10,781 research outputs found
Kondo correlation and spin-flip scattering in spin-dependent transport through a quantum dot coupled to ferromagnetic leads
We investigate the linear and nonlinear dc transport through an interacting
quantum dot connected to two ferromagnetic electrodes around Kondo regime with
spin-flip scattering in the dot. Using a slave-boson mean field approach for
the Anderson Hamiltonian having finite on-site Coulomb repulsion, we find that
a spin-flip scattering always depresses the Kondo correlation at arbitrary
polarization strength in both parallel and antiparallel alignment of the lead
magnetization and that it effectively reinforces the tunneling related
conductance in the antiparallel configuration. For systems deep in the Kondo
regime, the zero-bias single Kondo peak in the differential conductance is
split into two peaks by the intradot spin-flip scattering; while for systems
somewhat further from the Kondo center, the spin-flip process in the dot may
turn the zero-bias anomaly into a three-peak structure.Comment: 4 pages, 2 figure
RNA-RNA interaction prediction based on multiple sequence alignments
Many computerized methods for RNA-RNA interaction structure prediction have
been developed. Recently, time and space dynamic programming
algorithms have become available that compute the partition function of RNA-RNA
interaction complexes. However, few of these methods incorporate the knowledge
concerning related sequences, thus relevant evolutionary information is often
neglected from the structure determination. Therefore, it is of considerable
practical interest to introduce a method taking into consideration both
thermodynamic stability and sequence covariation. We present the \emph{a
priori} folding algorithm \texttt{ripalign}, whose input consists of two
(given) multiple sequence alignments (MSA). \texttt{ripalign} outputs (1) the
partition function, (2) base-pairing probabilities, (3) hybrid probabilities
and (4) a set of Boltzmann-sampled suboptimal structures consisting of
canonical joint structures that are compatible to the alignments. Compared to
the single sequence-pair folding algorithm \texttt{rip}, \texttt{ripalign}
requires negligible additional memory resource. Furthermore, we incorporate
possible structure constraints as input parameters into our algorithm. The
algorithm described here is implemented in C as part of the \texttt{rip}
package. The supplemental material, source code and input/output files can
freely be downloaded from \url{http://www.combinatorics.cn/cbpc/ripalign.html}.
\section{Contact} Christian Reidys \texttt{[email protected]}Comment: 8 pages, 9 figure
Is the Number of Giant Arcs in LCDM Consistent With Observations?
We use high-resolution N-body simulations to study the galaxy-cluster
cross-sections and the abundance of giant arcs in the CDM model.
Clusters are selected from the simulations using the friends-of-friends method,
and their cross-sections for forming giant arcs are analyzed. The background
sources are assumed to follow a uniform ellipticity distribution from 0 to 0.5
and to have an area identical to a circular source with diameter 1\arcsec. We
find that the optical depth scales as the source redshift approximately as
\tau_{1''} = 2.25 \times 10^{-6}/[1+(\zs/3.14)^{-3.42}] (0.6<\zs<7). The
amplitude is about 50% higher for an effective source diameter of 0.5\arcsec.
