Master's Theses (Plan A and Professional Engineering Design Projects)

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A 0.45 V low power high PSRR subthreshold CMOS voltage reference
(2017-10) Palamedu Sundaram, Prakash
Voltage references are broadly used in analog and digital systems to generate a DC voltage independent of process, supply voltage and temperature (PVT) variations. Conventional band gap references (BGR) add the forward bias voltage across a PN junction with a voltage that is proportional to absolute temperature to produce an output that is insensitive to changes in temperature. BGRs generate a nearly temperature independent reference, of about 1.25 V, and therefore they require a higher supply voltage, which might not meet the low voltage constraints for low-power applications such as passive RFID’s, wearable and implantable medical devices. Also, BGRs use resistors that need more area on silicon. One possible solution to meet the low power requirement is to operate MOSFETs in subthreshold region. Most often, forward biased PN-junctions of BGRs are substituted with MOSFETs biased in the subthreshold region and achieves a supply voltage down to 0.6 V.\par This paper presents a sub-1V voltage reference circuit that has only MOS transistors, all working in subthreshold region with a supply voltage down to 0.45 V and a supply current of 1nA at room temperature for ultra-low power applications. The circuit is designed and simulated in 0.13um technology.
A 10,000-year lake-sediment based reconstruction of precipitation isotope values in the Canadian Rocky Mountains and implications for past changes in North American hydroclimate
(2019-01) Wagner, Zachary
Hydroclimate change in the Canadian Rocky Mountains is an important area of research, as demand for water resources in the Great Plains has been continuously increasing in recent years. The population of Alberta has one of the fastest growth rates in Canada, and cities like Calgary and Edmonton are dependent on surface and groundwater resources that originate from precipitation in the mountains. Recent increases in petroleum exploration have also amplified demands for water, along with the growing water requirements of industrial agriculture. The application of sound water resource management policies is essential, and historical records span only ~200 years, a time frame too short to capture the full range of climate variability. The development of paleoclimate proxy records from the Rocky Mountains is therefore necessary to attain a thorough perspective on potential changes in climate. Such data can, for example, inform water resource managers of possible shifts in precipitation seasonality and drought/pluvial events on timescales of decades to millennia. To this end, we present a 10,000-year oxygen isotope record as a proxy for precipitation seasonality linked to the Pacific North American pattern (PNA) which adds to a growing body of research in a region of high spatial complexity of hydroclimate. Shark Lake in Alberta, CA (50.8412°N, 115.3990°W; 1857 m above sea level) is a hydrologically open basin lake in the Canadian Rocky Mountains with one large outlet and numerous small inlets and groundwater springs. Winter precipitation is more depleted in the heavier 18O isotope relative to summer precipitation due to equilibrium fractionation from rain-out and phase changes. δ18O and δD values of Shark Lake water samples (collected during the summer) range from -18.9 to -20.0 ‰ and -141 to -150 ‰, respectively. The annual weighted average precipitation isotope ratios are -16.6 and -126 ‰ for oxygen and hydrogen, respectively. This indicates that Shark Lake principally receives water inputs from runoff or shallow groundwater that originated as precipitation during the cold season. We collected 1 m and 1.5 m long sediment cores using a modified Livingstone corer and used loss-on-ignition (LOI), x-ray diffraction (XRD), x-ray fluorescence (XRF) analyses to destermine sediment texture and composition. The sediment was dated using 14C from terrestrial plant fossils, as well as 210Pb and 137Cs for the surface sediment. We analyzed the isotopic composition (δ18O) of authigenic carbonate sediment from Shark Lake using mass spectrometry and applied these results as a proxy for precipitation seasonality. Lake water oxygen isotope ratios are captured by authigenic carbonates, which form during the spring and summer in response to pH changes associated with primary production. These carbonate minerals (calcite) precipitate in isotopic equilibrium and are deposited on the lakebed where they are preserved. The Shark Lake δ18O record demonstrates a transition from lower to higher average δ18O values from the middle to the late-Holocene at around 4500 yr BP. This is consistent with previous findings of changes in PNA-like atmospheric patterns during the middle Holocene, when a gradual shift from a more negative to a more positive mean state