Structure-sensitive coefficient

Analysis of experimental kinetic dependences of vibrocompaction of heavily-loaded composites showed that the structure-sensitive coefficient B in Eq. (87) correlates best with the free volume of dispersions in compact state cpfi -i. This dependence is shown in Fig. 12 (the correlation coefficient is 0.951). 

Fig. 12. Correlation between the value of the structure-sensitive coefficient B from Eq. (87) and the free volume of composites...

Outputs Predictions of pharmacokinetic behavior or tissue dose associated with given set of parameters or structure. Sensitivity coefficients Population distributions (probability) of dose metric for an exposure situation Percentage of variance in the output (e.g., dose metric) attributed to each parameter s variance... 

Very recently, considerable effort has been devoted to the simulation of the oscillatory behavior which has been observed experimentally in various surface reactions. So far, the most studied reaction is the catalytic oxidation of carbon monoxide, where it is well known that oscillations are coupled to reversible reconstructions of the surface via structure-sensitive sticking coefficients of the reactants. A careful evaluation of the simulation results is necessary in order to ensure that oscillations remain in the thermodynamic limit. The roles of surface diffusion of the reactants versus direct adsorption from the gas phase, at the onset of selforganization and synchronized behavior, is a topic which merits further investigation. 

Because protein ROA spectra contain bands characteristic of loops and turns in addition to bands characteristic of secondary structure, they should provide information on the overall three-dimensional solution structure. We are developing a pattern recognition program, based on principal component analysis (PCA), to identify protein folds from ROA spectral band patterns (Blanch etal., 2002b). The method is similar to one developed for the determination of the structure of proteins from VCD (Pancoska etal., 1991) and UVCD (Venyaminov and Yang, 1996) spectra, but is expected to provide enhanced discrimination between different structural types since protein ROA spectra contain many more structure-sensitive bands than do either VCD or UVCD. From the ROA spectral data, the PCA program calculates a set of subspectra that serve as basis functions, the algebraic combination of which with appropriate expansion coefficients can be used to reconstruct any member of the... 

Figure 6.9 Effect of CITREM concentration on the molecular and thermodynamic parameters of complex protein-surfactant nanoparticles in aqueous medium (phosphate buffer, pH = 7.2, ionic strength = 0.05 M 20 °C) (a) extent of protein association, k = Mwcomplex/Mwprotem (b) structure-sensitive parameter, p (c) second virial coefficient, A2 (rnolal scale) (d) effective charge, ZE (net number n of moles of negative charges per mole of original sodium caseinate nanoparticles existing at pH = 7.2 (Mw = 4xl06 Da)). The indicated cmc value refers to the pure CITREM solution. Reproduced from Semenova et al. (2007) with permission.

A summary of physical and chemical constants for beryllium is compiled in Table 1 (3—7). One of the more important characteristics of beryllium is its pronounced anisotropy resulting from the close-packed hexagonal crystal structure. This factor must be considered for any property that is known or suspected to be structure sensitive. As an example, the thermal expansion coefficient at 273 K of single-crystal beryllium was measured (8) as 10.6 x 10-6 parallel to the -axis and 7.7 x 10-6 parallel to the t-axis. The actual expansion of polycrystalline metal then becomes a function of the degree of preferred orientation present and the direction of measurement in wrought beryllium. 

Non-additivity of substituent effects has been proposed as a criterion for the operation of the RSR so the linearity argues against its applicability in this system. In a description of transition states by structure-reactivity coefficients (Jencks and Jencks, 1977), two alternative types of behaviour were discussed. In Hammond -type reactions the more endothermic reactions have later transition states, whereas anti-Hammond behaviour is characterized by an adjustment of the transition-state structure to take advantage of favourable substituent effects. These results illustrate that different systems can display quite different behaviour in linear free energy correlations. Thus, in alkene protonations, such correlations cover vast ranges in reactivity with only modest changes in sensitivities, while in solvolytic reactions the selectivity p varies depending on the electron supply at the electron-deficient centre (Johnson, 1978). 

Tests of notched specimens (Figure 26) and determination of notch sensitivity coefficient (K) show that, despite thickness of rolled semiproducts, the Kt coefficient (for a dendritic structure) is less than K2 (for a nondendritic structure) by 20—25% for room and cryogenic temperatures. Thus, K2 > 1.5 for plates and K2 = 1 for thick sheets, which indicates their full insensitivity to a notch. 

Recent single-crystal studies reveal the surface-structure sensitivity and anisotropy of self-diffusion (70, 71]. Depending on the structure of the crystal face, diffusion coefficients may vary by orders of magnitude. This is shown for rhodium adatom diffusion on various rhodium crystal faces in Figure 4.14. Diffusion rates parallel to steps are greater than diffusion rates perpendicular to them. 

Table 3. Structural information, parameterization, sensitivity coefficients and normal modes for HjO...

A special type of sensitivity coefficient probes the structural responses of a biomolecule to perturbations introduced to different parts of the biomolecule. In molecular mechanics, a Green s function matrix containing this information can be derived as follows. The x, y, or z component of a force F. acting on an atom of a molecule is given by... 

Dislocations must also be taken into consideration as possible high mobility paths for particles. The density Pe> 2ind the spatial arrangement of dislocations are very difficult to control. Thus, even for single crystals, transport coefficients can be structure-sensitive at temperatures less than about half the melting temperature where volume diffusion no longer predominates. 

No kinetic oscillations, rather just bistability, could be detected with the Pt(l 11) surface, whereas the other orientations of the crystal showed bistability and oscillations [8]. The reason for this is that the lifting of the reconstruction enhances the oxygen sticking coefficient. Consequently, oscillatory behavior occurs when the partial pressures pco and po are adjusted in such a way that the CO adsorption rate is faster (slower) than the O2 uptake on the reconstructed (1x1) surface. The reconstructed surface will take up CO and the 1 X 1 will form, which adsorbs oxygen faster, which, in turn, reduces the CO coverage by reactive removal. (Note that CO adsorption is not noticeably structure sensitive.)... 

Radiation differs from conduction and convection not only in mathematical structure but in its much higher sensitivity to temperature. It is of dominating importance in furnaces because of their temperature, and in ciyogenic insulation because of the vacuum existing between particles. The temperature at which it accounts for roughly half of the total heat loss from a surface in air depends on such factors as surface emissivity and the convection coefficient. For pipes in free convection, this is room temperature for fine wires of low emissivity it is above red heat. Gases at combustion-chamber temperatures lose more than 90 percent of their energy by radiation from the carbon dioxide, water vapor, and particulate matter. 

There is an excellent correlation between these data and the gas-phase data, in terms both of the stability order and the energy differences between carbocations. A plot of the gas-phase hydride affinity versus the ionization enthalpy gives a line of slope 1.63 with a correlation coefficient of 0.973. This result is in agreement with the expectation that the gas-phase stability would be somewhat more sensitive to structure than the solution-phase stability. The energy gap between tertiary and secondary ions is about 17kcal/mol in the gas phase and about 9.5 kcal/mole in the SO2CIF solution. 

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