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  • 1
    Electronic Resource
    Electronic Resource
    Mixing with helical ribbon agitators: Part III. Non-Newtonian fluids (1979)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 25 (1979), S. 516-521 
    Details
    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 use of helical ribbon agitators to mix viscous non-Newtonian fluids has been investigated. A generalized model, based on an appropriate definition of effective viscosity, is proposed to predict power consumption. This model is most successful with fluids that do not have a high degree of elasticity.It was found that the efficiency of mixing of pseudoplastic fluids was about half of that of Newtonian fluids in the same mixer, while the efficiency of mixing viscoelastic fluids was still lower and approximately independent of the mixer geometry. Blade width was the primary variable affecting the mixing efficiency on inelastic fluids.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690250318
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  • 2
    Electronic Resource
    Electronic Resource
    Mixing with helical ribbon agitators: Part II. Newtonian FluidsPart I of this paper was published in Can. J. Chem. Eng., 54, 135 (1976). (1979)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 25 (1979), S. 508-516 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Of necessity, the mixing process is sometimes restricted to the laminar regime, although turbulent mixing is generally more desirable. Common examples of laminar mixing are found when the fluid has a very high viscosity, or when one of the mixture components is shear sensitive. It has been pointed out that the helical ribbon agitator (HRA) is admirably suited to the low Reynolds number mixing process. This work derives a model to predict the power consumption of the HRA. The model has been developed with the aid of experimental data and tested extensively using literature data. For a wide range of mixer geometries and sizes, it predicts power consumption with an average deviation of 13%.The concept of relative efficiency of mixers is also described as an aid to comparing different HRA mixer geometries. Finally, the problem of scale-up of different HRA configurations is discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690250317
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  • 3
    Electronic Resource
    Electronic Resource
    Correlation between steady-state cell concentration and cell death of hybridoma cultures in chemostat (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 18-26 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; cell death ; chemostat ; autoinhibitor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the present study, the steady-state cell density (X) of chemostat cultures of murine hybridoma was varied by the concentration of glucose and glutamine in culture medium and the dissolved oxygen partial pressure. Except at low glutamine and low oxygen levels, the specific death rate (kd) of the cultures was found to decrease with increasing dilution rate (D). However, the plot of kd vs. X/D yielded linear relation, which suggests that cell death was due to a non-growth-linked inhibitory product of the cells. The kd value measured at low glutamine and low oxygen levels remained practically unchanged over a wide range of D between 0.020 and 0.029 h-1. The kd for low oxygen cultures was always lower than the values obtained in low glucose and low glutamine cultures. A low-molecular-weight component of possibly less than 3000 MW was detected to be cell-death-inducing in the supernatant of exponentially growing cultures. It was neither lactate nor ammonium. The autoinhibitor was not cell-line specific. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450104
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  • 4
    Electronic Resource
    Electronic Resource
    Substantial overproduction of antibodies by applying osmotic pressure and sodium butyrate (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 601-610 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; antibody productivity ; osmolarity ; butyrate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Much of the current cell technology has enabled increased antibody production levels due to judicious nutrient feeding to raise cell densities and design better bioreactors. This study demonstrates that hybridomas can be hyperstimulated to produce higher immunoglobulin (lg) levels by suppressing cell growth and increasing culture longevity through adaptation to higher osmolarity media and addition of sodium butyrate. Prior to adaptation, cells placed in higher osmotic pressures (350 and 400 mOsm) were severely suppressed in growth down to 25% of the control (300 mOsm), although total lg titers achieved were similar to the control, approximately 140 mg/L. After a week of adaptation to 350 and 400 mOsm media, cell growth was not as dramatically suppressed, but considerably higher lg levels were attained at these elevated osmolarities. The highest yield of 265 mg/L was obtained at 350 mOsm compared to 140 mg/L at 300 mOsm, while maximum viable cell numbers dropped from 35 × 105 cells/mL to 31 × 105 cells/mL and culture longevity was extended by 20 h more than the control. Sodium butyrate, known to enhance protein production in other cell types, was then supplemented at a range of concentrations between 0.01 and 0.4 mM to the 350 mOsm culture to further enhance the lg levels. Butyrate at a concentration of 0.1 mM, in combination with osmotic pressure at 350 mOsm, further elevated the lg levels to 350 mg/L. Concomitantly, maximum viable cell numbers were reduced to 22 × 105 cells/mL, but culture longevity was extended by 40 h in the 0.1 mM butyrate supplemented culture compared to the control condition. Specific antibody productivity, qMab, continued to stay high during the stationary phase and was further elevated during the decline phase: thus, overall lg levels can be increased by 2.3 times by combining osmotic pressure and butyrate treatment. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420508
