6,953 research outputs found
The rotational shear layer inside the early red-giant star KIC 4448777
We present the asteroseismic study of the early red-giant star KIC 4448777,
complementing and integrating a previous work (Di Mauro et al. 2016), aimed at
characterizing the dynamics of its interior by analyzing the overall set of
data collected by the {\it Kepler} satellite during the four years of its first
nominal mission. We adopted the Bayesian inference code DIAMOND (Corsaro \& De
Ridder 2014) for the peak bagging analysis and asteroseismic splitting
inversion methods to derive the internal rotational profile of the star. The
detection of new splittings of mixed modes, more concentrated in the very inner
part of the helium core, allowed us to reconstruct the angular velocity profile
deeper into the interior of the star and to disentangle the details better than
in Paper I: the helium core rotates almost rigidly about 6 times faster than
the convective envelope, while part of the hydrogen shell seems to rotate at a
constant velocity about 1.15 times lower than the He core. In particular, we
studied the internal shear layer between the fast-rotating radiative interior
and the slow convective zone and we found that it lies partially inside the
hydrogen shell above and extends across the core-envelope
boundary. Finally, we theoretically explored the possibility for the future to
sound the convective envelope in the red-giant stars and we concluded that the
inversion of a set of splittings with only low-harmonic degree , even
supposing a very large number of modes, will not allow to resolve the
rotational profile of this region in detail.Comment: accepted for publication on Ap
3D mosaic documentation using close range photogrammetry
The paper describes the close range photogrammetric survey of a roman mosaic stored at Regional Archaeological Museum âAntonino Salinasâ in Palermo (Italy). The aim of the work is the production of a full-scale representation (scale 1:1) of the mosaic useful for documentation and restoration processes. The research has allowed evaluating limit and potentiality of image-based approach using photogrammetric and computer vision (Structure for Motion) techniques in a context where the metric point of view is a very important factor
Study of GEM-like detectors with resistive electrodes for RICH applications
We have developed prototypes of GEM-like detectors with resistive electrodes
to be used as RICH photodetectors equipped with CsI photocathodes. The main
advantages of these detectors are their intrinsic spark protection and
possibility to operate at high gain (~10E5) in many gases including poorly
quenched ones, allowing for the adoption of windowless configurations in which
the radiator gas is also used in the chamber. Results of systematic studies of
the resistive GEMs combined with CsI photocathodes are presented: its quantum
efficiency, rate characteristics, long-term stability, etc. On the basis of the
obtained results, we believe that the new detector will be a promising
candidate for upgrading the ALICE RICH detectorComment: Presented at the International Workshop RICH-2007, Trieste, Italy,
October 200
La âdimensione oscuraâ. Viaggio dentro Piansano (VT)
Il sottosuolo di Piansano Ăš un incredibile intreccio di cavitĂ , alcune recenti altre forse antiche di millenni, che interessano lâintero odierno edificato e si spingono anche oltre i limiti delle costruzioni.
In tempi recenti, Ăš stato avviato uno studio di dettaglio, strutturato in formato gis-oriented, finalizzato alla conoscenza di tutti gli ipogei (attualmente sono stati mappati oltre 200), sia in termini di estensione e dimensioni, che in relazione alla definizione di tutte le caratteristiche litologiche delle formazioni a spese delle quali sono state realizzate le cavitĂ , senza peraltro trascurare gli aspetti relativi alle loro condizioni statiche ed agli interventi da mettere in atto per la loro messa in sicurezza.
