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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.
41

Development and application of surfactant-mediated methods for the extraction and analysis of biological and herbal materials

Choi, Pik Kwan 01 January 2002 (has links)
No description available.
42

Surfactant adsorption and Marangoni flow in liquid jets

Weiss, Michael January 2004 (has links)
No description available.
43

The destabilising effects of various cations on a surfactant derivative of poly iso-butenyl succinic anhydride.

Rutherford, Christine Elizabeth. January 1990 (has links)
The interfacial behaviour of two amphiphillic poly iso-butenyl succinic anhydride (PIBSA)-derived surfactants and the effect of their interaction with various nitrate salts on the stability of a water-in-oil type emulsion has been investigated. The adsorption of the esterification product of PIBSA and coco-diethanolamide (PICDEA) and of Experse-70 (E-70) at the equilibrated aqueous-fuel oil interface was investigated via the measurement of interfacial tension using the ring detachment method.The interfacial pressure of PICDEA decreased in the presence of excess unreacted coco-diethanolamide (CDE) and for both PICDEA and E-70 interfacial pressure decreased with an increase in the length of the poly iso-butenyl (PIB) hydrocarbon tail. Interfacial tension-concentration curves and the Gibbs Equation were used to determine surfactant surface excess concentration and the packing efficiency of the surfactant in the interphase. The double hydrocarbon PICDEA molecule was found to occupy a larger interfacial area than the single hydrocarbon E-70 molecule. The pH of the aqueous phase effects the interfacial activity and nature of, PICDEA and E-70 at the interface. PICDEA is protonated at pH values less than 4.6 and deprotonated at higher pH values. E-70 is neutral at low pH and deprotonated at pH values greater than approximately 2.The effect of sodium, calcium and ferric nitrate salts on the interfacial free energy of the surfactant saturated interface was also determined. The interfacial tension at the E-70 aqueous nitrate interface was dependent on ionic strength alone with a general decrease in interfacial free energy as nitrate concentration was increased. In the case of PICDEA, however, a surfactant-cation orientation effect was observed. The divalent Ca2+ cation attracts two adjacent PICDEA anions resulting in the adverse interaction of hydrocarbon tails in the interphase. This produces an interface with a higher than expected interfacial free energy. The Na+ cation produces an interface with a more energetically stable orientation. PICDEA in the presence of a ferric nitrate solution (pH 1 to 2) is protonated and therefore the univalent nitrate anion forms the counterion layer at the positively charged surfactant interface. Stability studies were carried out on aqueous nitrate salt in diesel emulsions using PICDEA as the stabilizing surfactant. Droplet coalescence rates were determined from droplet size distribution data in the presence of varying concentrations of sodium, calcium and ferric nitrate salts. Droplets were sized microscopically at progressive time intervals and the rate of coalescence determined from the change in droplet concentration with time. Coalescence was found to follow two or more consecutive first order reactions. After an initial period of rapid droplet coalescence, involving small droplets with diameters of 5~m and less, a droplet distribution is attained conducive to a more stable emulsion which then undergoes a slower rate of coalescence involving larger droplets. The effect of the nitrate salt type on the initial droplet coalescence rate (in order of increasing rate) is as follows: Ca2+< Na+< Fe3+. The opposite trend was observed for the slower long term rate of coalescence, i.e. Fe3+< Na+< Ca2+. These trends are explained in terms of the surfactant cation orientation effect, the effect of the droplet's radius of curvature on the potential energy barrier against coalescence and the effect of the droplet distribution of the emulsion system. / Thesis (M.Sc.)-University of Natal, Durban, 1990.
44

The use of surface-active agents as a source of carbon by the coliform group

Taylor, Wilbur Spencer January 1950 (has links)
Typescript, etc.
45

Synthesis and characterization of novel [Pt(diimine) (acylthiourea)]+ complexes as potential anticancer agents and exploring the use of sulphobutyl-ether-B-cyclodextrin and surfactant micelles as a drug delivery system

