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

Ash aggregation during the 11 February 2010 partial dome collapse of the Soufrière Hills Volcano, Montserrat

On 11 February 2010, Soufrière Hills Volcano, Montserrat, underwent a partial dome collapse (~ 50 × 106 m3) and a short-lived Vulcanian explosion towards the end. Three main pyroclastic units were identified N and NE of the volcano: dome-collapse pyroclastic density current (PDC) deposits, fountain-collapse PDC deposits formed by the Vulcanian explosion, and tephra-fallout deposits associated with elutriation from the dome-collapse and fountain-collapse PDCs (i.e. co-PDC fallout deposit). The fallout associated with the Vulcanian explosion was mostly dispersed E and SE by high altitude winds. All units N and NE of the volcano contain variable amounts and types of particle aggregates, although the co-PDC fallout deposit is associated with the largest abundance (i.e. up to 24 wt%). The size of aggregates found in the co-PDC fallout deposit increases with distance from the volcano and proximity to the sea, reaching a maximum diameter of 12 mm about 500 m from the coast. The internal grain size of all aggregates have nearly identical distributions (with Mdϕ ≈ 4–5), with particles in the size categories > 3 ϕ (i.e. < 250 μm) being distributed in similar proportions within the aggregates but in different proportions within distinct internal layers. In fact, most aggregates are characterized by a coarse grained central core occupying the main part of the aggregate, coated by a thin layer of finer ash (single-layer aggregates), while others have one or two additional layers accreted over the core (multiple-layer aggregates). Calculated aggregate porosity and settling velocity vary between 0.3 and 0.5 and 11–21 m s− 1, respectively. The aggregate size shows a clear correlation with both the core size and the size of the largest particles found in the core. The large abundance of aggregates in the co-PDC fallout deposits suggests that the buoyant plumes elutriated above PDCs represent an optimal environment for the formation (particle collision) and development (aggregate layering) of particle aggregates. However, specific conditions are required, including i) a large availability of water (in this case provided by the steam plumes associated with the entrance of PDCs into the ocean), ii) presence of plume regions with different grain-size features (i.e. both median size and sorting) that allows for the development of multiple layers, iii) strong turbulence that permits both particle collision and the transition of the aggregates through different plume regions, iv) presence of hot regions (e.g. PDCs) that promote aggregate preservation (in this case also facilitated by the presence of sea salt)

The paroxysmal event and its deposits

The 5 April 2003 eruption of Stromboli volcano (Italy) was the most violent in the past 50 years. It was also the best documented due to the accurate geophysical monitoring of the ongoing effusive eruption. Detailed field studies carried out a few hours to a few months after the event provided further information that were coupled with visual documentation to reconstruct the explosive dynamics. The eruption consisted of an 8-min-long explosive event preceded by a short-lived precursory activity that evolved into the impulsive ejection of gas and pyroclasts. Meter-sized ballistic blocks were launched to altitudes of up to 1400 m above the craters falling on the volcano flanks and on the village of Ginostra, about 2 km far from the vent. The vertical jet of gas and pyroclasts above the craters fed a convective plume that reached a height of 4 km. The calculated erupted mass yielded values of 1.1–1.4 × 108 kg. Later explosions generated a scoria flow deposit, with an estimated mass of 1.0–1.3 × 107 kg. Final, waning ash explosions closet the event. The juvenile fraction consisted of an almost aphyric, highly vesicular pumice mingled with a shallow-derived, crystal-rich, moderately vesicular scoria. Resuming of the lava emission a few hours after the paroxysm indicate that the shallow magmatic system was not significantly modified during the explosions. Combination of volume data with duration of eruptive phases allowed us to estimate the eruptive intensity: during the climactic explosive event, the mass discharge rate was between 106 and 107 kg/s, whereas during the pyroclastic flow activity, it was 2.8–3.6 × 105 kg/s. Strong similarities with other historical paroxysms at Stromboli suggest similar explosion dynamics

The properties of large bubbles rising in very viscous liquids in vertical columns

Very viscous liquids (>100 Pa s) are found in form of heavy oils and polymers in industry as well as in the natural environment (silicatic magma). Little is known of their behaviour as gas bubbles up through them in vertical columns. Using advanced tomographic instrumentation, the characteristics of these flows have been quantified. It was found that: the gas mainly travels as very large bubbles which occupy a significant part of the column cross-section and that very small bubbles (~100 lm) are created and trapped within the liquid. There is a periodic rising and falling of the top surface of the gas/liquid column as the large bubbles rise to the top and burst