Tutto ciĂČ Ăš stato reso necessario per contrastare gli effetti sugli ipogei stessi dovuti al traffico veicolare, sempre piĂč marcato, alla presenza di impianti tecnologici (fognature, linee idriche, ecc), ma anche a seguito di una maggiore sensibilitĂ nei confronti di quelle problematiche che, nei casi piĂč gravi, possono creare dissesti a danno delle abitazioni, delle strade, dei monumenti e delle strutture di superficie, con conseguente rischio per lâincolumitĂ delle persone e costi aggiuntivi per la collettivitĂ .Underground Piansano is an amazing tangle of caves, either recent or, possibly, thousands of years old, extended within the present-day settlement and even beyond its limits. Recently, a detailed gis-oriented study has been carried out aiming at defining all the underground sites (up to now more than 200 of them have been mapped) in terms of their location and extension, as also related to the lithological characteristics of the hosting formations. Moreover, the aspects concerning their conditions of stability have been also addressed, as well as the related interventions to be put in place as safety measures. This is in order not only to prevent the effects on the underground sites of the increasing traffic and of the presence of technological systems (e.g., sewers, water lines, etc.), but also in light of a greater sensitivity to hazard issues. In fact, the most severe cases of underground instabilities may result into damages to homes, roads, monuments and other surface structures, with consequent risk to the safety of people and additional costs for the community
A cost-effectiveness analysis of different therapies in patients with chronic hepatitis B in Italy
Fan similarity model for the fan-intake interaction problem
Very high bypass ratio turbofans with large fan tip diameter are an effective way of improving the propulsive efficiency of civil aero-engines. Such engines, however, require larger and heavier nacelles, which partially offset any gains in specific fuel consumptions. This drawback can be mitigated by adopting thinner walls for the nacelle and by shortening the intake section. This binds the success of very high bypass ratio technologies to the problem of designing an intake with thin lips and short diffuser section, which is well matched to a low speed fan. Consequently, the prediction of the mutual influence between the fan and the intake flow represents a crucial step in the design process. Considerable effort has been devoted in recent years to the study of models for the effects of the fan on the lip stall characteristics and the operability of the whole installation. The study of such models is motivated by the wish to avoid the costs incurred by full, three-dimensional (3D) computational fluid dynamics (CFD) computations. The present contribution documents a fan model for fanâintake computations based on the solution of the double linearization problem for unsteady, transonic flow past a cascade of aerofoils with finite mean load. The computation of the flow in the intake is reduced to a steady problem, whereas the computation of the flow in the fan is reduced to one steady problem and a set of solutions of the linearized model in the frequency domain. The nature of the approximations introduced in the fan representation is such that numerical solutions can be computed inexpensively, while the main feature of the flow in the fan passage, namely the shock system and an approximation of the unsteady flow encountered by the fan are retained. The model is applied to a well-documented test case and compares favorably with much more expensive 3D, time-domain computations
Fan similarity model for the fan-intake interaction problem
Very high bypass ratio turbofans with large fan tip diameter are an effective way of improving the propulsive efficiency of civil aero-engines. Such engines, however, require larger and heavier nacelles, which partially offset any gains in specific fuel consumptions. This drawback can be mitigated by adopting thinner walls for the nacelle and by shortening the intake section. This binds the success of very high bypass ratio technologies to the problem of designing an intake with thin lips and short diffuser section, which is well matched to a low speed fan. Consequently, the prediction of the mutual influence between the fan and the intake flow represents a crucial step in the design process. Considerable effort has been devoted in recent years to the study of models for the effects of the fan on the lip stall characteristics and the operability of the whole installation. The study of such models is motivated by the wish to avoid the costs incurred by full, threedimensional (3D) computational fluid dynamics (CFD) computations. The present contribution documents a fan model for fan-intake computations based on the solution of the double linearization problem for unsteady, transonic flow past a cascade of aerofoils with finite mean load. The computation of the flow in the intake is reduced to a steady problem, whereas the computation of the flow in the fan is reduced to one steady problem and a set of solutions of the linearized model in the frequency domain. The nature of the approximations introduced in the fan representation is such that numerical solutions can be computed inexpensively, while the main feature of the flow in the fan passage, namely the shock system and an approximation of the unsteady flow encountered by the fan are retained. The model is applied to a well-documented test case and compares favorably with much more expensive 3D, time-domain computations.</p
Beneficial effect of sodium dichloroacetate in muscle cytochrome C oxidase deficiency
Beneficial Effect of Sodium Dichloroacetate in Muscle Cytochrome C Oxidase Deficienc
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Annealing studies of visible light emission from silicon nanocrystals produced by implantation
The annealing behavior of silicon implanted SiO{sub 2} layers is studied using continuous and time-gated photoluminescence (PL). Two PL emission bands are observed. A band centered at 560 nm is present in as implanted samples and it is still observed after 1000 {degrees}C annealing. The emission time is fast (0.2 -2 ns). A second band centered at 780 nm further increases when hydrogen annealing was performed. The emission time is long (1 {mu}s - 0.3 ms)
Two-photon excitation and relaxation of the 3d-4d resonance in atomic Kr
Two-photon excitation of a single-photon forbidden Auger resonance has been observed and investigated using the intense extreme ultraviolet radiation from the free electron laser in Hamburg. At the wavelength 26.9 nm (46 eV) two photons promoted a 3d core electron to the outer 4d shell. The subsequent Auger decay, as well as several nonlinear above threshold ionization processes, were studied by electron spectroscopy. The experimental data are in excellent agreement with theoretical predictions and analysis of the underlying multiphoton processes
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