562 research outputs found
Auto-adaptive multistage curing epoxy coatings
Corrosion is an expensive issue for the Navy. Epoxy based protective coatings are used by the Navy to minimize corrosion. The goal of this work is to reduce the cost of corrosion by improving the reliability of the coating application. A better application process decreases defects and reduces early failures. A novel hybrid epoxy coating system composed of two layers has been developed. A first layer with two curing stages (an epoxy/amine polycondensation combined with a vinyl free radical polymerization) and a standard second layer were created and tested. A room temperature free radical initiator system was selected to perform the free radical polymerization. Diffusion predictions were carried out in order to determine the viability of the initiator diffusion. Kinetics measurements and theoretical modeling were performed in order to characterize the curing behavior. A novel formulation was developed and showed a potential for practical application
A computational framework for the morpho-elastic development of molluskan shells by surface and volume growth
Mollusk shells are an ideal model system for understanding the morpho-elastic
basis of morphological evolution of invertebrates' exoskeletons. During the
formation of the shell, the mantle tissue secretes proteins and minerals that
calcify to form a new incremental layer of the exoskeleton. Most of the
existing literature on the morphology of mollusks is descriptive. The
mathematical understanding of the underlying coupling between pre-existing
shell morphology, de novo surface deposition and morpho-elastic volume growth
is at a nascent stage, primarily limited to reduced geometric representations.
Here, we propose a general, three-dimensional computational framework coupling
pre-existing morphology, incremental surface growth by accretion, and
morpho-elastic volume growth. We exercise this framework by applying it to
explain the stepwise morphogenesis of seashells during growth: new material
surfaces are laid down by accretive growth on the mantle whose form is
determined by its morpho-elastic growth. Calcification of the newest surfaces
extends the shell as well as creates a new scaffold that constrains the next
growth step. We study the effects of surface and volumetric growth rates, and
of previously deposited shell geometries on the resulting modes of mantle
deformation, and therefore of the developing shell's morphology. Connections
are made to a range of complex shells ornamentations.Comment: Main article is 20 pages long with 15 figures. Supplementary material
is 4 pages long with 6 figures and 6 attached movies. To be published in PLOS
Computational Biolog
