The Experts below are selected from a list of 28368 Experts worldwide ranked by ideXlab platform
Richard Auria - One of the best experts on this subject based on the ideXlab platform.
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hydrogen production by the hyperthermophilic bacterium thermotoga maritima part ii modeling and experimental approaches for hydrogen production
Biotechnology for Biofuels, 2016Co-Authors: Richard Auria, Celine Boileau, Sylvain Davidson, Laurence Casalot, Pierre Christen, Pierrepol Liebgott, Yannick CombetblancAbstract:Thermotoga maritima is a hyperthermophilic bacterium known to produce hydrogen from a large variety of substrates. The aim of the present study is to propose a mathematical model incorporating kinetics of growth, consumption of substrates, product formations, and inhibition by hydrogen in order to predict hydrogen production depending on defined culture conditions. Our mathematical model, incorporating data concerning growth, substrates, and products, was developed to predict hydrogen production from batch fermentations of the hyperthermophilic bacterium, T. maritima. It includes the inhibition by hydrogen and the liquid-to-gas mass transfer of H2, CO2, and H2S. Most kinetic parameters of the model were obtained from batch experiments without any fitting. The mathematical model is adequate for glucose, yeast extract, and thiosulfate concentrations ranging from 2.5 to 20 mmol/L, 0.2–0.5 g/L, or 0.01–0.06 mmol/L, respectively, corresponding to one of these compounds being the growth-Limiting factor of T. maritima. When glucose, yeast extract, and thiosulfate concentrations are all higher than these ranges, the model overestimates all the variables. In the window of the model Validity, predictions of the model show that the combination of both variables (increase in Limiting factor concentration and in inlet gas stream) leads up to a twofold increase of the maximum H2-specific productivity with the lowest inhibition. A mathematical model predicting H2 production in T. maritima was successfully designed and confirmed in this study. However, it shows the Limit of Validity of such mathematical models. Their Limit of applicability must take into account the range of Validity in which the parameters were established.
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Hydrogen production by the hyperthermophilic bacterium Thermotoga maritima Part II: modeling and experimental approaches for hydrogen production
Biotechnology for Biofuels, 2016Co-Authors: Richard Auria, Celine Boileau, Sylvain Davidson, Laurence Casalot, Pierre Christen, Pierrepol Liebgott, Yannick Combet-blancAbstract:Background: Thermotoga maritima is a hyperthermophilic bacterium known to produce hydrogen from a large variety of substrates. The aim of the present study is to propose a mathematical model incorporating kinetics of growth, consumption of substrates, product formations, and inhibition by hydrogen in order to predict hydrogen production depending on defined culture conditions. Results: Our mathematical model, incorporating data concerning growth, substrates, and products, was developed to predict hydrogen production from batch fermentations of the hyperthermophilic bacterium, T. maritima. It includes the inhibition by hydrogen and the liquid-to-gas mass transfer of H-2, CO2, and H2S. Most kinetic parameters of the model were obtained from batch experiments without any fitting. The mathematical model is adequate for glucose, yeast extract, and thiosulfate concentrations ranging from 2.5 to 20 mmol/L, 0.2-0.5 g/L, or 0.01-0.06 mmol/L, respectively, corresponding to one of these compounds being the growth-Limiting factor of T. maritima. When glucose, yeast extract, and thiosulfate concentrations are all higher than these ranges, the model overestimates all the variables. In the window of the model Validity, predictions of the model show that the combination of both variables (increase in Limiting factor concentration and in inlet gas stream) leads up to a twofold increase of the maximum H-2-specific productivity with the lowest inhibition. Conclusions: A mathematical model predicting H-2 production in T. maritima was successfully designed and confirmed in this study. However, it shows the Limit of Validity of such mathematical models. Their Limit of applicability must take into account the range of Validity in which the parameters were established.
Oleg D Lavrentovich - One of the best experts on this subject based on the ideXlab platform.
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nanosecond electro optics of a nematic liquid crystal with negative dielectric anisotropy
Physical Review E, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Oleg D LavrentovichAbstract:We study a nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field $\mathbf{E}$ modifies the tensor order parameter but does not change the orientation of the optic axis (director $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{N}}$). We use a nematic with negative dielectric anisotropy with the electric field applied perpendicularly to $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{N}}$. The field changes the dielectric tensor at optical frequencies (optic tensor) due to the following mechanisms: (a) nanosecond creation of the biaxial orientational order, (b) uniaxial modification of the orientational order that occurs over time scales of tens of nanoseconds, and (c) the quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field on a time scale of nanoseconds. The paper provides a useful guidance in the current search for the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a time scale of nanoseconds, the classic model with constant viscoelastic material parameters might reach its Limit of Validity. The effect of nanosecond electric modification of the order parameter can be used in applications in which one needs to achieve ultrafast (nanosecond) changes in optical characteristics, such as birefringence.
