Cyclovoltammetrische Messungen der Ferrocenalkylthiole 1 – 3 belegen, dass homogene, gemischte Monolagen aus redoxaktiven Verbindungen und redoxinaktiven Alkylthiolen gebildet werden. Die von Creager et al. bestimmten ET Raten der Ferrocenalkylthiole 1 – 3 konnten hierbei verifiziert werden. Wie erwartet erfolgt eine Abnahme der ET Geschwindigkeit bei einer Kettenverlängerung des Alkylspacers von 2 nach 3. Eine unterschiedliche Konnektivität zwischen Redoxzentrum und Alkylspacer, z. B. die Einführung einer Carbonyl-Funktion im Falle von 1, unter Beibehaltung der Kettenlänge zeigt keinen bemerkbaren Einfluß auf den ET. Trotzt vergleichbaren Abstands der aromatischen Ferrocenthiole 4 und 5 zu der C8-Alkyl-Verbindung 2 zwischen Redoxzentrum und Elektrode, weisen diese aufgrund ihrer starken Konjugation sehr hohe ET Geschwindigkeiten auf. Die elektronischen Kopplungsfaktoren selbst deuten auf einen nichtadiabtischen ET zwischen Redoxzentrum und Elektrode hin. Wie erwartet kommt es zu einem Anwachsen der Kopplungsfaktoren bei sich verkürzender Kettenlänge oder bei Einführung konjugierter Spacersysteme. Zusammenfassend kann gesagt werden, dass Erfahrungen hinsichtlich der Präparation der Monolagen gesammelt, die gemessenen ET Raten für der literaturbekannten Verbindungen 1 – 3 bestätigt und diese Informationen auf die konjugierten Verbindungen 4 und 5 angewandt werden konnten. Im zweiten Teil wurden die Triarylamin- (29, 32) und Phenothiazinalkylthiole (35) bezüglich ihres ET Verhaltens in gemischten Monolagen untersucht. Mittels Cyclovoltammetrie konnte gezeigt werden, daß einheitlich geformte, verdünnte Monolagen vorliegen. Die ET Raten der Triarylamin- (29, 32) und Phenithiazinalkylthiole (35) sind jedoch um den Faktor 10 bis 100 höher als vergleichbare Ferrocenalkylthiole gleicher Kettenlänge [1, 2], wohingegen für Monolagen, welche [Ru(bpy)2(pp)]+-Alkythiole enthalten, äquivalente Werte gefunden wurden [3]. Die ET Geschwindigkeit wird von zwei Parametern beeinflusst: dem elektronischen Kopplungsmatrixelement und der Regorganisationsenergie  [4]. Die ET Geschwindigkeit in Donor-substituierten Alkylthiolen wird hauptsächlich durch  beeinflusst und sogar kleine Änderungen dieser zeigen eine große Auswirkung auf die zu untersuchenden Prozesse. Aus diesem Grund wird eine Zunahme der ET Geschwindigkeit von Ferrocen (hohe Reorganisationsenergie) über die Phenothiazinverbindung 35 und [Ru(bpy)2(pp)]+ zu den Triarylaminchromophoren 29 und 32 (niedrige Reorganisationsenergie) beobachtet. Weiterhin spielt, im Gegensatz zu Beobachtung von Creager et al. an äquivalenten Ferrocenverbingungen, die Anbindung des Redoxzentrums an den Alkylspacer eine bedeutende Rolle. Im Falle der elektronenreichen Ether-verbrückten Verbindung 29 wird der ET nicht alleine durch , sondern ebenso durch mesomere Effekte bestimmt. Bei 29 kommt es durch Lokalisation der positiven Ladung nahe der Ether Funktion formal zu einer Kettenverkürzung um eine „Methyleneinheit“, welche schließlich in höheren ET Geschwindigkeiten resultiert. Im dritten Teil dieser Dissertation wurde ein Serie „molekularer Drähte“ bestehend aus Methoxy- oder Chlorid-substituierten Triarylamin- und Phenothiazinverbindungen mit unterschiedlichen Brückeneinheiten und Brückenlängen zwischen Redoxzentrum und Ankerfunktion dargestellt und im Hinblick auf ihr ET Verhalten untersucht. Durch cyclovoltammetrische und UV/Vis-spektroskopische Untersuchungen konnte gezeigt werden, dass sowohl die Oxidationspotentiale als auch die energetischen Zustände der Chromophore recht gut durch Einführung unterschiedlicher Redoxzentren und Brückeneinheiten beeinflusst werden können. Trotz erfolgreicher Kontrolle der Dichte der Chromophoreinheiten in den gemischten Monolagen konnte nur für die Verbindungen 49, 52 und 87 mit Nitril-substituierten Brückeneinheiten verlässliche ET Geschwindigkeiten erhalten werden. Bei diesen Chromphoren ist ein Absinken der ET Geschwindigkeit bei zunehmender Dichte der redoxaktiven Moleküle in den gemischten Monolagen zu beobachten, welche auf eine Änderung der Adsorptionsgeometrie hindeutet. Bei zunehmender Packungsdichte der Chromophore führt dies zu einer aufrechteren Stellung der redoxaktiven Spezies. Für alle anderen Verbindungen konnten keine Werte aufgrund der zu schnellen ET Geschwindigkeiten ermittelt werden. Konformelle, wie auch die sehr geringe Abstandsabhängigkeit des ET, resultieren in hohen ET Geschwindigkeiten oder auch ungünstige HOMO-LUMO Energien bezüglich des Donors, der Brücke und der Elektrode sind Gründe für dieses Verhalten. Die Tatsache, dass Verbindung 49 und 52 beinahe die gleichen Geschwindigkeitskonstanten des ETs unabhängig von der Anzahl der Brückeneinheiten (n = 2, n = 3) besitzen, deutet darauf hin, dass ein Hopping-Prozess stattfindet, bei welchem eine geringere Längenabhängigkeit des ETs als bei eine Superexchange-Mechanismus zu erwarten ist. / In this work the influence of “active” bridge units on the electron transfer (ET) mechanism within organic donor-bridge-electrode arrays in self-assembled monolayers (SAMs) was studied by spectroscopic and electrochemical methods. In the first part of this work ferrocenealkanethiols 1 – 3 and the ferrocenearylthiols 4, 5 were investigated to get experience in the monolayer preparation for measuring ET rates. Cyclic voltammetry of the monolayers indicates that homogeneously mixed monolayers containing redox active molecules and dummy molecules were formed. For the known ferrocenealkanethiols 1 – 3 the ET rates could be confirmed compared to the ones measured by Creager et al. [206]. As expected the ET rate decreases by increasing chain length of the alkane spacer from 2 to 3. Changing the bonding between the redox centre and the alkane spacer with the same bridge lenght, e. g. by using a carboxy-group in case of 1, does not influence the ET behaviour very strong. The aromatic ferrocenethiols 4 and 5 show very high ET rates due to the strong conjugated system although the distance between the redox centre and the electrode is comparable to the C8-alkyl compound 2. The electronic coupling factors all indicate a nonadiabatic ET between the redox centre and the electrode. As expected the electronic coupling factors increase with decreasing spacer length or with an enlarged conjugated system. To sum up, experience in monolayer preparation could be obtained, the measured ET rates for well known ferrocenealkane-compounds 1 - 3 could be verified and the information could be transferred to the conjugated systems 4 and 5. In the second part the triarylamine- 29, 32 and the phenothiazinealkanethiol 35 have been examined relative to their ET behaviour in mixed monolayers. The cyclic voltammograms of the diluted monolayers indicate that homogeneously formed monolayers are present. The ET rates of triarylamine- 29, 32 and phenothiazinealkanethiols 35 are 10 to 100 times higher than compared to ferrocenealkanethiols with equal chain length[183, 206], whereas in a [Ru(bpy)2(pp)]+-containing monolayer the same value was observed [177]. Almost two parameters influence the ET rate constant: the electronic coupling matrix element and the reorganisation energy  [209]. The ET rate in donor substituted alkanethiols is mainly influenced by the reorganisation energy  [177] and even small changes have a dramatic effect on the observed processes, therefore an increasing ET rate from the ferrocene (high reorganisation energy) over the phenothiazine 35 and the [Ru(bpy)2(pp)]+ to the triarylamine chromophores 29 and 32 (low reorganisation energy) is observed. Furthermore the bonding between the redox centres and the alkane spacer plays an important role on the ET rate in case of the triarylamines 29 and 32 opposite to the assumption made by Creager et al. that the connection does not play any role. For the electron rich ether connected compound 29 the ET is not only dominated by the reorganisation energy but also by mesomeric effects where the positive charge of the electron rich derivative 29 is more located at the ether function so that the chain is formally shortend by one atom resulting in higher ET rates than compared to 32. In the third part of the thesis a series of “molecular wires” consisting of methoxy- or chloro-substituted triarylamines and phenothiazines with different bridge units and bridge length between the redox centre and the anchor thiol function have been prepared in order to investigate their ET-behaviour. Cyclic voltammetry and UV/vis-spectroscopy show that the oxidation potential and the energetic states could be controlled very well by introducing different redox centres and bridge units resulting in a decreasing oxidation potential of the redox centres and a bathochromic shift of the absorption bands in the UV/vis-spectra. Also the densitiy of the chromophores in mixed monolayers could be controlled very well for only three compounds (49, 52 and 87) with nitrile-substituted bridges reliable ET rates could be obtained. In these chromophores the ET rate decreases by increasing the density of the redox active molecules in the mixed monolayers indicating that the adsorption geometry changes with coverage with the chromophores tilting to a more upright orientation as the surface becomes more crowded. For all other compounds the measurements were limited by the fast ET rates. Conformational, as well as a very weak distance dependence of the ET resulting in very high ET rates [172] or unfavourable HOMO-LUMO energies of the donor, bridge and the electrode are reasons for this behaviour. The fact that compound 49 shows almost the same rate constant independent of the length (n = 2 or n = 3) may indicate that a hopping process is operating for which a much weaker length dependence is expected than in the case of a superexchange.