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Jingyuan Guan,Xiao Xiao,Shengjuan Xu,Fen Gao,Jianbo Wang,Tietao Wang,Yunhong Song,Junfeng Pan,Xihui Shen,Yao Wang 한국미생물학회 2015 The journal of microbiology Vol.53 No.9
RpoS (σS), the stationary phase/stress σ factor, controls the expression of a large number of genes involved in cellular responses to a variety of stresses. However, the role of RpoS appears to differ in different bacteria. While RpoS is an important regulator of flagellum biosynthesis, it is associated with biofilm development in Edwardsiella tarda. Biofilms are dense communities formed by bacteria and are important for microbe survival under unfavorable conditions. The type VI secretion system (T6SS) discovered recently is reportedly associated with several phenotypes, ranging from biofilm formation to stress sensing. For example, Vibrio anguillarum T6SS was proposed to serve as a sensor for extracytoplasmic signals and modulates RpoS expression and stress response. In this study, we investigated the physiological roles of RpoS in Yersinia pseudotuberculosis, including bacterial survival under stress conditions, flagella formation, biofilm development and T6SS expression. We found that RpoS is important in resistance to multiple stressors–including H2O2, acid, osmotic and heat shock–in Y. pseudotuberculosis. In addition, our study showed that RpoS not only modulates the expression of T6SS but also regulates flagellum formation by positively controlling the flagellar master regulatory gene flhDC, and affects the formation of biofilm on Caenorhabditis elegans by regulating the synthesis of exopolysaccharides. Taken together, these results show that RpoS plays a central role in cell fitness under several adverse conditions in Y. pseudotuberculosis.
Effects on Quality of Strawberry Fruits by Dipping of Calcium Solution and MA Packaging
박형우,Junfeng Guan,김윤호,김상희,박혜란 한국식품저장유통학회 2006 한국식품저장유통학회지 Vol.13 No.1
The strawberry was dipped into 1% CaCl2 solution at 20℃ and 45℃ for 15 min. respectively, and then packaged with or without PE film (thickness : 0.011 mm) before putting into the cold storage at 5℃. The results showed the lowest rate of rot incidence and the highest firmness with higher Vitamin C content and the best superficial appearance in the treatment of CaCl2 dipping at 45℃ with packaging. It also showed lower pH and higher titratable acidity in the treatment. However, no significant difference of SSC was found among various treatments. The results suggested that the combination of postharvest calcium dipping and packaging could result in more effective preservation for strawberry compared with the individual treatment.
A Unified Formula for Calculation of Crack Width and Spacing in Reinforced Concrete Beams
Xianhua Yao,Junfeng Guan,Lei Zhang,Junyi Xi,Lielie Li 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.6
Crack distribution and widths were experimentally examined in a series of reinforced concrete (RC) beams. Concretes of different strengths were used, and beams were reinforced with 600 MPa yield strength steel bars. The features of cracks, which need to be considered in the design, were determined by using statistical analysis of different crack patterns observed in RC beams. The methods for determining the depth of effective influence zone of 600 MPa steel bars in RC beams were experimentally obtained. Based on the experimental data obtained in this study and from the data on RC beams with 335-600 MPa yield strength steel bars from other studies, the applicability of different formulas for the determination of the maximum widths (provided in codes and by scholars) was analyzed. Methods for the calculation of average crack spacing and maximum crack widths in RC beams with steel bars of various yield strengths were proposed. A unified formula for the calculation of maximum crack width in such beams was also established. Highlights • Reinforced concrete beam cracking behavior was experimentally examined with a new type of seismic bar. • New methods for the calculation of average crack spacing and maximum crack width were presented. • A unified formula for the calculation of maximum crack width was proposed.
Nijiati Kudulaiti,Tianming Qiu,Junfeng Lu,Huiwei Zhang,Zhengwei Zhang,Yihui Guan,Dongxiao Zhuang,Jinsong Wu 대한영상의학회 2019 Korean Journal of Radiology Vol.20 No.6
Objective: To evaluate whether the combination of magnetic resonance spectroscopy (MRS) and 11C-methionine positron emission tomography (11C-MET PET) could increase accurate diagnostic sensitivity for non-enhancing supratentorial gliomas. Materials and Methods: Between February 2012 and December 2017, 109 patients with non-enhanced supratentorial lesions on contrast-enhanced MRI were enrolled. Each patient underwent MRS and 11C-MET PET before treatment. A lesion was considered to be a glioma when either the MRS or 11C-MET PET results reached the diagnostic threshold. The radiological diagnosis was compared with the pathological diagnosis or medical diagnostic criteria. Results: The sensitivity and specificity were 60.0% and 50.0% for MRS and 75.8% and 50.0% for 11C-MET PET, respectively. Upon combining the two modalities, the sensitivity and specificity of the imaging-based diagnosis prior to surgery reached 89.5% and 42.9%, respectively. Statistically significant differences in the sensitivities were observed between the combined and individual approaches (MRS alone, 89.5% vs. 60.0%, p < 0.001; 11C-MET PET alone, 89.5% vs. 75.8%, p = 0.001). However, no significant differences in specificity were observed between the combined and individual modalities. Conclusion: The combination of MRS and 11C-MET PET findings significantly increases accurate diagnostic sensitivity for nonenhancing supratentorial gliomas without significantly lowering the specificity. This finding suggests the potential of the combined MRS and 11C-MET PET approach in clinical applications.
