Continuous fabrication of calcium sulfate whiskers with adjustable aspect ratio in microdroplets

Hemi-hydrate and anhydrous CaSO₄ whiskers with adjustable aspect ratio were continuously synthesized by the reactive crystallization of CaCl₂ to K₂ S₂ O₈ in microdroplets. The effects of solvent and reactive temperature were examined, with SEM and XRD characterizations. Hemi-hydrate and anhydrous CaSO₄ whiskers can be, respectively, obtained in aqueous and N,N-dimethylformamide solutions at 90 °C in 180 s. The addition of ethylene glycol or glycerol as well as increasing temperature could lead to the increase in length and aspect ratio of the whiskers. Thus this preparation technique provides a simple continuous route to synthesize CaSO₄ whiskers with two kinds of crystal structures in a short time, and adjustable lengths and aspect ratios

The Genomes of Oryza sativa: A History of Duplications

We report improved whole-genome shotgun sequences for the genomes of indica and japonica rice, both with multimegabase contiguity, or almost 1,000-fold improvement over the drafts of 2002. Tested against a nonredundant collection of 19,079 full-length cDNAs, 97.7% of the genes are aligned, without fragmentation, to the mapped super-scaffolds of one or the other genome. We introduce a gene identification procedure for plants that does not rely on similarity to known genes to remove erroneous predictions resulting from transposable elements. Using the available EST data to adjust for residual errors in the predictions, the estimated gene count is at least 38,000–40,000. Only 2%–3% of the genes are unique to any one subspecies, comparable to the amount of sequence that might still be missing. Despite this lack of variation in gene content, there is enormous variation in the intergenic regions. At least a quarter of the two sequences could not be aligned, and where they could be aligned, single nucleotide polymorphism (SNP) rates varied from as little as 3.0 SNP/kb in the coding regions to 27.6 SNP/kb in the transposable elements. A more inclusive new approach for analyzing duplication history is introduced here. It reveals an ancient whole-genome duplication, a recent segmental duplication on Chromosomes 11 and 12, and massive ongoing individual gene duplications. We find 18 distinct pairs of duplicated segments that cover 65.7% of the genome; 17 of these pairs date back to a common time before the divergence of the grasses. More important, ongoing individual gene duplications provide a never-ending source of raw material for gene genesis and are major contributors to the differences between members of the grass family

Tuning the magnetic and electronic properties of bilayer graphene nanoribbons on Si(001) by bias voltage

We report on a systematic study of bias-voltage-induced modulation of magnetic and electronic properties of bilayer zigzag graphene nanoribbons (Z-GNRs) on Si(001) substrate by first-principles calculations. We show that the intrinsically nonmagnetic bilayer Z-GNRs exhibit magnetic ordering on the top layer while the bottom layer serves as a nonmagnetic buffer layer when adsorbed on the substrate. Interestingly, the adsorbed bilayers display distinct ribbon-width-dependent magnetoelectric effect under bias voltages. The magnetoelectric coefficient oscillates with increasing ribbon width, which arises from an interesting interplay of the interaction of the bottom ribbon layer with the substrates and the decay length of the localized edge states in Z-GNRs. Moreover, our calculations reveal that the electronic band gap of the top ribbon layer also can be effectively modulated by the applied bias voltage, which can lead to a semiconductor-to-metal transition in the top magnetic semiconductor layer. These results provide insights into the intriguing behaviors of Z-GNRs on substrates and raise the prospects of developing an innovative path toward graphene-based electronic and spintronic devices by integrating the emerging nanoscale graphene systems with existing silicon technology

Complex Emulsions by Extracting Water from Homogeneous Solutions Comprised of Aqueous Three-Phase Systems

Multiple emulsions can be obtained by binary and ternary liquid phase separation. And the use of the aqueous two-phase system provides a simple route to prepare water-in-water-in-oil (W/W/O) or water-in-water-in-water (W/W/W) multiple emulsions. It is thus expected that we can fabricate more complex emulsions by using an aqueous three-phase system. Herein, we present a simple and versatile method to generate complex emulsions based on phase separation in homogeneous droplets made up of aqueous three-phase system: poly­(ethylene glycol) (PEG), poly­(vinyl alcohol) (PVA) and dextran (DEX) through extracting water from droplets. We examine the formation process and the effect of mass ratio of each two components in the three phase system. Emulsion droplets with five types of morphologies, i.e., binary-core/shell, core/shell-single phase Janus, ellipsoid Janus, multicore-in-matrix and single core-double shell morphologies can be formed, depending on the mass ratio of each two components and modification of PEG with Fe₃O₄ nanoparticles. We observe transition of core/shell-single phase Janus to binary-core/shell and single core-double shell to core/shell-single phase Janus geometry with prolongation of extracting time, and obtain the geometry map for the formation of different shaped droplets. Due to different affinities of PEG, PVA and DEX to certain materials, we functionalize each compartment in the complex emulsion droplets, and apply the resulting droplet for glucose sensing and the construction of antibody-mediated targeting drug delivery. This emulsion generation method is simple and the choice for the component of the aqueous three-phase system is broad, which can be further extended to generate complex emulsions from aqueous multiphase systems

Tree-ring-based drought variability in northern China over the past three centuries

Droughts are the most frequent natural disaster in regions at the margins of the East Asian summer monsoon (EASM), which pose threats to agriculture, the economy, and human lives. However, the limitations of only approximately 60 years of meteorological observations hamper our understanding of the characteristics and mechanisms of local hydroclimate. Trees growing in the marginal region of the EASM are usually sensitive to moisture variations and have played important roles in past hydroclimatic reconstructions. Here, a 303-year tree-ring-width chronology of Pinus tabulaeformis from Mt. Lama, which is located in the junction of the Liaoning Province and Inner Mongolia, China, was used to reconstruct the May-August Palmer drought severity index (PDSI) in the marginal region of the EASM. The transfer function explains 48.0% (or 47.2% after adjusting for the loss of the degrees of freedom) of the variance over the calibration period from 1946 to 2012. A spatial correlation analysis demonstrates that our PDSI reconstruction can represent the drought variability on the northernmost margin of the EASM. The winter Asian polar vortex area index showed a delayed impact on the summer EASM precipitation in the following year