Processus physicochimiques intervenant dans la preparation des membranes de diacetate de cellulose— recherche de criteres pour l'optimisation des performances I—Collodions renfermant des additifs mineraux

The fabrication of desalination membranes from cellulose acetate casting dopes containing aqueous solution of inorganic salts has been analysed by determining the water concentration required for precipitating the polymer from concentrated solutions and the time necessary for coagulation. The results enable us to correlate the water concentration to the flow rate and the coagulation time to the salt rejection.     

Altération et rupture d'échantillons d'argilite lors de sollicitations thermomécaniques en conditions humides contrôlées

The objective of this work was to undertake creep tests on shale and describe the microtextural phenomena which initiate internal damage/rupture under thermomechanical loading and relative humidity conditions. The CGI test cell is a system developed at the Centre de Geologie de l'Ingénieur specifically to allow observation of the fabric of a thick slide (50×40×5?mm) at different magnifications during the test. The CGI test cell imposes both an axial and a planar strain on the sample. The first step is to prepare a thick slide from a core and to describe its "initial" state. The second stage is to undertake a creep test to rupture, while the third step is to study the fragments of the ruptured material using XRD (X-ray diffractometry), SEM (scanning electron microscopy) and EDS (energy dispersive spectrometry). The samples studied are from the shales of the Callovo-Oxfordian of the Paris Basin, to the south of Bar-le-Duc in the east of France. These rocks consist of clay minerals (illite and kaolinite), quartz, calcite (22.8%), dolomite, feldspar and pyrite (1%). The pyrite is essentially found in the bioclasts. The creep test is carried out under thermomechanical loading with an axial stress of up to 12?MPa and a temperature rising to 80??°C. The relative humidity is maintained at more than 90%. After 33?days the axial strain reached 0.76%, with rupture of the thick slide occurring 10?days later. The deformation was related to the texture/heterogeneity of the rock and occurred mainly along fissuring. Rupture also occurred along bedding planes, particularly where oxidized pyritic bioclasts were present. The chemical phenomena noted were in part related to the formation of iron hydroxides and sulphuric acid. This reacts with the calcite to form gypsum, which has a lower density than the original pyrite and calcite. The XRD indicated that the iron hydroxides observed on the discontinuities are dominantly limmonite. Examination of the SEM and EDS suggested an increase in porosity, even at some distance from the macroscopic fissures.     

Towards an integrated neonatal brain and cardiac examination capability at 7 T: electromagnetic field simulations and early phantom experiments using an 8-channel dipole array

Objective

Neonatal brain and cardiac imaging would benefit from the increased signal-to-noise ratio levels at 7 T compared to lower field. Optimal performance might be achieved using purpose designed RF coil arrays. In this study, we introduce an 8-channel dipole array and investigate, using simulations, its RF performances for neonatal applications at 7 T.

Methods

The 8-channel dipole array was designed and evaluated for neonatal brain/cardiac configurations in terms of SAR efficiency (ratio between transmit-field and maximum specific-absorption-rate level) using adjusted dielectric properties for neonate. A birdcage coil operating in circularly polarized mode was simulated for comparison. Validation of the simulation model was performed on phantom for the coil array.

Results

The 8-channel dipole array demonstrated up to 46% higher SAR efficiency levels compared to the birdcage coil in neonatal configurations, as the specific-absorption-rate levels were alleviated. An averaged normalized root-mean-square-error of 6.7% was found between measured and simulated transmit field maps on phantom.

Conclusion

The 8-channel dipole array design integrated for neonatal brain and cardiac MR was successfully demonstrated, in simulation with coverage of the baby and increased SAR efficiency levels compared to the birdcage. We conclude that the 8Tx-dipole array promises safe operating procedures for MR imaging of neonatal brain and heart at 7 T.

     

Chitosan and cyanoguanidine-crosslinked chitosan coated glass beads and its application in fixed bed adsorption

Abstract

The aim of this work was to coat glass beads with chitosan and cyanoguanidine-crosslinked chitosan and, afterward, to verify the potential of the coated beads as adsorbent for the FD&C Red 40 dye in fixed bed column. The coating was realized in eight experimental conditions, varying the technique (dip coating or casting) and the coating solution composition (different proportions of chitosan, cyanoguanidine, glycerol, sorbitol, sodium alginate, NaOH and CaCl₂). The beads coated in the eight experimental conditions were then applied to adsorb FD&C Red 40 in a fixed bed column, from aqueous solutions at pH 3.0 and 6.0. The breakthrough curves were fitted according to Thomas and Yoon-Nelson dynamic models. The coating was dependent of the solution composition. The casting technique presented coating percentage values of 92%, while the dip coating technique presented only 43%. The breakthrough curves revealed that the use of glass beads coated with cyanoguanidine-crosslinked chitosan had good performance, attaining adsorption capacity values higher than 80?mg g^?1. Thomas and Yoon-Nelson models were able to predict the breakthrough curves in all conditions.     

Sex recognition inDiglyphus isaea walker (Hymenoptera: Eulophidae): Role of an uncommon family of behaviorally active compounds

The sexual behavior of the ectoparasitoidDiglyphus isaea is described. Recognition of the female by the male occurs at close range. Males initiate courtship behavior in the presence of a living female regardless of age, as well as in the presence of a female killed by freezing. Courtship behavior is not observed in the presence of a dead female washed with organic solvents but could be elicited using a lure covered with a female organic extract. These findings demonstrate that each sex develops a specific chemical signature that can be dissolved in hexane and transferred to a lure. Analysis of organic extracts by gas chromatography revealed chemical dimorphism between the two sexes. Gas chromatography coupled with mass spectrometry showed that the main components in females were esters of medium-chain fatty acids and long-chain 11-alcohols. There were few hydrocarbons. Female esters, which were present in only small proportions in males, were recovered in the nonhydrocarbon fraction obtained after fractionation of the total extract on a silica-filled microcolumn as a mixture containing 11-heneicosyl, 11-docosyl, 11-tricosyl, 11-tetracosyl, and 11-pentacosyl octanoate, and 11-docosyl, 11-tricosyl, 11-tetracosyl, and 11-pentacosyl decanoate. These results demonstrate that there is a specific gender-related chemical signature.     

Influence of Host-Plant Surface Chemicals on the Oviposition of the Cereal Stemborer Busseola Fusca

The chemical composition of plant surfaces plays a role in selection of host plants by herbivorous insects. Once the insect reaches the plant, these cues determine host acceptance. Laboratory studies have shown that the stem borer Busseola fusca (Lepidoptera: Noctuidae), an important pest of sorghum and maize in sub-Saharan Africa, is able to differentiate between host and non-host plant species. However, no information is available on the cues used by this insect to seek and accept the host plant. Thus, the role of surface phytochemical stimuli on host selection and oviposition by B. fusca was studied in the laboratory using two host plants, sorghum, Sorghum bicolor, and maize, Zea mays, and one non-host plant, Napier grass, Pennisetum purpureum. The numbers of eggs and egg masses deposited on the three plant species were compared first under no-choice and choice conditions. In both cases, more eggs and egg masses were laid on maize and sorghum than on the non-host. Artificial surrogate stems treated with a water or chloroform surface extract of each plant were then compared with surrogate stems treated with, respectively, water or chloroform as controls, under similar conditions. Surrogate stems treated with plant water extracts did not show an increase in oviposition when compared to controls, indicating that the major compounds in these extracts, i.e., simple sugars and free amino acids, are not significantly responsible for the oviposition preference. By contrast, a chloroform extract of sorghum enhanced oviposition on the surrogate stems compared to the control, while those of maize and Napier grass showed no significant effects. Analysis of the chloroform extract of sorghum showed higher amounts of α-amyrin, ß-amyrin, and n-nonacosane compared to those of maize and Napier grass. A blend of the three chemicals significantly increased oviposition compared to the chloroform-treated control, indicating that these compounds are part of the surface chemical signature of the plant responsible for host recognition and oviposition by B. fusca.