Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates h...Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates has been elucidated by microscopy,the detailed dynamic properties of proteins/peptides during the LLPS process remain poorly characterized.Here,site-directed spin labeling-electron paramagnetic resonance(SDSL-EPR)spectroscopy was employed to characterize the dynamic properties of a minimal model LLPS system consisting of positively charged peptides and RNA.The degree of phase separation,indicated by broadening of the EPR spectrum of the spin-labeled peptide due to slow molecular tumbling,was monitored by EPR.In addition,three distinct populations with varying molecular motion during LLPS,featuring different spectral lineshapes,were identified.These populations included a fast motion component(Ⅰ),a slower motion component(Ⅱ)associated with peptides in the dispersed phase and an immobile component(Ⅲ)observed in the dense phase.With gradual titration of the peptides to RNA,the EPR spectrum gradually shifted,refiecting changes in the populations of the components.Together,SDSL-EPR method not only provides new insights into the dynamic behavior of biomolecules during LLPS,but also offers a sensitive method for biomolecular phase separation processes at the molecular level.展开更多
This work revisits the temperature dependence of^(1)H paramagnetic shift in nickelocene as a potential nuclear magnetic resonance(NMR)thermometer under fast magic angle spinning(MAS)rate.Surprisingly,an abnormal tempe...This work revisits the temperature dependence of^(1)H paramagnetic shift in nickelocene as a potential nuclear magnetic resonance(NMR)thermometer under fast magic angle spinning(MAS)rate.Surprisingly,an abnormal temperature dependence of^(1)H paramagnetic shift has been observed.In addition to a 1/T dependence term,a 1/T^(2)dependence term must be included to correctly describe the curvature behavior of the δ^(1)H-T correlation under fast MAS rate.展开更多
The formation and qualification of redox sites in transition metal oxides are always the active fields related to electronics, catalysis, sensors, and energy-storage units. In the present study, the temperature depend...The formation and qualification of redox sites in transition metal oxides are always the active fields related to electronics, catalysis, sensors, and energy-storage units. In the present study, the temperature dependence of thermal reduction of MoO3 was surveyed at the range of 350℃ to 750℃. Upon reduction, the formed redox species characterized by EPR spectroscopy are the MoVion and superoxide anion radical (O2-) when the reduction was induced at the optimal temperature of 300-350℃. When heating-up from 350℃, the EPR signals started to decline in amplitude. The signals in the range of 400-450℃ decreased to half of that at 350℃, and then to zero at ~600℃. Further treatment at even higher temperature or prolonged heating time at 500℃ caused more reduction and more free electrons were released to the MoO3 bulk, which results in a delocalized means similar to the antiferromagnetic coupling. These data herein are helpful to prepare and study the metal-oxide catalysts.展开更多
On account of excellent thermal physical properties, molten nitrates/nitrites salt has been widely employed in heat transfer and thermal storage industry, especially in concentrated solar power system. The thermal sta...On account of excellent thermal physical properties, molten nitrates/nitrites salt has been widely employed in heat transfer and thermal storage industry, especially in concentrated solar power system. The thermal stability study of molten nitrate/nitrite salt is of great importance for this system, and the decomposition mechanism is the most complicated part of it. The oxide species O2^2- and O2^- were considered as intermediates in molten KNO3-NaNO3 while hard to been detected in high temperature molten salt due to their trace concentration and low stability. In this work, the homemade in situ high temperature UV- Vis instrument and a commercial electron paramagnetic resonance were utilized to supply evidence for the formation of superoxide during a slow decomposition process of heat transfer salt （HTS, 53 wt% KNO3/40 wt% NaNO2/7 wt% NaNO3）. It is found that the superoxide is more easily generated from molten NaNO2 compared to NaNO3, and it has an absorption band at 420-440 nm in HTS which red shifts as temperature increases. The band is assigned to charge-transfer transition in NaO2 or KO2, responsible for the yellow color of the molten nitrate/nitrite salt. Furthermore, the UV absorption bands of molten NaNO2 and NANO3 are also obtained and compared with that of HTS.展开更多
Paramagnetic polymer microspheres were synthesized by the inverse suspension polymerizationmethod through polymerization of glycidyl methacrylate,ally glycidyl ether and methacrylamide onthe surface of silica‐coated ...Paramagnetic polymer microspheres were synthesized by the inverse suspension polymerizationmethod through polymerization of glycidyl methacrylate,ally glycidyl ether and methacrylamide onthe surface of silica‐coated Fe3O4nanoparticles using N,N’‐methylene‐bis(acrylamide)as across‐linking agent.Penicillin G acylase(PGA)was covalently immobilized on the surface of theparamagnetic microspheres by reacting the amino groups of the PGA molecules with the epoxygroups of the paramagnetic polymer microspheres.The effect of the SiO2coating and the amount ofparamagnetic Fe3O4nanoparticles on the initial activity and the operational stability of the immobilizedPGA was investigated.The results indicated that SiO2played an important role in the polymerization process and paramagnetic polymer microspheres with a SiO2‐coated Fe3O4nanoparticles mass content of7.5%are an optimal support material for PGA immobilization.Immobilized PGA on the paramagnetic polymer microspheres shows a high initial activity of430U/g(wet)and retains99%of its initial activity after recycling10times.Furthermore,immobilized PGA exhibits high thermal stability,pH stability and excellent reusability,which can be rapidly recycled by the aid of magnet.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.展开更多
This article studies the asymptotic behaviors of the solution for a stochastic hydrodynamical equation in Heisenberg paramagnet in a two-dimensional periodic domain. We obtain the existence of random attractors in H1.
