Tye7 regulates yeast Ty1 retrotransposon sense and antisense transcription in response to adenylic nucleotides stress

Transposable elements play a fundamental role in genome evolution. It is proposed that their mobility, activated under stress, induces mutations that could confer advantages to the host organism. Transcription of the Ty1 LTR-retrotransposon of Saccharomyces cerevisiae is activated in response to a severe deficiency in adenylic nucleotides. Here, we show that Ty2 and Ty3 are also stimulated under these stress conditions, revealing the simultaneous activation of three active Ty retrotransposon families. We demonstrate that Ty1 activation in response to adenylic nucleotide depletion requires the DNA-binding transcription factor Tye7. Ty1 is transcribed in both sense and antisense directions. We identify three Tye7 potential binding sites in the region of Ty1 DNA sequence where antisense transcription starts. We show that Tye7 binds to Ty1 DNA and regulates Ty1 antisense transcription. Altogether, our data suggest that, in response to adenylic nucleotide reduction, TYE7 is induced and activates Ty1 mRNA transcription, possibly by controlling Ty1 antisense transcription. We also provide the first evidence that Ty1 antisense transcription can be regulated by environmental stress conditions, pointing to a new level of control of Ty1 activity by stress, as Ty1 antisense RNAs play an important role in regulating Ty1 mobility at both the transcriptional and post-transcriptional stages

Evaluation of the proportion of phases and mechanical strength of two-phase steels using Barkhausen noise measurements: application to commercial dual phase steel

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Characterization of the residual stresses in plastically deformed ferrite-martensite steels using Barkhausen noise measurements

International audienceIn this work, we show that the measurement of the Barkhausen noise allows the residual stresses in each of the two phases of ferrite-martensite steels to be characterized. We have first studied the effect of a tensile and a compressive stress on the Barkhausen noise signature. We observed that for a ferrite-martensite steel, the application of a tensile stress increases the Barkhausen activity of the martensite and ferrite phases, whereas a compressive one reduces it. In a second time, we induced residual stresses by applying a plastic deformation to ferrite-martensite steels. After a tensile plastic deformation, we observed that (i) compressive residual stresses appear in ferrite, and (ii) tensile residual stresses appear in martensite. An opposite behavior is observed after a compressive plastic deformation. These results show that the Barkhausen noise measurement makes it possible to highlight in a nondestructive way the distribution of the stresses in each of the two phases of a ferrite-martensite steel. This result could be used to characterize industrial Dual-Phases steels that are plastically deformed during mechanical processes

Structural stability and defect mobility of HfO2-based materials

International audienceAccording to the European regulation REACh, a new low-toxicity green propellant must be developed in order to replace the toxic, mutagen and carcinogen hydrazine-based fuels for spacecraft thrusters. The research concerns a monopropellant development offering optimized physical-chemical properties and unparalleled propulsive performance. This gain in performance implies arduous operating conditions: gases temperature of 3000 K and an oxidizing environment in the combustion chamber. Currently, the materials used are only able to withstand temperatures around 1700 K1, 2. Thus, it is necessary to develop new ultra-high temperature materials able to sustain 3000 K. Functionally graded materials are well-known as resistant materials for high temperature, thanks to an environmental and thermal barrier. Hafnia (HfO2)-based materials are promising candidates for the barrier component, due to their low thermal conductivity and relatively low thermal expansion. However, to avoid destructive structural transformation during thermal cycling, HfO2 must be stabilized in its high temperature structure: the cubic phase (space group Fm3̅m). The cubic phase stability is obtained through doping with yttrium3 or rare earth oxide (RE2O3)4. The relative stability of allotropic phases is modelled using Density Functional Theory (DFT). Nevertheless, doping generates defects in the structure, in particularly oxygen vacancies, leading to ionic conductivity property variation. Several parameters influence the ionic conductivity (oxygen vacancies mobility), such as the ionic radius (RE3+), the volume fraction or the molecular weight of the dopant. The aim of this project is to know and study the influence of the amount and the nature of dopants (yttrium, lutetium and gadolinium) by computational method. All calculations were performed by using the plane wave pseudopotential methods within DFT as implemented in the VASP code. Generalized Gradient Approximation (GGA-PBE) exchange-correlation functionals were used. Beforehand, the three allotropic phases of HfO2 (monoclinic, tetrahedral and cubic) were fully optimized with respect to the unit cell shape and atom positions at several fixed volumes. These first calculations permitted to determine the optimal calculation parameters (cutoff energy and number of k-points) through the HfO2 without defects. Preliminary results are based on supercells non-doped and doped cubic-HfO2 with only one vacancy. Supercells (2x2x2 and 3x3x3) were created with the aim to avoid interaction between the periodic defects (oxygen vacancy or dopant). The results show that the vacancy formation energy is about 4 eV. In order to determine the transition state energies for the oxygen vacancy hopping between the nearest-neighbour O sites, and the energy barrier, Nudged Elastic Band (NEB) method is employed. After that, phonons calculations should be done to determine the vacancy jumping rate. Thenceforth, the doping rate (4, 8, and 12 %) is studied at different configurations sites to figure out its influence. Cell parameters resulting from the calculations are in adequacy with those obtained experimentally. Finally, the investigation of the vacancy variation rate is planned at fixed doping rate (8% for example). Those futures results might give some precious information about the vacancies mobility and so the ionic conductivity of the material

