Synthesis and characterization of multiferroic BiMn7_7O12_{12}

We report on the high pressure synthesis of BiMn$_7$O$_{12}$, a manganite displaying a "quadruple perovskite" structure. Structural characterization of single crystal samples shows a distorted and asymmetrical coordination around the Bi atom, due to presence of the $6s^{2}$ lone pair, resulting in non-centrosymmetric space group Im, leading to a permanent electrical dipole moment and ferroelectric properties. On the other hand, magnetic characterization reveals antiferromagnetic transitions, in agreement with the isostructural compounds, thus evidencing two intrinsic properties that make BiMn$_7$O$_{12}$ a promising multiferroic material.Comment: 4 pages, 3 figure

Validation of traffic flow models on processed GPS data

Macroscopic traffic flow models allow describing the spatio-temporal evolution of traffic density. Their sound mathematical structure consisting of partial differential equations of hyperbolic type and the related efficient numerical schemes enable fast computations to monitor traffic evolution. The aim of the internship was to validate these models against processed data provided by the industrial partners Autoroutes Trafic and VINCI Autoroutes. Targeted applications included congestion detection, congestion starting and ending points location, congestion evolution in time and traveling time estimation. To this end, we used the first-order Lighthill-Whitham-Richards model with a parabolic-linear flux function. The first part of the internship has been devoted to parameters identification, performing different calibration methods and finally choosing a hybrid compromise in order to exploit to the best the available data. Afterwards, numerical simulations have been performed on a selected case study, and results have been compared to real data to assess the validity and relevancy of the model. Numerical simulations consisted in established finite volume discretization of the hyperbolic partial differential equation. Numerical results show that, while reproducing traffic evolution during all the morning is really challenging, short term predictions are reliable

Thermally activated magnetization reversal in bulk BiFe0.5Mn0.5O3

We report on the synthesis and characterization of BiFe0.5Mn0.5O3, a potential type-I multiferroic compound displaying temperature induced magnetization reversal. Bulk samples were obtained by means of solid state reaction carried out under the application of hydrostatic pressure at 6 GPa and 1100{\deg}C. The crystal structure is an highly distorted perovskite with no cation order on the B site, where, besides a complex scheme of tilt and rotations of the TM-O6 octahedra, large off-centering of the bismuth ions is detected. Below T1 = 420 K the compound undergoes a first weak ferromagnetic transition related to the ordering of iron rich clusters. At lower temperatures (just below RT) two distinct thermally activated mechanisms are superimposed, inducing at first an enhancement of the magnetization at T2 = 288 K, then a spontaneous reversal process centered at T3 = 250 K, finally giving rise to a negative response. The application of fields higher than 1500 Oe suppresses the process, yielding a ferromagnetic like behaviour. The complementary use of SQuID magnetometry and M\"ossbauer spectroscopy allowed the interpretation of the overall magnetic behaviour in terms of an uncompensated weak competitive coupling between non-equivalent clusters of interactions characterized by different critical temperatures and resultant magnetizations. PACS numbers: 75.85.+t, 75.60.Jk, 76.80.+y, 75.30.Et, 75.30.KzComment: 30 pages, 13 figure

A new geochemical approach to estimate the distribution of air pollutants from natural and anthropogenic sources: examples from Solfatara Crater (Campi Flegrei, Southern Italy) and Mt. Amiata Volcano (Siena, Central Italy)

