The Experts below are selected from a list of 596937 Experts worldwide ranked by ideXlab platform
Andrew L. Zydney - One of the best experts on this subject based on the ideXlab platform.
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Optimization of ultrafiltration/diafiltration processes for partially bound impurities
Biotechnology and bioengineering, 2004Co-Authors: Jiahui Shao, Andrew L. ZydneyAbstract:Ultrafiltration and diafiltration processes are used extensively for removal of a variety of small impurities from biological products. There has, however, been no experimental or theoretical analysis of the effects of Impurity- product binding on the rate of Impurity removal during these processes. Model calculations were performed to account for the effects of equilibrium binding between a small Impurity and a large (retained) product on Impurity clearance. Experiments were performed using D-tryptophan and bovine serum albumin as a model system. The results clearly demonstrate that binding interactions can dramatically reduce the rate of small Impurity removal, leading to large increases in the required number of diavolumes. The optimal product concentration for performing the diafiltration shifts to lower product concentrations in the presence of strong binding interactions. Approximate analytical expressions for the Impurity removal were developed which can provide a guide for the design and optimization of industrial ultrafiltration/diafiltration processes.
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optimization of ultrafiltration diafiltration processes for partially bound impurities
Biotechnology and Bioengineering, 2004Co-Authors: Jiahui Shao, Andrew L. ZydneyAbstract:Ultrafiltration and diafiltration processes are used extensively for removal of a variety of small impurities from biological products. There has, however, been no experimental or theoretical analysis of the effects of Impurity- product binding on the rate of Impurity removal during these processes. Model calculations were performed to account for the effects of equilibrium binding between a small Impurity and a large (retained) product on Impurity clearance. Experiments were performed using D-tryptophan and bovine serum albumin as a model system. The results clearly demonstrate that binding interactions can dramatically reduce the rate of small Impurity removal, leading to large increases in the required number of diavolumes. The optimal product concentration for performing the diafiltration shifts to lower product concentrations in the presence of strong binding interactions. Approximate analytical expressions for the Impurity removal were developed which can provide a guide for the design and optimization of industrial ultrafiltration/diafiltration processes.
Jiahui Shao - One of the best experts on this subject based on the ideXlab platform.
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Optimization of ultrafiltration/diafiltration processes for partially bound impurities
Biotechnology and bioengineering, 2004Co-Authors: Jiahui Shao, Andrew L. ZydneyAbstract:Ultrafiltration and diafiltration processes are used extensively for removal of a variety of small impurities from biological products. There has, however, been no experimental or theoretical analysis of the effects of Impurity- product binding on the rate of Impurity removal during these processes. Model calculations were performed to account for the effects of equilibrium binding between a small Impurity and a large (retained) product on Impurity clearance. Experiments were performed using D-tryptophan and bovine serum albumin as a model system. The results clearly demonstrate that binding interactions can dramatically reduce the rate of small Impurity removal, leading to large increases in the required number of diavolumes. The optimal product concentration for performing the diafiltration shifts to lower product concentrations in the presence of strong binding interactions. Approximate analytical expressions for the Impurity removal were developed which can provide a guide for the design and optimization of industrial ultrafiltration/diafiltration processes.
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optimization of ultrafiltration diafiltration processes for partially bound impurities
Biotechnology and Bioengineering, 2004Co-Authors: Jiahui Shao, Andrew L. ZydneyAbstract:Ultrafiltration and diafiltration processes are used extensively for removal of a variety of small impurities from biological products. There has, however, been no experimental or theoretical analysis of the effects of Impurity- product binding on the rate of Impurity removal during these processes. Model calculations were performed to account for the effects of equilibrium binding between a small Impurity and a large (retained) product on Impurity clearance. Experiments were performed using D-tryptophan and bovine serum albumin as a model system. The results clearly demonstrate that binding interactions can dramatically reduce the rate of small Impurity removal, leading to large increases in the required number of diavolumes. The optimal product concentration for performing the diafiltration shifts to lower product concentrations in the presence of strong binding interactions. Approximate analytical expressions for the Impurity removal were developed which can provide a guide for the design and optimization of industrial ultrafiltration/diafiltration processes.
J M Garciaregana - One of the best experts on this subject based on the ideXlab platform.
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impact of main ion pressure anisotropy on stellarator Impurity transport
Nuclear Fusion, 2020Co-Authors: I Calvo, Felix I Parra, J L Velasco, J M GarciareganaAbstract:Main ions influence Impurity dynamics through a variety of mechanisms; in particular, via Impurity-ion collisions. To lowest order in an expansion in the main ion mass over the Impurity mass, the Impurity-ion collision operator only depends on the component of the main ion distribution that is odd in the parallel velocity. These lowest order terms give the parallel friction of the impurities with the main ions, which is typically assumed to be the main cause of collisional Impurity transport. Next-order terms in the mass ratio expansion of the Impurity-ion collision operator, proportional to the component of the main ion distribution that is even in the parallel velocity, are usually neglected. However, in stellarators, the even component of the main ion distribution can be very large. In this article, such next-order terms in the mass ratio expansion of the Impurity-ion collision operator are retained, and analytical expressions for the neoclassical radial flux of trace impurities are calculated in the Pfirsch-Schluter, plateau and 1/ν regimes. The new terms provide a drive for Impurity transport that is physically very different from parallel friction: they are associated to anisotropy in the pressure of the main ions, which translates into Impurity pressure anisotropy. It is argued that main ion pressure anisotropy must be taken into account for a correct description of Impurity transport in certain realistic stellarator plasmas. Examples are given by numerically evaluating the analytical expressions for the Impurity flux.
