Focus of Study

Wliile the earliest TR-CIDNP work focused on radical pairs, biradicals soon became a focus of study. Biradicals are of interest because the exchange interaction between the unpaired electrons is present tliroiighoiit the biradical lifetime and, consequently, the spin physics and chemical reactivity of biradicals are markedly different from radical pairs. Work by Morozova et al [28] on polymethylene biradicals is a fiirther example of how this method can be used to separate net and multiplet effects based on time scale [28]. Figure Bl.16.11 shows how the cyclic precursor, 2,12-dihydroxy-2,12-dimethylcyclododecanone, cleaves upon 308 mn irradiation to fonn an acyl-ketyl biradical, which will be referred to as the primary biradical since it is fonned directly from the cyclic precursor. The acyl-ketyl primary biradical decarbonylates rapidly k Q > 5 x... 

Physical Properties Electrical. Electrical properties have been the main focus of study of organic semiconductors, and conductivity studies on organic materials have led to the development of materials with extremely low resistivities and large anisotropies. A discussion of conductivity behaviors for various classes of compounds follows. 

During the past decade, the main focus of studies related to the well-known349 CeCl3- or SnCl2-catalyzed reactions of allylzinc and benzylzinc halides with imines was the application of polymer-supported chiral imines.350,351 An example of such reactions is shown in Scheme 135.350 It should be noted that attempts using arylzinc reagents in... 

Within this common core structure, modifications have been identified that provide catalases with further unique properties. The large-subunit enzymes have extensions at both the amino and carboxyl ends, the latter having a flavodoxinlike structure, a unique His-Tyr bond, a protected cysteine, and a modified heme. NADPH binding and an oxidized methionine are found in small subunit enzymes. Identification and assignment of roles to channels providing access to and egress from the deeply buried heme have recently become the focus of study. Analysis of the structure of catalase HPII of E. coli has been facilitated by the construction of more than 75 mutants (Table I). 

The stabihty of collagen is due to the formation of triple helixes, which is due to the presence of a Gly-Pro (OH)-Pro triplet. The influence of the replacement of 4-(R)-OH-Pro by 4-F-Pro on the stability of collagen has been the focus of studies on polypeptide models. These studies highlight the importance of stereoelectronic... 

Through numerous studies on the mechanism of pathogenesis of cerebral ischemia, various compounds were proposed that could effectively protect the brain against ischemia. Because free radicals are one of the focuses of study in the mechanism of cerebral ischemic injury, a variety of agents that have antioxidant capacity have been developed ... 

Natural and engineered zeolites have been used extensively in wastewater treatment (e.g., Clifford, 1990). For in situ barrier applications, the focus of study has been a natural clihoptilolite supplied by Teague Mineral Products (Adrian, Oregon), primarily because of its low cost and strong affinity for Sr. 

Cambridge, UK, are presently the focus of study in a large number of research laboratories, and topics of development in ever-growing numbers of both small and large industrial laboratories, world wide . 

Photosensitized Dissociation of Water using Dispersed Suspensions of n-Type Semiconductors Focus of study on Ti02 and SrTi03 using EDTA as an electron donor and Fe3+ as acceptor for tests of water reduction and oxidation activity respectively (c.f. Figs, lb and lc). 251... 

Equilibration with water vapor Substantially less work was done in this area in the early phase of research on PFSAs because of previous emphasis on membranes which would be in contact with liquid water or aqueous solutions (e.g., for chlor-alkali technology). However, water supplied from the vapor phase could be a principal mode of external hydration of the membrane in a PEFC, particularly hydration of the anode side, and thus it is an important focus of study in fuel cell R D. The shape of the sorption isotherms shown in Fig. 29 (a) and (b) is generic for ion-exchange polymers. With increasing PhsO. water is sorbed in two steps as evidenced by the sorption isotherm ... 

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