The chemical profiling, characterization of Aloe products and phytochemical properties of Aloe vera were studied. The adulteration of commercial products derived from medicinal plants has been a major muddle for both the society and the pharmaceuticalindustry. Economically motivated adulteration includes the potential for contaminated, sub‐potent or counterfeit medication to enter the supply chain at several levels, from the production of raw ingredients through to the point of retail sale. Darwin’s theory of evolution states that, species undergo genetic variation with time to adapt to environmental changes. Therefore, the same species growing in widely different habitats may drift from the original genetic makeup as a mechanism of adaptation and that may result in them having different chemical profiles. Therefore this study aimed at investigating the phytochemical properties of Aloe vera growing in South Africa. Also, this study aims to utilize Thin Layer Chromatography to profile this plant, as well as use Infra Red spectroscopy to characterize commercial Aloe vera products. A large quantity of Aloe vera plant was collected from AloeWay, Iphofolo Game Farm, Polokwane in the Limpopo province of South Africa. The identity of the plant was confirmedrom literature and authenticated by Professor DS Grierson of Botany Department, University of Fort Hare, Alice. The plant leaves were divided into two portions. One portion was extracted fresh while the other was cut into pieces and oven dried at 400C then and milled to a homogenous powder once dried completely. The phytochemical composition of the gel and leaf extracts revealed the presence of alkaloids, flavonoids, saponins, tannins and phenols at different concentrations. Results showed that the dry plant material yielded more phytochemicals than the fresh plant material. In particular, it was found that the acetone extract showed much more amounts ofphychemicals than the dichloromethane and aqueous extracts. The percentage compositions of phenols (71.86), flavonols (36.61), proanthocyanidins (82.71), saponins (37.73) and alkaloids (13.29) were significantly high in the acetone extract, followed by the dichloromthane extract with values of 46.85, 37.73, 49.51, 89.0 and 11.11 respectively, while the least composition was found in the aqueous extract. Furthermore, flavonoids were somewhat high in composition in both the aqueous extract of the dried and of the fresh plant material while others were very low. Tannins levels were significantly very low in all the solvent extracts. It was found that the acetone extract showed great amounts of phytochemicals than dichloromethane and aqueous extracts. Since A. vera is used in the treatment of different ailments such as skin wounds and abrasions, eczema, constipation, rheumatoid arthritis etc, the medicinal uses of this plant could be associated to such analysed bioactive compounds. Acetone, hexane, ethanol, water and dichloromethane were used to extract the Aloe vera leaf and the best solvent extract was determined. Thin layer chromatography was used to profile the leaf extracts with the aim of documenting the main phytochemicals present in the Aloe vera growing in South Africa. The best spraying reagent was determined. Fourier transform infrared spectrophotometer was used to validate the presence of Aloe vera ingredients in commercial products. The yield extraction ability of the solvent was the order: water>ethanol> hexane >dichloromethane and acetone for the dry portion. However, for the plant extracted fresh, the order of yield produced was ethanol-acetone-dichloromethane > and water. The different solvent systems separated the compounds differently. Hexane: acetone: ethanol (20 : 5: 2) and Benzene: ethanol: ammonium (80): ethanol (10): ammonium solvent systems were noted to be the best mobile phase as they gave the best separation compared to other systems.EMW [ethyl acetate (81): methanol (11): water (8)] showed better separation than the other two separating solvent systems. Vanillin- sulphuric acid spray was seen to be the best spraying reagent as compared to vanillin- phosphoric acid. Fourier transform infrared spectrophotometer validated the presence aloe ingredients in aloe vera commercial products.

This thesis is concerned with the mechanical stress generated in thin layers applied on a substrate. The application takes place at high temperatures and due to different coefficients of thermal expansion of materials, the sample is deformed, and thereby the stress is generated. The first part of the thesis includes the derivation of the Stoney formula for uniaxial and biaxial stress in a layer. Besides, analytical calculations of the normal stress in the layer for the simplified link model, and shear stress on the layer interface were evaluated. The main part of the work consists of solving the problem using FEM modeling. Because the actual temperature behavior during the application was not known, a fictitious temperature load was used as an input. For the samples, the coefficients of thermal expansion of the layer were then searched so that the thermal load resulting deflection corresponds to the experimental data. Three types of models were created, namely the link body model, the axisymmetric model, and the solid model. The axisymmetric model was used for the calculation of samples forming circular isolines during deformation and a volume model for samples forming elliptical isolines. The result of the FEM calculations was the normal stress in the applied layers, for which corresponding relationships were created using regression analysis.

This dissertation describes advances in the microfabrication of thin layer chromatography (TLC) plates. These plates are prepared by the patterning of carbon nanotube (CNT) forests on substrates, followed by their infiltration with an inorganic material. This document is divided into ten sections or chapters. Chapter 1 reviews the basics of conventional TLC technology. This technology has not changed substantially in decades. This chapter also mentions some of the downsides of the conventional approach, which include unwanted interactions of the binder in the plates with the analytes, relatively slow development times, and only moderately high efficiencies. Chapter 2 focuses primarily on the tuning of the iron catalyst used to grow the CNTs, which directly influences the diameters of the CNTs grown that are produced. Chapter 3 focuses on the atomic layer deposition (ALD) of SiO2 from a silicon precursor and ozone onto carbon-nanotubes to obtain an aluminum free stationary phase. This approach allowed us to overcome the tailing issues associated with the earlier plates prepared in our laboratory. Chapter 4 is a study of the hydroxylation state of the silica in our TLC plates. A linear correlation was obtained between the SiOH+/Si+ time-of-flight secondary ion mass spectrometry (ToF-SIMS) peak ratio and the isolated silanol peak position at ca. 3740 cm-1 in the diffuse reflectance infrared spectroscopy (DRIFT) spectra. We also compared the hydroxylation efficiencies on our plates of ammonium hydroxide and HF. Chapter 5 reports a series of improvements in TLC plate preparation. The first is the low-pressure chemical vapor deposition (LPCVD) of silicon nitride onto CNTs, which can be used to make very robust TLC plates that have the necessary SiO2 surfaces. These TLC plates are the best we have prepared to date. We also describe here the ALD deposition of ZnO into these devices, which can make them fluorescent. Chapters 6 – 10 consist of contributions to Surface Science Spectra (SSS) of ToF-SIMS spectra of the materials used in our microfabrication process. SSS is a peer-reviewed database that has been useful to many in the surface community. The ToF-SIMS spectra archived include those of (i) Si/SiO2, (ii) Si/SiO2/Al2O3, (iii) Si/SiO2/Al2O3/Fe, (iv) Si/SiO2/Fe (annealed at 750 °C in H2), and (v) Si/SiO2/Al2O3/Fe(annealed)/CNTs. Both positive and negative ion spectra have been submitted. In summary, the present work is a description of advances in the development, thorough characterization, optimization, and application development of microfabricated thin layer chromatography plates that are superior to their commercial counterparts.

The lipid composition of sperm membranes is crucial for fertilization and differs among species. As the evolution of internal fertilization modes in fishes is not understood, a comparative study of the sperm lipid composition in freshwater representatives of externally and internally fertilizing fishes is needed for a better understanding of taxa-specific relationships between the lipid composition of the sperm membrane and the sperm physiology. The lipidomes of spermatozoa from stingray, a representative of cartilaginous fishes possessing internal fertilization, and sterlet, a representative of chondrostean fishes with external fertilization, have been studied by means of nuclear magnetic resonance (NMR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), electrospray MS, gas chromatography-(GC) MS, and thin-layer chromatography (TLC). NMR experiments revealed higher cholesterol content and the presence of phosphatidylserine in stingray compared to sterlet sperm. Unknown MS signals could be assigned to different glycosphingolipids in sterlet (neutral glycosphingolipid Gal-Cer(d18:1/16:0)) and stingray (acidic glycosphingolipid sulpho-Gal-Cer(d18:1/16:0)). Free fatty acids in sterlet sperm indicate internal energy storage. GC-MS experiments indicated a significant amount of adrenic acid, but only a low amount of docosahexaenoic acid in stingray sperm. In a nutshell, this study provides novel data on sperm lipid composition for freshwater stingray and sterlet possessing different modes of fertilization.

No description available.

No description available.

