742 research outputs found
Negative phase velocity in nonlinear oscillatory systems --mechanism and parameter distributions
Waves propagating inwardly to the wave source are called antiwaves which have
negative phase velocity. In this paper the phenomenon of negative phase
velocity in oscillatory systems is studied on the basis of periodically paced
complex Ginzbug-Laundau equation (CGLE). We figure out a clear physical picture
on the negative phase velocity of these pacing induced waves. This picture
tells us that the competition between the frequency of the
pacing induced waves with the natural frequency of the oscillatory
medium is the key point responsible for the emergence of negative phase
velocity and the corresponding antiwaves. and
are the criterions for the waves with negative
phase velocity. This criterion is general for one and high dimensional CGLE and
for general oscillatory models. Our understanding of antiwaves predicts that no
antispirals and waves with negative phase velocity can be observed in excitable
media
Time-reversal symmetry breaking superconducting ground state in the doped Mott insulator on the honeycomb lattice
The emergence of superconductivity in doped Mott insulators has been debated
for decades. In this paper, we report the theoretical discovery of a
time-reversal symmetry breaking superconducting ground state in the doped Mott
insulator (described by the well known t-J model) on honeycomb lattice, based
on a recently developed variational method: the Grassmann tensor product state
approach. As a benchmark, we use exact diagonalization and density-matrix
renormalization methods to check our results on small clusters. We find
systematic consistency for the ground-state energy as well as other physical
quantities, such as the staggered magnetization. At low doping, the
superconductivity coexists with antiferromagnetic ordering.Comment: 7 pages, 9 figures (published version
Pseudogap, Superconducting Energy Scale, and Fermi Arcs in Underdoped Cuprate Superconductors
Through the measurements of magnetic field dependence of specific heat in
in zero temperature limit, we determined the nodal slope
of the quasiparticle gap. It is found that has a very
similar doping dependence of the pseudogap temperature or value
. Meanwhile the virtual maximum gap at () derived from
is found to follow the simple relation upon
changing the doping concentration. This strongly suggests a close relationship
between the pseudogap and superconductivity. It is further found that the
superconducting transition temperature is determined by both the residual
density of states of the pseudogap phase and the nodal gap slope in the zero
temperature limit, namely, , where
is the extracted zero temperature value of the normal state
specific heat coefficient which is proportional to the size of the residual
Fermi arc . This manifests that the superconductivity may be formed by
forming a new gap on the Fermi arcs near nodes below . These observations
mimic the key predictions of the SU(2) slave boson theory based on the general
resonating-valence-bond (RVB) picture.Comment: 6 pages, 6 figures, to be published in Phys. Rev.
Production of squeezed state of single mode cavity field by the coupling of squeezed vacuum field reservoir in nonautonomous case
The dissipative and decoherence properties as well as the asymptotic behavior
of the single mode electromagnetic field interacting with the time-dependent
squeezed vacuum field reservoir are investigated in detail by using the
algebraic dynamical method. With the help of the left and right representations
of the relevant algebra, the dynamical symmetry of the nonautonomous
master equation of the system is found to be . The unique equilibrium
steady solution is found to be the squeezed state and any initial state of the
system is proved to approach the unique squeezed state asymptotically. Thus the
squeezed vacuum field reservoir is found to play the role of a squeezing mold
of the cavity field.Comment: 5 pages, no figure, Revtex
Kondo effect of an adatom in graphene and its scanning tunneling spectroscopy
We study the Kondo effect of a single magnetic adatom on the surface of
graphene. It was shown that the unique linear dispersion relation near the
Dirac points in graphene makes it more easy to form the local magnetic moment,
which simply means that the Kondo resonance can be observed in a more wider
parameter region than in the metallic host. The result indicates that the Kondo
resonance indeed can form ranged from the Kondo regime, to the mixed valence,
even to the empty orbital regime. While the Kondo resonance displays as a sharp
peak in the first regime, it has a peak-dip structure and/or an anti-resonance
in the remaining two regimes, which result from the Fano resonance due to the
significant background leaded by dramatically broadening of the impurity level
in graphene. We also study the scanning tunneling microscopy (STM) spectra of
the adatom and they show obvious particle-hole asymmetry when the chemical
potential is tuned by the gate voltages applied to the graphene. Finally, we
explore the influence of the direct tunneling channel between the STM tip and
the graphene on the Kondo resonance and find that the lineshape of the Kondo
resonance is unaffected, which can be attributed to unusual large asymmetry
factor in graphene. Our study indicates that the graphene is an ideal platform
to study systematically the Kondo physics and these results are useful to
further stimulate the relevant experimental studies on the system.Comment: 8 pages, 5 figure
Discovery of Stable and Selective Antibody Mimetics from Combinatorial Libraries of Polyvalent, Loop-Functionalized Peptoid Nanosheets.
