• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 965
  • 137
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 2102
  • 393
  • 271
  • 211
  • 204
  • 197
  • 189
  • 170
  • 169
  • 166
  • 159
  • 153
  • 149
  • 143
  • 131
  • 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.
771

Wide-angle seismic refraction and reflection studies of the northern California and southern Oregon continental margins

Keser, Judith 11 August 1978 (has links)
Recently obtained airgun-sonobuoy wide-angle refraction and reflection profiles provide data to study crustal velocities and structures along the continental margin of northern California and Southern Oregon. In the thick sedimentary wedge at the base of the continental slope, as many as five distinct layers can be seismically observed, which range in velocity from 2.13 to 3.32 km/sec. The basement layers beneath the wedge are disrupted. The profile which crosses the southeasternmost portion of the Gorda Basin near Cape Mendocino shows evidence of compression at the base of the slope. Velocities of 3.14 to 5.15 km/sec were obtained for this line. Off the central Oregon margin on the abyssal plain near the base of the slope, oceanic layers and 3 overlie a shallow mantle of velocity 7.65 km/sec. Basement velocities average 4.75 km/sec and sediment velocities varied from 1.60 to 2.78 km/sec. The lower slope of the northern California-southern Oregon margin is characterized by rough, folded structures which trend north-south. Little recent sediment cover is seen. A velocity of 2.25 km/sec was obtained for a 520 m-thick surface layer underlain by material with a refraction velocity of 2.68 km/sec. The abyssal plain sediments near Cape Mendocino appear to be in the process of being uplifted and folded into the lower slope, while near Cape Blanco the lower slope displays sediments which abut against the base of the slope below a prominent lower shelf bench. The upper slope shows large anticlinal folds which form the basement of the upper slope basins, particularly beneath the Klamath Plateau off Northern California. Velocities obtained from the sediments of the Klamath Plateau vary from 1.73 to 2.63 km/sec. The inner shelf region is formed by a synclinal basin controlled by an outer continental high which parallels the shelf break. Velocities were studied mainly from refraction arrivals with an assumed surface sediment velocity of 1.66 km/sec. The underlying sediment velocities range from 2.07 to 2.75 km/sec. Evidence of uplift, basement deformation, sediment deformation within structurally controlled basins, compression features, and the north-south trending folds all support an imbricate thrust model for this continental margin. / Graduation date: 1979
772

Women, poverty, and educational success : a critical exploration of low-income women's experience in community colleges

Barry, Kate R. 01 May 2012 (has links)
The purpose of this study is to critically explore low-income women's experience as they negotiate post secondary education in community colleges. Three research questions explore the context through which low-income women have entered the college experience, what that experience is like for them, and how the community college experience has impacted their consciousness and view of their futures. This study has significance because poverty is a critical social issue for women, post secondary education is a route out of poverty yet social welfare policy does not support access to education, community colleges have traditionally provided access to education but supports for women have been diminished, and poor women's voices and their own definitions of educational access and success are missing from the public and academic debate of these issues. Past qualitative studies that focus on poor women's experience of college are smaller parts of quantitative studies. Other existing in depth studies have focused on obstacles, persistence, and support systems, or have been studies of special transitional programs formed specifically for welfare eligible women. There is little knowledge of women's experience and sense of self from their perspective as students who are also in poverty. This study uses the research technique of in depth unstructured interviews with eight welfare eligible women student parents in Oregon's Parents as Scholars Program. Six themes emerge from the narrative interviews with the participants that that have implications for educational practice and add to and expand the small body of qualitative work that has been done on the college experiences of low-income women students. / Graduation date: 2012
773

Deconvolving orbital surface waves for the source duration of large earthquakes and modeling the receiver functions for the earth structure beneath a broadband seismometer array in the Cascadia subduction zone

Li, Xiao-qing, 1963- 04 September 1996 (has links)
Graduation date: 1997
774

Geothermal and structural implications of magnetic anomalies observed over the southern Oregon Cascade Mountains and adjoining Basin and Range province

