Réactions aux interfaces de bicristaux compatibles et incompatibles

La rupture intergranulaire peut apparaître suite à la non accommodation des contraintes au voisinage de l'interface. La transmission du glissement au travers d'une interface est un des modes de relaxation possible qui dépend des paramètres suivants : facteurs géométriques (caractéristiques de l'interface et systèmes de glissement activés), constantes élastiques de chacune des phases. Dans cette étude, la microscopie électronique à transmission (MET) est utilisée pour analyser les configurations de dislocations résultant d'une déformation par fatigue de bicristaux d'acier austénoferritique de désorientations contrôlées. Deux types de bicristaux sont étudiés, compatible et incompatible plastiquement. Pour chacun d'eux, la déformation est initiée soit dans la phase ferritique $\alpha$ soit dans la phase austénitique $\gamma$ selon la localisation d'une entaille préalable à l'essai mécanique. Les résultats permettent de remonter aux mécanismes élémentaires qui régissent le transfert “direct” ou “indirect” des dislocations à travers l'interface. Une corrélation avec le comportement des bicristaux à l'échelle macroscopique est également tentée

Infrasound monitoring for atmospheric studies : challenges in middle atmosphere dynamics and societal benefits

Violent volcanic eruptions, common especially in Southeast Asia, pose an ongoing serious threat to aviation and local communities. However, the physical conditions at the eruptive vent are difficult to estimate. In order to tackle this problem, satellite imagery and infrasound can rapidly provide information about strong eruptions of volcanoes not closely monitored by on-site instruments. For example, the recent infrasonic array at Singapore, installed to support the coverage of the International Monitoring System, allows identification of nearby erupting volcanoes based on the characteristics of the recorded signal. But, due to its location close to the equator, seasonal changes in the wind velocity structure of the atmosphere strongly affect its potential to detect small volcanic eruptions at certain azimuths. To overcome this limit, infrasound could be augmented with satellite data. Yet, with the high average cloud cover in Southeast Asia, there are also challenges to identify weak volcanic plumes using satellite based monitoring techniques. In this chapter, we aim to examine the relative strengths and weaknesses of the two technologies to better understand the possibility to improve overall detection capability by combining infrasound with satellite imagery

An overview of lava dome evolution, dome collapse and cyclicity at Soufriere Hills Volcano, Montserrat, 2005-2007

The third episode of lava dome growth at Soufrière Hills Volcano, Montserrat was characterised by higher average magma discharge rates than either previous dome growth episode at this volcano and yet fewer collapses. During sustained dome growth at moderate‐high average rates (>6 m3/s), we identified 2–6 week discharge pulses that each supplied c.20 Mm3 magma from depth. Our observations are consistent with some existing models but we explain discrepancies by a combination of higher volatile contents and higher ascent rates. Cycles of c. 11–16 days were evident in rockfall, LP rockfall and shallow LP earthquake counts related to dome growth and degassing. We speculate that degassing at the conduit margins together with stick‐slip conduit flow may drive these cycles. Only one major collapse >10 Mm3 occurred during the third episode (on May 20, 2006) as a new magma pulse entered the dome and coincided with heavy rainfall

On the use of remote infrasound and seismic stations to constrain the eruptive sequence and intensity for the 2014 Kelud eruption

info:eu-repo/semantics/publishe

The damaging November 2022 Mw 5.6 earthquake in West Java, Indonesia

On 21 November 2022, a MW 5.6. earthquake hit Cianjur area in West Java, Indonesia. The small magnitude earthquake claimed 329 people’s lives, and about 114,414 people were taking shelter in refugee camps as of 1 December 2022 according to the National Disaster Mitigation Agency (BNPB) of Indonesia. We produced maps of coseismic deformation and surface disturbance (a.k.a. Damage Proxy Map, DPM) using Synthetic Aperture Radar (InSAR) data acquired by the ALOS-2 satellite about 11 hours after the earthquake. We combine and analyze ground observations, coseismic deformation and surface disturbance maps derived from ALOS-2 and Sentinel-1 SAR data, seismic waveforms of the mainshock and aftershocks, high-rate GNSS data, and tiltmeter data to characterize the source parameters of the earthquake and damage caused by the strong ground motion, landslides, and liquefaction, and study the potential impact of the event on the geohazards of the area

Induction of antigen-specific cytotoxic T lymphocytes in humans by a malaria DNA vaccine

CD8⁺ cytotoxic T lymphocytes (CTLs) are critical for protection against intracellular pathogens but often have been difficult to induce by subunit vaccines in animals. DNA vaccines elicit protective CD8⁺ T cell responses. Malaria-naı̈ve volunteers who were vaccinated with plasmid DNA encoding a malaria protein developed antigen-specific, genetically restricted, CD8⁺ T cell–dependent CTLs. Responses were directed against all 10 peptides tested and were restricted by six human lymphocyte antigen (HLA) class I alleles. This first demonstration in healthy naı̈ve humans of the induction of CD8⁺ CTLs by DNA vaccines, including CTLs that were restricted by multiple HLA alleles in the same individual, provides a foundation for further human testing of this potentially revolutionary vaccine technology