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Articles by Jian Zhang
Total Records ( 16 ) for Jian Zhang
  LiJuan Wan , WenLi Gong , KeWei Jiang , HuiLin Li , BaiRui Tao and Jian Zhang
  In this paper, the selective growth of silicon nanowires (SiNWs) was studied. With the aid of photolithography, the vertically aligned silicon nanowires were selectively formed on the patterned substrates via an electroless metal deposition (EMD) method under normal conditions (room temperature, 1atm). Low-pressure chemical vapor deposition (LPCVD) silicon nitride was used as the masking layer for SiNWs preparation. The scanning electron microscope was used to examine the etching results. Both the patterned and the unpatterned silicon substrates were used for study. The results indicated that the growth rates of the SiNWs upon the patterned and the unpatterned substrates are different. For the patterned substrates, the growth rate of SiNWs is dependent upon the pattern shape. The influence of length-to-width ratio for the rectangular-shaped patterns was studied. It is concluded that by designing the proper length-to-width ratio, the nanowires with different lengths can be fabricated simultaneously on the same substrate.
  Xingli Li , Jian Zhang , Zhipeng Li and Xianglin Han
  Two traffic cellular automata models corresponding to two different traffic management measures around the merging point of lane reduction bottleneck are proposed. One is the control scheme of first-arrive and first-in, the other is the periodic control scheme. The numerical simulations show that the consideration of different traffic measures could lead to the variation of the bottleneck capacity against the length of section B. And increasing signal period is helpful for improving the bottleneck capacity under Scheme 2. Moreover, the phenomenon of density inversion caused by the bottleneck may disappear under some traffic control regulations.
  Jian Zhang , Huaqiang Yuan and Xiaoheng Pan
  A novel non-generative probabilistic framework is proposed for extractive lecture speech summarization. Rhetorical structure hidden in lecture speech is one of the most underutilized characteristics. Rhetorical State Support Vector Machine (RSSVM) is proposed for automatically decoding rhetorical structure in speech and summarizing the speech data. RSSVM gives a 57.2% ROUGE-L F-measure, a 5.6% absolute increase in lecture speech summarization performance compared with the baseline system without using rhetorical information. It also outperforms the extractive summarization directly using the rhetorical structure produced by Rhetorical-State Hidden Markov Models.
  Xiaoyang Yu , Xue Yang , Jiaying Jia , Yuan Gao and Jian Zhang
  In this study an auto-block coding method was proposed. This method regulates the number of quantization levels in each block automatically according to its characteristics. The method uses the mean quantified level quantification, two-level quantification and four-level quantification integrated multi-level approach to quantify the image coding image. It can recover the detail information of the image accurately and improve the quality of decoding image. This study introduces the principle of the auto-block coding method in detail and compare with two-level block coding method. Experimental results with MATLAB® are provided to demonstrate the effectiveness of the proposed method.
  Xin Fu , Weihua Li , Jian Zhang and YingHui Xu
  To study the role of P21/53 in directly regulating and controlling TIMP-2 and the important mechanism for promoting invasion of GSCs by P21/53. Transwell in vitro invasion experiment was used to test invasion ability of GSCs and GCs as well as effect of P21/53 on GSCs invasion. Techniques of qRT-PCR and Western blot were used to test and transfect expression variation of TIMP-2, MMP2 and MMP9 in GSCs of P21/53 inhibitor. The luciferase reporter gene experiment was used to test the role of P21/53 in directly regulating and controlling TIMP-2. The number of invasive GSCs significantly decreased following transfection of P21/53 inhibitor (p<0.05). The expression levels of TIMP-2 mRNA in the U87 cell line and GSCs from the two primary glioma specimens rose compared with the control group, respectively while the expression levels of MMP2 mRNA and MMP9 mRNA fell compared with the control group (p<0.05) following transfection of P21 inhibitor. Expression of protein level of TIMP-2, MMP2 and MMP9 were consistent with mRNA level and had significant difference compared with those of the control group following transfection of P21 inhibitor and P53 inhibitor. The luciferase activity of the reporter vector containing wiled-type TIMP-2-3'UTR increased significantly following transfection of P21/53 while the luciferase activity of the reporter decreased significantly following transfection of P21/53 simulator (p<0.05). High expression of P21/53 promotes invasiveness of GSCs and its mechanism is achieved by down-regulating expressions of TIMP-2 and up-regulating expressions of MMP2 and MMP9 as a minimum.
