Ni0.3Co2.7O4 spinel particles/polypyrrole composite electrode: Study by X-ray photoelectron spectroscopy

In this work we have studied the multilayered polypyrrole/oxide composite electrode on glassy carbon having the structure GC/PPy/PPy(Ni0.3Co2.7O4)/PPy, in which the spinel oxide Ni0.3Co2.7O4 is known to be an electrocatalyst of the oxygen reduction reaction in alkaline medium. The successive GC/PPy, GC/PPy/PPy(Ni0.3Co2.7O4) and GC/PPy/PPy(Ni0.3Co2.7O4)/PPy parts of the electrode were examined by X-ray photoelectron spectroscopy. The results indicate that the electronic structure of the PPy is independent of the thickness of the PPy used to prepare the electrodes. The XPS data also show that cobalt is present in both divalent and trivalent states. The PPy doping degree by Cl− ions (in terms of the Cl−/N) and the oxide/PPy mass ratio observed by XPS were 19 and 4.5%, respectively.The authors acknowledge the support of CNRS/CONICYT cooperation program (project 10070 and 11949) and CSIC/USACH scientific cooperation. J.L.G. thanks to CONICYT (Fondecyt grant 1020066) and V.G.G. thanks to CONACYT for a doctoral fellowship (SFERE/CONACYT)

2,6-Bis(2,6-diethylphenyliminomethyl)pyridine coordination compounds with cobalt(II), nickel(II), copper(II), and zinc(II): synthesis, spectroscopic characterization, X-ray study and in vitro cytotoxicity

Metals in Catalysis, Biomimetics & Inorganic Material

Development of a small-plant bioassay to assess banana grown from tissue culture for consistent infection by Fusarium oxysporum F. sp. cubense

Two reliable small-plant bioassays were developed using tissue-cultured banana, resulting in consistent symptom expression and infection by Fusarium oxysporum f. sp. cubense (Foc). One bioassay was based on providing a constant watertable within a closed pot and the second used free-draining pots. Culture medium for spore generation influenced infectivity of Foc. Inoculation of potted banana by drenching potting mix with a conidial suspension, consisting mostly of microconidia, few macroconidia and no chlamydospores, generated from one-quarter-strength potato dextrose agar + streptomycin sulfate, resulted in inconsistent infection. When a conidial suspension that consisted of all three spore types, microconidia, macroconidia and chlamydospores, prepared from spores generated on carnation leaf agar was used, all plants became infected, indicating that the spore type present in conidial suspensions may contribute to inconsistency of infection. Inconsistency of infection was not due to loss of virulence of the pathogen in culture. Millet grain precolonised by Foc as a source of inoculum resulted in consistent infection between replicate plants. Sorghum was not a suitable grain for preparation of inoculum as it was observed to discolour roots and has the potential to stunt root growth, possibly due to the release of phytotoxins. For the modified closed-pot system, a pasteurised potting mix consisting of equal parts of bedding sand, perlite and vermiculite plus 1 g/L Triabon slow release fertiliser was suitable for plant growth and promoted capillary movement of water through the potting mix profile. A suitable potting mix for the free-draining pot system was also developed

A Solar Axion Search Using a Decommissioned LHC Test Magnet

Previous solar axion searches have been carried out in Brookhaven (1990) and in Tokyo (2000- ), tracking the Sun with a dipole magnet. QCD inspired axions should be produced after the Big Bang, being thus candidates for the dark matter. The Sun is a very useful source of weakly interacting particles for fundamental research. Axions can be produced also in the Sun's core through the scattering of thermal photons in the Coulomb field of electric charges (Primakoff effect). In a transverse magnetic field the Primakoff effect can work in reverse, coherently converting the solar axions or other axion-like particles (ALPS) back into X-ray photons in the keV range. The conversion efficiency increases with $(B⋅L)^2$. In the CAST experiment an LHC prototype dipole magnet (B = 9 T and L = 10 m) with straight beam pipes provides a conversion efficiency exceeding that of the two earlier solar axion telescopes by almost a factor of 100. This magnet is mounted on a moving platform and coupled to both gas filled and solid-state low-background X-ray detectors on either end allowing it to observe the Sun for nearly 1.5 hours at both sunrise and sunset. The rest of the day is devoted to background measurements and, because of the Earth motion, to observations of a large portion of the sky. The 43 mm aperture of the LHC magnet beam pipe requires correspondingly large X-ray detectors, implying a large level of noise. To overcome this problem, CAST uses state-of-the-art analog TPC detectors of the Micromegas type, and in addition, for the first time, an X-ray mirror system from the German space program; the converted X-rays are focused to a few mm spot, improving the signal-to-noise ratio significantly over the original CAST proposal and the earlier solar axion telescopes. Recently, CAST has successfully commissioned and took data with a second X-raysoptics from LLNL, using a technology developed for the NuSTAR space mission. CAST has thus reached its optimum axion detection sensitivity, which is about ten times higher than that of the previous experiments, entering for the first time, the axion searches beyond the limit dictated by astrophysical considerations. CAST data have been used to provide new limits on Hidden Sector particles (“paraphotons”). A fifth line installed in CAST, a BaRBE detector being sensitive to a few eV photons, allowed to reach new limits on paraphotons. Revisiting in 2013-2014 the rest mass range below 0.02 eV, CAST could improve its performance for axion-like particles from the Sun, thanks to better performing detectors and the installed second XRT. In addition, with the scheduled lower energy detector threshold, CAST was also able to search for the first time for solar Chameleons (or other as yet not predicted exotica) in an energy region previously inaccessible. Chameleons are candidates for the dark energy in the Universe, eventually the biggest mystery in physics