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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Biokinetic behaviour of <i>Chlorella vulgaris</i> in a continuous stirred bioreactor and a novel circulating loop photobioreactor

Sasi, Divya 21 September 2009
Capture of CO2 by algae is an important mechanism for removal of this greenhouse gas from the atmosphere. For this reason, <i>Chlorella vulgaris</i> has beeen studied extensively over the years. A high growth rate of the microalgae is essential in order to increase the fixation rate of CO2 through photosynthesis. Though a number of studies have been carried out to optimize growth of <i>C. vulgaris</i>, high growth rates have not been achieved (Kleinheinz & Keffer, 2002).<p> In this study, a novel circulating loop photobioreactor with enhanced light distribution, gas mass transfer rate and mixing properties was used for the biokinetic study of <i>C. vulgaris</i>. The objective was to study individual effects of light intensity and CO2 concentration on the specific growth rate of <i>C. vulgaris</i>. Studies in this photobioreactor could generate high growth rates of 0.043 h-1. The effect of light intensity on the growth of the <i>C. vulgaris</i> was determined by varying intensity of light to the photobioreactor within a range of 26.945 mW to 431.128 mW, while the flow of air and CO2 were held constant. An increase in light intensity to the photobioreactor resulted in an increase in cell density and variation in the chlorophyll content of the <i>C. vulgaris</i> cells. Enhanced growth rates of <i>C. vulgaris</i> cells in this novel circulating loop photobioreactor could be attributed to the combined effect of the CO2 concentration and the uniform distribution of light throughout the reactor volume.<p> Interacting effects of dilution rate, light intensity and concentration of carbon dioxide on specific growth rate was studied in an externally illuminated, continuous flow stirred bioreactor. Steady flow of nutrient medium and air flow was maintained in the bioreactor. This study proved that the dilution rate has major significance at high concentrations of CO2 and high intensities of light. At high concentrations of CO2 at 10% (v/v) and 15% (v/v), increasing dilution rate from 0.005 h-1 to 0.01 h-1 could result in increasing growth rate by a factor of 1.45 and 2.16 respectively.
32

Is personality dependent of growth rate in red junglefowl (Gallus gallus)?

Calais, Andreas January 2013 (has links)
Personality has been reported in a large variety of animal species, but it is not obvious why animals have personality. Variation in physiological traits, such as growth rate, should theoretically affect variation in behaviours and thus can explain why we observe variation in personalities. Growth rate is, theoretically, positively correlated with active personality types. Empirical studies have reported this pattern in different fish species, but there are not yet many studies on endothermic animals. I have therefore scored behaviours of 100 red junglefowl (Gallus gallus) chicks in four personality assays; novel arena, novel object, tonic immobility, and a proactive-reactive test, together with recording variation in growth rate of these individuals. The chicks individual growth rate (% day-1) were calculated and the relationship between personality and growth rate investigated. There was significant difference in growth rate between the sexes, where males grew faster than females, detected already at one week of age. However, no significant correlations between behavioural traits and growth rate were observed, indicating that personality seem to be independent of growth rate. Further studies should therefore investigate the generality of this finding, and alternative underlying mechanisms for variation in personality should be explored.
33

Biokinetic behaviour of <i>Chlorella vulgaris</i> in a continuous stirred bioreactor and a novel circulating loop photobioreactor

