Pelosi, Hebe Carmen. Argentinos en Francia. Franceses en Argentina, una historia colectiva. Prólogo de Paúl Dijoud. Buenos Aires, Argentina, 1999, 527p.

Fil: Ferrazzini de Otero, Verónica

Genetic variability and population divergence in the rare Fritillaria tubiformis subsp. moggridgei Rix (Liliaceae) as revealed by RAPD analysis

Fritillaria tubiformis subsp. moggridgei Rix. is a rare alpine geophyte with shiny yellow flowers. This plant is sporadically distributed across the southwestern Alps where it is biogeographically close to F. tubiformis var. burnatii Planch. The latter has dark purple flowers and ranges in the majority of the Western and Central Alps. In order to develop appropriate strategies of conservation, a RAPD based analysis was conducted to study the genetic status of these taxa and the distribution of genetic variability of the subspecies by sampling seven populations distributed across the subspecies' range. Four populations of var. burnatii were chosen within this range and included in the genetic analysis. Some 264 individuals were analysed and 201 polymorphic loci were scored. Genetic diversity scored in the subspecies was in line with expectations for endemic species (He  = 0.194). F. tubiformis var. burnatii showed lower intraspecific diversity (He  = 0.173), notwithstanding a wider range than the subspecies. Most of the total phenotypic variation (about 83%) was allocated within populations, and significant lower proportions between taxa (6.45%) and between populations of the same taxon (10.64%). Moreover, PCoA analysis and Bayesian clustering separated populations into two genetically differentiated groups corresponding with the subspecific taxa. However, three populations ascribed to the subsp. moggridgei repeatedly showed genetic admixture with var. burnatii populations. Our findings suggest that: i) although the different flower colour, the two taxa are genetically very similar and share a consistent part of their gene pool, ii) the majority of genetic variability is allocated within populations rather than among them, iii) a representative amount of genetic diversity can be preserved by sampling from a restricted number of populations. The efficacy of RAPD markers in analysing genetic variation, and the contribution of the results to the preservation of biodiversity of the species, are discussed

Imaging the dynamics of magma propagation using radiated seismic intensity.

International audienceAt shallow depth beneath the Earth's surface, magma propagates through strongly heterogeneous volcanic material. Inversion of buoyancy and/or solidification have strong impacts on the dynamics of propagation without any change of magma supply. In this paper, we study the spatial and time evolution of magma intrusions using induced seismicity. We propose a new method based on ratio analysis of estimates of radiated seismic intensities recorded at different stations during seismic swarms. By applying this method to the January 2010 Piton de la Fournaise volcano eruption, we image complex dike propagation dynamics which strongly differ from a model of constant velocity dike propagation. We provide a new method to image in real time the dynamics of dike propagation and to infer the position of eruptive fissures

Basaltic calderas: Collapse dynamics, edifice deformation, and variations of magma withdrawal

International audienceThe incremental caldera collapses of Fernandina (1968), Miyakejima (2000), and Piton de la Fournaise (2007) are analyzed in order to understand the collapse dynamics in basaltic setting and the associated edifice deformation. For each caldera, the collapse dynamics is assessed through the evolution of the (1) time interval T between two successive collapse increments, (2) amount of vertical displacement during each collapse increment, and (3) magma outflow rate during the whole collapse caldera process. We show from the evolution of T that Piton de la Fournaise and Fernandina were characterized by a similar collapse dynamics, despite large differences in the caldera geometry and the duration of the whole collapse caldera process. This evolution significantly differs from that of Miyakejima where T strongly fluctuated throughout the whole collapse process. Quantification of the piston vertical displacements enables us to determine the magma outflow rates between each collapse increment. Displacement data (tiltmeter and/or GPS) for Piton de la Fournaise and Miyakejima are used to constrain the edifice overall deformation and the edifice deformation rates. These data reveal that both volcanoes experienced edifice inflation once the piston collapsed into the magma chamber. Such a deformation, which lasts during the first collapse increments only, is interpreted as the result of larger volume of piston intruded in the magma chamber than magma withdrawn before each collapse increment. Once the effect of the collapsing rock column vanishes, edifice deflates. We also determine for each caldera the critical amount of magma evacuated before collapse initiation and compare it to analog models. The significant differences between models and nature are explained by the occurrence of preexisting weak zones in nature, i.e., the ring faults, that are not taken into account in analog models. Finally, we show that T at Piton de la Fournaise and Fernandina was equally controlled by the frictional resistance along the ring faults and the magma outflow rate. In addition to these two parameters, the collapse dynamics of Miyakejima was also influenced by variations of the magma bulk modulus, which changed after the influx of deep gas-rich magma into the collapse-related magma chamber. Altogether, our results show that the dynamics of caldera collapse in basaltic volcanoes proceeds in two phases: Phase 1, starting with the first collapse, is characterized by the largest collapse amplitude, an incremental edifice inflation, and a step-by-step increase of the rate of magma outflow. Phase 2 shows a rapid decrease of the magma discharge rate to a low level concomitant with the continuous edifice deflation. If deep magma is injected into the magma chamber, as at Miyakejima, an additional phase occurs (phase 3)

Monitoring volcanoes using seismic noise correlations Surveillance des volcans à partir du bruit de fond sismique

