Theses and Dissertations - Department of Chemical & Biological Engineering

Permanent URI for this collection

https://ir.ua.edu/handle/123456789/87

Browse

Now showing 1 - 20 of 50

Advanced solvents for CO2 separation applications
(University of Alabama Libraries, 2016) Flowers, Brian Steven; Bara, J. E.; University of Alabama Tuscaloosa
The objective of this dissertation is to advance the understanding of several novel solvents for CO2 capture and separation applications. Many of the solvents investigated were imidazole based, as these compounds are highly tunable, neutral, and less expensive analogs to imidazolium based ionic liquids (ILs). While much is known about the physical properties of ILs, the physical properties of these neutral compounds have not been researched as thoroughly, and so there is a need to explore these compounds as potential CO2 capture media. It has been further proven that the most effective means of predicting CO2 capture performance in imidazole based compounds is by examining the fractional free volume (FFV) using a molecular simulation program like COSMOTherm. Other non-imidazole based physical solvents were synthesized and compared to commercially available processes. 1,2,3-Trimethyoxypropane (1,2,3 TMP) was found to compare favorably with regard to CO2 absorption and viscosity to the current industry standard for CO2/CH4 pre-combustion separation techniques, Selexol, while being significantly less toxic. Chemical solvents for post-combustion CO2 capture were also investigated. It was determined that changing the substituents on 1-(3-aminopropyl)imidazole increases the CO2 solubility by increasing the basicity of the imidazole ring. The advantages in vapor pressure of these substituted aminopropylimidazole over traditionally used alkanolamines could potentially provide massive operational savings by reducing solvent losses through evaporation and increased solvent life.
Atomic Layer Deposition for Surface Modifications and Solid Film Fabrication
(University of Alabama Libraries, 2021) Yan, Haoming; Peng, Qing; University of Alabama Tuscaloosa
Along with the unceasing development of the surface and material science, modification of substrates surfaces in nanoscale, to fabricate the functional materials with precisely controlled dimensions, refined composition and desired properties becomes crucial. In this report, atomic layer deposition (ALD), a vapor phase, sequential and self-limiting deposition process, has been used as an alternative strategy to modify the surface of materials and fabricates nanometer or micrometer level of functional materials with precise control. In the first part of this dissertation, ALD was used to modify the surface of the shape-engineered nanocrystals (SENCs), which enhanced the thermal stability of the SENCs from 300˚C to 700˚C and enhanced the catalytic activities of the nanocrystals as well. We also proposed a new reaction mechanism of metal-organic precursor with oxide surface, in which the conventional layered ALD growth does not happen but the oxide surface was modified via controlled metal doping. In the second part of this dissertation, ALD precursors were used to reacting with liquid substrates to fabricate freestanding solid thin films. Benefits from the unique reaction mechanism of the ALD metal-organic precursors, the thickness and the compositions of the fabricated films can be controlled. The fundamental of gas-liquid reaction has been discussed in this study. In the third part of this dissertation, area-selective ALD (AS-ALD) has been reported using carboxylic acid self-assembled monolayer as a growth inhibitor. Excellent selectivity of AS-ALD has been achieved by using this method, which could potentially be used in microfabrication as a substitution step for photolithography.
Bioengineering of Heterogenous Glioblastoma Multiforme Microenvironment
(University of Alabama Libraries, 2021) Park, Seungjo; Kim, Yonghyun; University of Alabama Tuscaloosa
Glioblastoma (GBM) is the most aggressive brain tumor that originates from glioblastoma stem cells (GSCs). In the brain, GSCs are supported by a tumor microenvironment (TME) wherein the perivascular niche and hypoxic region are present. The glioblastoma microenvironment (GBME) exhibits high heterogeneity, vast cell-to-cell interactions, and stiff mechanical properties. To produce in vitro models mimicking the GBME features, GBM organoid (GBO) models have been developed. Conventional organoid studies rely on growing them in serum-free media, resulting in sphere formation. However, this conventional method is not scalable and often fails in recapitulating inter- and intratumor heterogeneity. Also, the conventional method is not ideal to produce adequate quantities of GBOs to screen drugs for personalized medicine. Therefore, development of a reproducible and scalable GBO culture method can provide a better platform to simulate novel treatments.First, the bioreactor design was optimized by using different diameters of impellers and bioreactor vessels. Even with similar shear stresses, cell proliferation was inhibited or promoted depending on the ratio of the impeller diameters to the vessel diameters. With the optimized vessel geometry, shear stress and media supplements were optimized for GBO production. The bioreactor GBOs (bGBOs) were produced in uniform size, not by clonal aggregations, but by cell proliferation. With the optimal agitation rate, bGBOs displayed upregulation of genes involved in stemness, hypoxia, angiogenesis, proliferation, and migration. The statistical analysis revealed the synergetic effects of the high agitation rate and the size of the bGBOs. Next, bGBO models were characterized by their morphologies and transcriptional and translational profiles. The bGBOs exhibited high and strong cell-to-cell contact. Multivariate gene analysis found a significant correlation between gene expression and the size of the bGBOs. GBME was established and spatially organized in bGBOs greater than 800 Âµm in diameter. Hypoxic TME was developed in bGBOs greater than 400 Âµm in diameter. Inside the bGBOs, spatially separated features of the hypoxic niche and the perivascular niche were demonstrated. Also, the large bGBOs displayed angiogenesis features. Self-established GBME was organized by transdifferentiated GBM into endothelial cells, pericytes, and astrocytes. GBME containing necrotic regions displayed more spatially distinctive and hierarchically organized GSC niches. The GSCs in the niche were regulated by transcription factors involved in dedifferentiation. Hydrogels have been employed to further understand underlying mechanisms of the transformation of GBM in the bGBO model. Mechanical properties of GBME was engineered using hyaluronic acid (HA)-based hydrogels. Cell behavior in response to the hydrogel stiffness was examined. Transcription factors dedifferentiating GBM into GSCs were translocated to the nucleus in response to stiffer substrates. Collectively, these studies provided a small-scale model for a high-throughput production of GBOs that recapitulate in vivo GBM features, including high heterogeneity and high cell-to-cell interactions. Hydrogel model and the bioreactor culture conditions described here suggest that GBOs can be biomanufactured by modulating mechanical stress.
