14,981 research outputs found
Optimization of Stone Cutting Techniques for the Seismic Protection of Archaeological Sites
Since the beginning of civilization, history tells of the movement of art pieces, monuments and manufacts from site to site. The causes are multiple: the displacements due to the "spoils of war", ordered by kings and emperors, the movements caused by the need for reuse, especially in the early Christian period, and so forth. Considerations about the events of the past, yield a possible strategy to transform this concept into a technique for earthquake prevention of archaeological sites. The seismic safety retrofits have often proven to be scarcely effective, because of the difficulties involved in complex sites. The aim of this study is to analyze an "alternative" method of preventing natural disaster like floods, eruption and earthquakes, through the movimentation of the most representative structural elements of archaeological sites by decomposition of the masonry and marbles [1]. The procedure considers a process of "cutting optimization," calibrated on the characteristics of the specific material that has to be cut and then displaced in safer places (i.e., MEP, "manufact evacuation plan"). This process should not create excessive problems to the structure, and aims to reassembly the manufact in contexts able to guarantee safety through advanced earthquake-resistant expedients. From these considerations, the work develops a procedure to safeguard the archaeological site of Pompei (Naples), through an appropriate analysis of representative portions of the site, aimed to a careful handling and to a proper reconstruction in a safe location, from the seismic point of vie
Influence of disordered porous media in the anomalous properties of a simple water model
The thermodynamic, dynamic and structural behavior of a water-like system
confined in a matrix is analyzed for increasing confining geometries. The
liquid is modeled by a two dimensional associating lattice gas model that
exhibits density and diffusion anomalies, in similarity to the anomalies
present in liquid water. The matrix is a triangular lattice in which fixed
obstacles impose restrictions to the occupation of the particles. We show that
obstacules shortens all lines, including the phase coexistence, the critical
and the anomalous lines. The inclusion of a very dense matrix not only suppress
the anomalies but also the liquid-liquid critical point
Multiphase gas flows in the nearby Seyfert galaxy ESO428-G14
We present ALMA rest-frame 230 GHz continuum and CO(2-1) line observations of
the nearby Compton-thick Seyfert galaxy ESO428-G14, with angular resolution 0.7
arcsec (78 pc). We detect CO(2-1) emission from spiral arms and a
circum-nuclear ring with 200 pc radius, and from a transverse gas lane with
size of pc, which crosses the nucleus and connects the two portions
the circumnuclear ring. The molecular gas in the host galaxy is distributed in
a rotating disk with intrinsic circular velocity km/s,
inclination deg, and dynamical mass within a radius of kpc. In the inner 100 pc region CO is
distributed in a equatorial bar, whose kinematics is highly perturbed and
consistent with an inflow of gas towards the AGN. This inner CO bar overlaps
with the most obscured, Compton-thick region seen in X-rays. We derive a column
density of in this region,
suggesting that molecular gas may contribute significantly to the AGN
obscuration. We detect a molecular outflow with a total outflow rate , distributed along a bi-conical structure with
size of pc on both sides of the AGN. The bi-conical outflow is also
detected in the emission line at 2.12 m, which traces a warmer
nuclear outflow located within 170 pc from the AGN. This suggests that the
outflow cools with increasing distance from the AGN. We find that the hard
X-ray emitting nuclear region mapped with Chandra is CO-deprived, but filled
with warm molecular gas traced by - thus confirming that the hard
(3-6 keV) continuum and Fe K emission are due to scattering from dense
neutral clouds in the ISM.Comment: Submitted to Ap
Diffusion anomaly and dynamic transitions in the Bell-Lavis water model
In this paper we investigate the dynamic properties of the minimal Bell-Lavis
(BL) water model and their relation to the thermodynamic anomalies. The
Bell-Lavis model is defined on a triangular lattice in which water molecules
are represented by particles with three symmetric bonding arms interacting
through van der Waals and hydrogen bonds. We have studied the model diffusivity
in different regions of the phase diagram through Monte Carlo simulations. Our
results show that the model displays a region of anomalous diffusion which lies
inside the region of anomalous density, englobed by the line of temperatures of
maximum density (TMD). Further, we have found that the diffusivity undergoes a
dynamic transition which may be classified as fragile-to-strong transition at
the critical line only at low pressures. At higher densities, no dynamic
transition is seen on crossing the critical line. Thus evidence from this study
is that relation of dynamic transitions to criticality may be discarded
Baryon loading and the Weibel instability in gamma-ray bursts
The dynamics of two counter-streaming electron-positron-ion unmagnetized
plasma shells with zero net charge is analyzed in the context of magnetic field
generation in GRB internal shocks due to the Weibel instability. The effects of
large thermal motion of plasma particles, arbitrary mixture of plasma species
and space charge effects are taken into account. We show that, although thermal
effects slow down the instability, baryon loading leads to a non-negligible
growth rate even for large temperatures and different shell velocities, thus
guaranteeing the robustness and the occurrence of the Weibel instability for a
wide range of scenarios.Comment: 6 pages, 4 figures. Accepted for publication in MNRA
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