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Identification of aromatic-inducible promoters and heterologous biosensors as tuning elements for styrene production in E. coli

Description

One of the primary bottlenecks to chemical production in biological organisms is the toxicity of the chemical. Overexpression of efflux pumps has been shown to increase tolerance to aromatic compounds such as styrene and styrene oxide. Tight control of pum

One of the primary bottlenecks to chemical production in biological organisms is the toxicity of the chemical. Overexpression of efflux pumps has been shown to increase tolerance to aromatic compounds such as styrene and styrene oxide. Tight control of pump expression is necessary to maximize titers and prevent excessive strain on the cells. This study aimed to identify aromatic-sensitive native promoters and heterologous biosensors for construction of closed-loop control of efflux pump expression in E. coli. Using a promoter library constructed by Zaslaver et al., activation was measured through GFP output. Promoters were evaluated for their sensitivity to the addition of one of four aromatic compounds, their "leaking" of signal, and their induction threshold. Out of 43 targeted promoters, 4 promoters (cmr, mdtG, yahN, yajR) for styrene oxide, 2 promoters (mdtG, yahN) for styrene, 0 promoters for 2-phenylethanol, and 1 promoter for phenol (pheP) were identified as ideal control elements in aromatic bioproduction. In addition, a series of three biosensors (NahR, XylS, DmpR) known to be inducible by other aromatics were screened against styrene oxide, 2-phenylethanol, and phenol. The targeted application of these biosensors is aromatic-induced activation of linked efflux pumps. All three biosensors responded strongly in the presence of styrene oxide and 2-phenylethanol, with minor activation in the presence of phenol. Bioproduction of aromatics continues to gain traction in the biotechnology industry, and the continued discovery of aromatic-inducible elements will be essential to effective pathway control.

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2018-05

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What Do Chemical Engineers Do, Exactly?

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When it comes to the topic of chemical engineering, the general public has a set of neutral, if slightly uninformed perceptions that are largely tempered by the initial emotional responses to the field and its associated topics. These topics include

When it comes to the topic of chemical engineering, the general public has a set of neutral, if slightly uninformed perceptions that are largely tempered by the initial emotional responses to the field and its associated topics. These topics include the differentiation between chemical engineers and chemists, the importance and potential danger of the products they produce, as well as the association of the subject matter with less than favorable secondary education experiences. This thesis consists of first assessing the opinions of a population meant to represent the general public regarding these subjects, then exploring the potential improvements of opinion and understanding that may be yielded from presenting the subject matter by way of a concise learning tool, such as a video. The results of this effort showed that factual understanding can be at least incrementally improved for 18% of participants through this method, while the effect on opinions can range from being improved to maintaining an enduring indifference, with an average of 17% of participants seeing improvement. Further iteration of this methodology with more consistent, impartial survey methods and refined questions could potentially yield more noteworthy improvements within the subjective domain, with the resultant learning tool of that iteration being applicable as not only an instrument of educating the general public, but also as a means to recruit potential students to the ASU chemical engineering degree program.

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2019-05

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Healing Mechanophore-Incorporated Epoxy Through UV Dimerization

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This study aims to determine the feasibility of producing mechanophore-incorporated epoxy that can be healed. This was accomplished by grafting a synthesized mechanophore into tris(2-aminoethyl)amine to create a new epoxy hardener. Then this branched hardener was combined with a second

This study aims to determine the feasibility of producing mechanophore-incorporated epoxy that can be healed. This was accomplished by grafting a synthesized mechanophore into tris(2-aminoethyl)amine to create a new epoxy hardener. Then this branched hardener was combined with a second hardener, diethylenetriamine (DETA). A proper ratio of the branched hardener to the DETA will ensure that the created epoxy will retain the force responsive characteristics without a noticeable decline in both the physical and thermal properties. Furthermore, it was desired that the natural structure of the epoxy would be left in place, and there would only be enough branched hardener present to elicit a force response and provide the possibility for healing. The two hardeners would then be added to Diglycidyl Ether of Bisphenol F (DGEBPF), which is the epoxy resin. The mechanophore-incorporated epoxy was compared to a standard epoxy—just DETA and DGEBPF—and it was determined that the incorporation of the mechanophore led to an 8.2 degrees Celsius increase in glass transition temperature, and a 33.0% increase in cross link density. This justified the mechanophore-incorporated epoxy as a feasible alternative to the standard, as its primary thermal and physical properties were not only equal, but superior. Then samples of the mechanophore-incorporated epoxy were damaged with a 3% tensile strain. This would cause a cycloreversion in the central cyclobutane inside of the mechanophore. Then they were healed with UV light, which would redimerize the severed hardener moieties. The healed samples saw a 4.69% increase in cross-link density, demonstrating that healing was occurring.

