2,051 research outputs found
Correlation of interfacial bonding mechanism and equilibrium conductance of molecular junctions
We report theoretical investigations on the role of interfacial bonding
mechanism and its resulting structures to quantum transport in molecular wires.
Two bonding mechanisms for the Au-S bond in an
Au(111)/1,4-benzenedithiol(BDT)/Au(111) junction were identified by ab initio
calculation, confirmed by a recent experiment, which, we showed, critically
control charge conduction. It was found, for Au/ BDT/Au junctions, the hydrogen
atom, bound by a dative bond to the Sulfur, is energetically non-dissociative
after the interface formation. The calculated conductance and junction
breakdown forces of H-non-dissociative Au/BDT/Au devices are consistent with
the experimental values, while the H-dissociated devices, with the interface
governed by typical covalent bonding, give conductance more than an order of
magnitude larger. By examining the scattering states that traverse the
junctions, we have revealed that mechanical and electric properties of a
junction have strong correlation with the bonding configuration. This work
clearly demonstrates that the interfacial details, rather than previously
believed many-body effects, is of vital importance for correctly predicting
equilibrium conductance of molecular junctions; and manifests that the
interfacial contact must be carefully understood for investigating quantum
transport properties of molecular nanoelectronics.Comment: 18 pages, 6 figures, 2 tables, to be appeared in Frontiers of Physics
9(6), 780 (2014
Random Spin-orbit Coupling in Spin Triplet Superconductors: Stacking Faults in Sr_2RuO_4 and CePt_3Si
The random spin-orbit coupling in multicomponent superconductors is
investigated focusing on the non-centrosymmetric superconductor CePt_3Si and
the spin triplet superconductor Sr_2RuO_4. We find novel manifestations of the
random spin-orbit coupling in the multicomponent superconductors with
directional disorders, such as stacking faults. The presence of stacking faults
is indicated for the disordered phase of CePt_3Si and Sr_2RuO_4. It is shown
that the d-vector of spin triplet superconductivity is locked to be d = k_y x -
k_x y with the anisotropy \Delta T_c/T_c0 \sim \bar{\alpha}^2/T_c0 W_z, where
\bar{\alpha}, T_c0, and W_z are the mean square root of random spin-orbit
coupling, the transition temperature in the clean limit, and the kinetic energy
along the c-axis, respectively. This anisotropy is much larger (smaller) than
that in the clean bulk Sr_2RuO_4 (CePt_3Si). These results indicate that the
helical pairing state d = k_y x - k_x y in the eutectic crystal
Sr_2RuO_4-Sr_3Ru_2O_7 is stabilized in contrast to the chiral state d = (k_x
\pm i k_y) z in the bulk Sr_2RuO_4. The unusual variation of T_c in CePt_3Si is
resolved by taking into account the weak pair-breaking effect arising from the
uniform and random spin-orbit couplings. These superconductors provide a basis
for discussing recent topics on Majorana fermions and non-Abelian statistics.Comment: J. Phys. Soc. Jpn. 79 (2010) 08470
Climatically driven changes in the supply of terrigenous sediment to the East China Sea
Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 19 (2018): 2463-2477, doi:10.1029/2017GC007339.We examine the paleoceanographic record over the last ∼400 kyr derived from major, trace, and rare earth elements in bulk sediment from two sites in the East China Sea drilled during Integrated Ocean Drilling Program Expedition 346. We use multivariate statistical partitioning techniques (Q‐mode factor analysis, multiple linear regression) to identify and quantify five crustal source components (Upper Continental Crust (UCC), Luochuan Loess, Xiashu Loess, Southern Japanese Islands, Kyushu Volcanics), and model their mass accumulation rates (MARs). UCC (35–79% of terrigenous contribution) and Luochuan Loess (16–55% contribution) are the most abundant end‐members through time, while Xiashu Loess, Southern Japanese Islands, and Kyushu Volcanics (1–22% contribution) are the lowest in abundance when present. Cycles in UCC and Luochuan Loess MARs may indicate continental and loess‐like material transported by major rivers into the Okinawa Trough. Increases in sea level and grain size proxy (e.g., SiO2/Al2O3) are coincident with increased flux of Southern Japanese Islands, indicating localized sediment supply from Japan. Increases in total terrigenous MAR precede minimum relative sea levels by several thousand years and may indicate remobilization of continental shelf material. Changes in the relative contribution of these end‐members are decoupled from total MAR, indicating compositional changes in the sediment are distinct from accumulation rate changes but may be linked to variations in sea level, riverine and eolian fluxes, and shelf‐bypass processes over glacial‐interglacials, complicating accurate monsoon reconstructions from fluvial dominated sediment.U.S. National Science Foundation Grant Numbers: NSF‐EAR1434175, NSF‐EAR1433665, NSF‐EAR143413
Axial anomaly in the reduced model: Higher representations
The axial anomaly arising from the fermion sector of \U(N) or \SU(N)
reduced model is studied under a certain restriction of gauge field
configurations (the ``\U(1) embedding'' with ). We use the
overlap-Dirac operator and consider how the anomaly changes as a function of a
gauge-group representation of the fermion. A simple argument shows that the
anomaly vanishes for an irreducible representation expressed by a Young tableau
whose number of boxes is a multiple of (such as the adjoint
representation) and for a tensor-product of them. We also evaluate the anomaly
for general gauge-group representations in the large limit. The large
limit exhibits expected algebraic properties as the axial anomaly.
