Role of self-irradiation defects on the ageing of 239PuCoGa5

6 pages, 18 referencesInternational audienceLow-temperature accumulation and annealing experiments, in conjunction with electrical resistivity and critical current density measurements, were used to study the ageing of the actinide superconductor PuCoGa5. These measurements reveal that 2-nm sized non-superconducting point-like regions are the main damage formed during room temperature ageing; smaller point-like defect were irrelevant to transport properties. Defect sizes and densities deduced from experiment agree with Transmission Electron Micoscopy observations

Prioritization of candidate causal genes for asthma in susceptibility loci derived from UK Biobank

Kim Valette et al. perform a genomic study on asthma integrating genome-wide association study, functional mapping using lung and blood transcriptome-wide profiles, as well as Mendelian randomization. They show candidate causal genes expressed in lung and blood tissues that are putative therapeutic targets for asthma

Twenty-three unsolved problems in hydrology (UPH) – a community perspective

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through on-line media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focussed on process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come

Pressure Effects on PuMGa5 Systems (M=Co, Rh, Ir)

We report high-pressure resistivity of PuMGa5 (M 1/4 Co; Rh, Ir) up to 20GPa from 300 down to 1.4 K. For PuCoGa5 and PuRhGa5 superconductivity takes place over the whole pressure domain investigated and a non-Fermi liquid behaviour (rT T1:3) in the normal state is observed. A strong correlation between the temperature–pressure diagrams of PuCo; RhGa5 and CeCo; IIn5 is inferred. Interestingly, PuIrGa5 does not show superconductivity up to 10 GPa and down to 1.4K but rather develops a Fermi liquid regime.JRC.E.6-Actinides researc

Tuning the Superconducting Behaviour of the PuTGa5 Compounds

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Magnetic Diagrams of PuGa3 under Pressure

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A New Family of Heavy-fermion Compounds - U4TGa12 (T = Fe, Co, Rh and Pd)

U4TGa12 (T = Fe, Co, Rh and Pd) compounds represent a new family of isostructural heavy-fermion materials. They crystallize in the cubic structure typeY4PdGa12 (Im 3m) which consists of the doubling of the UGa3 (AuCu3-type, Pm 3m) elementary cell with a partial ordered occupancy (1/4) of the gallium octahedra by the transition metal atoms. Their magnetic and electronic properties (resistivity, magnetization and specific heat) have been investigated. All compounds display a moderately enhanced value of the Sommerfeld coefficient γ (80–140 mJ/molUK2) whereas only U4PdGa12 shows the occurrence of an antiferromagnetic order below TN =43K.JRC.E.6-Actinides researc

Influence of Self-Irradiation Damages on the Superconducting Behaviour of Pu-Based Compounds

Ageing effects on the critical parameters (Tc, Hc2) of the superconductors PuCoGa5 and PuRhGa5 are presented. A linear diminution of the critical temperature versus sample ageing is observed. The diminution rate of Tc is larger for PuRhGa5 (DTc/Dt 0.39 K/month) than for PuCoGa5 (DTc/Dt 0.24 K/month). The damages created by selfirradiation (from 239Pu decay) also actas pinning centres, enhancing Hc2(0) with ageing. After 532 days, the PuCoGa5 sample shows an increase of its Hc2(0) up to1350 kOe, whereas in the case of PuRhGa5, the damages produced after only 323 days of ageing destroy the superconductivity. These results suggest that both compounds are surprisingly not equally sensitive to radiation damages.JRC.E.6-Actinides researc

Influence of Self-irradiation Damages on the Superconducting Behaviour of Plutonium -based Compounds

External irradiation of materials creates defects and induces lattice disorders. Interestingly, defects are sometimes helpful for technological purposes. Hence, controlled defect creation has drawn prime attention, in particular on superconductors (especially A15 phases and high temperature superconductors), to make them economically viable by improving their critical current density (irradiation-induced defects act as pinning centres for vortices, which are quantized magnetic fluxes entering the material)1. In this context, the discovery of PuCoGa5 2 and PuRhGa5 3 superconductors is very interesting: first, they represent two new cases of non-conventional superconductors4,5 and second, they provide unique cases to study the impact of self-radiation damage (due to the α-decay of the Pu atoms) on the superconducting critical parameters. In this work, we report about ageing effects in 239PuCo1-xRhxGa5 solid solutions to improve our understanding of the interactions between defects and vortices, without performing any extra irradiation experiment. The evolution with time of the critical parameters (Tc, Hc2, Jc) has been followed by SQUID magnetometry and electrical resistivity measurements.JRC.E.6-Actinides researc