Establishment of occupation chronicles in Grotte Mandrin using sooted concretions: Rethinking the Middle to Upper Paleolithic transition.

Soot marks, witnesses of past human activities, can sometimes be noticed in concretions (speleothem, travertine, carbonated crust, etc.) formed in cavities. We demonstrate here that these deposits, generally ignored in archaeological studies, turned out to be a perfectly suitable material for micro-chronological study of hominin activities in a site. At the Grotte Mandrin (Mediterranean France), thousands of clastic fragments from the rock walls were found in every archaeological level of the shelter. Calcareous crusts containing soot deposits are recorded on some of their surfaces. They appear in thin section as thin black laminae. Microscopic observation of these crusts revealed that they kept track of many occupations. We show that is possible to link them with the archaeological units identified during the excavation. Minimum Number of Occupations (MNO) can be built out of these sooted crusts. MNO are usually high and attest to the cumulative nature of each archaeological unit. They are witnesses of each occupation of hominin groups in each archaeological level of the cave. This study also shows that, in Grotte Mandrin, a very short time separates the first Middle/Upper Paleolithic transitional groups' occupations from those of the last Mousterians. The research perspectives on soot deposits are diversified and raise the possibility of studying multiple aspects of past human life, and in this case, to rethink the Middle/Upper Paleolithic transition, with an unmatched temporal resolution. Sooted concretion analysis provides high temporal resolution archaeology. There is a real possibility of extending this study with chronological implications to cavities of all ages and areas.

Directed Organization of Platinum Nanocrystals through Organic Supramolecular Nanoporous Templates.

We propose a novel approach to trap 2 nm Pt nanocrystals using nanoporous two-dimensional supramolecular networks for cavity-confined host-guest recognition process. This will be achieved by taking advantage of two features of supramolecular self-assembly at surfaces: First, its capability to allow the formation of complex 2D architectures, more particularly, nanoporous networks, through noncovalent interactions between organic molecular building-blocks; second, the ability of the nanopores to selectively host and immobilize a large variety of guest species. In this paper, for the first time, we will use isotropic honeycomb networks and anisotropic linear porous supramolecular networks to host 2 nm Pt nanocrystals.

Binary Superlattices from {Mo132} Polyoxometalates and Maghemite Nanocrystals: Long-Range Ordering and Fine-Tuning of Dipole Interactions.

In the present article, the successful coassembly of spherical 6.2 nm maghemite (γ-Fe2O3) nanocrystals and giant polyoxometalates (POMs) such as 2.9 nm {Mo132} is demonstrated. To do so, colloidal solutions of oleic acid-capped γ-Fe2O3 and long-chain alkylammonium-encapsulated {Mo132 } dispersed in chloroform are mixed together and supported self-organized binary superlattices are obtained upon the solvent evaporation on immersed substrates. Both electronic microscopy and small angles X-ray scattering data reveal an AB-type structure and an enhanced structuration of the magnetic nanocrystals (MNCs) assembly with POMs in octahedral interstices. Therefore, {Mo132} acts as an efficient binder constituent for improving the nanocrystals ordering in 3D films. Interestingly, in the case of didodecyldimethylammonium (C12)-encapsulated POMs, the long-range ordered binary assemblies are obtained while preserving the nanocrystals magnetic properties due to weak POMs-MNCs interactions. On the other hand, POMs of larger effective diameter can be employed as spacer blocks for MNCs as shown by using {Mo132} capped with dioctadecyldimethylammonium (C18) displaying longer chains. In that case, it is shown that POMs can also be used for fine-tuning the dipolar interactions in γ-Fe2O3 nanocrystal assemblies.

Lower selfing rates in metallicolous populations than in non-metallicolous populations of the pseudometallophyte Noccaea caerulescens (Brassicaceae) in Southern France.

