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Title: THE EVALUATION OF THERMAL INACTIVATION OF COXIELLA BURNETII NINE MILE PHASE II IN BOVINE AND NON-BOVINE MILKS BY MOST PROBABLE NUMBER-POLYMERASE CHAIN REACTION (MPN-PCR) ASSAY
Creator: Zhang, Cheng
Date: 2016, 2016-05
Description: As non-bovine milks become popular for human consumption, ensuring that standard bovine milk pasteurization conditions provide enough...
Show moreAs non-bovine milks become popular for human consumption, ensuring that standard bovine milk pasteurization conditions provide enough treatment for non-bovine milks is significant for food safety. Coxiella burnetii, an obligate intracellular bacterium, has been used as the reference microorganism for defining milk pasteurization conditions. To evaluate C. burnetii thermal inactivation in bovine and non-bovine milks at commercial pasteurization temperature, an MPN-PCR assay was developed to quantitate viable C. burnetii in milk. Using this assay, the thermal inactivation of C. burnetii and a potential nonpathogenic surrogate, Micrococcus luteus, was tested in bovine, buffalo, camel and goat milks. Milk in sealed glass vials was pre-heated in a water bath at 72°C and inoculated via a syringe with C. burnetii and M. luteus at a final concentration of ~6.5 log10 ge/mL (CFU/mL) each. The inoculated milk was heat-treated at 72°C for up to 16 sec, cooled in a crushed ice bath and serially diluted. Viable M. luteus was quantitated by plating on BHIA plates. For C. burnetii detection, 1 mL of each dilution was inoculated into 9 mL Acidified Citrate Cysteine Medium-2 (ACCM-2) in triplicate T-25 flasks to produce a 3- flask Most Probable Number (MPN) assay. Viability of C. burnetii was considered positive if an increase of ≥0.5 log10 ge/mL was detected by qPCR after 14 d growth in ACCM-2 media. The numbers of positive flasks at each dilution were used to calculate the remaining viable C. burnetii by MPN method. The average D-values for 72°C inactivation were 1.99 ± 0.21 sec, 0.79 ± 0.28 sec, 1.43 ± 0.30 sec, and 2.06 ± 0.71 sec for C. burnetii, and 5.47 ± 0.94 sec, 3.65 ± 0.45 sec, 3.48 ± 0.83 sec and 5.34 ± 1.54 sec for M. luteus in bovine, buffalo, camel and goat milks, respectively. For C. burnetii, D-values in camel and goat milks were not significantly different (p>0.05) from bovine milk, but the D-value in buffalo milk was significantly lower (p<0.05). These results indicate that non-bovine milks may not be a safety concern under standard milk pasteurization conditions, and M. luteus could be a good surrogate for C. burnetii thermal inactivation in milk.
M.S. in Food Safety and Technology, May 2016
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Title: SURVIVAL AND ATTACHMENT OF SALMONELLA ENTERICA ON SELECT LOW MOISTURE NUT SURFACES
Creator: Zhang, Bo
Date: 2017, 2017-07
Description: Salmonella can contaminate various nuts and lead to human foodborne disease outbreaks and related product recalls in the United States. Nuts...
Show moreSalmonella can contaminate various nuts and lead to human foodborne disease outbreaks and related product recalls in the United States. Nuts have been identified as an increasingly common vector for human salmonellosis. The objective of this study was to evaluate the influence of environmental factors and Salmonella enterica serotypes on the survival and attachment of this pathogen on the surface of low moisture, raw in shell nuts. Two S. enterica strains (Enteritidis and Typhimurium) were individually tested on three different food samples (almonds, hazelnuts and black peppers) at 4°C or 25°C for up to 14 days. The storage relative humidity was maintained at 20±2% throughout the study. Nut samples were collected at 0, 1, 3, 7 and 14 days. The population of bacteria was calculated based on the plate count data. The results showed that S. Typhimurium attached and survived better than S. Enteritidis on almonds, hazelnuts and black peppers at both 4 and 25°C. A lower storage temperature led to a better survival of Salmonella on raw nuts during storage. The surface characteristics of hazelnuts resulted in the least Salmonella attachment compared to almond and black pepper.
M.S. in Food Safety and Technology, July 2017
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Title: FUNCTIONAL ANALYSIS OF UBIQUITIN-LIKE PROTEIN 4A
Creator: Zhao, Yu
Date: 2015, 2015-12
Description: Ubiquitin-like protein 4A (Ubl4A) was identified as a housekeeping gene at X chromosome. It involves in the guided entry of tail-anchored (GET...
