Institut de Physique de Rennes

The partners of an ecological association tend to copy the biological system of their hosts. We hypothesized that microorganisms, particularly pathogens, have acquired the ability to express short peptides (pathoPEPs) homologous to host miPEPs, thus modulating the expression of the corresponding host microRNA (miRNA) and the function of miRNA-targeted genes. The pathosystem involving interactions between Brassica napus and its pathogen Plasmodiophora brassicae was studied. The data set contains RNA-seq and ribosomal profiling from two plant genotypes inoculated with one pathogen isolate. Using in silico analysis, we identified three putative pathoPEPs produced by P. brassicae and their targeted plant miRNA genes. A link between the level of infection of B. napus by P. brassicae and the expression of pathoPEPs and their targeted miRNA genes was found, with the expression of the latter two being inversely related. Finally, we identified differential expression and translation of genes predicted to be targets of pathoPEP-regulated miRNAs. These genes, involved in auxin pathway, immune defense, root architecture, or carbohydrate metabolism, are thought to enable P. brassicae, through its pathoPEPs, to hijack plant's metabolic pathways (e.g., hormonal pathways, sugar synthesis, root morphology), thereby facilitating its invasion. Using in silico approaches, the involvement of miPEPs from this host-pathogen system as a host post-transcriptional regulatory pathway is described herein for the first time.

Ultrafast control of functional materials by light is key for developing optoelectronic devices. Still, the mechanisms by which microscopic photoinduced excitations evolve into a macroscopic phase transformation remain poorly understood, partly due to the experimental challenges of isolating multiscale electronic and structural dynamics. Here we use femtosecond X-ray techniques to track the non-equilibrium dynamics leading to macroscopic transformation in a ferroelastic charge-transfer Prussian blue analogue. The experimental data evidence a sequence of phenomena. The initial electronic excitation leads to reverse Jahn-Teller distortion within 50 fs, causing intermetallic charge-transfer polarons within 200 fs. Polarons generate considerable lattice strain and trigger phase nucleation within 60 ps. This elastically driven cooperativity, launched by the photoinduced polarons, offers an efficient route to the generation and stabilization of photoinduced phases in many volume-changing materials.

• A hypersonic flow excites the vibration of CH 4 molecule while cooling its rotation. • CRDS is used to record rotationally cold hot band transitions of methane in the IR. • A new ab initio effective model is used to assign 2525 lines in the tetradecad. The SMAUG device is used to thermally populate the vibrational states of the methane molecule and depopulate its rotational states through its supersonic expansion in argon. The methane molecule is probed during expansion by cavity ringdown spectroscopy (CRDS) between 5880 and 6220 cm −1 . The laser beam passes through both the isentropic core of the flow, characterized by a very low rotational temperature of 40.4 ± 0.8 K, and the hotter boundary layers surrounding it, which are characterized by an average rotational temperature of 364.3 ± 7.7 K. Analysis of the spectrum reveals that the vibrational population does not follow a Boltzmann distribution. A special procedure is developed to assign an effective vibrational temperature to each vibrational state, ranging from 532.4 ± 32.2 to 1112.0 ± 81.7 K for molecules in the isentropic core, and from 811.6 ± 43.1 to 851.8 ± 45.6 K for those in the shear layer. Only the first vibrational states of each methane polyad remain significantly populated leading to detectable transitions. A total of 2525 transitions from the cold gas of the isentropic core and from the warmer gas of the boundary layers are assigned from a new ab initio effective model and 1000 are confirmed by lower state combination differences (LSCD). Among these transitions, 718 originates from cold bands and 1807 from hot bands starting from vibrational states ν 4 , ν 2 (dyad), 2ν 4 (pentad) and 3ν 4 (octad).

In the first part of this paper, a methodology has been developed for tracking moving material points within infrared images, by coupling full kinematic and thermal field measurements. The kinematic field is determined with the Digital Image Correlation (DIC) technique and the temperature field is measured with an infrared (IR) camera. This methodology enables us to provide simultaneously the strain field, the thermal field, the heat power density (the heat source) field and, if applicable, the crystallinity field under large heterogeneous deformations. Its metrological performances have been fully characterized. The technique is the only one providing all these results from the same test, which avoids bias due to the repetition of the test with different specimens, different testing machines and differences in the boundary conditions applied. In this second part, the methodology is applied to a stretched crack tip in an unfilled natural rubber specimen. The crack tip is observed after several hundred of mechanical cycles applied to the notched specimen. The quantitative analysis of the different fields and profiles plotted (along the crack lips and behind the crack tip) enables us to characterize and to compare the different gradients in terms of strain, temperature, heat source and crystallinity. Quantitative analysis of the results supports the assumption that under the conditions of the experiment, the crack tip is the most stretched zone but not the most crystallized one, compared to the zones on both sides of it. The results also suggest that cavitation and/or decohesion might locally occur at the crack tip and frustrate the crystallization. • Full kinematics, thermal and calorimetric fields are mapped at the crack tip of a NR. • The crack tip is observed after several hundred of mechanical cycles. • A quantitative analysis is performed from profiles along the crack and in depth. • The crack tip is the most stretched zone but not the most crystallized one. • Cavitation and/or decohesion might occur and frustrate SIC at the crack tip.

