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Electron spin resonance study of the Ba-doping manganite Nd_(0.5)Sr_(0.5)MnO_3 被引量:2
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作者 赵建军 邢茹 +7 位作者 鲁毅 浩斯巴雅尔 赵明宇 金香 郑琳 宁伟 孙阳 成昭华 《Chinese Physics B》 SCIE EI CAS CSCD 2008年第7期2721-2724,共4页
We have performed magnetization measurements and electron spin resonance (ESR) on polycrystalline manganites of Nd0.5Sr0.5-xBaxMnO3 (x = 0.1). Phase separation and phase transitions are observed from the susceptib... We have performed magnetization measurements and electron spin resonance (ESR) on polycrystalline manganites of Nd0.5Sr0.5-xBaxMnO3 (x = 0.1). Phase separation and phase transitions are observed from the susceptibility and the ESR spectra data. Between 260 K (~ Tc) and 185 K (~ TN), the system coexists of the paramagnetic phase and the ferromagnetic (FM) phase. Between 185 K and 140 K, the system coexists of the FM phase and the antiferromagnetic (AFM) phase. These results indicate that the system has a very complex magnetic state due to the origin of the instability stemming from manganite Nd0.5Sr0.4Ba0.1MnO3 by partially substituting the larger Ba^2+ ions for the smaller Sr^2+ ions. 展开更多
关键词 MANGANITE electron spin resonance phase separation
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Theory of phonon-modulated electron spin relaxation time based on the projection reduction method
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作者 Nam Lyong Kang Sang Don Choi 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第8期436-443,共8页
This paper introduces a new method for a formula for electron spin relaxation time of a system of electrons interacting with phonons through phonon-modulated spin-orbit coupling using the projection-reduction method. ... This paper introduces a new method for a formula for electron spin relaxation time of a system of electrons interacting with phonons through phonon-modulated spin-orbit coupling using the projection-reduction method. The phonon absorption and emission processes as well as the photon absorption and emission processes in all electron transition processes can be explained in an organized manner, and the result can be represented in a diagram that can provide intuition for the quantum dynamics of electrons in a solid. The temperature (T) dependence of electron spin relaxation times (T1) in silicon is T1 ∝ T-1.07 at low temperatures and T1 ∝ T-3.3 at high temperatures for acoustic deformation constant Pad = 1.4 × 10^7 eV and optical deformation constant Pod = 4.0 × 10^17 eV/m. This means that electrons are scattered by the acoustic deformation phonons at low temperatures and optical deformation phonons at high temperatures, respectively. The magnetic field (B) dependence of the relaxation times is T1 ∝ B-2.7 at 100 K and T1 ∝ B-2.3 at 150 K, which nearly agree with the result of Yafet, T1 ∝ B-3.0- B -2.5. 展开更多
关键词 electron spin resonance spin-orbit coupling projection-reduction method phonon scattering
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An electron spin resonance study of Eu doping effect in La_(4/3)Sr_(5/3)Mn_2O_7 single crystal
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作者 何利民 冀钰 +5 位作者 吴鸿业 徐宝 孙运斌 张雪峰 鲁毅 赵建军 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第7期717-719,共3页
The effect of Eu3+ ion doping in the La sites of single-crystal La4/3Srs/3Mn2O7 was investigated. Electron spin resonance (ESR) was applied to La4/3Sr5/3Mn2O7 and (Lao.8Euo.2)4/3Sr5/3Mn2O7 single crystals. A phas... The effect of Eu3+ ion doping in the La sites of single-crystal La4/3Srs/3Mn2O7 was investigated. Electron spin resonance (ESR) was applied to La4/3Sr5/3Mn2O7 and (Lao.8Euo.2)4/3Sr5/3Mn2O7 single crystals. A phase separation and phase transitions were observed from the ESR spectra data. Between 350 K and 300 K, both paramagnetic resonance (PMR) and anisotropic ferromagnetic resonance (FMR) lines were observed in the ab plane and the c axis direction, suggesting a coexistence of the paramagnetic (PM) phase and the ferromagnetic (FM) phase. The magnetization measurement reveals a spin-glass-like behavior in single-crystal (Lao.8Euo.2)4/3 Sr5/3Mn2O7 below the temperature of spin freezing Tf (- 29.5 K). 展开更多
关键词 electron spin resonance manganite single crystal phase separation ANISOTROPY
