Amperometric Determination of Nitrite at Poly(Methylene Blue)-Modified Glassy Carbon Electrode

Xu, Guang-Ri,Xu, Guifang,Xu, Ming-Lu,Zhang, Zhengqing,Tian, Yuan,Choi, Han-Nim,Lee, Won-Yong Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.2

Electrochemical characteristics of nitrite ion were investigated at a poly(methylene blue)-modified glassy carbon electrode by cyclic voltammetry and differential pulse voltammetry. The poly(methylene blue)-modified glassy carbon electrode exhibited enhanced anodic signals for nitrite. The effects of key parameters on the detection of nitrite were evaluated at the modified electrode, such as pH, accumulation time, and scan rate. Under optimum condition, the chemically modified electrode can detect nitrite in the concentration range $2.0{\times}10^{-6}$ to $5.0{\times}10^{-4}$ M with the detection limit of $2.0{\times}10^{-6}$ M and a correlation coefficient of 0.999. The detection of nitrite using the chemically modified electrode was not affected by common ions such as $Na^+$, $K^+$, $Ca^{2+}$, $Cl^-$, $HPO_4^{2-}$ and $H_2PO_4^- $. The modified electrode showed good stability and reproducibility. The practical application of the present method was successfully applied to the determination of nitrite ion in cabbage samples.

Amperometric Determination of Nitrite at Poly(Methylene Blue)-Modified Glassy Carbon Electrode

Guang-Ri Xu,Guifang Xu,Ming-Lu Xu,Zhengqing Zhang,Yuan Tian,최한님,이원용 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.2

Electrochemical characteristics of nitrite ion were investigated at a poly(methylene blue)-modified glassy carbon electrode by cyclic voltammetry and differential pulse voltammetry. The poly(methylene blue)-modified glassy carbon electrode exhibited enhanced anodic signals for nitrite. The effects of key parameters on the detection of nitrite were evaluated at the modified electrode, such as pH, accumulation time, and scan rate. Under optimum condition, the chemically modified electrode can detect nitrite in the concentration range 2.0 × 10−6 to 5.0 × 10−4 M with the detection limit of 2.0 × 10−6 M and a correlation coefficient of 0.999. The detection of nitrite using the chemically modified electrode was not affected by common ions such as Na+, K+,Ca2+, Cl−, HPO42− and H2PO4−. The modified electrode showed good stability and reproducibility. The practical application of the present method was successfully applied to the determination of nitrite ion in cabbage samples.

Photosensitive Al2O3 slurry with high solid content and low viscosity

Zhang Xu,Zhang Jingde,Tian Yuhang,Xiao Shikang,Li Jianzhang,Han Guifang 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.3

Slurries with high solid content and low viscosity are highly necessary to lower the sintering shrinkage and avoid possible defects for ceramic components fabricated by vat photopolymerization technique. However, the viscosity of slurry dramati- cally arises with the increase of solid content, which severely affects the printing process and the quality of preformance. To solve this issue, a novel combined strategy of powder surface modification and selection of dispersant was proposed to significantly increase the solid load without too much increase in viscosity. The surface of Al 2O3 particles was modified by Silane A174 to improve its wettability with resins, and then the use of KOS 110 formed steric hindrance between particles achieving good dispersion. The synergistic effect of the modifier and dispersant was realized. Al 2O3 slurry with a high solid loading up to 65 vol% and low viscosity of 20.0 Pa·s at 30  s −1 was prepared for stereolithography-based DLP 3D printing, which had among the highest performance in photosensitive Al 2O3 slurries.

Event-triggered H∞ Control for Switched Systems Under Multiple Attacks

Ying Xu,Xiaowu Mu,Guifang Cheng 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.4

This article investigates the event-triggered H∞ control for networked switched systems under multiple attacks and transmission delay. A novel model of multiple attacks is constructed by considering stochastic false data injection attack and periodic denial-of-service (DoS) attack. The event-triggered strategy is proposed by using the mode information of switched system and periodicity of DoS attack. Then, sufficient conditions are obtained to ensure mean-square exponential stability and H∞ performance of the closed-loop switched system. Furthermore, the controller gains and event-triggered parameters of subsystems are derived. Finally, a numerical example is given to verify the effectiveness and feasibility of the results.

