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1	Dithiocarbonate and trithiocarbonate interactions with pyrite and copper Venter, Jan Albert 24 April 2008 (has links) Extensive research has been performed on the interaction of dithiocarbonates (xanthate) with a wide variety of substrates. This study the focuses on the interaction of trithiocarbonates (TTC) with pyrite and copper. The mechanism of adsorption of the xanthate is compared to that of the TTC. For the xanthate to adsorb it is necessary for an oxidant to be present, since xanthate adsorbs via charge transfer processes (electrochemical processes). It was found by the use of cyclic voltammetry and contact angle measurements that collector adsorption of the TTC can occur in both oxidising and reducing (thus the absence of an oxidant) conditions. Neither the TTC monomer nor the dimer could be detected on the surface by the use of Raman spectroscopy. The collector species on the surface was the TTC decomposition products namely the thiol or thiolate. Electrochemical impedance spectroscopy (EIS) confirmed that the TTC can interact under oxidising and reducing conditions. EIS showed that the rate of adsorption of the collector species for anodic currents increases relatively to the rate of adsorption for cathodic currents. Different adsorption mechanisms are realised for the different polarisation conditions. It is postulated that the TTC species serves as an intermediate for the adsorption of the thiol or thiolate on the surface, ultimately rendering the surface hydrophobic. Decomposition tests, performed by employing UV/Vis spectroscopy, indicated that the TTC is very unstable between a pH of 4 and 11. The thiol or thiolate however does not readily adsorb onto the substrates (indicated by the EIS measurements). Microflotation tests confirmed the thiolate’s inability to render pyrite hydrophobic. The microflotation tests also indicated that the TTC became less effective in recovering pyrite after it was left to decompose for a couple of hours. / Dissertation (MSc (Metallurgy))--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / unrestricted Raman spectroscopy Uv/vis spectroscopy and microflotation Xanthate Contact angle measurements Eis Ttc Pyrite Copper Cyclic voltammetry UCTD
2	Infuence of Escherichia coli feedstock properties on the performance of primary protein purification Råvik, Mattias January 2006 (has links) <p>Abstract</p><p>The aim of the present study was to increase the understanding of how the cell surface properties affect the performance of unit operations used in primary protein purification. In particular, the purpose was to develop, set up and apply methods for studies of cell surface properties and cell interactions.</p><p>A method for microbial cell surface fingerprinting using surface plasmon resonance (SPR) is suggested. Four different <em>Escherichia coli </em>strains were used as model cells. Cell surface fingerprints were generated by registration of the interaction between the cells and four different surfaces, with different physical and chemical properties, when a cell suspension was flown over the surface. Significant differences in fingerprint pattern between some of the strains were observed. The physical properties of the cell surfaces were determined using microelectrophoresis, contact angle measurements and aqueous two-phase partitioning and were compared with the SPR fingerprints. The generated cell surface fingerprints and the physical property data were evaluated with multivariate data analysis that showed that the cells were separated into individual groups in a similar way using principal component analysis plots (PCA).</p><p>Studies of the behaviour of the model cells on stirred cell filtration and in an interaction test with different expanded bed adsorption (EBA) adsorbents were performed. It could be concluded that especially one of the strains behaved differently. Differences in the properties of the model cells were indicated by microelectrophoresis and aqueous two-phase partitioning which to some extent correlated with observed differences in behaviour during filtration and in an interaction test with EBA adsorbents.</p><p>The impact of high-pressure homogenisation of <em>E. coli </em>cell extract was examined, with a lab scale and a pilot scale technique. The DNA-fragmentation, visualised with agarose gel electrophoresis, and the resulting change in viscosity was analysed. A short homogenisation time resulted in increased viscosity of the process solution that correlated with increased concentration of released non-fragmented DNA. With longer homogenisation time the viscosity decreased with increasing degree of DNA-fragmentation.</p><p>The results show that strain dependant cell surface properties of<em> E. coli</em> may have an impact on several primary steps in downstream processing.</p> Downstream processing cell surface properties surface plasmon resonance contact angle measurements microelectrophoresis aqueous two-phase partitioning filtration EBA adsorbents high-pressure homogenisation Biochemistry Biokemi
3	Synthesis and characterization of fluorinated linear and (hyper)branched (co)polymers via self-condensing vinyl polymerization (SCVP) in minimeulsion Shaaban, Ahmad Mohammad Ragab 02 July 2019 (has links) No description available. Polymer Chemistry Polymers Chemistry Materials Science Nanoscience Nanotechnology Miniemulsion Polymerization Atom transfer radical polymerization Self-condensing vinyl polymerization Hyperbranched polymers Fluoropolymers nanoparticles contact angle measurements
