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- Tulet, Pierre, et al.
(författare)
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First results of the Piton de la Fournaise STRAP 2015 experiment: multidisciplinary tracking of a volcanic gas and aerosol plume
- 2017
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 17:8, s. 5355-5378
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Tidskriftsartikel (refereegranskat)abstract
- The STRAP (Synergie Transdisciplinaire pour Répondre aux Aléas liés aux Panaches volcaniques) campaign was conducted in 2015 to investigate the volcanic plumes of Piton de La Fournaise (La Réunion, France). For the first time, measurements at the local (near the vent) and at the regional scales around the island were conducted. The STRAP 2015 campaign has become possible thanks to a strong cross-disciplinary collaboration between volcanologists and meteorologists. The main observations during four eruptive periods (85 days) are summarized. They include the estimates of SO2, CO2 and H2O emissions, the altitude of the plume at the vent and over different areas of La Réunion Island, the evolution of the SO2 concentration, the aerosol size distribution, and the aerosol extinction profile. A climatology of the volcanic plume dispersion is also reported. Simulations and measurements showed that the plume formed by weak eruption has a stronger interaction with the surface of the island. Strong SO2 and particles concentrations above 1000 ppb and 50 000 cm−3, respectively, are frequently measured over 20 km of distance from the Piton de la Fournaise. The measured aerosol size distribution shows the predominance of small particles in the volcanic plume. A particular emphasis is placed on the gas-particle conversion with several cases of strong nucleation of sulfuric acid observed within the plume and at the distal site of the Maïdo observatory. The STRAP 2015 campaign gave a unique set of multi-disciplinary data that can now be used by modellers to improve the numerical paramameterizations of the physical and chemical evolution of the volcanic plumes.
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| 2. |
- Holland, Linda Z, et al.
(författare)
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The amphioxus genome illuminates vertebrate origins and cephalochordate biology
- 2008
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 18:7, s. 1100-1111
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Tidskriftsartikel (refereegranskat)abstract
- Cephalochordates, urochordates, and vertebrates evolved from a common ancestor over 520 million years ago. To improve our understanding of chordate evolution and the origin of vertebrates, we intensively searched for particular genes, gene families, and conserved noncoding elements in the sequenced genome of the cephalochordate Branchiostoma floridae, commonly called amphioxus or lancelets. Special attention was given to homeobox genes, opsin genes, genes involved in neural crest development, nuclear receptor genes, genes encoding components of the endocrine and immune systems, and conserved cis-regulatory enhancers. The amphioxus genome contains a basic set of chordate genes involved in development and cell signaling, including a fifteenth Hox gene. This set includes many genes that were co-opted in vertebrates for new roles in neural crest development and adaptive immunity. However, where amphioxus has a single gene, vertebrates often have two, three, or four paralogs derived from two whole-genome duplication events. In addition, several transcriptional enhancers are conserved between amphioxus and vertebrates--a very wide phylogenetic distance. In contrast, urochordate genomes have lost many genes, including a diversity of homeobox families and genes involved in steroid hormone function. The amphioxus genome also exhibits derived features, including duplications of opsins and genes proposed to function in innate immunity and endocrine systems. Our results indicate that the amphioxus genome is elemental to an understanding of the biology and evolution of nonchordate deuterostomes, invertebrate chordates, and vertebrates.
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| 3. |
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| 4. |
- Peltier, Aline, et al.
(författare)
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Volcano Crisis Management at Piton de la Fournaise (La Reunion) during the COVID-19 Lockdown
- 2021
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Ingår i: Seismological Research Letters. - : Seismological Society of America (SSA). - 1938-2057 .- 0895-0695. ; 92:1, s. 38-52
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Tidskriftsartikel (refereegranskat)abstract
- In March 2020, the coronavirus disease 2019 outbreak was declared a pandemic by the World Health Organization and became a global health crisis. Authorities worldwide implemented lockdowns to restrict travel and social exchanges in a global effort to counter the pandemic. In France, and in French overseas departments, the lockdown was effective from 17 March to 11 May 2020. It was in this context that the 2-6 April 2020 eruption of Piton de la Fournaise (La Reunion Island, Indian Ocean) took place. Upon the announcement of the lockdown in France, a reduced activity plan was set up by the Institut de Physique du Globe de Paris, which manages the Observatoire Volcanologique du Piton de la Fournaise (OVPF). The aim was to (1) maintain remote monitoring operations by teleworking and (2) authorize fieldwork only for critical reasons, such as serious breakdowns of stations or transmission relays. This eruption provided an opportunity for the observatory to validate its capacity to manage a volcanic crisis with 100% remotely operated monitoring networks. We thus present the longand short-term precursors to the eruption, and the evolution of the eruption recorded using the real-time monitoring data as communicated to the stakeholders. The data were from both continuously recording and transmitting field instruments as well as satellites. The volcano observatory staff remotely managed the volcano crisis with the various stakeholders based only on these remotely functioning networks. Monitoring duties were also assured in the absence of ad hoc field investigation of the eruption by observatory staff or face-to-face communications. The density and reliability of the OVPF networks, combined with satellite observations, allowed for trustworthy instrument-based monitoring of the eruption and continuity of the OVPF duties in issuing regular updates of volcanic activity in the context of a double crisis: volcanic and health.
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| 5. |
- van Leeuwen, F., et al.
(författare)
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Gaia Data Release 1 : Open cluster astrometry: Performance, limitations, and future prospects
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 601
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Tidskriftsartikel (refereegranskat)abstract
- Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information. Aims. We investigate the scientific potential and limitations of the TGAS component by means of the astrometric data for open clusters. Methods. Mean cluster parallax and proper motion values are derived taking into account the error correlations within the astrometric solutions for individual stars, an estimate of the internal velocity dispersion in the cluster, and, where relevant, the effects of the depth of the cluster along the line of sight. Internal consistency of the TGAS data is assessed. Results. Values given for standard uncertainties are still inaccurate and may lead to unrealistic unit-weight standard deviations of least squares solutions for cluster parameters. Reconstructed mean cluster parallax and proper motion values are generally in very good agreement with earlier Hipparcos-based determination, although the Gaia mean parallax for the Pleiades is a significant exception. We have no current explanation for that discrepancy. Most clusters are observed to extend to nearly 15 pc from the cluster centre, and it will be up to future Gaia releases to establish whether those potential cluster-member stars are still dynamically bound to the clusters. Conclusions. The Gaia DR1 provides the means to examine open clusters far beyond their more easily visible cores, and can provide membership assessments based on proper motions and parallaxes. A combined HR diagram shows the same features as observed before using the Hipparcos data, with clearly increased luminosities for older A and F dwarfs.
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