On the basis of geophysical observations, cosmochemical constraints, and high-pressure experimental data, the Earth's liquid outer core consists of mainly liquid iron alloyed with about ten per cent (by weight) of light elements. Although the concentrations of the light elements are small, they nevertheless affect the Earth's core: its rate of cooling, the growth of the inner core, the dynamics of core convection, and the evolution of the geodynamo. Several light elements-including sulphur, oxygen, silicon, carbon and hydrogen-have been suggested, but the precise identity of the light elements in the Earth's core is still unclear. Oxygen has been proposed as a major light element in the core on the basis of cosmochemical arguments and chemical reactions during accretion. Its presence in the core has direct implications for Earth accretion conditions of oxidation state, pressure and temperature. Here we report new shockwave data in the Fe-S-O system that are directly applicable to the outer core. The data include both density and sound velocity measurements, which we compare with the observed density and velocity profiles of the liquid outer core. The results show that we can rule out oxygen as a major light element in the liquid outer core because adding oxygen into liquid iron would not reproduce simultaneously the observed density and sound velocity profiles of the outer core. An oxygen-depleted core would imply a more reduced environment during early Earth accretion.

Serving as an important second messenger, calcium ion has unique properties and universal ability to transmit diverse signals that trigger primary physiological actions in cells in response to hormones, pathogens, light, gravity, and stress factors. Being a second messenger of paramount significance, calcium is required at almost all stages of plant growth and development, playing a fundamental role in regulating polar growth of cells and tissues and participating in plant adaptation to various stress factors. Many researches showed that calcium signals decoding elements are involved in ABA-induced stomatal closure and plant adaptation to drought, cold, salt and other abiotic stresses. Calcium channel proteins like AtTPC1 and TaTPC1 can regulate stomatal closure. Recently some new studies show that Ca 2+ is dissolved in water in the apoplast and transported primarily from root to shoot through the transpiration stream. The oscillating amplitudes of [Ca 2+ ] o and [Ca 2+ ] i are controlled by soil Ca 2+ concentrations and transpiration rates. Because leaf water use efficiency (WUE) is determined by stomatal closure and transpiration rate, so there may be a close relationship between Ca 2+ transporters and stomatal closure as well as WUE, which needs to be studied. The selection of varieties with better drought resistance and high WUE plays an increasing role in bio-watersaving in arid and semi-arid areas on the globe. The current paper reviews the relationship between calcium signals decoding elements and plant drought resistance as well as other abiotic stresses for further study.

High temperature at grain filling can severely reduce wheat yield. Heat shock factors (Hsfs) are central regulators in heat acclimation. This study investigated the role of TaHsfC2a, a member of the monocot-specific HsfC2 subclass, in the regulation of heat protection genes in Triticum aestivum. Three TaHsfC2a homoeologous genes were highly expressed in wheat grains during grain filling and showed only transient up-regulation in the leaves by heat stress but were markedly up-regulated by drought and abscisic acid (ABA) treatment. Overexpression of TaHsfC2a-B in transgenic wheat resulted in up-regulation of a suite of heat protection genes (e.g. TaHSP70d and TaGalSyn). Most TaHsfC2a-B target genes were heat, drought and ABA inducible. Transactivation analysis of two representative targets (TaHSP70d and TaGalSyn) showed that TaHsfC2a-B activated expression of reporters driven by these target promoters. Promoter mutagenesis analyses revealed that heat shock element is responsible for transactivation by TaHsfC2a-B and heat/drought induction. TaHsfC2a-B-overexpressing wheat showed improved thermotolerance but not dehydration tolerance. Most TaHsfC2a-B target genes were coup-regulated in developing grains with TaHsfC2a genes. These data suggest that TaHsfC2a-B is a transcriptional activator of heat protection genes and serves as a proactive mechanism for heat protection in developing wheat grains via the ABAmediated regulatory pathway.

We report n-type conductivity in phosphorus ion implanted ultrananocrystalline diamond films annealed at 800 °C and above. The amorphous carbon transits to diamond with an increase of stress after 900 °C annealing, which exhibits lower resistivity with Hall mobility of 143 cm2/Vs. After 1000 °C annealing, the diamond transits to amorphous carbon with the stress release, which has higher carrier concentration and lower Hall mobility. Both P+-implanted nano-sized diamond grains and amorphous carbon give contributions to the n-type conductivity in the films. The microstructure evolution and electrical properties are relative to the hydrogen diffusion and desorption under high temperature annealing.

