Real-Time Geophysical Monitoring of Particle Size Distribution During Volcanic Explosions at Stromboli Volcano (Italy)

Of all the key parameters needed to inform forecast models for volcanic plumes, real-time tracking particle size distribution (PSD) of pyroclasts leaving the vent coupled with plume modeling has probably the highest potential for effective management of volcanic hazard associated with plume dispersal and sedimentation. This paper presents a novel algorithm capable of providing syn-emission horizontal size and velocity of particles in real time, converted in mass discharge rates, and its evolution during an explosion, using thermal infrared videos. We present data on explosions that occurred at the SW crater of Stromboli volcano (Italy) in 2012. PSDs and mass eruption rate (MER) data, collected at frequencies of 40 Hz, are then coupled with particle and gas speed data collected with traditional image analysis techniques. The dataset is used to quantify for the first time the dynamics of the explosions and the regime of magma fragmentation. We find that explosive evacuation of magma from a Strombolian conduit during a single explosion proceeds at a constant rate while the explosive dynamics are marked by a pattern that includes an initial transient and short phase until the system stabilizes at equilibrium. These stationary conditions dominate the emission. All explosions begin with a gas jet (onset phase), with maximum recorded vertical velocities above 150 m/s. These high velocities are for small particles carried by the faster moving gas or pressure wave, and larger particles typically have slower velocities. The gas jets are followed by a particle-loaded plume. The particles increase in number until the explosion dynamics become almost constant (in the stationary phase). MER is either stable or increases during the onset to become stable in the stationary phase. The shearing at the interface between the magma and the gas jets controls fragmentation dynamics and particles sizes. Quantification of the Reynolds and Weber numbers suggests that the fragmentation regime changes during an explosion to affect particle shape. The algorithm proposed requires low-cost thermal monitoring systems, and low processing capability, but is robust, powerful, and accurate and is able to provide data with unprecedented accuracy. In general terms, its applicability is limited by the size of individual pixels recorded by the camera, which depends on the detector, the recording distance, and the optical system, particle temperature, which has to be significantly higher than the background

O efeito dos fatores bióticos sobre a distribuição de espécies exóticas marinhas, um estudo latitudinal

Resumo: A bioinvasão e uma das maiores ameaças aos ecossistemas marinhos, sendo de fundamental importância compreender quais fatores regulam a introdução de espécies nesses ambientes. Sabe-se que a predação e a disponibilidade de recursos alteram a resistência biótica das comunidades. Neste contexto, o objetivo deste trabalho foi compreender como a predação e a disponibilidade de recurso (substrato livre) atuam para a determinação da invasão em áreas de risco, bem como avaliar o efeito destes fatores na determinação dos padrões latitudinais de bioinvasão por invertebrados da comunidade incrustante. Para isto dois experimentos foram realizados em quatro pontos ao longo da costa brasileira: Santa Catarina, São Paulo, Bahia e Ceara, incluindo uma faixa de latitudes entre 3o e 27oS. O primeiro capitulo da tese visou compreender como a predação regula as comunidades incrustantes em áreas de substrato artificial ao longo da costa brasileira, enfatizando a capacidade dos predadores presentes nestas áreas em limitar a colonização e estabelecimento exitoso de espécies exóticas. Para isso um grupo de unidades amostrais foi submetida a predação, enquanto em outro grupo houve a exclusão de predadores. Foi observado que a predação é um fator-chave para a determinação das comunidades incrustantes, selecionando espécies com uma melhor estrutura de defesa. Ainda, a predação atuou como um importante fator controlador de espécies exóticas, já que houve diminuição da abundancia dessas espécies nas placas sujeitas a predação. O objetivo do segundo capitulo foi entender como a perturbação não seletiva atua para a estruturação da comunidade. O experimento consistiu na liberação de espaço pela remoção dos organismos presentes de modo a disponibilizar espaço para a colonização de espécies. Após três meses de desenvolvimento da comunidade, foram aplicados os tratamentos que consistiram na liberação de 6, 12, 25 e 50% da área da placa. Foi observado que comunidades de substratos artificiais são bastante resilientes à perturbação, voltando rapidamente ao estagio anterior. Ainda, a intensidade de perturbação não influenciou a porcentagem de cobertura de espécies exóticas ou nativas. O terceiro capitulo teve como objetivo avaliar a presença de espécies exóticas e testar mecanismos de resistência biótica em uma perspectiva latitudinal. Não foi observado declínio do numero de espécies exóticas nas regiões tropicais. Também não foi observado aumento das interações bióticas nas menores latitudes, já que a intensidade de predação e a utilização do recurso limitante espaço não foi maior em sentido as menores latitudes. Desta forma, observa-se que comunidades marinhas incrustantes de substratos artificiais ao longo da costa brasileira são fortemente controladas por predadores, porem bastante resilientes à liberação de espaço, independentemente da latitude estudada. Assim a predação, apesar de não apresentar um padrão latitudinal, pode limitar a abundância de espécies exóticas, enquanto processos de interações entre as espécies durante a ocupação do espaço não foram capazes de controlar bioinvasão

