250 research outputs found
Mining for a week or for centuries: Variable aims of flint extraction sites in the Mons Basin (Province of Hainaut, Belgium) within the lithic economy of the Neolithic
The Mons Basin (Province of Hainaut, western Belgium) is a geologically rich region, particularly from the point of view of Upper Cretaceous sedimentary deposits, conducive to an important flint gathering activity during the whole regional Prehistory. Focusing on the Neolithic period, indications of flint procurement as early as the end of the 6th millennium have been recorded, but there are concrete evidences of mining sites in the region since the second half of the 5th millennium. Flint extraction activities have lasted at least until the second half of the 3rd millennium. According to literature and recent researches, eleven sites could be extraction sites, including the World Heritage site of Spiennes. This paper critically assesses the accuracy of the data available and focuses on the issue of the unequal function of these extraction sites and their socio-economic function for Neolithic communities. Is it really possible to establish a hierarchy between the extraction sites? Can different acquisition-production strategies be highlighted? These questions are dealt with by synthesizing the data concerning the methods of flint exploitation in the Mons Basin, the qualitative and quantitative characteristics of the products relative to the production intentions but also by addressing the issue of their importance in exchange networks
De la mine Ă lâhabitat:Ăconomie des productions miniĂšres du Bassin de Mons au NĂ©olithique. De la fin du 5e millĂ©naire Ă la fin du 3e millĂ©naire.
info:eu-repo/semantics/nonPublishe
Multi-resonant absorption in ultra-thin silicon solar cells with metallic nanowires
International audienceWe propose a design to confine light absorption in flat and ultra-thin amorphous silicon solar cells with a one-dimensional silver grating embedded in the front window of the cell.We show numerically that multi-resonant light trapping is achieved in both TE and TM polarizations. Each resonance is analyzed in detail and modeled by Fabry-Perot resonances or guided modes via grating coupling. This approach is generalized to a complete amorphous silicon solar cell, with the additional degrees of freedom provided by the buffer layers. These results could guide the design of resonant structures for optimized ultra-thin solar cells
Hot Carrier Solar Cell: From Simulation to Devices
International audienceSingle junction III-V heterostructures based devices could overtake the Shockley-Queisser limit if thermalisation of photogenerated carriers can be strongly limited as in the hot carrier solar cell concept. Previous modelling and experiments have shown the interest of Multiple Quantum Wells heterostructures in the antimonide system and the importance of very thin structures. In this paper we report new data on the thermalisation rates in antimonide and phosphide heterostructures measured at ambient temperature. For the first time electrical control of hot carrier population is performed on hot carrier heterostructures device
Identification des paramÚtres d'une loi de comportement élastoplastique par indentation continue sphérique
Nous proposons une Ă©tude numĂ©rique et expĂ©rimentale de l'indentation instrumentĂ©e sphĂ©rique. L'Ă©tude numĂ©rique nous a permis de suivre l'Ă©volution d'un certain nombre de grandeurs pouvant ĂȘtre dĂ©duites d'une courbe d'indentation. Pour chacune de ces grandeurs, un modĂšle a Ă©tĂ© dĂ©terminĂ© pour deux lois de comportement, l'Ă©tude de ces modĂšles a conduit Ă la proposition d'une dĂ©marche de caractĂ©risation des matĂ©riaux. L'Ă©tude expĂ©rimentale nous a permis de dĂ©terminer l'enfoncement de l'indenteur dans le matĂ©riau Ă partir du dĂ©placement mesurĂ© de l'indenteur sans aucune calibration empirique. Nous prĂ©sentons de plus les rĂ©sultats expĂ©rimentaux issus de l'identification des paramĂštres de deux lois de comportement
La production laminaire du site minier de Spiennes (Hainaut, Belgique):premiĂšre approche technologique
Design of Electric Machine Taking Into Account the Partial Discharges Phenomena for Future Hybrid Propelled Aircrafts
Designing the electric motors to propel an aircraft represents a huge challenge. The constraint of weight requires such machines to be compact. Besides, the high specific power necessary (a few kW/kg, machine cooling included) leads to an increase of the voltage range of stator winding. Such characteristics increase considerably the risk of partial discharges (PD) in the stator winding. In this paper, the design of electric motors aimed to propel a future hybrid aircraft will be presented. It will be realized using 2 tools
Studying Neolithic lithics â from a cross-border dialogue to a common language
