Drug delivery to the brain has challenged medical professionals for several decades, with 98% of small molecules and 100% of large molecules unable to cross the blood brain barrier (BBB). Biocompatible, biodegradable polymers have been extensively researched for the oral delivery of therapeutic agents, but to date has not been successfully manipulated for the formulation of an implantable device. We have therefore utilised such polymers for the formulation and design of an implantable nanoenabled multipolymeric drug delivery device (NMDDD) for the management of AIDS Dementia Complex (ADC). ADC is a central nervous system (CNS) complication of HIV, associated with a host of debilitating cognitive, motor and behavioural symptoms. ADC remains a serious manifestation of HIV/AIDS in both developing and developed countries, affecting both adults and children, with death expected within 6 months of initial diagnosis. Zidovudine (AZT), the current gold standard for the management of ADC, has demonstrated the best penetration into the CNS. It is capable of reducing viral replication in the CNS and managing neurological abnormalities associated with ADC, with clinical efficacy evidenced by the decline in morbidity and mortality of patients treated with this drug. Nanotechnology, an interdisciplinary field of research, involving the manipulation of matter on a submicron level, is receiving emerging interest for the formulation of novel drug delivery systems. As they can potentially be manipulated to react in a bioresponsive manner, nanopharmaceuticals have received much attention for site-specific drug delivery and were therefore employed in the formulation of an implantable NMDDD, with AZT employed as the model drug, for the management of ADC. Nanoparticles were prepared by means of an approach utilising controlled gelation of alginate, employing cationic crosslinking of the anionic alginate to precipitate nanoparticles. A 3-factor Box-Behnken statistical design was employed for the optimisation of nanoparticle and multipolymeric scaffold formulations. Nanoparticles measuring 68.04nm (SD<0.0002) in size with a zeta potential of -13.4mV (SD<0.0005) were formulated. Nanoparticles presented with a mean dissolution time (MDT) of 46.046 hours 30 days post exposure to phosphate buffered saline (PBS), pH 7.4. In an attempt to further retard drug release and to formulate a device for implantation in the frontal lobe of the brain, nanoparticles were dispersed within a robust multipolymeric matrix. Matrix erosion was calculated at 28%w/w (SD<0.001) for multipolymeric scaffold and a matrix resilience of 4.451%w/w (SD<0.007) was observed 30 days post exposure to PBS, indicating slow degradation of the NMDDD. MDT was reduced to 12.570 hours (SD<0.0005) with dispersion of the nanoparticles within a polymer matrix, supporting the application of the drug-loaded MDDD in the management of ADC patients. The optimised multipolymeric nanoparticulate scaffold was implanted into the frontal lobe of the rat brain, for investigation of drug release characteristics and tissue response to the device following in vivo administration.

The ~132 Ma Paraná-Etendeka Large Igneous Province consists of an extensive succession of bimodal flood volcanic rocks and intrusions across Brazil, Paraguay, Uruguay, Argentina, Namibia and southern Angola. This magmatism has been attributed to the impact of the Tristan mantle plume and the associated opening of the South Atlantic Ocean, during the Early Cretaceous breakup of West Gondwana. In southern Africa, this is preserved as the Etendeka flood volcanic succession and dyke suites, and the Damaraland Intrusive Suite, a series of subvolcanic intrusions that occur in a north-east-trending band within the Neoproterozoic Damara Orogenic Belt. The Doros Gabbroic Complex is a relatively small (~3.5 km x 7.5 km) layered mafic intrusion that forms part of the Damaraland Suite in north-western Namibia. It is hosted by deformed Damaran metaturbidites, Damaran granitoids and Karoo-age metasedimentary strata in the Southern Kaoko Zone of the Damara Belt. The intrusion is a shallow lopolith, with an estimated thickness of at least 500 m, which consists of a sequence of roughlyconcordant, sill-like gabbro layers, dipping in towards the centre, cross-cut by dolerite and bostonite dykes. It is undeformed and unmetamorphosed. The fundamental mineralogy is essentially the same throughout the main body of the intrusion (plagioclase + calcic clinopyroxene + oxy-exsolved Fe-Ti oxides ± olivine). However, variations in the modal proportions of these