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nanosecond electro optics of a nematic liquid crystal with negative dielectric anisotropy
Physical Review E, 2014Co-Authors: Volodymyr Borshch, Sergij V Shiyanovskii, Bingxiang Li, Oleg D LavrentovichAbstract:: We study a nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field E modifies the tensor order parameter but does not change the orientation of the optic axis (director N ). We use a nematic with negative dielectric anisotropy with the electric field applied perpendicularly to N . The field changes the dielectric tensor at optical frequencies (optic tensor) due to the following mechanisms: (a) nanosecond creation of the biaxial orientational order, (b) uniaxial modification of the orientational order that occurs over time scales of tens of nanoseconds, and (c) the quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field on a time scale of nanoseconds. The paper provides a useful guidance in the current search for the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a time scale of nanoseconds, the classic model with constant viscoelastic material parameters might reach its Limit of Validity. The effect of nanosecond electric modification of the order parameter can be used in applications in which one needs to achieve ultrafast (nanosecond) changes in optical characteristics, such as birefringence.
Yannick Combetblanc - One of the best experts on this subject based on the ideXlab platform.
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hydrogen production by the hyperthermophilic bacterium thermotoga maritima part ii modeling and experimental approaches for hydrogen production
Biotechnology for Biofuels, 2016Co-Authors: Richard Auria, Celine Boileau, Sylvain Davidson, Laurence Casalot, Pierre Christen, Pierrepol Liebgott, Yannick CombetblancAbstract:Thermotoga maritima is a hyperthermophilic bacterium known to produce hydrogen from a large variety of substrates. The aim of the present study is to propose a mathematical model incorporating kinetics of growth, consumption of substrates, product formations, and inhibition by hydrogen in order to predict hydrogen production depending on defined culture conditions. Our mathematical model, incorporating data concerning growth, substrates, and products, was developed to predict hydrogen production from batch fermentations of the hyperthermophilic bacterium, T. maritima. It includes the inhibition by hydrogen and the liquid-to-gas mass transfer of H2, CO2, and H2S. Most kinetic parameters of the model were obtained from batch experiments without any fitting. The mathematical model is adequate for glucose, yeast extract, and thiosulfate concentrations ranging from 2.5 to 20 mmol/L, 0.2–0.5 g/L, or 0.01–0.06 mmol/L, respectively, corresponding to one of these compounds being the growth-Limiting factor of T. maritima. When glucose, yeast extract, and thiosulfate concentrations are all higher than these ranges, the model overestimates all the variables. In the window of the model Validity, predictions of the model show that the combination of both variables (increase in Limiting factor concentration and in inlet gas stream) leads up to a twofold increase of the maximum H2-specific productivity with the lowest inhibition. A mathematical model predicting H2 production in T. maritima was successfully designed and confirmed in this study. However, it shows the Limit of Validity of such mathematical models. Their Limit of applicability must take into account the range of Validity in which the parameters were established.
Yannick Combet-blanc - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen production by the hyperthermophilic bacterium Thermotoga maritima Part II: modeling and experimental approaches for hydrogen production
Biotechnology for Biofuels, 2016Co-Authors: Richard Auria, Celine Boileau, Sylvain Davidson, Laurence Casalot, Pierre Christen, Pierrepol Liebgott, Yannick Combet-blancAbstract:Background: Thermotoga maritima is a hyperthermophilic bacterium known to produce hydrogen from a large variety of substrates. The aim of the present study is to propose a mathematical model incorporating kinetics of growth, consumption of substrates, product formations, and inhibition by hydrogen in order to predict hydrogen production depending on defined culture conditions. Results: Our mathematical model, incorporating data concerning growth, substrates, and products, was developed to predict hydrogen production from batch fermentations of the hyperthermophilic bacterium, T. maritima. It includes the inhibition by hydrogen and the liquid-to-gas mass transfer of H-2, CO2, and H2S. Most kinetic parameters of the model were obtained from batch experiments without any fitting. The mathematical model is adequate for glucose, yeast extract, and thiosulfate concentrations ranging from 2.5 to 20 mmol/L, 0.2-0.5 g/L, or 0.01-0.06 mmol/L, respectively, corresponding to one of these compounds being the growth-Limiting factor of T. maritima. When glucose, yeast extract, and thiosulfate concentrations are all higher than these ranges, the model overestimates all the variables. In the window of the model Validity, predictions of the model show that the combination of both variables (increase in Limiting factor concentration and in inlet gas stream) leads up to a twofold increase of the maximum H-2-specific productivity with the lowest inhibition. Conclusions: A mathematical model predicting H-2 production in T. maritima was successfully designed and confirmed in this study. However, it shows the Limit of Validity of such mathematical models. Their Limit of applicability must take into account the range of Validity in which the parameters were established.