phase of the PNA occurred. This produced enhanced zonal atmospheric circulation in the Pacific Basin that led to a reduction in winter precipitation in northwestern North America and drier conditions in the southwestern part of the continent in the late Holocene relative to the middle Holocene. The Shark Lake δ18O record has a positive, significant correlation with other similar records from the Pacific Northwest, specifically those from Lime Lake (WA) and the OCNM (OR) speleothem, and has a negative, significant correlation with records from the southern Rocky Mountains and eastern North America, namely those from Bison Lake (CO), Cheeseman Lake (NL), Grinnell Lake (NJ), and the Buckeye Creek Cave speleothems (WV). Decadally resolved records are useful for tracking changes in PNA state and its interaction with other related climate oscillations such as the El Niño Southern Oscillation (ENSO) and the associated Pacific Decadal Oscillation (PDO). Open-basin lake records can also be combined with hydrologically closed-basin lake records to reconstruct pluvial and drought periods over the Holocene. The Shark Lake record increases the spatial resolution of mid- to late Holocene hydroclimate climate data in the Rocky Mountains and provides a baseline for natural variability in precipitation seasonality in a hydrologically important region.
1H-NMR Metabolomics Characterizes Transition From Ebb To Flow In A Porcine Model Of Smoke Inhalation And Severe Burn Injury
(2018-06) Hendrickson, Cole
Burn injury initiates a metabolic response that, even when treated, causes muscle wasting and organ dysfunction in burn patients as long as two years following injury. This increased metabolic rate, termed “flow” phase in burn physiology, is initially masked by low blood pressure and inadequate oxygen supply in burn shock, known as “ebb” phase. Our study examined the metabolic transition between the “ebb” and “flow” phases of burn recovery using proton nuclear magnetic resonance (1H-NMR) spectroscopy in a porcine model of severe burn injury with additional smoke inhalation. We hypothesized the serum metabolomes of porcine subjects would be distinguishable by time point, and the changes in individual metabolite concentrations would characterize the shift from “ebb” to “flow” in burn physiology. Fifteen pigs received 40% total body surface area (TBSA) thermal burns with additional pine bark smoke inhalation treatment. Subjects were resuscitated and kept anesthetized until 72 hours post-burn or death. Arterial blood samples were drawn at baseline (pre-burn) and every 24 hours until 72 hours post-injury or death. The aqueous portion of each sample was analyzed in a 700MHz spectrometer and metabolite peaks were fit to spectra using Chenomx software. Thirty-eight metabolites were detected in 39 samples, and principal component analysis (PCA) was conducted to separate samples by time point. 51.6% of metabolite variability was captured in the first two principal components. We found post-burn metabolomes of porcine subjects to be distinguishable by time point using 1H-NMR and principal component analysis. We also constructed a framework for non-lactic acidosis in resuscitated burn subjects that emphasized oxidative stress and increased fatty acid catabolism as root causes of organic acid accumulation. Further studies will be required to confirm and elaborate on the post-burn metabolic pathways suggested by this analysis.
2-Alkoxycarbonyl Allyl Ester Conjugates of NSAIDs as Potential Anticancer Agents
(2017-09) Lueth, Erica
Enzyme cyclooxygenase (COX) inhibition with non-steroidal anti-inflammatory drugs (NSAIDs) has long been utilized to treat inflammation and relieve pain. Several studies have shown that NSAIDs have also cancer preventative and tumor regressive effects. Prostaglandin E2 which acts as an inflammatory mediator influences many mechanisms that plays a significant role in tumorigenesis such as cell proliferation, angiogenesis, and metastasis. COX overexpression is a characteristic feature of most malignant tumors and contributes to poor outcomes in multiple malignancies. It has been reported that cancer incidence can be reduced by 25-40% in patients regularly taking low dose COX inhibitor aspirin on a daily basis, with the most compelling evidence acquired for colorectal cancer. We envisioned that NSAID conjugates derived from 2-alkoxycarbonyl allyl esters would have cytotoxicity enhancing prodrug properties with dual anti-inflammatory and intracellular alkylation. In the current work, 2-alkoxycarbonyl allyl ester conjugates of several common NSAIDs have been synthesized and tested for their cell proliferation inhibition properties in breast (MDA-MB-231, 4T1), pancreatic (MIA PaCa-2), and colorectal adenocarcinoma (WiDr) cell lines. Several of the synthesized derivatives exhibit good potency against all four cancer cell lines. The synthesized compounds have also been tested for their COX inhibition properties.
