490 research outputs found
New families of 5-hydroxymethylfurfural derived biopolymers via acyclic diene metathesis polymerization
No full textDiminishing oil reserves, increasing demand, and the rising costs of petroleum-based raw materials associated with waste production have has encouraged the industry to seek substitute feedstocks from renewable sources especially for plastics [1]. As a result, the interest in polymers synthesized from natural resources - such as polysaccharides, lignin and furan-based derivatives - has been growing worldwide. Among these compounds, 5-(hydroxymethyl)furfural (HMF)- synthesized easily from a carbohydrate source (mainly fructose) in high yield [2]- has quickly become the archetype of the bio-based platform chemicals having a wide range of applicability. HMF incorporates two functional units and an aromatic structure that renders this compound a versatile structure for the production of various derivatives. This derivatives in turn may be used as monomers for the synthesis of a selection of bio-based polymers. One well known example are polymers based on 2,5-furandicarboxylic acid (FDCA): poly(ethylene-2,5-furandicarboxylate) (PEF) and poly(butylene-2,5-furandicarboxylate) (PBF), which have the potential to replace their petroleum-derived counterparts: polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) [3], due to their enhanced thermal an mechanical properties. Although over the past few years furan-based polymers have gathered special attention in the scientific community, their industry it’s still in its infancy. With that in mind, in this project we developed new furanic bio monomers, starting from HMF, that can be used has building block to synthetize via addition polymerization and acyclic diene metathesis (ADMET) polymerization, several families of furanic based biopolymers. The structure and the properties of the novel furanic-based polymers were then studied to evaluate their potential industrial applications
The Effects of a "Fat Tax" on the Nutrient Intake of French Households
No full textThis article assesses the effects of a "fat tax" on the nutrient intake of French households across different income groups using a method that estimates the nutrient elasticities of French households. We estimate a complete demand system by aggregating an individual demand system over cohorts. The use of a cohort model is justified by the incompleteness of our data. We find that a "fat tax" would have ambiguous and extremely small effects on the nutrient intake of French households, and its associated economic welfare costs would be similarly weak.Household survey data, demand system, nutrient elasticities., Food Consumption/Nutrition/Food Safety,
New families of 5-hydroxymethylfurfural derived biopolymers
No full textDiminishing oil reserves, increasing demand, and the rising costs of petroleum-based raw materials associated with waste production has encouraged the plastic industry to seek substitute feedstocks from renewable sources [1]. As a result, the interest in polymers synthesized from natural resources - such as polysaccharides, lignin and furan-based derivatives - has been growing worldwide. One of these compounds, 5-(hydroxymethyl)furfural (HMF), which can be produced easily and in high yield from a carbohydrate source (mainly fructose) [2], has quickly emerged as the prototypical bio-based platform chemical with a broad range of applications. Having both aldehyde and alcohol functional groups and an aromatic structure HMF is considered a versatile starting material for a variety of high value chemicals that can be used as monomers for the synthesis of a selection of bio-based polymers. One very promising example are polymers based on 2,5-furandicarboxylic acid (FDCA): poly(ethylene-2,5-furandicarboxylate) (PEF) and poly(butylene-2,5-furandicarboxylate) (PBF), which have the potential to replace their petroleum-derived counterparts: polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) [3], due to their enhanced thermal an mechanical properties. Although furan-based polymers have received particular attention from the scientific community in recent years, the industry is still in its infancy. With this in mind, this project developed a new furan bio-monomers starting from HMF, that can be used has building block to synthetize via addition polymerization and acyclic diene metathesis (ADMET) polymerization, several families of furanic based biopolymers. The structure and the properties of the novel furanic-based polymers were then studied to evaluate their potential industrial applications.
[1] R. Bielski and G. Grynkiewicz, “Furan platform chemicals beyond fuels and plastics,” Green Chemistry, vol. 23, no. 19, pp. 7458–7487, Oct. 2021
[2] G. Trapasso, G. Mazzi, B. Chícharo, M. Annatelli, D. Dalla Torre, and F. Aricò, “Multigram Synthesis of Pure HMF and BHMF,” Organic Process Research and Development, vol. 26, no. 10. American Chemical Society, pp. 2830–2838, Oct. 21, 2022
[3] M. Jiang, Q. Liu, Q. Zhang, C. Ye, and G. Zhou, “A series of furan-aromatic polyesters synthesized via direct esterification method based on renewable resources,” J Polym Sci A Polym Chem, vol. 50, no. 5, pp. 1026–1036, Mar. 201
Bloggerati, Twitterati: How Blogs and Twitter are transforming popular culture
No full textThe author investigates the use and functions of two social media -blogs and twitter- and their role in the American society
Le discours mystificateur chez Alphonse Allais /
No full textThrough the use of the texts published from 1893 to 1903 by Alphonse Allais, we analyse what we call the mystifying discourse, in other words the power of fiction. We show how the author succeeds to deceive the reader. We emphasize the artificial aspects of the language and the style used by Allais to make fun of his readers. This technical study of the writing of Allais allows us to compare with other kinds of works, notably the dreamlike images and the vaudeville.We study therefore the tricks and the traps of the language employed by Allais with the aim of laughing at our expectations. From this point, we will demonstrate that, most of the time, a rupture between the conclusion and the beliefs of the readers exists regarding the fiction which is presented in the tales. Emphasizing the absurd in the texts, we accentuate the various literary techniques. As a result, we illustrate how the humour of Alphonse Allais turns out to be a technical work
Three Families of Furan-Based α,ω-Diene Monomers
No full textEven though furan-based polymers have attracted the attention of the scientific community, their exploitation is still in its infancy and mostly focussed on polymers derived from furan 2,5-furandicarboxylic acid (FDCA). Various polycondensation methods have been used for the synthesis of FDCA-derived furanic polyesters[1] that often require harsh reaction conditions, environmentally hazardous procedures and limited control over the polymer structures. In turn, acyclic diene metathesis (ADMET) as the advantage to synthesize polymers with precise control over polymer structures under mild conditions.[2] In this view, over the last few years, we have focussed our research on preparing a library of new furanics biomonomers, namely furanic α,ω-diene monomers (Figure 1) that will then be used to prepare several families of biopolymers via Acyclic Diene Metathesis (ADMET) polymerization
Thiol-Ene UV-Cured Biodegradable Coatings from α,ω-Diene Furanic Monomers
No full textBiobased monomers are gaining significant attention in today’s global efforts toward sustainable development. C6-furanic platform chemicals, derived from biomass, are considered to be promising building blocks for biorefineries, offering the potential for the development of sustainable polymer materials. This study investigates the synthesis and photocuring of two biobased α,ω-diene furanic monomers─diallyl furandicarboxylate ester (All-FDE) and diallyl furanmethyl carbonate (All-FMC)─for use in UV-cured coatings. These monomers, derived from renewable resources and synthesized using green chemistry principles, were used in thiol-ene photocuring reactions with trimethylolpropane tris(3-mercaptopropionate) as the thiol. Real-time FTIR and photo-DSC analyses showed rapid, near-complete conversion under UV light. All-FDE formulations exhibited higher glass transition temperatures (Tg) compared to All-FMC due to increased cross-linking density. Both materials were fully degradable in alkaline conditions, with All-FDE degrading faster. This research demonstrates the potential of biobased monomers for ecofriendly, degradable coatings via UV curing
Implementation of an Enzyme Membrane Reactor to Intensify the α-O-Glycosylation of Resveratrol Using Cyclodextrins
No full textThis Book Chapter is a republication of an article published by Florent Allais, et al. at Pharmaceuticals in April 2021. (Ioannou, I.; Barboza, E.; Willig, G.; Marié, T.; Texeira, A.; Darme, P.; Renault, J.-H.; Allais, F. Implementation of an Enzyme Membrane Reactor to Intensify the α-O-Glycosylation ofResveratrol Using Cyclodextrins. Pharmaceuticals 2021, 14, 319. https://doi.org/10.3390/ph14040319)International audienceThe O-glycosylation of resveratrol increases both its solubility in water and its bioavailability while preventing its oxidation, allowing a more efficient use of this molecule as bioactive ingredient in pharmaceutical and cosmetic applications. Resveratrol O-glycosides can be obtained by enzymatic reactions. Recent developments have made it possible to obtain selectively resveratrol α-glycosides from the β-cyclodextrin-resveratrol complex in water with a yield of 35%. However, this yield is limited by the partial hydrolysis of the resveratrol glycosides produced during the reaction. In this study, we propose to intensify this enzymatic reaction by coupling the enzymatic reactor to a membrane process. Firstly, membrane screening was carried out at the laboratory scale and led to the choice of a GE polymeric membrane with a cutoff of 1 kDa. This membrane allowed the retention of 65% of the β-cyclodextrin-resveratrol complex in the reaction medium and the passage of 70% of the resveratrol α-O-glycosides in the permeate. In a second step, this membrane was used in an enzymatic membrane reactor and improved the yield of the enzymatic glycosylation of up to 50%
Implementation of an Enzyme Membrane Reactor to Intensify the α-O-Glycosylation of Resveratrol Using Cyclodextrins
No full textThis Book Chapter is a republication of an article published by Florent Allais, et al. at Pharmaceuticals in April 2021. (Ioannou, I.; Barboza, E.; Willig, G.; Marié, T.; Texeira, A.; Darme, P.; Renault, J.-H.; Allais, F. Implementation of an Enzyme Membrane Reactor to Intensify the α-O-Glycosylation ofResveratrol Using Cyclodextrins. Pharmaceuticals 2021, 14, 319. https://doi.org/10.3390/ph14040319)International audienceThe O-glycosylation of resveratrol increases both its solubility in water and its bioavailability while preventing its oxidation, allowing a more efficient use of this molecule as bioactive ingredient in pharmaceutical and cosmetic applications. Resveratrol O-glycosides can be obtained by enzymatic reactions. Recent developments have made it possible to obtain selectively resveratrol α-glycosides from the β-cyclodextrin-resveratrol complex in water with a yield of 35%. However, this yield is limited by the partial hydrolysis of the resveratrol glycosides produced during the reaction. In this study, we propose to intensify this enzymatic reaction by coupling the enzymatic reactor to a membrane process. Firstly, membrane screening was carried out at the laboratory scale and led to the choice of a GE polymeric membrane with a cutoff of 1 kDa. This membrane allowed the retention of 65% of the β-cyclodextrin-resveratrol complex in the reaction medium and the passage of 70% of the resveratrol α-O-glycosides in the permeate. In a second step, this membrane was used in an enzymatic membrane reactor and improved the yield of the enzymatic glycosylation of up to 50%
Should the laws of gravitation be reconsidered?: the scientific legacy of Maurice Allais
No full textMaurice Allais was one of the most original of France's scientific thinkers of the 20th century. In the early 1950’s he was the author of Allais paradox in decision making under uncertainty, and in 1988 he became the only French citizen to receive the Nobel Prize in Economics for his contributions to the theory of non-equilibrium markets. Allais’s research in physics was also important, but very little known. In the mid 1950’s Allais designed and built a highly sensitive ball-borne pendulum – which he named paraconical pendulum. This apparatus reacts to the gravitational force of the Sun and the Moon, and exhibited unexpected behaviour during the solar eclipse of 30 June 1954, which was partial in Paris. This local gravity anomaly is now called the Allais eclipse effect. As a tribute to Allais on the 100th anniversary of his birth, this book concentrates on his contributions to physics, in particular to the exciting and controversial field of gravity anomalies, which may open unexpected and completely new avenues in gravity theory. In addition to a short sampling of Allais papers, the book describes experimental efforts to reproduce the Allais eclipse effect, an endeavour that has turned out to be harder than expected because all eclipses are different. Several papers describe optical and geological anomalies that also interested Allais. A final section contains theoretical essays sketching novel gravity models. The book will be of interest not only to students and practitioners of physics, but also to the informed lay public, and even to philosophers of science, and researchers studying the epistemology and politics behind scientific investigation
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