Thesis (MSc.(Chemistry)--University of Pretoria, 2006. / Includes bibliographical references.

Han, Fangyuan. / Thesis submitted in: November 2007. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 68-72). / Abstracts in English and Chinese. / Title Page --- p.I / Thesis Committee --- p.II / Acknowledgements --- p.III / Abstract --- p.IV / 摘要 --- p.V / Table of Contents --- p.1 / List of Figures --- p.4 / List of Tables --- p.6 / Chapter Chapter 1 --- Introduction --- p.7 / Chapter Chapter 2 --- Fourier Transform Spectroscopy --- p.10 / Chapter A. --- The Michelson Interferometer and the Interferogram --- p.10 / Chapter B. --- The Link between the Interferogram and the Spectrum: the Fourier Transform --- p.12 / Chapter C. --- "Resolution, Apodization and Spectral Folding" --- p.13 / Chapter D. --- Advantages and Disadvantages of FTIR Spectroscopy --- p.17 / Chapter E. --- Time-resolved FTIR Spectroscopy --- p.18 / Chapter (1) --- Time-resolved Rapid Scan Scheme --- p.18 / Chapter (2) --- Step-scan Scheme --- p.19 / Chapter F. --- Several Considerations in Step-scan Time-resolved Spectroscopy / Chapter Chapter 3 --- Molecular Fluorescence --- p.24 / Chapter A. --- Transitions Between Electronic States --- p.24 / Chapter B. --- Absorption and Vibrational Relaxation --- p.26 / Chapter C. --- Internal Conversion and Fluorescence --- p.26 / Chapter D. --- Intersystem Crossing and Phosphorescence --- p.27 / Chapter E. --- Fluorescence Lifetime and Quantum Yield --- p.29 / Chapter Chapter 4 --- Fourier Transform Spectroscopy of Zinc Phthalocyanine and Derivatives --- p.32 / Chapter A. --- Introduction --- p.32 / Chapter B. --- Apparatus --- p.35 / Chapter (1) --- VERTEX 70 FTIR Spectrometer --- p.35 / Chapter (2) --- Excitation Source --- p.38 / Chapter (3) --- Detectors and the Transient recorder --- p.38 / Chapter (4) --- Samples and Sample Cells --- p.39 / Chapter C. --- Experimental Setup --- p.40 / Chapter (1) --- Absorption Experiments --- p.40 / Chapter (2) --- Emission Experiments --- p.42 / Chapter D. --- Results and Discussion --- p.45 / Chapter (1) --- Absorption and Fluorescence Spectra --- p.45 / Chapter (2) --- Fluorescence Lifetimes and Quantum Yields --- p.51 / Chapter (3) --- Time-resolved Fluorescence Spectra --- p.54 / Chapter E. --- Some Experimental Details --- p.60 / Chapter (1) --- Choice of Windows for Regular Tests of the Instrument Performance --- p.60 / Chapter (2) --- Configurations of the Transient Recorder in OPUS --- p.61 / Chapter (3) --- Configurations of Detectors in OPUS --- p.61 / Chapter (4) --- The Standard Method of Extracting Time Slices --- p.62 / Chapter (5) --- Parameters that Easily Cause Problems --- p.63 / Chapter (6) --- Elimination of Background Noises --- p.64 / Chapter Chapter 5 --- Concluding Remarks --- p.66 / Reference --- p.68

Thesis (MSc.(Chemistry))--University of Pretoria, 2008. / Includes bibliographical references.

