We report on the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Pd/Ti/n-InP Schottky barrier diodes (SBDs) in the temperature range 160-400 K in steps of 40 K. The barrier heights and ideal...We report on the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Pd/Ti/n-InP Schottky barrier diodes (SBDs) in the temperature range 160-400 K in steps of 40 K. The barrier heights and ideality factors of Schottky contact are found in the range 0.35 eV (I-V), 0.73 eV (C-V) at 160 K and 0.63 eV (I-V), 0.61 eV (C-V) at 400 K, respectively. It is observed that the zero-bias barrier height decreases and ideality factor n increase with a decrease in temperature, this behaviour is attributed to barrier inhomogeneities by assuming Gaussian distribution at the interface. The calculated value of series resistance (Rs) from the forward I-V characteristics is decreased with an increase in temperature. The homogeneous barrier height value of approximately 0.71 eV for the Pd/Ti Schottky diode has been obtained from the linear relationship between the temperature-dependent experimentally effective barrier heights and ideality factors. The zero-bias barrier height ( ) versus 1/2kT plot has been drawn to obtain evidence of a Gaussian distribution of the barrier heights and values of = 0.80 eV and = 114 mV for the mean barrier height and standard deviation have been obtained from the plot, respectively. The modified Richardson ln(I0/T2)- ( ) versus 1000/T plot has a good linearity over the investigated temperature range and gives the mean barrier height ( ) and Richardson constant (A*) values as 0.796 eV and 6.16 Acm-2K-2 respectively. The discrepancy between Schottky barrier heights obtained from I-V and C-V measurements is also interpreted.展开更多
目的:通过检测1型糖尿病(type 1 diabetes mellitus,T1DM)、2型糖尿病(type 2 diabetes mellitus,T2DM)患者以及健康对照外周血T细胞亚群免疫负调控分子程序性死亡蛋白1(programmed cell death protein 1,PD-1)m RNA相对表达水平和记忆...目的:通过检测1型糖尿病(type 1 diabetes mellitus,T1DM)、2型糖尿病(type 2 diabetes mellitus,T2DM)患者以及健康对照外周血T细胞亚群免疫负调控分子程序性死亡蛋白1(programmed cell death protein 1,PD-1)m RNA相对表达水平和记忆性T细胞(memory T cells,Tm)表面PD-1表达情况,从分子生物学、细胞免疫学等多种角度研究记忆性T细胞PD-1表达异常与以胰岛β细胞破坏为主要机制的T1DM发生发展的相关性。方法:分离T1DM、T2DM患者以及健康对照组外周血单个核细胞(peripheral blood mononuclear cells,PBMCs);从PBMCs中分离出CD4^+T细胞和CD8^+T细胞,使用荧光定量PCR分别检测其细胞内PD-1 m RNA相对表达水平;将PBMCs分别标记荧光抗体CD4-FITC、CD45RO-PE、CCR7-APC、CD8-FITC、PD-1-Per Cp,应用流式细胞术分别检测CD4^+CD45RO^+CCR7^+Tcm细胞、CD4^+CD45RO^+CCR7-Tem细胞、CD8^+CD45RO^+CCR7^+Tcm细胞、CD8^+CD45RO^+CCR7^-Tem细胞表面免疫负调控分子PD-1的表达水平。结果:(1)T1DM组患者外周血中CD4^+T细胞内PD-1 m RNA相对表达水平低于T2DM组和正常对照组,差异有统计学意义;(2)T1DM组患者外周血中CD8^+T细胞内PD-1 m RNA相对表达水平未见明显异常;(3)T1DM组患者外周血中CD4^+CD45RO^+CCR7-Tem细胞亚群与CD4^+CD45RO^+CCR7^+Tcm细胞亚群PD-1表达水平均显著低于正常对照组和T2DM组患者,差异有统计学意义;(4)T1DM组患者外周血中CD8^+CD45RO^+CCR7-Tem细胞亚群与CD8^+CD45RO^+CCR7^+Tcm细胞亚群PD-1表达水平均无明显异常。结论:胰岛β细胞可通过细胞表面PD-L1与CD4^+Tm细胞表面PD-1结合从而负调节后者细胞免疫作用,因此当CD4^+Tm细胞PD-1表达异常而失去负调控作用时,细胞效应则会进一步增强,最终可能通过破坏胰岛β细胞而导致T1DM的发生发展。展开更多