minerals, and in the mineral and rock textures and compositions, define a series of layers. The stratigraphy broadly comprises: 1) a fine-grained gabbroic sill with chilled margin, present mostly as subcrop; 2) a sequence of massive, olivine-cumulate melagabbros (the Lower Zone), with a basal chilled margin, that form the outer ring of the complex; 3) a massive, plagioclase-cumulate olivine gabbro (the Intermediate Zone), comprising the inner ring of the complex; and 4) a sequence of variable, strongly foliated, plagioclase-, olivine- or magnetitecumulate gabbros (the Upper Foliated Series), in the core of the complex. A syenitic (bostonite) phase occurs as cross-cutting dykes or enclaves within the gabbros. In this thesis, I present a detailed petrographic study, an extensive set of whole-rock and mineral major and trace element analyses, whole-rock Sr-, Nd- and Pb-isotopic analyses, melt inclusion analyses and aeromagnetic data for the Doros intrusion. Interpretation of these data, combined with major element and trace element modelling, shows that the stratigraphic order of appearance of cumulus minerals and overall trends in rock compositions in the Doros intrusion are consistent with the fractional crystallisation of olivine, clinopyroxene, plagioclase, magnetite, K-feldspar and apatite, accompanied by variable degrees of accumulation, from a basaltic parental magma. From this combined evidence, I have put forward a compelling argument in favour of an origin for the Doros Complex by multiple, closely-spaced influxes of crystal-bearing magmas (magma mushes). This evidence includes intrusive layer relations, textural evidence for primocrysts, disequilibrium features, and stratigraphic reversals in mineral and whole-rock chemistry and magnetic properties. At least seven distinct major injections of magma have been identified in the stratigraphy, as well as several smaller pulses. Based on this interpretation, a comprehensive emplacement history for the Doros intrusion has been compiled. These findings represent a departure from the traditional model for the formation of such intrusions by the postemplacement differentiation of a single batch of crystal-free melt, and have fundamental implications for our understanding of layered mafic intrusions in general, which I elaborate on. The Doros suite shows depleted ɛNd of +3.67 to +6.46, moderate initial 87Sr/86Sr = 0.703970 - 0.709525, 206Pb/204Pb = 18.17 - 18.47, 207Pb/204Pb = 15.55 - 15.59 and 208Pb/204Pb = 37.93 - 38.42, at 132 Ma. The clustering of isotopic data and trends in incompatible trace element ratios indicate that all the magmas in the complex were derived from the same mantle source. I demonstrate, with the assistance of quantitative isotopic modelling, that this source comprised a dominant depleted MORB-like mantle component (60 - 80%), with a significant Tristan plume-derived, asthenospheric component (20 - 40%) and a minor contribution likely from recycled oceanic crust (< 5%). I further demonstrate that chilled margin to the complex is the only rock type that shows significant evidence of crustal contamination, due to local assimilation of the Damaran host rock on emplacement. In addition, this research shows that the Doros suite has strong geochemical affinities with the Tafelkop group “ferropicrite” lavas of the Etendeka Province. Common features include their near-Bulk Silicate Earth initial Sr ratios, low positive εNd, trends in 207Pb-space and relatively low heavy rare earth element concentrations. Furthermore, trace element modelling of the Doros cumulates from their whole-rock chemistry suggests primary liquid compositions remarkably similar to the Tafelkop magma type. This provides crucial evidence in support of Doros as the eruptive site for the Tafelkop lavas, and thereby links the Doros magmatism to the earliest eruptive phase in the Paraná-Etendeka event. The distinctive chemistry of this magma group is attributed to the early, relatively deep, decompression melting of pyroxenitic material in the heterogeneous Tristan plume starting head, corresponding with the initial impact of the plume on the base of the lithosphere.

Being a dissertation presented in fulfilment of the requirements governing the degree of Masters of Science in the Faoulty of Medicine, University of the Witwatersrand / Recent investigations have shown enhanced or aberrant expression of major histocompatibility system (MHC) antigens on cells lines derived from human hepatocellular carcinoma (HCC) in vitro and HCC in vivo. ( Abbreviation abstract ) / AC2017

No description available.

