Mass transfer rates have been measured for streams of CO₂ bubbles of controlled frequency being absorbed into water in cocurrent pipeline flow. Superficial liquid Reynolds number varied from 1810 to 24000. Mass transfer coefficients based on equivalent spherical areas were between 0.6 and 4.5 cm/min. For 5/16- and 5/8 inch I.D. tubes oriented both horizontally and vertically, the mass transfer coefficients were proportional to (Reynolds number)⁰•⁵² and (tube diameter) ⁻⁰•⁸⁵ at high Reynolds number. Bubble velocities were measured for all test sections and flow conditions. Photographs of bubbles in turbulent flow were obtained by a high speed flash technique. The mass transfer results support a postulated mechanism of surface renewal by turbulent eddies which result from the mean flow of liquid through the tube. Two theoretical approaches have been described in an attempt to relate the surface renewal rate to the pipe flow turbulence. A model based on mixing length theory gives good agreement with the experimental results. In this model the larger scales of motion dominate. A second model was based on the assumption that the very small scales dominate. The flow and convective diffusion equations were solved for idealized viscous eddy cells which represent the small motions. The size, velocity and mass transfer rate of these cells were linked to the turbulent energy spectrum for both solid/liquid and gas/liquid interfaces. The predicted dependence of mass transfer coefficient on Schmidt number and energy dissipation is identical with experimental results for solid surfaces. However, the Reynolds number dependence (Re•⁶⁹) is higher than for the present experiments. Nevertheless, the eddy cell model maybe valid for bubbles and solids in sufficiently highly developed turbulence. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Water availability for uptake by tree seedlings is determined both by the soil water potential in relation to seedling needle water potential and by the resistance to flow of water through the soil, root and stem, to the needles. This study was designed to focus principally on water uptake resistances. The effects of soil texture and tree species on this water uptake resistance were quantified through the use of an Ohm's Law model suited to water flow through the soil-plant system. The study was conducted on one-year-old potted seedlings in a controlled environment growth chamber. Needle water potential (ΨN) of Douglas-fir is not much affected by soil water potential (Ψs) down to about -2.5 MPa, where the calculated water uptake rate becomes very small. However, soil texture does significantly affect the resistance to flow into the seedling and thus affects the water uptake rate by the seedling. The total resistance to water uptake increases as the soil dries. Coarser textured soils show consistently higher water uptake resistances over the soil water potential range -0.5 to -2.5 MPa. It is inferred that differences in resistance are associated with unsaturated, hydraulic conductivity characteristics of the soil and soil-root contact. Unlike Douglas-fir, both western and mountain hemlock show a large decrease in needle water potential as the soil dries down to a Ψs of about -3.0 MPa. The water potential difference (Ψs - ΨN) for hemlocks is less where Ψs is higher than -1.8 MPa, and greater where Ψs is less than -1.8 MPa, than (Ψs - ΨN ) for Douglas-fir in these s s N experiments. Despite these differences, the resistance to water uptake for both hemlock species is much greater over the soil water potential range -0.5 to -2.5 MPa, and thus the water uptake rates are much less than for Douglas-fir with the same soil, even though root densities and root surface areas are much larger for the hemlocks. This behavior is most pronounced with mountain hemlock. These differences are thought to be related to higher tissue and (perhaps) soil-root contact resistances in the hemlock species. The soil resistance appears to be small, at least down to Ψs of about -2.0 MPa, in these experiments. However, root densities are probably much greater than one might expect in the field. / Forestry, Faculty of / Graduate

