Chemical, Textural and Thermal Analyses of Local Interactions Between Lava Flow and a Tree – Case Study From Pāhoa, Hawai’i

Because many volcanoes are densely vegetated, understanding of the interactions between active lava flows and trees is essential for robust hazard modeling. Tree molds − lava flow features generated when advancing lava engulfs and combusts trees − are widely documented but have, to date, only been described qualitatively. Detailed, quantitative studies of molds can, however, provide insights into the nature of lava-forest interactions. Here, we present a unique characterization of the chemical, textural and thermal interactions between lava and a tree (an Albizia), taking as a case type a basaltic pāhoehoe lava flow that traveled 20 km through Hawaiian rainforest on Kilauea’s East Rift Zone between June and December 2014. The dataset includes chemical analyses of lava (major, trace and volatile species) at the lava-tree contact, quantitative descriptions of lava texture (density, vesicle and crystal populations), and thermal analysis to fingerprint the devolatilization and combustion of wood as well as with cooling and crystallization of lava around the tree. We use these results to construct a three-stage thermal model to describe heat transfer between the lava and the tree, showing how the interaction facilitates combustion of wood and release of its volatile species (CO2 and H2O) into the lava, whilst triggering enhanced cooling and crystallization of lava surrounding the tree. Chemical analyses reveal that the inflating pāhoehoe at the lava-tree contact was strongly CO2-enriched (up to 1200 ppm), and textural data show that lava is denser at the contact. Moreover, lava crystallinity indicates a cooling rate of ∼70°C min–1 at the lava-tree contact, a rate well above the expected cooling rates (30°C min–1) for pāhoehoe more distant (40 m away) from the tree. We conclude that the tree had a local cooling effect on the lava that could potentially influence lava properties at larger scale if tree density, trunk diameter and moisture content are sufficiently hig

Un Paradis perdu. Restaurer ou les effets de l'intervention humaine sur le cours du temps – à propos de quelques réalités monumentales (France, Cambodge)

Les interventions sur les monuments anciens en milieu rural gagneront à être plus « légères » qu’en milieu urbain, dès lors que la part du temps est prise en considération. En France comme au Cambodge, toute restauration complète appelle d’autres travaux à un rythme plus rapproché, plus difficiles d’exécution, plus importants en moyens et plus impactants sur les architectures et sculptures. Entre le XIIe et le XIXe siècle, les maçonneries des églises romanes d’Auvergne ont été peu entretenues, mais l’épiderme des matériaux de construction a globalement bien tenu. Un siècle après les restaurations du XIXe siècle, du fait de l’utilisation des ciments durs et de matériaux exogènes, la dégradation des parties restaurées et non restaurées impose de nouvelles interventions rapprochées dans le temps, alors que la première période n’avait connu aucune grande phase de restauration, l’entretien seul ayant suffi.La déforestation est quant à elle la principale cause de la dégradation accélérée des maçonneries assemblées à sec des temples khmers, mais on tirera une leçon utile de l’exemple du temple de Ta Prohm à Angkor qui conserve son couvert forestier protecteur. Dès lors que l’exubérance de la végétation est contrôlée, au Cambodge comme en France, un édifice ancien supporte aisément la présence de mousses, lichens et cyanobactéries, voire de graminées, qui enveloppent le site dans un biofilm protecteur. À l’inverse, chaque restauration ou nettoyage déclenche l’installation rapide d’organismes jeunes plus agressifs que les organismes âgés vivant au ralenti et finissant par former une « biopatine » protectrice. Face aux bouleversements industriels, le XIXe siècle a restauré ses édifices emblématiques. Notre siècle doit probablement conserver de manière raisonnée des références monumentales synonymes d’une lente disparition. Pourtant un édifice ayant subi de multiples interventions se corrigeant les unes les autres, produit d’une économie de loisirs, ne produira jamais l’émotion d’une ruine discrètement entretenue dans laquelle il est possible de se perdre, en dehors de tout itinéraire balisé et de toute proposition pédagogique. Le « réensauvagement » de sites ruraux est donc un enjeu qui dépasse « l’absolue nécessité », en réalité toute relative des restaurations.Interventions on ancient monuments in rural areas will benefit from being "lighter" than in urban areas, as long as the time issue is taken into account. In France as in Cambodia, any complete restoration calls for other works at a closer pace, more difficult to carry out, more important in terms of resources and more impacting on architectures and sculptures. Between the 12th and the 19th century, the masonry of Romanesque churches in Auvergne was poorly maintained, but the building materials epidermis has generally held up quite well. A century and a half after the 19th century restorations, due to using hard cements and exogenous materials, degradation of the restored and unrestored parts requires new close in time interventions, whereas the first period had not seen any major restoration phase, maintenance alone did suffice.Deforestation is the main cause of the accelerated degradation of dry-assembled masonry of Khmer temples, but a useful lesson will be learned from the example of Ta Prohm temple in Angkor which retains its protective forest cover. As soon as the vegetation exuberance is controlled, in Cambodia as in France, an old building easily supports the presence of mosses, lichens and cyanobacteria, even grasses, which envelop the site in a protective biofilm. Conversely, each restoration or cleaning triggers the rapid installation of young organisms that are more aggressive than older organisms living in slow motion and eventually forming a protective “biopatin”. Faced with industrial upheavals, the 19th century restored its iconic monuments. Our century must probably preserve in a reasoned way monumental references reflecting a slow disappearance. However, a building that has undergone multiple interventions correcting each other, in a leisure economy, will never produce the emotion of a discreetly maintained ruin in which on can get lost, apart from any marked route and any educational proposal. Rural sites “going back to the wild” is therefore an issue that goes beyond the restorations “absolute – actually all relative – necessity”

