Seismicity, seismotectonics and crustal velocity structure of the Messina Strait (Italy)

The Messina Strait is the most important structural element interrupting the southernmost part of the Alpine-Apenninic orogenic belt, known as the Calabro-Peloritan Arc. It is being a narrow fan-shaped basin linking the Ionian Sea to the Tyrrhenian Sea. This region is affected by considerable seismic activity which mirrors the geodynamic processes due to the convergence between the African and the Eurasian plates. In the last four centuries, a significant number of disastrous earthquakes originated along the Arc. Among these, the most noteworthy event occurred on December 28, 1908 (known as the Reggio Calabria-Messina earthquake), in the Messina Strait area and caused a large tsunami and more than 100,000 casualties. In this research we focus on the relationships between the general tectonic setting, which characterize the Messina Strait and adjacent areas, seismicity patterns and the crustal structure. We analyzed a data set consisting of more than 300 events occurring in the years from 1999 to 2007, having a magnitude range from 1.0 to 3.8. This data set was exploited in a local earthquake tomography, by carrying out a simultaneous inversion of both the three-dimensional velocity structure and the distribution of seismic foci. We applied the “tomoADD” algorithm, which uses a combination of absolute and differential arrival times and a concept of self-adapting grid geometry, accounting for ray density encountered across the volume. With this method the accuracy of event locations is improved and velocity structure near the source region is resolved in more detail than standard tomography. Fault plane solutions were obtained for the major and best-recorded earthquakes. The obtained velocity images highlight vertical and lateral heterogeneities that can be associated with structural features striking from NNE-SSW to NE-SW. These results are consistent with important tectonic elements visible at the surface and the pattern delineated by earthquake locations and focal mechanisms

Estimation of an optimum velocity model in the Calabro-Peloritan mountains – Assessment of the variance of model parameters and variability of earthquake locations

Accurate earthquake locations are of primary importance when studying the seismicity of a given area, they allow important inferences on the ongoing seismo-tectonics. Both, for standard, as well as for earthquake relative location techniques, the velocity parameters are kept fixed to a-priori values, that are assumed to be correct, and the observed traveltime residuals are minimised by adjusting the hypocentral parameters. However, the use of an unsuitable velocity model, can introduce systematic errors in the hypocentre location. Precise hypocentre locations and error estimate, therefore, require the simultaneous solution of both velocity and hypocentral parameters. We perform a simultaneous inversion of both the velocity structure and the hypocentre location in NE-Sicily and SW-Calabria (Italy). Since the density of the network is not sufficient for the identification of the 3D structure with a resolution of interest here, we restrict ourselves to a 1D inversion using the well-known code VELEST. A main goal of the paper is the analysis of the stability of the inverted model parameters. For this purpose we carry out a series of tests concerning the initial guesses of the velocity structure and locations used in the inversion. We further assess the uncertainties which originate from the finiteness of the available datasets carrying out resampling experiments. From these tests we conclude that the data catalogue is sufficient to constrain the inversion. We note that the uncertainties of the inverted velocities increases with depth. On the other hand the inverted velocity structure depends decisively on the initial guess as they tend to maintain the overall shape of the starting model. In order to derive an improved starting model we derive a guess for the probable depth of the MOHO. For this purpose we exploit considerations of the depth distribution of earthquake foci and of the shear strength of rock depending on its rheological behaviour at depth. In a second step we derived a smooth starting model and repeated the inversion. Strong discontinuities tend to attract hypocentre locations which may introduce biases to the earthquake location. Using the smooth starting model we obtained again a rather smooth model as final solution which gave the best travel-time residuals among all models discussed in this paper. This poses severe questions as to the significance of velocity discontinuities inferred from rather vague a-priori information. Besides this, the use of those smooth models widely avoids the problems of hypocentre locations being affected by sudden velocity jumps, an effect which can be extremely disturbing in relative location procedures. The differences of the velocity structure obtained with different starting models is larger than those encountered during the bootstrap test. This underscores the importance of the choice of the initial guess. Fortunately the effects of the uncertainties discussed here on the final locations turned out as limited, i. e., less than 1 km for the horizontal coordinates and less than 2 km for the depth

Accurate hypocentre locations in the Middle-Durance Fault Zone, South-Eastern France

A one-dimensional velocity model and station corrections for the Middle-Durance fault zone (south-eastern France) was computed by inverting P-wave arrival times recorded on a local seismic network of 8 stations. A total of 93 local events with a minimum number of 6 P-phases, RMS<0.4 s and a maximum gap of 220° were selected. Comparison with previous earthquake locations shows an improvement for the relocated earthquakes. Tests were carried out to verify the robustness of inversion results in order to corroborate the conclusions drawn from our findings. The obtained minimum 1-D velocity model can be used to improve routine earthquake locations and represents a further step toward more detailed seismotectonic studies in this area of south-eastern France

Miniaturization and Optimization of the Standard Spectrophotometric Analysis for Autonomous, Continuous and On-site Heavy Metal Detection in Water

Water environmental monitoring is an important key to control both human life and environment health. When water quality is poor, it affects not only aquatic life but the surrounding ecosystem as well. The greatest limitation of detection devices, today on the market, is that they are limited to the measurement phase, burdening the operator of the previous sample treatment. The development of a threshold monitoring device, designed for real time water environmental monitoring, was the aim of this study. The focus was on the design of an autonomous system for detection of dissolved heavy metals in water by spectrophotometric analysis. The ground-breaking idea is the implementation of a system inspired to the latest innovative techniques in the field of the microfluidic analysis, based on Lab-on-Chip concept. Such a choice is due to the unique advantages in terms of reduction of sample and reagents volumes, energy budget and analysis times, besides the possible multi-element analysis on the same sample

