State-defining experiment

Interrogative kinetics involves two types of experiments that are performed in sequence to reveal complex mechanisms and structure-activity relationships. The first type is a "state-defining" experiment that does not significantly perturb the lanetic state of the catalyst, but provides information that can characterize the state. The second type is a "state-altering" (typical) experiment that perturbs the catalyst and changes its composition or structure in some predetermined fashion. To complete the sequence another state-defining experiment is performed to characterize the new state of the catalyst. 

If the change in catalyst composition is due to adsorbed species, then the change can be estimated from 0. The order of magnitude of shown in Table 1 is sufficiently small that the change in a catalyst after one pulse can be considered negligible. Consequently, a typicd TAP vacuum pulse response experiment (one pulse experiment) can be considered a state-defining experiment. 

Domain of the experimental parameters for multipulse state-defining experiments... 

Table 2 reports the domain of experimental parameters for a multipulse state-defining experiment in a one-zone-reactor , or reactor that is completely packed with a single... 

Assumption of insignificant change of the system characteristics during an experiment involving a small perturbation of the system a state-defining experiment. 

At sufficiently small pulse intensities, a one-pulse TAP experiment can be considered a state-defining experiment, since the number of molecules in a reactant pulse is typically much smaller (10 -10 times smaller) than the number of surface atoms in the catalyst sample being probed [82]. As a result, the reactant pulse does not significantly perturb the catalyst surface. 

S. O. Shekhtman, G. S. Yablonsky, J. T. Cleaves, and R. Fushimi. State defining experiment in chemical kinetics—primary characterization of catalyst activity in a TAP experiment. Chemical Engineering Science, vol. 58, pp. 4843-4859, 2003. 

An important parameter determined in steady-state fluorescence experiments is the fluorescence quantum yield tp, which is defined by eq 1... 

The steady-state flow numerical experiment was primarily designed to evaluate the phasic relative permeability relations. The numerical experiment is devised within the two-phase lattice Boltzmann modeling framework for the reconstructed CL microstructure, generated using the stochastic reconstruction technique described earlier. Briefly, in the steady-state flow experiment two immiscible fluids are allowed to flow simultaneously until equilibrium is attained and the corresponding saturations, fluid flow rates and pressure gradients can be directly measured and correlated using Darcy s law, defined below. 

The thermodynamic functions have been defined in terms of the energy and the entropy. These, in turn, have been defined in terms of differential quantities. The absolute values of these functions for systems in given states are not known.1 However, differences in the values of the thermodynamic functions between two states of a system can be determined. We therefore may choose a certain state of a system as a standard state and consider the differences of the thermodynamic functions between any state of a system and the chosen standard state of the system. The choice of the standard state is arbitrary, and any state, physically realizable or not, may be chosen. The nature of the thermodynamic problem, experience, and convention dictate the choice. For gases the choice of standard state, defined in Chapter 7, is simple because equations of state are available and because, for mixtures, gases are generally miscible with each other. The question is more difficult for liquids and solids because, in addition to the lack of a common equation of state, limited ranges of solubility exist in many systems. The independent variables to which values must be assigned to fix the values of all of the... 

Values of the terms on the RHS of equation (3) are obtained from steady state diffusion experiments and the flow permeability apparatus. The data are summarized in Fig.2, which shows that they are compatible, since they converge to common values for each of the gases at low pressures. The corresponding tortuosity factor of 1.7 is also well defined. Using these data... 

One way to obtain highly resolved, selective, solid state information plus uniquely defined information on the orientation-dependencies of spin interactions is to perform NMR experiments on oriented single crystals. However, for various reasons, such single crystal NMR experiments appear impractical in standard applications to organometallic chemistry. The vast majority of solid state NMR experiments on organometallic compounds are— and probably will be— performed on polycrystalline powder samples. In principle, also for polycrystalline powders, all relevant information on spin interactions is contained in the shape of the powder patterns obtained imder static conditions. The problem then is the extraction of well-defined single parameters from such lineshapes resulting from either a multitude of resonances and/or the simultaneous presence of multiple spin interactions. In practice, it turns out that only very rarely is this possible. 

A unique strength of solid-state NMR is its ability to probe molecular dynamics with site selectivity.9132 In this section, we present some specific examples that illustrate the considerable insight into dynamic processes provided by advanced solid-state NMR experiments applicable to as-synthesized samples, i.e., without the requirement for isotopic labeling. These examples focus on well-defined processes that are fast as compared to the time scale of the H DQ MAS experiment, this being on the order of 10-6 to 10 4 s. In addition, it should be noted that the extraction of dipolar couplings by following the buildup of DQC in a H DQ MAS experiment has been shown to provide insight into the complex dynamic processes in polymer melts,172 block copolymers,173 and elastomers.174... 

This property contributes two important features to the experiment. First, the fluorescence decay time r (in the absence of quencher) is a well-defined quantity, facilitating interpretation of steady state fluorescence experiments. Second, in complex systems, non-exponential decay traces may be observed. These can be interpreted in terms of a non-uniform distribution of quenchers in the system. 

The diffusion flux M, g/cm /s) of the species is defined as the amount of matter passing perpendicularly through the unit area during the unit time. Different solutes have different solubilities and diffusion coefficients, in a LM. tn a steady-state permeation experiment, the flux of a species S through a membrane of thickness h is related to the concentration gradient through Fick s first law ... 

Production history for a foam generated in a displacement of surfactant solution by gas at fixed pressures, and then subjected to a series of stepwise AP increases, is shown in Figure 7. An initial trickle of gas appears some time after the foam front has reached the outlet, and reaches a constant flow rate at a time that coincides with the overall water saturation, 5W, stabilizing at 0.05 as production of liquid phase ceases. The vertical portions of the dotted line occur at the time of each differential pressure increase. In this case, the gas rate stabilizes at five successive gas-blocking states. The sequence of gas-blocking states defines a AP-dependent permeability such as that shown in Figure 8 for three repeat experiments. The rather broad error band is ascribed to the random nature... 

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