W.Y. Wang

Nonlinear electrical behavior and dielectric properties of (Ca, Ta)-doped TiO2 ceramics

TiO2 ceramics doped with 2.5 mol% Ta and different concentrations of Ca were obtained by sintering at 1300degreesC. As a varistor material, the nonlinear electrical behavior and dielectric properties of these ceramics were investigated. The ceramics have nonlinear coefficients a in the range 2.0-5.5 and high relative dielectric constants. The effects of Ca on the density, nonlinear electrical behavior, resistivity and dielectric properties of the Ta-doped TiO2 ceramics were also studied. The sample doped with 0.75 mol% Ca and 2.5 mol% Ta exhibits the highest nonlinear coefficient and a comparatively lower relative dielectric constant. By analogy to a grain-boundary defect model, the nonlinear electrical behavior of the TiO2 system is explained

Modulation of acid-sensing ion channels by Cu2+ in cultured hypothalamic neurons of the rat

Acid-sensing ion channels (ASICs) are known to distribute throughout the nervous system and serve important roles in various physiological and pathological processes. However, the properties of ASICs in the hypothalamus, an important region of diencephalon, are little known. We herein used whole-cell patch-clamp recordings to characterize proton-induced cation currents in cultured hypothalamic neurons of the rat, and attributed these transient inward currents to ASICs based on their electrophysiological and pharmacological properties. We further examined the effects of Cu(2+), the third most abundant trace element, on ASICs in hypothalamic neurons. Our results showed that this divalent cation reversibly and concentration-dependently inhibited the amplitude of ASIC currents, and slowed down the desensitization of ASIC channels. Our results also displayed that Cu(2+) modulated ASICs independent of change in membrane potential and extracellular protons, suggesting a noncompetitive mechanism. Furthermore, micromolar concentration of Cu(2+) attenuated the acid-induced membrane depolarization. Taken together, our data demonstrate a modulatory effect of Cu(2+) on ASICs in native hypothalamic neurons and suggest a role of this endogenous metal ion in negatively modulating the increased neuronal membrane excitability caused by activation of ASICs.

Genomic variation in 3,010 diverse accessions of Asian cultivated rice

Here we analyse genetic variation, population structure and diversity among 3,010 diverse Asian cultivated rice (Oryza sativa L.) genomes from the 3,000 Rice Genomes Project. Our results are consistent with the five major groups previously recognized, but also suggest several unreported subpopulations that correlate with geographic location. We identified 29 million single nucleotide polymorphisms, 2.4 million small indels and over 90,000 structural variations that contribute to within- and between-population variation. Using pan-genome analyses, we identified more than 10,000 novel full-length protein-coding genes and a high number of presence–absence variations. The complex patterns of introgression observed in domestication genes are consistent with multiple independent rice domestication events. The public availability of data from the 3,000 Rice Genomes Project provides a resource for rice genomics research and breeding.Analyses of genetic variation and population structure based on over 3,000 cultivated rice (Oryza sativa) genomes reveal subpopulations that correlate with geographic location and patterns of introgression consistent with multiple rice domestication events.

Genome and Comparative Transcriptomics of African Wild Rice Oryza longistaminata Provide Insights into Molecular Mechanism of Rhizomatousness and Self-Incompatibility

Dear Editor, Oryza Iongistaminata is an African wild rice species with AA genome type possessing special traits that are highly valued for improving cultivated rice,such as strong resistance to biotic and abiotic stresses (Song et al.,1995) for improving resistance of cultivars,rhizomatousness for perennial breeding (Glover et al.,2010),and self-incompatibility (SI) for new ways to produce hybrid seeds (Ghesquiere,1986).Deciphering the genome of O.longistaminata will be the key to uncovering the mechanism of these hallmark traits and improving cultivated rice.

Tuning the stress induced martensitic formation in titanium alloys by alloy design

Two novel titanium alloys, Ti–10V–2Cr–3Al and Ti–10V–1Fe–3Al (wt%), have been designed, fabricated, and tested for their intended stress-induced martensitic (SIM) transformation behavior. The results show that for Ti–10V–1Fe–3Al the triggering stress for SIM transformation is independently affected by the β domain size and β phase stability, when the value of the molybdenum equivalent is higher than ~9. The triggering stress was well predicted using the equations derived separately for the commercial Ti–10V–2Fe–3Al alloy. For samples containing β with a lower molybdenum equivalence value, pre-existing thermal martensite is also present and this was found to have an obstructive effect on SIM transformation. In Ti–10V–2Cr–3Al, the low diffusion speed of Cr caused local gradients in the Cr level for many heat treatments leading even to martensite free zones near former β regions.

