Structure and Dynamics of Solvated Polymers near a Silica Surface: On the Different Roles Played by Solvent

Whereas it is experimentally known that the inclusion of nanoparticles in hydrogels can lead to a mechanical reinforcement, a detailed molecular understanding of the adhesion mechanism is still lacking. Here we use coarse-grained molecular dynamics simulations to investigate the nature of the interface between silica surfaces and solvated polymers. We show how differences in the nature of the polymer and the polymer--solvent interactions can lead to drastically different behavior of the polymer--surface adhesion. Comparing explicit and implicit solvent models, we conclude that this effect cannot be fully described in an implicit solvent. We highlight the crucial role of polymer solvation for the adsorption of the polymer chain on the silica surface, the significant dynamics of polymer chains on the surface, and details of the modifications in the structure solvated polymer close to the interface

SCExAO as a precursor to an ELT exoplanet direct imaging instrument

The Subaru Coronagraphic Extreme AO (SCExAO) instrument consists of a high performance Phase Induced Amplitude Apodisation (PIAA) coronagraph combined with an extreme Adaptive Optics (AO) system operating in the near-infrared (H band). The extreme AO system driven by the 2000 element deformable mirror will allow for Strehl ratios >90% to be achieved in the H-band when it goes closed loop. This makes the SCExAO instrument a powerful platform for high contrast imaging down to angular separations of the order of 1lambda/D and an ideal testbed for exploring coronagraphic techniques for ELTs. In this paper we report on the recent progress in regards to the development of the instrument, which includes the addition of a visible bench that makes use of the light at shorter wavelengths not currently utilized by SCExAO and closing the loop on the tip/tilt wavefront sensor. We will also discuss several exciting guest instruments which will expand the capabilities of SCExAO over the next few years; namely CHARIS which is a integral field spectrograph as well as VAMPIRES, a visible aperture masking experiment based on polarimetric analysis of circumstellar disks. In addition we will elucidate the unique role extreme AO systems will play in enabling high precision radial velocity spectroscopy for the detection of small companions.Comment: 7 pages, 2 figures Proceedings of AO4ELTs3 conference, paper 13396, Florence, Italy, May 201

Complex nature of apparently balanced chromosomal rearrangements in patients with autism spectrum disorder

Background: Apparently balanced chromosomal rearrangements can be associated with an abnormal phenotype, including intellectual disability and autism spectrum disorder (ASD). Genome-wide microarrays reveal cryptic genomic imbalances, related or not to the breakpoints, in 25% to 50% of patients with an abnormal phenotype carrying a microscopically balanced chromosomal rearrangement. Here we performed microarray analysis of 18 patients with ASD carrying balanced chromosomal abnormalities to identify submicroscopic imbalances implicated in abnormal neurodevelopment. Methods: Eighteen patients with ASD carrying apparently balanced chromosomal abnormalities were screened using single nucleotide polymorphism (SNP) arrays. Nine rearrangements were de novo, seven inherited, and two of unknown inheritance. Genomic imbalances were confirmed by fluorescence in situ hybridization and quantitative PCR. Results: We detected clinically significant de novo copy number variants in four patients (22%), including three with de novo rearrangements and one with an inherited abnormality. The sizes ranged from 3.3 to 4.9 Mb; three were related to the breakpoint regions and one occurred elsewhere. We report a patient with a duplication of the Wolf-Hirschhorn syndrome critical region, contributing to the delineation of this rare genomic disorder. The patient has a chromosome 4p inverted duplication deletion, with a 0.5 Mb deletion of terminal 4p and a 4.2 Mb duplication of 4p16.2p16.3. The other cases included an apparently balanced de novo translocation t(5;18)(q12;p11.2) with a 4.2 Mb deletion at the 18p breakpoint, a subject with de novo pericentric inversion inv(11)(p14q23.2) in whom the array revealed a de novo 4.9 Mb deletion in 7q21.3q22.1, and a patient with a maternal inv(2)(q14.2q37.3) with a de novo 3.3 Mb terminal 2q deletion and a 4.2 Mb duplication at the proximal breakpoint. In addition, we identified a rare de novo deletion of unknown significance on a chromosome unrelated to the initial rearrangement, disrupting a single gene, RFX3. Conclusions: These findings underscore the utility of SNP arrays for investigating apparently balanced chromosomal abnormalities in subjects with ASD or related neurodevelopmental disorders in both clinical and research settings

