Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1974. / Bibliography: leaves 272-278. / by Donald B. Anthony. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1989. / Includes bibliographical references (v. 2, leaves 199-205). / by Larry S. Monroe. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 79-82). / The organization and intricacy of the central and peripheral nervous systems pose special criteria for the selection of a suitable scaffold to aid in regeneration. The scaffold must have sufficient mechanical strength while providing an intricate network of passageways for axons, Schwann cells, oligodendrocytes, and other neuroglia to populate. If neural regeneration is to occur, these intricate passageways must not be impeded by macrophages, neutrophils, or other inflammatory cells. Therefore it is imperative that the scaffold does not illicit a severe immune response. Biodegradable electrospun fibers are an appealing material for tissue engineering scaffolds, as they strongly resemble the morphology of extracellular matrix. In this study, electrospun fibers composed of poly(L-lactic acid) (PLLA) and polycaprolactone (PCL) were prepared with and without the steroid anti-inflammatory drug, dexamethasone, encapsulated. Histological analysis of harvested subcutaneous implants demonstrated the PLLA fibers encapsulating dexamethasone (PLLA/dex fibers) evoked a much less severe immune response than any other fiber. These findings were supported by in vitro drug release data showing a controlled release of dexamethasone from the PLLA/dex fibers and a burst release from the PCL/dex fibers. The ability of the PLLA/dex fibers to evade an immune response provides a very powerful tool for fabricating tissue engineering scaffolds, especially when the stringent demands of a neural tissue engineering scaffold are considered. Structural support and contact guidance are crucial for promoting peripheral nerve regeneration. A method to fabricate peripheral nerve guide conduits with luminal, axially aligned, electrospun fibers is described and implemented in this study. The method includes the functionalization of the fibers with the axonal outgrowth promoting protein, laminin, to further enhance regeneration. The implantation of stem cells at the. site of a spinal cord or peripheral nerve lesion has been shown to promote nerve regeneration. Preliminary work to isolate and culture pluripotent, adult neural stem cells for seeding on the above mentioned scaffold is also described here. / by Nathaniel Vacanti. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Organic photovoltaics (OPVs) have received significant interest for their potential low cost, high mechanical flexibility, and unique functionalities. OPVs employing semiconducting polymers in the photoactive layer have traditionally been fabricated almost exclusively with solution-based techniques due to a lack of suitable alternatives. This has thus limited polymer solar cells and other polymer electronic devices to using polymers that are soluble. Here we explore the use of oxidative chemical vapor deposition (oCVD), a vacuum-based method, for the deposition of semiconducting polymers. Polymer deposition by oCVD occurs at moderate vacuum (~0.1 Torr) and low temperature (25 - 150°C). oCVD offers the well-cited processing benefits of vacuum processing, including parallel and sequential deposition, well-defined thickness control and uniformity, and inline integration with other standard vacuum processes (e.g. vacuum thermal evaporation). Various semiconducting polymers, including insoluble polymers that are difficult to process using conventional methods, are successfully deposited via oCVD by changing the monomer precursor. The optoelectronic properties of unsubstituted polyisothianaphthene (PITN) and unsubstituted polythiophene (PT) are first investigated under various oCVD deposition conditions. Higher stage temperatures are shown to increase conjugation in PITN films, resulting in a significant red-shift in the absorption spectrum and a decrease in the optical bandgap from 1.14 to 1.05 eV. The effects of oCVD chamber pressure on the properties of PT are then investigated. Higher chamber pressures are found to correlate with greater conjugation, increased absorption, and larger field effect mobilities in PT films. oCVD PT films are then successfully integrated into planar heterojunction OPVs as the electron donor layer, achieving power conversion efficiencies up to 0.8%. Several alternative device architectures are investigated as means to improve OPV device performance. Promisingly, a ternary energy cascade device architecture is shown to more than double the OPV device performance to over 2%. / by David Christopher Borrelli. / Ph. D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1930. / Includes bibliographical references (leaf 39). / by Elmer W. Harmon, Morris N. Young. / B.