Effect of Bohm potential on a charged gas

Bohm's interpretation of Quantum Mechanics leads to the derivation of a Quantum Kinetic Equation (QKE): in the present work, propagation of waves in charged quantum gases is investigated starting from this QKE. Dispersion relations are derived for fully and weakly degenerate fermions and bosons (these latter above critical temperature), and the differences underlined. Use of a kinetic equation permits investigation of "Landau-type" damping: it is found that the presence of damping in fermion gases is dependent upon the degree of degeneracy, whereas it is always present in boson gases. In fully degenerate fermions a phenomenon appears that is akin to the "zero sound" propagation.Comment: 11 pages, no figures, pdf forma

IRAS 23385+6053: a candidate protostellar massive object

We present the results of a multi-line and continuum study towards the source IRAS 23385+6053,performed with the IRAM-30m telescope, the Plateau de Bure Interferometer, the Very Large Array Interferometer and the James Clerk Maxwell Telescope. The new results confirm our earlier findings, namely that IRAS 23385+6053 is a good candidate high-mass protostellar object, precursor of an ultracompact H$_{II}$ region. The source is roughly composed of two regions: a molecular core $\sim0.03\div0.04$ pc in size, with a temperature of $\sim40$ K and an H$_{2}$ volume density of the order of 10$^{7}$ cm$^{-3}$, and an extended halo of diameter $\leq$0.4 pc, with an average kinetic temperature of $\sim 15$ K and H$_{2}$ volume density of the order of 10$^{5}$ cm$^{-3}$. The core temperature is much smaller than what is typically found in molecular cores of the same diameter surrounding massive ZAMS stars. We deduce that the core luminosity is between 150 and $1.6\times10^{4}L_{\odot}$, and we believe that the upper limit is near the ``true'' source luminosity. Moreover, by comparing the H$_{2}$ volume density obtained at different radii from the IRAS source, we find that the halo has a density profile of the type $n_{\rm H_{2}}\propto r^{-2.3}$. This suggests that the source is gravitationally unstable. Finally, we demonstrate that the temperature at the core surface is consistent with a core luminosity of $10^3 L_{\odot}$ and conclude that we might be observing a protostar still accreting material from its parental cloud, whose mass at present is $\sim 6 M_{\odot}$.Comment: 18 pages, 20 figure

Not a galaxy: IRAS 04186+5143, a new young stellar cluster in the outer Galaxy

We report the discovery of a new young stellar cluster in the outer Galaxy located at the position of an IRAS PSC source that has been previously mis-identified as an external galaxy. The cluster is seen in our near-infrared imaging towards IRAS 04186+5143 and in archive Spitzer images confirming the young stellar nature of the sources detected. There is also evidence of sub-clustering seen in the spatial distributions of young stars and of gas and dust. Near- and mid-infrared photometry indicates that the stars exhibit colours compatible with reddening by interstellar and circumstellar dust and are likely to be low- and intermediate-mass YSOs with a large proportion of Class I YSOs. Ammonia and CO lines were detected, with the CO emission well centred near the position of the richest part of the cluster. The velocity of the CO and NH$_3$ lines indicates that the gas is Galactic and located at a distance of about 5.5 kpc, in the outer Galaxy. Herschel data of this region characterise the dust environment of this molecular cloud core where the young cluster is embedded. We derive masses, luminosities and temperatures of the molecular clumps where the young stars reside and discuss their evolutionary stages.Comment: 14 pages, 15 figure

Growth and equilibrium size of water droplets in air

A model is presented to describe the growth in time of the average water drop in supersaturated air, and predict their radius at equilibrium. Many previous works consider the growth of an isolated drop, whereas in the present work the effect of the presence of a large number of drops, with the ensuing depletion in water content in the surrounding air, is considered: it is shown that the effect of depletion is crucial to obtain the equilibrium radius. Preliminary results, obtained under some simplifying assumptions, are presented: expressions accounting for this depletion effect are given for the time evolution of the liquid-water temperature and of the number of water molecules in the drop and drop radius near equilibrium, and for their asymptotic equilibrium values

A 100 pc Elliptical and Twisted Ring of Cold and Dense Molecular Clouds Revealed by Herschel Around the Galactic Center

Thermal images of cold dust in the Central Molecular Zone of the Milky Way, obtained with the far-infrared cameras on board the Herschel satellite, reveal a ~3 × 10^7 M_☉ ring of dense and cold clouds orbiting the Galactic center. Using a simple toy model, an elliptical shape having semi-major axes of 100 and 60 pc is deduced. The major axis of this 100 pc ring is inclined by about 40° with respect to the plane of the sky and is oriented perpendicular to the major axes of the Galactic Bar. The 100 pc ring appears to trace the system of stable x_2 orbits predicted for the barred Galactic potential. Sgr A⋆ is displaced with respect to the geometrical center of symmetry of the ring. The ring is twisted and its morphology suggests a flattening ratio of 2 for the Galactic potential, which is in good agreement with the bulge flattening ratio derived from the 2MASS data

TOWARDS A DIGITAL ARCHAEOLOGICAL ARCHIVE: THE CASE STUDY OF THE ARTEFACTS OF THE AREA OF FORI IMPERIALI

Abstract. The following research aims to exploit the low-cost technologies, for the survey and mapping of historical archaeology in the Roman context. The main purposes of the research is to implement a large-scale survey campaign to understand the geometry and the materiality of the artefacts examined. Three-dimensional survey from photography, allows an immediate mapping of the materiality, of the degradation and of the architectural elements characteristic of the architecture in question. From the model it is possible to obtain an image that is faithful to the reality that can be the basis for developments in many disciplines such as, for example, in the restoration project, for the material analysis and the mapping of the degradation. The applications for this type of mapping are numerous, one of those proposed in this research concerns the virtual musealisation of historical artifacts. More and more in recent years, museums are exploiting the capabilities of three-dimensional modeling software of architectural elements to interactively convey architectural elements. A methodology of work that in recent archaeological excavations is not based solely on the didactic divulgation of the history of a place, but during the excavation phase on the mapping and cataloging of uncovered finds.</p