Etude théorique du transport électronique par la simulation Monte Carlo dans le quaternaire In0.863Ga0.137As0.3P0.7

Afin de simuler le comportement d'un laser à semi-conducteur, nous devons disposer de modèles mathématiques décrivant de façons aussiprécise que possible les propriétés physiques des matériaux considérés.Ces dernières années plusieurs recherches ont été consacrées aux lasers de type InGaAsP-InP. Plusieurs paramètres physiques sont connus avec une précision plus ou moins satisfaisante. Nous avons tenté, de reproduire au mieux l'ensemble des mesures rapportées dans la littérature et d’étudier le phénomène de transport dans les semiconducteurs quaternaire. Pour cela nous avons effectué des simulations microscopiques, basées sur la méthode Monte Carlo. Nous avonsappliqué cette méthode au cas du quaternaire "In0.863Ga0.137As0.3P0.7-InP", considérant une bande de conduction à trois vallées (Γ, L, X), isotropes et quasi paraboliques. Les interactions prises en compte sont dues aux phonons optiques polaires, optiques non polaires, acoustiques, intervallées, piézoélectriques ainsi que les interactions d'alliage et sur impuretés ionisées. Dans un premier temps, nous présentons l’ensemble des résultats obtenus par la simulation de Monte Carlo dans l'In0.863Ga0.137As0.3P0.7 en régime stationnaire. Nous considérons ensuite les effets liés à l’application d’un champ électrique variant très rapidement en fonction du temps. Nous étudions en particulier les phénomènes non stationnaires qui font leur apparition dans le matériau quaternaire.Mots-clés : simulation de Monte Carlo, In0.863Ga0.137As0.3P0.7, interaction, composants électroniques

Situations complexes chez l’adulte avec déficience intellectuelle sévère - Un nouveau modèle d’accompagnement [Complex situations in adults with severe intellectual disabilities - A new support model]

Challenging behaviors constitute a real pitfall in supporting people with severe intellectual disabilities. Undermining patients and host institutions as well as psychiatric services, these crisis situations are usually underpinned by many factors including somatic, psychiatric, educational and environmental factors. New models, including the one developed by our team in Lausanne, offer a more specific approach for these complex cases, involving individualized, collaborative and multidisciplinary care to resolve the crisis but also for the overall improvement of the person's life course. This article aims to present the model set up by the Psychiatry Department of the CHUV (UPCHM unit)

Study of the slant fracture in solid and hollow cylinders: Experimental analysis and numerical prediction

This paper is devoted to the numerical and experimental study of ductile fracture in bulk metal forming of the 2017A-T4 aluminum alloy. From an experimental standpoint, the ductile fracture of the2017A-T4aluminum alloy is investigated under compressive load. Two cross-sections of solid and hollow specimens are considered. The mechanical behavior and the microstructure of the 2017A-T4 aluminum alloy were characterized. It is found that the well-known barrel shape is obtained when a compressive load is applied. Analyses of fracture topographies show a ductile fracture with dimples under tension and coexistence of ductile fracture with dimples and slant under compression. The classical physically-based Gurson-Tvergaard-Needleman (GTN) model and its extension to incorporateshear mechanisms to predict failure at low-stress triaxiality are considered. These two models have been extended to take into account the thermal heating effect induced by the mechanical dissipation within the material during the metal forming process. The two models have been implemented into the finite element code Abaqus/Explicit using a Vectorized User MATerial (VUMAT) subroutine. Numerical simulations of the forging process made for hollow and solid cylindrical specimens show good agreement with experimental results. In contrast with the GTN model, the modified GTN model incorporating shear mechanisms can capture the final material failure

Atypical coordination of cortical oscillations in response to speech in autism.

Subjects with autism often show language difficulties, but it is unclear how they relate to neurophysiological anomalies of cortical speech processing. We used combined EEG and fMRI in 13 subjects with autism and 13 control participants and show that in autism, gamma and theta cortical activity do not engage synergistically in response to speech. Theta activity in left auditory cortex fails to track speech modulations, and to down-regulate gamma oscillations in the group with autism. This deficit predicts the severity of both verbal impairment and autism symptoms in the affected sample. Finally, we found that oscillation-based connectivity between auditory and other language cortices is altered in autism. These results suggest that the verbal disorder in autism could be associated with an altered balance of slow and fast auditory oscillations, and that this anomaly could compromise the mapping between sensory input and higher-level cognitive representations

Functional outcomes in adult patients with herpes simplex encephalitis admitted to the ICU: a multicenter cohort study

PURPOSE: We aimed to study the association of body temperature and other admission factors with outcomes of herpes simplex encephalitis (HSE) adult patients requiring ICU admission. METHODS: We conducted a retrospective multicenter study on patients diagnosed with HSE in 47 ICUs in France, between 2007 and 2017. Fever was defined as a body temperature higher or equal to 38.3 °C. Multivariate logistic regression analysis was used to identify factors associated with poor outcome at 90 days, defined by a score of 3-6 (indicating moderate-to-severe disability or death) on the modified Rankin scale. RESULTS: Overall, 259 patients with a score on the Glasgow coma scale of 9 (6-12) and a body temperature of 38.7 (38.1-39.2) °C at admission were studied. At 90 days, 185 (71%) patients had a poor outcome, including 44 (17%) deaths. After adjusting for age, fever (OR = 2.21; 95% CI 1.18-4.16), mechanical ventilation (OR = 2.21; 95% CI 1.21-4.03), and MRI brain lesions > 3 lobes (OR = 3.04; 95% CI 1.35-6.81) were independently associated with poor outcome. By contrast, a direct ICU admission, as compared to initial admission to the hospital wards (i.e., indirect ICU admission), was protective (OR = 0.52; 95% CI 0.28-0.95). Sensitivity analyses performed after adjustment for functional status before admission and reason for ICU admission yielded similar results. CONCLUSIONS: In HSE adult patients requiring ICU admission, several admission factors are associated with an increased risk of poor functional outcome. The identification of potentially modifiable factors, namely, elevated admission body temperature and indirect ICU admission, provides an opportunity for testing further intervention strategies