Allopolyploids are formed by interspecific hybridization and whole genome duplication, with the resulting organism contains multiple distinct subgenomes in one nucleus. Subgenomic interactions result in massive genetic and epigenetic reconstruction, contributing to variable phenotypic traits noted in newly formed allopolyploids. To better understand these mechanisms in the context of molecular biology, evolution, and plant breeding, plant biologists study the model organism Brassica napus (farmed as canola or oilseed rape). With white-flowering and yellow-flowering progenitors, flower color phenotype of B. napus presents an opportunity to examine subgenomic interactions. CAROTENOID CLEAVAGE DIOXYGENASE 4 (CCD4) is known to play a major role in determining flower color phenotype of carotenoid-synthesizing angiosperms. Here, we investigate the genetic and epigenetic role of CCD4 orthologs and their role in flower color phenotype of B. napus.

<p> A microscopic study of two samples of the Gowganda Formation, both having undergone pure shear deformation at greenschist f acies metamorphism has shown: Sample A -Reduction in quartz grain size, and pressure solution shadows were evidence for strong pressure solution activity. Pre-lithification fractures provided channelways for the removal of quartz and water out of the system. Matrix quartz was not recrystallized. Sample B -Extensive local recrystallization of quartz due to pressure solution activity caused metamorphic segregation and the formation of a cleavage. Cleavage behaviour differs in the matrix from that observed in an area of contact strain, as produced by a buckled quartz vein. There is no evidence for removal of quartz from the system. </p> <p> A comparison between the two samples suggests that (a) water, in this case at least, is necessary to produce metamorphic segregation, (b) the system has to be closed to reach metamorphic segregation and (c) original features may be preserved through limited metamorphism if the rock is dried out early in its history. </p> / Thesis / Bachelor of Science (BSc)

<p> The key objective of this research was to study the rates of the chemical cleavage of benzyl-silicon bonds in small model molecules, oligomers, polymers, copolymers, and crosslinked microspheres and microgels.</p> <p> Substrate species including benzyltrimethylsilane (BTMS), p-isopropylbenzyltrimethylsilane (ISO-BTMS), oligomeric and polymeric vinylbenzyltrimethylsilane (VBTMS), and their copolymers with styrene and methyl methacrylate as well as microspheres and microgels of bis(vinylbenzyl)dimethylsilane (BVBDMS) were synthesized using Grignard reaction, free radical polymerization, and precipitation polymerization.</p> <p> Narrow dispersed microspheres were synthesized from bis(vinylbenzyl)dimethylsilane (BVBDMS) by precipitation polymerization in acetonitrile. The reactivities of para/para, meta/meta, and meta/para isomers of BVBDMS in precipitation polymerization were found to be similar and to obey first-order kinetics. Their apparent rate of polymerization is comparable with that of meta and para divinylbenzene isomers under identical polymerization conditions. FT-IR analysis of BVBDMS microspheres shows that there are only few pendant double bonds in the particles. This is likely due to the similar reactivity of isolated double bonds of BVBDMS.</p> <p> Two nucleophilic (hydroxide and fluoride ion) and one oxidative (ceric ammonium nitrate) reagents have been used to cleave the benzylic-silicon bonds of the substrates. The cleavage reactions were quantitatively monitored by 1H-NMR / 29Si-NMR or FT-IR to derive the reaction kinetic parameters. The reaction behavior of most of the substrates differed from that expected based on the Flory's principle of equal reactivity.</p> <p> Among the hydroxide ion initiated cleavage reactions, the small molecules and the oligomeric analogs obeyed first-order kinetics, but the homopolymer and the copolymers deviated from first-order kinetics. This could be due to the low concentration of hydroxide ion in the polymer matrix, arising from the exclusion of polar hydroxide ion from the hydrophobic polymer matrix. The p-isopropylbenzyltrimethylsilane exhibited a lower pseudo first-order rate than benzyltrimethylsilane. This is attributed to an electron releasing substituent effect. Methyl methacrylate can accelerate the reaction on poly(vinylbenzyltrimethylsilane-co-methyl methacrylate) by increasing the overall copolymer polarity. The reverse is true for the corresponding styrene copolymers owing to the steric hindrance offered by the phenyl ring of styrene, and the enhanced hydrophobic repulsion against the access of hydroxide ion into the polymer matrix. An electrophilically assisted process was proposed as a principal reaction mechanism for this cleavage reaction. It was found that the only nucleophile attacking on silicon would be the hydroxide ion in KOH/EtOH/THF promoted reactions.</p> <p> Fluoride ion initiated cleavage reactions of substrates containing benzylic-silicon bonds were found to follow first-order kinetics. The reaction on small molecules was not studied due to their very rapid reaction at room temperature. The homopolymer of vinylbenzyltrimethylsilane exhibited a higher rate of reaction than the corresponding oligomer. However, the change in the reaction rate within a copolymer series, differing in molecular weight and composition, was not significant. Poly(VBTMS-co-MMA) exhibited a rate higher than that of styrene copolymers for polarity or steric reasons.</p> <p> Oxidative cleavage of benzylic-silicon bond by ceric ammonium nitrate (CAN) was found to obey first-order kinetics at 1:3 substrate to cerium(IV) ratio, and did not show any deviation in reaction order even at higher CAN concentration. The electron releasing isopropyl group reduces the oxidation potential of p-isopropylbenzyltrimethylsilane (ISO-BTMS), resulting in an enhanced reaction rate compared to benzyltrimethylsilane (BTMS). This rate accelerating substituent effect, together with a much higher negative value (-5.4) of Hammett reaction constant p is in accordance with the radical-cation mechanism operating in ceric ammonium nitrate promoted oxidation reactions. Significant loss of silane functionality was observed in reactions with polymeric substrates. This is attributed to the benzylic radical coupling reactions. The possibility of polymer backbone cleavage is ruled out for the following reasons: A) lack of significant molecular weight reduction in the oxidation products of polymeric substrates. B) about 100 times easier breaking of benzylic-silicon bond as trimethylsilyl cation than a hydrogen from carbon as proton, and the steric congestion offered by the polymer chain favors the benzylic radical formation only at the primary carbon, not on tertiary methine (C-H) on the chain.</p> / Thesis / Master of Science (MSc)

