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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
561

Analysis of the sulfur system in waters from the Galapagos Ridge hydrothermal vents

Huested, Sarah Stuart January 1979 (has links)
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1979. / Microfiche copy available in Archives and Science. / Bibliography: leaves 68-71. / by Sarah S. Huested. / M.S.
562

Short-Term Forecasting of Power Flows over Major Pacific Northwestern Interties: Using Box and Jenkins ARIMA Methodology

Paretkar, Piyush S. 17 November 2008 (has links)
The deregulation of the Electricity Sector in US has led to a tremendous increase in the inter-regional wholesale electricity trade between neighboring utilities or regions. For instance, the generation deficit regions may choose to import power from surplus regions; thus the wholesale electricity market prices in the regions are also affected by the dynamics of its electricity trade with other regions. Valuable insights into such imports/exports ahead of time have become crucial market intelligence for the various academicians and the market players associated with the industry. In this thesis, the task of short-term forecasting of the power flows over three major transmission interties of the Pacific Northwest region, namely the Pacific AC Intertie, the Pacific DC Intertie and the Northern Intertie, is successfully accomplished. The Pacific AC and the Pacific DC interties connect the Pacific Northwest region of US with the state of California. The Northern Intertie is the only intertie connecting the British Columbia region in Canada with the Pacific Northwest US. Box-Jenkins ARIMA (Auto Regressive Integrated Moving Average) and Transfer function methodologies are used as the statistical tools to identify the forecasting models in this thesis. The data requirement for all of the models is restricted to publicly available data. / Master of Science
563

Factors Surrounding Mental Health Well-Being for Male Adolescent Pacific Islanders

Garrett, Melia Fonoimoana 10 June 2024 (has links) (PDF)
Despite increasing mental health concerns, individuals from the Pacific Islands largely do not utilize the resources available to them (National Survey of Drug Use and Health, 2020). This is of particular concern among male adolescents within the population who are more at risk of mental health concerns. An interpretative phenomenological analysis focus group study was conducted in person with male adolescent Pacific Islanders (PI; ages 14–16) residing in one Western state (n = 3). Male adolescents reported that admitting to mental health concerns would greatly limit their academic, career, and personal ambitions due to the stigma attached. They also discussed religiosity as a protective factor and gave a number of individuals within their lives that could potentially be helpful to them in this area. In terms of stigma and perception, some participants described situations in which they discussed their mental health concerns to others within their community and their feelings were dismissed as being invalid or unimportant. In addition, several participants discussed the familial shame they would experience if they were to utilize mental health services. With regard to the cultural fit between practitioners and students, many students explained they felt uncomfortable being vulnerable with therapists outside their ethnic community. They felt that being open with their mental health concerns would give a poor impression of their PI community to therapists outside of their community. More research is needed to discover which groups to target within the community to impact the largest change in perception of mental health services across the community.
564

The role of oxygen and other environmental variables on survivorship, abundance, and community structure of invertebrate meroplankton of Oregon nearshore coastal waters

