Effect of Different Cooling Rates in High Rheological Rate Forming Process on Mechanical Properties of Zr57Cu20Al10Ni8Ag5 Bulk Metallic Glass

Xiao‑Bo Mei,Bao‑Chuan Liu,Wei Jiang,Quan Xu,Qi‑Dong Zhang,Yu‑Bai Ma,Fang‑Qiu Zu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.9

The influence of cooling rates on the mechanical properties of a Zr-based bulk metallic glass prepared with high rheologicalrate forming (HRRF) was investigated and compared with traditional suction cast methods. Amorphous samples of Zr57Cu-20Ni8Al10Ag5 were prepared in copper molds with different sizes in order to obtain different cooling rates for both HRRFand traditional cast methods. These specimens were subjected to compression experiments, including microhardness testing,X-ray diffraction testing and differential scanning calorimetry analysis. The results indicate that the plasticity of the samplesformed by HRRF are higher than that of the as-cast ones at the same cooling rates, while the microhardness manifests theopposite principle. As the cooling rate increases further, the difference in plasticity further increases between two methods,indicating that the plasticity of metallic glasses is more sensitive to cooling rates during the HRRF process. At the core ofthis phenomenon is the fact that HRRF methods can introduce more free volume into glasses than traditional cast methodswith an elevated cooling rate are able to.

Nanoparticle Realgar Powders Induce Apoptosis in U937 Cells through Caspase MAPK and Mitochondrial Pathways

Xiao-bo Wang,Hui-yuan Gao,Bai-ling Hou,Jian Huang,Rong-gang Xi,Li-jun Wu 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.5

Nanoparticle realgar powders (NRP) inhibited U937 cell growth in a time and dose-dependent manner. U937 cells treated with NRP showed typical characteristics of apoptosis including the morphological changes and DNA fragmentation. Caspase family inhibitor (z-VAD-fmk), caspase-8, -9 inhibitor (z-IETD-fmk, Ac-LEHD-CHO, respectively) and caspase-3 inhibitor (z- DEVD-fmk) partially prevented NRP -induced apoptosis. Moreover, the classical substrates of caspase-3, poly-ADP ribose polymerase (PARP) was degraded after U937 cells treatment with NRP. In addition, NRP increased the ratio of Bax/Bcl-2 protein expression. Although p38 inhibitor (SB203580) and ERK inhibitor (PD98059) failed to block cell death, JNK inhibitor (SP600125) had marked inhibitory effects on NRP -induced apoptosis. Furthermore, the phosphorylation of JNK was up-regulated, suggesting that JNK was responsible for NRP -induced apoptosis in U937 cells. These results suggested that the caspase, mitochondria and MAPK signal pathways were involved in NRP-induced U937 apoptosis.

Theoretical Analysis and Optimization of Extrinsic Fabry-Perot Interferometer Optical-fiber Humidity-sensor Structures

Xiao Lei Yin,Ning Wang,Xiao Dan Yu,Yu Hao Li,Bo Zhang,Dai Lin Li 한국광학회 2021 Current Optics and Photonics Vol.5 No.6

The theoretical analysis and optimization of extrinsic Fabry-Perot interferometer (EFPI) opticalfiber humidity sensors are deeply investigated. For a typical dual-cavity structure composed of an optical fiber and a humidity-sensitive membrane (HSM), the changes in refractive index (RI) and initial length are discussed for polymer materials and porous oxide materials when relative humidity (RH) increases. The typical interference spectrum is simulated at different RH using MATLAB. The spectral change caused by changing HSM RI and initial length are simulated simutineously, showing different influences on humidity response. To deeply investigate the influence on RH sensitivity, the typical response sensitivity curves for different HSM lengths and air-cavity lengths are simulated. The results show that the HSM is the vital factor. Short HSM length can improve the sensitivity, but for HSM RI and length the influences on sensitivity are opposite, because of the opposite spectral-shift trend. Deep discussion and an optimization method are provided to solve this problem. According to analysis, an opaque HSM is helpful to improve sensitivity. Furthermore, if using an opaque HSM, a short air cavity and long HSM length can improve the sensor’s sensitivity These results provide deep understanding and some ideas for designing and optimizing highly sensitive EFPI fiber humidity sensors.