Conduit Processes at the Haukadalur Geyser‐Hosting Hydrothermal Field (Iceland) Revealed by In Situ Temperature and High‐Speed Camera Measurements

Geysers fascinate scientists and visitors for several centuries. However, many driving mechanisms such as heat transfer in the conduit and in the subsurface remain poorly understood. We document for the first time transient temperature variations inside the active Strokkur's and nearby quasi-dormant Great Geysir's conduits, Iceland. While recording temperature inside the conduit, we visually monitored Strokkur's activity at the vent with a high-speed camera, providing a high temporal resolution of the eruptions. Our results reveal heat transfer from a bubble trap to and through the conduit. We propose a model for the eruptive cycle of Strokkur that includes vapor slug rise, eruption, and conduit refill. Each water jet of an eruption is marked by an initial pulse of liquid water and vapor, emitted at a velocity between 5 and 28 m/s and generally followed by a second pulse less than a second later. The timing of eruptions coincides with temperature maxima in the conduit. After the eruption, the conduit is refilled by water falling back in the pool and drained from neighboring groundwater-saturated geological units. This results in a temperature drop, the amplitude of which increases with depth while its period is reduced. This reflects faster heat transfer in the deeper than shallower part of the conduit. The amplitude of temperature drop following an eruption also increases with the eruption order, implying larger heat release by higher-order eruptions. Temperature in the conduit subsequently increases until the next eruption, starting then a new cycle

Determination of the largest clast sizes of tephra deposits for the characterization of explosive eruptions: a study of the IAVCEI commission on tephra hazard modelling

The distribution of clasts deposited around a volcano during an explosive eruption typically contoured by isopleth maps provides important insights into the associated plume height, wind speed and eruptive style. Nonetheless, a wide range of strategies exists to determine the largest clasts, which can lead to very different results with obvious implications for the characterization of eruptive behaviour of active volcanoes. The IAVCEI Commission on Tephra Hazard Modelling has carried out a dedicated exercise to assess the influence of various strategies on the determination of the largest clasts. Suggestions on the selection of sampling area, collection strategy, choice of clast typologies and clast characterization (i.e. axis measurement and averaging technique) are given, mostly based on a thorough investigation of two outcrops of a Plinian tephra deposit from Cotopaxi volcano (Ecuador) located at different distances from the vent. These include: (1) sampling on a flat paleotopography far from significant slopes to minimize remobilization effects; (2) sampling on specified-horizontal-area sections (with the statistically representative sampling area depending on the outcrop grain size and lithic content); (3) clast characterization based on the geometric mean of its three orthogonal axes with the approximation of the minimum ellipsoid (lithic fragments are better than pumice clasts when present); and (4) use of the method of the 50th percentile of a sample of 20 clasts as the best way to assess the largest clasts. It is also suggested that all data collected for the construction of isopleth maps be made available to the community through the use of a standardized data collection template, to assess the applicability of the new proposed strategy on a large number of deposits and to build a large dataset for the future development and refinement of dispersal model

Gas rising through a large diameter column of very viscous liquid: Flow patterns and their dynamic characteristics

Gas-liquid flows are affected strongly by both the liquid and gas properties and the pipe diameter, which control features and the stability of flow patterns and their transitions. For this reason, empirical models describing the flow dynamics can be applied only to limited range of conditions. Experiments were carried out to study the behaviour of air passing through silicone oil (360 Pa.s) in 240 mm diameter bubble column using Electrical Capacitance Tomography and pressure transducers mounted on the wall. These experiments are aimed at reproducing expected conditions for flows including (but not limited to) crude oils, bitumen, and magmatic flows in volcanic conduits. The paper presents observation and quantification of the flow patterns present. It particularly provides the characteristics of gas-liquid slug flows such as: void fraction; Taylor bubble velocity; frequency of periodic structures; lengths of liquid slugs and Taylor bubbles. An additional flow pattern, churn flow, has been identified. The transition between slug and churn has been quantified and the mechanism causing it are elucidated with the assistance of a model for the draining of the liquid film surrounding the Taylor bubble once this has burst through the top surface of the aerated column of gas-liquid mixture. It is noted that the transition from slug to churn is gradual