  Yun Fang , Xi Li , Jian Zhang and Liying Wu
  In order to reduce the computational cost of the finite-difference time-domain method, the pseudospectral time-domain method is applied to the glass substrate direction with a large surface and smooth internal media, while the finite-difference time-domain method is applied to the thickness direction of a cell with a small thickness and fine structures. A fast Fourier transform algorithm, instead of the central-difference in the finite-difference time-domain method, is used to represent the spatial derivatives in the pseudospectral time-domain method, which greatly reduces the spatial sampling rate in the glass substrate direction. Both the hybrid method and the finite-difference time-domain method are used to simulate the propagation of light through the same twisted nematic pixel in the on state for 100 fs. The maximum deviation of the transmittance obtained using both methods is less than 5.1%; the memory capacity and computational time required for the hybrid method are about 8.5% and 21% respectively compared with those required for the finite-difference time-domain method. The use of the hybrid method reduces the memory capacity and computational time required for the finite-difference time-domain method while its accuracy is preserved.
  Weiguo Feng , Jian Huang , Jian Zhang and Trevor Williams
  Tcfap2a, the gene encoding the mouse AP-2α transcription factor, is required for normal development of multiple structures during embryogenesis, including the face and limbs. Using comparative sequence analysis and transgenic-mouse experiments we have identified an intronic enhancer within this gene that directs expression to the face and limb mesenchyme. There are two conserved sequence blocks within this intron, and the larger of these directs tissue-specific activity and is found in all vertebrate Tcfap2a genes analyzed. To assess the role of the enhancer in regulating endogenous mouse Tcfap2a expression, we have deleted this cis-regulatory sequence from the genome. Loss of this element severely impairs Tcfap2a expression in the limb bud mesenchyme but generates only a modest reduction in the facial mesenchyme. The reduction in Tcfap2a transcription is accompanied by altered patterning of the forelimb, resulting in postaxial polydactyly. These results indicate that the major role for this enhancer resides within the limb bud, and it serves to maintain a level of Tcfap2a expression that limits the size of the hand plate and the associated number of digit primordia. The potential role of this cis-acting sequence in modeling the size and shape of the face and limbs during evolution is discussed.
  Guilin Qiao , Zhenping Li , Luciana Molinero , Maria-Luisa Alegre , Haiyan Ying , Zuoming Sun , Josef M. Penninger and Jian Zhang
  It has previously been shown that E3 ubiquitin ligase Casitas B-lineage lymphoma-b (Cbl-b) negatively regulates T-cell activation, but the molecular mechanism(s) underlying this inhibition is not completely defined. In this study, we report that the loss of Cbl-b selectively results in aberrant activation of NF-κB upon T-cell antigen receptor (TCR) ligation, which is mediated by phosphatidylinositol 3-kinase (PI3-K)/Akt and protein kinase C-θ (PKC-θ). TCR-induced hyperactivation of Akt in the absence of Cbl-b may potentiate the formation of caspase recruitment domain-containing membrane-associated guanylate kinase protein 1 (CARMA1)-B-cell lymphoma/leukemia 10 (Bcl10)-mucosa-associated lymphatic tissue 1(MALT1) (CBM) complex, which appears to be independent of PKC-θ. Cbl-b associates with PKC-θ upon TCR stimulation and regulates TCR-induced PKC-θ activation via Vav-1, which couples PKC-θ to PI3-K and allows it to be phosphorylated. PKC-θ then couples IκB kinases (IKKs) to the CBM complex, resulting in the activation of the IKK complex. Therefore, our data provide the first evidence to demonstrate that the down-regulation of TCR-induced NF-κB activation by Cbl-b is mediated coordinately by both Akt-dependent and PKC-θ-dependent signaling pathways in primary T cells.
  Juan Yu , Ming-chuan Zhang and Jian Zhang
  The model that takes chemical reactions, heat and mass transfers in the boundary layer of the particle into account simultaneously, is developed for simulating the combustion of a pulverized coal particle. The FTIR in situ temperature-measurements and the comparison between numerical simulations for the pulverized coal and the devolatilized char show that the volatile flame induces the combustion of the primary product of surface oxidation CO. Due to the influence of volatile flame, the char particle can be ignited at temperature lower than its heterogeneous ignition temperature, which elucidates the physical essence of joint hetero-homogeneous ignition mode discovered by Juntgen.
  Bairui Tao , Jian Zhang , Fengjuan Miao , Huilin Li , Lijuan Wan and Yiting Wang
  In this paper, Ni/SiNWs nanocomposites, constructed by wet chemical etching silicon nanowires (SiNWs) coated with electroless plating nickel, were prepared and studied for the detection of humidity. The Ni/SiNWs nanocomposites were annealed at different temperatures under argon atmosphere to optimize the sensitive properties and characterized by Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) to obtain the information on the structural and morphological properties. The capacitive humidity sensing characteristics have been investigated with the Ni/SiNWs nanocomposites as the sensitive material. It is concluded that the humidity sensor based on as-synthesized nanocomposites exhibited high sensitivity and fast response time due to its unique large surface-to-volume ratio and electrical properties. The results demonstrated that the Ni/SiNWs nanocomposites are the potential sensing material for high performance humidity sensors.