This paper aims at introducing a recent European collaborative project dedicated to lithic studies of the Neolithic. It unites a group of archaeologists from France, the United Kingdom, Belgium, the Netherlands and Germany, who belong to different research traditions. Our first meetings stressed the need for a cross-border dialogue and a common language for lithic analysis, including raw material analysis, blank production and tool production. We began by highlighting the differences and proximities between the different approaches, the potentialities to bridge these differences, the archaeological goals and the training needed. Our project, therefore, aims to harmonise our study practices in order to promote international communication and collaboration.In diesem Beitrag soll ein kuÌrzlich ins Leben gerufenes europaÌisches Gemeinschaftsprojekt vorgestellt werden, das sich mit lithischen Studien des Neolithikums befasst. Es vereint eine Gruppe von ArchaÌolog*innen aus Frankreich, dem Vereinigten KoÌnigreich, Belgien, den Niederlanden und Deutschland, die unterschiedlichen Forschungstraditionen angehoÌren. Unsere ersten Treffen verdeutlichten die Notwendigkeit eines grenzuÌber- schreitenden Dialogs und einer gemeinsamen Sprache fuÌr die lithische Analyse, zu der die Analyse des Rohmaterials, der Grundformproduktion und der Werkzeugproduktion gehoÌren. Wir begannen damit, die Unterschiede und Gemeinsamkeiten zwischen den verschiedenen AnsaÌtzen, die MoÌglichkeiten zur UÌberbruÌckung dieser Unterschiede, die archaÌologischen Ziele und die erforderliche Ausbildung herauszustellen. Unser Projekt zielt darauf ab, unsere Untersuchungspraktiken zu vereinheitlichen, um die internationale Kommunikation und Zusammenarbeit zu foÌrdern
Clinical and MRI outcomes 10 years after repair of massive posterosuperior rotator cuff tears
BACKGROUND: Massive rotator cuff tears are challenging to treat, with few or no studies on long-term outcomes of repair. The purpose of this study was to report 10-year outcomes following repair of massive posterosuperior rotator cuff tears, with and without extension into the subscapularis, and to determine prognostic factors that could influence clinical scores and retear rates. METHODS: The records of 234 patients who underwent repair of a massive posterosuperior rotator cuff tear at a total of 15 centers were retrieved. Patients were asked to return for evaluation at 10 years; 78 patients could not be contacted, 7 had died, and 19 had undergone a reoperation. A total of 130 patients (68% men) with a mean age (and standard deviation) of 56.1 ± 7.7 years (range, 26 to 79 years) were evaluated clinically, and 102 of them were also evaluated using magnetic resonance imaging (MRI). The tear was confined to the supraspinatus and infraspinatus tendons in 94 shoulders and also involved the superior portion of the subscapularis in 36 shoulders. Univariable and multivariable regressions were performed to determine whether 10-year total Constant-Murley scores and repair integrity were associated with patient characteristics, tear patterns, or repair techniques. RESULTS: In the study cohort, complications were noted in 14 shoulders (11%) (stiffness in 10 and infection in 4). For the 130 shoulders evaluated clinically, the mean total Constant-Murley score improved from 53.1 ± 15.9 (range, 14 to 83) preoperatively to 78.5 ± 11.3 (range, 36 to 98) at 10 years. Of the 102 shoulders evaluated using MRI, 32 had a retear (Sugaya type IV or V). Of the 19 shoulders that underwent a reoperation (excluded from the study cohort), 9 had a retear. The overall prevalence of retears was 34%. Multivariable regression analysis revealed a significant association between the 10-year Constant-Murley score and preoperative retraction of the infraspinatus tendon, but no association between retears and any of the variables. Involvement of the subscapularis had no significant effect on preoperative or postoperative Constant-Murley scores or retear rates. CONCLUSIONS: Patients who had repair of a massive posterosuperior rotator cuff tear maintained considerable improvements in clinical and radiographic outcomes at 10 years. Partial concomitant tears of the subscapularis did not affect the total postoperative Constant-Murley scores or retear rates
A nanoparticle ink allowing the high precision visualization of tissue engineered scaffolds by MRI
Hydrogels are widely used as cell scaffolds in several biomedical applications. Once implanted in vivo, cell scaffolds must often be visualized, and monitored overtime. However, cell scaffolds appear poorly contrasted in most biomedical imaging modalities such as magnetic resonance imaging (MRI). MRI is the imaging technique of choice for high-resolution visualization of low-density, water-rich tissues. Attempts to enhance hydrogel contrast in MRI are performed with ânegativeâ contrast agents that produce several image artifacts impeding the delineation of the implantâs contours. In this study, a magnetic ink based on ultra-small iron oxide nanoparticles (USPIONs; <5 nm diameter cores) is developed and integrated into biocompatible alginate hydrogel used in cell scaffolding applications. Relaxometric properties of the magnetic hydrogel are measured, as well as biocompatibility and MR-visibility (T1-weighted mode; in vitro and in vivo). A 2-week MR follow-up study is performed in the mouse model, demonstrating no image artifacts, and the retention of âpositiveâ contrast overtime, which allows very precise delineation of tissue grafts with MRI. Finally, a 3D-contouring procedure developed to facilitate graft delineation and geometrical conformity assessment is applied on an inverted template alginate pore network. This proof-of-concept establishes the possibility to reveal precisely engineered hydrogel structures using this USPIONs ink high-visibility approach
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