In this study, two regenerative thermal oxidizers (RTO) were used to test the thermal destruction, thermal recovery efficiency and the gas pressure drop over the beds characteristics when burning, respectively, airborne chlorine- and nitrogen-containing volatile organic compounds (VOCs). First, an electrically-heated RTO containing two 0.5 m ¡Ñ 0.5 m ¡Ñ 2.0 m (L ¡Ñ W ¡Ñ H) beds, both packed with gravel particles with an average diameter of around 0.0116 m and a height of up to 1.48 m with a void fraction of 0.41 in the packed section was used to study the destruction characteristics of chlorine-containing VOCs (trichloroethane, TCE and dichloromethane, DCM). With a valve switch time (ts) of 1.5 min, preset maximum destruction temperatures (TS) of 500-800 oC and superficial gas velocity (Ug) of 0.17-0.33 m/s (evaluated at an influent air temperature of around 27 ¢J), tests on the thermal recovery efficiency (TRE) and the pressure drop for the air stream without VOC in the influent air stream have been performed. With a ts of 1.5 min, Ts of 500-800 oC and Ug of 0.17-0.24 m/s (evaluated at an influent air temperature of around 27 ¢J), tests on the degree thermal destruction of VOCs with influent air streams containing one of the two VOCs: trichloroethylene (TCE) and dichloromethane (DCM) have been done. Second, an electrically-heated RTO containing two 0.152 m ¡Ñ 0.14 m ¡Ñ 1.0 m (L ¡Ñ W ¡Ñ H) beds, both packed with gravel particles with an average diameter of around 0.0111 m and a height of up to 1.0 m with a void fraction of 0.42 in the packed section was used to study the destruction and NOx formation characteristics of DMF (N, N-dimethylformamide). With a ts of 1.5 min, Ts of 750-850 ¢Jand Ug of 0.39-0.78 m/s (evaluated at an influent air temperature of around 30 ¢J), TRE and the pressure drop for the air stream without VOC in the influent air stream have been tested. With a ts of 1.5 min, a Ug of 0.39 m/s (evaluated at an influent air temperature of around 30 ¢J), and Ts of 750-950 ¢J and, thermal destruction efficiencies and nitrogen oxides (NOx) formation characteristics in burning air streams containing either DMF or DMF mixed with methyl ethyl ketone (MEK) were performed. Results demonstrate that: (1) a RTO is suitable for destruction of low concentrations (<1,000 ppm as methane) of airborne highly chlorinated VOCs such as TCE and DCM and the destructed products contain no chlorine and only trace of COCl2 (< 1% of the influent VOC); (2) for TS = 800 oC and Ug = 0.17-0.24 m/s, complete oxidation products of TCE and DCM are HCl, CO2, and H2O, and the main intermediates are CO and COCl2; (3) with ts of 1.5 min, a Ug of 0.39 m/s (evaluated at an influent air temperature of around 30 oC) and TS of 750-950 ¢J, no NOx was present in the effluent gas from the RTO when it was loaded with DMF-free air; (4) when only DMF was present in the influent air, the average destruction efficiencies exceeded 96%, and increased with the influent DMF concentration from 300 to 750 mg/Nm3. The ¡§NOx-N formation/DMF-N destruction¡¨ mass ratios were in the range 0.76-1.05, and decreased as the influent DMF concentration increased within the experimental range; (5) when both DMF and MEK were present in the influent gas, the NOx formation ratio was almost the same and the DMF destruction efficiency increased with the influent MEK/DMF ratio from 150/300 to 4500/300 (mg/mg) and in the preset temperature range. The NOx formation ratios were in the range 0.75-0.96; (6) the TRE decreased as Ug increased but was invariant with Ts; and (7) the Ergun equation was found to suffice in the estimation of the pressure drop when the gas flowed over the packing beds.

Os objetivos dos experimentos foram primeiro testar a presença da dimetilformamida (DF) nas soluções crioprotetoras e segundo avaliar a viabilidade in vitro pós aquecimento de blastocistos Mus domesticus domesticus vitrificados em microcapilares manufaturados industrialmente. O primeiro experimento testou a capacidade de vitrificação das diferentes soluções de vitrificação, compostas pelas combinações de etileno glicol (EG) ou 1-2 propanediol (PROH) com as diferentes porcentagens de DF. No segundo experimento se testou a toxicidade de 3 soluções de equilíbrio: ES1 (PBSm + 10% PROH + 10% DF + 0.5% PVA), ES2 (PBSm+ 10% EG+ 10% DF + 0.5% PVA), ES3 (PBSm + 