McLain, William Henry 21 July 1981 (has links)
Graduation date: 1982
775

Residue management and yield characteristics of fine fescue seed crops

Schumacher, Derek David 29 April 2005 (has links)
Chewings fescue [Festuca rubra L. subsp. fallax (Thuill.) Nyman] is a desired turfgrass with dense sod forming capabilities and superior shade tolerance. Thermal residue management (open-field burning) has traditionally been used to remove post-harvest residue and maintain seed yield over the life of the stand. However, alternative non-thermal residue management practices have been observed to produce adequate seed yields dependent upon cultivar. Strong creeping red fescue (F. rubra L. subsp. rubra) is desired for its prolific tillering capacity and creeping rhizomatous growth habit. In contrast to Chewings fescue, maintenance of seed yield in strong creeping red fescue has only been profitably produced under thermal residue management. Slender creeping red fescue [F. rubra L. var. littoralis (Vasey)] is a desired turfgrass with a compact, less rhizomatous growth habit, similar to Chewings fescue in desirable turf attributes. However, little is known about the effects of post-harvest residue management in slender creeping red fescue. The objectives of this study were: 1) to evaluate seed yield and yield components among different cultivars to thermal (open-burning), and non-thermal (flail low and flail high) post-harvest residue management; 2) to evaluate harvest index and percent cleanout to thermal and non-thermal residue management in different cultivars; and 3) and to provide an economic analysis of thermal and non-thermal residue management in all cultivars based on partial budgeting. Three post-harvest residue management treatments (burn, flail low and flail high) were applied over the course of two years. Seed yield components measured included: total dry weight, fertile tiller number, spikelets per panicle, florets per spikelet, and panicle length. Final seed yield in each cultivar and residue management treatment method was determined after seed harvest and conditioning. Seed yield component analysis was conducted over three production seasons. Chewings fescue, strong creeping red fescue, and slender creeping red fescue cultivars responded differently to residue management as indicated by a residue management by cultivar interaction. In 2003 and 2004, residue management by cultivar interactions were evident in seed number, seed weight, fertile tiller number, percent cleanout, harvest index, and seed yield. Residue management by cultivar interactions occurred in spikelets per panicle in 2003, whereas in 2004 a residue management by cultivar interaction occurred in panicle length and florets per spikelet. In 2004, non-thermal flail low, and thermal residue management resulted in significantly greater spikelets per panicle in all cultivars. Thermal residue management resulted in the greatest number of spikelets per panicle. Results indicate that thermal residue management best maintained seed yield in most subspecies and cultivars across both years. However, in 2003, non-thermal flail low residue management produced profitable seed yield in only Marker slender creeping red fescue. In contrast, thermal residue management resulted in poor seed yields in Marker slender creeping red fescue and enhanced yields in Seabreeze slender creeping red fescue in 2003. However, following the second year of thermal treatment in 2004, Marker and Seabreeze both had lower seed yields, thus exhibiting the only negative impact of thermal management among the cultivars tested in this study. Moreover, upon review of an economic analysis, Marker slender red fescue was the only cultivar that produced a positive net return of $78 and $4 ha⁻¹ under non-thermal residue management in 2003 and 2004, respectively. Furthermore, in 2003, thermal residue management net return increases ranged from $104 ha⁻¹ to -$996 ha⁻¹ in Barnica and Shademark, respectively. In 2004, thermal residue management net return increases ranged from $115 ha⁻¹ and $1,332 ha⁻¹ in Seabreeze and Shademark, respectively. Poor seed yields were observed in all strong creeping red fescue cultivars under non-thermal residue management across both years of the study. This may be attributed to an observed reduction in fertile tiller number and seed yield. In addition, percent seed cleanout was increased with non-thermal residue management. In 2004, as stand age increased, thermal residue management resulted in greater seed yields in all cultivars and species, except both cultivars of slender creeping red fescue. Thus, this study provided substantial evidence that thermal residue management has the potential to maintain or increase fine fescue seed yield as stands age as well as to maintain stand profitability. / Graduation date: 2005
776

Understory herb and shrub responses to root trenching, pre-commercial thinning, and canopy closure in Douglas-fir forest of the western Cascades, Oregon

Lindh, Briana C. 23 May 2003 (has links)
This thesis examines factors limiting understory herb presence and flowering in young second-growth Douglas-fir (Pseudotsuga menziesii) forests on the west side of the Cascade Mountains, Oregon, USA. I studied the belowground effects of canopy trees on understory herbs and shrubs in old-growth forests using trenched plots from which tree roots were excluded. Effects of tree density and stand age were tested by comparing the understory community composition of old-growth stands and pre-commercially thinned and unthinned young second-growth stands. I also examined the effect of conifer basal area on understory herb presence and flowering within one young second-growth watershed. In young stands, I focused on three groups of understory herb species: disturbance-responsive (release), forest generalist and old-growth associated. The effects of root trenching on vegetation and soil moisture were tested in closed-canopy and gap locations in two old-growth Douglas-fir (Pseudotsuga menziesii) forests. Ten years after installation, trenched plots averaged 92% total understory cover while untrenched plots averaged 47% cover. Trenched plots under closed canopies were moister than control plots throughout the growing season; the trenching effect on soil moisture became apparent in the generally wetter gaps only at the end of the growing season. Vegetation responses to trenching were concomitantly larger under closed canopies than in gaps. Stands that had been pre-commercially thinned 20 years earlier exhibited understory composition more similar to old growth than did unthinned stands. Thinned stands exhibited higher frequencies, abundances and density of flowering of old-growth associated herbs than did unthinned stands, but lower than did old-growth stands. Forest generalist and release species showed mixed responses to thinning. I used both general linear models and classification and regression tree models to explore the association of herb species presence and flowering with conifer basal area and abiotic variables. Both modeling approaches yielded similar biological insights. Flowering was more sensitive than presence to current stand basal area. Flowering of old-growth associated and release species was negatively correlated with conifer basal area. Linear models allowed clearer hypothesis tests, while tree-based models had greater explanatory power and provided information about interactions between variables. / Graduation date: 2004
777

