No abstract

Realization of topological superconductors (TSCs) hosting Majorana fermions is a central challenge in condensed-matter physics. One approach is to use the superconducting proximity effect (SPE) in heterostructures, where a topological insulator contacted with a superconductor hosts an effective p-wave pairing by the penetration of Cooper pairs across the interface. However, this approach suffers a difficulty in accessing the topological interface buried deep beneath the surface. Here, we propose an alternative approach to realize topological superconductivity without SPE. In a Pb(111) thin film grown on TlBiSe 2 , we discover that the Dirac-cone state of substrate TlBiSe 2 migrates to the top surface of Pb film and obtains an energy gap below the superconducting transition temperature of Pb. This suggests that a Bardeen-Cooper-Schrieffer superconductor is converted into a TSC by the topological proximity effect. Our discovery opens a route to manipulate topological superconducting properties of materials.

Considering the cost-effectiveness of bioethanol production, there is a need for a yeast strain which can convert glucose and xylose into ethanol at elevated temperatures. We succeeded in isolating a yeast strain, designated strain ATY839, which was capable of ethanolic fermentation at temperatures above those previously reported for yeasts able to ferment both glucose and xylose. Strain ATY839 was capable of producing a substantial amount of ethanol at up to 37°C from 2% glucose or 2% xylose. The results of a phylogenetic analysis suggest that strain ATY839 belongs to Candida shehatae. In additional, ethanol production from rice straw by strain ATY839 was examined. Compared with the control strains (Saccharomyces cerevisiae NBRC 0224, Scheffersomyces stipitis NBRC 10063, and C. shehatae ATCC 22984), strain ATY839 produced more ethanol in SSF even at 37°C. The theoretical maximum yield of strain ATY839 was 71.6% at 24 h. Thus, strain ATY839 is considered to be the most tolerant to high temperature of the C. shehatae strains.