Effect of La(NO3)3 and Ce(NO3)3 on shoot induction and seedling growth of in vitro cultured anoectochilus roxburghii

Yingya Xu,Guifang Zhang,Yan Wang,Ge Guo 한국식물학회 2016 Journal of Plant Biology Vol.59 No.2

Anoectochilus roxburghii, a highly valuable medicinal plant species, is threatened in its native habitat. To ensure the sustainability of this useful resource, we studied the effect of La(NO3)3 and Ce(NO3)3 on plant tissue culturepropagated A. roxburghii. Apical buds, mid-stem segments, and basal rhizome segments were taken from aseptic seedlings of A. roxburghii and cultured in vitro on half-strength Murashige-Skoog medium containing different concentrations (up to 5.0 mg/L) of La(NO3)3 or Ce(NO3)3. After 100 d of culturing, average heights of plantlets derived from apical buds were 6.0 cm with 5.0 mg/L La(NO3)3 and 6.2 cm with 2.0 mg/L Ce(NO3)3, which respectively increased by 28.0% and 32.0% as compared with that in the non-treated control group. The optimum concentration for shoot induction from mid-stem segments was 1.0 mg/L Ce(NO3)3 which had a better proliferation times of 1.5-fold and an average length of 3.0 cm compared with 1.0-fold and 2.2 cm in the control group. Optimum growth from basal rhizome segments was achieved on media supplemented with 3.0 mg/L Ce(NO3)3, which provided a better proliferation times of 5.1-fold and an average shoot length of 4.5 cm compared with corresponding control values of 2.0-fold and 3.5 cm. Our results showed that La(NO3)3 and Ce(NO3)3 can accelerate A. roxburghii regeneration, which was probably due to the effect on chlorophyll contents, enzymes activity (superoxide dismutase, catalase and peroxidase) and malonldialedhyde contents caused by the addition of La(NO3)3 or Ce(NO3)3.

Changes of Carbohydrates Metabolism and Enzymes Activities in Low Temperature Storage for Bulbs of Lilium Oriental hybrids

Yiping Xia,Chunhui Huang,Guifang He,Weiwei Xu 한국원예학회 2006 한국원예학회 기타간행물 Vol.- No.-

큰방가지똥 추출물의 항당뇨 및 항고혈압효과

왕명현,허명록,Lan Wang,Guifang Xu 한국생약학회 2011 생약학회지 Vol.42 No.1

In this study, we evaluated the bioactivities of methanol extract and its solvent fractions of Sonchus asper (L.) Hill. The EtOAc fraction of S. asper exhibited more strong antioxidant activity than other extracts as evidenced by the strongest 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity with a EC_50 value at 33.55 µg/mL and reducing power, the total polyphenol (180.71 mg GAE/g) and flavonoid contents (145.86 mg QE/g) of S. asper extract were higher than other extracts. The EtOAc fraction of the S. asper also showed 47.38% mushroom tyrosinase inhibition activity, 56.22% α-glucosidase inhibition and 46.58% α-amylase inhibition ratio at 1 mg/mL. Both methylene chloride and EtOAc fractions of methanol extract of S. asper effectively reduced of the 86.34% and 62.03% angiotensin I converting enzyme (ACE) activity at 2 mg/mL, respectively. These findings suggest that the EtOAc fraction of the S. asper could be a potential antioxidant in food additive, medicinal,and industry product.

Airbag Damping of the Hollow Fiber Composite with Different Porosity in the Fiber Wall

Mingjun Li,Guoqun Zhou,Yongwen Xu,Guifang Wang 한국섬유공학회 2019 Fibers and polymers Vol.20 No.2

The inner cavity of the hollow fiber with porosity in its fiber wall constitutes a damping airbag with slow passage of gas. The magnitude of the damping value of the airbag and its damping influencing factors need to be researched, which adds the nonlinear airbag damping to the damping of the raw materials and increases the total damping loss factor of the structure. In this paper, the hollow fiber damping materials with different hollow inside diameters, different fiber wall thicknesses, different wall porosity and different wall pore structure were prepared by adjusting and controlling the technological parameters of the hollow fiber spinning and the formula of spinning casting solution. Meanwhile, we have a comprehensive study on the relationship between the factors and performances. It was found and confirmed that the size of the airbag, the wall pore structure, the wall porosity and the wall thickness of the airbag were the most crucial parameters, which can affect the additional damping of the airbag in the hollow fiber. And the controlling method of the four key parameters was also obtained. Finally, the mechanism and effect of hollow fiber airbag damping was proved.