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2018-12

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Statistical Design of Experiment on Homemade Sourdough

Description

This report investigates the effects of autolyzing, fermentation medium, fermentation temperature, and proofing medium on the growth and porosity of 50% whole wheat sourdough bread. A model was designed using a 24 statistical design of experiment with replicates to screen

This report investigates the effects of autolyzing, fermentation medium, fermentation temperature, and proofing medium on the growth and porosity of 50% whole wheat sourdough bread. A model was designed using a 24 statistical design of experiment with replicates to screen and quantify the individual and combined effects of the aforementioned factors on the area of a 1 cm cross-sectional cut from each loaf. Fermentation temperature had the single largest effect, with colder fermented loaves being on average 10 cm2 larger than their warmer fermented counter parts. Autolyzing had little individual effect, but the strengthened gluten network abated some of the degassing and overproofing that is a consequent handling the dough or letting it ferment too much. This investigation quantifies how to maximize gluten development and yeast growth to create the airiest whole wheat sourdough, a healthier and easier to digest bread than many commercially available.

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2018-05

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Enhancing the Profile of Chemical Engineers as Relevant to Society amongst Middle School and High School Students

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The objective of this research study is to assess the effectiveness of a poster-based messaging campaign and engineering-based activities for middle school and high school students to encourage students to explore and to pursue chemical engineering. Additionally, presentations are incorporated

The objective of this research study is to assess the effectiveness of a poster-based messaging campaign and engineering-based activities for middle school and high school students to encourage students to explore and to pursue chemical engineering. Additionally, presentations are incorporated into both methods to provide context and improve understanding of the presented poster material or activity. Pre-assessments and post-assessments are the quantitative method of measuring effectiveness. For the poster campaign, ASU juniors and seniors participated in the poster campaign by producing socially relevant messages about their research or aspirations to address relevant chemical engineering problems. For the engineering-based activity, high school students participated in an Ira A. Fulton Schools of Engineering program "Young Engineers Shape the World" in which the students participated in six-hour event learning about four engineering disciplines, and the chemical engineering presentation and activity was conducted in one of the sessions. Pre-assessments were given at the beginning of the event, and the post-assessments were provided towards the end of the event. This honors thesis project will analyze the collected data.

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Date Created
2017-05

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Optimization of Front Contact Design on Nickel-Plated Si Solar Cells

Description

As global population and demand for electrical power increase, humanity is faced with the growing challenge of harnessing and distributing enough energy to sustain the developing world. Currently, fossil fuels (coal
atural gas) are our main sources of electricity. However,

As global population and demand for electrical power increase, humanity is faced with the growing challenge of harnessing and distributing enough energy to sustain the developing world. Currently, fossil fuels (coal
atural gas) are our main sources of electricity. However, their cost is increasing, they are nonrenewable, and they are very harmful to the environment. Thus, capacity expansion in the renewable energy sector must be realized to offset higher energy demand and reduce dependence on fossil fuels. Solar energy represents a practical solution, as installed global solar capacity has been increasing exponentially over the past 2 decades. However, even with government incentives, solar energy price ($/kWh) continues to be highly dependent on political climate and raw material (silicon and silver) cost. To realistically and cost effectively meet the projected expansions within the solar industry, silver must be replaced with less costly and more abundant metals (such as copper) in the front-grid metallization process of photovoltaic cells. Copper, while offering both higher achievable efficiencies and a raw material cost nearly 100 times cheaper than silver, has inherent disadvantages. Specifically, copper diffuses rapidly into the silicon substrate, requires more complex and error-prone processing steps, and tends to have less adhesive strength, reducing panel robustness. In this study, nickel deposition via sputtering was analyzed, as well as overall potential of nickel as a seed layer for copper plating, which also provides a barrier layer to copper diffusion in silicon. Thermally-formed nickel silicide also reduces contact resistivity, increasing cell efficiency. It was found that at 400 \u00B0C, ideal nickel silicide formation occurred. By computer modeling, contact resistivity was found to have a significant impact on cell efficiency (up to 1.8%). Finally, sputtering proved useful to analyze nickel silicide formation, but costs and time requirements prevent it from being a practical industrial-scale metallization method.