Aluminum nitride (AlN), diamond, and β-phase gallium oxide (β-Ga2O3) belong to the family of ultra-wide bandgap (UWBG) semiconductors and exhibit remarkable properties for future power and optoelectronic applications. Compared to conventional wide bandgap (WBG) materials such as silicon carbide (SiC) and gallium nitride (GaN), they demonstrate clear advantages in terms of high-voltage, high-temperature, and high-frequency operation, as well as extremely high breakdown fields. In this work, numerical simulations are performed to evaluate and compare the radiative responses of AlN, diamond, and β-Ga2O3 when exposed to neutron irradiation covering the full atmospheric spectrum at sea level, from 1 meV to 10 GeV. The Geant4 simulation framework is used to model neutron interactions with the three materials, focusing on single-particle events that may be triggered. A detailed comparison is conducted, particularly concerning the generation of secondary charged particles and their distributions in energy, linear energy transfer (LET), and range given by SRIM. The contribution of the 14N(n,p)14C reaction in AlN is also specifically investigated. In addition, the study examines the consequences of these interactions in terms of electron-hole pair generation and charge deposition, and discusses the implications for the radiation sensitivity of these materials when exposed to atmospheric neutrons.

This perspective offers a viewpoint on how the challenges of molecular scattering investigations of astrophysical interest have evolved in recent years. Computational progress has steadily expanded collisional databases and provided essential tools for modeling non-LTE astronomical regions. However, the observational leap enabled by the JWST and new observational facilities has revealed critical gaps in these databases. In this framework, two major frontiers emerge: the characterization of collisional processes involving heavy projectiles, and the treatment of ro-vibrational excitation. The significant computational effort of these investigations emphasizes the need to test and develop robust theoretical methods and approximations, capable of extending the census of collisional coefficients required for reliable astrophysical modeling. Recent developments in these directions are outlined, with particular attention to their application and their potential to broaden the coverage of molecular systems and physical environments.

Laser cutting is an old and multi-physical process that was quickly adopted by the metallurgical industry. However, this fast industrialisation has had a significant impact on quality control. Several studies have been carried out to characterise and minimise different types of cutting defects. Reviews published between 2008 and 2022 highlight that research often focuses on single-criterion ___quality' approaches, aiming to minimise specific defects such as the Heat-Affected Zone, surface roughness, or kerf geometry. Consequently, efforts have been directed at optimising specific aspects of quality rather than adopting a complete approach. Furthermore, these reviews reveal that cutting quality can be enhanced through the careful selection of laser manufacturing parameters and part parameters. However, while parameters such as material and thickness have been investigated, the influence of part morphology on cutting quality remains underexplored.___ Although some studies have examined the effects of material and thickness, part morphology is often limited to simple segments with varying cutting lengths or angles. While other research has investigated the impact of angle size on cutting quality, no established method exists to systematically determine the influence of each part morphology on cutting quality.______ In response to this gap, the present study proposes to evaluate the criticality of cutting defects, as defined by existing standards, across various part morphologies using a method adapted from Failure Modes, Effects, and Criticality Analysis (FMECA). The objective is to develop a global approach that examines the influence of all morphologies on all types of cutting defects. An industrial application shows that cutting defects, particularly thermal ones, are strongly influenced by morphologies, while thickness affects them irregularly. Improvement priorities target critical defects shaped by both factors. Burrs and adherent slag are critical in angles and arcs, while segments, often used in studies, are less sensitive._________ These observations lead to the definition of design limits. This method offers a detailed analysis of the influence of design data on quality, providing practical tools for improving industrial processes._________

Relative motion between the pin and the clip of a semi-permanent connector, caused by vibration and temperature variations, is well known to be the main cause of fretting-corrosion failure in electrical connectors. Displacements induced by temperature variations are generally of low amplitude and very low frequency, in the order of a milli-hertz. These are difficult to measure with a motion sensor, which tends to drift over time. This study aims to quantify the relative displacements in the contact point of the pin and clip of an automotive electrical connector due to temperature variations. An original test bench was designed allowing coupling vibrations and temperature variations. A series of tests were carried out. Firstly, temperature cycles on static terminals were carried out at 100 °C and 180 °C for 6 days, at a rate of 8 hours per day. Hysteresis loops revealed that the electrical contact resistance (ECR) behaved differently during the heating and cooling phases and its areas are related to Joule losses. Secondly, the relative motion transfer function (RMFT) of the connector with all its components, established over a frequency range of 100 to 1000 Hz with an acceleration of 20G at room temperature (RT) and 120 °C, showed a significant variation in relative motion. Finally, a long duration fretting test carried out on the terminals, when a nominal current of 10A is imposed with voltages of 16 VDC, shows that the erosion and perforation of the fretting track of the pin are due to the occurrence of arcing in the contact point and not to resistive heating.

Abstract In this article, we provide a brief perspective on recent developments in the study of shear thickening in dense suspensions. We give a rapid overview of the state of the art and discuss current models aiming to describe this particular rheology. Although most of the experiments and simulation studies are conducted in “ideal” flows, where the sample is confined without an open boundary condition, we have decided to highlight more realistic flow conditions. We further provide an overview on how to relate the recently proposed constitutive models to these more practical flow conditions like pipe flow or flow down an incline.