Graduation date: 1991

The synthesis of fused nitrogen heterocycles has been investigated. Chapter 1 describes the synthesis of quinolones through a copper catalyzed amide coupling to ortho acetyl aryl halide followed by an aldol condensation that produces the quinolone in modest to good yields. The reaction works well with lactam partners and leads to tricyclic ring systems. Chapter 2 describes the synthesis of 8 membered enamide rings through a [3,3] sigmatropic rearrangement ring expansion of N-vinyl β-lactams. The N-vinyl β-lactams also undergo a 6π electrocyclization following the [3,3] sigmatropic rearrangement to furnish amino cyclobutanes. Previously reported amino cyclobutanes have been made using [2+2] photocycloaddition and resulted in a mixtures of diastereoisomers. Our method produces the amino cyclobutanes in good to high yields and with excellent levels of diastereoselectivity. Chapter 3 describes the synthesis and applications of reduced hydantoins from aziridine aldehydes and isocyanates. The resulting heterocycles contain an aziridine ring fused to a 5 membered urea. We also demonstrate that the reduced portion of the hydantoin, namely the hydroxyl group, can undergo further displacement with β-ketoesters similar to iminium ion chemistry.

In recent years, N-hetereocyclic carbenes (NHCs) have received considerable attention as organocatalysts due to their unusual ability to induce a reversal of reactivity (Umpolung) in aldehydes. Indeed, NHCs unique properties have been applied to the efficient and metal-free synthesis of organic compounds that have proven elusive using traditional approaches.<p> My Masters research program has been focused on the use of NHCs as organocatalysts in ring expansion reactions and their applications to cascade reactions.<p> During my Masters studies, an NHC-catalyzed efficient ring expansion of 4-, 5-, and 6-membered oxacycloalkane-2-carboxaldehydes to generate the corresponding lactone derivatives was developed. This reaction provides access to a variety of lactones using readily available NHCs under mild conditions.<p> Then, the ring-expansion lactonization has been successfully extended to an efficient lactamization using azacycloalkane-carboxaldehydes, which could provide functionalized lactams in moderate yields under mild conditions.<p> In addition, intrigued by the possibility of effecting the Umpolung of electron-poor dienes using NHC catalysts, the ring-expansion lactonization was applied to an attempted Diels-Alder-ring expansion cascade reaction. Though no cascade reactions were observed, some very interesting results were obtained, and those results will guide future investigations in this area.

In the interests of synthetic efficiency several cascade reactions involving iminium ion intermediates have developed to allow for the rapid assembly of complex molecules from relatively simple starting materials. A cascade methodology for the rapid, diastereoselective synthesis of quinolizidine ring systems has been expanded to encompass a greater range of substrates. The utility of this extension was demonstrated in the efficient syntheses of the tricyclic core structures found in halichlorine and the cylindricine family of alkaloids. Additionally a second cascade sequence has been developed that progresses through an S[subscript N]1 followed by nucleophilic attack on an N-acyl iminium ion to deliver the products of a formal [4+3] cycloaddition. This methodology has been successfully employed to synthesize a [3.3.2] bridgehead system that serves as a key intermediate in a proposed synthesis of (±)-actinophyllic acid. Synthesis of this compound represent progress in the ongoing effort to synthesize this natural product.

The objective of this study is to reconstruct the history of glaciation from the start of Fraser (Late Wisconsinan) Glaciation to the end of deglaciation, for three areas in the Cascade Mountains. The Cascade Mountains are located between the Coast Mountains and the Interior Plateau in southwestern British Columbia. The Coast Mountains were glaciated by mountain glaciation followed by frontal retreat, whereas the Interior Plateau underwent ice sheet glaciation followed by downwasting and stagnation. The Cascades were supposed to have undergone a style of glaciation transitional between these two. Terrain mapping on air photographs followed by field checking was used to locate surficial materials and landforms indicative of glaciation style and pattern. All three study areas were glaciated by mixed mountain and ice sheet glaciation. At the start of Fraser Glaciation, alpine and valley glaciers formed around higher summits as occurred in the Coast Mountains. At the glacial maximum the entire area was covered by the Cordilleran Ice Sheet. Deglaciation was largely by continuous downvalley retreat of active glaciers, contrasting with downwasting and stagnation in the Interior Plateau, and frontal retreat in the Coast Mountains. The scarcity of fresh moraines in the cirques suggests that, unlike in the Coast Mountains, most cirque glaciers were not active at the end of glaciation. Only the highest north facing cirques remained above the local snowline throughout deglaciation and, as a result, glaciers in these valleys remained active and retreated up valley. The pattern of glaciation in the Cascade Mountains was similar to that of other areas which underwent mixed mountain and ice sheet glaciation, such as the Presidential Range in New Hampshire, the Green Mountains in Vermont, mountain ranges in west central Maine and the Insular Mountains on Vancouver Island. However, deglaciation in al l areas was complex and depended strongly on local conditions. For this reason local patterns cannot be predicted easily on the basis of glaciation style. The value of an understanding of glaciation style to improve the accuracy of terrain mapping was also investigated. It was found that the model developed for the Cascade Mountains was of some use in predicting the presence of fine-textured material in valley bottoms and for the prediction of glaciofluvial material overlying till . However fine-textured sediments were not found in al l valleys which were predicted to contain them. The model appears to be most useful as an indicator of where to concentrate field checking in order to locate fine-textured sediments.

