SFGP 2007 - Investigation of a Novel Principle of Chemical Grafting for Modification of Cellulose Fibers

Natural cellulose fibres have been employed for packaging applications for a long time. Their use, however, has been hampered by their high hydrophilicity and their moisture sensitivity. It has, thus, been proposed to circumvent this problem through the hydrophobic modification of their surface thanks to the use of molecular grafting approaches. In this work, we describe the use of a novel solvent-free chemical pathway for molecular grafting that we have coined chromatogenic chemistry. It involves a reaction between a solid substrate and a reagent which is in a vapour-liquid equilibrium and diffuses within the solid substrate through a mechanism of adsorption/desorption akin to gas chromatography. Chromatogenic chemistry phenomenon has been studied and modelled through the extensive use of a new specific test, the Droplet Surface Migration Test. It involves the deposition upon a porous substrate of a small amount of reagent and in studying its subsequent migration and grafting. Whatman paper and various long chain acid chlorides were used for this modelling. The acid chloride carboxylic ends react with the external hydroxyl groups of cellulose fibres to give rise to the formation of long chain hydrophobic ester bonds. Upon immersion of the paper sheet in distilled water, a hydrophobic spot, extending well over the initial depot zone, could then be clearly visualized, allowing to follow conveniently the reagent migration and reaction. Grafting densities were performed by using the HPLC technique. The results obtained through the use of this test allowed a better understanding of chromatogenic chemistry phenomenon and an identification of the main parameters which affect the process: the nature of the reagent, the temperature, the reaction time, the nature of the substrate, etc. We have more particularly shown that the diffusion and grafting yields were maximal for a specific temperature which increases with the boiling point and therefore with the chain length of the reagents. We have proposed that this temperature should correspond to a compromise between the diffusion and reactivity properties of the reagent, its evaporation and its degradation by hydrolysis

A comparison of leaf crystal macropatterns in the two sister genera Piper and Peperomia (Piperaceae)

Premise of the study: This is the first large-scale study comparing leaf crystal macropatterns of the species-rich sister genera Piper and Peperomia. It focuses on identifying types of calcium oxalate crystals and their macropatterns in leaves of both genera. The Piper results are placed in a phylogenetic context to show evolutionary patterns. This information will expand knowledge about crystals and provide specific examples to help study their form and function. One example is the first-time observation of Piper crystal sand tumbling in chlorenchyma vacuoles. Methods: Herbarium and fresh leaves were cleared of cytoplasmic content and examined with polarizing microscopy to identify types of crystals and their macropatterns. Selected hydrated herbarium and fresh leaf punches were processed for scanning electron microscopy and x-ray elemental analysis. Vibratome sections of living Piper and Peperomia leaves were observed for anatomical features and crystal movement. Key results: Both genera have different leaf anatomies. Piper displays four crystal types in chlorenchyma-crystal sand, raphides, styloids, and druses, whereas Peperomia displays three types-druses, raphides, and prisms. Because of different leaf anatomies and crystal types between the genera, macropatterns are completely different. Crystal macropattern evolution in both is characterized by increasing complexity, and both may use their crystals for light gathering and reflection for efficient photosynthesis under low-intensity light environments. Conclusions: Both genera have different leaf anatomies, types of crystals and crystal macropatterns. Based on Piper crystals associated with photosynthetic tissues and low-intensity light, further study of their function and association with surrounding chloroplasts is warranted, especially active crystal movement

compte rendu d'ouvrage: Persyn-Vialard, Sandrine, La linguistique de Karl Bühler, Examen critique de la Sprachtheorie et de sa filiation

Histoire Epistémologie Langage, 30, 1, 163-165compte rendu de: Persyn-Vialard, Sandrine, La linguistique de Karl Bühler, Examen critique de la Sprachtheorie et de sa filiation, Presses Universitaires de Rennes, 2005, 280 p., ISBN 2-7535- 0149-1

Verhuellia is a segregate lineage in Piperaceae: more evidence from flower, fruit and pollen morphology, anatomy and development

Background and Aims The perianthless Piperales, i.e. Saururaceae and Piperaceae, have simple reduced flowers strikingly different from the other families of the order (e.g. Aristolochiaceae). Recent molecular phylogenies proved Verhuellia to be the first branch in Piperaceae, making it a promising object to study the detailed structure and development of the flowers. Based on recently collected material, the first detailed study since 1872 was conducted with respect to morphology, anatomy and development of the inflorescence, pollen ultrastructure and fruit anatomy. Methods Original Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Light Microscopy (LM) observations on Verhuellia lunaria were compared with Piperaceae, Saururaceae and fossils. Key results The inflorescence is an indeterminate spike with sessile flowers, each in the axil of a bract, developing in acropetal, helical succession. Flowers consist of two (occasionally three) stamens with basifixed tetrasporangiate anthers and latrorse dehiscence by a longitudinal slit. The gynoecium lacks a style but has three to four stigma branches and a single, basal orthotropous, and unitegmic ovule. The fruit is a drupe with large multicellular epidermal protuberances. The pollen is very small, inaperturate, and areolate with hemispherical microechinate exine elements. Conclusions Despite the superficial similarities with different genera of Piperaceae and Saururaceae, the segregate position of Verhuellia revealed by molecular phylogenetics is supported by morphological, developmental and anatomical data presented here. Unitegmic ovules and inaperturate pollen, which are synapomorphies for the genus Peperomia, are also present in Verhuellia