The Platreef has been the site of platinum mining since the 1920’s. The reef itself comprises a series of pyroxenites, gabbronorites and norites that contain xenoliths/rafts of footwall rocks. The Platreef is irregularly mineralised with PGE, Cu and Ni, and has a greater abundance of sulphides than the Merensky Reef. The main base metal sulphides within the Platreef are pyrrhotite, pyrite, pentlandite, and chalcopyrite. Extremely varied platinum group minerals occur as tellurides, bismuthotellurides, antimonides and arsenides. This study aimed to gain a clearer understanding of the formation of sulphides within the Platreef. In order to do this, cores from both the northern and southern sectors of the Platreef were sampled. A detailed study of the sulphides within these cores was conducted to identify different styles of mineralisation and their occurrences. Four different styles of mineralisation were identified: massive, net-textured, blebby and interstitial. In general, sulphides in the southern sector of the Platreef are concentrated in the lower portion of the package, whereas in the northern sector they are concentrated in the upper part although in both sectors the sulphide occurrences are associated with metasedimentary xenoliths. Conventional and multiple sulphur isotope analyses were undertaken on sulphides from cores from both the southern and the northern sectors. This was done in order to determine the source of the sulphur. These analyses were also conducted to examine sulphur isotope variations with changing footwall. Previous sulphur isotope data predominantly obtained from the central sector of the Platreef indicated a crustal contribution to the sulphur budget but did not provide much data on footwall sulphides so the nature of the crustal component was only implied. In this thesis sulphur from an external source was identified as having contributed to the formation of sulphides in both the southern and the northern sectors of the Platreef, especially for sulphides in proximity to metasedimentary xenoliths. In the southern sector of the Platreef this source was identified as most likely being pyritic shales of the Lower Duitschland Formation. In the northern sector, Malmani dolomites, which are suggested to have collapsed from the roof of the Platreef, are the most likely source of sulphur. Importantly, in the northern sector no sulphur is thought to have come from the Archaean granite footwall. Oxygen isotope analyses were conducted on samples from the southern sector of the Platreef to verify the presence of crustal contamination. Data collected indicated that there had been a crustal oxygen component involved in the formation of silicates that led to their partial recrystallisation. When compared to oxygen isotope data from the central sector of the Platreef it appears that there are variations along strike that most likely result due to the changing footwall. This data indicates a major contribution of oxygen-, sulphur- and other volatile-rich fluids to the Platreef. This led to the partial re-crystallisation of silicates, and in areas in close proximity to sulphur-bearing metasedimentary xenoliths aided in the formation of sulphides. These volatile-rich fluids most likely originated from metasedimentary xenoliths during metamorphism that then migrated through the Platreef package. When the observations from both the southern and northern sectors of the Platreef are compared and combined with pre-existing data for the central sector, several general observations can be made. 1. The entire length of the Platreef has been affected by contamination from crustal sulphur sources to some degree. This contamination is suggested to be from volatile-rich fluids which were released from metasedimentary crustal xenoliths and footwall during metamorphism. 2. The proximity between sulphide enrichment and sulphur-bearing sediments (as footwall or xenoliths) is important and indicates the source of the sulphur which led to sulphide formation. 3. Contamination occurred on a localised scale, depending on the composition of the sedimentary lithologies and the proximity of the contaminant to the magma. In the southern sector of the Platreef the source of the sulphur is almost certainly pyritic shales of the Lower Duitschland Formation. In the central sector, sulphur has most likely come from sulphur-rich dolomites and evaporites from the Malmani dolomites. In the northern sector, sulphur-rich fluids were released from Malmani dolomite rafts that collapsed from the roof into the magma during the emplacement of the Platreef. The Archaean footwall in this area has had little or no control on the formation of the sulphides within the Platreef.