2-hydrazinoquinoline as a novel derivatization agent for LC-MS-based metabolomic investigation of ketoacidosis in streptozotocin-elicited diabetes
(2013-07) Lu, Yuwei
Short-chain carboxylic acids, aldehydes, and ketones are important intermediates and end products of many metabolic processes. Their levels in biofluids and tissues can reflect the status of specific metabolic reactions, the homeostasis of whole metabolic system, and the well-being of a biological entity. Traditionally, GC-MS has been widely used for analyzing carboxylic acids, aldehydes, and ketones in biological samples after chemical derivatization. However, due to poor compatibility of common GC columns with water, the derivatization process in GC-MS is often complicated and time consuming, especially for the metabolites in biofluids and tissues. Recently, new chemical derivatization techniques have been developed to enhance the sensitivity and performance of LC-MS for analyzing these metabolites. In this study, the use of 2-hydrazinoquinoline (HQ) as a novel derivatization agent for LC-MS analysis of carboxylic acids, aldehydes, and ketones in biological samples was explored, and the conditions for the derivatization reaction were optimized. The metabolites in urine, serum, and tissue extracts can be conveniently derivatized in a 60-min process. The formation of carboxylic acid derivatives is attributed to the esterification reaction between HQ and carboxyl group, while the production of aldehyde and ketone derivatives is through the formation of Schiff bases between HQ and carbonyl group. Compared to other known hydrazine derivatization agents, including 2-hydrazinopyridine, 2-picolylamine and dansyl hydrazine, HQ can react with a broader spectrum of intermediary metabolites in biological samples, and can achieve better chromatographic performance in reversed phase LC system and higher ionization efficiency in electrospray source. Using this HQ-based approach, the metabolic disorder induced by streptozotocin-elicited diabetes was examined by the LC-MS-based metabolomics. The results showed the time-dependent separation of mouse urine samples from STZ treatment in a multivariate model of urinary metabolites. Both known and novel small-molecule biomarkers associated with STZ-induced ketoacidosis were conveniently identified and subsequently elucidated, reflecting the dramatic changes in nutrient (glucose, amino acid, and lipid) and energy metabolism after STZ treatment. Overall, HQ derivatization of carboxylic acids, aldehydes, and ketones can be an effective platform for the LC-MS-based metabolomic investigation of endogenous metabolism.
2-Swappability and the Edge-Reconstruction Number of Regular Graphs
(2018-05) Ross, Michael
The edge-reconstruction number of a graph $G$, denoted $\ERN(G)$, is the size of the smallest multiset of unlabeled, edge-deleted subgraphs of $G$, from which the structure of $G$ can be uniquely determined. That there was some connection between the areas of edge reconstruction and swapping numbers has been known since the swapping number of a graph was first introduced by Froncek, Hlavacek, and Rosenberg in 2014\cite{edgeswap}. The present paper illustrates the depth of that connection by proving several bridging results between those areas; in particular, when the graphs in question are both regular and 2-swappable. Formerly, it had been conjectured that for $r\geq 3$ regular graphs, $\ERN(G) \leq 2.$ However, results of the present paper led to the discovery of four infinite families of $r\geq 3$ regular graphs with $\ERN(G) \geq 3$, while giving some promising leads for further discoveries in edge reconstruction.
