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.

This thesis presents the results of open stope stability and dilution research which focused on evaluating and quantifying stress, undercutting, blasting and exposure time and their effect on open stope stability and dilution. Open stope mining is the most common method of underground mining in Canada. Unplanned stope dilution is a major cost factor for many mining operations. Significant advances in empirical stability and dilution design methods have improved our ability to predict probable dilution from open stoping operations. However, some of the factors that influence hanging wall dilution are either ignored or assessed in purely subjective terms in existing designs. This thesis attempts to quantify these factors, from a geomechanics perspective, to assist in predicting and minimizing dilution. A comprehensive database was established for this study based on two summers of field work. Site geomechanics rock mass mapping and classification were conducted and case histories were collected from Cavity Monitoring System (CMS) surveyed stopes from Hudson Bay Mining and Smelting Co. Ltd. (HBMS) operations. The stope hanging wall (HW) zone of stress relaxation was quantified based on extensive 2D and 3D numerical modelling. Stress relaxation was linked to the stope geometry and the degree of adjacent mining activity. The influence of undercutting on stope HW stability and dilution was analysed using the case histories collected from HBMS mines. An undercutting factor (UF) was developed to account for the undercutting influence on stope HW dilution. Numerical simulations were conducted to provide a theoretical basis for the undercutting factor. A relationship was observed between the degree of undercutting, expressed by the UF term and the measured dilution. Many factors can significantly and simultaneously affect a blast performance, which may result in blast damage to stope walls. Major blasting factors which influence stope HW stability were identified. The influence of blasting on stope HW stability and dilution was evaluated based on the established database. The HBMS database, Bieniawskis stand-up time graph, as well as Geco mine case histories were used to evaluate the influence of exposure time on stope stability and dilution. Relating increased mining time to increased dilution allows the mining engineer to equate mining delays to dilution costs. Each of the factors assessed in this study was studied independently to assess its influence on stope dilution, based on the HBMS database. The factors influencing dilution often work together, so a multiple parameter regression model was used to analyze the available parameters in the HBMS database. The findings of this research greatly improve an engineers ability to understand and to predict the influence of mining activities and stoping plans on hanging wall dilution.

This thesis presents the results of open stope stability and dilution research which focused on evaluating and quantifying stress, undercutting, blasting and exposure time and their effect on open stope stability and dilution. Open stope mining is the most common method of underground mining in Canada. Unplanned stope dilution is a major cost factor for many mining operations. Significant advances in empirical stability and dilution design methods have improved our ability to predict probable dilution from open stoping operations. However, some of the factors that influence hanging wall dilution are either ignored or assessed in purely subjective terms in existing designs. This thesis attempts to quantify these factors, from a geomechanics perspective, to assist in predicting and minimizing dilution. A comprehensive database was established for this study based on two summers of field work. Site geomechanics rock mass mapping and classification were conducted and case histories were collected from Cavity Monitoring System (CMS) surveyed stopes from Hudson Bay Mining and Smelting Co. Ltd. (HBMS) operations. The stope hanging wall (HW) zone of stress relaxation was quantified based on extensive 2D and 3D numerical modelling. Stress relaxation was linked to the stope geometry and the degree of adjacent mining activity. The influence of undercutting on stope HW stability and dilution was analysed using the case histories collected from HBMS mines. An undercutting factor (UF) was developed to account for the undercutting influence on stope HW dilution. Numerical simulations were conducted to provide a theoretical basis for the undercutting factor. A relationship was observed between the degree of undercutting, expressed by the UF term and the measured dilution. Many factors can significantly and simultaneously affect a blast performance, which may result in blast damage to stope walls. Major blasting factors which influence stope HW stability were identified. The influence of blasting on stope HW stability and dilution was evaluated based on the established database. The HBMS database, Bieniawskis stand-up time graph, as well as Geco mine case histories were used to evaluate the influence of exposure time on stope stability and dilution. Relating increased mining time to increased dilution allows the mining engineer to equate mining delays to dilution costs. Each of the factors assessed in this study was studied independently to assess its influence on stope dilution, based on the HBMS database. The factors influencing dilution often work together, so a multiple parameter regression model was used to analyze the available parameters in the HBMS database. The findings of this research greatly improve an engineers ability to understand and to predict the influence of mining activities and stoping plans on hanging wall dilution.

