No description available.

No description available.

I present a theoretical study of fault tolerant properties in Quantum-dot Cellular Automata (QCA) devices. The study consists of modeling and simulation of various possible manufacturing, fabrication and operational defects. My focus is to explore the effects of temperature and dot displacement defects at the cell level of various QCA devices. Results of simple devices such as binary wire, logical gates, inverter, cross-over and XOR will be presented. A Hubbard-type Hamiltonian and the inter-cellular Hartree approximation have been used for modeling the QCA devices. Random distribution has been used for defect simulations. In order to show the operational limit of a device, defect parameters have been defined and calculated. Results show fault tolerance of a device is strongly dependent on the temperature as well as on the manufacturing defects. / Cell design -- Basic logic gates -- The exclusive or gate. / Department of Physics and Astronomy

The conduction band of InAs lies lower in energy than the GaSb valence band. In order to preserve continuity of the Fermi level across the interface, charge transfer takes place resulting in a confined quasi two dimensional electron gas (2DEG) in the In As and a confined quasi two dimensional hole gas (2DHG) in the GaSb. This is the first detailed study into vertical transport in an n-InAs/p-GaSb single heterojunction (SHET). Application of a forward bias (InAs negative with respect to GaSb) increases the 2DEG and 2DHG concentrations and, therefore, their confinement energies. Eventually a critical bias is reached where the electron confinement energy moves above the hole confinement energy (the theoretical voltage induced semimetallsemiconductor transition V_c). Any subsequent increase in voltage is expected to result in a current decrease, and a region of negative differential resistance (NDR) should occur. The SHET can be grown with two distinct interface types, 'InSb-like' and 'GaAslike'. This study shows for the first time that the SHET vertical transport characteristic is very dependent upon this interface monolayer. For example, the temperature dependence of the I/V trace in a SHET with a 'GaAs-like' interface is found to be weak, with similar current peak to valley ratios (PVR) at 300 and 77K. The 'InSblike' SHET, however has a PVR that is very close to 1 at 300K, rising above 2 at 77K. Hydrostatic pressure is used to alter reversibly the InAs conduction/GaSb valence band overlap Δ. Vertical transport measurements taken at pressure confirm that Δ reduces at the same rate for both interface types and that it is larger for the 'InSb-like' interface. Experimental I/V traces at various pressures are compared with the corresponding results from self-consistent band profile calculations. The subsequent discoveries are that NDR occurs after V_c for both interfaces, and that each interface supports a different conduction mechanism - with the 'GaAs-like' interface exhibiting NDR when the band overlap is calculated to be ~ -100 meV. Magnetic fields have been applied both perpendicular and parallel to the SHET interface. The perpendicular field results provide additional evidence that the conduction process must be different at both interfaces and that NDR occurs after V_c. Parallel field I/V traces reveal an entirely different response for the two interface types.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 203-209). / Microfiche. / xxiv, 209 leaves, bound ill. 29 cm

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2011. / Lithium 7 (⁷Li⁺) is an isotope, which is used in the nuclear industry as lithium hydroxide (⁷LiOH) for the chemical control (pH control) of the high purity reactor coolant water process in order to prevent corrosion in the Pressurised Water Reactor (PWR). Furthermore, the ⁷Li⁺ isotope is used in an ionic form in the nuclear grade cation ion-exchange resin. This resin is used to purify the nuclear reactor coolant water by reducing cationic corrosion by-products such as Cesium and Cobalt, which are generated from nuclear fission reactions. In view of the fact that an inorganic salt of the isotope is used as an alkali sing agent in the PWR, the use of lithiated resin prevents the removal of the ⁷Li⁺ isotope in the coolant water. As most users of the nuclear grade resin purchase their resin in bulk, it follows that the resin has to be evaluated in order to determine its usability. In certain cases, the resin may be considered unusable as a result of the degradation caused by unsuitable transportation and storage conditions. These, in turn, perpetuate the release of leachates, which may further contribute to corrosion in the PWR. This necessitated the undertaking of this study, which was to evaluate whether it is possible to recover the high value ⁷Li⁺ isotope from a degraded nuclear grade resin in such a way that the isotope may be used in the PWR.

