HYDRODYNAMICS AND MASS TRANSFER IN A SPOUTED BED DRYER

The disposal of sludge generated by water treatment plants poses major financial and environmental problems. Drying of the sludge is an essential pan of any disposal process which may include incinerating, landfilling or upgrading. In the present study, experiments were carried out to investigate the drying of sludge in a spouted bed and to characterize the hydrodynamics and mass transfer mechanisms. The effect of bed moisture content on the minimum spouting velocity (U_ms) was examined for sludge granules. U_ms was found to increase with increasing the moisture content of the sludge particles. The gas phase mass transfer coefficient in the dryer was determined using porous calcined alumina particles and the results were compared with predictions by correlations available in the literature. The existing correlations gave poor predictions for the mass transfer coefficient. A new correlation for the mass transfer coefficient in a spouted bed dryer was developed based on the experimental results.     

Application of a non-ionic amphiphilic maleic diester as polymerizable surfactant in free-radical emulsion polymerization

Summary A non ionic amphiphilic maleic diester with a poly(ethylene oxide) hydrophilic chain was used as a copolymerizable surfactant in batch free-radical emulsion polymerizations of styrene and n-butylacrylate. A good stability during the polymerization process was observed together with a high incorporation of the surfactant. Received: 14 December 1998/Revised version: 10 February 1999/Accepted: 10 February 1999     

Lateral motion and interaction of gas bubbles growing over spherical and plate heaters

This work investigates the motion of CO₂ bubbles emerging in n-heptane when a heat pulse given to a submerged heater creates local supersaturation. The ensuing slow diffusion-induced bubble expansion makes bubble motion easy to observe. The low gravity environment of a parabolic flight allows bubbles to reach large sizes without departing from the heater while retaining their spherical shape. A fast lateral displacement of single bubbles has often been noticed on two type of heaters. In cases where many bubbles grow adjacent to each other, they soon start to interact. Phenomena such as bubbles clustering, coalescence and lift-off from the heater of a large bubble induced by neighboring small ones, have been repeatedly observed. An interesting thermocapillary attraction has also been noticed between bubbles adhering to the heater and others free-floating in the nearby liquid.     

Aluminum multiple implantations in 6H–SiC at 300 K

A complete study was driven in order to elaborate a p⁺–n junction in 6H–SiC. The chosen techniques were aluminum multiple implantations, followed with high-temperature furnace annealings. First, we had to configure the furnace geometry aiming at optimizing the annealed material characteristics. We evidenced the beneficial effects of a SiC plate inside the furnace reactor on the surface stoichiometry of the annealed sample, and also on its crystal reordering velocity. Then, the fivefold aluminum implantation necessary for the 0.5 μm depth p⁺-region creation has been studied, especially the energy order influence on the junction steepness. It was found that the increasing energy order implantations lead to a channeling effect less important, a deeper amorphized zone, and a defect interface at volume more abrupt. After an annealing performed with the optimized furnace, the best electrical activation obtained equated the degree of ionization even though the as-implanted material was totally amorphized up to 0.25 μm. Moreover, the three different multiple implantations investigated during this study induced different amorphized layer depths, despite they all have the same total aluminum dose with the same highest energy value. All along the paper, we propose to explain this fact. This is probably due to distinct mechanisms involved in the amorphization phenomena, which were tentatively estimated with a specific Monte Carlo simulator recently developed.     

Intestinal in vitro cell culture models and their potential to study the effect of food components on intestinal inflammation

Abstract

Cell cultures are widely used in pharmaceutical, medical, food/nutrition and biological sciences. In food and nutrition science, intestinal cell culture models of human origin are attracting increasing interest but are still rarely used in investigations of the effects of bioactive food compounds on intestinal inflammation. However, such in vitro models would, among other benefits, limit the use of in vivo models and could provide new molecular data.

