Catalytic ozonation of N-methyldiethanolamine over mixed oxides derived from Mg/Fe-LDH.

The aim of this study was to evaluate the efficiency of catalytic ozonation to increase the degradation of aqueous N-methyldiethanolamine (MDEA) solutions, using two lamellar double hydroxides, namely MgxFe-LDH with x = Mg/Fe = 2, 3, were synthesized by the simple and rapid co-precipitation method. Then, the obtained materials were calcined at 400 °C for 6 h. The calcined products were respectively designated as HTcMg2Fe and HTcMg3Fe, and characterized by powder X-ray diffraction (XRD), N2 physisorption (BET), Fourier transform infrared spectra (FT-IR), and scanning electron microscopy (SEM). The powders produced were used in the ozonation reaction to remove MDEA from aqueous solutions. Experimental results showed that the highest MDEA removal efficiency is in the catalytic ozonation process. Under the optimal conditions for heterogeneous catalytic ozonation of MDEA: initial concentration of 4 Wt% MDEA, 30 °C, catalyst mass of 30 mg/100 ml solution, and contact time of 60 min. The results showed the highest percentage of COD removal, which was up to 80.76% for HTcMg2Fe higher than that of HTcMg3Fe 80.36%.

Shear Properties of Brain Tissue over a Frequency Range Relevant for Automotive Impact Situations: New Experimental Results.

This research aims at improving the definition of the shear linear material properties of brain tissue. A comparison between human and porcine white and gray matter samples was carried out over a new large frequency range associated with both traffic road and non-penetrating ballistic impacts. Oscillatory experiments were performed by using an original custom-designed oscillatory shear testing device. The findings revealed that no significant difference occured between the linear viscoelastic behavior of the porcine and the human brain tissue. On the average, the storage modulus (G') and the loss modulus (G") of the white matter increased respectively from 2.1 +/- 0.9 kPa to 16.8 +/- 2.0 kPa and from 0.4 +/- 0.2 kPa to 18.7 +/- 2.3 kPa between 0.1 and 6300 Hz at 37 degrees C. In addition, the gray and white matter behaviors seemed to be similar at small strains. The reliability of the data and the robustness of the experimental protocol were checked using a standard rheometer (Bohlin C-VOR 150). A good agreement was found between the data obtained in the frequency and time field. As a result, the linear relaxation modulus was determined over an extensive time range (from 10(-5) s to 300 s). In a first approach, the nonlinear behavior of brain tissue was studied using stress relaxation tests. Brain tissue showed significant shear softening for strains above 1% and the time relaxation behavior was independent of the applied strain. On this basis, a visco-hyperelastic model was proposed using the generalized Maxwell model and the Ogden hyperelastic model. These models respectively describe the linear relaxation modulus and the strain dependence of the shear stress.