An 81-Year-Old Man with a 6-Year History of Chronic Lymphocytic Leukemia Presenting with Disease Flare Following Ibrutinib Discontinuation

Patient: Male, 81-year-old Final Diagnosis: Chronic lymphocytic leukemia Symptoms: Fever Medication: — Clinical Procedure: — Specialty: Hematology Objective: Background: Case Report: Conclusions: Unusual clinical course Chronic lymphocytic leukemia (CLL) is a mature B-cell neoplasm and the most common leukemia in adults in Western countries. Novel agents, including BTK inhibitors and the BCL2 inhibitor venetoclax, have dramati-cally changed the treatment landscape. Moreover, a disease flare, characterized by sudden worsening of clinical symptoms, radiographic findings of rapidly worsening splenomegaly or lymphadenopathy, and laboratory changes (increased absolute lymphocyte count or lactate dehydrogenase), is a phenomenon described in up to 25% of patients with CLL after ibrutinib discontinuation. We describe a patient with CLL with disease flare after ibrutinib discontinuation due to disease progression and describe the subsequent management of vene-toclax initial treatment in the course of the disease flare. We describe the case of an 81-year-old man with a 6-year history of CLL who was treated with multiple lines of therapy and developed worsening of disease-related signs and symptoms with fever, marked increase of lym-phocyte count, acute worsening of renal function, and increase in lymph nodes and spleen size following ces-sation of targeted therapy with ibrutinib at the time of disease progression. There was subsequent overlap-ping of ibrutinib during the venetoclax dose escalation period to prevent disease flare recurrence. Our report highlights the problem of disease flare after ibrutinib discontinuation in order to avoid associated patient morbidity, underscoring the importance of awareness of this phenomenon and focusing on the addition of venetoclax at time of progression in ibrutinib-treated patients, as a temporary overlap strategy, to prevent disease flare

The machine protection system for the ELI-NP gamma beam system

The new Gamma Beam System (GBS) of the ELI-NPproject [1], currently under installation in Magurele (RO)by INFN, as part of EuroGammas consortium, can providegamma rays that open new possibilities for nuclear photonicsand nuclear physics.ELI-NP gamma rays are produced by Compton back-scattering to get monochromaticity (0,1% bandwidth), highflux (1013photons), tunable direction and energy up to19.5 MeV. Such gamma beam is obtained when a high-intensity laser collides a high-brightness electron beam withenergies up to740 MeV, a repetition rate of100 Hz, withtrains of 32 bunches within the same RF bucket.An advanced Machine Protection System (MPS) has beendeveloped, in order to ensure proper operation for this chal-lenging facility. The MPS operates on different layers of thecontrol system and is interfaced with all its sub-systems. Forinstance, it comprises different kind of beam loss monitors(based on Cherenkov optical fiber), hall probes, fast currenttransformer together with BPMs, and an embedded systembased on FPGA with distributed I/O over EtherCAT, to mon-itor vacuum and RF systems [2], which require fast responseto be interlocked within one RF pulse

High power test results of the Eli-NP S-Band gun fabricated with the new clamping technology without brazing

High gradient RF photoguns have been a key development to enable several applications of high quality electron beams. They allow the generation of beams with very high peak current and low transverse emittance, thus satisfying the tight demands of free-electron lasers, energy recovery linacs, Compton/Thomson sources and high-energy linear colliders. A new fabrication technique for this type of structures has been recently developed and implemented at the Laboratories of Frascati of the National Institute of Nuclear Physics (INFN-LNF, Italy). It is based on the use of special RF-vacuum gaskets, that allow a brazing-free realization process. The S-band gun of the ELI-NP gamma beam system (GBS) has been fabricated with this new technique. It operates at 100 Hz with 120 MV/m cathode peak field and 1.5 μs long RF pulses to house the 32 bunches necessary to reach the target gamma flux. High gradient tests, performed at full power and full repetition rate, have shown extremely good performances of the structure in terms of breakdown rate. In the paper, we report and discuss all the experimental results, the electromagnetic design and the mechanical realization processes