A 24-channel radio frequency receive array for magnetic resonance imaging of primates at 10.5 T
(2023-08) Jungst, Steve
Magnetic resonance imaging (MRI) is a unique modality which offers many advantages and challenges compared to other imaging technologies. The radio frequency (RF) coil is one of the key hardware sub-systems, which drives overall MRI system performance to enable higher resolution imaging and the collection of high fidelity information about organism structure and function. To optimize RF coil performance, notably the signal-to-noise ratio (SNR) of the received signal, it is imperative that each coil be custom made to the specific static field strength of the MRI system, the anatomical region of interest, and the desired experimental constraints. This thesis explores some of the technical underpinnings of MRI with a focus on RF coil construction for non-human primate (NHP) imaging. A 24-channel RF receive array coil with integrated transmitter is presented, followed by a discussion of its performance, imaging results, and future directions.
A 250-year assessment of human impacts on Lake Superior: an updated paleolimnological perspective
(2013-05) Chraibi, Victoria Lindsay Shaw
To understand environmental conditions in Lake Superior over the last two centuries, we conducted a paleolimnological study on two sediment cores collected in the eastern and western regions of the lake. We examined the diatom community assemblages, trace metals, sediment characteristics, and GIS-reconstructed human land use to evaluate the historical impacts of human activities. During European settlement and agricultural development, there is clear indication the diatom community reorganized due to nutrient enrichment. Trace metal profiles tracked a period of mining and ore processing which temporarily increased metal loads to the lake in the mid- to late-20th century. In recent decades, more oligotrophic diatom species were favored, suggesting nutrient decreases associated with remedial activities. The diatom community has reorganized to be dominated by Cyclotella species, providing evidence that water quality changes are being influenced by atmospheric nitrogen deposition and changes in the lake's physical and chemical processes associated with climate change.
3-Dimensional Changes in Position and Inclination of Ectopically Erupting Maxillary Canines in Response to Slow Maxillary Expansion: A Retrospective Study
(2024-04) Ng, Casey
At an incidence of 0.8-2.8%, the impacted maxillary canine constitutes one of the more challenging orthodontic problems to manage, often involving interdisciplinary coordination of surgical exposure of the impacted tooth followed by orthodontic traction to align the canine within the dental arch. In addition to the increased orthodontic treatment time, cost, and complexity, other sequelae of impacted canines include root resorption of adjacent teeth, cyst formation, and malocclusion. Interceptive treatment with maxillary expansion has been shown to reduce the risk of ectopically erupting canines (EECs) developing into impacted canines. Although effects of maxillary expansion on ectopic canine eruption have been studied, most have focused on rapid, rather than slow, maxillary expansion protocols and either clinical outcomes or canine localization on 2-dimensional imaging. Therefore, little is known about positional effects in the buccopalatal direction. The novel approach of investigating changes in eruption path in response to slow maxillary expansion based on cone beam computed tomography (CBCT) measurements was used in this study to facilitate precise localization of erupting maxillary canines in all 3 dimensions. In this retrospective study, CBCT records of 24 EECs treated with quad helix slow maxillary expansion (EEC 2x4 + QH group) were compared against those of 15 EECs treated with 2x4 fixed appliance (EEC 2x4 group, control treatment), 39 normally erupting canines (NECs) treated with quad helix appliance (NEC 2x4 + QH group, control diagnosis), and 24 NECs treated with 2x4 appliance (NEC 2x4 group). Linear and angular measurements pertaining to canine position and angulation were made in all 3 dimensions to determine differences at pre-treatment and post-treatment timepoints, as well as change across timepoints. Results showed that 67% of EECs corrected to a normal position, as defined by sector location, in both 2x4 appliance and quad helix appliance treatment groups. Significantly greater uprighting of the erupting canine angulation from a coronal view was found in EECs treated with 2x4 appliance, compared to EECs undergoing the same treatment. On the other hand, the quad helix appliance was found to significantly normalize medial displacement of EECs at cusp tip and apical levels, cause greater uprighting of the EEC inclination from a sagittal view compared to NEC controls, and maintain a normal vertical eruption rate in EECs. Therefore, the improvement in canine eruption path effected by the 2x4 appliance and quad helix appliance are brought about by mechanisms in differing planes of space.
