Naturally Occurring Asbestos in France: Geological Mapping, Mineral Characterization and Regulatory Developments

International audienceIn France, the asbestos banning is subject to a national decree (n° 96-1133), published in 1996. The regulatory texts and standards adopted to control this banning concern in particular asbestos-bearing manufactured products, but remain difficult to apply to asbestos-bearing natural materials (ie. rocks, soils). Considering problems related to such asbestos-bearing natural materials, the Ministry of Ecological and Solidary Transition has mandated the French Geological Survey to locate the impacted areas. Mappings were priority carried out in geological domains where NOA was predictable (French Alps, Corsica). These studies integrated field expertise, sampling and laboratory analyses, in order to characterize the potential of geological units to contain NOA. Furthermore, some expertises were carried out on geological formations exploited in France to produce aggregates. These studies concerned the quarries exploiting massive basic or ultrabasic rocks, likely to contain NOA, and quarries exploiting alluvium likely to contain asbestos-bearing rock pebbles. These studies highlight the difficulty of establishing robust diagnoses for natural materials. Indeed, distinction between cleavage fragments resulting from the fragmentation of non-asbestos particles and proper asbestos fibers is particularly problematic for laboratories. Thus, a recent study of the National Agency for Health Safety, Food, Environment and Work (2015) recommends to apply the asbestos regulation for elongated mineral particles (L/D > 3:1, L > 5 μm, D < 3 μm) with chemical composition corresponding to one of the five regulated amphibole species, irrespective of their mode of crystallization (asbestiform or non-asbestiform). The upcoming regulatory changes are part of a decree published in 2017, including the prior identification of asbestos in natural soils or rocks likely to be impacted by the execution of work. Specific protocols will be defined for sampling, analysis and characterization of natural materials that may contain asbestos

The olfactory basis of orchid pollination by mosquitoes.

Mosquitoes are important vectors of disease and require sources of carbohydrates for reproduction and survival. Unlike host-related behaviors of mosquitoes, comparatively less is understood about the mechanisms involved in nectar-feeding decisions, or how this sensory information is processed in the mosquito brain. Here we show that Aedes spp. mosquitoes, including Aedes aegypti, are effective pollinators of the Platanthera obtusata orchid, and demonstrate this mutualism is mediated by the orchid's scent and the balance of excitation and inhibition in the mosquito's antennal lobe (AL). The P. obtusata orchid emits an attractive, nonanal-rich scent, whereas related Platanthera species-not visited by mosquitoes-emit scents dominated by lilac aldehyde. Calcium imaging experiments in the mosquito AL revealed that nonanal and lilac aldehyde each respectively activate the LC2 and AM2 glomerulus, and remarkably, the AM2 glomerulus is also sensitive to N,N-diethyl-meta-toluamide (DEET), a mosquito repellent. Lateral inhibition between these 2 glomeruli reflects the level of attraction to the orchid scents. Whereas the enriched nonanal scent of P. obtusata activates the LC2 and suppresses AM2, the high level of lilac aldehyde in the other orchid scents inverts this pattern of glomerular activity, and behavioral attraction is lost. These results demonstrate the ecological importance of mosquitoes beyond operating as disease vectors and open the door toward understanding the neural basis of mosquito nectar-seeking behaviors

Coupling SEM-EDS and confocal Raman-in-SEM imaging: A new method for identification and 3D morphology of asbestos-like fibers in a mineral matrix

International audienceAsbestos consists in natural minerals crystallized in a specific habit and possessing in particular properties. In the case of Naturally Occurring Asbestos, usual methods applied to the identification of mineral fibers and the determination of their possible asbestiform nature seems not efficient, especially in the case of mineral fibers included in mineral matrix. We present a new in-situ method based on the use of confocal Raman-in-SEM imaging implemented in a Scanning Electron Microscope as an efficient method for in-situ mineralogy. The limitation of conventional methods is discussed. We applied 2D-Raman imaging to the identification of sub-micrometric fibers included in different mineral matrix. We were able to identify actinolite fibers down to 400 nm in diameter, included in feldspar, quartz and/or calcite matrix. Moreover, Confocal Raman allows the collection of 3D data that would provide access to critical information on the morphology of the amphibole fibers in the volume, such as aspect ratio, fibers distribution and amphibole volume fraction. We performed this method on various examples of rocks containing actinolite fibers of mean structural formula is: Na0,04-0,12Mg2,79-3,73Al0,29-0,58K0,01Ca1,79-1,98Mn0,01-0,09Fe 2+ 0,99-1,91Fe 3+ 0,12-0,25Si7,64-7,73O22(OH)2. We demonstrated that coupling confocal Raman imaging and SEM is a new and efficient in-situ method for identification and morphological characterization of amphibole fibers. Highlights New methods are requested for characterizing asbestos fibers in a mineral matrix SEM-Raman imaging is efficient for characterizing mineral fibers in-situ Confocal Raman imaging makes 3D analysis possible 3D analysis provides information on the aspect ratio and volume fraction of asbestos Fibers thinner than 400nm can be identified by confocal Raman in SEM ( = 532 nm

