ALBERT

Description: Author(s): J. L. Ma, H. L. Wang, X. L. Wang, and J. H. Zhao By varying both the carrier momentum and spin orientation separately, the anisotropic Berry-phase effect in MnAs films is explicitly investigated. Specifically, the Berry-phase effect is characterized by the intrinsic anomalous Hall conductivity γ , which is extracted via treating various scattering ... [Phys. Rev. B 97, 064402] Published Mon Feb 05, 2018

Description: The electronic transport properties of molecular bridges constructed by C 60 and B 80 molecules which have the same symmetry are investigated by first principles calculations combined with a non-equilibrium Green's function technique. It is found that, like C 60 , monomer B 80 is a good conductor arising from the charge transfer from the leads to the molecule, while the dimer (B 80 ) 2 and (C 60 ) 2 are both insulators due to the potential barrier formed at the molecule-molecule interface. Our further study shows that, although both the homogeneous dimer (B 80 ) 2 and (C 60 ) 2 display poor conductivity, the heterogeneous dimer B 80 C 60 shows a very high conductance as a result from the decreased HOMO-LUMO gap and the excess charge redistribution. Finally, we find that the conductivity of both (B 80 ) 2 and (C 60 ) 2 can be significantly improved by electron doping, for example, by doping C in (B 80 ) 2 and doping N in (C 60 ) 2 .

Description: Several tectonic models have been proposed for the Neoproterozoic amalgamation of the South China block during the assembly of Rodinia. However, the timing of the end of arc magmatism between the two subblocks in the South China block (i.e., the Yangtze and Cathaysia blocks) remains controversial because it is unclear whether the 860–820 Ma magmatic rocks and coeval sedimentary basins in this area are related to subduction or plume activity. Here, we present new detrital zircon U-Pb and Hf isotopic data for the sediments directly overlying early Neoproterozoic arc volcanic rocks in this region. These data reveal a rhythmic change in source coincident with a progressive increase in the amount of juvenile and old crustal detritus within these sediments. This result, combined with the presence of a fining-upward grain-size trend and horizontal bedding within these sediments, provides evidence of bidirectional sources that are consistent with a backarc setting. The juvenile crustal material within these sediments was sourced from adjacent arc terranes to the east, whereas the old crustal detritus was derived from the Yangtze block to the west. In addition, sensitive high-resolution ion microprobe zircon U-Pb dating of mafic rocks within equivalent sedimentary sequences yielded ages of ca. 860–840 Ma, and these mafic rocks have arc- or mid-ocean-ridge basalt–like geochemical features that indicate the initiation of backarc spreading associated with Neoproterozoic NW-directed subduction. The data from the sediments and mafic rocks suggest the presence of a backarc basin system at ca. 860–820 Ma within the southeastern margin of the Yangtze block. This in turn indicates that Rodinia assembly was not completed until ca. 820 Ma, with the South China block possibly acting as a connection between a Neoproterozoic Andean-type active continental margin and Grenvillian belts on the paleo–western margin of the Rodinia supercontinent.

Description: Author(s): H. Zhang, B. F. Shen, W. P. Wang, S. H. Zhai, S. S. Li, X. M. Lu, J. F. Li, R. J. Xu, X. L. Wang, X. Y. Liang, Y. X. Leng, R. X. Li, and Z. Z. Xu We present experimental studies on ion acceleration using an 800-nm circularly polarized laser pulse with a peak intensity of 6.9 × 10 19     W / cm 2 interacting with an overdense plasma that is produced by a laser prepulse ionizing an initially ultrathin plastic foil. The proton spectra exhibit spectral pe... [Phys. Rev. Lett. 119, 164801] Published Tue Oct 17, 2017