A dissertation submitted to the Faculty of Science, University of Witwatersrand in the fulfillment of the requirements for the degree of Master of Science (Geology) 2017 / The LG-6 chromitite layer is the thickest (0.90 to 1.20 m thick) chromitite layer in the Lower Group chromitites of the Bushveld Complex and is of economic significance owing to the relatively high Cr-content. It can be traced across the entirety of the western limb and is mined in both the western limb and the eastern limb. This study evaluates previously published models of chromitite formation using data from the LG-6 chromitite at Ruighoek Mine, western Bushveld Complex. Data includes petrographic studies of the reef and host rocks, whole rock analysis of the silicate host rocks and reef, and mineral chemistry for orthopyroxene, olivine and Cr-spinel using electron probe microanalysis (EPMA). In the Ruighoek region the LG-6 chromitite comprises up to 95 vol. % chromite and is typically hosted by orthopyroxenite. Borehole data indicated an area (about 250 m2 in size) where the LG-6 is entirely hosted by harzburgite (42% orthopyroxene, 11% Cr-spinel, 14% olivine, 32% serpentine and 1% other) rather than orthopyroxenite. The whole rock and mineral chemistry revealed that the LG-6 chromitite in this area has an exceptionally high Cr/Fe ratio, up to 2.1. The whole rock data also indicated several compositional reversals in terms of MgO, Al2O3, Cr2O3, FeO, and Mg# (Mg/ [Mg+Fe2+]) for the unenriched borehole 13R-3, and compositional reversals in Cr/Fe and Cr# (Cr/ [Cr+Al]) for the enriched borehole 13R-9 upwards through the chromitite layer. The hanging wall harzburgites are characterized by an increase in Mg# for the mineral chemistry of the Cr-spinel, orthopyroxene and olivine compared to those in the footwall harzburgite. Importantly, spatial 3D modelling of borehole data at Ruighoek mine (19 drill-cores) indicates that the elevated Cr/Fe ratio in LG-6 chromitite is coincident with a depression in the topography of the chamber floor at the time of formation of the LG-6 chromitite. These data are difficult to reconcile with existing models for chromitite formation in layered intrusions, such as the models for gravity settling, addition of a Cr-spinel crystal-laden magma, or a pressure increase. Thus, this work has developed a new model for formation of the LG-6 chromitite at Ruighoek Mine. The exceptionally high Cr/Fe ratio of LG-6 chromitite and its close association with harzburgite is attributed to multiple replenishments of the chamber by relatively primitive magmas. These are inferred to either be saturated in olivine and chromite, or chromite alone. The occurrence of relatively primitive rocks within the depression is suggested to be related to a local feeder situated within the depression. Injection of new, relatively dense magma pulses from the feeder are inferred to spread out across the chamber floor as basal flows owing to compositional stratification of the resident magma at the time of development of the LG-6 chromitite. The replenishing magmas contributed to the existing compositional stratification in the chamber, resulting in the most primitive composition within the depression of the chamber floor. Subsequent crystallisation of the most primitive magmas within the depression resulted in local development of LG-6 chromitite with exceptionally high Cr/Fe ratios together with the enclosing harzburgitic rocks. The thickness of the LG-6 chromitite is attributed to continuous replenishment by large volumes of new, chromite-saturated, magmas via the feeder channel located in the depression. This study suggests that magma stratification and the replenishment of the chamber by chromite-saturated magmas played an important role in the development of the chromitite layers of the Bushveld Complex. / MT 2018

