Influence of vision on short-term sound localization training with non-individualized HRTF

International audiencePrevious studies have demonstrated that it is possible for humans to adapt to new HRTF, non-individualized or altered, in a short time period. While natural adaptation, through sound exposure, takes several weeks [1], some training programs have been employed to accelerate adaptation and improve performance on sound localization in a few days (see [2] for a review). The majority of these training programs are based on audio-visual positional or response feedback learning [3] (participants correct their answer after seeing the target position), or on active learning, for example through audio-proprioceptive manipulations [4] (blindfolded participants actively explore the sphere around them by playing a mini sonified version of hot-and-cold game). While all training programs are based on a bimodal coupling (audio-vision [3] or audio-proprioception [4]), they are rarely based on a trimodal one. Therefore, if vision is not necessary for adaptation [4], and audio-visual training can even be less efficient than other methods [1,2], the role of vision in short-term audio localization training remains unclear, especially when action and proprioception are already involved. Our study compares two versions of active trainings: an audio-proprioceptive one and an audio-visuo-proprioceptive one. We hypothesize that combining all modalities leads to better adaptation inducing better performances and a longer remaining effect.The experiment is developed in virtual reality using a HTC Vive as a head- and hand-tracker. 3D audio spatialization is obtained through Steam Audio’s non-individualized built-in HRTF. When applicable, 3D visual information is displayed directly on the Vive screen. A total of 36 participants, equally distributed in 3 groups (G1 to G3), participate in this between-subject design study.G1 is a control group receiving no training session, while the 2 other groups receive a training session of 12 minutes during 3 consecutive days. All the participants also had to perform 5 sound localization tests (no feedback, hand-pointing techniques, 2 repetitions × 33 positions, frontal space): one before the experiment, one after each training session, and the last one 1 week after the first day in order to evaluate the remaining effect. G2 receives an audio-proprioceptive training as exposed in [4]. Participants have to freely scan the space around them with their hand-held Vive controller to find an animal sound hidden around them. The controller-to-target angular distance is sonified and spatialized at the controller position. No visual information is provided. G3 receives the same task as in G2 but, a visual representation of a sphere is also displayed at the hand position during all training sessions (audio-visuo-proprioceptive situation). We measure the angular error in azimuth and elevation during localization tests. Performances are also analyzed in interaural polar coordinate system to discuss front/back and up/down confusion errors. Data from training sessions are logged (total number of found animals and detailed sequence of hand positions) to evaluate how training and vision influence scanning strategy. The experimental phase is taking place right now (10 participants have completed it for the moment) and extends until the end of April. Complete results will be available for the final version of the paper in June. References [1] Carlile, S., and Blackman, T. Relearning auditory spectral cues for locations inside and outside the visual field. J. Assoc. Res. Otolaryngol. 15, 249–263 (2014)[2] Strelnikov, K., Rosito, M., and Barrone, P. Effect of audiovisual training on monaural spatial hearing in horizontal plane. PLoS ONE 6:e18344 (2011)[3] Mendonça, C. A review on auditory space adaptation to altered head-related cues. Front. Neurosci. 8, 219 (2014)[4] Parseihian, G. & Katz, B.F.G. Rapid head-related transfer function adaptation using a virtual auditory environment. J. Acous. Soc. of America 131, 2948–2957 (2012

Optimal Trajectory Generation for Manipulator Robots under Thermal Constraints

International audienceWe propose here to deal with the optimization of velocity profiles of manipulator robots with a minimum time criterion subject to thermal constraints. This paper deals with the real impact of thermal limitations on optimal velocity profiles and the methods to calculate the corresponding optimal trajectories. We first calculate analytically the optimal solution in a simple case in order to verify the validity of the numerical algorithm and also to present a general methodology to calculate optimal trajectories in robotics using results from the theory of calculus of variations and not from the theory of optimal control. We derive then a numerical algorithm based on the discretization of the time law through an interpolation with non uniform cubic splines. This algorithm shows robust and efficient convergence properties and the trajectories thus generated were executed successfully on a Staubli Rx90

Optimization of complex robot applications under real physical limitations

International audienceThis paper deals with minimum time trajectory optimization along a specified path subject to thermal constraints. We point out here that robots are often integrated in complex robotic cells, and the interactions between the robot and its environment are often difficult or even impossible to model. The structure of the optimization problem allows us to decompose the optimization in two levels, the first one being based on models and results of the theory of the calculus of variations, the second one being based on measurements and derivative free algorithms. This decomposition allows us to optimize the velocity profiles efficiently without knowing in advance the interactions between the robot and is environment. We propose here two numerical algorithms for these two levels of the decomposition which show good convergence properties. The resulting optimal velocity profiles are 5 to 10% faster than classical ones, and have been executed successfully on a real Stäubli Rx90 manipulator robot

Optimization of Industrial Applications with Hardware in the Loop

International audienceThis paper deals with optimizing the task cycle time of industrial robots integrated in complex robot cells. Trajectory optimizers are usually based on models and can't properly deal with uncertainties due to interactions between the robot and its environment. We propose here a trajectory optimizer with hardware in the loop which can take into account constraints such as maximum authorized temperature and maximum authorized torque. Our approach is based on unconstrained optimization algorithms without derivatives and penalty methods. Experiments on real industrial applications showed good robustness properties of this algorithm even with a high number of parameters and with changes of the robot task