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science, 2017 / Six different plant species that grow in a natural wetland impacted by old gold mining and other industrial activities were randomly selected with surface sediments. These included: Cyperus eragrostis (Nutgrass), Datura stramonium (Jimson weed), Melilotus alba (White sweetclover), Panicum coloratum (Blue panicgrass), Persicaria lapathifolia (Pale smartweed) and Phragmites australis (Common reed). These were used to investigate the levels of mercury in the wet and dry seasons, as well as to evaluate which of the species could be utilized for the remediation of mercury contaminated areas. The results obtained indicated that metal contamination could be determined from sediments and plant tissues. The pH values of the sediment samples were mostly neutral to slightly acidic and the redox potential was high in the wet season. On the other hand the dry season was characterised by very acidic and moderately oxidizing conditions. In summer all six plant species had higher concentration of HgT in sediments, whereas in winter the levels of HgT were elevated in the aerial tissues of the plants. The mercury accumulation patterns differed according to individual plant species and seasonality. Seasonal differences were significant but generally the MeHg concentrations in the wet season were higher in both surface sediments and plant tissues. Mercury methylation differed between species but concentration of MeHg was in general higher in plants with high concentration of mercury in sediments. The conversion of bioavailable HgT seemed more pronounced in tissues of the plants sampled in the wet season unlike those sampled in the dry season. Generally bioaccumulation factors were less than 1 in both the wet and dry seasons for all the plant species indicating that Hg was mainly retained in sediments. The translocation factor values were greater than 1 meaning metals were accumulated fundamentally in aboveground tissues for the plants D. stramonium, P. lapathifolia, P. coloratum and C. eragrostis in both the wet and dry seasons. The small bioaccumulation factors combined with translocation factor values greater than 1 were an indication that mercury present in the sediments was not the only source of mercury for the plant species growing in a contaminated environment. For P. australis the translocation of mercury was heavily influenced by seasonality, however this was not the case with M. alba. All the selected plant species demonstrated the capacity to grow in a heavily contaminated area, where P. australis and M. alba seemed to have developed an exclusion strategy to deal with toxic heavy metals therefore suitable for phytostabilisation. D. stramonium, P. lapathifolia, P. coloratum and C. eragrostis on the other hand exhibited characteristics of plants that can be successfully used for phytoextraction and phytovolatilization. / XL2018

PhD, Faculty of Health Sciences, University of the Witwatersrand / The South African gold-mining workforce has an unusually high incidence of Mycobacterium kansasii disease, yet little is known about the possible sources of M. kansasii infection, genetic diversity and the basis for this organism’s pathogenicity. The purpose of this study was to investigate these issues in a gold-mining environment. Five M. kansasii isolates and 10 other potentially pathogenic mycobacteria were cultured mainly from showerhead biofilms. PCR-restriction analysis (PRA) of the hsp65 gene on 191 clinical and on the 5 environmental M. kansasii isolates revealed 160 subtype I (157 clinical and 3 environmental), 8 subtype II (clinical) and 6 subtype IV (5 clinical and 1 environmental) strains. Twenty-two isolates (21 clinical and 1 environmental) did not show the typical M. kansasii PRA patterns. After confirmation by DNA sequencing as belonging to the M. kansasii species, the results suggested that these isolates were probably new subtypes of M. kansasii. In contrast to the clonal population structure found amongst the subtype I isolates from studies in other countries, DNA fingerprinting of 114 subtype I clinical and environmental isolates showed genetic diversity amongst the isolates. One of the 2 environmental isolates showed 100% identity with a clinical isolate, suggesting that water