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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A comparative study of autotrophic and heterotrophic denitrification using sulphide and acetate

An, Shijie 29 June 2010
Sulphide containing streams must be treated before releases to environment due to the toxicity, corrosivity and unpleasant odour of sulphide. Anaerobic chemolithotrophic desulphurization under denitrifying conditions is the preferred process when compared with others like physicochemical processes, photoautotrophic and aerobic chemolithotrophic desulphurizations as the catalysts, high pressure, high temperature, light energy and oxygen are not needed. Another main advantage of this process is that the denitrification can be achieved with desulphurization simultaneously. In this work, the anaerobic chemolithotrophic desulphurization under denitrifying conditions (autotrophic denitrification) and heterotrophic denitrification processes were studied. Desulphurization under denitrifying conditions was studied in continuous stirred tank bioreactors (CSTB), while batch, continuous stirred tank and biofilm reactors were used to investigate the heterotrophic denitrification. The kinetics of desulphurization, autotrophic and heterotrophic denitrifications obtained in different systems and under various conditions were compared.<p> Using three different feed sulphide concentrations in the range 10-20 mM, a linear relationship between sulphide loading rates and sulphide removal rates was observed in continuous stirred tank reactors, regardless of initial sulphide concentration. The highest sulphide removal rate of 1.79 mM h-1 was obtained in CSTB fed with 15 mM sulphide. In these systems cell washout occurred at lower dilution rates as sulphide concentration in the feed was increased from 10 to 20 mM. The ratio of sulphide to nitrate loading rates influenced the composition of the sulphur oxidation end products where higher ratios favored the formation of elemental sulphur and lower ratios promoted the formation of sulphate.<p> In the batch system initial concentration of nitrate (5 to 50 mM) did not have a notable effect on denitrification process. Nitrate was converted to nitrite first and the produced nitrite was then converted to other gaseous end products such as nitrogen. Increases of temperature in the range of 15 to 35ºC increased the bacterial growth rate significantly with the value of apparent activation energy for specific growth rate being 60.6 kJ mol-1. Using the experimental data generated in two continuous bioreactors operated with feeds containing 10 and 30 mM nitrate biokinetic coefficients for heterotrophic denitrification were determined. The values of µm, Ks, ms, YMX/S, kd for initial nitrate concentrations of 10 and 30 mM were 0.087 and 0.082 h-1, 2.01 and 5.27 mM (NO3-), 1.441 and 1.096 mM (NO3-) (g biomass) -1 h-1, 0.011 and 0.013 g (biomass) (mM NO3-)-1, and 0.016 and 0.014 h-1 respectively. In the biofilm system the linear relationship between nitrate loading rate and nitrate removal rate was observed again for the whole range of tested nitrate loading rate range (up to 183 mM h-1), regardless of the approach used to increase the loading rate (increases in feed flow rate or feed nitrate concentration). The highest nitrate removal rate was 183 mM h-1 which was around 194 times higher than that achieved in the continuous stirred tank bioreactor with free cells.<p> A comparison of the autotrophic and heterotrophic denitrification processes studied in the CSTB system indicated that in case of autotrophic denitrification wash-out occurred suddenly and at a much lower loading rate of 0.75 to 0.96 mM (NO3-) h-1 for initial sulphide concentrations 10 to 20 mM, while in case of heterotrophic denitrification increase of nitrate loading rate did not have such a drastic effect and removal rate of nitrate decreased slowly with the increases of nitrate loading rate. A comparison of the kinetic data obtained in the biofilm reactor in the present work and those generated for autotrophic denitrification in an earlier work conducted at University of Saskatchewan (Tang, 2008) showed that the dependency of nitrate removal rate on its loading rate were linear in either case and somewhat similar. However, the maximum nitrate removal rate obtained in the heterotrophic system (183 mM h-1) was much higher than that obtained in the autotrophic system with sulphide.
2

A comparative study of autotrophic and heterotrophic denitrification using sulphide and acetate