Desiccation tolerance is a crucial characteristic for desert moss surviving in arid regions. Desiccation procedure always induces amphiphiles transferring from the polar cytoplasm into lipid bodies. The behavior of am...Desiccation tolerance is a crucial characteristic for desert moss surviving in arid regions. Desiccation procedure always induces amphiphiles transferring from the polar cytoplasm into lipid bodies. The behavior of amphiphiles transferring can contribute to the enhancement of desiccation tolerance and the reduction of plasma membrane integrity simultaneously. The effects of amphiphiles partitioning into the lipid phase during water loss has been studied for pollen and seeds using electron paramagnetic resonance （EPR） spectroscopy. However, desiccation-tolerant high plants occur among mosses, several angiosperms and higher plants seeds or pollens. They have different strategies for survival in dehydration and rehydration. A desiccation-tolerant moss Tortula desertorurn was used to investigate the behaviors of amphiphilic molecules during drying by spin label technology. There are small amount of amphiphilic probes partitioning into membrane during moss leaves dehydration, comparing with that in higher plants. Cytoplasm viscosity changed from 1.14 into glass state only dehydration less than 60 min. Moss leaves lost plasma membrane integrity slightly,from 0.115 to 0.237, occurred simultaneously with amphiphiles partition. The results showed the more advantages of mosses than higher plants in adapting fast dehydration. We propose that EPR spin label is feasible for studying the amphiphiles partitioning mechanisms in membrane protection and damage for desiccation-tolerant mosses.展开更多
Europium oxyhydroxide crystals were synthesized by the flux method. The as-grown crystals were transparent and had a plate-like shape with natural flat surfaces. The powder XRD data were refined by assuming a monoclin...Europium oxyhydroxide crystals were synthesized by the flux method. The as-grown crystals were transparent and had a plate-like shape with natural flat surfaces. The powder XRD data were refined by assuming a monoclinic structure of the space group P21/m and lattice parameters of a=0.4346 nm, b=0.3744 nm, c=0.6107 nm, and β=108.62°. The magnetic susceptibility of the EuOOH crystals exhibited typical Van Vleck temperature-independent paramagnetism below 120 K. The calculated susceptibility, based on Van Vleck＇s theory, agreed with the experimental data to some extent, with the coupling constant λ=458±10 K. The experimental results were in close agreement with the results calculated using a modified formula with λ=505±2 K and a constant term C=4.6×10^-4 emu/（mol·Oe）.展开更多
The electron paramagnetic resonance spectra of the chelate-based ionic liquid[C_(10)mim][Cu(F_6-acac)_3]in different solvents have been obtained at 120 K.It was found that the values of the^(63)Cu hyperfine coupling c...The electron paramagnetic resonance spectra of the chelate-based ionic liquid[C_(10)mim][Cu(F_6-acac)_3]in different solvents have been obtained at 120 K.It was found that the values of the^(63)Cu hyperfine coupling constants(A_(IL))of[C_(10)mim][Cu(F_6-acac)_3]in molecular solvents were from 116 to 180 Gauss.Moreover,the A_(IL)values in general ionic liquids are more complicated,and two sets of peaks can often be observed in their electron paramagnetic resonance spectra.Based on the Kamlet-Taft parameters,relative permittivity,the experimental results were discussed in terms of solvation effect and coordination of the solvents.展开更多
Deep-level defects in silicon carbide(SiC)are critical to the control of the performance of SiC electron devices.In this paper,deep-level defects in aluminumion-implanted 4H-SiC after high-temperature annealingwere st...Deep-level defects in silicon carbide(SiC)are critical to the control of the performance of SiC electron devices.In this paper,deep-level defects in aluminumion-implanted 4H-SiC after high-temperature annealingwere studied using electron paramagnetic resonance(EPR)spectroscopy at temperatures of 77 K and 123 K under different illumination conditions.Results showed that the main defect in aluminum ion-implanted 4H-SiC was the positively charged carbon vacancy(VC+),and the higher the doping concentration was,the higher was the concentration of VC+.Itwas found that the type of material defectwas independent of the doping concentration,although more VC+defects were detected during photoexcitation and at lower temperatures.These results should be helpful in the fundamental research of p-type 4H-SiC fabrication in accordance with functional device development.展开更多
