Jianjun Gao

Publications (21)27.6 Total impact

• Article: Impaired autophagic function in rat islets with aging.

  Yu Liu, Suozhu Shi, Zhaoyan Gu, Yingzhen Du, Minyan Liu, Shuangtong Yan, Jianjun Gao, Jian Li, Yinghong Shao, Wenwen Zhong, Xiangmei Chen, Chunlin Li
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  ABSTRACT: Type 2 diabetes is characterized by a deficit in β-cell function and mass, and its incidence increases with age. Autophagy is a highly regulated intracellular process for degrading cytoplasmic components, particularly protein aggregates and damaged organelles. Impaired or deficient autophagy is believed to cause or contribute to aging and age-related disease. Autophagy may be necessary to maintain structure, mass, and function of pancreatic β-cells. In this study, we investigated the effects of age on β-cell function and autophagy in pancreatic islets of 4-month-old (young), 14-month-old (adult), and 24-month-old (old) male Wistar rats. We found that islet β-cell function decreased gradually with age. Protein expression of the autophagy markers LC3/Atg8 and Atg7 exhibited a marked decline in aged islets. The expression of Lamp-2, a good indicator of autophagic degradation rate, was significantly reduced in the islets of old rats, suggesting that autophagic degradation is decreased in the islets of aged rats. However, protein expression of beclin-1/Atg6, which plays an important role in the induction and formation of the pre-autophagosome structure by associating with a multimeric complex of autophagy regulatory proteins (Atg14, Vps34/class 3 PI3 kinase, and Vps15), was most prominent in the islets of adult rats, and was higher in 24-month-old islets than in 4-month-old islets. The levels of p62/SQSTM1 and polyubiquitin aggregates, representing the functions of autophagy and proteasomal degradation, were increased in aging islets. 8-Hydroxydeoxyguanosine, a marker of mitochondrial and nuclear DNA oxidative damage, exhibited strong immunostaining in old islets. Analysis by electron microscopy demonstrated swelling and disintegration of cristae in the mitochondria of aged islets. These results suggest that β-cell and autophagic function in islets decline simultaneously with increasing age in Wistar rats, and that impaired autophagy in the islets of older rats may cause accumulation of misfolded and aggregated proteins and reduce the removal of abnormal mitochondria in β-cells, leading to reduced β-cell function. Dysfunctional autophagy in islets during the aging process may be an important mechanism leading to the development of type 2 diabetes.
  Age 07/2012; · 6.28 Impact Factor
• Conference Proceeding: Microwave modeling and parameter extraction method for PHEMT

  Jianjun Gao, Xiuping Li
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  ABSTRACT: This paper reviews the characterization technique of pseudomorphic high electron mobility transistors (PHEMT). The linear, nonlinear and noise modeling and corresponding parameter extraction methods are described. The on wafer measurement methods for S parameters and noise parameters are also highlighted.
  Microwave and Millimeter Wave Technology, 2008. ICMMT 2008. International Conference on; 05/2008
• Article: A Semianalytical Method to Determine Parasitic Elements of Quantum-Well Laser

  Jianjun Gao, Xiuping Li
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  ABSTRACT: A parameter-extraction approach for the quantum- well laser, which combines the analytical approach and the empirical optimization procedure, is developed in this paper. The initial values of the parasitic pad capacitance and the feedline inductance are extracted by using a set of closed-form expressions derived from above-threshold mode input reflection coefficient on wafer measurement, and the extrinsic contact resistance and capacitance determined by using the analytical method are described as functions of the parasitic pad capacitance and the feedline inductance. Advanced Design System (Agilent commercial software) is then used to optimize only the parasitic pad capacitance and the feedline inductance with very small dispersions of initial values. An excellent fit between measured and simulated input reflection coefficients under cutoff and above-threshold biased conditions in the frequency range of 50 MHz-40 GHz is obtained.
  Journal of Lightwave Technology 11/2007; · 2.78 Impact Factor
• Conference Proceeding: Microwave noise modeling for PHEMT using artificial neural network technique