文摘We report on the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Pd/Ti/n-InP Schottky barrier diodes (SBDs) in the temperature range 160-400 K in steps of 40 K. The barrier heights and ideality factors of Schottky contact are found in the range 0.35 eV (I-V), 0.73 eV (C-V) at 160 K and 0.63 eV (I-V), 0.61 eV (C-V) at 400 K, respectively. It is observed that the zero-bias barrier height decreases and ideality factor n increase with a decrease in temperature, this behaviour is attributed to barrier inhomogeneities by assuming Gaussian distribution at the interface. The calculated value of series resistance (Rs) from the forward I-V characteristics is decreased with an increase in temperature. The homogeneous barrier height value of approximately 0.71 eV for the Pd/Ti Schottky diode has been obtained from the linear relationship between the temperature-dependent experimentally effective barrier heights and ideality factors. The zero-bias barrier height ( ) versus 1/2kT plot has been drawn to obtain evidence of a Gaussian distribution of the barrier heights and values of = 0.80 eV and = 114 mV for the mean barrier height and standard deviation have been obtained from the plot, respectively. The modified Richardson ln(I0/T2)- ( ) versus 1000/T plot has a good linearity over the investigated temperature range and gives the mean barrier height ( ) and Richardson constant (A*) values as 0.796 eV and 6.16 Acm-2K-2 respectively. The discrepancy between Schottky barrier heights obtained from I-V and C-V measurements is also interpreted.
文摘目的:通过检测1型糖尿病(type 1 diabetes mellitus,T1DM)、2型糖尿病(type 2 diabetes mellitus,T2DM)患者以及健康对照外周血T细胞亚群免疫负调控分子程序性死亡蛋白1(programmed cell death protein 1,PD-1)m RNA相对表达水平和记忆性T细胞(memory T cells,Tm)表面PD-1表达情况,从分子生物学、细胞免疫学等多种角度研究记忆性T细胞PD-1表达异常与以胰岛β细胞破坏为主要机制的T1DM发生发展的相关性。方法:分离T1DM、T2DM患者以及健康对照组外周血单个核细胞(peripheral blood mononuclear cells,PBMCs);从PBMCs中分离出CD4^+T细胞和CD8^+T细胞,使用荧光定量PCR分别检测其细胞内PD-1 m RNA相对表达水平;将PBMCs分别标记荧光抗体CD4-FITC、CD45RO-PE、CCR7-APC、CD8-FITC、PD-1-Per Cp,应用流式细胞术分别检测CD4^+CD45RO^+CCR7^+Tcm细胞、CD4^+CD45RO^+CCR7-Tem细胞、CD8^+CD45RO^+CCR7^+Tcm细胞、CD8^+CD45RO^+CCR7^-Tem细胞表面免疫负调控分子PD-1的表达水平。结果:(1)T1DM组患者外周血中CD4^+T细胞内PD-1 m RNA相对表达水平低于T2DM组和正常对照组,差异有统计学意义;(2)T1DM组患者外周血中CD8^+T细胞内PD-1 m RNA相对表达水平未见明显异常;(3)T1DM组患者外周血中CD4^+CD45RO^+CCR7-Tem细胞亚群与CD4^+CD45RO^+CCR7^+Tcm细胞亚群PD-1表达水平均显著低于正常对照组和T2DM组患者,差异有统计学意义;(4)T1DM组患者外周血中CD8^+CD45RO^+CCR7-Tem细胞亚群与CD8^+CD45RO^+CCR7^+Tcm细胞亚群PD-1表达水平均无明显异常。结论:胰岛β细胞可通过细胞表面PD-L1与CD4^+Tm细胞表面PD-1结合从而负调节后者细胞免疫作用,因此当CD4^+Tm细胞PD-1表达异常而失去负调控作用时,细胞效应则会进一步增强,最终可能通过破坏胰岛β细胞而导致T1DM的发生发展。
