Local Site Behaviour in the 1976 Friuli Earthquake

Soon after the main shock of Friuli, Italy, May 6th 1976 earthquake, two strong motion recorders accelerographs were installed in two sites about 650 meters distant one from the other. One instrument was installed on hard outcropping rock, the other at the surface of an alluvial deposit 20+25 meters thick underlain by a sloping bedrock. Among the numerous records obtained three aftershocks of magnitude about 6 and hypocentral distance within 20 Km, are investigated by comparing maximum accelerations, durations, Arias intensity and Husid ratios. A new numerical tool is proposed which consists of a series of plots of the Husid ratios of low-pass filtered accelerograms. The numerical tool seems to be very promising since it allows to describe at the same time energy, duration and frequencies content, of a given ground motion. Moreover the application to the records simultaneously obtained at the two stations suggests that it would be more appropriate to define an accelerogram according to the type of behavior shown by the site during a certain earthquake rather than according to the local site characteristics like soft or hard

Liquid-like behavior of supercritical fluids

The high frequency dynamics of fluid oxygen have been investigated by Inelastic X-ray Scattering. In spite of the markedly supercritical conditions ($T\approx 2 T_c$, $P>10^2 P_c$), the sound velocity exceeds the hydrodynamic value of about 20%, a feature which is the fingerprint of liquid-like dynamics. The comparison of the present results with literature data obtained in several fluids allow us to identify the extrapolation of the liquid vapor-coexistence line in the ($P/P_c$, $T/T_c$) plane as the relevant edge between liquid- and gas-like dynamics. More interestingly, this extrapolation is very close to the non metal-metal transition in hot dense fluids, at pressure and temperature values as obtained by shock wave experiments. This result points to the existence of a connection between structural modifications and transport properties in dense fluids.Comment: 4 pages, 3 figures, accepted by Phys. Rev. Let

Pressure-tuning of the electron-phonon coupling: the insulator to metal transition in manganites

A comprehensive understanding of the physical origin of the unique magnetic and transport properties of A_(1-x)A'^xMnO_3 manganites (A = trivalent rare-earth and A' = divalent alkali-earth metal) is still far from being achieved. The complexity of these systems arises from the interplay among several competing interactions of comparable strength. Recently the electron-phonon coupling, triggered by a Jahn-Teller distortion of the MnO_6 octahedra, has been recognised to play an essential role in the insulator to metal transition and in the closely related colossal magneto-resistance. The pressure tuning of the octahedral distortion gives a unique possibility to separate the basic interactions and, at least in principle, to follow the progressive transformation of a manganite from an intermediate towards a weak electron-phonon coupling regime. Using a diamond anvil cell, temperature and pressure-dependent infrared absorption spectra of La_(0.75)Ca_(0.25)MnO_3 have been collected and, from the spectral weight analysis, the pressure dependence of the insulator to metal transition temperature T_IM has been determined for the first time up to 11.2 GPa. The T_IM(P) curve we proposed to model the present data revealed a universality character in accounting for the whole class of intermediate coupling compounds. This property can be exploited to distinguish the intermediate from the weak coupling compounds pointing out the fundamental differences between the two coupling regimes.Comment: 8 pages, 4 figure

A non trivial extension of the two-dimensional Ising model: the d-dimensional "molecular" model

A recently proposed molecular model is discussed as a non-trivial extension of the Ising model. For d=2 the two models are shown to be equivalent, while for d>2 the molecular model describes a peculiar second order transition from an isotropic high temperature phase to a low-dimensional anisotropic low temperature state. The general mean field analysis is compared with the results achieved by a variational Migdal-Kadanoff real space renormalization group method and by standard Monte Carlo sampling for d=3. By finite size scaling the critical exponent has been found to be 0.44\pm 0.02 thus establishing that the molecular model does not belong to the universality class of the Ising model for d>2.Comment: 25 pages, 5 figure

