Elastic properties of the Non-Fermi liquid metal CeRu4Sb12Ce Ru_4 Sb_{12} and the Dense Kondo semiconductor CeOs4Sb12Ce Os_4 Sb_{12}

We have investigated the elastic properties of the Ce-based filled skutterudite antimonides CeRu$_{4}$Sb$_{12}$ and CeOs$_{4}$Sb$_{12}$ by means of ultrasonic measurements. CeRu$_{4}$Sb$_{12}$ shows a slight increase around 130 K in the temperature dependence of the elastic constants $C$$_{11}$, ($C$$_{11}$-$C$$_{12}$)/2 and $C$$_{44}$. No apparent softening toward low temperature due to a quadrupolar response of the 4$f$-electronic ground state of the Ce ion was observed at low temperatures. In contrast CeOs$_{4}$Sb$_{12}$ shows a pronounced elastic softening toward low temperature in the longitudinal $C$$_{11}$ as a function of temperature ($T$) below about 15 K, while a slight elastic softening was observed in the transverse $C$$_{44}$ below about 1.5 K. Furthermore, CeOs$_{4}$Sb$_{12}$ shows a steep decrease around a phase transition temperature of 0.9 K in both $C$$_{11}$ and$C$$_{44}$. The elastic softening observed in $C$$_{11}$ below about 15 K cannot be explained reasonably only by the crystalline electric field effect. It is most likely to be responsible for the coupling between the elastic strain and the quasiparticle band with a small energy gap in the vicinity of Fermi level. The elastic properties and the 4$f$ ground state of Ce ions in CeRu$_{4}$Sb$_{12}$ and CeOs$_{4}$Sb$_{12}$ are discussed from the viewpoint of the crystalline electric field effect and the band structure in the vicinity of Fermi level.Comment: 9 pages, 11 figures, regular pape

Identification of the sex-determining factor in the liverwort Marchantia polymorpha reveals unique evolution of sex chromosomes in a haploid system

半数体生物の性染色体上の性決定遺伝子を解明 --コケがもつ現生生物最古の起源の性染色体--. 京都大学プレスリリース. 2021-11-08.Sex determination is a central process for sexual reproduction and is often regulated by a sex determinant encoded on a sex chromosome. Rules that govern the evolution of sex chromosomes via specialization and degeneration following the evolution of a sex determinant have been well studied in diploid organisms. However, distinct predictions apply to sex chromosomes in organisms where sex is determined in the haploid phase of the life cycle: both sex chromosomes, female U and male V, are expected to maintain their gene functions, even though both are non-recombining. This is in contrast to the X-Y (or Z-W) asymmetry and Y (W) chromosome degeneration in XY (ZW) systems of diploids. Here, we provide evidence that sex chromosomes diverged early during the evolution of haploid liverworts and identify the sex determinant on the Marchantia polymorpha U chromosome. This gene, Feminizer, encodes a member of the plant-specific BASIC PENTACYSTEINE transcription factor family. It triggers female differentiation via regulation of the autosomal sex-determining locus of FEMALE GAMETOPHYTE MYB and SUPPRESSOR OF FEMINIZATION. Phylogenetic analyses of Feminizer and other sex chromosome genes indicate dimorphic sex chromosomes had already been established 430 mya in the ancestral liverwort. Feminizer also plays a role in reproductive induction that is shared with its gametolog on the V chromosome, suggesting an ancestral function, distinct from sex determination, was retained by the gametologs. This implies ancestral functions can be preserved after the acquisition of a sex determination mechanism during the evolution of a dominant haploid sex chromosome system