CdGd2 （WO4）4 -δ single crystal was grown using the Czochralski＇s method. The crystal structure was tetragonal seheelite with lattice parameters a = b = 0.5203 nm and c = 1. 1359 nm. There were vacancies of （WO4）...CdGd2 （WO4）4 -δ single crystal was grown using the Czochralski＇s method. The crystal structure was tetragonal seheelite with lattice parameters a = b = 0.5203 nm and c = 1. 1359 nm. There were vacancies of （WO4）^2- , therefore, there were some Gd^2＋ ions. Langevin paramagnetism and anisotropy were observed from the δ-T curves at room temperature. The susceptibility X//was 3.5018×10^-3, and X⊥ was 3.4403× 10^-2. The anisotropy was also observed in the electron spin resonance （ESR） experiments. The anisotropic Land6 factors were g//= 2. 1333 and g~ = 2. 8411. The direction of easy magnetization was in the α-b plane. Anisotropic paramagnetic Curie constants C//and C⊥ were not only related to macroscopic a that was observed through the experiment, but were also related to J⊥ and J//, which were the microscopic quantum numbers of the Gd^2＋ and Gd^3｜ ions. Based on the detailed analyses, the proportion of 36.8% of Gd^3＋ ions to 63.2% of Gd^2＋ ions in the Gd ions of the CdGd2（WO4）4-δ crystal was calculated, and δ was 0.638 in the single crystal.展开更多
The finite-temperature Pauli paramagnetic susceptibility of a three-dimensional ideal anyon gas obeying Haldane fractional exclusion statistics is studied analytically.Different from the result of an ideal Fermi gas,t...The finite-temperature Pauli paramagnetic susceptibility of a three-dimensional ideal anyon gas obeying Haldane fractional exclusion statistics is studied analytically.Different from the result of an ideal Fermi gas,the susceptibility of an ideal anyon gas depends on a statistical factor g in Haldane statistics model.The low-temperature and high-temperature behaviors of the susceptibility are investigated in detail.The Pauli paramagnetic susceptibility of the two-dimensional ideal anyons is also derived.It is found that the reciprocal of the susceptibility has the similar factorizable property which is exhibited in some thermodynamic quantities in two dimensions.展开更多
The bauxite mineral obtained from Araku, Vishakapatnam district of Andhra Pradesh, India is used in the present work. Structural characterization was performed by X-ray diffraction (XRD). The mineral was found to be g...The bauxite mineral obtained from Araku, Vishakapatnam district of Andhra Pradesh, India is used in the present work. Structural characterization was performed by X-ray diffraction (XRD). The mineral was found to be gibbsite in phase. The transitional metal ions present were investigated using electron paramagnetic resonance (EPR) and optical absorption spectra. The EPR results suggest that Fe3+ has replaced Al3+ in the unit cell of bauxite. The optical absorption spectrum is due to Fe3+ which indicates that it is in distorted octahedral environment. The near-infrared (NIR) spectrum is due to water fundamentals and combination overtones, which confirm the formula of the compound. The impurities in the mineral are identified using spectroscopic techniques.展开更多
Quartz grains in contact with uranium-bearing minerals or fluids are characterized by natural radiation-induced paramagnetic defects （e. g. , oxygen vacancy centers, silicon vacancy centers, and peroxy radicals）, wh...Quartz grains in contact with uranium-bearing minerals or fluids are characterized by natural radiation-induced paramagnetic defects （e. g. , oxygen vacancy centers, silicon vacancy centers, and peroxy radicals）, which are amenable to study by electron paramagnetic resonance （EPR） spectroscopy. These natural radiation-induced paramagnetic defects, except for the oxygen vacancy centers, in quartz are concentrated in narrow bands penetrated by α particles： （1） in halos around U- and Th-bearing mineral inclusions and （2） in outer rims or along fractures. The second type of occurrence provides information about uranium mineralization or remobilization （i. e. , sources of uranium, timing of mineralization or remobilization, pathways of uranium-bearing fluids）. It can also be used to evaluate sedimentary basins for potential of uranium mineralization. In particular, the peroxy radicals are stable up to 800℃ and, therefore, are useful for evaluating metasedimentary rocks （e. g. , Paleoproterozoic metasedimentary sequences in the central zone of the North China craton）. EPR study of the Changcheng Series can focus on quartz from the sediment-basement unconformity and faults to determine the presence and types of natural radiation-induced paramagnetic defects, with which to identify and prioritize uranium anomalies. Other potential applications of natural radiation-induced paramagnetic defects in quartz include uranium-bearing hydrocarbon deposits in sedimentary basins. For example, the Junggar, Ordos, and Tarim basins in northwestern China all contain important oil and natural gas fields and are well known for elevated uranium concentrations, including economic sandstone-hosted uranium deposits. Therefore, systematic studies on the distribution of natural radiation-induced paramagnetic defects in quartz from host sedimentary sequences are expected to provide information about the migration of oil and natural gas in those basins.展开更多
