Department: Chemical Engineering ![[clear]](close-x.png "Remove this limiter")
136 matches in the database.
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1.
Abraham, Thomas Kannankara.
Kinetic bounds on attainability in the reactor synthesis problem.
Degree: PhD, Chemical Engineering, 2005, Ohio State University
► For a given chemical reaction network with known kinetics, a specified feed…
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▼ For a given chemical reaction network with known kinetics, a specified feed composition, and specific process constraints, the attainable region for the reactor synthesis problem is the set of all composition vectors that are achievable through all constraint-consistent reactor configurations that invoke only reaction and mixing. The boundary of the attainable region gives useful information to a process designer in terms of yield and selectivity of a desired chemical species that might be achieved by any constraint-consistent design. Though much is known about necessary conditions for compositions to lie on the boundary of the attainable region, a definite method to calculate the true boundary of the attainable region is not known. Most of the existing methods compute “candidate” attainable regions by starting at the feed composition and attempt to enlarge the set of attainable compositions by considering various reactor configurations until no further enlargement is seen. These methods raise the question of whether the “candidate” attainable region has come close to the (currently unknown) true attainable region. These methods cannot preclude with certainty the existence of some novel reactor configuration that can enlarge the current set of achievable compositions. This thesis describes a new technique called the method of bounding hyperplanes that complements existing methods by “bounding from the outside” those composition vectors that are attainable. In other words, the method seeks to create a set of composition vectors such that all composition vectors lying outside this set are inaccessible from the feed. Thus, the true attainable region will be contained in or will coincide within the bounding set so created. The kinetic bounds do well in precluding a large set of compositions that would otherwise be considered feasible from stoichiometric considerations alone. In many instances, the computed bounds are sharp insofar as they come very close to compositions known to be attainable. The methods described in this thesis do not replace existing methods to find candidate attainable regions but rather complement them.
Advisors/Committee Members: Feinberg, Martin.
Subjects: Engineering, Chemical
Keywords: attainable region; process synthesis; process design; reactor design; kinetic bounds
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3.
Apte, Pankaj A.
Phase equilibria and nucleation in condensed phases: a statistical mechanical study.
Degree: PhD, Chemical Engineering, 2006, Ohio State University
► A molecular level understanding of nucleation occurring in condensed phases is important…
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▼ A molecular level understanding of nucleation occurring in condensed phases is important in a number of industrial applications like polymer foaming, sonolysis, manufacturing of drugs, polymorphic transformations, and metallic alloy production. The recently developed statistical mechanical approaches based on density functional theory and Monte Carlo (MC) simulation can provide valuable insight into these nucleation processes. In this work, we applied density functional theory to study bubble nucleation in a micellar solution. Our results showed that the presence of surfactant molecules lowers the free energy barrier of bubble nucleation. We also found that under moderate negative pressures, the stable micelle may evolve to form the critical bubble and the resulting free energy barrier is lower than that in the absence of this mechanism. A kinetic consideration revealed that the above mechanism is less effective at lower pressures closer to spinodal. Further, the mechanism of bubble nucleation from the stable micelle correlated well with the liquid-liquid miscibility. In another study, we aimed at understanding crystal nucleation in binary Lennard-Jones (LJ) mixtures. An important factor dictating the crystal nucleation behavior is the underlying phase diagram. Thus, we developed thermodynamic integration (TDI) methods that predict accurately the coexistence points on the phase diagram. In particular, we introduced a method to directly calculate Gibbs free energy difference between the solid and the liquid phases by connecting these phases by a reversible path. Further, we showed that this technique extends naturally to a binary mixture, which allows us to predict its melting temperature. We also developed a new technique to calculate sublimation temperature of single component and binary systems by TDI method. We used these methods to predict eutectic and spindle-shaped phase diagram for the LJ binary mixtures. We then studied the free energy surface for crystal nucleation using MC simulation aided by umbrella sampling technique at a few representative points on these phase diagrams. The emphasis in this work was to identify proper order parameters that correctly describe the crystal nucleation. Our work provides a useful starting point to study how the phase diagram affects the crystal nucleation behavior.
Advisors/Committee Members: Kusaka, Isamu.
Subjects: Engineering, Chemical
Keywords: Bubble Nucleation; Crystal Nucleation; Melting Temperature; Sublimation Temperature; Solid fluid equilibrium; Thermodynamic integration method
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4.
Aradhye, Hrishikesh Balkrishna.
Anomaly Detection Using Multiscale Methods.
Degree: PhD, Chemical Engineering, 2001, Ohio State University
► In an environment where most process maneuvers are automated, algorithms to detect…
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▼ In an environment where most process maneuvers are automated, algorithms to detect and classify abnormal trends in process measurements are of critical importance. The petrochemical industry in the United States loses billions of dollars annually due to improper abnormal situation management, and a staggering one in 16 plant accidents results in a fatality. Hence, Statistical Process Control and Monitoring (SPC) has been an active area of research for many decades and a variety of statistical and machine learning-based methods have been developed. However, most existing methods for process monitoring learn the signal characteristics at a fixed scale, and are best for detecting changes at that single scale. In contrast, data from most industrial processes are inherently multiscale in nature due to events occurring with different localization in time, space, and frequency. Unfortunately, existing techniques are unable to adapt automatically to the scale of these features. Many existing methods also require the measurements to be uncorrelated, whereas, in practice, autocorrelated measurements are very common in industrial processes. In this work, we have investigated the use of multiscale techniques to improve upon these shortcomings of existing single-scale approaches. Because of fundamental functional relationships such as process chemistry, energy and mass balances, measurements in multivariate processes are correlated. Our approach learns these correlations and clustering behaviors in the wavelet space using machine learning methods such as Adaptive Resonance Theory (ART-2) and Principal Component Analysis (PCA), resulting in higher detection accuracy coupled with noise reduction. The performance of our method, named Multi-Scale Statistical Process Control and Monitoring (MSSPC), is compared with existing methods based on the average detection delays for detecting shifts of different sizes. Our ART-2 based MSSPC detector is currently deployed in a large scale petrochemical plant to detect process anomalies in real time by incrementally learning normal process operation in the wavelet domain. Several case studies for the detection of real process malfunctions, including the comparison with the performance of human operators, are also presented in this work. These results indicate that MSSPC is a good method for monitoring of measurements with unknown and different types of changes.
Advisors/Committee Members: Davis, James F.
Subjects: Engineering, Chemical
Keywords: Wavelets; Principal Component Analysis; Adaptive Resonance Theory; Statistical Process Monitoring; Change Detection
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5.