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Date Created
2017-05

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Biochemical Methane Potential (BMP) Tests and Microbial Electrochemical Cells (MECs) Identify Differences in Pretreated Waste Activates Sludge (WAS) Streams

Description

Anaerobic digestion (AD), a common process in wastewater treatment plants, is traditionally assessed with Biochemical Methane Potential (BMP) tests. Hydrolysis is considered its rate-limiting step. During my research, I assessed the impact of pretreatment on BMPs and microbial electrochemical cells

Anaerobic digestion (AD), a common process in wastewater treatment plants, is traditionally assessed with Biochemical Methane Potential (BMP) tests. Hydrolysis is considered its rate-limiting step. During my research, I assessed the impact of pretreatment on BMPs and microbial electrochemical cells (MECs). In the first set of experiments, BMP tests were performed using alkaline and thermal pretreated waste activated sludge (WAS), a control group, and a negative control group as samples and AD sludge (ADS) as inoculum. The data obtained suggested that BMPs do not necessarily require ADS, since samples without inoculum produced 5-20% more CH4. However, ADS appears to reduce the initial methanogenesis lag in BMPs, as no pH inhibition and immediate CH4 production were observed. Consumption rate constants, which are related to hydrolysis, were calculated using three methods based on CH4 production, SSCOD concentration, and the sum of both, called the lumped parameter. All the values observed were within literature values, yet each provide a different picture of what is happening in the system. For the second set of experiments, the current production of 3 H-type MECs were compared to the CH4 production of BMPs to assess WAS solids' biodegradability and consumption rates relative to the pretreatment methods employed for their substrate. BMPs fed with pretreated and control WAS solids were performed at 0.42 and 1.42 WAS-to-ADS ratios. An initial CH4 production lag of about 12 days was observed in the BMP assays, but MECs immediately began producing current. When compared in terms of COD, MECs produced more current than the BMPs produced CH4, indicating that the MEC may be capable of consuming different types of substrate and potentially overestimating CH4 production in anaerobic digesters. I also observed 2 to 3 different consumption events in MECs versus 3 for BMP assays, but these had similar magnitudes, durations, and starting times in the control and thermal pretreated WAS-fed assays and not in alkaline assays. This might indicate that MECs identified the differences of alkaline pretreatment, but not between control WAS and thermal pretreated WAS. Furthermore, HPLC results suggest at least one hydrolysis event, as valerate, butyrate, and traces of acetate are observed in the reactors' effluents. Moreover, a possible inhibition of valerate-fixing microbial communities due to pretreatment and the impossibility of valerate consumption by ARB might explain its presence in the reactors' effluents.

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2017-05

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New insights into the pore development mechanism of layered hydroxides upon thermal activation

Description

Layered double hydroxides (LDHs), also known as hydrotalcite-like materials, are extensively used as precursors for the preparation of (photo-)catalysts, electrodes, magnetic materials, sorbents, etc. The synthesis typically involves the transformation to the corresponding mixed metal oxide via calcination, resulting in

