published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

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Typescript (photocopy). / Digitized by Kansas Correctional Industries

Pacific lampreys (Lampetra tridentata) have declined in abundance in the Columbia River Basin. Although, the reasons for the decline are unclear, we suggest that development of hydroelectric dams and habitat alterations in tributaries as the main causes. The available knowledge of life history of Pacific lampreys and status from dam counts (trend data) in the Columbia River Basin and the Umpqua River along the Oregon Coast shows that populations have been declining over the last 30 years. Even though Pacific lampreys have been shown to have ecological importance both as predator and prey, the declines in their populations have been largely ignored by fisheries agencies and the public. Recently, the National Marine Fisheries Service initiated studies on using radio-telemetry of Pacific lampreys in order to study the impact of hydroelectric dams on migration behavior. To address one of the fundamental assumptions of radio-telemetry, namely, that tagged fish are "normal," one must be able to measure whether or not an animal is stressed. We identified clinical indicators of stress in adult Pacific lampreys. Plasma glucose became elevated soon after acute stress and remained elevated for one week. Plasma lactate also became elevated by 30 minutes; however, it decreased to resting levels by one hour after stessor. Muscle lactate was shown to have an inverse relationship with glucose. Muscle lactate levels decreased by 4 hours and remained depressed for two days. Plasma chloride ions decreased by one hour, then returned to resting levels by 8 hours; by 24 hours, levels were again decreased with recovery occurring by 48 hours. The steroid cortisol was not found in the plasma of Pacific lampreys. The swimming performance and physiological effects of surgical implantation of three different sized dummy radio transmitters in Pacific lampreys were assessed. Intraperitoneal implantations of 3.4 g transmitters had no significant effect on circulating levels of glucose (an indicator of stress) 4 months after surgery, while 10 gram transmitters showed a significant increase in plasma glucose. Lampreys implanted with 7.4 g transmitters recovered from surgery by day 4 based on levels of plasma glucose. Lampreys implanted intraperitoneally with 7.4 g dummy transmitters showed no significant differences in circulating glucose 30, 60, 90, and 180 days after surgery in comparison to sham-implant controls. Ventilation rate decreased significantly by 30 minutes after surgery and was stable by 60 minutes; suggesting initial recovery from surgery is rapid. Swimming performance was impaired immediately after surgery; however, swimming was not compromised at 1 and 7 days after surgery. Tagged fish showed a significant difference in oxygen consumption when tested immediately after surgery; however, oxygen consumption was at control levels at 1 and 7 days after surgery. / Graduation date: 2001

The electron, gamma and neutron radiation degradation of III-V semiconductors and heterojunction bipolar transistors (HBTs) is investigated in this thesis. Particular attention is paid to InP and InGaAs materials and InP/InGaAs abrupt single HBTs (SHBTs). Complete process sequences for fabrication of InP/InGaAs HBTs are developed and subsequently employed to produce the devices, which are then electrically characterized and irradiated with the different types of radiation. A comprehensive analytical HBT model is developed and radiation damage calculations are performed to model the observed radiation-induced degradation of SHBTs. The most pronounced radiation effects found in SHBTs include reduction of the common-emitter DC current gain, shift of the collector-emitter (CE) offset voltage and increase of the emitter, base and collector parasitic resistances. Quantitative analysis performed using the developed model demonstrates that increase of the neutral bulk and base-emitter (BE) space charge region (SCR) components of the base current are responsible for the observed current gain degradation. The rise of the neutral bulk recombination is attributed to decrease in a Shockley-Read-Hall (SRH) carrier lifetime, while the SCR current increase is caused by rising SCR SRH recombination and activation of a tunneling-recombination mechanism. On the material level these effects are explained by displacement defects produced in a semiconductor by the incident radiation. The second primary change of the SHBT characteristics, CE offset voltage shift, is induced by degradation of the base-collector (BC) junction. The observed rise of the BC current is brought on by diffusion and recombination currents which increase as more defects are introduced in a semiconductor. Finally, the resistance degradation is attributed to deterioration of low-doped layers of a transistor, and to degradation of the device metal contacts. / Graduation date: 2001

