published_or_final_version / abstract / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

This thesis describes a model of speech timing, predicting at the syllable level, with sensitivity to rhythmic factors at the foot level, that predicts segmental durations by a process of accommodation into the higher-level timing framework. The model is based on analyses of two large databases of British English speech; one illustrating the range of prosodic variation in the language, the other illustrating segmental duration characteristics in various phonetic environments. Designed for a speech synthesis application, the model also has relevance to linguistic and phonetic theory, and shows that phonological specification of prosodic variation is independent of the phonetic realisation of segmental duration. It also shows, using normalisation of phone-specific timing characteristics, that lengthening of segments within the syllable is of three kinds: prominence-related, applying more to onset segments; boundary-related, applying more to coda segments; and rhythm/rate-related, being more uniform across all component segments. In this model, durations are first predicted at the level of the syllable from consideration of the number of component segments, the nature of the rhyme, and the three types of lengthening. The segmental durations are then constrained to sum to this value by determining an appropriate uniform quantile of their individual distributions. Segmental distributions define the range of likely durations each might show under a given set of conditions; their parameters are predicted from broad-class features of place and manner of articulation, factored for position in the syllable, clustering, stress, and finality. Two parameters determine the segmental duration . pdfs, assuming a Gamma distribution, and one parameter determines the quantile within that pdf to predict the duration of any segment in a given prosodic context. In experimental tests, each level produced durations that closely fitted the data of four speakers of British English, and showed performance rates higher than a comparable model predicting exclusively at the level of the segment.

Cellooligosaccharides are the reaction intermediates produced during the hydrolysis of cellulose to glucose. Hence, they have the same chemical structure as cellulose, just shorter chain lengths. Cellooligosaccharides up to DP eight are soluble in water. The soluble cellooligosaccharides can be used "as is" in the food industry as non-digestible oligosaccharides and in the laboratory as representative substrates for cellulolytic enzymes. The soluble cellooligosaccharides may also be chemically modified for use in the laboratory, in this case serving as affinity ligands, reporter groups, or model substrates. A number of methods are available for the separation of cellooligosaccharides differing only with respect to DP. This type of separation is relevant to both laboratory and industrial applications. A new approach to the chromatographic separation of cellooligosacchandes is presented in this thesis. It is shown that cellulose stationary phases, in conjunction with ethanol-water mobile phases, may be used for cellooligosaccharide fractionation. The system appears to behave as an affinity/partition system, with retention times increasing as the DP of the cellooligosaccharides increase. The feasibility of using such a chromatographic system for the "clean-up" of cellooligosaccharide mixtures is demonstrated. The relative merit of different chromatographic approaches putatively used for the fractionation of cellooligosaccharides was determined. Affinity-, adsorption-, ion-mediated- and molecular exclusion-approaches were tested. Adsorption chromatography, using a charcoal-celite stationary phase, was the most generally applicable method for the preparation of near gram quantities of pure cellooligosaccharides. Cellulose-based affinity/partition chromatography was found to be the least time consuming and most economical method for the preparation of cellotetraose and cellopentaose. Studies using chemically modified cellooligosaccharides are typically limited to derivatives whose aglycone group is conjugated to the reducing end of the sugar. This is because the chemistry involved in modifying the reducing end is typically much easier than that involved in selectively modifying other sites on the oligosaccharides. A portion of the studies presented herein was aimed at exploring approaches for the modification of the non-reducing end of cellooligosaccharides. Methyl 6-O-p-nitrobenzoyl-β-D-glucoside was synthesized by reacting methyl 4,6-O-p-nitrobenzylidine-β-Dglucoside with N-bromosuccinimide. This method has potential as a general method for the modification of the reducing terminus of oligosaccharides, including, cellooligosaccharides. / Graduation date: 2003

The purpose of this study was, first, to investigate whether there is a vitamin B-6 requirement for carnitine synthesis and, second, to investigate the effect of fasting on vitamin B-6 metabolism. An experimental group of 72 rats (6 per group) were fed either a vitamin B-6 deficient diet (-B6) (ad libitum, meal-fed) or a control diet (+B6) (ad libitum, pair-fed). These diets were fed for 6 weeks and then the rats were repleted with the control diet for 2 weeks. The animals were fasted for 3 days before and after repletion. Total acid soluble carnitine (TCN) and free carnitine (FCN) levels were compared in the plasma, liver, skeletal muscle, heart muscle and in the urine of rats fed +B6 diet and -B6 diets. The concentrations of pyridoxal 5'-phosphate (PLP) in the plasma, liver, skeletal muscle, and heart muscle and urinary 4-pyridoxic acid (4-PA) excretion were compared in rats fed the +B6 or -B6 diet. Similar comparisons were made in fasted and non-fasted rats. Also, plasma glucose, liver glycogen, and free fatty acid concentrations were compared. In rats fed the -B6 vs +B6 diet, the TCN concentration was significantly (P < 0.05) lower in the plasma, skeletal muscle, heart muscle and urine. With fasting, the liver TCN concentration of -B6 rats was also significantly lower than that of +B6 rats. After the -B6 rats were repleted with the +B6 diet, the TCN concentrations in the plasma, liver, skeletal muscle, heart muscle, and urine returned to those of the control rats. Thus, the decrease in TCN and FCN concentrations, and the increase of these concentrations after repletion provides evidence for a vitamin B-6 requirement in the biosynthesis of carnitine. Fasting resulted in increased concentrations of PLP in the plasma, liver, and heart muscle of rats fed a -B6 diet. The urinary 4-PA excretion of -B6 rats also increased with fasting. These changes are consistent with a redistribution of vitamin B-6 (as PLP) when there is a caloric deficit. Thus, with fasting, PLP is supplied by an endogenous source, possibly skeletal muscle glycogen phosphorylase. In -B6 vs +B6 rats, liver glycogen concentration was higher and plasma FFA concentration was lower. / Graduation date: 1987

The cyclopropene fatty acids, sterculic and malvalic, occur naturally in a major food lipid, cottonseed oil, and have been implicated in several physiological disorders. Rainbow trout in this study were fed semipurified diets containing 200 or 300 ppm methyl sterculate, and the effects on hepatic lipid and glycogen levels, lipid incorporation of radioactive phosphate and fatty acids, and mitochondrial energy production were investigated. Chronic ingestion of methyl sterculate caused numerous histological changes and some necrosis in the liver. Glycogen accumulated in irregular pockets, but the level in whole liver was not increased over controls. Hepatic lipid accumulation was noted after several weeks, reaching a level six times that of controls after six months. Liver weight of the sterculate-fed fish decreased in proportion to body weight during the first three weeks on the sterculate diet, but after three months became significantly greater than controls. Ingestion of 200 ppm methyl sterculate for two weeks by trout caused reduced incorporation of both phosphate and fatty acids into phospholipids. The major reductions were found in minor fractions. Label incorporation into cardiolipin, important for mitochondrial function, was reduced ten-fold by the dietary sterculate. Incorporation into a minor unknown phospholipid which constituted less than 1% of total phospholipids was reduced as much as 135-fold in the mitochondrial fraction. Incorporation of 1-¹⁴C-oleate into diglycerides was also inhibited. The major changes caused by methyl sterculate appear to occur in mitochondria. Neither the level of cytochrome P⁴⁵⁰ nor the activity of NADPH neotetrazolium reductase, both of which occur in the endoplasmic reticulum, was altered. P/0 ratios and the ability to oxidize oleic acid to CO₂ were curtailed after only two weeks on a diet containing methyl sterculate. / Graduation date: 1974

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