No description available.

South Africa's national power utility, Eskom, initiated a Demand Side Management (DSM) drive to help alleviate the electricity supply shortage experienced in South Africa. The focus of this study is on a load-shifting intervention applied in the mining environment. Load shifting is an appealing way of reducing peak demand. The mining sector is one of the largest consumers of electricity in South Africa. The application of DSM in this sector has the potential of yielding significant electrical load shifting. Firstly, this helps Eskom because they are struggling to keep up their supply. Secondly, the mines also benefit because electrical load is shifted to less expensive off-peak times. Electricity cost as a percentage of the total cost of mining output is bound to increase considerably the next few years. An investigation was conducted into the potential ofperforming load shifting on complex underground rock winders the mining sector. This involved a thorough study on existing load-shifting applications on rock winder systems. Simulations were performed on rock winder systems in their different configurations at deep-level gold mines. The simulation results indicated that there was potential for the application ofload shifting. Tau Tona was selected as a case study. This decision was based on simulations to establish which of the initially identified mines would be the best candidate for load shifting. Tau Tona has a complex underground rock winder system. Multiple rock winders feeding each other are used in a cascaded configuration. A potential load shifting target of 3' MW in the evening peak period was determined by means of simulation. The rock winder system was sequentially automated. An average evening peak demand load shift of 1 MW (or 4,2 MWh) was achieved. This translates to an average annual cost saving of R 240 000. If the load-shifting target of 3 MW could be obtained, the annual cost savings would increase by 30% to R 343 000. A study was also conducted on the feasibility of implementing maximum demand monitoring and control. Rock winders could be used in future to prevent the mines from exceeding their maximum demand. This is because rock winders consume very large amounts of electricity and can be stopped and restarted very quickly. Huge financial obligations can be prevented by making sure that the mines do not exceed their negotiated maximum demand. The necessary - and costly infrastructure to do this could not be procured during this study. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2010.

Hydroamination stands as a desirable approach to nitrogen-containing molecules, which have important applications ranging from pharmaceuticals (fine chemicals) to paints, coatings, insecticides and agrochemicals (bulk chemicals). It features the use of alkene and alkyne starting materials, which are abundant and rarely used in the formation of C-N bonds. This work aims at building on the improved Cope-type reactivity developed in the Beauchemin group by expanding the reach of the reaction and understanding its mechanistic complexities. The first part of this thesis describes the development of cascade reactions to provide a thermodynamic driving force for the intermolecular Cope-type hydroamination of alkenes. The methodology serves as a proof of concept that the dipolar reaction intermediates can be engineered to further react irreversibly to more stable products, and has shown potential in improving the syntheses of natural alkaloids. The second part of the thesis describes the expansion of Cope-type hydrazide hydroaminations through a systematic investigation of hydrazine analogs as reactants. Optimized reagents are featured in the first reported intermolecular Cope-type hydrohydrazidation of alkenes. Mechanistic investigations and isolation of ammonium ylide intermediates support a 5-membered concerted and planar mechanistic pathway for hydrazide hydroaminations, similar to that observed with hydroxylamines. The final section presents mechanistic data disproving a previously assumed difficult proton transfer step in the hydroamination using hydroxylamines. From such findings, early results are presented towards a hydrogen-bond catalyzed hydroamination, which has potential applicability across the field of Cope-type hydroaminations and beyond.