Confocal Raman-in-SEM Imaging: a New Method for 3D Morphology of Asbestos- like Fibers in a Mineral Matrix -Complementarity with SEM-FIB

International audienceAsbestos consists of natural mineral fibers crystallized in a specific way with specific properties including flexibility, high tensile strength, resistance to heat and chemical degradation. The term asbestos refers to one fibrous serpentine, and five asbestiform varieties of amphiboles [1][2]. Asbestos is considered a Category 1 human carcinogen (e.g. [1][3][4][5][6]), as inhalation of asbestos fibers causes respiratory diseases, in particular asbestosis, lung cancers and malignant mesothelioma. Due to the pathogenicity of asbestos fibers, their use has been banned in most countries around the world. The classification as "asbestos" comprises three main characteristics: sub-micrometric fibrous morphology (so-called asbestiform), chemistry and crystallography (i.e. mineralogy). The ban applies to natural materials, which are quarried and used for public works projects. Compliance with existing rules requires accurate diagnosis of the asbestos or non-asbestos nature of the materials likely to be exploited in a quarry or involved in the opening of a construction site. Conventional methods for asbestos diagnosis, mainly based on the use of TEM, are hard to apply to massive materials as the sample preparation protocol is complex, it is likely to release artifacts like cleavage fragments, or sample-piece thinning is costly and hard to achieve and thus not applicable in routine analysis. The use of a LV-FE-SEM-EDS (Low vacuum field emission gun scannning electron microscope equiped with energy dispersive spectroscopy) coupled to confocal Raman-in-SEM imaging (RISE) is a new and efficient method for identifying the mineral nature of sub-micrometer fibers or fibrous bundles. SEM coupled to EDS provides a qualitative or semi-quantitative composition of the fiber. The crystal structure is determined by confocal Raman spectroscopy (with lateral resolution down to 360 nm [7]). Thus the combination of these two kinds of information allows for accurate identification of both the nature and the morphology of the mineral. The combination of SEM, EDS and confocal Raman imaging in a unique analytical system (RISE) allows precise location of the same area / fiber and identification of its mineral nature. In addition, RISE allows the acquisition of 3D data, which is able to provide morphological information of the mineral distribution in the sample volume and leading to the determination of the aspect ratio, a critical parameter for asbestos (i.e. asbestiform or non-asbestiform). Moreover, this combination of techniques is not destructive. The coupling of SEM-EDS with RISE is a powerful analytical system that simplifies and reinforces existing analytical procedures. For highest resolution studies of fibers in the sample volume (3 D imaging), the RISE can be connected to a FIB-SEM [7]. Although FIB volume reconstruction is a destructive method, the resolution of the voxel can be extended to below 100 nm [8] – a resolution sufficient for visualizing even the thinnest fibers. Furthermore, Raman 3D view is an efficient tool for sampling TEM slices using the FIB

Alpine Corsica Metamorphic Core Complex

International audienceAlpine Corsica is an example where superficial nonmetamorphic allochtonous units rest upon a highly strained metamorphic complex. Early ductile deformation under high pressure-low temperature (HP-LT) conditions is due to the westward thrusting of oceanic material onto a continental basement as shown by previous studies. New thermobarometric estimates yield minimal peak HP-LT metamorphism conditions of 11 kbar at 400°C. The early deformation is overprinted by a ductile deformation with an eastward sense of shear postdating or contemporaneous with mineral recrystallizations in the greenschist facies conditions. Early compressive thrust contacts are reworked as east dipping ductile normal faults and the less competent units display only eastward shear criteria. The upper units are affected by an extensional brittle deformation, and east dipping brittle normal faults bound to the west the early to middle Miocene Saint-Florent half-graben. The greenschist metamorphic event lasted until 33 Ma, which is contemporaneous with the beginning of the extension in the Liguro-Provençal basin. We interpret the second deformation stage as the result of a ductile extension following the overthickening of the crust due to the westward thrusting. Extension reduces the thickness of the crust so that upper units free from early P-T conditions are brought into close contact with a HP-LT metamorphic core complex. The geometry of the late extension is controlled by that of the early compressive thrust