Discovery of a low-mass companion inside the debris ring surrounding the F5V star HD 206893

Aims: Uncovering the ingredients and the architecture of planetary systems is a very active field of research that has fuelled many new theories on giant planet formation, migration, composition, and interaction with the circumstellar environment. We aim at discovering and studying new such systems, to further expand our knowledge of how low-mass companions form and evolve. Methods: We obtained high-contrast H-band images of the circumstellar environment of the F5V star HD 206893, known to host a debris disc never detected in scattered light. These observations are part of the SPHERE High Angular Resolution Debris Disc Survey (SHARDDS) using the InfraRed Dual-band Imager and Spectrograph (IRDIS) installed on VLT/SPHERE. Results: We report the detection of a source with a contrast of 3.6 × 10[SUP]-5[/SUP] in the H-band, orbiting at a projected separation of 270 milliarcsec or 10 au, corresponding to a mass in the range 24 to 73 M[SUB]Jup[/SUB] for an age of the system in the range 0.2 to 2 Gyr. The detection was confirmed ten months later with VLT/NaCo, ruling out a background object with no proper motion. A faint extended emission compatible with the disc scattered light signal is also observed. Conclusions: The detection of a low-mass companion inside a massive debris disc makes this system an analog of other young planetary systems such as β Pictoris, HR 8799 or HD 95086 and requires now further characterisation of both components to understand their interactions.Peer reviewe

Concevoir la ville à partir des gares, Rapport final du Projet Bahn.Ville 2 sur un urbanisme orienté vers le rail

Expérimenter de nouvelles façons de faire de l'aménagement et du développement urbain autour des gares ? C'est l'objectif du projet franco-allemand Bahn.Ville 2, recherche-action qui vise à promouvoir « un urbanisme orienté vers le rail ». Valoriser les investissements faits sur les lignes ferroviaires régionales périurbaines par des mesures d'accompagnement dans le domaine de l'urbanisme, optimiser les conditions d'accessibilité aux gares de ces lignes, améliorer la qualité du service rendu aux usagers dans les lieux d'échanges autour de ces gare telles sont les ambitions de ce projet réalisé sur la période 2007-2009. Il s'agit de tester les conditions de la mise en œuvre d'un urbanisme orienté vers le rail

Investigating silica nanoparticles / polymer composites : a coarse-grained molecular dynamics study

La dynamique moléculaire gros-grain nous permet d'étudier l'interface polymère / silice. En particulier, nous comparons les comportements divergents du poly(acrylamide) (PAAm) et du poly(N,Ndimethylacrylamide) (PDMA) sur la surface de silice. Tout d'abord, nous montrons que les comportements macroscopiques du PAAm et du PDMA sont correctement représentés par un modèle contenant un solvant explicite. Nous utilisons ensuite la méthode d'énergie libre umbrella sampling afin d'examiner le détachement du PAAm et du PDMA de la surface de silice et d'étudier les caractéristiques importantes qui permettent ou non à la chaîne de polymère de rester adsorbée sur la surface de silice. Nous soulignons l'importance des interactions intra moléculaires au sein du polymère ainsi que les interactions polymère/surface qui déterminent l'adsorption du polymère sur la silice. De manière surprenante, les interactions solvant/polymère et solvant/surface ne sont pas des critères discriminants lors de l'adsorption des polymères sur la surface. Les polymères sont finalement contraints de s'adsorber sur deux surfaces de silice séparées de 200 Å. Ce système nous permet d'analyser l'évolution de la labilité des monomères ainsi que la force appliquée par les monomères sur la surface quand la distance entre les deux surfaces augmente.Polymer/silica interface is investigated using coarse-grained molecular dynamics simulations. In particular, the different behavior of poly(acrylamide) (PAAm) and of poly(N,N-dimethylacrylamide) (PDMA) on the silica surface is compared. First, we show that the macroscopic behavior of PAAm and of PDMA is correctly represented by a model containing an explicit solvent. Then, the umbrella sampling free energy method is used to probe the detachment of PAAm and of PDMA from a silica surface and to investigate important features that allow - or not - the polymer chain to remain adsorbed on the silica surface. We proved that intramolecular interactions within the polymer and polymer/surface interactions are of first importance for the polymer chain to adsorb on silica. Surprisingly, solvent/polymer as well as solvent/surface interactions are not discriminating criteria. Polymer chains are finally constrained to a particular configuration where one chain is adsorbed on two silica surfaces that are 200 Å apart. This yields interesting insights into the evolution of the monomers lability and of the surface/polymer strength interaction when the two silica surfaces are moved apart