South Africa's national power utility, Eskom, initiated a Demand Side Management (DSM) drive to help alleviate the electricity supply shortage experienced in South Africa. The focus of this study is on a load-shifting intervention applied in the mining environment. Load shifting is an appealing way of reducing peak demand. The mining sector is one of the largest consumers of electricity in South Africa. The application of DSM in this sector has the potential of yielding significant electrical load shifting. Firstly, this helps Eskom because they are struggling to keep up their supply. Secondly, the mines also benefit because electrical load is shifted to less expensive off-peak times. Electricity cost as a percentage of the total cost of mining output is bound to increase considerably the next few years. An investigation was conducted into the potential ofperforming load shifting on complex underground rock winders the mining sector. This involved a thorough study on existing load-shifting applications on rock winder systems. Simulations were performed on rock winder systems in their different configurations at deep-level gold mines. The simulation results indicated that there was potential for the application ofload shifting. Tau Tona was selected as a case study. This decision was based on simulations to establish which of the initially identified mines would be the best candidate for load shifting. Tau Tona has a complex underground rock winder system. Multiple rock winders feeding each other are used in a cascaded configuration. A potential load shifting target of 3' MW in the evening peak period was determined by means of simulation. The rock winder system was sequentially automated. An average evening peak demand load shift of 1 MW (or 4,2 MWh) was achieved. This translates to an average annual cost saving of R 240 000. If the load-shifting target of 3 MW could be obtained, the annual cost savings would increase by 30% to R 343 000. A study was also conducted on the feasibility of implementing maximum demand monitoring and control. Rock winders could be used in future to prevent the mines from exceeding their maximum demand. This is because rock winders consume very large amounts of electricity and can be stopped and restarted very quickly. Huge financial obligations can be prevented by making sure that the mines do not exceed their negotiated maximum demand. The necessary - and costly infrastructure to do this could not be procured during this study. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2010.

Kaskadinė fermentinė reakcija yra tokia cheminių reakcijų grandinė, kai vienos fermentinės reakcijos produktas yra panaudojamas kitose fermentinėse reakcijose tol, kol gaunamas galutinis rezultatas. Tokių reakcijų pavyzdžiai gamtoje yra kraujo krešėjimo reakcija, celiulozės skaidymas bei signalų perdavimas neuronuose. Norint, kad kaskadinė fermentinė reakcija vyktų efektyviai, fermentai, reikalingi reakcijai vykti, turi būti išsidėstę taip, kad po kiekvieno reakcijos etapo tarpinis produktas efektyviai pasiektų kitą reakcijai reikalingą fermentą. Tokių reakcijų efektyvumą galima bandyti pagerinti sutelkiant visus reikalingus reakcijai fermentus šalia vienas kito. Vienas iš variantų kaip būtų galima sukurti daugiafermentį kompleksą yra panaudojant segmentuotus metalinius nanostrypelius kaip koduojančią matricą bei genetiškai modifikuotas fermentų molekules. Prie fermentų molekulių būtų prijungiamos dideli giminiškumą reikalingam nanostrypelio metaliniam segmentui turinčios oligopeptidinės uodegėlės, kurios sukurtų sąlygas fermentams savaime organizuotis ant segmentuoto nanostrypelio paviršiaus. Magistrinio darbo užduotys buvo charakterizuoti susintetintus nanostrypelius, patikrinti ar modifikuotas giminiškomis sidabrui peptidinėmis uodegėlėmis streptavidinas sugeba prisijungti biotiną bei palyginti modifikuoto ir ir nemodifikuoto streptavidino giminiškumą sidabro paviršiui. Atlikus eksperimentus buvo nustatyta, kad naudojantis atominės jėgos mikroskopija nepavyko patikimai... [toliau žr. visą tekstą] / Biochemical enzyme cascade is a series of chemical reactions in which the products of one reaction are consumed in the next reaction. If one could organize all the necessary enzymes for the reaction in close quarters this could possibly lead to more effective cascade reactions. One way of organizing enzymes is by fusing them on barcoded nanowire matrices. This could be achieved by tayloring enzyme molecules with genetically engineered proteins for inorganics (GEPIs). My assignment was to characterise possible nanowire candidates for these biohybrid complexes using AFM and examine silver binding characteristics of GEPI taylored streptavidin using SERS. I could not realiably characterise nanowires because the interaction between AFM probe and nanowires was to interfering. Also the nanowires used to aggregate and it was difficult to separate them using ultrasound. 15nm diameter nanowires aggregated more thant 30nm diameter nanowires. Streptavidin taylored with Ag binding GEPIs showed stronger interaction with Ag electrode surface than ordinary streptavidin. Also this modified streptavidin was capable of binding with biotin. This proves that added oligopeptide chains did not negatively affect the chemical structure of streptavidin.