In this dissertation, the metathesis route of metal chalcogenide aerogel synthesis was expanded by conducting systematic studies between polysulfide building blocks and the 1st-row transition metal linkers. Resulting materials were screened as sorbents for selective gas separation and volatile organic compounds adsorption. They showed preferential adsorption of polarizable gases (CO2) and organic compounds (toluene). Ion exchange and heavy metal remediation properties have also been demonstrated. The effect of the presence of different counter-ion within chalcogel frameworks on the adsorption capacity of the chalcogels was studied on AFe3Zn3S17 (A= K, Na, and Rb) chalcogels. The highest adsorption capacity toward hydrocarbons and gases was observed on Rb based chalcogels. Adopting a new building block [BiTe3]3- with the 1st-row transition metal ions results in the formation of three high BET surface area chalcogels, KCrBiTe3, KZnBiTe3, and KFeBiTe3. The resulting chalcogels showed preferential adsorption of toluene vapor, and remarkable selectivity of CO2, indicating the potential future use of chalcogels in adsorption-based gas or hydrocarbon separation processes. The synthesis and characterization of the rare earth chalcogels NaYSnS4, NaGdSnS4, and NaTbSnS4 are also reported. Rare earth metal ions react with the thiostannate clusters in formamide solution forming extended polymeric networks by gelation. Obtained chalcogels have high BET surface areas, and showed notable adsorption capacity toward CO2 and toluene vapor. These chalcogels have also been engaged in the absorption of different organic molecules. The results reveal the ability of the chalcogels to distinguish among organic molecules on their electronic structures; hence, they could be used as sensors. Furthermore, the synthesis of metal chalcogenide aerogels Co0.5Sb0.33MoS4 and Co0.5Y0.33MoS4 by the sol-gel method is reported. In this system, the building blocks [MoS4]2- chelated with Co2+ and (Sb3+) or (Y3+) salts in nonaqueous solvents forming amorphous networks with gel properties. The chalcogels obtained after supercritical drying have high BET surface areas. These chalcogels showed higher adsorption capacity of toluene vapor over cyclohexane vapor and high selectivity of CO2 over CH4 or H2. The uptake capacity and selectivity of toluene and CO2 adsorption of Co0.5Sb0.33MoS4 were significantly enhanced by the post-synthetic modifications of various metal species like Ni2+, Li+, and Mg2+.

In order to analyse the radiant heat transfer characteristics of a concave source, two vital concepts must be clearly understood. The first is called the apparent emissivity Ea and is a function of both the local total emissivity E and of the geometry of the source. Although the total emissivities of ordinary substances range between zero and one, the two extremeties never occur. Surface emissivities which approach these values in the limit, must be created mechanically from materials in the range 0

The small intestine generally transports dietary fats to circulation in triglyceride (TG)-rich lipoproteins. The two main intestinal lipoproteins are chylomicron (CM) and very low-density lipoprotein (VLDL). Unfortunately, studies on the CM biogenesis and intestinal transport of dietary fats have been hampered by the lack of an adequate in vitro model. In this study, we investigated the possible factors that might increase the efficiency of CM production by Caco-2 cells. We utilized sequential NaCl gradient ultracentrifugation to isolate the CMs that were secreted by the Caco-2 cells. To confirm the successful isolation of the CMs, we performed Fat Red 7B staining, TG reading, apolipoprotein B (ApoB) measurement, and transmission electron microcopy (TEM) analysis. We then tested the effects of cell differentiation, oleic acid, mono-olein, egg lecithin, incubation time, and collagen matrix on CM secretion. We found that cell differentiation, oleic acid, and lecithin were critical for CM secretion. Using the Transwell system, we further confirmed that the CMs produced by our Caco-2 cells contained significant amount of TGs and ApoB-48 such that they could be detected without the use of isotope labeling. In conclusion, when fully differentiated Caco-2 were challenged with oleic acid, lecithin, and sodium taurocholate, 21% of their total number of lipoproteins were CMs with the diameter of 80-200 nm.

No description available.

No description available.

The subject of soil absorption is an old one, dating back to before 1850. The nature of soil absorption has been, and still is, a puzzle, in spite of the vast amount of work that has been done in the last few years. Two theories have been held as the cause of the absorption. The first is that the absorption is chemical, the compounds being changed into insoluble ones by double decomposition. The second is that the salts or radicals are physically held, that is, adsorbed by the soil particles. These theories have been held separately and combined.

<p> The effect of surface active on the rate of gas absorption into water was investigated. Pure oxygen was absorbed into quiescent de-gasified distilled water through-adsorbed monomolecular films of alkylbenzene Sulphonate (ABS) or sodium lauryl sulphate (NaLS).</p> <p> The rate of absorption was characterized by effective diffusivity as measured in detergent solutions up to 20 mg/1 and temperatures between 10 and 30°C.</p> <p> Gas transfer mechanistic models plus physical and chemical properties of surface films were reviewed in order to understand the fundamental processes of interfacial interference which would account for anomolies in results reported in the literature.</p> / Thesis / Master of Engineering (MEngr)

The ¹A₂ ← ¹A₁ (π* ← n) electronic absorption spectrum of thioformaldehyde vapour has been investigated. The six excited state fundamental frequencies for both CH₂S and CD₂S are determined from the vibrational analysis. The three rotation constants and three symmetric top distortion constants for the 0⁰₀, 4¹₀ and 3¹₀4³₀ bands of CH₂S and the 0⁰₀, 4¹₀ and 5¹₀ bands of CD2S are determined from a least squares rotational analysis of these bands. The rotational constants of the 0⁰₀ and 4¹₀ bands of CH₂S and CD₂S are used to determine the structure of the molecule in the excited state. / Thesis / Doctor of Philosophy (PhD)