1,565 research outputs found

    Soft Matter Roadmap

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    International audienceAbstract Soft materials are usually defined as materials made of mesoscopic entities, often self-organized, sensitive to thermal fluctuations and to weak perturbations. Archetypal examples are colloids, polymers, amphiphiles, liquid crystals, foams. The importance of soft materials in everyday commodity products, as well as in technological applications, is enormous, and controlling or improving their properties is the focus of many efforts. 

From a fundamental perspective, the possibility of manipulating soft material properties, by tuning interactions between constituents and by applying external perturbations, gives rise to an almost unlimited variety in physical properties. Together with the relative ease to observe and characterize them, this renders soft matter systems powerful model systems to investigate statistical physics phenomena, many of them relevant as well to hard condensed matter systems.
 
Understanding the emerging properties from mesoscale constituents still poses enormous challenges, which have stimulated a wealth of new experimental approaches, including the synthesis of new systems with, e.g., tailored self-assembling properties, or novel experimental techniques in imaging, scattering or rheology. Theoretical and numerical methods, and coarse-grained models, have become central to predict physical properties of soft materials, while computational approaches that also use machine learning tools are playing a progressively major role in many investigations.

This roadmap paper intends to give a broad overview of recent and possible future activities in the field of soft materials, with experts covering various developments and challenges in material synthesis and characterization, instrumental, simulation and theoretical methods as well as general concepts

    DataSheet_1_Data quality control considerations in multivariate environmental monitoring: experience of the French coastal network SOMLIT.docx

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    IntroductionWhile crucial to ensuring the production of accurate and high-quality data—and to avoid erroneous conclusions—data quality control (QC) in environmental monitoring datasets is still poorly documented.MethodsWith a focus on annual inter-laboratory comparison (ILC) exercises performed in the context of the French coastal monitoring SOMLIT network, we share here a pragmatic approach to QC, which allows the calculation of systematic and random errors, measurement uncertainty, and individual performance. After an overview of the different QC actions applied to fulfill requirements for quality and competence, we report equipment, accommodation, design of the ILC exercises, and statistical methodology specially adapted to small environmental networks (Results, Discussion, ConclusionThe examination of the temporal variations (2001–2021) in the repeatability, reproducibility, and trueness of the SOMLIT network over time confirms the essential role of ILC exercises as a tool for the continuous improvement of data quality in environmental monitoring datasets.</p

    Gradient descent with a general cost

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    We present a new class of gradient-type optimization methods that extends vanilla gradient descent, mirror descent, Riemannian gradient descent, and natural gradient descent. Our approach involves constructing a surrogate for the objective function in a systematic manner, based on a chosen cost function. This surrogate is then minimized using an alternating minimization scheme. Using optimal transport theory we establish convergence rates based on generalized notions of smoothness and convexity. We provide local versions of these two notions when the cost satisfies a condition known as nonnegative cross-curvature. In particular our framework provides the first global rates for natural gradient descent and Newton's method

    Chemical Profile, Antioxidant and Anti-Inflammatory Potency of Extracts of <i>Vitex madiensis</i> Oliv. and <i>Crossopteryx febrifuga</i> (Afzel ex G. Don)

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    Vitex madiensis Oliv. (Lamiaceae) and Crossopteryx febrifuga (Rubiaceae), two plants commonly used in traditional African medicines to treat malaria and pain, were studied either to determine their chemical profiles or to evaluate their antioxidant and anti-inflammatory activities. In this study, we investigated leaves, trunk bark, root bark and fruits methanolic extracts of both plants in order to find out which part of the plant is responsible for the activity. The analyses of the chemical profiles allowed us to confirm the presence of several ecdysteroids, especially 20-hydroxyecdysone in some parts of V. madiensis and to highlight the presence of organic acids and phenol derivatives in C. febrifuga. Among the four parts of the plants studied, only the fruits extract of C. febrifuga could present anti-inflammatory activity by decreasing ROS production. The leaves and trunk bark extracts of V. madiensis showed significant free radical scavenging activity compared to ascorbic acid, and the same extracts decrease ROS production significantly. The activity of these two extracts could be explained by the presence of ecdysteroids and flavonoids. The ROS production inhibition of V. madiensis is particularly interesting to investigate with further analyses

    Crossed clinical features between eating disorders and types of bipolar disorder: Results from the FondaMental Advanced Centers of Expertise - Bipolar Disorder cohort

