Nine male Physical Education students were selected to test the hypothesis that addition of CO₂ to the inspired air during recovery will cause significant increases in ventilation above control conditions and that recovery from submaximal exercise will be enhanced by the addition of 2.78% or 5.80% CO₂ to room air. The exercise was administered for six minutes at a workload predetermined to elicit 75% of his maximal oxygen uptake. The dependent variables (heart rate, ventilation, oxygen uptake, and carbon dioxide elimination) were subjected to a one way analysis of variance and significant F ratios evaluated using Dunnett's Test. Ventilation is increased significantly (p<.05) above control values with the addition of 5.80% CO₂ to room air during recovery however, there is no significant increase in oxygen uptake. The addition of 2.78% CO₂ to room air during recovery does not significantly (p>.05) increase ventilation; there is however a significant (p<.05) increase in oxygen uptake in the first 30 seconds of recovery. Neither treatment effect causes significant changes in heart rate. The addition of 5.80% CO₂ to the inspired air significantly (p<.05) reduces carbon dioxide elimination. In 4 subjects, the effect produced a carbon dioxide uptake at certain time intervals. The addition of 2.78% CO₂ to the inspired air caused a significant (p<.05) reduction of carbon dioxide elimination in the first minute of recovery. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

This research was concerned with some physiological effects of supra-normal CO₂ concentrations on cucumber, tomato and Japanese Morning Glory (Pharbitis nil), and with measurement of CO₂ levels in a commercial greenhouse. Measurements of CO₂ concentrations in a cucumber greenhouse showed that, in the early stages of crop development, early morning CO₂ levels reached 0.18% as a result of straw decomposition in the plant beds. Later in crop development, daytime levels were much lower and required gas combustion to restore high concentrations. Stomatal resistances in cucumber leaves were relatively insensitive to high greenhouse concentrations. Variation in stomatal resistance through the crop canopy was, however, detected. Generally, the two most recently developed leaves showed higher resistances than those of a slightly greater physiological age. Differences in leaf irradiance could not fully explain this effect, which may be related to the stage of leaf development. Subsequent experiments on greenhouse tomato crops showed that CO₂-enriched (0.09% CO₂) plants flowered earlier and produced 30% more fruit than those grown in normal air. Photosynthetic rates were inherently higher in apical and basal leaves developed under CO₂enrichment at irradiances above 50 m⁻²s⁻¹ .Behavioral indicies of photosynthetic efficiency indicated an enhanced capacity to utilize CO₂ in enriched plants. Measurements of CO₂ exchange in leaves of plants grown in chambers at 3 CO₂ concentrations (0.03, 0.1 and 0.5%) confirmed the enhancement of inherent photosynthetic rates in young leaves of 0.1% grown plants. Reduced rates of photorespiration, total O₂ inhibition of photosynthesis, glycolate oxidase (GaO) activity, and an increased rate of ribulose-biphosphate-carboxylase (RuBP-case) activity, contributed to this enhancement. Maximum photosynthetic rates in young leaves developed at 0.5% CO₂ were similar to those developed in 0.03% CO₂. Growth rates of the 0.1% CO₂-grown plants were higher than the similar rates of plants from the 0.03 and 0.5% regimes. Apparently maximum benefit from CO₂ enrichment is achieved by maintaining atmospheric CO₂ concentrations close to 0.1%. At a later stage of development, however, GaO and RuBP-case activities were similar in the 0.03 and 0.1% CO₂-grown plants and photosynthetic rates did not differ between growth regimes. Observations on the effects of 0.03, 0.1, 1.0 and 5.0% CO₂ on development in the Short-Day Plant Pharbitis nil revealed that 1.0 and 5.0% CO₂ modified normal flowering. These concentrations induced a weak flowering response in Long-Days and Short-Days and promoted stem elongation and leaf production under both photoperiods. These modifications were apparently unrelated to patterns of CO₂ exchange which showed a relatively small increase above 0.5% CO₂. These results are discussed in relation to possible mechanisms for the effects of supra-normal CO₂ concentrations on development. The diversity of physiological effects mediated by CO₂, and their relationship to one another are discussed. / Land and Food Systems, Faculty of / Graduate

