Large-Scale Electrochemical Degradation of Poly-and Perfluoroalkyl Substances (PFAS) by Magnéli Ti4O7 Electrodes

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals that are extremely persistent in the environment. They classified as emerging contaminants and have been linked to impacts on the developmental, liver, immune, and thyroid systems, and are possible carcinogens. PFAS’ resistance to biodegradation and conventional oxidation processes make them one of the hardest chemicals to remove from water. With the discovery of PFAS in public water supplies, existing technologies are not capable of removing these recalcitrant contaminants to levels expected for the health of the public. Even in cases when conventional technologies can remove PFAS compounds, removal is often the separation of the contaminants from water to another phase for further treatment. Electrochemical treatment has been shown to not just transfer PFAS to other phases, but to destroy these compounds. These electrochemical systems have emerged as a novel water treatment technology which has been performed at both bench-scale and pilot-scale. This study explored the degradation of six of the most commonly regulated PFAS compounds on a scale that could be used in industrial applications. Two designs of Magnéli phase Ti4O7 anodes, solid and microporous which differ in flow pattern, were tested. These reactors were evaluated for the ability to destroy individual PFAS compounds at two voltages, two amperages, and with the addition of sodium sulfate to the base conductivity of sodium chloride. Previous Aclarity research designated the settings that were tested. The reactors were not capable of removing shorter-chain compounds, such as PFOA, PFHpA, and PFHxS, likely due to the hydrophilic functional groups. While PFOS, PFNA, and PFDA were easily removed due to their hydrophobic functional groups. The reactors removed the most contaminants at higher voltages and amperages. Further investigation is required to remove short-chain compounds with this large-scale reactor and to make the system more energy efficient

Ecology and energetics of early life stages of walleye pollock in the eastern Bering Sea: the role of spatial variability across climatic regimes

Understanding mechanisms behind variability in early life survival of marine fishes can improve predictive capabilities for recruitment success under changing climate conditions. Ecosystem changes in response to climate variability in the eastern Bering Sea affect commercial species including walleye pollock (Theragra chalcogramma), which represent an ecologically important component of the ecosystem and support the largest commercial fishery in the United States. The goal of my dissertation was to better understand spatial and temporal dynamics in the ecology of early life stages of walleye pollock in the eastern Bering Sea through: (1) an examination of shifts in larval fish community composition in response to environmental variability across both warm and cold conditions; (2) a quantification of the seasonal progression in energy content of age-0 walleye pollock which provides critical information for predicting overwinter survival and recruitment to age-1 because age-0 walleye pollock rely on sufficient energy reserves to survive their first winter; and (3) a modeling approach to better understand the role of prey quality, prey composition, and water temperature on spatial and temporal patterns of juvenile walleye pollock growth with implications for year-class survival and recruitment success. In the community analysis, I identified a strong cross-shelf gradient delineating slope and shelf assemblages, an influence of water masses from the Gulf of Alaska on species composition, and the importance of nearshore areas for larval fish. Species assemblages differed between warm and cold periods, and larval abundances, including that of walleye pollock, were generally greater in warm years. I identified different energy allocation strategies indicating that distinct ontogenetic stages face different survival constraints. Larval walleye pollock favored allocation to somatic growth, presumably to escape size-dependent predation, while juveniles allocated energy to lipid storage in late summer. Finally, I provide evidence that a spatial mismatch between juvenile walleye pollock and growth 'hot spots' in 2005 contributed to poor recruitment while a higher degree of overlap in 2010 resulted in improved recruitment. I highlight the importance of climate-driven spatial patterns in community structure, prey dynamics, and environmental conditions that influence the growth and survival of an important gadoid population in a sub-arctic marine ecosystem.General introduction -- Chapter 1: Community-level response of larval fish to environmental variability in the southeastern Bering Sea -- Chapter 2: Conceptual model of energy allocation in walleye pollock (Theragra chalcogramma) from age-0 to age-1 in the southeastern Bering Sea -- Chapter 3: Spatial match-mismatch between juvenile fish and prey explains recruitment variability across contrasting climate conditions in the eastern Bering Sea