āđāļāļāļ āļēāļāļāļ§āļēāļĄāļāļāļāļāļāļāļāļąāđāļ§āļāļāļāđāļĨāļ°āļāļēāļāļāļ°āļ§āļąāļāļāļāļāļŠāļģāļŦāļĢāļąāļāļāļđāđāļāļĢāļīāđāļ āļāļāļĩāđāļāļēāļĻāļąāļĒāđāļāļāļąāļāļŦāļ§āļąāļāđāļāļĩāļĒāļāļĢāļēāļĒ(PREFERENCE MAPPING OF MUNG BEAN SPROUTS AND SUNFLOWER SPROUTS FOR CONSUMERS LIVING IN CHIANG RAI)
āļāļ§āļēāļĄāļŠāļāđāļāļāļāļāļāļđāđāļāļĢāļīāđāļ āļāļāļĩāđāļĄāļĩāļāđāļāļāļēāļŦāļēāļĢāđāļāļ·āđāļāļŠāļļāļāļ āļēāļāļĄāļĩāđāļāļ§āđāļāđāļĄāđāļāļīāđāļĄāļĄāļēāļāļāļķāđāļāđāļāļŦāļĨāļēāļĒāļāļĢāļ°āđāļāļĻāļĢāļ§āļĄāļāļķāļāļāļĢāļ°āđāļāļĻāđāļāļĒ āļāļąāļāļāļ·āļāļāļāļāļĄāļĩāļāļļāļāļŠāļĄāļāļąāļāļīāđāļāļāļēāļĢāļŠāđāļāđāļŠāļĢāļīāļĄāļŠāļļāļāļ āļēāļāđāļĨāļ°āļĒāļąāļāļāđāļ§āļĒāļĨāļāļāļ§āļēāļĄāđāļŠāļĩāđāļĒāļāđāļāļāļēāļĢāđāļāļīāļāđāļĢāļāļāđāļēāļāđ āđāļĄāđāļāļēāļāļāļ°āļ§āļąāļāļāļāļāļāļ°āļĄāļĩāļāļļāļāļāđāļēāļāļēāļāđāļ āļāļāļēāļāļēāļĢāđāļĨāļ°āļĄāļĩāļāļĢāļ°āđāļĒāļāļāļāđāļāļŠāļļāļāļ āļēāļāđāļāđāļāļĢāļīāļĄāļēāļāļāļēāļĢāļāļĢāļīāđāļ āļāļāļēāļāļāļ°āļ§āļąāļāļāļāļāđāļāļāļĢāļ°āđāļāļĻāđāļāļĒāļĒāļąāļāļāļāļĄāļĩāļāļģāļāļ§āļāļāļģāļāļąāļāđāļĄāļ·āđāļāđāļāļĩāļĒāļāļāļąāļāļāļĢāļīāļĄāļēāļāļāļēāļĢāļāļĢāļīāđāļ āļāļāļąāđāļ§āļāļāļ āļāļēāļāļ§āļīāļāļąāļĒāļāļĩāđāļĄāļĩāļ§āļąāļāļāļļāļāļĢāļ°āļŠāļāļāđāđāļāļ·āđāļāļĻāļķāļāļĐāļēāļāļēāļĢāļĒāļāļĄāļĢāļąāļāļāļāļāļāļđāđāļāļĢāļīāđāļ āļāđāļĨāļ°āļ§āļīāđāļāļĢāļēāļ°āļŦāđāļĨāļąāļāļĐāļāļ°āļāđāļāļāļĩāđāļāļ§āļēāļĄāļāļāļāļāļĩāđāļĄāļĩāļāđāļāļāļąāļ§āļāļĒāđāļēāļāļāļąāļāļāļ·āļāļāļāļ āļāļąāđāļ§āļāļāļāđāļĨāļ°āļāļēāļāļāļ°āļ§āļąāļāļāļāļāļāļąāđāļāđāļāļāļŠāļāđāļĨāļ°āļāđāļēāļāļāļēāļĢāļĨāļ§āļ āļāļģāļāļ§āļ 10 āļāļąāļ§āļāļĒāđāļēāļ āļāļđāļāļāļģāļāļēāļĢāļāļĢāļ°āđāļĄāļīāļāļĢāļ°āļāļąāļāļāļēāļĢāļĒāļāļĄāļĢāļąāļāļāļēāļāļāļēāļĢāļŠāļāļāļāļēāļĄāļāļđāđāļāļĢāļīāđāļ āļ āļāļģāļāļ§āļ 114 āļāļ āļāļĩāđāđāļāļĒāļĢāļąāļāļāļĢāļ°āļāļēāļāļāļąāļāļāļ·āļāļāļāļāļāļąāđāļ 2 āļāļāļīāļ āļ§āļīāļāļĩāļāļēāļĢāļ§āļīāđāļāļĢāļēāļ°āļŦāđāļāļĩāđāđāļāđāļāļĢāļ°āļāļāļāļāđāļ§āļĒ āļāļēāļĢāļ§āļīāđāļāļĢāļēāļ°āļŦāđāļāđāļ§āļĒāļāļēāļĢāļāļąāļāļāļĨāļļāđāļĄ āļāļēāļĢāļŠāļĢāđāļēāļāđāļāļāļ āļēāļāļāļ§āļēāļĄāļāļāļāļ āļēāļĒāđāļ āđāļĨāļ°āļāļēāļĢāļ§āļīāđāļāļĢāļēāļ°āļŦāđāđāļāļāļāļāļāļāļĒ āļāļēāļāļāļĨāļāļēāļĢāļāļąāļāļāļĨāļļāđāļĄāļāļđāđāļāļĢāļīāđāļ āļāļāđāļ§āļĒāļāļļāļāļĨāļąāļāļĐāļāļ°āļāļēāļāļāļĢāļ°āļŠāļēāļāļŠāļąāļĄāļāļąāļŠāļāđāļēāļāđ āļāļĢāļ°āļāļāļāļāđāļ§āļĒ āļāļ§āļēāļĄāļāļāļāđāļāļĒāļĢāļ§āļĄ āļāļ§āļēāļĄāļāļāļāđāļāļĨāļąāļāļĐāļāļ°āļāļĢāļēāļāļ āļāļ§āļēāļĄāļāļāļāđāļāļāļĨāļīāđāļāļĢāļŠ āđāļĨāļ°āļāļ§āļēāļĄāļāļāļāđāļāđāļāļ·āđāļāļŠāļąāļĄāļāļąāļŠ āļāļāļ§āđāļēāđāļāļāļļāļāļāļļāļāļĨāļąāļāļĐāļāļ°āļŠāļēāļĄāļēāļĢāļāļāļąāļāļāļĨāļļāđāļĄāļāļđāđāļāļĢāļīāđāļ āļāđāļāđāļāļģāļāļ§āļ 3 āļāļĨāļļāđāļĄāđāļāđāļēāļāļąāļ āđāļāļĒāđāļāļĨāļąāļāļĐāļāļ°āļāļ§āļēāļĄāļāļāļāđāļāļĒāļĢāļ§āļĄ āļāļđāđāļāļĢāļīāđāļ āļ 2 āđāļ 3 āļāļĨāļļāđāļĄāļāļāļāļāļąāļ§āļāļĒāđāļēāļāļāļąāđāļāļāļąāđāļ§āļāļāļāđāļĨāļ°āļāļēāļāļāļ°āļ§āļąāļāļāļāļ āļāļāļ°āļāļĩāđāļāļđāđāļāļĢāļīāđāļ āļāđāļāļāļĨāļļāđāļĄāļāļĩāđāđāļŦāļĨāļ·āļāļāļāļāļāļąāļ§āļāļĒāđāļēāļāļāļąāđāļ§āļāļāļāđāļāļāļŠāļāđāļāđāļēāļāļąāđāļ āļŠāļģāļŦāļĢāļąāļāļāļ§āļēāļĄāļāļāļāđāļāļĨāļąāļāļĐāļāļ°āļāļĢāļēāļāļāļāļāļ§āđāļēāļāļąāļ§āļāļĒāđāļēāļāļāļēāļāļāļ°āļ§āļąāļāļāļāļāļāļĩāđāļāđāļēāļāļāļēāļĢāļĨāļ§āļāđāļāđāļāļāļąāļ§āļāļĒāđāļēāļāļāļĩāđāļāļđāđāļāļĢāļīāđāļ āļāļāļļāļāļāļĨāļļāđāļĄāđāļĄāđāļāļāļ āļāļāļāļāļēāļāļāļąāđāļāļĒāļąāļāļāļāļ§āđāļēāļāļđāđāļāļĢāļīāđāļ āļāļŦāļāļķāđāļāđāļāļŠāļēāļĄāļāļĨāļļāđāļĄāļāļāļāļĨāļąāļāļĐāļāļ°āļāļĢāļēāļāļāļāļāļāļāļąāļ§āļāļĒāđāļēāļāļāļąāđāļ§āļāļāļāļāļļāļāđāļāļāļĄāļēāļāļāļĩāđāļŠāļļāļ āļāļāļ°āļāļĩāđāļāļđāđāļāļĢāļīāđāļ āļāđāļāļāļĩāļāļāļĨāļļāđāļĄāđāļŦāđāļāļ°āđāļāļāļāļ§āļēāļĄāļāļāļāđāļāļĨāļąāļāļĐāļāļ°āļāļĢāļēāļāļāđāļāļāļąāļ§āļāļĒāđāļēāļāļāļēāļāļāļ°āļ§āļąāļāļāļāļāļŠāļāļŠāļđāļāļāļ§āđāļēāļāļąāļ§āļāļĒāđāļēāļāļāļ·āđāļāđ āđāļĨāļ°āđāļāļāļĨāļļāđāļĄāļāļđāđāļāļĢāļīāđāļ āļāļāļĨāļļāđāļĄāļāļĩāđāđāļŦāļĨāļ·āļāļāļāļāļĨāļąāļāļĐāļāļ°āļāļĢāļēāļāļāļāļāļāļāļąāđāļāļāļąāđāļ§āļāļāļāđāļĨāļ°āļāļēāļāļāļ°āļ§āļąāļāļāļāļ āđāļāļŠāđāļ§āļāļāļāļāļāļ§āļēāļĄāļāļāļāļāđāļāļĢāļŠāļāļēāļāļīāļāļāļ§āđāļēāļāļđāđāļāļĢāļīāđāļ āļāļŠāļāļāļāļĨāļļāđāļĄāļĄāļĩāļāļ§āļēāļĄāļāļāļāļāļĩāđāđāļāļāļāđāļēāļāļāļąāļāļāļĒāđāļēāļāļāļąāļāđāļāļ āđāļāļĒāļāļđāđāļāļĢāļīāđāļ āļāļāļĨāļļāđāļĄāļāļĩāđāļŦāļāļķāđāļāļāļāļāļāļĨāļīāđāļāļĢāļŠāļāļāļāļāļąāļ§āļāļĒāđāļēāļāđāļāļāļĨāļ§āļāļāļąāđāļāļŦāļĄāļāļāļāļ°āļāļĩāđāļāļđāđāļāļĢāļīāđāļ āļāļāļĩāļāļāļĨāļļāđāļĄāļāļāļāļāļĨāļīāđāļāļĢāļŠāļāļāļāļāļąāļ§āļāļĒāđāļēāļāđāļāļāļŠāļāļāļąāđāļāļŦāļĄāļ āļāļāļāļāļēāļāļāļąāđāļāđāļāļāļĨāļļāđāļĄāļāļđāđāļāļĢāļīāđāļ āļāļāļĩāđāđāļŦāļĨāļ·āļāļāļ·āļāļāļĨāļļāđāļĄāļāļĢāļīāđāļ āļāļāļĩāđāļāļāļāļāļĨāļīāđāļāļĢāļŠāļāļāļāļāļēāļāļāļ°āļ§āļąāļāļāļāļāļāļąāđāļāđāļāđāļāļāļŠāļāđāļĨāļ°āđāļāļāļĨāļ§āļ āđāļāļāļĢāļāļĩāļāļāļāļāļ§āļēāļĄāļāļāļāđāļāđāļāļ·āđāļāļŠāļąāļĄāļāļąāļŠāļāļāđāļāļ§āđāļāđāļĄāđāļāđāļāđāļāļĩāļĒāļ§āļāļąāļāļāļąāļāļāļ§āļēāļĄāļāļāļāđāļāļāļĨāļīāđāļāļĢāļŠ āđāļāļĒāļāļāļ§āđāļēāļāļđāđāļāļĢāļīāđāļ āļāđāļāļāļĨāļļāđāļĄāļāļĩāđāļŦāļāļķāđāļāļāļāļāđāļāļ·āđāļāļŠāļąāļĄāļāļąāļŠāļāļāļāļāļąāļ§āļāļĒāđāļēāļāđāļāļāļĨāļ§āļāļāļąāđāļāļŦāļĄāļ āđāļĨāļ°āđāļāļāļēāļāļāļĢāļāļāđāļēāļĄāļāļĨāļļāđāļĄāļāļđāđāļāļĢāļīāđāļ āļāļāļĩāļāļāļĨāļļāđāļĄāļāļĨāļąāļāļāļāļāļĨāļąāļāļĐāļāļ°āđāļāļ·āđāļāļŠāļąāļĄāļāļąāļŠāļāļāļāļāļąāļ§āļāļĒāđāļēāļāđāļāļāļŠāļāđāļāđāļēāļāļąāđāļ āđāļāļĒāļāļĨāļļāđāļĄāļāļđāđāļāļĢāļīāđāļ āļāļāļĩāđāđāļŦāļĨāļ·āļāđāļāđāļāļāļĨāļļāđāļĄāļāļĩāđāļāļāļāđāļāļ·āđāļāļŠāļąāļĄāļāļąāļŠāļāļāļāļāļąāđāļ§āļāļāļāļāļąāđāļāđāļāļāļŠāļāđāļĨāļ°āđāļāļāļĨāļ§āļ āļāļĨāļīāđāļāļĢāļŠāđāļāđāļāļĨāļąāļāļĐāļāļ°āļāļĩāđāđāļāđāļāļāļąāļ§āļāđāļāļāļĩāđāļāļĩāđāļŠāļģāļāļąāļāļāļĩāđāļŠāļļāļāļāđāļāļĢāļ°āļāļąāļāļāļ§āļēāļĄāļāļāļāđāļāļĒāļĢāļ§āļĄ āđāļāļ·āđāļāļŠāļąāļĄāļāļąāļŠāđāļāđāļāļāļąāļ§āļāđāļāļāļĩāđāļāļĩāđāļŠāļģāļāļąāļāđāļāļĨāļģāļāļąāļāļāļĩāđāļŠāļāļ āđāļĨāļ°āļĨāļąāļāļĐāļāļ°āļāļĢāļēāļāļāđāļāđāļāļāļąāļ§āļāđāļāļāļĩāđāļāļĩāđāļĄāļĩāļāļ§āļēāļĄāļŠāļģāļāļąāļāļāđāļāļĒāļāļĩāđāļŠāļļāļāļāđāļāļĢāļ°āļāļąāļāļāļ§āļēāļĄāļāļāļāđāļāļĒāļĢāļ§āļĄ āļāđāļāļĄāļđāļĨāļāļĩāđāđāļāđāļāļēāļāļāļēāļāļ§āļīāļāļąāļĒāļāļĩāđāđāļāđāļāļāļĢāļ°āđāļĒāļāļāđāļāđāļāļāļąāļāļāļąāļāļāļēāļāļĨāļīāļāļ āļąāļāļāđāđāļĨāļ°āļāļđāđāļāļĢāļ°āļāļāļāļāļēāļĢāļāļĩāđāļāđāļāļāļāļēāļĢāļāļąāļāļāļēāļāļĨāļīāļāļ āļąāļāļāđāļāļēāļŦāļēāļĢāļāļĩāđāļĄāļĩāļŠāđāļ§āļāļāļŠāļĄāļŦāļĨāļąāļāđāļāđāļāļāļąāļāļāļ·āļāļāļāļāļāļĩāđāđāļāđāļĢāļąāļāļāļēāļĢāļāļĒāļĄāļĢāļąāļāļāļēāļāļāļđāđāļāļĢāļīāđāļ āļāđāļāđāļāđāļĨāļ°āļāļĨāļļāđāļĄāļāļģāļŠāļģāļāļąāļ: āļāļąāđāļ§āđāļāļĩāļĒāļ§ Â āļāļēāļāļāļ°āļ§āļąāļÂ āļāļąāļāļāļ·āļāļāļāļ Â āļāļēāļĢāļĒāļāļĄāļĢāļąāļāļāļāļāļāļđāđāļāļĢāļīāđāļ āļ Â āđāļāļāļ āļēāļāļāļ§āļēāļĄāļāļāļConsumer interest in healthy diet has been increasing in many countries including Thailand. Sprouts exert health-promoting effects and lower the risk of various diseases. Despite their nutritional and health benefits, sunflower sprouts consumption in Thailand is still limited compared with mung bean sprouts. The objectives of this research were to study the consumer acceptance and to identify the driver of liking towards sprout samples. Ten samples of mung bean and sunflower sprouts in both fresh and blanched forms were evaluated by 114 consumers who ever consumed both types of sprouts by asking to rate their acceptance scores. Cluster analysis, internal preference mapping, and regression analysis were analyzed. Three clusters were all found when performing cluster analysis based on overall degree of liking, appearance liking, flavor liking, and texture liking. For overall degree of liking, consumers in 2 of 3 clusters preferred both mung bean and sunflower sprouts whereas consumers in the other cluster preferred only fresh mung bean sprouts. As for appearance liking, blanched sunflower sprouts were not liked by any consumers. It was also found that consumers in one cluster liked the appearance of all mung bean sprouts most while consumers in another cluster gave the higher appearance liking scores on fresh sunflower sprouts. The last cluster was a group of consumers who liked the appearance in both types of sprouts. For flavor liking, there were two big groups of consumers which had opposite flavor liking. One group of consumers liked the flavor of all blanched sprouts, while the other group of consumers preferred the flavor of fresh sprouts. The smallest cluster was the consumers who liked sunflower sprouts in both fresh and blanched forms. In case of texture liking, the same trend was found as flavor liking. One group of consumers liked the texture of blanched sprouts whereas another group liked only fresh sprouts. The other group was a group of consumers who liked the texture of mung bean sprouts in both fresh and blanched forms. Flavor was the most important driver of liking. Texture was the second most important driver of liking and appearance was the least important driver of liking. This work could be useful to product developers or entrepreneurs who want to develop sprout-based products that are acceptable to consumers in each group.Keywords: Mung Bean, Sunflower, Sprout, Consumer Acceptance, Preference Ma
