Contributions of Other Research Groups

Almost all contributions of other research groups may be subdivided into the following three categories  

Studies of the depolymerisation of polymers with the purpose to isolate and characterize cyclic oligomers were already reported by Carothers et al. as mentioned in Chap. 3. However, Carothers used depolymerisation in the melt at high temperatures combined with distillation of the cycles in vacuo. In this way he obtained more than 60 new cyclic oligomers in yields around 10-25 %. Yet, he also performed depolymerisation of aliphatic polyesters in solution [13-15]. 

Further studies of equilibration reactions of aliphatic polyesters in solution catalyzed by titanium alkoxides were contributed by BiUmeyer et al. [16-18]. Semiyen et al. [19] used a dibutyltin salt for the preparation of cyclic oligomers by depolymerization of poly(tetraethyleneglycol succinate). Extraction and characterization of cyclic oligo(alkylene isophthalate)s and oligo(alkylene terephthalate)s [20-24] beg an in 1954 with the work of Ross et al. [20], who isolated the cyclic trimer from PET. A detailed study of 13 different polyesters was reported by Wick and Zeigler [25]. Semiyen et al. [26] were particularly interested in the depolymerisation of polyesters derived from tetra(ethyleneglycol) and phthalic, isophthalic and terephthalic acidacid, whereas Montaudo et al. [27] studied other polyesters of terephthalic acid. 

Preparation of cyclic oligo(ether sulfone)s by cesium fluoride-catalyzed depolymerisation in aprotic solvents was reported by Colquhoun et al. [36, 37]. The fluoride ion cleaves the C-O bonds at temperatures 140 °C and the resulting phenoxide ions attack the neighboring ether groups forming cyclics by backbiting . Several cyclic oligoethers up to the pentamer were isolated and characterized by X-ray crystal structure analyses. 

Carmichael et al. [55-61] developed a theoretical model for the calculation of Kx and measured values of cyclosiloxanes having DP s 11. The experimental Kx values were found to be independent of the reaction medium and to disagree with their own model and also with the JS theory. 

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The seventeen research groups listed below have made already (2000) significant contributions to the rapidly growing Electrochemical Promotion (NEMCA) literature. They are listed and discussed here, both in order to pay tribute to their valuable contributions, but also in order to facilitate contact with them of other research groups interested in entering the field of Electrochemical Promotion. 

In addition to those acknowledged in the text and references, many other people at Phillips have made important contributions to the development of heterogeneous metathesis catalysis. Contributions by other research groups, particularly those in the academic sector, to this new field are credited in various review articles, e.g., reference ( ). 

Abstract This account describes the circumstances leading to our group s innovations in the area of decarboxylative asymmetric allylic alkylation reactions and the initial discovery of palladium phosphinooxazoline complexes as efficient enantioselective catalysts. This chapter also chronicles the growth of the methodology to include several substrate classes, the expansion of the project into several other reaction manifolds, and the use of these reactions in natural product synthesis. Finally, important contributions from other research groups involving related methods or products similar to the ot-quatemary products that are the focus of our studies, as well as future directions for asymmetric alkylation reactions, are discussed. 

Finally, I wish to acknowledge the major contributions of a remarkable group of students and research associates who have contributed to this program. In a review of this kind, covering fully 35 years of research, it was possible to mention only some of the high spots and to make reference to only a fraction of their publications. I hope I have made amends to the others in my recently published book (67). 

Other research groups who have contributed either directly or indirectly to our current understanding of electron transfer processes involving POMs include (alphabetically by correspondence author(s)) Anson (reduction of 02 to H202 by PRun(H20)Wn0395- in good agreement with... 

LDL cholesterol values that underestimate cardiovascular risk because they exclude some of the atherogenic lipoproteins. Moreover, this might occur more frequently with patients with CHD or who are at risk for CHD based on their LDL cholesterol concentrations. Consequently, the NCEP Working Group on LDL cholesterol measurement suggested that LDL cholesterol values should not be corrected for the contribution of other atherogenic hpoproteins, and also recommended that further research be conducted to establish the individual contributions of IDL, Lp(a), and LDL cholesterol to the CHD risk as reflected in current LDL cholesterol measurements that include all three lipoprotein classes. The... 

Reactions in organic solids also appear to be influenced by the presence of dislocations. One of the first indications that such an influence is exerted in solid-state polymerization came from the researches of Adler et al. (145-148) and of Bamford and Eastmond (149-151). Although little or nothing is known about dislocations in the monomer solids used by these two groups, and although the contribution of other defects (for example, those introduced by y-irradiation) is also unknown, there are strong indications that polymerization is preferentially initiated in the vicinity of dislocation cores. Thus, Bamford and Eastmond (149-151) observed that the application of mechanical stress to crystals... 

We are indebted to the American Gas Association, Inc., for their generous support, without which this work might not have been accomplished. R. D. McCarty contributed the essential least-squares program, providing for constraints. Discussions, suggestions, references, and experimental data from other members of this research group have contributed substantially to make possible the developments reported here. 

Several other research groups are actively contributing in this field of CcO model chemistry. Naruta et al. have reported tris(2-pyridylmethyl)amine Cu complex-linked iron meso-tetra-phenylporphyrin derivatives and well-characterized Fe—(O2)—Cu species that are similar to [( L)Fe -(0 )-Cu ]+ (Structure (7)). A CcO model developed by Casella and co-workers is a natural porphyrin derivative, in which a polybenziimidazole residue for the Cu coordination site is attached to the propionic acid side chain of the deuteroporphyrin. A new class of picket porphyrin, bearing covalently linked, axially placed tris(heterocycle) chelates for a copper ion, has been synthesized and characterized by Wilson and co-workers. ... 

Until recently (93-96), little was known about the arsenic methylation intermediates, MMA(lll) and DMA(lll), in the human system, a result of the lack of techniques for the determination of these arsenic species. Recent developments of more sensitive and improved arsenic speciation techniques contribute to the discovery of these intermediary metabolites in human urine (93-96). Figure 3 shows typical chromatograms obtained from the analyses of arsenic compounds in deionized water and in urine samples. Coinjection of the urine sample with authentic MMA(lll) standard (Fig. 3c) demonstrates the coelution of the suspected MMA(lll) in the sample with that of the standard MMA(III), confirming the identity of MMA(lll) in the urine sample. Similarly, coinjection of the urine sample with standard DMA(III) (Fig. 3d) and As(V) (Fig. 3e) confirms the presence of DMA(lll) in the sample (96). Two other research groups have recently also found MMA(lll) and DMA(llI) in human urine samples (123,124). 

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