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  • Chemistry  (19)
  • diffusion cell  (2)
  • Angioplasty  (1)
  • Diffusion-weighted  (1)
  • active enzyme  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Frequency response analysis of a closed diffusion cell with two resonators (1996)
    Springer
    Adsorption 2 (1996), S. 265-277 
    Details
    ISSN: 1572-8757
    Keywords: frequency response ; diffusion cell ; kinetics ; diffusion ; heat effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This paper deals with frequency response (FR) analysis of a closed diffusion cell system with two resonators, that is both the LHS and RHS volumes are modulated. The analysis is made for a homogeneous particle described by a single effective diffusivity as well as a biporous pellet described by macropore and micropore diffusions. It is shown that if the perturbation of the volume of the reservoir #2 is lagged behind that of the reservoir #1 by 3π/2, the pressure response in reservoir #1 is significantly enhanced with larger amplitude as well as phase angle. When the perturbations of the two reservoirs are out of phase, the heat effect is reduced and can become insignificant when the two perturbations are completely out of phase (ψ = π). Under such a condition, the pressure difference between the two reservoirs could be doubled. In the case of biporous pellets, it is shown that the FR behaviours obtained for micropore diffusion control and macropore diffusion control are well distinguished. In the former case, the FR system reduces to a traditional batch adsorber one while in the latter case, the FR behaviour is the same as for a two resonator system with homogeneous particles. This difference can be used for the discrimination of micropore and macropore diffusion processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879541
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Diffusion-weighted MRI for monitoring neurovascular interventions (2000)
    Springer
    Neuroradiology 42 (2000), S. 134-138 
    Details
    ISSN: 1432-1920
    Keywords: Key words Magnetic resonance imaging ; Diffusion-weighted ; Carotid artery ; Stents ; Carotid stenosis ; Angioplasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Carotid stenting is increasingly considered as treatment for carotid artery disease. A reliable noninvasive method is desirable for assessing the safety of the procedure. Diffusion-weighted MRI (DWI) is sensitive to early brain ischaemia which becoming widely available and might therefore serve this purpose. We prospectively studied 19 patients referred for investigation of carotid artery disease by echo-planar whole-brain DWI before and within 24 h of stenting. The images obtained at a high b value were examined by two independent blinded reviewers for new high-signal areas consistent with ischaemia. We found that 15 patients had no new changes after stenting. One patient showed enlargement of a posterior watershed lesion after the procedure, which correlated with an increase in neurological deficit. Three other patients had presumed small embolic infarcts on DWI; two were asymptomatic and one had weakness at the hand that corresponded to an embolic infarct with a lesion on DWI in the hand notch. There were no false- positive or -negative results on DWI, when compared to clinical findings. DWI is thus a new method that can demonstrate neurologically silent or asymptomatic infants. It can be used to help to assess the safety and efficacy of neurovascular intervention.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050032
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  • 3
    Electronic Resource
    Electronic Resource
    Enzyme immobilization in porous solid supports - penetration of immobilized enzyme (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 1032-1037 
    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 process of enzyme immobilization under the diffusion-controlled regime (i.e., fast attachment of enzyme compared to its diffusion) is modeled and theoretically solved in this article. Simple and compact solutions for the penetration depth of immobilized enzyme and the bulk enzyme concentration versus time are presented. Furthermore, the conditions for the validity of our solutions are also given in this article so that researchers can discover when the theoretical solutions can be applied to their systems.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260260904
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  • 4
    Electronic Resource
    Electronic Resource
    Fundamental studies of glucose oxidase immobilization on controlled pore glass (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 842-851 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Immobilization experiments have been performed with glucose oxidase as enzyme and controlled-pore glass of different pore sizes as support for chemical coupling. The experimental results have been analyzed for comparison with the theoretical model predictions. Analysis of the initial stage of the process gives the fundamental characteristic of the immobilization reaction. These investigations allow us to study the influence of the degree of diffusional restriction on the evolution of the immobilization process and spatial distribution of immobilized enzyme. Nonuniformly distributed concentrations have been achieved within the porous matrix, and suggestions have been made in designing such profiles by choosing appropriate experimental parameters.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260270614
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  • 5
    Electronic Resource
