A giant overshoot effect in the Janssen granular column

We present new experimental results on the mechanical behavior of static granular assemblies confined in a vertical column. Our measurements confirm, for the first time, the universal Janssen's scaling for the stress saturation curve. We show consequently, in the context of isotropic elasticity, a relation between the Poisson ratio and granular packing fraction. Moreover, using a systematic study of the overshoot effect created by a top mass equal to the saturation mass, we show behaviors reproduced qualitatively by isotropic elastic materials but in the case of a granular assembly of a spectacular amplitude. These experimental results are strong tests for any theory of granular matter

Toughness improvement of polyamide 11 assessed via quasistatic tensile tests on notched round bars

International audienceToughening a polymeric material by adding rubber particles is a common technique used forglassy polymers and measured by means of Charpy or Izod impact tests. These latter aredetermined under dynamic conditions, thus at high strain rate or equivalently at very lowtemperature for polymeric materials.This work is devoted to three grades of semi-crystalline PolyAmide 11 (PA11), used in alarge number of engineering components. Service conditions are close to the glass transitiontemperature. Therefore, tests with quasi-static loading are expected to be more appropriate.The aim of the study is to find a methodology allowing the quantification of toughnessimprovement. To this end, an experimental database was constituted. Three grades of PA11were involved, that enable to analyze effects of: i) aging, ii) addition of a plasticizer iii)addition of rubber particles. Tensile tests were then carried out on notched round bars.Trends of load versus notch opening displacement curves are investigated. Longitudinalcross-sections on specimens issued from interrupted tests and fracture surfaces wereexamined in order to study deformation and damage mechanisms. An attempt is made to linktoughness improvement to the increase in global fracture energy

Planar measurements of spray-induced wall cooling using phosphor thermometry

The wall cooling induced by spray impingement is investigated using phosphor thermometry. Thin coatings of zinc oxide (ZnO) phosphor were applied with a transparent chemical binder onto a steel surface. Instantaneous spatially resolved temperatures were determined using the spectral intensity ratio method directly after the injection of UV-grade hexane onto the surface using a commercial gasoline injector. The investigations showed that 2D temperature measurements with high spatial and shot-to-shot precision of, respectively, 0.5 and 0.6 K can be achieved, allowing the accurate resolution of the cooling induced by the spray. The presence of a liquid film over the phosphor coating during measurements showed no noticeable influence on the measured temperatures. However, in some cases a change in the intensity ratio at the spray impingement area, in the form of a permanent “stain”, could be observed after multiple injections. The formation of this stain was less likely with increasing annealing time of the coating as well as lower plate operating temperatures during the injection experiments. Finally, the experimental results indicate a noticeable influence of the thickness of the phosphor coating on the measured spray-induced wall cooling history. Hence, for quantitative analysis, a compromise between coating thickness and measurement accuracy needs to be considered for similar applications where the heat transfer rates are very high

Simultaneous kHz-rate temperature and velocity field measurements in the flow emanating from angled and trenched film cooling holes

AbstractTo design more efficient film cooling geometries for gas turbines, non-intrusive measurements of the flow temperature, velocity and derived quantities like the turbulent heat flux are needed in well-defined, generic flow configurations. With this aim we have applied thermographic particle image velocimetry (thermographic PIV) to investigate the flow emanating from angled and trenched cooling holes in a closed-loop optically-accessible wind tunnel facility. BAM:Eu2+ thermographic phosphor particles were seeded into the flow as a tracer. A pulsed high-speed UV laser was used to excite the particles and the luminescence was detected using two high-speed cameras to determine the temperature field by a two-colour ratiometric approach. The velocity field was measured using ordinary high-speed PIV. The simultaneously measured fields were sampled at a rate of 6kHz in a vertical plane through the centreline of the symmetrical single-row cooling holes. The flowrate and temperature of the cooling air and heated main flow were chosen to achieve density and momentum flux ratios of 1.6 and 8 respectively. For these conditions the average and RMS temperature fields show that for ordinary angled holes the jet is detached from the surface. In contrast, the trenched geometry leads to a cooling film attached to the surface. However, time-resolved image sequences show instances where hot air breaks through the cooling film and almost reaches the surface. Similar image sequences for the angled holes show that the detached coolant jet becomes unstable downstream and pockets of cold air are ejected into the main flow. This intermittency may in part explain the observation that the measured turbulent heat flux is oriented towards the cold core, but deviates from the direction of the mean temperature gradient, thereby contradicting the simple gradient diffusion hypothesis commonly used in RANS simulations

Thermographic laser Doppler velocimetry using the phase-shifted luminescence of BAM:Eu2+ phosphor particles for thermometry

Simultaneous point measurements of gas velocity and temperature were recently demonstrated using thermographic phosphors as tracer particles. There, continuous wave (CW) excitation was used and the spectral shift of the luminescence was detected with a two-colour intensity ratio method to determine the gas temperature. The conventional laser Doppler velocimetry (LDV) technique was employed for velocimetry. In this paper, an alternative approach to the gas temperature measurements is presented, which is instead based on the temperature-dependence of the luminescence lifetime. The phase-shift between the luminescence signal and time-modulated excitation light is evaluated for single BaMgAl10O17:Eu2+ phosphor particles as they cross the probe volume. Luminescence lifetimes evaluated in the time domain and frequency domain indicate that in these experiments, interferences from in-phase signals such as stray excitation laser light are negligible. The dependence of the phase-shift on flow temperature is characterised. In the temperature sensitive range above 700 K, precise gas temperature measurements can be obtained (8.6 K at 840 K) with this approach

Improving the treatment and remission of major depression in homeless people with severe mental illness: the multicentric French Housing First (FHF) program. French Housing First Study Group Running title: Major depression in homeless people with severe mental disorders

