Assembly Planning from Observations under Physical Constraints

This paper addresses the problem of copying an unknown assembly of primitives with known shape and appearance using information extracted from a single photograph by an off-the-shelf procedure for object detection and pose estimation. The proposed algorithm uses a simple combination of physical stability constraints, convex optimization and Monte Carlo tree search to plan assemblies as sequences of pick-and-place operations represented by STRIPS operators. It is efficient and, most importantly, robust to the errors in object detection and pose estimation unavoidable in any real robotic system. The proposed approach is demonstrated with thorough experiments on a UR5 manipulator.Comment: See the project webpage at https://www.di.ens.fr/willow/research/assembly-planning

Peroxide grafted PDMS: hydrosilylation reaction study and thiol-ene chemistry as an alternative pathway

International audiencePeroxide containing PDMS were synthesized according to a new pathway. Although hydrosilylation is one of the main reaction carried out in silicone chemistry, the catalysts used are very sensitive to the chemical nature of the reactants and remained inefficient to graft allylic peroxide. Radical catalyzed thiol-ene chemistry was involved for the first time to yield an initiator group containing polymer. Peroxide grafted polysiloxane structure and decomposition were characterized using 1H, 13C and 29Si NMR, FT-IR and RAMAN spectroscopies, SEC and DSC. These macroinitiators can be used to obtain polysiloxane able to undergo cross-linking

Robust Visual Sim-to-Real Transfer for Robotic Manipulation

Learning visuomotor policies in simulation is much safer and cheaper than in the real world. However, due to discrepancies between the simulated and real data, simulator-trained policies often fail when transferred to real robots. One common approach to bridge the visual sim-to-real domain gap is domain randomization (DR). While previous work mainly evaluates DR for disembodied tasks, such as pose estimation and object detection, here we systematically explore visual domain randomization methods and benchmark them on a rich set of challenging robotic manipulation tasks. In particular, we propose an off-line proxy task of cube localization to select DR parameters for texture randomization, lighting randomization, variations of object colors and camera parameters. Notably, we demonstrate that DR parameters have similar impact on our off-line proxy task and on-line policies. We, hence, use off-line optimized DR parameters to train visuomotor policies in simulation and directly apply such policies to a real robot. Our approach achieves 93% success rate on average when tested on a diverse set of challenging manipulation tasks. Moreover, we evaluate the robustness of policies to visual variations in real scenes and show that our simulator-trained policies outperform policies learned using real but limited data. Code, simulation environment, real robot datasets and trained models are available at https://www.di.ens.fr/willow/research/robust_s2r/

Central venous O2 saturation and venous-to-arterial CO2 difference as complementary tools for goal-directed therapy during high-risk surgery

International audienceIntroduction: Central venous oxygen saturation (ScvO 2) is a useful therapeutic target in septic shock and high-risk surgery. We tested the hypothesis that central venous-to-arterial carbon dioxide difference (P(cv-a)CO 2), a global index of tissue perfusion, could be used as a complementary tool to ScvO 2 for goal-directed fluid therapy (GDT) to identify persistent low flow after optimization of preload has been achieved by fluid loading during high-risk surgery. Methods: This is a secondary analysis of results obtained in a study involving 70 adult patients (ASA I to III), undergoing major abdominal surgery, and treated with an individualized goal-directed fluid replacement therapy. All patients were managed to maintain a respiratory variation in peak aortic flow velocity below 13%. Cardiac index (CI), oxygen delivery index (DO 2 i), ScvO 2 , P(cv-a)CO 2 and postoperative complications were recorded blindly for all patients. Results: A total of 34% of patients developed postoperative complications. At baseline, there was no difference in demographic or haemodynamic variables between patients who developed complications and those who did not. In patients with complications, during surgery, both mean ScvO 2 (78 ± 4 versus 81 ± 4%, P = 0.017) and minimal ScvO 2 (minScvO 2) (67 ± 6 versus 72 ± 6%, P = 0.0017) were lower than in patients without complications, despite perfusion of similar volumes of fluids and comparable CI and DO 2 i values. The optimal ScvO 2 cutoff value was 70.6% and minScvO 2 < 70% was independently associated with the development of postoperative complications (OR = 4.2 (95% CI: 1.1 to 14.4), P = 0.025). P(cv-a)CO 2 was larger in patients with complications (7.8 ± 2 versus 5.6 ± 2 mmHg, P < 10-6). In patients with complications and ScvO 2 ≥71%, P(cv-a)CO 2 was also significantly larger (7.7 ± 2 versus 5.5 ± 2 mmHg, P < 10-6) than in patients without complications. The area under the receiver operating characteristic (ROC) curve was 0.785 (95% CI: 0.74 to 0.83) for discrimination of patients with ScvO 2 ≥71% who did and did not develop complications, with 5 mmHg as the most predictive threshold value