  Shuai Chen , Tiancen Hu , Jian Zhang , Jing Chen , Kaixian Chen , Jianping Ding , Hualiang Jiang and Xu Shen
  SARS-CoV 3C-like protease (3CLpro) is an attractive target foranti-severe acute respiratory syndrome (SARS) drug discovery,and its dimerization has been extensively proved to be indispensablefor enzymatic activity. However, the reason why the dissociatedmonomer is inactive still remains unclear due to the absenceof the monomer structure. In this study, we showed that mutationof the dimer-interface residue Gly-11 to alanine entirely abolishedthe activity of SARS-CoV 3CLpro. Subsequently, we determinedthe crystal structure of this mutant and discovered a completecrystallographic dimer dissociation of SARS-CoV 3CLpro. Themutation might shorten the α-helix A` of domain I and cause amis-oriented N-terminal finger that could not correctly squeezeinto the pocket of another monomer during dimerization, thusdestabilizing the dimer structure. Several structural featuresessential for catalysis and substrate recognition are severelyimpaired in the G11A monomer. Moreover, domain III rotates dramaticallyagainst the chymotrypsin fold compared with the dimer, fromwhich we proposed a putative dimerization model for SARS-CoV3CLpro. As the first reported monomer structure for SARS-CoV3CLpro, the crystal structure of G11A mutant might provide insightinto the dimerization mechanism of the protease and supply directstructural evidence for the incompetence of the dissociatedmonomer.
  Shibing Yu , Yu Jiang , Deborah L. Galson , Min Luo , Yumei Lai , Yi Lu , Hong-Jiao Ouyang , Jian Zhang and Guozhi Xiao
  ATF4 (activating transcription factor 4) is an osteoblast-enrichedtranscription factor that regulates terminal osteoblast differentiationand bone formation. ATF4 knock-out mice have reduced bone mass(severe osteoporosis) throughout life. Runx2 (runt-related transcriptionfactor 2) is a runt domain-containing transcription factor thatis essential for bone formation during embryogenesis and postnatallife. In this study, we identified general transcription factorIIAγ (TFIIAγ) as a Runx2-interacting factor in a yeast two-hybridscreen. Immunoprecipitation assays confirmed that TFIIAγ interactswith Runx2 in osteoblasts and when coexpressed in COS-7 cellsor using purified glutathione S-transferase fusion proteins.Chromatin immunoprecipitation assay of MC3T3-E1 (clone MC-4)preosteoblast cells showed that in intact cells TFIIAγ is recruitedto the region of the osteocalcin promoter previously shown tobind Runx2 and ATF4. A small region of Runx2 (amino acids 258–286)was found to be required for TFIIAγ binding. Although TFIIAγ interactswith Runx2, it does not activate Runx2. Instead, TFIIAγ bindsto and activates ATF4. Furthermore, TFIIAγ together with ATF4and Runx2 stimulates osteocalcin promoter activity and endogenousmRNA expression. Small interfering RNA silencing of TFIIAγ markedlyreduces levels of endogenous ATF4 protein and Ocn mRNA in osteoblasticcells. Overexpression of TFIIAγ increases levels of ATF4 protein.Finally, TFIIAγ significantly prevents ATF4 degradation. Thisstudy shows that a general transcription factor, TFIIAγ, facilitatesosteoblast-specific gene expression through interactions withtwo important bone transcription factors ATF4 and Runx2.
  Yinggang Luo , Shuangjun Lin , Jian Zhang , Heather A. Cooke , Steven D. Bruner and Ben Shen
  Neocarzinostatin, a clinical anticancer drug, is the archetypal member of the chromoprotein family of enediyne antitumor antibiotics that are composed of a nonprotein chromophore and an apoprotein. The neocarzinostatin chromophore consists of a nine-membered enediyne core, a deoxyaminosugar, and a naphthoic acid moiety. We have previously cloned and sequenced the neocarzinostatin biosynthetic gene cluster and proposed that the biosynthesis of the naphthoic acid moiety and its incorporation into the neocarzinostatin chromophore are catalyzed by five enzymes NcsB, NcsB1, NcsB2, NcsB3, and NcsB4. Here we report the biochemical characterization of NcsB1, unveiling that: (i) NcsB1 is an S-adenosyl-L-methionine-dependent O-methyltransferase; (ii) NcsB1 catalyzes regiospecific methylation at the 7-hydroxy group of its native substrate, 2,7-dihydroxy-5-methyl-1-naphthoic acid; (iii) NcsB1 also recognizes other dihydroxynaphthoic acids as substrates and catalyzes regiospecific O-methylation; and (iv) the carboxylate and its ortho-hydroxy groups of the substrate appear to be crucial for NcsB1 substrate recognition and binding, and O-methylation takes place only at the free hydroxy group of these dihydroxynaphthoic acids. These findings establish that NcsB1 catalyzes the third step in the biosynthesis of the naphthoic acid moiety of the neocarzinostatin chromophore and further support the early proposal for the biosynthesis of the naphthoic acid and its incorporation into the neocarzinostatin chromophore with free naphthoic acids serving as intermediates. NcsB1 represents another opportunity that can now be exploited to produce novel neocarzinostatin analogs by engineering neocarzinostatin biosynthesis or applying directed biosynthesis strategies.