A Dissertation submitted to the School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa in fulfilment of the requirements for the degree of Master of Science. May 2015 / The Upper Zone (UZ) of the Bushveld Complex (BC) comprises several magnetitite layers throughout the entire sequence with the most prominent layer, the 2 m thick Main Magnetitite Layer (MML), located towards the base of the sequence. Magnetite mineral separates have been obtained from the UZ with particular focus on the MML in vertical profiles through the MML, Layer 1 and bifurcations of the MML, as well as profiles along the base of the MML and bifurcations. Magnetite mineral separates were also collected from Bierkraal and UCAR mine drill cores. The magnetite mineral separates were analyzed primarily for Cr and V as these two elements have the highest partition coefficients (D>200 and D=20-25 respectively) in magnetite and can be used as magmatic tracers. Electron microprobe data from the Bellevue drill core are also included. The gradational upper contacts of magnetitite layers with overlying anorthosite could be interpreted to suggest that the magnetitite layers accumulated through crystal settling. However, vertical profiles through 1 m of the MML all show an upward exponential decrease in Cr content (12 000-580 ppm) which is inconsistent with crystal settling but better explained by diffusion controlled bottom crystallization. The sharp base of the MML with the underlying anorthosite may suggest that the MML crystallized due to an abrupt event. The MML is not entirely homogeneous as evidenced by lateral heterogeneity along the base of the MML, identified by irregular Cr concentrations along the base of the MML and magnetitite bifurcations. This heterogeneity further supports the contention that the magnetitite layers are a product of diffusion controlled bottom crystallization. Reversals in Cr content, of differing magnitudes, in 3 of 4 vertical profiles above a dome structure interrupting the MML and in 2 of 4 vertical profiles through the MML, are attributed to intermittent convection on various scales bringing primitive undepleted magma into the crystallization zone. The magnitude of the reversals depends on the level to which the convection descends. The feldspar parting, a 10 cm thick horizon with cumulus plagioclase 1 m above the base of the MML, appears at a fairly constant Cr content in magnetite. The lack of a chemical break immediately above the feldspar parting suggests a physical process, such as pressure change, as a mechanism to account for the mineralogical change from the feldspar parting into massive magnetite in the upper portion of the MML. Vanadium, unlike Cr shows no systematic trends. Vanadium content of magnetitite layers is found to be comparable to that of the disseminated magnetite thus ruling out the possibility of a change in fo2 as a mechanism to induce magnetite crystallization. Disseminated magnetite in the UZ is suggested to have re-equilibrated with pyroxene and/or olivine during subsolidus ii cooling resulting in lower MgO contents of the disseminated magnetite compared to that of massive magnetitite layers. Similarities between magnetitite layers in Magnet Heights (eastern lobe); UCAR mine drill core, east of Brits (western lobe); Bierkraal drill core, north of Rustenburg (western lobe) and Bellevue drill core (northern limb) suggest that the different lobes of the BC may be connected.

We identify three structures that lie in the parameter plane of the rational map F(z) = zⁿ + λ / zᵈ, for which z is a complex number, λ a complex parameter, n ≥ 4 is even, and d ≥ 3 is odd. There exists a Sierpindelbrot arc, an infinite sequence of pairs of Mandelbrot sets and Sierpinski holes, that limits to the parameter at the end of the arc. There exists as well a qualitatively different Sierpindelbrot arc, an infinite sequence of pairs of Mandelbrot sets and Sierpinski holes, that limits to the parameter at the center of the arc. Furthermore, there exist infinitely many arcs of each type. A parameter can travel along a continuous path from the Cantor set locus, along infinitely many arcs of the first type in a successively smaller region of the parameter plane, while passing through an arc of the second type, to the parameter at the center of the latter arc. This infinite sequence of Sierpindelbrot arcs is a Sierpinski Mandelbrot spiral.