Dynamic linkages of personality and health : the effect of traits and states in predicting health-goal progress

Choun, Soyoung 05 June 2012 (has links)
Optimal aging is strongly related to personality factors along with health-behavior habits. Personality has played a key role in understanding the interactions between human behavior and the environment and as a vital predictor in determining health outcomes of individuals. Although previous studies have found links between personality traits and health, less is known about more process-oriented personality constructs, such as goals and self-regulatory strategies as linkages between traits and health outcomes. The purpose of this study is to explore the dynamic linkages of personality and health by examining how daily health-goal progress is associated with daily positive and negative affect as well as whether the association between health-goal progress and positive and negative affect can be predicted by personality traits of neuroticism and conscientiousness. Main research questions are: 1) Are daily positive and negative affect associated with daily health-goal progress? 2) To what extent are the traits of neuroticism and conscientiousness related to the overall levels of daily health-goal progress over a 100-day time period? 3) Do neuroticism and conscientiousness moderate the relationships between daily positive affect and daily health-goal progress as well as between negative affect and daily health-goal progress? This study was guided by developmental systems theory (Ford & Lerner, 1992) and the six-foci model of personality (Hooker & McAdams, 2003). This study utilized data from the "Personal Understanding of Life and Social Experiences" (PULSE) project that was a 100 day internet-based, daily study of Oregon residents over the age of 50. The sample for this study (N = 76) included participants who have participated at both baseline (initial survey) and the microlongitudinal phase (over 100 days). Personal health goals, neuroticism, and conscientiousness were measured at baseline. Daily health-goal progress, daily positive affect, and negative affect were measured over 100 days. Multilevel modeling analysis was used to examine within-person variations and between-person differences in daily health-goal progress and daily positive and negative affect by estimating an intercept (initial status) and slope (change) for each individual. The results of this study show that first, daily health-goal progress was positively coupled with daily positive affect and negatively coupled with daily negative affect within persons. Second, the associations between daily positive affect and daily health-goal progress and between daily negative affect and daily health-goal progress varied between individuals. Third, health-goal progress on the previous day was positively related to concurrent positive affect and negatively related to concurrent negative affect. Fourth, individuals high in neuroticism and individuals high in conscientiousness were only marginally likely to experience higher levels of health-goal progress over the 100-day period compared to those with low scores. Fifth, individuals high in neuroticism when experiencing high levels of negative affect tended to report lower levels of daily health-goal progress. These findings may provide enhanced knowledge of patterns of day-to-day variability within persons and lead to better health care. Moreover, the findings of the current study suggest that health-improving interventions could be targeted individually to participants based on knowledge of the linkages between daily goal progress and daily affect and personality traits. Ultimately, the personality of older adults may act as risk factors and/or protective factors in the processes of aging during the second half of life. / Graduation date: 2013
778

Butterflies of the H.J. Andrews Experimental Forest : biological inventory and ecological analysis

Ross, Dana N. R. 31 October 2003 (has links)
A biological inventory of the butterflies of the H. J. Andrews Experimental Forest [HJA] in Linn/Lane County, Oregon was conducted during 1994 and 1995. It was the first comprehensive survey of HJA butterflies for the site and serves as a baseline for future butterfly research. A detailed ecological account is provided for each species documented during this and previous studies from the HJA. Patterns of butterfly richness and abundance are addressed both temporally and spatially. Within-year and between year differences in butterfly richness and abundance are explained. Butterfly richness and abundance were compared between forest, clear-cut, and meadow habitats, as well as along the roads within these habitats. Butterfly richness and abundance comparisons were also made between local butterfly hotspots and immediately adjacent areas. Lastly, the HJA butterfly fauna was compared to those of five other Oregon sites to put it into a regional perspective. Seventy-two species were recorded during this two year period and increased the total documented butterfly fauna of the HJA to seventy-nine species. Butterfly species richness was high from June through early August. Butterfly abundance increased gradually over the season and peaked in early August. Each butterfly species displayed one of four patterns of combined relative abundance and distribution: common and widespread, rare and local, common only at low elevations or common only at high elevations. The results of standardized butterfly counts suggested that subalpine meadows were much higher than clear-cuts or forests in butterfly richness and abundance, and that roads served to increase butterfly richness and abundance on a local scale in most cases. Butterfly hotspots on the HJA appear as relatively small areas of high butterfly richness and abundance and have a correspondingly high number of plant species when compared to adjacent areas. With virtually one-half of all butterfly species known for the state of Oregon, the HJA ranks among the most species-rich locations for its size within the state. This diversity originates from several biogeographical regions of origin, as defined within this study. A total of 31 HJA species have a generalized Western North American distribution, but several other biogeographical regions are also well represented. Some butterfly species appear to be at or near their geographical limits on the HJA. The assemblage of HJA butterfly species is virtually inclusive of those from Mary's Peak and McDonald Forest in northwestern Oregon, whereas it differs by 30% or more from the more biogeographically distinct faunas of Crater Lake National Park, Mount Ashland and Steens Mountain. Future butterfly work on the HJA is recommended. Oregon butterfly distribution maps suggest that several additional butterfly species should be found there. More biogeographical analyses combined with long term monitoring of HJA butterflies could help to both predict and document changes in the Pacific Northwest butterfly fauna due to human disturbance and global climate change. / Graduation date: 2004
779