Show moreUbiquitin-like protein 4A (Ubl4A) was identified as a housekeeping gene at X chromosome. It involves in the guided entry of tail-anchored (GET) protein pathway in which tail-anchored (TA) proteins are transported to endoplasmic reticulum (ER). However, Ubl4A also involves other functions not related to GET pathway, such as tumor suppression and DNA damage-mediated apoptosis. Up to date, the function of Ubl4A in mammals is still largely unknown. We found that either overexpression or knockdown of Ubl4A promoted cell death in cell culture system. Using an in vivo genetic knockout system, we found that Ubl4A knockout mice displayed a high neonatal mortality and had a defect in glycogen synthesis, which is mainly controlled by a key protein kinase Akt. Loss of Ubl4A resulted in the impairment of insulin-induced Akt translocation to the plasma membrane, an essential step for Akt activation. We demonstrated that Ubl4A directly interacted with actin-related protein 2/3 (Arp2/3) complex, further accelerated Arp2/3 complex-dependent actin branching, thereby bringing Akt to proximity into the plasma membrane for activation. Furthermore, we showed that Ubl4A-mediated actin branching also played important roles in other cellular activities, such as formations oflamellipodia and filopodia, macrophage phagocytosis, wound healing, and neutrophil chemotaxis. These findings provide us a new insight into understanding the roles of Ubl4A in cellular function and a molecular basis for treatment of related human diseases.
Ph.D. in Biology, December 2015
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Title: HIGH PERFORMANCE, HIGH STABILITY AND LOW POWER SRAM DESIGN BY USING CARBON NANOTUBE FIELD EFFECT TRANSISTORS
Creator: Wang, Wei
Date: 2012-07-07, 2012-07
Description: As the feature size of silicon semiconductor devices scales down to nanometer range, planar bulk CMOS design and fabrication encounter...
Show moreAs the feature size of silicon semiconductor devices scales down to nanometer range, planar bulk CMOS design and fabrication encounter significant challenges. This situation is exacerbated when it comes to SRAM, as SRAM takes a large part of power consumption and area overhead in modern VLSI processor designs. To achieve higher performance, stability and lower power consumption, carbon nanotube (CNT) has been introduced to SRAM design as an alternative material. The semiconducting single-walled CNTs are promising candidates for the channel material of CMOS devices because of two advantages over the other semiconductor materials: high ON current, leading to high speed and low OFF current, leading to less leakage power. In this research work, characterizing work of technology parameters for 6T carbon nanotube field effect transistor (CNFET) SRAM cell is performed for basic understanding of the relationship between SRAM delay/power and CNFET technology parameters. Stability issue is studied by investigating the diameter and transistor ratio impacts on the SRAM static noise margin (SNM). A stability-optimized 6T CNFET SRAM cell achieves 38.88% reading delay reduction, 21.61% writing delay reduction, 85.65% reading power reduction, 5.88% writing power reduction, 97.80% leakage power reduction, 41.41% SNM increment, 91.23% reading power-delay product (PDP) reduction and 26.23% writing PDP reduction, compared with conventional silicon MOSFET SRAM cell. To mitigate major CNT imperfection impacts on CNFET circuits, a misalignment immune SRAM design method is proposed to eliminate CNT misalignment problem by using etching region defined in circuit layout; and a diameter variation sensing and compensating system is designed to mitigate the negative impacts of CNT diameter variation on SRAM delay and power consumption. A hybrid silicon/CNT 4T SRAM cell design is proposed for low-power high-density cache application, which is better than conventionally used 6T SRAM in terms of power consumption and circuit area. Finally, a design flow of high performance, high stability and low power SRAM is summarized.
Ph.D. in Electrical Engineering, July 2012
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Title: Investigation of Fresh Produce Washing on E. Coli O157:H7 and Murine Norovirus with Peroxyacetic Acid and High Power Ultrasound
Creator: Yuan, Wen
Date: 2011-12-05, 2011-12
Description: E. coli O157:H7 and norovirus have each been responsible for outbreaks of foodborne illness involving fresh leafy green vegetables....
Show moreE. coli O157:H7 and norovirus have each been responsible for outbreaks of foodborne illness involving fresh leafy green vegetables. Peroxyacetic acid (POAA) has the potential to be an effective sanitizer during commercial fresh-cut produce washing. The addition of high power ultrasound (HPU) to the washing system may enhance the POAA efficacy. The purpose of this study was to reduce E. coli O157:H7 and norovirus contamination during commercial fresh-cut lettuce washing using POAA and HPU. Fresh-cut romaine lettuce leaves were inoculated with E. coli O157:H7 or murine norovirus (MNV, a surrogate for the human norovirus) and washed by POAA and HPU. Cross-contamination was tested by washing clean leaves in contaminated processing water where pre-inoculated leaves were washed previously. A high level of cross-contamination (4.5-log CFU/g E. coli) occurred after uninoculated leaves were rinsed in contaminated wash water for 2 min. A subsequent 2 min wash in POAA alone or in combination with HPU reduced counts by approximately 1.2-log and 2.3-log, respectively. More than 2-log norovirus was removed from washing 2 min in either DI water or POAA. However infectious MNV washed from leaves was not detected in wash water containing POAA. Those results implied a high possibility of cross-contamination during freshproduce washing, and indicate that adding POAA and HPU in addition to washing water in wash water can reduce cross-contamination rate.
M.S. in Food Safety and Technology, December 2011
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Title: DIFFERENTIAL SENSITIVITY OF BAXΔ2 POSITIVE AND NEGATIVE CELLS TO ANTI-TUMOR AGENT BORTEZOMIB IN COLON CANCER
Creator: Chen, Wenjing
Date: 2015, 2015-05
Description: Tumor suppressor BaxΔ2 is a functional Bax isoform that is found in microsatellite unstable (MSI) colon cancer. However, BaxΔ2 proteins are...
