Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1938. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed May 6, 2010) Includes bibliographical references (p. 42-44) and index (p. 45-47).

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 41, 81, 130, 183, 270, 315, 336).

Magister Scientiae - MSc (Chemistry) / Global climate change and geographical differences are two major parameters known to have, either, direct or indirect influence on the production of secondary metabolites in plants, which in-turn may affect the quality and/or quantity of the overall metabolites. The primary purpose of this thesis was to evaluate the phytochemistry of the whole leaf of Aloe succotrina Lam. spp. - a South African native plant - through a chromatographic spectroscopic approach-against available data accumulated for the cultivated population. Preliminary screening of the crude extracts i.e. HEX, DCM and EtOAc on TLC aluminium plates precoated with silica gel 60 F254 followed by various chromatographic separation, led to the isolation of five known compounds: ?-sitosterol (1) and two anthrone-C-glycosides (2 and 5), including two coumarin derivatives-the aglycone (3) and glycoside derivative (4). Notably, apart from 5 and 2, the accumulation of 1, 3 and 4 in A. succotrina Lam. spp. is reported for the first time. Structural elucidation of the individual compounds was achieved by extensive spectroscopic analysis i.e. MS, IR, 1H and 13C-NMR spectroscopy and in some cases comparison to the literature. A comparative HPLC chromatogram of the crude MeOH extract of the leaves of A. succotrina Lam. was developed for qualitative (and quantitative) identification of the active metabolites, which could be realized by VWD with detection at 290 nm.

No description available.

Experiments have been conducted to identify the fouling mechanism during the crossflow filtration of a model yeast fermentation broth of Vinyl Acetate particles suspended in a Bovine Serum Albumin (BSA) solution. These have been conducted with filter modules, to obtain quantitative data for the rate and the extent of flux decline due to membrane fouling, and with filter coupons, to obtain quantitative data for the build up of the fouling layer with each individual system and the mixed system. The data from the individual systems have been analysed and then used to determine their fouling mechanisms; this information has been used to predict the fouling mechanism for the mixed system. Finally, this prediction has been compared to the actual fouling mechanism determined by analysis of the mixed system data. For the model particulate suspension, the fouling was due to the build up of a cake layer, as with dead end filtration; however, fouling was limited by membrane scouring. For the model macromolecular solution, a four part fouling mechanism was identified: initially aggregates formed within the pores; the concentration at the membrane surface increased until protein came out of solution as strands; the strands disappeared causing increased aggregation in the pores; finally, a mesh formed on the membrane surface. For the mixed system, fouling was due to the formation of a particle cake on the membrane surface with protein aggregates forming in the pores. The fouling kinetics could be predicted by considering the results from the individual systems; however, the fouling mechanism could not be predicted without using visualisation experiments due to the interactions between the particles and the macromolecules.

The concept of a unique ceramifiable Ethylene vinyl acetate (EVA) based polymer composite was based on the incorporation of inorganic compounds such as aluminium hydroxide, calcium carbonate, muscovite mica, and calcined kaolinite within a 95 percent EVA/ 5 percent Polydimethylsiloxane (PDMS) polymer matrix such tha t upon heating to elevated temperatures of about 1000 oC, a solid end-product with ceramic-like properties would be formed. The ceramifiable EVA based polymer composite was developed to be used as electric cable insulation or sheath as the formation of a ceramic based material at elevated temperatures would provide flame retardant properties during fire situations. The flame retardant properties at elevated temperatures would ensure that the insulation remains at such temperatures due to some of the properties of the resultant ceramic such as reasonably high flexural strength, high thermal stability, non-reactivity and high melting point. During a fire this would ensure that flames would not be propagated along the length of the cable and also protect the underlying conducting wires from being exposed to the high temperatures of the fire. Its application as a cable insulation also required that the material functions as a cable insulator under ambient temperature conditions where the ceramifiable polymer composite should retain certain polymer properties such as the post-cure tensile strength (MPa), degree of polymer elongation (percent), thermal expansion, thermal slacking, limited oxygen index and electrical insulation. This study made use of a composite experimental design approach that would allow for the optimization of the amounts of the additives in the ceramifiable polymer composite giving both the desired mechanical properties of the material under normal operating temperatures as a polymer and also as a ceramic once exposed to elevated temperatures. The optimization of additives used in the ceramifiable polymer composite was done by using a D-optimal mixture design of experiments (DoE) which was analyzed by multiple linear regression.

Intraperitoneal administration of cyclophosphamide 100 mg/kg and 200 mg/kg significantly lowered plasma sodium and significantly increased plasma potassium but did not result in saline preference in a strain of wild-derived house mice given a choice between water and saline (0.15M) to drink. Deoxycorticosterone acetate treatment in dosages up to 1.5 mg for four days also failed to increase salt intake. The data suggest a possible absence of a sodium appetite mechanism in this species.

