Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone.

Materials that possess nontrivial topology and magnetism is known to exhibit exotic quantum phenomena such as the quantum anomalous Hall effect. Here, we fabricate a novel magnetic topological heterostructure Mn4Bi2Te7/Bi2Te3 where multiple magnetic layers are inserted into the topmost quintuple layer of the original topological insulator Bi2Te3. A massive Dirac cone (DC) with a gap of 40-75 meV at 16 K is observed. By tracing the temperature evolution, this gap is shown to gradually decrease with increasing temperature and a blunt transition from a massive to a massless DC occurs around 200-250 K. Structural analysis shows that the samples also contain MnBi2Te4/Bi2Te3. Magnetic measurements show that there are two distinct Mn components in the system that corresponds to the two heterostructures; MnBi2Te4/Bi2Te3 is paramagnetic at 6 K while Mn4Bi2Te7/Bi2Te3 is ferromagnetic with a negative hysteresis (critical temperature  ~20 K). This novel heterostructure is potentially important for future device applications.

Synthesis of bipyridylene-bridged bisporphyrin by nickel-mediated coupling reaction: ON-OFF control of cofacial porphyrin unit by reversible complexation.

Novel bipyridylene-bridged bisporphyrin 1a, in which two porphyrin units were attached directly to symmetrical 4,4'-positions of the 2,2'-bipyridyl group, was synthesized by a nickel(0)-mediated homocoupling reaction of 5,10,15-tris(n-heptyl)-20-(2'-bromo-4'-pyridyl)porphyrinatozinc (3a) in 58% yield. Spatial geometries of two porphyrins in 1a were regulated by reversible complexation of the bipyridyl part with PdCl(2). Thus, the addition of 2.2 equiv of palladium chloride to 1a converted the freely rotating conformation to the cofacial bisporphyrin 2a. The subsequent addition of 4,4'-dimethyl-2,2'-bipyridine 9 regenerated the initial bisporphyrin 1a.

A novel type of life cycle "delayed homothallism" in Saccharomyces cerevisiae wy2 showed slow interconversion of mating-type.

Saccharomyces cerevisiae wy2 segregated to 2 mater and 2 non-mater in relation to mating ability. The non-mater segregants behaved as the normal type of homothallic life cycle. On the other hand, the mater segregants gradually formed spores during successive subcultures, indicating that slow interconversion of mating-type happened to occur during subcultures. We termed this novel type of life cycle "delayed homothallism". The results of complementation tests with standard ho strains and introduction of a wild type HO gene showed that delayed homothallism was caused by a defective HO gene. The amino acid sequence deduced from the nucleotide sequence of the wy2 HO gene differed from the wild type HO gene in three amino acid residues. In the carboxy terminus of HO protein, there are three repeats of cysteine and histidine that are postulated to play a role in binding of HO protein to DNA. However, wy2 HO protein lacked one such repeat at residues Cys470-His475, where His was replaced by Leu.

Endomitotic diploidization of Saccharomyces cerevisiae by heat treatment during spore germination.

Diploid cells with ability to mate, hereafter referred to as diploid mater cells, were obtained at significant frequencies by the heat treatment of haploid spores at the early germination stage in Saccharomyces cerevisiae heterothallic strain CG5M (a/alpha diploid cells heterozygous for five auxotrophic markers). The highest frequency (ca. 11%) of diploidization was obtained from viable cells after heat treatment at 55 degrees C for 10 min when spores were precultivated for 30 min in liquid medium to initiate the germination. The diploid mater cells obtained were homozygous for mating type and for the auxotrophic markers. The diploidization of a spore is thus concluded to be due to endomitotic events in germinating heat-treated spores.

A new single band variant of the Gc subtypes determined by isoelectric focusing.

A new single band variant (Gc Ta) of the Gc subtypes which does not correspond with the known Gc variants has been detected in a healthy blood donor by isoelectric focusing. Using this technique the variant is represented by a single band, which is more cathodically located than the 1A8(fast) band and more anodically located than the 1A3(fast) band. It is well known that the single band Gc phenotypes remain unaltered after neuraminidase treatment. Nevertheless, the new single band variant (Gc Ta) is altered after neuraminidase treatment. In this case the new single band Gc variant also contained N-acetylneuraminic acid (NANA).