Kinetic parameters effective

The traditional way to calculate the physical characteristics of a fast reactor is to carry out the following steps (1) preparation of the effective cross sections for regions of the reactor (2) a three-dimensional calculation to obtain k-eff, and real and adjoint fluxes (3) edit the results of the previous steps to estimate the power and reaction rate distributions, neutron kinetics parameters, control rod effectiveness, etc., and (4) a bumup analysis, calculating the variation of the isotopic composition with time, and then recalculating the results obtained in the previous steps for particular bumup states. This scheme has been implemented, for example, in the TRIGEX code [4.49]. This code calculates k-eff, few group real and adjoint fluxes, power spatial distribution, dose factor and reaction rates distributions, breeding parameters, bumup effects, and kinetics parameters (effective delayed neutron Auction, etc.). 

Therefore, when equilibrium cannot be plausibly assumed, apparent kinetic parameters (effective rate constants) must be used to express the reaction rate. The parameters that describe the electrochemical reaction rate include the above-mentioned exchange current density, the transfer coefficient, the activation enthalpy, and the pre-exponential factor as well as the reaction order of the species involved. These parameters are not necessarily related to a single rate-determining step, as is often assumed in electrochemical theory. By investigating i-ri curves as functions of electrode potential, temperature, and concentration of the reacting species, insight may be gained into the reaction mechanism and microscopic transport processes (such as surface diffusion) that... 

Eig. 3. The effect on kinetic parameters of adding a competitive inhibitor. Reaction velocity as a function of [3] is shown. (—x —) Uninhibited reaction (---) inhibited reaction. As indicated on the figure, the parameter is increased by adding the competitive inhibitor both curves eventually reach the... 

Compared with the bonding groups (mol%) to aromatic ring of PS, the degree of acylation was observed when MA was used. These results was obtained by determination of kinetic parameters of PS with MA and AA under the same reaction conditions. As shown in Table 5, if the initial rate (Wo) and rate constant (K) of the acylation reaction between MA and AA are compared, the MA is almost 10-14 times higher than AA in the presence of BF3-OEt2 catalyst. This fact is due to the stretching structure of MA and the effect of the catalyst. 

In actual experiments we do not usually observe directly the desorbed amount, but rather the derived read-out quantities, as is the time dependence of the pressure in most cases. In a closed system, this pressure is obviously a monotonously increasing function of time. In a flow or pumped system, the pressure-time dependence can exert a maximum, which is a function of the maximum desorption rate, but need not necessarily occur at the same time due to the effect of the pumping speed S. If there are particles on the surface which require different activation energies Ed for their desorption, several maxima (peaks) appear on the time curve of the recorded quantity reflecting the desorption process (total or partial pressure, weight loss). Thereby, the so-called desorption spectrum arises. It is naturally advantageous to evaluate the required kinetic parameters of the desorption processes from the primarily registered read-out curves, particularly from their maxima which are the best defined points. 

ESI mass spectrometry ive mass spectrometry ESR spectroscopy set EPR spectroscopy ethyl acetate, chain transfer to 295 ethyl acrylate (EA) polymerizalion, transfer constants, to macromonomers 307 ethyl methacrylate (EMA) polymerization combination v.v disproportionation 255, 262 kinetic parameters 219 tacticity, solvent effects 428 thermodynamics 215 ethyl radicals... 

In a few studies, solvent viscosity was varied as a result of change in temperature [109, 165]. In transient flow, the direct effect of temperature on the scission rate was shown to be minimal (Sect. 5.7). Even so, it is desirable to look for a system where the solvent viscosity can be studied independently of the other kinetics parameters [166], Ideally, the solvents used should satisfy the following criteria ... 

References to the profitable exploitation of microscopic techniques in kinetic studies can be found in the work of Thomas and co-workers [91, 206—210], Herley et al. [211] and of Flanagan and his collaborators [212,213]. The rates of advance of reaction interfaces have been measured from direct observations on single crystals and the kinetic parameters so obtained are compared with results for mass loss determinations. The effects of the introduction of crystal imperfections and the role of such species in mechanisms of reaction are also considered. 

Otherwise, the effect of electrode potential and kinetic parameters as contained in the relevant expression for the PMC signal (21), which controls the lifetime of PMC transients (40), may lead to an erroneous interpretation of kinetic mechanisms. The fact that lifetime measurements of PMC transients largely match the pattern of PMC-potential curves, showing peaks in accumulation and depletion of the semiconductor electrode and a minimum at the flatband potential [Figs. 13, 16-18, 34, and 36(b)], demonstrates that kinetic constants are accessible via PMC transient measurements, as indicated by the simplified relation (40) derived for the depletion layer of an n-type electrode. 

It is important to note that and C2 are quantitative descriptors of the gel effect which depend only on the monomer, temperature and reaction medium. The full description of given by equation (11), requires g and g2 which are functions of the rate of initiation and extent of conversion. The kinetic parameters used in these calculations and their sources are given in Table 1. All data are in units of litres, moles and second. Figure 5 shows the temperature dependencies of and C2 and Table 2 lists these and other parameters determined by fitting the model to the data in Figures 1-4. 