3-year survival estimates of short (less than or equal to 6 mm) length implants and the relationship to crown-to-implant ratios.
(2011-12) Saldarriaga, Augusto V.
INTRODUCTION: The literature regarding survival of short implants is conflicting. Furthermore, excessive crown-to-implant ratios have been cited in the literature as being detrimental to implant survival. Hence, the purpose of this study was to determine the 3- year survival estimates, and the relationship between crown-to-implant ratios and survival of short, roughened, plateau-design implants. Additionally, risk factors for failure were evaluated. MATERIAL AND METHOD: This retrospective cohort study involved 341 patients who possessed at least 1 single ≤6mm length plateau-design implant supported restoration that had been surgically placed between August 2000 and June 2007. An electronic chart review was conducted to acquire data on patient demographics, implant location, bone density, length of time in function and/or implant failure, as well as the most recent digital periapical radiographs in which the entire crown and implant were visible. Data analysis was conducted utilizing appropriate univariate and multivariate regression statistics, as well as non-parametric Kaplan-Meier survival analysis in order to determine the overall 3-year survival rate. RESULTS: Data from 573 single implant-supported fixed restorations were tabulated and included in the study. 13 implants failed overall. The 3-year Kaplan-Meier survival analysis adjusted for clustered observations was found to be 93.9%. The average (SD) crown-to-implant ratio of implants that were in function was 2.06 (0.4), and the average (SD) crown-to-implant ratio of those that failed was 2.02 (0.3). This difference was not statistically significant. Results from the multivariate model found quality of bone, and history of adjacent endodontically treated teeth to be statistically associated with implant failure, with hazard ratios of 13.2 and 2.7 respectively (P ≤ 0.05). CONCLUSIONS:The results of this study suggest that the survival of short, roughened, plateau-design dental implants is comparable to implants of traditional lengths, which suggests that these implants are a clinically acceptable option where alveolar bone height is limited or anatomic limitations exist.
3D Printed Biocatalytic Silica Hydrogel Flow-Through Reactor For Atrazine Degradation
(2017-06) Han, Ryan
One of the most heavily used herbicides in the world, atrazine, provides a serious environmental challenge that we face presently. Atrazine has been consistently applied to farms due to its proven ability to remove broadleaf weeds, allowing for increased yields of corn crops, which is necessary to feed an ever-growing world population. However advantageous the use of atrazine is, toxic effects have been identified when humans ingest atrazine. Also, the high mobility of atrazine during run-off events after application to fields allows atrazine to be easily incorporated into water systems around agricultural land, creating a large-scale health and environmental problem as the increased atrazine concentrations negatively impact human health when ingested as well as ecological disturbances when affecting local algal communities. The presented work investigates the application of 3D printing as an approach to solving this significant problem. We hypothesize that with direct-write 3D printing of biologically active, printed materials to perform the bioremediation of atrazine, may enhance bioremediation capacity compared to conventional methods by utilizing the near limitless rapid design flexibility intrinsic to 3D printing to allow fabrication of structures with high surface area to volume ratio (SA:V), yielding lower diffusion length scales that allow improved encapsulated biocatalyst usage. We introduce a novel 3D printing method to produce application specific complex 3D geometries from a sol-gel based silica material with encapsulated biocatalysts. To produce a bioactive material with the incorporation of biocatalysts, silica hydrogel formed through a sol-gel process was used as the ink base. E. coli genetically engineered to overexpress the AtzA enzyme, which degrades the toxic herbicide atrazine to the non-toxic compound hydroxyatrazine, were encapsulated within the silica-based ink. This process leverages the strong mechanical properties, high chemical transport properties, and biocompatibility of the silica base material along with the full material customization, precision in spatial deposition, and design flexibility intrinsic to the 3D printing process to overcome obstacles that hinder the use of bioactive materials within conventional 3D printers (material constraints and biologically deadly processing). The developed 3D printer ink was characterized in terms of gelation kinetics, mechanical properties, cell distribution, and degradation capability. Results confirmed that the 3D printed AtzA biocatalysts sustained biodegradation ability through the removal of atrazine and production of