Varistor and dielectric properties of Cr2O3 doped SnO2eZn2SnO4 composite ceramics

Guo-Zhong Zang,Feng-Zi Zhou,Jing-Xiao Cao,Xiao-Fei Wang,Zhao-Wu Wang,Li-Ben Li,Guo-Rong Li 한국물리학회 2014 Current Applied Physics Vol.14 No.12

Cr2O3 doped SnO2eZn2SnO4 composite ceramics were prepared by traditional ceramic processing and the varistor, dielectric properties were investigated. With increasing Cr2O3 content, the breakdown electrical field EB increases from 11 to 92 V/mm and the relative dielectric constant εr measured at 1 kHz, 50 C decreases from 11,028 to 3412, respectively. The barrier height fB about 0.8e0.84 eV and the decreasing of SnO2 grain size suggest that the varistor behavior with high εr is originated from SnO2 eSnO2 or SnO2eZn2SnO4 grain boundary. In the dielectric spectra lower than 1 kHz, a dielectric peak is presented and depressed with increasing bias voltage. Similarly, at high temperature, the dielectric constant also presents a dielectric peak in the temperature spectra and the peak becomes faint with increasing frequency. The exhibition of the dielectric peak is thought to be attributed to the conduction of grain boundary since it is accompanied by the sharp increase of dielectric loss. In addition, a dielectric relaxation with the activation energy about 0.4e0.5 eV was observed in the temperature range of 20 e100 C. Based on the results, the formation mechanism of Schottky barriers at grain boundaries and the varistor behavior with high dielectric constant are well understood.

Molecular characterization and functional analysis of two trehalose transporter genes in the cabbage beetle, Colaphellus bowringi

Li Jia-Xu,Cao Zhen,Guo Shuang,Tian Zhong,Liu Wen,Zhu Fen,Wang Xiao-Ping 한국응용곤충학회 2020 Journal of Asia-Pacific Entomology Vol.23 No.3

The trehalose, major blood sugar in insects, enhances stress resistance of diapausing individuals in adverse environment and provides an energy source for reproduction. Trehalose transporters (TRETs) play an important role in transport of trehalose from trehalose-producing tissues, e.g. fat body, to trehalose-consuming tissues. Although studies have shown that trehalose contributes to diapause and reproduction, the function of TRETs in these processes remains unclear. In this work, we cloned two TRET genes, TRET1a and TRET1b, from the cabbage beetle Colaphellus bowringi, which is capable of entering reproductive diapause under long-day conditions. We also analyzed the expression profiles of these two genes and investigated their potential roles in diapause and reproduction. The results suggested that both TRET1a and TRET1b belong to sugar-transporter and major facilitator superfamilies. Interestingly, TRET1a was highly expressed in the fat bodies of diapause-destined (DD) females but TRET1b was predominantly expressed in the ovaries of non-diapause-destined (NDD) females. Hormonal induction indicated that juvenile hormone induced TRET1b but repressed TRET1a at transcriptional levels. Methoprene-tolerant and Krüppel homolog 1 mediated the JH-suppressed TRET1a expression but were not involved in the regulation of TRET1b expression by JH. RNAi of TRET1a in DD females elevated the trehalose content in the fat bodies and suppressed the expression of a couple of genes related to stress resistance, which is a critical diapause trait. Knockdown of TRET1b in NDD females reduced the trehalose content in the ovaries but had no apparent effect on the ovary development and yolk deposition. These data suggest that TRET1a and TRET1b could regulate the trehalose content in specific tissues and may play potential roles in reproductive diapause in the females of C. bowringi. Introduction Diapause is a survival strategy for many insects in adapting to adverse environmental conditions (Tauber and Tauber, 1976; Tougeron, 2019). Diapause is a dynamic successive process that consists of diapause induction, preparation, initiation, maintenance, termination, and post-diapause quiescence (Kostal, 2006). Insects accumulate enormous nutrients such as sugars and lipids to enter diapause during diapause preparation phase (Hahn and Denlinger, 2007, 2011). The trehalose is the major hemolymph sugar in insects. The sugar not only provides source of energy but also protects proteins and cellular membranes from dehydration, desiccation, heat, cold, and oxidation (Elbein et al., 2003; Li et al., 2002; Richards et al., 2002; Wyatt and Kalf, 1957; Yancey, 2005; Zhu et al., 2008). Therefore, trehalose can play roles in reproduction and diapause by mediating energy supply and stress tolerance, respectively (Kamei et al., 2011; Lu et al., 2019; Xu et al., 2009).