A method of beam–couch intersection detection

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134785/1/mp8509.pd

The shock expansion tube and its application as a sonic boom simulator

Shock expansion tube characteristics and use as sonic boom simulato

3D tumor localization through real-time volumetric x-ray imaging for lung cancer radiotherapy

Recently we have developed an algorithm for reconstructing volumetric images and extracting 3D tumor motion information from a single x-ray projection. We have demonstrated its feasibility using a digital respiratory phantom with regular breathing patterns. In this work, we present a detailed description and a comprehensive evaluation of the improved algorithm. The algorithm was improved by incorporating respiratory motion prediction. The accuracy and efficiency were then evaluated on 1) a digital respiratory phantom, 2) a physical respiratory phantom, and 3) five lung cancer patients. These evaluation cases include both regular and irregular breathing patterns that are different from the training dataset. For the digital respiratory phantom with regular and irregular breathing, the average 3D tumor localization error is less than 1 mm. On an NVIDIA Tesla C1060 GPU card, the average computation time for 3D tumor localization from each projection ranges between 0.19 and 0.26 seconds, for both regular and irregular breathing, which is about a 10% improvement over previously reported results. For the physical respiratory phantom, an average tumor localization error below 1 mm was achieved with an average computation time of 0.13 and 0.16 seconds on the same GPU card, for regular and irregular breathing, respectively. For the five lung cancer patients, the average tumor localization error is below 2 mm in both the axial and tangential directions. The average computation time on the same GPU card ranges between 0.26 and 0.34 seconds

Spatial and temporal changes in assemblage structure of zooplankton and pelagic fish in the eastern Bering Sea across varying climate conditions

Zooplankton and pelagic fish samples collected on the eastern Bering Sea shelf in late summer 2003-2010 were used to evaluate spatial and temporal changes in the plankton and nekton community structure. The zooplankton were sampled by vertical towing of a Juday net (168 μm mesh) and oblique towing of a Bongo net (505 μm mesh), and pelagic fish were caught by midwater rope trawl. The communities were compared across climate regimes (in relatively warm and cold years), by latitude (in the northern and southern parts of the shelf), and by water depth (in the inner, middle, and outer domains of the shelf). Zooplankton were dominated by the small copepod Oithona spp. in warm years but relatively larger copepods Pseudocalanus spp. and Acartia spp. in cold years. Notably, the large copepod Calanus spp., an important energy-rich prey for fish, were more abundant in cold years than warm years. Age-0 walleye pollock Gadus chalcogrammus were more abundant in warm years, while capelin Mallotus villosus were abundant within cold-year communities over the northern shelf. Latitudinal variations in communities were more prominent in the cold years, particularly in 2007 and 2010. Cross-shelf variations were evident, particularly for large zooplankton and fish, with communities corresponding to specific oceanographic domains. Outer shelf communities varied less than inner and middle shelf communities between warm and cold periods, suggesting that this region may be less impacted by climate variability. An understanding of the overlap of zooplankton (prey) and fish communities within specific shelf regions or climate regimes may provide information for ecosystem-based approaches to fisheries management

Quantum states and specific heat of low-density He gas adsorbed within the carbon nanotube interstitial channels: Band structure effects and potential dependence

We calculate the energy-band structure of a He atom trapped within the interstitial channel between close-packed nanotubes within a bundle and its influence on the specific heat of the adsorbed gas. A robust prediction of our calculations is that the contribution of the low-density adsorbed gas to the specific heat of the nanotube material shows pronounced nonmonotonic variations with temperature. These variations are shown to be closely related to the band gaps in the adsorbate density of states

Systematic model behavior of adsorption on flat surfaces

A low density film on a flat surface is described by an expansion involving the first four virial coefficients. The first coefficient (alone) yields the Henry's law regime, while the next three correct for the effects of interactions. The results permit exploration of the idea of universal adsorption behavior, which is compared with experimental data for a number of systems