hydroxyatrazine through batch reactor experiments. High SA:V geometries produced through 3D printing also showed improved degradation efficiency by encapsulated biocatalysts. This allowed for an advantage over previously presented work because by providing high SA:V structures, the atrazine did not have to diffuse over long length scales until it was biotransformed within a bacterial cell. Structures with low SA:V were shown to decrease in degradation efficiency because as the atrazine concentration gradient decreased, only the cells closer to the surface would perform the biotransformation of atrazine, the cells located more centrally would not contribute to the degradation. Therefore, with a decrease in diffusion length to all encapsulated biocatalysts, the overall function of the encapsulated population as the concentration of atrazine dropped would be improved over past methods. Additionally, a flow-through bioreactor was designed, simulated, and experimentally tested. ANSYS reaction-flow simulations were completed to determine experimental flow rates necessary to positively identify atrazine degradation in the flow-through bioreactor. Finally, atrazine degradation was proven in flow-through experiments at an inlet flowrate of 1 ml/min. Observed atrazine degradation equated to 15 ± 5% of overall inlet concentration atrazine. Through this work, we have shown as a proof of concept that 3D printed silica-encapsulated biocatalysts sustain the function to degrade an environmental pollutant. This work may be expanded further via the incorporation of multiple types of biocatalysts encapsulated in an organized pattern (multiple different 3D printer inks printed in a designed pattern) that enhances biotransformation and transport of products between the multiple biocatalysts. In addition, this work may be applied to advance fields where complex geometries of encapsulated biocatalysts are necessitated, which may include the fields of pharmaceutical, medical, environmental, and materials science.
3D Printing and Mechanical Performance of Silicone Elastomers
(2019-11) Holzman, Noah
3D printing of soft, elastomeric materials has potential to increase the accessibility while decreasing the cost of customizable soft robotics and biomedical devices. In this work, the steps to building a 3D printer capable of printing with an extrudable liquid are described. A moisture-cure room temperature vulcanizing (RTV) silicone elastomer was 3D printed. The relative density of printed specimens was determined as a function of infill density specified in the software and the relationship was found to be non-linear and dependent on the sample geometry. Printed test specimens with a range of infill densities and several infill geometries were characterized under uniaxial tension and compression. In tension, the stress-strain behavior is non-linear over the entire curve. Ultimate tensile strength was relatively unaffected by infill density over a range of relative densities from 0.35 to 1.0, while extension at break decreased with increasing infill density. The apparent Young’s modulus was determined in the small-strain limit and is tunable from 310-1150 kPa by adjusting the infill density. Tensile strength of fully-dense printed samples (1150±30 kPa) is comparable to that of the bulk cast samples (1150±40 kPa), indicating good performance of the printing process and few defects. In compression, three different infill patterns and a range of infill patterns were tested. The specimens exhibit stress-strain behavior typical of foams—a linear elastic region with a modulus dependent on infill density, followed by a buckling plateau region and densification at high strains. Negative stiffness due to snap-through buckling was observed in some cases. Results for both tension and compression tests show the tunability of mechanical response achievable through changing the software infill density.
3D Printing Of Large-Scale Integrated Microfluidic Devices
(2024) Kaarthik, Saravanan Sujit
The ability to manufacture large-scale integrated microfluidic devices (mLSI) in an automated fashion with high throughput could impact numerous areas, including single-cell assays, drug discovery, and multi-sample analysis of human fluids. Conventional microfluidics fabrication is labor-intensive and requires the use of specialized facilities. Our group previously pioneered a method to 3D print microfluidic channels and valves by extruding silicone filaments in angular stacks. This technique faced limitations in scaling due to slow printing speed (1 mm/s) and inability to generate multiplexed flows. Here, we present an approach to 3D print mLSI devices that introduces an innovative method to reinforce channels locally and reduce the printing time 20-fold by doubling the extrusion diameter of the filaments. This allows for the incorporation of a Boolean design strategy that requires specific valves to remain open when actuated. This work paves the way for point-of-need mLSI production for medical diagnostics and disease detection.
