Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Separation of the metal ions Cu2+, Pb2+, Cd2+ Mn2+, Cr3+, Fe3+ and Zn2+ with poly ethylenediamine tetra-acetic acid (EDTA), ethylenediamine disuccinic acid ([S,S']- EDDS) and ethylenediamine dimalonic acid (EDDM) was performed by Capillary Electrophoresis. The electropherograms obtained by Capillary Electrophoresis were validated with a speciation model Joint Expert Speciation System (JESS). Excellent agreement was observed for the speciation diagrams for these species with the pH curves determined by capillary electrophoresis with those determined by speciation modelling using JESS. The ligands EDDS and EDDM are readily biodegradable. They have been proposed as substitute ligands for EDTA. Detection of the above species was performed using both an electrochemical and a UV detector. The obtained electropherograms were used for the determination of the detection limits of these species. The electrochemical detector has a lower detection limit for these species than the UV detector in conformity with reported literature for these detectors. / AFRIKAANSE OPSOMMING: Skeiding van die metaal ione Cu2+, Pb2+, Cd2+, Cr3+, Fe3+ en Zn2+ met behulp van etileendiamientetra-asyn suur (EDTA), etileendiamiendisuksien suur ([S,S']-EDDS) en etileendiamiendimaleen suur (EDDM) was gedoen deur kapilêre elektroferose. Die elektroferogramme, verkry deur kapilêre elektroferose was gebruik om die spesiasie model "Joint Expert Speciation System (JESS)" te valideer. Uitstekende ooreenstemming was waargeneem vir die verspreidings diagramme van hierdie spesies as 'n funksie van pH wat verkry was deur kapilêre elektroferose met die' wat vasgestel was deur die spesiasie modeleeringsproses van JESS. Die ligande EDDS en EDDM toon onmiddelike biodigradeerbaarheid. Hulle was voorgehou as alternatiewe ligande vir EDTA. Bepaling van die bogenoemde spesies was ook gedoen deur beide elektrochemiese en UV deteksie. Deur gebruik te maak van hierdie detektore was die deteksie limiete van hierdie spesies bepaal. Die elektroochemiese detektor het 'n laer deteksie limiet vir hierdie spesies in vergelyking met die UV detector. Dit stem ooreen met die literatuur vir hierdie detektore.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Separation of the metal ions Cu2+, Pb2+, Cd2+ Mn2+, Cr3+, Fe3+ and Zn2+ with poly ethylenediamine tetra-acetic acid (EDTA), ethylenediamine disuccinic acid ([S,S']- EDDS) and ethylenediamine dimalonic acid (EDDM) was performed by Capillary Electrophoresis. The electropherograms obtained by Capillary Electrophoresis were validated with a speciation model Joint Expert Speciation System (JESS). Excellent agreement was observed for the speciation diagrams for these species with the pH curves determined by capillary electrophoresis with those determined by speciation modelling using JESS. The ligands EDDS and EDDM are readily biodegradable. They have been proposed as substitute ligands for EDTA. Detection of the above species was performed using both an electrochemical and a UV detector. The obtained electropherograms were used for the determination of the detection limits of these species. The electrochemical detector has a lower detection limit for these species than the UV detector in conformity with reported literature for these detectors. / AFRIKAANSE OPSOMMING: Skeiding van die metaal ione Cu2+, Pb2+, Cd2+, Cr3+, Fe3+ en Zn2+ met behulp van etileendiamientetra-asyn suur (EDTA), etileendiamiendisuksien suur ([S,S']-EDDS) en etileendiamiendimaleen suur (EDDM) was gedoen deur kapilêre elektroferose. Die elektroferogramme, verkry deur kapilêre elektroferose was gebruik om die spesiasie model "Joint Expert Speciation System (JESS)" te valideer. Uitstekende ooreenstemming was waargeneem vir die verspreidings diagramme van hierdie spesies as 'n funksie van pH wat verkry was deur kapilêre elektroferose met die' wat vasgestel was deur die spesiasie modeleeringsproses van JESS. Die ligande EDDS en EDDM toon onmiddelike biodigradeerbaarheid. Hulle was voorgehou as alternatiewe ligande vir EDT A. Bepaling van die bogenoemde spesies was ook gedoen deur beide elektrochemiese en UV deteksie. Deur gebruik te maak van hierdie detektore was die deteksie limiete van hierdie spesies bepaal. Die elektroochemiese detektor het 'n laer deteksie limiet vir hierdie spesies in vergelyking met die UV detector. Dit stem ooreen met die literatuur vir hierdie detektore.