10% PROH + 10% EG + 0.5% PVA), através da exposição dos embriões durante 3 períodos de tempo (1, 3 e 10 min). O cultivo in vitro após a exposição às soluções de equilíbrio foi realizado em meio de KSOM durante 72 h. Os resultados de re-expansão foram semelhantes entre as três soluções, quando os embriões foram expostos por 1 ou 3 min. Por outro lado, a exposição à ES3 por 10 min, revelou uma maior taxa de sobrevivência dos embriões, em relação às outras soluções testadas. No terceiro experimento, após expor-se os embriões às soluções de equilíbrio, ES1, ES2 e ES3 por 1 min, a vitrificação foi realizada utilizando-se as seguintes soluções: VS1 (PBSm + 20% PROH + 20% DF + 0.5% PVA); VS2 (PBSm + 20% EG + 20% DF+ 0.5%PVA) and VS3 (PBSm + 20% EG + 20% PROH + 0.5% PVA). Imediatamente após a exposição por 30 s às soluções de vitrificação os embriões foram envasados em micropipetas de vidro (GMPs) e mergulhados em nitrogênio líquido superresfriado. As GMPs foram aquecidas no ar durante 10 s e após os embriões foram expostos durante 5 min ao PBSm + 0,25 M sacarose a 37 °C, finalmente transferidos para gotas de meio KSOM e cultivados in vitro durante 72 horas. As taxas de re-expansão dos embriões após o cultivo in vitro foram as seguintes: ES1/VS1 = 12% (13/108); ES2/VS2 = 38% (46/111) e ES3/VS3 = 84% (89/105). A eclosão dos embriões observada após o cultivo in vitro foi de: ES1/VS1 = 3% (3/108); ES2/VS2 = 17% (19/111) e ES3/VS3 = 70% (73/105). As taxas de sobrevivência revelaram que a presença da dimetilformamida na solução crioprotetora reduz a viabilidade embrionária e que a associação de EG + PROH é eficiente na manutenção da viabilidade embrionária após a vitrificação. O segundo artigo descreve os experimentos de vitrificação, utilizando-se para o envase dos embriões um microcapilar de vidro (GMC), produzido industrialmente (Brand®). Blastocistos murinos após a coleta foram divididos em três grupos: Controle, embriões cultivados in vitro em KSOM por 72 horas; Grupo 1, vitrificados envasados em micropipetas de vidro (GMPs) esticadas manualmente; Grupo 2, vitrificados envasados nas GMCs (Brand® - 5 µL). O procedimento de vitrificação foi o seguinte: primeiro os embriões foram expostos à solução de equilíbrio (PBSm + 10% EG + 10% PROH and 0.5% PVA) por 1 min e após transferidos para a solução de vitrificação (PBSm + 20% EG + 20% PROH + 0.5% PVA) por 30 s, envasados nas GMPS ou GMCs e imediatamente mergulhados em nitrogênio superresfriado. As taxas de sobrevivência dos embriões após o aquecimento e cultivo in vitro, não apresentaram diferenças significativas entre os grupos. O envase dos embriões nas GMCs proporcionou sobreviênvia embrionária similar à observada nos embriões envasados nas GMPs. / The aims of these experiments were first, determine the effect of dimethylformamide (DF) into cryoprotectant solutions and sencondly, evaluated the in vitro viability of blastocyst Mus domesticus domesticus vitrified into glass microcapillaries (Brand®). The first article described the efficiency of DF in association with ethylene glycol (EG) and 1-2 propanediol (PROH) on in vitro viability of vitrified mouse blastocysts. Initially, the differents cryoprotectant solutions were tested on its capacities to induce virification. In the second experiment to determine the cryoprotectant toxicity the embryos were exposed during 1, 3 and 10 min to three different equilibrium solutions ES1 (PBSm + 10% PROH+ 10% DF + 0.5% PVA), ES2 (PBSm+10% EG+ 10% DF + 0.5% PVA), ES3 (PBSm + 10% PROH + 10% EG + 0.5% PVA). After 72 hours of in vitro culture in KSOM medium, re-expansion and hatching rates showed no differences among the tested cryoprotectant solutions for 1 or 3 min exposition interval time. However, for the 10 min exposition interval time, ES3 was more effective to promote embryo survival than the others tested cryoprotectant solutions. In the third experiment, blastocysts were vitrified after been exposed to one of the equilibrium solutions (ES1, ES2 or ES3) during 1 min. After that the embryos were transferred to one of the vitrification solutions (VS1 = PBSm + 20% PROH + 20% DF+ 0.5% PVA; VS2 = PBSm + 20% EG+ 20% DF+ 0.5% PVA and VS3 = PBSm + 20% EG+ 20% PROH+ 0.5% PVA) during 30 s, loaded into glass micro pipettes (GMPs) to be plungged into super-cooled liquid nitrogen. The GMPs were thawed in air during 10 