Thesis (Ph. D.)--Columbia University, 1929. / Vita. Printed in Great Britain. Index.

Title from second page of PDF document. Includes bibliographical references.

Thesis (doctoral)--Tübingen, 1935.

University, Diss., 2003--Frankfurt (Main).

Made available in DSpace on 2014-06-11T19:23:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-04-10Bitstream added on 2014-06-13T18:50:41Z : No. of bitstreams: 1 reis_ec_me_bauru.pdf: 1547855 bytes, checksum: c064de6707319508d31999121d801d42 (MD5) / Secretaria de Educação do Estado de São Paulo / Neste trabalho foi estudado o modo de ligação de três moléculas pequenas ao DNA 5'-CGCGAATTCGCG-3', através da simulação computacional e análise em tela gráfica. Verificou-se que é possível utilizar o programa GOLD, baseado em algoritmos genéticos, em estudos envolvendo o DNA, uma vez que até o momento há apenas dois trabalhos publicados na base de dados Scopus (Portal de Periódicos da Capes) onde esta metodologia é utilizada. Também foi verificado que 1vzk, complexo cristalográfico do DNA com 2-(5-{4-[amino (imino)metil]fenil}-2-tienil)-1h-benzimidazol-6-carboximida (DB818), obtido do PDB é uma estrutura representativa para estudos no sulco menor. Foram investigados os modos de ligação dos seguintes ligantes: (a) DB818, obtido a partir da estrutura cristalográfica 1 vzk; (b) DAZJOE; [Cr(1,2-bis(naftilidenoamino)etano)(H2O)2], estrutura obtida do Cambridge Structural Database e (c) CR3NC, [Cr(2,3-bis{[(2-hidroxi-4-dietilamino) (fenil) (metileno)]amino}2-butenodinitrila) (H2O)2], cuja estrutura foi obtida por modelagem molecular, tomando como modelo DAZJOE. Os estudos de docking do DAZJOE em DNA sugerem que seu modo de ligação seria no sulco menor, porém sua interação não se dá com as bases AATTC como no caso do DB818, mas sim entre as bases ATTC. Quando os cálculos de docking foram realizados com a molécula CR3NC, que tem volume maior e mais flexibilidade nas extremidades, observou-se que a mesma posiciona-se no sulco maior. Este resultado está em concordância com dados experimentais disponíveis. Um mecanismo de quebra do DNA é sugerido, não devido à influência do crômio, mas sim devido à presença dos nitrogênios. Observou-se que a influência do metal é menor do que a da molécula complexada ao íon nas interações. / In this work we studied the binding mode of some small molecules in the DNA 5'-CGCGAATTCGCG-3' through computer simulation and analysis in graphical screen. We found that it is possible to use the GOLD program, based on genetic algorithms in studies involving DNA, despite we found only two papers in the database Scopus (CAPES Portal of Journals) where this approach is used. It was also found that 1 vzk, crystallographic complex of the DNA with 2-(5-(a-[amino (imino) methyl] phenil) -2- thienyl)- 1h-benzimidazol-6-carboximide (DB818), obtained from PDB is a representative structure for studies in the minor groove. We investigated the binding mode of the following ligands: a) DB818, obtained from the 1vzk crystallographic structure, (d) DAZJOE, [Cr(1,2-bis(naphthylideneamino) ethane)(H2O)2], structure obtained from Cambridge Structural Database and (c) CR3NC, [Cr((2,3-bis[(2-hydroxy-4phenyl) (diethylamino) (methylene)] 2-amino butenedinitrile)(H2O)2, whose structure was obtained by molecular modeling, taking DAZJOE as model. The DAZJOE docking's studies in DNA suggest that its binding mode would be in the minor groove, but their interaction is not given with the bases AATTC as for the DB818, but between the bases ATTC. When the docking calculations were performed with CR3NC molecule, which has larger volume and more flexibility in the extremities, we observed that in take place in major groove. This result is in agreement with experimental data available. It is suggested a DNA break mechanism, but not due to the influence of chromium, but the nitrogens. It was observed that the influence of the metal is lower than the ionophore in interactions.