Photochemical oxidative addition of germane and diphenylgermane to ruthenium dihydride complexes

Photochemical reactions of germane and diphenylgermane with Ru(PP) 2 H 2 (PP = R 2 PCH 2 CH 2 PR 2 or DuPhos, R = Ph dppe, R = Et depe, R = Me dmpe) are reported. Reaction with GeH 4 generates a mixture of cis and trans isomers of Ru(PP) 2 (GeH 3 )H except for the DuPhos complex which yields the product only in the cis form. In situ laser photolysis (355 nm) demonstrates that the initial product is the cis isomer that undergoes thermal isomerization to the trans isomer. The complex cis-[Ru(dppe) 2 (GeH 3 )H] crystallizes selectively, allowing determination of its X-ray structure as a germyl hydride with a long Ru-H···Ge separation of 2.64(3) Å indicating that no residual interaction between the RuH and Ge is present. DFT calculations are also consistent with full oxidative addition. The structure of cis-[Ru(DuPhos) 2 (GeH 3 )H] reveals significant distortion from an octahedral geometry. The major species in the crystal (95%) exhibits a structure with a Ru-H···Ge distance of 2.42(5) Å suggesting negligible interaction between these centers. DFT calculations of the structure are consistent with the experimental determination. The reactions of Ru(PP) 2 H 2 with diphenylgermane yield cis-[Ru(PP) 2 (GePh 2 H)H] exclusively for PP = dmpe and depe, while the cis isomer is dominant in the case of dppe. A photochemical competition reaction between Ru(dppe) 2 (H) 2 and the two substrates Ph 2 SiH 2 and Ph 2 GeH 2 results in both Si-H and Ge-H oxidative addition activation with a kinetic preference (0.18:1) for the germyl hydride product. Thermal conversion of Ru(dppe) 2 (SiPh 2 H)H to Ru(dppe) 2 (GePh 2 H)H is observed on heating

Diversity and P-solubilizing ability of mycorrhizosphere bacteria associated with Pinus pinaster in the Landes forest ecosystem

Ectomycorrhizal fungi (ECM) and their associated mycorrhizosphere bacteria (MB) play a major role in phosphorous (P) nutrition of maritime pine, particularly in the Landes forest ecosystem considering the low bioavailability of P in its sandy-acidic soils. In order to characterize the MB associated to ECM, three collection campaigns of ECM root tips were performed from autumn 2005 to autumn 2006 throughout three forest stations. Five MB and nine ECM genera were identified overall through sequencing of 16S rDNA and mitochondrial large subunit rDNA fragment respectively. Dramatic seasonal changes were observed in the different MB-ECM associations especially in Burkholderia-Lactarius and Bacillus-Russula that were the most abundant ones. P-solubilizing ability of MB was shown to be taxon-dependent with a large majority of P-solubilizing isolates among Burkholderia, Pseudomonas and Paenibacillus contrary to Bacillus. Relationships between functional diversity of the MB-ECM associations and bioavailability of soil P remain to be investigated. (Résumé d'auteur)

Tensorpac: An open-source Python toolbox for tensor-based phase-amplitude coupling measurement in electrophysiological brain signals

Despite being the focus of a thriving field of research, the biological mechanisms that underlie information integration in the brain are not yet fully understood. A theory that has gained a lot of traction in recent years suggests that multi-scale integration is regulated by a hierarchy of mutually interacting neural oscillations. In particular, there is accumulating evidence that phase-amplitude coupling (PAC), a specific form of cross-frequency interaction, plays a key role in numerous cognitive processes. Current research in the field is not only hampered by the absence of a gold standard for PAC analysis, but also by the computational costs of running exhaustive computations on large and high-dimensional electrophysiological brain signals. In addition, various signal properties and analyses parameters can lead to spurious PAC. Here, we present Tensorpac, an open-source Python toolbox dedicated to PAC analysis of neurophysiological data. The advantages of Tensorpac include (1) higher computational efficiency thanks to software design that combines tensor computations and parallel computing, (2) the implementation of all most widely used PAC methods in one package, (3) the statistical analysis of PAC measures, and (4) extended PAC visualization capabilities. Tensorpac is distributed under a BSD-3-Clause license and can be launched on any operating system (Linux, OSX and Windows). It can be installed directly via pip or downloaded from Github (https://github.com/EtienneCmb/tensorpac). By making Tensorpac available, we aim to enhance the reproducibility and quality of PAC research, and provide open tools that will accelerate future method development in neuroscience