Explosive activity of the summit cone of Piton de la Fournaise volcano (La Réunion island): A historical and geological review

International audienceSummit explosive activity and collapses that form pit craters and calderas represent major volcanic hazards on a dominantly effusive, frequently active volcano like Piton de la Fournaise. Only three summit collapse events (1986, 2002, 2007) have been recorded since the foundation of the Piton de la Fournaise volcano observatory (OVPF) in 1979, and two of them (1986 and 2007) were associated with weak phreatic activity. At Piton de la Fournaise, the normal explosive activity consists of short-lived and mild (< 20 m-high) lava fountains, which quickly evolve into strombolian activity during the eruptions. Based on comprehensive literature review and high-resolution image analysis of surface outcrops and summit caldera walls, we reconstructed the time distribution of recent explosive events (phreatomagmatic; phreatic) and their link with summit collapses and lateral (flank) effusive eruptions. In historical time (post-1640 CE), we recognise two main clusters of explosive events. Frequent and violent phreatomagmatic to phreatic explosions occurred during the oldest cluster (1708–1878) and alternated with long-lasting periods (years to decades) of summit effusive activity. In contrast, scarce, and on average, weak explosions occurred during the youngest cluster (1897–2012), when discrete and short-lived (< 6 months) effusive eruptions represent the main eruptive dynamics. Historical summit collapses (pit craters and caldera), all localised at the top of the summit cone, were related to voluminous lateral eruptions and were followed by a significant decrease in eruptive rate. However, magma draining during lateral eruptions was not systematically associated with summit collapses or explosions. The long-lasting occurrence of magma at very shallow depth below the volcano summit, followed by a rapid lateral drainage, apparently represents a critical condition favouring magma–groundwater interaction to produce explosive activity. The prehistoric growth of the Piton de la Fournaise summit cone results chiefly from long-lasting to continuous activity, centred below its western side (Bory crater containing lava lakes). High lava fountains, long-lasting effusive activity, lava lakes, ash plumes and block ejections were common types of eruptive dynamics in the historical past, between 1640 and 1878. In this perspective, short-lived, small volume eruptions and long pauses, up to six years, during the last century of activity of Piton de la Fournaise can be considered as a lull, despite the high frequency of eruption (1 eruption/9 months on average). Temporal and spatial variations in recurrence rate and eruptive dynamics of basaltic volcanism, such as those recognised at Piton de la Fournaise, should be considered in the formulation of hazard assessments and in the interpretation of precursory patterns

Report on research activities carried out for determination of mercury neuro-toxicological effects on cetacean brain

In this study we analyzed Hg and Se concentrations in dolphin brain tissues of fifteen specimens of striped dolphin (Stenella coeruleoalba) and eight specimens of bottlenose dolphin (Tursiops truncatus) stranded in the Tyrrhenian and Adriatic Seas, in order to assess the toxicological risks associated with Hg exposure. High Hg concentrations were found in brain tissues of both analyzed specie (1.86–243mg/kg dw for striped dolphin and 2.1–98.7 mg/kg dw for bottlenose dolphin), exceeding levels associated with marine mammals neurotoxicity. Although the results clearly suggest that the protective effects of Se against Hg toxicity occur in cetaceans’ brain tissues, a molar excess of mercury with respect to selenium was found, particularly in adult specimens of Stenella coeruleoalba. On contrary, negligible neuro-toxicological risks were found for Tursiops truncatus specimens, due to detoxification processes. Data obtained allowed to prove a more marked neuro-toxicological risk for adult specimens of Stenella coeruleoalba in both Tyrrhenian and Adriatic Seas

COLESTEROL E BETA-HIDROXIBUTIRATO SÉRICO EM VACAS COM HIPOCALCEMIA SUBCLÍNICA

O objetivo deste trabalho foi avaliar os níveis de colesterol e beta-hidroxibutirato sérico em vacas leiteiras com hipocalcemia subclínica. Para isso foram utilizadas 14 vacas leiteiras da raça Holandesa no período de transição. O experimento foi dividido em duas etapas, onde na primeira os animais foram acompanhados quanto ao pH urinário no pré-parto e os níveis de cálcio sérico nos três primeiros dias pós-parto. Na segunda etapa, os animais foram divididos em dois grupos a partir dos níveis de cálcio sérico até as 24 horas pós-parto, sendo: G1: (n=6) animais com cálcio sérico acima de 8 mg/dL e G2 (n=8) animais com cálcio sérico inferior a 8 mg/dL. Foram avaliados os níveis de colesterol sérico no segundo e décimo dias pós-parto e os níveis de beta-hidroxibutirato sérico no décimo dia pós-parto. Observou-se uma redução nos valores de colesterol sérico tanto no segundo como no décimo dia pós-parto e um aumento nos níveis de beta-hidroxibutirato sérico no G2 quando comparado ao G1. Assim, pode-se concluir que a hipocalcemia subclínica afeta negativamente o metabolismo energético, isto demonstrado pela redução dos valores de colesterol sérico e elevação dos níveis séricos de beta-hidroxibutirato