BACKGROUND AND AIMS: The pseudometallophyte Noccaea caerulescens is an excellent model to study evolutionary processes, as it grows both on normal and on heavy-metal-rich, toxic soils. The evolution and demography of populations are critically impacted by mating system and, yet, information about the N. caerulescens mating system is limited. METHODS: Mean selfing rates were assessed using microsatellite loci and a robust estimation method (RMES) in five metallicolous and five non-metallicolous populations of N. caerulescens in Southern France, and this measure was replicated for two successive reproductive seasons. As a part of the study, the patterns of gene flow among populations were analysed. The mating system was then characterized at a fine spatial scale in three populations using the MLTR method on progeny arrays. KEY RESULTS: The results confirm that N. caerulescens has a mixed mating system, with selfing rates ranging from 0·2 to 0·5. Selfing rates did not vary much among populations within ecotypes, but were lower in the metallicolous than in the non-metallicolous ecotype, in both seasons. Effective population size was also lower in non-metallicolous populations. Biparental inbreeding was null to moderate. Differentiation among populations was generally high, but neither ecotype nor isolation by distance explained it. CONCLUSIONS: The consequences of higher selfing rates on adaptation are expected to be weak to moderate in non-metallicolous populations and they are expected to suffer less from inbreeding depression, compared to metallicolous populations.

Role of the nanocrystallinity on the chemical ordering of Co(x)Pt(100-x) nanocrystals synthesized by wet chemistry.

Co(x)Pt(100-x) nanoalloys have been synthesized by two different chemical processes either at high or at low temperature. Their physical properties and the order/disorder phase transition induced by annealing have been investigated depending on the route of synthesis. It is demonstrated that the chemical synthesis at high temperature allows stabilization of the fcc structure of the native nanoalloys while the soft chemical approach yields mainly poly or non crystalline structure. As a result the approach of the order/disorder phase transition is strongly modified as observed by high-resolution transmission electron microscopy (HR-TEM) studies performed during in situ annealing of the different nanoalloys. The control of the nanocrystallinity leads to significant decrease in the chemical ordering temperature as the ordered structure is observed at temperatures as low as 420 °C. This in turn preserves the individual nanocrystals and prevents their coalescence usually observed during the annealing necessary for the transition to an ordered phase.

Preparation of silver nanoparticles by a non-aqueous sol-gel process.

Using a non-aqueous sol-gel process with a direct calcination step in air after prior drying, silver nanoparticles with average size distribution ranging from 20 to 100 nm were synthesised. Studies in reduced atmosphere were also performed with mixed results, both in phase and particle size, as the samples were found to be mixed with an amorphous phase. In oxidising atmosphere, the temperature and dwelling time were found to be critical factors with the former playing a larger role than the latter. Optimally nanoparticles of silver are best prepared by direct calcination in air of the precursor gel at 250 degrees C for 1 hour. Compared to silver particles prepared by microemulsions, the particle size is larger due to the thermal treatment, which causes a growth of the silver particles.

Lateral river erosion impacts the preservation of Neolithic enclosures in alluvial plains.

Situating prehistoric sites in their past environment helps us to understand their functionality and the organization of early sedentary human societies. However, this is a challenge as the natural environment constantly evolves through time and erases these constructions, especially along riverbanks, thus biasing the archaeological record. This study introduces a reassessment of the paleo-landscape evolution around the Neolithic enclosures at the Noyen-sur-Seine site based on new field observations as well as the synthesis of (un)published and new radiocarbon dating. Contrary to the initial hypothesis, our results show that the Noyen enclosures were not built along a Neolithic Seine River: the nearby channels were active in the Middle Age and Early Modern periods. Therefore, the results show that the enclosures were originally much larger: only a fraction that survived river erosion (lateral migration rates up to 2-3 m yr-1 estimated during the nineteenth century) has been preserved. Instead, an abandoned Mesolithic Seine River served as a natural delimitation of the SE part of the Neolithic enclosures. These results indicate that Neolithic enclosures in alluvial settings are often only partly preserved and that societies from that period lived farther away from active rivers than originally thought, where they were protected from floods.

Influence of hydrogen on the morphology of platinum and palladium nanocrystals.

Palladium and platinum nanocrystals are synthesized by the liquid-liquid phase transfer method, which is a suitable way to produce anisotropic metallic nanoparticles and control their shape at the nanoscopic scale. The process leading to shape control is, however, quite complex as all the physical and chemical parameters could play an important role. In this paper, we have demonstrated the primordial role of the dissolved gases (O(2), H(2), N(2)) in the solvent medium on the nanomorphology of platinum and palladium nanocrystals. In particular, it shows the specific role of H(2) in the formation of platinum nanocubes.

