Thermodynamic modeling of the ternary Ce–Fe–Sb system: Assessment of the Ce–Sb and Ce–Fe systems

The two Ce–Sb and Ce–Fe binary systems have been evaluated using the calculation of phase diagram method (CALPHAD). All of the binary compounds are treated as stoichiometric compounds. Solution phases are described with an ordinary substitutional solution model. The model parameters were derived from an optimization procedure using all available experimental data. The reproduction of the thermochemical and phase diagram information is reported in a series of figures and tables.     

Process engineering and problems encountered by chemical and related industries in the near future. Revolution or continuity?

The evolution of process engineering is reviewed and it’s ability to cope with the problems encountered by chemical and related industries is appraised. It appears that the necessary progress should come via a pluridisciplinary and multiscale approach, that will allow us to satisfy both the market requirements for specific end-use properties as well as the environmental and social constraints. In this context, an increasingly important contribution will be required from basic disciplines such as physics, physical chemistry and mathematics, mechanics and ecotoxicology.     

Ultraporous monoliths of alumina prepared at room temperature by aluminium oxidation

The oxidation of aluminium through a mercury film usually leads to unorganized filaments or fibrous powders of hydrated alumina. Here, we show that the addition of a small amount of silver in the mercury considerably modifies the growth process, and that large sized monoliths can be obtained through a new process. Regular growth can be maintained at a typical rate of 2.1 μm s⁻¹ (∼0.75 cm/h) for several hours. The samples consist of tangled nanometric fibres and have an open porosity of 99%. The influence of various parameters has been studied and optimal conditions for regular growth have been determined. Anhydrous alumina monoliths with a nanometric microstructure and a high-specific area are obtained after thermal treatments that remove water.     

Network competition and branch differentiation with consumer heterogeneity

The paper provides a general framework for the analysis of noncooperative competition between multi-branch networks when consumers have heterogeneous preferences. This framework allows for ill-studied conditions, such as branch loyalty and economies of scope, to be explored in terms of their role in shaping address solutions and firm profits. Geographic and quality differentiation as well as firm profits are shown to be dependent upon the magnitude of the loyalty factor and upon the extend of economies of scope. Real world situations in the retail industry are interpreted in the light of the results of the analysis. Received: October 1998 / Accepted: June 1999     

Amélioration des performances et réduction de la puissance consommée des téléphones portables par l’égalisation conditionnelle

In TDMA systems, the autonomy of portable handsets is a major constraint. We propose a new method, conditional equalization, which minimises the power consumption due to equalization. The performance of our method is theoretically analysed for 2- path Rayleigh fading channels and simulated for the Cost 207 models. Conditional equalization enables the saving of at least 30 % of equalizations in urban environments with a loss in the SNR performance of less than 0.1 dB, and leads to a gain in the performance of 1.5 dB with 97 % of saved equalizations in rural area environment.     

Polysaccharides from the green alga Ulva rigida improve the antioxidant status and prevent fatty streak lesions in the high cholesterol fed hamster,an animal model of nutritionally-induced atherosclerosis

We investigated the effects of Ulva in hypercholesterolemic hamsters, before and after processing. Three groups of 12 hamsters were fed a high cholesterol diet for 12 wk (Control) or a high cholesterol diet where cellulose has been replaced for an equivalent fibre weight from Ulva or processed Ulva. Plasma cholesterol, non-HDL cholesterol and specially triglycerides were reduced by Ulva. Liver glutathione peroxidase activity was increased and thiobarbituric acid reactive substances were efficiently reduced by dietary treatments compared with controls, whereas plasma antioxidant capacity was increased and aortic fatty streak area was decreased by 70%. The results show for the first time that chronic consumption of polysaccharides supplied by Ulva prevent the fall of antioxidant defences and the development of atherosclerosis in hamsters. The underlying mechanism is related mainly to increased antioxidant status although improvement of the serum lipid profile was not ruled out.     