Characterization of bismuth telluride two-dimensional nanosheets for thermoelectric applications
(University of Alabama Libraries, 2015) Guo, Lingling; Wang, Hung-Ta; University of Alabama Tuscaloosa
Solid-state thermoelectric devices are compact, scalable, quiet, and environmentally friendly, which are widely used as thermal engines or refrigerators. Bismuth telluride (Bi2Te3) and other V-VI group chalcogenides are known as one of the best thermoelectric materials specifically for applications in a temperature environment from room temperature to 300 ℃. Recently, the unique topological surface states were discovered in Bi2Te3 family materials, and these novel surface states are arisen from a strong spin-orbit coupling in topological insulators. Topological surface states are protected against time-reversal perturbations (i.e., non-magnetic impurities or surface defects), making the electronic transport essentially dissipation-less. Such unique transport behavior with zero energy loss provides new opportunities to enhance thermoelectric properties. Although the promise in thermoelectric properties of topological insulators have been shown in theoretical reports, there is a lack of experimental investigations for a better understanding of their basic properties. This research work focuses on the characterizations of fundamental properties of Bi2Te3 two-dimensional (2D) nanosheets. Samples were prepared via respective solvothermal synthesis and van der Waals epitaxy. The charged surface properties of Bi2Te3 2D nanosheets were investigated using kelvin probe force microscopy. The measured electrical potential difference between aminosilane self-assembled monolayer and Bi2Te3 nanosheet surfaces is found to be ∼650 mV, which is larger than that (∼400 mV) between the silicon oxide substrate and Bi2Te3 nanosheet surface. The elastic properties of Bi2Te3 2D nanosheets (i.e., Young’s modulus and prestress) were acquired by analyzing the thickness dependence of 2D nanosheet deformations creating by atomic force microscopy tips. The Young's modulus by fitting linear elastic behaviors of 26 samples is found only 11.7–25.7 GPa, significantly smaller than the bulk in-plane Young's modulus (50–55 GPa). Furthermore, the thermoelectric properties of Bi2Te3 2D nanosheets were characterized in the cryostat system at a temperature range of 20-400 K. The results reveal that electrical conductivity of 2D nanosheets decreases with increasing temperature and thickness, while the measured Seebeck coefficient does not show a strong thickness dependence and the value is smaller than bulk Bi2Te3. These fundamental properties would help improve the basic understanding of topological surface states towards practical applications.
