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  • 1
    Electronic Resource
    Electronic Resource
    Membrane reactor coupled with electrophoresis for enzymatic production of aspartic acid (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 32 (1988), S. 647-654 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aspartic acid production by aspartase reaction on ammonium fumarate was carried out in a membrane reactor coupled with electrophoresis. A pressurized, stirred vessel attached with an ultrafiltration membrane was used as a membrane reactor. An electric field was applied across the membrane to preferentially remove the product aspartate from the reactor into the permeate stream. The charged molecule, aspartate, is much smaller than the molecular-weight cutoff of the membrane (104) so that the ions would move freely through pores of the membrane. The concentration of aspartate in the permeate stream is determined by the electromigration velocity of the ions and the permeation rate of solvent (water) through the membrane. The permeation rate of solvent could be controlled by the applied pressure, and the migration velocity of the ions could be controlled by the electric field strength applied. The equilibrium conversion of ammonium fumarate to the aspartate was 70%. In the presence of electric field, the aspartase activity was not disturbed. Also, it is shown that the aspartate concentration in the permeate stream was 20% higher than that in the reaction solution with the permeate flow rate of 0.7 mL/min. The steady-state conversion was 60%. Instead of aspartate, aspartic acid can be recovered directly from the permeate stream by controlling the circulation of buffer electrolyte in the anode compartment.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260320509
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  • 2
    Electronic Resource
    Electronic Resource
    Urea hydrolysis by immobilized urease in a fixed-bed reactor: Analysis and kinetic parameter estimation (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 951-963 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Urea hydrolysis by urease immobilized onto ion exchange resins in a fixed-bed reactor has been studied. A modified Michaelis-Menten rate expression is used to describe the pH-dependent, substrate- and product-inhibited kinetics. Ionic equilibria of product and buffer species are included to account for pH changes generated by reaction. An isothermal, heterogeneous plug-flow reactor model has been developed. An effectiveness factor is used to describe the reaction-diffusion process within the particle phase. The procedure for covalent immobilization of urease onto macroporous cation exchangers is described. Urea conversion data are used to estimate kinetic parameters by a simplex optimization method. The best-fitted parameters are then used to predict the outlet conversions and pH values for systems with various inlet pH values, inlet urea and ammonia concentrations, buffers, particle sizes, and spacetimes. Very good agreement is obtained between experimental data and model predictions. This immobilized urease system exhibits quite different kinetic behavior from soluble urease because the pH near the enzyme active sites is different from that of the pore fluid. This effect results in a shift of the optimal pH value of the Vmax (pH) curve from 6.6 (soluble urease) to ca. 7.6 in dialysate solution, and ca. pH 8.0 in 20mM phosphate buffer. The reactor model is especially useful for estimating intrinsic kinetic parameters of immobilized enzymes and for designing urea removal columns.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340710
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  • 3
    Electronic Resource
    Electronic Resource
    Theory of adsorbed solutions: Analysis of one-dimensional systems (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2155-2161 
    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: A general formulation for 1-D multicomponent localized adsorption is presented, as well as a new mixing function that varies with only temperature and spreading pressure. An understanding of this mixing function completely determines the solution thermodynamics of the system. A closed-form expression for the adsorbed-phase excess Gibbs energy exhibiting an explicit dependence on the spreading pressure is thus obtained. The empirical expression proposed in the literature for the adsorbed-phase excess Gibbs energy is found to be consistent with the exact solution obtained in one dimension. The new mixing function further suggests the possibility of considering a binary adsorbed solution as the adsorption of a pseudo adsorbate.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420807
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  • 4
    Electronic Resource
    Electronic Resource
    Unsteady-state operation of continuous fermentor for enhancement of cell mass production (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 30 (1987), S. 187-195 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transient behavior of continuous fermentation is studied concentrating on the time scale intrinsic to the system. The time scale is the time required for the fermentorto reach a stable steady state after the disturbance of cell mass is introduced. When the cell concentration is disturbed from the steady-state value, in particular, at the dilution rate near washout, the transient period becomes extended significantly, and the steady state is resumed sluggishly. This sluggish transient behavior could be turned to an advantage for enhancing the cell mass output rate. The proposed transient operation is a continuous fermentation whereby a positive disturbance in the cell mass is introduced, so that the cell concentration is higher than the steady-state value for an extended transient period. It is shown that a significantly higher cell mass production than that from the steady-state continuous fermentation can be achieved. Simple experiments were performed to demonstrate the improvement of cell (Candida utilis) productivity.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260300208
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  • 5
    Electronic Resource
    Electronic Resource
    Predicting fluid-bed reactor efficiency using adsorbing gas tracers (1987)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1727-1734 
    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: Gas tracers have been used frequently to predict conversion in chemical reactors. But in heterogeneous systems such as fluid-bed reactors, tracer residence time data usually overpredict actual contact time and conversion. In this work, the general two-phase countercurrent flow model is extended to include tracer adsorption, which is important in predicting contact time. The tracer used was SF6, whose adsorption on the solids could be varied over a wide range. The apparent reactor efficiency, calculated directly from tracer response, is shown to approach that estimated from the two-phase model when the fluid bed approached homogeneity. This is the case for many large-scale reactors that are operated in the turbulent fluidization regime. The use of horizontal baffles in methanol-to-gasoline cold flow models is shown to improve bed efficiency by staging the bed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690331016