Tuning Structure and Rheology of Silica-Latex Nanocomposites with the Molecular Weight of Matrix Chains: A Coupled SAXS-TEM-Simulation Approach
The structure of silica-latex nanocomposites of three matrix chain masses
(20, 50, and 160 kg/mol of poly(ethyl methacrylate)) are studied using a
SAXS/TEM approach, coupled via Monte Carlo simulations of scattering of fully
polydisperse silica nanoparticle aggregates. At low silica concentrations (1
vol. %), the impact of the matrix chain mass on the structure is quantified in
terms of the aggregation number distribution function, highest mass leading to
individual dispersion, whereas the lower masses favor the formation of small
aggregates. Both simulations for SAXS and TEM give compatible aggregate
compacities around 10 vol. %, indicating that the construction algorithm for
aggregates is realistic. Our results on structure are rationalized in terms of
the critical collision time between nanoparticles due to diffusion in viscous
matrices. At higher concentrations, aggregates overlap and form a percolated
network, with a smaller and lighter mesh in the presence of high mass polymers.
The linear rheology is investigated with oscillatory shear experiments. It
shows a feature related to the silica structure at low frequencies, the
amplitude of which can be described by two power laws separated by the
percolation threshold of aggregates
Construction d'un modÃĻle des flux de biomasses pour analyser avec les acteurs l'impact de l'introduction de l'agriculture de conservation sur la gestion de la fertilitÃĐ Ã l'ÃĐchelle du territoire villageois. Cas du Burkina Faso
International audienceLe dÃĐveloppement de la traction animale se sont traduits par une extension des surfaces cultivÃĐes et des tensions croissantes pour l'utilisation de l'espace agropastorale et des rÃĐsidus de rÃĐcolte. La recherche/dÃĐveloppement a promu des pratiques et technologies innovantes telles que les fosses fumures ou l'agriculture de conservation qui accentuent l'appropriation des rÃĐsidus de cultures et vraisemblablement les tensions à l'ÃĐchelle du territoire villageois. L'objectif de cet article est de prÃĐsenter un modÃĻle conceptuel d'analyse avec les acteurs de l'impact de l'agriculture de conservation. Cette ÃĐtude à ÃĐtÃĐ menÃĐe dans deux villages du Burkina situÃĐs en zones soudanienne et soudanosahÃĐlienne. Une cinquantaine de producteurs ont ÃĐtÃĐ enquÊtÃĐs afin de dÃĐcrire les ÃĐchanges de biomasses au sein de l'exploitation ainsi qu'avec les autres producteurs du village. Le modÃĻle conceptuel est composÃĐ de trois entitÃĐs. L'entitÃĐ exploitation qui est le lieu ou les dÃĐcisions sont prises pour les diverses pratiques (les changements des pratiques d'utilisation de terre, la gestion de la fertilitÃĐ, etc.), l'entitÃĐ parcelle oÃđ sont mises en oeuvre ces pratiques et qui ont une influence sur la fertilitÃĐ de sol et l'entitÃĐ bÃĐtail car les animaux par leurs activitÃĐs participent au transfert de la fertilitÃĐ et au flux de biomasses. Cet outil reste à implÃĐmenter sous la plateforme Cormas (Common-pool resources and multiagents systems) afin de rÃĐaliser des simulations avec la modÃĐlisation multi-agent. Il sera utilisÃĐ en tant qu'outil de discussion concernant diffÃĐrents scÃĐnarios d'agriculture de conservation co-construits avec les acteurs impliquÃĐs au sein des plateformes d'innovation mises en place dans le cadre du projet Abaco qui vise à expÃĐrimenter cette technique
SynthÃĻse de nouveaux tensioactifs macromolÃĐculaires complexants et ÃĐtude de leurs interactions avec le cobalt pour le dÃĐveloppement d'un procÃĐdÃĐ de dÃĐcontamination des textiles en milieu CO2 dense
Cette ÃĐtude porte sur la dÃĐcontamination de matrices textiles en milieu CO2 dense (CO2 liquide ou CO2 supercritique). Elle s'inscrit dans le cadre de la dÃĐcontamination des textiles utilisÃĐs dans l'industrie nuclÃĐaire. Le CO2 dense est proposÃĐ comme alternative au milieu aqueux utilisÃĐ dans le procÃĐdÃĐ actuel et qui gÃĐnÃĻre une importante quantitÃĐ d'effluents aqueux contaminÃĐs nÃĐcessitant un post-traitement. Le contaminant ÃĐtudiÃĐ est le cobalt qui peut se prÃĐsenter sous forme ionique ou particulaire. L'extraction du cobalt en milieu CO2 dense est assurÃĐe par un additif : un tensioactif macromolÃĐculaire CO2-phile/CO2-phobe complexant. Plusieurs familles d'additifs ont ÃĐtÃĐ synthÃĐtisÃĐes par polymÃĐrisation radicalaire contrÃīlÃĐe : des copolymÃĻres à gradient comportant des motifs CO2-philes, siliciÃĐs ou fluorÃĐs, et des motifs CO2-phobes complexants de types acÃĐtoacÃĐtoxys, diÃĐthylphosphonates ou acides phosphoniques. Le comportement de ces copolymÃĻres dans le CO2 dense a ÃĐtÃĐ ÃĐvaluÃĐ grÃĒce à la dÃĐtermination des diagrammes de phases copolymÃĻre-CO2 (par la mesure du point de trouble) et grÃĒce à l'ÃĐtude de leur autoorganisation dans le CO2 dense (par diffusion de neutrons aux petits angles). Les copolymÃĻres fluorÃĐs se sont avÃĐrÃĐs Être les plus avantageux en termes de solubilitÃĐ. NÃĐanmoins, les copolymÃĻres siliciÃĐs prÃĐsentent une solubilitÃĐ compatible avec le procÃĐdÃĐ et ils constituent donc une alternative intÃĐressante pour ÃĐviter la prÃĐsence de fluor gÊnant pour le conditionnement des dÃĐchets nuclÃĐaires. L'ÃĐtude de la complexation du cobalt par les copolymÃĻres (par spectromÃĐtrie UV-visible et par torche à plasma couplÃĐe à un spectromÃĻtre d'ÃĐmission atomique) a permis d'ÃĐtablir des relations entre le type de motif complexant et l'affinitÃĐ avec le cobalt. La solubilitÃĐ dans le CO2 dense de ces complexes copolymÃĻres-cobalt est comparable à celle des copolymÃĻres seuls. De plus, l'ÃĐtude de