Search

Arc‐related magmatic records in the southern Qiangtang Terrane play a key role in the complete understanding of the tectonic evolution of the Bangong–Nujiang Ocean during the late Mesozoic. In this study, we present new zircon U–Pb ages, whole‐rock geochemical, and Sr–Nd isotopic data for the Bilong Co basalts in the central segment of the southern Qiangtang Terrane. The results show that the studied basalts were most likely emplaced during the Kimmeridgian (Late Jurassic). They are characterized by low SiO2 (49.48–52.55 wt%), and high Al2O3 (14.75–15.89 wt%) and MgO (7.44–9.16 wt%), and belong to the high‐K calc‐alkaline to shoshonite series. All samples show significant enrichment in light rare earth elements (LaN/YbN = 14.99–17.47) and large‐ion lithophile elements, but depletion in high‐field‐strength elements with pronounced negative Nb‐Ta‐Ti anomalies. Six samples exhibit constant and depleted whole‐rock εNd(t) values ranging from 5.78 to 6.03. The Bilong Co basalts have high Nb (6.47–9.52 ppm) contents and Nb/Yb (3.49–4.30) ratios, which resemble those of the arc‐related Nb‐enriched basaltic rocks in the southern Qiangtang Terrane. These geochemical signatures reveal that the Bilong Co basalts were most likely derived from a mantle wedge metasomatized by slab‐derived melts and sediments in a continental arc setting, indicating the northward subduction of the Bangong–Nujiang oceanic lithosphere beneath the southern Qiangtang Terrane during the Late Jurassic. Our results, together with the previously published data, suggest that the Late Jurassic arc‐related magmatism is rather extensive in the southern Qiangtang Terrane, further supporting a Cretaceous closure of the Bangong–Nujiang Ocean. [ABSTRACT FROM AUTHOR]

Recent work has suggested that the chromosomally encoded TetA(L) transporter of Bacillus subtilis, for which no physiological function had been shown earlier, not only confers resistance to low concentrations of tetracycline but is also a multifunctional antiporter protein that has dominant roles in both [Na.sup.+]- and [K.sup.+]-dependent pH homeostasis and in [Na.sup.+] resistance during growth at alkaline pH. To rigorously test this hypothesis, TetA(L) has been purified with a hexahistidine tag at its C terminus and reconstituted into proteoliposomes. The TetA(L)-hexahistidine proteoliposomes exhibit high activities of tetracycline-cobalt/[H.sup.+], [Na.sup.+]/[H.sup.+], and [K.sup.+]/[H.sup.+] antiport in an assay in which an outwardly directed proton gradient is artificially imposed and solute uptake is monitored. Tetracycline uptake depends on the presence of cobalt and vice versa, with the cosubstrates being transported in a 1:1 ratio. Evidence for the electrogenicity of both tetracycline-cobalt/[H.sup.+] and [Na.sup.+]/[H.sup.+] antiports is presented. [K.sup.+] and [Li.sup.+] inhibit [Na.sup.+] uptake, but there is little cross-inhibition between [Na.sup.+] and tetracycline-cobalt uptake activities. The results strongly support the conclusion that TetA(L) is a multifunctional antiporter. They expand the roster of such porters to encompass one with a complex organic substrate and monovalent cation substrates that may have distinct binding domains, and provide the first functional reconstitution of a member of the 14-transmembrane segment transporter family.

The deletion of Bacillus subtilis chromosomal tetA(L) gene makes the strain JC112 more sensitive to low levels of tetracycline. The results of the study show that TetA(L) is the major Na+(K+)H+ antiporter that regulates pH homeostasis, and a Na2+ extrusion system. The JC112 strain shows defects in its growth at pH 7.0 and 8.3, and Na+ and K+ -dependent pH homeostases at alkaline pH.