Chemical vapor deposition of thin film materials for electronic and magnetic applications
(University of Alabama Libraries, 2011) Li, Ning; Klein, Tonya M.; University of Alabama Tuscaloosa
Chemical vapor deposition (CVD) has been employed to pursue high quality thin film growth for four different materials with excellent electronic or magnetic properties for certain device applications. The relationship between CVD processing conditions and various thin film properties has been systematically studied. Plasma enhanced atomic layer deposition (PEALD) is a special type of CVD technique and can be used for the deposition of very thin (few nanometers) and highly conformal thin films. PEALD of hafnium nitride (HfN) thin film is studied by using tetrakis (dimethylamido) hafnium (IV) (TDMAH) and hydrogen plasma. Prior to thin film deposition, TDMAH adsorption and reaction on hydrogenated Si(100) surface has been investigated by in-situ ATR-FTIR. It has been found that between 100˚C and 150˚C surface adsorbed TDMAH molecules start to decompose based on the ß-hydride elimination mechanism. The decomposition species on the surface has been found hard to desorb at 150˚C, which can contaminate the thin film if the purging/pumping time is insufficient. Uniform and moderately conductive HfNxCy films are deposited on hydrogen terminated Si(100) and thermally grown SiO2 (on Si) substrates by PEALD process. The dependence of thin film resistivity on plasma power is found to be related to the change of surface chemical composition. In vacuo XPS depth profile analysis showed the existence of hafnium carbide phase, which to a certain degree can improve the film conductivity. Direct liquid injection chemical vapor deposition (DLI-CVD) has been utilized for epitaxial growth of nickel ferrite (NiFe2O4), lithium ferrite (LiFe5O8) and barium titanate (BaTiO3) films on various lattice match substrates. For the deposition of nickel ferrite, anhydrous Ni(acac)2 and Fe(acac)3 (acac = acetylacetonate) are used as precursor sources dissolved in N,N-dimethyl formamide (DMF) for the DLI vaporizer system. Epitaxial nickel ferrite films of stoichiometric composition are obtained in the temperature range of 500-800 ºC on both MgO(100) and MgAl2O4(100). Film morphology is found to be dependent on the deposition temperature with atomically smooth films being obtained for deposition temperature of 600 and 700 ºC. Magnetic measurements reveal an increase in the saturation magnetization for the films with increasing growth temperature, which correlates well with the trend for improved epitaxial growth. Nickel ferrite films deposited on MgAl2O4 (100) at 800ºC exhibit saturation magnetization very close to the bulk value of 300 emu/cm3. Out-of-plane FMR measurement shows the narrowest FMR line width of ~160 Oe for films deposited at 600˚C. For lithium ferrite deposition, anhydrous Li(acac) and Fe(acac)3 are dissolved in DMF in a molar ratio of 1:5. Epitaxial growth of lithium ferrite films on MgO(100) are observed in the temperature range of 500˚C to 800˚C. The as grown films show increasing saturation magnetization with increasing deposition temperature due to the improved degree of crystal texture. For barium titanate thin film deposition, Ba(hfa)2*tetraglyme and Ti(thd)2(OPri)2 are dissolved in toluene in a molar ratio of 1:1. Epitaxial growth of barium titanate on MgO(100) has been found at the temperature of 750˚C. Film with a thickness of ~500 nm has a relatively large roughness of ~20 nm. Small amount of F elements, which exists in Ba-F bonds, has been detected in the thin film by XPS.
Chromium(III) Interaction with Transferrin and Transferrin Receptor
(University of Alabama Libraries, 2021) Edwards, Kyle Carter; Vincent, John B.; University of Alabama Tuscaloosa
Transferrin (Tf), the major iron transport protein in the blood, apparently also transports trivalent chromium via endocytosis. The release of chromium(III) from human serum transferrin has been examined under conditions mimicking an endosome during endocytosis. At pH 4.5 and 5.5, the release of Cr(III) from Tf occurs rapidly from the C-lobe binding site and slowly from the N-lobe binding site. The loss of N-lobe bound Cr(III) under these conditions is accelerated by the presence of a anionic chelating ligand. When Cr(III)-loaded transferrin is added to soluble transferrin receptor (sTfR), the loss of Cr(III) from both binding sites becomes rapid at acidic pH, more rapid than from either site in the absence of the receptor. Loss of Cr(III) from the Tf-sTfR complex is easily sufficiently rapid for Tf to serve as the physiological transporter of Cr(III) from the bloodstream to the tissues. Studies have also found that Cr(III)2-Tf can exist in multiple conformations giving rise to different spectroscopic properties and different rates of Cr(III) release. Time-dependent spectroscopic studies of the binding and release of Cr(III) from human serum Tf have been used to identify three conformations of Cr(III)2-Tf. The conformation formed between 5 and 60 minutes after the addition of Cr(III) to apoTf at pH 7.4 resembles the conformation of Cr(III)2-Tf in its complex with sTfR and loses Cr(III) rapidly at endosomal pH. Loss of Cr(III) from Cr2-Tf and Cr2-Tf-sTfR in the presence of apo-chromodulin (LMWCr) results in accumulation of Cr(III) bound to LMWCr and is rapid when sTfR is present indicating the species can form under endosomal conditions and may be the next carrier in the Cr(III) transport pathway. Techniques used throughout the projects were also applied to Mn(III)2-Tf, and the first parallel mode EPR signal for Mn(III)-Tf is reported, which could prove valuable for future studies.