Magwaza, Rachael Ntombikayise January 2017 (has links)
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirement for the degree Master of Science (MSc) in Chemistry. Johannesburg, March 2017. / A series of [Pt(diimine)(Ln-O,S)]Cl complexes, where Ln-O,S represents a series of N,N dialkyl-N’-acylthiourea ligands and diimine represents (1,10-Phenanthroline; 5,6-dimethyl 1,10-phenanthroline or [3,2-d:2’,3’-f]-quinoxaline were successfully synthesised and characterised. A new crystal structure was obtained for N,N-di(2-hydroxy)-N’ benzoylthiourea which revealed an interesting herringbone crystal packing arrangement. The cytotoxicity of the series of complexes was evaluated on H1975 lung cancer cell lines at 50 µM and 5 µM. All the complexes were highly cytotoxic with cell death of 90-98% at 50 µM. However, at 5 µM there were much more variations on cell viability percentages. Although the structure–activity relationship can only be established when the IC50 (the concentration of an inhibitor where the response is reduced by half) values are determined, it is clear that the complexes containing the methyl substituents on the 5 and 6 positions of the phenanthroline moiety were the most cytotoxic with almost 98% cell death at 5 µM. The solubility of the complexes did improve by using N,N-dialkyl-N’-acylthiourea as ancillary ligands, however aqueous solubility remains a major problem. Sulphobutyl-ether-β-cyclodextrin (captisol) and low-molecular-weight surfactant micelles as drug delivery systems were considered in attempt to improve the solubility. DOSY NMR Spectroscopy revealed that there was no inclusion complex formation between the complex and capstiol, although the chemical shift trend suggested that there is at least some interaction. The low-molecular-weight surfactant micelles were considered as an alternative, which showed some promise as a drug delivery system, since the aqueous solubility improved and a colloidal suspension was obtained. / LG2018
46

Enhanced biosurfactant production by Bacillus licheniformis stk 01 for hydrocarbons targeted for bioremediation

Ngwenya, Carol Zethu January 2016 (has links)
Thesis (MTech (Environmental Health))--Cape Peninsula University of Technology, 2016. / Environmental remediation of organic and inorganic contaminants such as hydrocarbons has been a research focus area of interest. Chemical surfactants have been extensively used for the remediation of contaminated sites for immobilisation of hydrocarbons from environmental matrices. The focus has been on the impact of chemical surfactants on the environment. These petroleum-based chemical surfactants have raised serious environmental concerns as: 1) they are toxic, 2) they deteriorate the environment owing to their non-biodegradability, 3) they are costly, and 4) most are not intended for environmental applications. As such, alternatives had to be found to mitigate concerns associated with the application of such synthetic surfactants in bioremediation. Biosurfactants produced by microorganisms are a potential alternative to these synthetic surfactants. They have minimal environmental impact, are biodegradable and can withstand extreme conditions. However, biosurfactants are associated with high production costs and low production yield. Currently, large-scale production of biosurfactants cannot be achieved. Most research focuses on improving production yield which will contribute to the reduction in production costs. A lichenysin lipopeptide biosurfactant producing Bacillus sp., which grew exclusively on Beta vulgaris agrowaste, was identified. The microorganism was found to be an effective emulsifier for high molecular weight hydrocarbons such as, lubricant oil and diesel. The aim of this study was to improve biosurfactant production yield from this Bacillus sp., including emulsification efficacy by optimising fermentation conditions by supplementing the broth with biocompatible nanoparticles synthesised using a green chemistry approach with B. vulgaris (B. vulgaris) extracts. This study also aimed at reducing production costs by using B. vulgaris agrowaste exclusively as the production medium, both for the biosurfactant and the nanoparticles.
47

A report on the surfactant system of the lung

Ray, Jeanette Susan January 2010 (has links)
Photocopy of typescript. / Digitized by Kansas Correctional Industries
48

Fundamental studies and methods development for the determination of cationic surfactants in capillary electrophoresis

So, Shi Kit 01 January 1999 (has links)
No description available.
49

Effects of surfactants and organic amendments on phytoremediation of polycyclic aromatic hydrocarbons (PAHs) contaminated soil

Cheng, Ka Yu 01 January 2005 (has links)
No description available.
50

Surface properties of polymeric surfactants

Court, Colin Edwin, University of Western Sydney, College of Science, Technology and Environment January 2001 (has links)
Polystyrenes with carboxyl end-groups (PS-COOH)and poly (tert-butyl acrylates) (PtBA) of different molar mass were synthesised by anionic polymerisation using n-butyllithium as the initiator. Gel permeation chromatography (GPC) was used to calculate the molecular weight and polydispersity of these polymers. The tacticity of these polymers was determined using Carbon 13 Nuclear Magnetic Resonance Spectroscopy (13C NMR). FT-IR was used to confirm the tacticity of the samples. Matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF) was used to confirm the presence of the carboxyl end-groups. All of the films studied in this project were transferred to mica substrates using the Langmuir-Blodgett deposition method. Both single layer and multiple layer films were constructed using this technique. Atomic force microscopy (AFM) was used to observe the surface topology of these films. / Doctor of Philosophy (PhD) (Science)

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