Theses and Dissertations
Permanent URI for this collection
Browse
Search Collection
1 - 5 of 32665
-
PublicationComputational complexity reduction in fractal image compression by adaptive codebook clustering( 1996)Fractal image coding has several advantages over conventional coding techniques such as faster and iterative decoding, higher compression, and resolution independence. These are highly desired coding properties in a broadband network environment. The weakness of a fractal coding system however is the computational complexity of the encoder, which prohibits a real-time implementation and makes fractal coding an unsuitable coding method in a symmetric point-to-point communication system. It is the objective of this thesis to develop and apply a new technique for image block classification and analysis in fractal image compression. This technique will be based on the concept of multi-dimensional keys that form a metric space. The Linde-Buzo-Gray algorithm is employed to cluster these keys so that one can search efficiently through the clusters for the nearest neighbor. A fractal coding scheme is presented that uses multi-dimensional keys to improve and accelerate block classification. As a consequence, the coding scheme can increase image fidelity while decreasing encoding time. The software implementation of this coding scheme validates the approach.
-
PublicationA model for initiation of aluminum etch tunnels( 1996)In the past, tunnel etching of aluminum has been used primarily in the production of electrolytic capacitors. Research has therefore focussed on the parameters which will increase capacity. The increase in capacity obtained is in direct proportion to the increase in effective surface area. However, the factors which control the tunnel shape, and finally control the etched area, are related to the mechanism of the formation of tunnels from etch pits, which is incompletely understood. This work will focus on understanding the transformation from cubic etch pits into tunnel shapes. The ability to quantitatively predict the transformation is a critical test of the model's description of oxide passivation. Thus, important fundamental information about passivation may be gained.
-
PublicationSyntheses and reactions of some polycyclic phosphorus compounds( 1996)The syntheses of 4-alkyl-1-trityl-1-phospha-2,6, 7- trioxabicyclo[2.2.2]octane tetrafluoroborates (alkyl group= Me, 4; Et, 5; tBu, 6) are described. Compounds 4, 5 and 6 in the presence of base (pyridine, DBU) or base (pyridine, DBU) and H20 undergo Arbuzov ringopening reactions to give pyridinium salts or a mixture of hydrolyzed products and pyridinium salts, respectively. The steric configurations of the products were addressed. The acyclic trityl salts [(R0)3CPhsJ+BF4- (R = Et, 7; neopentyl, 8) were also prepared and their reactions with base or base and H20 were carried out for comparison with these reactions of the polycyclic trityl salts. The precursor N(CH₂CH₂NHMe)₃ (2) of super base P(MeNCH₂CH₂)₃N (1) has been synthesized in a one pot reaction sequence for the first time. A novel reaction sequence was explored for the conversion of a primary amine to a secondary amine by protecting the primary amine with a TMS group followed by treating it with n-BuLi and TsOMe. The purity of the final product 2 was monitored by P NMR spectroscopy of its reaction with CIP(NMe₂)₂.
-
PublicationDigestibility and metabolism of soluble amylose and amylopectin starches in the rat( 1996)Modified water soluble potato (70-75 % amylopectin) and amylomaize-7 (70% amylose) starches were studied. Male rats were fed one of the 4 carbohydrates, commercial com starch, dextrose, modified potato starch, and modified amylomaize-7 starch at 55 g/100 g diet, from 5 to 9 wk of age. Body weights were similar in all groups. Food consumption was significantly higher in the two modified starch-fed groups. In the two experimental groups, especially in modified potato starch-fed group, high bulk feces were noticed, and the colons were fill of undigested starch and gas. Digestibilities were 100 ± 0 % for commercial com starch, 100 ± 0 % for dextrose, 69.0 ± 1.0 % for modified potato starch, and 91.5 ± 0.8 % for modified amylomaize-7 starch (n=9, X ± SEM). The modified potato starch-fed group deposited less fat, protein, and energy than the other three groups. Heart and epididymal fat pad weights were also lower in the modified potato starch-fed group. However, liver weights were elevated in the two groups fed the experimental starches. Mean fasting TG values were similar in all groups. Fasting serum free fatty acid concentration was higher in the modified potato starch-fed group than the two control groups. Free fatty acid concentrations were similar in the amylomaize-7 starch-fed group and the two control groups. Mean fasting serum protein concentration was significantly lower in the modified potato starch-fed group. Mean fasting serum glucose concentrations were significantly higher in the two experimental groups. The ratio o( insulin to glucagon was lowest in the modified potato starch-fed group; in the amylomaize-7 starch-fed group the ratio was lower than in the dextrose-fed group. The data indicate that the rats compensated for the lower digestibility of the two experimental starches by increasing food consumption. Products of fermentation might contribute to gluconeogenesis to account for the higher fasting serum glucose in the two experimental groups. These data indicate that only the modified amylomaize-7 starch may be useful to develop food product for liquid nutritional supplements.
-
PublicationADP-ribosylation of intermediate filament protein, desmin( 1996)Desmin is an intermediate filament protein which can be ADP-ribosylated by arginine specific mono(ADP-ribosyl) transferase. Stoichiometric modification of desmin by the transferase causes disassembly of intermediate filaments (Biochem. Biophys. Res. Comm. 197, 1993, 570-577). In this work, the site(s) of modification that can affect disassembly have been identified. ADP-ribosylated desmin (1.2 moles ADP-riboses/mole desmin) was digested with lysyl endopeptidase followed by trypsin. Two ADP-ribosylated peptides were obtained, sequenced by Edman degradation and analyzed by the use of matrix-assisted laser desorption/ionization mass spectrometry. Arginines 48 and 68 of the head domain were shown to be sites of modification, with arginine 48 the major ADP-ribosylation site. Also in this work, ADP-ribosylated desmin (4 moles ADP-riboses/mole desmin) was treated with arginine specific mono(ADP-ribosyl) hydrolase. Removal of 2 or 3 groups results in partial restoration of formation of the filaments. It is necessary to remove all ADP-ribose groups to restore complete formation of intermediate filaments. The fact that the effect of ADP-ribosylation on filamentous properties of desmin is fully reversible suggests that ADP-ribosylation alone is responsible for the changes noted in desmin. Desmin is a muscle specific intermediate filament protein which can be ADP-ribosylated by muscle arginine specific mono(ADP-ribosyl)transferase (70). Incubation of membrane fractions from 96-hr primary chick myotubes with [³²P] NAD resulted in labeling of two protein bands with molecular weight of 56 kDa and 36 kDa (94). Desmin was shown to be present in the 56 kDa band and labeling of both these two protein bands was due to ADP-ribosylation by muscle transferase (94). In this work, labeling membrane fractions of 5-day primary chick myotube with [³²P] NAD, resolving immunoprecipitated desmin on SDS-PAGE, and performing autoradiography showed the presence of radiolabeled desmin. This result strongly indicate that the labeling of 56 kDa protein band is indeed due to the ADP-ribosylation of desmin at the arginine residues by the muscle transferase from the membrane fractions of chick myotubes. Also in this work, by using R-28 polyclonal antibodies specific for ADP-ribosylated arginine, we have shown that soluble desmin immunoprecipitated from 4- or 5-day chick myotubes reacted specifically with this antibody and this reaction was weakened when soluble desmin was treated with neutral hydroxylamine. This result is consistent with ADP-ribosylation of arginine residue of desmin from the intact muscle cells. We also found that that desmin purified from turkey gizzard also strongly reacted with this R-28 antibody, which indicates that desmin from smooth muscle cell is ADP-ribosylated by the arginine specific mono(ADP-ribosyl)transferase.