Archer, Jared Rausch.
Synthesis, characterization, and application of thin films and mesostructured materials using self-assembled surfactant templates.
Degree: PhD, Chemical Engineering, 2005, Ohio State University
► Thin films and mesostructured materials were fabricated by a process in which…
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▼ Thin films and mesostructured materials were fabricated by a process in which the synthesis is directed by molecularly self-assembled surfactant templates. The formation of Langmuir monolayers and Langmuir-Blodgett (LB) films with insoluble lipid amphiphiles (DPPC), reactive surfactants (OTS), and biomolecules (collagen) were studied. The monolayer and LB film characteristics were investigated for combinations of the above materials. The motivation for including collagen in the products was to explore the effects of a biomolecule and the possible preparation of materials with a more complex hierarchical structure. The precursor sol presented in this research is an advance in long-term stability for this type of material. Unlike prior attempts reported in the literature to create suitable precursors, this sol is chemically stable on a time scale of years. The condensation polymerization proceeds to form silicate oligomers of a relatively low molecular weight, but the chemical nature of the sol prevents the reaction from proceeding to the point at which phase separation occurs. The silicate polymerization proceeded spontaneously with the introduction of water to complete the mesoporous silica films studied. The application of the precursor sol to a liquid/liquid interface proved to be a novel approach to obtaining structured mesoporous films that are not affected or templated by a substrate. Addition of collagen molecules in the reaction results in the formation of only cubic structures, even if the reaction conditions would normally create lamellar or hexagonal structures. Mesoporous particles were obtained from surfactant templates in the reaction mixture. The addition of collagen proved to be an effective processing agent for the produced materials. The analysis of mesoporous silica particles with molybdenum showed limited catalytic activity with regard to propane oxidative dehydrogenation (ODH). The particles maintained high surface area and pore structure, but displayed low conversion rates of propane. The formation of mixed oxide catalyst supports, using the same method for preparing mesoporous silica particles, proved to have much better potential. The SiO2—TiO2 mixed oxides with molybdenum had higher surface areas, stronger molybdenum-oxygen bonds, and a strong increase in the reduction temperature compared with research using a modified sol-gel/co-precipitation technique.
Advisors/Committee Members: Rathman, James F.
Subjects: Engineering, Chemical
Keywords: Mesoporous silica, collagen, surfactant, self-assembly, template, mixed oxide catalysis
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6.
Bai, He.
High temperature proton-exchange and fuel processing membranes for fuel cells and other applications.
Degree: PhD, Chemical Engineering, 2008, Ohio State University
► Proton-exchange membrane fuel cells (PEMFCs) have become a very active research area…
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▼ Proton-exchange membrane fuel cells (PEMFCs) have become a very active research area for both mobile and stationary applications, particularly for fuel cell vehicles. Compared to inner combustion engines, PEMFCs can decrease pollution and increase the energy efficiency. New proton-exchange membrane (PEM) materials and new technologies for fuel processing are the most important and challenging parts in this research field.Nafion® and other perfluorinated sulfonic acid membranes are still the only commercial PEM materials so far. However, their high cost and low performance at high temperatures significantly limit their applications. In this research, new five-member ring and six-member ring soft segment-containing sulfonated polyimide (SPI)-based membranes and new sulfonated polybenzimidazole (SPBI)-based membranes were successfully synthesized. The resulting membranes could outperform Nafion® at various conditions, particularly at high temperatures and low relative humidities (RHs). Moreover, the new membrane materials should be much more cost-effective since the starting materials are more than two orders of magnitude less expensive than those for Nafion® membranes. In the research on fuel processing, amine carriers were successfully incorporated into the SPBI copolymer or the crosslinked poly(vinyl alcohol) (PVA) matrix, which could react reversibly with acid gases, such as CO2. Thus, the resulting membranes have shown very promising CO2 selectivity vs. the other gas molecules, such as H2 and CH4, by the facilitated transport mechanism. These newly synthesized membranes have many applications in the field of gas separations, including the low pressure synthesis gas purification for fuel cell applications, the high pressure synthesis gas purification for refinery industrial applications, and the high pressure natural gas purification to obtain high purity CH4.
Advisors/Committee Members: Ho, W.S. Winston.
Subjects: Chemical engineering; Energy; Polymers
Keywords: fuel cell; proton-exchange membrane; high temperature; carbon dioxide removal; hydrogen purification; gas separation
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7.
Bai, Yunling.
Surface modifications for enhanced immobilization of biomolecules: applications in biocatalysts and immuno-biosensor.
Degree: PhD, Chemical Engineering, 2006, Ohio State University
► The goal of this study is to investigate the application of immobilization…
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▼ The goal of this study is to investigate the application of immobilization technology in various systems: immobilized cell/enzyme bioreactors, affinity chromatography, and BioMEM surface modification. These systems were investigated to solve a particular problem. A novel method for the co-immobilization of whole cells and LDH enzyme on cotton cloth was developed using poly (ethyleneimine) (PEI), which induced the formation of PEI-enzyme-cell aggregates and their adsorption onto cotton cloth, leading to multilayer co-immobilization of cells and enzyme with a high loading amount (0.5 g cell and 8 mg LDH per gram of cotton cloth) and activity yield (>95%). A fibrous bed bioreactor with cells and enzyme co-immobilized on the cotton cloth was then evaluated for R-HPBA production in fed-batch and repeated batch modes, which gave relatively stable reactor productivity. A novel surface treatment method using poly(ethyleneimine) (PEI), an amine-bearing polymer, was developed to enhance antibody binding on the poly(methyl methacrylate) (PMMA) microfluidic immunoassay device. By treating the PMMA surface of the microchannel on the microfluidic device with PEI, 10 times more active antibodies can be bound to the microchannel surface as compared to those without treatment or treated with the small amine-bearing molecule, hexamethylene diamine (HMD). Consequently, PEI surface modification greatly improved the immunoassay performance of the microfluidic device, making it more sensitive and reliable in the detection of IgG. The surface modification method was further simplified and optimized to enhance polymer-based microchannel ELISA for E. coli O157:H7 detection. By applying an amine-bearing polymer, poly (ethyleneimine) (PEI), onto a poly (methyl methacrylate) (PMMA) surface at pH higher than 11, PEI molecules were covalently attached and their amine groups were introduced to the PMMA surface. Zeta potential analysis and X-ray photoelectron spectroscopy (XPS) demonstrated that the alkaline condition is preferable for PEI attachment onto the PMMA surface. Compared to untreated PMMA microchannels, ~45 times higher signal and 3 times higher signal/noise ratio were achieved with the PEI surface treatment, which also shortened the time required for cells to bind to the microchannel surface to ~2 minutes, much less than that usually required for the same ELISA carried out in 96-well plates.