Eerkes-Medrano, Dafne I. 06 January 2013 (has links)
The high productivity of Eastern Boundary Upwelling Ecosystems (EBUE), some of the most productive ecosystems in the globe, is attributed to the nutrient rich waters brought up through upwelling. Climate change scenarios for coastal upwelling systems, predict an intensification of coastal upwelling winds. Associated with intensification in upwelling are biogeochemical changes such as ocean hypoxia and ocean acidification. In recent years, the California Current System (CCS) has experienced the occurrence of nearshore hypoxia and the novel rise of anoxia. This has been attributed to changes in the intensity of upwelling wind stress. The effects of some of the more severe hypoxia and anoxia events in the CCS have been mass mortality of fish and benthic invertebrates. However, the impacts on zooplankton in this system are not known. Meroplankton, those organisms which have a planktonic stage for only part of their life cycle, are an important component of zooplankton communities. The larval stage of benthic invertebrates forms an important link between benthic adult communities and planktonic communities. Larvae serve to disperse individuals to new locations and to link populations. They are also food for fish and planktonic invertebrates. This important life stage can spend long periods in the plankton (from days to months) where environmental conditions can affect larval health, subsequent settlement and recruitment success, and juvenile health. This research assesses the role of hypoxia and larval survivorship, and the relationship between individual abundance and community structure of larvae to environmental factors in the field. In laboratory experiments (Chapter 2), a suite of 10 rocky intertidal invertebrate species from four phyla were exposed to low oxygen conditions representative of the nearshore environment of the Oregon coast. Results revealed a wide range in tolerances from species with little tolerance (e.g. the shore crab Hemigrapsus oregonensis) to species with high tolerance (e.g. the California mussel Mytilus californianus). The differential responses across larvae to chronic hypoxia and anoxia potentially could affect their recruitment success and consequently, the structure and species composition of intertidal communities. Field studies (Chapter 3 & 4) explore the relationship between environmental variables and larval abundance and community structure. Chapter 3 focuses on broad taxonomic groups, while Chapter 4 focuses on larval decapods in particular. Fine focus was devoted to decapod larvae, due to laboratory findings of heightened sensitivity to hypoxia of decapod crabs. A finding that is also supported in the literature. The goal of field studies was to identify the environmental parameters that structure meroplankton and larval decapod communities and identify which of these parameters play a significant role in influencing larval abundance. A number of environmental variables contributed to meroplankton assemblage structure and larval decapod assemblage structure. These included distance from shore, depth, date, upwelling intensity, dissolved oxygen, and cumulative wind stress. Some of these factors occurred frequently in larval abundance models. In Chapter 3, individual abundance across broad taxonomic groups was most commonly explained by upwelling intensity while in Chapter 4, individual abundance of different decapod species was explained by cumulative wind stress, which is a proxy for upwelling intensity. The prominent role of upwelling related factors in explaining individual abundance is important considering climate change projections of an increased intensification of upwelling winds in EBUE. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from Jan. 6, 2012 - Jan. 6, 2013
565

The Impeccable Timing of the Apple Maggot Fly, <i>Rhagoletis pomonella</i> (Dipetera: Tephritidae), and its Implications for Ecological Speciation

Mattsson, Monte Arthur 24 November 2015 (has links)
Speciation is the process by which life diversifies into discrete forms, and understanding its underlying mechanisms remains a primary focus for biologists. Increasingly, empirical studies are helping explain the role of ecology in generating biodiversity. Adaptive radiations are often propelled by selective fitness tradeoffs experienced by individuals that invade new habitats, resulting in reproductive isolation from ancestral conspecifics and potentially cladogenesis. Host specialist insects are among the most speciose organisms known and serve as highly useful models for studying adaptive radiations. We are just beginning to understand the pace and degree with which these insects diversify. The apple maggot, Rhagoletis pomonella, is a well-studied insect whose eastern and southern populations are models for ecological speciation. Recently (40–65 ya), the fly has invaded the Pacific Northwestern United States through human-transported apples infested with larvae. There, populations of R. pomonella have rapidly colonized two novel hawthorn hosts whose fruiting times bracket apple’s (early-season native Crataegus douglasii and introduced C. monogyna, which fruits late in the season). The recent introduction might initiate host shifts, providing opportunities to examine the pace and mechanistic means with which host races (an evolutionary stage preceding speciation) become established. Here, I demonstrate that host-associated populations at a site in southwest Washington are partially allochronically isolated from one another, and life cycles temporally match with natal host fruit ripening times in sympatry. If spatially widespread, these temporal barriers could result in reproductive isolation and possibly cladogenesis. Implications of these findings reach beyond academic import, as R. pomonella is expanding not only its host range, but its geographic range is encroaching upon central Washington, the site of a multi-billion dollar per year apple-growing industry.
566

Exploring Colonization and Ethnogenesis through an Analysis of the Flaked Glass Tools of the Lower Columbia Chinookans and Fur Traders

