10,098 research outputs found
Oxygen reduction activity on perovskite oxide surfaces: a comparative first-principle study of LaMnO, LaFeO and LaCrO
The understanding of oxygen reduction reaction (ORR) activity on perovskite
oxide surfaces is essential for promising future fuel cell applications. We
report a comparative study of ORR mechanisms on LaO (=Mn, Fe, Cr)
surfaces by first-principles calculations based on density functional theory
(DFT). Results obtained from varied DFT methods such as generalized gradient
approximation(GGA), GGA+ and the hybrid Hartree-Fock density functional
method are reported for comparative purposes. We find that the results
calculated from hybrid-functional method suggest that the order of ORR activity
is LaMnO LaCrO LaFeO, which is in better agreement with
recent experimental results (Suntivich \textit{et al.}, Nature Chemistry 3, 546
(2011)) than those using the GGA or GGA+ method.Comment: submitte
Lateral Migration and Nonuniform Rotation of Biconcave Particle Suspended in Poiseuille Flow
A biconcave particle suspended in a Poiseuille flow is investigated by the
multiple-relaxation-time lattice Boltzmann method with the Galilean-invariant
momentum exchange method. The lateral migration and equilibrium of the particle
are similar to the Segr\'e-Silberberg effect in our numerical simulations.
Surprisingly, two lateral equilibrium positions are observed corresponding to
the releasing positions of the biconcave particle. The upper equilibrium
positions significantly decrease with the growth of the Reynolds number,
whereas the lower ones are almost insensitive to the Reynolds number.
Interestingly, the regular wave accompanied by nonuniform rotation is exhibited
in the lateral movement of the biconcave particle. It can be attributed to that
the biconcave shape in various postures interacts with the parabolic velocity
distribution of the Poiseuille flow. A set of contours illustrate the dynamic
flow field when the biconcave particle has successive postures in a rotating
period.Comment: 13 pages, 5 figure
A method for teleporting an unknown quantum state and its application
We suggest a method for teleporting an unknown quantum state. In this method
the sender Alice first uses a Controlled-Not operation on the particle in the
unknown quantum state and an ancillary particle which she wants to send to the
receiver Bob. Then she sends ancillary particle to Bob.
When Alice is informed by Bob that the ancillary particle is received, she
performs a local measurement on the particle and sends Bob the outcome of the
local measurement via a classical channel. Depending on the outcome Bob can
restore the unknown quantum state, which Alice destroyed, on the ancillary
particle successfully. As an application of this method we propose a quantum
secure direct communication protocol.Comment: 3 pages, no figur
Lifetimes of Doubly Charmed Baryons
The lifetimes of doubly charmed hadrons are analyzed within the framework of
the heavy quark expansion (HQE). Lifetime differences arise from spectator
effects such as -exchange and Pauli interference. The baryon
is longest-lived in the doubly charmed baryon system owing to the destructive
Pauli interference absent in the and . In the
presence of dimension-7 contributions, its lifetime is reduced from
to . The
baryon has the shortest lifetime of order due to a large
contribution from the -exchange box diagram. It is difficult to make a
precise quantitative statement on the lifetime of . Contrary to
baryons, becomes longer in the presence of
dimension-7 effects and the Pauli interference even
becomes negative. This implies that the subleading corrections are too large to
justify the validity of the HQE. Demanding the rate to be
positive for a sensible HQE, we conjecture that the lifetime lies
in the range of . The lifetime hierarchy
pattern is and the
lifetime ratio is predicted to be of
order 6.7.Comment: 17 pages, 1 figure, version to appear in PRD. arXiv admin note: text
overlap with arXiv:1807.0091
Congruences for sequences analogous to Euler numbers
For a given real number we define the sequence by
and , where is the greatest integer not
exceeding . Since is the n-th Euler number, can be
viewed as a natural generalization of Euler numbers. In this paper we deduce
some identities and an inversion formula involving , and establish
congruences for , and provided that is a
nonzero integer, where is the least nonnegative integer
such that p^{\a}\mid n but p^{\a+1}\nmid n.Comment: 16 page
Strange quark suppression and strange hadron production in pp collisions at RHIC and LHC
The parton and hadron cascade model PACIAE based on PYTHIA was utilized to
systematically investigate the strange particle production in pp collisions at
the RHIC and LHC energies. Taking the mechanism of reduction of the strange
quark suppression into account the STAR and ALICE data of strange particle
production in pp collisions are well reproduced. It turned out that the K/{\pi}
ratio as a function of reaction energy in pp collisions shows slightly
increasing from sqrt(s)=0.2 to 0.9 TeV and then turning to saturation
Some Comments on the Holographic Heavy Quark Potential in a Thermal Bath
The heavy quark potential of a thermal Yang-Mills theory in strong coupling
limit is explored in terms of the holographic principle. With a fairly general
AdS/QCD metric the heavy quark potential displays a kink-like screening in the
plasma phase. This behavior may conflict the causality of a field theory that
is mathematically equivalent to the thermal Yang-Mills.Comment: 9 pages, 5 figures, more references added, typo fixe
The Subtleties of the Wigner Function Formulation of the Chiral Magnetic Effect
We assess the applicability of the Wigner function formulation in its present
form to the chiral Magnetic Effect and noted some issues regarding the
conservation and the consistency of the electric current in the presence of an
inhomogeneous and time dependent axial chemical potential. The problems are
rooted in the ultraviolet divergence of the underlying field theory associated
with the axial anomaly and can be fixed with the Pauli-Villars regularization
of the Wigner function.Comment: 8 pages in Revtex, a new section is added about CME with
PV-regularized Wigner functio
The relativistic correction of the quarkonium melting temperature with a holographic potential
The relativistic correction of the AdS/CFT implied heavy quark potential is
examined within the framework of the potential model. For the typical range of
the coupling strength appropriate to heavy-ion collisions, we find the
correction is significant in size and lowers the dissociation temperature of
quarkonia.Comment: 11 pages, 2 tables in late
Fate of topological states and mobility edges in one-dimensional slowly varying incommensurate potentials
We investigate the interplay between disorder and superconducting pairing for
a one-dimensional -wave superconductor subject to slowly varying
incommensurate potentials with mobility edges. With amplitude increments of the
incommensurate potentials, the system can undergo a transition from a
topological phase to a topologically trivial localized phase. Interestingly, we
find that there are four mobility edges in the spectrum when the strength of
the incommensurate potential is below a critical threshold, and a novel
topologically nontrivial localized phase emerges in a certain region. We reveal
this energy-dependent metal-insulator transition by applying several numerical
diagnostic techniques, including the inverse participation ratio, the density
of states and the Lyapunov exponent. Nowadays, precise control of the
background potential and the -wave superfluid can be realized in the
ultracold atomic systems, we believe that these novel mobility edges can be
observed experimentally.Comment: 6 pages, 7 figure
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