FAMn:PbI<sub>3</sub> perovskite films were synthesized and probed mainly through electron spin resonance (ESR) spectroscopy. FAMn:PbI<sub>3</sub> with low (~1%) Mn concentration showed a hyperf...FAMn:PbI<sub>3</sub> perovskite films were synthesized and probed mainly through electron spin resonance (ESR) spectroscopy. FAMn:PbI<sub>3</sub> with low (~1%) Mn concentration showed a hyperfine sextet line originated from Mn<sup>++</sup> ions. FAMn:PbI<sub>3</sub> with high (10%) Mn concentration showed broad resonance (~500 G peak-to-peak linewidth). However, after bombardment of FAMn:PbI<sub>3</sub> with high Mn concentration by focused ion beams (FIB), a sharp ESR peak appeared. The peak-to-peak linewidth (ΔH<sub>pp</sub>) was ~8 G regardless of the temperature. The FIB-induced defect showed Curie behavior at low temperatures (5 K - 50 K), which indicates the presence of localized electrons at the defect sites at low temperatures. The g-value increased from g = 2.0002 to 2.0016 as the temperature increased from 5 K to 50 K. Together with the ongoing search for electron spin echo (ESE), this could potentially provide a platform for realizing magnetic bits, information storage, and increased manipulation speed.展开更多
Zn0.98Cu0.020 powders are prepared by the sol-gel method. A small number of CuO impurity phases are observed by the x-ray diffraction, indicating the solubility of Cu in ZnO is less than 2 at.%. The Zn0.98Cu0.020 powd...Zn0.98Cu0.020 powders are prepared by the sol-gel method. A small number of CuO impurity phases are observed by the x-ray diffraction, indicating the solubility of Cu in ZnO is less than 2 at.%. The Zn0.98Cu0.020 powders exhibit diamagnetism at 300 K and paramagnetism at 5 K. After subtracting the diamagnetic contribution of ZnO bulk and the paramagnetic contribution of defects, Cu ions exhibit weak paramagnetism. By codoping Cu with Co or Mn in ZnO, only paramagnetism is observed at room temperature.展开更多
Ultrasmall near-monodisperse Ba2ErF7 nanocrystals with average crystal size 9.6 nm were synthesized with solvothermal method. The X-ray diffraction （XRD） and transmission electron microscopy （TEM） assays reveal th...Ultrasmall near-monodisperse Ba2ErF7 nanocrystals with average crystal size 9.6 nm were synthesized with solvothermal method. The X-ray diffraction （XRD） and transmission electron microscopy （TEM） assays reveal that the as-synthesized Ba2ErF7 nanocrystals are of the cubic structure with the cell parameter of 5.943 A, instead of the reported orthorhombic and tetragonal structure. Two emission bands originated from 2Hwj4H3/2 → 4F5/2 and 4F9/2 ----＋ 4115,2 of Er3＋ can be observed under a 980 nm laser excitation. The magnetic mass susceptibility of the as-synthesized BazErF7 nanocrystals reaches 4.293 × 10-5 emu g-1 Oe-1.展开更多
Magnetic forces are widely used to influence the properties of materials.The main focus of recent investigations concerning oxide melts mainly was on the use of Lorentz forces either to mix glass melts to avoid an imp...Magnetic forces are widely used to influence the properties of materials.The main focus of recent investigations concerning oxide melts mainly was on the use of Lorentz forces either to mix glass melts to avoid an improved inhomogeneity or to measure the flow of these melts.In the last years also the use of magnetic gradient forces has become an object of research mainly in electrochemistry.On the basis of preliminary investigations the influence of these forces on paramagnetic ions such as Fe;in oxide melts is investigated to examine the potential of magnetic gradient forces as a tool to create defined gradient materials.展开更多
Electron paramagnetic resonance （EPR） and optical absorption studies were carried out at room temperature on copper doped mixed alkali cadmium phosphate （LiNaCdP） glasses to understand the nature and symmetry of d...Electron paramagnetic resonance （EPR） and optical absorption studies were carried out at room temperature on copper doped mixed alkali cadmium phosphate （LiNaCdP） glasses to understand the nature and symmetry of dopant. Three samples with varying concentrations of alkali ions have been prepared. The spin Harniltonian parameters obtained from room temperature EPR spectra are： gli=2.437, 9⊥=2.096, A‖=117×10-4 cm-1, A⊥=26×10-4 cm-1 for LiNaCdP1, g‖=2.441, g⊥=2.088, A‖=121×10-4 cm-1, A⊥=25×10-4 cm-1 for LiNaCdP2and g‖=2.433,g⊥=2.096, A‖=125×10 4cm-1, A⊥=32×10-4cm-1 for LiNaCdP3. TheseEPR results indicate that the dopant Cu2＋ ion enters the glass matrix into a tetragonally elongated octahedral site. The bonding parameters evaluated by correlating optical and EPR data suggest that bonding between the central metal ion and ligands is partially covalent. The mixed alkali effect in cadmium phosphate glasses was reported.展开更多
A simple theoretical method is introduced for studying the interrelation between electronic and molecular structures.By diagonalizing the 120 × 120 complete energy matrices,the relationships between zero-field sp...A simple theoretical method is introduced for studying the interrelation between electronic and molecular structures.By diagonalizing the 120 × 120 complete energy matrices,the relationships between zero-field splitting （ZFS） parameter D and local distortion parameter △θ for Cr^3＋ ions doped,separately,in α- and β- alums are investigated.Our results indicate that there exists an approximately linear relationship between D and △θ in a temperature range 4.2-297 K and the signs of D and △θ are opposite to each other.Moreover,in order to understand the contribution of spin-orbit coupling coefficient ζ to ZFS parameter D,the relation between D and ζ is also discussed.展开更多
