Bibliography: leaves 151-187.

Copies of author's previously published articles inserted. Bibliography: leaves 184-197.

Bibliography: leaves 132-159. Boron efficiency in oilseed rape (Brassica napua L. and B. juncea L.) was investigated in a wide range of genotypes. Using a solution culture screening of 10 day old seedlings, root length best described shoot growth response, and was used to characterise a total of 65 genotypes. Varieties and breeders lines tolerant of B-deficient growing conditions were identified, and the screening process validated through field trials. B responses in plants sampled at the 'green bud' stage indicated that vegetative growth is important in B efficiency. Studies were conducted to investigate the mechanism of B efficiency in oilseed rape. Results suggest no association between B efficiency and the capacity to acidify the root rhizosphere, or an increased translocation of B from root to shoot. Boron retranslocation was also studied as a mechanism of B efficiency.

Bibliography: leaves 89-104. In this study an EMS-mutated Arabidopsis mutant pho2, which accumulates Pi in leaves, was used to study Pi uptake and transport by comparing it to wild-type seedlings. The study aimed to define the physiological lesions in pho2 mutant and to obtain evidence regarding the function of the PHO2 gene in P nutrition in higher plants. Accumulation of Pi in leaves of pho2 was found to reside in the symplast and was not related to Zn-deficiency. The physiology of the pho2 mutant is consistent with either a block in Pi transport in phloem from shoots to roots or an inability of shoot cells to regulate internal Pi concentration. Southern block analysis revealed that the two transporter genes, APT1 and APT2 were not responsible for the pho2 mutant. Data from the mapping of the PHO2 gene along with information from the Arabidopsis genome sequencing will form the basis for cloning the PHO2 gene in the future.

No description available.

From 1998-2000, laboratory studies were conducted to examine factors that impact saltwater-entry behavior and saltwater preference (SWP) of juvenile chinook salmon, Oncorhynchus tshawytscha. These factors included bacterial kidney disease, stress and the presence of trout, O. mykiss. An additional study investigated the orientation of the startle response of chinook salmon within a salinity gradient. All experiments were conducted in 757-1 tanks in which a stable, vertical salinity gradient was established. SWP was decreased in fish suffering from bacterial kidney disease (31 �� 20.0%), compared with control fish (85 �� 17.6%). A mild chasing stressor resulted in a 26% decrease in SWP relative to unstressed fish. After a severe handling stressor, only 20% of fish preferred salt water, compared with 100% of unstressed controls. After exposure to an overhead predator model, severely stressed fish descended into the saltwater layer, but this response was transient. The presence of non-aggressive steelhead trout did not affect SWP of chinook salmon. Chinook salmon stocked with rainbow trout displayed decreased SWP. Aggression levels in tanks with rainbow trout were higher than in tanks with only chinook salmon. The orientation of the startle response was affected by the presence of salt water. Fish that preferred salt water within a gradient responded by moving horizontally within the saltwater layer. In contrast, control fish (held only in freshwater) moved vertically within the water colunm when startled. Prior preference for salt water superseded the inclination to move upward in the water column when startled. Smoltification involves physiological, behavioral and morphological changes that prepare healthy chinook salmon for seawater residence. However, disease, stress and aggressive interactions can decrease the SWP of fish at this life history stage. Avoidance of salt water during estuarine outmigration is likely maladaptive, and may have ecological ramifications including increased risk of avian predation during outmigration and decreased fitness in the marine environment. / Graduation date: 2002

