Effect of sintering temperature on humidity sensitivity of a MgCr2O4-TiO2 ceramics sensor

Haiyan He,Xiong Liu 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.2

Porous 80MgCr2O4–20TiO2 ceramics were investigated as humidity sensors. The ceramics sensors were obtained by cold isostatic pressing and sintering of the fine MgCr2O4 and TiO2 powders synthesized by sol-gel methods. The effects of sintering temperature on the humidity sensitivity were studied by measuring the electrical resistance in different relative humidities (R.H.) at 27 oC. The results indicated that the calcining temperature obviously affected the resistance variation of the sensor in the range of 11.3-84.7%RH. The resistance variation was small at a calcining temperature of 600 oC for 2 h. With an increase in the calcining temperature, the resistance variation increased to a maximum of 1.49 × 105% at 800 oC for 2 h, but decreased to 7.41 × 104% and 4.07 × 104% at 1000 oC for 2 h and 1200 oC for 2 h respectively. Resistance variations of 90% between 11.3%RH and 84.7%RH can be performed in 25 s and 50 s for the humidity adsorption and humidity desorption respectively. The completed response times are 55 s and 90 s for the adsorption and desorption respectively. The large sensitivity and swift response of 80MgCr2O4–20TiO2 ceramics to humidity are suitable for humidity sensing applications.

CO2 Adsorption on the B12N12 Nanocage Encapsulated with Alkali Metals: A Density Functional Study

Haiyan Zhu,Qiyan Zhang,Qinfu Zhao,He Zhao,Yifan Feng,Bingbing Suo,Huixian Han,Qi Song,Yawei Li,Wenli Zou,Haiyan Zhu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.3

Density functional theory (DFT) calculations have been carried out to study the capacity of the B12N12 nanocage encapsulated with alkali metals (Li, Na, K) for the CO2 adsorption and activation. It is found that after encapsulating alkali metals, the alkali metal atoms are closer to one side of clusters instead of exactly lying at the center, and a considerable charge transfers from the inner alkali metal atoms to the B12N12 cage. Besides, the HOMO–LUMO gap (HLG) values of Li@B12N12, Na@B12N12 and K@B12N12 are decreased to about 6 eV, being much smaller than that of the pristine B12N12. Although the geometry structure parameters and the energy differences of M06-2X are slightly different from the ones of ωB97X-D, some identical results of two kinds of functional can be obtained. CO2 can be adsorbed chemically and physically on majority bonds of all the clusters, except for some bonds with large change in bond length and bond indices. The encapsulation of alkali-metal atoms may enhance the physical and chemical adsorption of CO2 on the surface of the clusters, in which Na@B12N12 and K@B12N12 are the most powerful physical and chemical adsorbent for CO2, respectively.

Low pH stress responsive transcriptome of seedling roots in wheat (Triticum aestivum L.)

Haiyan Hu,Jie He,Junjie Zhao,Xingqi Ou,Hongmin Li,Zhengang Ru 한국유전학회 2018 Genes & Genomics Vol.40 No.11

Soil acidification is one of major problems limiting crop growth and especially becoming increasingly serious in China owing to excessive use of nitrogen fertilizer. Only the STOP1 of Arabidopsis was identified clearly sensitive to proton rhizotoxicity and the molecular mechanism for proton toxicity tolerance of plants is still poorly understood. The main objective of this study was to investigate the transcriptomic change in plants under the low pH stress. The low pH as a single factor was employed to induce the response of the wheat seedling roots. Wheat cDNA microarray was used to identify differentially expressed genes (DEGs). A total of 1057 DEGs were identified, of which 761 genes were up-regulated and 296 were downregulated. The greater percentage of up-regulated genes involved in developmental processes, immune system processes, multi-organism processes, positive regulation of biological processes and metabolic processes of the biological processes. The more proportion of down-regulation genes belong to the molecular function category including transporter activity, antioxidant activity and molecular transducer activity and to the extracellular region of the cellular components category. Moreover, most genes among 41 genes involved in ion binding, 17 WAKY transcription factor genes and 17 genes related to transport activity were up-regulated. KEGG analysis showed that the jasmonate signal transduction and flavonoid biosynthesis might play important roles in response to the low pH stress in wheat seedling roots. Based on the data, it is can be deduced that WRKY transcription factors might play a critical role in the transcriptional regulation, and the alkalifying of the rhizosphere might be the earliest response process to low pH stress in wheat seedling roots. These results provide a basis to reveal the molecular mechanism of proton toxicity tolerance in plants.

