Distortion effect

This complexation accentuates both the energy and orbital distortion effects of the substituent and enhances both the reactivity and selectivity of the dienophile, relative to the uncomplexed compound.The effects are well modeled by 3-21G-level computations on the transition-state stmctures. ... 

Figure 1 A dilute alloy system, showing a substitutional impurity, an interstitial impurity and an electromigration defect, and its reference system, the unperturbed host system. Some charge transfer effects are shown. Lattice distortion effects are omitted.

If the left-hand side of Eq. (11) is zero, dP/dt must be positive and d2P/dt2 negative, i.e. the maximum desorption rate is attained earlier than the maximum pressure. This distorting effect increases with an increasing value of d2P/dt2 (which depends on the kinetics of the surface process and therefore among others also on the heating rate) and with the increasing ratio... 

A phosphate-sludge conditioner blend may be employed because the deposit control agent or sludge conditioner limits and controls crystal formation (threshold and crystal distortion effects) and ensures particle fluidization (dispersion effect). 

Beckmann P. A., Burnell E. E. Nuclear spin relaxation and centrifugal distortion effects in dilute silane gas, Can. J. Phys. 55, 1354-5 (1977). 

Actually, symmetrical tetrahedral molecules like methane do have extremely small dipole moments, caused by centrifugal distortion effects these moments are so small that they can be ignored for all practical purposes. For CH4, p is 5.4 x 10 D Ozier, I. Phys. Rev. Lett., 1971, 27, 1329 Rosenberg, A. Ozier, I. Kudian, A.K. J. Chem. Phys., 1972, 57, 568. 

The concerns we have expressed are bound to get even more acute if the problem under study demands that we are able to adequately describe distortion effects induced in the electron distribution by external fields. The evaluation of linear (and, still more, non linear) response funetions [1] by perturbation theory then forces one to take care also of the nonoccupied portion of the complete orbital spectrum, which is entrusted with the role of representing the polarization caused by the external fields in the unperturbed electron distribution [4], ... 

A quantitative investigation of the influence exerted by a substrate on the properties of disperse catalysts is hampered by the distorting effects of many other factors, particularly the macrokinetic limitations and the size effects mentioned in Section 28.5.4. 

Step 3 Guinier Plot Separation of Size and Distortion Effects. The inner part of the correlation functions y0bs(h) (T) s readily expanded into a power series. For this purpose we resort to Eq. (8.14). Assuming that instrumental broadening is already eliminated we have... 

Figure 8.4. Graphical separation of lattice size and lattice distortion effects according to Warren-Averbach... 

Figure 8.5. Graphical separation of lattice distortion effects of the first and the second kind...

An example for a linearization of integral peak breadths and the corresponding separation of size and distortion effects is sketched in Fig. 8.6. It is clear that at least... 

Finally, in the sense that the imposition of conformational restrictions or specific solvent effects on an organic molecule are forms of strain, non-covalent catalysis by the cycloamyloses may provide a simple model for the investigation of strain and distortion effects in enzymatic reactions. 

In summary, for displaced oscillators, absorption and emission spectra show a mirror image relation and for the strong coupling case, a(oo) will exhibit a Gaussian band shape, absorption maximum independent of temperature, and bandwidth increasing with temperature. It should be noted that the distortion effect and Duschinsky effect have not been considered in this chapter, but these effects can be treated similarly. 

Because we are concerned only with the analysis of the absorption spectra of P band and B band, we consider the excitonic interactions among P, BL, and BM shown in Fig. 8. Here (oti, ot2,0C3,014) represent the diagonal matrix elements, while (p, (314, P23, P34) represent the off-diagonal matrix elements [67]. As shown in Introduction, a main feature of the P band is that its absorption maximum shows a pronounced temperature shift [42,52], According to the displaced oscillator model, the absorption maximum is independent of T. Although the distortion effect of potential surfaces will introduce some temperature shift, the effect cannot be as large as that shown in Fig. 2. 

