Electromagnetic response of LaO_0.94F_0.06FeAs: AC susceptibility and microwave surface resistance

We discuss on the electromagnetic response of a polycrystalline sample of LaO_0.94F_0.06FeAs exposed to DC magnetic fields up to 10 kOe. The low- and high-frequency responses have been investigated by measuring the AC susceptibility at 100 kHz and the microwave surface resistance at 9.6 GHz. At low as well as high DC magnetic fields, the susceptibility strongly depends on the amplitude of the AC driving field, highlighting enhanced nonlinear effects. The field dependence of the AC susceptibility exhibits a magnetic hysteresis that can be justified considering the intragrain-field-penetration effects on the intergrain critical current density. The microwave surface resistance exhibits a clockwise magnetic hysteresis, which cannot be justified in the framework of the critical-state models of the Abrikosov-fluxon lattice; it may have the same origin as that detected in the susceptibility.Comment: 8 pages, 4 embedded eps figures; Proceedings of the 9th EUCAS Conference (Dresden, Germany, September 13-17, 2009

Hellenic karst waters: geogenic and anthropogenic processes affecting their geochemistry and quality

Karst hydrosystems represent one of the largest global drinking water resources, but they are extremely vulnerable to pollution. Climate change, high population density, intensive industrial, and agricultural activities are the principal causes of deterioration, both in terms of quality and quantity, of these resources. Samples from 172 natural karst springs were collected in the whole territory of Greece. To identify any geogenic contamination and/or anthropogenic pollution, analyses of their chemical compositions, in terms of major ions and trace elements, were performed and compared to the EU limits for drinking water. Based on chloride content, the collected karst springs were divided into two groups: low-chloride (< 100 mg L− 1) and high-chloride content (> 100 mg L− 1). An additional group of springs with calcium-sulfate composition was recognised. Nitrate concentrations were always below the EU limit (50 mg L− 1), although some springs presented elevated concentrations. High contents in terms of trace elements, such as B, Sr, As, and Pb, sometimes exceeding the limits, were rarely found. The Greek karst waters can still be considered a good quality resource both for human consumption and for agriculture. The main issues derive from seawater intrusion in the aquifers along the coasts. Moreover, the main anthropogenic pollutant is nitrate, found in higher concentrations mostly in the same coastal areas where human activities are concentrated. Finally, high levels of potentially harmful trace elements (e.g. As, Se) are very limited and of natural origin (geothermal activity, ore deposits, etc.)

Degassing and Cycling of Mercury at Nisyros Volcano (Greece)

Nisyros Island (Greece) is an active volcano hosting a high-enthalpy geothermal system. During June 2013, an extensive survey on Hg concentrations in different matrices (fumarolic fluids, atmosphere, soils and plants) was carried out at Lakki Plain, an intra-caldera area affected by widespread soil and fumarolic degassing. Concentrations of gaseous elemental mercury (GEM), H2S and CO2, were simultaneously measured in both the fumarolic emissions and the atmosphere around them. At the same time, 130 samples of top soils and 31 samples of plants (Cistus Creticus and Salvifolius and Erica Arborea and Manipuliflora) were collected for Hg analysis. Mercury concentrations in fumarolic gases ranged from 10,500 to 46,300 ng/m3, while Hg concentrations in the air ranged from high background values in the Lakki Plain caldera (10-36 ng/m3) up to 7100 ng/m3 in the fumarolic areas. Outside the caldera, the concentrations were relatively low (2-5 ng/m3). The positive correlation with both CO2 and H2S in air highlighted the importance of hydrothermal gases as carrier for GEM. On the other hand, soil Hg concentrations (0.023-13.7 µg/g) showed no significant correlations with CO2 and H2S in the soil gases, whereas it showed a positive correlation with total S content and an inverse one with the soil-pH, evidencing the complexity of the processes involving Hg carried by hydrothermal gases while passing through the soil. Total Hg concentrations in plant leaves (0.010-0.112 μg/g) had no direct correlation with soil Hg, with Cistus leaves containing higher values of Hg respect to Erica. Even though GEM concentrations in air within the caldera are sometimes orders of magnitude above the global background, they should not be considered dangerous to human health. Values exceeding the WHO guideline value of 1000 ng/m3 are very rare (<0.1%) and only found very close to the main fumarolic vents, where the access to tourists is prohibited.PublishedID 47835146A. Geochimica per l'ambiente e geologia medicaJCR Journa

Geothermal mercury output at Nisyros Volcano (Greece)

Nisyros (Greece) is an active volcano in the eastern part of the South Aegean Active Volcanic Arc (SAAVA), hosting a high-enthalpy geothermal system. On June 2013, an extensive survey on Hg concentrations in different types of matrices (fumarolic fluids, atmosphere, soils and plants) was carried out at Lakki plain, an area affected by widespread soil degassing and fumarolic manifestations. To investigate the spatial distribution of mercury emission and its possible relationships with diffuse degassing of hydrothermal fluids, Hg concentrations in soils were related to their physicochemical parameters (e.g. temperature, soil-pH, hydrothermal gases and elemental C, N and S concentrations). Furthermore, leaves of Cistus and Erica (two local plants) were collected at the same sampling sites and their Hg contents were quantified. The concentrations of gaseous elemental mercury (GEM), H2S and CO2 were simultaneously measured in both the fumarolic emissions and in the atmosphere at the investigated sites. Mercury concentrations in the fumarolic gases ranged from 10,500 to 46,300 ng/m3, while the Hg concentrations in air showed high background values within the Lakki Plain caldera (from 10 to 36 ng/m3) with their maximum values (up to 7100 ng/m3) measured in the fumarolic areas. In the sites outside the caldera, the Hg concentrations in air were relatively low (from 2 to 5 ng/m3). A positive correlation between Hg and both CO2 and H2S values in the air exists, highlighting the important role of fumarolic and soil gases as carrier for GEM. On the other hand, soil Hg (concentrations from 0.023 to 13.7 g/g) showed no significant correlations with CO2 and H2S in the soil gases whereas a positive correlation with total S content and an inverse one with the soil-pH were noticed. These correlations evidenced the complexity of the processes involving Hg carried by hydrothermal gases while passing through the soil. Total Hg concentrations in plants, ranging from 0.010 to 0.112 g/g, had no direct correlation with soil Hg at the same sampling site. It is noteworthy that Cistus leaves presented higher values of total Hg than Erica leaves. Taking into consideration that Hg is a toxic element and is not readily absorbed by the roots, the main pathway of plant Hg uptake is probably transpiration through leaves; consequently, the higher specific leaf surface area of Cistus favoured Hg accumulation. Even though the GEM concentrations in air within the caldera of Nisyros are sometimes many orders of magnitude above the global background, the measured levels should not be considered dangerous for the human health. Values exceeding the WHO guideline value of 1000 ng/m3 are very rare (less than 0.1% of the measurements) and are only found in areas close to the main fumarolic vents, where the access to tourists is prohibited. Those areas are also characterized by elevated H2S concentrations, which are more dangerous than mercury\u2019s concentrations

Advances in Human-Robot Handshaking

The use of social, anthropomorphic robots to support humans in various industries has been on the rise. During Human-Robot Interaction (HRI), physically interactive non-verbal behaviour is key for more natural interactions. Handshaking is one such natural interaction used commonly in many social contexts. It is one of the first non-verbal interactions which takes place and should, therefore, be part of the repertoire of a social robot. In this paper, we explore the existing state of Human-Robot Handshaking and discuss possible ways forward for such physically interactive behaviours.Comment: Accepted at The 12th International Conference on Social Robotics (ICSR 2020) 12 Pages, 1 Figur