针对传统α能谱测量系统存在的本底噪声高、能量分辨率受限等问题,研制了基于FPGA技术的数字多道分析模块与PIPS半导体探测器相结合的新一代α能谱测量系统。该系统设计基于FPGA的多参数数字多道处理架构,利用硬件描述语言实现高速脉冲...针对传统α能谱测量系统存在的本底噪声高、能量分辨率受限等问题,研制了基于FPGA技术的数字多道分析模块与PIPS半导体探测器相结合的新一代α能谱测量系统。该系统设计基于FPGA的多参数数字多道处理架构,利用硬件描述语言实现高速脉冲幅度提取算法,开发了自适应基线恢复技术和波形动态甄别机制。实验数据表明,该系统能量分辨率最低可达到16.293 ke V@5.486 MeV(FWHM),支持8192道能谱分析,具备多探测器同步采集能力,为环境放射性监测、核安全保障、食品安全等领域的超低水平α核素分析提供了可靠的技术手段。展开更多
Effect factors of the absorption of the source,air,entrance window,and dead layer of a detector must be considered in the measurement of monoenergetic alpha particles,along with statistical noise and other factors tha...Effect factors of the absorption of the source,air,entrance window,and dead layer of a detector must be considered in the measurement of monoenergetic alpha particles,along with statistical noise and other factors that collectively cause the alpha spectrum to exhibit a well-known low-energy tail.Therefore,the estabUshment of an alpha spectrum detector response function from the perspective of a signaling system must consider the various factors mentioned above.The detector response function is the convolution of an alphaparticle pulse function,two exponential functions,and a Gaussian function,followed by calculation of the parameters of the detector response function using the weighted leastsquares fitting method as proposed in this paper.In our experiment,^(239)Pu alpha spectra were measured by a highresolution,passivated implanted planar silicon(PIPS)detector at 10 levels of vacuum and 10 source-detector distances.The spectrum-fitting results were excellent as evaluated by reduced Chi-square(x^2) and correlation coefficients.Finally,the variation of parameters with vacuum level and source-detector distance was studied.Results demonstrate that σ,τ_1,and τ_2 exhibit no obvious trend of variation with vacuum in the range 2000-20,000 mTorr,and at a confidence level of 95%,the values of τ_1 and τ_2 decline in a similar fashion with source-detector distance by the power exponential function,while the value of a declines linearly.展开更多
Water is an important component in plant cells with plant aquaporin being the major protein for water transport in and between plant cells.As a subfamily of plant aquaporins,the plasma membrane intrinsic proteins（PIP...Water is an important component in plant cells with plant aquaporin being the major protein for water transport in and between plant cells.As a subfamily of plant aquaporins,the plasma membrane intrinsic proteins（PIPs） located in the plasma membrane are classic,high water,selective channel proteins.This paper focuses on recent advances in the molecular biology of PIPs concerning structural characteristics,biological function,and a regulation mechanism.PIPs possess two highly conserved domains:GGGANXXXXGY and TGI/TNPARSL/FGAAI/VI/VFWF/YN.PIPs can also be divided into two phylogenetic subgroups named PIP1 and PIP2.PIP1 possesses longer N terminal sequences and shorter C terminal sequences than PIP2 with conserved amino acid sequences respectively.Studies of transgenic plants and expression in Xenopus oocytes cells indicate that PIPs not only may facilitate transport of water and small neutral solutes like CO<sub>2</sub> and glycerin,but they also possess many physiological functions. The functions of plant aquaporins are regulated by many factors including post-translational modification,heteromerization,pH value,and divalent cations.These results indicated that PIPs act as a pivotal role in water and small neutral solutes transport in plants.展开更多
文摘针对传统α能谱测量系统存在的本底噪声高、能量分辨率受限等问题,研制了基于FPGA技术的数字多道分析模块与PIPS半导体探测器相结合的新一代α能谱测量系统。该系统设计基于FPGA的多参数数字多道处理架构,利用硬件描述语言实现高速脉冲幅度提取算法,开发了自适应基线恢复技术和波形动态甄别机制。实验数据表明,该系统能量分辨率最低可达到16.293 ke V@5.486 MeV(FWHM),支持8192道能谱分析,具备多探测器同步采集能力,为环境放射性监测、核安全保障、食品安全等领域的超低水平α核素分析提供了可靠的技术手段。
基金supported by the National Natural Science Foundation of China(Nos.41374130 and 41604154)Opening Foundation of Sichuan Provincial Key Lab of Applied Nuclear Techniques in Geosciences(No.gnzds2014003)the Open Fund of Robot Technology Used for Special Environment Key Laboratory of Sichuan Province(13zxtk04)
文摘Effect factors of the absorption of the source,air,entrance window,and dead layer of a detector must be considered in the measurement of monoenergetic alpha particles,along with statistical noise and other factors that collectively cause the alpha spectrum to exhibit a well-known low-energy tail.Therefore,the estabUshment of an alpha spectrum detector response function from the perspective of a signaling system must consider the various factors mentioned above.The detector response function is the convolution of an alphaparticle pulse function,two exponential functions,and a Gaussian function,followed by calculation of the parameters of the detector response function using the weighted leastsquares fitting method as proposed in this paper.In our experiment,^(239)Pu alpha spectra were measured by a highresolution,passivated implanted planar silicon(PIPS)detector at 10 levels of vacuum and 10 source-detector distances.The spectrum-fitting results were excellent as evaluated by reduced Chi-square(x^2) and correlation coefficients.Finally,the variation of parameters with vacuum level and source-detector distance was studied.Results demonstrate that σ,τ_1,and τ_2 exhibit no obvious trend of variation with vacuum in the range 2000-20,000 mTorr,and at a confidence level of 95%,the values of τ_1 and τ_2 decline in a similar fashion with source-detector distance by the power exponential function,while the value of a declines linearly.
文摘Water is an important component in plant cells with plant aquaporin being the major protein for water transport in and between plant cells.As a subfamily of plant aquaporins,the plasma membrane intrinsic proteins（PIPs） located in the plasma membrane are classic,high water,selective channel proteins.This paper focuses on recent advances in the molecular biology of PIPs concerning structural characteristics,biological function,and a regulation mechanism.PIPs possess two highly conserved domains:GGGANXXXXGY and TGI/TNPARSL/FGAAI/VI/VFWF/YN.PIPs can also be divided into two phylogenetic subgroups named PIP1 and PIP2.PIP1 possesses longer N terminal sequences and shorter C terminal sequences than PIP2 with conserved amino acid sequences respectively.Studies of transgenic plants and expression in Xenopus oocytes cells indicate that PIPs not only may facilitate transport of water and small neutral solutes like CO<sub>2</sub> and glycerin,but they also possess many physiological functions. The functions of plant aquaporins are regulated by many factors including post-translational modification,heteromerization,pH value,and divalent cations.These results indicated that PIPs act as a pivotal role in water and small neutral solutes transport in plants.