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 231-249). / The noble metals (NMs) comprise ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au). Together, these corrosion-resistant elements serve as nature's universal catalysts by binding reactant molecules neither too strongly nor too weakly. This allows for rapid catalytic transformations of reactants into useful products. Modern society, its current technologies, and its emerging renewable energy technologies are underpinned by precious metal catalysts. However, the noble metals are the least abundant elements in the lithosphere, making them prohibitively scarce and expensive for future global-scale technologies. Furthermore, the traditional catalyst engineering toolkit is ill-equipped to optimize the reactivity, stability, and loading of NM catalysts. The technologies developed in this thesis have two overarching implications. First, a method is developed to engineer non-sintered and metal-terminated transition metal carbide (TMC) nanoparticles. Featuring "noble metal-like" surface reactivity, TMCs are earth-abundant and exhibit many useful catalytic properties, such as carbon monoxide and sulfur tolerance. By designing TMC nanoparticles with controlled surface properties, this thesis offers new avenues for replacing noble metal catalysts with inexpensive alternatives. Second, a method is developed to synthesize TMC nanoparticles coated with atomically-thin noble metal monolayers. This offers new directions for improved catalyst designs by substantially enhancing reactivity and stability while reducing overall noble metal loadings. These synthetic achievements in nanoscale core-shell catalyst engineering were guided by computational quantum chemistry, model thin film studies, and advanced spectroscopic techniques. Examination of the catalytic utility of these new materials was performed in the context of water electrolysis, proton exchange membrane fuel cells, direct methanol fuel cells, and high temperature thermal reforming. / by Sean Thomas Hunt. / Ph. D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1985. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 275-284. / by Myongsook Susan Oh. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1997. / Includes bibliographical references (leaves 278-299). / by Alice Weimin Liu. / Ph.D.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 134-145. / by Sang-Chun Rah. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2006. / Includes bibliographical references (p. 287-294). / Metabolic Flux Analysis (MFA) has emerged as a tool of great significance for metabolic engineering and the analysis of human metabolic diseases. An important limitation of MFA, as carried out via stable isotope labeling and GC/MS measurements, is the large number of isotopomer equations that need to be solved. This restriction reduces the ability of MFA to fully utilize the power of multiple isotopic tracers in elucidating the physiology of complex biological networks. Here, we present a novel framework for modeling isotopic distributions that significantly reduces the number of system variables without any loss of information. The elementary metabolite units (EMU) framework is based on a highly efficient decomposition algorithm identifies the minimum amount of information needed to simulate isotopic labeling within a reaction network using knowledge of atomic transitions occurring in the network reactions. The developed computational and experimental methodologies were applied to two biological systems of major industrial and medical significance. First, we describe the analysis of metabolic fluxes in E. coli in a fed-batch fermentation for overproduction of 1,3-propanediol (PDO). / (cont.) A dynamic 13C-labeling experiment was performed and nonstationary intracellular fluxes (with confidence intervals) were determined by fitting labeling patterns of 191 cellular amino acids and 8 external fluxes to a detailed network model of E. coli. We established for the first time detailed time profiles of in vivo fluxes. Flux results confirmed the genotype of the organism and provided further insight into the physiology of PDO overproduction in E. coli. Second, we describe the analysis of metabolic fluxes in the pathway of gluconeogenesis in cultured primary hepatocytes, i.e. isolated liver cells. We applied multiple 13C and 2H-labeled tracers and measured isotopomer distributions of glucose fragments. From this overdetermined data set we estimated net and exchange fluxes in the gluconeogenesis pathway. We identified limitations in current methods to estimate gluconeogenesis in vivo, and developed a novel [U-13C,2Hs]glycerol method that allows accurate analysis of gluconeogenesis fluxes independent of the assumption of isotopic steady-state and zonation of tracers. The developed methodologies have wide implications for in vivo studies of glucose metabolism in Type II diabetes, and other metabolic diseases. / by Maciek Robert Antoniewicz. / Ph.D.