    Electronic Resource
    Modeling of enzyme immobilization in porous membranes (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 1126-1135 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article deals with the mathematical modeling of the process of enzyme immobilization in porous membranes. During the initial period, an analytical solution is available to extract the rate constant for immobilization. Beyond this period, the model equations are solved numerically to yield the transient response of the enzyme concentration in the immobilizing solution and also the evolution of the enzyme loading profile inside the membrane. It is found that the immobilization practically ceases even through the attachment sites are still available within the membrane.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260270807
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  • 6
    Electronic Resource
    Electronic Resource
    A novel method of determination of the internal enzyme distribution within porous solid supports and the deactivation rate constant (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 28 (1986), S. 486-493 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article presents a method for determining the rate constant for deactivation and the internal distribution of immobilized enzyme. This method makes use of the parallel deactivation process in a diffusion-controlled regime, in which the internal activity profile behaves like a penetration front. This front basically traces through the initial active enzymatic profile, and one can determine the internal profile and the rate constant for deactivation from the experimentally observable bulk concentration versus time. This method is applied to the experimental data of the system of hydrogen-peroxide-immobilized catalase on controlled pore glass and Si-Al particles.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260280404
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of total and active immobilized enzyme distribution in porous solid supports (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 679-687 
    Details
    ISSN: 0006-3592
    Keywords: immobilized enzyme distribution ; diffusion cell ; active-site titration ; controlled-pore glass ; cell profile ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The total and active immobilized enzyme (IME) distributions in porous supports are studied both theoretically and experimentally. In order to determine experimentally the enzyme distribution profiles within a single particle, we construct a diffusion cell containing controlled-pore glass particles such that the cell would mimic a large pellet support. Our purpose is to study the interplay between the diffusion process within the interparticle void space and immobilization process in the controlled-pore glass particles onto the evolution of the (total and active) enzyme distributions. A mathematical model is developed to describe the interaction of various processes within the diffusion cell. The immobilized enzymes are determined for a system of trypsin and controlled-pore glass particles. The total amount of enzymes are determined by the amino acid analysis, and the active fraction is obtained by an active-site titration. The experimentally measured total IME profiles compare very well with that predicted by the model. The determined active enzyme profile is found to be nonuniform one, and it represents about 40% of the total enzyme immobilized in the support particles.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390613
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  • 8
    Electronic Resource
    Electronic Resource
    Revisiting approximate solutions for batch adsorbers: Explicit half time (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 426-429 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410223
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  • 9
    Electronic Resource
    Electronic Resource
    General theory of determining intraparticle active immobilized enzyme distribution and rate parameters (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 963-975 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general theory is presented in this article for determining the intrinsic rate constants for the main reaction and deactivation reaction, the effective diffusivity of the substrate, and the active enzyme distribution within porous solid supports from deactivation study of a continuous stirred-basket reactor (CSBR). For the parallel deactivation five reaction kinetics are considered: (a) Michaelis-Menten, (b) substrate inhibition, (c) product inhibition (competitive), (d) product inhibition (anticompetitive), and (e) zero-order kinetics. The experimental results of the system of hydrogen-peroxide-immobilized catalase on controlled-pore glass particles are analyzed to demonstrate the application of the theory developed for parallel deactivation of active immobilized enzyme (IME). For series deactivation only first-order kinetics is treated, and a numerical procedure is proposed to deter mine the rate parameters and the internal active enzyme distribution. The experimental data of the system of glucose-immobilized glucose oxidase on silica-alumina and controlled-pore glass particles are used to verify the theory.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330805
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of km and De from a one-shot experiment of enzyme immobilization (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 883-886 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260270619
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