Strong Carbon Features and a Red Early Color in the Underluminous Type Ia SN 2022xkq

We present optical, infrared, ultraviolet, and radio observations of SN 2022xkq, an underluminous fast-declining type Ia supernova (SN Ia) in NGC 1784 ($\mathrm{D}\approx31$ Mpc), from $<1$ to 180 days after explosion. The high-cadence observations of SN 2022xkq, a photometrically transitional and spectroscopically 91bg-like SN Ia, cover the first days and weeks following explosion which are critical to distinguishing between explosion scenarios. The early light curve of SN 2022xkq has a red early color and exhibits a flux excess which is more prominent in redder bands; this is the first time such a feature has been seen in a transitional/91bg-like SN Ia. We also present 92 optical and 19 near-infrared (NIR) spectra, beginning 0.4 days after explosion in the optical and 2.6 days after explosion in the NIR. SN 2022xkq exhibits a long-lived C I 1.0693 $\mu$m feature which persists until 5 days post-maximum. We also detect C II $\lambda$6580 in the pre-maximum optical spectra. These lines are evidence for unburnt carbon that is difficult to reconcile with the double detonation of a sub-Chandrasekhar mass white dwarf. No existing explosion model can fully explain the photometric and spectroscopic dataset of SN 2022xkq, but the considerable breadth of the observations is ideal for furthering our understanding of the processes which produce faint SNe Ia.Comment: 38 pages, 16 figures, accepted for publication in ApJ, the figure 15 input models and synthetic spectra are now available at https://zenodo.org/record/837925

Failure of hydrided zircaloy-4 fuel cladding tubes under RIA loading conditions

2-5 septembre 2008International audienceThe anisotropic viscoplastic behavior and the fracture of cold worked ...

Behavior and failure of uniformly hydrided Zircaloy-4 fuel claddings between 25 °C and 480 °C under various stress states, including RIA loading conditions

International audienceThe anisotropic plastic behavior and the fracture of as-received and hydrided Cold-Worked Stress Relieved Zircaloy-4 cladding tubes are investigated under thermal-mechanical loading conditions representative of Pellet-Clad Mechanical Interaction during Reactivity Initiated Accidents in Pressurized Water Reactors. In order to study the combined effects of temperature, hydrogen content, loading direction and stress state, Axial Tensile, Hoop Tensile, Expansion Due to Compression and hoop Plane Strain Tensile tests are performed at room temperature, 350 °C and 480 °C on the material containing various hydrogen contents up to 1200 wt. ppm (hydrides are circumferential and homogeneously distributed). These tests are combined with digital image correlation and metallographic and fractographic observations at different scales. The flow stress of the material decreases with increasing temperature. The material is either strengthened or softened by hydrogen depending on temperature and hydrogen content. Plastic anisotropy depends on temperature but not on hydrogen content. The ductility of the material decreases with increasing hydrogen content at room temperature due to damage nucleation by hydride cracking. The plastic strain that leads to hydride fracture at room temperature decreases with increasing hydrogen content. The influence of stress triaxiality on hydride cracking is negligible in the studied range. The influence of hydrogen on material ductility is negligible at 350 °C and 480 °C since hydrides do not crack at these temperatures. The ductility of the material increases with increasing temperature. The evolution of material ductility is associated with a change in both the macroscopic fracture mode of the specimens and the microscopic failure mechanisms

High temperature expansion due to compression test for the determination of a cladding material failure criterion under RIA loading conditions

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A model to describe the anisotropic viscoplastic mechanical behavior of fresh and irradiated Zircaloy-4 fuel claddings under RIA loading conditions

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Identification of Genomic Species in Agrobacterium Biovar 1 by AFLP Genomic Markers

