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Articles by Jun Zhang
Total Records ( 8 ) for Jun Zhang
  Jun Zhang , Alfred M. Blackmer , Jason W. Ellsworth and Kenneth J. Koehler
  Chlorophyll meters have been widely used to diagnose N deficiencies in research trials and to help refine N fertilizer recommendations in production agriculture. The diagnoses are based on the assumption that chlorophyll meters can detect a wide range of N deficiencies under field conditions according to relationships between chlorophyll meter readings (CMRs) and yield responses to N fertilization that are established from small-plot trials. We conducted a field-scale study to evaluate the sensitivity of chlorophyll meters when they are used to detect N deficiencies in corn (Zea mays L.) production. The multiple year–location data were gathered in three cornfields where N fertilizer was applied at different rates in strips that crossed several soil map units. Grain yields were related to CMRs taken on corn leaves in June, July, and August of 1998–1999. Results showed that the chlorophyll meters could detect severe N deficiencies early in the season, but small and moderate deficiencies of N could not be diagnosed with reasonable certainty until it was too late to make in-season fertilization. Two types of discontinuity are discussed in this paper as likely causes for the limited sensitivity of the chlorophyll meters. Our study suggests that problems associated with the use of chlorophyll meters to diagnose deficiencies of N in production agriculture are much greater than their use to help interpret results of well-controlled research trials where yields are also measured.
  Feng-Xian Jiang , Xiao-Hong Xu , Jun Zhang , Hai-Shun Wu and G.A. Gehring
  (In1−xFex)2O3 (x=0.02, 0.05, 0.2) powders were prepared by a solid state reaction method and a vacuum annealing process. A systematic study was done on the structural and magnetic properties of (In1−xFex)2O3 powders as a function of Fe concentration and annealing temperature. The X-ray diffraction and high-resolution transmission electron microscopy results confirmed that there were not any Fe or Fe oxide secondary phases in vacuum-annealed (In1−xFex)2O3 samples and the Fe element was incorporated into the indium oxide lattice by substituting the position of indium atoms. The X-ray photoelectron spectroscopy revealed that both Fe2+ and Fe3+ ions existed in the samples. Magnetic measurements indicated that all samples were ferromagnetic with the magnetic moment of 0.49–1.73μB/Fe and the Curie temperature around 783K. The appearance of ferromagnetism was attributed to the ferromagnetic coupling of Fe2+ and Fe3+ ions via an electron trapped in a bridging oxygen vacancy.
  ChunLei Song , XiuXing Wang , Xuguang Wang , Xueshan Ma , Jun Zhang , BeiBei Gao and Honglin Liu
  GGPPS is a member of prenyl transferase family catalyzing the synthesis of GGPP (Geranylgeranyl diphosphate) from Farnesyl diphosphate (FPP) and Isopentenyl diphosphate (IPP). Using cre/loxp system, researchers got oocyte specific knockout ggpps mice. Mutation of ggpps resulted in abnormality of follicular development, granulosa cell premature luteinization, theca cell hypertrophy and multi-oocyte follicles. Interaction of oocyte and granulosa cell was also changed. Oocyte-specific knockout of ggpps mice was acquired. Follicles grew abnormally in ggpps mutation mice. Interaction of oocyte and granulosa cell was also changed.
  Xiao-Li Yang , Shi-Bin Ren , Jun Zhang , Yi-Zhi Li , Hong-Bin Du and Xiao-Zeng You
  Using 4-methylbenzenethiolates of Zn or Cd as precursors and 4,4’-bipyridine (4,4’-bpy) as bridges, we have synthesized three new Zn(II)/Cd(II) coordination polymers, {[Cd(4,4’-bpy)2(NCS)2] · 2(SC6H4CH3-4)2}n (1), {[Zn(4,4’-bpy)(SC6H4CH3-4)2] · DMF}n (2) and {[Zn(4,4’-bpy)(SC6H4CH3-4)2] · H2O · 0.5CH3OH}n (3). Compound 1 is a 2-D sheet-like square polymer in which four 4,4’-bpy ligands and two isothiocyanate ligands complete the octahedral Cd(II) coordination sphere. Compounds 2 and 3 have similar coordination around Zn(II), but have different polymer structures. In 2, Zn(II) centers are linked via a bidentate 4,4’-bipyridine to form 1-D twisted arched chains, which is a new structural type for Zn(II). Compound 3 has 1-D zigzag chains. The 2-D sheets in 1 and 1-D chains in 2 and 3 are assembled via intermolecular C-H … π and C-H … S interactions into 3-D supramolecular networks. C-H …S interactions are a vital factor in constructing the sulfur-containing coordination polymers. Different coordination modes and packing schemes in 1-3 show that the guest molecule has a critical influence on formation of polymers.
  Jun Zhang , Shurong Wang , Yan Wang , Mijuan Xu , Huijuan Xia , Shoumin Zhang , Weiping Huang , Xianzhi Guo and Shihua Wu
  In this work, we report the large-scale synthesis of SnO2 nanoparticles with sizes in the range of 5–15 nm via a well-established metal alkoxide hydrolysis route. This solution method proves to be facile and environmentally benign without using any toxic organic solvent, surfactant and special laboratory apparatus. The morphology, size and phase of the SnO2 nanoparticles were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). A gas sensor was fabricated from the prepared SnO2 nanoparticles and applied to ethanol sensing test as well as some other gases. Obtained results show that the sensor exhibited high sensitivity, quick response and good selectivity to ethanol and n-butanol at an optimum operating temperature of 220 °C.
  Jun Zhang , Shurong Wang , Yan Wang , Mijuan Xu , Huijuan Xia , Shoumin Zhang , Weiping Huang , Xianzhi Guo and Shihua Wu
  ZnO hollow spheres were successfully prepared by using carbon microspheres as templates and characterized by X-ray diffraction (XRD) analysis, scanning electron microscope (SEM), transmission electron microscope (TEM) and selected area electron diffraction (SAED). A gas sensor was fabricated from the as-prepared ZnO hollow spheres and tested to different concentrations of NH3 and NO2 at different operating temperatures. The results showed that the ZnO hollow-sphere sensor exhibited extremely different sensing behaviors to NH3 and NO2. The optimum operating temperature of the sensor was 220 °C for NH3 and 240 °C for NO2, respectively. At 220 °C, the responses to 25, 50 and 75 ppm NH3 were 7.9, 11.1 and 20.4 and the response times were as long as several minutes. At 240 °C, the responses to 10, 50 and 100 ppm NO2 were 140.6, 172.8 and 286.8 and the corresponding response times were 31, 19 and 9 s. In addition, it is also shown that the gas sensor exhibited much higher response to NO2 than to other gases at 240 °C, implying the good selectivity and potential application of the sensor for detecting NO2.
  Jun Zhang and Lei Ye
 