Caractérisation de composites polymères / nanoparticules de silice : une étude de dynamique moléculaire gros-grains

Polymer/silica interface is investigated using coarse-grained molecular dynamics simulations. In particular, the different behavior of poly(acrylamide) (PAAm) and of poly(N,N-dimethylacrylamide) (PDMA) on the silica surface is compared. First, we show that the macroscopic behavior of PAAm and of PDMA is correctly represented by a model containing an explicit solvent. Then, the umbrella sampling free energy method is used to probe the detachment of PAAm and of PDMA from a silica surface and to investigate important features that allow - or not - the polymer chain to remain adsorbed on the silica surface. We proved that intramolecular interactions within the polymer and polymer/surface interactions are of first importance for the polymer chain to adsorb on silica. Surprisingly, solvent/polymer as well as solvent/surface interactions are not discriminating criteria. Polymer chains are finally constrained to a particular configuration where one chain is adsorbed on two silica surfaces that are 200 Å apart. This yields interesting insights into the evolution of the monomers lability and of the surface/polymer strength interaction when the two silica surfaces are moved apart.La dynamique moléculaire gros-grain nous permet d'étudier l'interface polymère / silice. En particulier, nous comparons les comportements divergents du poly(acrylamide) (PAAm) et du poly(N,Ndimethylacrylamide) (PDMA) sur la surface de silice. Tout d'abord, nous montrons que les comportements macroscopiques du PAAm et du PDMA sont correctement représentés par un modèle contenant un solvant explicite. Nous utilisons ensuite la méthode d'énergie libre umbrella sampling afin d'examiner le détachement du PAAm et du PDMA de la surface de silice et d'étudier les caractéristiques importantes qui permettent ou non à la chaîne de polymère de rester adsorbée sur la surface de silice. Nous soulignons l'importance des interactions intra moléculaires au sein du polymère ainsi que les interactions polymère/surface qui déterminent l'adsorption du polymère sur la silice. De manière surprenante, les interactions solvant/polymère et solvant/surface ne sont pas des critères discriminants lors de l'adsorption des polymères sur la surface. Les polymères sont finalement contraints de s'adsorber sur deux surfaces de silice séparées de 200 Å. Ce système nous permet d'analyser l'évolution de la labilité des monomères ainsi que la force appliquée par les monomères sur la surface quand la distance entre les deux surfaces augmente

Untersuchung von Siliziumdioxid-Nanopartikeln/Polymer-Verbundstoffen : eine grobkörnig modellierte Molekulardynamik-Simulation-Studie

