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« “Make Empathy Great Again” : la contestation aux États-Unis »
No full textTandis que les médias européens s’attardent sur les saillies de l’administration Trump II, des millions d’Étasuniens inventent des manières d’y résister. Le trumpisme n’y suscite pas qu’adhésion, sidération ou indifférence. À l’instar du mouvement #teslatakedown, les oppositions s’expriment, y compris de manière véhémente
Upgrading of glycerol to solketal over mesoporous gallosilicates with tuned hydrophobicity
No full textNovel mesoporous gallosilicates with tuned hydrophobicity were synthesized through methylation of extra small XS-SiO2 silica particle via condensation with trimethoxymethylsilane CH3Si(OCH3)3 followed by impregnation with gallium (III) precursors. The structural and textural properties of the solids obtained were extensively characterized by different techniques. The synthesized catalysts displayed excellent catalytic activity in the acetalization of acetone with glycerol to produce solketal. Among all the studied catalysts, the most active catalyst, XS-10 %Me-GaLac, displayed high turnover number and significantly improved glycerol conversion which is attributed to the relatively hydrophobic surface and high amount of accessible active acid sites. The high acidity and enhanced hydrophobicity of this catalyst was generated by the incorporation of the methyl groups which allowed a homogeneous dispersion of highly active gallium species on the silica matrix before calcination. The effect of reaction time, temperature, catalyst loading and acetone to glycerol molar ratio was investigated. Furthermore, the mesoporous gallosilicate materials were truly heterogeneous without leaching gallium active sites and can be efficiently reused in successive catalytic cycles.</p
Testing equivalent formulations of linear and nonlinear frequency-dependent electric-dipole polarizabilities
No full textIn response theory, the hypervirial relations provide alternative formulations for the dynamic (frequency-dependent) molecular response properties. In this contribution, though the length formulation is the most commonly used in the calculations, we derive the full velocity formulations of the dynamic electric-dipole polarizability, ααβ(-ω;ω), and the dynamic electric-dipole second-harmonic generation first hyperpolarizability, βαβγ(-2ω;ω,ω). Both formulations provide identical responses for exact wavefunctions and for variationally optimized wavefunctions in the limit of a complete basis set. To assess how the exact relations between the length and velocity formulations are satisfied for approximate wavefunctions, we performed TD-DFT and TD-HF calculations of the frequency-dependent polarizability and first hyperpolarizability of R-methyloxirane molecule, using increasingly large basis sets. For ααβ(-ω;ω), the results reproduce the expected qualitative and quantitative trends, with convergence toward the same values when the basis-set size increases. However, for βαβγ(-2ω;ω,ω), the results are more contrasted. Though the convergence with the basis-set size is evident, the first hyperpolarizability difference between the two formulations is frequency dependent, whereas it is not when the relations are satisfied. Moreover, for βαβγ(-2ω;ω,ω), we analyzed some of the hyper-Rayleigh scattering main observables and it is clear that the full velocity formulation converges slowly compared with the length formulation.</p
Robust binding energy distribution sampling on amorphous solid water models:Method testing and validation with NH<sub>3</sub>, CO, and CH<sub>4</sub>
No full textContext. The astrochemically efficient icy mantles surrounding dust grains in molecular clouds have been shown to be of an amorphous water-rich nature. This therefore implies a distribution of binding energies (BEs) per species instead of a single value. Methods proposed so far for inferring BEs and their distributions on amorphous ices rely on different approaches and approximations, leading to disparate results or BE dispersions with partially overlapping ranges. Aims. This work aims to develop a method based on a structurally reliable ice model and a statistically and physicochemically robust approach to BE distribution inference, with the aim of being applicable to various relevant interstellar species. Methods. A multiscale computational approach is presented, with a molecular dynamics heat and quench protocol for the amorphous water ice model, and an ONIOM(B3LYP-D3(BJ)/6-311+G(d,p):GFN2-xtb) scheme for the BE inference, with a prime emphasis onto the convergence of the computed BEs with the real system size. The sampling of the binding configurations is twofold, exploring both regularly spaced binding sites as well as various adsorbate-to-substrate orientations on each locally distinct site. This second source of BE diversity accounts for the local roughness of the potential energy landscape of the substrate. Three different adsorbate test cases are considered, NH3, CO, and CH4, owing to their significance in icy dust mantles, and their distinct binding behavior with water ices. Results. The BE distributions for NH3, CO, and CH4 have been inferred with converged statistics. The distribution for NH3 is better represented by a double Gaussian component profile. Three starting adsorbate orientations per site are required to reach convergence for both Gaussian components of NH3, while two orientations are sufficient for CO, and one unique one for CH4 (symmetric). Further geometrical and molecular surrounding insights have been provided. These results encompass previously reported results.</p
Amino-functionalized and Na<sup>+</sup> pre-intercalated three-dimensional Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> film aerogel with excellent electrochemical performances for supercapacitor
