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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.
1

The chemistry of naturally occurring long chain unsaturated compounds

Silk, M H January 1954 (has links)
[From Introduction, p. 3] Raw marine oils are subject to considerable variation in composition with season and are moreover very unbalanced oils for direct use in the paint industry. Further refining is undertaken chiefly by Messrs Marine Oil Refiners of Africa Ltd., whose factory is situated at Simonstown. In their plant marine oils and others are treated by the Solexol process involving counter current extraction of the oil with liquid propane in a tower over which a temperature gradient is maintained. The process achieves the removal of a large proportion of the relatively saturated glycerides, the natural antitioxidants, and the relatively highly unsaturated components, all of which are detrimental to the eventual formation of good paint films. The segregated marine oil from the Solexol process is then bodied or polymerised at high temperatures to yield a "drying oil" which is used as a substitute for bodied linseed oil in paints. The chemical reactions taking place during the polymerisation and drying of these oils are of an exemely complex nature, and for their understanding it is necessary to have an accurate knowledge of the chemical nature of the component fatty acids in the natural glycerides ... The term "marine oils" in this work should be understood to mean marine fish body oils, marine mammal oils being excluded from consideration.
2

Photocycloaddition of unsaturated sulphonyl derivatives

Ahmad, F. January 1984 (has links)
No description available.
3

Using stable isotopes to estimate groundwater recharge in a temperate zone

McConville, Ciara January 1999 (has links)
No description available.
4

Water flow and transport of chloride in unsaturated concrete

Kumar, Ajeet 15 July 2010
Concrete structures deteriorate in their operating environment under the combined action of harsh environmental conditions and external loading. Although the applied load can lead to a certain degradation of the structure, the main long-term deterioration mechanism involves moisture movement and the transport of chlorides within concrete. In order to build durable and reliable structures, it is necessary to be able to accurately predict the movement of moisture and chlorides within concrete.<p> In the case of unsaturated concrete, the transport of chloride ions is integrally associated with prediction of moisture fluxes in concrete. Even the diffusion of chloride ions depends on the degree of saturation of the concrete since concrete must have a continuous liquid phase for diffusion to occur. Therefore, simple diffusion theory, used in the current literature, is not sufficient to predict the diffusion of chloride ions in the case of unsaturated concrete. Most diffusion models described in the current published literature are applicable to concrete structures that are permanently wet and invariably underestimate the amount of chlorides penetrating the concrete of structures subjected to wetting and drying cycles. The research presented in this thesis reviews current knowledge, mathematical models and test methods pertinent to the movement of moisture and transport of chloride ions in unsaturated concrete.<p> A laboratory testing program was established to characterize the material properties of concrete mixes with water-cement ratios 0.4, 0.5 and 0.6. Concrete was characterized by its saturated hydraulic conductivity, moisture retention function and dependence of diffusion coefficient on degree of saturation. A geotechnical centrifuge was used to determine the saturated hydraulic conductivity of the concrete samples. Values of the saturated hydraulic conductivity of the samples were in the range of 10-11-10-12 m/s.<p> The moisture retention function of concrete samples was determined using a vapour equilibrium technique. The experimental moisture retention data was used to determine van Genuchten parameters for each of the concrete mixtures and subsequently used to determine the capillary pressure-degree of saturation relationship and relative permeability-degree of saturation relationship as a ``closed- form`` analytical expression. An electrical resistivity technique was used to determine the dependence of the chloride diffusion coefficient on the degree of saturation of the concrete. The result was compared with the Millington and Quirk model. Most of the experimental results should be useful to researchers in the field, as well as the engineering community at large, considering that they are rarely found in the concrete literature.<p> Simulations were made to determine the influence of various parameters measured during experiment on movement of moisture and transport of chloride ions in unsaturated concrete using TOUGH2, a multiphase, multicomponent, model that simulates coupled heat, moisture and salt transport in saturated and unsaturated rocks.
5