Volcanic and geothermal systems significantly contribute to the input of volatile contaminants, such as mercury and hydrogen sulfide, into the atmosphere. Mercury has a strong environmental impact. In the atmosphere the prevalent elemental form is Hg0 (~98 %), whose main physical-chemical features are: high volatility, low solubility and chemical inertness. Hydrogen sulfide (H2S), one of the most abundant gas compounds in volcanic fluids, is highly poisoning and corrosive and unpleasantly smells of rotten eggs. Measurements of Hg0 and H2S concentrations in air are commonly performed by means of passive samplers. However, real-time measurements, coupled with monitoring of local atmospheric conditions, are strongly recommended for a reliable reconstruction of the dispersion dynamics once such contaminants are discharged in air. In this paper, a new real-time measurement method for Hg0 and H2S is presented. A portable Zeeman atomic absorption spectrometer with high frequency modulation of light polarization (Lumex RA-915M) and a pulsed fluorescence gas analyzer (Thermo Scientific Model 450i) were used for Hg0 and H2S measurements, respectively. These instruments were synchronized and set to high-frequency acquisition. Measurements were carried out along transects at an average speed <10 km/h. GPS data and meteorological parameters (wind direction and intensity) were also recorded. The proposed method was applied in two different sites, characterized by natural (Solfatara Crater, Campi Flegrei, Southern Italy) and anthropogenic (Mt. Amiata Volcano, Siena, Central Italy) emissions. With this highly efficient and effective approach, a reliable and reproducible Hg0 and H2S distribution in air was provided, allowing to identify and characterize the gas sources from such different environments. At Solfatara, the distribution of Hg0 and H2S concentrations, the highest values being measured close to the fumarolized areas (>60 ng/m3 and >2,100 μg/m3, respectively), suggests that these gases were discharged from both fumaroles and diffuse degassing from the crater bottom. At Mt. Amiata, the maximum Hg0 and H2S concentrations (>100 ng/m3 and >35 μg/m3, respectively) were recorded close to the geothermal power plants of Piancastagnaio. According to detailed dot-maps constructed on the basis of the measured values, as expected, wind was the main environmental parameter able to control the behavior and the dispersion halo of the Hg0- and H2S-rich plumes emitted from the contaminant sources

Prognostic importance of emerging cardiac, inflammatory, and renal biomarkers in chronic heart failure patients with reduced ejection fraction and anaemia: RED-HF study

Aims: To test the prognostic value of emerging biomarkers in the Reduction of Events by Darbepoetin Alfa in Heart Failure (RED-HF) trial. Methods and results: Circulating cardiac [N-terminal pro-B-type natriuretic peptide (NT-proBNP), and high-sensitivity troponin T (hsTnT)], neurohumoral [mid-regional pro-adrenomedullin (MR-proADM) and copeptin], renal (cystatin C), and inflammatory [high-sensitivity C-reactive protein (hsCRP)] biomarkers were measured at randomization in 1853 participants with complete data. The relationship between these biomarkers and the primary composite endpoint of heart failure hospitalization or cardiovascular death over 28 months of follow-up (n = 834) was evaluated using Cox proportional hazards regression, the c-statistic and the net reclassification index (NRI). After adjustment, the hazard ratio (HR) for the composite outcome in the top tertile of the distribution compared to the lowest tertile for each biomarker was: NT-proBNP 3.96 (95% CI 3.16–4.98), hsTnT 3.09 (95% CI 2.47–3.88), MR-proADM 2.28 (95% CI 1.83–2.84), copeptin 1.66 (95% CI 1.35–2.04), cystatin C 1.92 (95% CI 1.55–2.37), and hsCRP 1.51 (95% CI 1.27–1.80). A basic clinical prediction model was improved on addition of each biomarker individually, most strongly by NT-proBNP (NRI +62.3%, P < 0.001), but thereafter was only improved marginally by addition of hsTnT (NRI +33.1%, P = 0.004). Further addition of biomarkers did not improve discrimination further. Findings were similar for all-cause mortality. Conclusion: Once NT-proBNP is included, only hsTnT moderately further improved risk stratification in this group of chronic heart failure with reduced ejection fraction patients with moderate anaemia. NT-proBNP and hsTnT far outperform other emerging biomarkers in prediction of adverse outcome

Internal-strain mediated coupling between polar Bi and magnetic Mn ions in the defect-free quadruple-perovskite BiMn3_3Mn4_4O12_{12}