This thesis presents new methods to improve open stope hangingwall (HW) design based on knowledge gained from site visits, observations, and data collection at underground mines in Canada, Australia, and Kazakhstan. The data for analysis was collected during 2 months of research at the Hudson Bay Mining and Smelting Ltd. Callinan Mine in Flin Flon, Manitoba, a few trips to the Cameco Rabbit Lake mine in northern Saskatchewan, and 3 years of research and employment at the Xstrata Zinc George Fisher mine near Mount Isa, Queensland, Australia. Other sites visited, where substantial stope stability knowledge was accessed include the Inco Thompson mines in northern Manitoba; BHP Cannington mine, Xstrata Zinc Lead Mine, and Xstrata Copper Enterprise Mine, in Queensland, Australia; and the Kazzinc Maleevskiy Mine in north-eastern Kazakhstan. An improved understanding of stability and design of open stope HWs was developed based on: 1) Three years of data collection from various rock masses and mining geometries to develop new sets of design lines for an existing HW stability assessment method; 2) The consideration of various scales of domains to examine HW rock mass behaviour and development of a new HW stability assessment method; 3) The investigation of the HW failure mechanism using analytical and numerical methods; 4) An examination of the effects of stress, undercutting, faulting, and time on stope HW stability through the presentation of observations and case histories; and 5) Innovative stope design techniques to manage predicted stope HW instability. An observational approach was used for the formulation of the new stope design methodology. To improve mine performance by reducing and/or controlling the HW rock from diluting the ore with non-economic material, the individual stope design methodology included creating vertical HWs, leaving ore skins or chocks where appropriate, and rock mass management. The work contributed to a reduction in annual dilution from 14.4% (2003) to 6.3% (2005), an increase in zinc grade from 7.4% to 8.7%, and increasing production tonnes from 2.1 to 2.6 Mt (Capes et al., 2006).

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.

Thèse de doctorat : Sciences Chimique : Physico-Chimie de la Matière Condensée : Bordeaux 1 : 2008. / Titre provenant de l'écran-titre.

This study used the isotope pool dilution method to estimate gross rates of mineralization, nitrification, NH4+ and NO3- consumption, and denitrification emissions over two growing seasons within a conventional barley-red clover-potato crop rotation on Prince Edward Island. Gross rates within the 2010 season were, in most cases, not significant across crop species or sampling date. In comparison, gross nitrification, NH4+ consumption, and NO3- consumption rates in 2011 were greatest within the potato crop following planting and hilling. However, rates were highly variable within both seasons. Error analysis indicated that variation in soil mineral nitrogen concentrations between duplicate cores was the greatest source of error. The use of the isotope pool dilution method to estimate gross nitrogen transformation rates using intact cores was not viable within this production system due to high and variable soil mineral nitrogen concentrations, particularly following fertilizer application.

The micronutrient intake of the average South African is not optimal. National fortification of staple foods does not solve all micronutrient deficiencies. Furthermore, urbanisation causes a shift in food intake, increasing the availability of cheaper and more energy dense food and drinks that are often lacking in micronutrients. It is unclear whether the current literature provides sufficient evidence of nutrient dilution by the moderate consumption of alcohol and/or added sugar. The aim of the present study was to evaluate the dietary intakes of a population in nutrition transition and determine the effect of intake of alcohol and added sugars on intakes of micronutrients and food groups to provide information for the development of preventive strategies in public health. A number of countries, including South Africa, suggest limited alcohol and sugar intakes in the Food Based Dietary Guidelines but do not quantify this recommendation. Data from the "Transition and Health during Urbanisation in South Africa" survey (THUSA) were analysed for dietary intakes (as determined by a validated quantified food frequency questionnaire), age and body mass index (BMI). The THUSA study was conducted during 1996 and 1998 in the North West Province and included 1854 "apparently healthy". Respondents aged 15 years and older from 37 randomly selected sites from rural and urban areas. Alcohol intake (absolute intake and percentage of energy) was the highest for men living in middle class urban areas. With increased urbanisation, the type of beer shifted from sorghum based to commercial beer. Sixty-one percent of men and 25% of women reported that they consumed alcohol at the time of the survey. Eighteen percent of men and 11.7% of women consumed more than 30g and 15g alcohol per day, respectively (intakes which are regarded as moderate). Men and women consuming the most alcohol had significantly higher mean intakes of most macro and micronutrients. However, the intake of vitamin Bi2, B6, folate, vitamin E and vitamin C did not meet the recommended dietary intake (RDA) across all levels of alcohol intake. Although the total energy intake increased with increased alcohol intake, there was no significant difference between the mean BMI of men or women with different levels of intake. One third of the population consumed more than a 100g of added sugar daily. Intake of sugar was the highest in the farm dwellers but the intake of sweets, cakes, cookies and cold drinks was the highest in the urban areas. As sugar intake increased so did energy, carbohydrates and most micronutrients. However, the intake of vitamin B12, folate, vitamin C and calcium did not meet the RDA across all levels of sugar intake. BMI did not differ between respondents with the highest and lowest sugar intake and no association was found between BMI and sugar intake. The THUSA study was conducted before fortification of staple food became law in October 2003. Maize meal and wheat flour are nowadays fortified with certain vitamins and minerals which may alleviate some micronutrient deficiencies. For future research it is imperative to establish the reasons for low intake of certain micronutrients rather than to look at a single food item in the diets of the South African adult population. Proper education on the intake of cheaper food sources of micronutrients needs to be highlighted at all levels of the health sector. / Thesis (M.Sc. (Dietetics)--North-West University, Potchefstroom Campus, 2009.

