Study on the lubrication film formation and characteristics of different graphite seal composites

Qili Wang,Jiarui Sun,Mingquan Yu,Yuehu Chen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8

In order to study the formation and characteristics of the lubricating film of graphite composites in solid lubrication, the mechanical properties, micro-structure, friction and wear properties of graphite and impregnated samples are compared and analysed. Results show that the graphite/antimony composites have compression strength of 300.2 MPa and hardness of 98.3 HS, which has excellent friction performance and exhibits the law of full film lubrication. The graphite/resin composites with compression strength of 244.9 MPa and hardness of 87.0 HS exhibit the law of residual film lubrication. Under the condition that the load is 24.1 MPa (heavy load) and the friction pair is 45# (small hardness), the lubrication state of the composite materials are close to full film lubrication. External environmental factors such as load, speed, and pair of grinding pairs have different effects on the friction coefficient and the formation of lubricating film.

Characterization of Choristoneura fumiferana Genes of the Sixth Subunit of the Origin Recognition Complex: CfORC6

Wang, Xaiochun,Carstens, Eric B.,Feng, Qili Korean Society for Biochemistry and Molecular Biol 2006 Journal of biochemistry and molecular biology Vol.39 No.6

A new protein was cloned and identified as the sixth subunit of Choristoneura fumiferana origin recognition complex (CfORC6). The newly identified 43 kDa protein CfORC6 is much bigger than DmORC6 (25.7 kDa) and HsORC6 (28.1 kDa), though it's 23.85% identical to DmORC6 and 23.81% identical to HsORC6. Although the molecular weight of CfORC6 is close to ScORc6 (50 kDa), CfORC6 is only 14.03% identical to ScORC6. By alignment, it was found that the N-terminal of CfORC6 has about 30% identities with other ORC6s, but about 100aa of C-terminal of CfORC6 has no identity with other ORC6s. Like ScORC6, CfORC6 has many potential phosphorylation sites, (S/T)PXK. Like DmORC6, CfORC6 has leucine-rich region in the relevant site. Northern Blot showed that CfORC6 mRNA is about 2,000nt. Southern Blot confirmed that there is one copy of CfORC6 gene in spruce budworm genome. Western blot showed that infection of Cf124T cells with CfMNPV didn't affect the expression levels of CfORC6, at least up to 26 hr post infection.

Probing the Key Binding Sequence and Improvement of the Stability of a β-Bungarotoxin-binding Aptamer in Snake Venom

Fengping Ye,Qili Mi,Ning Zhang,Xuemei Li,Jing Yu,Zhongping Gao,Ying Zheng,Quanshui Fan,Jie Wang,Jinglin Wang 대한화학회 2016 Bulletin of the Korean Chemical Society Vol.37 No.5

Chemical modifications of the nucleotides can improve the stability of aptamers against enzyme degradation in serum, but it is not clear whether these methods are effective in snake venom. In this study, a DNA aptamer, βB-1, which specifically recognize β-bungarotoxin and Bungarus multicinctus venom was chosen, and the key binding sequence of the aptamer was determined. Based on the secondary structure of the truncated aptamer, locked nucleic acids and 2′-O-methyl nucleotides were applied to modify the stem and loop sequences, respectively. In addition, a 3′-3′-thymidine cap was also adopted to block the 3′ end. It was shown that these chemical modifications can all enhance the stability of the aptamer in snake venom. Simultaneously, modified aptamer with the above modifications in one sequence exhibited a significantly elevated biostability, with the half-life improved from several minutes to 210 min while maintaining its binding affinity to the target.

Surface Modifications of Titanium Dental Implants with Strontium Eucommia Ulmoides to Enhance Osseointegration and Suppress Inflammation

Avery Rui Sun,Qili Sun,Yansong Wang,Liqiu Hu,Yutong Wu,Fenbo Ma,Jiayi Liu,Xiangchao Pang,Bin Tang 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Background Titanium (Ti) is now widely used as implant material due to its excellent mechanical properties and superior biocompatibilities, while its inert bioactivities might lead to insufficient osseointegration, and limit its performance in dental applications. Methods We introduced a robust and simple approach of modifying titanium surfaces with polysaccharide complexes. Titanium samples were subjected to hydrothermal treatment to create a uniform porous structure on the surface, followed by coating with a bioinspired and self-assembly polydopamine layer. Strontium Eucommia Ulmoides Polysaccharide (EUP-Sr) complexes are then introduced to the polydopamine-coated porous titanium. Multiple morphological and physiochemical characterizations are employed for material evaluation, while cell proliferation and gene expression tests using macrophages, primary alveolar bone osteoblasts, and vascular endothelial cells are used to provide an overall insight into the functions of the product. The significances of statistical differences were analyzed using student’s t-test. Results Microscopic and spectrometric characterizations confirmed that the Ti surface formed a porous structure with an adequate amount of EUP-Sr loading. The attachment was attributed to hydrogen bonding between the ubiquitous glycosidic linkage of the polysaccharide complex and the ring structure of polydopamine, yet the loaded EUP-Sr complex can be gradually released, consequently benefiting the neighboring microenvironment. Cell experiments showed no cytotoxicity of the material, and the product showed promising anti-inflammation, osseointegration, and angiogenesis properties, which were further confirmed by in vivo evaluations. Conclusion We believe the EUP-Sr modified titanium implant is a promising candidate to be used in dental applications with notable osteoimmunomodulation and angiogenesis functions. And the novel technique proposed in this study would benefit the modification of metal/inorganic surfaces with polysaccharides for future research.