Thesis (PhD)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Radiochemical separation of 103Pd from natAg, usmg a 66 MeV proton-induced reaction at iThemba LABS, was studied and a radiochemical method was developed for the separation. For the separation, which comprises the separation of Pd from a large amount of target material (16 g Ag), as well as Rh radioisotopes produced from decay of their Pd parents (mainly 101Rhand IOORh),three ion exchange resins were tested: a Chelex 100 chelating resin, the AG 1-X8 anion exchange resin and a AG MP-I anion exchange resin. For the optimum elution ofPd from the latter two resins, two elution curves using water and 5% ammonia solution, were obtained. With an average recovery of 97.4% and sharper elution curve from the macroporous AG MP-I, this resin was finally chosen for routine production. To achieve the separation, a simple, easily operated radiochemical processing system was designed and installed in a hot cell. Radiochemical separation of 103Pd from a Rh target was also studied and several cation and anion exchange resins were tested. A carrier-free separation of 103Pd was developed, using an AG 1-X8 anion exchange resin. Bombarded tablets of RhCh.3H20, as the targets, were used for these separations. The procedure, originally designed for the separation of Pd from Cu and Rh, was modified using H202 for the oxidation of Ru prior to the sorption on the resin and successfully used for the separation of isotopes of Rh from the isotopes of Pd, Ru, Tc, Nb, Mo, Zr and Y, which were produced by 400 MeV 160_ and 12C-induced RhCb.3H20 targets. To elute the Pd from the resin, 5% ammonia solution was used; the recovery was about 92%. To prepare the Rh target for routine production, an electroplating method of Rh on a Cu substrate was developed. Rh(CI04)3, in 0.5 M perchloric acid, was used as the electrolyte bath. The electroplated Rh was then dissolved by an alternating current technique, using 6 M HCI and a current density of 2 Alcm2. For production of the seeds, I03Pd was sorbed on the weakly basic anion exchange resin Amberlite IRA-93 (600-700 Il), by recycling a 0.5 M Hel solution of Pd through a 0.5 cm x 1 cm column for 2 hours. The distribution of I03Pd on the resin beads was measured and RSD of5.7% was obtained. A funnel was designed to transfer the I03Pd-loaded resin beads into the Ti tubes to prepare the seeds (0.7 mm LD., 0.8 mm D.D., and 4.5 mm length). To enclose the tubes as capsules, the end caps were made from 0.02 mm Ti sheet and several pieces were designed and machined for the welding of the caps to the tubes. A spotwelding machine was used for the welding, after small, but vital modifications. / AFRIKAANSE OPSOMMING: Palladium-l03 kan volgens twee produksieroetes by iThemba LABS vervaardig word, naamlik deur die volgende protongeïnduseerde reaksies: natAg(p,xn)lo3Cd (ty,=7.3 m) ~ 103Ag (ty,=1.1 h) ~ 103Pden I03Rh(p,n) ~ 103Pd. 'n Radiochemiese metode om 103Pd van die Ag-skyfmateriaal te skei, is ontwikkel. Hierdie metode, wat gebaseer is op anioonuitruilerchromatografie met die makroporeuse hars AG MP-I, behels die skeiding van I03Pd van 'n groot hoeveelheid skyfmateriaal (16g Ag), sowel as van Rh-radionukliede (hoofsaaklik looRh en IOlRh), wat geproduseer word deur die verval van hulle Pd-moederisotope. As die Pd met 5% ammonia oplossing geëlueer word, is 'n 97.4% herwinning moontlik. 'n Radiochemiese paneel is ontwerp, gebou en in 'n warmsel geïnstalleer vir roetine produksie. 'n Metode om Rh op 'n kopersubstraat te elektroplateer is ook ontwikkel om 'n Rh-skyf te verkry vir die protonbombardement. 'n Oplossing van 0.5 M HCI04 - Rh(HCI04)3 is as die elektrolietbad gebruik. Die geëlektroplateerde Rh is opgelos in 6 M HCI deur gebruik te maak van 'n wisselstroomtegniek, met 'n stroomdigtheid van 2A1cm2. 