s, transferred into drops of PBSm + 0,25 M sucrose at 37 °C for 5 min, and finally transferred to KSOM medium for in vitro culture. After 72 hours the expansion and hatched rates were evaluated. Results demonstrated a significantly difference between the vitrification solutions, showing better hatching rates the embryos vitrified into the ES3/EV3 solution. Therefore, these data shows that the cryoprotectants solutions containning dimethylformamide have deleterious effects on the developmental competence of vitrified mouse blastocysts, and the highest expansion and hatching rates were obtained when the cryoprotectant solution containning an EG and PROH association. The purpose of the second study was to determine the in vitro expansion and hatching rates of vitrified mouse blastocysts loaded into commercially available glass micro-capillaries (GMC - Brand® 5µL). In the early morning at day 4 of the pregnancy, collected blastocysts were divided in three groups: Control: embryos were in vitro culture during 72 hours into KSOM medium; Group 1, blastocyst vitrified into glass micropipettes (GMP); Group 2, blastocyst vitrified into GMC. The embryos were first exposed to the equilibrium solution (PBSm + 10% EG + 10% PROH + 0.5% PVA) for 1 min and then transferred into the vitrification solution (PBSm + 20% EG + 20% PROH + 0.5% PVA) for 30 sec. Blastocysts were loaded into GMP or GMC and plunged into super-cooled liquid nitrogen. Embryo warming was carried out by plunging the narrowest end of the capillaries into droplets of 0.25 M sucrose mantained at 37°C. After 5 min, embryos in vitro culture into KSOM medium for 72 hours. Blastocyst survival rates did not show significant differences between the groups. The tested manufacturated GMC (Brand®) showed the same efficiency as the GMP to load mouse blastocysts for vitrification.

Os objetivos dos experimentos foram primeiro testar a presença da dimetilformamida (DF) nas soluções crioprotetoras e segundo avaliar a viabilidade in vitro pós aquecimento de blastocistos Mus domesticus domesticus vitrificados em microcapilares manufaturados industrialmente. O primeiro experimento testou a capacidade de vitrificação das diferentes soluções de vitrificação, compostas pelas combinações de etileno glicol (EG) ou 1-2 propanediol (PROH) com as diferentes porcentagens de DF. No segundo experimento se testou a toxicidade de 3 soluções de equilíbrio: ES1 (PBSm + 10% PROH + 10% DF + 0.5% PVA), ES2 (PBSm+ 10% EG+ 10% DF + 0.5% PVA), ES3 (PBSm + 10% PROH + 10% EG + 0.5% PVA), através da exposição dos embriões durante 3 períodos de tempo (1, 3 e 10 min). O cultivo in vitro após a exposição às soluções de equilíbrio foi realizado em meio de KSOM durante 72 h. Os resultados de re-expansão foram semelhantes entre as três soluções, quando os embriões foram expostos por 1 ou 3 min. Por outro lado, a exposição à ES3 por 10 min, revelou uma maior taxa de sobrevivência dos embriões, em relação às outras soluções testadas. No terceiro experimento, após expor-se os embriões às soluções de equilíbrio, ES1, ES2 e ES3 por 1 min, a vitrificação foi realizada utilizando-se as seguintes soluções: VS1 (PBSm + 20% PROH + 20% DF + 0.5% PVA); VS2 (PBSm + 20% EG + 20% DF+ 0.5%PVA) and VS3 (PBSm + 20% EG + 20% PROH + 0.5% PVA). Imediatamente após a exposição por 30 s às soluções de vitrificação os embriões foram envasados em micropipetas de vidro (GMPs) e mergulhados em nitrogênio líquido superresfriado. As GMPs foram aquecidas no ar durante 10 s e após os embriões foram expostos durante 5 min ao PBSm + 0,25 M sacarose a 37 °C, finalmente transferidos para gotas de meio KSOM e cultivados in vitro durante 72 horas. As taxas de re-expansão dos embriões após o cultivo in vitro foram as seguintes: ES1/VS1 = 12% (13/108); ES2/VS2 = 38% (46/111) e ES3/VS3 = 84% (89/105). A eclosão dos embriões observada após o cultivo in vitro foi de: ES1/VS1 = 3% (3/108); ES2/VS2 = 17% (19/111) e ES3/VS3 = 70% (73/105). As taxas de sobrevivência revelaram que a presença da dimetilformamida na solução crioprotetora reduz a viabilidade embrionária e que a associação de EG + PROH é eficiente na manutenção da viabilidade embrionária após a vitrificação. O segundo artigo descreve os experimentos de vitrificação, utilizando-se para o envase dos embriões um microcapilar de vidro (GMC), produzido industrialmente (Brand®). Blastocistos murinos após a coleta foram divididos em três grupos: Controle, embriões cultivados in vitro em KSOM por 72 horas; Grupo 1, vitrificados envasados em micropipetas de vidro (GMPs) esticadas manualmente; Grupo 2, vitrificados envasados nas GMCs (Brand® - 5 µL). O procedimento de vitrificação foi o seguinte: primeiro os embriões foram expostos à solução de equilíbrio (PBSm + 10% EG + 10% PROH and 0.5% PVA) por 1 min e após transferidos para a solução de vitrificação (PBSm + 20% EG + 20% PROH + 0.5% PVA) por 30 s, envasados nas GMPS ou GMCs e imediatamente mergulhados em nitrogênio superresfriado. As taxas de sobrevivência dos embriões após o aquecimento e cultivo in vitro, não apresentaram diferenças significativas entre os grupos. O envase dos embriões nas GMCs proporcionou sobreviênvia embrionária similar à observada nos embriões envasados nas GMPs. / The aims of these experiments were first, determine the effect of dimethylformamide (DF) into cryoprotectant solutions and sencondly, evaluated the in vitro viability of blastocyst Mus domesticus domesticus vitrified into glass microcapillaries (Brand®). The first article described the efficiency of DF in association with ethylene glycol (EG) and 1-2 propanediol (PROH) on in vitro viability of vitrified mouse blastocysts. Initially, the differents cryoprotectant solutions were tested on its capacities to induce virification. In the second experiment to determine the cryoprotectant toxicity the embryos were exposed during 1, 3 and 10 min to three different equilibrium solutions ES1 (PBSm + 10% PROH+ 10% DF + 0.5% PVA), ES2 (PBSm+10% EG+ 10% DF + 0.5% PVA), ES3 (PBSm + 10% PROH + 10% EG + 0.5% PVA). After 72 hours of in vitro culture in KSOM medium, re-expansion and hatching rates showed no differences among the tested cryoprotectant solutions for 1 or 3 min exposition interval time. However, for the 10 min exposition interval time, ES3 was more effective to promote embryo survival than the others tested cryoprotectant solutions. In the third experiment, blastocysts were vitrified after been exposed to one of the equilibrium solutions (ES1, ES2 or ES3) during 1 min. After that the embryos were transferred to one of the vitrification solutions (VS1 = PBSm + 20% PROH + 20% DF+ 0.5% PVA; VS2 = PBSm + 20% EG+ 20% DF+ 0.5% PVA and VS3 = PBSm + 20% EG+ 20% PROH+ 0.5% PVA) during 30 s, loaded into glass micro pipettes (GMPs) to be plungged into super-cooled liquid nitrogen. The GMPs were thawed in air during 10 s, transferred into drops of PBSm + 0,25 M sucrose at 37 °C for 5 min, and finally transferred to KSOM medium for in vitro culture. After 72 hours the expansion and hatched rates were evaluated. Results demonstrated a significantly difference between the vitrification solutions, showing better hatching rates the embryos vitrified into the ES3/EV3 solution. Therefore, these data shows that the cryoprotectants solutions containning dimethylformamide have deleterious effects on the developmental competence of vitrified mouse blastocysts, and the highest expansion and hatching rates were obtained when the cryoprotectant solution containning an EG and PROH association. The purpose of the second study was to determine the in vitro expansion and hatching rates of vitrified mouse blastocysts loaded into commercially available glass micro-capillaries (GMC - Brand® 5µL). In the early morning at day 4 of the pregnancy, collected blastocysts were divided in three groups: Control: embryos were in vitro culture during 72 hours into KSOM medium; Group 1, blastocyst vitrified into glass micropipettes (GMP); Group 2, blastocyst vitrified into GMC. The embryos were first exposed to the equilibrium solution (PBSm + 10% EG + 10% PROH + 0.5% PVA) for 1 min and then transferred into the vitrification solution (PBSm + 20% EG + 20% PROH + 0.5% PVA) for 30 sec. Blastocysts were loaded into GMP or GMC and plunged into super-cooled liquid nitrogen. Embryo warming was carried out by plunging the narrowest end of the capillaries into droplets of 0.25 M sucrose mantained at 37°C. After 5 min, embryos in vitro culture into KSOM medium for 72 hours. Blastocyst survival rates did not show significant differences between the groups. The tested manufacturated GMC (Brand®) showed the same efficiency as the GMP to load mouse blastocysts for vitrification.

