Surface Modification of Titanium Based Biomaterials by Ion Beam

Liu, Xianghuai,Huang, Nan,Yang, Ping,Cai, Guanjun,Chen, Yuanru,Zheng, Zhi hong,Zhou, Zhuyao The Korean Vacuum Society 1995 Applied Science and Convergence Technology Vol.4 No.s2

Ion beam enhanced deopsition(IBED) was adopted to synthesize biocompatible titanium oxide film. Structure characteristics of titanium oxide film were investigated by RBS, AES and XRD. The blood compatibility of the titanium oxide film was studied by measurements of blood clotting time and platelet adhesion. The results show that the anticoagulation property of titanium oxide film is improved significantly. The mechanism of anticoagulation of the titanium oxide film was discussed.

Microstructure and strength of zirconia/stainless steel joints prepared by pressureless active brazing

Guiwu Liu,Hongjie Wang,Jianfeng Yang,Tianjian Lu,Guanjun Qiao 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.4

ZrO2 ceramic/stainless steel joints were fabricated by pressureless brazing using a Ag-Cu filler metal and a TiH2 powder precoating. The microstructure and microchemistry of the joint cross section were characterized and analyzed by means of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The effects of brazing conditions on the joint shear strength were also investigated. The results showed that there existed three zones with distinct microstructural differences crossing the brazing interlayer. A reaction layer and a Ti-rich sublayer were formed at the ZrO2/filler interface. The influence of the brazing temperature on the joint strength was more remarkable than that of the holding time. In the experimental condition ranges, the joint strength first increased, and the maximum shear strength was over 90MPa with the optimized condition. Most of the joint fractures developed in the ceramic matrix near the ceramic/filler interface. ZrO2 ceramic/stainless steel joints were fabricated by pressureless brazing using a Ag-Cu filler metal and a TiH2 powder precoating. The microstructure and microchemistry of the joint cross section were characterized and analyzed by means of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The effects of brazing conditions on the joint shear strength were also investigated. The results showed that there existed three zones with distinct microstructural differences crossing the brazing interlayer. A reaction layer and a Ti-rich sublayer were formed at the ZrO2/filler interface. The influence of the brazing temperature on the joint strength was more remarkable than that of the holding time. In the experimental condition ranges, the joint strength first increased, and the maximum shear strength was over 90MPa with the optimized condition. Most of the joint fractures developed in the ceramic matrix near the ceramic/filler interface.

STING Negatively Regulates Double-Stranded DNA-Activated JAK1-STAT1 Signaling via SHP-1/2 in B Cells

Dong, Guanjun,You, Ming,Ding, Liang,Fan, Hongye,Liu, Fei,Ren, Deshan,Hou, Yayi Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.5

Recognition of cytosolic DNA initiates a series of innate immune responses by inducing IFN-I production and subsequent triggering JAK1-STAT1 signaling which plays critical roles in the pathogenesis of infection, inflammation and autoimmune diseases through promoting B cell activation and antibody responses. The stimulator of interferon genes protein (STING) has been demonstrated to be a critical hub of type I IFN induction in cytosolic DNA-sensing pathways. However, it still remains unknown whether cytosolic DNA can directly activate the JAK1-STAT1 signaling or not. And the role of STING is also unclear in this response. In the present study, we found that dsDNA directly triggered the JAK1-STAT1 signaling by inducing phosphorylation of the Lyn kinase. Moreover, this response is not dependent on type I IFN receptors. Interestingly, STING could inhibit dsDNA-triggered activation of JAK1-STAT1 signaling by inducing SHP-1 and SHP-2 phosphorylation. In addition, compared with normal B cells, the expression of STING was significantly lower and the phosphorylation level of JAK1 was significantly higher in B cells from MRL/lpr lupus-prone mice, highlighting the close association between STING low-expression and JAK1-STAT1 signaling activation in B cells in autoimmune diseases. Our data provide a molecular insight into the novel role of STING in dsDNA-mediated inflammatory disorders.

Nonradiative energy transfer between colloidal quantum dot-phosphors and nanopillar nitride LEDs.