Sasi, Divya 21 September 2009 (has links)
Capture of CO2 by algae is an important mechanism for removal of this greenhouse gas from the atmosphere. For this reason, <i>Chlorella vulgaris</i> has beeen studied extensively over the years. A high growth rate of the microalgae is essential in order to increase the fixation rate of CO2 through photosynthesis. Though a number of studies have been carried out to optimize growth of <i>C. vulgaris</i>, high growth rates have not been achieved (Kleinheinz & Keffer, 2002).<p> In this study, a novel circulating loop photobioreactor with enhanced light distribution, gas mass transfer rate and mixing properties was used for the biokinetic study of <i>C. vulgaris</i>. The objective was to study individual effects of light intensity and CO2 concentration on the specific growth rate of <i>C. vulgaris</i>. Studies in this photobioreactor could generate high growth rates of 0.043 h-1. The effect of light intensity on the growth of the <i>C. vulgaris</i> was determined by varying intensity of light to the photobioreactor within a range of 26.945 mW to 431.128 mW, while the flow of air and CO2 were held constant. An increase in light intensity to the photobioreactor resulted in an increase in cell density and variation in the chlorophyll content of the <i>C. vulgaris</i> cells. Enhanced growth rates of <i>C. vulgaris</i> cells in this novel circulating loop photobioreactor could be attributed to the combined effect of the CO2 concentration and the uniform distribution of light throughout the reactor volume.<p> Interacting effects of dilution rate, light intensity and concentration of carbon dioxide on specific growth rate was studied in an externally illuminated, continuous flow stirred bioreactor. Steady flow of nutrient medium and air flow was maintained in the bioreactor. This study proved that the dilution rate has major significance at high concentrations of CO2 and high intensities of light. At high concentrations of CO2 at 10% (v/v) and 15% (v/v), increasing dilution rate from 0.005 h-1 to 0.01 h-1 could result in increasing growth rate by a factor of 1.45 and 2.16 respectively.
34

Seasonal dynamics of picophytoplankton population in the upstream Kuroshio

Huang, Chien-Chih 18 February 2011 (has links)
Population dynamics of picophytoplanktons, including Prochlorococcus, Synechococcus, and picoeukaryotes, were investigated in the upstream Kuroshio. Data were collected during eight cruises between July 2007 and May 2009. Sampling stations were located along 21¢X55¡¦N and between 121¢X00¡¦E and 122¢X10¡¦E in the Kuroshio off the Southeast Taiwan. Monitoring experiments including light shadding experiment, nutrient enrichment, temperature control, and grazing experiments were conducted to better understand the mechanisms that affect the growths of the picophytoplanktons. The abundances of the picophytoplanktons were measured using a flow cytometry.Water column integrated (0~200 m) abundance of Prochlorococcus was higher (26.63 ¡Ó 3.87 ¡Ñ 1012 cells m-2) in spring than either summer (19.07 ¡Ó 4.08 ¡Ñ 1012 cells m-2), autumn (16.05 ¡Ó 2.80 ¡Ñ 1012 cells m-2), or winter (17.89 ¡Ó 5.41 ¡Ñ 1012 cells m-2). During winter, the abundance was significantly (p<0.05) higher at the offshore station (17.89 ¡Ó 5.41 ¡Ñ 1012 cells m-2) than the inshore station (3.19 ¡Ó 2.07 ¡Ñ 1012 cells m-2). The abundance of Prochlorococcus was positively related to water temperature, nitracline depth (Dni), and euphotic depth (Deu), and negatively to surface concentration of N+N or SRP. Prochlorococcus was abundant (>100 ¡Ñ 103 cells ml-1) in the upper 100-m water column. Its maximum (200~300 ¡Ñ 103 cells ml-1) often occurred at the depth shallower than 75 m. The cell density sustained at >25 ¡Ñ 103 cells ml-1 between 100~150 m and was almost nil at the depth deeper than 150 m. There was no significant seasonal differences for either the abundances of Synechococcus (0.32~1.07 ¡Ñ 1012 cells m-2) or picoeukaryotes (0.16~0.24 ¡Ñ 1012 cells m-2). During winter, the abundances of Synechococcus was significantly (p<0.05) higher in the offshore Kuroshio water (2.94 ¡Ó 0.32 ¡Ñ 1012 cells m-2) than that of the inshore Kuroshio water. Similar trend of offshore (0.52 ¡Ó 0.05 ¡Ñ 1012 cells m-2) higher than the inshore was observed for picoeukaryotes in winter. The dynamics of Synechococcus abundance was positively related to surface SRP concentration and negatively to Dni. The picoeukaryotes abundance was positively related to surface N+N concentration, and SRP and negatively to Temp, Dni, and Deu. Vertical distribution of Synechococcus showed that the maximum abundance often occurred above 75 m, but was almost nil below 100 m. By contrast, the maximum abundance for picoeukaryotes often occurred between 50~125 m. The abundance of Synechococcus was positively related to the abundance of picoeukaryotes. And their abundance were negatively related to that of Prochlorococcus. Many environmental factors fluctualed parallelly. Dynamics of surface Temp, Dni and Deu were positively correlated to each other and either of them was negatively correlated to the dynamics of surface concentration of N+N or SRP. Surface N+N was positively correlated with surface SRP. The result of light shadding experiment showed that Prochlorococcus and picoeukaryotes, compared to Synechococcus, were much sensitive to high intensity of light. This suggest that Synechococcus was more tolerant to high light intensity or required more light energy than Prochlorococcus or picoeukaryotes. The results of nutrient enrichment experiments showed that addition of EDTA significantly enhanced the growth of three groups of picophytoplanktons. However, there was no significant difference after addition of either nitrate, Fe, or Cu. Prochlorococcus grew better at 27 ¢XC than 30 ¢XC in the temperature experiment. But there was no difference in the growth rate between 27 ¢XC and 30 ¢XC for Synechococcus or picoeukaryotes The result of grazing experiment showed that there was no difference between the growth rate with and without grazers in the incubation for any of the three groups of picophytoplanktons.
35

