Cluster stability driven by quantum fluctuations

By means of an accurate path-integral Monte Carlo we investigate a two-dimensional ensemble of particles interacting via a Lifshitz-Petrich-Gaussian potential. In particular, analysing structures described by a commensurate ratio between the two wave numbers that mark the pattern, the Lifshitz-Petrich-Gaussian boson model may display a stable and well-defined stripe phase lacking any global phase coherence but featuring a superfluid signal along the stripe direction only. Upon increasing quantum fluctuations and quantum-mechanical exchange of bosons, the double-degeneration of the negative minima in the Fourier transform of the potential is removed at the expense of a density modulation peculiar to a cluster triangular crystal. We also show that this last structure possess all features adhering to the definition of a supersolid phase.Comment: 7 pages, 6 figure

Absence of Superfluidity in 2D Dipolar Bose Striped Crystals

We present results of computer simulations at low temperature of a two-dimensional system of dipolar bosons, with dipole moments aligned at an arbitrary angle with respect to the direction perpendicular to the plane. The phase diagram includes a homogeneous superfluid phase, as well as triangular and striped crystalline phases, as the particle density and the tilt angle are varied. In the striped solid, no phase coherence among stripes and consequently no ``supersolid" phase is found, in disagreement with recent theoretical predictions.Comment: Accepted for publication as a Rapid Communication in the Journal of Low Temperature Physic

A superfluid-droplet crystal and a free-space supersolid in a dipole-blockaded gas

A novel supersolid phase is predicted for an ensemble of Rydberg atoms in the dipole-blockade regime, interacting via a repulsive dipolar potential "softened" at short distances. Using exact numerical techniques, we study the low temperature phase diagram of this system, and observe an intriguing phase consisting of a crystal of mesoscopic superfluid droplets. At low temperature, phase coherence throughout the whole system, and the ensuing bulk superfluidity, are established through tunnelling of identical particles between neighbouring droplets.Comment: 4 pages, 4 figure

Quantum Bubbles in Microgravity

The recent developments of microgravity experiments with ultracold atoms have produced a relevant boost in the study of shell-shaped ellipsoidal Bose-Einstein condensates. For realistic bubble-trap parameters, here we calculate the critical temperature of Bose-Einstein condensation, which, if compared to the one of the bare harmonic trap with the same frequencies, shows a strong reduction. We simulate the zero-temperature density distribution with the Gross-Pitaevskii equation, and we study the free expansion of the hollow condensate. While part of the atoms expands in the outward direction, the condensate self-interferes inside the bubble trap, filling the hole in experimentally observable times. For a mesoscopic number of particles in a strongly interacting regime, for which more refined approaches are needed, we employ quantum Monte Carlo simulations, proving that the nontrivial topology of a thin shell allows superfluidity. Our work constitutes a reliable benchmark for the forthcoming scientific investigations with bubble traps.Comment: 7 pages, 7 figures; published versio

Corrigendum to "Co-seismic surface effects from very high resolution panchromatic images: the case of the 2005 Kashmir (Pakistan) earthquake" published in Nat. Hazards Earth Syst. Sci., 11, 931–943, 2011

No abstract available

The case of the 2005 Kashmir earthquake

The use of Very High Resolution (VHR) satellite panchromatic image is nowadays an effective tool to detect and investigate surface effects of natural disasters. We specifically examined the capabilities of VHR images to analyse earthquake features and detect changes based on the combination of visual inspection and automatic classification tools. In particular, we have used Quickbird (0.6m spatial resolution) images for detecting the three main coseismic surface features: damages, ruptures and landslides. The present approach has been applied to the 8 October 2005, Mw7.6 Kashmir, Pakistan, earthquake. We have focused our study in and around the main urban areas hit by the above earthquake specifically at Muzaffarabad and Balakot towns. The automatic classification techniques provided the best results wherever dealing with the damage to man-made structures and landslides. On the other hand, the visual inspection method demonstrated in addressing the identification of rupture traces and associated features. The synoptic view (concerning landslide, more than 190 millions of pixels have been automatically classified), the spatiotemporal sampling and the fast automatic damage detection using satellite images provided a reliable contribution to the prompt response during natural disaster and for the evaluation of seismic hazard as well

Spatial distribution of arsenic, uranium and vanadium in the volcanic-sedimentary aquifers of the Vicano–Cimino Volcanic District (Central Italy)