Computational Predictions for the Interactions of Lewis Acid Gases with Each Other and with Materials of Interest
(University of Alabama Libraries, 2021) Lee, Zachary Ryan; Dixon, David A.; University of Alabama Tuscaloosa
This dissertation focuses on the computational chemistry predictions of the mechanisms and products of Lewis acid gases with materials of interest to understand the chemistry of these systems and to aid in the design of practical sorbents for acid gas separations and conversions. A detailed computational investigation of the species present prior to the introduction of a sorbent was performed. The barriers and overall thermodynamics of H2SO4, H2SO3, H2S2O3, and H2S2O2 formation from the reactions of SOx (x = 2 or 3) with H2O and H2S in both gas phase and in aqueous solution as well as the resulting acidities of these BrÃ¸nsted acids were predicted. These calculations were performed using the Feller-Peterson-Dixon (FPD) methodology with implicit MP2/aug-cc-pVTZ/COSMO corrections included for predicting energies in aqueous solution and predict favorable formation of strongly acidic H2SO4 and the experimentally elusive H2S2O3. The thermodynamics of a novel type of NO2 adsorption to Groups IV and VI transition metal oxide clusters, calculated at the CCSD(T)//B3LYP level, are compared directly to the previously predicted binding energies of CO2, SO2, and H2O to these oxides and correlated with the M-O bond dissociation enthalpy, vertical excitation energy, electron affinity, and ionization potential trends of the bare metal oxides themselves. The results provide key insight into the importance of band gaps and M-O bond strengths for the selection of metal oxides for NOx separations. The role of 4f electrons and the surrounding ligand environment on the acid gas interactions of H2O, NO2, and SO2 with a promising class of metal-organic frameworks (MOFs), the rare-earth 2,5-dihydroxyterephthalic acid frameworks, was studied using DFT for both a cluster model which explicitly treats the lanthanide 4f electrons and a periodic model to predict bulk interactions without the inclusion of active 4f electrons. Insight into the reaction mechanisms of the promising post-combustion capture of CO2 by aqueous and solid-state amines was studied primarily using the composite G3(MP2) methodology. As a whole, these studies provide a detailed understanding of the chemical thermodynamics and kinetics relevant to acid gas capture by promising materials of interest.
Computational Studies of Transition Metals and Small Molecules
(University of Alabama Libraries, 2021) Persaud, Rudradatt Randy; Dixon, David A.; University of Alabama Tuscaloosa
The chemistry that transition metals can access due to their d orbitals has expanded the horizons of many fields in chemistry. The work covered in this dissertation focuses on designing a computer system for performing computational studies, and a wide range of computational chemical studies of transition metals in various applications including predictions of bulk properties, homogenous/heterogenous catalysis, and the acidity of solvated transition metals for use in proteomics. Utilizing high-performance computers allows chemists to explore the d-block elements to aid in the analysis of experimental results or to explore new chemistry cheaply, safely, and ‘greenly’. Although a handful of high-performance computer cluster building recipes are available for general use, a free-open source recipe geared towards computational chemistry with compatibility for a broad range of computer hardware is provided. High level MO theory studies of coinage-metal trimers were done to study their potential energy surfaces. While exploring these potential energy surfaces, a novel, vibrationally bound, local minimum for the gold trimer was discovered, one of the first examples of bond angle isomerism. The normalized clustering energies of small metal clusters (n = 2-20) of the coinage metals were extrapolated to predict the cohesive energy of the bulk metal. The importance of spin orbit coupling for the binding energies of gold clusters was found. Density functional theory was used to calculate the binding energies of organic molecules including cyclohexane and benzene on a model of the rutile TiO2(110) surface, an important first step in heterogeneous catalysis of these species on a transition metal oxide. The calculated vibrational frequencies were used to predict reliable prefactors for analysis of temperature programmed desorption experiments. Mechanisms for the homogenous catalysis of the reduction of CO2 to formate using a triphosphine-ligated Cu(I) catalyst were developed. A mechanism of enhanced protonation involving transition metals in an electrospray ionization source in mass spectrometry for proteomic applications was developed.
Computer simulation of geologic sequestration of CO_2
(University of Alabama Libraries, 2012) Islam, Akand W.; Carlson, Eric S.; University of Alabama Tuscaloosa
The research conducted here is an attempt to develop a simulation framework of CO2 sequestration in geologic formations. One of the very important parts of this framework is centered on phase equilibrium computations between CO2 and Brines for a wide range of temperature and pressure. Besides accuracy of the models, time efficiency is extremely important to save computational expenses. Therefore, thorough investigations have been carried out to model the phase equilibrium of CO2 and Brines system over the temperature range 20 - 300 °C, and pressure range 1 - 600 bar from different perspectives, like, vapor state Equation of State (EoS), liquid state EoS, and Statistical Associating Fluid Theory (SAFT), in time efficient manner. First, a non intuitive scheme and a new EoS for CO2 has been proposed which gives more than 1000 times speed up after integrating with the simulator compared with other EoS's. To model the phase equilibrium for super critical CO2, currently available liquid state models such as UNIQUAC, LSG, NRTL, and GEM-RS have been modified which reproduce literature data within fair deviation. SAFT, which is a theoretically sound model, has also been modified to apply in the simulator. A comprehensive study is carried out to model the viscosity of CO2 and Brines applicable for the geologic environment. While modeling the viscosity, the effect of CO2 dissolution is taken into consideration. Double diffusive natural convection of CO2 in brine saturated porous media is investigated to show how CO2 dissolves over the time after injection.
