Changes to the Fossil Record of Insects through Fifteen Years of Discovery

The first and last occurrences of hexapod families in the fossil record are compiled from publications up to end-2009. The major features of these data are compared with those of previous datasets (1993 and 1994). About a third of families (>400) are new to the fossil record since 1994, over half of the earlier, existing families have experienced changes in their known stratigraphic range and only about ten percent have unchanged ranges. Despite these significant additions to knowledge, the broad pattern of described richness through time remains similar, with described richness increasing steadily through geological history and a shift in dominant taxa, from Palaeoptera and Polyneoptera to Paraneoptera and Holometabola, after the Palaeozoic. However, after detrending, described richness is not well correlated with the earlier datasets, indicating significant changes in shorter-term patterns. There is reduced Palaeozoic richness, peaking at a different time, and a less pronounced Permian decline. A pronounced Triassic peak and decline is shown, and the plateau from the mid Early Cretaceous to the end of the period remains, albeit at substantially higher richness compared to earlier datasets. Origination and extinction rates are broadly similar to before, with a broad decline in both through time but episodic peaks, including end-Permian turnover. Origination more consistently exceeds extinction compared to previous datasets and exceptions are mainly in the Palaeozoic. These changes suggest that some inferences about causal mechanisms in insect macroevolution are likely to differ as well

La métrologie de la dose au CEA : le Laboratoire National Henri Becquerel

On présente un bref exposé des activités de métrologie de la dose du Laboratoire National Henri Becquerel (LNE-LNHB), laboratoire national de métrologie pour les rayonnements ionisants. Les résultats des principaux travaux effectués ces dernières années dans ce domaine sont exposés, en particulier les développements se rapportant aux calculs par simulation Monte Carlo, aux instruments étalons (calorimètres, chambres d’ionisation) et aux références dosimétriques pour la radiothérapie, le radiodiagnostic et la radioprotection

Evaluation des caractéristiques dosimétriques d'un nouveau type de compteur équivalent au tissu destiné à la dosimétrie individuelle neutronique en radioprotection

Cet article présente l'évaluation des principales caractéristiques du prototype de compteur proportionnel multicellulaire équivalent au tissu étudié dans notre laboratoire pour la dosimetrie individuelle neutronique. Il comporte plusieurs centaines de canaux creusés dans la cathode en regard des fils anodiques. On montre que sa sensibilité est compatible avec une utilisation en radioprotection et que la dimension du volume simulé permet d'appliquer la méthode microdosimétrique. La distribution de la longueur des cordes, obtenue par simulation avec la méthode de Monte-Carlo dans le cas d'une irradiation isotrope, est proche d'une fonction de Dirac centrée sur la valeur moyenne de la distribution. Enfin, un mélange de gaz spécifique contenant de l'argon, du propane, du dioxyde de carbone et de l'azote est proposé pour le remplissage du compteur

Influence of drying conditions on hydration of cement pastes with substitution of Portland cement by a recycled cement paste fine

International audienc

Mortiers à base d’une fine issue du recyclage d’une pâte de ciment : impact du dosage en fine sur les propriétés physico-chimiques

International audienc

Accuracy of a dose-area product compared to an absorbed dose to water at a point in a 2 cm diameter field

International audiencePurpose: Graphite calorimeters with a core diameter larger than the beam can be used to establish dosimetric references in small fields. The dose-area product (DAP) measured can theoretically be linked to an absorbed dose at a point by the determination of a profile correction. This study aims at comparing the DAP-based protocol to the usual absorbed dose at a point protocol in a 2 cm diameter field for which both references exist. Methods: Two calorimeters were used, respectively, with a sensitive volume of 0.6 cm (for the absorbed dose at a point measurement) and 3 cm diameter (for the DAP measurement). Profile correction was calculated from a 2D dose mapping using three detectors: a PinPoint chamber, a synthetic diamond, and EBT3 films. A specific protocol to read EBT3 films was implemented and the dose-rate and energy dependences were studied to assure a precise measurement, especially in the penumbra and out-of-field regions. Results: EBT3 films were found independent on dose rates over the range studied but showed a strong under-response (18%) at low energies. Depending on the dosimeter used for calculating the profile correction, a deviation of 0.8% (PinPoint chamber), 0.9% (diamond), or 1.9% (EBT3 films) was observed between the calibration coefficient derived from DAP measurements and the one directly established in terms of absorbed dose to water at a point. Conclusions: The DAP method can currently be linked to the classical dosimetric reference system based in an absorbed dose at a point only with a confidence interval of 95% (k = 2). None of the detectors studied can be used to determine an absorbed dose to water at a point from a DAP measurement with an uncertainty smaller than 1.2%. (C) 2016 American Association of Physicists Medicine

The first megatheropod tracks from the Lower Jurassic upper Elliot Formation, Karoo Basin, Lesotho.

A palaeosurface with one megatheropod trackway and several theropod tracks and trackways from the Lower Jurassic upper Elliot Formation (Stormberg Group, Karoo Supergroup) in western Lesotho is described. The majority of the theropod tracks are referable to either Eubrontes or Kayentapus based on their morphological characteristics. The larger megatheropod tracks are 57 cm long and have no Southern Hemisphere equivalent. Morphologically, they are more similar to the Early Jurassic Kayentapus, as well as the much younger Upper Cretaceous ichnogenus Irenesauripus, than to other contemporaneous ichnogenera in southern Africa. Herein they have been placed within the ichnogenus Kayentapus and described as a new ichnospecies (Kayentapus ambrokholohali). The tracks are preserved on ripple marked, very fine-grained sandstone of the Lower Jurassic upper Elliot Formation, and thus were made after the end-Triassic mass extinction event (ETE). This new megatheropod trackway site marks the first occurrence of very large carnivorous dinosaurs (estimated body length >8-9 meters) in the Early Jurassic of southern Gondwana, an evolutionary strategy that was repeatedly pursued and amplified in the following ~135 million years, until the next major biotic crisis at the end-Cretaceous

The LNE-LNHB water calorimeter for primary measurement of absorbed dose at low depth in water: application to medium-energy x-rays

International audienceWater calorimeters are used to establish absorbed dose standards in several national metrology laboratories involved in ionizing radiation dosimetry. These calorimeters have been first used in high-energy photons of (60)Co or accelerator beams, where the depth of measurement in water is large (5 or 10 cm). The LNE-LNHB laboratory has developed a specific calorimeter which makes measurements at low depth in water (down to 0.5 cm) easier, in order to fulfil the reference conditions required by the international dosimetry protocols for medium-energy x-rays. This new calorimeter was first used to measure the absorbed dose rate in water at a depth of 2 cm for six medium-energy x-ray reference beams with a tube potential from 80 to 300 kV. The relative combined standard uncertainty obtained on the absorbed dose rate to water is lower than 0.8%. An overview of the design of the calorimeter is given, followed by a detailed description of the calculation of the correction factors and the calorimetric measurements