Under specific reaction types concentration

Kinetic approaches represent realistic and comprehensive description of the mechanism of network formation. Under this approach, reaction rates are proportional to the concentration of unreacted functional groups involved in a specific reaction times an associated proportionality constant (the kinetic rate constant). This method can be applied to the examination of different reactor types. It is based on population balances derived from a reaction scheme. An infinite set of mass balance equations will result, one for each polymer chain length present in the reaction system. This leads to ordinary differential or algebraic equations, depending on the reactor type under consideration. This set of equations must be solved to obtain the desired information on polymer distribution, and thus instantaneous and accumulated chain polymer properties can be calculated. In the introductory paragraphs of Section... 

Returning to the general liquid phase catalytic system, assume that you have chosen an appropriate spectroscopy to investigate the system under reaction conditions. The spectroscopy provides spectra, i. e. absorbance A(t), at specific intervals in time. If S denotes the complete set of all species that exist at any time in the physical system, then Sjo s is the subset of all observable species obtained using the in situ spectroscopy. This requires that the pure component spectra aj..as obs are obtainable from the multi-component solution spectra A t) without separation of constituents, and without recourse to spectral libraries or any other type of a priori information. Once reliable spectroscopic information concerning the species present under reaction are available, down to very low concentrations, further issues such as the concentrations of species present, the reactions present, and reaction kinetics can be addressed. In other words, more detailed aspects of mechanistic enquiry can be posed. 

Once a chemical is in systemic circulation, the next concern is how rapidly it is cleared from the body. Under the assumption of steady-state exposure, the clearance rate drives the steady-state concentration in the blood and other tissues, which in turn will help determine what types of specific molecular activity can be expected. Chemicals are processed through the liver, where a variety of biotransformation reactions occur, for instance, making the chemical more water soluble or tagging it for active transport. The chemical can then be actively or passively partitioned for excretion based largely on the physicochemical properties of the parent compound and the resulting metabolites. Whole animal pharmacokinetic studies can be carried out to determine partitioning, metabolic fate, and routes and extent of excretion, but these studies are extremely laborious and expensive, and are often difficult to extrapolate to humans. To complement these studies, and in some cases to replace them, physiologically based pharmacokinetic (PBPK) models can be constructed [32, 33]. These are typically compartment-based models that are parameterized for particular... 

Additional experimental data not presented here are summarized in Refs. [66, 67]. As was pointed out also in Ref. [64], these results highlight the important point that in membrane reactors, besides differences in local concentration profiles, different residence time distributions occur that lead to specific reactor behavior. Others [71] have also suggested that the flexibility of this type of distributor membrane reactors allows a certain target component to be produced efficiently within a complex reaction network. In the present example, there exist certain operating conditions under which the membrane reactor outperforms the conventional reactor in terms of the production of CO or CO2 (if these are considered as target products instead of ethylene). 

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