Molecularity pseudo

The 8-coordinate species [Mo(Et2dtc)4] can be obtained by reaction of Mo(CO)e with tetraethylthiuram disulfide (1 2) in acetone under N2. The X-ray structure revealed square-antiprismatic coordination, with a crystallographic, twofold axis coinciding with the molecular pseudo 4 axis (158). The magnetism and spectra of [M(dtc)4]"" (M = Mo or W n = 0 or 1) have been interpreted in terms of dodecahedral symmetry (159). 

Fig. 5. Three views of the NCP from Harp et al. [31]. (a) Ventral surface view, (b) Side view, (c) View down the molecular pseudo-dyad axis. The histones are represented by Ca ribbon models of the secondary structure elements, and the DNA model indicates the base pairing between complementary strands. The DNA is positioned asymmetrically by one-half base pair on the NCP. This results in a two sides arbitrarily referred to a dorsal and ventral (the surface shown here). The ventral surface of the NCP is best recognized by the extended N-terminal H3 tail protruding to the right. In these images, the pseudo-dyad axis is represented by vertical bars for both the ventral and side view. The pseudo-dyad axis passes through the center of the dyad view orthogonal to the plane of the page, (d) Color code for histone chains in the figures in this chapter. Note the change in hue denoting the two sides of the histone octamer.

A relatively explicit nomenclature is used to characterise the type of ions formed singly charged, multiply charged, monoatomic, polyatomic, molecular, pseudo-molecular, parent, daughter, metastable, secondary fragments, etc. 

Volume Mapping. One method of displaying molecular surfaces that retains the ability to transform the display interactively has been developed by Marshall and Barry (424). The procedure involves computing a molecular pseudo-electron density map on a... 

On the other hand, the more rigorous Maxwell-Stefan equations and the dusty gas model are seldom used in industrial reaction engineering applications. Nevertheless, the dusty gas model [64] represents a modern attempt to provide a more realistic description of the combined bulk and Knudsen diffusion mechanisms based on the multicomponent Maxwell-Stefan model formulation. Similar extensions of the Maxwell-Stefan model have also been suggested for the surface diffusion of adsorbed molecular pseudo-species, as well as the combined bulk, Knudsen and surface diffusion apparently with limited success [48] [49]. 

Figure 3. A perspective drawing of trans-tris(benzohydroxamato) chromium(III) looking down the molecular (pseudo) threefold axis...

This reaction would be described as first order in A and second order in B. The overall order is three. The order of a reaction depends on the mechanism and it is possible for the rate to be independent of concentration (zero order) or for the order to be a fraction. See also molecularity pseudo order. 

The projector augmented-wave (PAW) DFT method was invented by Blochl to generalize both the pseudopotential and the LAPW DFT teclmiques [M]- PAW, however, provides all-electron one-particle wavefiinctions not accessible with the pseudopotential approach. The central idea of the PAW is to express the all-electron quantities in tenns of a pseudo-wavefiinction (easily expanded in plane waves) tenn that describes mterstitial contributions well, and one-centre corrections expanded in tenns of atom-centred fiinctions, that allow for the recovery of the all-electron quantities. The LAPW method is a special case of the PAW method and the pseudopotential fonnalism is obtained by an approximation. Comparisons of the PAW method to other all-electron methods show an accuracy similar to the FLAPW results and an efficiency comparable to plane wave pseudopotential calculations [, ]. PAW is also fonnulated to carry out DFT dynamics, where the forces on nuclei and wavefiinctions are calculated from the PAW wavefiinctions. (Another all-electron DFT molecular dynamics teclmique using a mixed-basis approach is applied in [84].)... 

Mechanism. The thermal cracking of hydrocarbons proceeds via a free-radical mechanism (20). Siace that discovery, many reaction schemes have been proposed for various hydrocarbon feeds (21—24). Siace radicals are neutral species with a short life, their concentrations under reaction conditions are extremely small. Therefore, the iategration of continuity equations involving radical and molecular species requires special iategration algorithms (25). An approximate method known as pseudo steady-state approximation has been used ia chemical kinetics for many years (26,27). The errors associated with various approximations ia predicting the product distribution have been given (28). 