A physical model and a numerical solution procedure has been developed to predict heat transfer behaviour in supercritical fluids. A major area of concentration was the modelling of the turbulent components of shear stress and heat flux. Traditionally, the turbulent fluxes are modelled by algebraic expressions such as the familiar mixing length methods. However, the use of this technique has not been entirely satisfactory. Newer methods for constant-property flows which model turbulent fluxes by considering the transport of quantities such as turbulent kinetic energy and the dissipation rate of turbulence have been extended to supercritical fluids. This involves the solution of two additional partial differential equations that are solved simultaneously with the equations of continuity, energy, and momentum. The numerical scheme has been developed on a completely two-dimensional basis by extending the Pletcher-DuFort-Frankel finite difference method. Computed results for velocity and temperature profiles as well as wall temperature distributions exhibited reasonable agreement with previous experimental data and therefore indicate the viability of the present method. Computations were carried out for supercritical carbon dioxide flowing through a circular duct in the reduced pressure range 1.0037 to 1.098. A consideration of the influence of buoyancy on the mean momentum balance permitted the calculation of unusual velocity profiles in this investigation. The existance of such velocity profiles had been accepted previously but the nature of their growth along a pipe has probably not been suggested previous to this work. No attempt was made to include buoyancy generated turbulence or additional fluctuating property correlations in this work, but suggestions are made regarding possible avenues of approach. Some of the incidental outcomes of this work were a new continuous universal velocity profile implicit in cross stream distance an a new mixing length distribution for turbulent pipe flows. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

by Edwine Wiley Odom / Typescript / M.S. Florida State College for Women 1921 / Includes bibliographical references

Saudi Arabia is the greatest exporter of oil in the world and also the country with greatest desalination capacity. It is considered a rich country but not a developed one. Because water is scarce while energy is abundant, it becomes important to evaluate the environmental performance of populations in Saudi Arabia with regards to these two aspects. King Abdullah University of Science and Technology (KAUST) is a gated community in Saudi Arabia with high living standards where water and energy are free of cost (no constraint over use). Four environmental sustainability indicators were used to determine the environmental performance of KAUST in comparison to other countries. It was found that per capita, KAUST is between the five greatest water and energy consumers in the world. Important factors to this result are the fact that KAUST is still under construction, that the peak capacity for permanent residents has not yet been reached and that there is little control over the water and energy systems at KAUST. It was concluded that KAUST should reduce its water and energy consumption per capita. To this means, some proposed solutions were to have wide-spread awareness-raising campaigns to all people working and living in KAUST, and to improve control over air conditioning control systems.

The use of low-pressure membranes, mainly ultrafiltration (UF), has emerged in the last decade and began to show acceptance as a novel pretreatment process for seawater reverse osmosis (SWRO) desalination. This is mainly due to the superior water quality provided by these membranes, in addition to reduction in chemicals consumption compared to conventional methods. However, membrane fouling remains the main drawback of this technology. Therefore, frequent cleaning of these membranes is required to maintain water flux and its quality. Usually, after a series of backwash using UF permeate chemical cleaning is required under some conditions to fully recover the operating flux. Frequent chemical cleaning will probably decrease the life time of the membrane, increase costs, and will have some effects on the environment. The new cleaning method proposed in this study consists of using a solution saturated with carbon dioxide (CO2) to clean UF membranes. Under the drop in pressure, this solution will become in a supersaturated state and bubbles will start to nucleate on the surface of the membrane and its pores from this solution resulting in the removal of the fouling material deposited on the membrane. Different compositions of fouling solutions including the use of organic compounds such as sodium alginate and colloidal 5 silica with different concentrations were studied using synthetic seawater with different concentrations. This cleaning method was then compared to the backwash using Milli-Q water and showed an improved performance compared to it. An operational modification to this cleaning technique was then investigated which includs a series of sudden pressure drop during the backwash process. This enhanced technique showed an even better performance in cleaning the membrane, especially at severe fouling conditions. In most cases, the membrane permeability was fully recovered even at harsh conditions where conventional backwash failed to maintain a stable operation. Therefore, the new cleaning method might provide an efficient and environmentally friendly alternative cleaning technique to low-pressure membranes technology in the future.