Advisors/Committee Members: Yang, Shang-Tian.
Subjects: Engineering, Chemical
Keywords: Surface Modification; Enzyme Immobilization; Cofactor Regeneration; Formate Dehydrogenase Purification; Biotransformation; Microfluidic Biosensor; ELISA; Foodborne Pathogen Detection
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9.
Basu, Shubhayu.
Effects of three dimensional structure of tissue scaffolds on animal cell culture.
Degree: PhD, Chemical Engineering, 2004, Ohio State University
► Surface chemistry of the scaffold material, the fiber diameter, pore size, structure…
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▼ Surface chemistry of the scaffold material, the fiber diameter, pore size, structure and configuration and porosity can regulate tissue development. The overall objective was to study the effect of the three dimensional structure of tissue scaffolds on animal cell culture. To achieve this, the growth of human astrocyte cells, secreting Glial-cell-line Derived Neurotrophic Factor (GDNF), in non-woven polyethylene terephthalate (PET) matrices was specifically targeted. The ability of GDNF to selectively nourish and regenerate dopaminergic neurons makes it an ideal candidate for the treatment of Parkinson's disease. On the basis of cell morphology, density and GDNF secretion, compressed PET matrices (porosity 88.8%, mean pore diameter 64 microns), treated with boiling sodium hydroxide, were found to be very effective in supporting high density growth of astrocytes. Most scaffolds used thus far, are anisotropic in their architecture and have a wide pore size distribution, making the task of identifying optimum values of the parameters important for tissue development even more difficult. However, microfabricated poly(lactic co-glycolic acid) (PLGA) scaffolds with a uniform structure supported a higher cell density, longer cell proliferation times than in non-uniform fibrous matrices, and induced less apoptosis, implying that uniformity in scaffold microstructure was a more important parameter than the mean pore size of the scaffolds. Cytocompatibility studies on PLGA scaffolds also revealed that cells could span in three-dimensional space over distances greater than four times their average length. To develop a fast convenient cell based model to study cell culture in three dimensional (3D) scaffolds, cells were transfected with an Enhanced Green Fluorescent Protein (EGFP) based reporter system. This allowed fast, sensitive and noninvasive monitoring of cell growth in suspension and could be used to detect the spatial distribution of these cells in 3D scaffolds. The fluorescence of these cells was linked to the S-phase of the cell cycle and decreased in a dosage dependent manner when the cells were treated with chemotherapeutic drugs 5-fluorouracil and doxorubicin, making these cells an ideal and reliable model for reporting cellular proliferation and drug effects on cell growth.
Advisors/Committee Members: Yang, Shang-Tian.
Keywords: SCAFFOLDS; CELL; GDNF; PLGA; PET; PET matrices; astrocyte
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12.
Berdugo, Claudia.
Cell Damage Mechanisms and Stress Response in Animal Cell Culture.
Degree: PhD, Chemical Engineering, 2010, Ohio State University
► Animal cell culture is a widely used technology for producing recombinant proteins.…
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▼ Animal cell culture is a widely used technology for producing recombinant proteins. The ability to make post-translational modifications and secrete the active forms of the protein into the culture medium represents major advantages over other processes. The growing market demand for pharmaceuticals has created a need for increased production capacity; however, achieving productivity gains in both the upstream stage and downstream processes can subject cells to aggressive environments such as those involving hydrodynamic stresses. Although numerous studies have explored the consequences of cell damage due to hydrodynamic stress, there has been a lack of understanding of the mechanism of such damage at a cellular level. Cell damage can also influence biomedical applications. Cells manipulated in instruments such as diagnosis and analysis devices can experience hydrodynamic forces. The level of cell damage is influenced by the hydrodynamic conditions in the bioprocess or biomedical equipment as well as the cell line sensitivity. To evaluate and compare cell sensitivity among different cell lines, a flow contraction device, previously designed by our group was used. Cells were exposed to well defined and controlled hydrodynamic forces and cell damage was estimated as a function of energy dissipation rate (EDR). EDR is a scalar value that represents the rate of dissipation of kinetic energy per unit of mass or volume. Using this methodology we found human cell lines highly sensitive to hydrodynamic forces. Hydrodynamic evaluations were performed in ten different bioreactor configurations Impeller-Sparger. The best configurations were chosen based on kLa response surface model for testing in cell culture experiments. The configurations chosen were used to evaluate the expression of stress proteins under moderate hydrodynamic stress in bioreactors as well as cell cycle profile and its relationship to recombinant protein production. The results suggest that for a clonal cell line evaluated G1 phase of the cell cycle may be more conducive to producing the recombinant protein. In addition, a relationship between hydrodynamic stress and expression of stress proteins was observed. The type of stress protein and the level of expression seem to be dependent on cell type and differences could even be observed between clones of the same cell line. Cell damage was also evaluated in a fluorescent activated cell sorter (FACS) models Vantage and Aria. Cells can be exposed to very high hydrodynamic forces when flowing through channels and nozzle in the sorting process. Results indicate that not only are cells damaged in a flow cytometer, but that this damage can vary from cell line to cell line as well as from specific conditions/type of flow cytometer and flow conditions. In addition, studies were conducted to evaluate cell growth behavior after stress as well as the effect of sorting on cell cycle. Extended growth lag phase was observed in cells exposed to hydrodynamic stress, and the sensitivity of any specific cell line can be a function of the growth phase of the cell
Advisors/Committee Members: Chalmers, Jeffrey.
Subjects: Chemical engineering
Keywords: Mammalian cell culture, hydrodynamic stress, cell damage, shear stress, flow cytometry, CHO, THP1, bioreactors
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13.
Biddinger, Elizabeth Joyce.
Nitrogen-Containing Carbon Nanofibers as Non-Noble Metal Cathode Catalysts in PEM and Direct Methanol Fuel Cells.
