14,695 research outputs found
Leading Chiral Corrections to the Nucleon Generalized Parton Distributions
Using heavy baryon chiral perturbation theory we study the leading chiral
corrections to the complete set of nucleon generalized parton distributions
(GPDs). We compute the leading quark mass and momentum transfer dependence of
the moments of nucleon GPDs through the nucleon off-forward twist-2 matrix
elements. These results are then applied to get insight on the GPDs and their
impact parameter space distributions.Comment: 26 pages, 2 figures; minor revisio
Dynamically stabilized decoherence-free states in non-Markovian open fermionic systems
Decoherence-free subspaces (DFSs) provide a strategy for protecting the
dynamics of an open system from decoherence induced by the system-environment
interaction. So far, DFSs have been primarily studied in the framework of
Markovian master equations. In this work, we study decoherence-free (DF) states
in the general setting of a non-Markovian fermionic environment. We identify
the DF states by diagonalizing the non-unitary evolution operator for a
two-level fermionic system attached to an electron reservoir. By solving the
exact master equation, we show that DF states can be stabilized dynamically.Comment: 11 pages, 3 figures. Any comments are welcom
A statistical model to assess (allele-specific) associations between gene expression and epigenetic features using sequencing data
Sequencing techniques have been widely used to assess gene expression (i.e., RNA-seq) or the presence of epigenetic features (e.g., DNase-seq to identify open chromatin regions). In contrast to traditional microarray platforms, sequencing data are typically summarized in the form of discrete counts, and they are able to delineate allele-specific signals, which are not available from microarrays. The presence of epigenetic features are often associated with gene expression, both of which have been shown to be affected by DNA polymorphisms. However, joint models with the flexibility to assess interactions between gene expression, epigenetic features and DNA polymorphisms are currently lacking. In this paper, we develop a statistical model to assess the associations between gene expression and epigenetic features using sequencing data, while explicitly modeling the effects of DNA polymorphisms in either an allele-specific or nonallele-specific manner. We show that in doing so we provide the flexibility to detect associations between gene expression and epigenetic features, as well as conditional associations given DNA polymorphisms. We evaluate the performance of our method using simulations and apply our method to study the association between gene expression and the presence of DNase I Hypersensitive sites (DHSs) in HapMap individuals. Our model can be generalized to exploring the relationships between DNA polymorphisms and any two types of sequencing experiments, a useful feature as the variety of sequencing experiments continue to expand
Electric Current Focusing Efficiency in Graphene Electric Lens
In present work, we theoretically study the electron wave's focusing
phenomenon in a single layered graphene pn junction(PNJ) and obtain the
electric current density distribution of graphene PNJ, which is in good
agreement with the qualitative result in previous numerical calculations
[Science, 315, 1252 (2007)]. In addition, we find that for symmetric PNJ, 1/4
of total electric current radiated from source electrode can be collected by
drain electrode. Furthermore, this ratio reduces to 3/16 in a symmetric
graphene npn junction. Our results obtained by present analytical method
provide a general design rule for electric lens based on negative refractory
index systems.Comment: 13 pages, 7 figure
Thermodynamical description of the interacting new agegraphic dark energy
We describe the thermodynamical interpretation of the interaction between new
agegraphic dark energy and dark matter in a non-flat universe. When new
agegraphic dark energy and dark matter evolve separately, each of them remains
in thermodynamic equilibrium. As soon as an interaction between them is taken
into account, their thermodynamical interpretation changes by a stable thermal
fluctuation. We obtain a relation between the interaction term of the dark
components and this thermal fluctuation.Comment: 11 pages, accepted for publication in MPLA (2010
Cosmological Models and Latest Observational Data
In this note, we consider the observational constraints on some cosmological
models by using the 307 Union type Ia supernovae (SNIa), the 32 calibrated
Gamma-Ray Bursts (GRBs) at , the updated shift parameter from WMAP
5-year data (WMAP5), and the distance parameter of the measurement of the
baryon acoustic oscillation (BAO) peak in the distribution of SDSS luminous red
galaxies with the updated scalar spectral index from WMAP5. The tighter
constraints obtained here update the ones obtained previously in the
literature.Comment: 10 pages, 5 figures, 1 table, revtex4; v2: discussions added,
accepted by Eur. Phys. J. C; v3: published versio
ZINBA integrates local covariates with DNA-seq data to identify broad and narrow regions of enrichment, even within amplified genomic regions
ZINBA (Zero-Inflated Negative Binomial Algorithm) identifies genomic regions enriched in a variety of ChIP-seq and related next-generation sequencing experiments (DNA-seq), calling both broad and narrow modes of enrichment across a range of signal-to-noise ratios. ZINBA models and accounts for factors that co-vary with background or experimental signal, such as G/C content, and identifies enrichment in genomes with complex local copy number variations. ZINBA provides a single unified framework for analyzing DNA-seq experiments in challenging genomic contexts
Renormalization of tensor-network states
We have discussed the tensor-network representation of classical statistical
or interacting quantum lattice models, and given a comprehensive introduction
to the numerical methods we recently proposed for studying the tensor-network
states/models in two dimensions. A second renormalization scheme is introduced
to take into account the environment contribution in the calculation of the
partition function of classical tensor network models or the expectation values
of quantum tensor network states. It improves significantly the accuracy of the
coarse grained tensor renormalization group method. In the study of the quantum
tensor-network states, we point out that the renormalization effect of the
environment can be efficiently and accurately described by the bond vector.
This, combined with the imaginary time evolution of the wavefunction, provides
an accurate projection method to determine the tensor-network wavfunction. It
reduces significantly the truncation error and enable a tensor-network state
with a large bond dimension, which is difficult to be accessed by other
methods, to be accurately determined.Comment: 18 pages 23 figures, minor changes, references adde
Quantum gates implementations in the separated ion-traps by fast laser pulses
An approach is proposed to implement the universal quantum gates between the
ions confined individually in the separated traps. Instead of the typical
adiabatic operations, performed for manipulating the ion-ion coupling, here the
switchable couplings between ions are implemented non-adiabatically by using
the fast laser pulses. Consequently, the desirable quantum gates between the
ions could be implemented by using only a series of laser pulses. The proposal
may be conveniently generalized to the quantum computation with the scalable
ion-traps.Comment: 10 pages, 3figure
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