'n Metode om "draervrye" I03Pd vanaf die Rh-skyfmateriaal te skei, is ook ontwikkel. Gebombardeerde pille van RhCh.3H20 is as skywe gebruik in die onaktiewe studies. AGI-X8 anioonuitruilerhars is vir hierdie skeidings gebruik en daar is gebruik gemaak van 'n metode wat oorspronklik ontwerp is vir die skeiding van Pd van Cu en Rh. Hierdie prosedure is net effens aangepas deur H202 te gebruik vir die oksidasie van Ru, alvorens dit op die hars gesorbeer is. Hierdie metode is ook suksesvol gebruik vir die isolering van Rh van radionukliede van Pd, Ru, Tc, Nb, Mo, Zr, ens, wat geproduseer is deur 400 MeV 160_ en 12C-geïnduseerde reaksies met Rh in RhCi).3H20 skywe. 5% ammoniakoplossing is gebruik om die Pd uit die hars te elueer, met 'n herwinning van 92%. Om die saadjies vir implantering te maak, is 103Pd op 'n matige basiese anioonuitruilerhars Amberlite IRA-93 gesorbeer deur 'n 103pd-oplossing, in 0.5 M Hel, deur 'n 0.5 ' lcm kolom te hersirkuleer vir 2 uur. 'n Tregter is ontwerp om die I03Pd-gelaaide harskorrels oor te dra na die titaanbuisies (0.7 mm binnedeursnit, 0.8 mm buitedeursnit en 4.5 mm lank). Om die buisies te verseël, is dekseltjies uit 'n 0.02 mm titaanplaat gesny. Verskeie dekseltjies is gemasjieneer om op die buisies vas te sweis. 'n Punt-sweismasjien is gebruik vir die sweiswerk nadat geringe, maar belangrike, aanpassings aan die masjien gedoen is.

While humans can separate a sound of interest amidst a cacophony of contending sounds in an echoic environment, machine-based methods lag behind in solving this task. This thesis thus aims at improving performance of audio separation algorithms when they are informed i.e. have access to source location information. These locations are assumed to be known a priori in this work, for example by video processing. Initially, a multi-microphone array based method combined with binary time-frequency masking is proposed. A robust least squares frequency invariant data independent beamformer designed with the location information is utilized to estimate the sources. To further enhance the estimated sources, binary time-frequency masking based post-processing is used but cepstral domain smoothing is required to mitigate musical noise. To tackle the under-determined case and further improve separation performance at higher reverberation times, a two-microphone based method which is inspired by human auditory processing and generates soft time-frequency masks is described. In this approach interaural level difference, interaural phase difference and mixing vectors are probabilistically modeled in the time-frequency domain and the model parameters are learned through the expectation-maximization (EM) algorithm. A direction vector is estimated for each source, using the location information, which is used as the mean parameter of the mixing vector model. Soft time-frequency masks are used to reconstruct the sources. A spatial covariance model is then integrated into the probabilistic model framework that encodes the spatial characteristics of the enclosure and further improves the separation performance in challenging scenarios i.e. when sources are in close proximity and when the level of reverberation is high. Finally, new dereverberation based pre-processing is proposed based on the cascade of three dereverberation stages where each enhances the twomicrophone reverberant mixture. The dereverberation stages are based on amplitude spectral subtraction, where the late reverberation is estimated and suppressed. The combination of such dereverberation based pre-processing and use of soft mask separation yields the best separation performance. All methods are evaluated with real and synthetic mixtures formed for example from speech signals from the TIMIT database and measured room impulse responses.

No description available.

Marital disruption (i.e., marital separation, divorce) is associated with a wide range of poor mental and physical health outcomes, including increased risk for all-cause mortality. One biological intermediary that may help explain the association between marital disruption and poor health is accelerated cellular aging.