Water flow and transport of chloride in unsaturated concrete

Kumar, Ajeet 15 July 2010 (has links)
Concrete structures deteriorate in their operating environment under the combined action of harsh environmental conditions and external loading. Although the applied load can lead to a certain degradation of the structure, the main long-term deterioration mechanism involves moisture movement and the transport of chlorides within concrete. In order to build durable and reliable structures, it is necessary to be able to accurately predict the movement of moisture and chlorides within concrete.<p> In the case of unsaturated concrete, the transport of chloride ions is integrally associated with prediction of moisture fluxes in concrete. Even the diffusion of chloride ions depends on the degree of saturation of the concrete since concrete must have a continuous liquid phase for diffusion to occur. Therefore, simple diffusion theory, used in the current literature, is not sufficient to predict the diffusion of chloride ions in the case of unsaturated concrete. Most diffusion models described in the current published literature are applicable to concrete structures that are permanently wet and invariably underestimate the amount of chlorides penetrating the concrete of structures subjected to wetting and drying cycles. The research presented in this thesis reviews current knowledge, mathematical models and test methods pertinent to the movement of moisture and transport of chloride ions in unsaturated concrete.<p> A laboratory testing program was established to characterize the material properties of concrete mixes with water-cement ratios 0.4, 0.5 and 0.6. Concrete was characterized by its saturated hydraulic conductivity, moisture retention function and dependence of diffusion coefficient on degree of saturation. A geotechnical centrifuge was used to determine the saturated hydraulic conductivity of the concrete samples. Values of the saturated hydraulic conductivity of the samples were in the range of 10-11-10-12 m/s.<p> The moisture retention function of concrete samples was determined using a vapour equilibrium technique. The experimental moisture retention data was used to determine van Genuchten parameters for each of the concrete mixtures and subsequently used to determine the capillary pressure-degree of saturation relationship and relative permeability-degree of saturation relationship as a ``closed- form`` analytical expression. An electrical resistivity technique was used to determine the dependence of the chloride diffusion coefficient on the degree of saturation of the concrete. The result was compared with the Millington and Quirk model. Most of the experimental results should be useful to researchers in the field, as well as the engineering community at large, considering that they are rarely found in the concrete literature.<p> Simulations were made to determine the influence of various parameters measured during experiment on movement of moisture and transport of chloride ions in unsaturated concrete using TOUGH2, a multiphase, multicomponent, model that simulates coupled heat, moisture and salt transport in saturated and unsaturated rocks.
6

Determination of diffusion coefficient for unsaturated soils

Sood, Eeshani 29 August 2005 (has links)
The structures constructed on unsaturated soils are damaged by the movement of the soil underneath. The movement is basically due to the flow of moisture in and out of the soil. This change in moisture also affects the strength of the soil, thus resulting in failure of slopes of embankments constructed with these soils. Therefore, it is very important to study the diffusion properties of unsaturated soils. Study of the diffusion properties requires the determination of the diffusion coefficient (/). In this thesis improvements in the drying test, originally proposed by Mitchell (1979), have been discussed. The study also involves defining the evaporation coefficient (he) which has been ill-defined in previous research work. The flow through unsaturated soils is non-linear but due to the complexity involved it has been simplified to a linear problem. The nonlinear behavior has been studied during this research. Therefore, certain refinements have been applied in the determination of the diffusion coefficient. The laboratory procedure followed involves measuring the soil suction along the length of the sample and at different times using thermocouple psychrometers. The evaluation of the evaporation coefficient (he) has been made an integral part of the procedure. The diffusion coefficient is determined using the curve fitting procedure of Aubeny and Lytton, 2003.
7

Effect of structural heterogeneity on liquid phase adsorption and supercritical desorption equilibria on activated carbon /

Ismadji, Suryadi. January 2002 (has links) (PDF)
Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.
8

The Relationships Between the Volumetric Deformation Moduli of Unsaturated Soils

January 1988 (has links)
The International Conference on Soil Mechanics and Foundation Engineering in 1936 was perhaps the first international forum which brought unsaturated soil problems to the attention of geotechnical engineers. Since then, the understanding of unsaturated soil behaviour has been improved considerably. The theory for the volume change and shear strength behaviour of unsaturated soils has now developed to the point of potential application in geotechnical practice. A complete understanding of the volume change behaviour of an unsaturated soil requires a knowledge of volumetric deformation moduli on four state planes. These moduli must be determined in either a direct or indirect manner in order to solve practical problems involving volume change, moisture movement, bearing capacity and slope stability analysis. The measurement of these moduli generally requires modification to conventional laboratory equipment. The solution of unsaturated soil problems would be greatly facilitated if the relationships between the various moduli were known. Then it would be possible for all moduli to be determined by a few established conventional soil tests. The main objective of this dissertation is to develop and measure the relationships between the various volume change moduli. The study began with a literature review on the volume change constitutive relations for the soil structure and water phase of an unsaturated soil. Attempts were made to gather information pertinent to the relationships between different moduli. The theory chapter started with an examination of the most acceptable form for the soil structure and water phase constitutive surfaces on both arithmetic and semi-logarithaic scales. Approximate semi-logarithmic constitutive surfaces were then proposed. The geometry of the approximate semi-logarithmic constitutive surfaces is used to relate the moduli associated with a particular phase (i.e., the soil structure or water phase). When a soil. is saturated, the soil structure and water phase moduli with respect to the logarithm of net total stress are related by the relative density, Gs' of the soil. The inter-relationship of the three remaining moduli was then studied. A laboratory test program was designed to obtain experimental data showing the characteristic form of the semi-logarithmic constitutive surfaces on the net total stress and matric suction planes. Two soils, a uniform silt and a glacial till were tested. Specimens were formed by static compaction at half standard Proctor compaction effort with either dry of optimum or at optimum initial water contents. The investigation included specimens being loaded and unloaded under Ko and isotropic conditions. The results were analyzed and used to evaluate the relationships between the moduli. The knowledge of four moduli is needed to completely describe the volume change behaviour of an unsaturated soil in a monotonic volume change process. Special tests are required to determine these four moduli in the laboratory. For instance, the one-dimensional or isotropic compression test, the suction and unconfined shrinkage tests are necessary for solving settlement problems. The use of an approximate semi-logarithmic constitutive surface as a means to relate moduli for the same phase appears to be viable only for the soil structure. The geometry of the approximate soil structure constitutive surfaces is identifiable by two characteristic stress states namely the corrected swelling pressure (i.e., Pś) and the initial stress state translated to the matric suction plane e following a constant volume stress path (i.e., (ua - uw)e/i). Relationships between soil structure moduli can be written e in terms of log (Pś) and log(ua - uw)e/i. The experimental data has revealed empirical relationships between moduli for the water phase. As a whole, six relationships for the eight moduli associated with monotonic volume decrease and increase are suggested. The compressive and swelling indices with respect to the net total stress (i.e., Ct and Cts respectively) can be measured using conventional oedometer or triaxial equipment. These two are regarded as "basic" moduli. The remaining moduli can be estimated from the proposed relationships with the knowledge of the basic moduli and the characteristic stress states, Pś and (ua - uw)e/i.
9