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    International audienceBackground: Eating disorders (EDs) are liable to alter the disease course of bipolar disorder (BD). We explored the crossed clinical features between EDs and BD, particularly as a function of BD type (BD1 vs. BD2). Methods: 2929 outpatients attending FondaMental Advanced Centers of Expertise were assessed for BD and lifetime EDs with a semi-structured interview, and their sociodemographic, dimensional and clinical data were collected according to a standardized procedure. For each ED type, bivariate analyses were used to investigate associations between these variables and the type of BD type followed by multinomial regressions with the variables associated with EDs and BDs after Bonferroni correction. Results: Comorbid EDs were diagnosed in 478 (16.4 %) cases, and were more prevalent in patients with BD2 than in those with BD1 (20.6 % vs. 12.4 %, p < 0.001). Regression models showed no difference according to the subtype of bipolar disorder on the characteristics of patients with anorexia nervosa (AN), bulimia nervosa (BN) or binge eating disorder (BED). After multiple adjustments, the factors differentiating BD patients with versus without ED were primarily age, gender, body mass index, more affective lability and comorbidity with anxiety disorders. BD patients with BED also scored higher regarding childhood trauma. BD patients with AN also showed higher risk of past suicide attempts than those with BED. Conclusions: In a large sample of patients with BD, we found a high prevalence of lifetime EDs, especially for the BD2 type. EDs were associated with several severity indicators, but not with BD type-specific characteristics. This should prompt clinicians to carefully screen patients with BD for EDs, regardless of BD and ED types

    Upside down sulphate dynamics in a saline inland lake

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    International audienceThe sulphur cycle has a key role on the fate of nutrients through its several interconnected reactions. Although sulphur cycling in aquatic ecosystems has been thoroughly studied since the early 70's, its characterisation in saline endorheic lakes still deserves further exploration. Gallocanta Lake (NE Spain) is an ephemeral saline inland lake whose main sulphate source is found on the lake bed minerals and leads to dissolved sulphate concentrations higher than those of seawater. An integrative study including geochemical and isotopic characterization of surface water, porewater and sediment has been performed to address how sulphur cycling is constrained by the geological background. In freshwater and marine environments, sulphate concentration decreases with depth are commonly associated with bacterial sulphate reduction (BSR). However, in Gallocanta Lake sulphate concentrations in porewater increase from 60 mM at the water-sediment interface to 230 mM at 25 cm depth. This extreme increase could be caused by dissolution of the sulphate rich mineral epsomite (MgSO 4 •7H 2 O). Sulphur isotopic data was used to validate this hypothesis and demonstrate the occurrence of BSR near the water-sediment interface. This dynamic prevents methane production and release from the anoxic sediment, which is advantageous in the current context of global warming. These results underline that geological context should be considered in future biogeochemical studies of inland lakes with higher potential availability of electron acceptors in the lake bed compared to the water column

    Detection of wildtype Merkel cell polyomavirus genomic sequence and VP1 transcription in a subset of Merkel cell carcinoma

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    International audienceAims: Merkel cell carcinoma (MCC) is frequently caused by the Merkel cell polyomavirus (MCPyV). Characteristic for these virus-positive (VP) MCC is MCPyV integration into the host genome and truncation of the viral oncogene Large T antigen (LT), with full-length LT expression considered as incompatible with MCC growth.Methods and results: Whole-genome sequencing of MCC/trichoblastoma again provided evidence of a trichoblastoma-derived MCC. Although an MCC-typical LT-truncating mutation was detected, we could not determine an integration site and we additionally detected a wildtype sequence encoding full-length LT. Similarly, Sanger sequencing of the combined MCC/poroma revealed coding sequences for both truncated and full-length LT. Moreover, in situ RNA hybridization demonstrated expression of a late region mRNA encoding the viral capsid protein VP1 in both combined as well as in a few cases of pure MCC.Conclusion: The data presented here suggest the presence of wildtype MCPyV genomes and VP1 transcription in a subset of MCC

    Physical and Mental Health Status of Former Smokers and Non-Smokers Patients with Bipolar Disorder