Micro-beam and pulsed laser beam techniques for the micro-fabrication of diamond surface and bulk structures

Micro-fabrication in diamond is involved in a wide set of emerging technologies, exploiting the exceptional characteristics of diamond for application in bio-physics, photonics, radiation detection. Micro ion-beam irradiation and pulsed laser irradiation are complementary techniques, which permit the implementation of complex geometries, by modification and functionalization of surface and/or bulk material, modifying the optical, electrical and mechanical characteristics of the material. In this article we summarize the work done in Florence (Italy) concerning ion beam and pulsed laser beam micro-fabrication in diamond.Comment: 14 pages, 5 figure

Electrical and Raman-imaging characterization of laser-made electrodes for 3D diamond detectors

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Wine Lees as Source of Antioxidant Molecules: Green Extraction Procedure and Biological Activity

An ultrasound-assisted extraction method, employing ethanol and water as solvents at low temperature (30 °C) and reduced time (15 min), was proposed to extract bioactive molecules from different cultivars (Magliocco Canino, Magliocco Rosato, Gaglioppo, and Nocera Rosso) of wine lees. All the extract yields were evaluated and their contents of phenolic acids, flavonoids, and total polyphenols were determined by means of colorimetric assays and high-performance liquid chromatography coupled with diode-array detection (HPLC-DAD) and Fourier transform infrared (FTIR) techniques. Radical scavenging assays were performed and the Magliocco Canino extracted with a hydroalcoholic mixture returned the best results both against ABTS (0.451 mg mL−1) and DPPH (0.395 mg mL−1) radicals. The chemometric algorithms principal component analysis (PCA) and partial least square regression (PLS) were used to process the data obtained from all qualitative–quantitative sample determinations with the aim of highlighting data patterns and finding possible correlations between composition and antioxidant features of the different wine lees cultivars and the extraction procedures. Wine lees from Magliocco Canino and Magliocco Rosato were found to be the best vegetable matrices in terms of metabolite content and antioxidant properties. The components extracted with alcoholic or hydroalcoholic solvents, specifically (−)-epigallocatechin gallate, chlorogenic acid, and trans-caftaric acid, were found to be correlated with the antioxidant capacity of the extracts. Multivariate data processing was able to identify the compounds related to the antioxidant features. Two PLS models were optimized by using their concentration levels to predict the IC50 values of the extracts in terms of DPPH and ABTS with high values of correlation coefficient R2, 0.932 and 0.824, respectively, and a prediction error lower than 0.07. Finally, cellular (SH-SY5Y cells) antioxidant assays were performed on the best extract (the hydroalcoholic extract of Magliocco Canino cv) to confirm its biological performance against radical species. All these recorded data strongly outline the aptness of valorizing wine lees as a valuable source of antioxidants

High Pressure Insulator-Metal Transition in Molecular Fluid Oxygen

We report the first experimental evidence for a metallic phase in fluid molecular oxygen. Our electrical conductivity measurements of fluid oxygen under dynamic quasi-isentropic compression show that a non-metal/metal transition occurs at 3.4 fold compression, 4500 K and 1.2 Mbar. We discuss the main features of the electrical conductivity dependence on density and temperature and give an interpretation of the nature of the electrical transport mechanisms in fluid oxygen at these extreme conditions.Comment: RevTeX, 4 figure

Low-Energy Linear Structures in Dense Oxygen: Implications for the ϵ\epsilon-phase

Using density functional theory implemented within the generalized gradient approximation, a new non-magnetic insulating ground state of solid oxygen is proposed and found to be energetically favored at pressures corresponding to the $\epsilon$-phase. The newly-predicted ground state is composed of linear herringbone-type chains of O$_2$ molecules and has {\it Cmcm} symmetry (with an alternative monoclinic cell). Importantly, this phase supports IR-active zone-center phonons, and their computed frequencies are found to be in broad agreement with recent infrared absorption experiments.Comment: 4 pages, 4 figure