Behavior of Al/Cu/Ti electrodes in surface acoustic wave filter at high power

Qi Li,Sulei Fu,Zengtian Lu,Lirong Qian,Rui Wang,Tongjin Chen,Cheng Song,Fei Zeng,Weibiao Wang,Feng Pan 한국물리학회 2019 Current Applied Physics Vol.19 No.4

Driven by the need for high data-rates and continuous reduction in device size, surface acoustic wave filters are required to work under increasingly high power. In this work, a series of 2.7 GHz surface acoustic wave filters with Al/Cu/Ti three-layered electrode were fabricated and loaded with high power. Those three-layered electrodes showed weaker texture but higher stability than Al-Cu alloy electrode at high power. Morphologies, microstructures and elements distribution in cross section of fingers were analyzed carefully before and after high power loading. Results show that the circular-arc-shaped outline of fingers were appeared in most samples after high power loading, and the number of gains in the finger cross section changed from some into several with much larger volume. The features of distribution of Cu atoms also coincided with these microstructures. By finite element method and phase diagram analysis, the higher stability of Al/Cu/Ti three-layered electrodes are attributed to precipitation of θ-CuAl2 in the bottom edge of electrode finger and Cu-doped α-Al in the center top.

Highly Efficient Biotransformation of Notoginsenoside R1 into Ginsenoside Rg1 by Dictyoglomus thermophilum β-xylosidase Xln-DT

( Qi Li ),( Lei Wang ),( Xianying Fang ),( Linguo Zhao ) 한국미생물생명공학회 2022 Journal of microbiology and biotechnology Vol.32 No.4

Notoginsenoside R1 and ginsenoside Rg1 are the main active ingredients of Panax notoginseng, exhibiting anti-fatigue, anti-tumor, anti-inflammatory, and other activities. In a previous study, a GH39 β-xylosidase Xln-DT was responsible for the bioconversion of saponin, a natural active substance with a xylose group, with high selectivity for cleaving the outer xylose moiety of notoginsenoside R1 at the C-6 position, producing ginsenoside Rg1 with potent anti-fatigue activity. The optimal bioconversion temperature, pH, and enzyme dosage were obtained by optimizing the transformation conditions. Under optimal conditions (pH 6.0, 75℃, enzyme dosage 1.0 U/ml), 1.0 g/l of notoginsenoside R1 was converted into 0.86 g/l of ginsenoside Rg1 within 30 min, with a molar conversion rate of approximately 100%. Furthermore, the in vivo anti-fatigue activity of notoginsenoside R1 and ginsenoside Rg1 were compared using a suitable rat model. Compared with the control group, the forced swimming time to exhaustion was prolonged in mice by 17.3% in the Rg1 high group (20 mg/kg·d). Additionally, the levels of hepatic glycogen (69.9-83.3% increase) and muscle glycogen (36.9-93.6% increase) were increased. In the Rg1 group, hemoglobin levels were also distinctly increased by treatment concentrations. Our findings indicate that treatment with ginsenoside Rg1 enhances the anti-fatigue effects. In this study, we reveal a GH39 β-xylosidase displaying excellent hydrolytic activity to produce ginsenoside Rg1 in the pharmaceutical and food industries.

Highly Efficient Biotransformation of Astragaloside IV to Cycloastragenol by Sugar-Stimulated β-Glucosidase and β-Xylosidase from Dictyoglomus thermophilum

( Qi Li ),( Tao Wu ),( Linguo Zhao ),( Jianjun Pei ),( Zhenzhong Wang ),( Wei Xiao ) 한국미생물 · 생명공학회 2019 Journal of microbiology and biotechnology Vol.29 No.12

β-Glucosidases and β-xylosidases are two categories of enzymes that could cleave out nonreducing, terminal β-D-glucosyl and β-D-xylosyl residues with release of D-glucose and Dxylose, respectively. In this paper, two functional β-glucosidase Dth3 and β-xylosidase Xln-DT from Dictyoglomus thermophilum were heterologously expressed in E.coli BL21 (DE3). Dth3 and Xln-DT were relatively stable at 75oC and were tolerant or even stimulated by glucose and xylose. Dth3 was highly tolerant to glucose with a Ki value of approximately 3 M. Meanwhile, it was not affected by xylose in high concentration. The activity of Xln-DT was stimulated 2.13- fold by 1 M glucose and 1.29-fold by 0.3 M xylose, respectively. Furthermore, the β- glucosidase Dth3 and β-xylosidase Xln-DT showed excellent selectivity to cleave the outer C-6 and C-3 sugar moieties of ASI, which established an effective and green method to produce the more pharmacologically active CAG, an exclusive telomerase activator. We measured temperature, pH and dosage of enzyme using a single-factor experiment in ASI biotransformation. After optimization, the optimal reaction conditions were as follows: 75oC, pH 5.5, 1 U of Dth3 and 0.2 U of Xln-DT, respectively. Under the optimized conditions, 1 g/l ASI was transformed into 0.63 g/l CAG with a corresponding molar conversion of 94.5% within 3 h. This is the first report to use the purified thermostable and sugar-tolerant enzymes from Dictyoglomus thermophilum to hydrolyze ASI synergistically, which provides a specific, environment-friendly and cost-effective way to produce CAG.