Degree: PhD, Chemical Engineering, 2010, Ohio State University
► PEM and direct methanol fuel cells (DMFC) have great potential for use…
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▼ PEM and direct methanol fuel cells (DMFC) have great potential for use as alternative fuel energy conversion devices. Before this potential can be realized, however, performance improvements must be made and material costs reduced. The limiting reaction in the PEMFCs and DMFCs is the oxygen reduction reaction (ORR), which occurs at the cathode. In an attempt to improve the reaction kinetics, substantial loadings of Pt catalysts are required on the cathode. This significantly increases the overall cost of the fuel cell. Also, in DMFCs, methanol crossover from the anode allows for competing reactions at the cathode catalyst to occur, reducing the power output of the fuel cell. As the demand for fuel cells increase, the demand for Pt will far outpace the supply of Pt. Replacements studied for Pt cathode catalysts include Pt alloys, other noble metals, chalcogenides and nitrogen-containing carbons. Nitrogen-containing carbons made from simple precursors can provide an economical replacement to Pt catalysts. Before this can be realized, improvements in the activity and selectivity of the nitrogen-containing carbons need to occur. The work presented here involves the study of nitrogen-containing carbon nanostructures (CNx) as ORR catalysts for PEMFCs and DMFCs. Improving the ORR performance in both activity and selectivity for CNx catalysts, while gaining a better understanding of the catalyst materials and the way they are evaluated were the major driving forces behind this research. CNx catalyst performance was studied by incorporating heteroatoms beyond nitrogen and surface functional groups into the catalyst. Boron and sulfur heteroatoms were studied along with oxygen functional groups. It was found that the methods to introduce boron into the nanostructure had a large impact on the ORR performance. Sulfur did not have an effect on the ORR performance, but was successfully used as a CNx growth promoter in the form of thiophene during acetonitrile pyrolysis. An increase in oxygen functional groups on the surface of CNx catalysts improved the ORR selectivity to water formation. The role CNx catalyst nanostructure plays in ORR activity was studied using model nanofiber systems with both high levels of graphitic edge plane exposure and low levels of graphitic edge plane exposure. Experiments showed that un-doped graphitic edge planes were not the ORR active site. Incorporation of nitrogen into the graphitic edge planes significantly improved ORR activity compared to the nitrogen-free nanofibers. The use of electrochemical half cell methods have been evaluated and reported here. Rotating Ring Disk Electrode (RRDE) testing is commonly used to measure the ORR activity and selectivity of a catalyst. The factors affecting catalyst selectivity reporting including catalyst loading and RRDE catalyst ink aging were studied. In addition to these studies, the performance of CNx catalysts developed in the laboratory for use as cathode catalysts in DMFCs were evaluated. It was found that CNx catalysts are both methanol tolerant and inactive towards methanol oxidation , making them favorable potential DMFC catalysts. Throughout the studies, materials developed and evaluated were characterized using classic heterogeneous catalysis techniques to gain a better understanding of the systems being analyzed.
Advisors/Committee Members: Ozkan, Umit.
Subjects: Chemical engineering; Chemistry; Energy; Engineering
Keywords: fuel cell; oxygen reduction; CNx; cathode; nanofiber; catalyst
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16.
Boehm, Michael.
EXPERIMENTAL INVESTIGATION OF TWO-PHASE PENETRATING FLOW OF NEWTONIAN AND NON-NEWTONIAN POLYMERIC FLUIDS AND DEVELOPMENT OF PRACTICAL APPLICATIONS IN DRUG/GENE DELIVERY.
Degree: PhD, Chemical Engineering, 2009, Ohio State University
► Rheology, simply stated as the study of the flow and deformation of…
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▼ Rheology, simply stated as the study of the flow and deformation of matter, is afield with grand importance yet a meager following. Be it velocity distributions and turbulence within the Sun or the flow of jelly from your donut’s center, the field of rheology offers tools to understanding the simple to the complex. For example, one such simple experiment that hides far more complex dynamics is the flow of a low viscosity fluid through a much higher viscosity liquid. This is also known as coring flow and has been studied extensively for the macro-scale. The dynamics for coring flow have not been studied, to the best of the author's knowledge, on the micro-scale and it is that disparity the research detailed here addresses. There are many important aspects to consider before performing multiphase micro-fluidic research including what micro-fabrication methods are used, how the microchip is interfaced to the macro-world, how the fluids will behave, and how the micro-channel geometry will affect the dynamics. This dissertation addresses those topics as they apply to the research performed and detailed here. Three different fabrication techniques are explained, detailed, and used to highlight the benefits and drawbacks of working on the micro-scale. Bonding is also an important part of fabrication and so two different methods are discussed. Finally, the way a microchip is interfaced to the macro-world affects the correlations that can be made. Three different interfacing systems that worked well are presented. The fundamental process of coring on the micro-scale is investigated and explained for circular, square, and rectangular geometries. The simple case of a Newtonian coating fluid was researched first, followed by the case of a viscoelastic coating fluid, and finally the case where the coring fluid contained a surfactant. It was found that, in general, micro-scale coring matches that of the macro-scale except for the case of a viscoelastic coating fluid. New bubble behavior was observed for high flow rates through a viscoelastic coating fluid. As engineers, we wrestle something practical out of our understanding of the fundamental. This principle was the driving motivation behind the three practical applications of micro-scale coring flow that were. Coring flow was used to add a functional coating to capillaries for use in Capillary Electrophoresis, to coat a static mixer, and to create nozzle-like structures in a micro-channel. The final goal of these practical applications was to develop a toolbox of procedures and data that can be used in a wide array of fields including (a) coatings to reduce non-specific binding in drug/gene delivery applications, (b) coatings for separation and detection techniques like Capillary Electrophoresis, and (c) a simple means to smoothing rough channels made via micro-/nano-machining.
Advisors/Committee Members: Koelling, Kurt.
Subjects: Chemical engineering
Keywords: microfluidics; CNC machining; functional coatings; bubble; viscoelastic; micromixing
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17.
Cao, Xia.
Integrated Analysis of Low Profile Unsaturated Polyester and Vinylester Resins Cured at Low Temperatures.