The Deprotonation and Dissociation of Amino Acids and Peptides by Negative Ion Mode Mass Spectrometry
(University of Alabama Libraries, 2021) Cui, Can; Cassady, Carolyn J.; University of Alabama Tuscaloosa
Investigation of negative ion mass spectrometry (MS) is important to proteomics due to its superior ability to analyze acidic peptides and provide complementary information to positive ion mode. This dissertation focuses on the deprotonation and dissociation of amino acids and peptides, which provides fundamental knowledge and assists in development of negative ion MS. Gas-phase acidities (GA) of acidic peptides were determined experimentally and compared to computational values. In electrospray ionization (ESI), either one major structure or multiple structures with very similar GAs were formed. Peptides with acidic residues at the C-terminus are more acidic than those at the N-terminus. Replacing glutamic acid residues (E) with aspartic acid (D) can increase the acidities when E is at the C-terminus but has no effect if E is at the N-terminus. Bond dissociation energies of deprotonated amino acids, dipeptides, and their amides were investigated by combining MS and computations. The loss of H2O occurs in collision-induced dissociation (CID) from all amides except glycine amide. Loss of the C-terminus is only seen in CID of deprotonated dipeptides. In addition, an intense y1 ion forms from dipeptides and their corresponding amides. In the comparison among radical-based dissociation techniques, negative ion in-source decay (nISD) has the best performance for peptides. nISD gives the highest sequence coverage and consistently generated singly charged c- and z-ions. Besides, nISD produced the least neutral loss products and is the fastest technique. The disadvantage of nISD is its inability to select precursor ions. For the investigation of nISD with oxidizing matrices on acidic peptides, 4-nitro-1-naphthylamine (4N1NA) was used as a MALDI matrix for the first time and was found to be the most useful matrix. The overall sequence coverage obtained with 4N1NA is higher than with three other matrices. The formation of c- and a-ions indicates that 4N1NA has both reducing and oxidizing characteristics.
Development and characterization of high-performance functionalized membranes for antibody adsorption
(University of Alabama Libraries, 2012) Shethji, Jayraj Kiritbhai; Ritchie, Stephen M. C.; University of Alabama Tuscaloosa
Capacity and selectivity are the major bottlenecks for the development of affinity membrane adsorbers for protein and antibody purification. The focus of this doctoral research is to develop polyethersulfone (PES) microfiltration (MF) membranes containing multiple highly selective poly(styrene-co-hydroxystyrene) grafts mimicking the key dipeptide Phe-132/Tyr-133 motif of ligand protein A to selectively adsorb immunoglobulin G (IgG) under convective flow conditions. This research work consists of two phases. In phase 1, homopolymer and block copolymer grafts were synthesized and characterized in the membrane pores using monomers styrene, ethoxystyrene, and chloromethylstyrene. 1H NMR characterization showed successful incorporation of the sequential stages of graft chemistry, including: polystyrene, poly(chloromethylstyrene), poly(ethoxystyrene), poly(styrene-b-ethoxystyrene), and poly(styrene-b-chloromethylstyrene). A study of monomer reactivity showed that chloromethylstyrene reacted approximately 1.3 times slower than styrene and ethoxystyrene during formation of homopolymers and block copolymers. The ion-exchange capacity of sulfonated functionalized membranes was 4.9 meq/g with as many as 125 repeat units per chain. In phase 2, PES MF membranes tailored with two different graft chemistries including poly(styrene-co-hydroxystyrene) and glycine functionalized poly((styrene-co-hydroxystyrene)-b-chloromethylstyrene) grafts were developed and tested for selective IgG adsorption. 1H NMR characterization confirmed membrane pore functionalization by poly(styrene-co-hydroxystyrene), chloromethylstyrene block addition, and subsequent glycine functionalization of the chloromethyl block. The dynamic binding capacity (DBC) for IgG was as high as 95 mg/ml, more than 9 times as compared to Sartobind® and Ultrabind® membranes and twice as compared to affinity resin. The DBC was independent of flow rate and there was no significant loss (<5%) in capacity at higher linear velocities (230 cm/h) indicating that the transport of IgG to the adsorptive sites is predominantly by convection. Bind and elute experiments showed that there was no significant loss of DBC over a period of five cycles and the average recovery of antibody was >94%. Competitive sorption using membranes containing negatively charged spacer arms showed that the membrane was ~11 times more selective for IgG than BSA. Additionally, the DBC was 22% higher (115 mg/ml) than without spacer arms indicating that the negatively charged spacer arms moved the grafted chains apart and improved the accessibility of IgG to the binding sites.
