Urban wastewater treatment by a nutrient film technique system with a valuable commercial plant species (Chrysanthemum cinerariaefolium Trev.)

Urban wastewater causes rapid eutrophication of natural waters and requires treatment before discharge. This is expensive and produces huge quantities of sludge. In the European Community, it will no longer be lawful to dispose of this sludge as landfill after 2005 (European Directive 91/271/CEE of May 21, 1991). Wastewater treatment by the Chrysanthemum cinerariaefolium plants in horizontal flow was investigated using the nutrient film technique (NFT), a widely used hydroponic system in the commercial greenhouse industry. After a 48 h plant treatment, the purification efficiency was 95%, 91%, and 99% with respect to suspended solids (SS), biochemical oxygen demand (BOD5), and chemical oxygen demand (COD), and the elimination of nutrients (total nitrogen and total phosphorus) varied between 40% and 80%. SS and thus indirectly BOD5 and COD were removed by filtration and adsorption; the solids trapped in the root systems were then decomposed and mineralized. The system with 25 plants purified 30 L of wastewater in 48 h. One-hundred people communities wastewater could be treated with a 6 m2 area of production. Pyrethrin contents and chlorophyll a fluorescence of plants grown on raw urban waters were not significantly different from those grown on a standard nutrient solution.     

Selection and properties of alpha-acetolactate decarboxylase-deficient spontaneous mutants of Streptococcus thermophilus

Many lactic acid bacteria produce diacetyl, which is a desirable aroma compound in some fermented dairy products. Strains or mutants of Lactococcus lactis subsp. lactis biovar. diacetylactis that are deficient in alpha-acetolactate decarboxylase are used in some food processes for their ability to produce large amounts of diacetyl. However, up until now, the use of alpha-acetolactate decarboxylase-deficient mutants of Streptococcus thermophilus for increased diacetyl production has not been evaluated. The objective of the present study was to devise a procedure for selecting spontaneous alpha-acetolactate decarboxylase-deficient mutants of S. thermophilus. We observed that in a chemically defined medium (CDM) containing alpha-ketobutyrate plus leucine, or alpha-ketobutyrate plus leucine plus isoleucine, the alpha-acetolactate decarboxylase-deficient mutant TIL865, obtained by directed mutagenesis, grew faster than its parent strain. This property was used for selecting spontaneous alpha-acetolactate decarboxylase-deficient mutants on agar plates. The resulting mutants were able to grow in milk, and their acidifying activity was slightly lower than that of the parent strain. Under partial anaerobic or aerobic conditions, they produced approximately three times more diacetyl than the parent strain. Such spontaneous mutants may be useful for increasing the diacetyl content of fermented milks whose production involves S. thermophilus strains.     

Rayleigh-like instability in the ion-shaping of Au-Ag alloy nanoparticles embedded within a silica matrix

We have studied how spherical 23 ± 3 nm Au(45)Ag(55) nanoparticles embedded within a silica matrix transform into prolate nanorods and nanowires by irradiating them with swift heavy ions. Samples were irradiated at room temperature and normal incidence with 74 MeV Kr and 36 MeV S ions for fluences up to 1.0 × 10(15) cm(-2). We demonstrate the existence of two regimes: (i) below a critical fluence, ～ 2.0 × 10(14) cm(-2), the transformation of the spherical nanoparticle into a nanorod is an individual process, i.e. each nanoparticle transforms into a single nanorod; (ii) for larger fluences the transformation from nanorod to nanowire becomes a collective process, i.e. the break up and dissolution of unstable nanorods contribute to the growth of long nanowires. The passage from the first to the second regime can be interpreted in terms of a Rayleigh-like instability under irradiation. The latter becomes active when the diameter of the nanowire approaches its saturation width under irradiation. Furthermore, we show that the composition of the alloy is only slightly modified during the ion-shaping process. Finally, the energy and the fluence thresholds for deformation and the deformation strain-rate are estimated.     