Show moreTumor suppressor BaxΔ2 is a functional Bax isoform that is found in microsatellite unstable (MSI) colon cancer. However, BaxΔ2 proteins are not stable and are prone to be degraded by proteasomes in tumor cells. Bortezomib, a proteasome inhibitor, is an FDA approved anti-cancer drug mainly used for the treatment of myeloma and lymphoma. We tested if Bortezomib can block BaxΔ2 degradation and potentially be beneficial for the treatment of BaxΔ2 positive colon cancer. In this project, we compared the efficacy of Bortezomib-induced cell death in BaxΔ2-positive and BaxΔ2-negative colon cancer cells. We found that BaxΔ2-positive cells were highly sensitive to Bortezomib-induced cell death in comparison with that in BaxΔ2-negative cells. The half maximal inhibitory concentration (IC50) of cell viability for BaxΔ2-positive cells is 11.1 nM, while it is 453.8 nM for BaxΔ2-negative cells. The results indicate that Bortezomib has a selectivity towards BaxΔ2-expressive cells and could be a drug candidate for the treatment of BaxΔ2-positive colon cancer.
M.S. in Biology, May 2015
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Title: FIELD AND PHOTO-EMISSION IN A SHORT-PULSE, HIGH-CHARGE CESIUM TELLURIDE RF PHOTOINJECTOR
Creator: Wisniewski, Eric E.
Date: 2014, 2014-05
Description: A new high-charge RF gun is now operating at the Argonne Wakefield Accelerator (AWA) facility at Argonne National Laboratory (ANL). The 1.5...
Show moreA new high-charge RF gun is now operating at the Argonne Wakefield Accelerator (AWA) facility at Argonne National Laboratory (ANL). The 1.5 cell 1.3 GHz gun uses a Cesium telluride photocathode driven with a 248 nm laser to provide short-pulse, high charge electron beams for the new 75 MeV drive beamline. The high-gradient RF gun (peak field on the cathode > 80MV/m) is a key piece of the facility upgrade. The large Cs2Te photocathode (diameter > 30 mm) was fabricated in-house. The photo-injector will be used to generate high-charge, short pulse, single bunches (Q > 100 nC) and bunch-trains (Q>1000 nC) for wakefield experiments, typically involving dielectric-loaded accelerating structures. Details of the photocathode fabrication process and the results of associated diagnostic measurements are presented, including QE measurements and work function measurements performed with a Kelvin probe. Field-emitted dark current from the Cs2Te cathode was measured during RF conditioning and characterized. Fowler-Nordheim plots of the data are presented and compared to similar measurements made using a copper cathode in the initial phase of conditioning. The results for cesium telluride exhibited non-linear regions within the Fowler-Nordheim plots similar to previous experimental results for other p-type semiconductors. Results of quantum efficiency (QE) studies are presented with the cathode operating in both single and bunch-train modes. QE uniformity and lifetime studies are presented. During commissioning, the cesium telluride photocathode produced bunch-charge of 100 nC, breaking the previous record. No evidence of bunch-train position-dependence of QE was found when generating four-bunch trains with total charge up to 200 nC.
PH.D in Physics, May 2014
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Title: INDUSTRIAL UPGRADING IN KOREA
Creator: Woosiklee
Date: 2014, 2014-05
Description: One of the most difficult obstacles facing non-western nations is the issue of technology transfer. The main objective of this dissertation is...
Show moreOne of the most difficult obstacles facing non-western nations is the issue of technology transfer. The main objective of this dissertation is to analyze the how South Korea has succeeded through industrial upgrading through technology transfer in achieving the Han River Miracle- making it in 2011, the fourth largest economy in Asia and the 9th largest in the world. From 1910 to 1945, Korean modernization was continuously developed under the Japanese war economy and its military policy. Japanese capital, technology and entrepreneurs were transferred to Korea due to supplement the shortages of Japanese industries or to take advantage of the low labor costs in Korea in order to prepare for the Sino-Japanese War in 1936 and the Pacific War in 1941. There is no doubt that President Chung-Hee Park (1961-1979) was the architect of the Korean economic miracle. During his authoritarian regime, the government had played an important role in the creation and financing of the modern Korean industrial groupings, called the Chaebols. The government also intervened directly in the formation of their policies. In the 1980s, when the country embarked on financial liberalization, the degree of intervention started to decrease. And finally, the 1997 crisis will be examined, with special attention on the introduction of reforms required by the International Monetary Fund (IMF). In the industrial arena, the focus will be on the rationalization policies undertaken to increase the total factor productivity (TFP). It will cover the currently important industries of steel, automobiles and semiconductors, as well as those promising industries which have led the development of South Korea's knowledge-intensive economy. An integral part of the xi ii analysis will study the repercussions of the 1997 financial reforms on both the large and small and medium-size industries. Conventional wisdom assumes that it was under President Park's rule that South Korea had its first experience with industrialization. This assumption, however, ignores the significant industrialization that took place during the colonial period. It also does not take into account the admittedly limited industrial development that took place during the time before the 1961 coup d'état, when civilian governments were in charge. The dissertation would shed light on these overlooked periods.
