Luminescent molecules and polymers are active component in light-emitting diodes; however, the aggregation and excimer formation in concentrated solution or in the solid film states had limited their applications. Therefore, this study used poly(methyl methacrylate) (PMMA) as separator to prevent the formations of aggregate and excimer and to enhance quantum efficiency. Basically, two systems are involved: (1) Inorganic phosphorescent irdium complex PMMA was doped with inorganic iridium complex IrQB by using THF as solvent. IrQB/PMMA films prepared from dilute solutions exhibit two emissions centered at 560 and 640 nm, respectively; in contrast, only 640-nm emission was observed for films from concentrated solutions. Experimentally, these two bands showed variations on the emission intensity with increasing temperature. Aggregation of IrQB is suggested to be responsible for the 560-nm emission. Chain conformation of PMMA in the solution state strongly affects the incorporated IrQBs and their emission properties. (2) Polybenzoxazines Polybenzoxazines with the built-in fluorenscent fluorine moiety are linear in nature; however, the inherent hydrogen-bond (H-bond) interactions in polybenzoxazines decrease the inter-chain distance and cause the chain aggregation. With the added PMMAs, new H-bonding from the carbonyl groups in PMMA and the hydroxyl groups in polybenzoxazine enhances the mutual miscibility between these two components and decreases the possibility of aggregate formation in polybenzoxazines. Quantum efficiency is therefore promoted by this approach.

Graduation date: 1993

NMR Instrumentation

Soil salinity is a serious environmental stress threatening productivity of major crops worldwide. Among the various biotic and abiotic strategies that exist, transgenic technologies provide a promising avenue to reduce yield losses in crops under saline environments. Recently, transgenic technology involving the TMT gene encoding thiol methyltransferase enzyme has been suggested as an effective solution for engineering a chloride detoxification capability into a high value crops to improve tolerance against chloride ion toxicity under saline environments. This proposed mechanism, however, results in the emission of methyl chloride (CH3Cl) from plants, which has deleterious effects on stratospheric ozone. This study was performed to examine the relationship between salt tolerance and chloride volatilizing capacity of transgenic plants containing TMT gene as well as to explore the possibility of generating transgenic rice crop containing TMT gene for salinity tolerance. To achieve these objectives, transgenic tobacco plants containing TMT gene were grown in comparison with wild type tobacco plants under three levels of sodium chloride (NaCl) salinity (0, 100 and 200 mM), three levels of soil water content (40%, 60% and 80% of the field capacity) and their tolerance to NaCl and water stress was studied. Plant growth parameters recorded included plant height, number of leaves, leaf area, stem dry weight, leaf dry weight, root dry weight, plant dry biomass and root/shoot ratio. Similarly, both types of plants were exposed to five levels of NaCl concentrations (0, 50, 100, 150 and 200 mM) and three levels of soil water content (40%, 60% and 80% of the field capacity), and the quantity of CH3Cl emitted was recorded. Significant decrease in plants growth parameters of both types of plants were recorded upon exposure to salinity and water stress. Under 100 mM NaCl, however, transgenic plants showed better tolerance to salinity by suffering less reduction in growth parameters compared to wild type plants. Under 200 mM NaCl, growth of both types of plants was completely inhibited. The interactive effects of salinity and water stress were more pronounced in wild type plants than in transgenic plants. Results also showed that all engineered plants acquired an ability to efficiently transform chloride ion to CH3Cl, and the rate of such transformation was higher under greater NaCl and soil water content compared to lower NaCl concentrations and soil water content. In order to explore the possibility of generating a transgenic food crop using TMT gene, a hypothetical transgenic rice crop was grown over 27 million hectares of the saline coastal areas of south and southeast Asia and the possible emission of CH3Cl from such ecosystem was inferred based on the CH3Cl emission data obtained from transgenic tobacco plants. The estimates showed that the possible CH3Cl emission from such ecosystem would be 219.21 Gg which is equivalent to 5.36 % of the global atmospheric emissions of CH3Cl.

No description available.

No description available.

Nowadays, the common method to make an alignment layer of liquid crystal display is rubbing Polyimide (P.I.) thin film, Unfortunately, the rubbing method will reduce the yield of LCDs because of the particles, electrons, etc. created during rubbing on the surface of PI film. therefore many effort have been made to develop the non-contacting method such as photo alignment, plasma alignment, etc. This research focus on the non-contacting method, we hope it will reduce many pollution compared to rubbing alignment. Comparing with PI, polydimethylsiloxane (PDMS) possess higher transparency, batter stability in thermal and chemical, and lower surface free energy about 19 mJ/m^2. Due to the low surface free energy, PDMS can be used as a vertical alignment layer without any surface treatment. Methyl Red (MR) PDMS mixed with PDMS will be used as an alignment layer in this experiment. And the rod-like azo-dye will change its molecular to rotate because the absorption of linear polarized light. By changing the s MR to rotate, we can obtain a micro groove structure on PDMS surface and control the direction of liquid crystals further. Xenon lamp(100nm-1200nm) and the ultraviolet ray lamp (300-500nm) were used in this experiment for thin film. Samples were exposure with different incident angle and intensity of light, respectively, and discussed with different temperature as a factor. According to atomic force microscope ( AFM ) result, we can obtain a PDMS surface with micro groove structure by using Xe lamp and ultraviolet ray, and we can observe the changing tilt angle of liquid crystals by polarized optical microscope (POM).

The thiolate-alkylating protein (Ada protein) is a zinc protein that repairs the defective DNA by transferring methyl group on to itself. We have used the thiophenylphosphine ligand to provide sulfur-rich environment for model study. In this work, we have accidentally found that this zinc complex can activate CH2Cl2 to generate a methylenated complex (4). Carbon-halide activation is commonly used in organic synthesis. However activation of C-Cl bond is comparatively scarce compared to C-Br or C-I bonds. Varying the degree of deprotonation on the PS3 ligand, a simple zinc dimer (2) can be obtained instead of (4). The dimer (2) can even react with much milder alkyl-reagent, methylphosphotriester. Therefore (2) serves as a successful Ada protein model in this sense. Other related alkyl-transfer reactions using different ligand or zinc complexes were discussed to give insight of the methyl-transfer action of Ada protein.

Thesis (Ph. D.)--University of Michigan, 1928. / "By Willard H. Bennett and Charles F. Meyer." From Physical review, v. 32, Dec., 1928.

No description available.