By means of neutron powder diffraction, we investigated the effect of the polar Bi$^{3+}$ ion on the magnetic ordering of the Mn$^{3+}$ ions in BiMn$_3$Mn$_4$O$_{12}$, the counterpart with \textit{quadruple} perovskite structure of the \textit{simple} perovskite BiMnO$_3$. The data are consistent with a \textit{noncentrosymmetric} spacegroup $Im$ which contrasts the \textit{centrosymmetric} one $I2/m$ previously reported for the isovalent and isomorphic compound LaMn$_3$Mn$_4$O$_{12}$, which gives evidence of a Bi$^{3+}$-induced polarization of the lattice. At low temperature, the two Mn$^{3+}$ sublattices of the $A'$ and $B$ sites order antiferromagnetically (AFM) in an independent manner at 25 and 55 K, similarly to the case of LaMn$_3$Mn$_4$O$_{12}$. However, both magnetic structures of BiMn$_3$Mn$_4$O$_{12}$ radically differ from those of LaMn$_3$Mn$_4$O$_{12}$. In BiMn$_3$Mn$_4$O$_{12}$ the moments $\textbf{M}_{A'}$ of the $A'$ sites form an anti-body AFM structure, whilst the moments \textbf{M}$_{B}$ of the $B$ sites result from a large and \textit{uniform} modulation $\pm \textbf{M}_{B,b}$ along the b-axis of the moments \textbf{M}$_{B,ac}$ in the $ac$-plane. The modulation is strikingly correlated with the displacements of the Mn$^{3+}$ ions induced by the Bi$^{3+}$ ions. Our analysis unveils a strong magnetoelastic coupling between the internal strain created by the Bi$^{3+}$ ions and the moment of the Mn$^{3+}$ ions in the $B$ sites. This is ascribed to the high symmetry of the oxygen sites and to the absence of oxygen defects, two characteristics of quadruple perovskites not found in simple ones, which prevent the release of the Bi$^{3+}$-induced strain through distortions or disorder. This demonstrates the possibility of a large magnetoelectric coupling in proper ferroelectrics and suggests a novel concept of internal strain engineering for multiferroics design.Comment: 9 pages, 7 figures, 5 table

Etna International Training School of Geochemistry. Science meets Practice

Also this year, the “Etna International Training School of Geochemistry. Science meets practice” took place at Mt. Etna, now in its fourth edition. The school was hosted in the historical Volcanological Observatory “Pizzi Deneri”, one of the most important sites of the INGV - Osservatorio Etneo for geochemical and geophysical monitoring. Mount Etna, located in eastern Sicily, is the largest active volcano in Europe and one of the most intensely degassing volcanoes of the world [Allard et al., 1991; Gerlach, 1991]. Mt Etna emits about 1.6 % of global H2O fluxes from arc volcanism [Aiuppa et al., 2008] and 10 % of global average volcanic emission of CO2 and SO2 [D’Alessandro et al., 1997; Caltabiano et al., 2004; Aiuppa et al., 2008; Carn et al., 2017]. Furthermore, Gauthier and Le Cloarec, [1998] underscored that Mt. Etna is an important source of volcanic particles, having a mass flux of particle passively released from the volcano during non-eruptive period estimated between 7 to 23 tons/day [Martin et al., 2008; Calabrese et al., 2011]. In general, Etna is considered to be still under evolution and rather ‘friendly’, which, along with the above, makes it a favorable natural laboratory to study volcanic geochemistry. The Observatory Pizzi Deneri was sponsored by Haroun Tazieff, and it was built in 1978 by the CNR - International Institute of Volcanology under the direction of Prof. Letterio Villari. It is located at the base of the North-East crater (2,850 m a.s.l.), near the Valle del Leone and it was built on the rim of the Ellittico caldera. A picturesque building, consisting of two characteristics domes in front of the breath-taking panorama of the summit craters. Even though it is quite spartan as an accommodation facility, the dormitories, kitchen, seminar room and laboratory are well equipped. In other words, the Pizzi Deneri observatory is a unique place close to the top of the most active volcano of Europe. The observatory lies in a strategic location making it one of the most important sites for monitoring, research and dissemination of the scientific culture. After six field multidisciplinary campaigns (2010-2015) organized by a group of researchers of several institutions (INGV of Palermo, Catania, Naples, Bologna; Universities of Palermo, Florence, Mainz, Heidelberg), the idea of sharing and passing on the experience to the new generation of students has materialized, and the “Etna International Training School of Geochemistry. Science meets practice” was born in 2016. The four editions of the school were partially funded by INGV of Palermo and Catania, European Geoscience Union (EGU), Società Geochimica Italiana (SoGeI) and Associazione Naturalistica Geode. The conceptual idea of the school is to share scientific knowledge and experiences in the geochemical community, using local resources with a low-cost organization in order to allow as many students as possible access to the school. The “Etna International Training School of Geochemistry. Science meets practice” is addressed to senior graduate students, postdoctoral researchers, fellows, and newly appointed assistant professors, aiming to bring together the next generation of researchers active in studies concerning the geochemistry and the budget of volcanic gases. Introduce the participants with innovative direct sampling and remote sensing techniques. Furthermore, it gives young scientists an opportunity to experiment and evaluate new protocols and techniques to be used on volcanic fluid emissions covering a broad variety of methods. The teaching approach includes theoretical sessions (lectures), practical demonstrations and field applications, conducted by international recognized geochemists. We thank all the teachers who helped to make the school possible, among these: Tobias Fischer (University of New Mexico Albuquerque), Jens Fiebig (Institut für Geowissenschaften Goethe-Universität Frankfurt am Main), Andri Stefansson (University of Iceland, Institute of Earth Sciences), Mike Burton (University of Manchester), Nicole Bobrowski (Universität Heidelberg Institute of Environmental Physics and Max Planck Institute for Chemistry), Alessandro Aiuppa (Università di Palermo), Franco Tassi (Università di Firenze), Walter D’Alessandro (INGV of Palermo), Fatima Viveiros (University of the Azores). Direct sampling of high-to-low temperature fumaroles, plume measurement techniques (using CO2/SO2 sensors such as Multi-GAS instruments, MAX-DOAS instruments and UV SO2 cameras, alkaline traps and particle filters), measurement of diffuse soil gas fluxes of endogenous gases (CO2, Hg0, CH4 and light hydrocarbons), sampling of mud volcanoes, groundwaters and bubbling gases. Sampling sites include the active summit craters, eruptive fractures and peripheral areas. The students have shown an active participation both to the lessons and the fieldworks. Most of them describe the school as formative and useful experience for their future researches. Their enthusiasm is the real engine of this school

