京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22484号 / 農博第2388号 / 新制||農||1075(附属図書館) / 学位論文||R2||N5264(農学部図書室) / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 小川 順, 教授 加納 健司, 教授 栗原 達夫 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

The purpose of this work was to recover uranium from residue originating from the production of molybdenum -99. Carbonate solutions containing hydrogen peroxide or oxygen gas as oxidants were used as leachants. Experimental parameters included: different peroxide and carbonate concentrations, dissolution time and temperature. Results indicate complete dissolution of the residue at 60 oC, after thirty minutes, in ammonium carbonate solution enriched with hydrogen peroxide. Almost two hours were needed to achieve the same extent in the presence of oxygen. The yield and rate of uranium extraction were found to increase as a function of both temperature, in the range of 25-60 oC, and hydrogen peroxide concentration. The leaching kinetics were determined for various leaching conditions and the activation energy was found to be 45.5kJ/mol. The order of reaction with respect to uranium concentration was found to be unity. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Materials Science and Metallurgical Engineering / unrestricted

Thesis (M. Sc. Agriculture (Soil Science)) -- University of Limpopo, 2019 / One of the major constraints to crop productivity in South Africa is crop nutrient deficiency especially micronutrients. Laboratory, glasshouse and field studies were carried out during the 2016/2017 growing season to assess the effects of micronutrient (Zn, B and Mo) seed priming on maize growth and yield in micronutrient deficient soils of the Limpopo province. The laboratory experiment was carried out in a completely randomized design (CRD) laid out in a 3 x 5 x 3 factorial treatment structure with three replications. The assessments of the micronutrients were made at 0%, 0.01%, 0.05%, 0.1%, and 0.5% concentrations. The seeds were primed in the solutions for 24 h, 12 h and 8 h. The glasshouse experiment was carried out in a completely randomized design (CRD) laid out in a 3 x 4 x 2 factorial treatment structure with three replications. In the field, a single factor experiment in a randomised complete block design (RCBD) with three replications and a control was used, with micronutrient concentrations as levels. The laboratory study investigated the effect of seed priming with Zn, Mo and B on germination (germination percentage (GP), germination rate (GR), the coefficient velocity of germination (CVG), days to germination (DG) and mean germination time (MGT)). The interaction between seed priming duration and concentration levels of seeds primed with B had significant effect (P < 0.05) on germination. The interaction between seed priming duration and concentration levels of seeds primed with Zn had significant effect (P < 0.05) on germination. The interaction between seed priming duration and Mo concentration levels on CVG, MGT and DE had no significant different (P > 0.05). Meanwhile, the effect on GP and GR had significant (P < 0.05) effects. Seed priming with the micronutrients and water resulted in improved GP, MGT and CVG for seeds primed with 0.01, 0.05 and 0.1% for 24 h in laboratory conditions. The glasshouse study was established to investigate the effect micronutrient seed priming on seedling establishment and growth. The effects of the interaction between Mo concentration levels and duration, Zn concentration levels and duration, B concentration levels and duration and control had no significant (P > 0.05) effect on days to emergence (DE), seedling wet weight (WW), dry weight (DW), chlorophyll, stem diameter, plant height and final root length (RL). Furthermore, seeds primed at lower concentration levels (0.05, 0.01 and 0.1%) with longer duration priming period (24 hours) for Mo, Zn and B recorded higher results on the seedling emergence and establishment parameters. The field investigation showed that priming with micronutrients solutions had no significant difference on the final values of dry biomass, prolificacy, harvest index and grain yield. Seeds primed with 0.05, 0.01 and 0.1 % concentration levels with longer duration priming period (24 hours) showed improvement in germination and seedling establishment. The grain yield and grain nutrient content was not improved, meanwhile emergence was improved. This confirms that not only micronutrients limit yields maximization and crop nutrients content retention solely, rather that the complexity of the agricultural crop production environment should be well understood by all farmers to archive their goals. Keywords: Boron, Maize, Micronutrients, Molybdenum, Nutrient seed priming, Zinc. / National Research Foundation (NRF)

The growth mechanism of chemical vapor deposition (CVD) grown homo-epitaxial diamond (110) and (111) films was studied using ultrahigh vacuum (UHV) scanning tunneling microscopy (STM). In addition, the field emission properties of diamond coated molybdenum microtips were studied as a function of exposure to different gases.