Simmons, Stephanie Catherine 03 June 2014 (has links)
At the end of the 18th century, Anglo Americans and Europeans entered the mouth of the Columbia River for the first time. There they encountered large villages of Chinookan and other Native Americans. Soon afterwards, the Chinookan People became involved in the global fur trade. Pelts, supplies, and native made goods were exchanged with fur traders, who in return provided Chinookans with a number of trade goods. Over the next 40 years, life changed greatly for the Chinookans; new trade and political alliances were created, foreign goods were introduced, and diseases killed large portions of the population (Hajda 1984; Gibson 1992; Schwantes 1996; Boyd 2011; Boyd et al. 2013). Additionally, fur trade forts, like the Hudson's Bay Company's (HBC) Fort Vancouver, were established. At these forts, new multiethnic communities were created to support the fur trade economy (Hussey 1957; Kardas 1971; Warner and Munnik 1972; Erigero 1992; Burley 1997; Mackie 1997; Wilson 2010). This thesis is an historical archaeological study of how Chinookan peoples at three villages and employees of the later multicultural Village at Fort Vancouver negotiated the processes of contact and colonization. Placed in the theoretical framework of practice theory, everyday ordinary activities are studied to understand how cultural identities are created, reinforced, and changed (Lightfoot et al. 1998; Martindale 2009; Voss 2008). Additionally uneven power relationships are examined, in this case between the colonizer and the colonized, which could lead to subjugation but also resistance (Silliman 2001). In order to investigate these issues, this thesis studies how the new foreign material of vessel glass was and was not used during the everyday practice of tool production. Archaeological studies have found that vessel glass, which has physical properties similar to obsidian, was used to create a variety of tool forms by cultures worldwide (Conte and Romero 2008). Modified glass studies (Harrison 2003; Martindale and Jurakic 2006) have demonstrated that they can contribute important new insights into how cultures negotiated colonization. In this study, modified glass tools from three contact period Chinookan sites: Cathlapotle, Meier, and Middle Village, and the later multiethnic Employee Village of Fort Vancouver were examined. Glass tool and debitage analysis based on lithic macroscopic analytical techniques was used to determine manufacturing techniques, tool types, and functions. Additionally, these data were compared to previous analyses of lithics and trade goods at the study sites. This thesis demonstrates that Chinookans modified glass into tools, though there was variation in the degree to which glass was modified and the types of tools that were produced between sites. Some of these differences are probably related to availability, how glass was conceptualized by Native Peoples, or other unidentified causes. This study suggests that in some ways glass was just another raw material, similar to stone, that was used to create tools that mirrored the existing lithic technology. However at Cathlapotle at least, glass appears to have been relatively scarce and perhaps valued even as a status item. While at Middle Village, glass (as opposed to stone) was being used about a third of the time to produce tools. Glass tool technology at Cathlapotle, Meier, and Middle Village was very similar to the existing stone tool technology dominated by expedient/low energy tools; however, novel new bottle abraders do appear at Middle Village. This multifaceted response reflects how some traditional lifeways continued, while at the same time new materials and technology was recontextualized in ways that made sense to Chinookan peoples. Glass tools increase at the Fort Vancouver Employee Village rather than decrease through time. This response appears to be a type of resistance to the HBC's economic hegemony and rigid social structure. Though it is impossible to know if such resistance was consciously acted on or was just part of everyday activities that made sense in the economic climate of the time. Overall, this thesis demonstrates how a mundane object such as vessel glass, can provide a wealth of information about how groups like the Chinookans dealt with a changing world, and how the multiethnic community at Fort Vancouver dealt with the hegemony of the HBC. Chinookan peoples and the later inhabitants of the Fort Vancouver Employee Village responded to colonization in ways that made sense to their larger cultural system. These responses led to both continuity and change across time.
567

Microbial diversity, metabolic potential, and transcriptional activity along the inner continental shelf of the Northeast Pacific Ocean