ABSTRACT CuZn Alloy- Based Electrocatalyst for CO2 Reduction Amira Alazmi Carbon dioxide (CO2) is one of the major greenhouse gases and its emission is a significant threat to global economy and sustainability. Efficient CO2 conversion leads to utilization of CO2 as a carbon feedstock, but activating the most stable carbon-based molecule, CO2, is a challenging task. Electrochemical conversion of CO2 is considered to be the beneficial approach to generate carbon-containing fuels directly from CO2, especially when the electronic energy is derived from renewable energies, such as solar, wind, geo-thermal and tidal. To achieve this goal, the development of an efficient electrocatalyst for CO2 reduction is essential. In this thesis, studies on CuZn alloys with heat treatments at different temperatures have been evaluated as electrocatalysts for CO2 reduction. It was found that the catalytic activity of these electrodes was strongly dependent on the thermal oxidation temperature before their use for electrochemical measurements. The polycrystalline CuZn electrode without thermal treatment shows the Faradaic efficiency for CO formation of only 30% at applied potential ~−1.0 V vs. RHE with current density of ~−2.55 mA cm−2. In contrast, the reduction of oxide-based CuZn alloy electrode exhibits 65% Faradaic efficiency for CO at lower applied potential about −1.0 V vs. RHE with current density of −2.55 mA cm−2. Furthermore, stable activity was achieved over several hours of the reduction reaction at the modified electrodes. Based on electrokinetic studies, this improvement could be attributed to further stabilization of the CO2•− on the oxide-based Cu-Zn alloy surface.

Explosive volcanic eruptions are propelled to the surface by the exsolution of vapour bubbles from magma due to decompression. A long-held view is that the amount of H₂O dissolved in the magma at depth controls the intensity of an explosive eruption. Growing evidence from studies reporting H₂O concentrations of melt inclusions (MIs) do not support this view. Instead, the rate at which magma ascends to the surface may play an important role in modulating the eruption style. Slow magma ascent allows the vapour bubbles to rise ahead of the magma, thereby diffusing the driving force for an explosive eruption, whereas for fast magma ascent, the bubbles remain essentially trapped within the magma, causing acceleration and the potential for an explosive eruption. Chapter 1 presents a new modelling approach to constrain magma decompression rate based on the incomplete diffusive re-equilibration of H₂O in olivine-hosted melt inclusions. We apply this chronometer to two contrasting eruptions at Cerro Negro volcano in Nicaragua: the 1992 VEI 3 and 1995 VEI 2 eruptions. Both eruptions have the same basaltic composition (SiO₂ ∼ 50 wt%) and maximum volatile concentrations (H₂O ∼ 4.7 wt%). However, MIs from the less explosive 1995 eruption appear to have experienced more water loss compared to those from the 1992 eruption, which is consistent with slower magma ascent. We present a parameterization of the numerical diffusion model in chapter 2, which significantly reduces the calculation time, facilitating the use of Monte Carlo simulations to evaluate uncertainties. We use this parameterization to create a regime diagram that can be used to guide when melt inclusions may be used as magma hygrometers and when they are better suited to act as magma speedometers. We develop diagnostic tools to recognize where and when water loss has occurred in a magma’s ascent history, and we outline quantitative tools that may be used to restore the primary and/or pre-eruptive water content. We find that one of the largest sources of uncertainty in modelling diffusive re-equilibration of H₂O in MIs and olivines is the diffusivity of H+ in olivine. We present new experimental constraints on H+ diffusivity in olivines from Cerro Negro (1992 eruption) and Etna (3930 BP ‘Fall Stratified’ eruption) (chapters 1 and 3, respectively). Our results show that H+ diffusion is highly anisotropic with the diffusivity along the [100] direction more than an order of magnitude faster than along [010] or [001], implying a large role for the ‘proton-polaron’ diffusion mechanism, which shares this anisotropy. We also find that the lower forsterite (Fo ~ 80) olivines from Cerro Negro have significantly faster H+ diffusivity than higher forsterite (Fo ~ 90) olivines from Etna. The results for Etna agree well with other estimates on high forsterite olivines from San Carlos and Kilauea, suggesting that the Fe content of the olivine strongly affects the H+ diffusivity. In chapter 4, we apply the methods from the first three chapters to an unusually explosive eruption of picritic magma at Etna, Sicily in 3930 BP (termed the ‘Fall Stratified’ eruption). MIs from this eruption show limited evidence for water loss and so cannot be modelled to determine decompression rate. Instead, we model H+ diffusion profiles within the olivine crystals themselves and determine rapid ascent rates of ~15 m/s. We perform rehomogenization experiments on the MIs to accurately assess their pre-eruptive CO₂ concentrations, and find nearly 1 wt.% CO₂. Solubility modelling indicates that these MIs must have been trapped at near Moho depths (24–30 km). The magma’s high CO₂ concentration and deep initial pressures may have been responsible for the magma’s rapid ascent, which ultimately led to its great eruption intensity.