Celine Boileau - One of the best experts on this subject based on the ideXlab platform.
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hydrogen production by the hyperthermophilic bacterium thermotoga maritima part ii modeling and experimental approaches for hydrogen production
Biotechnology for Biofuels, 2016Co-Authors: Richard Auria, Celine Boileau, Sylvain Davidson, Laurence Casalot, Pierre Christen, Pierrepol Liebgott, Yannick CombetblancAbstract:Thermotoga maritima is a hyperthermophilic bacterium known to produce hydrogen from a large variety of substrates. The aim of the present study is to propose a mathematical model incorporating kinetics of growth, consumption of substrates, product formations, and inhibition by hydrogen in order to predict hydrogen production depending on defined culture conditions. Our mathematical model, incorporating data concerning growth, substrates, and products, was developed to predict hydrogen production from batch fermentations of the hyperthermophilic bacterium, T. maritima. It includes the inhibition by hydrogen and the liquid-to-gas mass transfer of H2, CO2, and H2S. Most kinetic parameters of the model were obtained from batch experiments without any fitting. The mathematical model is adequate for glucose, yeast extract, and thiosulfate concentrations ranging from 2.5 to 20 mmol/L, 0.2–0.5 g/L, or 0.01–0.06 mmol/L, respectively, corresponding to one of these compounds being the growth-Limiting factor of T. maritima. When glucose, yeast extract, and thiosulfate concentrations are all higher than these ranges, the model overestimates all the variables. In the window of the model Validity, predictions of the model show that the combination of both variables (increase in Limiting factor concentration and in inlet gas stream) leads up to a twofold increase of the maximum H2-specific productivity with the lowest inhibition. A mathematical model predicting H2 production in T. maritima was successfully designed and confirmed in this study. However, it shows the Limit of Validity of such mathematical models. Their Limit of applicability must take into account the range of Validity in which the parameters were established.
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Hydrogen production by the hyperthermophilic bacterium Thermotoga maritima Part II: modeling and experimental approaches for hydrogen production
Biotechnology for Biofuels, 2016Co-Authors: Richard Auria, Celine Boileau, Sylvain Davidson, Laurence Casalot, Pierre Christen, Pierrepol Liebgott, Yannick Combet-blancAbstract:Background: Thermotoga maritima is a hyperthermophilic bacterium known to produce hydrogen from a large variety of substrates. The aim of the present study is to propose a mathematical model incorporating kinetics of growth, consumption of substrates, product formations, and inhibition by hydrogen in order to predict hydrogen production depending on defined culture conditions. Results: Our mathematical model, incorporating data concerning growth, substrates, and products, was developed to predict hydrogen production from batch fermentations of the hyperthermophilic bacterium, T. maritima. It includes the inhibition by hydrogen and the liquid-to-gas mass transfer of H-2, CO2, and H2S. Most kinetic parameters of the model were obtained from batch experiments without any fitting. The mathematical model is adequate for glucose, yeast extract, and thiosulfate concentrations ranging from 2.5 to 20 mmol/L, 0.2-0.5 g/L, or 0.01-0.06 mmol/L, respectively, corresponding to one of these compounds being the growth-Limiting factor of T. maritima. When glucose, yeast extract, and thiosulfate concentrations are all higher than these ranges, the model overestimates all the variables. In the window of the model Validity, predictions of the model show that the combination of both variables (increase in Limiting factor concentration and in inlet gas stream) leads up to a twofold increase of the maximum H-2-specific productivity with the lowest inhibition. Conclusions: A mathematical model predicting H-2 production in T. maritima was successfully designed and confirmed in this study. However, it shows the Limit of Validity of such mathematical models. Their Limit of applicability must take into account the range of Validity in which the parameters were established.