Of course the observation of olefin-Br2 CTCs in solutions of olefins and Bt2 does not necessarily mean that these are essential intermediates in olefin bromination. However the above thermodynamic and kinetic parameters allowed us to answer the question of the mechanistic role played by the CTCs. In fact, if they were unreactive species whose only effect is to reduce the concentration of the actual reactants, Scheme 2 would be valid. The observed k3 would be given by... 

In the KjE plot, effects of structure on activity that are obscure in the equilibrium data become evident when the is resolved into kinetic parameters. Neosaxitoxin (7) differs from saxitoxin (1) by the presence of a hydroxyl group at... 

A single-event microkinetic description of complex feedstock conversion allows a fundamental understanding of the occurring phenomena. The limited munber of reaction families results in a tractable number of feedstock independent kinetic parameters. The catalyst dependence of these parameters can be filtered out from these parameters using catalyst descriptors such as the total number of acid sites and the alkene standard protonation enthalpy or by accounting for the shape-selective effects. Relumped single-event microkinetics account for the full reaction network on molecular level and allow to adequately describe typical industrial hydrocracking data. 

Such behavior is known as the compensation effecf . The important point is that if we ignore the additional term in Eq. (18), we essentially force the kinetic parameters to satisfy Eq. (19) resulting in a correlation between the prefactor and the desorption energy according to the compensation effect ... 

Habib and Hunt have continued the study of this reaction, obtaining further data with special reference to the effects of ionic strength, sulphate and hydrogen-ion concentrations. From data obtained on the dependence of the rate on the [H ] at various temperatures, values of the kinetic parameters differing slightly from those above have been obtained. Values of AFff and and AS and AS2 (at n = 1.0 M) obtained were 11.8, 5.3 kcal.mole and —17 and —31 cal.deg mole respectively. The value of 2 was estimated as 6.7 x 10 1. mole sec at 18 °C, n — 1.0 Af. 

The kinetic parameters are E = 6.3 kcal.mole" and AS = —38.4 eu, and at 25 °C the reaction exhibits a primary kinetic isotope effect of 6.6. When 0-labelled MnO was employed, no labelled oxygen appeared in the benzophenone. The mechanism involves abstraction of hydrogen, either as a hydride ion or a hydrogen atom, from the anion of the alcohol... 

KINETIC ISOTOPE EFFECTS AND ARRHENIUS PARAMETERS FOR THE OXIDATION OF FLUORAL HYDRATE BY Mn(VH) AND Mn(VI)... 

It is noteworthy that the value of this substrate is smaller by one order compared to non-cyclic compounds. According to the discussions proposed above, this is considered to be due to its conformation already being fixed to the one that fits to the binding site of the enzyme. This estimation was demonstrated to be true by the examination of the effect of temperature on the kinetic parameters. Arrhenius plots of the rate constants of indane dicarboxylic acid and phenyl-malonic acid showed that the activation entropies of these substrates are —27.6 and —38.5 calmol K , respectively. The smaller activation entropy for the cyclic compound demonstrates that the 5yn-periplanar conformation of the substrate resembles the one of the transition state. 

The variations in the kinetic parameters (E, m,n) with chlorine coverage shown in Fig. 5 are entirely consistent with our studies by thermal desorption spectroscopy, which show the effects of chlorine... 

Kinetic parameters for NOx reduction are summarized in Table 1. It is obvious that the addition of Ir to ln/H-ZSM-5 led to the decrease in reaction orders with respect to NO, CH4, and O2 in the NO-CH4-O2 reaction. The decrease in the order for NO can explain that lr/ln/H-ZSM-5 was effective for the reduction of NO at low concentrations. On the contrary, the reaction orders with respect to NO2, CH4, and O2 in the NO2-CH4-O2 reaction were not significantly changed by the addition of Ir. The retarding effect of CH4... 

The kinetic equations describing the joint effects of activation and concentration polarization are very complex and we shall consider only the the case of a simple first-order reaction of the type (6.2) proceeding in the presence in the solntion of an excess of a foreign electrolyte. To simplify the appearance of these equations (which even in this case are very cnmbersome), in this section we use a more compact notation that contains two new kinetic parameters ... 

It is a very important conclusion following from Eq. (13.8) that in the case considered, the rate of the overall reaction is determined wholly by the kinetic parameters of the first step ( i and k i), while the second step influences this rate only through the equilibrium concentration of the intermediate B. We say, therefore, that the first step (with its low value of parameter k.j) is the rate-determining step (RDS) of this reaction. Sometimes the term slow step is used, but this term is not very fortunate, inasmuch as the effective rates, and Uj, of the two steps actually are identical. Analogously, when k k2, we have... 

Wang JX, Markovic NM, Adzic RR. 2004. Kinetic analysis of oxygen reduction on Pt(ll 1) in acid solutions Intrinsic kinetic parameters and anion adsorption effects. J Phys Chem B 108 ... 

---