Description: Three-dimensional (3D) Dirac semimetals are new quantum materials and can be viewed as 3D analogues of graphene. Many fascinating electronic properties have been proposed and realized in 3D Dirac semimetals, which demonstrate their potential applications in next generation quantum devices. Bismuth-antimony Bi 1− x Sb x can be tuned from a topological insulator to a band insulator through a quantum critical point at x  ≈ 4%, where 3D Dirac fermions appear. Here, we report on a magnetotransport study of Bi 1− x Sb x at such a quantum critical point. An unusual magnetic-field induced semimetal-semiconductor phase transition was observed in the Bi 0.96 Sb 0.04 single crystals. In a magnetic field of 8 T, Bi 0.96 Sb 0.04 single crystals show giant magnetoresistances of up to 6000% at low-temperature, 5 K, and 300% at room-temperature, 300 K. The observed magnetoresistances keep linear down to approximate zero-field when the temperature is below 200 K. Our experimental results are not only interesting for the fundamental physics of 3D Dirac semimetals but also for potential applications of 3D Dirac semimetals in magnetoelectronic devices.

Description: TrmJ proteins from the SPOUT methyltransferase superfamily are tRNA Xm32 modification enzymes that occur in bacteria and archaea. Unlike archaeal TrmJ, bacterial TrmJ require full-length tRNA molecules as substrates. It remains unknown how bacterial TrmJs recognize substrate tRNAs and specifically catalyze a 2'- O modification at ribose 32. Herein, we demonstrate that all six Escherichia coli ( Ec ) tRNAs with 2'- O -methylated nucleosides at position 32 are substrates of Ec TrmJ, and we show that the elbow region of tRNA, but not the amino acid acceptor stem, is needed for the methylation reaction. Our crystallographic study reveals that full-length Ec TrmJ forms an unusual dimer in the asymmetric unit, with both the catalytic SPOUT domain and C-terminal extension forming separate dimeric associations. Based on these findings, we used electrophoretic mobility shift assay, isothermal titration calorimetry and enzymatic methods to identify amino acids within Ec TrmJ that are involved in tRNA binding. We found that tRNA recognition by Ec TrmJ involves the cooperative influences of conserved residues from both the SPOUT and extensional domains, and that this process is regulated by the flexible hinge region that connects these two domains.

Description: A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. Here we report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using a combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters. Scientific Reports 5 doi: 10.1038/srep10600

Description: Author(s): X. L. Wang et al. (Belle Collaboration) We report measurement of the cross section of e + e − → π + π − ψ ( 2 S ) between 4.0 and 5.5 GeV, based on an analysis of initial state radiation events in a 980     fb − 1 data sample recorded with the Belle detector. The properties of the Y ( 4360 ) and Y ( 4660 ) states are determined. Fitting the mass spectrum of π + π − ... [Phys. Rev. D 91, 112007] Published Fri Jun 12, 2015

Description: We studied 14 southern infrared dark clouds (IRDCs) using data taken from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey and the GLIMPSE and MIPSGAL mid-infrared surveys of the inner Galaxy. The physical and chemical characteristics of the 14 IRDCs were investigated using N 2 H + (1–0), HNC(1–0), HCO + (1–0) and HCN(1–0) molecular lines. We found that the 14 IRDCs are in different evolutionary stages, from ‘starless’ to sources with an ultra-compact H  ii region. Three IRDCs were detected to have star-forming activity. The integrated intensity ratios $I{\rm _{HCO^+/HCN}}$ , $I{\rm _{N_2H^+/HCN}}$ and I HNC/HCN are all ~1.5, which is different from previous measurements, suggesting that the integrated intensity ratios may be affected by the cloud environments. The integrated intensities of HNC, HCO + and HCN show a tight correlation for the 14 IRDCs, implying a close link to the chemical evolution of these three species in the IRDCs.The derived excitation temperature for each IRDC is less than 25 K. We estimated the abundances of the four molecules to be from 10 –11 to 10 –9 , and the average abundance ratios are N HNC / N HCN  = 1.47 ± 0.50, $N_{\rm HNC}/N_{\rm HCO^+}=1.74\pm 0.22$ and $N_{\rm HCN}/N_{\rm HCO^+}=1.21\pm 0.41$ .

Description: Nox4-dependent ROS modulation by amino endoperoxides to induce apoptosis in cancer cells Cell Death and Disease 4, e552 (March 2013). doi:10.1038/cddis.2013.68 Authors: P Zhu, B MK Tong, R Wang, J P Chen, S Foo, H C Chong, X L Wang, G Y Ang, S Chiba & N S Tan