Evaluation and comparison of analytical methods for monitoring polymer depolymerization: application to poly(bisphenol A carbonate) methanolysis

International audiencePolymer depolymerization after use represents a significant challenge to reduce both the environmental impact of plastic pollution and the utilization of non-sustainable raw materials. Recently, there has been a demand to form a coherent strategy for the analysis of polymer degradation, of which, some approaches have been observed to be used inappropriately or incompletely. This article proposes an analysis strategy for monitoring the depolymerization of poly(bisphenol-A carbonate) (PBPAC), using methanolysis as a model method. It is based on five analytical methods, which our study attempts to combine and compare according to their ideal use case: size exclusion chromatography (SEC), high-performance liquid chromatography (HPLC) and Fouriertransform infrared (FT-IR), nuclear magnetic resonance (NMR) and Matrix Assisted Laser Desorption Ionization -Time of Flight spectroscopy (MALDI-TOF). This strategy allows both a qualitative approach, where the depolymerization products can be identified and a quantitative one, where the percentage of polymer degradation can be determined, together with the detection limit of each associated technique (i.e. 0.06 %, 20 %, 10 %, 8 % and 0.5 % for SEC, HPLC, FT-IR, NMR and MALDI-TOF respectively). As a result, the range of applications for each analytical method is assessed, and a guide to determine the minimum methods to be used to qualify and quantify degradation is proposed, in relation to the progress of degradation and the yields obtained. This has enabled us to characterize and propose a new quantitative FT-IR-based methodology, compatible with high-throughput screening, to study the degradation of PBPAC, allowing for quantification of degradation from 10 % onwards

Fractures nationales : Retrait des services publics et dynamiques électorales

International audienc

SIMPLICIAL INTERSECTION HOMOLOGY REVISITED

International audienceIntersection homology is defined for simplicial, singular and PL chains. In the case of a filtered simplicial complex, it is well known that the three versions are isomorphic. This isomorphism is established by using the PL case as an intermediate between the singular and the simplicial situations. Here, we give a proof similar to the classical proof for ordinary simplicial complexes. We also study the intersection blown-up cohomology that we have previously introduced. In the case of a pseudomanifold, this cohomology owns a Poincaré isomorphism with the intersection homology, for any coefficient ring, thanks to a cap product with a fundamental class. We prove that the simplicial and the singular blown-up cohomologies of a filtered simplicial complex are isomorphic. From this result, we can now compute the blown-up intersection cohomology of a pseudomanifold from a triangulation. Finally, we introduce a blown-up intersection cohomology for PL-spaces and prove that it is isomorphic to the singular ones. We also show that the cup product in perversity 0 of a CS-set coincides with the cup product of the singular cohomology of the underlying topological space

Optimization of the Antibacterial Activity of a Three-Component Essential Oil Mixture from Moroccan Thymus satureioides, Lavandula angustifolia, and Origanum majorana Using a Simplex–Centroid Design

International audienceBackground/Objectives: The rise of antibiotic-resistant pathogens has become a global health crisis, necessitating the development of alternative antimicrobial strategies. This study aimed to optimize the antibacterial effects of essential oils (EOs) from Thymus satureioides, Lavandula angustifolia, and Origanum majorana, enhancing their efficacy through optimized mixtures. Methods: This study utilized a simplex–centroid design to optimize the mixture ratios of EOs for maximal antibacterial and antioxidant effectiveness. The chemical profiles of the EOs were analyzed using gas chromatography-mass spectrometry (GC-MS). The antibacterial activity was assessed against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa using minimum inhibitory concentration (MIC) tests, while antioxidant activity was evaluated through DPPH (2,2-diphenyl-1-picrylhydrazyl), and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assays. Results: The optimized essential oil mixtures demonstrated potent antibacterial activity, with MIC values of 0.097% (v/v) for E. coli, 0.058% (v/v) for S. aureus, and 0.250% (v/v) for P. aeruginosa. The mixture ratios achieving these results included 76% T. satureioides, and 24% O. majorana for E. coli, and varying proportions for other strains. Additionally, L. angustifolia essential oil exhibited the strongest antioxidant activity, with IC50 values of 84.36 µg/mL (DPPH), and 139.61 µg/mL (ABTS), surpassing both the other EOs and standard antioxidants like BHT and ascorbic acid in the ABTS assay. Conclusions: The study successfully demonstrates that optimized mixtures of EOs can serve as effective natural antibacterial agents. The findings highlight a novel approach to enhance the applications of essential oils, suggesting their potential use in food preservation and biopharmaceutical formulations. This optimization strategy offers a promising avenue to combat antibiotic resistance and enhance food safety using natural products

Alginate versus Chitosan for Templating Growth and Shaping HKUST‐1 as Porous CO2‐Adsorbent Beads

International audienceThis study aims at elucidating the role of the polysaccharide skeleton (alginate versus chitosan) during the growth and shaping of HKUST‐1 as porous beads. Although the two biopolymers afford an open porous hydrogel network, the freeze‐drying step was crucial with water medium being inappropriate to preserve the crystalline framework of HKUST‐1. Alternatively, drying in ethanol circumvented this drawback by keeping intact the structure of HKUST‐1. However, a contrasting behavior was observed in the resulting polysaccharide@HKUST‐1 beads, as HKUST‐1 grown in alginate underwent a dramatic collapse, whereas self‐standing, open porous microspheres could be obtained using the chitosan templating route. The resulting chitosan@HKUST‐1 cryogel displays an enhanced CO2 capture (2.67 mmol.g−1) compared to its analogs shaped by alginate, making consequently chitosan a better option for structuring MOF‐based adsorbents

Hereditarily frequently hypercyclic operators and disjoint frequent hypercyclicity

International audienceWe introduce and study the notion of hereditary frequent hypercyclicity, which is a reinforcement of the well known concept of frequent hypercyclicity. This notion is useful for the study of the dynamical properties of direct sums of operators; in particular, a basic observation is that the direct sum of a hereditarily frequently hypercyclic operator with any frequently hypercyclic operator is frequently hypercyclic. Among other results, we show that operators satisfying the Frequent Hypercyclicity Criterion are hereditarily frequently hypercyclic, as well as a large class of operators whose unimodular eigenvectors are spanning with respect to the Lebesgue measure.On the other hand, we exhibit two frequently hypercyclic weighted shifts $B_w,B_{w'}$ on $c_0(\mathbb{Z}_+)$ whose direct sum $B_w\oplus B_{w'}$ is not $\mathcal{U}$-frequently hypercyclic (so that neither of them is hereditarily frequently hypercyclic), and we construct a $C$-type operator on $\ell_p(\mathbb{Z}_+)$, 1\le p<\infty which is frequently hypercyclic but not hereditarily frequently hypercyclic. We also solve several problems concerning disjoint frequent hypercyclicity: we show that for every $N\in\mathbb{N}$, any disjoint frequently hypercyclic $N$-tuple of operators $(T_1,\dots ,T_N)$ can be extended to a disjoint frequently hypercyclic $(N+1)$-tuple $(T_1,\dots ,T_N, T_{N+1})$ as soon as the underlying space supports a hereditarily frequently hypercyclic operator; we construct a disjoint frequently hypercyclic pair which is not densely disjoint hypercyclic; and we show that the pair $(D,\tau_a)$ is disjoint frequently hypercyclic, where $D$ is the derivation operator acting on the space of entire functions and $\tau_a$ is the operator of translation by $a\in\mathbb{C}\setminus\{ 0\}$.Part of our results are in fact obtained in the general setting of Furstenberg families

Engaging Students in Spectroscopic Analysis of Organic Compounds: A Collaborative Tournament Approach for Third-Year Chemistry Students in Northern France

International audienceThe ability to elucidate the structure of organic compounds from their nuclear magnetic resonance (NMR), infrared (IR), and mass spectrometry (MS) spectra is an essential skill, particularly for those engaged in the fields of synthetic and analytical organic chemistry. Spectral analysis constitutes a fundamental component of the curriculum for all chemistry students, as it requires the development of critical thinking skills. To engage and motivate students in the structure’s elucidation course, a gamified learning activity was designed in the form of a tournament involving third-year chemistry students from three universities in Northern France. In this tournament, the students are divided into teams comprising of four to five individuals. They are tasked with elucidating the structures of organic compounds based on their NMR, IR, and MS spectra in the shortest possible time with the fewest possible incorrect answers. The tournament was conducted in two distinct phases, each with a duration of 1.5 h and 1 h, respectively. The initial phase is competitive and involves teams of students from the same university, while the subsequent phase is designed to facilitate interaction and comparison between students from different universities, allowing them to discuss and evaluate their respective knowledge and methodology. The students were invited to evaluate the tournament approach by a questionnaire. The students expressed appreciation for the tournament and recommended its repetition in future years, citing its value in advancing their spectroscopy skills. Additionally, the students found the opportunity to interact with students from other universities and engage in discussions about their training programs and methodologies to be a valuable experience

Étude prospective sur les déchets plastiques dans les sédiments de plusieurs canaux des Hauts de France

International audienc

The Dynamics, Degradation, and Afterlives of Pectins: Influences on Cell Wall Assembly and Structure, Plant Development and Physiology, Agronomy, and Biotechnology

International audiencePectins underpin the assembly, molecular architecture, and physical properties of plant cell walls and through their effects on cell growth and adhesion influence many aspects of plant development. They are some of the most dynamic components of plant cell walls, and pectin remodeling and degradation by pectin-modifying enzymes can drive developmental programming via physical effects on the cell wall and the generation of oligosaccharides that can act as signaling ligands. Here, we introduce pectin structure and synthesis and discuss pectin functions in plants. We highlight recent advances in understanding the structure–function relationships of pectin-modifying enzymes and their products and how these advances point toward new approaches to bridging key knowledge gaps and manipulating pectin dynamics to control plant development. Finally, we discuss how a deeper understanding of pectin dynamics might enable innovations in agronomy and biotechnology, unlocking new benefits from these ubiquitous but complex polysaccharides

Mode I crack propagation in polydimethylsiloxane-short carbon fiber composites

International audienc