Species identification of Klamath Basin suckers (Pisces : Catostomidae) and an assessment of hybridization using anonymous nuclear loci

Wagman, David Wolfe 12 November 2003 (has links)
Low copy number anonymous nuclear loci were used to search for species markers in four species of Klamath Basin suckers. We sequenced 28 randomly chosen loci representing 10,421 bp; 21 loci were similar to sequences in GenBank. Eight fixed sequence differences were found among Klamath species. Locus 120 contained rare but diagnostic markers for Deltistes luxatus and for Catostomus rimiculus. Locus 4 also contained three rare but unique sites in Catostomus rimiculus. No sequence differences were found between Chasmistes brevirostris and Catostomus snyderi. Loci 4 and 120 exhibited allele frequency differences between Rogue River C. rimiculus and all Klamath Basin suckers. Genotype BB of locus 4 was a fixed diagnostic marker and genotype BB of locus 120 was a frequency dependent marker for Rogue C. rimiculus. Although Klamath suckers represent three genera, very limited variation was found among 10,431 base pairs. We examined phylogenetic patterns of five loci in eleven catostomid genera and 25 species to determine if the homogeneity in the Upper Klamath Basin was due to massive hybridization and introgression or to retention of ancestral sequences. Two loci with no similarity to GenBank sequences (non-coding loci) and three loci with substantial similarity to GenBank sequences (coding loci) gave similar results, providing support for various subfamilies and tribes, more support for eastern genera and little support for western genera. Each locus was a mosaic of species or population markers, sometimes providing discriminatory power for allopatric populations of a species, such as C. macrocheilus, while not discriminating other species. Upper Klamath Basin species were noteworthy in their lack of autapomorphies, but had similar numbers of derived informative sites as other catostomins. Upper Klamath Basin species consistently shared ancestral or equivocal informative sites either with moxostomatins or a variable group of western species and shared derived sites with other western species, especially C. occidentalis. The data suggest that Upper Klamath Basin species have retained a largely ancestral genome at these loci. Thus, the failure of this technique to uncover significant variation in Upper Klamath Basin species may be a reflection of their plesiomorphic genome at these loci and not necessarily hybridization. / Graduation date: 2004
780

West Nile Virus preparedness in Multnomah County : efficacy, benefits, and limitations of adulticide use for mosquito-borne disease

Francis, Kristin A. 26 April 2004 (has links)
The objectives of this study were to provide a comprehensive review of the risks and benefits of using adulticides to reduce risk of mosquito-borne disease (particularly West Nile Virus) transmission to humans, as well as to decrease annoyance from nuisance mosquitoes. The study was designed with two major research components, including: 1) an extensive literature review to determine the efficacy of adulticide use, the adverse effects of adulticide use, the impact of mosquitoes on community livability, and the risks and benefits of pesticide use in controlling mosquitoes; and 2) interviews with selected vector districts in seven states to determine effective and ineffective practices in mosquito management. This study has demonstrated that an integrated mosquito management program may be beneficial in reducing risk of disease transmission and mosquito annoyance when performed appropriately. The contribution of adulticiding to reducing mosquito-borne disease transmission, however, is unknown. Research is needed to: 1) further assess the ecological and human impacts of adulticides using the dose and exposure rates realistic to an adulticide program; 2) gain an understanding of the human and ecological impacts of aggregate and cumulative exposures to pesticides, especially for special populations, such as children; and 3) determine the contribution of adulticiding in interrupting or reducing the enzootic amplification of arboviruses, as well as the transmission of WNV to humans. / Graduation date: 2004

Page generated in 0.0415 seconds