Isotropic round-wire multifilament cuprate superconductor for generation of magnetic fields above 30 T.

Magnets are the principal market for superconductors, but making attractive conductors out of the high-temperature cuprate superconductors (HTSs) has proved difficult because of the presence of high-angle grain boundaries that are generally believed to lower the critical current density, J(c). To minimize such grain boundary obstacles, HTS conductors such as REBa2Cu3O(7-x) and (Bi, Pb)2Sr2Ca2Cu3O(10-x) are both made as tapes with a high aspect ratio and a large superconducting anisotropy. Here we report that Bi2Sr2CaCu2O(8-x) (Bi-2212) can be made in the much more desirable isotropic, round-wire, multifilament form that can be wound or cabled into arbitrary geometries and will be especially valuable for high-field NMR magnets beyond the present 1 GHz proton resonance limit of Nb3Sn technology. An appealing attribute of this Bi-2212 conductor is that, being without macroscopic texture, it contains many high-angle grain boundaries but nevertheless attains a very high J(c) of 2,500 A mm(-2) at 20 T and 4.2 K. The large potential of the conductor has been demonstrated by building a small coil that generated almost 2.6 T in a 31 T background field. This demonstration that grain boundary limits to high Jc can be practically overcome underlines the value of a renewed focus on grain boundary properties in non-ideal geometries.

Performance Boost in Industrial Multifilamentary Nb3Sn Wires due to Radiation Induced Pinning Centers.

We report non-Cu critical current densities of 4. 09 ⋅ 10(9) A/m(2) at 12 T and 2.27 ⋅ 10(9) A/m(2) at 15 T obtained from transport measurements on a Ti-alloyed RRP Nb3Sn wire after irradiation to a fast neutron fluence of 8.9 ⋅ 10(21) m(-2). These values are to our knowledge unprecedented in multifilamentary Nb3Sn, and they correspond to a Jc enhancement of approximately 60% relative to the unirradiated state. Our magnetometry data obtained on short wire samples irradiated to fast neutron fluences of up to 2.5 ⋅ 10(22) m(-2) indicate the possibility of an even better performance, whereas earlier irradiation studies on bronze-processed Nb3Sn wires with a Sn content further from stoichiometry attested a decline of the critical current density at such high fluences. We show that radiation induced point-pinning centers rather than an increase of the upper critical field are responsible for this Jc enhancement, and argue that these results call for further research on pinning landscape engineering.

Phylogenetic and Biochemical Studies on Stomatococcus mucilaginosus.

The degree of relatedness of nine strains of Stomatococcus mucilaginosus (formerly classified as 'Micrococcus mucilaginosus') was investigated by deoxyribonucleic acid hybridization. We confirm that all strains are highly related. Differences in the peptidoglycan type and the cytochrome pattern between S. mucilaginosus and members of Micrococcus, together with the results of 23 S ribosomal ribonucleic acid cistron similarity studies and the analysis of the 16S ribosomal ribonucleic acid support the exclusion of this species from the genus Micrococcus and justifies its reclassification as a member of a new genus, Stomatococcus (Bergan and Kocur, 1982). Phylogenetically, S. mucilaginosus represents an independent line of descent within a broad group of Gram-positive bacteria that contains arthrobacteria, micrococci, cellulomonads, brevibacteria and microbacteria.