Os objetivos dos experimentos foram primeiro testar a presença da dimetilformamida (DF) nas soluções crioprotetoras e segundo avaliar a viabilidade in vitro pós aquecimento de blastocistos Mus domesticus domesticus vitrificados em microcapilares manufaturados industrialmente. O primeiro experimento testou a capacidade de vitrificação das diferentes soluções de vitrificação, compostas pelas combinações de etileno glicol (EG) ou 1-2 propanediol (PROH) com as diferentes porcentagens de DF. No segundo experimento se testou a toxicidade de 3 soluções de equilíbrio: ES1 (PBSm + 10% PROH + 10% DF + 0.5% PVA), ES2 (PBSm+ 10% EG+ 10% DF + 0.5% PVA), ES3 (PBSm + 10% PROH + 10% EG + 0.5% PVA), através da exposição dos embriões durante 3 períodos de tempo (1, 3 e 10 min). O cultivo in vitro após a exposição às soluções de equilíbrio foi realizado em meio de KSOM durante 72 h. Os resultados de re-expansão foram semelhantes entre as três soluções, quando os embriões foram expostos por 1 ou 3 min. Por outro lado, a exposição à ES3 por 10 min, revelou uma maior taxa de sobrevivência dos embriões, em relação às outras soluções testadas. No terceiro experimento, após expor-se os embriões às soluções de equilíbrio, ES1, ES2 e ES3 por 1 min, a vitrificação foi realizada utilizando-se as seguintes soluções: VS1 (PBSm + 20% PROH + 20% DF + 0.5% PVA); VS2 (PBSm + 20% EG + 20% DF+ 0.5%PVA) and VS3 (PBSm + 20% EG + 20% PROH + 0.5% PVA). Imediatamente após a exposição por 30 s às soluções de vitrificação os embriões foram envasados em micropipetas de vidro (GMPs) e mergulhados em nitrogênio líquido superresfriado. As GMPs foram aquecidas no ar durante 10 s e após os embriões foram expostos durante 5 min ao PBSm + 0,25 M sacarose a 37 °C, finalmente transferidos para gotas de meio KSOM e cultivados in vitro durante 72 horas. As taxas de re-expansão dos embriões após o cultivo in vitro foram as seguintes: ES1/VS1 = 12% (13/108); ES2/VS2 = 38% (46/111) e ES3/VS3 = 84% (89/105). A eclosão dos embriões observada após o cultivo in vitro foi de: ES1/VS1 = 3% (3/108); ES2/VS2 = 17% (19/111) e ES3/VS3 = 70% (73/105). As taxas de sobrevivência revelaram que a presença da dimetilformamida na solução crioprotetora reduz a viabilidade embrionária e que a associação de EG + PROH é eficiente na manutenção da viabilidade embrionária após a vitrificação. O segundo artigo descreve os experimentos de vitrificação, utilizando-se para o envase dos embriões um microcapilar de vidro (GMC), produzido industrialmente (Brand®). Blastocistos murinos após a coleta foram divididos em três grupos: Controle, embriões cultivados in vitro em KSOM por 72 horas; Grupo 1, vitrificados envasados em micropipetas de vidro (GMPs) esticadas manualmente; Grupo 2, vitrificados envasados nas GMCs (Brand® - 5 µL). O procedimento de vitrificação foi o seguinte: primeiro os embriões foram expostos à solução de equilíbrio (PBSm + 10% EG + 10% PROH and 0.5% PVA) por 1 min e após transferidos para a solução de vitrificação (PBSm + 20% EG + 20% PROH + 0.5% PVA) por 30 s, envasados nas GMPS ou GMCs e imediatamente mergulhados em nitrogênio superresfriado. As taxas de sobrevivência dos embriões após o aquecimento e cultivo in vitro, não apresentaram diferenças significativas entre os grupos. O envase dos embriões nas GMCs proporcionou sobreviênvia embrionária similar à observada nos embriões envasados nas GMPs. / The aims of these experiments were first, determine the effect of dimethylformamide (DF) into cryoprotectant solutions and sencondly, evaluated the in vitro viability of blastocyst Mus domesticus domesticus vitrified into glass microcapillaries (Brand®). The first article described the efficiency of DF in association with ethylene glycol (EG) and 1-2 propanediol (PROH) on in vitro viability of vitrified mouse blastocysts. Initially, the differents cryoprotectant solutions were tested on its capacities to induce virification. In the second experiment to determine the cryoprotectant toxicity the embryos were exposed during 1, 3 and 10 min to three different equilibrium solutions ES1 (PBSm + 10% PROH+ 10% DF + 0.5% PVA), ES2 (PBSm+10% EG+ 10% DF + 0.5% PVA), ES3 (PBSm + 10% PROH + 10% EG + 0.5% PVA). After 72 hours of in vitro culture in KSOM medium, re-expansion and hatching rates showed no differences among the tested cryoprotectant solutions for 1 or 3 min exposition interval time. However, for the 10 min exposition interval time, ES3 was more effective to promote embryo survival than the others tested cryoprotectant solutions. In the third experiment, blastocysts were vitrified after been exposed to one of the equilibrium solutions (ES1, ES2 or ES3) during 1 min. After that the embryos were transferred to one of the