The diffusion, location and interactions of guests in zeolite frameworks has been studied by in-situ Raman spectroscopy and Raman microscopy. For example, the location and orientation of crown ethers used as templates in the synthesis of faujasite polymorphs has been studied in the framework they helped to form [4.297]. Polarized Raman spectra of p-nitroaniline molecules adsorbed in the channels of AIPO4-5 molecular sieves revealed their physical state and orientation - molecules within the channels formed either a phase of head-to-tail chains similar to that in the solid crystalline substance, with a characteristic 0J3 band at 1282 cm , or a second phase, which is characterized by a similarly strong band around 1295 cm . This second phase consisted of weakly interacting molecules in a pseudo-quinonoid state similar to that of molten p-nitroaniline [4.298]. 

The equations may be simplified by choosing a unitary transformation (Chapter 13) which makes the matrix of Lagrange multipliers diagonal, i.e. Ay 0 and A This special set of molecular orbitals (f> ) are called canonical MOs, and they transform eq. (3.40) mto a set of pseudo-eigenvalue equations. 

The third structural possibility, the formulation of the compounds as pseudo-bases (445) was eliminated in the case of the anhydro-bases derived from p /r-iV -alkyl-l-methyl-3,4-dihydro-j8-carbolinium salts on the basis of their ultraviolet absorption spectra. A structure such as 445 demands indole-type absorption (A jax 280 mp) which was not encountered in the spectra of the anhydro-bases under discussion. This is in accord with general experience. Pseudo-bases are generally found only when dehydration to anhydro-bases is structurally impossible Indole-type absorption was indeed found in the case of the product obtained by treatment of 3,4-dihydro-)3-carboline methiodide (452 R = H) with alkali.In acid solution this compound gave the expected absorption (A jax 355 mp). In alkaline solution, however, an indole-type absorption (A jax 285 mp) was observed. On this basis formulation of the product as a derivative of 2-formylindole (454) ( max 315 mp) was rejected. Although the indole-type absorption is in accord with the pseudo-base structure 453 (R = H), the elemental analysis and molecular weight were not compatible with this formulation and the product was regarded as a dimeric anhydro-base (455). 

The use of the K-factor charts represents pure components and pseudo binary systems of a light hydrocarbon plus a calculated pseudo heavy component in a mixture, when several components are present. It is necessary to determine the average molecular weight of the system on a methane-free basis, and then interpolate the K-value between the two binarys whose heavy component lies on either side of the pseudo-components. If nitrogen is present by more than 3-5 mol%, the accuracy becomes poor. See Reference 79 to obtain more detailed explanation and a more complete set of charts. 

A kinetic resolution of racemic sulphoxides was observed in the reduction by chiral polyiminoalanes. The efficiency of this process depends on the molecular structure of the polyiminoalane. With open pseudo-cubic tetra [JV-(l-phenylethyl)]imidoalane, unreacted sulphoxides were isolated in enantiomeric enrichment up to 75%. Optical purity was shown to increase with increasing the reaction temperature, a maximum enrichment being observed between 55 and 70 °C336. 

Such considerations appear to be very relevant to the deformation of polymethylmethacrylate (PMMA) in the glassy state. At first sight, the development of P200 with draw ratio appears to follow the pseudo-affine deformation scheme rather than the rubber network model. It is, however, not possible to reconcile this conclusion with the temperature dependence of the behaviour where the development of orientation reduces in absolute magnitude with increasing temperature of deformation. It was proposed by Raha and Bowden 25) that an alternative deformation scheme, which fits the data well, is to assume that the deformation is akin to a rubber network, where the number of cross-links systematically reduces as the draw ratio is increased. It is assumed that the reduction in the number of cross-links per unit volume N i.e. molecular entanglements is proportional to the degree of deformation. 

The internal structure of the catalyst particle is often of a complex labyrinth-like nature, with interconnected pores of a multiplicity of shapes and sizes, In some cases, the pore size may be less than the mean free path of the molecules, and both molecular and Knudsen diffusion may occur simultaneously. Furthermore, the average length of the diffusion path will be extended as a result of the tortuousity of the channels. In view of the difficulty of precisely defining the pore structure, the particle is assumed to be pseudo-homogeneous in composition, and the diffusion process is characterised by an effective diffusivity D, (equation 10.8). 

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