基金supported by the National Natural Science Foundation of China(No.21927814)the National Key Research and Development Program of China(Nos.2019YFA0405600,2019YFA0706900,2021YFA1200104,2022YFC3400500)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB0540200,XDB37040201)Plans for Major Provincial Science&Technology Projects(No.202303a07020004)the Youth Innovation Promotion Association,CAS(No.2022455)。
文摘Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates has been elucidated by microscopy,the detailed dynamic properties of proteins/peptides during the LLPS process remain poorly characterized.Here,site-directed spin labeling-electron paramagnetic resonance(SDSL-EPR)spectroscopy was employed to characterize the dynamic properties of a minimal model LLPS system consisting of positively charged peptides and RNA.The degree of phase separation,indicated by broadening of the EPR spectrum of the spin-labeled peptide due to slow molecular tumbling,was monitored by EPR.In addition,three distinct populations with varying molecular motion during LLPS,featuring different spectral lineshapes,were identified.These populations included a fast motion component(Ⅰ),a slower motion component(Ⅱ)associated with peptides in the dispersed phase and an immobile component(Ⅲ)observed in the dense phase.With gradual titration of the peptides to RNA,the EPR spectrum gradually shifted,refiecting changes in the populations of the components.Together,SDSL-EPR method not only provides new insights into the dynamic behavior of biomolecules during LLPS,but also offers a sensitive method for biomolecular phase separation processes at the molecular level.
基金supported by grants from the National Natural Science Foundation of China(Nos.22172049,22272055).
文摘This work revisits the temperature dependence of^(1)H paramagnetic shift in nickelocene as a potential nuclear magnetic resonance(NMR)thermometer under fast magic angle spinning(MAS)rate.Surprisingly,an abnormal temperature dependence of^(1)H paramagnetic shift has been observed.In addition to a 1/T dependence term,a 1/T^(2)dependence term must be included to correctly describe the curvature behavior of the δ^(1)H-T correlation under fast MAS rate.
基金supported by the National Key R&D Program of China(No.2018YFA0306600)AnHui Initiative in Quantum Information Technologies(No.AHY050000)
文摘The formation and qualification of redox sites in transition metal oxides are always the active fields related to electronics, catalysis, sensors, and energy-storage units. In the present study, the temperature dependence of thermal reduction of MoO3 was surveyed at the range of 350℃ to 750℃. Upon reduction, the formed redox species characterized by EPR spectroscopy are the MoVion and superoxide anion radical (O2-) when the reduction was induced at the optimal temperature of 300-350℃. When heating-up from 350℃, the EPR signals started to decline in amplitude. The signals in the range of 400-450℃ decreased to half of that at 350℃, and then to zero at ~600℃. Further treatment at even higher temperature or prolonged heating time at 500℃ caused more reduction and more free electrons were released to the MoO3 bulk, which results in a delocalized means similar to the antiferromagnetic coupling. These data herein are helpful to prepare and study the metal-oxide catalysts.
基金This work was supported by the ＂Strategic Priority Research Program, TMSR＂ of the Chinese Academy of Sciences （No.XD02002400）, the National Natural Science Foundation of China （No.51506214）, the Hundred Talents Program, CAS and Shanghai Pujiang Program.
文摘On account of excellent thermal physical properties, molten nitrates/nitrites salt has been widely employed in heat transfer and thermal storage industry, especially in concentrated solar power system. The thermal stability study of molten nitrate/nitrite salt is of great importance for this system, and the decomposition mechanism is the most complicated part of it. The oxide species O2^2- and O2^- were considered as intermediates in molten KNO3-NaNO3 while hard to been detected in high temperature molten salt due to their trace concentration and low stability. In this work, the homemade in situ high temperature UV- Vis instrument and a commercial electron paramagnetic resonance were utilized to supply evidence for the formation of superoxide during a slow decomposition process of heat transfer salt （HTS, 53 wt% KNO3/40 wt% NaNO2/7 wt% NaNO3）. It is found that the superoxide is more easily generated from molten NaNO2 compared to NaNO3, and it has an absorption band at 420-440 nm in HTS which red shifts as temperature increases. The band is assigned to charge-transfer transition in NaO2 or KO2, responsible for the yellow color of the molten nitrate/nitrite salt. Furthermore, the UV absorption bands of molten NaNO2 and NANO3 are also obtained and compared with that of HTS.