distribution systems are the possible sources of M. kansasii infection for the miners. An investigation into the genetic differences between clinical (subtype I) and environmental (III, IV and V) isolates, using Hybridisation Monitored Differential Analysis (HMDA), identified 45 open reading frames (ORFs) encoding predominantly membrane-associated proteins that include six potential virulence factors, two family members of transcription regulators for drug and xenobiotic metabolism, three family members of multidrug efflux systems, a number of proteins associated with lipid and carbohydrate metabolism and transport, and a number of hypothetical proteins with unknown function. Immunological analysis of M. kansasii isolates, using the Lymphocyte Transformation and Cytometric Bead Array assays, showed that M. kansasii modulates immune responses through suppression of lymphocyte blastogenesis and by altering the expression of Th1/Th2/Th17 cytokines by human lymphocytes in vivo for its own survival. This study demonstrated for the first time that water distribution systems in South Africa are possible sources of M. kansasii infection, and showed that subtype I strains of M. kansasii from the study region display genetic diversity and have unique or divergent genes not found in other subtypes. It also demonstrated that immunosuppression is one of the pathogenic mechanisms employed by M. kansasii.

MSc, School of Chemistry, Faculty of Science, University of the Witwatersrand, 2011 / In this work, a detailed study of the evaluation of gold-based catalysts supported on manganese oxides for the oxidation of volatile organic compounds (VOCs) has been undertaken. Model catalysts were prepared by deposition-precipitation methods to establish the effect of the support on the catalytic activity of the gold catalysts. The catalysts were characterised by X-ray diffraction, transmission electron microscopy, N2–physisorption measurements and temperature programmed reduction techniques. The activity of the catalysts for VOC oxidation reactions were tested in a continuous flow fix bed glass reactor. The products were analysed by GC/TCD and GC/FID. The catalysts Au/TiO2, Au/Al2O3, Au/ZnO and Au/MnO2 were used for the VOC oxidation reaction. 2-propanol, 2-butanol and toluene were used as VOCs for the study. These were chosen because they are important indoor pollutants given their wide laboratory use and high volatility. Toluene was found to be the most difficult to oxidise, followed by 2-propanol. The effect of calcination temperature and preparation procedure was evaluated for the gold/manganese oxide catalysts. Au/b-MnO2 catalysts prepared by deposition-precipitation showed some catalytic performance which was less than the performance shown by Au/MnOx, prepared by co-precipitation. g-MnO2 proved to be more efficient in the oxidation of 2-propanol than pyrosulite phase MnO2. The addition of gold to any metal oxide support was found to enhance the oxidation of VOCs. Gold-based catalysts were more active than the Ce/MnO2 catalyst. Catalytic tests showed that Au/CeO2 was the superior catalyst for the total oxidation of toluene, 2-propanol and 2-butanol. Ceria is a highly reducible oxide and the formation of gold–ceria interactions produced an even more easily reduced material. University of the Witwatersrand, Johannesburg ii

A Thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy 2015. / Gold mining in South Africa has been the backbone of the economy for many years. With it came economic well-being, the growth and development of satellite towns, cities and metropolitan cities, e.g. Johannesburg-a place of gold. Unfortunately, it also came with adverse effects, most of which are now evident, after a century of mining, with little or no regard for pollution prevention or any form of remediation. Of interest, in this study, is the presence of tailings storage facilities (TSFs) found within the residential areas, in close proximity to commercial district and industry, having been built around them. Currently, some 270 TSFs lie dormant, pregnant with vast number of toxic heavy metals from the initially low efficient but selective gold processing techniques. This led to the deposition of the sand dumps, with high sulphur, iron, chromium, cadmium, arsenic, and mercury amongst other toxic metals. Exposure to oxygen, and water, the pyrites were oxidized and formed acid mine drainage (AMD), which resulted in the leaching out all toxic heavy metals into ground water and surface water causing serious water pollution and environmental degradation. Due to the low efficient gold processing technique, some gold amount was discarded together with the tailings materials. The