Polymer / silica interface is investigated using coarse-grained molecular dynamics simulations. In particular, the different behavior of poly(acrylamide) (PAAm) and of poly(N,Ndimethylacrylamide) (PDMA) on the silica surface is compared. First, we show that the macroscopic behavior of PAAm and of PDMA are correctly represented by a model containing an explicit solvent. Then, the umbrella sampling free energy method is used to probe the detachment of PAAm and of PDMA from a silica surface and to investigate important features that allow – or not – the polymer chain to remain adsorbed on the silica surface. We prove that intra molecular interactions within the polymer and polymer / surface interactions are of first importance for the polymer chain to adsorb on silica. Surprisingly, solvent / polymer as well as solvent / surface interactions are not discriminating criteria. Polymer chains are finally constrained to a particular configuration where one chain is adsorbed on two silica surfaces that are 200 Å apart. This yields interesting insights into the evolution of the monomers lability and of the surface / polymer strength interaction when the two silica surfaces are moved apart.Im Rahmen dieses Vorhabens wird der Polymer-Siliziumdioxid-Heteroübergang vermittels einer grobkörnig modellierten Molekulardynamik-Simulation untersucht, wobei insbesondere das unterschiedliche Verhalten von Polyacrylamiden (PAAm) und Poly(N,Ndimethylacrylamiden) (PDMA) auf der Siliziumoberfläche verglichen werden soll. Zunächst werden wir nachweisen, dass gleichermaßen das makroskopische Verhalten von PAAm und PDMA korrekt durch eine Modellierung repräsentiert werden kann, die einen expliziten Solventen enthält. Daran anschließend wird die Umbrella Sampling-Free-Energy-Methode angewandt werden, um die Ablösung von PAAm und PDMA von der Siliziumdioxidoberfläche zu untersuchen bzw. die maßgeblichen Merkmale zu analysieren, die es den Polymerketten ermöglichen, an der Siliziumdioxidoberfläche adsorbiert zu bleiben – oder ebendies verhindern. In diesem Zusammenhang werden wir belegen, dass die Adsorption in erster Linie durch die intramolekularen Wechselwirkungen innerhalb der Polymere sowie die Polymer-Oberflächen-Wechselverhältnisse gestattet werden und die Interaktionen zwischen den Solventen und den Polymeren bzw. die Polymer-Oberflächen-Wechselwirkung hierfür überraschenderweise keine ausschlaggebenden Kriterien sind. In einem letzten Schritt werden die Polymere schließlich auf eine spezifische Konfiguration hin beschränkt, in der eine Polymerkette auf zwei Siliziumoxidoberflächen adsorbiert wird, die sich in einem Abstand von 200 Å zueinander befinden. Dieses Projekt bietet einen hervorragenden Einblick in die Herausbildung von labilen Monomeren und die Intensität von Polymer-Oberflächen-Wechselwirkungen im Kontext zweier sich auseinander bewegenden Siliziumoxidoberflächen

The Montclus rock shelter (Gard) and the continuity hypothesis between 1st and 2nd Mesolithic in Southern France

International audienceExcavated in the 1960s, the Baume de Montclus rock shelter (Gard, France) contained a significant stratigraphic sequence covering the entire Mesolithic. The oldest layers (layer 30 to 17) belong to the first Mesolithic, and contain particular hyper-microlithic flint industries (Montclusian facies of the Sauveterrian). The overlying layers 14 to 7, underlying the Neolithic ones (layers 5 to 3), document a second Mesolithic sequence (Castelnovian). Layers 16 and 15 are the stratigraphical transition between those two main sets. The lithic industries from those two layers have characteristic elements referred both to the first and second Mesolithic. Generally, this duality was understood as evidence of the existence of a local transition facies between Sauveterrian and Castelnovian, and thus, of a permanent regional occupation. However, the analysis of spatial and stratigraphical data of those two layers 16 and 15, as well as that of their lithic industries, question this hypothesis. There is more probably a real break between the two main sets of occupation, Sauveterrian and Castelnovian. As generally noticed elsewhere in Southern France, we cannot highlight a transition facies between first and second Mesolithic. Consequently, the durability of human occupations at the end of the 6th millennium cal. BC in this region of Southern France is questioned