In this paper, we demonstrate a spin-controlled directional launching of surface plasmons at the subwavelength scale.Based on the principle of optical spin＇s effect for the geometric phase of light, the nanostructure...In this paper, we demonstrate a spin-controlled directional launching of surface plasmons at the subwavelength scale.Based on the principle of optical spin＇s effect for the geometric phase of light, the nanostructures were designed. The inclination of the structures decides the spin-related geometric phase and their relative positions decide the distance-related phase. Hence, the propagation direction of the generated surface plasmon polaritons（SPPs） can be controlled by the spin of photons. Numerical simulations by the finite difference time domain（FDTD） method have verified our theoretical prediction. Our structure is fabricated on the Au film by using a focused ion beam etching technique. The total size of the surface plasmon polariton（SPP） launcher is 320 nm by 180 nm. The observation of the SPP launching by using scanning near-field optical microscopy is in agreement with our theory and simulations. This result may provide a new way of spin-controlled directional launching of SPP.展开更多
Site-directed spin-labeling with continuous wave electron paramagnetic resonance spectroscopy was used to monitor autoproteolysis of HIV-1 protease, an enzyme essential for viral maturation. Two protein constructs wer...Site-directed spin-labeling with continuous wave electron paramagnetic resonance spectroscopy was used to monitor autoproteolysis of HIV-1 protease, an enzyme essential for viral maturation. Two protein constructs were examined, namely subtype F and the circulating recombinant form CRF01_A/E. As the protease undergoes self-cleavage, protein unfolds and small peptide fragments containing the spin label are generated, which collectively give rise to a sharp spectral component that is easily discernable in the high-field resonance line in the EPR spectrum. By monitoring the intensity of this spectral component over time, the autoproteolytic stability of each construct was characterized under various conditions. Data were collected for samples stored at 4 °C, 25 °C, and 37 °C, and on a subtype F HIV-1 protease sample stored at 25 °C and containing the FDA-approved protease inhibitor Tipranavir. As expected, the rate of autoproteolysis decreased as the storage temperature was lowered. Minimal autoproteolysis was seen for the sample that contained Tipranavir, providing direction for future spectroscopic studies of active protease samples. When compared to standard methods of monitoring protein degradation such as gel electrophoresis or chromatographic analyses, spin-labeling with CW EPR offers a facile, real-time, non-consuming way to monitor autoproteolysis or protein degradation. Additionally, mass spectrometry studies revealed that the N-termini of both constructs are sensitive to degradation and that the sites of specific autoproteolysis vary.展开更多
It is very difficult to directly spin the lignocellulose without pretreatment.Ionic liquids(ILs)are promising solvent to dissolve lignocellulose to prepare cellulose fiber.However,the degree of cellulose polymerizatio...It is very difficult to directly spin the lignocellulose without pretreatment.Ionic liquids(ILs)are promising solvent to dissolve lignocellulose to prepare cellulose fiber.However,the degree of cellulose polymerization(DP)is reduced when lignocellulose is dissolved in ILs,and the lignin removal rate is low.The elongation at break and tensile strength of the fibers obtained by spinning the lignocellulose dissolved in ILs are poor.In this paper,preparing cellulose fiber directly from lignocellulose based on dissolving corn stalk via[C4mim]Cl-L-arginine binary system is achieved.It shows that the removal rate of lignin can reach 92.35%and the purity of cellulose can reach 85.32%after corn stalk was dissolved at 150℃C for 11.5 h when the mass fraction of arginine is 2.5%.The elongation at break of fiber reached 10.12%and the tensile strength reached 420 MPa.It is mainly due to the fact that L-arginine not only inhibits the degradation of cellulose but also promotes the delignination.Without any pulping or pretreatment,preparing cellulose fibers via direct dissolution and extrusion may provide a simple and effective way to prepare many novel cellulose materials.展开更多
The crystal structures, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase Pr1-xTbxFe1.9 compounds are investigated in a temperature range between 5 K and 300 K. High resolution synchrotron x...The crystal structures, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase Pr1-xTbxFe1.9 compounds are investigated in a temperature range between 5 K and 300 K. High resolution synchrotron x-ray diffraction(XRD) analysis shows that different proportions of Tb in Pr1-xTbxFe1.9 alloys can result in different easy magnetization directions(EMD) below 70 K, i.e., [100] with x = 0.0, and [111] with x ≥ 0.1. This indicates Tb substitution can lead the EMD to change from [100] to [111] with x rising from 0.0 up to 0.1. The Tb substitution for Pr reduces the saturation magnetization Ms and the magnetostriction to their minimum value when x = 0.6, but it can increase low-field(0 ≤ H ≤9 kOe, the unit 1 Oe = 79.5775 A·m-1) magnetostriction when x = 0.8 and 1.0 at 5 K. This can be attributed to the larger magnetostriction of PrFe1.9 than that of TbFe1.9, as well as the decrease of the resulting anisotropy due to Tb substitution at low temperatures.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61176120,61378059,60977015,61422501,and 11374023)the National Basic Research Program of China(Grant Nos.2012CB933004 and 2015CB932403)Beijing Natural Science Foundation(Grant No.L140007)
文摘In this paper, we demonstrate a spin-controlled directional launching of surface plasmons at the subwavelength scale.Based on the principle of optical spin＇s effect for the geometric phase of light, the nanostructures were designed. The inclination of the structures decides the spin-related geometric phase and their relative positions decide the distance-related phase. Hence, the propagation direction of the generated surface plasmon polaritons（SPPs） can be controlled by the spin of photons. Numerical simulations by the finite difference time domain（FDTD） method have verified our theoretical prediction. Our structure is fabricated on the Au film by using a focused ion beam etching technique. The total size of the surface plasmon polariton（SPP） launcher is 320 nm by 180 nm. The observation of the SPP launching by using scanning near-field optical microscopy is in agreement with our theory and simulations. This result may provide a new way of spin-controlled directional launching of SPP.