  Jianjun Gao, Xiuping Li, Qi-jun Zhang
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  ABSTRACT: An improved noise model for pseudomorphic high electron mobility transistors (PHEMT) based on the conventional equivalent circuit modeling and artificial neural network (ANN) modeling technique is presented. The frequency dispersion of the noise model parameters which including noise parameters (P,R, imaginary and real parts of C) have taken into account by using an ANN model. The noise model parameters are determined directly from noise parameters on wafer measurement based on the noise correlation matrix technique. Good agreement is obtained between the measured and calculated results up to 26 GHz for 2 times 40 mum gate width (number of gate fingers times unit gate width) 0.25 mum double heterojunction delta-doped PHEMTs over a wide range of bias points.
  Microwave Conference, 2006. APMC 2006. Asia-Pacific; 01/2007
• Article: Printed dipole antenna design using artificial neural network modeling for RFID application

  Xiuping Li, Jianjun Gao, Georg Boeck
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  ABSTRACT: An approach to printed dipole antenna design using the artificial neural network (ANN) modeling technique is presented in this article. Three important antenna-layout dimensions are used to capture critical input/output relationships in the ANN model. Once fully developed, the ANN model has been shown to be as accurate as an EM simulator and much more efficient computationally in antenna design optimization. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.
  International Journal of RF and Microwave Computer-Aided Engineering 09/2006; 16(6):607 - 611. · 0.59 Impact Factor
• Article: Microwave nonlinear device modelling by using an artificial neural network

  Xiuping Li, Jianjun Gao, Georg Boeck
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  ABSTRACT: An approach for the microwave nonlinear device modelling technique based on a combination of the conventional equivalent circuit model and artificial neural network (ANN) is presented in this paper. The main advantage of the proposed method is that the integration and differential of an ANN can directly be carried out from the original ANN. The proposed technique is very useful for neural-based microwave computer-aided design, and for analytically unified dc, small signal and nonlinear device modelling. Examples of the Schottky diode and PHEMT linear/nonlinear modelling utilizing the proposed integration and differential technique are demonstrated.
  Semiconductor Science and Technology 05/2006; 21(7):833. · 1.72 Impact Factor
• Source

  Available from: ksu.edu.tw

  Article: An approach to determine small-signal model parameters for InP-based heterojunction bipolar transistors

  Jianjun Gao, Xiuping Li, Hong Wang, G. Boeck
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  ABSTRACT: A new method for the extraction of the small-signal model parameters of InP-based heterojunction bipolar transistors (HBT) is proposed. The approach is based on the combination of the analytical and optimization technology. The initial values of the parasitic pad capacitances are extracted by using a set of closed-form expressions derived from cutoff mode S-parameters without any test structure, and the intrinsic elements determined by using the analytical method are described as functions of the parasitic elements. An advanced design system is then used to optimize only the parasitic parameters with very small dispersion of initial values. Good agreement is obtained between simulated and measured results for an InP HBT with 5×5 μm² emitter area over a wide range of bias points up to 40 GHz.
  IEEE Transactions on Semiconductor Manufacturing 03/2006; · 0.72 Impact Factor
• Conference Proceeding: Bandpass filter design by artificial neural network modeling

  Xiuping Li, Jianjun Gao, Jong-Gwan Yook, Xiaodong Chen
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  ABSTRACT: This paper presents a design approach for a λ/2 resonator bandpass filter by using the artificial neural network (ANN) modeling technique. Three important dimensions of the filter layout are used to capture critical input-output relationships in the ANN model. Once fully developed, the ANN model has been shown to be as accurate as an EM simulator and much more efficient computationally in the design optimization of the filter.
  Microwave Conference Proceedings, 2005. APMC 2005. Asia-Pacific Conference Proceedings; 01/2006
• Article: Relationships between common source, common gate, and common drain FETs

  Jianjun Gao, G. Boeck
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  ABSTRACT: This paper comprehensively analyzes the relationship between common source (CS), common gate (CG), and common drain (CD) field-effect transistors (FETs). The signal and noise parameters of the CG and CD configuration can be obtained directly by using a simple set of formulas from CS signal and noise parameters. All the relationships provide a bi-directional bridge for the transformation between CS, CG, and CD FETs. This technique is based on the combination of an equivalent-circuit model and conventional two-port network signal/noise correlation matrix technique. The derived relationships have universal validity, but they have been verified at 2×40 μm gatewidth (number of gate fingers × unit gatewidth) double-heterojunction δ-doped AlGaAs/InGaAs/GaAs pseudomorphic high electron-mobility transistor with 0.25-μm gate length. Good agreement has been obtained between calculated and measured results.
  IEEE Transactions on Microwave Theory and Techniques 01/2006; · 1.85 Impact Factor
• Conference Proceeding: Nonlinear HEMT modeling using artificial neural network technique