Degree: PhD, Chemical Engineering, 2002, Ohio State University
► Unsaturated polyester and vinylester resins are used in a wide variety of…
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▼ Unsaturated polyester and vinylester resins are used in a wide variety of applications. These materials provide high structural stability, increased resistance to solvent and temperature, and improved mechanical stability. Low profile additives have been found highly effective in eliminating the polymerization shrinkage of unsaturated polyester resins in high temperature molding processes such as compression molding of SMC and injection molding of BMC. In recent years, the improvement focuses on the development of low temperature and low-pressure fabrication techniques, such as low temperature/low pressure SMC, RTM, SCRIMP, to significantly reduce the tooling cost. However, poor performance of low profile additives and high residual reactivity in low temperature molding processes unavoidably undermine further applications of unsaturated polyester and vinylester resins. Therefore, there is considerable potential for improving the process through greater technical understanding of reaction and volume shrinkage control mechanism in low temperature cure of unsaturated polyester and vinylester resins. An integrated analysis is carried out in this study to investigate the reaction kinetics and shrinkage control of unsaturated polyester or vinylester resins with low profile additives cured at low temperatures. A differential scanning calorimeter (DSC), a Fourier transform infrared spectrometer (FTIR), and a rheometrics dynamic analyzer (RDA) are used to study the reaction kinetics and rheological behaviors. A dilatometer is applied to study the volume change. A scanning electron microscopy (SEM) and an optical microscopy are employed to investigate the structure and morphology evolution during curing. The effects of curing agents including initiator, promoter, and comonomer on the low temperature polymerization are investigated. These experiments are designed to provide information regarding the polymerization mechanism and microstructure evolution throughout the free radical polymerization. In addition, this information along with the relation between morphology and properties of crosslinked polymeric materials will be used to optimize polymerization conditions of unsaturated polyester and vinylester resins with desired properties for applications in composite matrix.
Advisors/Committee Members: Lee, Li James.
Keywords: RESINS; shrinkage; LPA; POLYESTER; MEKP; MMA; shrinkage control
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18.
Chen, Hongshu.
Sampling-based Bayesian latent variable regression methods with applications in process engineering.
Degree: PhD, Chemical Engineering, 2007, Ohio State University
► Latent variable methods, such as Principal Component Analysis and Partial Least Squares…
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▼ Latent variable methods, such as Principal Component Analysis and Partial Least Squares Regression, can handle collinearity among variables by projecting the original data into a lower dimensional space. They are widely applied to build empirical models of chemical and biological processes. With the development of modern experimental and analytical technology, data sets from those processes are getting bigger and more heterogeneous. The increasing complexity of data sets causes traditional latent variables methods to often fail to provide satisfactory modeling results. Meanwhile, prior information about processes and data usually exist in different sources, such as expert knowledge, historical data etc. However, traditional latent variable methods are ill-suited to incorporate such information. Bayesian latent variable methods, such as Bayesian Latent Variable Regression (BLVR) and Bayesian Principal Component Analysis (BPCA) can combine prior information and data via a rigorous probabilistic framework. Since they make use of more information, they can provide models with better quality. However, BPCA and BLVR are optimization-based, which restricts them from modeling high dimensional data sets or providing error bars. They also make restrictive assumptions to make them suitable for the optimization routines. Because of those pitfalls, they have very limited applications in practice. This dissertation addresses the challenges of making Bayesian latent variable methods practical by developing novel algorithms and a toolbox of sampling-based methods, including a sampling-based BLVR (BLVR-S). BLVR-S is computationally efficient and is able to model high dimensional data sets. It can also readily provide confidence intervals for estimates. An iterative modeling procedure is proposed to deal with hybrid data sets with both continuous and discrete variables. An extended version of BLVR-S is developed to address lack of information about measurement noise in modeling. A generalized BLVR-S is developed to relax the restrictive assumptions of prior distributions. Those methods tackle some practical challenges in Bayesian modeling. The advantages of those Bayesian latent variable regression methods are illustrated in various case studies. Some practical aspects of applying Bayesian latent variable methods are also explored. Through those efforts, the Bayesian latent variable methods are expected to have more practical applications in building empirical models in process engineering.
Advisors/Committee Members: Bakshi, Bhavik R.
Subjects: Engineering, Chemical
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19.
Chen, Wen-shiang.
Bayesian estimation by sequential Monte Carlo sampling for nonlinear dynamic systems.
Degree: PhD, Chemical Engineering, 2004, Ohio State University
► Precise estimation of state variables and model parameters is essential for efficient…
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▼ Precise estimation of state variables and model parameters is essential for efficient process operation, including model predictive control, abnormal situation management, and decision making under uncertainty. Bayesian formulation of the estimation problem suggests a general solution for all types of systems. Even though the theory of Bayesian estimation of nonlinear dynamic systems has been available for decades, practical implementation has not been feasible due to computational and methodological challenges. Consequently, most existing methods rely on simplifying assumptions to obtain a tractable but approximate solution. For example, extended Kalman filtering (EKF) linearizes the process model and assumes Gaussian prior and noise. Moving horizon based least-squares estimation (MHE) also assumes Gaussian or other fixed-shape prior and noise to obtain a least-squares optimization problem. MHE can impose constraints, but is non-recursive and requires computationally expensive nonlinear or quadratic programming. This dissertation introduces sequential Monte Carlo sampling (SMC) for Bayesian estimation of chemical process systems. This recent approach approximates computationally expensive integration by recursive Monte Carlo sampling, and can obtain accurate estimates of posterior distributions efficiently with minimum assumptions. This approach has not been systematically compared with estimation methods popular for chemical processes, including EKF and MHE. In addition to comparing various estimation methods, this dissertation also develops a practical framework of SMC for handling process constraints based on an acceptance/rejection algorithm. Furthermore, a novel empirical Bayes approach is developed to deal with practical challenges due to degeneracy and a poor initial guess. The ability of the proposed approach to be more computationally efficient and at least as accurate as MHE is demonstrated via several case studies. A high-dimensional polymerization process is particularly studied to examine the effect of increasing dimensionality on computation load. Empirical results indicate that SMC does not necessarily increase its consumption of CPU cycles dramatically, and may only be slightly dependent on dimensionality. Although this research has only focused on data rectification of nonlinear dynamic systems, the approach is broadly applicable to most process engineering tasks. With increasing computational ability, and theoretical advances, SMC is expected to be an active area of research and application in near future.
Advisors/Committee Members: Bakshi, Bhavik R.
Subjects: Engineering, Chemical
Keywords: Bayesian statistics, sequential Monte Carlo sampling, nonlinear dynamic systems
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20.
Chiou, Nan-Rong.
Aligned and oriented polyaniline nanofibers: frabrication and applications.
