Loading-unloading hysteresis loop of randomly rough adhesive contacts

In this paper we investigate the loading and unloading behavior of soft solids in adhesive contact with randomly rough profiles. The roughness is assumed to be described by a self-affine fractal on a limited range of wave-vectors. A spectral method is exploited to generate such randomly rough surfaces. The results are statistically averaged, and the calculated contact area and applied load are shown as a function of the penetration, for loading and unloading conditions. We found that the combination of adhesion forces and roughness leads to a hysteresis loading-unloading loop. This shows that energy can be lost simply as a consequence of roughness and van der Waals forces, as in this case a large number of local energy minima exist and the system may be trapped in metastable states. We numerically quantify the hysteretic loss and assess the influence of the surface statistical properties and the energy of adhesion on the hysteresis process.Comment: 8 pages, 9 figures, published on Physical Review E, Volume 92, Issue 6, 8 December 2015, Article number 06240

DIAMANTE: A data-centric semantic segmentation approach to map tree dieback induced by bark beetle infestations via satellite images

International audienceForest tree dieback inventory has a crucial role in improving forest management strategies. This inventory is traditionally performed by forests through laborious and time-consuming human assessment of individual trees.On the other hand, the large amount of Earth satellite data that is publicly available with the Copernicus program and can be processed through advanced deep learning techniques has recently been established as an alternative to field surveys for forest tree dieback tasks. However, to realize its full potential, deep learning requires a deep understanding of satellite data since the data collection and preparation steps are essential as the model development step. In this study, we explore the performance of a data-centric semantic segmentation approach to detect forest tree dieback events due to bark beetle infestation in satellite images. The proposed approach prepares a multisensor data set collected using both the SAR Sentinel-1 sensor and the optical Sentinel-2 sensor and uses this dataset to train a multisensor semantic segmentation model. The evaluation shows the effectiveness of the proposed approach in a real inventory case study that regards non-overlapping forest scenes from the Northeast of France acquired in October 2018. The selected scenes host bark beetle infestation hotspots of different sizes, which originate from the mass reproduction of the bark beetle in the 2018 infestation.</div

Failure in granular materials based on acoustic tensor: a numerical analysis

We investigate localization in granular material with the support of numerical simulations based upon DEM (Distinct Element Method). Localization is associated with a discontinuity in a component of the incremental strain over a plane surface through the condition of the determinant of the acoustic tensor to be zero. DEM simulations are carried out on an aggregate of elastic frictional spheres, initially isotropically compressed and then sheared at constant pressure p0. The components of the stiffness tensor are evaluated numerically in stressed states along the triaxial test and employed to evaluate the acoustic tensor in order to predict localization. This occurs in the pre-peak region, where the aggregate hardens under the circumstance to be incrementally frictionless: it is a regime in which the tangential force does not change as the deformation proceedes and, consequently, the deviatoric stress varies only with the normal component of the contact force

Failure in granular materials based on acoustic tensor: a numerical analysis

We investigate localization in granular material with the support of numerical simulations based upon DEM (Distinct Element Method). Localization is associated with a discontinuity in a component of the incremental strain over a plane surface through the condition of the determinant of the acoustic tensor to be zero. DEM simulations are carried out on an aggregate of elastic frictional spheres, initially isotropically compressed and then sheared at constant pressure p0. The components of the stiffness tensor are evaluated numerically in stressed states along the triaxial test and employed to evaluate the acoustic tensor in order to predict localization. This occurs in the pre-peak region, where the aggregate hardens under the circumstance to be incrementally frictionless: it is a regime in which the tangential force does not change as the deformation proceedes and, consequently, the deviatoric stress varies only with the normal component of the contact force

Fluctuations and failure in granular materials: theory and numerical simulations

International audienceWe consider a dense aggregate of elastic, frictional particles isotropically compressed and next uniaxial strained at constant pressure. We show how failure can be predicted if fluctuations in the kinematics of contacting particles are introduced. We focus on the second order work and the possibility that at some stressed states it becomes negative under proper perturbations. Our analysis involves both a theoretical model and numerical simulations based upon the distinct element method (DEM). The theoretical model deals with contacting particles with incremental relative displacements that deviate from the average deformation in order to ensure their equilibrium. Because of this, the macroscopic stiffness tensor of the aggregate, that relates increments in stress with increments in strain, does not have the major symmetry. Consequently, in the hardening regime, we predict stressed states in which the second order work vanishes. The model seems transparent, and it makes clear and illustrative the role played by the fluctuations introduced in the kinematics of contacting particles in relation to the vanishing of second order work in an aggregate of compressed particles. The comparison with numerical simulations data supports the model. Graphical Abstract Statistical representation of the aggregate: conditional average