4	Influence of Escherichia coli feedstock properties on the performance of primary protein purification Råvik, Mattias January 2006 (has links) Abstract The aim of the present study was to increase the understanding of how the cell surface properties affect the performance of unit operations used in primary protein purification. In particular, the purpose was to develop, set up and apply methods for studies of cell surface properties and cell interactions. A method for microbial cell surface fingerprinting using surface plasmon resonance (SPR) is suggested. Four different Escherichia coli strains were used as model cells. Cell surface fingerprints were generated by registration of the interaction between the cells and four different surfaces, with different physical and chemical properties, when a cell suspension was flown over the surface. Significant differences in fingerprint pattern between some of the strains were observed. The physical properties of the cell surfaces were determined using microelectrophoresis, contact angle measurements and aqueous two-phase partitioning and were compared with the SPR fingerprints. The generated cell surface fingerprints and the physical property data were evaluated with multivariate data analysis that showed that the cells were separated into individual groups in a similar way using principal component analysis plots (PCA). Studies of the behaviour of the model cells on stirred cell filtration and in an interaction test with different expanded bed adsorption (EBA) adsorbents were performed. It could be concluded that especially one of the strains behaved differently. Differences in the properties of the model cells were indicated by microelectrophoresis and aqueous two-phase partitioning which to some extent correlated with observed differences in behaviour during filtration and in an interaction test with EBA adsorbents. The impact of high-pressure homogenisation of E. coli cell extract was examined, with a lab scale and a pilot scale technique. The DNA-fragmentation, visualised with agarose gel electrophoresis, and the resulting change in viscosity was analysed. A short homogenisation time resulted in increased viscosity of the process solution that correlated with increased concentration of released non-fragmented DNA. With longer homogenisation time the viscosity decreased with increasing degree of DNA-fragmentation. The results show that strain dependant cell surface properties of E. coli may have an impact on several primary steps in downstream processing. / QC 20101129 Downstream processing cell surface properties surface plasmon resonance contact angle measurements microelectrophoresis aqueous two-phase partitioning filtration EBA adsorbents high-pressure homogenisation Dentistry Odontologi
5	Structure of Self-Assembled Monolayers on Gold Studied by NEXAFS and Photoelectron Spectroscopy Watcharinyanon, Somsakul January 2008 (has links) Self-assembled monolayers (SAMs) provide well-defined and ordered films of molecules spontaneously chemisorbed on a surface. By designing molecules with desired functionalities, such molecular film can be interesting for a range of applications from molecular electronics to catalysis. Important parameters for SAM applications are the film structure and quality, which are dependent on the structure of molecular constituents, the substrate, and the self-assembly process. In this work, SAMs on Au(111) of a variety of functionalized molecules, with thiol and silane headgroups, have been studied using high-resolution X-ray photoemission spectroscopy (HRXPS), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, Infrared reflection absorption spectroscopy (IRRAS), contact angle measurements and Kelvin probe measurements. In particular, the effects of varying the size of the backbone, varying the headgroup, inclusion of a porphyrin tailgroup, different ways of deprotection of the headgroups, and mixed molecular layers have been investigated. The first part of thesis work is focused on SAMs of oligo(phenyleneethynylene) (OPE) derivatives. First the effect of the extent of the conjugated system on the structure of SAM was investigated. As the lateral π-system in the OPE backbone increases, molecular surface densities become lower and molecular inclinations larger. Subsequently, a bulky porphyrin tailgroup was added onto the OPE molecule. Porphyrin-functionalized OPE with several headgroups were compared and the thioacetyl anchor group was found to form a high quality SAM. In the second part of the work, the molecular orientation of thiol-derivatized tetraphenylporphyrin layers was studied. The geometry of the molecular layer and the number of linkers that bind to the gold surface depend strongly on preparation schemes, i.e. whether or not the acetyl protection groups on the thiol were removed before adsorption. Finally, mixed SAMs of a ferrocene-terminated alkanethiol and alkanethiols were studied. By diluting the ferrocene-functionalized molecules in unfunctionalized alkanethiols, the orientational order and the packing density improved. The geometrical structure and the fraction of the ferrocene-terminated molecules can be tuned by controlling the parameters in the preparation scheme. Self-assembled monolayer (SAMs) X-ray photoelectron spectroscopy (XPS) contact angle measurements Kelvin probe measurements oligo(phenyleneethynylene) (OPE) Porphyrin-functionalized OPE Tetraphenylporphyrin Ferrocene-terminated alkanethiol thiol silane Au(111) Physics Fysik
6	Catalysts with Increased Surface Affinity for Chemical Recycling of PET Waste ABEDSOLTAN, HOSSEIN 07 September 2022 (has links) No description available. Chemical Engineering Chemistry Materials Science Mechanical Engineering Organic Chemistry Packaging Polymer Chemistry Polymers Sustainability Engineering Environmental Engineering Environmental Science Experiments Mathematics Plastics Plastic Wastes Plastic Recycling Techniques for Plastic Waste Management Chemical Recycling Hydrolysis Wetting Contact Angle Measurements Shrinking-core Model Surface Interfaces Catalysts Catalysis Ionic Liquids Synthesis Polymers Degradation Kinetic Studies Polyesters Packaging Water Bottles PET TPA Aryl Sulfonic Acids.

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