Catalytic combustion of polycyclic aromatic hydrocarbons (PAHs) over zeolite type catalysts: Effect of water and PAHs concentration

The catalytic combustion of 1-methylnaphthalene (1-MN), a PAH representative molecule, was carried out over USHY and 0.8%PtUSHY catalysts in presence of steam. These catalysts are able to transform low concentration of 1-MN into carbon dioxide at 300 °C over USHY catalyst and at 200 °C over PtUSHY, without by-products formation. The presence of platinum on the USHY increases the catalytic activity, hence the reaction rate. The influence of platinum content showed that 0.5% of platinum deposited on the zeolite was sufficient to oxidize 900 ppm of 1-MN at 300 °C.The influence of water content in the feed was investigated and several assumptions were put forth to explain our results. The carbon dioxide yield decreases in the 0–12% range of relative humidity (RH). When RH increases up to 12% the carbon dioxide yield increases. Over USHY catalyst and for low water content (RH < 12%), water could be adsorbed over strong hydrophylic sites of USHY zeolite or via H₂O dimer (neutral complex form) formation. Over PtUSHY catalysts, water adsorption over the PtO phase could be considered. For high water content (RH > 12%), water cluster formation via H₂O dimer (ion-pair complex form) is proposed on both catalysts. This form of H₂O dimer (ion-pair complex) could generate an acidity, which facilitates the formation of oxygenated compounds easily degradable into carbon dioxide.     

Plasma lipoproteins and liver lipids in two breeds of geese with different susceptibility to hepatic steatosis: Changes induced by development and force-feeding

Susceptibility to fatty liver in the force-fed goose is partly under genetic control. However, the mechanisms leading to liver steatosis in this avian model are poorly understood, but may involve perturbation in hepatic lipoprotein synthesis. Plasma lipoproteins were fractionated by density gradient ultracentrifugation from plasma of geese differing in their susceptibility to liver steatosis (Landes breed, highly susceptible; Rhine breed, partly resistant). The concentrations and chemical compositions of the major lipoprotein classes (VLDL, IDL, LDL and HDL) were characterized at 8, 22 and 27 wk of age and compared to the lipid composition of the corresponding liver. In non-force-fed geese, the lipoprotein profile was typical of birds, with high-density lipoprotein (HDL) predominating (4–5 g/L). However, at 22 and 27 wk of age, very low-density lipoprotein (VLDL) levels were significantly lower in Landes geese suggesting that this breed may possess a lower ability to export liver lipids, which would explain its susceptibility to liver steatosis when overfed. The livers of force-fed geese were specifically enriched in triglyceride, and to a lesser extent, in cholesteryl esters and non-esterified fatty acids as compared to those of control geese of the same age (27 wk). This accumulation of lipids was more pronounced in the Landes breed and was responsible for the higher liver weight in that breed. In both breeds, liver steatosis was accompanied by an increase in plasma levels of HDL (11 g/L), whereas low-density lipoproteins were essentially absent. An increase in VLDL plasma levels occurred in the Landes breed only (2.51 g/Lvs 1.85 g/L in the Rhine breed), and was positively correlated with liver weight. However, VLDL in force-fed geese in both breeds were deficient in triglyceride (28–29% by wt) but enriched in cholesterol (41% by wt). These results indicate that a defect in the incorporation of triglyceride into nascent hepatic VLDL may result in liver steatosis in this species.     

Effect of temperature on the viscoelastic behaviour of entangled solutions of multisticker associating polyacrylamides

The viscoelactic behaviour of polyacrylamides (PAM) hydrophobically modified with small blocks (≈3 monomer units) of N,N-dihexylacrylamide (2 mol%) has been investigated in the entangled regime as a function of temperature by steady-flow and oscillatory experiments. The effect of temperature on the rheological behaviour of these systems was also investigated in the presence of surfactant. In both cases, the results were compared to those obtained for the unmodified analogue. The experimental data were analysed using a simple Maxwell model and the time-temperature superposition principle. The results indicate that the main effect of a change in temperature and/or addition of surfactant is to modify the lifetime of the physical crosslinks without changing their density, as inferred from a quasi-constant value of the plateau modulus. The comparison between the plateau moduli of the modified and unmodified systems shows unexpected higher values for the former systems.     

