Creat membership Creat membership
Sign in

Forgot password?

Confirm
  • Forgot password?
    Sign Up
  • Confirm
    Sign In
home > search

Now showing items 145 - 160 of 487

  • Enterochromaffin cell hyperplasia in the gut: Factors, mechanism and therapeutic clues

    Qin, Hong-yan   Xavier Wong, Hoi Leong   Zang, Kai-hong   Li, Xun   Bian, Zhao-xiang  

    Download Collect
  • The inverted U-shaped effect of urban hotspots spatial compactness on urban economic growth

    Xu, Weipan   Chen, Haohui   Frias-Martinez, Enrique   Cebrian, Manuel   Li, Xun  

    Download Collect
  • Glutathione Might Attenuate Cadmium-Induced Liver Oxidative Stress and Hepatic Stellate Cell Activation

    Ren, Longfei   Qi, Kuo   Zhang, Lei   Bai, Zhongtian   Ren, Chenghui   Xu, Xianyun   Zhang, Zeliang   Li, Xun  

    Download Collect
  • An efficient process for the synthesis of trans-2,3-disubstituted-2,3-dihydro-4H- 1-benzopyran-4-ones (Chroman-4-ones)

    Draper, Richard W.   Hu, Bin   Iyer, Radha V.   Li, Xun   Lu, Yuelie   Rahman, Mohammad   Vater, Eugene J.  

    The piperidine catalyzed Knoevenagel condensation of 2'-aryl/alkyl-2-hydroxyacetophenones 7 and aryl/alkylaldehydes 8 in refluxing isopropyl alcohol with azeotropic removal of water affords, in high yield, equilibrium mixtures of E- and Z-chalcones 9 and cis- and trans-chroman-4-ones 10 which are effectively isomerized in situ to the trans-2,3-diaryl/alkylchroman-4-ones, following the addition of 1,8-diazabicyclo(5,4,0)undec-7-ene (DBU) to the cooled reaction mixture and may be isolated in high purities (91-99%) by simple filtration, with good to excellent yields (70-95%).
    Download Collect
  • Design Optimization of Compact Wideband Optical Switch Exploiting Staircase Index MMI

    Swillam, Mohamed A.   Bakr, Mohamed H.   Li, Xun  

    We propose a new compact optical switch that works over a wide wavelength band. This switch has low cross talk and can be easily integrated with other components of the communication system. The device utilizes the self imaging theory of the parabolic index profile. A new methodology to formulate the design problem as an optimization problem is proposed. Both the response and the gradient of the response are utilized within a gradient-based optimization approach. The adjoint variable method is utilized to extract the gradient of the response using the wide angle BPM method.
    Download Collect
  • Effects of maize straw-derived biochar application on soil temperature,water conditions and growth of winter wheat

    Yan, Qiuyan   Dong, Fei   Li, Junhui   Duan, Zengqiang   Yang, Feng   Li, Xun   Lu, Jinxiu   Li, Feng  

    Biochar application to soil has been widely accepted as an approach to enhance soil carbon sequestration, promote nutrient use efficiency and improve crop yields. Maize straw-derived biochar application is also a novel practice for the sustainable use of straw waste. However, it remains unclear whether biochar modifies soil temperature, thereby influencing winter wheat growth. Field experiments were conducted for 2 years to answer this question. Maize straw-derived biochar was applied at rates of 0 (B0), 20 (B20), 40 (B40) and 60 (B60) t ha(-1) in the field plots. Biochar application increased the soil temperature compared to the unamended control plot for all growth stages. The highest soil temperatures occurred at 40-cm depth in the B40 treatment and 20-cm depth in the B60 treatment. Biochar application also enhanced the soil water content of the winter wheat fields during the growing seasons, with a maximum effect achieved at a rate of biochar application of 40 t ha(-1). However, water content did not increase with increasing rate of application. Biochar application decreased the soil bulk density, and this effect was enhanced with increasing rates of biochar application. The largest grain yield was obtained in the B40 treatment, resulting from an increase in aboveground biomass and effective spike number. Our study suggests that biochar application potentially improves the grain yield of winter wheat from the increased soil temperature. This conclusion needs to be confirmed by a long-term study on biochar application. Highlights The effects of rates of biochar application on wheat growth and yield were evaluated. Response of soil temperatures to biochar application improves understanding of underlying mechanisms involved. Warmer soil temperature and lower soil bulk density with large rates of biochar were unfavourable for water storage and wheat growth. Biochar application at a rate of 40 t ha(-1) was optimal to enhance wheat growth and grain yield.
    Download Collect
  • Sema6A-plexin-A2 axis stimulates RANKL-induced osteoclastogenesis through PLCγ-mediated NFATc1 activation