Sequential capillarity-assisted particle assembly in a microfluidic channel

The authors acknowledge support from an ETH Research Grant ETH-15 17-1 (R. S.), from an ETH Postdoctoral Fellowship FEL-21 15-2 and SNSF PRIMA Grant 179834 (E. S.), from a Postdoctoral fellowships programme “Beatriu de Pinós”, funded by the Secretary of Universities and Research (Government of Catalonia) and by the Horizon 2020 programme of research and innovation of the European Union under the Marie Sklodwoska-Curie grant agreement no. 801370 (Grant 2018 BP 00029) (M. A. F. R.) and from a Gordon and Betty Moore Foundation Investigator Award on Aquatic Microbial Symbiosis (grant GBMF9197) (R. S.). The authors thank Dr. Heiko Wolf at IBM Research Zurich for insightful discussions.Colloidal patterning enables the placement of a wide range of materials into prescribed spatial arrangements, as required in a variety of applications, including micro- and nano-electronics, sensing, and plasmonics. Directed colloidal assembly methods, which exploit external forces to place particles with high yield and great accuracy, are particularly powerful. However, currently available techniques require specialized equipment, which limits their applicability. Here, we present a microfluidic platform to produce versatile colloidal patterns within a microchannel, based on sequential capillarity-assisted particle assembly (sCAPA). This new microfluidic technology exploits the capillary forces resulting from the controlled motion of an evaporating droplet inside a microfluidic channel to deposit individual particles in an array of traps microfabricated onto a substrate. Sequential depositions allow the generation of a desired spatial layout of colloidal particles of single or multiple types, dictated solely by the geometry of the traps and the filling sequence. We show that the platform can be used to create a variety of patterns and that the microfluidic channel easily allows surface functionalization of trapped particles. By enabling colloidal patterning to be carried out in a controlled environment, exploiting equipment routinely used in microfluidics, we demonstrate an easy-to-build platform that can be implemented in microfluidics labs.ETH Research Grant ETH-15 17-1ETH Postdoctoral Fellowship FEL-21 15-2SNSF PRIMA Grant 179834Postdoctoral fellowships programme "Beatriu de Pinos" - Government of CataloniaHorizon 2020 programme of research and innovation of the European Union under the Marie Sklodwoska-Curie grant 801370 2018 BP 00029Gordon and Betty Moore Foundation Investigator Award on Aquatic Microbial Symbiosis GBMF919

Lack of COI variation for Clavelina oblonga (Tunicata, Ascidiacea) in Brazil: Evidence for its human-mediated transportation?

Recent studies indicate that ascidians are efficiently dispersed by human transport. We have chosen the mitochondrial gene cytochrome c oxidase subunit I (COI) to address whether Clavelina oblonga is an introduced species in the Brazilian coast. Colonies of C. oblonga were sampled in different localities along Atlantic coasts of USA, Panama, and Brazil. The sequencing of 92 colonies resulted in three haplotypes for the species, two unique to Florida and the other shared by exemplars collected in Brazil and Panama; the latter haplotype is identical to the published sequence of Azores. Our evidence, including the absence of C. oblonga in the country's northern tropical waters, its association with artificial habitats and lack of COI variation suggest that the species has been introduced in the southeastern and southern Brazilian coasts. Previous records (85 years old) suggest that it could be a relatively long-term introduction.CNPqCNPq [473408/2003-01]FAPESPFAPESP [2009/08941-3, 2009/08940-7

Hypertension and emergency medicine: an update

The objective of this paper is to evaluate the correct management of hypertension in emergency departments. Studies were identified searching PubMed up to April 30, 2012, combining the terms 'HYPERTENSIVE EMERGENCY' and 'HYPERTENSIVE URGENCY'. The search strategy was limited to English and Italian language papers on adult and pediatric patients. Hypertensive crises are commonly found in emergency departments. A range of pharmacological options are available in this setting, but each physician should tailor theoretical principles to the individual patient according to his or her clinical parameters

Brincar para aprender para brincar: as experiências e ações extensionistas do Projeto de Lixo a Bicho

Anais do 35º Seminário de Extensão Universitária da Região Sul - Área temática: Educação, Meio AmbienteO Projeto de extensão de “DE LIXO A BICHO: Ações de educação socioambiental por meio de materiais lúdico residuais” é d​ esenvolvido pelo Instituto Federal de Santa Catarina – IFSC, Câmpus Itajaí e tem como objetivo o fomento de vivências e ações extensionistas de educação ambiental junto à comunidade escolar, por meio da utilização de materiais lúdicos residuais oriundos de redes colaborativas. Os brinquedos são produzidos a partir de resíduos limpos obtidos de diversos ramos de atividades industriais e sua criação tem como foco a reflexão sobre as questões ambientais contemporâneas, visando à sensibilização de crianças e jovens no contexto da Educação Básica. As atividades descritas fazem parte de um conjunto de ações que têm como objeto principal os brinquedos criados e produzidos no âmbito desse projeto, cuja ênfase está no fomento às experiências lúdicas voltadas para a educação ambiental numa perspectiva crítica. O primeiro material lúdico desenvolvido pela equipe foi a BICHORUGA, ​ u m a ressignificação do jogo das cinco marias que traz elementos para reflexão sobre a produção, consumo, descarte e gestão de resíduos na sociedade e suas consequências. As ações de extensão têm sido propostas em diversos contextos, atendendo diferentes públicos, desde professores e gestores até crianças do Ensino Básico, na perspectiva do brincar para aprender ou do aprender para brinca