Development of hydroxypropyl cellulose-filled poly(2-hydroxyethyl methacrylate) semi-interpenetrating networks for drug delivery
(University of Alabama Libraries, 2010) Melnyczuk, John Michael; Brazel, Christopher S.; University of Alabama Tuscaloosa
Cancer is the second leading cause of death in the United States of America and the National Cancer Institute has released a paper stating that the ideal cancer therapy should have an imaging, targeting, reporting, and therapeutic part. The overall project goal is to be able to create a delivery system that can be triggered externally to the body and can release an anticancer agent in a controlled manner. The current project deals specifically with using hydroxypropyl cellulose (HPC) filled poly(2-hydroxyethyl methacrylate) (PHEMA) (HFPG) hydrogel to cause a release of theophylline when the hydrogel is placed at a temperature above the lower critical solution temperature (LCST) of HPC (57 ºC) and to have no release at normal body temperature, 37 ºC. In a series of polymerization reactions, various compositions of hydroxypropyl cellulose (HPC) filled crosslinked PHEMA gels were synthesized by free radical polymerization. The LCST for different average molecular weights, M̅_n, of HPC were found to be 44.8 ºC ± 0.8, 48.7 ºC ± 0.3, and 46.2 ºC ± 0.7 for 80,000, 100,000, and 370,000 M̅_n HPC respectively. A change in concentration of HPC with a M̅_n 80,000 from 0.01 to 0.05 g/mL showed an increase in the LCST from 44.8 ºC ± 0.8 to 46.6 ºC ± 1.0. Changing the media from water to 0.65M sodium chloride change LCST from 46.6 ºC ± 1.0 to 35.4 ºC ± 2.3. The swelling study showed the mesh size was unaffected by synthesis temperature, analytical temperature, and HEMA to HPC ratio, indicating that HPC was pore-filling. Mechanical testing confirmed the results of the swelling study, in that there was no net change in the calculated mesh size with a change in analytical or synthesis temperature by either method. This study showed that HPC did change the mesh size with a change in the HEMA:HPC ratio. Dissolution testing for the release of theophylline from the HFPG hydrogel showed an increased release rate with an increase in analytical temperature was possible. The increase in synthesis temperature increased the release rate. It is shown that an increase in the HEMA:HPC ratio with a decrease in the diffusion coefficient. The HPC collapsed and evolved out of the HFPG and this effect could produce a higher diffusion. Further investigations should be conducted to test the effects of different initiators and crosslinking ratio's on the release of HFPG hydrogels.
The effects of physiological fluid shear stress on circulating tumor cells
(University of Alabama Libraries, 2018) Triantafillu, Ursula Lea; Kim, Yonghyun; University of Alabama Tuscaloosa
The focus of this dissertation is on the effects of physiological fluid shear stress (FSS) on circulating tumor cells (CTCs). FSS occurs on cells both in vitro and in vivo. FSS is typically considered as a major variable in large scale bioprocessing while FSS is assumed to have a negligible role in bench scale culture. In physiological settings, FSS impacts cells in cancer where local, regional, and distant cancers experience FSS through interstitial, lymphatic, and hematological flow, respectively. CTCs in hematological flow experience the highest FSS and are involved in the transit stage of metastasis. One challenge of metastatic cancer is the lack of secondary tumor detection. Detection of CTCs largely relies on the epithelial cell adhesion molecule (EpCAM). CTC phenotype also includes expression of cancer stem cell (CSC) and epithelial to mesenchymal transition (EMT), which are correlated to increased resistance to chemotherapy. The study of FSS using an in vitro model can provide a better understanding on CTC phenotype expression and drug resistance. FSS was first examined using a baseline study with in vitro cell spheroid culture. Spheroids provide better representation of the stem and tumor cell environment than 2D culture. These cells experience FSS during cell dissociation. Since FSS can detrimentally affect cells, a gentler mechanical platform was developed for dissociation. Furthermore, this method, as well as traditional dissociation methods, was tested to study how FSS affects cell viability and expression. This platform was further used to model breast CTCs as suspension cells under FSS. This metastatic model allowed for testing the effects of FSS on CTC phenotype, and it was found that FSS increased CSC and CTC expression. Since an increase in CSC expression is correlated to increased drug resistance, drug resistance on CTCs under FSS was tested with chemotherapy drugs. It was found that the combination of FSS and drug resistance synergistically increases drug resistance expression in the model CTCs, corroborating clinical reports of CTC drug resistance. Finally, the effects of FSS and drug resistance was tested on estrogen receptor positive (ER+) molecular subtype. Collectively, these studies provide a better understanding on CTC behavior during metastasis.
Electrodeposition of Cobalt for Advanced Interconnect Applications
(University of Alabama Libraries, 2021) Hu, Yang; Huang, Qiang; University of Alabama Tuscaloosa
Copper (Cu) damascene processes have been used to produce back end of line (BEOL) interconnect structures in integrated circuits (IC). As the critical dimension of BEOL structures approaches the electron mean free path of Cu or below, the Cu resistivity exponentially increases, posing significant challenges on further scaling. Metals with shorter electron mean free path, for example cobalt (Co), have been explored as the alternative material to replace Cu in the finest metal levels.The Co electrodeposition process for interconnect applications must produce Co films that can reproducibly fill deep vias or trenches without any defects. It is can be achieved by adding small amounts of organic additives to the plating bath, which lead to the Co electrodeposition preferentially at the bottom of trench, known as bottom-up filling, or super conformal filling, or simply “super-filling”. As the size of interconnect continues to shrink, additives are becoming the key to the successful application of Co electrodeposition in IC manufacture. In this dissertation, a new class of organic additives, dioximes (dimethylglyoxime, cyclohexane dioxime, and furil dioxime), have been investigated for their effects on the electrochemical deposition process of cobalt. In Chapter 2, the nucleation and growth behavior of Co deposition with the addition of dimethylglyoxime and cyclohexane dioxime are studied. Double-peak nucleation curves are observed during Co deposition for the first time. In Chapter 3, a descriptive model is established for the Co nucleation process using furil dioxime, where the suppression effect on Co deposition and the catalytic effect on hydrogen evolution are both more pronounced among the dioxime molecules. Mercaptopropanesulfonate, or MPS, a well-known accelerator used in Cu damascene process, is investigated during the Co deposition in Chapter 4. A potential oscillation is observed during galvanostatic deposition for the first time and a kinetically controlled mechanism is proposed. In Chapter 5, Co films are electrodeposited with different additives including dimethylglyoxime, sodium chloride, and 3-mercapto-1-propanesulfonate. It is found that the addition of 3-mercapto-1-propanesulfonate into the electrolyte significantly increases the S incorporation level and decreases the grain size, both contributing to a higher sheet resistance of film.
