Effect of sonication conditions: solvent, time, temperature and reactor type on the preparation of micron sized vermiculite particles

International audienceThe effects of temperature, time, solvent and sonication conditions under air and Argon are described for the preparation of micron and sub-micron sized vermiculite particles in a double-jacketed Rosett-type or cylindrical reactor. The resulting materials were characterized via X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared (FTIR) Spectroscopy, BET surface area analysis, chemical analysis (elemental analysis), thermogravimetry analysis (TGA) and Laser Granulometry. The sonicated vermiculites displayed modified particle morphologies and reduced sizes (observed by scanning electron microscopy and laser granulometry). Under the conditions used in this work, sub-micron sized particles were obtained after 5 h of sonication, whereas longer times promoted aggregation again. Laser granulometry data revealed also that the smallest particles were obtained at high temperature while it is generally accepted that the mechanical effects of ultrasound are optimum at low temperatures according to physical/chemical properties of the used solvent. X-ray diffraction results indicated a reduction of the crystallite size along the basal direction [001]; but structural changes were not observed. Sonication at different conditions also led to surface modifications of the vermiculite particles brought out by BET surface measurements and Infrared Spectroscopy. The results indicated clearly that the efficiency of ultrasound irradiation was significantly affected by different parameters such as temperature, solvent, type of gas and reactor type

A Kalman filter adapted to the estimation of mean gradients in the large-eddy simulation of unsteady turbulent flows

A computationally-efficient method based on Kalman filtering is introduced to capture “on the fly” the low-frequency (or very large-scale) patterns of a turbulent flow in a large-eddy simulation (LES). This method may be viewed as an adaptive exponential smoothing in time with a varying cut-off frequency that adjusts itself automatically to the local rate of turbulence of the simulated flow. It formulates as a recursive algorithm, which requires only few arithmetic operations per time step and has very low memory usage. In practice, this smoothing algorithm is used in LES to evaluate the low-frequency component of the rate of strain, and implement a shear-improved variant of the Smagrosinky’s subgrid-scale viscosity. Such approach is primarily devoted to the simulation of turbulent flows that develop large-scale unsteadiness associated with strong shear variations. As a severe test case, the flow past a circular cylinder at Reynolds number (in the subcritical turbulent regime) is examined in details. Aerodynamic and aeroacoustic features including spectral analysis of the velocity and the far-field pressure are found in good agreement with various experimental data. The Kalman filter suitably captures the pulsating behavior of the flow and provides meaningful information about the large-scale dynamics. Finally, the robustness of the method is assessed by varying the parameters entering in the calibration of the Kalman filter

Categories of Resistance, Antibiosis and Tolerance, to Biotype I Greenbug (\u3ci\u3eSchizaphis graminum\u3c/i\u3e (Rondani) Homoptera: Aphididae) in Four Sorghum (\u3ci\u3eSorghum bicolor\u3c/i\u3e (L.) Moench. Poales:Gramineae) Hybrids

Resistance categories (antibiosis and tolerance) of four sorghum (Sorghum bicolor (L.) Moench) hybrids to biotype I greenbug, Schizaphis graminum (Rondani), were determined in environmental growth chamber and field studies. Greenbug weight and fecundity were lower on ‘Cargill 607E’ compared with ‘Cargill 797’. Percentage of leaf damage area was significantly less on two resistant hybrids (Cargill 607E and Cargill 797) after a 14-d greenbug feeding period compared to two susceptible hybrids (‘Golden Harvest 510B’ and Garst 5715). In growth chamber studies on sorghum seedlings, ‘Cargill 607E’ and ‘Cargill 797’ reduced greenbug weight significantly compared with ‘Golden Harvest 510B’ and ‘Garst 5715’. Greenbug weight was 2.9 mg/25 greenbugs on ‘Cargill 607E’, 3.1 mg/25 greenbugs on ‘Cargill 797’, 3.9 mg/25 greenbugs on ‘Golden Harvest 510B’, and 4.8 mg/25 greenbugs on ‘Garst 5715’. On field grown sorghum plants, ‘Cargill 797’ did not reduce greenbug growth compared with ‘Golden Harvest 510B’. ‘Cargill 607E’ had a negative impact on weight of greenbugs. Greenbug weight was 7.9 mg/25 greenbugs on ‘Cargill 607E’, 9.2 mg/25 greenbugs on ‘Cargill 797’, and 10.0 mg/25 greenbugs on ‘Golden Harvest 510B’. ‘Cargill 607E’ and ‘Cargill 797’ were resistant to biotype I greenbugs compared with susceptible ‘Golden Harvest 510B’ and ‘Garst 5715’. Antibiosis was confirmed as the primary category of resistance in ‘Cargill 607E.’ ‘Cargill 797’ was primarily tolerant but may have some level of antibiosis, because smaller greenbugs developed in some of the studies

Understanding the physical properties, toxicities and anti-microbial activities of choline-amino acid-based salts:Low-toxic variants of ionic liquids

International audienc

Bienfaits et méfaits de l’idéologie sportive

Interroger la pertinence de la notion d’idéologie sportive vise à expliquer ou éclairer certains comportements, réactions, prises de position des acteurs, sportifs eux-mêmes, mais aussi entraîneurs, dirigeants…Le caractère spéculatif de la réflexion universitaire qui suit, conceptuellement ancrée et discutée, n’exclura pas l’évocation de données observables sur le terrain sportif. Présumer du caractère idéologique du sport contemporain n’est pas vraiment une nouveauté ; d’une part certaines ..

La dimension corporelle de l'émotion sportive

Cet article invite à considérer la construction et la signification sociales de l'expression de l'émotion dans les compétitions sportives, sa place dans la communication avec la communauté sportive environnante, son lien avec les mécanismes structurels de l'économie affective

Aspects éthiques et déontologiques de l'intervention auprès des sportifs

L'intervention en psychologie du sport : particularités du milieu d'intervention, le milieu de la haute performance, les logiques qui le structurent, les possibles transgressions et dérives; les interactions entre le psychologue et ses interlocuteurs privilégiés, l'athlète, l'entraîneur, l'équipe d'encadrement, l'institution support