l'auto-organisation en milieu CO2 dense a rÃĐvÃĐlÃĐ un faible taux d'agrÃĐgation des complexes copolymÃĻres-cobalt. Enfin, les copolymÃĻres synthÃĐtisÃĐs ont ÃĐtÃĐ mis en oeuvre dans les procÃĐdÃĐs de dÃĐcontamination particulaire et ionique. Dans le cas du procÃĐdÃĐ de dÃĐcontamination ionique, l'emploi du copolymÃĻre à gradient poly(acrylate de 1,1,2,2-tÃĐtrahydroperfluorodÃĐcyle-co-diacide vinylbenzylphosphonique) a permis d'atteindre environ 70% de dÃĐcontamination grÃĒce à la formation d'une microÃĐmulsion d'eau dans le CO2 dense. L'efficacitÃĐ du procÃĐdÃĐ dedÃĐcontamination a ÃĐtÃĐ portÃĐe à 97% grÃĒce à l'emploi de pyridine comme tiers additif.This study is about textile decontamination in dense CO2 (liquid CO2 or supercritical CO2). The study is carried out in the framework of decontamination of textile used in the nuclear industry. The dense CO2 offers an alternative to aqueous medium used in the current process which generates a huge quantity of contaminated aqueous effluent requiring a post-treatment. Cobalt is the targeted contamination and can be found as ionic species or particles. The cobalt extraction in dense CO2 is achieved with an additive : a complexing CO2-philic/CO2-phobic macromolecular surfactant. Several types of additives were synthesized by controlled free radical polymerization : gradient copolymers made with CO2-philic groups (silicone-based or fluorinated moieties) and CO2-phobic complexing groups (acetoacetoxy, diethylphosphonate or phosphonic acid moieties). The copolymer behavior in dense CO2 was determined by phase diagram measurements (cloud point method) and their self-assembly in dense CO2 was investigated by small angle neutron scattering. The fluorinated copolymers were found advantageous in terms of solubility. Nevertheless, the silicone-based copolymers showed solubilities which are compatible with the process, therefore they are a good alternative to avoid fluorinated compounds which are unwanted in the conditioning of nuclear wastes. The study of cobalt complexation by the copolymers (UV-vis spectroscopy and inductively coupled plasma-mass spectroscopy) established relations between the type of complexing group and the affinity with the cobalt. The solubility of copolymer-cobalt complexes in dense CO2 is similar to those of copolymers. Moreover, the self-assembly study of the complex revealed a low aggregation. Finally, the synthesized copolymers were used in particle or ionic decontamination processes. In the case of ionic decontamination process, a rate of 70% of decontamination was reached with the use of gradient copolymer poly(1,1,2,2-tetrahydroperfluorodecyle acrylate-covinylbenzylphosphonic diacid) which allowed the formation of water-in-CO2 microemulsion. The efficiency of the decontamination process was even improved up to 97% with the addition of pyridine in the process.MONTPELLIER-Ecole Nat.Chimie (341722204) / SudocSudocFranceF