In general, the stability of suspension can be studied using two methods. <i>One</i> is to directly measure the forces between two interacting surfaces in media. <i>The other</i> is to study the interfacial surface free energies of the particles in suspension. Direct surface force measurements were conducted between silica surfaces in octadecyltrimetylammonium chloride (C₁₈TACl) solutions using an Atomic Force Microscope (AFM). The results showed that the hydrophobic force existed in both air-saturated and degassed C₁₈TACl solutions. The attraction decreased with NaCl addition, and was the strongest at the point of charge neutralization (p.c.n.) of silica substrate. The force measurement results obtained in C_nTACl solutions showed that the attractions decayed exponentially and became the maximum at the p.c.n.'s. The decay lengths (<i>D</i>) increased with surfactant chain length. The measured forces were fitted to a charged-patch model of Miklavic <i>et al</i>. (1994) with rather large patch sizes. It was also found that the decay length decreased linearly with the effective concentration of the CH2/CH3 groups raised to the power of -1/2. This finding is in line with the model of Eriksson <i>et al</i>. (1989). It suggested that the long-range attractions are hydrophobic forces originating from the changes in water structure across a hydrophobic surface-solution interface. For the TiO₂/water/TiO₂ system, the Hamaker constant was found to be 4±1×10^-20 J. The force curves obtained in the TiO₂/C_nTACl system showed a repulsion-attraction-repulsion transition with increasing surfactant concentration. The long-range attraction observed between TiO₂ surfaces in C_nTACl solutions reached maximum at the p.c.n., and the decay length increased with chain length. In present work, the thin-layer wicking technique was used to determine the surface free energy (γ_s) and its components of talc samples. The results showed that the basal surfaces of talc are weakly basic while the edge surfaces are acidic. The effect of chemicals on the surface free energies of talc was systemically studied. The results showed that CMC (carboxymethyl cellulose sodium salt) and EO/PO (ethylene oxide/propylene oxide) co-polymers made talc surface hydrophilic by increasing the surface free energies, especially γ^LW and γ^-. SOPA (sodium polyacrylate) increased greatly the zeta-potentials instead of the surface free energies. / Ph. D.

Les mémoires à changement de phase (PRAM) développées par l’industrie de la microélectronique utilisent la capacité d’un materiau chalcogénure à passer rapidement et de façon réversible d’une phase amorphe à une phase cristalline. Le passage de la phase amorphe à la phase cristalline s’accompagne d’un changement de la résistance électrique du matériau. La transition amorphe vers cristallin est obtenue par un chauffage qui porte la cellule mémoires au delà de la température de transition du verre. Le verre ternaire de chalcogène Ge2Sb2Te5 (GST-225) est probablement le matériau amené à être le plus utilisé dans la prochaine génération de dispositifs de stockage de masse. La thermoréflectométrie résolue en temps (TDTR) et la radiométrie photothermique modulée (MPTR) sont utilisées ici pour étudier les propriétés thermiques des constituants des PRAM déposés sous forme de couche mince sur des substrats de silicium. Les diffusivités thermiques et les résistances thermiques de contact des films PRAM sont estimées. Ces paramètres sont identifiés en utilisant un modèle d’étude des transferts de chaleur basé sur la loi de Fourier et utilisant le formalisme des impédances thermiques. Ces mesures ont été effectuées pour des températures allant de 25 à 400°C. Les modifications de structure et de compositions chimiques causées par les hautes températures au cours des expériences sont aussi étudiées via des analyses par les techniques de DRX, MEB, TOF-SIMS et ellipsométrie.Les propriétés thermiques des GST - 225, isolants, électrodes de chauffage et électrodes métalliques mise en œuvre dans ce type de dispositif de stockage sont ainsi mesuré a l’échelle submicrométrique. / The Phase change Random Access Memories (PRAM), developed by semiconductor industry are based on rapid and reversible change from amorphous to crystalline stable phase of chalcogenide materials. The switching between the amorphous and the crystalline phase leads to change of the electrical resistance of material. The amorphous-to-crystalline transition is performed by heating the memory cell above the glass transition temperature (~130°C). The chalcogenide ternary compound glass Ge2Sb2Te5 (GST-225) is probably the candidate to become the most exploited material in the next generation of mass storage architectures. The Time Domain ThermoReflectance (TDTR) and the Modulated PhotoThermal Radiometry (MPTR) have been implemented to study the thermal properties of constituting element of PRAM deposited as thin layer (~100 nm) on silicon substrate. The thermal diffusivity and the Thermal Boundary Resistance of the PRAM film are retrieved. These parameters are identified using a model of heat transfer based on Fourier’s Law and the thermal impedance formalism. The measurements were performed in function of temperature from 25°C to 400°C. Structural and chemical changes due to the high temperature during the experimentation have been also investigated by using XRD, SEM, TOF-SIMS and ellipsometry techniques. The thermal properties of GST-225, insulator, heating and metallic electrode involved in these kind of storage devices were thus measured at a sub micrometric scale.