Active real-time analyzers vs. passive/diffusive samplers for hydrogen sulfide (H2S) in air: a critical comparison

Hydrogen sulfide (H2S) is a gas pollutant discharged in air from a large number of natural and anthropogenic sources. Its peculiar rotten-egg smell, causing odor nuisance to neighboring communities, is detectable at concentrations between 0.7 and 42 μg/m3 (Schiffman & Williams, 2005). High H2S concentrations could cause eye irritation, damage to the upper respiratory apparatus and loss of smell. The effects of long-term low level (< 2,800 μg/m3) exposures to H2S are still matter of debate (Bates et al., 2013). Hence, the development of techniques for accurate measurements of H2S in air at a wide range of concentrations is a primary issue in environmental monitoring. Two different approaches are currently used: 1) passive samplers and 2) real-time measurements. The latter are generally expensive and require a power supply. On the contrary, passive samplers are low cost and can be deployed in the field with minimal maintenance. Therefore, passive samplers offer an appealing alternative to real-time measurements, especially for regional-scale monitoring. However, the reliability of passive samplers in outdoor applications strongly depends on several environmental factors, such as temperature, humidity and wind speed (Delgado-Saborit & Esteve-Cano, 2006). In this study a comparison between H2S measurements using diffusive radial-type passive samplers (Radiello) and a real-time gas analyzer (Thermo Scientific Model 450i) based on pulsed fluorescence, is presented. The measurements were carried out in areas affected by both anthropogenic and natural sources using both techniques. The results show substantial differences. The passive samplers systematically produce higher H2S concentrations than those of the active analyzer. The relative error was up to > 1,000% for concentrations < 7 μg/m3 and exposure duration ≥ 2 hours. H2S measurements by Radiello were affected by meteo parameters (wind, rain, humidity, temperature). The efficiency of this method was demonstrated to be also strongly dependent on H2S concentrations. In addition, passive samplers give an average concentration value for the exposure period, but are not able to detect short-term H2S increments. These results show that the use of passive samplers for environmental monitoring should thus be limited to preliminary largescale semi-quantitative assessment. A reliable study on the dispersion dynamics of contaminants in air cannot exclude the acquisition of high-frequency data through active analyzers