The optimal lens redshift for giant arcs with the length-to-width ratio ()
larger than 10 increases from 0.3 for \zs=1, to 0.5 for \zs=2, and to
0.7-0.8 for \zs>3. The optical depth is sensitive to the source redshift, in
qualitative agreement with Wambsganss et al. (2004). However, our overall
optical depth appears to be only 10% to 70% of those from previous
studies. The differences can be mostly explained by different power spectrum
normalizations () used and different ways of determining the
ratio. Finite source size and ellipticity have modest effects on the optical
depth. We also found that the number of highly magnified (with magnification
) and ``undistorted'' images (with ) is comparable to the
number of giant arcs with and . We conclude that our
predicted rate of giant arcs may be lower than the observed rate, although the
precise `discrepancy' is still unclear due to uncertainties both in theory and
observations.Comment: Revised version after the referee's reports (32 pages,13figures). The
paper has been significantly revised with many additions. The new version
includes more detailed comparisons with previous studies, including the
effects of source size and ellipticity. New discussions about the redshift
distribution of lensing clusters and the width of giant arcs have been adde
Enhancement of quantum correlations for the system of cavity QED by applying bang-bang pulses
We propose a scheme of increasing quantum correlations for the cavity quantum
electrodynamics system consisting of two noninteracting two-level atoms each
locally interacting with its own quantized field mode by bang-bang pulses. We
investigate the influence of the bang-bang pulses on the dynamics of quantum
discord, entanglement, quantum mutual information and classical correlation
between the two atoms. It is shown that the amount of quantum discord and
entanglement of the two atoms can be improved by applying the bang-bang pulses.Comment: 6 pages, 5 figure
Coherent population trapping in a dressed two-level atom via a bichromatic field
We show theoretically that by applying a bichromatic electromagnetic field,
the dressed states of a monochromatically driven two-level atom can be pumped
into a coherent superposition termed as dressed-state coherent population
trapping. Such effect can be viewed as a new doorknob to manipulate a two-level
system via its control over dressed-state populations. Application of this
effect in the precision measurement of Rabi frequency, the unexpected
population inversion and lasing without inversion are discussed to demonstrate
such controllability.Comment: 14 pages, 6 figure
Electromagnetic manipulation for anti-Zeno effect in an engineered quantum tunneling process
We investigate the quantum Zeno and anti-Zeno effects for the irreversible
quantum tunneling from a quantum dot to a ring array of quantum dots. By
modeling the total system with the Anderson-Fano-Lee model, it is found that
the transition from the quantum Zeno effect to quantum anti-Zeno effect can
happen as the magnetic flux and the gate voltage were adjusted.Comment: 6 pages, 5 figure
Tunnelling Effect and Hawking Radiation from a Vaidya Black Hole
In this paper, we extend Parikh' work to the non-stationary black hole. As an
example of the non-stationary black hole, we study the tunnelling effect and
Hawking radiation from a Vaidya black hole whose Bondi mass is identical to its
mass parameter. We view Hawking radiation as a tunnelling process across the
event horizon and calculate the tunnelling probability. We find that the result
is different from Parikh's work because is the function of
Bondi mass m(v)
Study on the extraction of dioscin by the ultrasonicassisted ethanol
With Dioscorea zingiberensis as row materials, and with the yield of diosgenin as assessment criteria, the effect on extraction yield of dioscin of frequency of ultrasonic, the period of ultrasonic and solidliquid ratio (D. zingiberensis : alcohol) was studied via orthogonal test. A new and unique method to accomplish this was by utilizing the technology of ultrasonic assisted ethanol extraction. The optimal processing parameters of this method were confirmed. The method was compared with solvent extraction process for the effect on extraction yield of dioscin. It was shown that the technology of ultrasonic assisted ethanol extraction which can significantly increase the extraction yield and extraction efficiency of dioscin. The ultrasonic did not destroy D. zingiberensis cell structure, but decreased the boundary layer thickness between D. zingiberensis (solid phase) and alcohol (medium), and accelerated cells inside and outside the material exchange. International rectifier (IR) further demonstrated that ultrasonic merely increased extraction yield of dioscin instead of destroying the cell structure.Keywords: D. zingiberensis, ultrasonic waves, extraction, diosgenin
Order-preserving Consistency Regularization for Domain Adaptation and Generalization
Deep learning models fail on cross-domain challenges if the model is oversensitive to domain-specific attributes, e.g., lightning, background, camera angle, etc. To alleviate this problem, data augmentation coupled with consistency regularization are commonly adopted to make the model less sensitive to domain-specific attributes. Consistency regularization enforces the model to output the same representation or prediction for two views of one image. These constraints, however, are either too strict or not order-preserving for the classification probabilities. In this work, we propose the Order-preserving Consistency Regularization (OCR) for cross-domain tasks. The order-preserving property for the prediction makes the model robust to task-irrelevant transformations. As a result, the model becomes less sensitive to the domain-specific attributes. The comprehensive experiments show that our method achieves clear advantages on five different cross-domain tasks
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