Rendre le baseball scolaire 'dynamique'

L'auteur propose ici quelques repères et astuces pour remédier à la passivité des élèves dans la pratique du baseball. L'enjeu est le développement des ressources informationnelles et décisionnelles de l'élève, en rendant le jeu dynamique et motivant, et en évitant les temps morts et le déséquilibre des équipes. Un système de notation est proposé

Sur l'extension des argiles noires du bassin tertiaire de Rennes

National audienc

Catalytic Intermolecular C(sp3)–H Amination: Selective Functionalization of Tertiary C–H Bonds vs Activated Benzylic C–H Bonds

International audienceA catalytic intermolecular amination of non-activated tertiary C(sp 3)−H bonds (BDE of 96 kcal.mol-1) is reported for substrates displaying an activated benzylic site (BDE of 85 kcal.mol-1). The tertiary C(sp 3)−H bond is selectively functionalized to afford a,a,a-trisubstituted amides in high yields. This unusual site-selectivity results from the synergistic combination of Rh2(Stfpttl)4, a rhodium(II) complex with a well-defined catalytic pocket, with tert-butylphenol sulfamate (TBPhsNH2), which leads to a discriminating rhodium-bound nitrene species under mild oxidative conditions. This catalytic system is very robust and the reaction was performed on a 50 mmoles-scale with only 0.01 mol% of catalyst. The TBPhs group can be removed under mild conditions to afford the corresponding NH-free amines

Methodology for Investigating the Mechanical Strength of Reforming Catalyst Beads

Reforming catalyst beads must exhibit strong resistance to the mechanical and thermal stresses they experience during their lifetime in a continuous regenerative catalytic unit. An inventory of the mechanical stresses, e. g. compressive, impact and shearing, is presented. It shows that a multitest approach must be designed in order to measure the particle strength and then optimise the production process to enhance their strength. This approach combines measurements reproducing the different types of stress generated in the catalytic process with an extensive characterisation of the physical and mechanical properties of the porous solid such as Young's modulus, hardness and fracture toughness. The methodology outlined here on alumina beads goes beyond the common practice of evaluating catalyst strength based on a comparative study using a single-crushing test and a bulk-crushing test. Prediction of bulk attrition and breakage behaviour, based on the above properties, is achieved using distinct element analysis (DEA)

Trends and prediction of antimicrobial susceptibility in urinary bacteria isolated in European emergency departments: the EuroUTI 2010-2016 Study.

To assess recent trends in susceptibility to antibiotics among urinary isolates isolated in European emergency departments (EDs) and to identify isolates with a high (90% or more) predicted probability of susceptibility to fluoroquinolones or third-generation cephalosporins (3GCs). In this cross-sectional study, we included urine cultures obtained from adult patients between 2010 and 2016 in 24 European EDs. Temporal trends were assessed using time-series analysis and multivariate logistic models. Multivariate logistic models were also used to predict susceptibility to fluoroquinolones or 3GCs from patient age and sex, year, month and ED. We included 88242 isolates. Time-series analysis found a significant increase in susceptibility to fluoroquinolones and no significant trend for susceptibility to 3GCs. Adjusting for patient age and sex, ED and organism, multivariate models showed that susceptibility to 3GCs decreased from 2014 to 2016, while susceptibility to fluoroquinolones increased in 2015 and 2016. Among isolates from 2016, multivariate models predicted high probability of susceptibility to fluoroquinolones in 11% of isolates (positive predictive value 91%) and a high probability of susceptibility to 3GCs in 35% of isolates (positive predictive value 94%). Susceptibility of ED urinary isolates to fluoroquinolones increased from 2014, while susceptibility to 3GCs decreased from 2015. Predictive models identified isolates with a high probability of susceptibility to fluoroquinolones or 3GCs. The ability of such models to guide the empirical treatment of pyelonephritis in the ED remains to be determined

Catalyst-Controlled Intermolecular Homobenzylic C(sp³)–H Amination for the Synthesis of β‑Arylethylamines

The combination of a tailored sulfamate with a C4-symmetrical rhodium(II) tetracarboxylate allows to uncover a selective intermolecular amination of unactivated homobenzylic C(sp3)–H bonds. The reaction has a broad scope (>30 examples) and proceeds with a high level of regioselectivity with homobenzylic/benzylic ratio of up to 35:1, thereby providing a direct access to β-arylethylamines that are of utmost interest in medicinal chemistry. Computational investigations evidenced a concerted mechanism, involving an asynchronous transition state. Based on a combined activation strain model and energy decomposition analysis, the regioselectivity of the reaction was found to rely mainly on the degree of orbital interaction between the [Rh2]–nitrene and the C–H bond. The latter is facilitated at the homobenzylic position due to the establishment of specific noncovalent interactions within the catalytic pocket

Catalyst-Controlled Intermolecular Homobenzylic C(sp³)–H Amination for the Synthesis of β‑Arylethylamines

The combination of a tailored sulfamate with a C4-symmetrical rhodium(II) tetracarboxylate allows to uncover a selective intermolecular amination of unactivated homobenzylic C(sp3)–H bonds. The reaction has a broad scope (>30 examples) and proceeds with a high level of regioselectivity with homobenzylic/benzylic ratio of up to 35:1, thereby providing a direct access to β-arylethylamines that are of utmost interest in medicinal chemistry. Computational investigations evidenced a concerted mechanism, involving an asynchronous transition state. Based on a combined activation strain model and energy decomposition analysis, the regioselectivity of the reaction was found to rely mainly on the degree of orbital interaction between the [Rh2]–nitrene and the C–H bond. The latter is facilitated at the homobenzylic position due to the establishment of specific noncovalent interactions within the catalytic pocket

Rhodium(II)-Catalyzed Enantioselective Intermolecular Aziridination of Alkenes

International audienc