PH.D in Management Science, May 2014
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Title: Large Scale Integration of Sustainable Energy and Congestion Management in Western Interconnection
Creator: Aflaki Khosrosha, Kaveh
Date: 2012-07-12, 2012-07
Description: Large scale sustainable energy like wind and solar energy integration to the bulk grid could introduce inevitable challenges to regional...
Show moreLarge scale sustainable energy like wind and solar energy integration to the bulk grid could introduce inevitable challenges to regional transmission and generation systems. The most important challenges for transmission system are the congestion management and planning for transmission expansion to transfer the zero cost generated electricity. Another big challenge is competition of current fuel based generation units in the electricity market with zero cost sustainable energy. In this dissertation all these challenges identified and analyzed for large scale grid. This thesis brings a new method used to study transmission congestions in Western Interconnection of the United States. The process involved Security-Constrained Unit Commitment (SCUC) formulation applying its results for analysis of transmission congestion. This thesis also presents results and findings in simulation of the system operation in the Western Interconnection of the United States with the inclusion of large scale wind and solar energy integration for year 2030. High level of wind and solar energy with the forecasted wind and solar time series profiles were integrated to the Western Interconnection grid. Their impact on different existing types of generation plants is studied. The sensitivity of the fuel prices, wind turbine power output, load volatility and demand side management as well as carbon tax are analyzed in different possible scenarios. In order to incorporate large scale of sustainable energy into a bulk electricity grid footprint, planned transmission expansion showed need to take place. Transmission expansion reduces grid congestion and balances Locational Marginal Prices (LMP). This thesis explores the advancements in high-performance computing and visual analytics of economic-based transmission expansion in the Western Electricity Coordinating Council (WECC). This expansion is based on 2018 and 2029 forecasted data. It identifies transmission congestions and average of LMP for each area, and expands the transmission system while accommodating large scale wind and solar energy to achieve the Department of Energy’s renewable energy vision for year 2030. An iterative transmission expansion analysis, based on the average LMP for each area, is used to identify the minimum WECC transmission lines required. All results are visualized on the Geographical Information System (GIS) format map of North America.
Ph.D. in Electrical Engineering, July 2012
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Title: CHARACTERIZATION OF A NOVEL TUMOR SUPPRESSOR BAX
Creator: Wang, Xin
Date: 2013-04-16, 2013-05
Description: Bax is a pro-death tumor suppressor. The loss of functional Bax expression can enhance the tumor growth. Recently we discovered a new family...
Show moreBax is a pro-death tumor suppressor. The loss of functional Bax expression can enhance the tumor growth. Recently we discovered a new family of functional Bax isoforms generated specifically in certain tumors; one of them is Bax 2 . In this thesis, I characterized the properties of Bax 2 protein by comparing with the parental Bax 2. Bax 2 was cloned into a GFP mammalian expression vector and transfected into the bax knockout cells. I examined Bax 2 expression, cellular distribution, and ability to induce cell death. The results show that the Bax 2 protein aggregated as granules around the nucleus in cytoplasm and induced more cell death than that from previously studied Bax 2. The results implicate that cancer patients with Bax 2 isoform might have better prognosis or response to treatment.
M.S. in Biology, May 2013
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Title: INFLUENCE OF FOUR BACILLUS SP. STRAINS ON GROWTH AND DESULFURIZATION ABILITY OF MYCOBACTERIUM STRAIN U
Creator: Tian, Fangzhou
Date: 2016, 2016-05
Description: Desulfurization is an important step in crude oil processing and is commonly achieved through a chemical process known as hydrodesulfurization...
Show moreDesulfurization is an important step in crude oil processing and is commonly achieved through a chemical process known as hydrodesulfurization (HDS). Because this process is expensive and produces H2S as a by-product, the alternative of biodesulfurization (BDS) has been investigated for many years. The most potentially useful biodesulfurization process is the 4S pathway, which is found in a number of bacterial species, including Mycobacterium Strain U, which was isolated in our lab. To reach the requirement of BDS for use in an actual industrial-scale process, U has to survive at temperatures approaching 60 OC. In work in our lab, natural selection methods have been introduced for improving the U strain. During this natural selection, four contaminant strains, identified by 16S rDNA sequencing as Bacillus sp., were isolated from extraordinary U cultures which have BDS activity at 54 OC. Meanwhile the BDS activity of U on its own was found to have an upper temperature limitation of 53 OC. Additional experiments proved that all four Bacillus strains interact with U and improve its BDS ability.
M.S. in Biology, May 2016
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Title: ENHANCEMENT OF BIODESULFURIZATION IN RHODOCOCCUS SPECIES (IGTS8) BY THE EXPRESSION OF VITREOSCILLA HEMOGLOBIN
Creator: Shivdas, Vrushali D.
Date: 2013, 2013-07
Description: The bacterium Rhodococcus sp. IGTS8 contains the dsz operon, which encodes a three enzyme pathway (the “4S pathway”) that is able to...
