Dedicated liaison office for cultural heritage at the SOLEIL synchrotron

Starting January 2004, the SOLEIL synchrotron has set up a dedicated interface for cultural heritage (art and technology history, archaeology, conservation and restoration). The present contribution aims at summarising the activities of the interface for the period 2004-06. A first step consisted in a detailed survey of the current context of synchrotron usage for cultural heritage through strong interactions with actors of the field, an extensive review of the existing publications and the co-organisation of specific workshops and round tables. From this preliminary survey, the interest of a dedicated project involving European research infrastructures is clearly emphasised. Such a project should focus on solving the major issues and limitations encountered by the heritage community in its use of advanced characterisations techniques

Morphological, ecological and genetic aspects associated with endemism in the Fly Orchid group

The European genus Ophrys (Orchidaceae) is famous for its insect-like floral morphology, an adaptation for a pseudocopulatory pollination strategy involving Hymenoptera males. A large number of endemic Ophrys species have recently been described, especially within the Mediterranean Basin, which is one of the major species diversity hotspots. Subtle morphological variation and specific pollinator dependence are the two main perceptible criteria for describing numerous endemic taxa. However, the degree to which endemics differ genetically remains a challenging question. Additionally, knowledge regarding the factors underlying the emergence of such endemic entities is limited. To achieve new insights regarding speciation processes in Ophrys, we have investigated species boundaries in the Fly Orchid group (Ophrys insectifera sensu lato) by examining morphological, ecological and genetic evidence. Classically, authors have recognized one widespread taxon (O. insectifera) and two endemics (O. aymoninii from France and O. subinsectifera from Spain). Our research has identified clear morphological and ecological factors segregating among these taxa; however, genetic differences were more ambiguous. Insights from cpDNA sequencing and amplified fragment length polymorphisms genotyping indicated a recent diversification in the three extant Fly Orchid species, which may have been further obscured by active migration and admixture across the European continent. Our genetic results still indicate weak but noticeable phylogeographic clustering that partially correlates with the described species. Particularly, we report several isolated haplotypes and genetic clusters in central and southeastern Europe. With regard to the morphological, ecological and genetic aspects, we discuss the endemism status within the Fly Orchid group from evolutionary, taxonomical and conservation perspectives

Granular Jamming as Controllable Stiffness Mechanism for Endoscopic and Catheter Applications

peer reviewe

Granular jamming as controllable stiffness mechanism for endoscopic and catheter applications

peer reviewe

Characterization and Modeling of Granular Jamming: Models for Mechanical Design

peer reviewedThe use of granular jamming is proposed for designing structures with tunable rigidity of their tools (with the ability of being flexible devices for shaping and deformation but rigid for shape-locking and force transmission). The granular jamming consists in modifying the apparent rigidity of a structure by controlling the vacuum in a membrane filled with granular material. When the difference of pressure is low, the grains are free to move with respect to each other and the structure is flexible. When the vacuum in the membrane is increased, the grains are blocked and the structure is more rigid. Different mechanical characterizations of the granular jamming have been performed (triaxial compression and tension and cantilever beam bending tests) for different glass bead sizes ranging between 100 μm and 1 mm (used as granular material) at different vacuum levels (between 0 kPa and 90 kPa ). The grain size slightly influences the stiffness while the pressure difference is the main parameter to tune the stiffness of the structure. Based on these experiments, analytical models have been developed and validated. The tension characteristics can be directly deduced from the compression behavior and the bending modulus can be obtained by a combination of the tension and compression moduli. The proposed analytical models present the advantage of a simple formulation and are suitable for estimating the performance of other structures based on the granular jamming. The models can estimate and predict satisfactorily the results of granular jamming and can be used for designing mechanical structures based on this mechanism

Encoding information onto the charge and spin state of a paramagnetic atom using MgO tunnelling spintronics

An electrical current that flows across individual atoms or molecules can generate exotic quantum-based behavior, from memristive effects to Coulomb blockade and the promotion of quantum excited states. These fundamental effects typically appear one at a time in model junctions built using atomic tip or lateral techniques. So far, however, a viable industrial pathway for such discrete state devices has been lacking. Here, we demonstrate that a commercialized device platform can serve as this industrial pathway for quantum technologies. We have studied magnetic tunnel junctions with a MgO barrier containing C atoms. The paramagnetic localized electrons due to individual C atoms generate parallel nanotransport paths across the micronic device as deduced from magnetotransport experiments. Coulomb blockade effects linked to tunnelling magnetoresistance peaks can be electrically controlled, leading to a persistent memory effect. Our results position MgO tunneling spintronics as a promising platform to industrially implement quantum technologies

Synthesis, photophysics and nonlinear optical properties of stilbenoid pyrimidine-based dyes bearing methylenepyran donor groups.

International audienceThe nonlinear properties and the photophysical behavior of two π-conjugated chromophores that incorporate an electron-deficient pyrimidine core (A) and γ-methylenepyrans as terminal donor (D) groups have been thoroughly investigated. Both dipolar and quadrupolar branching strategies are explored and rationalized on the basis of the Frenkel exciton model. Even though a cooperative effect is clearly observed if the dimensionality is increased, the nonlinear optical (NLO) response of this series is moderate if one considers the nature of the D/A couple and the size of the chromophores (as measured by the number of π electrons). This effect was attributed to a disruption in the electronic conjugation within the dyes' scaffold for which the geometry deviates from planarity owing to a noticeable twisting of the pyranylidene end-groups. This latter structural parameter also has a strong influence on the excited-state dynamics, which leads to a very efficient fluorescence quenching

A new 3D positioner for the analytical mapping of non-flat objects under accelerator beams

We report the development of a 3D positioner for the elemental mapping of non-flat surfaces of heritage targets and its implementation in the external beam of the AGLAE accelerator, a joint research activity of the IPERION-CH European program.The positioner operates in two steps: 1) object surface is digitized using a 3D scanner implemented in the beamline. Surface points are interpolated onto a rectangular grid suitable for beam scanning. 2) Object is scanned under the beam using X/Y/Z stages holding a hexapod robot for rotations. During scanning, target surface is positioned with the Z stage and oriented perpendicular to the beam using hexapod rotations. Areas up to 100 × 100 mm 2 with a resolution of 50 µ m and 30° curvature of can be mapped on objects of 200 mm and 5 kg max. System operation was tested by recording PIXE maps on the polychrome decoration of a curved porcelain pot

Awakening the control of the ankle dorsiflexors in the post-stroke hemiplegic subject to improve walking activity and social participation: the WAKE (Walking Ankle isoKinetic Exercise) randomised, controlled trial

Stroke is the leading cause of acquired disability in France. While 90% of patients recover the ability to walk, it is often limited with a steady speed of approximately 0.7 m/s. This limitation of walking activity is partly related to a decrease in strength associated with more or less significant spasticity. In particular, it seems that the strength of the dorsiflexor muscles is directly related to walking speed. We hypothesise that a protocol based on gestural repetition targeted at the ankle during the subacute phase potentiates the recovery of motor control, improving walking activity, and participates in recovering better social participation