Numerators under-reporting

R3 R2 and R2 Ri gauche interactions however, for the same set of substituents, an increase in the steric requirements of either Rj or R3 will influence only one set of vicinal steric interactions (Rj R2 or R3 R2). Some support for these conclusions has been cited (eqs. [6] and [7]). These qualitative arguments may also be relevant to the observed populations of hydrogen- and nonhydrogen-bonded populations of the aldol adducts as well (see Table 1, entries K, L). Unfortunately, little detailed information exists on the solution geometries of these metal chelates. Furthermore, in many studies it is impossible to ascertain whether the aldol condensations between metal enolates and aldehydes were carried out under kinetic or thermodynamic conditions. Consequently, the importance of metal structure and enolate geometry in the definition of product stereochemistry remains ill defined. This is particularly true in the numerous studies reported on the Reformatsky reaction (20) and related variants (21). 

Ciguatera is also an American problem and is grossly under-reported. My files contain numerous reports of poisonings which occurred while on vacation or from fish obtained in a hot area. 

Applications of many-body perturbation theory to the molecular electronic structure problem have been published during the reporting period in an ever increasing range of scientific areas. In particular, in its second order form, many-body perturbation theory continues to be the most widely used ab initio quantum chemical method for describing the effects of electron correlation. A review of the numerous applications reported during the period under consideration is given in Section 4. 

In spite of the numerous studies reported on photooxidation of polyolefins, the detailed mechanism of the complete process remains unresolved. The relative contribution by species involved in photoinitiation, the origins of the oxidative scission reaction, and the role played by morphology in the case of photoreactions in solid state are not completely understood. Primary initiator species in polyethylenes [123] and polypropylenes [124] are believed to be mainly ketones and hydroperoxides. During early oxidation hydroperoxides are the dominant initiator, particularly in polypropylene, and can be photolyzed by wavelengths in solar radiation [125]. Macro-oxy radicals from photolysis of polyethylene hydroperoxides undergo rapid conversion to nonradical oxy products as evidenced by ESR studies [126]. Some of the products formed are ketones susceptible to Norrish I and II reactions leading to chain scission [127,128]. Norrish II reactions predominate under ambient conditions [129]. Concurrent with chain scission, crosslinking, for instance via alkoxy macroradical combination [126], can take place with consequent gel formation [130,131]. 

The relationship between the NaCl holdup, a, at different flow rates under the fixed electric field is shown in Fig. 5b. The NaCl holdup a remains the same (0.35) for different volumetric flow rates in the absence of an externally applied electric field. This is because the volumetric flow rates ratio between the two liquids is kept unchanged, 1 1. This agrees very well with the previous theoretical and numerical study reported in the literature. As shown in Fig. 5b, it can be seen that as flow rate increases, holdup a converges to a constant value, 0.35, that is, the value without the externally applied electric field. The reason is that larger pressure-driven flow velocity makes the EOF effect almost insignificant... 

A strong numerical evidence supporting the above statements has been provided in Ref. [98]. Before discussing a few representative examples, let us emphasize that in all numerical calculations reported in Ref. [98] and reviewed here, we tested, for the first time ever, the exact theory, in which we used the unexpanded form of the exponential operator to define the E X) energy rather than the truncated power series expansion in X used in Ref. [97]. This was made possible by representing the operators H and X as matrices in the finite-dimensional 7V-electron Hilbert spaces relevant to a molecular system under consideration (using all symmetry-adapted Slater determinants ) and n = 1,..., TV, defining the... 

Despite numerous reviews reported on experimental degradation research, " very few reviews have been published on the topic of modelling of aging phenomena (e.g. Morimoto and Yamakawa ). The reason is perhaps that most of these models have been only very recently developed. Some of the key ingredients behind these models are now discussed, with the underlying challenges (Fig. 11.5). This discussion focuses on ME A materials degradation. 

When a polymer of (Xe > o-jon, such as polypyrrole in the oxidized state, is subjected to changes of the applied electrode potential, during the transient state electric fields develop in the polymer matrix and then disappear as electronic and ionic charge carriers migrate to new equilibrium positions [19,27,31,184]. The analyses may be based on the concepts derived for redox polymers under the condition that the hopping mobility of the electrons exceeds the counterion mobility. It has been shown [31] that in this case the system behavior is again diffusiona in character. The coated electrode behaves like a porous metal electrode with pores of limited depth. Numerous experimental reports on this behavior of conducting polymers have appeared in the literature the first was probably that of Bull et al. in 1982 [214]. 

Hydroxides. The hydrolysis of uranium has been recendy reviewed (154,165,166), yet as noted in these compilations, studies are ongoing to continue identifying all of the numerous solution species and soHd phases. The very hard uranium(IV) ion hydrolyzes even in fairly strong acid (- 0.1 Af) and the hydrolysis is compHcated by the precipitation of insoluble hydroxides or oxides. There is reasonably good experimental evidence for the formation of the initial hydrolysis product, U(OH) " however, there is no direct evidence for other hydrolysis products such as U(OH) " 2> U(OH)" 2> U(OH)4 (or UO2 2H20). There are substantial amounts of data, particulady from solubiUty experiments, which are consistent with the neutral species U(OH)4 (154,167). It is unknown whether this species is monomeric or polymeric. A new study under reducing conditions in NaCl solution confirms its importance and reports that it is monomeric (168). 8olubihty studies indicate that the anionic species U(OH) , if it exists, is only of minor importance (169). There is limited evidence for polymeric species such as Ug(OH) " 25 (1 4). 

Low Pressure Syntheses. The majority of metal carbonyls are synthesized under high pressures of CO. Early preparations of carbonyls were made under superpressures of 1 GPa (ca 10,000 atm). Numerous reports have appeared in the Hterature concerning low pressure syntheses of metal carbonyls, but the reactions have been restricted primarily to the carbonyls of the transition metals of Groups 8—10 (VIII). A procedure for preparing Mn2(CO)2Q, however, from commercially available methylcyclopentadienyknanganese tricarbonyl [12108-13-3] and atmospheric pressures of CO has been reported (117). The carbonyls of mthenium (118,119), rhodium (120,121), and iridium (122,123) have been synthesized in good yields employing low pressure techniques. In all three cases, very low or even atmospheric pressures of CO effect carbonylation. Examples of successful low pressure syntheses are... 

These early observations on the correlation of structure and pharmacological action in the morphine group have been greatly extended as a result of chemical, pharmacological and clinical work done under the auspices of the American National Committee on Drug Addiction. In addition to numerous papers, contributed by experts serving this Committee, to chemical and pharmacological journals, two important reports have been published —... 

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