Break up of spectator residues at ultra-relativistic energies

The 200GeV/u sulfur beam available at CERN was used to bombard a 1.5 mg/cm Au target. Light nuclei were detected at 60° in the laboratory using a silicon telescope. The shape of the inclusive atomic number distribution of intermediate mass fragments with an atomic numberZ ≥ 2 looks different from the one measured on theO +Au system at the same bombarding energy.     

Respiratory adaptations to the deep-sea hydrothermal vent environment: the case of Segonzacia mesatlantica, a crab from the Mid-Atlantic Ridge

Segonzacia mesatlantica (Crustacea; Decapoda; Brachyura) is the only endemic crab species known from the Mid-Atlantic Ridge (MAR) hydrothermal vents. Known from all explored sites in the Atlantic, its wide distribution makes this species a model to study physiological adaptation, and specifically respiratory strategies. Native haemocyanin (Hc) comprises four non-covalent associations in equilibrium formed by monomers, hexamers, dodecamers and octadecamers made up of approximately 75 kDa polypeptide chains. Four different amino acid chains are observed with a molecular mass ranging from 75,234 to 75,972 Da. Experiments carried-out under pressure suggested that the percentage of monomer increased in the haemolymph under hypoxic condition. We have also observed a shift of the proportion of the two dodecamer series, suggesting a rapid modification of the Hc phenotype between hypoxic and hyperoxic conditions. Native Hc possesses a high oxygen affinity ( P50 = 2.2 Torr at 15 degrees C and pH 7.5), a large Bohr effect (Deltalog P50 / DeltapH approximately -2.7) and a slightly reverse temperature effect (DeltaH = +17.19 kJ mol(-1). The composition of Segonzacia haemolymph is similar to that of other littoral species except for the large enrichment in free copper and zinc. As for other species from hydrothermal vent sites, Segonzacia haemolymph possesses a higher buffer capacity than littoral species. Moreover, species from the hydrothermal vent decapods from Pacific hydrothermal vent that encounter higher CO2 content in their environment have a higher buffer capacity than Atlantic vent species. The results presented are discussed in relation with the physico-chemical characteristics of the hydrothermal vent environment.     

Thermoregulation and spectral selectivity of the tropical butterfly Prepona meander: a remarkable example of temperature auto-regulation

In butterflies favouring direct absorption of solar energy through their wings, the absorption by the black areas situated at the wing bases provides the body with the most part of the exogenous energy. For the studied butterfly (Archeoprepona meander), absorption is very high over the whole solar spectrum (0.95). This absorption is due to both the dendritic structure of the scales and the melanin pigments. In the infrared range, the absorptivity reveals two strong peaks at 3 m and 6 m and then remains more or less constant at a relatively high value (0.4) up to 25 m. This situation contains the outline for a remarkable self-regulation phenomenon of the radiative balance, allowing the stabilization of temperature in the survival area of the butterfly. The first absorption peak, centred on 3 m, i.e. between the solar irradiance and the thermal emission spectra, is not involved in the radiative balance at these temperatures. However, the second, on the edge of the emission spectrum, plays a key role as a thermal regulator. Its marginal situation is such that, according to the wing temperature, it overlaps or not the emission spectrum, modifying the collector efficiency, and thus the temperature. PACS 44.40.+a; 78.20.Ci; 78.40.-q     

Synthesis of new artemisinin-derived dimers by self-cross-metathesis reaction

[reaction: see text] New artemisinin-derived dimers, fluorinated or not, have been prepared by a self-cross metathesis reaction in the presence of first- or second-generation ruthenium catalysts without degradation of the endoperoxide bridge and with a good E/Z selectivity (up to 100:0).     

63Cu NMR evidence for enhanced antiferromagnetic correlations around Zn impurities in YBa2Cu3O6.7

Doping the high- T(c) superconductor YBa2Cu3O6.7 with 1.5% of nonmagnetic Zn impurities in CuO2 planes is shown to produce a considerable broadening of 63Cu NMR spectra, as well as an increase of low-energy magnetic fluctuations detected in 63Cu spin-lattice relaxation measurements. A model-independent analysis demonstrates that these effects are due to the development of staggered magnetic moments on many Cu sites around each Zn and that the Zn-induced moment in the bulk susceptibility might be explained by this staggered magnetization. Several implications of these enhanced antiferromagnetic correlations are discussed.     

A laser fluorimeter for direct cardiac metabolism investigation

We have developed a device which includes two laser sources (nitrogen and dye lasers), an optical system, an optical fibre able to transmit both ultra-violet and infra-red light, photoreceivers, and an analogue circuit feeding a microcomputer in order to perform an in situ and on line study of NADH/NAD ratios by fluorimetry.The paper includes the scientific basis of the method, the characteristics of each part of the apparatus and possible applications to the study of cardiac metabolism or any organ that can be reached through catheterism, fibrescopy or simple transcutaneous puncture. Examples of experiments carried out to appreciate the effects of anoxia or ischemia on the tissular NADH level are presented.