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Search Results: 1 - 10 of 23414 matches for " Luping Shi "
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Single neutral substitutional 3d-transition metal in GeTe and GeSb2Te4 by the screened exchange functional
Huanglong Li,Luping Shi
Physics , 2015,
Abstract: Fe doped GST has shown experimentally the ability to alter its magnetic properties by phase change. In this work, we use screened exchange hybrid functional to study the single neutral substitutional 3d transition metal (TM) in crystalline GeTe and GeSb2Te4. By curing the problem of local density functional (LDA) such as over delocalization of the 3d states, we find that Fe on Ge/Sb site has its majority d states fully occupied while its minority d states are empty, which is different than previous predicted electronic configuration by LDA. From early transition metal Cr to heavier Ni, the majority 3d states are gradually populated until fully occupied and then the minority 3d states begin to be filled. In order to study the magnetic contrast, we use lower symmetry crystalline GeTe and GeSb2Te4 as the amorphous phases, respectively, which has been proposed to model the medium range disordering. We find that only Co substitution in r-GeSb2Te4 and s-GeSb2Te4 shows magnetic contrast. The experimental magnetic contrast for Fe doped GST may be due to additional TM-TM interaction, which is not included in our model. It can also be possible that these lower symmetry crystalline models are not sufficient to characterize the magnetic properties of real 3d TM doped amorphous GST.
Modeling Neuromorphic Persistent Firing Networks  [PDF]
Ning Ning, Guoqi Li, Wei He, Kejie Huang, Li Pan, Kiruthika Ramanathan, Rong Zhao, Luping Shi
International Journal of Intelligence Science (IJIS) , 2015, DOI: 10.4236/ijis.2015.52009
Abstract: Neurons are believed to be the brain computational engines of the brain. A recent discovery in neurophysiology reveals that interneurons can slowly integrate spiking, share the output across a coupled network of axons and respond with persistent firing even in the absence of input to the soma or dendrites, which has not been understood and could be very important for exploring the mechanism of human cognition. The conventional models are incapable of simulating the important newly-discovered phenomenon of persistent firing induced by axonal slow integration. In this paper, we propose a computationally efficient model of neurons through modeling the axon as a slow leaky integrator, which captures almost all-known neural behaviors. The model controls the switching of axonal firing dynamics between passive conduction mode and persistent firing mode. The interplay between the axonal integrated potential and its multiple thresholds in axon precisely determines the persistent firing dynamics of neurons. We also present a persistent firing polychronous spiking network which exhibits asynchronous dynamics indicating that this computationally efficient model is not only bio-plausible, but also suitable for large scale spiking network simulations. The implications of this network and the analog circuit design for exploring the relationship between working memory and persistent firing enable developing a spiking network-based memory and bio-inspired computer systems.
The role of single oxygen or metal induced defect and correlated multiple defects in the formation of conducting filaments
Ziyang Zhang,Huanglong Li,Luping Shi
Physics , 2015,
Abstract: We study the dependence of the formation energies of oxygen and metal induced defects in Ta2O5, TaO2, TaO, TiO2 and Ti4O7 on the chemical potential of electron and atomic constitutes. In the study of single defect, metal induced defects are found to be preferable to oxygen induced defects. This is against the experimental fact of the dominant role of oxygen induced defects in the RS process. A simple multiple defects picture without correlated atomic rearrangement does not cure this problem. The problem is resolved under the correlated multiple defect picture where the multiple defects result in correlated atomic rearrangement and the final products show certain atomic ordering.
The electronic structures of TiO2/Ti4O7, Ta2O5/TaO2 interfaces and the interfacial effects of dopants
Huanglong Li,Ziyang Zhang,Luping Shi
Physics , 2015, DOI: 10.1007/s11664-015-4249-8
Abstract: We study the electronic structures of TiO2/Ti4O7 and Ta2O5/TaO2 interfaces using the screened exchange (sX-LDA) functional. Both of these bilayer structures are useful infrastructures for high performance RRAMs. We find that the system Fermi energies of both interfaces are just above the conduction band edge of the corresponding stoichiometric oxides. According to the charge transition levels of the oxygen vacancies in Ta2O5 and TiO2, the oxygen vacancies are stabilized at the -2 charged state. We propose to introduce interfacial dopants to shift the system Fermi energies downward so that the +2 charged oxygen vacancy can be stable, which is important for the controlled switching under the electrical field. Several dipole models are presented to account for the ability of Fermi level shift due to the interfacial dopants.