基金This work was supported by the National Natural Science Foundation of China(91545103)Shu Guang Project of Shanghai Municipal Education Commission and Shanghai Education Development Foundation(10SG30)the Fundamental Research Funds for the Central Universities(222201717003)~~
文摘Paramagnetic polymer microspheres were synthesized by the inverse suspension polymerizationmethod through polymerization of glycidyl methacrylate,ally glycidyl ether and methacrylamide onthe surface of silica‐coated Fe3O4nanoparticles using N,N’‐methylene‐bis(acrylamide)as across‐linking agent.Penicillin G acylase(PGA)was covalently immobilized on the surface of theparamagnetic microspheres by reacting the amino groups of the PGA molecules with the epoxygroups of the paramagnetic polymer microspheres.The effect of the SiO2coating and the amount ofparamagnetic Fe3O4nanoparticles on the initial activity and the operational stability of the immobilizedPGA was investigated.The results indicated that SiO2played an important role in the polymerization process and paramagnetic polymer microspheres with a SiO2‐coated Fe3O4nanoparticles mass content of7.5%are an optimal support material for PGA immobilization.Immobilized PGA on the paramagnetic polymer microspheres shows a high initial activity of430U/g(wet)and retains99%of its initial activity after recycling10times.Furthermore,immobilized PGA exhibits high thermal stability,pH stability and excellent reusability,which can be rapidly recycled by the aid of magnet.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.
文摘This article studies the asymptotic behaviors of the solution for a stochastic hydrodynamical equation in Heisenberg paramagnet in a two-dimensional periodic domain. We obtain the existence of random attractors in H1.
基金the National Natural Science Foundation of China （No.30371002）.
文摘Desiccation tolerance is a crucial characteristic for desert moss surviving in arid regions. Desiccation procedure always induces amphiphiles transferring from the polar cytoplasm into lipid bodies. The behavior of amphiphiles transferring can contribute to the enhancement of desiccation tolerance and the reduction of plasma membrane integrity simultaneously. The effects of amphiphiles partitioning into the lipid phase during water loss has been studied for pollen and seeds using electron paramagnetic resonance （EPR） spectroscopy. However, desiccation-tolerant high plants occur among mosses, several angiosperms and higher plants seeds or pollens. They have different strategies for survival in dehydration and rehydration. A desiccation-tolerant moss Tortula desertorurn was used to investigate the behaviors of amphiphilic molecules during drying by spin label technology. There are small amount of amphiphilic probes partitioning into membrane during moss leaves dehydration, comparing with that in higher plants. Cytoplasm viscosity changed from 1.14 into glass state only dehydration less than 60 min. Moss leaves lost plasma membrane integrity slightly,from 0.115 to 0.237, occurred simultaneously with amphiphiles partition. The results showed the more advantages of mosses than higher plants in adapting fast dehydration. We propose that EPR spin label is feasible for studying the amphiphiles partitioning mechanisms in membrane protection and damage for desiccation-tolerant mosses.
基金Project supported by Japan Society for the Promotion of Science(JSPS)KAKENHI Grants(21560696,24560827)
文摘Europium oxyhydroxide crystals were synthesized by the flux method. The as-grown crystals were transparent and had a plate-like shape with natural flat surfaces. The powder XRD data were refined by assuming a monoclinic structure of the space group P21/m and lattice parameters of a=0.4346 nm, b=0.3744 nm, c=0.6107 nm, and β=108.62°. The magnetic susceptibility of the EuOOH crystals exhibited typical Van Vleck temperature-independent paramagnetism below 120 K. The calculated susceptibility, based on Van Vleck＇s theory, agreed with the experimental data to some extent, with the coupling constant λ=458±10 K. The experimental results were in close agreement with the results calculated using a modified formula with λ=505±2 K and a constant term C=4.6×10^-4 emu/（mol·Oe）.
基金supported by the National Natural Science Foundation,China(No.21573196)the Fundamental Research Funds for the Central Universities,Chinathe National High Technology Research and the National Natural Science Foundation,China(No.22073081)。
文摘The electron paramagnetic resonance spectra of the chelate-based ionic liquid[C_(10)mim][Cu(F_6-acac)_3]in different solvents have been obtained at 120 K.It was found that the values of the^(63)Cu hyperfine coupling constants(A_(IL))of[C_(10)mim][Cu(F_6-acac)_3]in molecular solvents were from 116 to 180 Gauss.Moreover,the A_(IL)values in general ionic liquids are more complicated,and two sets of peaks can often be observed in their electron paramagnetic resonance spectra.Based on the Kamlet-Taft parameters,relative permittivity,the experimental results were discussed in terms of solvation effect and coordination of the solvents.
