Importance of the catalytic effect of the substrate in the functionality of lubricant additives: the case of MoDTC

Molybdenum dithiocarbamates (MoDTCs) are lubricant additives very efficient in reducing the friction of steel and they are employed in a number of industrial applications. The functionality of these additives is ruled by the chemical interactions occurring at the buried sliding interface, which are of key importance for the improvement of the lubrication performance. Yet, these tribochemical processes are very difficult to monitor in real time. Ab initio molecular dynamics simulations are the ideal tool to shed light into such a complicated reactivity. In this work we perform ab initio simulations, both in static and tribological conditions, to understand the effect of surface oxidation on the tribochemical reactivity of MoDTC and we find that when the surfaces are covered by oxygen, the first dissociative steps of the additives are significantly hindered. Our preliminary tribological tests on oxidized steel discs support these results. Bare metallic surfaces are necessary for a stable adsorption of the additives, their quick decomposition, and the formation of a durable MoS$_2$ tribolayer. This work demonstrates the importance of the catalytic role of the substrate and confirms the full capability of the computational protocol in the pursuit of materials and compounds more efficient in reducing friction

Endosymbiont diversity and prevalence in herbivorous spider mite populations in South-Western Europe

International audienceBacterial endosymbionts are known as important players of the evolutionary ecology of their hosts. However, their distribution, prevalence and diversity are still largely unexplored. To this aim, we investigated infections by the most common bacterial reproductive manipulators in herbivorous spider mites of South-Western Europe. Across 16 populations belonging to three Tetranychus species, Wolbachia was the most prevalent (ca. 61%), followed by Cardinium (12%-15%), while only few individuals were infected by Rickettsia (0.9%-3%), and none carried Arsenophonus or Spiroplasma. These endosymbionts are here reported for the first time in Tetranychus evansi and Tetranychus ludeni, and showed variable infection frequencies between and within species, with several cases of coinfections. Moreover, Cardinium was more prevalent in Wolbachia-infected individuals, which suggests facilitation between these symbionts. Finally, sequence comparisons revealed no variation of the Wolbachia wsp and Rickettsia gtlA genes, but some diversity of the Cardinium 16S rRNA, both between and within populations of the three mite species. Some of the Cardinium sequences identified belonged to distantly-related clades, and the lack of association between these sequences and spider mite mitotypes suggests repeated host switching of Cardinium. Overall, our results reveal a complex community of symbionts in this system, opening the path for future studies

Radiomique : mode d’emploi. Méthodologie et exemples d’application en imagerie de la femme

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White matter hyperintensities and their role in major depressive episodes: a cross-sectional study in adults under 65

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Radiomic analysis of HTR-DCE MR sequences improves diagnostic performance compared to BI-RADS analysis of breast MR lesions

International audiencePurposeTo assess the diagnostic performance of radiomic analysis using high temporal resolution (HTR)-dynamic contrast enhancement (DCE) MR sequences compared to BI-RADS analysis to distinguish benign from malignant breast lesions.Materials and methodsWe retrospectively analyzed data from consecutive women who underwent breast MRI including HTR-DCE MR sequencing for abnormal enhancing lesions and who had subsequent pathological analysis at our tertiary center. Semi-quantitative enhancement parameters and textural features were extracted. Temporal change across each phase of textural features in HTR-DCE MR sequences was calculated and called “kinetic textural parameters.” Statistical analysis by LASSO logistic regression and cross validation was performed to build a model. The diagnostic performance of the radiomic model was compared to the results of BI-RADS MR score analysis.ResultsWe included 117 women with a mean age of 54 years (28–88). Of the 174 lesions analyzed, 75 were benign and 99 malignant. Seven semi-quantitative enhancement parameters and 57 textural features were extracted. Regression analysis selected 15 significant variables in a radiomic model (called “malignant probability score”) which displayed an AUC = 0.876 (sensitivity = 0.98, specificity = 0.52, accuracy = 0.78). The performance of the malignant probability score to distinguish benign from malignant breast lesions (AUC = 0.876, 95%CI 0.825–0.925) was significantly better than that of BI-RADS analysis (AUC = 0.831, 95%CI 0.769–0.892). The radiomic model significantly reduced false positives (42%) with the same number of missed cancers (n = 2).ConclusionA radiomic model including kinetic textural features extracted from an HTR-DCE MR sequence improves diagnostic performance over BI-RADS analysis

Gray-level discretization impacts reproducible MRI radiomics texture features

International audienceOBJECTIVES: To assess the influence of gray-level discretization on inter- and intra-observer reproducibility of texture radiomics features on clinical MR images.MATERIALS AND METHODS: We studied two independent MRI datasets of 74 lacrymal gland tumors and 30 breast lesions from two different centers. Two pairs of readers performed three two-dimensional delineations for each dataset. Texture features were extracted using two radiomics softwares (Pyradiomics and an in-house software). Reproducible features were selected using a combination of intra-class correlation coefficient (ICC) and concordance and coherence coefficient (CCC) with 0.8 and 0.9 as thresholds, respectively. We tested six absolute and eight relative gray-level discretization methods and analyzed the distribution and highest number of reproducible features obtained for each discretization. We also analyzed the number of reproducible features extracted from computer simulated delineations representative of inter-observer variability.RESULTS: The gray-level discretization method had a direct impact on texture feature reproducibility, independent of observers, software or method of delineation (simulated vs. human). The absolute discretization consistently provided statistically significantly more reproducible features than the relative discretization. Varying the bin number of relative discretization led to statistically significantly more variable results than varying the bin size of absolute discretization.CONCLUSIONS: When considering inter-observer reproducible results of MRI texture radiomics features, an absolute discretization should be favored to allow the extraction of the highest number of potential candidates for new imaging biomarkers. Whichever the chosen method, it should be systematically documented to allow replicability of results

Reproducible features using the in-house Matlab-based software and manual delineations on DATASET 1 according to the gray-level discretization method.

Reproducible features using the in-house Matlab-based software and manual delineations on DATASET 1 according to the gray-level discretization method.</p