X-ray imaging has become one of the most pervasive and effective means of diagnosis in medical clinics today. As more imaging systems transition to digital modes of capture and storage, new applications of x-ray imaging, such as tomosynthesis, become feasible. These new imaging modalities have the potential to expose patients to large amounts of radiation so the necessity to use sensitive imagers that reduce dose and increase contrast is essential. An experimental design that utilizes laterally oriented detectors and amorphous semiconductors on crystalline silicon substrates has been undertaken in this study. Emphasis on fabricating a device suitable for medical x-ray imaging is the key principle throughout the design process. This study investigates the feasibility and efficiency of a new type of x-ray imager that combines the high speed, low noise, and potential complexity of CMOS circuit design with the high responsivity, large area uniformity, and flexibility of amorphous semiconductors. Results show that the design tradeoffs made in order to create a low cost, high fill factor, and high speed imager are realistic. The device exhibits good responsively to optical light, possesses a sufficient capacitive well, and maintains CMOS characteristics. This study demonstrates that with sufficient optimization it may be possible to design and deploy real time x-ray system on chip imagers similar to those used in optical imaging.

Standard geochemical analysis methods, such as aqueous geochemistry analysis and mineralogical analysis, frequently are utilized to evaluate the effectiveness of passive treatment systems, though they do not necessarily provide information regarding the mechanism of removal. Two emerging analytical techniques have shown promise by providing additional information to improve characterization of treatment systems: X-ray absorption spectroscopy (XAS) and stable isotope analysis. In this thesis, these novel analytical techniques were integrated with standard geochemical measurements to better characterize contaminated sites as well as potential treatment technologies used to mitigate aqueous contaminant mobility. Laboratory experiments were used to evaluate the removal of Se(VI) form simulated groundwater using granular Fe0 (GI) and organic carbon (OC). Greater than 90 % removal of Se(VI) was observed for systems containing GI after 5 days of reaction time and only 15 % removal was observed in systems containing OC. Synchrotron radiation-based XAS analysis of the treatment materials indicated the presence of both Se(IV) and Se(0) on the edges of GI grains after 6 hours reaction time, with no evidence of oxidized Se after 5 days of reaction. Several analytical techniques were integrated to characterize sediment contaminated with Hg and other contaminants through previous industrial practices. Analysis of the sediment by XAS indicated the possible presence of mercury selenide and copper sulfide. Resuspension tests were performed in oxic and anoxic conditions to simulate the effects of changing geochemical conditions of Hg release from sediments during dredging operations. The results indicated a higher release of Hg under oxic conditions in some sediment locations, suggesting that oxidative degradation of organic carbon or oxidative dissolution of Hg sulfides contributed to Hg release. The treatment of aqueous Hg(II) was evaluated with a variety of treatment media, including clay and GI. Treatment with GI was rapid, with 90 % removal observed after 2 hours reaction time. Extended X-ray absorption fine structure (EXAFS) analysis indicated the presence of Hg-O bonding on GI, suggesting that Hg was bound to Fe oxides formed on the surface of corroded GI. A new conceptual model for tracking the stable isotope fractionation of sulfur was coupled to the reactive transport model MIN3P to determine the effects of secondary transformations on sulfur cycling in passive treatment systems. Minor differences were noted when comparing the transport model-derived fractionation factor to calculations using a simplified Rayleigh distillation model, possibly indicating the effect of SO4 precipitation. The incorporation of stable isotope modeling provides a framework for the modeling of other isotope systems in treatment technologies.

