scholarly journals Use of flux ratio measurements for the determination of the order of addition of substrates and products in enzyme reactions

1978 ◽  
Vol 169 (1) ◽  
pp. 29-37 ◽  
Author(s):  
H G Britton ◽  
L G Dann
Keyword(s):  
Steady State ◽  
Flux Ratio ◽  
Reaction Rates ◽  
Relative Significance ◽  
Relative Contribution ◽  
Steady State Method ◽  
Equilibrium Reaction ◽  
Inhibition Data ◽  
Relationship Of

1. Methods of determining the order of addition of substrates and dissociation of products by using flux ratios are investigated. Where an enzyme obeys hyperbolic steady-state velocity kinetics it is concluded that it may be particularly useful to compare the measured flux ratios with those calculated from the steady-state velocity parameters. 2. An expression is derived relating the relative contribution of the two pathways in a branched pathway to the flux ratios. 3. The relationship of equilibrium-reaction-rate measurements [Boyer & Silverstein (1963) Acta Chem. Scand. 17, Suppl. 1, S195] to the flux ratios is considered. Equilibrium-reaction rates are shown to be affected both by the addition of substrates and dissociation of products. Methods of analysing the data to distinguish between these events are discussed. 4. Methods of measurement of flux ratios are described, and it is concluded that the non-equilibrium steady-state method is preferable to measurements at chemical equilibrium. 5. The relative significance of flux ratio measurements and steady-state velocity inhibition data is discussed. It is concluded that flux ratios, when taken in conjunction with the inhibition data, provide the least ambiguous information about mechanism.

scholarly journals Determination of Permeability and Inertial Coefficients of Sintered Metal Porous Media Using an Isothermal Chamber

2018 ◽  
Vol 8 (9) ◽  
pp. 1670 ◽  
Author(s):  
Wei Zhong ◽  
Xiang Ji ◽  
Chong Li ◽  
Jiwen Fang ◽  
Fanghua Liu
Keyword(s):  
Porous Media ◽  
Steady State ◽  
Flow Rate ◽  
Pressure Difference ◽  
Testing Time ◽  
Sintered Metal ◽  
Steady State Method ◽  
Volume Limit ◽  
Inertial Coefficient

Sintered metal porous media are widely used in a broad range of industrial equipment. Generally, the flow properties in porous media are represented by an incompressible Darcy‒Forchheimer regime. This study uses a modified Forchheimer equation to represent the flow rate characteristics, which are then experimentally and theoretically investigated using a few samples of sintered metal porous media. The traditional steady-state method has a long testing time and considerable air consumption. With this in mind, a discharge method based on an isothermal chamber filled with copper wires is proposed to simultaneously determine the permeability and inertial coefficient. The flow rate discharged from the isothermal chamber is calculated by differentiating the measured pressure, and a paired dataset of pressure difference and flow rate is available. The theoretical representations of pressure difference versus flow rate show good agreement with the steady-state results. Finally, the volume limit of the isothermal chamber is addressed to ensure sufficient accuracy.

Determination of electrochemical heterogeneous electron-transfer reaction rates from steady-state measurements at ultramicroelectrodes

1986 ◽  
Vol 58 (14) ◽  
pp. 2961-2964 ◽  
Author(s):  
Andrea. Russell ◽  
Kari. Repka ◽  
Timothy. Dibble ◽  
Jamal. Ghoroghchian ◽  
Jerry J. Smith ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Steady State ◽  
Transfer Reaction ◽  
Reaction Rates ◽  
Electron Transfer Reaction ◽  
Heterogeneous Electron Transfer

Centrifugal Compressors During Fast Transients

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Matthew Blieske ◽  
Rainer Kurz ◽  
Augusto Garcia-Hernandez ◽  
Klaus Brun
Keyword(s):  
Steady State ◽  
Flow Speed ◽  
Operating Conditions ◽  
Nonstationary Heat Transfer ◽  
Fast Transients ◽  
Rapid Transients ◽  
Relationship Of ◽  
The Impact ◽  
Flow Head

Transient studies for compressor systems allow the prediction of the compressor system behavior during fast transients such as they occur during emergency shutdowns. For the system simulations, the compressor behavior is assumed to be quasi-steady-state. This means in particular that the steady-state compressor flow-head-efficiency-speed map remains valid. During well instrumented emergency shutdown tests conducted on a centrifugal compressor system under realistic operating conditions, data showing the head-flow-speed relationship of the rapidly decelerating compressor were taken. These data are compared with steady-state head-flow relationships taken at a number of speeds. This allows the determination of the relative deviation between the transient and steady-state head-flow-relationships and thus answers the question of the validity of steady-state assumptions during rapid transients. The impact of the fast transients on efficiency and consumed power, which can be derived from the speed decay of the system, as well as the impact of nonstationary heat transfer are also evaluated and reported.

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