Minors of a Class of Riordan Arrays Related to Weighted Partial Motzkin Paths
Yidong Sun,Luping Ma
Mathematics , 2013,
Abstract: A partial Motzkin path is a path from $(0, 0)$ to $(n, k)$ in the $XOY$-plane that does not go below the $X$-axis and consists of up steps $U=(1, 1)$, down steps $D=(1, -1)$ and horizontal steps $H=(1, 0)$. A weighted partial Motzkin path is a partial Motzkin path with the weight assignment that all up steps and down steps are weighted by 1, the horizontal steps are endowed with a weight $x$ if they are lying on $X$-axis, and endowed with a weight $y$ if they are not lying on $X$-axis. Denote by $M_{n,k}(x, y)$ to be the weight function of all weighted partial Motzkin paths from $(0, 0)$ to $(n, k)$, and $\mathcal{M}=(M_{n,k}(x,y))_{n\geq k\geq 0}$ to be the infinite lower triangular matrices. In this paper, we consider the sums of minors of second order of the matrix $\mathcal{M}$, and obtain a lot of interesting determinant identities related to $\mathcal{M}$, which are proved by bijections using weighted partial Motzkin paths. When the weight parameters $(x, y)$ are specialized, several new identities are obtained related to some classical sequences involving Catalan numbers. Besides, in the alternating cases we also give some new explicit formulas for Catalan numbers.
Research on Extraction Process of Gallic Acid from Penthorum chinense Pursh by Aqueous Ethanol  [PDF]
Luping Kang, Shanbin Yang, Yan Peng, Jiao Dai, Xingchun Ying
Green and Sustainable Chemistry (GSC) , 2015, DOI: 10.4236/gsc.2015.52009
Abstract: Penthorum chinense Pursh is rich in gallic acid, which has antioxidant, anti-inflammatory, anti-fungal and antitumor activities. In order to optimize their extraction conditions, various extraction parameters were chosen to identify their effects on gallic acid extraction. With extraction amount of gallic acid as index, based on single factor analysis, influence of solid/liquid ratio, ethanol concentration, fetch time and extraction temperature on extraction technology were investigated by orthogonal test. The optimization conditions for gallic acid extraction were determined as follows: ethanol concentration 60%, extraction time 2.5 h, temperature 90°C and solid/liquid ratio 1:30. The corresponding gallic acid content was 4.85%. This optimized extraction process was stable and feasible.
Mechanisms of Resistance to Epidermal Growth Factor Receptor Inhibitors and Novel Therapeutic Strategies to Overcome Resistance in NSCLC Patients
Luping Lin,Trever G. Bivona
Chemotherapy Research and Practice , 2012, DOI: 10.1155/2012/817297
Abstract: The epidermal growth factor receptor (EGFR) is a well-characterized oncogene that is frequently activated by somatic kinase domain mutations in non-small cell lung cancer (NSCLC). EGFR TKIs are effective therapies for NSCLC patients whose tumors harbor an EGFR activating mutation. However, EGFR TKI treatment is not curative in patients because of both primary and secondary treatment resistance. Studies over the last decade have identified mechanisms that drive primary and secondary resistance to EGFR TKI treatment. The elucidation of mechanisms of resistance to EGFR TKI treatment provides a basis for the development of therapeutic strategies to overcome resistance and enhance outcomes in NSCLC patients. In this paper, we summarize the mechanisms of resistance to EGFR TKIs that have been identified to date and discusses potential therapeutic strategies to overcome EGFR TKI resistance in NSCLC patients.
Mechanisms of Resistance to Epidermal Growth Factor Receptor Inhibitors and Novel Therapeutic Strategies to Overcome Resistance in NSCLC Patients
Luping Lin,Trever G. Bivona
Chemotherapy Research and Practice , 2012, DOI: 10.1155/2012/817297
Abstract: The epidermal growth factor receptor (EGFR) is a well-characterized oncogene that is frequently activated by somatic kinase domain mutations in non-small cell lung cancer (NSCLC). EGFR TKIs are effective therapies for NSCLC patients whose tumors harbor an EGFR activating mutation. However, EGFR TKI treatment is not curative in patients because of both primary and secondary treatment resistance. Studies over the last decade have identified mechanisms that drive primary and secondary resistance to EGFR TKI treatment. The elucidation of mechanisms of resistance to EGFR TKI treatment provides a basis for the development of therapeutic strategies to overcome resistance and enhance outcomes in NSCLC patients. In this paper, we summarize the mechanisms of resistance to EGFR TKIs that have been identified to date and discusses potential therapeutic strategies to overcome EGFR TKI resistance in NSCLC patients. 