Zhang, Fan,Liu, Jie,You, Guanjun,Zhang, Chunfeng,Mohney, Suzanne E,Park, Min Joo,Kwak, Joon Seop,Wang, Yongqiang,Koleske, Daniel D,Xu, Jian Optical Society of America 2012 Optics express Vol.20 No.2

<P>We present in this communication our study of the nonradiative energy transfer between colloidal quantum dot (QD) phosphors and nitride nanopillar light emitting diodes (LEDs). An epitaxial p-i-n InGaN/GaN multiple quantum-well (QW) heterostructure was patterned and dry-etched to form dense arrays of nanopillars using a novel etch mask consisting of self-assembled In3Sn clusters. Colloidal QD phosphors have been deposited into the gaps between the nanopillars, leading to sidewall coupling between the QDs and InGaN QW emitters. In this approach, close QW-QD contact and a low-resistance design of the LED contact layer were achieved simultaneously. Strong non-radiative energy transfer was observed from the InGaN QW to the colloidal QD phosphors, which led to a 263% enhancement in effective internal quantum efficiency for the QDs incorporated in the nanopillar LEDs, as compared to those deposited over planar LED structures. Time-resolved photoluminescence was used to characterize the energy transfer process between the QW and QDs. The measured rate of non-radiative QD-QW energy-transfer agrees well with the value calculated from the quantum efficiency data for the QDs in the nanopillar LED.</P>

STING Negatively Regulates Double-Stranded DNA-Activated JAK1-STAT1 Signaling via SHP-1/2 in B Cells

Yayi Hou,Guanjun Dong,Ming You,Liang Ding,Hongye Fan,Fei Liu,Deshan Ren 한국분자세포생물학회 2015 Molecules and cells Vol.38 No.5

Recognition of cytosolic DNA initiates a series of innate immune responses by inducing IFN-I production and subsequent triggering JAK1-STAT1 signaling which plays critical roles in the pathogenesis of infection, inflammation and autoimmune diseases through promoting B cell activation and antibody responses. The stimulator of interferon genes protein (STING) has been demonstrated to be a critical hub of type I IFN induction in cytosolic DNA-sensing pathways. However, it still remains unknown whether cytosolic DNA can directly activate the JAK1-STAT1 signaling or not. And the role of STING is also unclear in this response. In the present study, we found that dsDNA directly triggered the JAK1-STAT1 signaling by inducing phosphorylation of the Lyn kinase. Moreover, this response is not dependent on type I IFN receptors. Interestingly, STING could inhibit dsDNA-triggered activation of JAK1-STAT1 signaling by inducing SHP-1 and SHP-2 phosphorylation. In addition, compared with normal B cells, the expression of STING was significantly lower and the phosphorylation level of JAK1 was significantly higher in B cells from MRL/lpr lupus-prone mice, highlighting the close association between STING low-expression and JAK1-STAT1 signaling activation in B cells in autoimmune diseases. Our data provide a molecular insight into the novel role of STING in dsDNA-mediated inflammatory disorders.

Polymer-Assisted Pressure Sensor with Piezoresistive Suspended Graphene and Its Temperature Characteristics

Xin Lin,Ying Liu,Yong Zhang,Peng Yang,Xianzhe Cheng,Jing Qiu,Guanjun Liu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.10

A polymer-assisted pressure sensor with piezoresistive suspended graphene is proposed and fabricated with high yield. Our sensor exhibits a good pressure response comparable to that of commercial sensors. The sensitivity is estimated to be 2.87 x 10 -5 kPa -1, higher than that of similar Si-based pressure sensors. The influence of the temperature on the sensor performance is systematically analyzed. An inverse temperature response is observed, and a nonnegligible temperature effect on the sensor resistance is demonstrated. Considering the temperature-induced cavity pressure change, a new temperature–resistance model is built to explain the nonlinearity of the sensor response to the temperature variation. Experiments under different test voltages show the influence of the current thermal effect, which is similar to that of temperature and nonnegligible for high-precision pressure sensors. Our new sensor holds great potential for practical application, and the findings on the temperature characteristics open up a route to further improve the sensor performance.

Simulation Analysis on Seismic Performance of Assembled Composite Energy Dissipation Pipe Joint

Jianpeng Sun,Yingbiao Jiang,Guanjun Lv,Kai Liu,Ju Zhao 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.3

Based on the seismic ductility design concept, a kind of assembled composite energy dissipation pipe joint with rapid repair after the earthquake was proposed. We established the fi nite element models of assembled composite energy dissipation pipe joints with the 24 diff erent structural parameters, and carried out the low reversed cyclic loading simulation test. The strain cloud diagram, hysteretic curve, skeleton curve, stiff ness degradation curve and energy dissipation capacity curve of the pipe joints were obtained. The structural parameters’ infl uence on the performance indexes of the pipe joints was analyzed. The results show that the proposed assembled composite energy dissipation pipe joint has good ductility and energy dissipation capacity. The replacement of peripheral energy dissipation steel plate is simple and fast, and the mechanical properties can be restored after replacement. The diameter thickness ratio of peripheral energy dissipating steel pipe has more signifi cant impact on the seismic performance of the connecting parts. With the increase of the diameter thickness ratio of the peripheral energy dissipating steel pipe, the energy dissipation capacity gradually increases. The ratio of height to thickness has less eff ect on the seismic performance of the model, and the initial stiff ness and energy dissipation capacity of the model are signifi cantly enhanced after the stiff ened steel pipe is installed outside.