The effect of frost defoliation upon the respiratory rate of the sugar beet root has been determined. The leaves of 140 mature sugar beets were frozen until brittle and the petioles were frozen to within two inches of the crown on August 18, 1957. Twenty-five beet samples were taken one, four, eight, 12 and 16 days after freezing. A cylinder about 3.8 cm. in thickness was cut from the raid-region of each root, i.e. just below the region of greatest diameter. From this cylinder slices 1 mm. in thickness were cut and discs 1 cm. in diameter cut from the slices. Twenty discs were used in each reaction vessel. Nine manometers were used for the tissue from frost defoliated roots and nine for the controls. Respiration was determined as oxygen uptake and measured by Warburg's direct method. One day after defoliation the respiratory rate of defoliated beets was nine uls./hour (13%) higher than that of the controls on a fresh weight basis. From this point the respiratory rate of defoliated beets dropped slowly until after 12 days it was six uls./hour (9%) lower than that of the controls. Between 12 and 16 days after defoliation there was a rapid decrease in respiratory rate to a point 19 uls./hour (28%) lower than the control. On a dry weight basis there was a slight increase in the respiratory rate of defoliated beets until four days after defoliation. After four days there was a rapid decline in respiratory rate until at 16 days the rate was 80 uls./hour (22%) lower than the controls. Throughout the experiment the control beets respired at a fairly uniform rate. A series of selective inhibitors and specific substrates have been applied to tissue from mature sugar beet roots in an attempt to determine the terminal oxidase enzymes present. Potassium cyanide and sodium azide caused almost complete inhibition of oxygen uptake when applied to tissue slices in Warburg manometers. The residual (cyanide stable) respiration was approximately seven uls./hour/gm. fresh weight {10% of total). Sodium diethyldithiocarbamate (0.05M) caused approximately 40% inhibition of oxygen uptake, and resorcinol (0.01M) caused approximately 20% inhibition. Thiourea had no effect on the rate of oxygen uptake. The oxygen uptake by sugar beet root tissue was unaffected by lowering the oxygen partial pressure to 5%. Carbon monoxide (95/5::CO/02) caused approximately 16% inhibition as compared to tissue respiring in a 95/5::N2/02 gas atmosphere. This inhibition was light stable. 8-hydroxyquin-oline had no effect upon the respiration of the sugar beet root. On the basis of this evidence it appears that the terminal oxidase enzymes present are metallo-protein oxidases and that the copper-protein oxidases other than ascorbic acid oxidase are functional in oxygen uptake. Catalase activity was demonstrated by the evolution of 0₂ from H₂0₂. and peroxidase by oxidation of pyrogallol and catechol in the presence of H₂O₂. There was a great increase in oxygen uptake when ascorbic acid was added to tissue slices. This was due, however, to enzymes other than ascorbic acid oxidase. The presence of phenol oxidase was indicated by the increased O₂ consumption when catechol, protocatechuic acid and tyrosine are added to tissue slices. There was also a tendency for cut surfaces of beet roots to darken, particularly in the region of the vascular rings. The addition of hydroquinone and p-phenyl-enediamine to sugar beet tissue also caused an increased oxygen consumption. No oxidation of reduced cytochrome c has been demonstrated. There was no oxidation of glycolic or lactic acids. / Science, Faculty of / Botany, Department of / Graduate