3D Shape Memory Alloy Spacer Fabrics
(2024-02) Damame, Chaitanya
The emergence of smart materials is revolutionizing the way we interact with everyday objects by providing additional functionalities to previously conventional devices. As for smart technologies, shape memory alloys (SMA) show significant deformations, large actuation deformations and high energy absorption through thermally dependent solid-state phase transformations. SMA based spacer fabrics have immense potential as energy absorbing structures in areas such as prosthetic socket liners, military backpacks, treatment of pressure ulcers and vehicle seats, but remain limited by obstacles in design and manufacturing. This thesis provides a fundamental understanding of 3D SMA spacer fabrics by investigating the design parameters for their fabrication. The goal of this research is to investigate the impact of textile design (material, geometry and manufacturing) and material effect (superelasticity and shape memory effect) on the mechanical performance of 3D SMA spacer fabrics. Detailed experiments were conducted to analyze the superelasticity and shape memory effect by studying the interactions between different design parameters. We were able to understand the energy absorption through compression in our spacer fabrics. Hence, these fabrics have potential applications in fields of consumer electronics, medicine and sports where energy absorption is key. This research establishes fundamental understanding of SMA monofilaments within spacer architectures and enables us to design, manufacture and characterize 3D SMA spacer fabrics.
4-Hydroxy-2-Trans-Nonenal (HNE), a toxic degradation product of lipid oxidation, in fried chicken and donut
(2017-08) Yin, Ning
Alpha, beta-unsaturated-4-hydroxyaldehydes, a group of secondary lipid oxidation products, are highly interesting due to their high reactivity to various biological compounds including amino acids and DNA. 4-Hydroxy-2-trans-Nonenal (HNE), one of the most abundant and toxic compound in this group, was measured in commercial fried chicken breasts, chicken thighs, chicken nuggets and raised glazed donuts from different fast food stores and supermarkets. Samples were analyzed for fat content, fatty acids distribution and HNE concentration. Fried chickens and donuts were selected because they are very common fast food and they are deep-frying at high temperatures (160-190 °C). Preliminary experiments were conducted using the thiobarbituric acid (TBARS) assay to obtain the secondary lipid oxidation products such as aldehydes, ketones and related carbonyl compounds. HNE concentration was measured as 2,4-dinitrophenylhydrazone derivatives using an HPLC method. HNE concentrations in fried chickens from 3 different sources are between 10.02 and 11.89 µg HNE/100 g breast and between 19.80 and 24.41 µg HNE/100 g thigh. For chicken nuggets and popcorn chicken, HNE concentrations are between 9.00 and 47.93 µg HNE/100 g samples. For donut samples from 3 different brands, HNE concentrations were between 18.55 and 21.71 µg HNE/100 g donut. Measured HNE amount in chicken thighs samples is greater than chicken breasts samples, suggesting the heme iron content existed in dark meat possibly act as a catalyst to accelerate the lipid oxidation in the meat. These results indicated that HNE is incorporated into the fried chickens and glazed donuts samples from frying oils and might pose a public health concern for long-term consumption given the toxicity of HNE.
A 40,000 year geochemical record from Lake Chalco, Mexico.
(2012-04) Pierce, Megan Leigh
Water balances of Southwestern North America and of northern South America are dependent on positions of the North American (Mexican) Monsoon and the ITCZ respectively. The North American Monsoon leads to significant summer rainfall across a broad swath of the continent, and constitutes the major source of annual precipitation over the southwestern United States and northern Mexico. The position of the ITCZ and the strength of the accompanying monsoon are affected by variability in insolation. Northern hemisphere cooling results in a southerly displacement of both the ITCZ and North American Monsoon, whereas northern hemisphere warming results in a more northward position. The Basin of Mexico can be potentially impacted by both of these systems. A new geochemical climate record from Lake Chalco, Mexico, which couples inorganic (X-ray fluorescence) and organic (biomarkers and stable isotopes) geochemical proxies, reconstructs external forcings of volcanism and aridity over the past 40,000 years, as well as ecosystem responses to these forcings. The Basin of Mexico is a high altitude closed lacustrine basin (20ºN, 99ºW; 2240 m.a.s.l.) in the Trans Mexican Volcanic Belt. The relict paleolake, Lake Chalco, is located near Mexico City in the southern sub-basin, and has an area of 120 km2 and a catchment of 1100 km2. Though the present-day lake has been reduced to a small marsh due to historic diversion of its incoming rivers; over longer timescales the lake has been a sensitive recorder of hydroclimatic variations in the neotropics. Low Ca concentrations indicate greater aridity during the late glacial relative to the last interstadial or early Holocene. Peaks in Fe concentrations indicate volcanism and the deposition of tephra throughout the last 40ka, with more frequent episodic volcanism occurring in the most recent 23ka. N-alkane biomarkers, compound specific carbon isotopes, and XRF data provide evidence for ecosystem responses to both aridity and volcanism. The extent to which both of these external forcings affected ecosystem is assessed; and the extent to which global or local external forcings affect the Basin of Mexico is addressed.
Ab Initio and TDDFT investigations of the electronic spectra of [MoOCl4]- and of mixed-valency in polyferrocenyl pyrroles
(2013-09) Van Stappen, Casey Michael
The UV-Vis and magnetic circular dichroism (MCD) spectra of the d1 oxomolybdenum tetrachloride ([MoOCl4]-) anion in C4v symmetry have been calculated using the ab initio complete-active-space self-consistent-field (CASSCF)/multi-reference configurational interaction (MRCI) theory. The influence of active space used in these calculations was investigated, and the use of a differential treatment of charge-transfer and ligand-field type transitions through partitioning of active space was found to be effective. Additionally, the influence of Hartree-Fock exchange on the vertical excitation energies of [MoOCl4]- has been investigated through DFT/TDDFT methods. The combined results provide a promising direction for the prediction of MCD spectroscopy in oxomolybenal complexes. The mixed-valence properties of aromatic polyferrocenyl heterocycles have received considerable attention in recent years due to their model properties for electronic intercommunication. While α, β, and α-β saturated ferrocenyl pyrroles have been synthesized and characterized, current studies of these complexes have lacked a theoretical investigation of their electronic properties. In this study, these complexes are characterized using TDDFT methods, and their mixed-valence states explored in order to provide insight to the first oxidation process of 2,3,4,5-tetraferrocenyl-pyrrole.
The Ability Of A Cyclic Sound On Its Own, And When Coupled With An Air Curtain, To Block Ten Species Of Fish Including Carp In A Laboratory Flume
(2020-05) Feely, Jane
There is a critical need to stop the upstream movement of invasive Asian carps in the Mississippi River. One strategy to stop this would be to install sensory deterrent systems in navigation locks. Because carps have excellent hearing, sound is being considered. My thesis examined the ability of sound and sound coupled with air to block a range of fish species, including four species of carp, in the laboratory. Responses to sound alone did not appear to be related to the possession of hearing specializations. In particular, silver and grass carp were relatively unaffected. Coupling this sound with an air curtain increased its efficacy at repelling all fish species and generally corresponded with the presence of hearing specializations. This laboratory study suggests that although a cyclic sound has little potential to block all carp species, coupling the sound to an air curtain has greater potential with little species-specificity.
An Absolute Intelligence Scale: A Study in Method
(1918-08) Arthur, Mary Grace
Absorption from the Urinary Tract
(1922-03) Magoun, James Albert Hughes