The ability of antibodies to bind a wide variety of analytes with high specificity and high affinity makes them ideal candidates for therapeutic and diagnostic applications. However, the poor stability and high production cost of antibodies have prompted exploration of a variety of synthetic materials capable of specific molecular recognition. Unfortunately, it remains a fundamental challenge to create a chemically diverse population of protein-like, folded synthetic nanostructures with defined molecular conformations in water. Here we report the synthesis and screening of combinatorial libraries of sequence-defined peptoid polymers engineered to fold into ordered, supramolecular nanosheets displaying a high spatial density of diverse, conformationally constrained peptoid loops on their surface. These polyvalent, loop-functionalized nanosheets were screened using a homogeneous Förster resonance energy transfer (FRET) assay for binding to a variety of protein targets. Peptoid sequences were identified that bound to the heptameric protein, anthrax protective antigen, with high avidity and selectivity. These nanosheets were shown to be resistant to proteolytic degradation, and the binding was shown to be dependent on the loop display density. This work demonstrates that key aspects of antibody structure and function-the creation of multivalent, combinatorial chemical diversity within a well-defined folded structure-can be realized with completely synthetic materials. This approach enables the rapid discovery of biomimetic affinity reagents that combine the durability of synthetic materials with the specificity of biomolecular materials
Computational Identification of Gene Networks as a Biomarker of Neuroblastoma Risk
Neuroblastoma is a common cancer in children, affected by a number of genes that interact with each other through intricate but coordinated networks. Traditional approaches can only reconstruct a single regulatory network that is topologically not informative enough to explain the complexity of neuroblastoma risk. We implemented and modified an advanced model for recovering informative, omnidirectional, dynamic, and personalized networks (idopNetworks) from static gene expression data for neuroblastoma risk. We analyzed 3439 immune genes of neuroblastoma for 217 high-risk patients and 30 low-risk patients by which to reconstruct large patient-specific idopNetworks. By converting these networks into risk-specific representations, we found that the shift in patients from a low to high risk or from a high to low risk might be due to the reciprocal change of hub regulators. By altering the directions of regulation exerted by these hubs, it may be possible to reduce a high risk to a low risk. Results from a holistic, systems-oriented paradigm through idopNetworks can potentially enable oncologists to experimentally identify the biomarkers of neuroblastoma and other cancers
Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. I. Survey Design, Follow-up Program, and Binary Frequency
The chemical abundances of very metal-poor stars provide important
constraints on the nucleosynthesis of the first generation of stars and early
chemical evolution of the Galaxy. We have obtained high-resolution spectra with
the Subaru Telescope for candidates of very metal-poor stars selected with a
large survey of Galactic stars carried out with LAMOST. In this series of
papers, we report on the elemental abundances of about 400 very metal-poor
stars and discuss the kinematics of the sample obtained by combining the radial
velocities measured in this study and recent astrometry obtained with Gaia.
This paper provides an overview of our survey and follow-up program, and
reports radial velocities for the whole sample. We identify seven double-lined
spectroscopic binaries from our high-resolution spectra, for which radial
velocities of the components are reported. We discuss the frequency of such
relatively short-period binaries at very low metallicity.Comment: 24 pages, 9 figures, 5 tables, to appear in Ap
Equation of motion approach to the solution of Anderson model
Based on an equation of motion approach the single impurity Anderson
model(SIAM) is reexamined. Using the cluster expansions the equations of motion
of Green functions are transformed into the corresponding equations of motion
of connected Green functions, which provides a natural and uniform truncation
scheme. A factor of two missing in the Lacroix's approximation for the Kondo
temperature is gained in the next higher order truncation beyond Lacroix's. A
quantitative improvement in the density of states at the Fermi level is also
obtained.Comment: 4 pages, 2 figure
- …