Phylogeography and modes of reproduction in diploid and tetraploid halophytes of Limonium species (Plumbaginaceae): evidence for a pattern of geographical parthenogenesis

Background and Aims The genus Limonium (Plumbaginaceae) has long been recognized to have sexual and apomictic (asexual seed formation) modes of reproduction. This study aimed to elucidate phylogeographical patterns and modes of reproduction in diploid and tetraploid Limonium species, namely three putative sexual diploid species with morphological affinities (L. nydeggeri, L. ovalifolium, L. lanceolatum) and three related, probably apomict tetraploid species (L. binervosum, L. dodartii, L. multiflorum). Methods cpDNA diversity and differentiation between natural populations of the species were investigated using two chloroplast sequence regions (trnL intron and trnL–trnF intergenic spacer). Floral heteromorphies, ovule cytoembryological analyses and pollination and crossing tests were performed in representative species of each ploidy group, namely diploid L. ovalifolium and tetraploid L. multiflorum, using plants from greenhouse collections. Key Results and Conclusions Genetic analyses showed that diploid species have a higher haplotype diversity and a higher number of unique (endemic) haplotypes than tetraploid species. Network analysis revealed correlations between cpDNA haplotype distribution and ploidy groups, species groups and geographical origin, and haplotype sharing within and among species with distinct ploidy levels. Reproductive biology analyses showed that diploid L. ovalifolium mainly forms meiotically reduced tetrasporic embryo sacs of Gagea ova, Adoxa and Drusa types. Limonium multiflorum, however, has only unreduced, diplosporic (apomictic) embryo sacs of Rudbeckia type, and autonomous apomictic development seems to occur. Taken together, the findings provide evidence of a pattern of ‘geographical parthenogenesis’ in which quaternary climatic oscillations appear to be involved in the geographical patterns of coastal diploid and tetraploid Limonium speciesinfo:eu-repo/semantics/publishedVersio

Modulation of Host Learning in Aedes aegypti Mosquitoes

How mosquitoes determine which individuals to bite has important epidemiological consequences. This choice is not random; most mosquitoes specialize in one or a few vertebrate host species, and some individuals in a host population are preferred over others. Mosquitoes will also blood feed from other hosts when their preferred is no longer abundant, but the mechanisms mediating these shifts between hosts, and preferences for certain individuals within a host species, remain unclear. Here, we show that olfactory learning may contribute to Aedes aegypti mosquito biting preferences and host shifts. Training and testing to scents of humans and other host species showed that mosquitoes can aversively learn the scent of specific humans and single odorants and learn to avoid the scent of rats (but not chickens). Using pharmacological interventions, RNAi, and CRISPR gene editing, we found that modification of the dopamine-1 receptor suppressed their learning abilities. We further show through combined electrophysiological and behavioral recordings from tethered flying mosquitoes that these odors evoke changes in both behavior and antennal lobe (AL) neuronal responses and that dopamine strongly modulates odor-evoked responses in AL neurons. Not only do these results provide direct experimental evidence that olfactory learning in mosquitoes can play an epidemiological role, but collectively, they also provide neuroanatomical and functional demonstration of the role of dopamine in mediating this learning-induced plasticity, for the first time in a disease vector insect

A palaeoecological model for the late Mesoproterozoic – early Neoproterozoic Atar/El Mreïti Group, Taoudeni Basin, Mauritania, northwestern Africa

Reconstructing the spatial distribution of early eukaryotes in palaeoenvironments through Proterozoic sedimentary basins provides important information about their palaeocology and taphonomic conditions. Here, we combine the geological context and a reconstruction of palaeoenvironmental redox conditions (using iron speciation) with quantitative analysis of microfossil assemblages (eukaryotes and incertae sedis), to provide the first palaeoecological model for the Atar/El Mreïti Group of the Taoudeni Basin. Our model suggests that in the late Mesoproterozoic – early Neoproterozoic, the availability of both molecular oxygen and nutrients controlled eukaryotic diversity, higher in oxic shallow marginal marine environments, while coccoidal colonies and benthic microbial mats dominated respectively in anoxic iron-rich and euxinic waters during marine highstands or away from shore where eukaryotes are lower or absent