Reported here is an investigation to determine if azinphos-methyl (AZM), an organophosphate insecticide, adducts to hemoglobin, and if so, whether the hemoglobin adduct could be used as a quantitative marker of occupational AZM exposure. We hypothesized that AZM, or a metabolite of AZM, binds to hemoglobin in erythrocytes forming an adducted protein. We administered radiolabled AZM to rats and found a stable, dose-dependent association of radioactivity with hemoglobin. The decline in hemoglobin-associated radioactivity followed the expected kinetics of erythrocyte turnover in rats. We examined hemoglobin isolated from these rats by high-pressure liquid chromatography, liquid scintillation counting, and electrospray ionization mass spectrometry. These analyses provided evidence of AZM or an AZM metabolite binding to one of the beta proteins of hemoglobin. In vitro incubation of AZM with hemoglobin in a liver microsome system indicated an AZM adduct to heme. Further research is necessary to fully characterize the adduct and determine whether this biomarker will be useful for monitoring human exposure to AZM. / Graduation date: 2000

Most plant toxicology tests developed in support of environmental laws use a single stress applied to an individual plant. While tests using individual species or stresses require fewer resources and are easier to interpret, they are under increasing criticism for being unrealistic and missing important ecological interactions. The objective of this research was to increase our understanding of how plants and plant communities respond to a variety of stressors. Model plant communities of spring wheat (Triticum aestivum) and wild oats (Avena fatua) were planted at three densities and five proportions in the field. Puccinia recondita, the causal agent of wheat leaf rust, was inoculated on half of the plots. Disease severity was estimated as percent of wheat flag leaves covered by rust lesions. Plants were harvested at maturity and measured. Seeding density rarely had a significant influence on rust severity, probably because tiller density differed little as a result of compensation due to increased tillering at low seeding densities. In contrast, increasing the proportion of wheat in mixtures with wild oats consistently increased wheat leaf rust severity. There was no evidence to suggest that wild oats acted as a barrier to inoculum movement. Wild oats' effect on wheat leaf rust was probably through its competitive reduction of wheat tiller density. Both wheat and wild oats seed weight decreased as the proportion of wild oats increased in mixtures. This indicates that intraspecific competition was stronger in wild oats than was intraspecific competition with wheat in these mixtures. Wild oats generally did not respond to the presence of leaf rust on wheat, while wheat was negatively impacted. Thus, there was little competitive advantage to wild oats when its competitor (wheat) was diseased. A small subset of the field treatments was treated with ozone, because of the limited space available in the open-top ozone exposure chambers. Wheat height and aboveground biomass generally decreased with ozone exposure and with increasing disease severity in both years, while total grain weight decreased significantly only with disease and only in one year. There was no interaction between ozone and disease, regardless of cultivar, density, or plant response variable measured. There was little evidence that ozone exposure affected the severity of wheat leaf rust. In general, there seemed to be a lack of interactions among the different stressors and the results varied considerably depending on year and wheat cultivar. / Graduation date: 1998

Graduation date: 1991

Recently the semiconductor industry tends to develop a smaller volume device and system with lower power consumption, lower leakage current, and high speed performance. SOI technology having many unique characteristics is one of the most hopeful methods in the direction. As semiconductor memory is concerned, The 1T-DRAM cell realized by the concept of floating body effect in a PD-SOI nMOSFET, that can allow DRAM cell to be scaled down in depth with less area occupied .In this paper, we will propose a new structure of 1T-DRAM cell, which has the buried oxide and block oxide around its body. It can suppress the junction capacitor between the S/D and the body of the cell. In addition it can also improve the programming window of the 1T-DRAM cell more than 80% by utilizing its own structural characteristic. We fabricated our new device in National Nano Device Laboratories. The device was carried out by depositing oxide and poly film on bulk Si wafer, just like TFT process. But doing by this way it has some issues about the polycrystalline channel and the S/D. Although it has some issues, but we made it successful using bulk Si wafer rather than expensive SOI wafer. It indeed reduces the cost of process.