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Stability notion

Another important concept is the notion of stabilization by means of coordination, A classic example is the. stabilization of the fugitive species cyclobutadiene, C4H4I by coordination to (Fe(CO)3l (p. 936). As the C atom is isoclectronic with (BH], so (C4H4] is isoelectronic with the borane fragment (BaH which is similarly stabilized by coordination to (Fe(CO)3l or the isoelectronic (Cofr/ -CsHs)) (see Panel on p. 174), Indeed it is a general feature of metallaboranc chemistry that such clusters are often much more stable than are the parent boranes themselves. [Pg.164]

Aeeording to your Lewis structure(s) and to the actual geometry of the molecule, is the bonding in planar corannulene fully delocalized (as in benzene), or are some CC bonds long and some short Do your results support the notion that planar corrannulene is resonance stabilized Explain. [Pg.179]

The third approach is called the thermodynamic theory of passive systems. It is based on the following postulates (1) The introduction of the notion of entropy is avoided for nonequilibrium states and the principle of local state is not assumed, (2) The inequality is replaced by an inequality expressing the fundamental property of passivity. This inequality follows from the second law of thermodynamics and the condition of thermodynamic stability. Further the inequality is known to have sense only for states of equilibrium, (3) The temperature is assumed to exist for non-equilibrium states, (4) As a consequence of the fundamental inequality the class of processes under consideration is limited to processes in which deviations from the equilibrium conditions are small. This enables full linearization of the constitutive equations. An important feature of this approach is the clear physical interpretation of all the quantities introduced. [Pg.646]

Another way to view the barycentre rule is to consider first the bringing up to the metal of a spherical shell of negative charge which increases the energies of all five d orbitals equally. Then, in this notional picture, if the spherical shell of charge redistributes towards the apices of an octahedron, those orbitals directed towards those apices suffer a further repulsion and energy increase, while those directed in between, acquire a relative stability. [Pg.31]

Climate is often viewed as the aggregate of all of the elements of weather, with quantitative definitions being purely physical. However, because of couplings of carbon dioxide and many other atmospheric species to both physical climate and to the biosphere, the stability of the climate system depends in principle on the nature of feedbacks involving the biosphere. For example, the notion that sulfate particles originating from the oxidation of dimethylsulfide emitted by marine phytoplankton can affect the albedo (reflectivity) of clouds (Charlson et ai, 1987). At this point these feedbacks are mostly unidentified, and poorly quantified. [Pg.12]

The notion of stability. The notion of stability for three-layer schemes is of our initial concern. By a two-layer scheme we mean a set of operator-difference equations (4) depending on the parameters h and t. We preassumed here that the operators A and B are given on the entire space Bh-... [Pg.388]

Inequality (12) expresses the property of continuous dependence which is uniform in h and t of the Cauchy problem (4) upon the input data. Here and below the meaning of this property is stability. A difference scheme is said to be absolutely stable if it is stable for any r and h (not only for all sufficiently small ones). It is fairly common to distinguish the notion of stability with respect to the initial data and that with respect to the right-hand side. Scheme (4) is said to be stable with respect to the initial data if a solution to the homogeneous equation... [Pg.389]

The basic notions of the theory of difference schemes are the error of approximation, stability, convergence, and accuracy of difference scheme. A more detailed exposition of these eoncepts will appear in Chapter 2. They are illustrated by considering a number of difference schemes for ordinary differential equations. In the same chapter we also outline the approach to the general formulations without regard to the particular form of the difference operator. [Pg.778]

The reactions and compound presented in this chapter support the notion that the formation of o-QMs from the parent phenols is a quite complex process. In the case of the oxidation by Ag20 but also likely in other oxidations, a zwitterionic intermediate is involved that can be stabilized intermolecularly, for example, by electrostatic interaction with other suitable zwitterions, or intramolecularly by neighboring groups or inductive/mesomeric effects. By stabilizing the zwitterionic intermediate and destabilizing the o-QM, the energetic gap between these two intermediates is lowered and... [Pg.186]

In order to compare the structural options for transition metal compounds and to estimate which of them are most favorable energetically, the ligand field stabilization energy (LFSE) is a useful parameter. This is defined as the difference between the repulsion energy of the bonding electrons toward the d electrons as compared to a notional repulsion energy that would exist if the d electron distribution were spherical. [Pg.77]

In one sense, the gold standard already was a moral notion for economists. It was the prime manifestation of what Nicholas Mayhew has called a moral idea of money (2000, xi)—the idea that a gold-backed currency is a constant and unchanging currency unit with which to measure personal or public obligations (xi). The gold standard was meant to ensure stability in both the domestic economy and international trade, and it was almost an article of faith for most economists. As Mayhew notes, So irrevocable did it all seem that when the [British] National government of 1931 did eventually devalue and abandon gold, its Labour Cabinet predecessors complained that no one had told them you could do that (214-15). [Pg.136]

De Steiger concludes her 34 9-page treatise by folding together into a mystical framework concepts of permanence that evoke the material world of economics—the gold standard—and notions of stability, such as the Stable Atom derived from mysticism but echoing the science of radioactivity. Beneath the world of material transmutation asserted by atomic scientists and by alchemists lies a substratum of immutable spiritual value ... [Pg.137]

At this point, our notion and implications of the term stability must be clarified. At the most basic level, and as utilized in Section VILA, dynamic stability implies that the system returns to its steady state after a small perturbation. More quantitatively, increased stability can be associated with a decreased amount of time required to return to the steady state as for example, quantified by the largest real part within the spectrum of eigenvalues. However, obviously, stability does not imply the absence of variability in metabolite concentrations. In the face of constantperturbations, the concentration and flux values will fluctuate around their... [Pg.220]

The notion of stabilized and sensitized protectors is pertinent to solid-phase synthesis in particular. Practically all of the linkers through which carboxy-terminal residues are attached to the solid support are composed of benzyl that has been substituted with functional groups such as dialkoxy, dimethoxyphenyl, phenyl (ben-zhydryl), diphenyl (trityl), chlorodiphenyl (chlorotrityl, see Section 5.23), or other to modify the stability of the linking bond.9-63-73... [Pg.89]


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See also in sourсe #XX -- [ Pg.7 , Pg.8 ]




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