    Zhuang, Jinliang   Li, Xun   Zhang, Yi   Shi, Ruixin   Shi, Ce   Yu, Dongsheng   Bao, Xingfu   Hu, Min  

    Download Collect
  • Synthesis, photophysical and cellular characterisation of folate and methotrexate labelled luminescent lanthanide complexes.

    Du, Zhangli   Sun, Jing   Bader, Christie A   Brooks, Doug A   Li, Minqi   Li, Xun   Plush, Sally E  

    In this work we have developed a series of highly emissive europium(III) and terbium(III) complexes tethered to either folic acid (FA) or methotrexate (MTX), with the aim of developing visual probes that enable the imaging of folate receptors in cancer cells. The synthesis, photophysical properties and cellular behaviour are reported for four new lanthanide Ln(III) complexes, where either FA or MTX are tethered to 1,4,7-tris(carbonylmethyl)-10-(4'-quinolineacetic acid, (7'-acetamido)-1',2'-dihydro-2'-oxo)-1,4,7,10-tetraazacyclododecane Ln(III) complex, and Ln(III)=3DEu(III) or Tb(III); herein referred to as Eu-FA, Eu-MTX, Tb-FA or Tb-MTX. All four complexes were found to be sensitive to the presence of the folate receptor in a range of cell lines. The MTX conjugates showed different cellular specificity in an oral adenosquamous carcinoma cell line (CAL-27) compared with the analogous FA conjugates. This suggests that it is viable to explore differences in folate receptors using folate vs. anti-folate probes, with labels that have different emissive properties (e.g. Eu-FA vs. Tb-MTX). The MTX complexes were found to be the most cytotoxic, with Eu-MTX showing greater cytotoxicity than free MTX or the isostructural Tb-MTX. This suggested that there could be a synergistic effect on toxicity for the Eu(III) chelate and the MTX components of the complex. Crown Copyright =C2=A9 2017. Published by Elsevier Inc. All rights reserved.
    Download Collect
  • Optimization of Iterative Algorithms for Focusing Light Through Scattering Media

    Zhou, Yulan   Li, Xun  

    A light beam transmitted through scattering media usually turns into disordered speckles. Fortunately, there are iterative algorithms to focus light transmitted through scattering media using a spatial phase modulator (SPM). In this work, we optimized the conventional iterative algorithms to achieve greater efficiency via theory and simulations. Two independent processes, characterizing the transmission matrix (TM) of the scattering media and calculating the phase compensation of the SPM, are included in our optimized algorithm. While the TM of the scattering media is determined through the interference effect and the light reciprocity principle, the phase compensation of the SPM is calculated using the Rayleigh-Sommerfeld diffraction theory. By addressing these two processes separately, accelerating the process of characterizing the TM of the scattering media, and theoretically calculating the phase compensation of the SPM, our optimized algorithm is helpful for fast imaging through scattering media.
    Download Collect
  • A Memory-Efficient Implementation of TLM-Based Adjoint Sensitivity Analysis