Bertagnolli, Anthony D. 12 April 2012 (has links)
Continental shelves located along eastern boundary currents occupy relatively small volumes of the world’s oceans, yet are responsible for a large proportion of global primary production. The Oregon coast is among these ecosystems. Recent analyses of dissolved oxygen at shallow depths in the water column has suggested increasing episodes of hypoxia and anoxia, events that are detrimental to larger macro-faunal species. Microbial communities, however, are metabolically diverse, capable of utilizing alternative electron donors and acceptors, and can withstand transient periods of low dissolved oxygen. Understanding the phylogenetic and metabolic diversity of microorganisms in these environments is important for assessing the impact hypoxic events have on local and global biogeochemistry. Several molecular ecology tools were used to answer questions about the distribution patterns and activities of microorganisms residing along the coast of Oregon in this dissertation. Ribosomal rRNA fingerprinting and sequence analyses of samples collected during 2007-2008 suggested that bacterial community structure was not substantially influenced by changes in dissolved oxygen. However, substantial depth dependent changes were observed, with samples collected in the bottom boundary layer (BBL) displaying significant differences from those collected in the surface layer. Phylogenetic analyses of bacterial rRNA genes revealed novel phylotypes associated with this area of the water column, including groups with close evolutionary relationships to putative or characterized sulfur oxidizing bacteria (SOB). Analysis of metagenomes and metatranscriptomes collected during 2009 suggested increasing abundances of chemolithoautrophic organisms and their activities in the BBL. Thaumarchaea displayed significant depth dependent increases during the summer, and were detected at maximal frequencies during periods of hypoxia, suggesting that nitrification maybe influenced by local changes in dissolved oxygen. Metagenomic analysis of samples collected from 2010 revealed substantial variability in the metabolic potential of the microbial communities from different water masses. Samples collected during the spring, prior to upwelling clustered independently of those collected during the summer, during a period of upwelling, and did not display any clear stratification. Samples collected during the summer did cluster based on depth, consistent with previous observations, and increases in the relative abundances of chemolithotrophic gene suites were observed in the BBL during stratified conditions, suggesting that the metabolic potential for these processes is a repeatable feature along the Oregon coast. Overall, these observations suggest that depth impacts microbial community diversity, metabolic potential, and transcriptional activity in shallow areas of the Northeast Pacific Ocean. The increase in lithotrophic genes and transcripts in the BBL suggests that this microbial community includes many organisms that are able to use inorganic electron donors for respiration. We speculate that the dissolved organic material in the BBL is semi-labile and not available for immediate oxidation, favoring the growth for microorganisms that are able to use alternative electron donors. / Graduation date: 2012
568

Analysis of the regional carbon balance of Pacific Northwest forests under changing climate, disturbance, and management for bioenergy

Hudiburg, Tara W. 14 June 2012 (has links)
Atmospheric carbon dioxide levels have been steadily increasing from anthropogenic energy production, development and use. Carbon cycling in the terrestrial biosphere, particularly forest ecosystems, has an important role in regulating atmospheric concentrations of carbon dioxide. US West coast forest management policies are being developed to implement forest bioenergy production while reducing risk of catastrophic wildfire. Modeling and understanding the response of terrestrial ecosystems to changing environmental conditions associated with energy production and use are primary goals of global change science. Coupled carbon-nitrogen ecosystem process models identify and predict important factors that govern long term changes in terrestrial carbon stores or net ecosystem production (NEP). By quantifying and reducing uncertainty in model estimates using existing datasets, this research provides a solid scientific foundation for evaluating carbon dynamics under conditions of future climate change and land management practices at local and regional scales. Through the combined use of field observations, remote sensing data products, and the NCAR CESM/CLM4-CN coupled carbon-climate model, the objectives of this project were to 1) determine the interactive effects of changing environmental factors (i.e. increased CO���, nitrogen deposition, warming) on net carbon uptake in temperate forest ecosystems and 2) predict the net carbon emissions of West Coast forests under future climate scenarios and implementation of bioenergy programs. West Coast forests were found to be a current strong carbon sink after accounting for removals from harvest and fire. Net biome production (NBP) was 26 �� 3 Tg C yr�����, an amount equal to 18% of Washington, Oregon, and California fossil fuel emissions combined. Modeling of future conditions showed increased net primary production (NPP) because of climate and CO��� fertilization, but was eventually limited by nitrogen availability, while heterotrophic respiration (R[subscript h]) continued to increase, leading to little change in net ecosystem production (NEP). After accounting for harvest removals, management strategies which increased harvest compared to business-as-usual (BAU) resulted in decreased NBP. Increased harvest activity for bioenergy did not reduce short- or long-term emissions to the atmosphere regardless of the treatment intensity or product use. By the end of the 21st century, the carbon accumulated in forest regrowth and wood product sinks combined with avoided emissions from fossil fuels and fire were insufficient to offset the carbon lost from harvest removals, decomposition of wood products, associated harvest/transport/manufacturing emissions, and bioenergy combustion emissions. The only scenario that reduced carbon emissions compared to BAU over the 90 year period was a 'No Harvest' scenario where NBP was significantly higher than BAU for most of the simulation period. Current and future changes to baseline conditions that weaken the forest carbon sink may result in no change to emissions in some forest types. / Graduation date: 2013
569

Evaluation of a U.S. West coast groundfish habitat conservation regulation via analysis of spatial and temporal patterns of trawl fishing efforts