Show moreThe bacterium Rhodococcus sp. IGTS8 contains the dsz operon, which encodes a three enzyme pathway (the “4S pathway”) that is able to mineralize the sulfur contained in dibenzothiophene (DBT), an organic sulfur containing molecule found in petroleum. The gene vgb, which encodes Vitreoscilla hemoglobin (VHb), has shown wide usefulness in enhancing productivity and other useful properties when expressed in heterologous hosts. We engineered strain IGTS8 to express VHb and measured the effects on growth and desulfurization of DBT, using minimal medium containing DBT as the sole source of sulfur. VHb was clearly detected in the engineered strain using the standard COdifference spectral analysis, but its level (0.38-0.63 nmoles/gm wet weight of cells) was about 10-fold lower than commonly seen for expression of VHb in other heterologous bacterial hosts. The VHb-expressing strain was tested for growth at both low and high aeration in minimal medium containing DBT as sole sulfur source; growth was about 50% lower at low aeration compared with high aeration. Despite this, metabolism of DBT (as detected by accumulation of the end product of the 4S pathway, 2-Hydroxy biphenyl (2-HBP), in the growth medium) was about 30 % higher in the low aeration compared to the high aeration culture. A possible explanation for these results is direct enhancement of the first two (monooxygenase) steps in conversion of DBT to 2-HBP. It was thus concluded from the studies that the expression of vgb in Rhodococcus sp. IGTS8 enhances the process of biodesulfurization under conditions of low aeration
M.S. in Biology, July 2013
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Title: DEVELOPMENT OF COMPUTER-AIDED DIAGNOSIS METHODS IN MAMMOGRAPHY
Creator: Wang, Juan
Date: 2015, 2015-12
Description: Computer-aided diagnosis (CAD) is developed as a diagnostic aid to provide a “second opinion” in diagnosis of breast cancer in early stage....
Show moreComputer-aided diagnosis (CAD) is developed as a diagnostic aid to provide a “second opinion” in diagnosis of breast cancer in early stage. Clustered microcalcifications (MCs) can be an important early sign of breast cancer. The goal of this work is to develop automatic CAD methods in mammography for breast cancer. Its contribution consists of both development of machine learning algorithms and study of related issues in detection and diagnosis of breast cancer with clustered MCs. First, a bi-thresholding scheme is proposed for reduction of false-positives (FPs) associated with linear structures in MC detection. An unified classifier with dummy variable modeling is further developed to reduce the FPs caused by both linear structures and MC-like noise patterns. It is demonstrated that both of the proposed algorithms can reduce FPs in MC detection, and thus, improve the detection accuracy significantly. Second, a spatial density modeling approach is investigated to quantify the spatial distribution of the MCs in a cluster when the MC detection is inaccurate. A spatial density function (SDF) is defined such that the extracted features are more robust to the presence of FPs and false-negatives (FNs) in MC detection. The results show that the features extracted from the SDF can achieve better class separation while being robust to the variations in MC detection when compared with those extracted from a traditional region-based method. Third, a retrieval-boosted approach is studied to discriminate between the benign and malignant MC lesions. A retrieval strategy is proposed to boost the classification performance by taking into account the similarity both in image features and in pathology. An adaptive Adaboost classifier, which can be adapted to the retrieved cases at a low computational cost, is applied to demonstrate the benefit of the retrieval strategy. The results show that the retrieval-boosted approach can signifishow that the features extracted from the SDF can achieve better class separation while being robust to the variations in MC detection when compared with those extracted from a traditional region-based method. Third, a retrieval-boosted approach is studied to discriminate between the benign and malignant MC lesions. A retrieval strategy is proposed to boost the classification performance by taking into account the similarity both in image features and in pathology. An adaptive Adaboost classifier, which can be adapted to the retrieved cases at a low computational cost, is applied to demonstrate the benefit of the retrieval strategy. The results show that the retrieval-boosted approach can significantly outperform its baseline classifier and that inclusion of pathology information in the retrieval can further improve the classification accuracy. Fourth, the perceptual similarity of MC lesions by radiologists is studied. The issues investigated include the degree of variability in the similarity ratings, the impact of this variability on agreement between readers in retrieval of similar lesions, and the factors contributing to the readers’ similarity ratings. The results indicate that perceptually similar lesions could be of diagnostic value in diagnosis for clustered MCs. Fifth, the feasibility of modeling the perceptual similarity of MC lesions is investigated. A support vector regression (SVR) is applied to model the perceptual similarity of clustered MCs, and a feature saliency analysis derived from SVR is used to determine the most relevant image features among a large set of candidate features. The results demonstrate that the relevant features are consistent in radiologists’ similarity ratings among different MC lesions, indicating that the perceptual similarity of MC lesions by radiologists can be effectively modeled. Finally, whether retrieval of similar images can effectively assist radiologists in diagnosis of clustered MCs is investigated. A retrieval system for relevant images is designed by considering both perceptually similar image features and the likelihood of malignancy of the lesion under consideration. An observer study is conducted to evaluate the diagnostic value of the proposed retrieval system. The results indicate that the proposed retrieval system has the potential to improve the reader’s ability in diagnosis of breast cancer with clustered MCs.