Trichoderma reesei Sch9 and Yak1 regulate vegetative growth, conidiation, and stress response and induced cellulase production

Xinxing Lv,Weixin Zhang,Guanjun Chen,Weifeng Liu 한국미생물학회 2015 The journal of microbiology Vol.53 No.4

Protein kinases are key players in controlling many basiccellular processes in almost all the organisms via mediatingsignal transduction processes. In the present study, we characterizedthe cellulolytic Trichoderma reesei orthologs ofSaccharomyces cerevisiae Sch9 and Yak1 by sequence alignmentand functional analysis. The T. reesei Trsch9Δ andTryak1Δ mutant strains displayed a decreased growth rateon different carbon sources and produced less conidia. Theabsence of these two kinases also resulted in different butabnormal polarized apical growth as well as sensitivity tovarious stresses. In addition, disruption of the genes Trsch9 orTryak1 resulted in perturbation of cell wall integrity. Interestingly,while the induced production of cellulases was slightlycompromised in the Trsch9Δ strain, the extracellular productionof cellulases was significantly improved in the absenceof Yak1. The results indicate that TrSch9 and TrYak1play an important role in filamentous growth, stress responseand induced production of cellulases in T. reesei.

Low-Cost Flexible Strain Sensor Based on Thick CVD Graphene

Bailiang Chen,Ying Liu,Guishan Wang,Xianzhe Cheng,Guanjun Liu,Jing Qiu,Kehong Lv 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.11

Flexible strain sensors, as the core member of the family of smart electronic devices, along with reasonable sensing range and sensitivity plus low cost, have rose a huge consumer market and also immense interests in fundamental studies and technological applications, especially in the field of biomimetic robots movement detection and human health condition monitoring. In this paper, we propose a new flexible strain sensor based on thick CVD graphene film and its low-cost fabrication strategy by using the commercial adhesive tape as flexible substrate. The tensile tests in a strain range of ~30% were implemented, and a gage factor of 30 was achieved under high strain condition. The optical microscopic observation with different strains showed the evolution of cracks in graphene film. Together with commonly used platelet overlap theory and percolation network theory for sensor resistance modeling, we established an overlap destructive resistance model to analyze the sensing mechanism of our devices, which fitted the experimental data very well. The finding of difference of fitting parameters in small and large strain ranges revealed the multiple stage feature of graphene crack evolution. The resistance fallback phenomenon due to the viscoelasticity of flexible substrate was analyzed. Our flexible strain sensor with low cost and simple fabrication process exhibits great potential for commercial applications.

A Fiber Spool’s Vibration Sensitivity Optimization Based on Orthogonal Experimental Design

Jing Gao,Linbo Zhang,Dongdong Jiao,Guanjun Xu,Xue Deng,Qi Zang,Honglei Yang,Ruifang Dong,Tao Liu,Shougang Zhang 한국광학회 2024 Current Optics and Photonics Vol.8 No.1

A fiber spool with ultra-low vibration sensitivity has been demonstrated for the ultra-narrowlinewidth fiber-stabilized laser by the multi-object orthogonal experimental design method, which can achieve the optimization object and analysis of influence levels without extensive computation. According to a test of 4 levels and 4 factors, an L 16 (4 4 ) orthogonal table is established to design orthogonal experiments. The vibration sensitivities along the axial and radial directions and the normalized sums of the vibration sensitivities are determined as single objects and comprehensive objects, respectively. We adopt the range analysis of object values to obtain the influence levels of the four design parameters on the single objects and the comprehensive object. The optimal parameter combinations are determined by both methods of comprehensive balance and evaluation. Based on the corresponding fractional frequency stability of ultra-narrow-linewidth fiber-stabilized lasers, we obtain the final optimal parameter combination A3B1C2D1, which can achieve the fiber spool with vibration sensitivities of 10 −12 /g magnitude. This work is the first time to use an orthogonal experimental design method to optimize the vibration sensitivities of fiber spools, providing an approach to design the fiber spool with ultra-low vibration sensitivity.