Degree: PhD, Chemical Engineering, 2006, Ohio State University
► In this thesis, two novel, simple, and scalable techniques (called “dilute polymerization”,…
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▼ In this thesis, two novel, simple, and scalable techniques (called “dilute polymerization”, and “porous membrane controlled polymerization (PMCP)”) to control the formation of the aligned and ordered nanofibers (or nanowires) of polyaniline and its derivatives are reported. Through appropriate synthesis conditions, there are nearly ~100% of nanofibers formed in the bulk solution and of large arrays of aligned and oriented nanofibers formed on the surfaces of the substrates. For polyaniline nanofibers formed in the bulk solution, the diameters of nanofibers ranging from 20nm to 250nm are tunable via the selection of polymerization conditions. The lengths vary from sub-micrometers to several micrometers. A single nanofiber can be easily isolated from the agglomeration. X-ray diffraction patterns show that doped polyaniline nanofibers are substantially crystalline. Thin films deposited on a variety of sizes of the substrates shows highly uniform aligned and oriented polyaniline nanofibers that are perpendicular to the substrates. Those aligned and oriented uniform nanofibers have the tips ranging from 20nm to 40nm. UV/vis spectra of polyaniline nanofibers formed in the both bulk and substrates are consistent with nonfibrous polyaniline powders prepared by the conventional chemical synthesis. The nanofibrous morphology has no significant change when redoped/dedoped multiple times by the acid/base solutions. The formation mechanism of the nanofibers is discussed. Moreover, molecular modification of polyaniline nanostructures is also memtioned, thereby allowing preparation of nanofibers of a wide variety of polyaniline nanofibers and also control of the chemical, processing and electrical properties. Finally, polyaniline nanostructures offer wide, exciting and interesting applications, such as DNA stretching, surface modification (e.g. superhydrophilicity and superhydrophobicity), etc
Advisors/Committee Members: Epstein, Arthur J.
Keywords: polyaniline; polypyrrole; self-doped polyaniline; sulfonated polyaniline; polytoluidine; polyaniline nanofiber; polyaniline nanostructure; nanowire; nanostructure; superhydrophobic; superhydrophilic; Lotus effect; Anti-fog; surface response
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21.
Clogston, Jeffrey.
Applications of the lepidic cubic phase: from controlled release and uptake to in meso crystallization of membrane proteins.
Degree: PhD, Chemical Engineering, 2005, Ohio State University
► The lipidic cubic phase consists of a pair of interpenetrating but non-contacting…
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▼ The lipidic cubic phase consists of a pair of interpenetrating but non-contacting aqueous channels separated by a single, highly curved continuous lipid bilayer. Because of its unique microstructure and dual nature (hydrophobic/hydrophilic character), the cubic phase finds use in controlled release and uptake. With a view to exploiting these features in combination with small molecule and proteinaceous drugs, a systematic approach aimed at understanding how the transport properties of the cubic phases are controlled by phase identity and microstructure (aqueous channel size) and by the physical and chemical properties of the drug itself (molecular size, shape) was taken. Furthermore, tailored release was demonstrated by adjusting electrostatic interaction strength and by His-tag displacement. Additional control was demonstrated by alkylating a water-soluble additive in such a manner that it interacted with the lipid bilayer. The results show that by varying the alkyl chain length, the release from the cubic phase can be controlled/prolonged in a systematic manner. While the previous study examined diffusion within the water channels, the study was extended to include lipid-soluble additives. For this purpose, the diffusion of three hydrophobic additives ranging in size from a small molecule (354 g/mol) to a huge multisubunit membrane protein (~129 kDa) in the lipid bilayer was quantified. This made use of commercial quartz tubing (microcuvettes), which allowed for the measurement of small sample volumes (1-5 uL). The results compare well with those obtained using more complicated techniques. Finally, the possibility of exploiting the "sponge-like" properties of the cubic phase in wastewater remediation was investigated. For this purpose, Myverol 18-99K, a relatively inexpensive commercial and biocompatible material, was used as the source lipid. Accordingly, the uptake of phenol, a wastewater contaminant of note, into pre-formed cubic phase prepared from Myverol has been quantified. This was compared to uptake by "neat" or pure Myverol, by a colloidal dispersion of the Myverol-based cubic phase referred to as cubosomes and by activated carbon.
Advisors/Committee Members: Tomasko, David.
Subjects: Engineering, Chemical
Keywords: diffusion coefficients; lipidic cubic phase; drug delivery; monoolein
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22.
Cui, Zhe.
Hydrodynamics in a bubble column at elevated pressures and turbulence energy distribution in bubbling gas-liquid and gas-liquid-solid flow systems.
Degree: PhD, Chemical Engineering, 2005, Ohio State University
► Bubble columns are widely used as multiphase reactors in chemical industries due…
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▼ Bubble columns are widely used as multiphase reactors in chemical industries due to many advantages. The transport behavior in these systems is complex and a comprehensive knowledge of the transport phenomena, including hydrodynamics and turbulence properties are required. The hydrodynamics in a high pressure bubble column is experimentally investigated. The liquid velocities are measured using a LDV (Laser Doppler velocimetry). The Reynolds stresses are obtained. The effect of the pressure on the transition of the flow regime, flow field and the Reynolds stresses are studied. Furthermore, the effects of the liquid properties on the hydrodynamics of the bubble column are discussed. The turbulence energy distributions in the bubble columns are investigated using the LDV and PIV. The energy containing ranges for the bubble-induced and shear-induced turbulence are determined from the power spectra. Experimental results indicate that the bubble-induced turbulence dominates over the shear-induced turbulence under the operating conditions. The bubble-induced turbulence includes the turbulence in the bubble wake and that from the drift velocity change. The interaction between two turbulence field can only be observed when the turbulence in both fields is strong and the interaction tends to enhance the turbulence in both fields. The liquid phase turbulence is enhanced in the presence of particles at high superficial gas velocities while it is attenuated under low superficial gas velocity conditions. A criterion based on the variation of the ratio, Ug( r )/umf is proposed to account for the effect of the solids on the liquid phase turbulence. The prediction based on this criterion matches well with the experimental results. The behavior of a 6 mm mesobubble in an acoustic standing wave field is examined both experimentally and numerically. The acoustic standing waves at 16 kHz and 20 kHz are generated using two Nickel magnetostrictive transducers. The bubble rise velocity is significantly lower than that in the absence of an acoustic field. The behavior of bubble volume contraction and expansion can be accounted for by a 3-D direct numerical simulation of the bubble dynamics and flow field based on the compressible N-S equations coupled with the level-set method.
Advisors/Committee Members: Fan, LiangShih.
Subjects: Engineering, Chemical
Keywords: BUBBLE COLUMN; TURBULENCE; liquid phase; velocity; liquid; gas velocity
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24.
Du, Bing.
Hydrodynamics and flow structure, gas and solids mixing behavior, and choking phenomena in gas-solid fluidization.