Ph.D. in Electrical Engineering, December 2015
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Title: CHANGES OF BACTERIAL SPECIES AND HEME PROTEIN OCCURRENCE IN ACTIVATED SLUDGE COMMUNITIES CULTURED IN THE LABORATORY
Creator: Wang, Xiaomeng
Date: 2016, 2016-05
Description: An activated sludge sample that had originally been collected from an aeration tank of the Stickney wastewater treatment plant in Chicago, and...
Show moreAn activated sludge sample that had originally been collected from an aeration tank of the Stickney wastewater treatment plant in Chicago, and had previously been cultured at low dissolved oxygen (DO) for 48 weekly passages was used as starting material for continuation of the low DO acclimation. The culture was continued at low dissolved oxygen in synthetic wastewater for 25 additional weekly passages to study what would happen to the activated sludge if the low DO continued. In order to do that, some important data were measured during the culture, including the specific oxygen uptake rates (SOUR) which could reflect the ability of oxygen utilization, 16S rDNA information which could tell the community diversity of sludge, and the dominant species genome data which suggested what really happened to the sludge and some reasons. The results showed that SOUR decreased modestly during the course of low DO adaptation, which was contrary to the results of the previous study. There were significant changes in community structure with respect to bacterial species during the first fifteen additional passages. Species known to produce both flavohemoglobins (FHbs) and truncated hemoglobins (trHbs) were common at all passages tested, although the dominant species were totally different from passage to passage. Specifically, during the course of the experiment, the frequency of cells encoding an FHb decreased substantially, from 84% to 50%, while the percentage of cells encoding a trHb decreased slightly from 84% to 78%. The overall content in the culture of heme b (the heme type found in bacterial hemoglobins) decreased, however, during continuation of the low DO conditions. So it is indicated that the oxygen utilization ability of the activated sludge does not increase all the time.
M.S. in Biology, May 2016
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Title: OPTIMIZATION OF POWER TRENCH MOSFETS FOR HIGH EFFICIENCY SYNCHRONOUS BUCK CONVERTERS
Creator: Wang, Wendi
Date: 2016, 2016-05
Description: Synchronous buck converter might be one of the most widely used and fabricated circuitry in the world for its favorable trade-off on many...
Show moreSynchronous buck converter might be one of the most widely used and fabricated circuitry in the world for its favorable trade-off on many subjects. However, the ever higher operation frequency has lead to increasing power loss in power switches and imposed new challenge to MOSFET engineering. One promising alternative for the traditionally used trench MOSFET is the shield gate MOSFET. Shield gate MOSFET has superior conduction performance as well as fast switching transient response due to its Reduced Surface Electric Field (RESURF) effect. In recent years, characterization of power MOSFET has developed along with MOSFET technology itself. New Figure of Merits (FOMs) have come into people's sight as they serve as better standards to fully describe MOSFET's overall performance. Being the same case for many other device structures, this new characterizing system also puts advanced requirements to shield gate MOSFET. And one of the most crucial problems is the rather large output capacitance this structure is having. To improve the property of shield gate MOSFET and meet the requirements of new standards, several ways of structure refinement have been proposed in this work. Both shield gate MOSFET and conventional MOSFET rated at 40V have been designed and simulated in the second chapter. The outcome shows that shield gate MOSFET has superior performance in almost every respect except for its large output charge. Then new structure for COSS reduction has been introduced in the following section, with decrement of about 50% in QQS-1 being achieved. Finally, another issue that has been tackled with is the shoot through of synchronous buck converter. Equivalent circuit model for shoot through analysis is built in this section to study the effect of each parasitic element. And a p type pillar added structure has been verified as an effective way to suppress shoot through gate bounce.
M.S. in Electrical Engineering, May 2016
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Title: YIELD STRESS MEASUREMENTS USING NOVEL SQUEEZING FLOWS
Creator: Ward, Daniel
Date: 2015, 2015-12
Description: Techniques for measuring the yield stress of materials are numerous, but often plagued with diffculties and uncertainties in measurement. The...
Show moreTechniques for measuring the yield stress of materials are numerous, but often plagued with diffculties and uncertainties in measurement. The primary methods include shear rheometry and, more recently, squeezing ow. Shear rheometry requires care on the part of the experimentalist to generate uniform flow fields and avoid shear banding or wall slip which may interfere with measurements. Squeezing fow tests are often performed with poorly controlled boundary conditions creating complicated flow fields. Further, the effects of the experimental modifications made to produce these boundary conditions in measurements are often not investigated and simply ignored. The main objective of this study was to develop a novel measuring technique to study the yield stress behavior of a model material, Carbopol. First attempts were made towards a novel lubricant injection squeezing (LIS) ow technique based on the continuous lubricated squeezing ow (CLSF) setup, as well as a novel lubricant film squeezing (LFS) technique which will allow measurement of the yield stress without the complicated treatment of either the sample or experimental setup required by currently favored methods. The novel techniques were developed and validated by direct comparison with shear measurements, the current gold standard for determining yield stress. Common squeezing techniques for characterizing yield stress fluids were also compared and found to be inadequate and inconsistent when compared to the shear measurements. The results from this study showed that the LIS and LFS methods are able to qualitatively determine a yield stress, but further investigation is required before they can be achieve their full potential as viable methods for determine yield stress.