    Ahmed, Osman S.   Bakr, Mohamed H.   Li, Xun  

    We present a memory efficient algorithm for the estimation of adjoint sensitivities with the 2D transmission line modeling (TLM) method. The algorithm is based on manipulating the local scattering matrices to reduce the required storage for the original structure simulation associated with lossy dielectric discontinuities. Only one value per cell is stored for two dimensional simulations. Moreover, the connection step for the scattered sensitivity storage is embedded during the adjoint simulation and the sensitivity estimates are calculated on the fly. The required memory storage for our implementation is only 10% of the original implementation of AVM sensitivity with TLM.
    Download Collect
  • Hydrogen-Bonding Interactions in Hard Segments of Shape Memory Polyurethane: Toluene Diisocyanates and 1,6-Hexamethylene Diisocyanate. A Theoretical and Comparative Study

    Zhang, Cuili   Hu, Jinlian   Li, Xun   Wu, You   Han, Jianping  

    In this study, the hydrogen-bonding interactions of three widely used diisocyanate-based hard-segment (HS) models in polyurethane, 2,4-toluenediisocyanate-methanol (2,4-TDI-MeOH), 2,6-toluenediisocyanate-methanol (2,6-TDI-MeOH), and 1,6-hexamethylenediisocyanate-methanol (HDI-MeOH), were investigated theoretically by density functional theory (DFT). The B3LYP/6-31G* method was used to calculate the equilibrium structures, Mulliken charges, hydrogen-bonding energies, and infrared (IR) spectra, in good agreement with previous experimental data. The HS models with benzene ring have much longer hydrogen bonds (HB), due to steric hindrance of benzene ring, whereas the aliphatic model forms much shorter hydrogen bonds. Different positions of the methyl group on the benzene ring for 2,4-TDI-MeOH and 2,6-TDI-MeOH result in different types of hydrogen bonds with various strengths. The style of hydrogen bonding for HDI-MeOH is more flexible due to simple aliphatic chemical structure without the benzene ring. The charge transfer on atoms N, H, and O involved in hydrogen bonding occurs with the forming of a hydrogen bond. The hydrogen bonding of 2,4-TDI-MeOH is much stronger than the others, and 2,6-TDI-MeOH froms the weakest hydrogen bonds. This study can supply guidance for the selection of a hard segment in the design of polyurethane and in-depth understanding of the hydrogen-bonding mechanism in the hard segments of polyurethane.
    Download Collect
  • Vaccine potential of hemocyanin from Oncomelania hupensis against Schistosoma Japonicum

    Guo, Daoyi   Wang, Hua   Zeng, Dan   Li, Xun   Fan, Xiaolin   Li, Yongdong  

    Hemocyanin, a giant oxygen transport protein which is usually found in many arthropods and mollusks was isolated and purified from Oncomelania hupensis. In this study, we showed that Oncomelania hupensis hemocyanin (OhH) shared carbohydrate epitopes with different developmental stages of Schistosoma japonicum (Cercaria, Schistosomulum, Adult worm and Egg) and exhibited serological cross-reaction with these stages of S. japonicum immune sera, which had a potential for use in diagnostic and therapeutic studies of schistosomasis. OhH was used as a vaccine in combination with Freund's adjuvant to evaluate the induction of immune responses and protection against S. japonicum infection in mice. Mice immunized with OhH induced a Th1 type of immune responses. Strong protection against S.japonicum were observed in adult worm and egg burdens after 42 days post-challenge, which showed a significant worm reduction of 52.5% and egg reduction of 69.2% compared to the control groups, respectively. These results indicated that OhH was a potential candidate to compose an anti-schistosome vaccine. (C) 2011 Elsevier Ireland Ltd. All rights reserved.
    Download Collect
  • Adjoint variable method for general material models towards efficient sensitivity analysis of subwavelength structures

