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Now showing items 17 - 32 of 383

  • Isolation and characterization of cytotoxic cyclotides from Viola tricolor

    Jun Tang   Conan K. Wang   Xulin Pan   He Yan   Guangzhi Zeng   Wenyan Xu   Wenjun He   Norelle L. Daly   David J. Craik   Ninghua Tan  

    Many plants of the Violaceae plant family have been used in traditional remedies, and these plants often contain cyclotides, a particular type of plant cyclopeptide that is distinguished by a cyclic cystine knot motif. In general, bioactive plant cyclopeptides are interesting candidates for drug development. In the current study, a suite of 14 cyclotides, which includes seven novel cyclotides [vitri B, C, D, E, F, varv Hm, and He], together with seven known cyclotides [varv A, D, E, F, H, vitri A, and cycloviolacin O2], was isolated from Viola tricolor, a common flower. A chromatography-based method was used to isolate the cyclotides, which were characterized using tandem mass spectrometry and NMR spectroscopy. Several of the cyclotides showed cytotoxic activities against five cancer cell lines, U251, MDA-MB-231, A549, DU145, and BEL-7402. Three cyclotides, vitri A, vitri F, and cycloviolacin O2, were the most cytotoxic. The cytotoxic activity of the cyclotides did not correlate well with their hemolytic activity, indicating that different interactions, most likely with membranes, are involved for cytotoxic and hemolytic activities. Homology modeling of the structures was used in deriving structure–activity relationships.
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  • Isolation and characterization of cytotoxic cyclotides from Viola tricolor

    Jun Tang   Conan K. Wang   Xulin Pan   He Yan   Guangzhi Zeng   Wenyan Xu   Wenjun He   Norelle L. Daly   David J. Craik   Ninghua Tan  

    Many plants of the Violaceae plant family have been used in traditional remedies, and these plants often contain cyclotides, a particular type of plant cyclopeptide that is distinguished by a cyclic cystine knot motif. In general, bioactive plant cyclopeptides are interesting candidates for drug development. In the current study, a suite of 14 cyclotides, which includes seven novel cyclotides [vitri B, C, D, E, F, varv Hm, and He], together with seven known cyclotides [varv A, D, E, F, H, vitri A, and cycloviolacin O2], was isolated from Viola tricolor, a common flower. A chromatography-based method was used to isolate the cyclotides, which were characterized using tandem mass spectrometry and NMR spectroscopy. Several of the cyclotides showed cytotoxic activities against five cancer cell lines, U251, MDA-MB-231, A549, DU145, and BEL-7402. Three cyclotides, vitri A, vitri F, and cycloviolacin O2, were the most cytotoxic. The cytotoxic activity of the cyclotides did not correlate well with their hemolytic activity, indicating that different interactions, most likely with membranes, are involved for cytotoxic and hemolytic activities. Homology modeling of the structures was used in deriving structure–activity relationships.
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  • Collaboration data proxy system in cloud computing platforms

    In various embodiments, methods and systems for enhanced access to storage data based on a collaboration data proxy system are provided. A plurality of metadata tables on one or more peer nodes are referenced for data corresponding to a data request of a requesting node. The metadata tables indicate availability of chunks of data in the one or more peer nodes. A determination is made that the data corresponding to the data request is downloadable from the one or more node; the determination is based on the metadata tables. A download operation configuration instance is generated for a data request of a requesting node. The download operation configuration instance comprises configuration settings for downloading data corresponding to the data request from the one or more peer nodes. The chunk of data is downloaded from the corresponding one or more peer nodes where the chunk is located, using the configuration settings.
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  • Selective deposition of charged nanoparticles by self-electric focusing effect