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compressible Impurity flow in the tj ii stellarator
Nuclear Fusion, 2014Co-Authors: J Arevalo, J L Velasco, J M Garciaregana, J A Alonso, K J Mccarthy, Matt LandremanAbstract:Fully ionized carbon Impurity flow is studied in ion-root, neutral beam heated plasmas by means of charge exchange recombination spectroscopy (CXRS) in the TJ-II stellarator. Perpendicular flows are found to be in reasonable agreement with neoclassical calculations of the radial electric field. The parallel flow of the Impurity is obtained at two locations of the same flux surface after subtraction of the calculated Pfirsch–Schluter parallel velocity. For the medium density plasmas studied, , the measured Impurity flow is found to be inconsistent with a total incompressible flow, i.e. ∇ uz ≠ 0, thus implying a non-constant Impurity density on those flux surfaces. The experimentally observed velocity deviations are compared with the parallel return flow calculated from a modelled Impurity density redistribution driven by ion-Impurity friction. Although the calculated return flow substantially modifies the incompressible velocity pattern, modifications at the locations of the CXRS measurements are generally smaller in magnitude and opposite in sign when compared to the experimentally observed deviations. Small inhomogeneities of the electrostatic potential in a surface are also shown to affect the Impurity redistribution but do not provide a better understanding of the measurements.
G. Latu - One of the best experts on this subject based on the ideXlab platform.
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Neoclassical Impurity flux in presence of turbulent generated poloidal asymmetries and pressure anisotropy
Plasma Physics and Controlled Fusion, 2018Co-Authors: P. Donnel, X. Garbet, Y. Sarazin, V. Grandgirard, N Bouzat, E Caschera, G. Dif-pradalier, P Ghendrih, C. Gillot, G. LatuAbstract:Poloidal asymmetries of impurities are commonly observed experimentally. Density asymmetry is already known to impact significantly neoclassical prediction of Impurity flux. In this article, the effect of Impurity pressure asymmetry and anisotropy on the neoclassical flux of Impurity is derived analytically. This prediction is compared with results coming from a simulation performed with the gyrokinetic code GYSELA, featuring both turbulent and neoclassical transports. A fair agreement is found between the analytical prediction and the result of the simulation. On the special case which is considered, the effect of Impurity pressure asymmetry and anisotropy are shown to play a predominant role on the neoclassical Impurity transport.
J L Velasco - One of the best experts on this subject based on the ideXlab platform.
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impact of main ion pressure anisotropy on stellarator Impurity transport
Nuclear Fusion, 2020Co-Authors: I Calvo, Felix I Parra, J L Velasco, J M GarciareganaAbstract:Main ions influence Impurity dynamics through a variety of mechanisms; in particular, via Impurity-ion collisions. To lowest order in an expansion in the main ion mass over the Impurity mass, the Impurity-ion collision operator only depends on the component of the main ion distribution that is odd in the parallel velocity. These lowest order terms give the parallel friction of the impurities with the main ions, which is typically assumed to be the main cause of collisional Impurity transport. Next-order terms in the mass ratio expansion of the Impurity-ion collision operator, proportional to the component of the main ion distribution that is even in the parallel velocity, are usually neglected. However, in stellarators, the even component of the main ion distribution can be very large. In this article, such next-order terms in the mass ratio expansion of the Impurity-ion collision operator are retained, and analytical expressions for the neoclassical radial flux of trace impurities are calculated in the Pfirsch-Schluter, plateau and 1/ν regimes. The new terms provide a drive for Impurity transport that is physically very different from parallel friction: they are associated to anisotropy in the pressure of the main ions, which translates into Impurity pressure anisotropy. It is argued that main ion pressure anisotropy must be taken into account for a correct description of Impurity transport in certain realistic stellarator plasmas. Examples are given by numerically evaluating the analytical expressions for the Impurity flux.
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compressible Impurity flow in the tj ii stellarator
Nuclear Fusion, 2014Co-Authors: J Arevalo, J L Velasco, J M Garciaregana, J A Alonso, K J Mccarthy, Matt LandremanAbstract:Fully ionized carbon Impurity flow is studied in ion-root, neutral beam heated plasmas by means of charge exchange recombination spectroscopy (CXRS) in the TJ-II stellarator. Perpendicular flows are found to be in reasonable agreement with neoclassical calculations of the radial electric field. The parallel flow of the Impurity is obtained at two locations of the same flux surface after subtraction of the calculated Pfirsch–Schluter parallel velocity. For the medium density plasmas studied, , the measured Impurity flow is found to be inconsistent with a total incompressible flow, i.e. ∇ uz ≠ 0, thus implying a non-constant Impurity density on those flux surfaces. The experimentally observed velocity deviations are compared with the parallel return flow calculated from a modelled Impurity density redistribution driven by ion-Impurity friction. Although the calculated return flow substantially modifies the incompressible velocity pattern, modifications at the locations of the CXRS measurements are generally smaller in magnitude and opposite in sign when compared to the experimentally observed deviations. Small inhomogeneities of the electrostatic potential in a surface are also shown to affect the Impurity redistribution but do not provide a better understanding of the measurements.
