Radical chemistry is a crucial tool to organic chemists. Recent trends in the field have been directed towards the development of photocatalysts capable of generating a radical through a renewable source like sunlight using a single electron transfer mechanism. The use of Au2dppm2Cl2, having a stronger reducing potential, allows an expansion of the reactivity to those achieved by iridium and ruthenium catalysts.1 The focus of this thesis is axed on the development of Au2dppm2Cl2 as an efficient photoredox catalyst for a tandem one-pot catalysis and its application in a dual catalytic system. The use of Au2dppm2Cl2 in a dual catalysis for the synthesis of β-amino acids was undertaken. The problems encountered over the course of the investigation showed an insufficient oxidation potential of the photoredox catalyst in addition to the facile homolytic cleavage of the C-halogen bond under UV light. However, this shows great promise for the achievement of beta amino acids using solely organocatalysis. The development of a tandem one-pot radical cyclization for the synthesis of fused- carbocycles, which are frequently encountered scaffolds in diterpenoid natural products, is reported. The initial experiments were conducted on a model substrate, enabling the verification of the proposed hypothesis. The success of this methodology was then applied to various substrates affording the desired fused 5 membered rings in good yields. These reactions show tremendous potential in the field of total synthesis for the rapid access of complex molecular structures. (1) Revol, G.; McCallum, T.; Morin, M.; Gagosz, F.; Barriault, L. Angew. Chem. Int. Ed. 2013, 52, 13342.

Trends in soil chemistry are studied on a 300 meter long hillslope in the Cascade Mountain Range of southwestern British Columbia. Although trends are not wholly consistent from horizon to horizon, the following general statements can be made: pH tends to increase downslope; exchangeable calcium, exchangeable magnesium and cation exchange capacity decrease noticeably downslope; carbon may decrease slightly downslope; nitrogen, carbon/nitrogen ratio, percent base saturation, exchangeable sodium and exchangeable potassium remain effectively constant downslope. Soil chemistry is shown to be related to horizon, slope position and parent material. Variability among chemical species increases in the sequence: pH, percent base saturation, carbon/nitrogen ratio, cation exchange capacity, nitrogen, exchangeable calcium, percent carbon, exchangeable potassium, exchangeable sodium, exchangeable magnesium. Variability fluctuates among soil horizons but not so noticeably with slope position. A slight increase in variability with the size of the area sampled is evident. / Land and Food Systems, Faculty of / Graduate

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

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Approved for public release; distribution is unlimited / The main focus in the design of the next generation combatant, DD(X), is the US Navy's proposed Integrated Power System (IPS) which includes an all-electric propulsion drive system. The reduction of current waveform harmonics is critical in combatant propulsion systems such as the IPS. One method of reducing the current harmonics is to utilize a multilevel converter topology. The multi-level converter, as compared to a standard converter, features low dv/dt losses and low switching losses. This thesis examines the design, construction and testing of two multi-level converters operated in tandem, called a Cascaded Multi-Level Converter (CMLC). A digital logic switching circuit is designed and constructed to control the CMLC during the operational testing phase. The CMLC is demonstrated in a three-phase high-voltage configuration with 178.5 V zero-to-peak voltage, 2.10 A zero-to-peak current achieved using an R-L load. / Lieutenant Commander, United States Navy

Images are forming an increasingly large part of modern communications, bringing the need for efficient and effective compression. Many techniques developed for this purpose include transform coding, vector quantization and neural networks. In this thesis, a new neural network method is used to achieve image compression. This work extends the use of 2-layer neural networks to a combination of cascaded networks with one node in the hidden layer. A redistribution of the gray levels in the training phase is implemented in a random fashion to make the minimization of the mean square error applicable to a broad range of images. The computational complexity of this approach is analyzed in terms of overall number of weights and overall convergence. Image quality is measured objectively, using peak signal-to-noise ratio and subjectively, using perception. The effects of different image contents and compression ratios are assessed. Results show the performance superiority of cascaded neural networks compared to that of fixedarchitecture training paradigms especially at high compression ratios. The proposed new method is implemented in MATLAB. The results obtained, such as compression ratio and computing time of the compressed images, are presented.

Measuring habitat selection by bats is complicated by their intricate life cycle. Scaling habitat measurements to reflect a hierarchal habitat selection process can help to define habitat associations of bats. I assessed day roost habitat of female long-legged myotis at four scales: the roost structure, micro-habitat surrounding the roost, the stand level, and landscape level. I radio-tracked 16 female long-legged myotis (Myotis volans) for an average of eight days per bat, July through August of 1993, 1994, and 1995 in two drainages in the central Oregon Cascades (Quentin Creek and Lookout Creek) to locate day roost structures. Forty-one day roost structures were identified, of which 1 was a rock face, 4 were green trees, and 36 were snags. The average height of all roost structures was 40 m (SE=2.5). The average dbh for all snags and trees used as day roosts was 100 cm (SE=6.1). Large snags including partially live, hollow western redcedar trees (Thuja plicata) averaging 97 cm dbh (SE=6.6) and 38 m (SE=2.8) high were the most commonly used roost structures. Individuals radio-marked at the same night roost did not use one common day roost. Individual bats were found roosting in one roost for several days, or using multiple day roosts within discrete roost areas. The area which encompassed one night roost and all known day roosts covered 3,258 ha in the Quentin Creek drainage and 6,391 ha in Lookout Creek. I compared physical characteristics and habitat within 20 meters of 33 roost snags with 66 randomly selected snags. The odds that a snag is used as a day roost is associated with roost height; given height, the odds of use is associated with the height of the stand within 20 meters of the snag. There is some indication that the presence of an open canopy around the snag, and the percentage of bark on the snag also could be factors that influence the selection of snags as day roosts. The frequency of occurrence of roost structures within young and late seral stands did not differ from what was expected to occur by chance in these two stand conditions. Roosts did not occur in stands with a harvest history vs. stands without a harvest history disproportionate to availability. I compared the distance to class I (largest) through class IV (smallest) streams between 34 day roosts and 102 randomly selected points. Day roosts were located closer to streams than randomly selected locations in both Lookout and Quentin Creek drainages with 1 exception (Lookout class III). In two cases day roosts were significantly closer to streams than randomly selected locations. Day roosts tended to be closer to streams where night roosts were located than did randomly selected points, regardless of stream class. / Graduation date: 1997