    Jun Tang   E. Verrelli   D. Tsoukalas  

    A process for the selective deposition of nanoparticles by a self-electric focusing effect is discussed. The negatively charged Nickel nanoparticles were fabricated by a DC magnetron sputtering system, and were deposited on a photoresist-patterned silicon substrate. Because of the different conductance between silicon and photoresist, the charges were accumulated on the photoresist as the nanoparticles were deposited, which caused a focusing electric field to drive the nanoparticles towards the silicon substrate. We have demonstrated that the self-focusing effect of the charged nanoparticles is responsible for increasing the density of nanoparticles in the lines patterned on silicon substrate by two orders of magnitude with respect to that on photoresist. The width of the silicon line and the width ratio between photoresist line and silicon line are the two most important parameters that will affect the self-focusing effect.
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  • Selective deposition of charged nanoparticles by self-electric focusing effect

    Jun Tang   E. Verrelli   D. Tsoukalas  

    A process for the selective deposition of nanoparticles by a self-electric focusing effect is discussed. The negatively charged Nickel nanoparticles were fabricated by a DC magnetron sputtering system, and were deposited on a photoresist-patterned silicon substrate. Because of the different conductance between silicon and photoresist, the charges were accumulated on the photoresist as the nanoparticles were deposited, which caused a focusing electric field to drive the nanoparticles towards the silicon substrate. We have demonstrated that the self-focusing effect of the charged nanoparticles is responsible for increasing the density of nanoparticles in the lines patterned on silicon substrate by two orders of magnitude with respect to that on photoresist. The width of the silicon line and the width ratio between photoresist line and silicon line are the two most important parameters that will affect the self-focusing effect.
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  • On detection performance of MIMO radar for Rician target

    Jun Tang   Yong Wu   YingNing Peng   XiuTan Wang  

    By using spatial diversity, multiple-input-multiple-output (MIMO) radar can improve detection performance for fluctuating targets. In this paper, we propose a spatial fluctuation target model for MIMO radar, where targets are classified as non-fluctuating target, Rayleigh target and Rician target. Based on Stein's lemma, we use relative entropy to study detection performance of optimum detector for Rician target. It is found that in low signal noise ratio (SNR) region, the performance improvement of MIMO radar for detecting Rician target depends on array gain, which is related to the number of receivers. In high SNR region, the improvement of performance depends on diversity gain, which is related to the product of the number of receivers and the number of transmitters. The conclusions of this paper are important for designing MIMO radar system.
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  • On detection performance and system configuration of MIMO radar

    Jun Tang   Yong Wu   YingNing Peng   XiuTan Wang  

    Multiple-input multiple-output (MIMO) radar is a new concept with some new characteristics, such as multiple orthogonal waveforms and omnidirectional coverage. Based on Stein's lemma, we use relative entropy as a precise and general measure of error exponent to study detection performance for both MIMO radar and phased array radar. And based on derived analytical results, we further study the system configuration problem of Bistatic MIMO radar systems, where transmitters and receivers are located in different positions. Some interesting results are presented. For phased array radar, when the total numbers of transmitters and receivers are fixed, we should always make the number of transmitters equal to the number of receivers. For MIMO radar, we should use a small number of transmitters in low signal noise ratio (SNR) region, and make the number of transmitters equal to the number of receivers in high SNR region. These results are instructive for deployment of bistatic MIMO radar systems in the future.
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  • Oxygen separation through U-shaped hollow fiber membrane using pure CO2 as sweep gas

    Yanying Wei   Jun Tang   Lingyi Zhou   Jian Xue   Zhong Li and Haihui Wang  

    A number of U-shaped K2NiF4-type oxide hollow fiber membranes based on (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+δ (PLNCG) were successfully prepared by a phase inversion spinning process. The PLNCG hollow fiber membranes were then used to investigate the effect of CO2 concentration in both the sweep gas and the feed air on the oxygen permeation flux. With pure CO2 as the sweep gas and even 10% CO2 in the feed air, a steady oxygen permeation flux of 0.9 mL/min·cm2 (STP) is obtained at 975°C during 310 h, and no decline of the oxygen permeation flux is observed. XRD, SEM and EDS characterizations show the spent membrane still maintains the intact microstructure and perfect K2NiF4-type phase structure without carbonate, which indicates that the U-shaped PLNCG hollow fiber membrane is a very stable membrane under CO2 atmosphere and has great potential for the practical application in oxyfuel techniques for CO2 capture and storage.
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  • Electroluminescent Performances of Iridium Complexes with Dibenzo-18-crown-6