Ferrite-Martensite steels characterization using magnetic Barkhausen noise measurements

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Dual-Phase Steels Characterization Using Magnetic Barkhausen Noise Measurements

International audienceMagnetic Barkhausen noise measurements have been carried out to characterize ferrite-martensite duplex microstructures and industrial Dual-Phase steels. We have first studied ferrite-martensite duplex steels, for which the volume fraction and the carbon content of martensite were higher than for industrial Dual-Phase steels. We found linear evolutions between ferrite peak parameters and its proportion. We applied these results to industrial Dual-Phase steels and show that Barkhausen noise measurement can be successfully used for Dual-Phase steels characterization, and in particular for assessment of ferrite proportion

Consistency of muscle activation signatures across different walking speeds

Background: Using a machine learning algorithm, individuals can be accurately identified from their muscle activation patterns during gait, leading to the concept of individual muscle activation signatures. Research question: Are muscle activation signatures robust across different walking speeds? Methods: We used an open dataset containing electromyographic (EMG) signals from 8 lower limb muscles in 50 asymptomatic adults walking at 5 speeds (extremely slow, very slow, slow, spontaneous, and fast). A machine learning approach classified the EMG profiles based on similar (intra-speed classification) or different (inter-speed classification) walking speeds as training and testing conditions. Results: Intra-speed median classification rates of muscle activation profiles increased with walking speed, from 92 % for extremely slow, to 100 % for self-selected fast walking conditions. Inter-speed median classification rates increased when the speed of the training condition was closer to that of the testing condition. Higher median classification rates were found across slow, spontaneous, and fast walking speed conditions, from 56 % to 96 %, compared with classification rates involving extremely and very slow walking speed conditions, from 6 % to 62 %. Significance: Our findings reveal that i) muscle activation signatures are detectable for a large range of walking speeds, even those involving different gait strategies (intra-speed median classification rates from 92 % to 100 %), and ii) muscle activation signatures observed during very low walking speeds are not consistent with those observed at higher speeds, suggesting a difference in motor control strategy. Caution should therefore be exercised when assessing gait deviations of a slow walking patient against a normative database obtained at higher speed. Identifying the robustness of individual muscle activation signatures across different movements could help in detecting changes in motor control, otherwise difficult to detect on classical time-varying EMG patterns.</p

Characterization of Metallurgical Transformations in Multi-Phase High Strength Steels by Barkhausen Noise Measurement

International audienceThe potentialities of using the magnetic Barkhausen noise measurement in characterization of metallurgical transformations have been highlighted in multi-phase High Strength (HS) steels. This kind of steels are composed of different metallurgical constituents, such as ferrite, bainite, martensite or residual austenite. Recently, we found that it was possible to assess the proportion of phases in ferrite-martensite steels and in industrial Dual-Phase steels too. In this work, we show that the Barkhausen noise measurements can be also suitable to follow bainitic transformation in a TRIP steel