International audienceObjectiveThe aim of this study was to investigate the factors associated with violent behavior in a large multicenter sample of Homeless Schizophrenia (SZ) and Bipolar Disorder (BD) (HSB) subjects.MethodsThis multicenter study was conducted in 4 French cities: Lille, Marseille, Paris and Toulouse. Violent behavior was defined by at least one episode of verbal or physical violence in the last 6 months.ResultsOverall, 675 HSB patients, mean aged 38 years and 82.5% men were included, 458 SZ (68.4%) and 212 BD (31.6%). During the 6 months before evaluation, 213 (34.3%) committed at least one physical or verbal violence. In multivariate analysis, violence has been associated with younger age (aOR = 0.96[0.94–0.99], p = .001), number of nights in the street (aOR = 1.01[1.01–1.01]), BD diagnosis (aOR = 1.63[1.01–2.65], p = .04), higher current illness severity (CGI score) (aOR = 1.32[1.07–1.64], p = .01), higher rates of current manic episode (aOR = 2.24[1.32–3.81], p = .002), current alcohol use disorder (aOR = 2.05 [1.33–3.15], p = .001), antisocial personality disorder (aOR = 2.51[1.55–4.07], p < .001) and with antidepressant consumption (aOR = 2.01[1.01–4.04], p = .04). No specific antipsychotic or mood stabilizer has been associated with decreased rates of violent behavior, however clozapine, lithium and carbamazepine remained poorly prescribed.ConclusionIn case of violent behavior in HSB subjects, clinicians should focus in priority on the treatment of mania, antidepressant iatrogenic effect and alcohol use disorder by pharmacological and non-pharmacological treatments. Clozapine, lithium and carbamazepine should be chosen as the treatments of reference in this population but may be hard to manage in some cases.The current clinical trial number is NCT01570712

First-year French medical students consume antidepressants and anxiolytics while second-years consume non-medical drugs.

International audienc

Psychiatric and psychological follow-up of undergraduate and postgraduate medical students: prevalence and associated factors. Results from the national BOURBON study. Running title: mental health and addictive behavior of medical students

International audienceBackgroundPhysicians are at risk of burnout, anxiety and depression. Prevention is needed from the beginning of the medical studies to detect early poor mental health outcomes.ObjectiveTo determine the prevalence and associated of psychiatric or psychological follow-up in a national sample of undergraduate and postgraduate medical students (UPMS).MethodsUPMS of the 35 French Medicine faculties were recruited through mailing lists and social networks between December 2016 and May 2017 and fulfilled Internet anonymised questionnaires.ResultsOverall, 10,985 UPMS were included in the present study (2165 (19.7%) postgraduate, 31.6% males, mean aged 21.8 years). Overall, 1345 (12.2%) were followed-up by a psychiatrist and/or a psychologist, 20.5% of them were regular anxiolytic consumers and 17.2% of them were regular antidepressant consumers. In multivariate analyses, being followed-up by a psychiatrist and/or psychologist was associated with older age (aOR = 1.2[1.2–1.2], p < 0.0001), female gender (aOR = 0.5[0.5–0.7], p < 0.0001), current alcohol use disorder (aOR = 1.3[1.3–1.5], p < 0.0001), higher anxiolytic (aOR = 3.1[2.5–3.7],p < 0.0001) and antidepressant (aOR = 11.7[7.6–18.0],p < 0.0001) consumption, and with lower self-reported general health, social functioning and mental health quality of life (all aORs = 0.9, all p < 0.05). The UPMS followed-up by psychiatrist and/or psychologist reported to have been more frequently exposed to sexual assault (5.1% vs. 0.9%, aOR = 2.5[1.3–4.7], p < 0.0001), domestic violence (3.3% vs. 0.8% aOR = 2.1[1.2–4.0], p = 0.01) and parents divorce (11% vs. 6.4%, aOR = 1.5[1.2–1.9], p = 0.001). Students followed-up by a psychiatrist and/or psychologist reported more frequently to seek alleviating anxiety (aOR 1.9[1.6–2.3], p < 0.0001), depression (aOR 1.7[1.3–2.1],p < 0.0001), coping with studies difficulties (aOR 1.5[1.2–1.8],p < 0.0001), experiencing more stress at hospital (aOR = 2.3[1.6–3.5],p < 0.001) and more burnout syndrome (aOR = 1.4[1.1–1.8], p = 0.03).ConclusionsAround 12% of UPMS are followed-up by a psychiatrist and/or a psychologist. These students reported higher antidepressant and anxiolytic consumption, psychic suffering and altered quality of life, associated with professional pressure and personal issues. Public health programs should be developed to help these students through their studies to prevent later mental /addictive issues and professional suffering. Improving UPMS mental health may also improve the later quality of care of their patients and global stress at hospital

On the vertical distribution of chemical constituents in the shelf waters off Waltair

The chemical composition of the shelf water has been investigated and examples of the vertical chemical structure are given in the table. From these values and other related hydrographic information the chemical factors controlling the composition of the shelf water may be discussed. The range of salinity between surface and bottom was greater during the period of sinking and lower during upwelling. The high values of salinity, phosphate, silicates and oxygen were influenced by upwelling. The advection of Northern Dilute water and Southern Bay of Bengal water also affect the vertical and horizontal chemical structure of the water. These were further modified by planktonic consumption during periods of accelerated production. A detailed report is under preparation

Psychiatric and psychological follow-up of undergraduate and postgraduate medical students: prevalence and associated factors. Results from the national BOURBON study. Running title: mental health and addictive behavior of medical students

International audienceBackground. Physicians are at risk of burnout, anxiety and depression. Prevention i