The negative photoconductance (NPC) effect, defined as an increase in resistance upon exposure to illumination, holds great potential for application in photoelectric devices. A prepared memristor with the structure of Ag|graphene quantum dots (GQDs)|TiOx|F‐doped SnO2 exhibits typical bipolar resistive switching (RS) memory behavior. The NPC effect is impressively observed in the high resistance state branch of the RS memory, enabling the memristor function to be extended to both memory logic display and multistate data storage. The observed NPC effect is attributed to the excitation, migration, and compensation of oxygen vacancy at the GQDs/TiOx interface, at which the electron transportation is efficiently restricted because of the variation in the charge distribution and electrostatic potential under illumination. Experiments, theoretical calculations, and physical models are used to provide engineer the interface with the aim of building the NPC effect in the memristive device. These results unveil a new horizon on extending the functionality of the memristor. [ABSTRACT FROM AUTHOR]

Three kinds of Ti3C2Tx modified metal sulfide composites have been prepared via a universal one-step strategy. First, three Ti3C2Tx MXene supported MoS3 composites with different surface F/O ratios and layer distances are synthesized. The abundant –OH groups on the surface of LiOH-treated Ti3C2Tx facilitate the effective bonding with MoS3, forming a robust sandwich-like structure (LF/O-Ti3C2Tx/MoS3). As anode material for sodium-ion batteries (SIBs), it shows outstanding long-term cycling performance in comparison with the other two Ti3C2Tx supported MoS3 composites. Its reversible capacity can be maintained at 611 mA h g−1 after 1000 long cycles at 2 A g−1, obviously superior to those of single LF/O-Ti3C2Tx and MoS3. Besides SIBs, LF/O-Ti3C2Tx/MoS3 also exhibits satisfying lithium storage performance. Kinetics analysis and theoretical calculation further explain the outstanding performance of LF/O-Ti3C2Tx/MoS3. Moreover, LF/O-Ti3C2Tx modified CuS/SnS2 composites also show similar and excellent electrochemical results for SIBs and LIBs. This facile synthesis strategy opens a door to prepare high-performance Ti3C2Tx supported conversion-type anode materials for large-scale energy storage. [ABSTRACT FROM AUTHOR]

Although extensive efforts have been made to stabilize metal sodium anodes and prevent dendrite formation, it is still difficult to achieve long‐term stability at large area capacity and high current density due to a series of complex failure modes, including uneven Na nucleation and subsequent dendrite formation. Herein, an oxygen‐containing carbonized coconut framework (O‐CCF) with a 3D tubular structure is designed to inhibit dendrite growth. The 3D tubular structure can regulate the uniform distribution of electric field, making Na+ diffuse evenly on the electrode surface. The oxygen functional groups with sodiophilicity contribute to the adsorption of Na+ and reduce the Na nucleation energy on the surface of O‐CCF. The interaction of 3D tubular structure and oxygen functional groups enable Na stripping/plating over 10 000 cycles at 50 mA cm−2, as well as cycling stably for 1000 cycles with coulombic efficiency of 99.6% at 5 mA cm−2 and high areal capacity of 10 mAh cm−2. As a proof of concept, full cells of O‐CCF//Na‐Na3V2(PO4)3 (NVP) and Na‐O‐CCF//Fe7S8 are assembled and exhibit outstanding electrochemical performance. This work presents a promising strategy for fabrication of safe Na metal anodes. [ABSTRACT FROM AUTHOR]

Mesoproterozoic red beds near ancient coasts have not aroused extensive interest. A new geochemical study of the alternating red and grey dolostones from the Yangzhuang Formation provides a better understanding of the redox conditions of nearshore sedimentary environments. In this contribution, whole-rock samples are characterized by positive correlations of rare earth elements (REE) vs. Th and FeT vs. Th and flat-type REE distribution patterns, indicating massive terrigenous input, which is considered to be inherited from felsic rocks. Relatively high (Femag+Feox)/FeT and Fe3+/Fe2+ ratios in red beds indicate more oxidized conditions in supratidal environments compared with the lower oxygen contents in intertidal environments. Under these two distinct chemical sedimentary conditions, acetic acid-leached red and grey samples both have HREE-depleted distributions, suggesting significant freshwater invasion. Moreover, limited terrigenous redox-sensitive elements (RSEs) can reach the coast where the red beds are deposited, whereas relatively high RSE enrichment factors originating from shallow oceans are recorded in grey beds. In the Mesoproterozoic, limited oxidative weathering, shallow seawater desalination, and low organic production occurred near the coast. Meanwhile, a prolonged period of low Mo and U availability preserved in carbonate minerals confirmed that marine oxygen levels failed to satisfy the deposition of offshore red beds. During the regression, potentially exposed sediments connected to atmospheric oxygen guaranteed the oxidation of iron and the formation of red beds, and these events were coupled with negative δ13Ccarb shifts in the Yanliao rift zone. [ABSTRACT FROM AUTHOR]