Degree: PhD, Chemical Engineering, 2005, Ohio State University
► In this study, the dynamic flow behavior and gas and solids mixing…
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▼ In this study, the dynamic flow behavior and gas and solids mixing behavior in the turbulent fluidized beds are investigated by using Electrical Capacitance Tomography (ECT) technique and tracer technique. The ECT study reveals that the time-averaged solids holdup distribution exhibits radial symmetry in the turbulent regime. The addition of 10% fine particles decreases the solids concentration in the emulsion phase. The flow behavior in the turbulent fluidized beds is not appreciably affected by the temperature up to 400 °C. More than one spiral motion of bubble swarms is observed in the bubbling regime for the 0.3 m ID fluidized bed. The gas and solids mixing behavior varies significantly with the flow regimes. A small quantity of fine particles is noted to drastically affect the gas and solids mixing behavior in the turbulent fluidized bed. For Group A particles, the flow in the bed transits from the dilute regime to the turbulent regime when the gas velocity is below Utr or the solids circulation rate is lower than Gs,tr. Such flow transition can be signified as the choking transition. For Group B particles, choking is initiated by the formation of the square-nosed slugs (0.05 m ID column) or the wall slugs (0.1 m ID CFB) when the gas velocity is below Utr or the solids circulation rate is lower than Gs,tr. When the gas velocity is above Utr or the solids circulation rate is higher than Gs,tr, choking is characterized by the formation of open slugs. These regime transitions are characterized as the choking transition. A model based on the movement of the solids blob at the center of the bed is developed to predict the critical lifetime of a solids blob in a circulating fluidized bed. The criterion for the occurrence of choking transition in a circulating fluidized bed for both Group A and Group B particles is given.
Advisors/Committee Members: Fan, Liang-Shih.
Subjects: Engineering, Chemical
Keywords: hydrodynamics; flow structure; mixing behavior; turbulent fluidized bed; circulating fluidized bed; choking; regime transition
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25.
Ellis, Jeffrey LeClair.
Dense Carbon Dioxide Assisted Polymer Processing at the Nanoscale.
Degree: PhD, Chemical Engineering, 2009, Ohio State University
► Nanotechnology is continually becoming more integrated into consumer products used by the…
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▼ Nanotechnology is continually becoming more integrated into consumer products used by the general public on a daily basis. Consumers reap the benefits of enhanced properties for these commercial products, and yet they are still affordable. For biomedical products, that include nanofeatures, this is not yet a reality. The materials and methods used to fabricate these products are still far too expensive. There are many inexpensive and commercially available polymers that have potential to be used in these advanced biomedical products, but the fabrication techniques still lack the simplicity required to create an inexpensive end product.Supercritical CO2 has been used to overcome the polymeric nanofabrication barriers for high throughput production of biomedical devices. Novel CO2-assisted low temperature polymer nanoprocessing fabrication techniques have been implemented for use in biomedical product creation. Polymer nanofabrication techniques such as bonding, imprinting, and active biomolecule immobilization were demenonstrated. Due to being CO2-assisted techniques, these processes are intrinsically inexpensive and environmentally benign. In order to thoroughly investigate these nanofabrication techniques the interactions between CO2 and the polymer were examined on a thermodynamic level. Thermodynamic modeling results of high pressure CO2/polystyrene systems were used along with experimental bonding, imprinting, and immobilization results. It was found that the solubility of CO2 in a polymer matrix and the resulting reduction of the polymer glass transition temperature (Tg) largely dictate the polymer chain mobility and therefore the polymer's processability. For instance, it was shown that the polymer bond strength of polystyrene, bonded via a CO2-assisted technique, depended largely on the proximity of the processing conditions to the reduced Tg curve. It was also found that low aspect ratio nanofeatures could be patterned by CO2-assisted nanoimprint lithography in polystyrene at conditions near the reduced Tg curve. These CO2-assisted low temperature polymer processing techniques are now better understood in terms of the CO2/polymer thermodynamic properties, thus making these, and other similar, techniques easier to control. This fundamental information can be applied to scaling-up these technologies so that inexpensive polymer biomedical products with nanofeatures can soon be commercially produced, thus benefiting the health of society.
Advisors/Committee Members: Tomasko, David.
Subjects: Chemical engineering
Keywords: polymer processing, polystyrene, supercritical CO2, nanotechnology, polymer bonding
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26.
Elsass, Michael J.
Multipurpose Sharable Engineering Knowledge Repository.
Degree: PhD, Chemical Engineering, 2001, Ohio State University
► The chemical process industry devotes considerable time and effort on decision support…
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▼ The chemical process industry devotes considerable time and effort on decision support systems for process engineering applications. Increasing the reusability of the industrial knowledge in these systems leverages significant resources in developing these systems. Creating a unified representational framework leverages the knowledge overlap in multiple applications and processes. This work describes a multipurpose representation for decision support applications in continuous chemical processes involving malfunction or abnormal situations, e.g. diagnosis, HAZOP. With respect to previous efforts, this work presents an overhauled version of Functional Representation (FR) that extends its flexibility for knowledge reuse, its ability to capture complex process devices and its capacity for multiple applications. The application focus of previous efforts, while adequate for the tasks at hand, was insufficient from a multipurpose perspective. FR is a representation formalism that models behavior, function and mode of operation in a hierarchical structure. Behavioral descriptions are represented with Causal Process Descriptions (CPDs), and an associated causal state directed graph. Function constructs classify behaviors with similar functional characteristics. Modes categorize Functions (and therefore behaviors) around modes of operation such as normal, or malfunction. The new formalism addresses reusable representations for causal reasoning about complex devices. A complex device is modeled as an aggregation of connected component models. Knowledge reuse is enhanced by modeling every device with a single construct (from components to systems). Causal propagation is a critical operation associated with all targeted applications. Knowledge is structured to facilitate the task of managed causal branching of automated, real-time causal propagation. Behavioral knowledge is structured from a snapshot perspective, which models the device state at an instant in time. By adopting this perspective, temporal knowledge is removed from the causal transitions, and propagation constraints can be employed. Methodologies such as causal pruning and propagation order are implemented to further limit causal branching. To demonstrate and validate the multipurpose capacity of a knowledge repository, two different industrial processes were modeled for use in two different engineering applications. A HAZOP analysis interface was built and operated on a fines removal unit FR model, while a diagnostic system interface operated on a demethanizer unit FR model.
Advisors/Committee Members: Davis, James F.
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27.
Fei, Zhengzheng.
Membrane Sandwich Electroporation for In Vitro Gene Delivery.