vitrification solutions (VS1 = PBSm + 20% PROH + 20% DF+ 0.5% PVA; VS2 = PBSm + 20% EG+ 20% DF+ 0.5% PVA and VS3 = PBSm + 20% EG+ 20% PROH+ 0.5% PVA) during 30 s, loaded into glass micro pipettes (GMPs) to be plungged into super-cooled liquid nitrogen. The GMPs were thawed in air during 10 s, transferred into drops of PBSm + 0,25 M sucrose at 37 °C for 5 min, and finally transferred to KSOM medium for in vitro culture. After 72 hours the expansion and hatched rates were evaluated. Results demonstrated a significantly difference between the vitrification solutions, showing better hatching rates the embryos vitrified into the ES3/EV3 solution. Therefore, these data shows that the cryoprotectants solutions containning dimethylformamide have deleterious effects on the developmental competence of vitrified mouse blastocysts, and the highest expansion and hatching rates were obtained when the cryoprotectant solution containning an EG and PROH association. The purpose of the second study was to determine the in vitro expansion and hatching rates of vitrified mouse blastocysts loaded into commercially available glass micro-capillaries (GMC - Brand® 5µL). In the early morning at day 4 of the pregnancy, collected blastocysts were divided in three groups: Control: embryos were in vitro culture during 72 hours into KSOM medium; Group 1, blastocyst vitrified into glass micropipettes (GMP); Group 2, blastocyst vitrified into GMC. The embryos were first exposed to the equilibrium solution (PBSm + 10% EG + 10% PROH + 0.5% PVA) for 1 min and then transferred into the vitrification solution (PBSm + 20% EG + 20% PROH + 0.5% PVA) for 30 sec. Blastocysts were loaded into GMP or GMC and plunged into super-cooled liquid nitrogen. Embryo warming was carried out by plunging the narrowest end of the capillaries into droplets of 0.25 M sucrose mantained at 37°C. After 5 min, embryos in vitro culture into KSOM medium for 72 hours. Blastocyst survival rates did not show significant differences between the groups. The tested manufacturated GMC (Brand®) showed the same efficiency as the GMP to load mouse blastocysts for vitrification.

The Refcoal process is being developed to produce graphite from coal. Coal is dissolved in dimethylformamide (DMF) and sodium hydroxide (NaOH) is used as additive. After separation, the extracted coal (Refcoal) is precipitated with water and dried. The extraction process and subsequent solid-liquid separation processes have to be as efficient and cost-effective as possible. The purpose of the study was therefore to complete research on various unresolved aspects of the processes as identified by the candidate and supervisor. Extraction at 95 °C (DMF:coal:NaOH = 100:10:1), has an induction period of approximately 60 minutes observed, after which the reaction rate increases considerably. The reaction reaches completion after 360 minutes. An increase in stirring rate decreases extraction time due to the elimination of external mass-transfer limitations. The progress curves obtained for extraction at 135 °C with lower solvent-to-coal ratios differ dramatically from those obtained in previous studies, which indicates that changes in the raw materials and the experimental set-up have a great influence on the extraction at higher temperatures and concentrations. These extractions at higher temperatures using DMF:coal:NaOH ratios between 100:30:3 and 100:30:2 take approximately 360 minutes to complete and do not have an induction period as is the case with the extractions at 95 °C. It was found that the optimum DMF:coal ratio for an operating temperature of 135 °C, is 10:3. The high-temperature extractions reach completion in different time periods, depending on the amount of NaOH added to the reaction mixture. When very low concentrations of NaOH are added, the extraction will take much longer to complete and vice versa. The amount of NaOH used influences various aspects of the process. The cost analysis of the process falls beyond the scope of this investigation, but it is recommended that a thorough financial study is done to determine the optimum balance between raw materials, heat load and plant availability. The relationships between the concentration of Refcoal in the Refcoal solution and the absorbance values measured are polynomial expressions ending in downward concaves. The kinetics for the low-concentration (DMF:coal:NaOH = 100:10:1) extraction are best described by an autocatalytic reaction rate equation which is a function of coal, coal complex and NaOH concentration. A good fit was also obtained for the high temperature extractions. The rate expression is a function of both the coal and NaOH concentrations, but not of the coal complex. The sedimentation