References appear at the end of each chapter / The importance of gold in the development of South Africa as an industrialised economy cannot be over - emphasised. Towards the end of the 19th century the economy depended almost entirely on the production of gold and diamonds which laid the foundation for a highly - developed national economy. With gold still continuing to play an important role coupled with the recent price increases, a need was felt to investigate the potential effect of higher prices on gold production in South Africa. For reasons set out in the study, it was decided to compare potential out put for five different gold prices. A gold price received by the mines of 050 per ounce was used as abase. Further calculations were made at 060, 070, 0100 and 0150 per ounce. The calculations for all the cases were done duri ng the period when the Rand was floating with the Pound Sterling and a Rand : Dollar parity of 1:1, 2 4 was used. Since then two parity changes occured : the Rand was pegged to the Dollar on the 25th October, 1972 to give a Rand : Dollar parity of 1:1,27732, and the Dollar was devalued on the 13th February, 1973 by 1 1,1 % to give the present Rand : Dollar parity of 1:1, 4192. The e ffect of the above two parity changes is that revenue in Dollar terms is overstated by 14,45 5%. It is suggested that for purposes of this study the Rand figures be accepted and wherever Dollars are used in future estimates these be increased by the afore-mentioned 14, 455%. In Dollar terms the five Cases analised will change as follows: Case A : 5350 becomes 057, 23 per ounce Case B : 260 becomes 068, 67 per ounce Case C : 270 becomes 080,12 per ounce Case D : 0100 becomes 0114 ,46 per ounce Case E : 0150 becomes 0171, 68 per ounce To do an in-depth investigation into the effects of higher gold prices on each individual mine, it was necessary to analyse the various parameters required in the determination of gold p r oduction, revenue, lease and tax payments , and dividends. For each mine the pay limits at the various gold prices and at estimated working cost levels, were determined . Graphs of the estimated tonnages at various pay limits as well as the average grade of ore mineable at these limits were determined. From these graphs it is possible to obtain the total tonnage mi neable at various pay limits. Once the foregoing parameters were obtained for each mine, it was possible to determine annual gold production, revenue, lease and tax payments and amounts available to share holders which are then summarised in tables and illustrated in graphs. For ease of reference the mines were divided up into geographica l areas. Gold production revenue, lease and tax payments to the State and the amounts available to shareholders are summarised and compared for the various gold prices. The summaries show bold production remaining fairly constant at or just below the present level of about 900 000 kilograms per year until 1978 for Case A, 1979 for Cases B and C, 1983 for Case D, and 1984 for Case E. before declining progressively thereafter. Revenue following the same pattern as gold production for Case A , as is to be expected, but increasing to a peak of R1 466 million in 1977 for Case B before progressively declining, increasing to a peak of R2 434 million in 1982 for Case D before progressively declining, increasing to a peak of R3 478 million in 1983 for Case E but remaining above the 1973 level of R1 254 million until the year 2005. Lease and tax payments and amounts available to share-holders following the same pattern as that indicated by revenue reaching peaks of respectively R390 million and R268 million for Case B R485 million and R339 million for Case C R756 million and R536 million for Case D R1 000 million and R779 million for Case E. Following the recent monetary unrest, gold prices assumed for 1973 are too conservative. Should the present gold price of about $80 and the 1972 level of production of 909 000 kilograms continue for the remainder of 1973, then gold production, revenue, lease and tax payments and dividends as shown for Case C for the year 1975 will be applicable for 1973. This shams gold production of 919 520 kilograms, gold revenue of R 1690 million, lease and tax payments of R465 million, and dividends of R339 million. The effect of the higher gold price can be clearly seen when the fore-going figures are compared with the 1971 totals of gold production of 97 6,600 kilogr ams , revenue of R396 million from gold, lease and tax payments of approximately R139 million, and dividends of R142 million . Despite a decline in gold production, revenue is expected to be up by 8 9 % whilst lease and tax payments increase by 2 35% compared with a dividend increase of 139%. Finally certain tax concessions to increase productivity and the rebuy alleviate the labour shortage, prolong the li ves of the mines by mining lower grade ore, and encourage exploration was investigated and suggestions made. / Business Management / D. Com.