  Kelly Orlando , Jian Zhang , Xiaoyu Zhang , Peng Yue , Teresa Chiang , Erfei Bi and Wei Guo
  Establishment of cell polarity is important for a wide range of biological processes, from asymmetric cell growth in budding yeast to neurite formation in neurons. In the yeast Saccharomyces cerevisiae, the small GTPase Cdc42 controls polarized actin organization and exocytosis toward the bud. Gic2, a Cdc42 effector, is targeted to the bud tip and plays an important role in early bud formation. The GTP-bound Cdc42 interacts with Gic2 through the Cdc42/Rac interactive binding domain located at the N terminus of Gic2 and activates Gic2 during bud emergence. Here we identify a polybasic region in Gic2 adjacent to the Cdc42/Rac interactive binding domain that directly interacts with phosphatidylinositol 4,5-bisphosphate in the plasma membrane. We demonstrate that this interaction is necessary for the polarized localization of Gic2 to the bud tip and is important for the function of Gic2 in cell polarization. We propose that phosphatidylinositol 4,5-bisphosphate and Cdc42 act in concert to regulate polarized localization and function of Gic2 during polarized cell growth in the budding yeast.
  Xiao-Ling Yu , Tiancen Hu , Jia-Mu Du , Jian-Ping Ding , Xiang-Min Yang , Jian Zhang , Bin Yang , Xu Shen , Zheng Zhang , Wei-De Zhong , Ning Wen , Hualiang Jiang , Ping Zhu and Zhi-Nan Chen
  CD147, a member of the immunoglobulin superfamily (IgSF), plays fundamental roles in intercellular interactions in numerous pathological and physiological processes. Importantly, our previous studies have demonstrated that HAb18G/CD147 is a novel hepatocellular carcinoma (HCC)-associated antigen, and HAb18G/CD147 stimulates adjacent fibroblasts and HCC cells to produce elevated levels of several matrix metalloproteinases, facilitating invasion and metastasis of HCC cells. In addition, HAb18G/CD147 has also been shown to be a novel universal cancer biomarker for diagnosis and prognostic assessment of a wide range of cancers. However, the structural basis underlying the multifunctional character of CD147 remains unresolved. We report here the crystal structure of the extracellular portion of HAb18G/CD147 at 2.8Å resolution. The structure comprises an N-terminal IgC2 domain and a C-terminal IgI domain, which are connected by a 5-residue flexible linker. This unique C2-I domain organization is distinct from those of other IgSF members. Four homophilic dimers exist in the crystal and adopt C2-C2 and C2-I dimerization rather than V-V dimerization commonly found in other IgSF members. This type of homophilic association thus presents a novel model for homophilic interaction between C2 domains of IgSF members. Moreover, the crystal structure of HAb18G/CD147 provides a good structural explanation for the established multifunction of CD147 mediated by homo/hetero-oligomerizations and should represent a general architecture of other CD147 family members.
  Jian Zhang and Chu Chen
  Endocannabinoids are involved in synaptic signaling and neuronal protection; however, our understanding of the mechanisms by which endocannabinoids protect neurons from harmful insults remains elusive. 2-Arachidonoylglycerol (2-AG), the most abundant endogenous cannabinoid and a full agonist for cannabinoid receptors (CB1 and CB2), is a substrate for cyclooxygenase-2 (COX-2) and can be metabolized by COX-2. Here we show, however, that 2-AG is also capable of suppressing elevation of hippocampal COX-2 expression in response to proinflammatory and excitotoxic stimuli. 2-AG prevents neurodegeneration from toxic assaults that elevate COX-2 expression and inhibits the COX-2 elevation-enhanced excitatory glutamatergic synaptic transmission. The action of 2-AG on suppression of COX-2 appeared to be mediated via the pertussis toxin-sensitive G protein-coupled CB1 receptor and MAPK/NF-ĸB signaling pathways. Our results reveal that 2-AG functions as an endogenous COX-2 inhibitor protecting neurons from harmful insults by preventing excessive expression of COX-2, which provides a mechanistic basis for opening up new therapeutic approaches for protecting neurons from inflammation- and excitotoxicity-induced neurodegeneration.
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