<p>It is commonly accepted that aerobic exercise increases hippocampal neurogenesis, learning and memory, as well as stress resiliency. However, human populations are widely variable in their inherent aerobic fitness as well as their capacity to show increased aerobic fitness following a period of regimented exercise. It is unclear whether these inherent or acquired components of aerobic fitness play a role in neurocognition. To isolate the potential role of inherent aerobic fitness, we exploited a rat model of high (HCR) and low (LCR) inherent aerobic capacity for running. At a baseline, HCR rats have two- to three-fold higher aerobic capacity than LCR rats. We found that HCR rats also had two- to three- fold more young neurons in the hippocampus than LCR rats as well as rats from the heterogeneous founder population. We then asked whether this enhanced neurogenesis translates to enhanced hippocampal cognition, as is typically seen in exercise-trained animals. Compared to LCR rats, HCR rats performed with high accuracy on tasks designed to test neurogenesis-dependent pattern separation ability by examining investigatory behavior between very similar objects or locations. To investigate whether an aerobic response to exercise is required for exercise-induced changes in neurogenesis and cognition, we utilized a rat model of high (HRT) and low (LRT) aerobic response to treadmill training. At a baseline, HRT and LRT rats have comparable aerobic capacity as measured by a standard treadmill fit test, yet after a standardized training regimen, HRT but not LRT rats robustly increase their aerobic capacity for running. We found that sedentary LRT and HRT rats had equivalent levels of hippocampal neurogenesis, but only HRT rats had an elevation in the number of young neurons in the hippocampus following training, which was positively correlated with accuracy on pattern separation tasks. Taken together, these data suggest that a significant elevation in aerobic capacity is necessary for exercise-induced hippocampal neurogenesis and hippocampal neurogenesis-dependent learning and memory. To investigate the potential for high aerobic capacity to be neuroprotective, doxorubicin chemotherapy was administered to LCR and HCR rats. While doxorubicin induces a progressive decrease in aerobic capacity as well as neurogenesis, HCR rats remain at higher levels on those measures compared to even saline-treated LCR rats. HCR and LCR rats that received exercise training throughout doxorubicin treatment demonstrated positive effects of exercise on aerobic capacity and neurogenesis, regardless of inherent aerobic capacity. Overall, these findings demonstrate that inherent and acquired components of aerobic fitness play a crucial role not only in the cardiorespiratory system but also the fitness of the brain.</p> / Dissertation

Thesis (PhD)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: A new membrane based affinity separation system that is bio-specific, biocompatible, well characterised and capable of being regenerated or re-used is described. The amphiphilic non-ionic surfactant Pluronic® F108, was covalently derivatised to form two novel bioligands (Pluronic-Biotin and Pluronic-DMDDO) for the bio-specific immobilisation of avidin conjugated proteins and histidine tagged proteins respectively. Pluronic was also used to non-covalently functionalise nonporous membranes for ligand attachment and to simultaneously shield the surfaces from non-specific protein adsorption. Each component of this bioaffinity system (from the membrane matrix to the elution/desorption of the ligate/ligand system) was studied with the aim of producing a well characterised system and key quantitative data for the development of a robust, reliable, re-usable and scalable technology. Specifically, this study describes: 1. The fabrication and partial characterisation of nonporous planar and capillary membranes as model affinity matrices. 2. The development and evaluation of a robust protocol for solvent desorption and accurate colorimetric quantification of Pluronic® F108 and its derivatives. 3. Interfacial analysis of Pluronic adsorption onto nonporous affinity membranes, including the direct solid-state analysis of model, halogenated Pluronic derivatives using nuclear microprobe analysis. 4. Development of a surfactant based protocol for affinity membrane regeneration and re-use. 5. Specific bioaffinity immobilisation of avidin conjugated peroxidase onto biotinylated membranes in the presence of model protein foulants. 6. Cloning and expression of C-terminal hex-histidine tagged human cytochrome b5 into the bacterial expression system E. coli BL-21 DE3. 