The micronutrient intake of the average South African is not optimal. National fortification of staple foods does not solve all micronutrient deficiencies. Furthermore, urbanisation causes a shift in food intake, increasing the availability of cheaper and more energy dense food and drinks that are often lacking in micronutrients. It is unclear whether the current literature provides sufficient evidence of nutrient dilution by the moderate consumption of alcohol and/or added sugar. The aim of the present study was to evaluate the dietary intakes of a population in nutrition transition and determine the effect of intake of alcohol and added sugars on intakes of micronutrients and food groups to provide information for the development of preventive strategies in public health. A number of countries, including South Africa, suggest limited alcohol and sugar intakes in the Food Based Dietary Guidelines but do not quantify this recommendation. Data from the "Transition and Health during Urbanisation in South Africa" survey (THUSA) were analysed for dietary intakes (as determined by a validated quantified food frequency questionnaire), age and body mass index (BMI). The THUSA study was conducted during 1996 and 1998 in the North West Province and included 1854 "apparently healthy". Respondents aged 15 years and older from 37 randomly selected sites from rural and urban areas. Alcohol intake (absolute intake and percentage of energy) was the highest for men living in middle class urban areas. With increased urbanisation, the type of beer shifted from sorghum based to commercial beer. Sixty-one percent of men and 25% of women reported that they consumed alcohol at the time of the survey. Eighteen percent of men and 11.7% of women consumed more than 30g and 15g alcohol per day, respectively (intakes which are regarded as moderate). Men and women consuming the most alcohol had significantly higher mean intakes of most macro and micronutrients. However, the intake of vitamin Bi2, B6, folate, vitamin E and vitamin C did not meet the recommended dietary intake (RDA) across all levels of alcohol intake. Although the total energy intake increased with increased alcohol intake, there was no significant difference between the mean BMI of men or women with different levels of intake. One third of the population consumed more than a 100g of added sugar daily. Intake of sugar was the highest in the farm dwellers but the intake of sweets, cakes, cookies and cold drinks was the highest in the urban areas. As sugar intake increased so did energy, carbohydrates and most micronutrients. However, the intake of vitamin B12, folate, vitamin C and calcium did not meet the RDA across all levels of sugar intake. BMI did not differ between respondents with the highest and lowest sugar intake and no association was found between BMI and sugar intake. The THUSA study was conducted before fortification of staple food became law in October 2003. Maize meal and wheat flour are nowadays fortified with certain vitamins and minerals which may alleviate some micronutrient deficiencies. For future research it is imperative to establish the reasons for low intake of certain micronutrients rather than to look at a single food item in the diets of the South African adult population. Proper education on the intake of cheaper food sources of micronutrients needs to be highlighted at all levels of the health sector. / Thesis (M.Sc. (Dietetics)--North-West University, Potchefstroom Campus, 2009.

Fuel flexibility in gas turbines is of particular importance because of the main fuel source, natural gas. Blends of methane, ethane, and propane are big constituents in natural gas and consequently are of particular interest. With this level of importance comes the need for baseline data such as laminar flame speed of said fuels. While flame speeds at standard temperature and pressure have been extensively studied in the literature, experimental data at turbine-like conditions are still lacking currently. This thesis discusses the theory behind laminar flames; new data acquisition techniques; temperature and pressure capability improvements; measured flame speeds; and a discussion of the results including stability analysis. The measured flame speeds were those of methane, ethane, and propane fuel blends, as well as pure methane, at an elevated pressure of 5 atm and temperatures of 298 and 473 K, using a constant-volume, cylindrical combustion vessel. The current Aramco mechanism developed in conjunction with National University of Ireland Galway compared favorably with the data, while the literature data showed discrepancies at stoichiometric to rich conditions. An in-depth flame speed uncertainty analysis yielded a wide range of values from 0.5 cm/s to 21.5 cm/s. It is well known that high-pressure experiments develop flame instabilities when air is used as the oxidizer. In this study, the hydrodynamic instabilities were restrained by using a high diluent-to-oxygen ratio. The thermal-diffusive instabilities were inhibited by using helium as the diluent. To characterize this flame stability, the Markstein length and Lewis number were calculated for the presented conditions. The resultant positive Markstein lengths showed a low propensity of flame speed to flame stretch, while the larger-than-unity Lewis numbers showed the relatively higher diffusivity of helium to that of nitrogen.