A New Application of the Lunar Laser Retroreflectors: Searching for the "Local" Hubble Expansion

Precise measurements of the Earth-Moon distance by the lunar laser ranging (LLR), which begun in the early 1970's, contributed significantly to geodesy, geophysics, and lunar planetology, as well as enabled astrophysicists to perform several fine tests of the relativistic gravitational field theory (General Relativity). Yet another promising application of LLR arises just now in the context of recent cosmological models, whose dynamics is substantially affected by some kinds of the dark matter (or the so-called "dark energy") uniformly distributed in space, and therefore should be accompanied by some residual Hubble expansion at any spatial scales, particularly, in the Earth-Moon system. The "local" Hubble expansion can be revealed by comparing the rate of increase in the lunar semi-major axis measured by LLR (which should be produced both by the well-known tidal exchange of angular momentum between the Earth and Moon and the local Hubble expansion) with the same quantity derived indirectly from astrometric data on the Earth's rotation deceleration (which is produced only by the tidal interaction). Such analysis really points to the discrepancy 1.3 cm/yr, which corresponds to the local Hubble constant H_0^(loc) = 33 +/- 5 (km/s)/Mpc. This value is about two times less than at intergalactic scales but many orders of magnitude greater than was predicted in earlier theoretical works.Comment: Single PS file, 6 pages, submitted to "Advances in Space Research". Substantial new explanations, requested by the reviewers', were introduced; minor misprints were correcte

Characterization of non-aged and aged modern Prussian Blue pigments by Mössbauer spectroscopy, x-ray powder diffraction and x-ray absorption spectroscopy

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Consistency between hydrological model, large aperture scintillometer and remote sensing based evapotranspiration estimates for a heterogeneous catchment

The catchment averaged actual evapotranspiration rate is a hydrologic model variable that is difficult to quantify. Evapotranspiration rates - up till present - cannot be continuously observed at the catchment scale. The objective of this paper is to estimate the evapotranspiration rates (or its energy equivalent, the latent heat fluxes LE) for a heterogeneous catchment of 102.3 km(2) in Belgium using three fundamentally different algorithms. One possible manner to observe this variable could be the continuous measurement of sensible heat fluxes (H) across large distances (in the order of kilometers) using a large aperture scintillometer (LAS), and converting these observations into evapotranspiration rates. Latent heat fluxes are obtained through the energy balance equation using a series of sensible heat fluxes measured with a LAS over a distance of 9.5 km in the catchment, and point measurements of net radiation (R-n) and ground heat flux (G) upscaled to catchment average through the use of TOPLATS, a physically based land surface model. The resulting LE-values are then compared to results from the remote sensing based surface energy balance algorithm ETLook and the land surface model. Firstly, the performance of ETLook for the energy balance terms has been assessed at the point scale and at the catchment scale. Secondly, consistency between daily evapotranspiration rates from ETLook, TOPLATS and LAS is shown

Evolutionary dynamics of hom(oe)ologous haplotypes (bacs) within the highly polyploid sugarcane genome

Sugarcane (Saccharum spp.) has been recognized as one of the world's most efficient crops in converting solar energy into chemical energy and having the most favorable input/output ratio. Beside its importance for sugar production it is thus also a primary energy crop. Sugarcane also presents one the most complex crop genomes studied to date. Modern sugarcane cultivars derive from the combination of two polyploid species: S. officinarum, the domesticated sugar-producing species with x=10 and 2n=8x=80, and S. spontaneum, a vigorous wild species with x=8 and 2n=5x=40 to 16x=128 and many aneuploid forms. Both species are thought to have an autopolyploid origin. Modern sugarcanes are highly polyploid (more than decaploid) and aneuploid, with around 120 chromosomes and a genome size of around 10 Gb. They typically display 70 to 80% of chromosomes entirely derived from S. officinarum, 10 to 20% from S. spontaneum and a few chromosomes derived from interspecific recombination. Their meiosis mainly involves bivalent pairing and chromosome assortment results from a combination of polysomy and preferential pairing. We investigated genome dynamics in this highly polyploid context by analyzing the sequence of hom(oe)ologous haplotypes (BAC clones) from the sugarcane cultivar R570. We first analyzed two homoeologous haplotypes from a gene-rich region bearing the Adh1 gene (Jannoo et al 2007), knowing that this region has been thoroughly studied within the Poaceae family. We then analyzed seven hom(oe)ologous haplotypes from a second gene-rich region. Our results indicated that the two Saccharum species diverged 1.5-2 mya from one another and 8-9 mya from sorghum. The sugarcane hom(oe)ologous haplotypes showed a very high colinearity as well as very high gene structure and sequence conservation. A high homology was also observed along the non-transcribed regions to the exception of transposable elements (TEs). Conversely, TEs that represent in average 33% of the BAC clones studied, were not conserved between hom(oe)ologous haplotypes. Compared to sorghum, the sugarcane haplotypes displayed a high colinearity and a remarkable homology in most of the non-coding parts of the genome. On this basis, the high ploidy of sugarcane does not seem to have induced a major reshaping of its genome (at least at the gene level). In addition, the coexistence of potentially in average 12 hom(oe)ologous alleles at each locus does not seems to induce a decrease of conservative selection at the gene sequence level. (Texte intégral