Os avanços da tecnologia e das pesquisas científicas na área de fármacos crescem a cada ano, em busca de novas espécies com potencial terapêutico e da melhoria de medicamentos já consolidados, sendo a liberação sustentada uma das áreas mais relevantes. Polímeros de coordenação estão ganhando certo destaque como matrizes alternativas para carregamento e liberação de fármacos. O objetivo desse trabalho foi preparar um polímero de coordenação (PC) de cobre(II) e verificar a viabilidade de sua interação com os fármacos anti-inflamatórios não-esteróides: ibuprofeno (Hibp) e naproxeno (Hnpx). A matriz polimérica investigada foi um polímero de cobre-isoftalato-bipiridina, de fórmula [Cu(ip)(bipy)]n·3,5H2O. Este foi preparado por método descrito na literatura e sua caraterização foi completada usando-se técnicas adicionais àquelas relatadas, incluindo medidas de área superficial e determinação de tamanho de poros. Materiais híbridos inorgânico-orgânicos contendo os fármacos incorporados no PC (PC/Hibp e PC/Hnpx) foram isolados e caracterizados por meio de espectroscopias eletrônica e vibracional, difração de raios x, análise térmica e microscopia eletrônica de varredura. Para o ibuprofeno foram também realizados ensaios para monitorar a liberação do fármaco a partir de seu correspondente material híbrido PC/Hibp. / The development of technology and scientific research in the pharmaceutical area is increasing every year in the search of new species with therapeutic potential and of an improvement of known medicines. Coordination polymers are gaining considerable emphasis as alternative matrices for carrying and releasing drugs. The main goal of the present work was to prepare a coordination polymer (CP) based on copper(II) and to study the viability of its interaction with the non-steroidal anti-inflammatory drugs: ibuprofen (Hibp) and naproxen (Hnpx). The polymer matrix was a copper-isophtalate-bipyridine polymer of formula [Cu(ip)(bipy)]n·3.5H2O. It was prepared according to previously described procedure and its characterization was performed by using additional techniques to those reported, including superficial area measurements and pore size determination. Inorganic-organic hybrid materials of the drugs incorporated into the CP (CP/Hibp and CP/Hnpx) were isolated and characterized by electronic and vibrational spectroscopies, x-ray diffraction, thermoanalysis and scanning electronic microscopy. For ibuprofen, some experiments were also performed to follow the releasing of the drug from its corresponding CP/Hibp hybrid material.

Kathleen Shuk Man Poon. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 93-94). / Abbreviations --- p.v / Lists of Figures --- p.vi / Lists of Schemes --- p.vii / Lists of Tables --- p.viii / Part I / Chapter Chapter 1 --- Introduction --- p.2 / Chapter 1.1 --- Thermal stability of metallacycles --- p.2 / Chapter 1.2 --- General Synthetic methods of Metallacycle --- p.5 / Chapter 1.3 --- Objective of this work --- p.6 / Chapter 1.4 --- Features of Ligands --- p.6 / Chapter 1.5 --- References --- p.10 / Chapter Chapter 2 --- Synthesis of Transfer Reagents --- p.11 / Chapter 2.1 --- Brief Survey of various Transfer Reagents --- p.11 / Chapter 2.2 --- Introduction to metallation reaction --- p.13 / Chapter 2.3 --- Result and Discussion --- p.16 / Chapter 2.3.1 --- Lithiation and Derivatization of Ligand --- p.16 / Chapter 2.3.2 --- Charge Migration --- p.18 / Chapter 2.3.3 --- Characterization of compounds --- p.23 / Chapter 2.4 --- Experimental --- p.27 / Chapter 2.5 --- References --- p.33 / Chapter Chapter 3 --- Synthesis of Metallacycles --- p.35 / Section I --- p.35 / Chapter 3.1 --- Introduction --- p.35 / Chapter 3.2 --- Results and Discussion --- p.36 / Chapter 3.2.1 --- Synthesis of Metallacycles of Group 14 elements --- p.36 / Chapter 3.2.2 --- Characterization of Group 14 metallacycles --- p.42 / Chapter 3.2.3 --- Experimental --- p.57 / Section II --- p.64 / Chapter 3.3 --- Introduction --- p.64 / Chapter 3.4 --- Result and Discussion --- p.65 / Chapter 3.4.1 --- Synthesis of Metallacycles of Group 4 elements --- p.65 / Chapter 3.4.2 --- Experimental --- p.68 / Chapter 3.5 --- Attempted synthesis of Group 12 Metallacycles --- p.70 / Chapter 3.5.1 --- Results and Discussion --- p.70 / Chapter 3.5.2 --- Experimental --- p.71 / Chapter 3.6 --- References --- p.73 / Part II --- p.75 / Chapter Chapter 4 --- Synthesis of Bimetallic Complex --- p.76 / Chapter 4.1 --- Brief Review on Bimetallic Complexes --- p.76 / Chapter 4.2 --- Results and Discussion --- p.80 / Chapter 4.2.1 --- Synthesis of bimetallic complexes --- p.80 / Chapter 4.2.2 --- Characterization of bimetallic complexes --- p.87 / Chapter 4.2.3 --- Experimental --- p.90 / Chapter 4.3 --- References --- p.93 / Appendix I General Experimental Procedure --- p.95