Bioactive glass coating on gelatin scaffolds at ambient temperature: easy route to make polymer scaffolds become bioactive

International audienceIncreasing the bioactivity of polymeric materials used for bone repair is a concern that can be achieved by loading growth factors or using in vitro tissue engineering approach. However, these techniques may have to address regulatory issues as the implants are shifted from the medical device class to the more constraining drug delivery systems. Alternatively, implants can be coated with bioceramics to achieve bioactivity, but existing coating processes can hardly be applied to polymers because they usually involve thermal treatments or sintering. Here we report an efficient way of coating a bioactive glass phase onto a complex polymeric substrate, namely gelatin scaffolds with controlled spherical porosity, at ambient temperature through a dip-coating process. A multiscale analysis of the bioactive glass-coated gelatin scaffolds properties has been carried out. Homogeneous and remarkably uniform layer of SiO 2-CaO bioactive glass is obtained. The bioactive glass coating exhibits a very high and fast apatite-forming ability, with full mineralization of the coating being achieved in less than 24 h contact with body fluids. Importantly, the mineral-ization takes place homogeneously throughout the scaffold while the remarkable uniformity and thickness regularity of the coating are preserved. These features should enhance the in vivo behaviour of polymer scaffolds and make reconsider the interest of non-bioactive polymers for tissue engineering

Spatial variation of volcanic rock geochemistry in the Virunga Volcanic Province: Statistical analysis of an integrated database

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Transcriptional analysis reveals specific niche factors and response to environmental stresses of enterohemorrhagic Escherichia coli O157:H7 in bovine digestive contents

International audienceEnterohemorrhagic Escherichia coli (EHEC) are responsible for severe diseases in humans, and the ruminant digestive tract is considered as their main reservoir. Their excretion in bovine feces leads to the contamination of foods and the environment. Thus, providing knowledge of processes used by EHEC to survive and/or develop all along the bovine gut represents a major step for strategies implementation. Results We compared the transcriptome of the reference EHEC strain EDL933 incubated in vitro in triplicate samples in sterile bovine rumen, small intestine and rectum contents with that of the strain grown in an artificial medium using RNA-sequencing (RNA-seq), focusing on genes involved in stress response, adhesion systems including the LEE, iron uptake, motility and chemotaxis. We also compared expression of these genes in one digestive content relative to the others. In addition, we quantified short chain fatty acids and metal ions present in the three digestive contents. RNA-seq data first highlighted response of EHEC EDL933 to unfavorable physiochemical conditions encountered during its transit through the bovine gut lumen. Seventy-eight genes involved in stress responses including drug export, oxidative stress and acid resistance/pH adaptation were over-expressed in all the digestive contents compared with artificial medium. However, differences in stress fitness gene expression were observed depending on the digestive segment, suggesting that these differences were due to distinct physiochemical conditions in the bovine digestive contents. EHEC activated genes encoding three toxin/antitoxin systems in rumen content and many gene clusters involved in motility and chemotaxis in rectum contents. Genes involved in iron uptake and utilization were mostly down-regulated in all digestive contents compared with artificial medium, but feo genes were over-expressed in rumen and small intestine compared with rectum. The five LEE operons were more expressed in rectum than in rumen content, and LEE1 was also more expressed in rectum than in small intestine content. Conclusion Our results highlight various strategies that EHEC may implement to survive in the gastrointestinal environment of cattle. These data could also help defining new targets to limit EHEC O157:H7 carriage and shedding by cattle

Plasma Formed in Argon, Acid Nitric and Water Used in Industrial ICP Torches

International audienceInductively coupled plasmas (ICPs) are used in spectrochemical analyses. The introduction of the sample by means of an aerosol are widely used. The introduction and the total evaporation of the aerosol is required in order to obtain a good repeatability and reproducibility of analyses. To check whether the vaporization of the aerosol droplets inside the plasma is completed, a solution could be used to compare the experimental results of the emission spectral lines with theoretical results. An accurate calculation code to obtain monatomic spectral lines intensities is therefore required, which is the purpose of the present paper. The mixtures of argon, water and nitric acid are widely used in spectrochemical analyses with ICPs. With these mixtures, we calculate the composition, thermodynamic functions and monatomic spectral lines intensities of the plasma at thermodynamic equilibrium and at atmospheric pressure. To obtain a self su±cient paper and also to allow other researchers to compare their results, all required data and a robust accurate algorithm, which is simple and easy to compute, are given

Petrogenesis and Geochemistry of Tabas Black Land volcanic field: implications for volcanic activity along the Nayband fault, East Iran

