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  • 11
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 249 (1974), S. 593-594 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR,-In an attempt to measure proton mobility, Roberts and Nor they, used signal line broadening from steady state nuclear magnetic resonance (NMR) to study slices of sintered glass with a pore size of ~ 15 pun (reif. 1). They infer "long range modification of the water structure by sintered ...
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 261 (1976), S. 540-540 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR,?It has been suggested in your columns that both electric power (November 6, 1975, page 9) and water (February 12, 1976, page 444) could easily be generated from the flow of seawater into the valley of the Dead Sea (surface at ?390m). Besides using this head for turbine generated energy, both ...
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Company
    Nature biotechnology 8 (1990), S. 327-330 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] We have developed nuclear magnetic resonance (NMR) flow imaging techniques to measure fluid flow in a cell-free hollow fiber bioreactor (HFBR). Using 1H NMR we track the motion of protons and obtain velocity distributions as a function of position and time. These measurements enable the ...
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 447-466 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Although cross-flow membrane filtration is a very attractive option for harvesting cells and recovering enzymes from cell homogenates, the process is not without its problems. Foremost of these is the deposit of dissolved and suspended solutes onto the membrane surface during operation. The formation of these dense and sometimes compressive sublayers (often called cakes) offers additional resistance to axial and permeate flows and often affects the retention characteristics of the process. In view of the complex nature of the sublayer formation process and its sensitivity to cross-flow velocity, this investigation was undertaken to determine the main factors responsible for the decline in performance during the harvesting of B. polymyxa broth by membrane microfiltration. System parameters varied include axial flow rate, concentration of cells, proteins and other components in the feed, membrane materials (ceramic, polypropylene, and stainless steel), and cleaning methods. To help explain the observed results, a new mass transport model - the solids flux model - based on the assumptions that back migration of particles from the sublayer or membrane surface is negligible and that particles that reach the solid-solution interface attach (stick) completely, is tested. Using a variety of diagnostic methods, magnesium ammonium phosphate precipitate is formed during steam sterilization of the medium and is implicated as the major foulant in this study.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 21-36 
    ISSN: 0006-3592
    Keywords: affinity sorption ; microporous membrane ; metal chelate ; protein fractionation ; radial dispersion model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new group-specific affinity membrane using metal chelates as ligands and inorganic glass hollow fiber microfiltration membranes as support matrices is developed and tested. The study focused on developing the optimum activation and coupling procedures to bind the chelating agent (iminodiacetic acid, IDA) to the surface of the microporous glass hollow fiber membrane and testing the resultant affinity membrane. Starting with three different glass surfaces, five modification reactions were evaluated. All the modified “active surfaces” were first tested for their protein adsorptive properties in batch mode with suspended microporous glass grains using model proteins with known binding characteristics with Cu-IDA systems. The metal loading capacities of the surfaces exhibiting favorable fractionation were then measured by atomic absorption spectroscopy.The results were compared with the results obtained with a commercial material used in immobilized metal affinity column chromatography. The protein binding characteristics of the hollow fiber affinity membranes were also evaluated under conditions of convective flow. This was performed by flowing single solute protein solutions through the microporous membrane at different flow rates. These results were then used to estimate the optimum loading and elution times for the process. A mathematical model incorporating radial diffusion was solved using a finite difference discretization method. Comparison between model predictions and experimental results was performed for four different proteins at one flow rate. These results suggested that the kinetics of adsorption was concentration dependent. Finally, the hollow fiber affinity membranes were challenged with two component mixtures to test their ability to fractionate mixed protein solutions. Efficient separation and good purity were obtained.The results presented here represent the development of a new fast flow affinity membrane process-immobilized metal affinity membranes (IMAM). © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 1592-1602 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The velocity contour profiles within Dean vortices produced by flowing water in a solid-walled curved tube are quantitatively measured. Magnetic resonance flow imaging using flow encoding with spin warp imaging is used in two and three dimensions to obtain these velocities. These experimental measurements are then compared with simulations obtained from solutions of the Navier-Stokes and continuity equations for three axial flow rates. Numerical solutions were obtained with a finite volume method for curved tube Poiseuille flow.