Catalytic Investigations of Rhodium Acetate Derivatives to Develop Sturdier Insecticides Authors: Alexandria Marshall, Alain Beauparlant, Cassandra Eagle* Department of Chemistry, College of Arts and Sciences East Tennessee State University Johnson City, TN Permethrins are a class of naturally occurring, low-toxicity insecticides that are extracted from the chrysanthemum flower. This class of insecticides is primarily utilized for the treatment of head lice for humans and flea and tick treatment for pets. These naturally occurring permethrins have a low Lethal Dose for 50% (LD50) of the bug population and a high LD50 for mammalian species. Unfortunately, permethrins are sensitive to heat and light, which precludes their use in industries such as the Christmas tree industry and other outside sources of bugs. Pyrethroids, on the other hand, are lab-synthesized insecticides that have the same biological activity as permethrins but are light and heat stable. Rhodium acetate is a catalyst that is used during the synthesis of pyrethroids. This means rhodium acetate is a chemical that speeds up the rate of the reaction without getting consumed. The goal of this research is to understand the mode of action of rhodium acetate so that we can develop sturdier derivatives of permethrin insecticides that can be used in a wider variety of applications. Rhodium acetate catalyzes the most difficult step in the synthesis of pyrethroids, the formation of a cyclopropane ring where there are two bulky groups on the same side of the ring. The catalytically active species, a rhodium (II) acetate carbene species, where the carbene is created from ethyl diazoacetate, is, unfortunately, too unstable and short-lived to characterize thoroughly. We have synthesized a more stable model of the catalyst using nitrile and iso-nitrile adducts of the active site and have been able to study it with extreme precision using X-ray crystallography. The derivative we have synthesized is Rh2(OAc)4.2X, where OAc is the acetate group (the same active ingredient in household vinegar) and X is benzonitrile, NC-C6H5. This nitrile derivative is similar to a carbene in that they both have a lone pair of electrons capable of serving as a Lewis base to initiate sigma bonding with the dirhodium core. Another similarity they share is that both species have empty orbitals capable of accepting electron density to form pi-backbonds. The derivative was synthesized by using 10-30 mg of Rh2(OAc)4 in approximately 10 mL of ethanol. 1-200 equivalents of the benzonitrile are dissolved in ethanol in a separate container. Then, the Rh2(OAc)4 in ethanol and benzonitrile in ethanol were mixed together and kept in a container covered with a tissue to prevent dust from entering. The slow evaporation of the ethanol solvent results in high-quality crystals that are suitable for single crystal X-ray crystallography. The results from X-ray crystallography have provided us important information regarding the rhodium-rhodium bond distance, the rhodium-nitrogen bond distance, the nitrogen-carbon bond distance, and the rhodium-nitrogen-carbon bond angle. This data will poise us to determine the steric and electronic parameters of the cavity used for carbene coordination. The next steps of this project will be to apply these findings to actual carbene chemistry reactions to verify that the parameters are correct. Thus, it will reveal exactly what is necessary for a particular reaction to take place in terms of reactants.

No / The performance of batch reactive distillation process involving the esterification of acetic acid with methanol to produce methyl acetate and water is considered in this work. Two cases studies with varying amount of the reactants are considered. The reflux ratio (single time interval) is selected as the control variable to be optimised (treated as piecewise constant) for different but fixed batch time ranging from 5 to 15 h, so as to maximise the conversion of methanol subject to product purity of methyl acetate. The dynamic optimisation problem is converted to a nonlinear programming problem by Control Vector Parameterization (CVP) technique and is solved by using efficient SQP method. The optimisation results show that as the methanol and methyl acetate are wide boiling, the separation of methyl acetate is easier without losing much of methanol reactant. The conversion improves by 6.4 % due to sufficient amount of acetic acid being reacted with methanol. Moreover an excess of acetic acid leads to high operation temperature and therefore high reflux operation (to reduce loss of methanol from the top of the column) to maximise the conversion.

<p> The acetate-catalyzed bromination of acetone is shown to occur by an enolization mechanism, although the reactions involved in this process are more complex than has been supposed.</p> <p> A study of the activation parameters for the enolization of some bromoacetones, and an observed linear free energy relationship between enolization rate constants, and acid ionization constants, shows that the transition state for this process resembles enolate and not enol.</p> <p> Bromine substitution in ketones accelerates enolization rates on both sides of the carbonyl group.</p> <p> The acetate-catalyzed enolization of 2-butanone favours the methylene group by a factor of nearly two. This fact is interpreted in terms of methyl groups being inductively electron-withdrawing in their effect in forming an enolate transition state.</p> / Thesis / Doctor of Philosophy (PhD)