquitin conjugating enzyme (E2). The sequence homology analysis of the cloned gene fragments reveled that the genes detected have roles in ubiquitinylation, programmed cell death (apoptosis), putative antifungal activities, disease resistance, pathogen related responses, including a few with no known function. In addition to DD analysis, using wheat Affymetrix &ldquo / GeneChip&rdquo / , we identified 93 differentially expressed ESTs of wheat in response to avirulent pathogen attack. We also investigated the differential expression profiles of wheat leaves during the virulent infections and determined 75 differentially regulated ESTs. 1Selected ESTs were further analyzed using QRT-PCR analysis and 15 were confirmed to be differentially regulated. For the further characterization of the identified genes, such as determination of their putative roles in disease response, functional studies have to be performed. For this purpose, BSMV (Barley Stripe Mosaic Virus) mediated virus induced gene silencing (VIGS) method is optimized in this thesis for wheat. We have successfully managed to silence the endogenous PDS gene (Phytoene desaturase) of wheat which can be used as a positive control for the monitoring of silencing of the genes we have identified. Our results show that BSMV mediated VIGS can be used efficiently and effectively to silence wheat genes that we identified through differential display and microarray analysis and can be used to study the functions of those genes

The Koulekoun Gold project is the most important prospect of Avocet Mining plc. It is one of the projects within the TriK-block in Guinea (West Africa) for which an exploration permit has been granted. The Koulekoun deposit is located within the Siguiri basin of Birimian age in the Eastern Guinea region; where most Guinea’s gold mines are situated. The present study involves the investigation of structural elements (S₀, S₁, S₂, intrusive contacts, faults and veins) from selected drill cores from drill sections that intersect the Koulekoun orebody in four parts of the deposit; characterizes the principal orientations of measured structures and determines their relationships using stereonet; in order to predict important intersections to focus on in exploration programs within the TriK-block and suggests a possible structural model of the Koulekoun deposit. Raw data used for the present research was collected from half-core samples due to the absence of surface outcrop from which direct measurements could have been made. Measured data were interpreted using stereographic projection. Often no preferred orientations of structural elements exist in the area, suggesting a complex structural situation, particularly with regard to hydrothermal vein attitudes. Thus, it has been illustrated from structural data analysis and S₀ data 3d interpolation of the four sub-structural domains (North-East, North-West, Central and South) that NE-SW structures (S₂, intrusive contact, fault and vein) have controlled the occurrency of gold mineralization in the Koulekoun deposit area. Geometrical relationships between structure main cluster orientation from stereonet analysis show the majority of S₀ moderately E-dipping; intrusive contacts dip at moderate angle to the SE in all zones, except in the North-East zone where they are sub-vertical and SE-dipping. Fault planes show variable orientation of NE-SW, NW-SE and E-W, and steeply SE-dipping. Vein planes correspond to fault systems and show high variability in their orientation with numerous orders of vein direction in each domain. The cross-cutting relationships suggest two principal generations of faults: the NE-SW fault (F1) and the NW-SE fault (F2). These two fault systems and their associated vein intersection areas preferably define the ore shoot zones within the Koulekoun deposit. The proposed structural model of the Koulekoun deposit suggests the intersection and interference of major NW-SE and minor NE-SW structures. The interference of folds formed basin-dome structures with oval shape geometries striking NW-SE and that dominantly occur in North-East, North-West and Central zones. The South Zone is characterized by NE-SW gently plunging and moderately inclined folds with NW-SE striking axial surface. Gold mineralization occurs at the edges of basin-dome structures in North-East, North-West and Central zones. Mineralized porphyry intrusions are likely located within the axial surface of the South zone folds and extend toward the Central zone. The proposed model is compliant with the earlier model of the Koulekoun deposit presented by Tenova (2013); Fahey et al. (2013) describing the Koulekoun deposit as an auriferous NE-SW trending fault zone, intersecting a major NW-striking and steeply E-dipping porphyry units. The model also fits within the regional structural context suggested by Lahondere et al. (1999a) related to the E-W vein structures attributed to NW-SE fractures and to the conjugated fault of NE-SW direction. Comparatively to the three industrial gold deposits (Siguiri, Lero, Kiniero) being currently mined in the Siguiri Basin, and defined as mesothermal vein and lode mineralization hosted in Birimian meta-sedimentary rocks (Lalande, 2005), the Koulekoun gold deposit appears to be a porphyry hosted orogenic disseminated style mineralization system (Fahey et al., 2013). Although, similarities between the Koulekoun gold deposit and these three industrial deposits (Siguiri, Lero, Kiniero) constitute of the intensive extends of the weathering profile and at some stages, by the existence of numerous ring-shaped and curved lineaments enhanced by drag folding (Lero deposit for instance). It is therefore recommended that targets selection around the Koulekoun deposit and within the TriK-block for further exploration programs be concentrated along NW-SE structures, in objective to determine possible intersection zones with NE-SW structures.