  Jianjun Gao, Lei Zhang, Jianjun Xu, Qi-jun Zhang
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  ABSTRACT: An improved nonlinear modeling technique for high electron mobility transistors (HEMT) based on the combination of the conventional equivalent circuit and artificial neural network (ANN) modeling techniques is presented. Effective initial values of the artificial neural network for each nonlinear element in HEMT model are evaluated from a semi-analytical parameter extraction technique. A multi-goal DC, S-parameter, and harmonic (DC/S/HB) training process has been formulated. Good agreement is obtained between the model and data of the DC, S-parameter, and harmonic performance for a 200μm gate width 0.25μm PHEMT (FHX04LG) over a wide range of bias points.
  Microwave Symposium Digest, 2005 IEEE MTT-S International; 07/2005
• Article: A new method for determination of parasitic capacitances for PHEMTs

  Jianjun Gao, Xiuping Li, Hong Wang, Georg Boeck
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  ABSTRACT: A new direct extraction method for the determination of the parasitic capacitances of PHEMTs is presented in this paper. This method is based on a general scalable small signal equivalent circuit model under pinch-off bias condition. The main advantage of this approach is that all parasitic capacitances including Cpg, Cpd and Cpgd can be extracted simultaneously by using PHEMTs of different sizes but with the same pad structure. Good agreement is obtained between modelled and measured results for 2 × 20 µm, 2 × 40 µm, 2 × 60 µm and 2 × 100 µm gate width (number of gate fingers × unit gate width) double heterojunction δ-doped PHEMTs.
  Semiconductor Science and Technology 04/2005; 20(6):586. · 1.72 Impact Factor
• Article: Authors' reply [to Comments on "Microwave noise modeling for InP-InGaAs HBTs"]

  Jianjun Gao, Xiuping Li, Hong Wang, G. Boeck
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  ABSTRACT: For original article by J. Gao, X. Li, H. Wang, and G. Boeck see ibid., vol.52, no.4, p.1624-72, April 2004. For comments by L. Escotte and J. Graffeuil see ibid., vol.53, no.1, p.415-16, January 2005.
  IEEE Transactions on Microwave Theory and Techniques 02/2005; 53(1):417-. · 1.85 Impact Factor
• Article: Direct extraction of InP HBT noise parameters based on noise-figure measurement system

  Jianjun Gao, Xiuping Li, Lin Jia, Hong Wang, G. Boeck
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  ABSTRACT: A new method for the determination of the four noise parameters of an InP double heterojunction bipolar transistor (DHBT) based on a 50-Ω noise measurement system without a microwave tuner is presented. The noise parameters are determined based on the noise correlation matrix technique by fitting the measured noise figure of the active device. On-wafer experimental verification up to 20 GHz is presented and a comparison with a tuner based method is given. Good agreement is obtained between measured and calculated results up to 20 GHz for the InP/InGaAs DHBT with a 1.6×20 μm² emitter over a wide range of bias points.
  IEEE Transactions on Microwave Theory and Techniques 02/2005; · 1.85 Impact Factor
• Article: Direct parameter-extraction method for laser diode rate-equation model

  Jianjun Gao, Xiuping Li, J. Flucke, G. Boeck
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  ABSTRACT: A new direct extraction method to determine the small-signal and rate-equation model parameters for laser diode is presented in this paper. This method differs from previous ones by extracting the whole model parameters without global numerical optimization techniques. The main advantage of this method is that a unique and physically meaningful set of extrinsic and intrinsic parameters are extracted by using a set of closed-form expressions based on the input reflection coefficients and modulation responses taken from on-wafer measurement. Simulated and measured results for the input reflection coefficients and modulation responses exhibit good agreement over a wide range of bias points.
  Journal of Lightwave Technology 07/2004; · 2.78 Impact Factor
• Source