基金supported by the National Natural Science Foundation of China (No. 51575389, 51761135106)the National Key Research and Development Program of China (2016YFB1102203)+2 种基金the State Key Laboratory of Precision Measurement Technology and Instruments (Pilt1705)the ‘111’ Project by the State Administration of Foreign Experts Affairsthe Ministry of Education of China (Grant No. B07014)
文摘Deep-level defects in silicon carbide(SiC)are critical to the control of the performance of SiC electron devices.In this paper,deep-level defects in aluminumion-implanted 4H-SiC after high-temperature annealingwere studied using electron paramagnetic resonance(EPR)spectroscopy at temperatures of 77 K and 123 K under different illumination conditions.Results showed that the main defect in aluminum ion-implanted 4H-SiC was the positively charged carbon vacancy(VC+),and the higher the doping concentration was,the higher was the concentration of VC+.Itwas found that the type of material defectwas independent of the doping concentration,although more VC+defects were detected during photoexcitation and at lower temperatures.These results should be helpful in the fundamental research of p-type 4H-SiC fabrication in accordance with functional device development.
基金Project supported by the National Natural Science Foundation of China (69977005)
文摘CdGd2 （WO4）4 -δ single crystal was grown using the Czochralski＇s method. The crystal structure was tetragonal seheelite with lattice parameters a = b = 0.5203 nm and c = 1. 1359 nm. There were vacancies of （WO4）^2- , therefore, there were some Gd^2＋ ions. Langevin paramagnetism and anisotropy were observed from the δ-T curves at room temperature. The susceptibility X//was 3.5018×10^-3, and X⊥ was 3.4403× 10^-2. The anisotropy was also observed in the electron spin resonance （ESR） experiments. The anisotropic Land6 factors were g//= 2. 1333 and g~ = 2. 8411. The direction of easy magnetization was in the α-b plane. Anisotropic paramagnetic Curie constants C//and C⊥ were not only related to macroscopic a that was observed through the experiment, but were also related to J⊥ and J//, which were the microscopic quantum numbers of the Gd^2＋ and Gd^3｜ ions. Based on the detailed analyses, the proportion of 36.8% of Gd^3＋ ions to 63.2% of Gd^2＋ ions in the Gd ions of the CdGd2（WO4）4-δ crystal was calculated, and δ was 0.638 in the single crystal.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11275082 and 11178001
文摘The finite-temperature Pauli paramagnetic susceptibility of a three-dimensional ideal anyon gas obeying Haldane fractional exclusion statistics is studied analytically.Different from the result of an ideal Fermi gas,the susceptibility of an ideal anyon gas depends on a statistical factor g in Haldane statistics model.The low-temperature and high-temperature behaviors of the susceptibility are investigated in detail.The Pauli paramagnetic susceptibility of the two-dimensional ideal anyons is also derived.It is found that the reciprocal of the susceptibility has the similar factorizable property which is exhibited in some thermodynamic quantities in two dimensions.
文摘The bauxite mineral obtained from Araku, Vishakapatnam district of Andhra Pradesh, India is used in the present work. Structural characterization was performed by X-ray diffraction (XRD). The mineral was found to be gibbsite in phase. The transitional metal ions present were investigated using electron paramagnetic resonance (EPR) and optical absorption spectra. The EPR results suggest that Fe3+ has replaced Al3+ in the unit cell of bauxite. The optical absorption spectrum is due to Fe3+ which indicates that it is in distorted octahedral environment. The near-infrared (NIR) spectrum is due to water fundamentals and combination overtones, which confirm the formula of the compound. The impurities in the mineral are identified using spectroscopic techniques.
基金This paper is supported by the Natural Science and Engineering Re-search Council (NSERC) of Canada and the Cameco Corporation .
文摘Quartz grains in contact with uranium-bearing minerals or fluids are characterized by natural radiation-induced paramagnetic defects （e. g. , oxygen vacancy centers, silicon vacancy centers, and peroxy radicals）, which are amenable to study by electron paramagnetic resonance （EPR） spectroscopy. These natural radiation-induced paramagnetic defects, except for the oxygen vacancy centers, in quartz are concentrated in narrow bands penetrated by α particles： （1） in halos around U- and Th-bearing mineral inclusions and （2） in outer rims or along fractures. The second type of occurrence provides information about uranium mineralization or remobilization （i. e. , sources of uranium, timing of mineralization or remobilization, pathways of uranium-bearing fluids）. It can also be used to evaluate sedimentary basins for potential of uranium mineralization. In particular, the peroxy radicals are stable up to 800℃ and, therefore, are useful for evaluating metasedimentary rocks （e. g. , Paleoproterozoic metasedimentary sequences in the central zone of the North China craton）. EPR study of the Changcheng Series can focus on quartz from the sediment-basement unconformity and faults to determine the presence and types of natural radiation-induced paramagnetic defects, with which to identify and prioritize uranium anomalies. Other potential applications of natural radiation-induced paramagnetic defects in quartz include uranium-bearing hydrocarbon deposits in sedimentary basins. For example, the Junggar, Ordos, and Tarim basins in northwestern China all contain important oil and natural gas fields and are well known for elevated uranium concentrations, including economic sandstone-hosted uranium deposits. Therefore, systematic studies on the distribution of natural radiation-induced paramagnetic defects in quartz from host sedimentary sequences are expected to provide information about the migration of oil and natural gas in those basins.