Bellman, Marlene A. 13 April 2004 (has links)
Recent emphasis on linkages between essential fish habitat and fish stock productivity has raised concerns about the management of fishing activities such as trawling, which have the potential to impact fish habitat. Knowing specifically where and how intensively trawl effort has occurred over time provides ecologists with the necessary background for habitat impact and recovery studies, and provides fishery managers with an assessment of how habitat conservation objectives are being met. The objectives of this study were to (1) examine the extent to which the 2000 Pacific Fishery Management Council footrope restriction has shifted and reduced trawl fishing effort on Oregon fishing grounds, (2) to relate these changes in distribution to the benthic habitat type over which they occur, and (3) to develop methods for enhancing fine-scale spatial review of targeted fishing effort. Density analysis of available trawl start locations provided a spatial and temporal understanding of how fishing efforts increased and decreased in relation to habitat distribution and fishery management actions between 1995 and 2002. Trawl effort patterns exhibit significant inter-annual variability and patchy distribution. Areas of increased fishing effort were still evident between years, despite an overall decline in trawl tows across the time scale of this study. Tow end point locations for the years 1998-2001 were retrieved from manual logbooks for five reference sites located in the proximity of rock habitat features. Trawl towlines were mapped from start to end point and demonstrated a marked enhancement of fine-scale fishing effort resolution, with increased ability to identify effort shifts over benthic habitat. Distinct spatial shifts in fishing intensity (measured as km towed) away from rock habitat were evident at all reference sites, with an average reduction of 86%. Some slight shifts into surrounding unconsolidated sediments also occurred, indicating effort displacement as well as reduction. Fishing intensity was calculated from commercial trawl and research trawl survey towlines to achieve the most accurate assessment of fishing impacts and potential habitat recovery areas. Research trawling intensity was less than 1% of commercial trawl effort originating from the same sites. A brief comparison of Oregon vessel towlines and California vessel towlines demonstrated similar targeted fishing patterns by both fleets, except at one site. Results indicate that the footrope restriction, in conjunction with associated landing limits, was effective in protecting rocky habitats from trawl fishing impacts. Reference areas were identified where essential fish habitat (EFH) recovery is likely occurring off the coast of Oregon. Substantial regulatory changes continue in this fishery, with trip limits and gear restrictions continuously adjusted. Continued monitoring and review of spatial trawl data would assist in fishery management decision-making and assess conservation objectives for depleted groundfish and associated habitats. Future research should incorporate analysis of catch data and expand the review of trawl towlines for the entire US West coast groundfish fishery. The trawl towline spatial analysis developed in this work is a credible method for reviewing fishing effort at the scale of the fishery and in relation to detailed habitat data. The research presented here provides an example of how an interdisciplinary approach and critical assessment of data can work to resolve marine management challenges. / Graduation date: 2004
570

Regional scale sandbar variability : observations from the U.S. Pacific Northwest

Di Leonardo, Diana R. 28 November 2012 (has links)
Understanding sandbar dynamics and variability is integral to developing a predictive capacity for nearshore flows, sediment transport, morphological change, and ultimately for determining coastline exposure to damaging storm waves. Along the high-energy U.S. Pacific Northwest (PNW) coast, sandbars typically dominate the bathymetry of the active zone. Here we report on a nearshore bathymetric data set that covers an exceptionally long stretch of coast and crosses several littoral cell boundaries. Our study area stretches from Point Grenville, Washington to Cascade Head, Oregon, including 8 littoral cells and approximately 250 km in the alongshore. We describe and quantify the morphological variability of sandbars in the PNW over large spatial scales as well as attempt to explain the inter-littoral cell variability via trends and variability in environmental parameters. From 560 bathymetric profiles (~1000 km of measurements) we have extracted over 500 distinct subtidal sandbars. The bar zone extends to over 1km from the shoreline in the northern part of the study area, but only to about 600m in the southern part. Maximum bar crest depths are typically 7m below MLLW. Bar heights range from a step in the cross-shore profile to over 3m from crest to trough. The northernmost littoral cells typically have two or more bars per cross-shore profile whereas the littoral cells in the southern part of our study area have only one bar. The mean depths of the bars, however, are much more consistent across littoral cells. The mean depths remain consistent even while the upper shoreface slope significantly increases from north to south, requiring that the maximum bar distance from the shoreline decreases from north to south. This regional gradient in upper shoreface slope is likely a response, at least in part, to a general coarsening trend in the sediment from north to south and hence linked to variations in regional geology. / Graduation date: 2013

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