The effect of very high barium content in the precursor on the properties of GdBCO single grain bulk superconductors

A new melt processing route for the fabrication of large grain Gd-Ba-Cu-O (GdBCO) bulk superconductors has been developed based on the use of novel GdBa4Cu3O8−δ (Gd-143) and GdBa6Cu3O10−δ (Gd-163) precursor compositions. The new processing route enables the fabrication of large single grains from precursor powders that contain high concentrations of Ba. The superconducting properties and microstructures of GdBCO single grains with extra Ba fabricated via this new processing route are reported. Most importantly, the possible formation of a new form of Gd1+xBa2−xCu3O7−δ solid solution (Gd-123ss) with x < 0 in single grains fabricated from the Ba-rich precursor are discussed for the first time based on the superconducting, chemical, and structural properties of the large GdBCO grains.

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The Influence of CeO2 Addition on Microstructure and Superconducting Properties of GdBCO-Ag Single Grain Bulk Superconductors

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2021.161697 ◽

2021 ◽

pp. 161697

Author(s):

Petra Hajdova ◽

Pavel Diko ◽

Michal Rajnak ◽

Jozef Bednarcik ◽

Vitaliy Antal ◽

...

Keyword(s):

Superconducting Properties ◽

Bulk Superconductors ◽

Single Grain ◽

Grain Bulk

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Novel Aminoglycoside-Tolerant Phoenix Colony Variants of Pseudomonas aeruginosa

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00623-20 ◽

2020 ◽

Vol 64 (9) ◽

Author(s):

Devin Sindeldecker ◽

Kelly Moore ◽

Anthony Li ◽

Daniel J. Wozniak ◽

Matthew Anderson ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Calcium Sulfate ◽

Bacterial Pathogen ◽

Wild Type ◽

Antibiotic Resistant ◽

Content Type ◽

Persistent Infections ◽

High Concentrations ◽

First Time ◽

Very High

ABSTRACT Pseudomonas aeruginosa is an opportunistic bacterial pathogen and is known to produce biofilms. We previously showed the emergence of colony variants in the presence of tobramycin-loaded calcium sulfate beads. In this study, we characterized the variant colonies, which survived the antibiotic treatment, and identified three distinct phenotypes—classically resistant colonies, viable but nonculturable colonies (VBNC), and phoenix colonies. Phoenix colonies, described here for the first time, grow out of the zone of clearance of antibiotic-loaded beads from lawn biofilms while there are still very high concentrations of antibiotic present, suggesting an antibiotic-resistant phenotype. However, upon subculturing of these isolates, phoenix colonies return to wild-type levels of antibiotic susceptibility. Compared with the wild type, phoenix colonies are morphologically similar aside from a deficiency in green pigmentation. Phoenix colonies do not recapitulate the phenotype of any previously described mechanisms of resistance, tolerance, or persistence and, thus, form a novel group with their own phenotype. Growth under anaerobic conditions suggests that an alternative metabolism could lead to the formation of phoenix colonies. These findings suggest that phoenix colonies could emerge in response to antibiotic therapies and lead to recurrent or persistent infections, particularly within biofilms where microaerobic or anaerobic environments are present.

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