    Ahmed, Osman S.   Bakr, Mohamed H.   Li, Xun   Nomura, Tsuyoshi  

    In this paper, we propose to extend the adjoint variable method (AVM) to the sensitivity analysis of dispersive materials. In the optical range, most common materials are frequency dependent. The complexity of the modeling approaches of these materials delayed the development of simulation-based AVM techniques. We circumvent the mathematical difficulties through utilizing the Z-domain representation of the dispersive models. We exploit the time domain modeling technique (transmission line modeling) for efficient calculation of the structure sensitivities. The theory is developed for general dispersive materials modeled by Drude or Lorentz models. Adjoint variable method is known to be the ultimate efficient sensitivity calculation modality. The sensitivity is calculated with respect to all the designable parameters utilizing at most one extra simulation. This is far more efficient than the regular finite difference approaches with a computational overhead that scales linearly with the number of design parameters. The theory has been successfully applied to a subwavelength structure of 180 bend utilizing metamaterial slab where the design variables are the shape parameters and material parameters of the metamaterial slab. The results are compared to the accurate yet expensive finite difference approach and good agreement is achieved.
    Download Collect
  • Insulin regulation of glutathione and contractile phenotype in diabetic rat ventricular myocytes

    Li, Shumin   Li, Xun   Li, Yu-Long   Shao, Chun-Hong   Bidasee, Keshore R.   Rozanski, George J.  

    Cardiovascular complications of diabetes mellitus involve oxidative stress and profound changes in reduced glutathione ( GSH), an essential tripeptide that controls many redox- sensitive cell functions. This study examined regulation of GSH by insulin to identify mechanisms controlling cardiac redox state and to define the functional impact of GSH depletion. GSH was measured by fluorescence microscopy in ventricular myocytes isolated from Sprague- Dawley rats made diabetic by streptozotocin, and video and confocal microscopy were used to measure mechanical properties and Ca2+ transients, respectively. Spectrophotometric assays of tissue extracts were also done to measure the activities of enzymes that control GSH levels. Four weeks after injection of streptozotocin, mean GSH concentration ([ GSH]) in isolated diabetic rat myocytes was similar to 36% less than in control, correlating with decreased activities of two major enzymes regulating GSH levels: glutathione reductase and gamma- glutamylcysteine synthetase. Treatment of diabetic rat myocytes with insulin normalized [ GSH] after a delay of 3 - 4 h. A more rapid but transient upregulation of [ GSH] occurred in myocytes treated with dichloroacetate, an activator of pyruvate dehydrogenase. Inhibitor experiments indicated that insulin normalized [ GSH] via the pentose pathway and gamma- glutamylcysteine synthetase, although the basal activity of glucose-6- phosphate dehydrogenase was not different between diabetic and control hearts. Diabetic rat myocytes were characterized by significant mechanical dysfunction that correlated with diminished and prolonged Ca2+ transients. This phenotype was reversed by in vitro treatment with insulin and also by exogenous GSH or N- acetylcysteine, a precursor of GSH. Our data suggest that insulin regulates GSH through pathways involving de novo GSH synthesis and reduction of its oxidized form. It is proposed that a key function of glucose metabolism in heart is to supply reducing equivalents required to maintain adequate GSH levels for the redox control of Ca2+ handling proteins and contraction.
    Download Collect
  • A radius compensation method of barrel tool based on macro variables in five-axis flank machining of sculptured surfaces

    Xu, Rufeng   Li, Xun   Zheng, Guangming   Cheng, Xiang   Tian, Yebing  

    Download Collect
  • RFRP-3, the Mammalian Ortholog of GnIH, Is a Novel Modulator Involved in Food Intake and Glucose Homeostasis

    Huo, Konglin   Li, Xun   Hu, Wen   Song, Xingxing   Zhang, Duoni   Zhang, Xin   Chen, Xinyi   Yuan, Jingzhi   Zuo, Jianyu   Wang, Xiaoye  

    Download Collect
5 6 7 8 9 10 11 12 13 14

Contact

If you have any feedback, Please follow the official account to submit feedback.

Turn on your phone and scan

Submit Feedback