Biovar 1 of the genus Agrobacterium consists of at least nine genomic species that have not yet received accepted species names. However, rapid identification of these organisms in various biotopes is needed to elucidate crown gall epidemiology, as well as Agrobacterium ecology. For this purpose, the AFLP methodology provides rapid and unambiguous determination of the genomic species status of agrobacteria, as confirmed by additional DNA-DNA hybridizations. The AFLP method has been proven to be reliable and to eliminate the need for DNA-DNA hybridization. In addition, AFLP fragments common to all members of the three major genomic species of agrobacteria, genomic species G1 (reference strain, strain TT111), G4 (reference strain, strain B6, the type strain of Agrobacterium tumefaciens), and G8 (reference strain, strain C58), have been identified, and these fragments facilitate analysis and show the applicability of the method. The maximal infraspecies current genome mispairing (CGM) value found for the biovar 1 taxon is 10.8%, while the smallest CGM value found for pairs of genomic species is 15.2%. This emphasizes the gap in the distribution of genome divergence values upon which the genomic species definition is based. The three main genomic species of agrobacteria in biovar 1 displayed high infraspecies current genome mispairing values (9 to 9.7%). The common fragments of a genomic species are thus likely “species-specific” markers tagging the core genomes of the species

Ductility and Failure Behaviour of both Unirradiated and Irradiated Zircaloy-4 Cladding Using Plane Strain Tensile Specimens

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Clarifying the taxonomy of the causal agent of bacterial leaf spot of lettuce through a polyphasic approach reveals that Xanthomonas cynarae Trébaol et al. 2000 emend. Timilsina et al. 2019 is a later heterotypic synonym of Xanthomonas hortorum Vauterin et al. 1995

International audienceAssessment of the taxonomy and diversity of Xanthomonas strains causing bacterial leaf spot of lettuce(BLSL), commonly referred to as Xanthomonas campestris pv. vitians, has been a long-lasting issue whichheld back the global efforts made to understand this pathogen. In order to provide a sound basis essentialto its study, we conducted a polyphasic approach on strains obtained through sampling campaigns oracquired from collections. Results of a multilocus sequence analysis crossed with phenotypic assaysrevealed that the pathotype strain does not match the description of the nomenspecies provided byBrown in 1918. However, strain LMG 938 = CFBP 8686 does fit this description. Therefore, we proposethat it replaces LMG 937 = CFBP 2538 as pathotype strain of X. campestris pv. vitians.Then, whole-genome based phylogenies and overall genome relatedness indices calculated on taxo-nomically relevant strains exhibited the intermediate position of X. campestris pv. vitians between closelyrelated species Xanthomonas hortorum and Xanthomonas cynarae. Phenotypic profiles characterized usingBiolog microplates did not reveal stable diagnostic traits legitimizing their distinction. Therefore, we pro-pose that X. cynarae Trébaol et al. 2000 emend. Timilsina et al. 2019 is a later heterotypic synonym ofX. hortorum, to reclassify X. campestris pv. vitians as X. hortorum pv. vitians comb. nov. and to transferX. cynarae pathovars in X. hortorum as X. hortorum pv. cynarae comb. nov. and X. hortorum pv. gardnericomb. nov. An emended description of X. hortorum is provided, making this extended species a promisingmodel for the study of Xanthomonas quick adaptation to different host

RNA polymerase II depletion from the inactive X chromosome territory is not mediated by physical compartmentalization.

Subnuclear compartmentalization has been proposed to play an important role in gene regulation by segregating active and inactive parts of the genome in distinct physical and biochemical environments. During X chromosome inactivation (XCI), the noncoding Xist RNA coats the X chromosome, triggers gene silencing and forms a dense body of heterochromatin from which the transcription machinery appears to be excluded. Phase separation has been proposed to be involved in XCI, and might explain the exclusion of the transcription machinery by preventing its diffusion into the Xist-coated territory. Here, using quantitative fluorescence microscopy and single-particle tracking, we show that RNA polymerase II (RNAPII) freely accesses the Xist territory during the initiation of XCI. Instead, the apparent depletion of RNAPII is due to the loss of its chromatin stably bound fraction. These findings indicate that initial exclusion of RNAPII from the inactive X reflects the absence of actively transcribing RNAPII, rather than a consequence of putative physical compartmentalization of the inactive X heterochromatin domain