Spectrophotometric Detection of Nickel in Water by Lab-on-a-chip Technology: Application to Electroplating

Nickel is a metal member of the transition series in the periodic table, and as such shows outstanding properties interesting to the world of industry, namely corrosion resistance to air, water and alkali and electrical conductivity. In fact, nickel is widely employed in electroplating, where high analyte concentrations, up to 100g/L, are required to achieve excellent final results. The process monitoring is required not only to ensure constant and adequate metal-finishing concentration but also to guarantee the safety of wastewater products. To detect nickel, either in high and low metal concentration, a colorimetric method was selected. The spectrophotometric study reveals a well-defined absorption peak at 396nm, giving a calibration curve with remarkable linearity toward metal concentrations, ranging from 1 to 22g/L. By proper optimization process, the detection field can be simply enlarged at least from 100 g/L (100000ppm) to 3*10-3 g/L (3ppm). Due to the presence of an acid part in the electroplating bath, the behaviour of the metal in an acid solution has also been investigated, and the calibration curve still depicts a good linearity of the system. Achieved results pointed out the suggested colorimetric method as a promising candidate for addressing the requirement for capillary and regular monitoring of nickel in water, throughout a wide range of concentrations.The laboratory method may be readily improved and adapted for microfluidic technology by lowering sample and reagent amounts, miniaturizing sensors, and automating the entire process, from sampling to data recover

Routine Monitoring of Trace Arsenic in Water by Lab-on-a-chip Technology: a Preliminary Study

Water contamination by Arsenic poses a serious risk for human health, due to its manifold toxic effects. The concern is mainly for drinking water, regarded as the most imperative route of Arsenic exposure to human beings. The maximum concentration limit for Arsenic in drinking water was fixed by World Health Organisation (WHO) at 10 μg L−1 but in many developing nations it is increased to 50 μg L−1 due to economic constraints to detect lower concentrations. In this scenario, the design of an affordable Arsenic sensor, for routine monitoring of water, is crucial. The answer to these requirements can be the lab-on–a-chip technology applied to a microfluidic device. Available detection methods for Arsenic are investigated, focusing on their potential application on a portable monitoring device: among them a colorimetric method, based on Rodamine B as indicator, and chronopotentiometry were selected as suitable for the required purpose. Preliminary laboratory tests were aimed to determine the limit of Arsenic concentration detectable by both the methods; the lower value of 1 μg L−1 was detected by chronopotentiometry, in good agreement with the required resolution of the measurement. Moreover, a process optimization adapted the method for the microfluidic technology. Obtained results point out the new developing lab-on-a-chip technology as good candidate to address the need for a capillary and frequent monitoring of Arsenic contamination of water by an easy and cheap portable device

Micro-structured rough surfaces by laser etching for heat transfer enhancement on flush mounted heat sinks

Abstract. The aim of this work is to improve heat transfer performances of ush mounted heat sinks used in electronic cooling. To do this we patterned 1.23 cm2 heat sinks surfaces by micro- structured roughnesses built by laser etching manufacturing technique, and experimentally measured the convective heat transfer enhancements due to dierent patterns. Each roughness diers from the others with regards to the number and the size of the micro-ns (e.g. the micro- n length ranges from 200 to 1100 m). Experimental tests were carried out in forced air cooling regime. In particular fully turbulent ows (heating edge based Reynolds number ranging from 3000 to 17000) were explored. Convective heat transfer coecient of the best micro-structured heat sink is found to be roughly two times compared to the smooth heat sinks one. In addition, surface area roughly doubles with regard to smooth heat sinks, due to the presence of micro-ns. Consequently, patterned heat sinks thermal transmittance [W/K] is found to be roughly four times the smooth heat sinks one. We hope this work may open the way for huge boost in the technology of electronic cooling by innovative manufacturing techniques

Antimicrobial activity of zinc-doped hydroxyapatite coatings formed on titanium Ti6A14V surface for orthopedic implant

Prosthetic joint infection (PJI) is one of the most serious complications of prosthetic joint implantation leading to a longer hospitalization. S. aureus is the predominant cause of PJI followed by Pseudomonas aeruginosa and Stafilococci spp. coagulase negative. Several studies focused on the development of effective antibacterial surfaces that prevent bacterial adhesion, colonisation and proliferation into the surrounding tissues and it has been widely demonstrated that zinc ions (Zn2+) exhibit antimicrobial activity against various bacterial and fungal strains. In addition to its antimicrobial activities, zinc is important in healthy bone growth and development. The aim of this study was to evaluate the in vitro activity of Zn2+ generated from the partial dissolution of Zn particles on surface of titanium discs, against S. aureus ATCC 29213. Hydroxyapatite (HA), and HA/Zn2+ doped discs were used. Each disc was incubated with bacterial suspension following standard ASTM (American Society for Testing and Materials) method. After, colony-forming unit (CFU) were counted. The results showed 1,7 log10 (97,8 %) CFU decrease vs untreated samples (p&lt; 0.05), after 6 hours of incubation. To confirm quantitative data, morphological analysis was performed by Scanning Electron Microscope (SEM). On HA disc, bacteria, recognized by the typical spherical shape, colonized micro and nano porosities surface assuming an homogeneous distribution, while on the surface doped with Zn2+, being smoother and less porous, the bacteria adhered to the surface in small colonies of about 2-10 bacteria. This new formulation of zinc coating could represent a promising approach for prevention and treatment of peri-implant diseases