Electrodeposition of materials from novel solvents
(University of Alabama Libraries, 2019) Sides, William Donald; Huang, Qiang; University of Alabama Tuscaloosa
The electrodeposition of metals and alloys is explored with a focus on solvents and additives capable of reducing or eliminating hydrogen evolution while operating at highly cathodic potentials. The nucleation and growth behavior of binary codepositing systems are modelled in Chapter 2. Deep eutectic solvents based on choline chloride and urea are demonstrated to be capable of electrodepositing metallic manganese for the first time in Chapter 3. Chapter 4 describes the first time manganese has been incorporated into an electrodeposited magnetic iron-group alloy. Water-in-salt electrolytes are applied to the electrodeposition of metals in Chapters 5 and 6. These electrolytes are shown to suppress the proton reduction reaction and subsequent hydrogen evolution in aqueous systems. The tetrabutylammonium ion is also shown to be capable of suppression of proton reduction. The origins of this suppression are examined in Chapter 6, and it is determined that the additive adsorbs onto the electrode surface, blocking proton access. The suppressing behaviors of tetrabutylammonium and water-in-salt electrolytes are combined to achieve significant suppression of proton reduction and the ability to electrodeposit metals at highly negative cathodic potentials. Chapter 6 describes the use of these solvents to electrodeposit ruthenium for interconnect applications. The origin of enhanced superconductivity in rhenium electrodeposited from water-in-salt electrolytes is explored in Chapter 5. A disordered atomic structure is found to be highly correlated with enhanced superconductivity.
Engineering Approaches to Study and Target Breast Cancer Brain Metastasis
(University of Alabama Libraries, 2020) Narkhede, Akshay; Rao, Shreyas S; University of Alabama Tuscaloosa
Breast cancer brain metastasis marks the most advanced stage of the disease with the median survival period of only 4-16 months. A major hurdle in developing therapeutic strategies to tackle breast cancer brain metastasis is our limited understanding of mechanisms involved in metastatic progression of breast cancer to the brain. This is, in part, due to lack of biomimetic in vitro models to study the interactions between metastatic breast cancer cells and the brain microenvironment. In addition, challenges associated with ineffectiveness of current diagnostic as well as therapeutic techniques in crossing the blood-brain barrier, and specifically labeling and targeting cancer cells pose further difficulties in treating metastatic brain malignancies. To address this issue, this dissertation focuses on engineering an in vitro hyaluronic acid (HA) hydrogel-based platform to investigate the microenvironmental regulation of breast cancer brain metastasis. HA hydrogel was chosen as it recapitulates key bio-physical and bio-chemical aspects of the native brain microenvironment. Specifically, this in vitro HA hydrogel-based platform was utilized to elucidate the mechanobiology underlying breast cancer brain metastasis. Further, the HA hydrogel-based platform was also adapted to model dormancy associated with brain metastatic breast cancer cells. Taken together, the in vitro biomimetic HA hydrogel-based platform for studying microenvironmental regulation of breast cancer brain metastasis, as presented in this dissertation, is a promising first step towards development of robust biomimetic strategies for studying breast cancer brain metastasis in a controlled setting. Finally, this dissertation also focuses on investigating the potential of ultrasmall iron oxide nanoparticles (< 4 nm) for labeling primary and metastatic brain cancer cells in vitro; to be utilized as a platform for tumor-targeted drug delivery and in imaging and early detection. Ultimately, such engineering approaches could provide mechanistic insight into the progression of breast cancer brain metastasis and enable the development of targeted therapeutics for the metastatic disease.