Ponatinib-Induced Graft-versus-Host Disease/Graft-versus-Leukemia Effect in a Patient with Philadelphia-Positive Acute Lymphoblastic Leukemia without the T315I Mutation Relapsing after Allogeneic Transplant

We describe the case of a patient with Philadelphia-positive acute lymphoblastic leukemia treated with dasatinib plus steroids as first-line therapy, who achieved a major molecular response (MMR) before undergoing matched, unrelated donor allogeneic stem cell transplant. Eleven months after the transplant, she experienced molecular relapse. Mutational screening showed negativity for the T315I mutation, The patient underwent a salvage chemotherapy regimen with clofarabine + cyclophosphamide + steroids and ponatinib (clofarabine 70 mg i.v., days 1-5, cyclophosphamide 700 mg i.v., days 1-5, and ponatinib 45 mg p.o., daily starting at day 15). We observed a rapid decrease in minimal residual disease on molecular assessment with an MMR of P190-BCR-ABL/ABL = 0.01% confirmed by bone marrow revaluations at days +23, +59, +108, and +191 after the first day of salvage chemotherapy. After starting ponatinib, the patient experienced skin graft-versus-host disease, suggesting that the efficacy of ponatinib could be related not only to the direct antileukemic effect but also to its ability to promote an indirect graft-versus-leukemia effect. Ponatinib treatment was well tolerated and considered safe with easily manageable side effects

Early long-term L-T3 replacement rescues mitochondria and prevents ischemic cardiac remodeling in rats.

Abstract Aims. 3,5,3'-Levo-triiodothyronine (L-T3) is essential for DNA transcription, mitochondrial biogenesis and respiration, but its circulating levels rapidly decrease after myocardial infarction (MI). The main aim of our study was to test whether an early and sustained normalization of L T3 serum levels after MI exerts myocardial protective effects through a mitochondrial preservation. Methods. Seventy-two hours after MI induced by anterior interventricular artery left coronary artery ligation, rats were infused with synthetic L-T3 (1.2 mug/kg/day) or saline over 4 weeks. Results. Compared to saline, L-T3 infusion restored FT3 serum levels at euthyroid state (6.5+/-0.5 vs 4.6+/- 0.3 pmol/L), improved LV ejection fraction (39.5+/-2.5 vs 65.5+/-6.9%), preserved LV end-systolic wall thickening in the peri-infarct zone (6.34+/-3.1 vs 33.7+/-6.21%) and reduced LV infarct-scar size by approximately 50% (all P<0.05). Moreover, L-T3 significantly increased angiogenesis and cell survival and enhanced the expression of nuclear-encoded transcription factors involved in these processes. Finally, L-T3 significantly increased the expression of factors involved in mitochondrial DNA transcription and biogenesis, such as HIF-1alpha, mtTFA and PGC-1alpha, in the LV peri-infarct zone. To further explore mechanisms of L-T3 protective effects, we exposed isolated neonatal cardiomyocytes to H2O2 and found that L-T3 rescued mitochondrial biogenesis and function and protected against cell death via a mitoKATP dependent pathway. Conclusion. Early and sustained physiological restoration of circulating L-T3 levels after MI halves infarctscar size and prevents the progression towards heart failure. This beneficial effect is likely due to enhanced capillary formation and mitochondrial protection

CanB, a Druggable Cellular Target in Mycobacterium tuberculosis

Treatment against tuberculosis can lead to the selection of drug-resistant Mycobacterium tuberculosis strains. To tackle this serious threat, new targets from M. tuberculosis are needed to develop novel effective drugs. In this work, we aimed to provide a possible workflow to validate new targets and inhibitors by combining genetic, in silico, and enzymological approaches. CanB is one of the three M. tuberculosis β-carbonic anhydrases that catalyze the reversible reaction of CO2 hydration to form HCO3– and H+. To this end, we precisely demonstrated that CanB is essential for the survival of the pathogen in vitro by constructing conditional mutants. In addition, to search for CanB inhibitors, conditional canB mutants were also constructed using the Pip-ON system. By molecular docking and minimum inhibitory concentration assays, we selected three molecules that inhibit the growth in vitro of M. tuberculosis wild-type strain and canB conditional mutants, thus implementing a target-to-drug approach. The lead compound also showed a bactericidal activity by the time-killing assay. We further studied the interactions of these molecules with CanB using enzymatic assays and differential scanning fluorimetry thermal shift analysis. In conclusion, the compounds identified by the in silico screening proved to have a high affinity as CanB ligands endowed with antitubercular activity