Recent progress in the synthesis of imogolite and imogolite-like clay minerals. A focus on the sphree-tube transition

International audienceImogolite has been discovered more than 50 years ago in the weathering produc of volcanic soils in Japan. It has been quickly realjzed that imogoli lets a ubiquitous clay mineral which can be readly synthesized in the laborarory using ralber simple co-precipitation receipt

MOMAC: a SAXS/WAXS laboratory instrument dedicated to nanomaterials

International audienceThis article presents the technical characteristics of a newly built small-and wide-angle X-ray scattering (SAXS/WAXS) apparatus dedicated to structural characterization of a wide range of nanomaterials in the powder or dispersion form. The instrument is based on a high-flux rotating anode generator with a molybdenum target, enabling the assessment of highly absorbing samples containing heavy elements. The SAXS part is composed of a collimation system including a multilayer optic and scatterless slits, a motorized sample holder, a vacuum chamber, and a two-dimensional image-plate detector. All the control command is done through a TANGO interface. Normalization and data correction yield scattering patterns at the absolute scale automatically with a q range from 0.03 to 3.2 A ˚ À1. The WAXS part features a multilayer collimating optic and a two-dimensional image-plate detector with variable sample-to-detector distances. The accessible q range is 0.4–9 A ˚ À1 , ensuring a large overlap in q range between the two instruments. A few examples of applications are also presented, namely coupled SAXS/WAXS structure and symmetry determination of gold nanocrystals in solution and characterization of imogolite nanotubes and iron-filled carbon nanotube samples

A fragmentary leptonectid ichthyosaurian from the lower Pliensbachian of Luxembourg

peer reviewedDespite abundant fossils, the quality of the fossil record of Early Jurassic marine reptiles strongly fluctuates with time and space. Pliensbachian strata have yielded very few marine reptile remains, especially outside of England, obscuring the evolution of marine reptiles during the middle part of the Early Jurassic. We report a new Pliensbachian locality from Luxembourg that contains abundant marine fauna and ichthyosaurian remains likely representing a single individual, composed of a partial snout, a possible surangular, two centra, and several ribs and gastralia. Ammonites and belemnites place this locality within the Valdani-Luridum Ammonite subzones of the Ibex Ammonite Zone, lower Pliensbachian. We assign the new ichthyosaur specimen to the clade Leptonectidae, using a combination of features from the snout and teeth. This specimen indicates that large neoichthyosaurians were present in multiple places of the European archipelago in all stages of the Early Jurassic and suggests that the ichthyosaurian faunae of western Europe remained essentially similar across the Sinemurian-Pliensbachian interval.Malgré d’abondants fossiles, la qualité de l’enregistrement fossile des reptiles marins du Jurassique inférieur fluctue largement à travers le temps et l’espace. Les strates pliensbachiennes ont fourni très peu de fossiles de reptiles marins, singulièrement hors d’Angleterre, occultant l’évolution des reptiles marins durant la partie centrale du Jurassique inférieur. Nous rapportons une nouvelle localité pliensbachienne au Luxembourg, contenant une faune marine abondante et des restes d’ichthyosaures représentant probablement un seul individu composé d’un museau partiel, un possible surangulaire, deux centra, ainis que plusieurs côtes et gastralia. Les ammonites et les bélemnites placent cette localité au sein des sous-zones à ammonites Valdini-Luridum, zone Ibex, Pliensbachien inférieur. Nous attribuons le nouveau specimen d’ichtyosaure au clade Leptonectidae, en utilisant une combination de caractrères issus du museau et des dents. Ce specimen indique que de large néoichthyosaures étaient présents à de multiples endroits au sein de l’archipel européen durant chaque étage du Jurassique inférieur et suggère que les faunes d’ichtyosaures d’Europe de l’Ouest sont restées essentiellement similaires durant l’intervalle Sinémurien-Pliensbachien.Trotz zahlreicher Fossilien unterliegt die Vollständigkeit der fossilen Überlieferung von Meeresreptilien aus dem frühen Jura starken zeitlichen und geographischen Schwankungen. Die Schichten des Pliensbachium haben nur sehr wenige marine Reptilienreste hervorgebracht, vor allem außerhalb Englands. Aus diesem Grund ist die Entwicklung der Meeresreptilien während des mittleren Teils des frühen Juras verhältnismäßig wenig bekannt. Wir berichten über einen neuen Fundort aus dem Pliensbachium Luxemburgs, der eine reichhaltige Meeresfauna geliefert hat, darunter Ichthyosaurier-Überreste, die wahrscheinlich ein einzelnes Individuum darstellen, bestehend aus einem Teil der Schnauze, einem möglichen Surangular, zwei Wirbelzentren und mehreren Rippen und Gastralia. Anhand von Ammoniten und Belemniten lässt sich die Fundschicht in die Valdani-Luridum Ammoniten-Subzonen der Ibex Ammoniten-Zone im unteren Pliensbachium einordnen. Eine Kombination von Merkmalen der Schnauze und der Zähne erlaubt eine Einordnung des Ichthyosaurier-Exemplars in die Kladus Leptonectidae. Das Exemplar deutet darauf hin, dass große Neoichthyosaurier in allen Phasen des frühen Jura an mehreren Orten des europäischen Archipels vorkamen, und legt nahe, dass die Ichthyosaurier-Fauna Westeuropas während des Sinemurium-Pliensbachium im Wesentlichen ähnlich blieb

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P &lt; 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

From Molecular Precursor to Imogolite Nanotubes

International audienceImogolite is not available in large quantities from natural deposits, and its extraction requires several purification steps. Even though some research studies still use purified natural imogolite, most research activities and actual industrial applications use synthetic imogolite, which has been available since it was devised by Farmer et al. (1977). The various synthesis pathways and the current understanding of the imogolite formation mechanism are reviewed in this chapter

Characterisation of Imogolite by Microscopic and Spectroscopic Methods

International audienceThe main techniques needed to characterise imogolite are reviewed. The global quality of an imogolite sample can be assessed by a simple visual inspection. It should be transparent and should display some birefringence if sufficiently concentrated when observed between crossed polarisers. To gain a deep knowledge about a particular sample, the most often used techniques are infrared (IR) spectroscopy, transmission electronic microscopy (TEM) and X-ray diffraction. The main results are reviewed and some less commonly used techniques are also described. It is stressed that emerging techniques (namely, cryo-TEM and small-angle X-ray scattering) are particularly useful for assessing the global shape and the diameter of imogolite samples. Some characterisation developments are still needed, especially for obtaining reliable and fast measurements of the nanotube length distribution