Joule Heating Effect on Oxide Whisker Growth Induced by Current Stressing in Cu/Sn-58Bi/Cu Solder Joint

Hongwen He,Liqiang Cao,Lixi Wan,Haiyan Zhao,Guangchen Xu,Fu Guo 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.4

The electromigration test was conducted in Cu/Sn-58Bi/Cu solder joint with high current density of 104 A/cm2. Results showed that a large number of whiskers with natural weed appearance were observed at the cathode side in such a short current stressing time. Furthermore, some secondary whiskers were attached to the primary whiskers, which has never been reported before. We presumed the vapor-solid (VS) mechanism to explain the oxide whiskers growth, which was quite different from the traditional theory that the compressive stress took on the driving force. In conclusion, due to the over-Joule heating effect, the metal oxide whiskers were synthesized in bulk quantities by thermal evaporation of Sn oxide and Bi oxide.

Differences in Phase Change Processes Upon Heating Between Co and Zn-ZIF-4 Compounds

Kaihui Li,Haiyan Xiao,Jianxiong He,Hong Jiang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.3

Zn and Co-ZIF-4 meta-stable compounds adopt the same topology of Zeolitic imidazolate frameworks (ZIF)-4, but differ in the metal nodes (Zn versus Co). Using calorimetric and thermogravimetric analysis, here we characterized their differences in phase change processes. Upon heating, the framework of Co-ZIF-4 meta-stable crystal undergoes the crystal-to-amorphous phase transition at 590 K, which is somewhat lower than the corresponding transition previously reported in the corresponding Zn-ZIF-4. In addition, the recrystallization rate for amorphous Co-ZIF-4 is relatively higher than the corresponding one of Zn-ZIF-4. Finally, the forming Co–zni crystal begins to melt at about 824K, accompanied by quick decomposition, whereas Zn–zni undergoes complete melting which finishes at around 850K without any decomposition. Based on their differences in chemistry for Co and Zn, we elucidated the chemical origin of the discrepancies of phase transition process for Zn and Co-ZIF-4 compounds upon heating.

A prevalence survey of Wolbachia in Polytremis fukia (Lepidoptera: Hesperiidae)

Weibin Jiang,Yajuan Wu,Haiyan He,Jianqing Zhu,Weidong Yu 한국응용곤충학회 2016 Journal of Asia-Pacific Entomology Vol.19 No.2

Wolbachia are endosymbiotic bacteria that infect arthropod and nematode hosts. Only a few studies have been made on Wolbachia in butterflies. In this study, we identified and determined the molecular characteristics of Wolbachia strains in Polytremis fukia (Lepidoptera: Hesperiidae), from seven locations in China. We also sequenced three portions of the mitochondrial DNA from the individuals of P. fukia to infer the effect of Wolbachia on host mitochondrial variation. The results show that 47% (15/32) are Wolbachia positive among all specimens. The infection rates in female and male are 69% (11/16) and 25% (4/16). Phylogenetic analysis of variation in the ftsZ gene from the two strains of Wolbachia (wFuk1 and wFuk2) showed they belonged to supergroup A. On the phylogeny of the mitochondrialDNA fromP. fukia, the sequences are split into three clades. Clade I and II are consistent with the distribution of geographical population. Clade III consists of eight females invariably infected with wFuk1which showed aweak association existed between mitochondrial DNA haplotypes andwFuk1 infection status.

Effects of Brain Mechanical Properties on Child Head Responses under Linear Load

Shihai Cui,Yue Chen,Haiyan Li,Lijuan He,Shijie Ruan 대한의용생체공학회 2016 Biomedical Engineering Letters (BMEL) Vol.6 No.2

Purpose It is usually difficult to obtain the accurate mechanicalproperties of pediatric brain and skull because of the absenceof pediatric cadaver experiments. The goal of this work is todiscuss how different brain mechanical properties influencepediatric head response. Methods A validated finite element model of a 3-year-oldchild head with detailed anatomical structures was used toparametrically investigate the effects of mechanical propertieson child head. Taguchi orthogonal method was adopted todecrease the numbers of the simulation under direct impactload. Results With the increase of the skull elastic modulus, thecoup pressure decreases significantly (P < 0.001) whereasthe contrecoup pressure (P < 0.001) and maximum vonMises stress of skull (P < 0.001) increase significantly. Withthe increase of the short-time shear modulus of brain tissue,maximum shear stress of brain tissue (P < 0.001) increasessignificantly whereas the maximum principal strain (P < 0.01)decreases significantly. Conclusions Both Elastic modulus of skull and linearviscoelastic material parameters of brain tissues have statisticallysignificant effects on impact responses of child head. Differentmaterial parameters can lead to a great difference on impactresponses of child head.