<p> The greywackes of the Goldenville Formation, Meguma Group, Nova Scotia display a well developed spaced cleavage. The cleavage is characterized by zones of mica enrichment and associated quartz depletion and forms a network of anastomosing cleavage rhombs. Parallelism between cleavage and water escape structures suggests that the cleavage was emplaced perpendicular to bedding early in the deformational history of the rocks. Subsequent passive rotation of cleavage and water escape structures reduced the bedding-cleavage angle to its present values.</p> <p> XRF whole rock analyses of cleavage planes and lithons from two different sample locations show that the cleavage is depleted in SiO2, CaO, Na2O and enriched in Al2O3, Fe2O3, MgO, K2O, TiO2, MnO and P2O5 relative to lithons. Mass balance calculations based on the Gresens (1967) approach indicate that the cleavage with respect to the lithon represents a 40%-60% volume loss. Using the volume loss it can be shown that the cleavage lost SiO2, Na2O, CaO, MnO, P2O5, Pb, Sr, Nb, and Y and gained MgO, K2O, Ba, Rb, and W during its formation. TiO2, Al2O3, Fe2O3 and Zr remain relatively immobile during the cleavage forming processes. The behavior of Au, Sb, As, Ce, Nd, and La can not be discerned.</p> <p> The cleavage was initiated by pressure solution at grain contacts. However, several of the above mentioned chemical migrations increased the solubility of quartz and therefore greatly enhanced the development of the cleavage.</p> / Thesis / Master of Science (MSc)

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京都大学 / 新制・課程博士 / 博士(理学) / 甲第24082号 / 理博第4849号 / 新制||理||1694(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 柘植 知彦, 教授 森 和俊, 教授 川口 真也 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1979. / Microfiche copy available in Archives and Science. / Bibliography: leaves 118-124. / by Herman William Cooper. / Ph.D.