Dynamic Characteristics Identification of an Arch Dam Model via the Phase-Based Video Processing

Qi Li,Gaohui Wang,Aral Sarrafi,Xinqiang Niu,Wenbo Lu,Zhu Mao 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.1

In recent years, the extraction of structural dynamic characteristics by using phase-based video processing has attracted considerable attention. Edge detection routine is oftentimes employed to obtain the quantified operational deflection shape (ODS) vectors of structures. However, this approach is unreliable because of intensive human supervision and correction. To reduce operational uncertainty, a hybrid computer-vision-based approach called edge detection-region labeling, which involves vision sensor preparation, bottom-hat filtering, edge detection, hole filling, and region labeling, was presented in this work to extract the quantified ODS’s. The performance of this method was firstly evaluated by conducting a lab-scale cantilever beam test and subsequently the phase-based video processing was applied to extract the dynamic characteristics of an arch dam model. The operational modal analysis (OMA) test was conducted on the benchmark dam model. In-plane motions of the dam were captured and processed to identify the natural frequencies of the dam. The structural ODS’s were quantified using the proposed method. A comparison of the modal parameters of the dam identified from the video data with those obtained in the OMA test revealed that the two sets of results were consistent, and the video processing approach was able to bypass the requirement of human supervision, which facilitates the application of the phase-based video processing for complex structures.

Development, characterization, and inheritance of 113 novel EST-SSR markers in the Pacific oyster (Crassostrea gigas)

Qi Li,Qingzhi Wang,Mingjun Qi,Jianlong Ge,Rihao Cong 한국유전학회 2011 Genes & Genomics Vol.33 No.3

A total of 113 novel EST-derived simple sequence repeat (EST-SSR) markers were developed in the Pacific oyster (Crassotrea gigas). Polymorphisms of these markers were evaluated in a wild population of 30 individuals. The number of alleles per locus ranged from 2 to 27 with an average of 6.3, and the observed and expected heterozygosities varied from 0 to 0.9667 and from 0.0333 to 0.9701, respectively. Mendelian segregations were tested for 24 of the markers that were polymorphic in one family produced by single-pair mating. Null alleles were discovered at four loci. Nine tests of segregation ratios revealed significant departures from expected Mendelian ratios. As a useful addition to the collection of the microsatellites that are now available for C. gigas, these EST-SSR markers will help the advance in investigation of QTL mapping and genetic diversity in this species.

Failure Mechanism of Weak Rock Slopes considering Hydrological Conditions

Qi Li,Yimin Wang,Kunbiao Zhang 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.2

Landslides frequently occur on cutting slopes with weak rock during the rainy season. An understanding of the failure mechanism is essential for designers to adopt effective measures to mitigate potential impacts caused by landslides. Based on an enormous number of highway slope practices in Guangdong Province, China, this paper presents a whole train of numerical investigations on the hydraulic response and stability of weak rock slopes subject to a subtropical climate where the average annual rainfall is approximately 1,800 − 2,000 mm. This study explored a different failure mechanism of three different types of weak rock slopes in a modeling approach. A physics-based slope model coupled with a hydrological model is used to simulate the factor of safety and porewater pressure development of unsaturated slopes with various rock masses under diverse rainfall scenarios. The input parameters were determined from the rainfall intensity–duration–frequency (IDF) curves of regional hydrological conditions to comprehensively consider the impact of rainfall. The general suction range of rock masses was acquired using three hydraulic characteristic curves associated with sandstone, siltstone, and mudstone. Furthermore, the failure models of weak rock slopes under different rainfall conditions were assessed. Based on the theory of regional hydrology, a unified rainfall and intensity-duration threshold for different weak rock slopes was established. The results indicate that both siltstone and mudstone slopes are more sensitive to long-term rainfall than short-term rainstorms. However, the sandstone slope appears to be unstable under regional rainfall conditions of 40-year return periods. This also proves that the instability mode of the siltstone slope exhibits a retrogressive type in which the sliding surface of the slope increases with an increase in rainfall duration. Translational shallow landslides occurred in the transient saturation zone of the sandstone slope, and the depth of the failure plane was independent of rainfall patterns and duration. This study revealed the instability mechanism and provided a robust early warning measure for weak rock slopes by fusing engineering geology and regional hydraulics, providing insightful information for mitigating potential landslide disasters. The proposed model can also be used to predict the possible infiltration depth of rainfall and the spatial location of the sliding surface, prior to construction to assess whether slope stabilization and reinforcement measures are needed.