Chemical Evolution of Pt-Zn Nanoalloys Dressed in Oleylamine.

We report on the shape, composition (from Pt95Zn5 to Pt77Zn23), and surface chemistry of Pt-Zn nanoparticles obtained by reduction of precursors M2+(acac)2- (M2+: Pt2+ and Zn2+) in oleylamine, which serves as both solvent and ligand. We show first that the addition of phenyl ether or benzyl ether determines the composition and shape of the nanoparticles, which point to an adsorbate-controlled synthesis. The organic (ligand)/inorganic (nanoparticles) interface is characterized on the structural and chemical level. We observe that the particles, after washing with ethanol, are coated with oleylamine and the oxidation products of the latter, namely, an aldimine and a nitrile. After exposure to air, the particles oxidize, covering themselves with a few monolayer thick ZnO film, which is certainly discontinuous when the particles are low in zinc. Pt-Zn particles are unstable and prone to losing Zn. We have strong indications that the driving force is the preferential oxidation of the less noble metal. Finally, we show that adsorption of CO on the surface of nanoparticles modifies the oxidation state of amine ligands and attribute it to the displacement of hydrogen adsorbed on Pt. All the structural and chemical information provided by the combination of electron microscopy and X-ray photoelectron spectroscopy allows us to give a fairly accurate picture of the surface of nanoparticles and to better understand why Pt-Zn alloys are efficient in certain electrocatalytic reactions such as the oxidation of methanol.

Approach of Pavement Surface Layer Degradation Caused by Tire Contact Using Semi-Analytical Model.

New methods of degradations on the pavement's surface, such as top-down cracking and delamination, caused by the repeated passage of heavy vehicles led to questions about the impact of the contact between the tire and the pavement. In fact, to increase the service life of the structures, future road design methods must have a precise knowledge of the consequences of the contact parameters on the state of stress and deformation in the pavement. In this paper, tractive rolling contact under the effect of friction is modeled by Kalker's theory using a semi-analytical method (SAM). A tire profile is performed thanks to a digitization by fringes or a photogrammetry technique. The effect of rolling on the main surface extension deformations is then highlighted to study top cracking. At the end of the SAM calculation, contact areas are closed to 200 µdef, exceeding the allowable micro-deformation limit for the initiation of cracking. In addition, results on the main strain directions also give information on the direction of cracking (initiation of longitudinal or transverse cracks). The cracking then becomes evident, leading to a reduced service life.

The five shades of oleylamine in a morphological transition of cobalt nanospheres to nanorods.

Understanding of cobalt nanorods' (Co NRs) formation still remains challenging when it comes to enhancing their anisotropic properties applicable in magnetic or catalytic areas. Herein, we propose a mechanism for the morphological transition from spherical cobalt nanoparticles (NPs) to Co NRs over time (9 h) in a mixture of [CoCl(PPh3)3] and oleylamine (OAm). In the literature, we described how spherical Co NPs are synthesized via a disproportionation process. Based on in situ and pseudo in situ observations, two steps of this unique mechanism are characterized first by the dissolution of the spheres and then the regrowth in rods' shape in the presence of an OAm template. Furthermore, ex situ experiments show that these steps are the result of interdependent reactions occurring between Co NPs, cobalt(ii) and OAm. The latter plays numerous roles in this synthesis: as a surfactant, a disproportionation promoter, and a hydrogen source allowing the reduction of cobalt(ii) complexes; its ammonium salt derivative is involved in oxidative etching of Co NPs and it promotes the anisotropic growth in NRs. These coupling actions of reduction and etching generate two cobalt reservoirs of nuclei under thermodynamic conditions.

Composition study of CoPt bimetallic nanocrystals of 2 nm.

The synthesis of bimetallic alloy nanocrystals with a well-controlled relative composition is a real challenge and requires chemical analysis techniques with high accuracy. A new chemical route has been used to synthesize cobalt-platinum nanocrystals of 2-nm diameter in a wide range of relative stoichiometry. A study of the elemental composition of the nanoalloy was carried out by X-ray fluorescence (XRF) spectroscopy and energy-dispersive X-ray analysis. We have developed a set-up for XRF analysis using a silicon wafer as a support to determine the elemental composition with only a small amount of sample. The calibration step and the measurement capabilities are described. In a composition range of 25-75% cobalt, the results of both analytical methods are discussed and compared in detail.

