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Search Results: 1 - 10 of 104364 matches for " Yongchao Zhang "
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Majorana neutrino mass matrices with three texture zeros and the sterile neutrino
Zhang, Yongchao
High Energy Physics - Phenomenology , 2013, DOI: 10.1103/PhysRevD.87.053020
Abstract: As a consequence of the LSND anomaly and other hints of an eV scale sterile neutrino from particle physics and cosmology, the neutrino sector of the standard model of particle physics has to be extended and the smallest extension is the (3+1) model, i.e. three active neutrinos plus one sterile one. In this work we study the neutrino mass matrix $M_\nu$ with three texture zeros in the (3+1) model, assuming all the neutrino states are of Majorana type. With the mass hierarchy between the active and sterile neutrinos as well as the smallness of the reactor neutrino mixing and active-sterile mixing, the analytical expressions can be greatly simplified. We systematically examine all the 120 texture zeros, via both analytical and numerical analysis, and find that the 100 textures with zeros in the fourth column and row of $M_\nu$ can hardly be compatible with experiments whereas 19 of the other 20 are feasible. We can foresee that the active neutrino masses are required to be around 0.01 eV and the next generation neutrinoless double beta decay experiments are promising to test these textures. Many other phenomenologically meaningful predictions are also obtained. All the CP conserving (3+1) textures with three zeros are excluded by experiments.
Optimal Stopping Problems with Regime Switching: A Viscosity Solution Method
Na Zhang,Yongchao Zhang
Mathematics , 2014,
Abstract: We employ the viscosity solution technique to analyze optimal stopping problems with regime switching. Specifically, we obtain the viscosity property of value functions, the uniqueness of viscosity solutions, the regularity of value functions and the form of optimal stopping intervals. Finally, we provide an application of the results.
A Positive Solution for a Nonlocal Schr?dinger Equation
Yongchao Zhang,Gaosheng Zhu
Mathematics , 2014, DOI: 10.1017/S0004972714000501
Abstract: We provide an existence result of radially symmetric, positive, classical solutions for a nonlinear Schr\"{o}dinger equation driven by the infinitesimal generator of a rotationally invariant L\'{e}vy process.
Individual Risk and Lebesgue Extension without Aggregate Uncertainty
Yeneng Sun,Yongchao Zhang
Mathematics , 2008,
Abstract: Many economic models include random shocks imposed on a large number (continuum) of economic agents with individual risk. In this context, an exact law of large numbers and its converse is presented in Sun (2006) to characterize the cancelation of individual risk via aggregation. However, it is well known that the Lebesgue unit interval is not suitable for modeling a continuum of agents in the particular setting. The purpose of this paper is to show that an extension of the Lebesgue unit interval does work well as an agent space with various desirable properties associated with individual risk.
Vacuum Stability and Higgs Diphoton Decay Rate in the Zee-Babu Model
Wei Chao,Jian-Hui Zhang,Yongchao Zhang
Physics , 2012, DOI: 10.1007/JHEP06(2013)039
Abstract: Although recent Higgs data from ATLAS and CMS are compatible with a Standard Model (SM) signal at $2\sigma$ level, both experiments see indications for an excess in the diphoton decay channel, which points to new physics beyond the SM. Given such a low Higgs mass $m_H \sim 125 {\rm GeV}$, another sign indicating the existence of new physics beyond the SM is the vacuum stability problem, i.e., the SM Higgs quartic coupling may run to negative values at a scale below the Planck scale. In this paper, we study the vacuum stability and enhanced Higgs diphoton decay rate in the Zee-Babu model, which was used to generate tiny Majorana neutrino masses at two-loop level. We find that it is rather difficult to find overlapping regions allowed by the vacuum stability and diphoton enhancement constraints. As a consequence, it is almost inevitable to introduce new ingredients into the model, in order to resolve these two issues simultaneously.
L1pred: A Sequence-Based Prediction Tool for Catalytic Residues in Enzymes with the L1-logreg Classifier
Yongchao Dou, Jun Wang, Jialiang Yang, Chi Zhang
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035666
Abstract: To understand enzyme functions, identifying the catalytic residues is a usual first step. Moreover, knowledge about catalytic residues is also useful for protein engineering and drug-design. However, to experimentally identify catalytic residues remains challenging for reasons of time and cost. Therefore, computational methods have been explored to predict catalytic residues. Here, we developed a new algorithm, L1pred, for catalytic residue prediction, by using the L1-logreg classifier to integrate eight sequence-based scoring functions. We tested L1pred and compared it against several existing sequence-based methods on carefully designed datasets Data604 and Data63. With ten-fold cross-validation, L1pred showed the area under precision-recall curve (AUPR) and the area under ROC curve (AUC) of 0.2198 and 0.9494 on the training dataset, Data604, respectively. In addition, on the independent test dataset, Data63, it showed the AUPR and AUC values of 0.2636 and 0.9375, respectively. Compared with other sequence-based methods, L1pred showed the best performance on both datasets. We also analyzed the importance of each attribute in the algorithm, and found that all the scores contributed more or less equally to the L1pred performance.
Partial inhibition of CDK4 gene expression leads to the extension of G1 phase of V79-8 cells
Weiqun Xiao,Siqing Zhang,Yongchao Wang,Yue Wang
Chinese Science Bulletin , 1999, DOI: 10.1007/BF02884740
Abstract: V79-8 is an abnormal cell line which does not have detectable G1 and G2 phases in its cell cycle. This cell line is derived from V79 cell line which has G1 phase but lacks G2 phase. By using an anti-sense approach, CDK4 gene expression was partially inhibited to find whether CDK4 might contribute to the lack of G1 phase in V79-8 cells. Anti-CDK4 anti-sense plasmid was constructed and used to transfect V79-8 cells. Clones of transfected cells (V79-8-asCDK4) were examined, in comparison with V79-8 cells, to determine its growth curve, cell doubling-time (GT), the level of CDK4 gene expression and the levels of expression of some other growth related genes. V79-8-asCDK4 cells showed a slower growth rate with a doubling time 2.5-h longer than that of V79-8 cells. A flow cytometry (FCM) analysis demonstrated that the 2.5 h increase of the doubling time of V79-8-asCDK4 cells was mainly due to the appearance of G1 phase because its G2 + M phase was not significantly different from that of V79-8 cells. The decrease of CDK4 gene expression in V79-8-asCDK4 cells was shown by Northern-blot. Changes in the expression levels of the growth-related genes TGF-β, cyclin Dl and Rb were also detected in V79-8-asCDK4 cells. CDK4 functions mainly in G1 and at the transition between G1 and S phases. Expression of an anti-sense CDK4 gene fragment reduces the levels of endogenous CDK4, CDK4/cyclinD kinase activity and the phosphorylation of Rb. These events may postpone the inactivation of the check-point leading to the delay of entry into S phase and the reappearance of G1 phase in V79-8-asCDK4 cells.
Impact of climate change and variability on water resources in Heihe River Basin