  Available from: 140.120.11.121

  Article: Microwave noise modeling for InP-InGaAs HBTs

  Jianjun Gao, Xiuping Li, Hong Wang, G. Boeck
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  ABSTRACT: Analytical expressions for the noise parameters of microwave InP double heterojunction bipolar transistors (DHBTs) are presented in this paper. These expressions are derived from an accurate small-signal and noise equivalent-circuit model, which takes into account the influences of the base-collector capacitance and the base resistance distributed nature. Pad capacitances and series inductances are also included. Further simplified expressions for noise parameters in the low-frequency range are given. Good agreement is obtained between measured and calculated results up to 20 GHz for InP-InGaAs DHBTs with a 5×5 μm² emitter area over a wide range of bias points.
  IEEE Transactions on Microwave Theory and Techniques 05/2004; · 1.85 Impact Factor
• Article: A new method for pHEMT noise-parameter determination based on 50-Ω noise measurement system

  Jianjun Gao, Choi Look Law, Hong Wang, S. Aditya, G. Boeck
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  ABSTRACT: A new method for determining the four noise parameters of pseudomorphic high electron-mobility transistors (pHEMTs) based on a 50-Ω noise measurement system without a microwave tuner is presented. The noise parameters are determined based on the noise correlation matrix technique by fitting the measured noise figure of the active device. On-wafer experimental verification up to 26 GHz is presented and a comparison with a tuner-based method is given. The scaling rules for noise parameters have also been determined. Good agreement is obtained between simulated and measured results for 2×20 μm, 2×40 μm, and 2×60 μm gatewidth (number of gate fingers × unit gatewidth) 0.25-μm double-heterojunction δ-doped pHEMTs.
  IEEE Transactions on Microwave Theory and Techniques 11/2003; · 1.85 Impact Factor
• Article: An Improved On-Wafer Measurement Method for PHEMT Modeling for Millimeter Wave Application

  Xiuping Li, Jianjun Gao, Choi Look Law, Sheel Aditya, Georg Boeck
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  ABSTRACT: An improved on-wafer measurement method by using coaxial calibration instead of on-wafer calibration for PHEMT modeling is proposed in this paper. The advantage is that S-parameters of PHEMT device can be measured on wafer without impedance standard substrate (ISS) after the S-parameters of the microprobes have been determined. Excellent agreement is obtained between on-wafer calibration measurement and coaxial calibration measurements, respectively.
  International Journal of Infrared and Millimeter Waves 09/2003; 24(10):1759-1766. · 0.58 Impact Factor
• Conference Proceeding: An approach for microprobe measurement and modeling for millimeter-wave application

  Xiuping Li, Jianjun Gao, Choi Look Law, Sheel Aditya
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  ABSTRACT: This paper describes a simple method to check the performance of microprobe, since it will directly affect the accuracy of measurement results. The two-port S-parameters of the microprobe are determined by one-port S-parameters measurement using HP 8510XF Network Analyzer. Based on the measurement, an equivalent circuit model is given and good agreement between the measurement results and modeling results is obtained.
  Antennas and Propagation Society International Symposium, 2003. IEEE; 07/2003
• Article: An Approach to Linear Scalable DH-PHEMT Model for Millimeterwave Application

  Jianjun Gao, Choi Look Law, Hong Wang, Sheel Aditya
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  ABSTRACT: This paper describes a scalable small-signal equivalent circuit for 0.25 m gatelength Double Heterojunction delta-doped PHEMTs. The scaling rules for all elements except the pad capacitances and bondwire inductances have been determined. Good agreement is obtained between simulation results and measured results for 2 times 20 m , 2 times 40 m, 2 times 60 m, 2 times 100 m gate width (number of gate fingers times unit gate width) DH PHEMT.
  International Journal of Infrared and Millimeter Waves 11/2002; 23(12):1787-1801. · 0.58 Impact Factor
• Article: An Approach for Extracting Small-Signal Equivalent Circuit of Double Heterojunction δ-Doped PHEMTs for Millimeter Wave Applications

  Jianjun Gao, ChoiLook Law, Hong Wang, Sheel Aditya
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  ABSTRACT: Pseudomorphic high electron mobility transistors (PHEMTs) are very important in millimeterwave application. A simple and accurate method for extracting small-signal equivalent curcuit for Double Heterojunction -doped PHEMT valid up to 40GHz is presented. First, the parasitic parameters of the equivalent circuit are determined using pinch off PHEMT except for PAD capacitances. The initial intrinsic elements are then determined by conventional analytical method. Advanced Design System is then used to optimize the whole model parameters with very small dispersion of initial values. Good agreement is obtained between simulation results and measured results for a 0.25um DH PHEMT.
  International Journal of Infrared and Millimeter Waves 01/2002; 23(3):345-364. · 0.58 Impact Factor