Combining tensile tests and nanoindentation to explore the strengthening of high and medium entropy alloys

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Combining experiments and modeling to explore the solid solution strengthening of high and medium entropy alloys

International audienceThe mechanical properties due to solid solution strengthening are explored within the single phase fcc domain of the Co-Cr-Fe-Mn-Ni high entropy alloy (HEA) system. This is achieved by combining an efficient and reproducible metallurgical processing of alloys to X-ray diffraction and nanoindentation characterization techniques, thus enabling to get access to 24 different bulk alloys. Large variations of nanohardness are seen with composition. Experimental results are rationalized in terms of lattice misfit and elastic constant variations with alloy-composition, through the use of an analytical mechanistic theory for the temperature-, composition-and strain-rate-dependence of the initial yield strength of fcc HEAs, with predictions made using only experimental inputs. The good agreement obtained by comparing model predictions to experiments provides the basic framework for mechanical properties optimization within the Co-Cr-Fe-Mn-Ni system; the approach could be systematically applied to all classes of fcc HEAs

Listeria monocytogenes-associated respiratory infections: a study of 38 consecutive cases

International audienceObjectives: Listeria monocytogenes (Lm) is a foodborne human pathogen responsible for severe infections, including septicaemia, neurolisteriosis, and maternalefoetal and focal infections. Little is known about Lm-associated respiratory tract or lung infections. Methods: We conducted a retrospective study of culture-proven cases of Lm pleural infections and pneumonia Results: Thirty-eight consecutive patients with pleural infection (n ¼ 32), pneumonia (n ¼ 5), or both (n ¼ 1) were studied; 71% of these were men. Median age was 72 (range 29e90). Two patients presented with concomitant neurolisteriosis. All patients but one reported at least one immunosuppressive condition (97%), with a median number of 2 (range 0e5), including 29% (8/28) with current exposure to immunosuppressive therapy and 50% (17/34) with ongoing neoplasia; 75% (21/28) reported previous pleural or pulmonary disease. Antibiotic therapy mostly consisted in amoxicillin (72%) associated with aminoglycoside in 32%. Chest-tube drainage was performed in 7/19 patients with empyema (37%); 25% of the patients (7/30) required intensive care management. In-hospital mortality reached 35% and occurred after a median time interval of 4 days (range 1e33 days). Three patients had recurrence of empyema (time interval of 1 week to 4 months after treatment completion). Altogether, only 13/31 patients (42%) diagnosed with Lm respiratory infection experienced an uneventful outcome at 2-year follow-up. Conclusion: Lm is a rare but severe cause of pneumonia and pleural infection in older immunocom-promised patients, requiring prompt diagnosis and adequate management and follow-up

Normal faulting in chalk: Tectonic stresses vs. compaction-related polygonal faulting

This paper documents normal fault sets observed in chalks exposed in widely separated localities in the UK and France. These faults are characterized by having a wide range of strikes at any one locality, are developed entirely within the chalk succession and do not seem to interconnect to deeper or shallower structures. These structures may result from two different mechanisms: (1) complex polyphase deformational histories involving contrasting stress states; or (2) a single deformational phase in which the faults develop to accommodate compactional strains. Evidence is presented from microstructural and petrographic data to support the latter interpretation. In particular, the association of calcite and marcasite mineralizations with fracture surfaces and fault zones and textural observations relating flint occurrence to early fault formation point towards fault propagation at a very early stage of burial and compaction of the chalky sediments. An analogy is drawn between these outcrop-scale structures and polygonal fault systems at a larger scale recognised from seismic observations of chalk sequences deposited at passive continental margins. The origin of these structures may be related to syneresis at an early stage of deformation followed by pressure solution phenomena that may reactivate this early-inherited polygonal fault pattern until the present day

THORAX INJURY CRITERIA ASSESSMENT THROUGH NON-LETHAL IMPACT USING AN ENHANCED BIOMECHANICAL MODEL

International audienceBallistic injury refers to the interaction of a projectile and the human body, resulting in penetration or blunt trauma. In order to consider both consequences, a hydrodynamic elastoplastic constitutive law was implemented in a numerical FE model of the human torso to simulate soft tissues behavior and to evaluate their injury risk. This law, derived from 20% ballistic gelatin, was proven to be very efficient and biofidelic for penetrating ballistic simulation in soft tissues at very high velocity. In this study, the ability of the hydrodynamic law to simulate blunt ballistic trauma is evaluated by the replication of Bir et al.’s (2004) experiments, which is a reference test of the literature for nonpenetrating ballistic impact. Lung injury criteria were also investigated through the Bir et al.’s experiments numerical replication. Human responses were evaluated in terms of mechanical parameters, which can be global (acceleration of the body, viscous criteria and impact force) or local (stress, pressure and displacement). Output results were found to be in experimental corridors developed by Bir et al., and the maximum pressure combined with the duration of the peak of pressure in the lungs seems to be a good predictor for lung injury