Protective Effect of Polyoxometalates in {Mo132}/Maghemite Binary Superlattices Under Annealing.

The binary assembly DDA-{Mo132}/OA-γ-Fe2O3 (DDA = didodecyldimethylammonium, {Mo132} = [Mo132O372(CH3COO)30(H2O)72]42-, OA = oleic acid) constitutes one of the two examples in the literature of binary superlattices made of a mixing of nanocrystals and oxo-clusters. In a precedent work, we reported in details the preparation of such magnetic binary systems and studied the effect of the nature of the polyoxometalates (POMs) on the magnetic properties. In the present paper, we study the stability of this model binary assembly under heating at various temperatures. Indeed, especially if magnetic and/or transport properties are targeted, an annealing can be essential to change the phase of the nanocrystals in a more magnetic one and/or to desorb the organic capping of the nano-objects that can constitute an obstacle to the electronic communication between the nano-objects. We gave evidence that the maghemite organization in the binary assembly is maintained until 370°C under vacuum thanks to the presence of the POMs. This latter evolve in the phase MoO3, but still permits to avoid the aggregation of the nanocrystals as well as preserve their periodical arrangement. On the contrary, an assembly made of pure γ-Fe2O3 nanocrystals displays a clear aggregation of the nano-objects from 370°C, as attested by transmission and scanning electronic microscopies and confirmed by magnetic measurements. The stability of the magnetic nanocrystals in such POMs/nanocrystals assemblies opens the way to (i) the elaboration of new binary assemblies from POMs and numerous kinds of nanocrystals with a good control on the magnetic properties and to (ii) the investigation of new physical properties as exchange coupling, or magneto-transport in such systems.

Consequences of low mate availability in the rare self-incompatible species Brassica insularis.

Self-incompatibility systems prevent self-fertilization in angiosperms. Although numerous S alleles are usually maintained by negative frequency-dependent selection, the number of S alleles can be low in small populations, which limits mate availability and reduces fecundity in endangered populations of self-incompatible plants. Despite the increasing evidence of the negative effect of self-incompatibility in small populations, the direct link between the number and the distribution of S alleles and their reproductive consequences has been rarely reported. Brassica insularis is a rare self-incompatible species with medium to very small populations. Results of a previous study showed that the smallest population has very few S alleles. We investigated whether reduced mate availability affects reproduction in this species. We compared the pollination success and the fruit set in 4 populations differing in population size and number of S alleles. Our results suggest that reproduction may be negatively affected by the low S-allele diversity in the smallest population. Nevertheless, other populations also had reduced fruit set that could not be attributed to self-incompatibility alone.

Probing the in-air growth of large area of 3D functional structures into a 2D supramolecular nanoporous network.

Surface-confined host-guest chemistry at the air/solid interface is used for trapping a functionalized 3D Zn-phthalocyanine complex into a 2D porous supramolecular template allowing the large area functionalization of an sp2-hybridized carbon-based substrate as evidenced by STM, resonance Raman spectroscopy, and water contact angle measurements.

Platinum and platinum based nanoalloys synthesized by wet chemistry.

Platinum nanocrystals and their derivatives with palladium and cobalt are of fundamental interest due to their wide field of application in chemistry and physics. Their properties are strongly dependent on their shape and composition. However the chemical route is far from allowing control of both shape and composition. In this paper, we show both experimentally and theoretically the important role of the interaction of small adsorbed molecules on the shape but also on the composition. This has been studied by comparing the case of pure palladium and platinum nanocrystals and the case of PtPd and PtCo nanoalloys synthesized by the liquid-liquid phase transfer method.

Influence of Dietary Experience on the Induction of Preference of Adult Moths and Larvae for a New Olfactory Cue.