This review is an overview of two-dimensional (2D) and three-dimensional (3D) intestinal cell culture models and their potential use in gut inflammation studies. After describing the features of healthy and inflamed intestinal barriers, we describe the main intestinal cell lines (Caco2, HT29, T84) and their use in investigations of the transport and antioxidant/anti-inflammatory potential of some bioactive food compounds. Finally, different co-culture models of gut inflammation, in association with immune cells (PBMC, THP1 and RAW 264.7 cell lines) in both 2D and 3D models are presented. 3D models called organs-on-chips or biochips are the most recent and very promising approach made possible by bioengineering and biotechnological improvements and more accurately mimic the gut microenvironment.     

Exposure assessment of fetus and newborn to brominated flame retardants in France: preliminary data

Brominated flame retardants (BFR) are chemicals extensively used in many manufactured products to reduce the risk of fire, but also environmental pollutants. In order to assess the potential risk linked to these compounds in human, a French monitoring study was initiated to evaluate the exposure of fetus and newborn. A previously described multi-residue analytical method was used, for measuring the main classes of BFR (hexabromocyclododecane, tetrabromobisphenol-A, and tri- to deca-polybromodiphenylethers) in various biological matrices. These analyzed samples (maternal and umbilical serum, adipose tissue and breast milk) were collected on volunteer women during caesarean deliveries. Preliminary results obtained on 26 individuals (mother/newborn pairs) mainly demonstrated the presence of polybromodiphenylethers (PBDE) and tetrabromobisphenol A both in maternal and fetal matrices, and a possible risk of overexposure of newborns through breastfeeding. Contaminations levels were found globally in the ng/g lipid weight range, consistent with other published European data. Exposure results regarding highly brominated PBDE congeners (octa- to deca-BDE) appeared particularly informative and non-commonly reported, these compounds accounting for around 50% of the total PBDE load. Additional data collection and metabolism investigations are now on-going. A more complete statistical analysis related to this BFR exposition study will be provided in a next future.     

Multiscale approach of fish responses to different types of environmental contaminations: a case study

In order to study the responses of wild fish to environmental contaminations, different sites (two references and three contaminated) were sampled across the Walloon hydrographical network (southern Belgium). The status of fish communities was characterized according to an index of biotic integrity (IBI). Furthermore, population structure, reproductive parameters and biochemical assays were performed on chub (Leuciscus cephalus) as sentinel species. The results showed impaired responses in fish sampled downstream paper mill effluents (BKME), in a polychlorinated biphenyls (PCB) contaminated site, and in a river receiving pesticides (i.e. atrazine and hexachlorocyclohexane). High level of hepatic 7-ethoxyresorufin-Odeethylase (EROD) activity were evidence of direct toxicant exposure, while population structures showed unbalanced size-frequency distributions. Moreover, in the pesticide contaminated site, a higher proportion of atretic oocytes was found in females and abnormally high plasma alkali-labile phosphorus (ALP) values were noticed in males, compared to reference sites, suggesting that chubs were exposed to estrogenic compounds. IBI scores from both sites were also lower than in reference sites. On the other hand, no particular response was found in hepatic glutathione-S-transferase (GST) activities, hepatic heat-shock protein HSP70 concentrations and plasma sex steroids (estradiol-17beta, 11-ketotestosterone and testosterone) in chubs from any sites. By using a multiparametric approach, a better understanding of response mechanisms to pollution in fish may be achieved in order to improve the ecological status of river ecosystems.     

Applications of Catalytic Asymmetric Sulfide Oxidations to the Syntheses of Biologically Active Sulfoxides

Optically active sulfoxides are important compounds for medicinal and pharmaceutical chemistry. Driven by the increasing demand for efficient, selective and environmentally friendly industrial processes, several catalytic methodologies have been developed in recent years for the stereoselective oxidation of sulfides for the preparation of biologically active sulfoxides. Both small‐scale approaches to the problem as well as some large‐scale applications that are already in industrial use are described in this review.