Effects of Smoking on Lipid Content, Macromolecular Structure and Rheological Properties of Hevea brasiliensis Sheet Rubber

ABSTRACT Natural rubber ribbed smoked sheet (RSS) production process involves a drying step in a wood smoke dryer. The purpose of this work was to know whether this smoke drying step affected the lipid composition and the properties of sheet rubber. This study consisted of a comparative study between unsmoked sheets (USS) and ribbed smoked sheets (RSS) obtained from monoclonal latices from RRIM600, BPM24 and PB235 clones. The rubber was sampled in Chantaburi province, Thailand. It was found that the smoking process increased significantly the amount of lipid extract but decreased significantly the free fatty acid content. No significant effect of smoking was detected on macromolecular parameters such as gel content or molar mass distribution and on rheological parameters such as initial plasticity (P 0 ) and Mooney viscosity (ML (1+4)100 ). In terms of resistance to thermal oxydation estimated by Plasticity retention index (PRI), smoked sheets displayed a tendency to have lower PRI than unsmoked sheets. This difference was significant for PB235 clone. A clonal effect was detected for most of the measured parameters. Indeed, PB235 clone displayed a higher lipid extract, higher P 0 , higher ML (1+4)100 , higher molar mass than those of the other studied clones while its PRI was lower

The CHEOPS mission

The CHaracterising ExOPlanet Satellite (CHEOPS) was selected in 2012, as the first small mission in the ESA Science Programme and successfully launched in December 2019. CHEOPS is a partnership between ESA and Switzerland with important contributions by ten additional ESA Member States. CHEOPS is the first mission dedicated to search for transits of exoplanets using ultrahigh precision photometry on bright stars already known to host planets. As a follow-up mission, CHEOPS is mainly dedicated to improving, whenever possible, existing radii measurements or provide first accurate measurements for a subset of those planets for which the mass has already been estimated from ground-based spectroscopic surveys and to following phase curves. CHEOPS will provide prime targets for future spectroscopic atmospheric characterisation. Requirements on the photometric precision and stability have been derived for stars with magnitudes ranging from 6 to 12 in the V band. In particular, CHEOPS shall be able to detect Earth-size planets transiting G5 dwarf stars in the magnitude range between 6 and 9 by achieving a photometric precision of 20 ppm in 6 hours of integration. For K stars in the magnitude range between 9 and 12, CHEOPS shall be able to detect transiting Neptune-size planets achieving a photometric precision of 85 ppm in 3 hours of integration. This is achieved by using a single, frame-transfer, back-illuminated CCD detector at the focal plane assembly of a 33.5 cm diameter telescope. The 280 kg spacecraft has a pointing accuracy of about 1 arcsec rms and orbits on a sun-synchronous dusk-dawn orbit at 700 km altitude. The nominal mission lifetime is 3.5 years. During this period, 20% of the observing time is available to the community through a yearly call and a discretionary time programme managed by ESA.Comment: Submitted to Experimental Astronom

Synthese et etude de resines microlithographiques styreniques siliciees sensibles aux UV lointains et resistantes aux plasmas d'oxygene

SIGLEINIST T 77047 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

An uncommon cause of allergic fungal sinusitis: Rhizopus oryzae.

International audienceWe report what we believe is the first case of allergic fungal rhinosinusitis (AFRS) caused by the fungus Rhizopus oryzae. Our patient was a 32-year-old woman who presented with unilateral nasal polyps and chronic nasal dysfunction. Computed tomography of the sinuses detected left-sided pansinusitis and bone erosion. T2-weighted magnetic resonance imaging demonstrated a signal void that suggested the presence of a fungal infection. The patient underwent unilateral ethmoidectomy. Histologic examination of the diseased tissue identified allergic mucin with 70% eosinophils and no fungal hyphae. Mycologic culture detected R oryzae. After a short period of improvement, the patient experienced a recurrence, which was confirmed by radiology. A second surgery was performed, and the same fungal hyphae were found in the mucus and on culture, which led us to suspect AFRS. Since no IgE test for R oryzae was available, we developed a specific immunologic assay that confirmed the presence of specific IgG, which identified a high degree of immunologic reaction against our homemade R oryzae antigens. With a long course of systemic antifungal treatment, the patient's symptoms resolved and no recurrence was noted at 5 years of follow-up

Characterization of natural rubber using siez-exclusion chromatography with online multi-angle light scattering. Study of the phenomenon behind the abnormal elution profile

Correspondance: [email protected] audienceNatural and synthetic poly(cis-1,4-isoprene) were characterized by size-exclusion chromatography coupled with an online multi-angle light scattering detector (SEC-MALS) Unlike synthetic poly (cis-1,4- isoprene) (SR), natural rubber (NR) samples showed anomalous elution profiles. The beginning of elution was very similar to SR but, after a certain elution volume, the molar masses of the eluting macromolecules increased with elution volume instead of continuing to decrease, which resulted in an upturn curve profile. Adding tetrabutylammonium bromide (TBABr) to THF (solvent and mobile phase) removed this phenomenon. In addition. using different concentrations of TBABr showed that TBABr had two simultaneous actions. TBABr reduced the abnormal elution profiles and the quantity of aggregates (insoluble part or gel). These results mean that the main phenomenon involved in abnormal elution was delayed entities adsorbing on the column packing. Their delayed elution was responsible for the artificial increase in molar masses, especially at high elution volumes. The results obtained suggest that these entities are very compact and have a sphere-like structure

Coagulation methods and drying step are the key drivers of the dynamics of structuration of natural rubber during the maturation of coagula

International audienceThe evolution of the mesostructure (structuring dynamics) of natural rubber (NR) during maturation after different modes of coagulation is poorly known, especially inside wet coagula. Therefore, coagula made from 3 different coagulation modes (sulfuric acid, formic acid, and natural coagulations) with different maturation durations (0, 2, 9, 16, 30, and 44 days) were studied. The mesostructure of NR samples was analyzed using SEC-MALS on wet coagula and on wet and dry crepes. For wet coagula coagulated with acids, only Mz and Mw decreased slightly with maturation time, while Mn and Gel>1 mu had no significant evolution during maturation. On the other hand, for wet coagula after natural coagulation, all mesostructure indicators evolved significantly with maturation time. The results showed that structuration increased along maturation time, generating microaggregates with larger size and more structured macrogel inside wet coagula after natural coagulation. This study found that creping process (comparison of wet coagula and wet crepes) had only a moderate effect on the structuration of NR samples. However, the drying process (comparison of wet and dry crepes) had an important effect on the structuration of rubber, especially for natural coagulation and formic acid coagulation. Coagulation with sulfuric acid appeared to slow down the phenomena related to the structuration of microaggregates and macrogel