Ultra-Stable and Robust Response to X-Rays in 2D Layered Perovskite Micro-Crystalline Films Directly Deposited on Flexible Substrate

2D layered hybrid perovskites have recently attracted an increasing interest as active layers in LEDs and UV–Vis photodetectors. 2D perovskites crystallize in a natural self-assembled quantum well-like structure and possess several interesting features among which low-temperature (<100 °C) synthesis and low defect density. Here are presented solid-state ionizing radiation direct detectors based on the 2D layered hybrid perovskite PEA2PbBr4 (PEA = C6H5C2H4NH3+) deposited from solution using scalable techniques and directly integrated onto a pre-patterned flexible substrate in the form of micro-crystalline films displaying crystal-like behavior, as evidenced by the ultra-fast (sub-microsecond) and good detection performances under UV light. The effective detection of X-rays (up to 150 kVp) is demonstrated with sensitivity values up to 806 µC Gy−1 cm−2 and Limit of Detection of 42 nGy s−1, thus combining the excellent performance for two relevant figures of merit for solid-state detectors. Additionally, the tested devices exhibit exceptionally stable response under constant irradiation and bias, assessing the material robustness and the intimate electrical contact with the electrodes. PEA2PbBr4 micro-crystalline films directly grown on flexible pre-patterned substrate open the way for large-area solid-state detectors working at low radiation flux for ultra-fast X-ray imaging and dosimetry

Fourier Modeling of the Left Ventricle Parasternal Boundary

Any parasternal boundary of the left ventricle of the heart, manually extracted from an echocardiographic image, can be modeled using smoothing by truncating the Fourier serie of its polar development round an inner origin . The choice of a central origin, that annulates the Fourier coefficient at the first harmonic, minimizes the quadratic distance between the manual boundary and the modeled one. The parameters of the model are the coordinates of this central origin, and the non-truncated Fourier coefficients. The geometrical interpretation of each of these parameters, very simple, gives them a useful significance for the medical diagnosis. In an other hand, the analysis of the smoothed boundaries evolution for a complete cardiac cycle yields to measuring the isotropy of the contractions. Finally, it is possible to extract the parameters ofa non-closed boundary by implicit interpolation on the lacking portions.ZRToéuts cuonmtéour parasternal du ventricule gauche du coeur, extrait manuellement sur une image échocardiographique, est modélisable par lissage en tronquant la série de Fourier de son développement polaire autour d'une origine interne . Le choix d'une origine centrale, qui correspond à l'annulation du coefficient de Fourier au premier harmonique, minimise l'écart quadratique entre le contour manuel et le contour modélisé . Les paramètres du modèle sont les coordonnées de cette origine centrale ainsi que les coefficients de Fourier non tronqués . L'interprétation géométrique de ces paramètres, très simple, leur confère une signification utile pour le diagnostic médical. D'autre part, l'analyse de l'évolution des contours lissés pendant le cycle cardiaque conduit à une mesure de l'isotropie des contractions . Enfin, il est possible d'extraire les paramètres d'un contour non fermé par interpolation implicite sur les portions manquantes

X-Ray-Induced Modification of the Photophysical Properties of MAPbBr3Single Crystals

Methylammonium lead tribromide (MAPbBr3) perovskite single crystals demonstrate to be excellent direct X-ray and gamma-ray detectors with outstanding sensitivity and low limit of detection. Despite this, thorough studies on the photophysical effects of exposure to high doses of ionizing radiation on this material are still lacking. In this work, we present our findings regarding the effects of controlled X-ray irradiation on the optoelectronic properties of MAPbBr3 single crystals. Irradiation is carried out in air with an imaging X-ray tube, simulating real-life application in a medical facility. By means of surface photovoltage spectroscopy, we find that X-ray exposure quenches free excitons in the material and introduces new bound excitonic species. Despite this drastic effect, the crystals recover after 1 week of storage in dark and low humidity conditions. By means of X-ray photoelectron spectroscopy, we find that the origin of the new bound excitonic species is the formation of bromine vacancies, leading to local changes in the dielectric response of the material. The recovery effect is attributed to vacancy filling by atmospheric oxygen and water

Stromal cell-derived factor 1 (SDF-1) and antenatal human B cell lymphopoiesis: Expression of SDF-1 by mesothelial cells and biliary ductal plate epithelial cells