The project area is situated within the Tugela Valley, located in the Northern Marginal Zone of the Natal Structural and Metamorphic Province, and this work outlines the different styles of gold mineralization found in the Tugela Valley. Two different styles have been recognized and both have economic significance:- 1) Epigenetic shear zone-hosted gold occurs in late-stage relatively undeformed thin quartz veins confined to shear zones, and is present in both the greenschist facies Natal Thrust Belt and the amphibolite facies Natal Nappe Complex. However the vast majority of these occurrences are concentrated within the thrust front (i.e. the Natal Thrust Belt). The gold grades (up to 7 g/t) and the hydrothermal alteration assemblages associated with the epigenetic deposits have been documented. 2) An as yet unrecognized occurrence of syngenetic gold mineralization is found associated with the sediment-hosted exhalative massive, to semi-massive, sulphides of the iThuma prospect, located within the amphibolite facies Natal Nappe Complex. Here gold (up to 3 g/t) is concentrated together with the main sulphide are, as well as some gold enrichment (230ppb) in the hydrothermally altered footwall feeder pipe. It is proposed that the epigenetic mineralization was formed as a consequence of the northward directed abduction of the major thrust slices of the Natal Nappe Complex. This increased the permeability of the rocks and provided channelways for the focussing of fluids. Deposition took place at the thrust front where metamorphic hydrothermal fluids interacted with meteoric water.

This dissertation investigates the heterogeneous electron transfer dynamics and electrocatalytic behaviour of the following molecules immobilized on gold electrode: (a) 2-dimethylaminoethanethiol (DMAET), with and without integration with poly (m-aminobenzenesulfonic acid) functionalised single-walled carbon nanotubes (SWCNT-PABS); (b) SWCNT-PABS and iron (II) phthalocyanine nanoparticles (nanoFePc); (c) Colloidal gold / Gold nanoparticles (AuNP) and nanoFePc (d) ; water-soluble iron (II) tetrasulfophtalocyanine (FeTSPc) and SWCNT-PABS, and (e) novel monolayer protected gold nanoparticles (MPCAuNPs) by means of either (i) layer-by-layer (LBL) self-assembly or (ii) self-assembled monolayer (SAM) fabrication strategy. Atomic force microscopy and electrochemical studies (cyclic voltammetry, and electrochemical impedance spectroscopic) were used to monitor the substrate build-up, via strong electrostatic interaction. The surface pKa of DMAET was estimated at 7.6, smaller than its solution pKa of 10.8. It is also shown that SWCNT-PABS is irreversibly attached to the DMAET SAM. For layered films involving SWCNT-PABS and nanoFePc (Au-DMAET- SWCNT-PABS-nanoFePc) n (n=1-5 layers) as the number of bilayers increase, the electron transfer kinetics of the [Fe(CN) 6]3-/4 redox probe decreases. On the contrary, LBL assembly involving AuNP and nanoFePc (Au-DMAET-AuNP-nanoFePc) n (n=1-4 layers) shows an increase followed by a decrease in electron transfer kinetics subsequent to the adsorption of nanoFePc and AuNP layers, respectively. For SAMs involving FeTSPc and SWCNT-PABS, the mixed hybrid (Au-DMAET-SWCNT-PABS/FeTSPc) exhibited fastest charge transport compared to other electrodes. For the novel MPCAuNPs, the protecting or stabilizing ligands investigated were the (1-sulfanylundec-11-yl) tetraethylene glycol (PEG-OH) and the (1-sulfanylundec-11-yl) polyethylene glycolic acid (PEG-COOH). Three different mass percent ratios (PEG-COOH : PEG-OH), viz. 1:99 (MPCAuNP-COOH1%), 50:50 (MPCAuNP-COOH50%) and 99:1 (MPCAuNP-COOH99%) were used to protect the gold nanoparticles. The impact of these different ratios on the electron transfer dynamics in organic and aqueous media was explored. The average electron transfer rate constants (ket / s-1) in organic medium decreased as the concentration of the surface-exposed –COOH group in the protecting monolayer ligand increased: MPCAuNP-COOH1% (~ 10 s-1) > MPCAuNP-COOH50% (~ 9 s-1) > MPCAuNP-COOH99% (~ 1 s-1). In aqueous medium, the trend is reversed. This behaviour has been interpreted in terms of the hydrophobicity (quasi-solid nature) and hydrophilicity (quasi-liquid nature) of the terminal –OH and –COOH head groups, respectively. The ionization constants of the terminal groups (i.e., surface pKa) was estimated as ~ 8.2 for the MPCAuNP-COOH1%, while both MPCAuNP-COOH50% and MPCAuNP-COOH99% showed two pKa values of about 5.0 and ~ 8.0, further confirming the hydrophilicity / hydrophobicity of these surface functional groups. Hydrogen peroxide (H2O2), epinephrine (EP) and ascorbic acid (AA) were used as model analytes to examine electrocatalytic ability of these nanostructured assemblies. The electrochemical reduction of H2O2 at a constant concentration was amplified upon increasing bilayer formation of SWCNT-PABS and nanoFePc, while SWCNT-PABS/FeTSPc showed the best response towards the detection of epinephrine. MPCAuNP-COOH99% showed an excellent suppression of the voltammetric response of the AA and an enhanced electrocatalytic activity towards the detection of EP compared to the other MPCAuNPs. / Thesis (PhD)--University of Pretoria, 2010. / Chemistry / unrestricted