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  • 5
    Electronic Resource
    Electronic Resource
    Comparative studies of Escherichia coli strains using different glucose uptake systems: Metabolism and energetics (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 583-590 
    Details
    ISSN: 0006-3592
    Keywords: 31P NMR ; PTS mutant ; Escherichia coli ; metabolism ; energetics ; glucose uptake system ; galactose symport system ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modifying substrate uptake systems is a potentially powerful tool in metabolic engineering. This research investigates energetic and metabolic changes brought about by the genetic modification of the glucose uptake and phosphorylation system of Escherichia coli. The engineered strain PPA316, which lacks the E. coli phosphotransferase system (PTS) and uses instead the galactose-proton symport system for glucose uptake, exhibited significantly altered metabolic patterns relative to the parent strain PPA305 which retains PTS activity. Replacement of a PTS uptake system by the galactose-proton symport system is expected to lower the carbon flux to pyruvate in both aerobic and anaerobic cultivations. The extra energy cost in substrate uptake for the non-PTS strain PPA 316 had a greater effect on anaerobic specific growth rate, which was reduced by a factor of five relative to PPA 305, while PPA 316 reached a specific growth rate of 60% of that of the PTS strain under aerobic conditions. The maximal cell densities obtained with PPA 316 were approximately 8% higher than those of the PTS strain under aerobic conditions and 14% lower under anaerobic conditions. In vivo NMR results showed that the non-PTS strain possesses a dramatically different intracellular environment, as evidenced by lower levels of total sugar phosphate, NAD(H), nucleoside triphosphates and phosphoenolpyruvate, and higher levels of nucleoside diphosphates. The sugar phosphate compositions, as measured by extract NMR, were considerably different between these two strains. Data suggest that limitations in the rates of steps catalyzed by glucokinase, glyceraldehyde-3-phosphate dehydrogenase, phosphofructokinase, and pyruvate kinase may be responsible for the low overall rate of glucose metabolism in PPA316. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 583-590, 1997.
    Additional Material: 7 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Genetically structured mathematical modeling of trp attenuator mechanism (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 502-509 
    Details
    ISSN: 0006-3592
    Keywords: genetically structured mathematical model ; trp operon ; cloned gene expression control ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A genetically structured mathematical model of the trp attenuator in Escherichia coli based on known coupling mechanisms of the transcription of the trp leader region and translation of the trp leader peptide region is proposed. The model simulates, both qualitatively and quantitatively, the effects of tryptophan on the repression of cloned gene products. It shows that repression by attenuation mechanism alone operates over a narrow trp concentration range of 1 to 5 μM compared with 1 to 100 μM for trp repressor mechanism. This implies that attenuation by transcription termination is not relaxed until tryptophan starvation is severe. Simulation results show that the attenuator starts to derepress when the repressor is about 40% repressed, and becomes significantly derepressed only when the repressor repression decreased to about 20%. Unlike the case of repressor-operator interaction, the operating range of tryptophan concentration in the attenuator mechanism is not sensitive to plasmid copy number. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 502-509, 1998.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    A Simple genetically structured model of trp repressor-operator interactions (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 707-714 
    Details
    ISSN: 0006-3592
    Keywords: genetically structured mathematical model ; trp operon ; cloned gene expression control ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A genetically structured mathematical model of the trp operon based on known molecular interactions of aporepressor, corepressor, and inducer is proposed. The model simulates, both qualitatively and quantitatively, the influence of these regulatory species on the extent of repression and expression of cloned gene products. It shows that at low aporepressor concentration, full repression is not possible even with high tryptophan levels, resulting in leaky expression. Calculations based on the model enabled predictions of optimum levels of aporepressor and tryptophan for effective repression and, concurrently, the β-indoleacrylic acid concentrations required for induction for both low and high plasmid copy number clones. Using the model we attempted to provide explanations for seemingly anomalous and sometimes contradictory observations by researchers when working with the trp promoter. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410705