The neutron and electron radiation effects in Ill-V compound semiconductor heterostructure devices are studied in this thesis. Three types of devices investigated are AlGaAs/GaAs high electron mobility transistors (HEMTs), AlGaAs/InGaAs/GaAs heterostructure insulated gate field effect transistors (HIGFETs), and InP/InCaAs/InGaAs single heterojunction bipolar transistors (SHBTs). HEMTs and HIGFETs are primarily investigated for neutron irradiation effects. Detailed optimized processing of HEMT devices is introduced. Numerical as well as analytical models that incorporate radiation induced degradation effects in HEMTs and HIGFETs are developed. The most prominent radiation effects appearing on both HEMT and HIGFET devices are increase of threshold voltage (V[subscript T]) and decrease of transconductance (g[subscript m]) as radiation dose increases. These effects are responsible for drain current degradation under given bias conditions after irradiation. From our experimental neutron irradiation study and our theoretical models, we concluded that threshold voltage increase is due to the radiation-induced acceptor-like (negatively charged) traps in the GaAs channel region removing carriers. The mobility degradation in the channel is responsible for g[subscript m] decrease. Series resistance increase is also related to carrier removal and mobility degradation. Traps introduced in the GaAs region affect the device performance more than the traps in the AlGaAs doped region. V[subscript T] and g[subscript m] of HIGFET devices are less affected by neutron radiation than they are in HEMTs. This difference is attributed to different shapes of the quantum well in the two devices. The main effects of electron and neutron irradiation of SHBTs are decrease of collector current (I[subscript c]), decrease of common-emitter DC gain, increase of the collector output conductance (��I[subscript c]/��V[subscript CE]), and increase of collector-collector offset voltage. The decrease of breakdown voltage of reverse biased base-emitter junction diode is responsible for increasing the output conductance after irradiation. Base-collector junction degradation also induces collector-emitter offset voltage increase. / Graduation date: 2003

In order to examine the potential impact of military jet overflights and other disturbances on productivity of peregrine falcons (Falco peregrinus), we observed behavioral reactions of peregrines to disturbances at nests along the Tanana River, Alaska during the 1995-1997 breeding seasons. Military jets conducted low-altitude flights over a sample of nests under observation in each year (experimental nests), while other nests were not intentionally overflown (reference nests). Other disturbances occurred at random. Animal noise monitors (ANMs), which collect and store data on noise disturbance levels, were deployed at each observed nest. A total of 878 above-threshold (��� 85 dB) overflights were recorded by the ANMs during the course of the study. A total of 401 close (defined as ��� 1000 m slant distance from the nest) overflights by subsonic F-16, F-15, A-10, Harrier, Jaguar, or Tornado jet aircraft were recorded during observations. Close overflights by military jets accounted for 63% of all observed potential disturbances at experimental nests; they accounted for 2.6% of all observed potential disturbances at reference nests. Other potential disturbances at reference nests included civilian fixed-wing aircraft (41%), boats (33%), avian predators (17%), helicopters (5%), and mammalian predators (1%). Peregrine falcons responded differently to animate and inanimate sources of disturbance, and responded most intensely and most frequently to other raptors, particularly conspecifics. Flight reactions were common, but not in response to inanimate sources. Among inanimate potential disturbances, falcons responded most intensely to boats (6% of reactions involved flight), and least intensely to helicopters (3%) and fixed-wing aircraft (2%). Intensity of reactions to military jets was indistinguishable from that to either boats or other aircraft. Intense behavioral responses (including flight reactions) to military jet overflights were rarely observed in this study, even at slant distances <500 m, and no intense behavioral responses were observed at slant distances >550 m. Peregrine falcon productivity (number of fledglings produced per nesting attempt) in the study area was within the normal range for Interior Alaska and the Tanana River. Dose of jet aircraft disturbance was not correlated with productivity. Productivity was, however, negatively correlated with reactivity of both individual falcons and mated pairs. Those falcons that responded more intensely to overflights tended to have lower productivity. The sensitivity of breeding peregrine falcons to low-altitude jet overflights is a better indicator of subsequent productivity than actual dose of overflights. This is likely a reflection of lower parental quality/investment among breeding pairs with high reactivity (i.e., younger, less experienced parents are less likely to be productive). / Graduation date: 1999

Graduation date: 1996

Graduation date: 1996