This review summarises the factors which control the formation and distribution of surficial gold placer deposits. Regional tectonic and climatic conditions as well as gold source are considered. The characteristics of eluvial, alluvial, marine, glacial and fluvioglacial gold placer deposits are described. Particular attention is paid to the gold grains within these placers. These gold grains have a distinctive morphology and chemical composition which reflect the manner in which they were transported, deposited and concentrated within the placers. The knowledge of the processes which lead to the formation and location of surficial gold placers is then used to guide exploration and target potential deposits, which can then be evaluated.

Gold mineralization is hosted within gossanous quartz-haematite veins in volcano-sedimentary lithologies of the Klein Aub - Rehoboth basin of the Irumide Belt, Namibia. Mineralization and hydrothermal alteration are restricted to deformed lithologies particularly the metasediments. Lithological relationships, geochemistry and metallogenic characteristics of the Irumide Belt suggest an intra-continental rift setting. Copper mineralization is well known along the length of the belt, from Klein Aub in the southwest to Ghanzi in the northeast, whereas gold mineralization appears restricted to the Klein Aub Rehoboth basin. The gold is envisaged as having being leached initially from graben fill sequences during rift closure and basin dewatering. Location of the mineralization is strongly controlled by structure and lithological contact zones. Such zones are percieved as having acted as conduit zones for escaping mineralized fluids during basin closure and deformation. Apart from the lack of an effective mineralizing trap, all features consistent with the development of an ore deposit are present. The largest mineralization traps within the area studied are shear zones followed by lithological contact zones. The Mebi and Blanks gold mines are developed over large shear zones while the Swartmodder and Neuras gold mines are situated over mineralized lithological contacts. The Swartmodder copper mine yielded ore from a mineralized schist enclave within granite. Copper and gold occurrences are attributed to two contrasting styles of mineralization. Copper mineralization is suggested to have developed during initial rifting of the belt (ie. stratabound sedimentary exhalative type), while the gold and minor copper resulted from rift closure and basin dewatering. Although no economical orebody was realized during the course of this study a model is proposed for the development of mineralization within the Irumide basement lithologies as a working hypothesis for future exploration.