Chronic constipation diagnosis and treatment evaluation: The "CHRO.CO.DI.T.E." study

Background: According to Rome criteria, chronic constipation (CC) includes functional constipation (FC) and irritable bowel syndrome with constipation (IBS-C). Some patients do not meet these criteria (No Rome Constipation, NRC). The aim of the study was is to evaluate the various clinical presentation and management of FC, IBS-C and NRC in Italy. Methods: During a 2-month period, 52 Italian gastroenterologists recorded clinical data of FC, IBS-C and NRC patients, using Bristol scale, PAC-SYM and PAC-QoL questionnaires. In addition, gastroenterologists were also asked to record whether the patients were clinically assessed for CC for the first time or were in follow up. Diagnostic tests and prescribed therapies were also recorded. Results: Eight hundred seventy-eight consecutive CC patients (706 F) were enrolled (FC 62.5%, IBS-C 31.3%, NRC 6.2%). PAC-SYM and PAC-QoL scores were higher in IBS-C than in FC and NRC. 49.5% were at their first gastroenterological evaluation for CC. In 48.5% CC duration was longer than 10 years. A specialist consultation was requested in 31.6%, more frequently in IBS-C than in NRC. Digital rectal examination was performed in only 56.4%. Diagnostic tests were prescribed to 80.0%. Faecal calprotectin, thyroid tests, celiac serology, breath tests were more frequently suggested in IBS-C and anorectal manometry in FC. More than 90% had at least one treatment suggested on chronic constipation, most frequently dietary changes, macrogol and fibers. Antispasmodics and psychotherapy were more frequently prescribed in IBS-C, prucalopride and pelvic floor rehabilitation in FC. Conclusions: Patients with IBS-C reported more severe symptoms and worse quality of life than FC and NRC. Digital rectal examination was often not performed but at least one diagnostic test was prescribed to most patients. Colonoscopy and blood tests were the "first line" diagnostic tools. Macrogol was the most prescribed laxative, and prucalopride and pelvic floor rehabilitation represented a "second line" approach. Diagnostic tests and prescribed therapies increased by increasing CC severity

Stratification of asthma phenotypes by airway proteomic signatures

© 2019 Background: Stratification by eosinophil and neutrophil counts increases our understanding of asthma and helps target therapy, but there is room for improvement in our accuracy in prediction of treatment responses and a need for better understanding of the underlying mechanisms. Objective: We sought to identify molecular subphenotypes of asthma defined by proteomic signatures for improved stratification. Methods: Unbiased label-free quantitative mass spectrometry and topological data analysis were used to analyze the proteomes of sputum supernatants from 246 participants (206 asthmatic patients) as a novel means of asthma stratification. Microarray analysis of sputum cells provided transcriptomics data additionally to inform on underlying mechanisms. Results: Analysis of the sputum proteome resulted in 10 clusters (ie, proteotypes) based on similarity in proteomic features, representing discrete molecular subphenotypes of asthma. Overlaying granulocyte counts onto the 10 clusters as metadata further defined 3 of these as highly eosinophilic, 3 as highly neutrophilic, and 2 as highly atopic with relatively low granulocytic inflammation. For each of these 3 phenotypes, logistic regression analysis identified candidate protein biomarkers, and matched transcriptomic data pointed to differentially activated underlying mechanisms. Conclusion: This study provides further stratification of asthma currently classified based on quantification of granulocytic inflammation and provided additional insight into their underlying mechanisms, which could become targets for novel therapies

Community-Level Responses to Iron Availability in Open Ocean Plankton Ecosystems

Predicting responses of plankton to variations in essential nutrients is hampered by limited in situ measurements, a poor understanding of community composition, and the lack of reference gene catalogs for key taxa. Iron is a key driver of plankton dynamics and, therefore, of global biogeochemical cycles and climate. To assess the impact of iron availability on plankton communities, we explored the comprehensive bio-oceanographic and bio-omics data sets from Tara Oceans in the context of the iron products from two state-of-the-art global scale biogeochemical models. We obtained novel information about adaptation and acclimation toward iron in a range of phytoplankton, including picocyanobacteria and diatoms, and identified whole subcommunities covarying with iron. Many of the observed global patterns were recapitulated in the Marquesas archipelago, where frequent plankton blooms are believed to be caused by natural iron fertilization, although they are not captured in large-scale biogeochemical models. This work provides a proof of concept that integrative analyses, spanning from genes to ecosystems and viruses to zooplankton, can disentangle the complexity of plankton communities and can lead to more accurate formulations of resource bioavailability in biogeochemical models, thus improving our understanding of plankton resilience in a changing environment