Arsenic concentrations were analysed for 328 water samples collected in the Vicano–Cimino Volcanic District (VCVD), an areawhere severe contamination of groundwater has become a serious problemfollowing the recent application of the EU Directive on the maximum allowable concentration level for As in drinking waters. In addition, uranium and vanadium concentrations were also analysed in light of the enhanced interest on their environmental toxicity. Waters were collected from springs and wells fed by cold and shallow volcanic–sedimentary aquifers, which locally represent the main drinking water source. Thermal springs (≤63 °C) related to an active hydrothermal reservoir and waters associated with a CO2-rich gas phase of deep provenance were also analysed. The collected data showed that the As concentrations in the shallow aquifers varied in a wide range (0.05–300 μg/L) and were primarily controlled by water–rock interaction processes. High As concentrations (up to 300 μg/L) were measured in springs and wells discharging from the volcanic products, and about 66% exceeded the limit of 10 μg/L for drinkingwaters,whereaswaters circulatingwithin the sedimentary formations displayed much lower values (0.05–13 μg/L; ~4% exceeding the threshold limit). Thermal waters showed the highest As concentrations (up to 610 μg/L) as the result of the enhanced solubility of As-rich volcanic rocks during water–rock interaction processes at high temperatures. Where the local structural setting favoured the rise of fluids from the deep hydrothermal reservoir and their interaction with the shallow volcanic aquifer, relatively higher concentrations were found. Moreover, well overexploitation likely caused the lateral inflow of As-rich waters towards not contaminated areas. Uraniumand vanadiumconcentrations ofwaters circulating in the volcanic rocks ranged from0.01 to 85 μg/L and 0.05 to 62 μg/L, respectively. Less than 2% of analysed samples exceeded theWorld Health Organization's provisional guidelines for U (30 μg/L), while none of them was above the Italian limit value of V in drinking water (120 μg/L). Lower U (0.07–22 μg/L and 0.02–13 μg/L, respectively) and V concentrations (0.05–24 μg/L and 0.18–17 μg/L, respectively) were measured in the water samples from the sedimentary aquifer and thermal waters. Local lithology appeared as the main factor affecting the U and V contents in the shallow aquifers, due to the high concentrations of these two elements in the volcanic formations when compared to the sedimentary units. In addition, high U concentrations were found in correspondence with U mineralization occurring within the VCVD, fromwhich U is released in solution mainly through supergene oxidative alteration. Redox conditions seem to play amajor role in controlling the concentrations of U and V inwaters. Oxidizing conditions characterizing the cold waters favour the formation of soluble U- and V-species, whereas thermal waters under anoxic conditions are dominated by relatively insoluble species. Geostatistical techniques were used to draw contour maps by using variogram models and kriging estimation aimed to define the areas of potential health risk characterized by As, U and V-rich waters, thus providing a useful tool for water management in a naturally contaminated area to local Authorities

Validation of an optical, computer-assisted technique for intraoperative tracking of 3-dimensional canine stifle joint motion

Background: Cranial cruciate ligament (CCL) rupture is the most common orthopedic pathology in dog and in men. In human, optical computer-assisted technique is considered as a repeatable and reliable method for the biomechanical assessment of joint kinematics and laxity in case of CCL surgery. Aim: To evaluate the repeatability and reliability afforded by clinical tests in terms of laxity measured by means of a computer-assisted tracking system in two canine CCL conditions: CCL-Intact, CCL-Deficient. Methods: Fourteen fresh frozen canine stifles were passively subjected to Internal/External (IE) rotation at 120\ub0 of flexion and Cranial drawer test (CC). To quantify the repeatability and the reliability, intra-class correlation coefficient (ICC) and the mean percent error were evaluated (\u394 r %). Results: The study showed a very good intra-class correlation, before and after CCL resection for kinematics tests. It was found a minimum ICC = 0.73 during the IE rotation in CCL-Intact and a maximum value of ICC = 0.97 for the CC displacement in CC-Deficient. IE rotation with CCL-Intact is the condition with the greatest \u394 r % = 14%, while the lowest \u394 r % = 6% was obtained for CC displacement in CCL-Deficient. Conclusion: The presented work underlined the possibility of using a computer-assisted method also for biomechanical studies concerning stifle kinematics and laxity

Mantle wedge dynamics vs crustal seismicity in the Apennines (Italy)

In the Apennines subduction (Italy), earthquakes mainly occur within overriding plate, along the chain axis. The events concentrate in the upper 15 km of the crust above the mantle wedge and focal solutions indicate normal faulting. In the foreland, the seismogenic volume affects the upper 35 km of the crust. Focal solutions indicate prevailing reverse faulting in the northern foreland and strike-slip faulting in the southern one. The deepening of the seismogenic volume from the chain axis to the foreland follows the deepening of the Moho and isotherms. The seismicity above the mantle wedge is associated with uplift of the chain axial zone, volcanism, high CO2 flux, and extension. The upward pushing of the asthenospheric mantle and the mantle-derived, CO2-rich fluids trapped within the crust below the chain axis causes this seismicity. All these features indicate that the axial zone of Apennines is affected by early rifting processes. In northern Italy, the widespread and deeper seismicity in the foreland reflects active accretion processes. In the southern foreland, the observed dextral strike-slip faulting and the lack of reverse focal solutions suggest that accretion processes are not active at present. In our interpretation of the Apennines subduction, the shallower seismicity of the overriding plate is due to the dynamics (uprising and eastward migration) of the asthenospheric wedge