A snapshot of the inner dusty regions of a RCrB-type variable

R Coronae Borealis variable stars are suspected to sporadically eject optically thick dust clouds causing, when one of them lies on the line-of-sight, a huge brightness decline in visible light. Mid-infrared interferometric observations of RYSgr allowed us to explore the circumstellar regions very close to the central star (~20-40 mas) in order to look for the signature of any heterogeneities. Using the VLTI/MIDI instrument, five dispersed visibility curves were recorded with different projected baselines oriented towards two roughly perpendicular directions. The large spatial frequencies visibility curves exhibit a sinusoidal shape whereas, at shorter spatial frequencies visibility curves follow a Gaussian decrease. These observations are well interpreted with a geometrical model consisting in a central star surrounded by an extended circumstellar envelope in which one bright cloud is embedded. Within this simple geometrical scheme, the inner 110AU dusty environment of RYSgr is dominated at the time of observations by a single dusty cloud which, at 10mic represents ~10% of the total flux of the whole system. The cloud is located at about 100stellar radii from the centre toward the East-North-East direction (or the symmetric direction with respect to centre) within a circumstellar envelope which FWHM is about 120stellar radii. This first detection of a cloud so close to the central star, supports the classical scenario of the RCrB brightness variations in the optical spectral domain

Neutron scattering study of a quasi-2D spin-1/2 dimer system Piperazinium Hexachlorodicuprate under hydrostatic pressure

We report inelastic neutron scattering study of a quasi-two-dimensional S=1/2 dimer system Piperazinium Hexachlorodicuprate under hydrostatic pressure. The spin gap {\Delta} becomes softened with the increase of the hydrostatic pressure up to P= 9.0 kbar. The observed threefold degenerate triplet excitation at P= 6.0 kbar is consistent with the theoretical prediction and the bandwidth of the dispersion relation is unaffected within the experimental uncertainty. At P= 9.0 kbar the spin gap is reduced to 0.55 meV from 1.0 meV at ambient pressure.Comment: 4 pages, 5 figure

Spectral classification and properties of the O Vz stars in the Galactic O-Star Spectroscopic Survey (GOSSS)

On the basis of the Galactic O-Star Spectroscopic Survey (GOSSS), a detailed systematic investigation of the O Vz stars is presented. The currently used spectral classification criteria are rediscussed, and the Vz phenomenon is recalibrated through the addition of a quantitative criterion based on the equivalent widths of the He I 4471, He II 4542, and He II 4686 spectral lines. The GOSSS O Vz and O V populations resulting from the newly adopted spectral classification criteria are comparatively analyzed. The locations of the O Vz stars are probed, showing a concentration of the most extreme cases toward the youngest star forming regions. The occurrence of the Vz spectral peculiarity in a solar-metallicity environment, as predicted by the fastwind code, is also investigated, confirming the importance of taking into account several processes for the correct interpretation of the phenomenon.Comment: Accepted for publication in The Astronomical Journa

AN ITALIAN VIEW OF ENTREPRENEURSHIP : INTERVIEW WITH ALBERTO MARTINELLI

Alberto Martinelli \ue9 professor de Sociologia Econ\uf4mica e Ci\uea ncia Pol\uedtica na Universit\ue0 degli Studi di Milano (Universidade de Mil\ue3o). Tamb\ue9m leciona Sociologia na Universit\ue0 Bocconi e trabalhou em outras universidades, como as de Berkeley, Stanford e New York. Suas \ue1reas de pesquisa incluem empreendedorismo, rela\ue7\uf5es internacionais e pol\uedticas sociais. Martinelli \ue9 autor de v\ue1rios artigos e livros, dentre os quais Global Modernization (Sage, 2005), Il Bilancio Sociale (com A. Chiesi e M. Pellegatta, Il Sole/24 ore, 2000), Recent Social Trends in Italy (com A. Chiesi e S. Stefanizzi, McGill- Queen\u2019s University Press, 1999), International Markets and Global Firms (Sage, 1991) e Economy and Society (organizado com N. J. Smelser, Sage, 1990). Martinelli veio ao Brasil para proferir a palestra de abertura do XXXI Encontro da ANPAD no Rio de Janeiro. A entrevista que se segue, realizada ainda na It\ue1lia, aborda o campo do Empreendedorismo e sua rela\ue7\ue3o com a Sociologia Econ\uf4mica, imigra\ue7\ue3o, e se estende a quest\uf5es de global governance e rela\ue7\uf5es internacionais, temas com os quais vem trabalhando na Universidade de Mil\ue3o

Effects of leaf removal and shoot trimming on physiological and agronomic characteristics of Syrah grapevine in Northeast Brazil: preliminary results.

The São Francisco Valley, Northeast Brazil, is one of the most important wine regions with tropical conditions in the world. lt is located between parallels 8 and 1OoS, with an average annual temperature of 26.5 OC and 3,000 hours of sunshine per year. This work shows preliminary results on physiological and agronomic characteristics of Syrah vines.subjected to the practices of leaf removal and shoot trimming. The physiological and agronomical characteristics evaluated were the following: mass of cluster, mass of canes after pruning, mass of fresh and dry leaves, net photosynthesis (An), stomatal conductance (gs), intrinsic water use eficience (WUEi), leaf area (LA) and specific leaf area (SLA). The treatments did not show difJerences related to net photosynthesis (An), stomatal conductance (gs) and intrinsic water use ejJiciency (WUEi). The initial measurements of leaf area showed no difJerence between treatments. The individual leaf area was initially a.ffected by treatments, but during ripening these e.ffects were not revealed in the experimento Reverse e.ffects were observed for specific leaf area, which proved not to be a.ffected by treatments during the immature cluster phenological phase. The studies should be continued for three more seasons .in order to understand how the canopy management of Syrah, growing in a tropical environment, can injluence the agronomical and physiological plant behavior, and the implications for the quality of grapes and wines