Optimization of complex robot applications under thermal constraints

This paper deals with minimum time trajectory optimization along a specified path subject to thermal constraints. We point out here that robots are often integrated in complex robotic cells, and the interactions between the robot and its environment are often difficult or even impossible to modelize. The structure of the optimization problem allows us to decompose the optimization in two levels, the first one being based on models and results of the theory of the calculus of variations, the second one being based on measurements and derivative free algorithms. This decomposition allows us to optimize the velocity profiles efficiently without knowing in advance the interactions between the robot and is environment. We propose here two numerical algorithms for these two levels of the decomposition which show good convergence properties. The resulting optimal velocity profiles are 5 to 10\% faster than classical ones, and have been executed on successfully on a real Stäubli Rx90 manipulator robot

Microscopic structural study of collagen aging in isolated fibrils using polarized second harmonic generation

International audiencePolarization resolved second harmonic generation (PSHG) is developed to study, at the microscopic scale, the impact of aging on the structure of type I collagen fibrils in two-dimensional coatings. A ribose-glycated collagen is also used to mimic tissue glycation usually described as an indicator of aging. PSHG images are analyzed using a generic approach of the molecular disorder information in collagen fibrils, revealing significant changes upon aging, with a direct correlation between molecular disorder and fibril diameters

Diagnosis of chylous abdominal effusions: what is the triglyceride threshold value?

IntroductionChylous abdominal effusions are serious complications that can be triggered by various aetiologies. The biochemical diagnosis of chyle leakage in ascites or in peritoneal fluid capsules relies on the detection of chylomicrons. Assaying the fluid’s concentration of triglycerides is still the first-line tool. Given that only one comparative study has sought to quantify the value of the triglyceride assay for diagnosing chylous ascites in humans, our objective was to provide practical triglyceride thresholds. Materials and methodsWe conducted a 9-year, retrospective, single-centre study of adult patients and compared a triglyceride assay with lipoprotein gel electrophoresis for the analysis of 90 non-recurring abdominal effusions (ascites and abdominal collections) of which 65 were chylous. ResultsA triglyceride threshold of 0.4 mmol/L was associated with a sensitivity > 95%, and a threshold of 2.4 mmol/L was associated with a specificity > 95%. According to Youden index, the best threshold was 0.65 mmol/L with a sensitivity of 88 (77-95)%, a specificity of 72 (51-88)%, and, in our series, a positive predictive value of 89 (79-95)% and a negative predictive value of 69 (48-86)%. ConclusionsIn our series, cut-off of 0.4 mmol/L could be used for ruling-out diagnosis of chylous effusions, while cut-off of 2.4 mmol/L could be used for reasonably confirming diagnosis

JWST/NIRSpec Prospects on Transneptunian Objects

The transneptunian region has proven to be a valuable probe to test models of the formation and evolution of the solar system. To further advance our current knowledge of these early stages requires an increased knowledge of the physical properties of Transneptunian Objects (TNOs). Colors and albedos have been the best way so far to classify and study the surface properties of a large number TNOs. However, they only provide a limited fraction of the compositional information, required for understanding the physical and chemical processes to which these objects have been exposed since their formation. This can be better achieved by near-infrared (NIR) spectroscopy, since water ice, hydrocarbons, and nitrile compounds display diagnostic absorption bands in this wavelength range. Visible and NIR spectra taken from ground-based facilities have been observed for ~80 objects so far, covering the full range of spectral types: from neutral to extremely red with respect to the Sun, featureless to volatile-bearing and volatile-dominated (Barkume et al., 2008; Guilbert et al., 2009; Barucci et al., 2011; Brown, 2012). The largest TNOs are bright and thus allow for detailed and reliable spectroscopy: they exhibit complex surface compositions, including water ice, methane, ammonia, and nitrogen. Smaller objects are more difficult to observe even from the largest telescopes in the world. In order to further constrain the inventory of volatiles and organics in the solar system, and understand the physical and chemical evolution of these bodies, high-quality NIR spectra of a larger sample of TNOs need to be observed. JWST/NIRSpec is expected to provide a substantial improvement in this regard, by increasing both the quality of observed spectra and the number of observed objects. In this paper, we review the current knowledge of TNO properties and provide diagnostics for using NIRSpec to constrain TNO surface compositions

A microscopic and macroscopic study of aging collagen on its molecular structure, mechanical properties, and cellular response

During aging, collagen structure changes, detrimentally affecting tissues' biophysical and biomechanical properties due to an accumulation of advanced glycation end-products (AGEs). In this investigation, we conducted a parallel study of microscopic and macroscopic properties of different-aged collagens from newborn to 2-yr-old rats, to examine the effect of aging on fibrillogenesis, mechanical and contractile properties of reconstituted hydrogels from these collagens seeded with or without fibroblasts. In addition to fibrillogenesis of collagen under the conventional conditions, some fibrillogenesis was conducted alongside a 12-T magnetic field, and gelation rate and AGE content were measured. A nondestructive indentation technique and optical coherence tomography were used to determine the elastic modulus and dimensional changes, respectively. It was revealed that in comparison to younger specimens, older collagens exhibited higher viscosity, faster gelation rates, and a higher AGE-specific fluorescence. Exceptionally, only young collagens formed highly aligned fibrils under magnetic fields. The youngest collagen demonstrated a higher elastic modulus and contraction in comparison to the older collagen. We conclude that aging changes collagen monomer structure, which considerably affects the fibrillogenesis process, the architecture of the resulting collagen fibers and the global network, and the macroscopic properties of the formed constructs