RPAN: rice pan-genome browser for ∼3000 rice genomes

A pan-genome is the union of the gene sets of all the individuals of a clade or a species and it provides a new dimension of genome complexity with the presence/absence variations (PAVs) of genes among these genomes. With the progress of sequencing technologies, pan-genome study is becoming affordable for eukaryotes with large-sized genomes. The Asian cultivated rice, Oryza sativa L., is one of the major food sources for the world and a model organism in plant biology. Recently, the 3000 Rice Genome Project (3K RGP) sequenced more than 3000 rice genomes with a mean sequencing depth of 14.3×, which provided a tremendous resource for rice research. In this paper, we present a genome browser, Rice Pan-genome Browser (RPAN), as a tool to search and visualize the rice pan-genome derived from 3K RGP. RPAN contains a database of the basic information of 3010 rice accessions, including genomic sequences, gene annotations, PAV information and gene expression data of the rice pan-genome. At least 12 000 novel genes absent in the reference genome were included. RPAN also provides multiple search and visualization functions. RPAN can be a rich resource for rice biology and rice breeding. It is available at http://cgm.sjtu.edu.cn/3kricedb/ or http://www.rmbreeding.cn/pan3k.

OsLG3 contributing to rice grain length and yield was mined by Ho-LAMap

BackgroundMost agronomic traits in rice are complex and polygenic. The identification of quantitative trait loci (QTL) for grain length is an important objective of rice genetic research and breeding programs.ResultsHerein, we identified 99 QTL for grain length by GWAS based on approximately 10 million single nucleotide polymorphisms from 504 cultivated rice accessions (Oryza sativa L.), 13 of which were validated by four linkage populations and 92 were new loci for grain length. We scanned the Ho (observed heterozygosity per locus) index of coupled-parents of crosses mapping the same QTL, based on linkage and association mapping, and identified two new genes for grain length. We named this approach as Ho-LAMap. A simulation study of six known genes showed that Ho-LAMap could mine genes rapidly across a wide range of experimental variables using deep-sequencing data. We used Ho-LAMap to clone a new gene, OsLG3, as a positive regulator of grain length, which could improve rice yield without influencing grain quality. Sequencing of the promoter region in 283 rice accessions from a wide geographic range identified four haplotypes that seem to be associated with grain length. Further analysis showed that OsLG3 alleles in the indica and japonica evolved independently from distinct ancestors and low nucleotide diversity of OsLG3 in indica indicated artificial selection. Phylogenetic analysis showed that OsLG3 might have much potential value for improvement of grain length in japonica breeding.ConclusionsThe results demonstrated that Ho-LAMap is a potential approach for gene discovery and OsLG3 is a promising gene to be utilized in genomic assisted breeding for rice cultivar improvement.

Debye temperature of 4H-SiC determined by X-ray powder diffraction

Crystal structure of 4H-SiC was refined from room-temperature X-ray powder diffraction data using the Rietveld refinement method. The refined lattice constants were determined to be a=b=3.079 93(0) angstrom, c=10.082 22(2) angstrom, and the refined overall temperature factor B=0.383(3) angstrom(2). Using the Debye approximation, the Debye temperature was successfully determined to be 1194.8 K

Crystal structure and luminescence properties of a novel promising phosphor Ba3ScB9O18

A novel borate compound Ba3ScB9O18 has been synthesized by solid-state reaction and its structure has been determined and refined from powder X-ray diffraction data. This compound crystallizes in a hexagonal cell (space group P6(3)/m) with lattice parameters a=7.1360(4) angstrom and c=16.5420(9) angstrom, and each unit cell contains two formulas. Its crystal structure is made up of planar B3O6 groups parallel to each other along the [001] direction, regular SCO6 octahedra, irregular BaO6 hexagons, and BaO9 polyhedra to form an analogue structure of Ba3YB9O18. DTA and TGA curves for Ba3ScB9O18 show that it is a chemically stable and congruent melting compound. Luminescence properties for Ba3ScB9O18 were investigated using fluorescence spectroscopy and X-ray excited luminescence measurements. Its emission spectrum upon UV excitation (330 nm) has exhibited a prominent blue-green emission band at about 490 nm, and its XEL spectra show an intense emission band in the range of 360 to 500 nm with peak center at 400 nm. The light yield of Ba3ScB9O18 powders is about 23% as large as that of BGO powders under the same measurement conditions. There seems to be a certain relationship between the scintillation properties and the structural features of Ba3ScB9O18

The effects of grain boundary response and electrode contact response on the dielectric properties of CaCu3Ti4O12

The influences of dc bias on complex impedance, complex module and dielectric response of CaCu 3 Ti 4 O 12 for different sintering durations have been investigated to elucidate the origin of its dielectric properties. It is found that both the electrode contact response and grain boundary response contribute to the dielectric constant of CaCu 3 Ti 4 O 12 . The origins of the semicircles in complex impedance plots of CaCu 3 Ti 4 O 12 have also been investigated. At 120 °C, the mid-frequency semicircle in complex impedance plots represents the electrode contact response and the low-frequency semicircle may correspond to the oxygen-vacancy relevant response. The semicircle of the grain boundary response in the complex impedance plot is covered by the semicircle of the electrode contact response at this temperature.