>Magister Scientiae - MSc / In this thesis we describe the synthesis of several carbonyl complexes of molybdenum and tungsten, compounds (Cl-ClO). The compounds Cl- C4 are zero valent carbonyl complexes containing N-base ligands prepared by following a common synthetic procedure. Compounds Cl and C2 were metal pentacarbonyl of 3-(1-methylpyrrolidin-2-yl) pyridine while C3 and C4 are metal tetracarbonyl complexes of 3, 5- dimethylpyrazole, (M=Mo, W). The compounds C5-C10 are divalent metal carbonyl complexes. Compounds CS and C6 were 3,5-dimethylpyrazole dibromotricarbonyl metal complexes prepared from the dibromotetracarbonyl metal dimers at room temperature while the compounds C7 and C8 were cyclopentadienyl halogenoaryltricarbonyl complexes prepared from the cyclopentadienyl metal dimers. Compounds C9 and ClO were prepared from cyclopentadienyl metal dimers by reacting the [CpM(C0)3r anion with CCl4 to obtain [CpM(C0)3Cl] and further reacted with 3-(1- methylpyrrolidin-2-yl) pyridine. All the compounds, Cl-ClO, were characterized by the standard analytical techniques such as FTIR, 1H, 13C NMR; and UV-Vis spectroscopy. Compound C4 was characterized by X-ray crystallography. The structure is depicted as having a distorted octahedral geometry around the metal centre. The compounds Cl-ClO were then tested towards the epoxidation of selected cyclic and straight chain alkenes. The substrates used were cis-cyclooctene (Cyg), 1-octene (C8) cyclohexene (Cy6), 1-hexene (C6) and styrene (Sty). The epoxidation reactions were carried out at a temperature of 55 °C using tertbutylhydroperoxide (TBHP) as the oxidant and dichloroethane (DCE) as the solvent. The metal carbonyl complexes were pre-activated by first reacting them with the oxidant TBHP to obtain the metal-oxo complexes which are the active compounds for epoxidation reactions. The products were analyzed using GC techniques. The compounds, Cl-ClO showed a promising activity towards epoxidation reactions owing to the high conversions obtained by these compounds. For example, conversions of 81% (1-octene), 90% (cis-cyclooctene) were obtained by compound C5, 87% (cis-cyclooctene-compound C3, 95% (cis-cyclooctene-compound · C7) and 69% (ciscyclooctene- compound C4) for an average period of 24 h. The divalent metal carbonyl complexes showed a higher activity but with poor selectivity towards the expected epoxides compared to the zero valent metal carbonyl complexes.

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Weanling male rats were made anemic and fed diets supplemented with 20 ppm iron and/or 2 ppm molybdenum. A decrease in serum iron was observed in the rats supplemented only with iron and a significant decrease in hemoglobin was observed in rats given no supplementation. In a second experiment, pregnant female rats were also fed diets supplemented with 20 ppm iron and/or 2 ppm molybdenum. An inverse relationship was apparent between iron and copper in both the serum and the liver of the female rats. The livers of their pups displayed an inverse relationship between molybdenum and copper. Hemoglobin in both dams and pups tended to decrease when: (1) supplemental molybdenum was absent but supplemental iron was present; (2) supplemental iron was absent but supplemental molybdenum was present; and (3) no supplementation was given at all. While there appeared to be little placental transfer of molybdenum, iron and copper seemed to be transferred from the dams' liver. In a third experiment, serum was collected from pregnant women in first, second, and third trimester, and at postpartum. Both serum iron and serum molybdenum decreased significantly at postpartum. Inverse relationships were apparent between (1) serum iron and serum copper, and (2) serum molybdenum and serum copper.

abstract: A highly uniform and repeatable method for synthesizing the single-layer transition metal dichalcogenides (TMDs) molybdenum disulfide, MoS2, and tungsten disulfide, WS2, was developed. This method employed chemical vapor deposition (CVD) of precursors in a custom built cold-wall reaction chamber designed to allow independent control over the growth parameters. Iterations of this reaction chamber were employed to overcome limitations to the growth method. First, molybdenum trioxide, MoO3, and S were co-evaporated from alumina coated W baskets to grow MoS2 on SiO2/Si substrates. Using this method, films were found to have repeatable coverage, but unrepeatable morphology. Second, the reaction chamber was modified to include a pair of custom bubbler delivery systems to transport diethyl sulfide (DES) and molybdenum hexacarbonyl (MHC) to the substrate as a S and Mo precursors. Third, tungsten hexacarbonyl (WHC) replaced MHC as a transition metal precursor for the synthesis of WS2 on Al2O3, substrates. This method proved repeatable in both coverage and morphology allowing the investigation of the effect of varying the flow of Ar, varying the substrate temperature and varying the flux of DES to the sample. Increasing each of these parameters was found to decrease the nucleation density on the sample and, with the exception of the Ar flow, induce multi-layer feature growth. This combination of precursors was also used to investigate the reported improvement in feature morphology when NaCl is placed upstream of the substrate. This was found to have no effect on experiments in the configurations used. A final effort was made to adequately increase the feature size by switching from DES to hydrogen sulfide, H2S, as a source of S. Using H2S and WHC to grow WS2 films on Al2O3, it was found that increasing the substrate temperature and increasing the H2S flow both decrease nucleation density. Increasing the H2S flow induced bi-layer growth. Ripening of synthesized WS2 crystals was demonstrated to occur when the sample was annealed, post-growth, in an Ar, H2, and H2S flow. Finally, it was verified that the final H2S and WHC growth method yielded repeatability and uniformity matching, or improving upon, the other methods and precursors investigated. / Dissertation/Thesis / Doctoral Dissertation Physics 2019

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