Draft Genome Sequence of Frankia sp. Strain BCU110501, a Nitrogen-Fixing Actinobacterium Isolated from Nodules of Discaria trinevis

Frankia forms a nitrogen-fixing symbiosis with actinorhizal plants. We report a draft genome sequence for Frankia sp. strain BCU110501, a nitrogen-fixing actinobacterium isolated from nodules of Discaria trinevis grown in the Patagonia region of Argentina

Dichotomous dynamics of magnetic monopole fluids

A recent advance in the study of emergent magnetic monopoles was the discovery that monopole motion is restricted to dynamical fractal trajectories [J. N. Hallén et al., Science 378, 1218 (2022)], thus explaining the characteristics of magnetic monopole noise spectra [R. Dusad et al., Nature 571, 234 (2019); A. M. Samarakoon et al., Proc. Natl. Acad. Sci. U.S.A. 119, e2117453119 (2022)]. Here, we apply this novel theory to explore the dynamics of field-driven monopole currents, finding them composed of two quite distinct transport processes: initially swift fractal rearrangements of local monopole configurations followed by conventional monopole diffusion. This theory also predicts a characteristic frequency dependence of the dissipative loss angle for AC field–driven currents. To explore these novel perspectives on monopole transport, we introduce simultaneous monopole current control and measurement techniques using SQUID-based monopole current sensors. For the canonical material Dy2Ti2O7, we measure Φ(t), the time dependence of magnetic flux threading the sample when a net monopole current J(t) = Φ̇ (t)∕0 is generated by applying an external magnetic field B0(t). These experiments find a sharp dichotomy of monopole currents, separated by their distinct relaxation time constants before and after t ~600 μs from monopole current initiation. Application of sinusoidal magnetic fields B0(t) = Bcos(t) generates oscillating monopole currents whose loss angle ( f ) exhibits a characteristic transition at frequency f ≈ 1.8 kHz over the same temperature range. Finally, the magnetic noise power is also dichotomic, diminishing sharply after t ~600 μs. This complex phenomenology represents an unprecedented form of dynamical heterogeneity generated by the interplay of fractionalization and local spin configurational symmetry

Isothermal and cyclic oxidation behaviour of hot-pressed MSi2 compounds (with M = V, Ti, Cr)

International audienceThe oxidation resistance of MSi2 compounds with M = V, Ti, Cr was investigated from 450 to 950 degrees C in air under isothermal and cyclic conditions. Vanadium, chromium and titanium disilicide were not subjected to the pest phenomenon at 650 degrees C over 800 1-h cycles. The results demonstrated very low weight gains regardless of the testing conditions. Oxidation tests were also performed over long duration (1000 h) to identify the oxidation products. The MSi2 compounds were all subjected to the simultaneous oxidation of M and Si despite the formation of a protective silica scale. Increasing the duration of oxidation enhanced the protective properties of the silica scale. Therefore, short-term measurements (by thermogravimetry) did not allow an extrapolation of the MSi2 lifetime. The formation of molten V2O5 induced a higher oxidation rate of VSi2 and delayed the establishment of the protective silica scale compared with CrSi2 and TiSi2

The ability of silicide coating to delay the catastrophic oxidation of vanadium under severe conditions

International audienceV-4Cr-4Ti vanadium alloy is a potential cladding material for sodium-cooled fast-neutron reactors (SFRs). However, its affinity for oxygen and the subsequent embrittlement that oxygen induces causes a need for an oxygen diffusion barrier, which can be obtained by manufacturing a multi-layered silicide coating. The present work aims to evaluate the effects of thermal cycling (using a cyclic oxidation device) and tensile and compressive stresses (using the three-point flexure test) on the coated alloy system. Tests were performed in air up to 1100 degrees C, which is 200 degrees C higher than the accidental temperature for SFR applications. The results showed that the VSi2 coating was able to protect the vanadium substrate from oxidation for more than 400 1-h cycles between 1100 degrees C and room temperature. The severe bending applied to the coated alloy at 950 degrees C using a load of 75 MPa did not lead to specimen breakage. It can be suggested that the VSi2 coating has mechanical properties compatible with the V-4Cr-4Ti alloy for SFR applications

Thermodynamic modeling of the V-Cr-Si system

International audienceIn the present work, an assessment of the V-Cr-Si system was done. Mainly based on previously ternary experimental data on the isothermal section at 1200 C and on the liquid-solid equilibria, a thermodynamic modeling of the ternary system was performed within the CALPHAD approach using the Thermo-Calc and the Pandat software packages and taking into account data from existing assessment of binary sub-systems. Four intermediate phases were considered as stoichiometric compounds (Cr,V)(Si)y with substitution of Cr and Vat Si ratio constant: (Cr,V)Si, (Cr,V)5Si3, (Cr,V)liSi5 and (Cr,V)6Si5. Two others phases (Cr,V)Si2 and (Cr,V)3Si presenting a slight domain of homogeneity, were described as (Cr,Si,V)1(Cr,S02 and (Cr,Si,V)3(Cr,Si,V)1 respectively. The metallic liquid phase and the terminal solid solutions of chromium and vanadium were described by the disordered solutions model as (Cr,Si,V)1(Va)3. The silicon admitting any solubility, its description was limited to (Si). The resulting thermodynamic optimization led to a good agreement with experimental data