Amorphous selenium (a-Se) and its alloys are important photoconductor materials used in direct conversion flat panel digital x-ray detectors. The performance of these detectors is determined, in part, by the electronic transport properties of the a-Se photoconductor layer namely, the charge carrier mobility m and the deep trapping lifetime t. The product of the mobility and the lifetime mt, referred to as the charge carrier range, determines the average distance that photo-generated charge will travel before being removed from the transport band by deep localized states in the mobility gap of the semiconductor. The loss of carriers to these deep states reduces the amount of charge collected per unit of x-ray exposure, and, hence, limits the x-ray sensitivity of the detector. Two experimental techniques that may be used to measure the transport properties of holes and electrons in high resistivity semiconductors are described in this thesis. The Time-of-Flight (TOF) transient photoconductivity technique is used to evaluate the charge carrier mobility by measuring the time required for the charge carriers to transit a fixed distance under the influence of an applied electric field. The Interrupted-Field Time-of-Flight (IFTOF) technique is used to determine the charge carrier deep trapping time; the drift of the injected carriers is temporarily interrupted at a position in the sample by removing the applied field. When the field is reapplied the number of charge carriers has decreased due to trapping events. The carrier lifetime is determined from the dependence of the fraction of recovered charge carriers before and after the interruption with the interruption time. <p> TOF and IFTOF measurements were carried out on a number of samples of vacuum deposited selenium alloy x-ray photoconductors. Device quality photoconductor films are fabricated by evaporating a-Se source material that has been alloyed with a small quantitiy of As (~0.3 at. %) and doped with a halogen (typically Cl) in the p.p.m. range. The dependence of the carrier range on the composition of the photoreceptor film was accurately measured using both TOF and IFTOF measurements. It was found that the transport properties of the film could be controlled by suitably adjusting the composition of the alloy. Combined IFTOF and TOF measurements were also performed on several samples to examine the effects of trapped electrons on the hole transport properties in a-Se films. It was found that drifting holes recombine with the trapped electrons, and that this process could be described by a Langevin recombination process. This finding is important for the correct modeling of amorphous selenium digital x-ray detector designs. Finally, the effects of x-ray exposure on a-Se films were examined. A temporary reduction in the effective hole lifetime was observed due to an increase in the number of hole capture centers following an x-ray exposure. The capture coefficient between free holes and the x-ray induced hole capture centers was measured using combined TOF and IFTOF measurements. It was shown that this capture process was governed by the Langevin recombination mechanism. From these observations it was concluded that trapped electrons from a previous x-ray exposure act as recombination centers for subsequently generated holes, thereby reducing the effective hole lifetime in the sample.

Environmental conditions on wintering or spring-staging areas may influence subsequent reproductive performance in migratory birds. These cross-seasonal effects may result from habitat loss and degradation (e.g., via contamination) which in turn reduce reproductive success, particularly in waterfowl that use stored nutrients for reproduction. North American lesser scaup (<i>Aythya affinis</i>) and white-winger scoter (<i>Melanitta fusca</i>) numbers have declined over the past 20 years, particularly in the boreal forest, and remain well below conservation goals, whereas ring-necked duck (<i>A. collaris</i>) numbers have increased. Environmental changes on scaup and scoter wintering and staging areas have raised concern about possible cross-seasonal effects on birds arriving on breeding grounds. The spring condition hypothesis (SCH) purports that many female scaup fail to acquire sufficient nutrients in late winter and spring, causing a decrease in breeding propensity and productivity. The contaminant hypothesis proposes that increased exposure to contaminants (particularly selenium [Se]) on wintering and staging areas has decreased scaup productivity. Accordingly, I compared body condition and studied Se concentrations in scaup, scoters and ringnecks to test the condition and contaminant hypotheses. <p>Scaup had similar body condition to ringnecks, and had similar body mass compared to scaup collected near Yellowknife, NT, in 1968-70. There was no relationship between scaup and ringneck nutrient levels and claw tip carbon, nitrogen or hydrogen isotope values, suggesting that arrival body condition likely was not related to location or diet several months prior. Instead, scaup and ringnecks nutrient levels may be more affected by feeding or habitat conditions on or near the breeding grounds. Scaup had slightly higher liver Se concentrations than ringnecks, but levels in both species were below recognized harmful threshold concentrations; I found no relationship between Se and breeding propensity, or between Se and somatic lipid or protein stores. Scoters had much higher Se concentrations, yet contrary to predictions, there were positive relationships between Se and both lipid stores and breeding status. Follicle [Se] in scaup was below threshold concentrations; despite high liver Se in scoters, egg and follicle levels also were well below threshold concentrations. Using both body composition analysis and stable-isotope analysis I determined that scoters derive egg protein from their breeding ground diet, which likely prevents Se deposition from somatic protein to eggs, and egg lipids are apparently derived from somatic tissues. In all three species, liver Se concentrations were significantly correlated with claw tip ä15N. As the claw tip likely represents assimilated diet from 2-5 months prior to sampling, this correlation suggests that Se in these boreal breeding species is carried over from wintering and staging areas. <p>Overall, results did not support either the spring condition or contaminant hypotheses. Scaup and scoters are late-nesting species, with highest pair densities occurring at the northern extent of their range. Maximum ring-neck pair densities occur at more southern latitudes. Ring-necks also nest earlier and appear to be more flexible in timing of nest initiation. Therefore, it is possible that due to climate change, early spring conditions alter the optimal timing of nest initiation to the detriment of late-nesting species such as scaup and scoters, and favour earlier nesters like ringnecks. Further research into this mismatch hypothesis is warranted.

