Interaction indirect

Between the limits of small and large r, the pair distribution function g(r) of a monatomic fluid is detemrined by the direct interaction between the two particles, and by the indirect interaction between the same two particles tlirough other particles. At low densities, it is only the direct interaction that operates through the Boltzmaim distribution and... 

At higher densities, the effect of indirect interactions is represented by the cavity function > (r,p,7), which multiplies tire Boltzirramr distribution... 

Interactions refers to any jobs, tasks, or operations carried out by people who could directly or indirectly cause the hazard to be released. Direct interactions with the plant might involve breaking open pipework, opening reactors, etc. Indirect interactions would include remote activation of valves from a control room, or the performance of maintenance on critical plant items. Errors that might occur during these interactions could allow the harm potential to be released. This could occur directly (for example, a worker could be overcome by a chlorine release if an incorrect valve line-up was made) or indirectly (for example, if a pump bearing in a critical cooling circuit was not lubricated, as in the example in Chapter 1). The procedure as described above... 

The theory of interaction between a pair of orbitals, (J) and (Scheme la) is well established (Chapter Elements of a Chemical Orbital Theory by Inagaki in this volume) and snccessfnlly applied to nnderstanding and designing molecnles and reactions (Chapter A Mechanistic Spectrum of Chemical Reactions by Inagaki in this volnme). Here, we describe a theory of the interaction of three orbitals, (j), (J), and (j), (Scheme lb). The interactions include indirect interactions of... 

Scheme 2 Indirect interactions between orthogonal orbitals, (f) and through a perturbing orbital (p ...

In molecules with more than one unpaired electron, electron-electron interactions can have a significant role in the stabilization of the system. Bond formation that results from direct overlap is highly favorable and, thus is an overriding consideration in all low-spin polyradicals, even to the extent that the system sometimes adopts a strained, closed-shell state as opposed to a polyradical. In cases in which bonding cannot occur, indirect interactions that are usually insignificant, such as electron exchange and spin-polarization, can have significant impact. The presence of these interactions is often reflected in the thermochemical properties. 

In order to understand the observed shift in oxidation potentials and the stabilization mechanism two possible explanations were forwarded by Kotz and Stucki [83], Either a direct electronic interaction of the two oxide components via formation of a common 4-band, involving possible charge transfer, gives rise to an electrode with new homogeneous properties or an indirect interaction between Ru and Ir sites and the electrolyte phase via surface dipoles creates improved surface properties. These two models will certainly be difficult to distinguish. As is demonstrated in Fig. 25, XPS valence band spectroscopy could give some evidence for the formation of a common 4-band in the mixed oxides prepared by reactive sputtering [83],... 

Within the effects clause, there is no strong difference between participants and parameters both can be affected by the action. The distinction is intended to document a partial design decision. The participants exist or will be built as separate entities, with some direct or indirect interaction between them to realize the action. Together, the parameters represent information that is passed between the participants, encoded in a form not documented here, and possibly communicated differently. 

The above 1-dimensional model may be extended to 3-dimensions, in a straightforward manner, and yields a substrate whose surface is completely covered by adatoms. The TBA again leads to a difference equation and boundary conditions which can be solved directly (Grimley 1960). We do not intend to discuss the 3-dimensional case here and, instead, direct the reader to the loc. sit. articles. However, in passing, we note that, even when there is no direct interaction between the atoms in the adlayer, an important indirect interaction occurs between them via the substrate by a delocalization of the bonding electrons in directions parallel to the surface (Koutecky 1957, Grimley 1960). This topic is discussed in Chapter 8. 

In another interesting development, Gumhalter and Brenig (1995a,b) proposed that, in H-Ni(llO) and H-Cu(llO) systems, adatom-induced reconstruction of the surface gives rise to quasi-one-dimensional surface states, which mediate the indirect interaction. The greatly reduced dimensionality... 

The interaction energy, AIT, is the contribution (positive or negative) to AE, due to the (indirect) interaction between the two adatoms. In other words, AIT is the difference between the chemisorption energy AE for the doubleadsorption system and the sum of the chemisorption energies A (A = a or b) for the two individual single-adsorption systems, i.e.,... 

An analysis of the calculated values of AW shows that the damping factor in the indirect interaction is dr1, as exemplified in Fig. 8.8, for Cr and Ti substrates and 77 = 1.667. Envelope curves of the form ad x are shown, where a is chosen, so that the curve passes through the data point corresponding to d = 4. The fit to d 1 is seen to improve as d increases, agreeing with the asymptotic nature of the interaction law. 

Summarizing, it is clear that the indirect interaction between adatoms has a significant effect on the chemisorption properties of the system. Most noticeably, the chemisorption energy has a damped, oscillatory dependence on the adatom separation, as first quantified in (8.1) by Grimley. Thus, multi-atom adsorption occurs preferentially with the atoms at certain sites relative to one another. 

The term direct electrochemistry of proteins means the possibility to detect the direct exchange of electrons between the active site(s) of a protein and a (metallic or inert material) electrode without the help of redox mediators, which might favour an indirect interaction between the electrode and the protein (see the discussion on Electrocatalysis in Chapter 2, Section 1.4.4). This aspect of electrochemistry is not yet as widely explored as it deserves, but the relevant results are now analysed in a rather comprehensive fashion.1 ... 

Further inspection of Fig. 4.5 demonstrates that the O atoms are surrounded by dark zones. The STM technique probes not only the atomic topography but also the electronic structure, and the dark zones reflect the modification of the local electronic density in the vicinity of the adsorbates, this modification being responsible for the operation of indirect interactions (which may be either repulsive or attractive) between adsorbed particles mediated through the substrate. 

Theoretical work has been undertaken to address directly the predicted magnitude of the near surface electronic perturbations by impurity atoms. Early work by Grimley and coworkers and Einstein and Schrieffer concentrated on the indirect interactions between adsorbates which occur via the surface conduction electrons. These calculations suggested that atom-atom interactions through several lattice spacings can occur. More recently, Feibelman and Hamann and Joyner et have calculated the change in... 

Each of the subunits, a and P (as well as the closely related myoglobin molecule), has a prosthetic heme group to which the oxygen molecule binds. There are no covalent bonds between the subunits of Hb. The aggregate is maintained by a combination of weak direct subunit-subunit interactions as well as by indirect interactions mediated by the solvent. 

The copper pairs are 42 A apart within a dimer, so that the coopera-tivity exhibited by this protein clearly involves indirect interactions. The fact that partially oxygenated hemocyanin can be found in the same crystal form (albeit with higher concentrations of dimethyl sulfoxide, which is a denaturant) argues that the structural changes either are not large or are within the variability already exhibited by the fact that the crystals at present cannot diffract to better than 3.2 A. 

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