Characterization, Crystallization, Melting and Morphology of Poly(ethylene succinate), Poly(trimethylene succinate) and their Copolyesters

Chang, Wei-che 03 July 2006 (has links)
Poly(ethylene succinate) (PES), poly(trimethylene succinate) (PTS) and their copolyesters (PETSAs) with various compositions were used to investigate the structure-property relationship. The results of intrinsic viscosity and GPC have proven successful in preparing high molecular weight polyesters. The chemical compositions and the sequence distribution of co-monomers in the copolyesters were determined by NMR spectroscope. The distributions of ES unit and TS unit were found to be random. Their thermal properties were characterized using differential scanning calorimeter (DSC). The thermal stability of polyesters was analyzed by thermogravimeter (TGA) and polarized light microscope (PLM) under nitrogen. The results of TGA show that all of the samples have similar thermal stability (Tstart : 246¡Ó3 ¢XC), but the thermal degradation temperature of PES and PETSA(95/05) are 213 and 200 ¢XC, respectively, estimated from the isothermal growth rates after pre-melting at various temperatures. The degradation temperature analyzed by PLM is more sensitive than that obtained from TGA. The incorporation of 5 mol% of TS units into PES significantly reduces the thermal stability of PES. In addition, wide-angle X-ray diffractograms (WAXD) were obtained for polyesters which were crystallized isothermally at a temperature 5~10 ¢XC below their melting temperatures. The results of WAXD and DSC indicate that the incorporation of TS units into PES significantly inhibit the crystallization behavior of PES. In the second part of this study, PES and PETSA(95/05) were studied in detail. The crystallization kinetics and the melting behavior were investigated by using DSC in both conventional mode and modulated mode (TMDSC). The reversing, total, and non-reversing heat flow curves were analyzed. The Hoffman-Weeks plots gave an equilibrium melting temperature of 112.7 and 108.3 ¢XC for PES and PETSA(95/05), XI respectively. Only one crystal form was found from WAXD for specimens crystallized isothermally at various temperatures. Based on the WAXD patterns, DSC and TMDSC thermograms, multiple endothermic melting peaks can be explained by two mechanisms, melting-recrystallization-remelting and dual morphologies. PLM was used to study the growth rates and morphology of the spherulites. The growth rates measured in isothermal conditions were very well comparable with those measured by the non- isothermal procedure. In addition, the temperature range of growth rates detected by the non- isothermal procedure is wider than that by the isothermal method, which is time consuming. The regime II&#x00AE;III transition of PES was estimated at ~ 71 ¢XC which is very close to the literature values, and that of PETSA(95/05) was found at ~ 65 ¢XC.
36