No full textPrecise modulation of the pore structure and modification of the surface groups (–NH2) of MXene aerogels by the solid foaming method in combination with Na+ pre-intercalation can significantly increase the layer spacing and change the electronic structure of MXene, thereby significantly optimizing its electrochemical performance. The three-dimensional (3D) network structure provides numerous active sites on the surface of MXene and provides more ion transfer pathways and the large layer spacing allows electrolyte ions fast transport and the surface groups provide more active sites for the pseudocapacitive reaction. As a result, the prepared Na-Ti3C2Tx (where T is –O, –OH, –F, and/or –NH2, and x represents the number of such groups) film aerogel delivers a high mass specific capacitance of 560 F·g−1 and excellent cycling performance of 94.5% capacitance retention after 12,000 cycles in 0.5 M H2SO4. In addition, the flexible all-solid-state supercapacitor (ASC) composed of MXene film electrodes has excellent specific capacitance ~ 277 F·g−1 and high energy density ~ 52.8 Wh·kg−1 at 1600 W·kg−1. Therefore, this work not only proposes a feasible synthetic method that can precisely regulate the pore structure and surface features of film aerogels, but also demonstrates the broad application prospects of aerogel materials in wearable power devices.</p
Exploring the Computational Complexity of Uniform Random Sampling and SAT Counting with Phase Transitions
No full textUniform Random Sampling (URS) and Model Counting (#SAT) are two intrinsically linked, theoretical problems with relevant practical applications in software engineering. In particular, in configurable system engineering, URS and #SAT can support studying configurations’ properties unbiasedly. Despite the community efforts to provide scalable URS and #SAT tools, solving these problems efficiently remains challenging for a large number of formulae. Contrary to the classical SAT problem, whose complexity has been an object of fundamental studies, little is known about what makes a formula hard to sample from. For the first time, we investigate how phase transitions can explain the practical complexity of sampling. Our results, computed on 11,409 synthetic formulae and 4656 real-world formulae, show that phase transitions occur in both cases, but at a different clause-to-variable ratio than for SAT tasks. We further reveal that low formula modularity is correlated with a higher URS/#SAT time. Overall, our work contributes to a principled understanding of URS and #SAT complexity
Unbiased and comprehensive identification of virus-derived circular RNAs in a large range of viral species and families
No full textNon-coding RNAs play a significant role in viral infection cycles, with recent attention focused on circular RNAs (circRNAs) originating from various viral families. Notably, these circRNAs have been associated with oncogenesis and alterations in viral fitness. However, identifying their expression has proven more challenging than initially anticipated due to unique viral characteristics. This challenge has the potential to impede progress in our understanding of viral circRNAs. Key hurdles in working with viral genomes include: (1) the presence of repetitive regions that can lead to misalignment of sequencing reads, and (2) unconventional splicing mechanisms that deviate from conserved eukaryotic patterns. To address these challenges, we developed vCircTrappist, a bioinformatic pipeline tailored to identify backsplicing events and pinpoint loci expressing circRNAs in RNA sequencing data. Applying this pipeline, we obtained novel insights from both new and existing datasets encompassing a range of animal and human pathogens belonging to Herpesviridae, Retroviridae, Adenoviridae, Flaviviridae and Orthomyxoviridae families. Subsequent RT-PCR and Sanger sequencings validated the accuracy of the developed bioinformatic tool for a selection of new candidate virus-derived circRNAs. These findings demonstrate that vCircTrappist is an open and unbiased approach for comprehensive identification of virus-derived circRNAs.</p
Senescence Under the Lens: X-ray vs. Proton Irradiation at Conventional and Ultra-High Dose Rate
No full textConventional radiotherapy based on X rays is used to treat more than 50% of cancers. Although effective, radiotherapy can damage healthy tissues around the tumor due to the X-ray dose deposition profile, as well as the safety margin needed to compensate for dose uncertainties. A notable side effect is cellular senescence, characterized by the cessation of cell division while maintaining metabolic activity and promoting the secretion of various components, called the senescence-associated secretory phenotype. To minimize toxicity in healthy tissues, proton therapy holds great promise as it enables tumors to be targeted more precisely while sparing healthy tissues beyond the tumor site. Another innovative method is ultra-high dose rate irradiation, which seems to induce less damage to healthy tissues while generating an anti-tumor response similar to standard dose rate irradiation. In this work, we aimed to compare the effects of X rays and protons at conventional dose rate (2 Gy/min) and ultra-high dose rate (454 Gy/s), on the induction of senescence in primary normal human dermal fibroblasts by analyzing several senescence biomarkers. Irradiation with ultra-high dose rate protons caused more pronounced cellular and nuclear morphological changes in normal human dermal fibroblasts than irradiation with conventional protons or X-rays. For other biomarkers, all three types of irradiations induced an increase in the proportion of senescence-associated beta-gal-positive cells, an irreversible cell cycle arrest and an accumulation of unrepaired DNA damage, but did not affect senescence-associated secretory phenotype