文摘Site-directed spin-labeling with continuous wave electron paramagnetic resonance spectroscopy was used to monitor autoproteolysis of HIV-1 protease, an enzyme essential for viral maturation. Two protein constructs were examined, namely subtype F and the circulating recombinant form CRF01_A/E. As the protease undergoes self-cleavage, protein unfolds and small peptide fragments containing the spin label are generated, which collectively give rise to a sharp spectral component that is easily discernable in the high-field resonance line in the EPR spectrum. By monitoring the intensity of this spectral component over time, the autoproteolytic stability of each construct was characterized under various conditions. Data were collected for samples stored at 4 °C, 25 °C, and 37 °C, and on a subtype F HIV-1 protease sample stored at 25 °C and containing the FDA-approved protease inhibitor Tipranavir. As expected, the rate of autoproteolysis decreased as the storage temperature was lowered. Minimal autoproteolysis was seen for the sample that contained Tipranavir, providing direction for future spectroscopic studies of active protease samples. When compared to standard methods of monitoring protein degradation such as gel electrophoresis or chromatographic analyses, spin-labeling with CW EPR offers a facile, real-time, non-consuming way to monitor autoproteolysis or protein degradation. Additionally, mass spectrometry studies revealed that the N-termini of both constructs are sensitive to degradation and that the sites of specific autoproteolysis vary.
基金This research was financially supported by the National Natural Science Foundation of China(No.21878292,No.21606240,No.21878314)K.C.Wong Education Foundation(No.GJTD-2018-04)the Strategic Priority Research Program of Chinese Academy of Science(No.XDA21060300).
文摘It is very difficult to directly spin the lignocellulose without pretreatment.Ionic liquids(ILs)are promising solvent to dissolve lignocellulose to prepare cellulose fiber.However,the degree of cellulose polymerization(DP)is reduced when lignocellulose is dissolved in ILs,and the lignin removal rate is low.The elongation at break and tensile strength of the fibers obtained by spinning the lignocellulose dissolved in ILs are poor.In this paper,preparing cellulose fiber directly from lignocellulose based on dissolving corn stalk via[C4mim]Cl-L-arginine binary system is achieved.It shows that the removal rate of lignin can reach 92.35%and the purity of cellulose can reach 85.32%after corn stalk was dissolved at 150℃C for 11.5 h when the mass fraction of arginine is 2.5%.The elongation at break of fiber reached 10.12%and the tensile strength reached 420 MPa.It is mainly due to the fact that L-arginine not only inhibits the degradation of cellulose but also promotes the delignination.Without any pulping or pretreatment,preparing cellulose fibers via direct dissolution and extrusion may provide a simple and effective way to prepare many novel cellulose materials.
基金Project supported by the National Natural Science Foundation of China(Grant No.51901052)the Science Foundation of Guangxi Zhuang Autonomous Region,China(Grant No.2018GXNSFAA281294)
文摘The crystal structures, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase Pr1-xTbxFe1.9 compounds are investigated in a temperature range between 5 K and 300 K. High resolution synchrotron x-ray diffraction(XRD) analysis shows that different proportions of Tb in Pr1-xTbxFe1.9 alloys can result in different easy magnetization directions(EMD) below 70 K, i.e., [100] with x = 0.0, and [111] with x ≥ 0.1. This indicates Tb substitution can lead the EMD to change from [100] to [111] with x rising from 0.0 up to 0.1. The Tb substitution for Pr reduces the saturation magnetization Ms and the magnetostriction to their minimum value when x = 0.6, but it can increase low-field(0 ≤ H ≤9 kOe, the unit 1 Oe = 79.5775 A·m-1) magnetostriction when x = 0.8 and 1.0 at 5 K. This can be attributed to the larger magnetostriction of PrFe1.9 than that of TbFe1.9, as well as the decrease of the resulting anisotropy due to Tb substitution at low temperatures.