Effect of a polyunsaturated fatty acid mimetic on the development of atherosclerosis in the apoE deficient mouse.

Moheimani, Fatemeh January 2005 (has links)
Atheroma, heart attacks and strokes continue to be a major cause of morbidity and mortality in our community. Atherosclerosis is a chronic inflammatory vascular disease, characterised by thickening of the vascular wall due to lipid accumulation, infiltration by circulating monocytes and T cells and proliferation of smooth muscle cells. Leukocyte adherence to the blood vessel wall is promoted by the up-regulation of cell adhesion molecules (CAM) by atherogenic substances such as tumour necrosis factor (TNF-α) and oxidised low density lipoprotein (oxidised-LDL). Recently our group has synthesised a novel polyunsaturated fatty acid, β-oxa 23:4n-6 which inhibits CAM up-regulation in blood vessel walls. It was therefore the objective of this thesis to determine whether this fatty acid protects against atherosclerosis. Advantage was taken of an experimental model of this disease, the apoE deficient mouse (apoE [superscript -/-]) which spontaneously develop atherosclerosis. To assist our studies on MP3, we established an appropriate classification of different stages of atherosclerotic lesions and defined the kinetics of development of the disease in this model. By examining of the sections at the level of aortic roots the atherosclerotic lesions were classified into six categories. This classification was based on the histological characteristics of the plaque component including the degree of macrophage infiltration and foam cells formation, the presence of cholesterol clefts and confluent lipid cores, calcification and ossification, the composition of the fibrous cap, the media involvement and the incipient/actual aneurysm formation and inflammation, including neutrophils. Kinetics of plaque development under the influence of a high fat and high cholesterol diet followed an exponential relationship of y= -e [ superscript -x ]. The asymptotic characteristic of this lesion development was however a function of compensatory aortic enlargement which accompanied the increase in lesion development and size. Thus it is concluded that the level of atherosclerosis needs to be gauged by the size of the lesion per se. This may be particularly important for the assessment of anti-atherogenic effects of drugs. Therefore attempts to develop a quantitative system to assess plaques revealed that expression of plaque size as % of occupation of blood vessel had limitations. Using this model we were able to demonstrate that injections of the novel polyunsaturated fatty acid, MP3 led to a significant reduction/inhibition (70%) of plaque area and a corresponding 60% inhibition of aortic size. As expected this inhibition was not as evident when results were expressed as % of aortic lumen size. The results also suggested that protection by MP3 was dependent on conditions which promoted increased uptake into tissues by, for example, preloading animals with MP3 prior to commencing the high fat high cholesterol diet. The protective effects of MP3 are consistent with a role for the activation of the transcriptional factor, NFkB and up-regulation of cell adhesion molecules in this disease, and the ability of MP3 to inhibit these targets. Thus the objective of this research has been achieved and the hypothesis proven. / Thesis (M.Med.Sc.)--Univesity of Adelaide, School of Paediatrics & Reproductive Health, 2005.
10

The action of anhydrous aluminium chloride upon unsaturated organic compounds

Gangloff, Wilmer Charles, January 1917 (has links)
Thesis (Ph. D.)--Ohio state University, 1917. / Bibliography: p. 26-31.

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