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of mixing on the performance of periodic chemical reactors (1974)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 20 (1974), S. 74-81 
    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 interaction between imperfect mixing and cyclic operation is examined for several continuous polymerizations in stirred-tank reactors. The reactor is represented by a mixed model involving two interconnected ideal stirred vessels. Cyclic fluctuations in the concentration of a chain transfer agent during Ziegler-catalyzed olefin polymerization can yield molecular weight distributions significantly different from those of a conventional steady state reactor. This result is consistent with the available experimental data. It is especially interesting that the cyclic reactor effluent with a modified molecular weight distribution is of approximately time-invariant composition when the period of cycling is on the order of the reactor holding time. Imperfect mixing has a lesser effect on cycled reactors for free-radical and polycondensation polymerization than it has on cycled olefin polymerization reactors.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690200109
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  • 7
    Electronic Resource
    Electronic Resource
    Pneumatic bursting characteristics of plastics films (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 504-512 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The bursting strength and inflated deflection of linear low density polyethylene (LLDPE), oriented polypropylene (OPP), flexible poly(vinyl chloride) (PVC), poly(ethylene terephthalate) (PET), and polyurethane (PUR) films of different thicknesses were investigated with the pneumatic bursting method. The study showed the bursting air pressure is directly proportional to the thickness of LLDPE, OPP, and PET films. The effect of different membrane diameters on the change of the bursting properties in OPP and PUR film was also investigated. The results showed that the bursting properties are inversely proportional to the membrane diameter. Furthermore, biaxial stress-strain exerted on the pole region of the tested films was studied. The results denoted that the relationship between the biaxial and uniaxial tensile stress-strain was considered for two types of film: (1) Film that presented an isotropic tensile behavior showed that the tangential stress-strain is higher than the tensile stress-strain. (2) Film that presented an anisotropic tensile behavior showed that the tangential stress-strain is determined by the weaker tensile stress-strain values between two directions.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760330810
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  • 8
    Electronic Resource
    Electronic Resource
    Chain scission in polystyrene by impact fracture (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 1123-1130 
    Details
    ISSN: 0887-6266
    Keywords: fracture of polystyrene on impact, chain scission in ; polystyrene, chain scission by impact fracture in ; chain scission in impact fracture of polystyrene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The number of chain scissions ns per unit fracture area by impact in high-molecular weight polystyrene is determined to be approximately 3.3 × 1014/cm2 at room temperature. This is almost 20 times larger than would be expected if chain scissions took place only at, or very close to, fracture surfaces. This result was obtained by measuring the molecular weight decrease and the total fracture area of the impact fragments by using size exclusion chromatography and statistical particle size measurements, respectively. The large ns strongly indicates that significant chain breakage occurs during crazing before the propagation of cracks. An average craze thickness before breakdown under impact is estimated from ns to be around 2 μm. In a diluted polymer, ns is found to be significantly lower than the extrapolated value, assuming a linear dilution of entangled chain crossings at the fracture surface. This low chain scission density, however, can be explained by taking into account the reduction of craze breakdown strain in the diluted polymers. Finally, the broken chain ends of polystyrene appear to be stable under ambient conditions. © 1992 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090301007
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  • 9
    Electronic Resource
    Electronic Resource
    On solving nearly incompressible 2D problems using an adaptive refinement procedure (1998)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 14 (1998), S. 409-418 
    Details
    ISSN: 1069-8299
    Keywords: adaptive refinement procedure ; nearly incompressible problems ; error estimation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical study is carried out employing some selected 2D elements and an automatic adaptive refinement procedure for the solution of a problem involving a nearly incompressible material. For a material with Poisson's ratio close to 0·5, it is found that both hybrid elements and high-order Lagrangian triangles can be used to provide a reliable solution. Furthermore, the rate of convergence of the elements is not affected by the high value of Poisson's ratio, and a near-optimal convergence rate is achieved in all the numerical tests run. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    An automatic adaptive refinement finite element procedure for 2D elastostatic analysis (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1967-1989 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An automatic adaptive refinement procedure for finite element analysis is presented. The procedure is applied to two-dimensional elastostatic problems to obtain solutions of prescribed accuracy. Through the combined use of new mesh generator using contour developed by Lo1 and the concept of strain energy concentration, high-quality graded finite element meshes are generated. The whole process is fully automatic and no user intervention is required during the successive cycles of the mesh refinements. The Zienkiewicz and Zhu2 error estimator is found to be effective and has been adopted for the present implementation. In the numerical examples tested, the error estimator gives an accurate error norm estimation and the effectivity index of the estimator converges to a value close to unity.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620351004
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