37 research outputs found
Compact groups in the UZC galaxy sample
Applying an automatic neighbour search algorithm to the 3D UZC galaxy
catalogue (Falco 1999) we have identified 291 compact groups (CGs) with
redshifts between 1000 and 10000 km/s. The sample is analysed to investigate
whether Triplets display kinematical and morphological characteristics similar
to higher order CGs (Multiplets). It is found that Triplets constitute low
velocity dispersion structures, have a gas-rich galaxy population and are
typically retrieved in sparse environments. Conversely Multiplets show higher
velocity dispersion, include few gas-rich members and are generally embedded
structures. Evidence hence emerges indicating that Triplets and Multiplets,
though sharing a common scale, correspond to different galaxy systems. Triplets
are typically field structures whilst Multiplets are mainly subclumps (either
temporarily projected or collapsing) within larger structures. Simulations show
that selection effects can only partially account for differences, but
significant contamination of Triplets by field galaxy interlopers could
eventually induce the observed dependences on multiplicity.Comment: 13 pages, 12 figures. The file is in latex (A & A style) format. The
figures are in postscript. A & A accepte
Comprehensive Monitoring of Wildfires in Europe: The European Forest Fire Information System (EFFIS)
Geometries of Light and Shadows, from Piero della Francesca to James Turrell
This chapter addresses the problem of representing light and shadow in the artistic culture, from its uncertain beginnings, related to the studies on conical linear perspective in the Fifteenth Century, to the applications of light projection in the installations of contemporary art.
Here are examined in particular two works by two artists, representing two different conceptual approaches to the perception and symbolism of light and shadow. The first is the so-called Brera Madonna by Piero della Francesca, where the image projected from a luminous radiation is employed with a narrative purpose, supporting the apparently hidden script of the painting and according to the artist\u2019s own speculations about perspective as a means to clarify the phenomenal world.
The second is one of James Turrell\u2019s Dark Spaces installations, where quantum electrodynamics interpretation of light is taken into account: for Turrell, light is physical and thus can shape spaces where the visitors, or viewers, can \u201csee themselves seeing.\u201d In his body of work, perceptual deceptions are carefullyproduced by the interaction of the senses with his phenomenal staging of light and darkness, but a strong symbolic component is always present, often related to his own speculative interests.
In both cases, light and shadow, through their geometries, emphasize both phenomenal and spiritual contents of the work of art, intended as a device to expand the perception and the knowledge of the viewer
Analisi Delle Complicanze Intra- E Post-Operatorie Della Chemioterapia Neoadiuvante M.V.C. Nel Carcinoma Vescicale Infiltrante
Constraint on a Varying Proton-Electron Mass Ratio 1.5 Billion Years after the Big Bang
A molecular hydrogen absorber at a lookback time of 12.4 billion years, corresponding to 10% of the age of the Universe today, is analyzed to put a constraint on a varying proton-electron mass ratio, μ. A high resolution spectrum of the J1443+2724 quasar, which was observed with the Very Large Telescope, is used to create an accurate model of 89 Lyman and Werner band transitions whose relative frequencies are sensitive to μ, yielding a limit on the relative deviation from the current laboratory value of Δμ/μ=(-9.5±5.4stat±5.3syst)×10-6