1. Introduction Lung cancer is the leading cause of cancer mortality in the United States and worldwide, accounting for 28% of cancer-related deaths in males and 26% of cancer-related deaths in females [1, 2]. Most lung cancer patients present with advanced stage disease, for which conventional chemotherapies patients are only modestly effective. Thus, the 5-year-survival rate of lung cancer patients with metastatic disease is less than 15% [3]. In the last decade, the discovery of mutated oncogenes that encode activated signaling molecules that drive cellular proliferation and promote tumor growth has led to the development of more effective and less toxic targeted drugs for lung cancer patients. Systemic therapies that act against specific activated oncogenes in lung cancers have the potential for improving outcomes for lung cancer patients in an unprecedented manner. Yet, a significant challenge that must be overcome in order to realize the full potential of targeted cancer therapy in lung cancer patients is resistance to treatment with an oncogene inhibitor as monotherapy. The epidermal growth factor receptor (EGFR) is a well-characterized mutated oncogene in non-small cell lung cancer (NSCLC) that is found in ~10–20% of cases in western countries and is associated predominantly with adenocarcinoma histology. EGFR-mutated tumors are dependent to EGFR signaling for their proliferation and survival [4–7]. In lung cancer patients, EGFR mutations are generally exclusive with KRAS and BRAF mutations, and tumors with either KRAS (15–25%) or BRAF (2-3%) mutations are relatively insensitive to EGFR TKIs [8, 9]. The most common activating mutations (~90%) are
Simulations of High-Current Plasma Beam by Continuum and Statistical Mechanical Models  [PDF]
Hossam A. Gabbar, Luping Zhang, Daniel Bondarenko, C. A. Barry Stoute
World Journal of Nuclear Science and Technology (WJNST) , 2016, DOI: 10.4236/wjnst.2016.62011
Abstract: The paper builds the high-current plasma beams model under different dimensions (1D, 2D, and 3D) by continuum (magnetohydrodynamics MHD) and statistical (Monte Carlo MC) mechanics under conditions of low pressures (10-3 Pa). After detailed presentation of the model, two methods firstly have been analyzed in terms of plasma beam properties. Then, we compare the simulation results of MHD numerical simulation with MC stochastic particles simulation. Finally, through further analysis, it is demonstrated that integrated hybrid MHD and MC method (IMHDMC) provides an innovative practical tool to capture essential properties of high-current plasma beams.
The Role and Significance of Bcl-2 and Bax in the Hepatic Carcinoma El Rol y la Importancia de Bcl-2 y Bax en el Carcinoma Hepático
Liu Hongfu,Zhang Luping,Chen Shaojie,Wang Zengxian
International Journal of Morphology , 2012,
Abstract: This study aimed to observe the regularity of liver cell apoptosis and expression of apoptosis related gene Bcl-2 and Bax in the induced cancer, and explore the relationship between apoptosis and the development of liver cancer. In this study, 84 rats were used, 72 rats as experimental group induced by drinking water containing DEN, 12 rats as control group (CG). After laparotomy, the form, color, texture of the liver and metastatic tumor in both control and experimental groups were observed and recorded. The metastatic tumor and the liver tissue were sectioned and stained with hematoxylin-eosin staining to demonstrate the characteristic in morphological changes, the Hoechst 33342 fluorescent staining was applied to show and count the rate of apoptotic cell, and the in situ hybridization technique was used to detect the Bcl-2 and Bax expression. The results showed that the process of carcinogenesis can be divided into three periods: hepatic toxic lesion, hepatic proliferation/cirrhosis and hepatic carcinogenesis. The Hoechst 33342 fluorescent staining showed that the rate of apoptosis in the CG, hepatic toxic lesion, hepatic proliferation/cirrhosis and hepatic carcinogenesis were 6.7%,18.8%,17.4% and 51.2% c2=33.62, P<0.05 respectively. In situ hybridization showed the yellow positive reaction products of Bcl-2 and Bax located in the nucleus and cytoplasm of cell in diffusive distribution. The average optical densities of Bcl-2 and Bax expression were 0.1697±0.0101 and 0.1383±0.0093 in the control group, 0.1431±0.0072 and 0.1523±0.0103 in hepatic toxic lesion, 0.1261±0.0164 and 0.1639±0.0133 in hepatic proliferation/cirrhosis, 0.1034± 0.0124 and 0.1785±0.0191 in hepatic carcinogenesis, indicating that the expression of Bcl-2 decreased, but that of Bax increased with the development of liver cancer in experimental groups. In DEN induced liver cancer, the origination and development of liver cancer were accompanied with proliferation and abnormal apoptosis, which was related to the abnormal expression of gene Bcl-2 and Bax. Este estudio tuvo como objetivo observar la regularidad de la apoptosis en células del hígado y la expresión de apoptosis relacionada con los genes Bcl-2 y Bax en el cáncer inducido, además de explorar la relación entre apoptosis y desarrollo de cáncer hepático. Fueron utilizadas 84 ratas, 72 como grupo experimental inducido con el consumo de agua conteniendo DEN, y 12 como grupo de control (CG). Después de la laparotomía, la forma, color, textura del hígado, y del tumor metastásico fueron observadas y registradas en ambos grupos. El tu
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