The thermal fouling data of Watkinson were recomputed on the assumption that increases in pressure drop were caused entirely by roughness of the fouling deposit and not at all by blockage. The results indicate that roughness played some role in the sand-water runs, but no role in the gas oil runs. The anomalous increases in overall heat transfer coefficient with degree of fouling in the first two sand-water runs were thus explained by the effect of roughness on liquid film heat transfer coefficient. The original loop was modified, the principal change being the replacement of the manual temperature recording system by a digital Data Logging System. Fluid and wall temperatures, as well as differential pressure, could thus be automatically recorded as a function of time. Better control of independent operating variables such as fluid velocity, inlet temperature and heat flux could therefore be achieved, and the effects of temporary fluctuations in these operating conditions could be observed and separated from fouling effects. Thermal fouling runs were made in the modified heat transfer loop on samples of Bayer Process spent liquor from the ALCAN aluminum refinery in Arvida, P.Q. The only discernible trends in the results were increases in rate and degree of fouling with increasing heat flux to a maximum value, followed by a sharp decrease, at liquor velocities less than 5 ft/sec, and the absence of thermally detectable fouling at higher velocities. The unreproducibi1ity of the results is believed to be attributable, at least in part, to changes in chemical composition of the liquor throughout the experiments. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The objective of this study was to determine how the rice plant responds to combinations of temperature and photoperiod. Both temperature and photoperiod are important for normal completion of the life cycle, but there has been little study of their combined effects in rice. Controlled temperature and photoperiod experiments were conducted in growth cabinets using 4 temperatures; 35/18, 35/26.5, 35/35 and 40.5/18°C day/night. There were 4 photoperiods of 8, 10, 12 and 14 hours. Light was provided by cool white fluorescent tubes. The day temperature periods corresponded to the photoperiods. Four varieties were selected: Kangni-27 and Dokribasmati from Dokri, Pakistan; Caloro from California, U.S.A.; and Bluebonnet-50 from Texas, U.S.A. Growth characteristics, net photosynthesis rates, and flowering were measured and chlorophyll a and b, carotenoid, carbohydrate and ash concentrations were determined. The effect of photoperiod on flowering was most pronounced at 35/26.5. The delays in flowering at 14 hours for this temperature were 30, 30, 21 and 63 days in Kangni, Caloro, Dokri and Bluebonnet compared to the optimum, photoperiod which varied among varieties. The delays observed at 35/18 were 23, 14, 6 and 2 days. At 35/26.5 all varieties showed a significant photoperiodic effect on flowering, but at 35/18, Dokri and Bluebonnet did not show a significant photoperiodic effect. 35/35 was most unsatisfactory for flowering. A similar but less serious effect was found at 40.5/18. Final dry matter production was high at 35/35 and 40.5/18; an increase of 3 to 8 g per pot was noted at these temperatures compared with 35/26.5 and 35/18. There was an increase of about 5 g per pot at maturity for each increase of 2 hours in photoperiod. Panicle characteristics were generally unaffected by temperature, but there were some photoperiod effects. At the 12-hour photoperiod panicles of all varieties were 2 to 4 cm longer than at other photoperiods and at 10-and 12-hour photoperiods there were 10 to 32 more spikelets per panicle than at 8 and 14 hours. Sterility was very high at 35/35 (95%) and 40.5/18 (69%). Average sterility at 35/18 and 35/26.5 was about 36%. There was 8 to 24% less sterility at 10- and 12-hour photoperiod compared with 8 or 14 hours. Hundred-grain weight was unaffected by photoperiod or temperature. High numbers of tillers were consistently observed at 40.5/18 and 35/18 and low numbers at 35/35. The differences varied with the stage of growth. Plants at 14-hour photoperiod had consistently more tillers than those at other photoperiods. Kangni and Dokri had higher numbers of tillers than Caloro and Bluebonnet. Leaf development was fastest at 40.5/18 and the 12-hour photoperiod. This was especially so at 6 and 8 weeks. Kangni and Dokri had faster development than Caloro and Bluebonnet. Plant height was 2 to 5 cm greater at 2 weeks at 35/26.5 and 35/35 but at 4, 6 and 8 weeks, plant height was greater at 35/18. The shortest plants were observed at 40.5/18. The rate of net photosynthesis on a leaf blade weight basis was highest at 2 weeks in all varieties at all photoperiods and temperatures. The rate generally declined with the aging of plants. The greatest decline at 8 weeks, compared to 2 weeks, was 71% in Dokri and least was 65% in Bluebonnet. Except at 2 weeks, the highest rate of photosynthesis was at 40.5/18 but at 6 and 8 weeks there were also high rates at 35/35. The rate was consistently higher in plants growing in the 8-hour photoperiod. The rate was higher in the 8-hour photoperiod compared to the 14-hour by 28 and 25% at 6 and 8 weeks respectively. Both Caloro and Bluebonnet had higher net photosynthetic rates than Kangni and Dokri. In all varieties chlorophyll and carotenoid content declined with age. Both chlorophyll and carotenoid were high at 40.5/18 at all stages. Chlorophyll concentration was also high at 35/18 at 2, 4 and 6 weeks. A definite correlation between chlorophyll content and photosynthesis was not shown, but there was a significant correlation between chlorophyll and fresh weight at all temperatures and photoperiods except at 2 weeks. Total water soluble carbohydrate and total ash content did not show definite trends according to stages of growth. No relationship could be shown between floral initiation and combined carbohydrate and ash content. / Land and Food Systems, Faculty of / Graduate

Six varieties of rice, representative of those cultivated in California and other southern regions of the United States were grown in a series of nine experiments. In a greenhouse, seeds were sown into pots placed in a constant temperature water bath possessing compartments maintained at water temperatures of 60°, 75°, 60° and 90°F. Many characteristics of plant growth and development were influenced by water temperature. Generally shoot lengths and weights, root lengths and weights, leaf lamina, leaf sheath lengths and stomata number were greater at the higher, than at the lower, temperatures. The type and intensity of silica crystal formation in the leaves increased with increase in temperature. Stomata sizes were larger at lower, than at higher, temperatures. Irrespective of plants being submerged or non-submerged, at continuous or changed temperatures, the higher temperatures produced the greatest response. Californian varieties were found to be more sensitive than other southern varieties in their response to both low and high temperature treatments, indicating a greater range of adaptability. / Land and Food Systems, Faculty of / Graduate