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  • 8
    Electronic Resource
    Electronic Resource
    Vinculin localization and actin stress fibers differ in thyroid cells organized as monolayers or follicles (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 32 (1995), S. 318-331 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeleton ; cyclic AMP ; vinculin ; E-cadherin ; ZO-1 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In epithelial cells interactions between the actin cytoskeleton and cell-cell junctions regulate paracellular permeability and partcipate in morphogenesis. We have studied the relationship between supracellular morphology and actin-junction interactions using primary cultures of porcine thyroid cells grown either as three-dimensional follicles or as open monolayers. Regardless of morphology, thyroid cells assembled occluding and adhesive junctions containing ZO-1 and E-cadherin, respectively, and showed F-actin staining in apical microvilli and a perijunctional ring. In monolayers, actin stress fibers were also observed in the apical and basal poles of cells, where they terminated in the vinculin-rich zonula adherens and in cell-substrate focal adhesions, respectively. Surprisingly, we were unable to detect vinculin localization in follicular cells, which also did not form stress fibers. Immunoblotting confirmed significantly greater vinculin in triton-insoluble fractions from monolayer cells compared with follicular cells. Incubation of monolayers with 8 chloro(phenylthio)-cyclic AMP decreased the level of immunodetectable vinculin in the zonula adherens, indicating that junctional incorporation of vinculin was regulated by cyclic AMP. In monolayer cultures, cytochalasin D (1 μM) caused actin filaments to aggregate associated with retraction of cells from one another and the disruption of cell junctions. Despite morphologically similar perturbations of actin organization in follicular cultures treated with cytochalasin D, junctional staining of ZO-1 and E-cadherin was preserved and cells remained adherent to one another. We conclude that in cultured thyroid cells structural and functional associations between actin filaments and cellular junctions differ depending upon the supracellular morphology in which cells are grown. One important underlying mechanism appears to be regulation of vinculin incorporation into adhesive junctions by cyclic AMP. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970320408
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  • 9
    Electronic Resource
    Electronic Resource
    [(TptBu, Me)CrR]: A New Class of Mononuclear, Coordinatively Unsaturated Chromium(II) Alkyls with cis-Divacant Octahedral Structure (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1668-1674 
    Details
    ISSN: 0947-6539
    Keywords: alkenes ; chromium ; cis-divacant octahedral geometry ; polymerizations ; tris(pyrazolyl)borate complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of CrCl2 with TptBu, MeK yielded [TptBu, MeCr(3-tBu, 5-MepzH)Cl] (1) and [TptBu, MeCrCl] (2), while the same reaction in the presence of pyridine gave 1 and [TptBu, MeCr(py)Cl] (3). Alkylation of 3 with Grignard reagents produced the chromium(II) alkyls [TptBu, MeCrR] (4, R = Et; 5, R = Ph; 6, R = CH2SiMe3), which reversibly added to pyridine to form the five-coordinate adducts [TptBu, MeCr(py)R] (7, R = Et; 8, R = Ph; 9, R = CH2SiMe3). 1, 2, 4, and 5 were structurally characterized by X-ray diffraction. The four-coordinate molecules 2, 4, and 5 adopt a highly unusual cis-divacant octahedral coordination geometry, while 1 is the first five-coordinate TptBu, Me-complex of a first-row transition metal. Despite their coordinative unsaturation, chromium alkyls 4-6 do not polymerize ethylene, or even react with it. This observation is inconsistent with the catalytic activity commonly ascribed to divalent chromium in heterogeneous polymerization catalysts. Attempts to oxidize 4-6 (e.g., with [Cp2Fe]BPh4) to cationic chromium(II) alkyls failed, yielding [TptBu, MeCr(thf)][BPh4] (10) instead.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031016
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  • 10
    Electronic Resource
    Electronic Resource
    An investigation of pressure transients in pipelines with two-phase bubbly flow (1989)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1207-1219 
    Details
    ISSN: 0271-2091
    Keywords: Centre implicit method ; Pressure transients ; Two-phase pipe flow ; Bubbly pipe flow ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper presents a two-dimensional model for the analysis of the pressure transient of a two-phase homogeneous bubbly mixture flowing in a pipeline and the numerical integration using the centre implicit method (CIM). Experiments were conducted to confirm the proposed sonic speed equation of an air-water mixture for an air concentration of less than 1%. The 2D CIM model is compared with the method of characteristics (MoC) for a two-phase bubbly flow in a pipeline. The comparisons show that the proposed 2D CIM model generally gives good agreement with the method of characteristics.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650091004
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