Multivariate approaches to infer volcanic system parameters, timing, and size of explosive eruptions

Volcanoes can exhibit a wide range of activities: from effusive eruptions, low-energy bursts, and mild explosive Strombolian eruptions that can cause minor localized effects on human populations, to more severe Plinian eruptions, which are characterized by large emission of ash in the atmosphere with consequent regional to global impacts on human life. To monitor the associated risk, volcanologists apply several ground-based and satellite techniques to analyse geophysical signals associated with the mechanisms happening deep inside the earth that can lead to an eruption. These techniques allow, with the appropriate instruments in place, to estimate the time and intensity of coming events and, in case a large eruption is ongoing, can provide information on ash ejection rates and column heights. Despite technological advancements, many active volcanoes still lack an adequate permanent monitoring network; moreover, harsh climatic conditions can complicate the application of the existing remote sensing techniques. Therefore, there is the need for complementing volcano monitoring with new supportive tools to enhance the current systems. Accordingly, in this thesis we propose two different methods based on volcano tilt observations and ionospheric sounding, respectively for close field and remote sensing applications, to detect and characterize eruptions prior, and during the event. We propose a method to exploit the time series of tilt signals recorded by a single station during Strombolian explosions to forecast the time and magnitude of a coming event. This is achieved by estimating, by mean of the Bayesian statistics and a physics‐based model, the range of controlling parameters. To validate the proposed model and test its uncertainties we performed analogue experiments in a controlled environment. To date, analogue experiments in controlled environments have been focused on the uncertainties related to the dynamics of slugs inside rigid conduits, but little is known about how the slug dynamics changes in the elastic conduit, and how the slug ascent affects surface deformation. We finally focused on the development of a new tool that can support remote sensing techniques to detect and assess the intensity of eruptions. We tested whether the analysis of ionospheric Total Electron Content (TEC) can provide additional information to complement the existing monitoring system. To this end, we mined GNSS data recorded during 22 volcanic eruptions to measure the ionospheric TEC perturbation associated with the acoustic-gravity waves generated by volcanic explosions. We evaluated the relationship between a metric related to the energy of atmospheric disturbances, called TEC Intensity Index (TECII), and several well-known metrics obtained by seismology, and satellite remote sensing. The results presented in this thesis support the use of techniques based on the analysis of tilt observations and ionospheric sounding as complementary methods for volcano monitoring. The synergy of these new techniques and the classic ones will augment the possibility of preventing losses of life and mitigating damages by providing useful information for volcano observatories and alert systems.Doctor of Philosoph

A Bayesian approach to infer volcanic system parameters, timing, and size of Strombolian events from a single tilt station

Persistently active volcanoes are characterized by frequent eruptions, in which volatiles dissolved in magma play an important role in controlling the explosivity. Inverting techniques on geodetic data sets have been used to retrieve information about key controlling parameters of these eruptions. However, up to date, several data sets are combined to obtain reliable estimates of the physical parameters using a physical model, hindering the possibility to provide forecasting tools for time and magnitude of eruptions at volcanoes with limited monitoring network. In this work, we propose an approach to extract valuable information out of limited data sets through inverting techniques dealing with limited number of sensors, but high frequency of events. Our method exploits time series of tilt signals recorded by a single station to estimate, by mean of the Bayesian statistics and a physics‐based model, the range of the controlling parameters. The method was developed and tested on a synthetic volcanic system before being applied on data from Semeru volcano (Indonesia). Finally, we tested the possibility to forecast explosion magnitude and timing using data recorded by a single tilt station. Results show that data from a limited network or even a single tilt station is sufficient to estimate the controlling parameters. The information obtained is shown to be useful for estimating the time and magnitude of future events, which can enhance the monitoring systems of those volcanoes characterized by frequent, potentially dangerous events.Published versio

New insight Into a volcanic system : analogue investigation of bubble-driven deformation in an elastic conduit

Analogue and numerical simulations have been widely used to describe the mechanisms of bubble and slug ascent during volcanic eruptions as well as their formation and explosion mechanisms. Nevertheless, little is known about the mechanical interaction between the fluid and the surrounding medium. In this work, we report the results from analogue experiments designed to show how deformation of the conduit walls induced by the rising slugs is related to the radiation and propagation of seismic and geodetic signals. For the first time, we investigate the dynamics of bubbles in an elastic conduit unveiling the relationship between slugs and crustal strain accumulation around the conduit. Moreover, we discuss the retroactive effects of the deformed conduit wall on the dynamics of a rising slug, particularly, how the flow is affected, and the eventual implications on the intensity of the eruption. Our results show that the combination of an elastic conduit with a large volume of gas may lead to the development of a new type of slug, here defined as a “super slug,” characterized by tapering towards the tail and a much higher ascent velocity and inner pressure compared with ordinary slugs. This newly observed behavior could be linked to vigorous explosive events.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Published versio