ZHANG Jishi,KANG Ersi,LAN Yongchao,CHEN Rensheng,

地理学报 , 2003,
Abstract: Studies indicate that the climate has experienced a dramatic change in the Heihe River Basin with scope of temperature rise reaching 0.5-1.1oC in the 1990s compared to the mean value of the period 1960-1990, precipitation increased 18.5 mm in the 1990s compared to the 1950s, and 6.5 mm in the 1990s compared to the mean value of the period 1960-1990, water resources decreased 2.6×108 m3 in the 1990s compared to the 1950s, and 0.4×108 m3 in the 1990s compared to the mean value of the period 1960-1990. These changes have exerted a greater effect on the local environment and socio-economy, and also made the condition worsening in water resources utilizations in the Heihe Rver Basin.
The relationship between ENSO cycle and temperature, precipitation and runoff in the Qilian mountain area

LAN Yongchao,DING Yongjian,KANG Ersi,ZHANG Jishi,

地理学报 , 2003,
Abstract: El Nino and La Nina are the events concerned internationally. The corresponding relationship between El Nino events, temperature, precipitation and runoff in the Qilian mountain area are analyzed according to the date from the weather and the hydrometric stations in the area, the results show that effects of El Nino events to temperature, precipitation and runoff are different in the different time and zones. When El Nino occurs, temperature rises, but precipitation and runoff decrease in the whole Qilian mountain area, especially in the east and middle parts of the area. Temperature rises, precipitation and runoff still decrease in the eastern Qilian mountain area in the next year El Nino occurring, but decrease extent is fewer. There are not obvious relationship between temperature, precipitation and runoff with El Nino events in the western Qilian mountain area.
Partial inhibition of CDK4 gene expression leads to the extension of G1 phase of V79-8 cells

Weiqun Xiao,Siqing Zhang,Yongchao Wang,Yue Wang,

科学通报(英文版) , 1999,
Abstract: V79-8 is an abnormal cell line which does not have detectable G1 and G2 phases in its cell cycle. This cell line is derived from V79 cell line which has G1 phase but lacks G2 phase. By using an anti-sense approach, CDK4 gene expression was partially inhibited to find whether CDK4 might contribute to the lack of G1 phase in V79-8 cells. Anti-CDK4 anti-sense plasmid was constructed and used to transfect V79-8 cells. Clones of transfected cells (V79-8-asCDK4) were examined, in comparison with V79-8 cells, to determine its growth curve, cell doubling-time (GT), the level of CDK4 gene expression and the levels of expression of some other growth related genes. V79-8-asCDK4 cells showed a slower growth rate with a doubling time 2.5-h longer than that of V79-8 cells. A flow cytometry (FCM) analysis demonstrated that the 2.5 h increase of the doubling time of V79-8-asCDK4 cells was mainly due to the appearance of G1 phase because its G2 + M phase was not significantly different from that of V79-8 cells. The decrease of CDK4 gene expression in V79-8-asCDK4 cells was shown by Northern-blot. Changes in the expression levels of the growth-related genes TGF-β, cyclin Dl and Rb were also detected in V79-8-asCDK4 cells. CDK4 functions mainly in G1 and at the transition between G1 and S phases. Expression of an anti-sense CDK4 gene fragment reduces the levels of endogenous CDK4, CDK4/cyclinD kinase activity and the phosphorylation of Rb. These events may postpone the inactivation of the check-point leading to the delay of entry into S phase and the reappearance of G1 phase in V79-8-asCDK4 cells.
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