An, Shijie 29 June 2010 (has links)
Sulphide containing streams must be treated before releases to environment due to the toxicity, corrosivity and unpleasant odour of sulphide. Anaerobic chemolithotrophic desulphurization under denitrifying conditions is the preferred process when compared with others like physicochemical processes, photoautotrophic and aerobic chemolithotrophic desulphurizations as the catalysts, high pressure, high temperature, light energy and oxygen are not needed. Another main advantage of this process is that the denitrification can be achieved with desulphurization simultaneously. In this work, the anaerobic chemolithotrophic desulphurization under denitrifying conditions (autotrophic denitrification) and heterotrophic denitrification processes were studied. Desulphurization under denitrifying conditions was studied in continuous stirred tank bioreactors (CSTB), while batch, continuous stirred tank and biofilm reactors were used to investigate the heterotrophic denitrification. The kinetics of desulphurization, autotrophic and heterotrophic denitrifications obtained in different systems and under various conditions were compared.<p> Using three different feed sulphide concentrations in the range 10-20 mM, a linear relationship between sulphide loading rates and sulphide removal rates was observed in continuous stirred tank reactors, regardless of initial sulphide concentration. The highest sulphide removal rate of 1.79 mM h-1 was obtained in CSTB fed with 15 mM sulphide. In these systems cell washout occurred at lower dilution rates as sulphide concentration in the feed was increased from 10 to 20 mM. The ratio of sulphide to nitrate loading rates influenced the composition of the sulphur oxidation end products where higher ratios favored the formation of elemental sulphur and lower ratios promoted the formation of sulphate.<p> In the batch system initial concentration of nitrate (5 to 50 mM) did not have a notable effect on denitrification process. Nitrate was converted to nitrite first and the produced nitrite was then converted to other gaseous end products such as nitrogen. Increases of temperature in the range of 15 to 35ºC increased the bacterial growth rate significantly with the value of apparent activation energy for specific growth rate being 60.6 kJ mol-1. Using the experimental data generated in two continuous bioreactors operated with feeds containing 10 and 30 mM nitrate biokinetic coefficients for heterotrophic denitrification were determined. The values of µm, Ks, ms, YMX/S, kd for initial nitrate concentrations of 10 and 30 mM were 0.087 and 0.082 h-1, 2.01 and 5.27 mM (NO3-), 1.441 and 1.096 mM (NO3-) (g biomass) -1 h-1, 0.011 and 0.013 g (biomass) (mM NO3-)-1, and 0.016 and 0.014 h-1 respectively. In the biofilm system the linear relationship between nitrate loading rate and nitrate removal rate was observed again for the whole range of tested nitrate loading rate range (up to 183 mM h-1), regardless of the approach used to increase the loading rate (increases in feed flow rate or feed nitrate concentration). The highest nitrate removal rate was 183 mM h-1 which was around 194 times higher than that achieved in the continuous stirred tank bioreactor with free cells.<p> A comparison of the autotrophic and heterotrophic denitrification processes studied in the CSTB system indicated that in case of autotrophic denitrification wash-out occurred suddenly and at a much lower loading rate of 0.75 to 0.96 mM (NO3-) h-1 for initial sulphide concentrations 10 to 20 mM, while in case of heterotrophic denitrification increase of nitrate loading rate did not have such a drastic effect and removal rate of nitrate decreased slowly with the increases of nitrate loading rate. A comparison of the kinetic data obtained in the biofilm reactor in the present work and those generated for autotrophic denitrification in an earlier work conducted at University of Saskatchewan (Tang, 2008) showed that the dependency of nitrate removal rate on its loading rate were linear in either case and somewhat similar. However, the maximum nitrate removal rate obtained in the heterotrophic system (183 mM h-1) was much higher than that obtained in the autotrophic system with sulphide.
3

Estudo molecular epilepsia mioclônica progressiva de UnverrichtLundborg (emp1) na população brasileira / Molecular progressive myoclonic epilepsy study of UnverrichtLundborg (emp1) in the Brazilian population

Andrade, Bianca Mara Alves de 12 September 2018 (has links)
A doença de Unverricht-Lundborg (DUL) é considerada uma doença rara, autossômica recessiva, sendo também denominada de Epilepsia Mioclônica Progressiva do tipo1 (emp1), causada por mutações no gene codificador (CSTB) da proteína cistatina B. A cistatina B é uma proteína essencial para a regulação dos processos fisiológicos do ser humano, e sua expressão reduzida parece ser a causa primária da EMP1. A doença em geral se inicia entre os seis e dezesseis anos, manifestando-se tanto como crises mioclônicas como por crises tônicoclônicas generalizadas. Trata-se de uma doença grave e limitante, cujo diagnóstico preciso é extremamente importante para as condutas apropriadas, incluindo aconselhamento genético. Este estudo tem como objetivo o estudo molecular e caracterização da expansão instável de repetição dodecamérica (CCCCGCCCCGCG) da região promotora 5\' não traduzida do gene CSTB entre pacientes com suspeita de EMP1 na população brasileira. No presente estudo, selecionamos 64 pacientes entre eles 54 casos índices do Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto (HCFMRP-USP) com suspeita de EMP1. Os restantes 10 casos eram parentes dos casos índices. Os 54 pacientes foram seguidos no setor de Epilepsia com diagnostico clinico e eletrofisiológico de EMP1, e foram encaminhados para o setor de Neurogenética para diagnostico molecular. Destes 54 casos índices, apenas 5 foram diagnosticados através da biologia molecular com expansão dodecamera acima de 30 repetições, sugestivo de DUL. Espera-se, com este estudo, identificar a população de pacientes com EPM1 que tenham mutação no gene CSTB e com os resultados de este projeto possibilitar assim um melhor entendimento da etiopatogenia e proporcionar um diagnóstico preciso dos casos de DUL. / Unverricht-Lundborg disease (ULD) is considered a rare autosomal recessive disease, also known as Progressive Myoclonic Epilepsy Type 1 (EMP1), caused by mutations in the CSTB gene, which provides instructions for making a protein called Cystatin B. Such protein is essential for regulating a person\'s physiological processes, and its reduced expression seems to be the first cause of EMP1. Affected individuals usually begin showing signs and symptoms of the disorder between the ages of 6 and 16, which manifests both as myoclonus or as generalized tonic-clonic crises. It is a grave and limiting condition whose precise diagnosis is extremely important for appropriate conducts, including genetic counseling. This study has as a goal the molecular evaluation and characterization of the unstable expansion of the decametric repetition (CCCCGCCCCGCG) from the non-translated CSTB\'s 5\' gene promoter region among Brazilian patients with suspected EMP1. In this study, 64 patients were selected, among them 54 key figures from Hospital das Clínicas of Faculdade de Medicina de Ribeirão Preto (HCFMRP-USP) with suspected EMP1. The other 10 figures were related to the key figures. The 54 patients were followed in the Epilepsy sector with EMP1 clinical and electrophysiological diagnostics and were forwarded to the neurogenetics sector for a molecular diagnostic. From such 54 key figures, only 5 were diagnosed through molecular biology with decametric expansion above 30 repetitions, suggestive of ULD. This study is aimed to identify the EPM1 patients with CSTB genetic mutation and hopefully the results of this identification will enable a better understanding of the etiopathogeny and provide with a exact diagnosis of ULD cases.

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