reprocessing of these dumps led to the generation of dust, which is easily distributed over large areas of land. The unrehabilitated, semi-rehabilitated, and the abandoned TSFs contributed to all forms of pollution, majorly, windblown dust from unprotected tops and sides, AMD leaching toxic heavy metals. In this study, mercury, one of the most toxic elements found within the vast TSFs was determined. This was carried out as part of a larger environmental impact assessment on the effects and scale of pollution from the gold mining in the Witwatersrand. The study area consisted of the greater Johannesburg area, covering commercial business district (CBD), the industrial areas (Aeroton, City Deep, Germiston, Selby, Springs), and the residential areas (Alberton, Boksburg, Centurion, Germiston, Greenside, Sandton, Springs). Dust samples were collected from paved surfaces in the streets, and accessible buildings, were sieved into three sieved into three fractions (PM100, PM50, PM25), and most of the work focused on the smallest size fraction (PM25) in order to study impact of inhalable and respirable dust. Three sequential extraction procedures (modified BCR-the European Community Bureau of Reference, selective sequential procedure (SSE), and novel sequential extraction procedure (n-SEP)) were applied for partitioning and evaluating the mobility, availability and persistence of mercury in urban dusts. Bioavailability of mercury was assessed by leaching dust with artificial gastric and lung fluids which mimicked body conditions. Contamination levels were assessed based on the enrichment factor (EF), contamination factor (Cf) and geoaccumulation index (Igeo) were calculated to further assess the environmental risk and provide a preliminary estimate of the main sources of mercury in street dust. Non-carcinogenic effects and carcinogenic effects due to exposure to urban street dusts were assessed for both children and adults. The total mercury (HgTOT) ranged from 269 to 1350 μg kg-1. In the PM25 size fraction, mercury exhibited the following decreasing order of HgTOT: industrial area > CBD > residential area. This order shows that the HgTOT concentration in the street dust decreased with increased distance from the TSFs. The highlight was that the highest HgTOT was reported in industrial areas next to the TSFs, tailings reprocessing areas, and tailings footprints. Furthermore, in residential areas grossly affected by TSFs and tailings reprocessing, reported high HgTOT values similar to those reported for industrial samples. These results indicated that the presence of TSFs were largely responsible for the mercury found in the dust. The results from the characterization of the dust showed a large concentration of fine particulate matter, with the characteristically high quartz (74 – 98 wt. %), and minor minerals phases such as chloritoid, chlorite, K-feldspar, jarosite, mica, muscovite, pyrite, and pyrophyllite, all below 10 wt. %. These have been known to enrich trace metals, hence a high concentration of mercury. The close proximity of the tailings to the communities led to the determination of bioavailability of mercury from dust. The bioaccessible Hg extracted by lung fluid (up to 3% of HgTOT) was higher than that of gastric fluid (up to 1% of HgTOT) and was related to the mobile pool of Hg in dust. This suggests that human exposure to Hg in dust via inhalation is greater than that via the gastric tract. These values were very similar to the values obtained from water soluble phase in the sequential extraction procedure (average 1.4% of HgTOT). This indicated that these fluids were able to extract the most bioavailable fraction of Hg, which is responsible for most of the transformation reactions involving mercury. Contamination assessment factor was carried out to classify the pollution levels and indicate whether they are from natural or anthropogenic sources. Based on the EF, Cf, and Igeo, 70, 82, and 84% of the street dust samples were classified as heavily enriched, very highly contaminated, and strongly polluted by mercury, respectively, indicating that they are of anthropogenic origin. The human health risk model was useful in identifying the areas of health risks from exposure to mercury pollution. It showed that children were more vulnerable than adults when exposed to mercury in dust via ingestion. The cancer risk for exposure to As, Cd, and Cr by both children and adults was significantly high for oral ingestion of dust. Cr (VI) was the highest contributor followed by As and lastly Cd. For inhalation pathway, the possibility of developing cancer after a lifetime exposure was low and below the acceptable limits (10-6).

