Conservatoire national des arts et métiers

About: Conservatoire national des arts et métiers is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Context (language use). The organization has 3573 authors who have published 7127 publications receiving 141430 citations. The organization is also known as: CNAM & Conservatoire des arts et métiers.

Effect of Mixing Conditions on the Behavior of Lipoxygenase, Peroxidase, and Catalase in Wheat Flour Doughs

Abstract: The effect of mixing has been tested on the extractable activities of lipoxygenase, peroxidase, and catalase from dough after 2, 5, and 20 min of mixing, and 30 min of rest period after 20 min of mixing. Different mixing conditions have been studied including temperature, atmosphere, speed, amount of water added to the dough, buffer solutions between pH 3.6 and 7.5 added to the dough, and different additives (linoleic acid, guaiacol, hydrogen peroxide, ascorbic acid, cysteine, yeast, and sodium chloride). In all the mixing conditions tested, the dough peroxidase activity remains equivalent to the initial flour activity, whereas losses in lipoxygenase and catalase activities largely varied according to mixing conditions. The results show that a self-destruction mechanism as well as physicochemical denaturation are responsible for these losses. Lipoxygenase losses seem mainly associated with the former mechanism, whereas catalase losses are highly increased in acidic conditions (physicochemical den...

Unsteady confined buoyant plumes

Abstract: Two-dimensional time-dependent buoyancy-induced flows above a horizontal line heat source inside rectangular vessels, with adiabatic sidewalls and top and bottom walls maintained at uniform temperature, are studied numerically. Transitions to unsteady flows are performed by direct simulations for various depths of immersion of the source in the central vertical plane of air-filled vessels. For a square vessel and a line source near the bottom wall, the numerical solutions exhibit a sequence of instabilities, called natural swaying motion of confined plumes, beginning with a periodic regime having a high fundamental frequency followed by a two-frequency locked regime. Then, broadband components appearing in the spectra indicate chaotic behaviour and a weakly turbulent motion arises via an intermittent route to chaos. For rectangular vessels of aspect ratio greater than 2 and depths of immersion greater than the width, the flow undergoes a pitchfork bifurcation. This symmetry breaking is driven by the destabilization of an upper unstable layer of stagnant fluid above the plume. Then a subcritical Hopf bifurcation occurs. On the other hand, if the depth of immersion is lower than the width of the vessel, a stable layer of fluid is at rest below the line source. Then penetrative convection sets the whole air-filled vessel in motion and an oscillatory motion of very low frequency arises through supercritical Hopf bifurcation followed by a two-frequency locked state.

PEDOT nanostructures synthesized in hexagonal mesophases

Abstract: We describe a single step preparation of nanostructures of poly(3,4-ethylenedioxythiophene), PEDOT, in the hydrophobic domains of cationic surfactant-based hexagonal mesophases via chemical oxidative polymerization of EDOT monomers using FeCl3 as an oxidizing agent. After polymerization, the hexagonal structure of the mesophases is preserved as demonstrated by polarized light microscopy and X-ray scattering measurements. After extraction from mesophases, the chemical structure of PEDOT is confirmed by Fourier transform infrared spectroscopy. Moreover, PEDOT morphology is checked by transmission and scanning electron microscopies. PEDOT nanostructures with spindle-like or vesicle-like shapes are obtained depending on the experimental conditions. In the original method, high resolution atomic force microscopy, coupled with infrared nanospectroscopy, is used to probe the local chemical composition of PEDOT nanostructures. Finally, the as-prepared PEDOT polymers are characterized by both good thermal stability up to 200 °C and a relatively high conductivity value up to 0.4 S cm−1 as determined by thermogravimetric analysis and four probe measurements respectively.