Comparative Baeyer-Villiger oxidation of cyclohexanone on Fe-pillared clays and iron tetrasulfophthalocyanine covalently supported on silica

The Baeyer-Villiger oxidation of cyclohexanone to caprolactone has been investigated at room temperature over AlFe-pillared clays, using oxygen as oxidant in the presence of benzaldehyde. A nearly complete conversion is observed with a selectivity into caprolactone above 80%. The observation of an induction period in the kinetics, of high activity of the non-pillared clay, and the detection of Fe traces in the reaction medium, suggest a process involving homogenous catalysis. The reaction is indeed catalysed in homogeneous phase by a few ppm of Fe. By contrast, iron phthalocyanine covalently supported on silica appears as a true heterogeneous catalyst, giving a selectivity above 95% to caprolactone at 61% conversion.     

Decay rates at low and high frequencies for a plate equation with feedback concentrated in interior curves

In this paper we study the stabilization of plate vibrations by means of piezoelectric actuators. In this situation the geometric control condition of Bardos, Lebeau and Rauch [6] is not satisfied. We prove that we have exponential stability for the low frequencies but not for the high frequencies. We give an explicit decay rate for regular initial data at high frequencies while clarifying the behavior of the constant which intervenes in this estimation there function of the frequency of cut n. The method used is based on some trace regularity which reduces stability to some observability inequalities for the corresponding undamped problem. Moreover, we show numerically at low frequencies, that the optimal location of the actuator is the center of the domain Ω.     

Approximation numérique d'un problème de membrane non linéaire

We study numerically the deformations of a nonlinearly elastic membrane. We consider the nonlinear membrane model obtained by Le Dret and Raoult using Γ-convergence. In this model, membrane deformations minimize a highly nonquadratic energy. We consider a conforming finite element approximation of the problem and use a nonlinear conjugate gradient algorithm to minimize the discrete energy. To cite this article: N. Kerdid et al., C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

Structural and nanomechanical properties of porous silicon: Cheap substrate for CMOS process industry

The surface topology of porous silicon (PSi) is a relevant parameter that decides the compatibility of such substrate with CMOS process. Using standard resistivity (1–10 Ω·cm) of Si substrate to fabricate PSi-S is a low cost solution for the industry. In this paper, through an atomic force microscopy (AFM) analysis, the root mean square (RMS) roughness, the power spectral density and the correlation length were determined for different PSi layers. Furthermore, the measured hardness, Young's modulus, and stress have been made for different thicknesses of PSi: 5, 10, 50, and 200 μm. The obtained results demonstrated that very interesting properties have been achieved with the 50 μm-thick PSi-S layer with a maximum porosity around 65%, a surface roughness less than 1 nm and a hardness value of (~1 GPa). The realized results encourage the utilization the PSi-based substrate into the industry process and thus the development of a Systems-on-Chip (SoC).     

Synthesis and characterization of highly ordered mesoporous nanomaterials Al-MCM-41 and Al-SBA-15 from bentonite as efficient catalysts for the production of biodiesel MELA and EELA

Research on Chemical Intermediates - Low-cost Al-MCM-41 and Al-SBA-15 mesoporous materials are successfully synthesized from bentonite as silicon and aluminum sources instead of laboratory reagents...     

Batch and continuous fixed-bed column adsorption of Cs+ and Sr2+ onto montmorillonite–iron oxide composite: Comparative and competitive study

A montmorillonite–iron oxide composite (MIOC) was prepared to assess its effectiveness in the removal of Cs⁺ and Sr²⁺ from aqueous solution. A comparative and competitive adsorption study was conducted in single and binary systems. Used materials have been characterized by X-ray diffraction (XRD) and Infrared spectroscopy. Adsorption of Cs⁺ and Sr²⁺ as a function of contact time and pH was investigated, adsorption data of single metal solutions were well fitted to the Freundlich–Langmuir isotherm models. Equilibrium isotherms for the binary removal of Cs⁺ and Sr²⁺ by MIOC have been analyzed by using non modified and extended Langmuir models with a satisfactory R ² values. Neutral solution pH was found to be favorable for both single and binary systems. The adsorption model analysis revealed that MIOC was more selective for Sr than Cs. The maximum adsorption capacities for individual Cs⁺ and Sr²⁺ solutions were 52.6 and 55.5 mg g^?1, respectively. While the maximum uptakes in the binary system were 41.6 and 47.6 mg g^?1 for Cs⁺ and Sr²⁺, respectively. Column adsorption experiments were carried out at room temperature under the effect of various operating parameters such as bed depth, initial cation concentration and flow rate, Breakthrough curves were well fitted to the Thomas model. Desorption experiments were also conducted to assess the possibility for the reuse of adsorbent and the recovery of cations.     

Investigations of the Effects of Xanthan and Sodium Caseinate on the Formation and Stability of an Oil-in-Water Emulsion Stabilized by a Nonionic Surfactant Using a Response Surface Method

Effects of xanthan and sodium caseinate concentrations on the rheological properties and stability of an oil-in water emulsion stabilized by a nonionic surfactant (Tween 20) were investigated. In order to evaluate the influence of component concentrations on the emulsion properties, a response surface method was applied. It was shown by polynomial simulation and modelization of responses of storage modulus and creaming index that in absence of Tween 20, the oily droplets were flocculated by bridging of sodium caseinate macromolecules, when those are insufficient to cover the entire interface. Additionally, it was noted that xanthan reinforces the polymeric network in the aqueous phase when the caseinate is not moved toward the phase. On the other hand, in presence of nonadsorbed caseinate, the polysaccharide develops segregative interactions by thermodynamic incompatibility. These nonadsorbed macromolecules can also flocculate the fatty globules by depletion.     

Multiple positive solutions of the one-dimensional p-Laplacian

In this work we investigate the existence of positive solutions of the p-Laplacian, using the quadrature method. We prove the existence of multiple solutions of the one-dimensional p-Laplacian for α?0, and determine their exact number for α=0.     

Combinatorial optimization and Green Logistics

The purpose of this paper is to introduce the area of Green Logistics and to describe some of the problems that arise in this subject which can be formulated as combinatorial optimization problems. The paper particularly considers the topics of reverse logistics, waste management and vehicle routing and scheduling.      

Volatile oils from the plant and hairy root cultures of Ageratum conyzoides L

Two lines of hairy root culture of Ageratum conyzoides L. induced by Agrobacterium rhizogenes ATCC 15834 were established under either complete darkness or 16 h light/8 h dark photoperiod conditions. The volatile oil yields from aerial parts and roots of the parent plant, the hairy root culture photoperiod line and the hairy root culture dark line were 0.2%, 0.08%, 0.03% and 0.02%, (w/w), respectively. The compositions of the volatiles from the hairy roots, plant roots and aerial parts were analysed by GC and GC-MS. The main components of the volatiles from the hairy root cultures were β-farnesene, precocene I and β-caryophyllene, in different amounts, depending on light conditions and also on the age of cultures. Precocene I, β-farnesene, precocene II and β-caryophyllene were the main constituents of the volatile oils from the parent plant roots, whereas precocene I, germacrene D, β-caryophyllene and precocene II were the main constituents of the aerial parts of the parent plant. Growth and time-course studies of volatile constituents of the two hairy root lines were compared. Qualitative and quantitative differences were found between the volatile oils from the roots of the parent plant and those from the hairy roots.