A neuro-evolutionary approach to control surface segmentation for micro aerial vehicles

This paper addresses control surface segmentation in micro aerial vehicles (MAVs) by leveraging neuro-evolutionary techniques that allow the control of a higher number of control surfaces. Applying classical control methods to MAVs is a difficult process due to the complexity of the control laws with fast and highly non-linear dynamics. These methods are mostly based on models that are difficult to obtain for dynamic and stochastic environments. Moreover, these problems are exacerbated when both the number of control surfaces increases and the model’s accuracy in determining the impact of each control surface decreases. Instead, we focus on neuro-evolutionary techniques that have been successfully applied in many domains with limited models and highly non-linear dynamics. Wind tunnel simulations with Athena Vortex Lattice show that MAV performances are improved in terms of both reduced deflection angles and reduced drag (up to 5%) over a simplified model in two sets of experiments with different objective functions. We also show robustness to actuator failure with desired roll moment values still attained with failed actuators in the system through the neuro-controller.     

Mechanism of Dilute Acid Hydrolysis of Cellulose Accounting for its Degradation in the Solid State

It is known that dilute acid hydrolysis of cellulose at high temperature results in yields not exceeding 60–65% of the potential glucose. All the models presented in the literature are based on the sequence: cellulose #x00BB; glucose #x00BB; degradation products. The underlying assumption of this sequence is that the unconverted cellulose retains its chemical integrity during the course of the hydrolysis reaction. Experimental evidence based on physico-chemical characterization of cellulosic residues obtained from dilute acid hydrolysis processes allows us to propose a new mechanism for cellulose hydrolysis accounting for its degradation in the solid state. Such degradation results in the formation of a non- carbohydrate residue.     

Experimental protocol to determine the ability of PET to crystallise

PET [poly(ethylene terephtalate)] is a semi-crystalline thermoplastic that is very suitable for forming processes and is widely used in various technologies. For specific applications, it is necessary to avoid the crystallization of the material by quenching from the melting state while for other applications this crystallization is required. It follows that the ability of PET to crystallize could be a crucial industrial problem, particularly because of the large range of PET proposed by plastic suppliers. This work deals with a calorimetric method able to discriminate this aptitude between various PET rapidly and to give a criterion of crystallizability.     

Bioaccessibility of fatty acids from conjugated linoleic acid-enriched milk and milk emulsions studied in a dynamic in vitro gastrointestinal model

The present study evaluated the in vitro bioaccessibility of milk fatty acids (FA) and cis-9, trans-11 18:2 using the TIM-1 gastrointestinal model from TNO, Zeist, The Netherlands. Milk naturally enriched with cis-9, trans-11 18:2 (46 mg g⁻¹ FA) was obtained from a lactating dairy cow fed safflower oil. The other treatments consisted of synthetic conjugated linoleic acids as triacylglycerols or free FA incorporated into milk containing a low level of cis-9, trans-11 18:2. Treatments were standardised at 3.25% fat and pasteurised. Chyme was analysed for FA composition and lipid classes. FA bioaccessibility was 81.8 ± 3.1% and was not different between treatments. The degree of absorption of saturated FA decreased with chain length. Bioaccessibility was higher for unsaturated FA than for their saturated counterparts. Bioaccessibility of cis-9, trans-11 18:2 was similar among treatments and averaged 87.0 ± 3.4%. Results suggest that regiospecific distribution of cis-9, trans-11 18:2 on triacylglycerol structure does not influence its accessibility for intestinal absorption.     

Analysis of arabic gum: Study of degradation and water desorption processes

Arabic gum is very much used in the agroalimentary industry, mainly as an emulsifier. It is a natural origin polysaccharide and therefore subject to more or less important variabilities of its properties. This work deals with two similar polysaccharides exuded by Acacia senegal of different history and an Acacia seyal sample. To characterize these samples, wide angle X-ray scattering (WAXS) and thermogravimetric analysis in dynamic and isothermal mode are used.The initial structure checked by X-ray diffraction allows to affirm that samples are equivalent in their crystalline structure. The activation energy used to characterize the main degradation process is the same for A. senegal samples, but higher for the A. seyal gum sample. Differences are furthermore observed for the kinetics of water desorption. We conclude that the samples from the same type of gum (A. senegal) are very similar and that A. seyal exudates can be detected by this technique. The water desorption of the two exudates is different.