test showed promising results. The use of a thickener instead of a centrifuge to separate the insoluble material from the Refcoal solution would be a feasible cost-saving method. Filtration of the Refcoal solution (after centrifugation) using suitable filter media decreases the amount of impurities in the Refcoal. Filtration constants were determined for the best filter medium. The use of a hydrocyclone to separate the insoluble material from the extract is not recommended as it did not give the required efficiency to make the process viable. It is recommended that more tests be done under different conditions. Useful expressions were obtained for the change in viscosity with temperature for three different concentrations of Refcoal solution. It was determined that the viscosity of the Refcoal solution increases with time and it is therefore recommended that this be taken into account when equipment is being designed and plant scheduling is being done. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2007. / Chemical Engineering / MEng / unrestricted

A new process is being developed to produce graphite from prime coking coal. Coal is dissolved in dimethylformamide (DMF), on addition of sodium hydroxide. The minerals and undissolved coal are separated by centrifugation and filtration to give a solution (referred to as Refcoal solution or RCS). Over 90 wt % of the organic part of a flotation product, from the Tshikondeni mine, can be dissolved at temperatures ranging from room temperature to 135°C. The purified coal (referred to as Refcoal) and DMF need to be separated. the Refcoal to be coked and the DMF to be purified and recycled. This process should be as efficient as possible, whilst both products should be low in water content to minimise drying costs. The addition of water to the Refcoal solution causes precipitation to take place, forming a gel (referred to as Refcoal gel) liquid system. This mixture can be either centrifuged or filtered to give a denser gel, containing water, DMF and coal solids, and supernatant or filtrate, containing water and DMF. Different techniques and processes can be used to improve the separation of the DMF from the Refcoal by achieving a denser Refcoal gel: • Longer centrifugation times improve the density and therefore the separation, but this technique has its limits. • The use of low-temperature water improves the separation. • The use of syneresis could improve separation at a lower cost: heated standing tanks are used to expel the supernatant and therefore increase the density of the gel, thereby decreasing the required number of washing stages. • The addition of toluene at the beginning of a wash improved the removal of DMF by 20%, using centrifugation as separation method. • Pressure filtration gave a 20% improvement on centrifugation, with no additives. • The addition of toluene to the pressure filtration process gave another improvement of 15%, and after three stages the percentage of solids in the gel was 28%, the highest so far achieved. This method also resulted in the highest removal of DMF in the first stage (73% of the original DMF in the RCS was removed). Counter-current washing shows the greatest potential, using the least amount of water. The concentration of DMF in the wash solution, to gel the Refcoal solution, is a limitation of this process. If the concentration is too high, no gelling and therefore no separation can take place in the first stage. It is recommended that counter-current washing using pressure filtration should be investigated; however, this will be difficult on a laboratory scale due to the mass losses during transfers. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2009. / Chemical Engineering / unrestricted

This thesis deals with a study of lithium-ion batteries. It is focused into negative electrode materials and electrolytes. In this thesis is presented synthesis, electrochemical properties, possibilities to improving negative electrode materials as LTO (Lithium Titanate Oxid) and graphite. These electrode materials were investigated with respect to their compatibility at electrolytes with carbonate solvents, Sulfolane and DMF (DiMethylFormamide) in detail. The main aim of this thesis is to characterize electrode materials and electrolyte properties depending on wide range of temperatures and their comparison for the purpose of achievement of the best solution. The thesis is divided into two main parts. The theoretical part of thesis describes composition, process of synthesis and analysis of lithium-ion cell. Practical part contains measuring and evaluating of charge-discharge and irreversible capacity characteristics related to variety of environmental temperatures.