M.S. in Chemical Engineering, December 2015
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Title: EUTECTIC γ(NI)/γ′(NI3AL)-δ(NI3NB) POLYCRYSTALLINE NICKEL-BASE SUPERALLOYS: CHEMISTRY, PROCESSING, MICROSTRUCTURE AND PROPERTIES
Creator: Xie, Mengtao
Date: 2012-12-03, 2012-12
Description: Directionally solidified γ(Ni)/γ′(Ni3Al)-δ(Ni3Nb) eutectic alloys possess attrac- tive high temperature mechanical properties and were...
Show moreDirectionally solidified γ(Ni)/γ′(Ni3Al)-δ(Ni3Nb) eutectic alloys possess attrac- tive high temperature mechanical properties and were considered as candidate tur- bine blade materials. Currently, the properties of polycrystalline γ/γ′-δ alloys are of interest as they inherit many advantageous attributes from the directionally solidi- fied γ/γ′-δ alloys, including high volume fraction of reinforcing phases, exceptional thermal stability and resistance to segregation-induced defect formation. If these at- tributes are properly harnessed, these γ/γ′-δ eutectic alloys might provide a unique solution to the problems experienced by traditional γ/γ′ polycrystalline Ni-base su- peralloys. This thesis is therefore dedicated towards the development of a funda- mental understanding of this novel class of eutectic alloys from several important perspectives. To enrich our understanding of this alloy system, this thesis will first be focused on quantifying the specific effect of individual alloying element on this γ/γ′-δ eutectic system. A set of quaternary Ni-Cr-Al-Nb alloy compositions with increasing levels of Chromium(Cr) was designed to investigate the detailed influence of this element on the primary phase formation, solidus and liquidus temperatures and γ-δ eutectic morphology. The alloying effect of Tantalum(Ta), which shares many similarities to Niobium(Nb), was studied by designing a matrix of multi-component γ/γ′-δ alloy compositions with nominally the same overall (Ta+Nb) content but varying Ta/Nb ratios. Here, different solidification segregation and solid state partitioning behaviors of Ta and Nb in this γ/γ′-δ eutectic system will be discussed, as well as the influ- ence of Ta/Nb ratio on solidification characteristics and equilibrium/non-equilibrium phase volume fractions. Thermodynamic calculations using the Computherm Pandat database (PanNi7) were compared to experimental results in these investigations. The second part of this thesis will aim to provide a more general understand- xvii ing of the effect of various alloying elements, including Cr, Co, Al, Ti, Mo, W, Ta and Nb, on this γ/γ′-δ system. A large number of experimental γ/γ′-δ alloys covering a broad range of compositions was selected for the analysis in this study. Important alloy attributes, such as primary phase formation, overall δ volume fraction, phase transformation temperatures and ternary eutectic initiation, were quantitatively char- acterized as a function of individual alloying element concentrations or combined con- tent of more elements. Linear regression analysis was performed to reveal the relative effectiveness of these elements on this eutectic system. Meanwhile, an extensive com- parison between the experimental observations and Pandat predictions was provided to critically evaluate the strength and weakness of existing thermodynamic database model in predicting trends in this eutectic alloy system with substantially higher Nb content compared to traditional γ/γ′ superalloys. The last part of this thesis emphasizes the development of cast and wrought manufacturing processes for cast γ/γ′-δ eutectic alloys as a cost effective alternative to the powder metallurgy route. Hot rolling of workpieces encapsulated within a steel can was performed on a simple model cast γ/γ′-δ alloy (897) to stimulate the ingot to billet. The influence of different deformation levels on breaking down the dendritic structure and promoting fine and homogenized microstructure was investi- gated. The mechanical soundness associated with different microstructures generated by different hot rolling processes was compared via compression and creep testing. Microstructural parameters that contribute to better mechanical properties will be discussed.
PH.D in Materials Science and Engineering, December 2012
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Title: DIRECTED EVOLUTION TO IMPROVE BIODESULFURIZATION OF PETROLEUM
Creator: Khayyat, Naghmeh Hassanzadeh
Date: 2013, 2013-12
Description: Dibenzothiophene (DBT) is an organosulfur compound found in petroleum that is refractory to the current hydrodesulfurization (HDS) method in...
Show moreDibenzothiophene (DBT) is an organosulfur compound found in petroleum that is refractory to the current hydrodesulfurization (HDS) method in refineries and raises the need for alternative methods such as biodesulfurization. Rhodococcus erythropolis strain IGTS8 naturally contains a dszABC operon, which encodes enzymes that can desulfurize DBT through the 4S pathway. Desulfurization-negative Rhodococcus opacus was transformed with plasmids pRESXdszABC and pRESXdszAS1BC, conferring the ability to desulfurize DBT. pRESXdszAS1BC had been modified from pRESXdszABC by placing a synthetic “sulpeptide gene” (S1) within the operon between dszA and dszB; S1 encodes a short polypeptide with high methionine and cysteine content, which puts additional sulfur demands on the 4S pathway when DBT is the only source of sulfur. Here we performed directed evolution on the two transformed R. opacus strains for 50 passages in a minimal (CDM) medium with DBT as the sole sulfur source in an attempt to drive evolution of greater DBT desulfurization activity. Desulfurization specific activity experiments were performed every 4 to 10 passages to compare the specific activities of these strains through the production of 2-HBP as measured by the Gibbs assay. Desulfurization positive strain Rhodococcus erythropolis IGTS8 was used as the control culture. R. opacus/pRESXdszABC demonstrated a maximum increase of 28-fold in desulfurization specific activity after 40 passages to a level as high as that of the control culture R. erythropolis IGTS8. Thereafter (passages 41-50), there was a 7% decrease from the maximum of desulfurization activity level (passage 40). R. opacus/pRESXdszAS1BC, however, showed only a maximum increase of 4-fold in specific activity after 37 passages. Moreover, there was a 61% decrease from the ix maximum of desulfurization activity level (passage 37) thereafter (passage 38-50). These could be due to the unexpected mutations and/or epigenetic changes in the pRESXdszAS1BC plasmid or host genomic sequences. Further DNA sequence analysis will be helpful in identification of these possible mutations.