文摘FAMn:PbI<sub>3</sub> perovskite films were synthesized and probed mainly through electron spin resonance (ESR) spectroscopy. FAMn:PbI<sub>3</sub> with low (~1%) Mn concentration showed a hyperfine sextet line originated from Mn<sup>++</sup> ions. FAMn:PbI<sub>3</sub> with high (10%) Mn concentration showed broad resonance (~500 G peak-to-peak linewidth). However, after bombardment of FAMn:PbI<sub>3</sub> with high Mn concentration by focused ion beams (FIB), a sharp ESR peak appeared. The peak-to-peak linewidth (ΔH<sub>pp</sub>) was ~8 G regardless of the temperature. The FIB-induced defect showed Curie behavior at low temperatures (5 K - 50 K), which indicates the presence of localized electrons at the defect sites at low temperatures. The g-value increased from g = 2.0002 to 2.0016 as the temperature increased from 5 K to 50 K. Together with the ongoing search for electron spin echo (ESE), this could potentially provide a platform for realizing magnetic bits, information storage, and increased manipulation speed.
基金supported by the National Natural Science Foundation of China (Grant No. 50802041)the National Key Projects for Basic Research of China (Grant No. 2010CB923404)Southeast University
文摘Zn0.98Cu0.020 powders are prepared by the sol-gel method. A small number of CuO impurity phases are observed by the x-ray diffraction, indicating the solubility of Cu in ZnO is less than 2 at.%. The Zn0.98Cu0.020 powders exhibit diamagnetism at 300 K and paramagnetism at 5 K. After subtracting the diamagnetic contribution of ZnO bulk and the paramagnetic contribution of defects, Cu ions exhibit weak paramagnetism. By codoping Cu with Co or Mn in ZnO, only paramagnetism is observed at room temperature.
文摘Ultrasmall near-monodisperse Ba2ErF7 nanocrystals with average crystal size 9.6 nm were synthesized with solvothermal method. The X-ray diffraction （XRD） and transmission electron microscopy （TEM） assays reveal that the as-synthesized Ba2ErF7 nanocrystals are of the cubic structure with the cell parameter of 5.943 A, instead of the reported orthorhombic and tetragonal structure. Two emission bands originated from 2Hwj4H3/2 → 4F5/2 and 4F9/2 ----＋ 4115,2 of Er3＋ can be observed under a 980 nm laser excitation. The magnetic mass susceptibility of the as-synthesized BazErF7 nanocrystals reaches 4.293 × 10-5 emu g-1 Oe-1.
基金Item Sponsored by Deutsche Forschungsgemeinschaft(HA 2338/4-1)
文摘Magnetic forces are widely used to influence the properties of materials.The main focus of recent investigations concerning oxide melts mainly was on the use of Lorentz forces either to mix glass melts to avoid an improved inhomogeneity or to measure the flow of these melts.In the last years also the use of magnetic gradient forces has become an object of research mainly in electrochemistry.On the basis of preliminary investigations the influence of these forces on paramagnetic ions such as Fe;in oxide melts is investigated to examine the potential of magnetic gradient forces as a tool to create defined gradient materials.
文摘Electron paramagnetic resonance （EPR） and optical absorption studies were carried out at room temperature on copper doped mixed alkali cadmium phosphate （LiNaCdP） glasses to understand the nature and symmetry of dopant. Three samples with varying concentrations of alkali ions have been prepared. The spin Harniltonian parameters obtained from room temperature EPR spectra are： gli=2.437, 9⊥=2.096, A‖=117×10-4 cm-1, A⊥=26×10-4 cm-1 for LiNaCdP1, g‖=2.441, g⊥=2.088, A‖=121×10-4 cm-1, A⊥=25×10-4 cm-1 for LiNaCdP2and g‖=2.433,g⊥=2.096, A‖=125×10 4cm-1, A⊥=32×10-4cm-1 for LiNaCdP3. TheseEPR results indicate that the dopant Cu2＋ ion enters the glass matrix into a tetragonally elongated octahedral site. The bonding parameters evaluated by correlating optical and EPR data suggest that bonding between the central metal ion and ligands is partially covalent. The mixed alkali effect in cadmium phosphate glasses was reported.
基金Project supported by the National Natural Science Foundation of China (Grant No 10774103)the Doctoral Education Fund of Education Ministry of China (Grant No 20050610011)
文摘A simple theoretical method is introduced for studying the interrelation between electronic and molecular structures.By diagonalizing the 120 × 120 complete energy matrices,the relationships between zero-field splitting （ZFS） parameter D and local distortion parameter △θ for Cr^3＋ ions doped,separately,in α- and β- alums are investigated.Our results indicate that there exists an approximately linear relationship between D and △θ in a temperature range 4.2-297 K and the signs of D and △θ are opposite to each other.Moreover,in order to understand the contribution of spin-orbit coupling coefficient ζ to ZFS parameter D,the relation between D and ζ is also discussed.