Poloxamer 407 as a Thermogelling and Adhesive Polymer for Rectal Administration of Short-Chain Fatty Acids

Objectives: The purpose of the study was to gel a rectal solution of short-chain fatty acids to decrease the loss of active materials in the colonic lumen and thereby optimize their absorption. Methods: Five thermogels were prepared with poloxamer 407 at concentrations ranging from 17% to 20%. Their viscosities were measured at room temperature and 37°C, and their gelling temperatures were determined. The adhesive properties of each gel were assessed in vitro at 37°C. Short-chain fatty acid release was studied using Guyot cells. Results: From the threshold concentration of 17.5%, the solutions, Newtonian at room temperature (50-80 mPa · s), gelled at 37°C. The higher the concentration, the higher the viscosity (1750 to 49,000 mPa · s), the lower the gelling temperature (27.6°C to 23.4°C), and the stronger the work of adhesion (2.2 to 4.5 mJ). Short-chain fatty acid release from the 18% polymer gel was decreased by 60% compared to the rectal solution. Conclusion: The 18% poloxamer 407 concentration provided a solution that was liquid at room temperature, that gelled at 37°C, possessed adhesive properties, and controlled short-chain fatty acid release.     

Development of silica/vanadia/titania catalysts for removal of elemental mercury from coal-combustion flue gas

SiO2/V2O5/TiO2 catalysts were synthesized for removing elemental mercury (Hg0) from simulated coal-combustion flue gas. Experiments were carried out in fixed-bed reactors using both pellet and powder catalysts. In contrast to the SiO2-TiO2 composites developed in previous studies, the V2O5 based catalysts do not need ultraviolet light activation and have higher Hg0 oxidation efficiencies. For Hg0 removal by SiO2-V2O5 catalysts, the optimal V2O5 loading was found between 5 and 8%, which may correspond to a maximum coverage of polymeric vanadates on the catalyst surface. Hg0 oxidation follows an Eley-Rideal mechanism where HCI, NO, and NO2 are first adsorbed on the V2O5 active sites and then react with gas-phase Hg0. HCI, NO, and NO2 promote Hg oxidation, while SO2 has an insignificant effect and water vapor inhibits Hgo oxidation. The SiO2-TiO2-V2O5 catalysts exhibit greater Hg0 oxidation efficiencies than SiO2-V2O5, may be because the V-O-Ti bonds are more active than the V-O-Si bonds. This superior oxidation capability is advantageous to power plants equipped with wet-scrubbers where oxidized Hg can be easily captured. The findings in this work revealed the importance of optimizing the composition and microstructures of SCR (selective catalytic reduction) catalysts for Hg0 oxidation in coal-combustion flue gas.     

Safety assessment of dairy microorganisms: the Enterococcus genus

Unlike most of lactic acid bacteria, the Enterococcus genus is not considered "generally recognized as safe" (GRAS). Safety assessment for enterococci remains controversial. While enterococci are considered "positive" or useful in cheese technology, isolates of this genus have emerged as opportunistic pathogens for humans. Thus these bacteria have the paradoxical position of being useful in dairy fermentations, but also potentially dangerous. The aim of this review is to summarize both the positive and negative traits of enterococci that illustrate the controversial nature of this bacterial genus. According to food safety assessment guidelines, we propose a case-by-case evaluation of each potential technological strain and suggest several lines of research before using enterococci in fermented food products.     

Electrochemical performance of La1.6Sr0.4NiO4-Ag composite cathodes for intermediate-temperature solid oxide fuel cells

La_1.6Sr_0.4NiO₄-Ag (LSN-Ag) composite cathodes are prepared and characterized by XRD and SEM, respectively. The electrochemical properties of the composite cathodes are investigated using AC impedance and DC polarization methods from 500 to 700 °C under different oxygen partial pressures. The polarization resistance (R_p) decreases with the increase of Ag content in the composite electrode. The addition of 5 vol.% Ag in LSN results in the lowest R_p of 0.21 Ω cm² at 700 °C in air. Oxygen partial pressure dependence study indicates that the charge transfer process is the reaction rate limiting step, while the diffusion process has no sensitive to the Ag loading. LSN-5Ag cathode exhibits the lowest overpotential of about 32 mV at a current density of 144 mA cm⁻² at 700 °C in air.