Extracellular Proteome Profiling of Bacillus pumilus SCU11 Producing Alkaline Protease for Dehairing^s

( Chao Wang ),( Shiqiang Yu ),( Ting Song ),( Tingting He ),( Huanhuan Shao ),( Haiyan Wang ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.11

Bacillus pumilus is one of the most characterized microorganisms that are used for high-level production of select industrial enzymes. A novel B. pumilus SCU11 strain possessing high alkaline protease activity was obtained in our previous work. The culture supernatant of this strain showed efficient dehairing capability with minimal collagen damage, indicating promising potential applications in the leather industry. In this study, the strain`s extracellular proteome was identified by LC-MS/MS-based shotgun proteomic analysis, and their related secretory pathways were characterized by BLAST searches. A total of 513 proteins, including 100 actual secreted and 413 intracellular proteins, were detected in the extracellular proteome. The functions of these secreted proteins were elucidated and four complete secretory systems (Sec, Tat, Com, and ABC transporter) were proposed for B. pumilus. These data provide B. pumilus a comprehensive extracellular proteome profile, which is a valuable theoretical and applicative basis for future genetic modifications and development of industrial enzymes.

Simultaneous Determination of Phenobarbital, Pentobarbital, Amobarbital and Secobarbital in Raw Milk via Liquid Chromatography with Electron Spray Ionization Tandem Mass Spectrometry

Huaixiang Tian,Xingxin Zhou,Chen Chen,Yabin He,Haiyan Yu,Xiaoping Zheng 한국축산식품학회 2017 한국축산식품학회지 Vol.37 No.6

A rapid, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/ MS) method was developed for the simultaneous determination of four barbiturates (phenobarbital, pentobarbital, amobarbital and secobarbital) in raw milk. The barbiturates were extracted using liquid-liquid extraction, ultrasonication and centrifugation, and purified on an SPE column. Analytes were separated by HPLC on a CSH C18 column eluted using an acetonitrile- water system with a linear gradient dilution programme, and detected by MS/MS. The recoveries of the barbiturates were 85.0-113.5%, and the intra- and inter-assay RSDs were less than 9.8% and 7.3%, respectively. The limit of detection was 5 ng/mL for all four of the barbiturates. The analytical method exhibited good linearity from 10 to 1000 ng/mL; the correlation coefficient (r2) was greater than 0.9950 for each barbiturate. This method was also applied to the determination of barbiturates in real milk samples and was found to be suitable for the determination of veterinary drug residues in raw milk.

Formation Mechanisms for (Cr,Co)7C3/(Cr,Co)23C6 Heterogeneous Precipitates and Stacking Faults Around Carbides in Surfacing Welding of Stellite Alloy on Stainless Steel

Jiankun Xiong,Haibo Zhang,Fuheng Nie,Fen He,Jianping Yang,Zhan Hu,Zhongbo Wen,Haiyan Zhao,Xinjian Yuan 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7

The formation mechanisms for two carbides with co-existence and increasing stacking faults nearby the carbides duringsurfacing welding were investigated in this study. The results indicated that the surfacing layer had a two-phase structure ofa matrix phase and a second phase, the density of the second phase was relatively small and the second phase was discontinuous,by contrast with the as-received welding wire. Relatively uniform microstructure of surfacing layer and the weldinginterface without melting of base metal were obtained, resulting in an inapparent change in the microhardness. A few carbideswith blocky shape were identified in the surfacing layer. The mechanisms for (Cr,Co)23C6 of face-centered cubic crystalstructure co-existing with (Cr,Co)7C3 of hexagonal close-packed crystal structure and (Cr,Co)23C6 subsequently forming closeto the pre-formed (Cr,Co)7C3 during the cooling process were discussed in alloying element, calculated equilibrium phasediagram, Gibbs energy, etc. The relatively higher density of the stacking fault present around the carbides was understoodfrom forming energy of stacking faults.