Enhanced biogas production through the optimization of the anaerobic digestion of sewage sludge
(University of Alabama Libraries, 2011) Beam, Ryan Grant; Ritchie, Stephen M. C.; Clark, Peter E.; University of Alabama Tuscaloosa
The anaerobic digestion of sewage sludge has long been used for solids reduction by wastewater treatment facilities, but has gained recognition as a form of energy production. Biogas is formed as a byproduct of anaerobic digestion and is composed mostly of methane and carbon dioxide with other trace elements. The focus of this thesis is the enhancement of biogas production through the optimization of the anaerobic digestion of sewage sludge. Batch experiments showed that digest pH is indicative of the current stage of digestion. This will provide wastewater treatment facilities with a way to monitor digester activity, as each stage of digestion was identified through constant pH monitoring. The digestion process was optimized through various parametric studies designed to determine the effect of each parameter and find an optimal range for operation. The optimum range for pH was 7.0-7.5. Testing of temperature showed that the mesophilic range (30-40°C) provided the highest, most constant gas production. Alkalinity adjustment with magnesium hydroxide increased both pH and alkalinity. Biogas production was highest in samples with alkalinity ranging from 2,000-2,500 mg/L as CaCO_3 . Volatile fatty acid (VFA) adjustment with sodium propionate increased both alkalinity and VFA content within the digest. High levels of VFA caused digestion to struggle while small adjustments showed an increase in production. Pressure measurement showed that an increase in pressure during digestion improved both the quality and quantity of produced biogas. Semi-continuous experimentation showed consistent biogas production. However, high VFA content resulted in poor gas quality. Digester energy balances completed at the Hilliard-Fletcher Wastewater Treatment Plant showed that 1,705 m^3/day biogas are required for daily operation (basis: 60:40 ratio CH_4 :CO_2 ). Parametric tests showed the ability to provide up to 1,944 m^3/day at a methane content of 80%. Increasing the methane content from 60 to 80% increases the heating value of the gas by one-third, requiring less gas for daily operation. This allows for better energy efficiency. All gas volumes are reported at atmospheric pressure and a temperature of 35°C. Future work will focus on the effect of pressure to identify the extent with which it affects digestion.
Enhanced oil recovery simulation study for Citronelle field, Alabama
(University of Alabama Libraries, 2012) Cox, William Brannon; Carlson, Eric S.; University of Alabama Tuscaloosa
The world is on the verge of an energy crisis due to rising demand for fossil fuel to meet both domestic and industrial energy requirements. In order to meet this rising fossil fuel need, it is important that enhanced oil recovery (EOR) schemes, which are more efficient hydrocarbon recovery techniques than primary and secondary recovery methods, are used to recover conventional oil reserves from already discovered fields. Continuous CO2 and the Water Alternating Gas (WAG) injection schemes are two basic EOR techniques for gasflooding reservoirs. The primary objective of this research project focuses on enhancing oil recovery from a very small pilot area of Citronelle oil field using CO2 miscible flooding. The miscible flood performance of carefully targeted CO2 injection was modeled using a fine-scale open source compositional simulator nSpyres. The simulation runs were performed using regular grids with a total of 8.2 million cells. The CO2 injection pilot did not result in any new recovery. However, it helped identify many crucial characteristics for consideration in a comprehensive CO2 project for entire Citronelle field, such as non-workability of WAG scheme due to loss of injectivity after converting back to water injection, presence of natural and induced fractures that affects flood performance, as well as operational issues - down-hole pumps, well integrity, and difficulties with data collection due to the mixing of "power oil" with produced oil - which will need thorough consideration.
Enhancing the pre-polymerization coordination of 1-vinylimidazole in bulk solution with ionic liquid additions
(University of Alabama Libraries, 2015) Hamilton, Jackie Ryan; Turner, C. Heath; University of Alabama Tuscaloosa
Recent experimental investigations have found that the photopolymerization of 1-vinylimidazole (VIm) can be significantly accelerated with the addition of lithium bis(trifluoromethylsulfonyl)-imide (LiTf2N). However, a clear explanation for this phenomenon is lacking, and the underlying molecular level interactions in such a system are unknown. The two components, VIm and LiTf2N, are soluble over a wide range of concentrations at ambient temperature, and if the fundamental behavior of this mixture can be clearly quantified, there are significant opportunities for tuning the polymerization dynamics, polymer structure, and properties. In this work, molecular dynamics simulations are used to model the underlying pre-polymerization structure of VIm/LiTf2N mixtures at several different concentrations. It is found that the Li+ enhances the site-site interactions of key sites involved in the polymerization, and this is suggested to play a major role in the experimentally-observed enhancement of the polymerization behavior.
Evaluation of fluid dynamic effect on thin film growth in a horizontal type meso-scale chemical vapor deposition reactor using computational fluid dynamics
(University of Alabama Libraries, 2013) Tabatabaei Sadeghi, Sahar; Klein, Tonya M.; University of Alabama Tuscaloosa
To design and analyze chemical vapor deposition (CVD) reactors, computer models are regularly utilized. The foremost aim of this thesis research is to understand how thin film uniformity can be controlled in a CVD reactor. A complete understanding of chemical reactions that take place both in gas phase and at the deposition surface is required to predict thin film properties such as growth rate and composition precisely, however, deposition rates and surface topography can be determined by the arrival flux of reactants in a mass-transfer limited regime. In order to understand experimental thickness and roughness uniformity, a predictive model has been developed to study the fluid dynamic effect on thin film growth in a horizontal type reactor using velocity, temperature, pressure and viscosity as tunable parameters upon which velocity profiles within a CVD reactor have been evaluated using computational fluid dynamic (CFD) calculations. Through this predictive model, it is shown that fluid velocity is the major variable contributing to transverse roll cell formation compared to temperature and pressure gradients present during thin film deposition in a meso-scale CVD reactor. These results provide a physical insight regarding improved reactor operation conditions that influence uniformity.

Browse

Browsing Theses and Dissertations - Department of Chemical & Biological Engineering by Title

Results Per Page

Sort Options