M.S. in Biology, December 2013
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Title: BIODESULFURIZATION IMPROVEMENT OF A SYMBIOTIC PAENIBACILLUS CULTURE UTILIZING VITREOSCILLA HEMOGLOBIN
Creator: Liu, Benjamin Kwan
Date: 2015, 2015-05
Description: Biodesulfurization (BDS) of petroleum has been investigated as an alternative method to conventional chemical desulfurization for many years....
Show moreBiodesulfurization (BDS) of petroleum has been investigated as an alternative method to conventional chemical desulfurization for many years. Despite its potential to be an environmentally benign method, it has not been developed sufficiently to be useful in real world applications. This is due to its low efficiency and the necessity for it to work at temperatures high enough to lower the viscosity of petroleum so that mixing can be achieved. This study places the spotlight on two strains of Paenibacillus isolated in our laboratory that, together, possess biodesulfurization ability at moderately high temperatures and attempts to enhance biodesulfurization by expression of Vitreoscilla hemoglobin (VHb) in the Paenibacillus strains. The effects of expression of the VHb gene (vgb) on growth and desulfurizing activity was examined in a symbiotic system between the Paenibacillus strains 32O-Y and 32O-W. Of the two, 32O-Y is the one with the ability to metabolize dibenzothiophene (DBT), a common compound in petroleum that contains organic sulfur, while 32O-W enhances this ability, forming a symbiotic relationship between the two. The transformant of 32O-Y bearing vgb cloned into the shuttle vector pNW33N had been previously constructed in our laboratory. Presence of pNW33N-vgb was verified in one strain of 32O-Y through isolation of DNA, PCR, and gel electrophoresis. Mixtures of 32O-Y/32O-W or 32O-Y[pNW33N-vgb]/32O-W were cultured in minimal medium (CDM) with DBT as the sole sulfur source and subjected to multiple trials of growth and assay of DBT metabolism at varying temperatures. At 45 ˚C there was a substantial increase in both growth and DBT metabolizing coincident with VHb expression, whereas at lower (37 ˚C) and higher (50 ˚C) temperatures, VHb expression had little to no effect on either parameter. For both growth and DBT metabolism tested at 37 ˚C, 45 ˚C and 50 ˚C the highest absolute levels were seen at 37 ˚C, and the lowest at 45 ˚C.
M.S. in Biology, May 2015
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Title: INVESTIGATION OF THE EFFICACY OF REACTIVE OXYGEN SPECIES GENERATED BY BOVINE AORTIC ENDOTHELIAL CELLS FOR INITIATING FREE-RADICAL POLYMERIZATION
Creator: Lu, Chenlin
Date: 2013, 2013-12
Description: Reactive oxygen species are reported to be generated by bovine aortic endothelial cells during ischemia followed by reperfusion. This...
Show moreReactive oxygen species are reported to be generated by bovine aortic endothelial cells during ischemia followed by reperfusion. This biological response, believed to be the cause of post-ischemic reperfusion injury, inspired us to investigate the possibility of coupling it with the initiation of free-radical polymerization to produce polymer hydrogels for cell encapsulation. In this work, the generation of reactive oxygen species during ischemia and reperfusion was examined by fluorescence detection and the feasibility of initiating free-radical polymerization by generated reactive oxygen species was investigated in two sets of experiments. The generation of reactive oxygen species by bovine aortic endothelial cells when subjected to anoxia followed by reoxygenation was investigated in both attached and suspended cells. Both intracellular and extracellular generations of ROS appeared to occur in the experiments of attached cells. Cell viability experiments demonstrated that the generation of ROS was sufficient to cause cell damage and death. The feasibility of initiating free-radical polymerization by reactive oxygen species generated by bovine aortic endothelial cells subjected to anoxia followed by reoxygenation was investigated in two sets of experiments. One set involved the linear polymerization of NVP which allowed us to quantify the extent of polymerization and characterization of the weight conversion of PVP polymer. The other set involved the formation of PEGDA hydrogels which were characterized by imaging and staining methods. To our knowledge this is the first evidence of cell induced polymerization initiated by reactive oxygen species and gelation which can be used for a variety of biomedical applications.
M.S. in Chemical and Biological Engineering, December 2013
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