The design and development of a cryogenic Ultra-Low-Noise Signal Amplification (ULNA) and detection system for spectroscopy of ultra-cold systems are reported here for the operation in the 0.5 - 4 GHz spectrum of freq...The design and development of a cryogenic Ultra-Low-Noise Signal Amplification (ULNA) and detection system for spectroscopy of ultra-cold systems are reported here for the operation in the 0.5 - 4 GHz spectrum of frequencies (the “L” and “S” microwave bands). The design is suitable for weak RF signal detection and spectroscopy from ultra-cold systems confined in cryogenic RF cavities, as entailed in a number of physics, physical chemistry and analytical chemistry applications, such as NMR/NQR/EPR and microwave spectroscopy, Paul traps, Bose-Einstein Condensates (BEC’s) and cavity Quantum Electrodynamics (cQED). Using a generic Low-Noise Amplifier (LNA) architecture for a GaAs enhancement mode High-Electron Mobility FET device, our design has especially been devised for scientific applications where ultra-low-noise amplification systems are sought to amplify and detect weak RF signals under various conditions and environments, including cryogenic temperatures, with the least possible noise susceptibility. The amplifier offers a 16 dB gain and a 0.8 dB noise figure at 2.5 GHz, while operating at room temperature, which can improve significantly at low temperatures. Both dc and RF outputs are provided by the amplifier to integrate it in a closed-loop or continuous-wave spectroscopy system or connect it to a variety of instruments, a factor which is lacking in commercial LNA devices. Following the amplification stage, the RF signal detection is carried out with the help of a post-amplifier and detection system based upon a set of Zero-Bias Schottky Barrier Diodes (ZBD’s) and a high-precision ultra-low noise jFET operational amplifier. The scheme offers unique benefits of sensitive detection and very-low noise amplification for measuring extremely weak on-resonance signals with substantial low- noise response and excellent stability while eliminating complicated and expensive heterodyne schemes. The LNA stage is fully capable to be a part of low-temperature experiments while being operated in cryogenic conditions down to about 500 mK.展开更多
When ultra-thin graphite intercalation compounds（GICs） are deposited on the SiO2/Si substrate, it is found that their colors are dependent on the thickness of GIC flakes. The sample colors of ultrathin GIC flakes ca...When ultra-thin graphite intercalation compounds（GICs） are deposited on the SiO2/Si substrate, it is found that their colors are dependent on the thickness of GIC flakes. The sample colors of ultrathin GIC flakes can no longer provide qualitative information on the stage index. Here, multi-wavelength Raman spectroscopy is thus applied to study the doping inhomogeneity and staging of ultra-thin GICs by FeCl3 intercalation. The G band intensity of stage-1 GIC flakes is strongly enhanced by 532-nm laser excitation, while that of stage-2 and stage-3 flakes exhibits strong intensity enhancement for 785-nm laser excitation. The near-infrared lasers are suggested to probe the doping inhomogeneity and staging of ultra-thin GIC flakes.展开更多
This paper briefly summarizes the development of magnetic resonance imaging and spectroscopy in medicine.Aspects of magnetic resonancephysics and-technology relevant at ultra-high magnetic fields as well as current li...This paper briefly summarizes the development of magnetic resonance imaging and spectroscopy in medicine.Aspects of magnetic resonancephysics and-technology relevant at ultra-high magnetic fields as well as current limitations are highlighted.Based on the first promising studies,potential clinical applications at 7 Tesla are suggested.Other aims are to stimulate awareness of the potential of ultra-high field magnetic resonance and to stimulate active participation in much needed basic or clinical research at 7 Tesla or higher.展开更多
蛋壳品质对蛋品孵化、贮存和运输均有重要影响。为了探索近红外光谱技术快速检测蛋壳品质的方法,该文在鸡蛋蛋壳品质指标相关性分析的基础上进行了蛋壳品质的近红外光谱检测分析,研究比较了不同建模方法、不同光谱预处理方法和不同波段...蛋壳品质对蛋品孵化、贮存和运输均有重要影响。为了探索近红外光谱技术快速检测蛋壳品质的方法,该文在鸡蛋蛋壳品质指标相关性分析的基础上进行了蛋壳品质的近红外光谱检测分析,研究比较了不同建模方法、不同光谱预处理方法和不同波段范围对预测结果的影响。结果表明:在5段特征波长范围内建立的经过多元散射校正的偏最小二乘回归(PLSR,partial least squares regression)模型对蛋壳强度的预测结果最好,相关系数r为0.86,校正、预测均方根误差分别为4.42、7.53N;同时蛋壳百分比(蛋壳质量/蛋质量)的PLSR模型的相关系数r为0.92,校正、预测误差分别为0.313%、0.529%;蛋壳厚度的PLSR模型的相关系数r为0.81,校正、预测误差分别为0.0176、0.0234mm。研究结果表明应用近红外光谱技术预测蛋壳品质是可行的,为蛋壳品质的快速无损检测提供了一种新的方法。展开更多