This report investigates the application of digital computer simulation models to the analysis and optimization of complex mine water reticulation systems- A simulation program is developed and documented, Guidelines in the construction and use of mine water models are applied in a case study of water quality and quantity aspects of Unisel Gold Mine.

PhD, Faculty of health Sciences, University of the Witwatersrand, 2000

I believe that my research work will provide an in-depth understanding of the basic chemical and physical properties of plasmonic gold nanorods. These works can inspire future applications of plasmonic nanostructures on biotechnology, optoelectronics and solar energy conversion. - / I will first introduce my studies on high-index-faceted gold nanocrystals. Elongated tetrahexahedral (THH) gold nanocrystals have been prepared in high yields using a seed-mediated growth method. Structural characterizations reveal that they are single crystals enclosed by 24 high-index facets. Electrochemical measurements have proven that these THH Au nanocrystals are more chemically active than octahedral Au nanocrystals that are enclosed by low-index {1111} facets. Next, I will demonstrate the formation of large-area, 3D ordered assemblies of Au nanostructures that have different sizes and shapes, including nanorods, polyhedra, nanocubes, and bipyramids, by droplet evaporation. The nature of the resultant assemblies is strongly dependent on the shape of Au nanostructures for single-component systems; while the assembly of binary nanorod mixtures is dependent on the relative diameters of two nanorod samples for the nanorods used in our experiments. / Most applications of plasmonic nanostructures are based on their interactions with other chemical/physical species. In my research work, gold nanorods interacting with photochromic molecules and fluorophores are extensively studied. For the case of photochromic molecules, I have demonstrated a plasmonic switch on the basis of the resonance coupling between single Au nanorods and photochromic molecules. An individual plasmonic switch is composed of a single nanorod and the surrounding photochromic molecules. Its modulation depth reaches 7.2 dB. The estimated power and energy required for operating such a single-nanorod plasmonic switch are ∼13 pW and ∼39 pJ. For the case of fluorophores, I will give a systematic description of my research on plasmon-fluorophore interactions. Excitation polarization-dependent plasmon-enhanced fluorescence, polarized emission, and modulation of fluorophore emission spectra by localized plasmon resonances will be experimentally demonstrated. The interactions between the plasmonic nanorods and the fluorophore molecules can be temporally separated into plasmon-enhanced excitation and coupled emission processes under unsaturated excitation conditions. Finite-difference time-domain (FDTD) method will be employed to explain the origin of the excitation and emission polarization dependence. A term "plasmophore", which is corned by Lakowicz et al., is quoted to describe the artificially prepared quantum emitters that are composed of plasmonic structure and fluorophore. / Noble metal nanocrystals have drawn great attention in a wide range of research fields due to their extraordinary localized surface plasmon resonances, which are essentially collective charge density oscillations confined in metallic nanostructures. Their applications range from bioimaging, sensing and therapy in life sciences to plasmonic circuits and optical data storage in micro-optoelectronics. More attractively, they can be used to enhance light harvesting in solar energy conversion systems. In this thesis, I will systematically describe the preparation and assembly of gold nanorods and their interactions with fluorophores and photochromic molecules, both experimentally and theoretically. / Ming, Tian = 金納米棒的生長、組裝以及他們與螢光團或光至變色分子的相互作用 / 明天. / Adviser: Jianfang Wang. / Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Ming, Tian = Jin na mi bang de sheng chang, zu zhuang yi ji ta men yu ying guang tuan huo guang zhi bian se fen zi de xiang hu zuo yong / Ming Tian.