Yu Dong,Liqin Liu,Yingying Zhang,Junfeng Guan 한국원예학회 2014 Horticulture, Environment, and Biotechnology Vol.55 No.5
‘Jingbaili’ pear (Pyrus ussuriensis Maxim.) fruit shows rapid softening, yellowing and short shelf-life atambient temperature storage. In this study, ‘Jingbaili’ pear fruits were treated with 1.0 μL·L-1 1-methylcyclopropene(1-MCP) for 24 hours at 25 ± 2°C and then stored at 0°C. After 60 and 120 days of cold storage at 0°C, pearfruits were removed and stored at 20 ± 2°C to assess their shelf-life. The results indicated that the 1-MCP treatmentdelayed the decrease in firmness and chlorophyll (a, b, and a+b) content of peel, reduced the rates of respiration andethylene production, and inhibited the accumulation of hydrogen peroxide (H2O2), which was observed in the untreatedfruits during and after cold storage. Less difference was found in soluble solids content (SSC) between the controland 1-MCP-treated fruits during storage. The correlation analysis showed that flesh H2O2 content was negativelyrelated to firmness and also peel H2O2 content to peel chlorophyll a+b content. These results suggested that the1-MCP treatment could delay the fruit softening and chlorophyll degradation by suppressing the accumulation ofH2O2 content during and after cold storage in ‘Jingbaili’ pear.
Design and Manufacture of High Accurate Aerostatic Guideway with Glass Material
Tao Lai,Xiaoqiang Peng,Meng Guo,Guipeng Tie,Chaoliang Guan,Junfeng Liu,Aihua Chen 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.6
Universal materials such as metal and marble are applied for aerostatic guideway. However, metal or marble guideway is usually manufactured by traditional turning and grinding. The corresponding geometric error, load and stiffness of the guideway are limited by the accuracy of traditional manufacture. Glass guideway can be measured by the optical method, thereby improving the performance. This paper presents a guideway designed and manufactured with the K9 glass. The guideway is manufactured by computer controlled optical surfacing and magnetorheological finishing. Moreover, the optical measurement is applied to measure the flatness and the geometric error of the guideway. Besides, the slider on the guideway is designed based on orifice compensated. The working surface error of the guideway is less than 0.1 μm, and the gas film is smaller than traditional aerostatic bearing. Therefore, the load and stiffness of the aerostatic sliders are higher than the traditional slider. Additionally, the effects of configuration and load onto the accuracy of guideway are introduced. The motional geometric error is measured after assembling, with the results that the pitch is better than 0.4 arcsecs and the yaw is better than 0.9 arcsecs. Furthermore, the straightness is compensated at 50 nm/200 mm. At last, the guideway is applied for an ultra-precision profilometer, and a flat is measured by the profilometer, giving 0.1 μm repeatable flatness.
Yu Dong,Liqin Liu,Zhe Zhao,Huanhuan Zhi,Junfeng Guan 한국원예학회 2015 Horticulture, Environment, and Biotechnology Vol.56 No.2
1-methylcyclopropene (1-MCP) has been shown to delay fruit ripening and senescence during storage. In this study, we investigated the effects of 1.0 μL·L-1 1-MCP on the biochemical changes and cellular ultra-structure of the core tissue in ‘Yali’ pear (Pyrus bretschneideri Rehd.) fruits stored at 25 ± 2°C. Our results showed that 1-MCP treatment significantly decreased the rates of respiration and ethylene production before their climacteric peaks, inhibited the development of core browning, lowered the chlorogenic acid content and polyphenol oxidase activity before the onset of core browning, and preserved high levels of superoxide dismutase activity, ascorbic acid, and glutathione contents. Furthermore, it suppressed the accumulation of hydrogen peroxide, superoxide anion, and malondialdehyde in the core tissue, maintained the integral structure of the cell membrane and organelle, and delayed the accumulation of electron-opaque matters in the vacuoles of core cells. These results suggested that 1-MCP treatment could reduce the injury caused by reactive oxygen, inhibit the oxidation of phenolics, and keep the cell membrane intact in core cells, thus, delaying the core browning in ‘Yali’ pear during storage.