采用荧光光谱、紫外-可见光谱研究了有/无金属Zn2+存在下甲基百里酚蓝(MTB)与牛血清白蛋白(BSA)的相互作用.实验结果表明,无论Zn2+离子存在与否,MTB与BSA之间均为一形成复合物的静态猝灭过程.根据Stern-Volmer方程和Lineweaver-Burk方...采用荧光光谱、紫外-可见光谱研究了有/无金属Zn2+存在下甲基百里酚蓝(MTB)与牛血清白蛋白(BSA)的相互作用.实验结果表明,无论Zn2+离子存在与否,MTB与BSA之间均为一形成复合物的静态猝灭过程.根据Stern-Volmer方程和Lineweaver-Burk方程求出了其结合常数与热力学参数,发现Zn2+离子存在时,MTB与BSA间的作用力由静电力转为氢键和Van der Waals力作用为主,认为金属Zn2+以"离子架桥"的方式参与MTB与BSA的结合过程,从而ΔH对ΔG的贡献增大.展开更多
文摘The design and development of a cryogenic Ultra-Low-Noise Signal Amplification (ULNA) and detection system for spectroscopy of ultra-cold systems are reported here for the operation in the 0.5 - 4 GHz spectrum of frequencies (the “L” and “S” microwave bands). The design is suitable for weak RF signal detection and spectroscopy from ultra-cold systems confined in cryogenic RF cavities, as entailed in a number of physics, physical chemistry and analytical chemistry applications, such as NMR/NQR/EPR and microwave spectroscopy, Paul traps, Bose-Einstein Condensates (BEC’s) and cavity Quantum Electrodynamics (cQED). Using a generic Low-Noise Amplifier (LNA) architecture for a GaAs enhancement mode High-Electron Mobility FET device, our design has especially been devised for scientific applications where ultra-low-noise amplification systems are sought to amplify and detect weak RF signals under various conditions and environments, including cryogenic temperatures, with the least possible noise susceptibility. The amplifier offers a 16 dB gain and a 0.8 dB noise figure at 2.5 GHz, while operating at room temperature, which can improve significantly at low temperatures. Both dc and RF outputs are provided by the amplifier to integrate it in a closed-loop or continuous-wave spectroscopy system or connect it to a variety of instruments, a factor which is lacking in commercial LNA devices. Following the amplification stage, the RF signal detection is carried out with the help of a post-amplifier and detection system based upon a set of Zero-Bias Schottky Barrier Diodes (ZBD’s) and a high-precision ultra-low noise jFET operational amplifier. The scheme offers unique benefits of sensitive detection and very-low noise amplification for measuring extremely weak on-resonance signals with substantial low- noise response and excellent stability while eliminating complicated and expensive heterodyne schemes. The LNA stage is fully capable to be a part of low-temperature experiments while being operated in cryogenic conditions down to about 500 mK.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11225421,11474277,and 11434010)
文摘When ultra-thin graphite intercalation compounds（GICs） are deposited on the SiO2/Si substrate, it is found that their colors are dependent on the thickness of GIC flakes. The sample colors of ultrathin GIC flakes can no longer provide qualitative information on the stage index. Here, multi-wavelength Raman spectroscopy is thus applied to study the doping inhomogeneity and staging of ultra-thin GICs by FeCl3 intercalation. The G band intensity of stage-1 GIC flakes is strongly enhanced by 532-nm laser excitation, while that of stage-2 and stage-3 flakes exhibits strong intensity enhancement for 785-nm laser excitation. The near-infrared lasers are suggested to probe the doping inhomogeneity and staging of ultra-thin GIC flakes.
文摘This paper briefly summarizes the development of magnetic resonance imaging and spectroscopy in medicine.Aspects of magnetic resonancephysics and-technology relevant at ultra-high magnetic fields as well as current limitations are highlighted.Based on the first promising studies,potential clinical applications at 7 Tesla are suggested.Other aims are to stimulate awareness of the potential of ultra-high field magnetic resonance and to stimulate active participation in much needed basic or clinical research at 7 Tesla or higher.
文摘蛋壳品质对蛋品孵化、贮存和运输均有重要影响。为了探索近红外光谱技术快速检测蛋壳品质的方法,该文在鸡蛋蛋壳品质指标相关性分析的基础上进行了蛋壳品质的近红外光谱检测分析,研究比较了不同建模方法、不同光谱预处理方法和不同波段范围对预测结果的影响。结果表明:在5段特征波长范围内建立的经过多元散射校正的偏最小二乘回归(PLSR,partial least squares regression)模型对蛋壳强度的预测结果最好,相关系数r为0.86,校正、预测均方根误差分别为4.42、7.53N;同时蛋壳百分比(蛋壳质量/蛋质量)的PLSR模型的相关系数r为0.92,校正、预测误差分别为0.313%、0.529%;蛋壳厚度的PLSR模型的相关系数r为0.81,校正、预测误差分别为0.0176、0.0234mm。研究结果表明应用近红外光谱技术预测蛋壳品质是可行的,为蛋壳品质的快速无损检测提供了一种新的方法。
文摘采用荧光光谱、紫外-可见光谱研究了有/无金属Zn2+存在下甲基百里酚蓝(MTB)与牛血清白蛋白(BSA)的相互作用.实验结果表明,无论Zn2+离子存在与否,MTB与BSA之间均为一形成复合物的静态猝灭过程.根据Stern-Volmer方程和Lineweaver-Burk方程求出了其结合常数与热力学参数,发现Zn2+离子存在时,MTB与BSA间的作用力由静电力转为氢键和Van der Waals力作用为主,认为金属Zn2+以"离子架桥"的方式参与MTB与BSA的结合过程,从而ΔH对ΔG的贡献增大.