3D time-lapse seismics, also known as 4D seismics, have great potential for monitoring the migration of CO2 at underground storage sites. This thesis focuses on time-lapse analysis of 3D seismic reflection data acquired at the Ketzin CO2 geological storage site in order to improve understanding of the reservoir and how CO2 migrates within it. Four 3D seismic surveys have been acquired to date at the site, one baseline survey in 2005 prior to injection, two repeat surveys in 2009 and 2012 during the injection period, and one post-injection survey in 2015. To accurately simulate time-lapse seismic signatures in the subsurface, detailed 3D seismic property models for the baseline and repeat surveys were constructed by integrating borehole data and the 3D seismic data. Pseudo-boreholes between and beyond well control were built. A zero-offset convolution seismic modeling approach was used to generate synthetic time-lapse seismograms. This allowed simulations to be performed quickly and limited the introduction of artifacts in the seismic responses. Conventional seismic data have two limitations, uncertainty in detecting the CO2 plume in the reservoir and limited temporal resolution. In order to overcome these limitations, complex spectral decomposition was applied to the 3D time-lapse seismic data. Monochromatic wavelet phase and reflectivity amplitude components were decomposed from the 3D time-lapse seismic data. Wavelet phase anomalies associated with the CO2 plume were observed in the time-lapse data and verified by a series of seismic modeling studies. Tuning frequencies were determined from the balanced amplitude spectra in an attempt to discriminate between pressure effects and CO2 saturation. Quantitative assessment of the reservoir thickness and CO2 mass were performed. Time-lapse analysis on the post-injection survey was carried out and the results showed a consistent tendency with the previous repeat surveys in the CO2 migration, but with a decrease in the size of the amplitude anomaly. No systematic anomalies above the caprock were detected. Analysis of the signal to noise ratio and seismic simulations using the detailed 3D property models were performed to explain the observations. Estimation of the CO2 mass and uncertainties in it were investigated using two different approaches based on different velocity-saturation models.

Surfaces that exhibit a gradual change in their chemical and/or physical properties are termed as surface gradients. Based on the changes in properties they are classified either as physical or chemical gradients. Chemical gradients show variations in properties like polarity, charge, functionality concentration and have found potential applications in fields of biology, physics, biosensing, catalysis and separation science. In this dissertation, surface gradients have been prepared using controlled rate infusion (CRI). CRI is a simple method in which a surface gradient is formed by carrying out the infusion of organoalkoxysilane in a time-dependent fashion using a set infusion rate. Depending on concentration of silane, rate of infusion and time of infusion, the gradient profiles on surfaces can be varied and the surface chemistry of the substrate can be altered. Initial work in the dissertation focuses on demonstrating different gradient profiles and selectivity obtained using amine and/ or phenyl functionalized gradient stationary phases on thin layer chromatography (TLC) plates prepared by CRI. The presence of amine and phenyl on the surfaces were confirmed by X-ray Photoelectron Spectroscopy (XPS) and diffuse reflectance spectroscopy, respectively. The change in surface chemistry was demonstrated by changes in the selectivities of water and fat soluble vitamins. After successful preparation and characterization of single and multi-component stationary phase gradients for planar chromatography, single-component gradients were prepared for column chromatography (Silica monolithic columns). Similar to that observed for planar chromatography, the selectivity was evaluated from retention factors and was found to be different for a weak acid/weak base mixture. The results obtained showed the promising approach of using gradient stationary phases in column chromatography. This work was further extended to prepare amine and phenyl multi-component gradients on silica monolithic columns to investigate mixed-mode and synergistic effects. Finally, amine, phenyl and thiol gradients were also prepared on cellulose substrates, particularly water color paper, The goal was to study the formation of functionality gradients on cellulose substrates particularly the interaction between hydroxyl groups on cellulose and silanols and to study the stability of the silanes on the cellulose surface.