Helical stereochemistry and chiral apple halves. 2. La coupe du roi via double helical complexation using oligo(bipyridine) strands and Cu(I)/Ag(I)

Oligo(bipyridine) strands and Cu(I)/Ag(I) form duplexes having a 2₁-screw coincidental with a C₂-axis. A segment containing a complete turn of the duplex can be considered to be a coupe du roi ensemble of two homochiral strands. Moreover, for D_2d symmetry monocationic Cu(I) complexes of bipyridine trimers and pentamers, addition of the requisite Cu(I) cations is a true chemical example of la coupe du roi. In this reaction, an achiral monocationic complex is converted into a multiple-cationic duplex of two homochiral and homotopic 2₁-helical halves. The chirality of the resulting duplex is a function of the particular set of bipyridine enantiotopic faces which are used for binding the additional cations. © 1993 Wiley-Liss, Inc.     

Discovery of a new fossil soldier beetle in Eocene Baltic amber,with the establishment of the new tribe Cacomorphocerini

Eocene forest ecosystems can be considered as rich biodiversity hotspots regarding soldier beetles (family Cantharidae). Paleogene European ambers, for instance, comprised many genera that are still extant in Europe, but also extinct forms and lineages such as the tribe established herein, or the tribe Mimoplatycini Kazantsev, 2013 that mimics the lycids. In this note, the authors describe Cacomorphocerus wiszniewskii sp. nov., and the new tribe Cacomorphocerini tri. nov. is proposed for Cacomorphocerus Schaufuss, 1892 and Sucinocantharis Ku?ka and Kania, 2010. The new tribe is characterized by antennae with 12 or 16 articles, with saucer-shaped or dilated central antennomeres and is distributed in Eocene Baltic and Rovno amber. Furthermore, Cacomorphocerus is transferred from the subfamily Dysmorphocerinae Brancucci, 1980 to Cantharinae Imhoff, 1856.     

Documents pour servir à la reconstitution de la fronde chez certaines Neuroptéridées

Some datas recently collected are presented to show that the frond in the genus Neuropteris, built on a pseudopennate sympodial dichotomous type, eventually bears, at least in some species, a certain number of lateral portions below the general ending as an apical bifurcation.     

Les vagues de peuplements humains au Pléistocène inférieur et moyen dans le bassin de la Loire moyenne, région Centre, France. Apports de l’étude des formations fluviatiles

Evidence of earliest human settlements had been searched in the alluvial formations laid down in the Middle Loire Basin. Many stepped sheets deposited during the successive interglacial-glacial quaternary cycles are studied in four valleys of the Loire tributaries: the Creuse, Indre, Cher and Loir rivers. These sandy remnants are systematically dated, using the Electron Spin Resonance method applied on bleached fluvial quartz. Five settlements which contain very Early Palaeolithic industries with Mode 1 technology were occupied during the Lower Pleistocene. About eighty sites with hand-axe assemblages are observed in Middle Pleistocene remnants; nine of these are described in this paper. The results theorize that the geographical center of France (47°N) would be reached by two influxes of human populations with an interval around 400 years, because major climatic pejorations, particularly at the end of the Lower Pleistocene. These two populations produced lithic industries with many differences in supply of raw materials and in techniques of striking. Not any typologic link had been observed joining the two industrial unities.