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    International audienceObjectives Up to 70% individuals with bipolar disorder (BD) are lifetime tobacco smokers, a major modifiable risk factor for morbidity. However, quitting smoking is rarely proposed to individuals with BD, mainly because of fear of unfavorable metabolic or psychiatric changes. Evaluating the physical and mental impact of tobacco cessation is primordial. The aim of this study was to characterize the psychiatric and non-psychiatric correlates of tobacco smoking status (never- versus current vs former smokers) in individuals with BD.Methods 3,860 individuals with ascertained BD recruited in the network of Fondamental expert centers for BD between 2009 and 2020 were categorized into current, former, and never tobacco smokers. We compared the sociodemographic and clinical characteristics assessed by standard instruments (e.g. BD type, current symptoms load, and non-psychiatric morbidity \textendash including anthropometric and biological data) of the three groups using multinomial regression logistic models. Corrections for multiple testing were applied.Results Current smokers had higher depression, anxiety, and impulsivity levels than former and never-smokers, and also higher risk of comorbid substance use disorders with a gradient from never to former to current smokers \textendash suggesting shared liability. Current smokers were at higher risk to have a metabolic syndrome than never-smokers, although this was only evidenced in cases, who were not using antipsychotics.Conclusions Tobacco smoking was associated with high morbidity level. Strikingly, as in the general population, quitting smoking seemed associated with their return to the never-smokers' levels. Our findings strongly highlight the need to spread strategies to treat tobacco addiction in the BD population

    Vibration-based wheel-terrain slip detection for skid-steer rovers

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    To fulfill their mission properly, planetary exploration rovers must often be able to travel long distances and traverse various terrain types. Some terrain types and topologies may present traversability challenges. In difficult situations, such as slopes and loose soil, rover wheel slip may increase to a level leading to entrapment risks. Autonomous slip detection allows a rover to detect potentially dangerous terrain and take precautions. While visual odometry slip estimation solutions exist, numerous external factors, such as luminance, haze and shadows, may negatively impact quality of imaging sensor data and consequently slip estimation. Visual odometry also requires significant computational resources. Previous studies have shown promise in the use of Machine Learning algorithms to process IMU-measured vibration data to detect and classify slip events. This research develops a low-latency and computationally efficient vibration-based system to detect wheel-terrain slip events for skid-steer rovers with modest hardware requirements. To this end, vibration datasets corresponding to various wheel-terrain slip values are generated. A Husky rover with two Inertial Measurement Unit sensors is used in indoor and outdoor test environments. Slip is induced at specific values by mechanically constraining the rover to reduce the Actual Rover Speed below the Commanded Rover Speed. The vibration datasets are used to train and validate a Support Vector Machine classifier to differentiate abnormally high slip events from normal low slip. The training is done with various sensor outputs, sampling time, and sampling frequency. The performance of the system is then evaluated in order to find which combinations of parameters are effective and to qualify the trade-offs in performance which come with less ideal parameter values

    FACTEURS SOCIOCULTURELS : LEVIER D’ACCES AU FINANCEMENT INFORMEL DES TPE

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    Cet article vise principalement à identifier les facteurs socioculturels de l'environnement des TPE et leur contribution à l'accès au crédit des TPE auprès des circuits de financement informel. Pour mieux comprendre cette relation, nous avons mobilisé trois théories : la théorie du capital social (Bourdieu, 1980), la théorie de l'encastrement social (Granovetter, 1985) et la théorie du financement hiérarchique (Myers et Majluf, 1984). Notre approche méthodologique repose sur des entretiens qualitatifs menés auprès de 10 promoteurs de TPE dans les grandes villes de Douala et Yaoundé. Les résultats de notre travail indiquent que la relation entre les bailleurs de fonds des circuits de financement informel et les propriétaires de TPE, basée sur la proximité relationnelle, se manifeste à travers des modes de financement tels que l'entraide et le soutien familial. Ces modes de financement se caractérisent souvent par une plus grande tolérance quant aux délais de remboursement et une solidarité accrue. De plus, nous constatons que l'aspect social dans les situations de crédit est bénéfique, moins coûteux et favorise le maintien des liens de solidarité. À la lumière de ces résultats, nous formulons la recommandation suivante à l'attention des promoteurs-dirigeants de ces TPE : construire des relations de proximité durables avec les bailleurs de fonds des circuits de financement informel, établir un réseau relationnel et favoriser les échanges fréquents d'informations proactives, afin de faciliter l'accès aux sources informelles de financement pour les TPE. En résumé, cette étude souligne l'importance des facteurs socioculturels dans l'accès au crédit des TPE auprès des circuits de financement informel, met en évidence les avantages des liens sociaux et de la solidarité dans ces relations financières, et propose des recommandations pour renforcer les relations de proximité et faciliter l'accès aux sources informelles de financement pour les TPE
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