Thesis (M. Sc. (Chemistry)) --University of Limpopo, 2019. / Metal alloys are one of few materials that are capable of acting as catalyst precursors in Sabatier reactions, reducing poisonous CO2 gas into different useful hydrocarbons. However, optimal reduction of CO2 through these materials takes place at relatively elevated temperatures due to poisoning-intolerance and deterioration of hydrogen absorption/desorption kinetics resulting from the surface chemical action of electrophilic gases at lower or room temperature. This work presents results of the feasibility study focused on improving hydriding kinetics and poisoning-tolerance, which are prerequisites properties that a material should possess to be a suitable catalyst precursor for Sabatier reaction, of the metal hydride (MH) materials. The studies in this work included: (i) element substitution and (ii) surface modification procedure. The substrate alloys investigated had the compositions LaNi4.8-xSnx and TiMn1.52, where x was 0.2. The activation performances of the materials were estimated by measurement of H2 absorption kinetics in the absence of vacuum heating, after long-term exposure to air. The presence of oxide layers on the alloy surface resulted in the deterioration of H sorption kinetics for the parent alloys. To overcome impurity effects, surface-modification technique through autocatalytic palladium deposition was employed. The activation performances and kinetics of the surface-modified were found to be superior to that of the unmodified AB2 and AB5 alloys. Based on this observation, it was seen that surface-modified MH materials based on the alloy substrate and Pd nanostructured coatings may be utilised as catalysts precursors for CO2 reduction into hydrocarbons.

The functionalization of renewable and abundant carbon dioxide as a building block for industrial polymer production leads to safer designs in manufacturing of materials, decreases the dependence of fossil fuel feedstocks, and diminishes plastic waste generation due to engineered biodegradability. Through judicious catalyst design, the copolymerization of carbon dioxide and oxiranyl small molecules has not only opened new synthetic routes towards the manufacturing of novel polycarbonate architectures, but in addition, allows for the mass production of commodity plastics via raw materials derived entirely from biomass. This environmentally friendly methodology pioneered by Shohei Inoue not only accommodates polymer product with an eco-design, but in tandem serves as a means of carbon capture, mitigating the effects of global climate change. With a global market value anticipated to reach 2 billion dollars by 2026, polyacrylate resins are ubiquitous in the paint, automotive, and adhesive industries. However, the production of these non-degradable polymers compounds the rising concern of plastic pollution in the environment. Herein, the design and synthesis of polyacrylate mimetics bearing a degradable carbonate moiety in the backbone is described. The synthetic methodology utilizes a green pathway through the use of carbon dioxide as the C1 source. The thermal, chemical, and rheological properties of the materials are evaluated and compared to commercial acrylates and adhesives. Additional modification of the materials through terpolyermization is conducted, and their ability to perform as smart adhesive surfaces as well as clinical use in lung resection surgery is covered. / 2020-11-12T00:00:00Z