Surface quality prediction model of nano-composite ceramics in ultrasonic vibration-assisted ELID mirror grinding

Bo Zhao,Fan Chen,Xiao-feng Jia,Chong-yang Zhao,Xiao-bo Wang 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4

Ultrasonic vibration-assisted Electrolytic in-process dressing (ELID) grinding is a highly efficient and highly precise machining method. The surface quality prediction model in ultrasonic vibration-assisted ELID mirror grinding was studied. First, the interaction between grits and workpiece surface was analyzed according to kinematic mechanics, and the surface roughness model was developed. The variations in surface roughness under different parameters was subsequently calculated and analyzed by MATLAB. Results indicate that compared with the ordinary ELID grinding, ultrasonic vibration-assisted ELID grinding is superior, because it has more stable and better surface quality and has an improved range of ductile machining.

A direct-integration-based structural reliability analysis method using non-probabilistic convex model

Xiao-Bo Nie,Haibin Li 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.11

In practical structural reliability analysis, there is not only random uncertainty but also fuzzy uncertainty. Aiming at the fuzzy reliability of structure, a novel fuzzy reliability method is proposed based on direct integration method and ellipsoidal convex model. Firstly, the decomposition of fuzzy mathematics principle is used to convert fuzzy reliability model into non-probabilistic reliability model, in which fuzzy variables are converted into interval variables. The upper and lower bounds of interval variables are determined by the possibility distribution function on the membership value. Secondly, multidimensional ellipsoid convex models are constructed to quantify the uncertainty because of the complexity of non-probabilistic reliability. Finally, sigmoid function with adjustable parameter is introduced to direct integration method for approximating the step function, and then direct integration method is used to solve the fuzzy reliability. Numerical examples are investigated to demonstrate the effectiveness of the present method, which provides a feasible way for the structural fuzzy reliability analysis.

Adsorption of Nucleotides on ${\beta}$-Cyclodextrin Derivative Grafted Chitosan

Xiao Jian-Bo,Yu Hong-Zhu,Xu Ming,Chen Xiao-Qing The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.4

A novel ${\beta}$-cyclodextrin derivative (CCD-C) was synthesized with chitosan and carboxymethyl-${\beta}$-cyclodextrin. Its structure was characterized by elemental analysis, infrared spectra analysis, and X-ray diffraction analysis. The adsorption properties for guanosine 5'-monophosphate, cytidine 5'-monophosphate and uridine 5'-monophosphate were studied. Experimental results demonstrated that CCD-C had higher adsorption capability for guanosine 5'-monophosphate, and that the adsorption capacity for guanosine 5'-monophosphate was 74.20mg/g. The adsorption capacity was greatly influenced by pH, time and temperature. The introduction of chitosan enhanced the adsorption ability and adsorption selectivity of ${\beta}$-cyclodextrin for guanosine 5'-monophosphate. This novel derivative of chitosan is expected to have wide applications in the separation, concentration and analysis of nucleotides in biological samples.

Molecular cloning and characterization of two novel DREB genes encoding dehydration-responsive element binding proteins in halophyte Suaeda salsa

Xiao-Bo Sun,Hong-Xiang Ma,Xin-Ping Jia,Yu Chen,Xiao-Qing Ye 한국유전학회 2015 Genes & Genomics Vol.37 No.2

The dehydration-responsive element-binding(DREB) proteins play an important role in regulatingexpression of stress-inducible genes under abiotic stresses. In this study, two genes encoding putative DREB proteins,named SsDREBa and SsDREBb, were cloned from halophyteSuaeda salsa L. using RACE method. The deducedSsDREBa and SsDREBb proteins contain a typical AP2/ERF domain. Multiple sequence alignments and phylogeneticanalysis revealed that the two SsDREB genes of S. salsa were highly similar in AP2/ERF domains at thenucleotide and amino acid levels and belong to the A-6subgroup of the DREB transcription factor subfamily. Asubcellular localization assay showed that both SsDREBslocalized to the nucleus. Yeast one-hybrid experimentstestified that both proteins were able to specifically bind tothe DRE sequence and activate the expression of the downstreamHIS reporter gene in yeast. Quantitative real-timePCR analysis demonstrated that under normal conditions,the expression level of SsDREBa was the most high in theroots and no SsDREBa mRNAs were detected in the stems;SsDREBb expressed at relatively higher levels in the leavesthan in the roots and stems. The expression of SsDREa andSsDREBb genes in S. salsa roots and leaves was remarkablyinduced by high-salt and dehydration treatments, butnot by cold and ABA, and exhibited stronger induction inroots and leaves, respectively. These results indicate thatthe SsDREBa and SsDREBb are novel stress-responsivetranscription factors, which are involved in the drought andhigh-salt stress responses through ABA-independent pathwaysand could be used for production of stress-toleranttransgenic crops.