Mechanical basis of morphogenesis and convergent evolution of spiny seashells
Convergent evolution is a phenomenon whereby similar traits evolved independently in not closely related species, and is often interpreted in functional terms. Spines in mollusk seashells are classically interpreted as having repeatedly evolved as a defense in response to shell-crushing predators. Here we consider the morphogenetic process that shapes these structures and underlies their repeated emergence. We develop a mathematical model for spine morphogenesis based on the mechanical interaction between the secreting mantle edge and the calcified shell edge to which the mantle adheres during shell growth. It is demonstrated that a large diversity of spine structures can be accounted for through small variations in control parameters of this natural mechanical process. This physical mechanism suggests that convergent evolution of spines can be understood through a generic morphogenetic process, and provides unique perspectives in understanding the phenotypic evolution of this second largest phylum in the animal kingdom.\ud
\ud
Homoplasy, the appearance of similar traits in separate evolutionary lineages as a result of convergence, parallelism, or evolutionary reversals, is a major concern in phylogenetic analysis for which it is viewed as noise. However, over the past two decades, homoplasy has also become a subject of increasing interest, stimulated by the rise of evolutionary developmental biology (evo devo) and the wish to uncover the developmental basis of this phenomenon (1ââ3). Spines constitute the most prominent ornamentation of mollusk shells and have evolved in many distantly related fossil and current mollusk species (at least 55 genera and 21 families of current gastropods; 10 genera and 8 families of current bivalves; 11 genera and 8 families of ammonoids; and 6 fossil nautiloid genera; see Fig. 1 for examples). Convergent evolution of spines in mollusks has been addressed in functional terms, these structures being interpreted as having evolved as a defense in response to shell-crushing predators (4ââ6). This hypothesis is itself the basis of the widely cited âescalation hypothesis,â according to which long-term trends in the fossil record were caused by the evolutionary response of prey to predation pressure (7). The idea that convergent evolution of similar mollusk ornamentations might be fully explained in functional terms is based on the premise that similar characters, perceived as well designed for a presumed function, cannot conceivably have independently evolved fortuitously. Therefore, natural selection is thought to have repeatedly shaped similar functional traits out of random variations
- âĶ