22,215 research outputs found
Proper Scaling of the Anomalous Hall Effect
Working with epitaxial films of Fe, we succeeded in independent control of
different scattering processes in the anomalous Hall effect. The result
appropriately accounted for the role of phonons, thereby clearly exposing the
fundamental flaws of the standard plot of the anomalous Hall resistivity versus
longitudinal resistivity. A new scaling has been thus established that allows
an unambiguous identification of the intrinsic Berry curvature mechanism as
well as the extrinsic skew scattering and side-jump mechanisms of the anomalous
Hall effect.Comment: 5 pages, 4 figure
Nonleptonic two-body charmless B decays involving a tensor meson in the Perturbative QCD Approach
Two-body charmless hadronic B decays involving a light tensor meson in the
final states are studied in the perturbative QCD approach based on
factorization. From our calculations, we find that the decay branching ratios
for color allowed tree-dominated decays and modes are of order and , respectively.
While other color suppressed tree-dominated decays have very small branching
ratios. In general, the branching ratios of most decays are in the range of
to , which are bigger by one or two orders of magnitude than
those predictions obtained in Isgur-Scora-Grinstein-Wise II model and in the
covariant light-front approach, but consistent with the recent experimental
measurements and the QCD factorization calculations. Since the decays with a
tensor meson emitted from vacuum are prohibited in naive factorization, the
contributions of nonfactorizable and annihilation diagrams are very important
to these decays, which are calculable in our perturbative QCD approach. We also
give predictions to the direct CP asymmetries, some of which are large enough
for the future experiments to measure. Because we considered the mixing between
and , the decay rates are enhanced significantly for some
decays involving meson, even with a small mixing angle.Comment: 26 pages, 2 figure
Electronic heat current rectification in hybrid superconducting devices
In this work, we review and expand recent theoretical proposals for the
realization of electronic thermal diodes based on tunnel-junctions of normal
metal and superconducting thin films. Starting from the basic rectifying
properties of a single hybrid tunnel junction, we will show how the
rectification efficiency can be largely increased by combining multiple
junctions in an asymmetric chain of tunnel-coupled islands. We propose three
different designs, analyzing their performance and their potential advantages.
Besides being relevant from a fundamental physics point of view, this kind of
devices might find important technological application as fundamental building
blocks in solid-state thermal nanocircuits and in general-purpose cryogenic
electronic applications requiring energy management.Comment: 9 pages, 5 color figure
Further Development of the Improved QMD Model and its Applications to Fusion Reaction near Barrier
The Improved Quantum Molecular Dynamics model is further developed by
introducing new parameters in interaction potential energy functional based on
Skyrme interaction of SkM and SLy series. The properties of ground states
of selected nuclei can be reproduced very well. The Coulomb barriers for a
series of reaction systems are studied and compared with the results of the
proximity potential. The fusion excitation functions for a series of fusion
reactions are calculated and the results are in good agreement with
experimental data.Comment: 17 pages, 10 figures, PRC accepte
Observation of indirect ionization of W7+ in an electron-beam ion-trap plasma
In this work, visible and extreme ultraviolet spectra of W7+ are measured
using the high-temperature superconducting electron-beam ion trap (EBIT) at the
Shanghai EBIT Laboratory under extremely low-energy conditions (lower than the
nominal electron-beam energy of 130 eV). The relevant atomic structure is
calculated using the flexible atomic code package based on the relativistic
configuration interaction method. The GRASP2K code, in the framework of the
multiconfiguration Dirac-Hartree-Fock method, is employed as well for
calculating the wavelength of the M1 transition in the ground configuration of
W7+. A line from the W7+ ions is observed at a little higher electron-beam
energy than the ionization potential for W4+, making this line appear to be
from W5+. A hypothesis for the charge-state evolution of W7+ is proposed based
on our experimental and theoretical results; that is, the occurrence of W7+
ions results from indirect ionization caused by stepwise excitation between
some metastable states of lower-charge-state W ions, at the nominal
electron-beam energy of 59 eV
Phonon quarticity induced by changes in phonon-tracked hybridization during lattice expansion and its stabilization of rutile TiO
Although the rutile structure of TiO is stable at high temperatures, the
conventional quasiharmonic approximation predicts that several acoustic phonons
decrease anomalously to zero frequency with thermal expansion, incorrectly
predicting a structural collapse at temperatures well below 1000\,K. Inelastic
neutron scattering was used to measure the temperature dependence of the phonon
density of states (DOS) of rutile TiO from 300 to 1373\,K. Surprisingly,
these anomalous acoustic phonons were found to increase in frequency with
temperature. First-principles calculations showed that with lattice expansion,
the potentials for the anomalous acoustic phonons transform from quadratic to
quartic, stabilizing the rutile phase at high temperatures. In these modes, the
vibrational displacements of adjacent Ti and O atoms cause variations in
hybridization of electrons of Ti and electrons of O atoms. With
thermal expansion, the energy variation in this "phonon-tracked hybridization"
flattens the bottom of the interatomic potential well between Ti and O atoms,
and induces a quarticity in the phonon potential.Comment: 7 pages, 6 figures, supplemental material (3 figures
Expression, purification and kinase activity analysis of maize ZmSPK1, a member of plant SnRK2 subfamily
Kinase activity is essential for a protein kinase to perform its biological function. In previous study we have cloned a novel plant SnRK2 subfamily gene from maize and named it as ZmSPK1. In this study thecDNA of ZmSPK1 with dHA-His6 tag was amplified by PCR and was subcloned into the yeast expression vector p426GAL1. The constructed plasmid named as p426GAL1-SPK1-dHA-His6 was transformed into Saccharomyces cerevisiae. Under the induction of galactose the recombinant protein was expressed. The purified recombinant protein showed a single specific band by the analysis of the western-blot. In an in vitro kinase assay, the purified recombinant protein showed phosphorylation and autophosphorylation activity. This showed that ZmSPK1 encodes a functional protein kinase
First-principles calculations of phase transition, low elastic modulus, and superconductivity for zirconium
The elasticity, dynamic properties, and superconductivity of ,
, and Zr are investigated by using first-principles methods.
Our calculated elastic constants, elastic moduli, and Debye temperatures of
and phases are in excellent agreement with experiments.
Electron-phonon coupling constant and electronic density of states at
the Fermi level (\emph{E}) are found to increase with pressure
for these two hexagonal structures. For cubic phase, the critical
pressure for mechanical stability is predicted to be 3.13 GPa and at \emph{P}=4
GPa the low elastic modulus (=31.97 GPa) can be obtained. Besides, the
critical pressure for dynamic stability of phase is achieved by phonon
dispersion calculations to be 26 GPa. Over this pressure,
and (\emph{E}) of phase decrease upon further
compression. Our calculations show that the large value of superconducting
transition temperature \emph{T}_{\rm{c}} at 30 GPa for Zr is mainly
due to the TA1 soft mode. Under further compression, the soft vibrational mode
will gradually fade away.Comment: 15 pages, 5 figure
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