Nevertheless, when the gauge group is \SU(N), it does not have a structure
such as the trace of a product of traceless gauge-group generators which is
expected from the corresponding gauge field theory.Comment: 21 pages, uses JHEP.cls and amsfonts.sty, the final version to appear
in JHE
First Results from KamLAND: Evidence for Reactor Anti-Neutrino Disappearance
KamLAND has been used to measure the flux of 's from distant
nuclear reactors. In an exposure of 162 tonyr (145.1 days) the ratio of
the number of observed inverse -decay events to the expected number of
events without disappearance is for energies 3.4 MeV. The deficit of events is
inconsistent with the expected rate for standard propagation at
the 99.95% confidence level. In the context of two-flavor neutrino oscillations
with CPT invariance, these results exclude all oscillation solutions but the
`Large Mixing Angle' solution to the solar neutrino problem using reactor
sources.Comment: 6 pages, 6 figure
Measurement of Production Properties of Positively Charged Kaons in Proton-Carbon Interactions at 31 GeV/c
Spectra of positively charged kaons in p+C interactions at 31 GeV/c were
measured with the NA61/SHINE spectrometer at the CERN SPS. The analysis is
based on the full set of data collected in 2007 with a graphite target with a
thickness of 4% of a nuclear interaction length. Interaction cross sections and
charged pion spectra were already measured using the same set of data. These
new measurements in combination with the published ones are required to improve
predictions of the neutrino flux for the T2K long baseline neutrino oscillation
experiment in Japan. In particular, the knowledge of kaon production is crucial
for precisely predicting the intrinsic electron neutrino component and the high
energy tail of the T2K beam. The results are presented as a function of
laboratory momentum in 2 intervals of the laboratory polar angle covering the
range from 20 up to 240 mrad. The kaon spectra are compared with predictions of
several hadron production models. Using the published pion results and the new
kaon data, the K+/\pi+ ratios are computed.Comment: 10 pages, 11 figure
Search for the Invisible Decay of Neutrons with KamLAND
The Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) is used in a
search for single neutron or two neutron intra-nuclear disappearance that would
produce holes in the -shell energy level of C nuclei. Such holes
could be created as a result of nucleon decay into invisible modes (),
e.g. or . The de-excitation of the corresponding
daughter nucleus results in a sequence of space and time correlated events
observable in the liquid scintillator detector. We report on new limits for
one- and two-neutron disappearance: years
and years at 90% CL. These results
represent an improvement of factors of 3 and over previous
experiments.Comment: 5 pages, 3 figure
The long journey to a Systems Biology of neuronal function
Computational neurobiology was born over half a century ago, and has since been consistently at the forefront of modelling in biology. The recent progress of computing power and distributed computing allows the building of models spanning several scales, from the synapse to the brain. Initially focused on electrical processes, the simulation of neuronal function now encompasses signalling pathways and ion diffusion. The flow of quantitative data generated by the "omics" approaches, alongside the progress of live imaging, allows the development of models that will also include gene regulatory networks, protein movements and cellular remodelling. A systems biology of brain functions and disorders can now be envisioned. As it did for the last half century, neuroscience can drive forward the field of systems biology
Measurement of negatively charged pion spectra in inelastic p+p interactions at = 20, 31, 40, 80 and 158 GeV/c
We present experimental results on inclusive spectra and mean multiplicities
of negatively charged pions produced in inelastic p+p interactions at incident
projectile momenta of 20, 31, 40, 80 and 158 GeV/c ( 6.3, 7.7,
8.8, 12.3 and 17.3 GeV, respectively). The measurements were performed using
the large acceptance NA61/SHINE hadron spectrometer at the CERN Super Proton
Synchrotron.
Two-dimensional spectra are determined in terms of rapidity and transverse
momentum. Their properties such as the width of rapidity distributions and the
inverse slope parameter of transverse mass spectra are extracted and their
collision energy dependences are presented. The results on inelastic p+p
interactions are compared with the corresponding data on central Pb+Pb
collisions measured by the NA49 experiment at the CERN SPS.
The results presented in this paper are part of the NA61/SHINE ion program
devoted to the study of the properties of the onset of deconfinement and search
for the critical point of strongly interacting matter. They are required for
interpretation of results on nucleus-nucleus and proton-nucleus collisions.Comment: Numerical results available at: https://edms.cern.ch/document/1314605
Updates in v3: Updated version, as accepted for publicatio
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