Direct Observation of Nonequivalent Fermi-Arc States of Opposite Surfaces in Noncentrosymmetric Weyl Semimetal NbP

We have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) on noncentrosymmetric Weyl semimetal candidate NbP, and determined the electronic states of both Nb- and P-terminated surfaces corresponding to the "opposite" surfaces of a polar crystal. We revealed a drastic difference in the Fermi-surface topology between the opposite surfaces, whereas the Fermi arcs on both surfaces are likely terminated at the surface projection of the same bulk Weyl nodes. Comparison of the ARPES data with our first-principles band calculations suggests notable difference in electronic structure at the Nb-terminated surface between theory and experiment. The present result opens a platform for realizing exotic quantum phenomena arising from unusual surface properties of Weyl semimetals.Comment: 5 pages, 4 figure

An EST-SSR Linkage Map of Raphanus sativus and Comparative Genomics of the Brassicaceae†

Raphanus sativus (2n = 2x = 18) is a widely cultivated member of the family Brassicaceae, for which genomic resources are available only to a limited extent in comparison to many other members of the family. To promote more genetic and genomic studies and to enhance breeding programmes of R. sativus, we have prepared genetic resources such as complementary DNA libraries, expressed sequences tags (ESTs), simple sequence repeat (SSR) markers and a genetic linkage map. A total of 26 606 ESTs have been collected from seedlings, roots, leaves, and flowers, and clustered into 10 381 unigenes. Similarities were observed between the expression patterns of transcripts from R. sativus and those from representative members of the genera Arabidopsis and Brassica, indicating their functional relatedness. The EST sequence data were used to design 3800 SSR markers and consequently 630 polymorphic SSR loci and 213 reported marker loci have been mapped onto nine linkage groups, covering 1129.2 cM with an average distance of 1.3 cM between loci. Comparison of the mapped EST-SSR marker positions in R. sativus with the genome sequence of A. thaliana indicated that the Brassicaceae members have evolved from a common ancestor. It appears that genomic fragments corresponding to those of A. thaliana have been doubled and tripled in R. sativus. The genetic map developed here is expected to provide a standard map for the genetics, genomics, and molecular breeding of R. sativus as well as of related species. The resources are available at http://marker.kazusa.or.jp/Daikon

The Extracellular Matrix and Blood Vessel Formation: Not Just a Scaffold

The extracellular matrix plays a number of important roles, among them providing structural support and information to cellular structures such as blood vessels imbedded within it. As more complex organisms have evolved, the matrix ability to direct signalling towards the vasculature and remodel in response to signalling from the vasculature has assumed progressively greater importance. This review will focus on the molecules of the extracellular matrix, specifically relating to vessel formation and their ability to signal to the surrounding cells to initiate or terminate processes involved in blood vessel formation

TWO-DIMENSIONAL MAGNETIC ORDER IN HEXAGONAL LuFe2O4

Neutron diffraction measurements have been performed on a LuFe2O4 single crystal with a hexagonal layered structure. At low temperatures a 2:l ferrimagntic spin arrangement of Fe ions is realized in each layer consisting of two triangular nets. The magnetic interaction between the different layers is so weak that the magnetic order is quasi-two-dimensional

In optimized rubrene-based nanoparticle blends for photon upconversion, singlet energy collection outcompetes triplet-pair separation, not singlet fission

The conversion of near-infrared photons to visible light through triplet–triplet annihilation upconversion offers an enticing strategy for significantly boosting the efficiency of conventional solar cell technology. Rubrene is widely employed as the acceptor molecule for realising such upconversion, yet in the solid state, the reverse process of singlet fission is believed to hinder efficient upconversion. Consequently, rubrene is sometimes doped at low concentration (0.5 mol%) with the singlet energy collector tetraphenyldibenzoperiflanthene (DBP) which harvests singlet energy via Förster transfer. Although singlet fission is a multi-step process involving various intermediate triplet-pair states, the interplay between it, triplet recombination and singlet energy collection has not been studied in detail to date. Here we use both transient absorption and time-resolved fluorescence spectroscopy to investigate the dynamics of both singlet and triplet species in rubrene-based nanoparticle films. Strikingly, we find that energy transfer from rubrene to DBP does not outcompete the formation of triplet-pairs through singlet fission, despite the fact that DBP doping increases the photoluminescence quantum yield of the nanoparticle films from 3% to 61%. We rationalise this surprising result in the context of the well-known effects of triplet fusion and triplet-quenching defects on the photoluminescence yield of crystalline rubrene