Workers have shown theoretically that this effect can be caused both at the microstructural level (due to tunneling of the current near the TPB) as well as on a macroscopic level when the electrode is not perfectly electronically conductive and the current collector makes only intermittent contact. ° Fleig and Maier further showed that current constriction can have a distortional effect on the frequency response (impedance), which is sensitive to the relative importance of the surface vs bulk path. In particular, they showed that unlike the bulk electrolyte resistance, the constriction resistance can appear at frequencies overlapping the interfacial impedance. Thus, the effect can be hard to separate experimentally from interfacial electrochemical-kinetic resistances, particularly when one considers that many of the same microstructural parameters influencing the electrochemical kinetics (TPB area, contact area) also influence the current constriction. 

The dipole moment is a fundamental property of a molecule (or any dipole unit) in which two opposite charges are separated by a distance . This entity is commonly measured in debye units (symbolized by D), equal to 3.33564 X 10 coulomb-meters, in SI units). Since the net dipole moment of a molecule is equal to the vectorial sum of the individual bond moments, the dipole moment provides valuable information on the structure and electrical properties of that molecule. The dipole moment can be determined by use of the Debye equation for total polarization. Examples of dipole moments (in the gas phase) are water (1.854 D), ammonia (1.471 D), nitromethane (3.46 D), imidazole (3.8 D), toluene (0.375 D), and pyrimidine (2.334 D). Even symmetrical molecules will have a small, but measurable dipole moment, due to centrifugal distortion effects. Methane " for example, has a value of about 5.4 X 10 D. 

For a more accurate representation of the instrumental distortion effects see Section II.G of Chapter 2. The approximation given by Eq. (14) is convenient and for high-dispersion instruments observing weakly absorbing spectral lines it is often accurate enough for a number of experimental uses. 

We are forced to reflect that the failure of so many attempts to improve on the DH theory can be attributed to a premature rejection of the DH approach, and a tendency to include extra parameters without proper theoretical foundation. It is surprising that although ionic polarization is emphasized in studies of solvation (36), molten salts (37), and chemistry in general (38), the phenomenon has received little attention in interionic theory. In particular, our attention is drawn to the early work of Fajans and co-workers (39), who first noted the effects of concentration on the ionic molar refractivities of solutions, which were interpreted in terms of a distorting effect on the ions. For various reasons the significance of this work has not been appreciated in the field of electrochemistry. 

Our conclusions about dipole moments are all within the context of the Bom-Oppenheimer approximation and methane, for example, has in reality a small permanent moment whose magnitude is the order of 10 to 10 D. This moment is caused by centrifugal distortion effects. ... 

Not all of these distortion effects can be ascribed to differences in LP-BP and BP-BP repulsions. Some distortion is due to differences in electronegativity between M and the ligands. If the two have equal electronegativity, then of course the bond pairs are shared equally between M and L. If M is more electronegative than L, however, the bond pairs will be held more closely to M. But as they are drawn closer to M, the bond pairs also are drawn closer to each... 

For the HgH system numerical wavefunctions were obtained for Hg using both relativistic (Desclaux programme87 was used) and non-relativistic hamiltonians. The orbitals were separated into three groups an inner core (Is up to 3d), an outer core (4s—4/), and the valence orbitals (5s—6s, 6p). The latter two sets were then fitted by Slater-type basis functions. This definition of two core regions enabled them to hold the inner set constant ( frozen core ) whilst making corrections to the outer set, at the end of the calculation, to allow some degree of core polarizability. The correction to the outer core was done approximately via first-order perturbation theory, and the authors concluded that in this case core distortion effects were negligible. 

CCITT86sgl2con46, 1986] CCITT86sgl2con46 (1986). Objective evaluation of non-linear distortion effects on voice transmission quality. ITU-T Study Group 12. Contribution 46. 

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