Environmental Microbiology and Engineering : Immobilization and Characterization of Tannase from a Metagenomic Library and Its Use for Removal of Tannins from Green Tea Infusion

( Jian Yao ),( Qing Long Chen ),( Guo Xiang Zhong ),( Wen Cao ),( An Yu ),( Yu Huan Liu ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.1

Tannase (Tan410) from a soil metagenomic library was immobilized on different supports, including mesoporous silica SBA-15, chitosan, calcium alginate, and amberlite IRC 50. Entrapment in calcium alginate beads was comparatively found to be the best method and was further characterized. The optimum pH of the immobilized Tan410 was shifted toward neutrality compared with the free enzyme (from pH 6.4 to pH 7.0). The optimum temperature was determined to be 45°C for the immobilized enzyme and 30°C for the free enzyme, respectively. The immobilized enzyme had no loss of activity after 10 cycles, and retained more than 90% of its original activity after storage for 30 days. After immobilization, the enzyme activity was only slightly affected by Hg2+, which completely inhibited the activity of the free enzyme. The immobilized tannase was used to remove 80% of tannins from a green tea infusion on the first treatment. The beads were used for six successive runs resulting in overall hydrolysis of 56% of the tannins.

Effect of oxidizing treatment on electrocatalytic activity of boron‑doped amorphous carbon thin films

Chen‑Song Wang,Ni Suo,Hao Huang,Ai‑min Wu,Guo‑Zhong Cao,Gui‑Feng Zhang 한국탄소학회 2019 Carbon Letters Vol.29 No.5

Boron-doped amorphous carbon (BDAC) thin films with a regular oxygen reduction reaction (ORR) catalytic activity were synthesized in a hot filament chemical vapor deposition device using a mixture of CH4 and H2 as a gas source and B2O3 as a boron source and then oxidized in air at 380–470 °C for 15–75 min. Scanning electron microscope, transmission electron microscope, Raman spectroscopy, X-ray photoelectron spectroscopy, and electrochemical tests were used to characterize the physical and electrochemical properties of the BDAC catalysts. It was concluded that the BDAC catalyst oxidized at 450 °C for 45 min showed the best ORR catalytic activity in alkaline medium. The oxygen reduction potential and the transfer electron number n, respectively, are − 0.286 V versus Ag/AgCl and 3.24 from the rotating disk electrode experiments. The treated carbon film has better methanol resistance and stability than the commercial Pt/C catalyst.

Systematic Review of Single Large and/or Multinodular Hepatocellular Carcinoma: Surgical Resection Improves Survival

Yang, Xiang-Di,Pan, Ling-Hui,Wang, Lin,Ke, Yang,Cao, Ji,Yang, Chun,Zhong, Jian-Hong,Luo, Wang,Guo, Jiao,Li, Le-Qun Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.13

Background: The role of surgical resection for patients with single large (${\geq}5cm$) and/or multinodular (${\geq}2$) hepatocellular carcinoma (HCC) is still controversial. This systematic review was performed to evaluate the safety and efficacy of resection for patients with single large and/or multinodular HCC. Materials and Methods: Databases (the PubMed, Web of Science, Embase, and Cochrane databases) were systematically searched to identify relevant studies exploring the safety and efficacy of resection for single large and/or multinodular HCC, published between January 2000 and December 2014. Perioperative morbidity and mortality, overall survival, and disease-free survival of the resection group were calculated. In addition, these outcome variables were also calculated for the control group in the included studies. Results: One randomized controlled trial and 42 nonrandomized studies involving 9,580 patients were eligible for analysis. Eight (1,594 patients) of the 43 studies also reported the outcomes of transarterial chemoembolization (TACE). Although 51.4% of patients featured cirrhosis, 90.7% of them demonstrated Child-Pugh A liver function in the resection group. The median rates of morbidity (24.5%) and mortality (2.5%) after resection were significantly higher than that of TACE (11.0%, P<0.001; 1.9%, P<0.001). However, patients who underwent resection had significantly higher median one-, three-, and five-year overall survival (76.1%, 51.7%, and 37.4%) than those who underwent TACE (68.3%, 31.5%, and 17.5%, all P<0.001). The median 1-, 3-, and 5-year DFS rates after resection were 58.3%, 34.6%, and 24.0%, respectively. Conclusions: Although tumor recurrence after resection for patients with single large and/ or multinodular HCC continues to be a major problem, resection should be considered as a strategy to achieve long-term survival.

Effect of oxidizing treatment on electrocatalytic activity of boron-doped amorphous carbon thin films

Wang Chen-Song,Suo Ni,Huang Hao,Wu Ai-min,Cao Guo-Zhong,Zhang Gui-Feng 한국탄소학회 2019 Carbon Letters Vol.29 No.5

Boron-doped amorphous carbon (BDAC) thin films with a regular oxygen reduction reaction (ORR) catalytic activity were synthesized in a hot filament chemical vapor deposition device using a mixture of CH4 and H2 as a gas source and B2O3 as a boron source and then oxidized in air at 380–470 °C for 15–75 min. Scanning electron microscope, transmission electron microscope, Raman spectroscopy, X-ray photoelectron spectroscopy, and electrochemical tests were used to characterize the physical and electrochemical properties of the BDAC catalysts. It was concluded that the BDAC catalyst oxidized at 450 °C for 45 min showed the best ORR catalytic activity in alkaline medium. The oxygen reduction potential and the transfer electron number n, respectively, are − 0.286 V versus Ag/AgCl and 3.24 from the rotating disk electrode experiments. The treated carbon film has better methanol resistance and stability than the commercial Pt/C catalyst.