Phenomenological model for the formation of heterogeneous tracks in pyrochlores irradiated with swift heavy ions

Zirconate and titanate pyrochlores were irradiated with swift heavy ions in order to investigate the effects of the chemical composition on the structural changes induced by high electronic excitation. Both transmission electron microscopy and X-ray diffraction results show that the structural modifications induced by irradiation with 120-MeV U ions are strongly dependent on the sample composition: Gd₂Ti₂O₇ is readily amorphized, whereas Gd₂Zr₂O₇ is transformed into a radiation-resistant anion-deficient fluorite structure. For Sm₂Zr₂O₇, Eu₂Zr₂O₇ and Nd₂Zr₂O₇, more complex behavior is observed, since both pyrochlore-fluorite phase transformation and amorphization occur. A new phenomenological model (the heterogeneous track overlap model, HTOM), which assumes a direct impact mechanism coupled with a single track overlap process, is proposed to describe the formation of heterogeneous track structures consisting of mixed anion-deficient fluorite and amorphous domains. The pyrochlore composition mainly influences the structure of ion tracks (and weakly their diameter), and essentially concerns the amount of amorphous phase vs the amount of fluorite counterpart.     

Characterization and localization of a cheese georegion using edaphic criteria (Jura mountains, France)

Comté cheese, made from raw whole milk with local starter lactic acid bacteria, has been manufactured in the traditional manner in the French part of the Jura mountains since the 13th century. Its flavor vary not only by factors such as grass and hay, but also by geographical production sites. Connoisseurs are able to identify the origin of a certain number of cheeses, which raises the question of whether one can speak of georegions (terroirs) or specific geographical areas as in the case of wine. A new method of large-scale cartography (agro-pedological units) covering 20 cheese cooperatives provided a statistical comparison showing the different edaphic sectors. A sensory analysis of 106 cheeses from these 20 cooperatives (summer or winter cheese with 3 or 6 mo of ripening) has demonstrated Comté georegions corresponding to 85% of the edaphic sectors. Thus, these sectors are equivalent to cheese georegions that are natural entities represented synthetically by agropedological units that have their own vegetation and their own specific type of Comté cheese.     

Automatic verification of reduction techniques in Higher Order Logic

In this paper we propose an automatic methodology to verify the soundness of model checking reduction techniques. The idea is to use the consistency of the specifications to verify if the reduced model is faithful to the original one. The user provides the reduction technique, the specification and the system under verification. Then, using Higher Order Logic he verifies automatically if the reduction technique is soundly applied. The method is completely defined in an MDG–HOL special integration platform that combines an automatic high level model checking tool Multiway Decision Graphs (MDGs) within the HOL theorem prover. We provide two case studies, the first one is the reduction using SAT–MDG of an Island Tunnel Controller and the second one is the MDG–HOL assume-guarantee reduction of the Look-Aside Interface. The obtained results of our approach offer a considerable gain in terms of the correctness of heuristics and reduction techniques as applied to commercial model checking, however a small penalty is paid in terms of CPU time and memory usage.     

Numerical Validation of an Elastoplastic Formulation of the Conventional Limit Pressure Measured with the Pressuremeter Test in Cohesive Soil

An elastoplastic pressuremeter theory for cohesive soil has been used in the design of construction, such as retaining walls, slope stability, or foundation engineering. This theory takes into account the plasticity along the vertical and horizontal planes and allows for the determination of the conventional limit pressure. We compute here the conventional limit pressure using the Plaxis program to check the validity of the theoretical results. First, we present the theory used for the interpretation of the pressuremeter test in cohesive soil and its extension to the conventional limit pressure, which is defined as the pressure at the borehole wall for a volume increase ΔV equal to the initial volume of the borehole. One of the main results is the theoretical expression of the conventional limit pressure. This volume variation is linked to a radial strain of ?1. This conventional limit pressure can be directly measured with the pressuremeter, whereas the theoretical limit pressure is expressed as an infinite expansion and cannot be directly measured. Then, we validate this theory by using finite elements, and determine the conventional limit pressure with the Tresca standard model of Plaxis, which is compared to the theoretical expression. Conclusions are drawn on the validity of this new theory which allows the measurement and the control of the shearing modulus and shear strength of the natural soil.