1,721,089 research outputs found
FEKO/GRASP Simulations of Super-Resolution with a Reflective Metal-Mesh Toraldo Pupil on the 32m Medicina Radio Telescope
No full textWe are currently carrying out a project devoted to the implementation of super-
resolution on single-dish radio telescopes, aimed to obtain an angular resolution better than
the classical diffraction limit. A feasible method to achieve this goal consists of using variable
transmittance pupils, and specifically the simplest version of these pupils which consists of a
binary phase shift mask, also known as Toraldo pupil (TP). An attractive method to design
and fabricate TPs is to use the metal mesh-filter technology, which allows to fabricate both
transmissive and reflective TPs. In this work we show, through EM numerical simulations,
that super-resolution can indeed be achieved on a Cassegrain radio telescope using a previously
designed and tested reflective mesh-filter TP
ElettroChimioTerapia (ECT) sec. Nordenstroem nelle neoplasie pancreatiche: tecnica per l'applicazione perioperatoria
No full textThe structure and dynamics of the dense cores in the Perseus molecular cloud complex
No full textWe have produced wide-field (⪆0.1 deg2) images of the molecular gas around the dense cores observed by Ladd et al. (\cite{ladd94}) in the Perseus cloud complex in various CO (CO(1-0), 13CO(1-0), C18O(1-0)) and CS (CS(2-1), C34S(2-1)) isotopomers, and N2H+(1-0), using the 16-element focal plane array operating at a wavelength of 3 mm at the Five College Radio Astronomy Observatory. We also performed mosaic observations in the N2H+(1-0) line and in the adjacent 3 mm continuum with the OVRO interferometer. Only within one of the observed cores we unambiguously detected a 3 mm continuum compact source with the interferometer. The single-dish large-scale maps of the densest gas, which in Perseus is concentrated within two large filamentary structures roughly aligned along a NE-SW axis, allowed us to analyse the spatial and kinematical properties of the cores and of the surrounding ambient gas. In the PER4/PER5 and PER7 regions we find that the large-scale and core velocity gradients have the same sign and similar magnitudes. In at least three cases we then find pairs of nearby cores with differences in the CS and N2H+ emission and in the line profile, which may have been caused by evolutionary effects. The small fraction of cores with compact continuum sources, the chemical differentiation and the inward motions observed suggest that we are observing objects in a phase preceeding the collapse and the formation of stars
Constraints on star formation theories from the Serpens molecular cloud and protocluster
No full textWe have mapped the large-scale structure of the Serpens cloud core
using moderately optically thick (13CO(1–0) and
CS(2–1)) and optically thin tracers (C18O(1–0), C34S(2–1), and
N2H+(1–0)), using the 16-element focal plane array
operating at a wavelength of 3 mm at the Five College Radio Astronomy
Observatory.
Our main goal was to study the large-scale distribution of the molecular
gas in the Serpens region and
to understand its relation with the denser
gas in the cloud cores, previously studied at high angular resolution.
All our molecular tracers show two main gas condensations, or sub-clumps,
roughly corresponding to the North-West and South-East clusters
of submillimeter continuum sources.
We also carried out a kinematical study of the Serpens cloud.
The 13CO and C18O(1–0) maps of the centroid velocity show an increasing,
smooth gradient in velocity from East to West, which we think
may be caused by a global rotation of the Serpens molecular cloud whose
rotation axis is roughly aligned in the SN direction.
Although it appears that
the cloud angular momentum is not sufficient for being dynamically important
in the global evolution of the cluster, the fact that the observed
molecular outflows are roughly aligned with it may suggest a link between
the large-scale angular momentum and the circumstellar disks around
individual protostars in the cluster.
We also used the normalized centroid velocity difference as an infall
indicator. We find two large regions of the map, approximately coincident
with the SE and NW sub-clumps, which are undergoing an infalling motion.
Although our evidence is not conclusive, our data appear to be in qualitative
agreement with the expectation of a slow contraction followed by a rapid
and highly efficient star formation phase in localized high density regions
Archeopalinologia in siti archeologici di Castel San Pietro Terme (Bologna): il paesaggio vegetale dall’Età Romana al Basso Medioevo
No full textNell'ambito degli scavi della Soprintendenza per i Beni Archeologici dell'Emilia Romagna a Castel Sanpietro Terme (Bologna) in Piazza XX settembre e nell'area dell'ex cinema teatro Bios, sono stati effettuati studi archeopaliniologici per ricostruire il paesaggio vegetale e l'ambiente coevo ai siti indagati nei periodi romano, Tardo antico e medievale. Il paesaggio vegeale risulta piuttosto aperto e costantemente frequentato in tutti i periodi
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Reflective Toraldo pupil for high-resolution millimeter-wave astronomy
Full text linkA novel, to the best of our knowledge, beam-shaping reflective surface for high-resolution millimeter/ submillimeter-wave astronomy instruments is presented. The reflector design is based on Toraldo’s superresolution principle and implemented with annulated binary-phase coronae structure inspired by the achromatic magnetic mirror approach. A thin, less than half a free-space wavelength, reflective Toraldo pupil device operated in the W-band has been fabricated using mesh-filter technology developed at Cardiff University. The device has been characterized on a quasi-optical test bench and demonstrated expected reduction of the beam width upon reflection at oblique incidence, while featuring a sidelobe level lower than −10 dB. The proposed reflective Toraldo pupil structure can be easily scaled for upper millimeter and infrared frequency bands as well as designed to transform a Gaussian beam into a flat-top beam with extremely low sidelobe level
Il Laboratorio Archeoambientale del Centro Agricoltura Ambiente “Giorgio Nicoli”: dalla ricerca alla professione.
No full textIl CAA Giorgio Nicoli si occupa di ricerca e sperimentazione in campo ambientale e ha sviluppato diversi settori di ricerca che operano sia a livello nazionale che internazionale. Nel 1999 è stato attivato un nuovo settore di ricerca inerente indagini palinologiche e archeoambientali avvalendosi della professionalità di numerosi ricercatori
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