7. Development and characterisation of an immobilised metal affinity membrane system for metal chelation (Ni2+, Cu2+ and Zn2+) using a new chelator Pluronic- N,N-dicarboxymethyl-3,6-diazaoctanedioate and the bio-specific immobilisation of N-terminal hex-histidine tagged pantothenate kinase. / AFRIKAANSE OPSOMMING: 'n Nuwe membraan-gebaseerde affiniteitskeidingsisteem word beskryf wat biospesifiek, bioversoenbaar en goed gekarakteriseer is, en geregenereer of hergebruik kan word. Die amfifiliese nie-ioniese surfaktant Pluronic is kovalent gederivatiseer om twee nuwe bioligande (Pluronic-Biotien en Pluronic-DMDDO) te vorm vir biospesifieke immobilisering van proteïnligate. Pluronic is ook gebruik om nie-poreuse membrane niekovalent te funksionaliseer vir ligandaanhegting en om hulle oppervlaktes teen niespesifieke proteïen-adsorbsie af te skerm. Elke komponent van hierdie bioaffiniteitsisteem (van die membraanmatriks tot die uitwas/desorpsie van die ligaat/ligand sisteem) is ondersoek met die doel om 'n goed-gekarakteriseerde sisteem te produseer en om kwantitatiewe data te genereer vir die ontwikkeling van 'n robuuste, betroubare, herbruikbare en opskaleerbare tegnologie. Hierdie studie beskryf spesifiek: 1. Die fabrisering en gedeeltelike karakterisering van nie-poreuse planêre en kapillêre membrane as model affiniteitsmatrikse. 2. Die ontwikkeling en evaluering van 'n robuuste protokol vir oplosmiddel desorpsie en akkurate kolorimetriese kwantifikasie van Pluronic® F108 en afgeleides daarvan. 3. Intervlakanalises van Pluronic adsorpsie op nie-poreuse affiniteitsmembrane, insluitend die direkte vastetoestand analise van model ligand-gemodifiseerde Pluronic deur die gebruik van kern-mikrosonde analise. 4. Ontwikkeling van 'n surfaktant-gebaseerde protokol vir affiniteitsmembraan regenerering en hergebruik. 5. Spesifieke bioaffiniteitsimmobilisering van avidien-gekonjugeerde peroksidase op gebiotinileerde membrane in die teenwoordigheid van model bevuilende proteïne. 6. Klonering en uitdrukking van C-terminaal hex-histidien geëtiketeerde menslike sitochroom b5 in die bakteriële uitdrukkingsisteem E. coli BL-21 DE3. 7. Ontwikkeling en karakterisering van 'n geïmmobiliseerde metaalaffiniteitsmembraansisteem vir metaalchelering (Ni2+, Cu2+ en Zn2+) met behulp van die nuwe cheleerder Pluronic-N,N-dikarboksimetiel-3,6- diasaoktaandioaat en die bio-spesifieke immobilisering van N-terminaal hexhistidiengeëtiketerde pantotenaatkinase.

The research presented in this thesis aims to assess the capacity of metal organic frameworks with open metal sites for the separation of olefin mixtures. Chapter 1 provides a background to the field, including industrial separation techniques, metal organic frameworks and their applications and the current state-of-the- art for olefin separation. Chapter 3 describes the experimental techniques used in this research. Ethylene and propylene adsorption and desorption isotherms on Ni-CPO-27 and HKUST-1 at a range of temperatures are presented and compared in Chapter 4, and used to calculate isosteric heats of adsorption at varying coverages using the virial method. These pure component isotherms are used in Chapter 5 to predict selectivities for the separation of binary mixtures using ideal adsorbed solution theory. Temperature programmed desorption is used in Chapter 5 to calculate the enthalpy of desorption using Redhead's method and the heating rate variation method, and the two results are compared. The results presented in Chapters 4 and 5 conclude that propylene/ethylene separation is possible using adsorption onto metal organic frameworks with open metal sites. A new in situ environmental gas cell for single crystal X-ray diffraction is developed in Chapter 6, and the challenges encountered during this development process are discussed. The dehydration of one framework, Co-CPO-27, is studied in detail using the environmental gas cell. A dehydrated structure of HKUST-1, obtained using the gas cell, is presented for the first time. Crystal structures for the complete dehydration-adsorption-delivery cycle for biologically active NO on Co-CPO-27 are presented in Chapter 7, showing the utility of the in situ gas cell for prolonged experiments in multiple different gaseous environments. The crystal structure of NO-loaded Co-CPO-27 improves upon the models suggested in the literature, and the treatment of the dual occupancy of the open metal sites by water and NO is discussed in depth. A crystal structure of CO-loaded Co-CPO-27 is obtained for the first time, and crystal structures of Co-CPO-27 in ethylene and propylene environments are presented.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy