Geopolymers reinforced with natural fibers: A comparison among different sources

The performance of different natural fibers (hemp, kenaf and bamboo) used to formulate composites with an alkali-activated matrix based on metakaolin is evaluated. Short fibers were randomly dispersed up to about 3% of the binder weight, and the fresh and cured properties of the derived composites were determined. Up to the investigated fraction, it is still possible to obtain adequate workability without the supply of additional water or additives. Upon modification with fibers, the mechanical behavior changes from completely brittle to pseudoplastic with increased toughness. The flexural strength increases by up to 80% at the highest bamboo amount and up to 20% for kenaf. Hemp fibers have a negligible effect on flexural strength but strongly improve the materials’ toughness. Moreover, the addition of fibers does not change the manner in which the material interacts with moisture. Indeed, the water uptake of the modified samples was comparable to that of the unmodified samples, and the composites showed a decreased rate of water diffusion as the amount of fiber increased

Ergodic billiard and statistical energy analysis

International audienceThis paper highlights the importance of ergodicity of billiards in Statistical energy analysis (SEA), a statistical theory of sound and vibration. We show that the main relationship of statistical energy analysis, the so-called coupling power proportionality, is intimately linked with the establishment of a diffuse vibration field in subsystems. In particular, we show that when subsystems have ergodic geometries or when the nature of excitation enforces a diffuse field, the energy exchange between two weakly coupled subsystems is proportional to the difference of vibrational energies. But when the field is not diffuse (either non isotropic or non homogeneous), the exchange of energy does not generally follow this proportionality. Numerical simulations are provided to support the discussion

Bio-based furan-polyesters/graphene nanocomposites prepared by in situ polymerization

In situ intercalative polymerization has been investigated as a strategic way to obtain poly(propylene 2,5-furandicarboxylate) (PPF) and poly(hexamethylene 2,5-furandicarboxylate) (PHF) nanocomposites with different graphene types and amounts. Graphene (G) has been dispersed in surfactant stabilized water suspensions. The loading range in composites was 0.25–0.75 wt %. For the highest composition, a different type of graphene (XT500) dispersed in 1,3 propanediol, containing a 6% of oxidized graphene and without surfactant has been also tested. The results showed that the amorphous PPF is able to crystallize during heating scan in DSC and graphene seems to affect such capability: G hinders the polymer chains in reaching an ordered state, showing even more depressed cold crystallization and melting. On the contrary, such hindering effect is absent with XT500, which rather induces the opposite. Concerning the thermal stability, no improvement has been induced by graphene, even if the onset degradation temperatures remain high for all the materials. A moderate enhancement in mechanical properties is observed in PPF composite with XT500, and especially in PHF composite, where a significative increase of 10–20% in storage modulus E’ is maintained in almost all the temperature range. Such an increase is also reflected in a slightly higher heat distortion temperature. These preliminary results can be useful in order to further address the field of application of furan-based polyesters; in particular, they could be promising as packaging materials

Anti-laminin-1 antibodies in sera and follicular fluid of women with endometriosis undergoing in vitro fertilization.

There is increasing evidence that autoimmune phenomena, including auto-antibody production, may affect fertility in women with endometriosis. The aims of this study are to evaluate anti-laminin-1 antibody (aLN-1) presence in sera and in follicular fluids (FF) of women with endometriosis undergoing IVF and its impact on oocyte maturation and IVF outcome. aLN-1 were measured by a home-made enzyme linked immunosorbent assay in sera and FF obtained from 35 infertile women with endometriosis and in sera from 50 fertile controls and 27 infertile women without endometriosis (IWWE). aLN-1 serum levels were significantly higher in women with endometriosis in comparison with both fertile controls and IWWE (P<0.001 and P <0.05, respectively) and a positive correlation was found between serum-and FF- aLN-1 (r = 0.47, P = 0.004). According to the cut-off (mean+3 SD of fertile controls), 31% of women with endometriosis were aLN-1 positive. Metaphase II oocyte counts showed inverse correlation with FF-aLN-1 levels (r = −0.549, P = 0.0006). Ongoing pregnancy (i.e pregnancy progressing beyond the 12th week of gestation) occurred in 4/11 aLN-1 positive patients and in 7/24 aLN-1 negative with no significant difference (P= 0.7). In conclusion, our results highlight that aLN-1 are increased in women with endometriosis and their presence in FF may affect oocyte maturation leading to a reduced fertility. However, aLN-1 seem to have no effect on IVF outcome

From food waste to eco-friendly functionalized polymer composites: Investigation of orange peels as active filler

: The development of eco-friendly polymer composites with multifunctional properties aligns with the goals of the circular economy agenda, which aims to minimize waste and promote the sustainable use of resources by closing the loop of product life cycles. Eco-friendly polymer composites play a crucial role in achieving these objectives. The present work focuses on the preparation of fully biobased blends obtained by melt mixing a bio-polyester, poly(butylene succinate-co-adipate) (PBSA), with orange peels up to 20&nbsp;wt%, to yield active polymer composites. Orange peels, employed here as natural filler, are largely available from food wastes, they are rich in phenolic compounds and possess antioxidant activity as shown by the experimental tests carried out. The thermal stability of the formulated composites is almost unchanged by the filler addition, showing only a slight decrease of the crystallization temperatures and crystalline fraction within the composites. The mechanical properties of the compounds evidence an increase in the elastic modulus together with a decrease in the tensile strength, while the elongation at break remains almost constant. The incorporation of the natural filler enabled the integration of antioxidant and antibacterial properties, which were absent in the original pristine polymer

The Relationship between Gut Microbiota and Respiratory Tract Infections in Childhood: A Narrative Review

Respiratory tract infections (RTIs) are common in childhood and represent one of the main causes of hospitalization in this population. In recent years, many studies have described the association between gut microbiota (GM) composition and RTIs in animal models. In particular, the “inter-talk” between GM and the immune system has recently been unveiled. However, the role of GM in human, and especially infantile, RTIs has not yet been fully established. In this narrative review we provide an up-to-date overview of the physiological pathways that explain how the GM shapes the immune system, potentially influencing the response to common childhood respiratory viral infections and compare studies analysing the relationship between GM composition and RTIs in children. Most studies provide evidence of GM dysbiosis, but it is not yet possible to identify a distinct bacterial signature associated with RTI predisposition. A better understanding of GM involvement in RTIs could lead to innovative integrated GM-based strategies for the prevention and treatment of RTIs in the paediatric population

Valorization of wheat bran agro-industrial byproduct as an upgrading filler for mycelium-based composite materials

When considered by a biorefinery approach, an agroindustrial byproduct such as wheat bran can find a new standing in the field of fabrication of mycelium-based materials. The present work reports on a systematic study on the effect of wheat bran as an upgrading feedstock for the growth and development of fully biobased and biodegradable composites. Two families of materials based on bran/cotton and bran/hemp mixtures were fabricated on an industrial scale. The natural materials thus obtained were fully characterized and their end-life was assessed in composting conditions. The research focusses on two main aspects: the nutritional contribution of bran for the fungal growth and its effect on the mechanical properties as a filler in the final composites. It must be noted that the valorization and exploitation of a byproduct such as bran can have a considerable impact on the industrial production of mycelium-based composite materials, by reducing the time of production while increasing their mechanical performances

Triggering of Polymer-Degrading Enzymes from Layered Double Hydroxides for Recycling Strategies

The use of degrading enzymes in polymer formulation is a very attractive strategy to manage the end-of-life of plastics. However, high temperatures cause the denaturation of enzymes and the loss of their catalytic activity; therefore, protection strategies are necessary. Once protected, the enzyme needs to be released in appropriate media to exert its catalytic activity. A successful protection strategy involves the use of layered double hydroxides: cutinase, selected as a highly degrading polyester hydrolytic enzyme, is thermally protected by immobilization in Mg/Al layered double hydroxide structures. Different triggering media are here evaluated in order to find the best releasing conditions of cutinase from LDH. In detail, phosphate and citrate-phosphate buffers, potassium carbonate, sodium chloride, and sodium sulfate solutions are studied. After the comparison of all media in terms of protein release and activity retained, phosphate buffer is selected as the best candidate for the release of cutinase from LDH, and the effect of pH and concentration is also evaluated. The amount of the enzyme released is determined with the Lowry method. Activity tests are performed via spectrophotometry

Natural deep eutectic solvents as thermostabilizer for Humicola insolens cutinase

As a new generation of green solvents, deep eutectic solvents (DESs) are considered a promising alternative to current harsh organic solvents and find application in many chemical processing methods such as extraction and synthesis. DESs, normally formed by two or more components via various hydrogen bond interactions, offer high potential as medium for biocatalysis reactions where they can improve efficiency by enhancing substrate solubility and the activity and stability of the enzymes. In the current study, the stabilization of Humicola insolens cutinase (HiC) in natural deep eutectic solvents (NADESs) was assessed. The best hydrogen bond donor among sorbitol, xylitol, erythritol, glycerol and ethylene glycol, and the best acceptor among betaine, choline chloride, choline acetate, choline dihydrogen citrate and tetramethylammonium chloride, were selected, evaluating binding energies and molecular orientations through molecular docking simulations, and finally used to prepare NADES aqueous solutions. The effects of component ratio and NADES concentration on HiC thermostability at 90 degrees C were also investigated. The choline dihydrogen citrate:xylitol, in a 1:1 ratio with a 20 wt% concentration, was selected as the best combination in stabilizing HiC, increasing its half-life three-fold