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 347-358 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The velocity and pressure fields and the effect of wall flux on these fields in a spiral channel are presented. As fluid flows inward through a spiral channel with constant gap and permeable walls, the streamwise flux decreases while the curvature increases. Thus, by balancing the stabilizing effect of wall suction with the destabilizing effect of increasing curvature, established vortices can be maintained along the spiral channel. This approach is used to prescribe spiral geometries with different wall fluxes. Using a weakly nonlinear stability analysis, the influence of wall flux on the characteristics of Dean vortices is obtained. The critical Dean number is reduced when suction is through the inner wall only, is slightly reduced when suction is equal through both walls, and is increased when suction is through the outer wall only. The magnitude of change is proportional to a ratio of small numbers that measures the importance of the effect of curvature. In membrane filtration applications the wall flux is typically 2 to 5 orders of magnitude less than the streamwise flow. If the radius of curvature of the channel is of the order of 100 times the channel gap, the effect on the critical Dean number is within 2% of the no-wall flux case. If the radius of curvature is sufficiently large, however, it is possible to observe effects on the critical Dean number that approach O(1) in magnitude for certain parameter ranges.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 28 (1986), S. 646-658 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Growth of a hybridoma culture, along with production of monoclonal antibody, was demonstrated over extended periods in polysulfone hollow fiber membrane modules. The molecular weight cutoffs of the membranes were 70,000, 50,000, and 100,000 daltons. The hybridoma cell line, designated 65/26, produced IgG (2b/κ) directed at mouse thymus cell surface antigen, TL.1. Cell growth occurred in the shell space of the reactor, using supplemented RPMI 1640 (20% fetal bovine serum) supplied from a separate reservoir vessel through the hollow fiber lumen. The reservoir contained 125 mL media, which was changed every 4 days. Concentrations of immunoglobulin were determined by an enzyme immunoassay (using protein A and alkaline phosphatase-labeled antibody conjugate). For the 10K, 50K, and 100K hollow fiber membrane modules, the maximum IgG concentrations detected in the 2.5-mL shell space were 47.5-80, 510, and 740 μg/mL, respectively. In the 125-mL reservoir for the 100K hollow fiber membrane module, the IgG concentration was measured at 260 μg/mL These values compare with an IgG concentration of 1 μg/mL when grown in a standard tissue culture flask and 3.2-7.6 μg/mL when grown in 100 ml media in a spinner flask. In addition, 10K and 50K hollow fiber membrane modules were run in a mode that decreased the fetal bovine serum supplement with time. Differences between these systems suggest that it is possible to obtain high IgG accumulation rates, both during and after the exponential growth phase of the hybridoma population.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 979-990 
    ISSN: 0006-3592
    Keywords: glycidyl butyrate ; kinetic resolution ; membrane reactor ; immobilized enzyme ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A laboratory-scale multiphase hollow fiber membrane reactor was employed to investigate the lipase-catalyzed enzymatic resolution of racemic glycidyl butyrate. A mathematical formulation was feveloped to simulate the performance of this system. Model parameters were determined independently (except the effective rate constant, ks) and incorporated in the model simulations. In this study, two modes of operation are considered: subtractive resolution, in which the unreacted substrate is recovered in the organic stream; and product recovery, where the optically pure product of the enzymatic reaction is recovered in the aqueous stream. Good agreement was obtained between theoretical predictions and experimental results under a variety of conditions. The effect of mass transport limitations on the performance of this system was investigated. An increase in enzyme loading resulted in a higher Thiele modulus due to an elevated rate constant as well as a concomitant decrease in the effective diffusivity. Optical purity decreased in both subtractive resolution and product recovery at higher Thiele modulus with the effect being more pronounced in the product recovery mode. Finally, normalized plots were established to describe the effect of enzyme immobilization on both the effective enzymes activity and effective diffusivity. © 1993 Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 20
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Integrating the properties of synthetic membranes with biological catalysts such as cells and enzymes forms the basis of an exciting new technology called membrane bioreactors. The impetus behind this marriage comes from the recent spectacular advances in recombinant DMA and cell fusion technologies and the need to develop competitive bioprocessing schemes to produce complex and active biological molecules. The advantages and limitations of using membrane bioreactors for entrapping whole cells and enzymes are reviewed. Various membrane configurations such as microcapsules, hollow fibers, and flat sheets are compared. Several different entrapped membrane bioreactors, including single, laminated and microporous, for the conversion of optically active enantiomers are described. As with new and exciting technologies, the future of membrane bioreactors in biotechnology will depend on their ability to produce desired molecules at competitive costs.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
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