Degree: PhD, Chemical Engineering, 2009, Ohio State University
► Gene therapy is the delivery of therapeutic genes into cells and tissues…
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▼ Gene therapy is the delivery of therapeutic genes into cells and tissues with the aim of treating and curing a disease. As an enhanced understanding of the roles of genes in health and disease, gene therapy is showing promise against various diseases such as cancer, diabetes, Parkinson's disease, and several inherited physiological defects. Viral transduction is very efficient, but safety issues, such as immune and inflammatory responses, have hampered their clinical uses in humans. Non-viral methods, including either chemical transfection with cationic lipids/polymers or physical transfection using electroporation/microinjection, are becoming attractive approaches. Electroporation is one of the most popular non-viral gene transfer methods for in vitro cell transfection. Initial studies with electroporation experienced very low transfection efficiencies and cell viability, severely limiting the development of this technology. The emergence of nucleofection (a modified electroporation technology) provided an efficient means for transfecting cells in vitro. However, nucleofection still encounters many limitations such as the large number of cells required and high cost involved. Moreover, cell viability is still an issue due to the high electric voltage used and the non-uniform electric field strength distribution generated during the process. To address these problems, we propose to develop an electroporation system based on an innovative micro-/nanoengineering technology for in vitro gene delivery. In our approach, electroporation is carried out in a mild and uniform electric field, with potential for a wider process window that can be generated to cover a wide range of cell lines and even primary cells. A new membrane sandwich electroporation (MSE) approach was demonstrated using plasmids GFP and SEAP as model materials. NIH 3T3 fibroblasts were tested and a significant improvement in transgene expression was observed compared to current electroporation techniques. In the MSE method, the focused electric field enhances cell permeabilization at a low electric voltage, leading to high cell viability; more important, the sandwich membrane configuration is able to provide better gene confinement near the cell surface, facilitating gene delivery into the cells. Next, we demonstrated the use of femtosecond laser fabricated micro-nozzle arrays on a gelatin-coated PET membrane for MSE. Using micro-nozzle array enhanced MSE, we observed high and uniform gene transfection, and good cell viability of mouse embryonic stem (ES) cells compared to the bulk electroporation. Since typically cells or tissues from the patients are very limited and therapeutic materials such as plasmids and oligonucleotides are very expensive, the ability to treat a small number of cells (i.e. a hundred) offers great potential to work with hard-to-harvest patient cells for patient-specific ex vivo gene therapy and in vitro pharmaceutical kinetic studies. Numerical calculation of transmembrane potential qualitatively explains the observed differences between MSE and bulk electroporation. Since there’s a good correlation between transfection results and transmembrane potential calculations, the simulation process with the threshold experiments can be used to predict the transfection results, and thus largely reduced the trial-and-error window size. Furthermore, we successfully integrated an electrospun nanofiber scaffold as a cell-binding substrate into MSE, called nanofiber based MSE. With a micro-well spacer, the uniform size of mouse ES cell colonies were obtained, and plasmid transfection by electroporation were performed during colony formation. In addition, repeated plasmid SEAP transfection of NIH 3T3 fibroblasts was tested and better cell survival and recovery rate was observed using the electrospun nanofiber scaffold as compared to using micro-porous membrane. Due to its capacity of extend the exposure time with reprogramming factors, nanofiber based MSE demonstrated the potential for efficient induced pluripotent stem (iPS) cell generation by repeated plasmid transfection.
Advisors/Committee Members: Lee, Ly James.
Keywords: electroporation; gene delivery; cell culture; stem cells
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29.
Fraley, Brian J.
High-Throughput 3-D Cellular Assays Using Destabilized Green Fluorescence Protein.
Degree: MS, Chemical Engineering, 2009, Ohio State University
► Cell assays for high-throughput screening (HTS) of potential drug candidates are important…
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▼ Cell assays for high-throughput screening (HTS) of potential drug candidates are important tools in the process of drug discovery. Most cellular assays are currently based on 2-D monolayer cell cultures, but 3-D cell cultures could better mimic the in vivo characteristics of actual organism tissues. Unfortunately, assays using 3-D culture models usually require significant manual manipulation and are therefore not suitable for HTS. Research under Dr. Shang-Tian Yang has resulted in a functioning system for high-throughput 3-D cellular assays using engineered cells to express enhanced green fluorescence protein (EGFP) quantifiable through fluorometry. System improvement to allow rapid assessment of cellular events, such as specific gene expression or cell cycle progress is limited by the long persistence of the current reporter protein in the cells. In this study a new fluorescence reporting cell line was established using a destabilized EGFP (d4EGFP) expressed in Chinese hamster ovary (CHO) cells. Correlating fluorescence with cell number for the d4EGFP cell line in 2-D assays indicated that d4EGFP expression may be too low for use in high-throughput cell number reporting. The fluorescence and cell number correlation in 3-D assays indicated better performance could be achieved in 3-D but the fluorescence was sensitive to duration between sampling, possibly due to oxygen transfer limitation, hindering reliable use for cell number reporting. Response to such factors could still serve a purpose for culture condition monitoring, and could be applied in culture development and optimization.
Advisors/Committee Members: Yang, Shang-Tian.
Subjects: Cellular biology; Chemical engineering
Keywords: high-throughput screening; CHO; 3-D cellular assay; optical reporting; green fluorescence protein; destabilized green fluorescence protein; GFP; d4EGFP
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30.
Gandhi, Shikha.
Investigation Of The Effect Of Low Molecular Weight Peg On Lysozyme Interactions In Solution Using Composition Gradient Static Light Scattering.
Degree: MS, Chemical Engineering, 2008, Ohio State University
► Conventional approaches towards protein crystallization are based on predicting favorable solution conditions…
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▼ Conventional approaches towards protein crystallization are based on predicting favorable solution conditions for crystal formation through trial and error and are expensive. The second virial coefficient (protein-protein), a thermodynamic solution parameter, is a measure of protein interactions in solution, and more importantly- experimentally accessible. It allows a systematic approach for predicting solution conditions favorable to protein crystallization based on solution thermodynamics.Poly-ethylene glycol (PEG) is a commonly used salting-out agent in protein crystallization. Its effect on influencing protein-protein interactions in solution is attributed popularly to a "depletion effect" in the literature. This work provides experimental evidence that low molecular weight PEG induces repulsion between protein molecules, contrary to the predictions of depletion, if a third protein-protein-polymer virial coefficient is considered in the analysis, in addition to protein-protein and protein-polymer second virial coefficients.
Advisors/Committee Members: Paulaitis, Michael.
Subjects: Biophysics; Chemical engineering
Keywords: PEG; protein-protein interactions; second virial coefficient
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