The Socioeconomic Structures and Economic Development: The case of Taiwan

Ueng, Tsei-Hsia 15 August 2001 (has links)
During the past forty years and more, the economics in Taiwan have grown rapidly and staidly. It has been making the national income and the level of living life a huge upgrading there. As well as the income distribution has become more averagely and reasonably. That is why Taiwan is taken as a successful model for developing countries. The research objective of this study is to understand the relationship between the socioeconomic indicators and the dimensions of economic development. This study started with the related literatures and effected factors of economic development. Then collecting the statistic data and indicators that are from the Directorate-General of Budget, Accounting and Statistics, Executive Yuan, Department of Statistics, Ministry of Economic Affairs and Ministry of the Interior to construct the dimensions of economic development and its effected factors. The following work is using Factor Analysis to combine these socioeconomic indicators and form them to four main dimensions that including the Condition of Industrialization, Investment and Consumption, the Condition of Employment, Trading and Saving. Afterwards using the Multiple Linear Regression to find out the influence of these four socioeconomic dimensions against each dimension of economic development. Finally using the Canonical Correlation Analysis to find out the Canonical Weights and make the biggest correlation between the linear combination of socioeconomic dimensions and the linear combination of dimensions of economic development. The conclusions found in this study are: (1) Economic Growth Rate was effected mainly by the Trading and Saving, (2) Per Capita GNP was effected mainly by the Condition of Industrialization, (3) Ratio of Highest 5th¡¦s income to Lowest 5th¡¦s was effected mainly by the Condition of Employment and Trading and Saving. Therefore, this study suggests that to improve future economics based on ¡§knowledge¡¨ in order to increase international competitive ability and adapt the changes of industrial structure. Extending the national compulsory education and reforming the education system in order to improve the quality of manpower. In order to access the labor force soon, a policy encouraging the advanced courses on the job. Moreover, making use of resources in Taiwan to develop the tourist industries in order to increase employments.
37

Environmental and nutritional effects on beef tenderness in Texas

Peach, Jody Lynea 15 November 2004 (has links)
Effects of three environments and their native or rye pasture forage systems on subsequent carcass characteristics, composition, and meat palatability were examined following grain feeding. Calves (F2 Angus x Bos indicus) with similar pre-weaning management and genetics were randomly assigned to one of eight treatments (McGregor-Calf; McGregor-Low; Uvalde-Low; Uvalde-High; Overton-Low, Rotational; Overton-Low, Continuous; Overton-High, Rotational; and Overton-High, Continuous). After approximately five months of grazing, cattle in forage groups were transported to McGregor and finished on a corn-milo ration to visually assessed 10 mm fat thickness. Longissimus muscle sections were randomly assigned into aging periods of 1, 7, 14, 21, 28, or 35 days and two-2.54 cm steaks were removed per section for Warner-Bratzler shear force and trained sensory analysis. After grazing, steers fed diets designed to produce higher rates of gain weighed more than steers at the same location fed diets designed for lower rates of gain. Within the high nutrition treatments, Uvalde-High steers had a lower average daily gain than steers in the Overton-High treatments. Differences in environment and nutritional treatments induced differences in rate of gain during the stocker phase. All forage treatment groups increased average daily gain in the feedlot phase. After the feedlot phase, steers varied in live weight due to treatment. Nutritional/environmental treatments affected ribeye area; kidney, pelvic and heart fat; and hot carcass weight, but not final yield grade. Treatment had minimal affects on quality grade characteristics. There was no affect by treatment on Warner-Bratzler shear force or sensory panel perception of myofibrillar tenderness, connective tissue amount, overall tenderness, or overall flavor intensity. Storage day affected shear force; steaks were toughest at 1 and 7 days of storage with shear force values decreasing after 7 days of storage. There was no interaction between environmental/nutritional treatment and storage day. Juiciness and cook loss were affected by treatment (P=0.0001). Overall, environment and nutrition had little impact on eating quality. Despite differences in average daily gain, it appears that steers may be fed forage diets followed by grain feeding to a similar fat thickness endpoint and produce steaks that are similar in palatability to grain-fed steers.
38

