Formation of Radicals by Mechanical Processes

The application of e.s.r. spectroscopy to the study of radicals formed by mechanical means (grinding, shearing, bending, cutting, etc.) is discussed. Two mechanisms are considered, one being the homolytic breaking of main-chain bonds in polymers, and the other being charge-transfer (tribo-electric effect). The former is thought to occur for high polymers whilst the latter may be important for certain inorganic materials especially ionic solids.

Specific examples are given for the generation of radicals by cutting finger nails and by grinding bone. In both cases, well-defined e.s.r. spectra were obtained for which identifications are offered. Possible implications of the mechanical formation of radicals in bone are considered.     

Tropaeolaceae: 686. TROPAEOLUM SPECIOSUM

Tropaeolum speciosum Poepp. & Endl. is described and illustrated. Its habitat in the wild, and its pollination are discussed, and instructions for its successful cultivation are given.     

The Emperor's new clothes? A comment on

Many diatom-based methods have been proposed in recent years. Besse-Lototskaya et al. (2011) compare some of those developed for assessing inorganic nutrients. However, they fail to address the two questions of greatest interest to those who wish to use such metrics to inform decision-making. These questions are: what is the role of diatom-based trophic metrics in environmental management in Europe in the twenty-first century and do these indices represent causal relationships with underlying pressure gradients? The present economic climate means that Member States of the European Union will look more critically at all methods for assessing freshwater quality and developers need to ensure that their methods are “fit-for-purpose”.     

A new bonding mode for the bicyclic guanidinate, [hpp], in the tetrametallic yttrium oxide cluster, Y4(hpp)8Cl2(μ4-O)

Oxygen incorporation in the product of the reaction between YCl₃ and the lithium salt of 1,3,4,6,7,8-hexahydro-2Hpyrimido[1,2-a]pyrimidine (hppH) afforded the tetrametallic cluster Y₄(hpp)₈Cl₂(μ₄-O), in which four of the guanidinate anions are involved in a previously unreported μ,η²,η²-bridging mode between two metal centres.     

913. MEEHANIA FARGESII var. PEDUNCULATA

Meehania fargesii var. pedunculata (Hemsley) C. Y. Wu, from the mountains of western China, is illustrated. The history and variation in the species is discussed, and suggestions for its successful cultivation are given.