In Lepidoptera, host plant selection is first conditioned by oviposition site preference of adult females followed by feeding site preference of larvae. Dietary experience to plant volatile cues can induce larval and adult host plant preference. We investigated how the parent's and self-experience induce host preference in adult females and larvae of three lepidopteran stem borer species with different host plant ranges, namely the polyphagous Sesamia nonagrioides, the oligophagous Busseola fusca and the monophagous Busseola nairobica, and whether this induction can be linked to a neurophysiological phenotypic plasticity. The three species were conditioned to artificial diet enriched with vanillin from the neonate larvae to the adult stage during two generations. Thereafter, two-choice tests on both larvae and adults using a Y-tube olfactometer and electrophysiological (electroantennography [EAG] recordings) experiments on adults were carried out. In the polyphagous species, the induction of preference for a new olfactory cue (vanillin) by females and 3rd instar larvae was determined by parents' and self-experiences, without any modification of the sensitivity of the females antennae. No preference induction was found in the oligophagous and monophagous species. Our results suggest that lepidopteran stem borers may acquire preferences for new olfactory cues from the larval to the adult stage as described by Hopkins' host selection principle (HHSP), neo-Hopkins' principle, and the concept of 'chemical legacy.'

Synthesis of tin nanocrystals in room temperature ionic liquids.

The aim of this work was to investigate the synthesis of tin nanoparticles (NPs) or tin/carbon composites, in room temperature ionic liquids (RTILs), that could be used as structured anode materials for Li-ion batteries. An innovative route for the synthesis of Sn nanoparticles in such media is successfully developed. Compositions, structures, sizes and morphologies of NPs were characterized by high-energy X-ray diffraction (HEXRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Our findings indicated that (i) metallic tetragonal ß-Sn was obtained and (ii) the particle size could be tailored by tuning the nature of the RTILs, leading to nano-sized spherical particles with a diameter ranging from 3 to 10 nm depending on synthesis conditions. In order to investigate carbon composite materials for Li-ion batteries, Sn nanoparticles were successfully deposited on the surface of multi-wall carbon nanotubes (MWCNT). Moreover, electrochemical properties have been studied in relation to a structural study of the nanocomposites. The poor electrochemical performances as a negative electrode in Li-ion batteries is due to a significant amount of RTIL trapped within the pores of the nanotubes as revealed by XPS investigations. This dramatically affected the gravimetric capacity of the composites and limited the diffusion of lithium. The findings of this work however offer valuable insights into the exciting possibilities for synthesis of novel nano-sized particles and/or alloys (e.g. Sn-Cu, Sn-Co, Sn-Ni, etc.) and the importance of carbon morphology in metal pulverization during the alloying/dealloying process as well as prevention of ionic liquid trapping.

A dog's life: Multiple trauma and potential abuse in a medieval dog from Guimps (Charente, France).

Rescue excavations carried out around Guimps (Charente, France) in 2011 unearthed several medieval structures, including a silo containing a single dog burial. The animal, a young adult, exhibits numerous skeletal lesions. The excellent preservation of the remains allowed us to carry out a retrospective diagnosis and to demonstrate the presence of two independent pathologies, a radius-curvus and a medial patellar dislocation. These conditions are of traumatic origin, as are the many fractures the animal also displays. The possible causes of such multiple injuries are discussed and the chronology of the lesions and their skeletal distribution are examined in light of modern data. This leads us to suggest animal abuse as a probable cause and, as almost no comparable cases were found in the bibliographical record, raise the profile of the identification of animal abuse in archeology.

Colloidal nanocube supercrystals stabilized by multipolar Coulombic coupling.

We explore microscopic principles governing the self-assembly of colloidal octylamine-coated platinum nanocubes solvated in toluene. Our experiments show that regular nanocubes with an edge length of l(RC) = 5.5 nm form supercrystals with simple cubic packing, while slightly truncated nanocubes with an edge length of l(TC) = 4.7 nm tend to arrange in fcc packing. We model by averaged force fields and atomistic molecular dynamics simulations the coupling forces between these nanocrystals. Our detailed analysis shows that the fcc packing, which for cubes has a lower density than simple cubic packing, is favored by the truncated nanocubes due to their Coulombic coupling by multipolar electrostatic fields, formed during charge transfer between the octylamine ligands and the Pt cores.