In this paper, the cooperative effect of halogen bond with hydrogen bond has been used to make a halogen bond in FCl-CNH dimer vary from a chlorine-shared one to an ion-pair one. The halogen bond is strengthened in FCl-CNH-CNH trimer and its maximal interaction energy equals to -76 kJ/mol when the number of CNH in FCl-CNH-(CNH)n polymer approaches infinity. Once the free H atom in FCl-CNH-CNH trimer is replaced with alkali metals, the halogen bond becomes strong enough to be an ion-pair one in FCl-CNH-CNLi and FCl-CNH-CNNa trimers. An introduction of a Lewis acid in FCl-CNH dimer has a more prominent effect on the type of halogen bond. A prominent cooperative effect is found for the halogen bond and hydrogen bond in the trimers. FH-FCl-CNH-CNH and FH-FCl-CNH-CNLi tetramers have also been studied and the interaction energy of halogen bonding in FH-FCl-CNH-CNLi tetramer is about 12 times as much as that in the FCl-CNH dimer. The atoms in molecules and natural bond orbital analyses have been carried out for these complexes to understand the nature of halogen bond and the origin of the cooperativity. [ABSTRACT FROM AUTHOR]

Using ab initio calculations, we have studied the structures, properties, and nature of halogen bonds in H2CS-XY (XY = FF, ClF, ClCl, BrF, BrCl, and BrBr) complexes. The results show that the ring-shaped complexes are formed by a halogen bond (S···X) and a secondary hydrogen bond (H···X). We also analyzed the H2CS-ClF-ClF and FCl-H2CS-ClF complexes to investigate the cooperative and diminutive halogen bonding. The cooperative effect of halogen bonding is found in the former, while the diminutive effect is present in the latter. We finally considered the solvent effect on the halogen bond in H2CS-BrCl complex and found that the solvent has a prominent enhancing effect on it. The complexes have also been analyzed with natural bond orbital, atoms in molecules, and symmetry adapted perturbation theory method. [ABSTRACT FROM AUTHOR]

In this article, we performed quantum chemical calculations to study the π Au-bond in the HCCH···AuX (X = OH, F, Cl, Br, CH3, CCH, CN, and NC) system. For comparison, we also investigated the HCCH···Au+ and H2CCH2···AuF complexes. The equilibrium geometries and infrared spectra at the MP2 level were reported. The interaction energies were calculated at the MP2 and coupled-cluster single double triple levels. The natural bond orbital results support the Dewar-Chatt-Duncanson model. Moreover, we focused on the influence of X atom on the geometries, interaction energies, and orbital interactions as well as the comparison between HCCH···AuF and H2CCH2···AuF complexes. Although the π Au-bond in these complexes is electrostatic in nature, the weight of covalent nature is also important. [ABSTRACT FROM AUTHOR]

The structure and vibrational frequencies of the chiral antiferroelectric liquid-crystal molecule, 4-(1-methyheptyloxycarbonyl) phenyl-4-(4′-octyloxy) benzoate (MHOCPOOB), have been calculated using the density-functional theory (DFT) with the Becke-3 Lee–Yang–Parr/6-31G(d,p) level. The observed vibrational spectra have been resolved and assigned in detail by comparison to the computed values. The results indicate that the computed and observed spectra are in good agreement with each other. The stable molecular structure obtained with the DFT theory shows that the two hydrocarbon chains are all-trans zigzag conformer and nearly perpendicular to each other. The orientation of the mesogen part and the hydrocarbon chains for MHOCPOOB in the Sm–CA* phase are investigated by employing the polarization-angle-dependent infrared spectra in the electric-field induced and the two-dimensional correlation spectroscopy. After combining the experimental and theoretical results, it can be concluded that the azimuth of the achiral and chiral chains is opposite to each other, the orientation of the achiral chain is almost the same direction as the mesogen core, and the orientation of the chiral chain is nearly perpendicular to the mesogen part. The achiral and chiral CH2 chains are both a probable all-trans zigzag conformer. [ABSTRACT FROM AUTHOR]