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

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

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

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

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

Political parties’ ideological bias and convergence in economic outcomes

International audienceIn democracies, policies are jointly shaped by voters' preferences and politicians' (or parties’) ideological biases. We explore the relative importance of the latter on some key economic outcomes – growth rate, inflation and inequality – in a broad sample of 71 democracies from 1995 to 2019. We find evidence that both left-wing and right-wing governments deliver convergent outcomes as regards growth, inflation and inequality. The same applies to the policy outcome of economic freedom. This indicates that consolidated democracies maintain continuity in economic policies, and a change in government from one political ideology to another with a different ideology does not significantly alter economic policy outcomes. However, we find divergence in hybrid regimes; inequality and economic freedom are reduced under leftist governments, and economic freedom is enhanced by rightist governments

Assessing the potential of digital technology: an integrated measurement of economic, environmental, and social performance

International audienceGiven the rate of evolution in digital technology, it is important to assess its impact on different performance metrics. Despite relatively extensive research on the role of digital technology in driving economic and environmental performance, the number of studies assessing its impact on social wellbeing remains relatively limited. To bridge this gap, this paper proposes a three-pillar model integrating social indicators into the conventional two-dimensional performance evaluation framework. We rely on the directional distance function and a linear programming methodology to define a benchmark model incorporating economic, environmental, and social indicators. Our approach is operationalized using a sample of 280 Chinese prefecture-level cities from 2003 to 2019. Our results suggest an overall improvement in inclusive green growth across China, albeit with notable regional variations among its different economic zones. Results from spatial regression provide evidence of digital technology’s predominantly positive role in driving inclusive green growth, particularly across its economic dimension. Furthermore, digital technology might not reduce carbon emissions directly. As for the social performance pillar, while digital technology help promote social stability it simultaneously inhibits performance expressed in terms of access to healthcare and education

Comparative analysis of bio-based insulation materials with low-carbon binders: Mechanical, hygrothermal, and durability performance

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Robust control of a high-temperature synchronous machine with anodized aluminum coils

International audienceObjective – This paper presents a robust control strategy for wound rotor synchronous machine with anodized aluminum windings designed to operate at temperatures up to 300°C. At these high temperatures, resistance and magnetic flux can fluctuate significantly, challenging conventional control methods that depend on fixed machine parameters. This highlights the importance of a robust control strategy to effectively handle these variations.Findings – This control law has demonstrated its effectiveness in regulating machine speed and currents by enhancing the dynamics and reducing oscillations during steady-state operation. It also shows more adaptability compared to conventional control methods, such as Field-Oriented Control.Originality – Making a robust control for a high-temperature wound rotor aluminum coil machine by taking into account the losses and real-time parameters variations and estimating them. This problem is not a very present topic in the literature

Mechanosynthesis and Polymerization of Styrene Derivatives Based on Building Blocks of Lignin

International audienceGiven the constraints dictated by the environment and the current policies, it is urgent to conceive and developnovel molecular building blocks and materials from bio-sourced platforms in order to compete and replace thoseobtained from petroleum sources (styrene, bisphenol A, etc.). Bio-sourced monomers can be obtained from thetransformation of molecules extracted from five main sources, namely terpenes, carbohydrates, lignin, proteins andlipids from animal, plant, or sea origin. Thanks to the presence of alcohol, acid or amine functional groups, thesebio-sourced molecules can often be polymerized by condensation reaction and yield bio-based polyesters orpolyamides with mechanical properties that can compete with their petroleum-based counterparts.Step-growth polymerization remains therefore the most explored pathway to produce bioplastics nowadays.Recently, the number of publications reporting free-radical chain-reaction polymerization (FRP) of bio-monomershas strongly increased. However, it remains still limited, probably due to the little number of readily availableradically polymerizable bio-sourced structures. In this context, lignin, the second most abundant natural polymericconstituent of wood, accounting for around 20% of the lignocellulosic biomass11 and currently discarded as wasteby the paper industry, appears to be a suitable candidate. Indeed, the controlled degradation of lignin allows toproduce biofuels, precursors for organic synthesis or oligomers that can be applied to prepare functional materials.Among those examples, the compounds obtained from lignin degradation represent a promising alternative todesign bio-sourced polymers displaying interesting thermo-mechanical properties thanks to the presence ofaromatic cycles.In this communication, we report the synthesis of polystyrenes prepared in three steps from vanillin, 4-hydrobenzaldehyde, and syringaldehyde, compounds that can be obtained through lignin depolymerization underoxidative conditions. The synthesis involves the conversion of these biosourced platforms into polymerizablestyrene derivatives through a methylation of the hydroxyl group followed by an olefination of the aldehyde function.The monomers were first synthesized under conventional conditions using solvents. Then, the synthesis wasimproved from the sustainability point of view by using a ball mill under solventless conditions, generating muchless waste in the process. Mechanochemistry has successfully been transposed from material sciences to organicchemistry in the past decades. Compared to conventional procedures and solvent-based reactions, it usesmechanical energy to induce a chemical reaction in solvent-free conditions and can afford shorter reaction times,higher yields and more sustainable process.The three monomers were then converted into biosourced homopolymers through free radical polymerization inbulk, providing functional polystyrene derivatives with thermal properties comparable to those of common petrosourced polystyrene