International audienceIn this article, we summarize some recent results of measurements of temporal changes of active volcanoes using seismic noise cross-correlations. We first present a novel approach to estimate volcano interior temporal seismic velocity changes. The proposed method allows to measure very small velocity changes (≈ 0.1%) with a time resolution as small as one day. The application of that method to Piton de la Fournaise Volcano (La Réunion Island) shows velocity decreases preceding eruptions. Moreover, velocity changes from noise cross-correlations over 10 years allow to detect transient velocity changes that could be due to long-lasting intrusions of magma without eruptive activity or to pressure buildup associated to the replenishing of the magma reservoir. We also present preliminary results of noise cross-correlation waveform perturbation associated with the occurrence of dike injection and volcanic eruption. We show that such an analysis leads us to locate the areas of dike injection and eruptive fissures at Piton de la Fournaise Volcano. These recent results suggest that monitoring volcanoes using seismic noise correlations should improve our ability to forecast eruptions, their intensity and thus potential environmental impact

Identificación de potenciales áreas de alto valor de conservación según FSC® para el litoral Uruguay

Tribunal: Soria, Luis; Ponce, Mauricio; Giordano, HoracioLas Áreas de Alto Valor de Conservación (AAVC) son identificadas por cada empresa, con baja participación de las terceras partes y sin validación estadística. Por este motivo, surge la necesidad de preservar las AAVC y toma relevancia el hecho de que la selección de las mismas se haga de forma participativa y con validez estadística. Dicho esto, el objetivo general de este trabajo es la identificación de modo participativo de potenciales AAVC según la definición del Forest Stewardship Council (FSC) en el litoral de Uruguay. La metodología utilizada es conocida como el ¨Método Q¨ y permite identificar percepciones sobre una determinada temática. El análisis involucra la aplicación secuencial de tres procedimientos estadísticos: correlación, análisis factorial y cálculo de escores de los factores y provee información sobre los diferentes puntos de vista de los individuos relacionados con la protección de áreas, pudiéndolos agrupar de acuerdo con sus similitudes y diferencias en relación con la temática en cuestión. Los resultados muestran que tanto el Sistema Nacional de Áreas Protegidas (SNAP) como las AAVC, persiguen el mismo objetivo: la planificación de áreas para su conservación y que ambas pueden ser validadas como AAVC según el FSC. Los resultados muestran claramente que hay un gran interés por la conservación en términos generales y que esta sea a través de la delimitación y protección de sitios o áreas. En relación con los atributos a conservar, los resultados mostraron 3 perfiles diferenciados donde el mayor interés se evidencia por los atributos específicos ambientales. Con esta información se elabora un mapa de atributos identificados por las partes interesadas como prioritarios para conservar. Dicho mapa, que podrá ser utilizado como una fuente de información más a la hora de delimitar potenciales áreas a conservar, involucra a los actores afectados desde el principio del proceso siendo este aspecto el de mayor relevancia a destacar

Retinal layer segmentation in a cohort of healthy children via optical coherence tomography.

BACKGROUND High-resolution optical coherence tomography (OCT) allows the detection of macular pathology and involvement of the optic nerve in a wide spectrum of diseases. For the differentiation of diseased and healthy status, normal values of retinal layer segmentation are critical. Yet, normative values mostly cover adult populations with only sparse data for paediatric cohorts. We present data of retinal layer characteristics via OCT in a healthy paediatric cohort. METHODS This prospective cross-sectional study screened 75 healthy children (male = 42, female = 33, range 4-17 years) without visual problems. OCT was performed with a peripapillary ring and macula scan protocol to determine paediatric normative values for routine parameters (peripapillary retinal nerve fibre layer thickness (pRNFL), total macular volume (TMV), macular retinal thickness (RT)). The macula scan (6mm grid) was segmented using the device-inherent automated segmentation software (Heidelberg Eye Explorer) for retinal layers: RNFL, ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL) in 9 segments each and mean of the 9 segments. RESULTS We obtained OCT data of 72 children with mean age 12.49 years (standard deviation, SD, 2.18; minimum 3.93). Mean global pRNFL was 102.20 μm (SD 8.24), mean TMV 8.81 mm3 (0.30) and mean RT (all segments) 318.22 μm (10.19). Segmented macular retinal layer thicknesses (mean of all segments) were: RNFL 27.67 μm (2.14), GCL 41.94 μm (2.50), IPL 34.97 μm (2.10), INL 35.18 μm (2.15), OPL 29.06 μm (2.24), ONL 68.35 μm (6.20). CONCLUSION The OCT is a useful non-invasive imaging technique for the examination of the retina in children with short duration, high imaging resolution and no known adverse effects. Normative values may serve as a comparator for different neuropaediatric disorders and are first presented with this study using an up-to-date and standardized OCT imaging technique

Variabilità genetica del noce comune (Juglans regia) in Piemonte

Abstract: The European or common walnut is a large tree prized as a multipurpose species: it provides valuable timber and produces a high-quality edible nut. The diffusion of the species in Italy has been largely influenced by the human activity, mainly through germplasm movement, selection of genotypes most suited for wood or fruit production and adaptation induced on fruit crop reproductive materials. As a consequence, genetic variability has been reduced, so that programs aimed at its preservation appear of the utmost importance. 104 walnut plants growing in Piedmont, northwestern Italy, were investigated through genetic variation scored at RAPD loci, yielded by PCR amplification of 10 decamer primers. Among the 101 studied loci, only 53 were polymorphic, showing a low level of genetic variation within the studied material. Genetic differentiation was estimated both at individual and geographical area level. Only in few cases trees growing in the same area showed to be genetically similar, while the differentiation between areas accounted for about 10% of the total variation, according to AMOVA. No significant correlation was found between genetic and geographic distances. The results of the study showed that also in Piedmont (such as it was already demonstrated in other parts of Italy) the distribution of common walnut is a direct consequence of the human activity. The selection of individual trees, to be used as basic materials for seed supply, should therefore be based mainly on phenotypic traits, rather than ecological features of the location: in species characterized by artificial diffusion, the adoption of Region of Provenance has a scarce significance and prominence should be given to the phenotype selection