Wavelets and turbulence

We have used wavelet transform techniques to analyze, model, and compute turbulent flows. The theory and open questions encountered in turbulence are presented. The wavelet-based techniques that we have applied to turbulence problems are explained and the main results obtained are summarized     

Growth of titanium single crystals by electrotransport

Single crystals of H.C.P. Titanium may be grown by electrolysis in solid state. Because of the low phase transformation temperature, the samples are annealed in the B.C.C. phase for the primary recrystallization. With a good control of secondary recrystallization at the B.C.C. to H.C.P. transformation, we obtain, without any contamination, single crystals of the hexagonal phase of a few centimeters length.     

A 1D- and 2D-NMR Study of an Anionic Surfactant/Neutral Polymer Complex

NMR chemical shifts and linewidth measurements were examined for mixtures of sodium 10-phenyldecanoate (Na ω-PhDec) in deuterated aqueous solutions in the presence of varying compositions of poly(ethylene oxide) (PEO) polymers of 2000 and 4000 molecular weight. In addition, variable temperature NMR spectra and NMR spin lattice relaxation times (T ₁) were obtained for the PEO-4000/Na ω-PhDec system as a function of varying polymer concentrations. As expected, the polymer/surfactant systems exhibit the behaviour typical of that of an anionic surfactant/neutral polymer system with well defined critical aggregation concentrations (CMC) corresponding to the formation of polymer/surfactant complexes below the CMC of the free surfactant. The ¹H-NMR linewidths acquired for the Na ω-PhDec/PEO-4000 system before and after the CMC region of the surfactant indicate that the maximum in the linewidth of the PEO proton peak is reached at approximately twice the CMC of the free surfactant. 2D-NMR NOESY measurements on this system exhibit cross peaks between the PEO protons and the protons on the surfactant backbone, consistent with the location of the phenyl group in the micellar interior. All these NMR experiments are interpreted in terms of the structure of the polymer/surfactant complexes as a function of the system composition.

Enhanced model predictive control of a catalytic flow reversal reactor

The combustion of lean methane air mixtures in a catalytic flow reversal reactor (CFRR) is studied using a two dimensional heterogeneous continuum model, based on mole and energy balance equations for the solid (the inert and catalytic sections of the reactor) and the fluid phases. Following a design of experiments (DOE), many simulations were carried out to investigate the reactor performance. The results show the impact on the methane conversion and the maximum temperature in the reactor of key process parameters such as the methane inlet concentration, the superficial gas velocity, the switching time, and the mass extraction rate. A simple empirical model is deduced to predict the maximum temperature and conversion of methane in the reactor at stationary state. This model is combined with a model predictive control (MPC) strategy in the form of a terminal constraint to improve the controller performance. Results show that the control of the reactor is improved.     

In vitro and in vivo efficacy of sulfo‐carrabiose,a sugar‐based cosmetic ingredient with anti‐cellulite properties

Most of adult women exhibit cellulite on the hips, buttock and thighs. Although extracellular matrix and lymphatic system disorders can increase its appearance, cellulite basically results from an excessive fat storage in the adipose tissue which exerts considerable pressure on the surrounding skin tissue and creates a dimpled irregular appearance. Caffeine, the most widely used anti‐cellulite ingredient, favours fat break‐down by inhibiting the phosphodiesterase enzyme and encouraging a high intracellular level of cAMP. A series of studies has shown that spermine and spermidine, two ubiquitous polyamines, encouraged fat storage and slowed fat break‐down in the adipose tissue. Besides, it was shown that heparan sulfate glycosaminoglycans had a strong affinity for polyamines. To design a new cosmetic ingredient with anti‐cellulite properties, we used molecular modelling to screen several ingredients with a structure similar to that of heparan sulfate glycosaminoglycans. This way, we identified sulfo‐carrabiose as a potent molecule for trapping spermine and spermidine. These virtual results were first confirmed in tubo where sulfo‐carrabiose was shown to dose‐dependently inactivate spermine and spermidine. In vitro, adipocytes cultured with sulfo‐carrabiose exhibited a significant reduction of lipogenesis and a significant increase of lipolysis. When sulfo‐carrabiose was incorporated in a cosmetic formula, significant improvements were observed in thigh circumference, with better results than those obtained with caffeine after 28 days of use. Furthermore, a combination of caffeine and sulfo‐carrabiose led to results significantly better than those obtained with caffeine alone. As measured by fringe projection, thigh volume was also significantly reduced after sulfo‐carrabiose treatment. Finally, the appearance of cellulite assessed by clinical evaluation was also significantly reduced within 28 days.     

Mono- and diquaternary ammonium cellulose cottons prepared in nonaqueous media

Mono- and diquaternary ammonium cellulose anion exchangers in fabric form were prepared in nonaqueous media by reacting diethylaminoethyl (DEAE)-cotton with an alkyl halide, RX, or a dihaloalkane, X(CH₂)_nX, respectively. The alkyl group was varied from CH₃ to C₁₈H₃₅, and n varied from 5 to 10 in the dihaloalkanes. Electron emission spectroscopy for chemical analyses (ESCA) showed that approximately 70% of the amino groups in the original DEAE-cotton were free amines. ESCA data showed that highest degree of quaternization of the free amine groups was obtained with CH₃I but that diiodo and dibromo pentanes and decanes were also effective. Diquaternary ammonium cellulose exchangers of high nitrogen content had high wet and conditioned wrinkle recoveries, whereas the monoquaternary ammonium cellulose exchangers showed no improvement in wet or conditioned wrinkle recoveries. The monoquaternaries, like unmodified cottons and DEAE-cottons, were soluble in cupriethylenediamine hydroxide (cuene), and cross sections of their fibers expanded when subjected to layer expansion techniques. All diquaternaries were insoluble in cuene, and their cross sections did not layer.     

Diffuse and point sources of silica in the Seine River watershed

Dissolved silica (DSi) is believed to enter aquatic ecosystems primarily through diffuse sources by weathering. Point sources have generally been considered negligible, although recent reports of DSi inputs from domestic and industrial sources suggest otherwise. In addition, particulate amorphous silica (ASi) inputs from terrestrial ecosystems during soil erosion and in vegetation can dissolve and also be a significant source of DSi. We quantify here both point and diffuse sources of DSi and particulate ASi to the Seine River watershed. The total per capita point source inputs of Si (DSi + ASi) were found to be 1.0 and 0.8 g Si inhabitant(-1) d(-1) in raw and treated waters of the Achères wastewater treatment plant, in agreement with calculations based on average food intake and silica-containing washing products consumption. A mass balance of Si inputs and outputs for the Seine drainage network was established for wet and dry hydrological conditions (2001 and 2003, respectively). Diffuse sources of Si are of 1775 kg Si km(-2) y(-1) in wet conditions and 762 kg Si km(-2) y(-1) in dry conditions, with the proportion of ASi around 6%. Point sources of Si from urban discharge can contribute to more than 8% of the total Si inputs at the basin scale in hydrologically dry years. An in-stream retention of 6% of total inputs in dry conditions and 12% in wet conditions is inferred from the budget.