The search of new two-dimensional (2D) materials with novel optical and electronic properties is always desirable for material development. Here, we report a comprehensive theoretical prediction of 2D SiC compounds with different stoichiometries from C-rich to Si-rich. Besides the previously known hexagonal SiC sheet, we identified two types of hitherto-unknown structural motifs with distinctive bonding features. The first type of 2D SiC monolayer, including t-SiC and t-Si 2 C sheet, can be described by tetragonal lattice. Among them, t-SiC monolayer sheet is featured by each carbon atom binds with four neighboring silicon atoms in almost the same plane, constituting a quasi-planar four-coordinated rectangular moiety. More interestingly, our calculations demonstrate that this structure exhibits a strain-dependent insulator-semimetal transition, suggesting promising applications in strain-dependent optoelectronic sensors. The second type of 2D SiC sheet is featured by silagraphyne with acetylenic linkages(-C≡C-). Silagraphyne shows both high pore sizes and Poisson's ratio. These properties make them a potentially important material for applications in separation membranes and catalysis. Moreover, one of the proposed structures, γ-silagraphyne, is a direct-band-gap semiconductor with a bandgap of 0.89 eV, which has a strong absorption peak in the visible-light region, giving a promising application in ultra-thin transistors, optical sensor devices and solar cell devices.Since the demonstration of the first isolated graphene sheet in 2004, 2D atomic crystals have received much attention. For graphene, due to its many extraordinary properties, it has potential applications in a wide range of areas. However, the pristine graphene is a gapless semi-metal, which means that it is difficult to control the number of carriers. This dramatically limits its applications in the field effect transistor, photovoltaic cell, and etc. Thus, the subject of finding new 2D materials beyond graphene is one of the most active fields of current material research. These research include graphyne, single-layer hexagonal boron nitride (h-BN), [ [5] Particularly, besides graphene and graphyne, a strong research topic in group-IV 2D elemental monolayers have sprung up in recent years. However, these group-IV 2D elemental derivatives show the properties of Dirac fermion behavior without spin-orbit coupling, which create a set of challenges for application in conventional electronic devices due to the lack of band gap at the Fermi level.2D SiC have recently emerged as a promising material with tunable band gaps for potential applications in optoelectronics and electronics.11 Especially, inspired by the successful syntheses of the graphene-like hexagonal SiC sheet in experiment,12 a few carbon-rich SiC monolayers, such as paraSiC 3 ,[6] g-SiC 2 , [7] and pt-SiC 2 , [8] were predicted at one particular stoichiometry. Among all of these newly structures, g-SiC 2 sheet, a direct band gap of 1.09 eV is nearly ideal material for flexible optoelectro...

It was disclosed in our group for the first time that the flavonoids in Lonicera japonica Thunb. are related to its therapy for gastric ulcer. Based on this finding, 20 flavonoids were selected for Helicobacter pylori urease inhibitory activity evaluation, and quercetin showed excellent potency with IC(50) of 11.2 ± 0.9 μM. Structure-activity relationship analysis revealed that removal of the 5-, 3-, or 3'-OH in quercetin led to a sharp decrease in activity. Thus, 3- and 5-OH as well as 3',4'-dihydroxyl groups are believed to be the key structural characteristics for active compounds, which was supported by the molecular docking study. Meanwhile, the results obtained from molecular docking and enzymatic kinetics research strongly suggested that quercetin is a noncompetitive urease inhibitor, indicating that quercetin may be able to tolerate extensive structural modification irrespective of the shape of the active site cavity and could be used as a lead candidate for the development of novel urease inhibitors.

[1] Using a two-stage light gas gun, we obtained new shock wave Hugoniot data for an iron-sulfur alloy ) over the pressure range of 94-204 GPa. A least-squares fit to the Hugoniot data yields a linear relationship between shock velocity D S and particle velocity u, D S (km/s) =3.60 (0.14) +1.57(0.05) u. The measured Hugoniot data for Fe-11.8wt%S agree well with the calculated results based on the thermodynamic parameters of Fe and FeS using the additive law. By comparing the calculated densities along the adiabatic core temperature with the PREM density profile, an iron core with 10 wt.% sulfur (S) provides the best solution for the composition of the Earth's outer core.

Understanding the effect of carbon on the density of hcp (hexagonal-close-packed) Fe-C alloys is essential for modeling the carbon content in the Earth’s inner core. Previous studies have focused on the equations of state of iron carbides that may not be applicable to the solid inner core that may incorporate carbon as dissolved carbon in metallic iron. Carbon substitution in hcp-Fe and its effect on the density have never been experimentally studied. We investigated the compression behavior of Fe-C alloys with 0.31 and 1.37 wt % carbon, along with pure iron as a reference, by in-situ X-ray diffraction measurements up to 135 GPa for pure Fe, and 87 GPa for Fe-0.31C and 109 GPa for Fe-1.37C. The results show that the incorporation of carbon in hcp-Fe leads to the expansion of the lattice, contrary to the known effect in body-centered cubic (bcc)-Fe, suggesting a change in the substitution mechanism or local environment. The data on axial compressibility suggest that increasing carbon content could enhance seismic anisotropy in the Earth’s inner core. The new thermoelastic parameters allow us to develop a thermoelastic model to estimate the carbon content in the inner core when carbon is incorporated as dissolved carbon hcp-Fe. The required carbon contents to explain the density deficit of Earth’s inner core are 1.30 and 0.43 wt % at inner core boundary temperatures of 5000 K and 7000 K, respectively.