The chemokine stromal cell-derived factor 1 (SDF-1) stimulates the growth of pre-B cells in vitro, and mice with a disrupted SDF-1 gene have abnormal fetal liver B cell lymphopoiesis. The origin of SDF-1 production has not been determined yet. Using an anti-SDF-1 mAb, we performed immunohistochemical studies in four human embryos and five fetuses to define which cells express the SDF-1 protein at sites of antenatal B cell lymphopoiesis. All mesothelial cells contained SDF-1 at all stages of development, including in the intraembryonic splanchnopleuric mesoderm early into gestation. In fetal lungs and kidneys, SDF-1 was expressed by epithelial cells, and a few B lymphoid precursors, expressing V pre-B chains, were also detected. In the fetal liver, in addition to mesothelial cells, biliary epithelial cells were the only cells to contain SDF-1. Pre-B cells expressing V chains were abundant and exclusively located around the edge of portal spaces, in close contact with biliary ductal plate epithelial cells. They did not colocalize with biliary collecting ducts. Biliary ductal plate epithelial cells and liver B cell lymphopoiesis display a parallel development and disappearance during fetal life. These results indicate that early B cell lymphopoiesis in the splanchnopleura may be triggered by mesothelial cells producing SDF-1. Later into gestation, biliary ductal plate epithelial cells may support B cell lymphopoiesis, thus playing a role similar to that of epithelial cells in the avian bursa of Fabricius, and of thymic epithelial cells for T cell lymphopoiesis

GEOMETRIC DESCRIPTORS OF ROAD SURFACE TEXTURE IN RELATION TO TIRE-ROAD NOISE

The paper deals with the determination of geometric parameters for studying the relationship between tire-road noise and texture of road surfaces. The approach was found to be an alternative to classical spectral analyses and numerical simulations of the tire-road contact. Texture parameters were derived from previous works at the Laboratoire Central des Ponts et Chausses related to the influence of the microtexture of road surfaces on skid resistance. Use of these parameters was justified by consideration of generation mechanisms of rolling noise. Texture, rolling noise, and absorption measurements were performed on 12 road surfaces. The measuring devices and the test methods produced texture profile analyses, including the spectral and geometric approaches. Geometric parameters were defined. Correlation between the noise and texture spectra showed results similar to those published in previous works. Fair tendencies were found between the global noise level at 90 km/h and the geometric parameters. Unexpected results obtained on the porous asphalt surfaces were partially explained by the attenuation effect, which was quantified by means of existing models. Results from the correlation between the third-octave-band noise levels and the geometric parameters corroborated those of the spectral analyses

«Adrienne» a European method to qualify road noise barriers on site

Adrienne is a method developed in a European research project, the aim of which was the measurement on site of sound absorption and sound transmission of any road noise barrier. In order to get the impulse response of the device (absorption measurement), a M.L.S. (Maximum Length Sequence) method was selected mainly for its excellent signal/noise ratio. The introduction of a subtraction technique improves the low frequency information. For flat barriers, measurement results showed a good agreement with well-known models or other experimental methods. For non flat barriers, numerical predictions resulted in the requirement of an averaging performed on many source and receiver positions. An encouraging agreement between measurements and predictions was found. Round robin tests on a specially built platform proved a good repeatability of the method

Intra-specific variation in movement and habitat connectivity of a mobile predator revealed by acoustic telemetry and network analyses

Few studies have considered linkages of mobile predators across large spatial scales despite their significant and often critical role in maintaining ecosystem function and health. The bull shark (Carcharhinus leucas) is a large, widespread coastal predator capable of undertaking long-range movement, but there is still limited understanding of intra-regional differences in movement and habitat connectivity across latitudes within the same coastline. This study used acoustic telemetry data and network analyses to investigate long-range movements, residency patterns and seasonal habitat linkages of sub-adult and adult C. leucas along the east coast of Australia. Our results revealed that C. leucas tagged in Sydney Harbour were mainly present within this temperate estuary in summer and autumn; the rest of the year individuals were detected in tropical and subtropical habitats from southern and central Queensland. In contrast, the detection probability of C. leucas tagged in the Townsville Reefs (central Great Barrier Reef) peaked in spring, with a portion of the tagged population migrating south during the summer months. Differences in residency time between tagging locations were also detected, as all C. leucas tagged in Sydney Harbour were absent between June and November, but 35% of the tropical-reef tagged population remained resident year-round. Network analyses complemented these findings by revealing different seasonal habitat use between regions, thus highlighting complex seasonal-habitat linkages of C. leucas along the coast. Our findings support the hypothesis that the timing, duration, and drivers involved in the long-range movements and connectivity of sub-adult and adult C. leucas vary between latitudinal regions, most likely driven by the interaction between seasonal temperature changes, foraging and reproduction