In content-based image retrieval (CBIR), feature aggregation is an approach to obtain image similarity by combining multiple feature distances. Most existing feature aggregation methods focus on heuristic-based or linear combination functions, which cannot sufficiently explore the interdependencies between features. Instead, a single aggregation function is always applied to all query images without considering the special features of each query image. In this paper, aggregation is formulated as a classification problem in a feature similarity space and solved by support vector machines (SVMs). The new method can learn an aggregation function for each query image and extend the linear aggregation to a nonlinear one using the kernel trick. Experiments demonstrate that the image retrieval performance of the proposed method is superior.

  Guo-Dong Li , Xi Zhang , Rong Li , Yue-Dan Wang , Yan-Li Wang , Ke-Jun Han , Xiao-Ping Qian , Cheng-Gang Yang , Ping Liu , Qun Wei , Wei-Feng Chen , Jun Zhang and Yu Zhang
  CHP2 (calcineurin B homologous protein 2) was initially identified as a tumor-associated antigen highly expressed in hepatocellular carcinoma. Its biological function remains largely unknown except for a potential role in transmembrane Na+/H+ exchange. In the present study, we observed that ectopic expression of CHP2 promoted the proliferation of HEK293 cells, whereas knockdown of endogenous CHP2 expression in HepG2 inhibited cell proliferation. When inoculated into nude mice, CHP2 transfected HEK293 cells displayed markedly increased oncogenic potential. In analysis of the underlying molecular mechanisms, we found that like calcineurin B, CHP2 was able to bind to and stimulate the phosphatase activity of calcineurin A. In accord with this, CHP2-transfected cells showed increased nuclear presence of NFATc3 (nuclear factor of activated T cells) and enhanced NFAT activity. Finally, both accelerated cell proliferation and NFAT activation following CHP2 transfection could be suppressed by the calcineurin inhibitor cyclosporine A, suggesting an intrinsic connection between these events. Taken together, our results highlighted a potential role of CHP2 in tumorigenesis and revealed a novel function of CHP2 as an activator of the calcineurin/NFAT signaling pathway.
 
 
 
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