Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001. / Includes bibliographical references. / (cont.) The vectorial energy transfer design of sensory films to harvest and direct energy to the surface detection layer toward ultimate signal amplification has been discussed. Third, the role of chemical structure of a sensory polymer in the selectivity of a conjugated polymer-based fluorescent sensor has been examined. In two different sensory systems for the detection of potassium ions and a nitroaromatic explosive TNT, respectively, key chemical design parameters governing their selectivity have been rationalized. Finally, the combination of the conclusions of this thesis provided an idealized structure of a fluorescent conjugated polymer-based sensory film with optimized sensitivity and selectivity. / A sensor is one of the many important applications of conjugated polymers. Poly(p-phenylene ethynylene)s (PPEs) have been studied for fluorescence-based sensor applications. The chemical structure and nano-structure of a polymer in the solid-state are two critical parameters that determine sensitivity and selectivity of a conjugated polymer-based sensor. In this thesis, both parameters have been systematically investigated. First, the Langmuir-Blodgett method was used to control the nano-structure of PPEs in the solid-state. Rational design of surfactant PPEs made it possible to control the conformation of a single polymer strand and interpolymer spatial arrangement at the air-water interface. In situ UV-Vis and fluorescence spectroscopy on the Langmuir film in controlled nano-structures revealed the effects of conformation and spatial arrangement of conjugated polymers on their intrinsic optical properties. Since the controlled structure of a monolayer at the air-water interface can be transferred to a solid substrate, structurally well-defined multilayer LB films of PPEs with confined optical properties were fabricated. This made it possible to study the role of interpolymer aggregation in the photophysical properties of conjugated polymer films. The results provided a general design principle to make a highly emissive conjugated polymer film. Second, an ideal thickness of a sensory film for optimizing sensitivity was determined by experimental and theoretical analysis of energy transport phenomena in multilayer PPE films. / y Jinsang Kim. / Ph.D.

Thesis: S.B. in Archaeology and Materials, Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 46-49). / Obsidian is known to have been used for tool making in Kenya since the Early Stone Age, appearing as early as 974 thousand years ago (Durkee and Brown, in press). Past research has shown that the study of obsidian artifacts, and the determination of their provenance, can be very useful in reconstructing past civilizations and analyzing the spread of technology and trade. A number of different analytical techniques have previously been utilized to characterize obsidian sources for such studies, including magnetic analysis. This thesis reports the results of a preliminary study to explore the potential of utilizing magnetic analysis for the characterization of obsidian sources in Kenya. A total of 192 samples from 23 localities, belonging to 6 broadly defined petrologically distinct source groups, were analyzed using a vibrating sample magnetometer to test saturation magnetization (Ms), remanence magnetization (Mr), and coercivity (Hc). Comparing the ratio of Mr/Ms with Hc allowed clear differentiation among three of the analyzed obsidian sources (Groups 14, 19, and 29 from Merrick and Brown 1984a). The magnetic signatures reveal clues about the microscopic Fe mineral grains present in the samples, suggesting that magnetic characterization also has the potential to provide additional value as a supplementary technique to chemical analysis. Based on these preliminary results, it is proposed that future studies could examine the temperature dependence of the magnetic properties of obsidian to provide more complete characterization of the obsidian sources. / by Elizabeth A. Krueger. / S.B. in Archaeology and Materials

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1990. / Vita. / Includes bibliographical references (leaves 221-229). / by Hee-Kyung Moon. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994. / Includes bibliographical references (leaves 73-74). / by Jun Funatsu. / B.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, June 2004. / "May 2004." / Includes bibliographical references (leaves 18-19). / Magnetostriction measurements were taken on samples of Fe-Ga alloys (Galfenol) containing between 18% and 35% Ga in fields of 5 kOe to 24 kOe from room temperature to liquid nitrogen temperature. In addition, room temperature magnetic anisotropy measurements were conducted on samples between 8% Ga and 25% Ga. No major hysteresis was found in any of the samples and the field dependence was found to be modest (-2%). Anomalous temperature dependence was found in 22-24% Galfenol, where magnetostriction decreased with decreasing temperature, and 35% Galfenol, where magnetostriction increased dramatically (over 50% to values up to about 250 parts per million) with decreasing temperature. Quenching to retain [alpha]-iron and B2 (CsCl) phases was found to increase magnetostriction, with the B2 structure creating the largest magnetostriction. The reasons for the atypical temperature dependence and the B2 structure enhancing magnetostriction are still unexplained. K anisotropy constants were found to decrease with increasing Ga concentration, but more samples need to be measured to validate this trend. / by Jenny Lichter. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004. / Includes bibliographical references. / by Whitney Gaynor. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1989. / Includes bibliographical references (leaves 114-116). / by Thomas Miller Harris. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996. / Includes bibliographical references (p. 79-82). / by Lawrence J. Foley. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 195-203). / The research objective is to design a micro-bioreactor for the culture of Chinese Hamster Ovary (CHO) cells. There is an increasing demand for upstream development in high-throughput micro-bioreactors specifically for the recombinant CHO cell line, an important cell line for producing recombinant protein therapeutics. In order to translate a micro-bioreactor originally designed by our group for bacteria to CHO cells, there would need to be significant modifications in the design of the micro-bioreactor due to the extreme sensitivity of CHO cells to physical and chemical stresses. Shear stresses inside the growth chamber will have to be reduced by three orders of magnitude. Moreover, the long doubling time of CHO cells requires a 2 weeks long culture. In a high surface to volume ratio micro-bioreactor, evaporation becomes a major problem. Contamination control is also vital for CHO cultures. In addition, the offline sampling volume required for validation necessitates a doubling of the working volume to 2mL. The newly designed Resistive Evaporation Compensated Actuated (RECA) micro-bioreactor is fully characterized in this thesis to ensure that the design meets the physical specifications of the required CHO cell culture conditions. The RECA micro-bioreactor will be tested with industrial recombinant CHO cell lines. This work is done in collaboration with Genzyme, USA and Sanofi-Aventis, Frankfurt. In this thesis, we also propose the use of dielectric spectroscopy electrodes for online cell viability sensing of CHO cells in micro-bioreactors. The electrodes are fabricated on polycarbonate, a biocompatible and optically clear thermoplastic that will be one of the future base material for microfluidic devices which can be rapidly prototyped. To demonstrate the viability of dielectric spectroscopy as an online viability sensor for CHO cells in a micro-bioreactor, the electrodes are used to characterize samples taken daily from a CHO shake flask batch culture without any sample modifications. Two different electrode geometries and correction methods will be compared to find the optimal system for viability measurements in a micro-bioreactor. / by Shireen Goh. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references (leaves 166-169). / Model bicrystals made by adhering pieces of near-single-crystal styrene-isoprene-styrene (SIS) cylindrical block copolymer (BCP), produced by a roll-casting process; yield various types of pure tilt grain boundaries. The study of the deformation of the bicrystals, each containing one grain boundary, enables a deeper understanding of the influences grain boundaries and the incompatibilities between them have on mechanical behavior. Mechanical properties and deformation of near-single-crystal systems provide a reference base for the expected bicrystal behavior. We consider various aspects of incompatibility that can arise from joining two highly anisotropic grains together (i.e. Young's modulus, Poisson's ratio, deformation mode(s)). Experimentally, the structure of grain boundaries was characterized using atomic force microscopy (AFM). In deformation experiments, optical microscopy was employed to examine the deformation gradient in the specimen and in situ small angle x-ray scattering (SAXS) was used to monitor the microdomain structural evolution. Finally, finite element simulations illustrated the state of strains of the bicrystal. The symmetric (45-45) bicrystal turns out to be the most complex system, despite of the simplest geometry. / (cont.) Due to the opposite orientation of the grains, the deformation of the symmetric bicrystal results in a rigid translation of the grain boundary. A triangular shaped influence region indicates that the influence distance varies along the grain boundary length. A portion of the influence region has limited expansion and is slightly sheared along the grain boundary. Another portion of the influence region experiences high tension. For the asymmetric (90-45) bicrystal, the deformation is mostly influenced by the difference in deformation modes: dilation vs. shearing. The distortion due to deformation in the diagonal grain induces rotation and advances the deformation in the perpendicular grain near the grain boundary. For the asymmetric (90-0) bicrystal, the most influential factors are the Young's modulus and the Poisson's ratio. The much softer perpendicular grain assumes most of the deformation by extensive dilation and lateral contraction. Near the grain boundary, the perpendicular grain is constrained by the rigid parallel grain such that its deformation is impeded. The influence region in the perpendicular grain is narrow and invariant along the grain boundary length. / by Panitarn Wanakamol. / Ph.D.