Layered double hydroxides (LDHs), also known as hydrotalcite-like materials, are extensively used as precursors for the preparation of (photo-)catalysts, electrodes, magnetic materials, sorbents, etc. The synthesis typically involves the transformation to the corresponding mixed metal oxide via calcination, resulting in atomically dispersed mixed metal oxides (MMOs). This process alters the porosity of the materials, with crucial implications for the performance in many applications. Yet, the mechanisms of pore formation and collapse are poorly understood. Combining an integrated in situ and ex situ characterization approach, here we follow the evolution of porosity changes during the thermal decomposition of LDHs integrating different divalent (Mg, Ni) and trivalent (Al, Ga) metals. Variations in porous properties determined by high-resolution argon sorption are linked to the morphological and compositional changes in the samples by in situ transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, which is facilitated by the synthesis of well crystallized LDHs of large crystal size. The observations are correlated with the phase changes identified by X-ray diffraction, the mass losses evidenced by thermogravimetric analysis, the structural changes determined by infrared and nuclear magnetic resonance spectroscopy, and the pore connectivity analyzed by positron annihilation spectroscopy. The findings show that the multimetallic nature of the LDH governs the size and distribution (geometry, location, and connectivity) of the mesopores developed, which is controlled by the crystallization of the MMO phase, providing key insights for the improved design of porous mixed metal oxides.

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2017-05

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A Quantitative Study on the Effects of Operating Conditions on Heat Transfer in a Rotary Drum

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Rotary drums are commonly used for their high heat and mass transfer rates in the manufacture of pharmaceuticals, cement, food, and other particulate products. These processes are difficult to model because the particulate behavior is governed by the process conditions

Rotary drums are commonly used for their high heat and mass transfer rates in the manufacture of pharmaceuticals, cement, food, and other particulate products. These processes are difficult to model because the particulate behavior is governed by the process conditions such as particle size, particle size distribution, shape, composition, and operating parameters, such as fill level and rotation rate. More research on heat transfer in rotary drums will increase operating efficiency, leading to tremendous energy savings on a global scale. This study investigates the effects of drum fill level and rotation rate on the steady-state average particle bed temperature. 3 mm silica beads and a stainless steel rotary drum were used at fill levels ranging from 10 \u2014 25 % and rotation rates from 2 \u2014 10 rpm. Four heat guns were used to heat the system via conduction and convection, and an infrared camera was used to record temperature data. A three-level, two-factor, full-factorial design of experiments was employed to determine the effects of each factor on the steady-state average bed temperature. Low fill level and high rotation rate resulted in higher steady-state average bed temperatures. A quantitative model showed that rotation rate had a larger impact on the steady-state bed temperature than fill level.

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2018-05

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Characterizing Buffers to Maximize Peroxide Production in the Cathode Chamber of Microbial Fuel Cells

Description

Microbial fuel cells (MFCs) facilitate the conversion of organic matter to electrical current to make the total energy in black water treatment neutral or positive and produce hydrogen peroxide to assist the reuse of gray water. This research focuses on

Microbial fuel cells (MFCs) facilitate the conversion of organic matter to electrical current to make the total energy in black water treatment neutral or positive and produce hydrogen peroxide to assist the reuse of gray water. This research focuses on wastewater treatment at the U.S. military forward operating bases (FOBs). FOBs experience significant challenges with their wastewater treatment due to their isolation and dangers in transporting waste water and fresh water to and from the bases. Even though it is theoretically favorable to produce power in a MFC while treating black water, producing H2O2 is more useful and practical because it is a powerful cleaning agent that can reduce odor, disinfect, and aid in the treatment of gray water. Various acid forms of buffers were tested in the anode and cathode chamber to determine if the pH would lower in the cathode chamber while maintaining H2O2 efficiency, as well as to determine ion diffusion from the anode to the cathode via the membrane. For the catholyte experiments, phosphate and bicarbonate were tested as buffers while sodium chloride was the control. These experiments determined that the two buffers did not lower the pH. It was seen that the phosphate buffer reduced the H2O2 efficiency significantly while still staying at a high pH, while the bicarbonate buffer had the same efficiency as the NaCl control. For the anolyte experiments, it was shown that there was no diffusion of the buffers or MFC media across the membrane that would cause a decrease in the H2O2 production efficiency.

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2016-05