Living organisms constantly respond to changing environmental conditions, and some changes can be far from optimal for many organisms. Insects represent the majority of species in many ecosystems and play an important role in bioaccumulation and biotransformation of environmental contaminants such as selenium and arsenic. Some insectivorous predators feeding on these insects are highly sensitive to such elements resulting in reduced growth, reproductive failures and low population numbers. The mechanisms of selenium and arsenic uptake through the food chain are poorly understood. The determination of chemical speciation is a prerequisite for a mechanistic understanding of a contaminants bioavailability and toxicity to an organism. Synchrotron-based X-ray absorption spectroscopy was used to identify the chemical form of selenium and arsenic in insects in both the field and laboratory conditions. Insects living in streams near Hinton, Alberta affected by coal mine activities were examined for selenium speciation. Results showed higher percentages of inorganic selenium in primary consumers, detritivores and filter feeders than in predatory insects. Selenides and diselenides constitute a major fraction of selenium in these insects. In another field setting, speciation of selenium was studied in insects attacking selenium hyperaccumulating plant <i>Astragalus bisulcatus</i>. The effect of selenate and arsenate alone and the combined effects of selenate and arsenate on insects and parasitoids were monitored using a laboratory-reared moth (<i>Mamestra configurata</i>). Hosts receiving selenium biotransformed selenate to organic selenides and diselenides, which were transferred to the parasitoids in the third trophic level. Arsenic fed larvae biotransformed dietary arsenate to yield predominantly trivalent arsenic coordinated with three aliphatic sulfurs. Larvae receiving arsenate used a novel six-coordinated arsenic form as an excretory molecule in fecal matter and cast skin. X-ray absorption spectroscopy imaging with micro X-ray fluorescence imaging on selenate and arsenate fed larvae revealed highly localized selenium and arsenic species, zinc and copper within the gut. The results provide insights into how the insects cope with their toxic cargo, including how selenium and arsenic are biotransformed into other chemical forms and how they can be eliminated from the insects. The implication of selenium and arsenic species in the diet of predators and detritivores is discussed.

Determination of arsenic and selenium compounds in water samples organotin compounds in fish samples by LC-ICP-MS

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Includes bibliographical references.

Testing is a vital part of software development and test automation is an increasingly common practise. Performing automated testing on web-based applications is more complicated than desktop applications, which is particularly clear when it comes to testing a web based user interface as they are becoming more complex and dynamic. Depending on the goals and needed complexity of the testing, a variety of different frameworks/tools are available to help implementing it. This thesis investigates how automated testing of a web-based user interface can be implemented. Testing methods and a selection of relevant testing frameworks/tools are presented and evaluated based on given requirements. Out of the selected frameworks/tools, the Selenium WebDriver framework is chosen and used for implementation. The implementation results in automated test cases for regression testing of the functionality of a user interface created by Infor AB.

In this thesis CIGS absorber layers have been deposited by gas flow sputtering with an extra supply of selenium, a method that displays promise for large scale production because of its one-step sputtering route which deposits low energy particles in a high deposition rate. In this thesis a method was developed where selenium was added to the sputtering process inside the sputter chamber in a controllable manner and in larger amount than done in previous projects. A total of five samples were manufactured with altered evaporation temperatures and an extra supply of selenium which then were finalized to solar cells using the standard baseline process of the Ångström solar center. The characteristics of the CIGS layer and solar cells were analyzed by XRF, IV- and QE measurements. A cell with a conversion efficiency of 11.6 %, Jsc of 27.9 mA/cm2, Voc of 0.63 V and fill factor of 66.2 % was obtained on a 0.5 cm2 cell area without an antireflective coating. All samples contained cells with obtained efficiencies above 10 %, but over the whole samples the efficiencies varied considerably. The samples that were deposited with moderately large selenium evaporation provided the highest efficiencies with a relatively good homogeneity over the substrate. Results show a deficiency of copper in the CIGS films compared to the target composition. The copper content was lower than 70 % expressed in Cu/(Ga+In), which probably resulted in a low diffusion length for electrons, leading to limited cell efficiencies.  Through the duration of the thesis issues that concerned the power supply- and the controls to the substrate heaters as well as the control of the evaporation temperature during the depositions arose that required problem solving and needs to be resolved for the future progression of this work. The conclusions drawn from this thesis are that it is possible to vary the temperature of the selenium source and thereby control the amount of selenium that evaporates during the deposition process even though there is a lot of additional heating in the sputter chamber from both the substrate heaters and the sputter source which could affect the ability to control the amount of selenium being evaporated. That the most likely reason for the limited efficiencies is due to the low copper content in the CIGS films and that a larger amount of evaporated selenium compared to previous work did not result in higher obtained efficiencies.