This thesis includes four separate studies. The first two studies assessed edge effects in a 700-year-old forest. After 20 years of exposure, epiphyte assemblages on the clearcut edge were similar to those of the forest interior, but there were some differences in vertical distribution patterns. Several species restricted to the upper canopy of the forest interior occurred farther down in the crowns of trees on the clearcut edge. Many species were associated with thick moss mats. Thalli of two cyanolichen species were reciprocally transplanted among four tree crowns. Lobaria oregana grew less on the clearcut edge than in the forest interior. Populations of Pseudocyphellaria rainierensis had acclimated to the edge environment. The third study evaluated whether these two species require old growth and/or thick, underlying moss mats to achieve normal rates of growth and mortality. Thalli were transplanted into tree crowns in 13 forest stands representing 4 age classes: old growth, mature, young, and recent clearcut. Wooden racks were used instead of trees in clearcuts. Half of the cyanolichen thalli were transplanted onto thick moss mats, half onto bare bark. Both species grew at least as well in the younger forests as they did in old growth, but growth rates were significantly lower in clearcuts. Mortality rates were very low in young, mature, and old-growth forests but high in clearcuts. P. rainierensis grew significantly better on moss than bare bark. The fourth study evaluated the long-term potential of live tree retention for cyanolichen conservation. Lichen litterfall was sampled in a natural, multiple-age stand containing remnant trees and regenerating forest. Two lichen species (L. oregana and Sphaerophorus globosus) were strongly associated with remnant trees. Biomass of both species was highest near remnant trees and was significantly higher within groves of remnant trees than at the edges of these groves or near isolated trees. Cyanolichen populations appear to have persisted on remnant trees since before the last fire. They are slowly recolonizing the regenerating forest. Retention of live trees, including hardwoods, combined with longer rotation periods, has great potential to maintain cyanolichens in managed forests. / Graduation date: 1996

Resonant or near resonant optical nonlinearities in semiconductor coupled quantum-well systems are discussed. Quantum engineered coupled or cascade quantumwell structures can provide giant nonlinear susceptibilities for various optical nonlinear processes. Nonlinearities integrated within quantum cascade lasers (QCL) showed great potential in various applications in the infrared range. Several schemes of nonlinearities are proposed and discussed in this work. Integrating difference frequency generation (DFG) with QCL can yield long wavelength radiation, such as terahertz light. The DFG process does not require population inversion at a transition associated with low photon energy; however, this requirement is necessary to lasers, such as QCL, and is hard to meet, because of the thermal backfilling and inefficient injection or pumping at room temperature. Therefore terahertz radiation due to DFG QCL for room temperature is proposed. On the other hand, the second harmonic generation can double laser frequency, and then push radiation frequency of AlInAs/GaInAs/InP based QCL to short wavelengths such as 3 μm and shorter. Optical nonlinearities can extend working frequencies of light sources, and also can help to improve light detection. For example, a sum frequency generation can upconvert mid/far-IR signal into near-IR signal with strong near-IR pump light, namely high efficient near-IR photon detector could be employed to detect mid/far-IR light. A specific designed quantum well structure of this frequency up-conversion scheme is discussed. A scheme of monolithic in-plane integration of the optical nonlinearities with QCL is also proposed. In this scheme, an optical nonlinear section is made from the same quantum well structure of a QCL, and is under an independent applied bias. Due to the independence of the applied bias, the nonlinearities can be tuned flexibly. In particular, a widely tunable Raman laser based on this scheme could be achieved. A frequency up-conversion based on sum frequency generation process in coupled quantum-well structure is also proposed for mid-infrared detection. By converting mid-IR signal to near-IR, superior near-IR detector such as silicon avalanche photo diode (APD) can be employed. The scheme can provide lower noise equivalent power (NEP) or higher detectivity compared with regular semiconductor photo detectors. A scheme of lasing without inversion (LWI) based on QCL for THz radiation is proposed. A ladder type three-level system for LWI process is integrated into a boundto- continue high power QCL at 10 μm. The proposed LWI generates THz signal at 69 μm. An optical gain about 80 cm-1 is achieved, against a waveguide loss about 30 cm-1 in a semi insulator (SI) surface plasmon waveguide.

Producing more reaction regions on the PEMFC cathode using cavities with micro structures can be used to add more reaction points on the electrode. The original ladder type cavity is limited by the laser diffraction in its manufacture. The flat electrode has its performance improved for 58%. The energy density is increased from 462 mW/cm2 to 720mW/cm2. Pressure required in the micro-structure imprinting is reduced, so as the fuel transportation blocked by mold releasing. The total catalyst amount is cut from 0.5mg/cm2 to 0.25mg/cm2. No obvious performance drop can be found. This shows that most of the reactions happen in the region between catalyst layer and micro hole layer. Limited by the pattern of micro-structure, the electrospray does not perform as expected. In the future, this issue should be considered in making micro-structure.