Characterization of a Copolyester and Six Metal-Ceramic Crowns

Yang, Chao-sen 19 August 2008 (has links)
This thesis contains two parts of materials characterization. Part I is a poly(butylene succinate) copolymer with minor amount of 2-methyl-propylene succinate. In the second part, six kinds of implant crowns made from five dental casting alloys and one Zircoina ceramic are studied. Copolyester was synthesized and characterized as having 89.0 mol% butylene succinate units and 11.0 mol% 2-methyl-propylene succinate units in a random sequence, revealed by NMR. Isothermal crystallization kinetics was studied in the temperature range (Tc) from 75 to 91 ¢XC using differential scanning calorimeter (DSC). The melting behavior after isothermal crystallization was studied by using DSC by varying the Tc, the crystallization time and the scanning rate. DSC curves showed triple melting peaks. Multiple melting behaviors indicate that the upper melting peaks are associated with the primary and the recrystallized crystals, or the crystals with different lamellar thickness. As the Tc increases, the contribution of recrystallization slowly decreases and finally disappears. A Hoffman-Weeks linear plot gives an equilibrium melting temperature of 118.4 ¢XC. The spherulitic growth rates of this copolyester were measured at Tc between 69 and 91 ¢XC using an optical microscope equipped with a CCD camera. The kinetic analysis of the growth rates gave a regime II-III transition temperature at about 77.2 ¢XC. Rectangular specimens of 10 ¡Ñ 9 ¡Ñ 4 mm were made of five kinds of casting alloys, separately. They were treated in the same procedures as crowns did. Their surfaces after oxidation were analyzed using x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Rectangular specimens after applying porcelains were ~5.5 mm thick. The cross-section areas were studied by electron probe micro analyzer (EPMA). Standardized maxillary premolar crowns were fabricated with five different alloys and one Zircoina ceramic. The crown specimens were positioned in a custom testing apparatus and vertically loaded on the middle of the occlusal surface with a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. Mean values of load at fracture were calculated in each alloy and compared with a one-way analysis of variance and Tukey test (£\=0.05). The fracture surfaces were examined using SEM. The results of XPS, SEM and EPMA indicate that on the surface there was an oxidation layer (or interface between metal and ceramic) of indium (or/and tin, zinc, etc.). The concentration of oxide metal increased, whereas that of precious metal decreased, from bulk to interface. The fracture strength and the fracture path of the crowns were correlated with the metal-ceramic interface of the rectangular specimens that was characterized using XPS, SEM and EPMA.
39

The Determinants of Financial Development : A Focus on African Countries

Benyah, Francella Ewurama Ketsina January 2010 (has links)
<p>This thesis attempts to establish what determines financial development in Africa by making use of cross sectional and panel data techniques. Financial development, the dependent variable, is measured using the banking sector indicator liquid liabilities (M3) while trade openness, financial openness and the GDP growth rates are used as independent variables. The data used in this research ranges from 1975-200, though for the cross sectional analysis particular years (1975, 1985, 1995, and 2005) are focused on.</p><p>The empirical results from both regression types generally suggest that trade openness has a significantly positive effect on Africa’s financial development. Cross-sectional results show that financial openness and the GDP growth rate are significantly negative in 2005. With the panel data results, financial openness is significantly negative in explaining financial development, while the GDP growth rate is insignificant suggesting that it is not an important determinant of financial development for African countries.</p>
40

Extending the utility of machine based height sensors to spatially monitor cotton growth

Geiger, David William 30 September 2004 (has links)
The recommended procedures for implementing COTMAN; a cotton management expert system; suggest frequent crop scouting at numerous locations for each field. Machine based height sensors coupled with the ability to spatially record height values make it possible to locate regions of a field that are height representative of the entire field. A machine based height measurement system called HMAP was used to assess plant height in various fields in the 2003 growing season while the same fields were monitored with COTMAN. The plant height data was used to determine an optimal COTMAN sampling scheme for each field consisting of significantly fewer sampling locations than recommended by COTMAN. It was possible to ascertain equivalent information from COTMAN using two sites selected from height data in place of six sites selected per COTMAN recommendations. The HMAP system was extended to monitor rate of growth in real time in addition to plant height by comparing historical plant height data recorded on previous field passes to current height values. The rate of growth capable HMAP system will make it possible to track cotton growth and development with an automated system.

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