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Search Results: 1 - 10 of 120209 matches for " Yupeng Wang "
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Exact solution of a spin-ladder model
Yupeng Wang
Physics , 1999, DOI: 10.1103/PhysRevB.60.9236
Abstract: An integrable spin-ladder model with nearest-neighbor exchanges and biquadratic interactions is proposed. With the Bethe ansatz solutions of the model hamiltonian, it is found that there are three possible phases in the ground state, i.e., a rung-dimerized phase with a spin gap, and two massless phases. The possible fixed points of the system and the quantum critical behavior at the critical point $J=J_+^c$ are discussed.
Fermi liquid features of the one-dimensional Luttinger liquid
Yupeng Wang
Physics , 1997, DOI: 10.1142/S0217979298002817
Abstract: We show that the one-dimensional (1D) electron systems can also be described by Landau's phenomenological Fermi-liquid theory. Most of the known results derived from the Luttinger-liquid theory can be retrieved from the 1D Fermi-liquid theory. Exact correspondence between the Landau parameters and Haldane parameters is established. The exponents of the dynamical correlation functions and the impurity problem are also discussed based on the finite size corrections of elementary excitations with the predictions of the conformal field theory, which provides a bridge between the 1D Fermi-liquid and the Luttinger liquid.
Non-exclusion statistics: a generalization of Bose-Einstein's principle
Yupeng Wang
Physics , 2001,
Abstract: By constructing the super-particle representation of the free boson gas, we propose a new statistics in which the particles are non-exclusive. This statistics can be considered as a generalization of Bose-Einstein's. The possible condensation of this statistical system is studied. It is found that the chemical potential below the condensation temperature is linearly proportional to the temperature rather than a constant. With an proper choice of the exclusion factors $\gamma_l$, Hadane-Wu's fractional statistics is retrieved in this representation.
Exact solution of the open Heisenberg chain with two impurities
Yupeng Wang
Physics , 1998, DOI: 10.1103/PhysRevB.56.14045
Abstract: We propose an integrable model of the spin-1/2 Heisenberg chain coupled to two impurity moments. With the open boundary conditions at the impurity sites, the model can be exactly solved for arbitrary impurity spin and arbitrary exchange constants between the bulk and the impurities. The absence of redundant terms in the hamiltonian makes the model very reasonable. The hamiltonian is diagonalized via algebraic Bethe ansatz. It is found that the impurity spins can only be screened (partially for $S>1/2$) for antiferromagnetic coupling between the impurity and the bulk. Otherwise the impurity spins can not be screened. The residual entropy of the ground state and the Kondo temperature are also derived explicitly based on the thermodynamic Bethe ansatz and the local Fermi liquid theory.
Comment on "The Hubbard Quantum Wire"
Yupeng Wang
Physics , 1998,
Abstract: %auto-ignore Paper has been withdrawn by the author.
Modulation structure of a frustrated spin ladder
Yupeng Wang
Physics , 1999, DOI: 10.1142/S0217979299003040
Abstract: We study a two-leg spin-1/2 ladder with isotropic exchanges and biquadratic interactions in the basic plaquettes. It is shown that for the extremely frustrated case, the system exhibits a self-organized phase separation. In some parameter regions, the singlet rungs form a Wigner-like lattice in the triplet-rung host. There are three types of elementary excitations in this modulation phase, i.e., the spinons in a triplet domain, the broken singlet rungs and the deformation of the Wigner-like lattice. The flux phase induced by an external magnetic field in the rung-dimerized phase is also discussed.
Exact solution of a Kondo lattice model
Yupeng Wang
Physics , 1999,
Abstract: An integrable Kondo lattice model, which describes a strongly correlated electron host interacting with a spin-1/2 lattice, is proposed. It is found that with the variations of the Kondo coupling J, the hole concentration n_h and the magnetic field H, the system may fall into a variety of phases. The phase boundaries of the ground state are determined exactly. The marginal excitations and the quantum critical behavior at the phase boundaries are discussed.
LSOSS: Detection of Cancer Outlier Differential Gene Expression
Yupeng Wang and Romdhane Rekaya
Biomarker Insights , 2012, DOI: 10.4137/BMI.S5175
Abstract: Detection of differential gene expression using microarray technology has received considerable interest in cancer research studies. Recently, many researchers discovered that oncogenes may be activated in some but not all samples in a given disease group. The existing statistical tools for detecting differentially expressed genes in a subset of the disease group mainly include cancer outlier profile analysis (COPA), outlier sum (OS), outlier robust t-statistic (ORT) and maximum ordered subset t-statistics (MOST). In this study, another approach named Least Sum of Ordered Subset Square t-statistic (LSOSS) is proposed. The results of our simulation studies indicated that LSOSS often has more power than previous statistical methods. When applied to real human breast and prostate cancer data sets, LSOSS was competitive in terms of the biological relevance of top ranked genes. Furthermore, a modified hierarchical clustering method was developed to classify the heterogeneous gene activation patterns of human breast cancer samples based on the significant genes detected by LSOSS. Three classes of gene activation patterns, which correspond to estrogen receptor (ER)+, ER- and a mixture of ER+ and ER-, were detected and each class was assigned a different gene signature.
LSOSS: Detection of Cancer Outlier Differential Gene Expression
Yupeng Wang,Romdhane Rekaya
Biomarker Insights , 2010,
Abstract: Detection of differential gene expression using microarray technology has received considerable interest in cancer research studies. Recently, many researchers discovered that oncogenes may be activated in some but not all samples in a given disease group. The existing statistical tools for detecting differentially expressed genes in a subset of the disease group mainly include cancer outlier profile analysis (COPA), outlier sum (OS), outlier robust t-statistic (ORT) and maximum ordered subset t-statistics (MOST). In this study, another approach named Least Sum of Ordered Subset Square t-statistic (LSOSS) is proposed. The results of our simulation studies indicated that LSOSS often has more power than previous statistical methods. When applied to real human breast and prostate cancer data sets, LSOSS was competitive in terms of the biological relevance of top ranked genes. Furthermore, a modified hierarchical clustering method was developed to classify the heterogeneous gene activation patterns of human breast cancer samples based on the significant genes detected by LSOSS. Three classes of gene activation patterns, which correspond to estrogen receptor (ER)+, ER- and a mixture of ER+ and ER-, were detected and each class was assigned a different gene signature.
A Comprehensive Analysis of Gene Expression Evolution Between Humans and Mice
Yupeng Wang,Romdhane Rekaya
Evolutionary Bioinformatics , 2009,
Abstract: Evolutionary changes in gene expression account for most phenotypic differences between species. Advances in microarray technology have made the systematic study of gene expression evolution possible. In this study, gene expression patterns were compared between human and mouse genomes using two published methods. Specifically, we studied how gene expression evolution was related to GO terms and tried to decode the relationship between promoter evolution and gene expression evolution. The results showed that (1) the significant enrichment of biological processes in orthologs of expression conservation reveals functional significance of gene expression conservation. The more conserved gene expression in some biological processes than is expected in a purely neutral model reveals negative selection on gene expression. However, fast evolving genes mainly support the neutrality of gene expression evolution, and (2) gene expression conservation is positively but only slightly correlated with promoter conservation based on a motif-count score of the promoter alignment. Our results suggest a neutral model with negative selection for gene expression evolution between humans and mice, and promoter evolution could have some effects on gene expression evolution.
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