Predictive membrane transport model for nanofiltration processes in water treatment

AIChE Journal ◽  
2001 ◽  
Vol 47 (6) ◽  
pp. 1346-1362 ◽  
Author(s):  
Shih-Chieh Tu ◽  
Varadarajan Ravindran ◽  
Walter Den ◽  
Massoud Pirbazari
Keyword(s):  
Water Treatment ◽  
Membrane Transport ◽  
Transport Model

scholarly journals Use of experimental isotope-exchange fluxes in reversible enzyme and membrane transport models, assessed by simultaneous computer simulation of unidirectional and net chemical rates

1992 ◽  
Vol 286 (1) ◽  
pp. 295-303 ◽  
Author(s):  
I W Plesner
Keyword(s):  
Steady State ◽  
Exchange Rates ◽  
Membrane Transport ◽  
Isotope Exchange ◽  
Transport Model ◽  
Total Concentration ◽  
Rate Equations ◽  
Tracer Transport ◽  
Transport Models ◽  
Experimental Conditions

Steady-state rate equations for unidirectional (isotope-exchange) rates can become so complex, even for rather simple (reversible) enzyme or membrane transport models, that they are useless for detailed data analysis. In this paper a procedure is described for simultaneous simulation of net (chemical) and isotope-exchange rates. The method employs an expanded version of the basic model to monitor explicitly the fate of the label in an experiment. The procedure is quite general, and can be used for steady-state as well as transient kinetic situations, or it can be used in conjunction with existing interactive computer programs for steady-state model analysis. Three numerical examples are presented. First, it is shown, using the conventional (Post-Albers) model for Na+/K(+)-ATPase, that the change in concentration of a labelled intermediate after a change in experimental conditions does not in general reflect the change in the total concentration of that intermediate, and thus labelled intermediate concentrations may be misleading. Second, using a standard co-transport model and a prototype active-transport model (equivalent to a ligand-ATPase), it is shown that the ratio of tracer transport fluxes at steady state yields transport stoichiometries which depend on the experimental conditions, are different from the net apparent stoichiometries, and whose changes with conditions are also different from that of the net stoichiometries. It follows that conclusions drawn on the basis of experimentally determined tracer fluxes should be viewed with some caution. Specifically, a measured influx stoichiometry ligand/ATP (in the ATPase case) of higher than 1:1 does not necessarily imply the existence of more than one site for either ligand on the enzyme.

A novel membrane transport model for polymer electrolyte fuel cell simulations

2014 ◽  
Vol 39 (13) ◽  
pp. 7077-7088 ◽  
Author(s):  
L. Karpenko-Jereb ◽  
P. Innerwinkler ◽  
A.-M. Kelterer ◽  
C. Sternig ◽  
C. Fink ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Membrane Transport ◽  
Polymer Electrolyte ◽  
Transport Model ◽  
Polymer Electrolyte Fuel Cell

scholarly journals Oscillations in plant membrane transport: model predictions, experimental validation, and physiological implications

2005 ◽  
Vol 57 (1) ◽  
pp. 171-184 ◽  
Author(s):  
Sergey Shabala ◽  
Lana Shabala ◽  
Dietrich Gradmann ◽  
Zhonghua Chen ◽  
Ian Newman ◽  
...  
Keyword(s):  
Membrane Transport ◽  
Experimental Validation ◽  
Transport Model ◽  
Model Predictions

scholarly journals Contrasting trends in element incorporation in hyaline and miliolid foraminifera

2016 ◽  
Author(s):  
Inge van Dijk ◽  
Lennart de Nooijer ◽  
Gert-Jan Reichart
Keyword(s):  
Trace Elements ◽  
Calcium Channels ◽  
Membrane Transport ◽  
Transport Model ◽  
Free Ions ◽  
Element Partitioning ◽  
The Impact ◽  
Carbonate Complexes ◽  
Similar Element

Abstract. We analyzed trends in element incorporation between hyaline (perforate) and miliolid (imperforate) foraminifera in order to investigate processes involved in calcification affecting element incorporation into foraminiferal carbonate. For both groups, we observed similar trends in element incorporation with pCO2, suggesting there some mechanisms to transports ions to the site of calcification are similar for both calcification pathways, although the impact might be different across species. A previously published trans-membrane transport model assumes foraminifera utilize Ca2+ channels to transport calcium to the site of calcification. These channels are somewhat a-specific, leading to (accidental) transport of other free ions. By modelling the activity of free ions as a function of pCO2, we observed that speciation of some elements (like Zn and Ba) are heavily influenced by the formation of carbonate complexes. This leads to an increase in availability of free Zn and Ba with increasing pCO2, which leads to more transport to the site of calcification and subsequently incorporation in the foraminiferal shell. We further observed that incorporation of the trace elements studied here is positively correlated between the hyaline test building species. This could be due to dissimilar activity and/or selectivity of calcium channels between species, perhaps due to differences in size. For miliolid calcification, part of the calcium is obtained not only through channels but by also included seawater vesicles, which leads to similar element to calcium ratios between species and element partitioning which is more in line with inorganic carbonates.

scholarly journals Development of the Membrane Transport Model for PEMFC Simulations

2012 ◽  
Vol 44 ◽  
pp. 388-390 ◽  
Author(s):  
L.V. Karpenko-Jereb ◽  
P. Innerwinkler ◽  
A.-M. Kelterer ◽  
C. Fink ◽  
P. Prenninger ◽  
...  
Keyword(s):  
Membrane Transport ◽  
Transport Model

Determination of Multiple Steady States in an Active Membrane Transport Model

1999 ◽  
Vol 54 (3-4) ◽  
pp. 245-250 ◽  
Author(s):  
Hsing-Ya Li
Keyword(s):  
Membrane Transport ◽  
Transport Model ◽  
Steady States ◽  
Metabolic Energy ◽  
Multiple Steady States ◽  
Necessary And Sufficient Condition ◽  
Active Membrane ◽  
Positive Steady States ◽  
Necessary And Sufficient

A necessary and sufficient condition is applied to determine the possibility of multiple positive steady states in a complex, active membrane transport model with a cycle, which is performed by pump pro-teins coupled to a source of metabolic energy. A set of rate constants and two corresponding steady states are computed. Hysteresis phenomena are observed. A signature of multiplicity is derived, which can be applied in mechanism identifications if steady-state concentrations for some species are measured. The bifurcation of multiple steady states is also displayed.

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