To overcome the challenge in radiation therapy of delivering the prescribed dose to cancer cells while sparing normal tissue, preferential introduction of high Z material to tumour cells works as a method of radiation sensitization. Gold nanoparticles (GNPs) are very useful in this respect. It has been shown that the size, shape, and surface properties of GNPs affect their cellular uptake. Manipulation of the cell cycle to arrest cells at different stages offers a unique strategy to study the molecular and structural events as the cell cycle progresses. To optimize delivery of GNPs into tumour cells and enhance the effect of radiosensitization, nanoparticle (NP) uptake in synchronized populations of MDA-MB-231 breast cancer cells was investigated. Populations of MDA-MB-231 cells were first synchronized in S-phase using double-thymidine block, and allowed to progress through cell cycle in synchronization. Synchronized cells were incubated with 5 nm GNPs, 15 nm GNPs, 46 nm GNPs and two formulations of lipid NP encapsulated 5 nm GNPs. Uptake of NPs was visualized using hyperspectral optical imaging and quantified with inductively coupled plasma mass spectrometry (ICP-MS). Following internalization of GNPs, cells were irradiated with 6 MV photon beams from a linear accelerator, and the survival fraction and induced deoxyribonucleic acid (DNA) damage were studied. Cell cycle analysis after a double-thymidine block showed that the cell population was well synchronized. Uptake of NPs was 1.5-2 times higher in synchronized cell population compared to the control where cells were at different stages of the cell cycle. Clonogenic studies were used to evaluate the cell survival following radiation treatment. After a dose of 2 Gy, there was a decrease in cell survival fraction in synchronized cells treated with GNPs prior to radiation treatment compared to unsynchronized cells (control) indicating GNP-mediated dose-enhancement. The protein γ-H2AX, which is recruited to sites of DNA double strand breaks, was fluorescently labeled to evaluate damage due to the radiation treatment. Our results show more DNA double strand breaks in cells treated with GNPs prior to radiation. Interaction of ionization radiation with GNPs inside of cells produce secondary electrons. These secondary electrons can interact with water molecules and produce additional free radicals. These low energy electrons and free radicals interact with important cell structures and could cause cellular damage. Cell cycle synchronization has been shown to enhance GNP/PEG/RGD uptake in MDA-MB-231 cells resulting in greater cell radiosensitization and cellular damage. Cell synchronization is therefore an additional method available that can be employed to improve GNP uptake in cells. / Graduate

Enhanced adaptive capacity is increasingly being pursued as an objective of agricultural development interventions due to the perceived vulnerability of smallholder farming communities to a range of shocks and stresses. This research used two case studies of agricultural development interventions in Northern Ghana to examine diverse understandings of adaptive capacity, potential indicators of enhanced adaptive capacity, and the implications of this for sustainable agricultural livelihoods. The thesis reviews relevant theoretical literature to situate the study among complex adaptive systems thinking and sustainability discourses. Associated policy documentation is reviewed to set the context in which, and identify why, development interventions seek to enhance adaptive capacity. The primary methods of data collection were interviews, focus groups, and ethnography, as well as secondary data in the form of documentation from the case studies. Multiple understandings of adaptive capacity were identified in both case studies, including ‘formal' understandings of the projects' funders and management, and ‘informal' understandings of field staff and participating farmers. The findings contribute to theory, policy and practice through explicit recognition of the diversity of understandings of adaptive capacity, which has not been appreciated or analysed previously. Indicators of enhanced adaptive capacity emerged from the findings. Findings show how features of social capital were integral to enhanced adaptive capacity and played a dominant role in beneficial outcomes, even when not the priority of the interventions. This implies a set of indicators of enhanced adaptive capacity that can inform theoretical discourse, policy and programme planning, and monitoring and evaluation in practice. Finally, this research identified the role of social capital in contributing to enhanced adaptive capacity, which supports sustainable agricultural livelihoods. These findings contribute lessons for similar ongoing and future agricultural development interventions and recommend a focus on features of social capital rather than physical and technological capital.