    Aihui Liang   Jun Tang   Xiulan Yang   Ping Cai…  

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  • Numerical Study of Pollutant Transport in Breaking Random Waves on Mild Slope Zone

    Jun Tang   Lei Cui  

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  • Minimum fluidisation velocities of burned oil sand particles

    Jun Tang   Xiaona Chen   Yongmin Zhang   Chunxi Lu and Zhiyuan Shen  

    The minimum fluidisation velocities of burned oil sand particles were investigated in a fluidised bed of I.D. 0.3 m and height 3 m based on de-fluidisation method. The solid particles were four types of burned oil sand particles from different regions and depths and in different physical properties. A modified Noda equation [Noda et al., 46, 149–154 (1986)] was built to predict the minimum fluidisation velocities of the burned oil sand particles. The results showed that the burned oil sand particles had very wide size distribution and their fluidisation processes could be divided into fixed, partial fluidisation and full fluidisation stages, similar with binary-particle fluidised beds. The calculated minimum fluidisation velocities were in good agreement with the experimental data.
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  • 5p Electronic properties of Gd in Gd@C82(OH)xstudied by synchrotron radiation XPS

    Jun Tang   Gengmei Xing   Hui Yuan   Xingfa Gao   Long Jing   Shukuan Wang   Yue Cheng   Yuliang Zhao  

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  • Numerical study on water waves and wave-induced longshore currents in Obak?y coastal water

    Jun Tang   Yigang Lyu   Yongming Shen  

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  • Isolation and Characterization of Bioactive Cyclotides from Viola labridorica

    Jun Tang   Conan K. Wang   Xulin Pan   He Yan   Guangzhi Zeng   Wenyan Xu   Wenjun He   Norelle L. Daly   David J. Craik   Ninghua Tan  

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  • Multi-chip antenna diversity picture-in-picture architecture

    A multi-chip antenna diversity architecture and method includes a first receiver chip that receives a first input signal from a first antenna. The first receiver chip includes a first tuner that amplifies the first input signal, a crystal operatively connected to a first crystal oscillator circuit, and a first crystal oscillator clock buffer that receives a clock signal from the first crystal oscillator circuit. A first demodulator demodulates the input signal received from the first tuner. A second receiver chip receives a second input signal from a second antenna. The second receiver chip includes a second crystal oscillator circuit, a second crystal oscillator clock buffer, a second tuner, and a second demodulator that receives diversity data from the first demodulator. The first crystal oscillator clock buffer drives the clock signal to the second crystal oscillator clock buffer, the second tuner, and the second demodulator of the second receiver chip.
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  • Fast super-resolution estimation of DOA and DOD in bistatic MIMO Radar with off-grid targets

    Dong Zhang   Yongshun Zhang   Guimei Zheng   Cunqian Feng   Jun Tang  

    In this paper, we focus on the problem of joint DOA and DOD estimation in Bistatic MIMO Radar using sparse reconstruction method. In traditional ways, we usually convert the 2D parameter estimation problem into 1D parameter estimation problem by Kronecker product which will enlarge the scale of the parameter estimation problem and bring more computational burden. Furthermore, it requires that the targets must fall on the predefined grids. In this paper, a 2D-off-grid model is built which can solve the grid mismatch problem of 2D parameters estimation. Then in order to solve the joint 2D sparse reconstruction problem directly and efficiently, three kinds of fast joint sparse matrix reconstruction methods are proposed which are Joint-2D-OMP algorithm, Joint-2D-SL0 algorithm and Joint-2D-SOONE algorithm. Simulation results demonstrate that our methods not only can improve the 2D parameter estimation accuracy but also reduce the computational complexity compared with the traditional Kronecker Compressed Sensing method.
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