International audienceThe 14 Ma Tabas Black Land volcanic field lies on the major active Nayband Fault, Western Lut Block, central-east Iran. Eroded cones and broad craters are surrounded by lavas. Eastern lavas are fault-deformed, partly covered by sediments, while western undeformed lavas stand out as inverted relief. We study the magmatic evolution of this volcanic field and assess relationships with regional tectonics. Compositions are intraplate basaltic trachyandesite-basaltic-andesite, produced from postcollisional asthenospheric melting. Modelling indicates 5-10 wt.% partial melting of primary garnet peridotite mantle with residual garnet. Modest K 2 O values are consistent with limited source hydrous phases (e.g. phlogopite). Low P 2 O 5 /K 2 O indicates little crustal contamination. Geothermobarome-try results point towards lower crust (480-760 MPa = 18-29 km) magma storage and differentiation, where olivine and clinopyroxene fractionated to produce differentiated trachybasalt to basaltic trachyandesite at magma temperatures of 1150-1200 • C. Compared to other Lut Block volcanics, there is more partial melting in Tabas, with the lowest level of crustal contamination. The ongoing 14 million year period of volcanism along the Nayband Fault appears to have had the same source, migrating southwards over time from the Tabas Black Lands with decreasing partial melting. Nayaband magmatism seems to be dwindling, even if the fault itself remains active.هنهپ یناشفشتآ نيمزرس هايس سبط اب نس 14 نويليم لاس رب یور لسگ لاعف و یلصا دنبيان عقاو رد شخب یبرغ کولب تول رد قرش یزکرم ناريا رارق هتفرگ تسا . رد نياهقطنم یاهطورخم شياسرف هتفاي و هناهد یاه یناشفشتآ رد هنيمز یا زا هزادگ هدنکارپ دنا . رد شخب یقرش هزادگ اه طسوت لسگ رييغت لکش هتفاي و هاگهگ اب تابوسر هديشوپ هدش،دنا رد هکيلاح هب تمس برغ هزادگ اه رييغت لکش هتفاين و یگتسجرب ( فيلر ) سوکعم ار هب شيامن هتشاذگ دنا . ام رد نيا شهوژپ هب هعلاطم لماکت یيامگام نيا هنهپ یناشفشتآهتخادرپ و طابترا نآ ار اب نيمز تخاس هيحان یا یبايزرا هدومن ميا . بيکرت یاهگنس یناشفشتآ نيمزرس هايس سبط تيزدنآ یتلازاب و یکارت یاهتيزدنآ یتلازاب طوبرم هب نوردتاحفص هراق یا هدوب هک رد رثا بوذ هتشوگ یا و رد هلحرم سپ زا دروخرب رد دنيارف یيازهوک ليکشت هديدرگ دنا . لدم یزاس ناشن یم دهد هک اهنآ زا بوذ یشخب هب رادقم 5 ات10 دصرد یمجح زا کي هتشوگ هيلوا اب بيکرت تنراگ تيتوديرپ و ماوت اب دنامسپ تنراگ دوجوب هدمآ دنا . ريداقم زيچان K2O رد نيا اهگنس رد لداعت اب روضح دودحم یاهزاف رادبآ K2O /رد نيا اهگنس یکاح زا لقادح یگدولآ هتسوپ یا تسا . جياتن نيمز امد و یجنسراشف هب عمجت و قيرفت 2O5 ) هب دننام تيپوگولف ) رد عبنم هتشوگ یا یم دشاب . تبسن نيياپ Pباذم رد یاهشخب هتسوپ نيريز 480 )ات 760 لاکساپاگم و قمع 18 ات 29 یرتموليک ) هراشا ،دراد یياج هک نيويلا و نسکوريپونيلک اه ادج هدش دنا ات یکارت یاهتيزدنآ یتلازاب ویکارت یاهتلازاب قيرفت هتفاي ار رد یامد 1150 ات 1200 هجرد دارگيتناس داجيا دنيامن . رد هسياقم اب رياس قطانم یناشفشتآ کولب ،تول رد نيمزرس هايس سبط اب بوذ یشخب رتشيبو حوطس یرتنيياپ زا یگدولآ هتسوپ یا هجاوم ميتسه . رظنب یم دسر دنيارف 14 نويليم هلاس یناشفشتآ رد دادتما لسگ دنبيان دجاو اشنم دننامه هدوب و اب تشذگ نامز زا نيمزرس هايسسبط ماوت اب شهاک رد خرن بوذ یشخب هب تمس بونج ترجاهم هدومن تسا . رگا هچ یم ناوت تفايرد هک تيلاعف یناشفشتآ رد دادتما لسگ دنبيان ليلحت هتفر یلو نيا لسگ زا رظنیکينوتکت نانچمه لاعف تس

Steel Slag Characterisation—Benefit of Coupling Chemical, Mineralogical and Magnetic Techniques

International audienceSteel-making slag is largely used today in road construction and other applications,but significant volumes are landfilled and cannot be recycled for excessive contents in hazardousmetals, such as chromium or vanadium. The long-term behaviour of this material is still littleknown, and the characterisation of large volume slag dumps remains an environmental challenge.In this study various analytical techniques are used to characterise Electric Arc Furnace (EAF) slaglandfilled for several decades and exposed to chemical weathering and erosion. Coupling chemical,mineralogical and magnetic techniques helps to understand the relations between hazardous metalsand mineral phases. A special interest is given to Fe-bearing minerals microstructure so as tolink the magnetic properties of the material to its mineralogical composition. The studied slagpresents high amounts of chromium (between 1 and 3 wt. %) and very high magnetic susceptibilityvalues(near 60×10−6m3/kg), explained by the presence of magnetite and a spinel solid solution.Some correlations are found between magnetic susceptibility and potentially hazardous metals,providing new perspectives for future environmental investigations

High-resolution analysis of a tsunami deposit: case-study from the 1755 Lisbon tsunami in southwestern Spain

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