Bacterial and Fungal Diversity in the Starter Production Process of Fen Liquor, a Traditional Chinese Liquor

Xiao-Ran Li,En-Bo Ma,Liang-Zhen Yan,Han Meng,Xiao-Wei Du,Zhe-Xue Quan 한국미생물학회 2013 The journal of microbiology Vol.51 No.4

Fermented foods and beverages are important parts of human diet. Fen liquor, a Chinese liquor is a fermented beverage that uses a traditional fermentation process. Starters are the main microbial source and also provide nutrients for microorganisms during fermentation. In this study, starters of Fen liquor were produced through a complex traditional fermentation process. To investigate the community structure and the composition of microorganisms in the starter production process, bacterial 16S rRNA and fungal internal transcribed spacer (ITS) regions were sequenced using clone libraries and pyrosequencing, respectively. There was much higher diversity among the bacteria than among the fungi in the starter production process. Bacteria on the surface of the starters belonged mostly to the Lactobacillaceae family,while members of the Bacillacae family were dominant in the interior of the samples that lacked access to air and water. In the fungi population, diversity was high only in the raw material. In all other samples, nearly all of the fungal sequences were from Pichia kudriavzevii, a member of the Saccharomycetaceae family. Nearly all samples showed similar fungal community structures, indicating that there was little change in the fungal community. To the best of our knowledge, this is the first report to reveal the whole process of the starter production of Chinese traditional liquor. The findings obtained in this study provide new insights into understanding the composition of the microbial community during the traditional Chinese liquor starter production process and information about the production process control and monitoring.

Enhancement of Butanol Tolerance and Butanol Yield in Clostridium acetobutylicum Mutant NT642 Obtained by Nitrogen Ion Beam Implantation

Xiao-Bo Liu,Qiu-Ya Gu,Xiao-Bin Yu,Wei Luo 한국미생물학회 2012 The journal of microbiology Vol.50 No.6

As a promising alternative biofuel, biobutanol can be produced through acetone/butanol/ethanol (ABE) fermentation. Currently, ABE fermentation is still a small-scale industry due to its low production and high input cost. Moreover, butanol toxicity to the Clostridium fermentation host limits the accumulation of butanol in the fermentation broth. The wild-type Clostridium acetobutylicum D64 can only produce about 13 g butanol/L and tolerates less than 2% (v/v) butanol. To improve the tolerance of C. acetobutylicum D64 for enhancing the production of butanol, nitrogen ion beam implantation was employed and finally five mutants with enhanced butanol tolerance were obtained. Among these, the most butanol tolerant mutant C. acetobutylicum NT642 can tolerate above 3% (v/v) butanol while the wide-type strain can only withstand 2% (v/v). In batch fermentation, the production of butanol and ABE yield of C. acetobutylicum NT642 was 15.4 g/L and 22.3 g/L, respectively, which were both higher than those of its parental strain and the other mutants using corn or cassava as substrate. Enhancing butanol tolerance is a great precondition for obtaining a hyperyield producer. Nitrogen ion beam implantation could be a promising biotechnology to improve butanol tolerance and production of the host strain C. acetobutylicum.

Lentivirus-mediated RNA interference targeting E2F-1 inhibits human gastric cancer MGC-803 cell growth in vivo

Xiao-Tong Wang,Qiang Xiao,Yu-Bo Xie 생화학분자생물학회 2011 Experimental and molecular medicine Vol.43 No.11

The E2F-1 transcription factor is post-translationally modified and stabilized in response to various forms of DNA damage to regulate the expression of cell-cycle and pro-apoptotic genes. The sustained overexpression of E2F-1 is a characteristic feature of gastric cancer. In this study, we investigated the role of short hairpin RNA (shRNA) targeting E2F-1 gene on human gastric cancer MGC-803 cell growth in vivo, and preliminarily revealed the mechanism. Thus, we constructed recombinant pGCSIL-GFP-shRNA-E2F-1 lentiviral vector to knock down E2F-1 expression in human gastric cancer MGC-803 cells in vivo, and studied the effect of E2F-1 shRNA on growth of MGC-803 tumor and evaluated its treatment efficacy. Our data demonstrated that in a mouse model of established gastric cancer, intratumor injection of lentiviral shRNA targeting E2F-1 definitely decreased the endogenous E2F-1mRNA and protein expression in MGC-803 tumor, and inhibited tumor growth and promoted tumor cells apoptosis. Moreover, we found that E2F-1 shRNA increased the expression of phosphatase and tensin homolog (PTEN), activated caspase-3 and caspase-9,and suppressed nuclear factor (NF)-κB expression in tumor tissue as determined by reverse transcription (RT)-PCR and western blotting. In summary, shRNA targeting of E2F-1 can effectively inhibits human gastric cancer MGC-803 cell growth in vivo and may be a potential therapeutic strategy for gastric cancer.