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EARLY DIAGNOSIS OF TUMOR WITH ELECTRON SPIN RESONANCE (ESR): METHOD OF ELECTRONIC SATURATION OF ENERGY LEVEL
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作者 齐子荣 刘金伟 +4 位作者 孙海光 唐发宽 孙玲 张寅 周林 《Chinese Journal of Cancer Research》 SCIE CAS CSCD 1993年第4期69-75,共7页
ESR saturation power point of the hair of healthy, lung cancer, esophageal cancer, as well as silicosis, tuberculosis and cardiovascular disease were detected. The results show that the positive rate is 1.69%, 85.42%,... ESR saturation power point of the hair of healthy, lung cancer, esophageal cancer, as well as silicosis, tuberculosis and cardiovascular disease were detected. The results show that the positive rate is 1.69%, 85.42%, 90.4%, 20.00%, 27.27% and 0% respectively. There is a significant difference between lung cancer, esophageal cancer and healthy persons (P<0. 001). ESR saturation power point elevates sharply after treatment of lung cancer, 71. 43% of total cases ranged from 7. 9 to 24. 0 (mW), after treatment of esophageal cancer, 71. 23% ranged from 7.9 to 19.9 (mW). All patients with cardiovascular disease were examined to be negative, i. e. , above 10. 0 (mW). 展开更多
关键词 electron spin Resonance (ESR) Saturation power point (mW) Tumro Diagnosis.
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Electron spin resonance investigation of the substitution of Fe^(3+) for Ti^(4+) ions in rutile TiO_2 single crystal
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作者 李国科 张向群 +4 位作者 吴鸿业 黄万国 靳金玲 孙阳 成昭华 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第8期3551-3554,共4页
A Fe doped rutile TiO2 single crystal is grown in an O2 atmosphere by the floating zone technique. Electron spin resonance (ESR) spectra clearly demonstrate that Fe^3+ ions are substituted for the Ti^4+ ions in th... A Fe doped rutile TiO2 single crystal is grown in an O2 atmosphere by the floating zone technique. Electron spin resonance (ESR) spectra clearly demonstrate that Fe^3+ ions are substituted for the Ti^4+ ions in the rutile TiO2 matrix. Magnetization measurements reveal that the Fe:TiO2 crystal shows paramagnetic behaviour in a temperature range from 5 K to 350 K. The Fe^3+ ions possess weak magnetic anisotropy with an easy axis along the c axis. The annealed Fe:TiO2 crystal shows spin-glass-like behaviours due to the aggregation of the ferromagnetic clusters. 展开更多
关键词 RUTILE electron spin resonance diluted magnetic semiconductors
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Application of Theories of Free Radicals and Electron Spin Resonance for Research of Traditional Chinese Medicine
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作者 段绍瑾 《Journal of Traditional Chinese Medicine》 SCIE CAS CSCD 2000年第1期51-58,共1页
The present paper reviews new findings in redoxproperties of the active constituent of Chinese herbalmedicine(CHM),a kind of CHM or a compoundprescription as an antioxidant.Firstly,we have studiedtheir antioxidant and... The present paper reviews new findings in redoxproperties of the active constituent of Chinese herbalmedicine(CHM),a kind of CHM or a compoundprescription as an antioxidant.Firstly,we have studiedtheir antioxidant and prooxidant actions with electronspin resonance(ESR).The results show that the activecomponents from over 10 kinds of CHM are able toscavenge the oxygen free radicals but propyl gallate 展开更多
关键词 Medicine Chinese Traditional ANTIOXIDANTS Drugs Chinese Herbal electron spin Resonance Spectroscopy Free Radical Scavengers Humans Neurosecretory Systems Oxidative Stress
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Evaluation of Hydroxyl Radical and Alkyl-oxy Radical Scavenging Activity of Coffee by ESR Spin Trapping Method 被引量:2
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作者 Hiromi Kameya 《Journal of Food Science and Engineering》 2017年第6期305-311,共7页
We evaluated the hydroxyl and alkyl-oxy radical scavenging activity of instant coffee using an electron spin resonance (ESR) spin-trapping method, which was based the spin-trapping reagent 5-(2,2-dimethy-l,3-propox... We evaluated the hydroxyl and alkyl-oxy radical scavenging activity of instant coffee using an electron spin resonance (ESR) spin-trapping method, which was based the spin-trapping reagent 5-(2,2-dimethy-l,3-propoxycyclophosphoryl)-5-methyl-l-pyrroline N-oxide (CYPMPO). In this method, very pure hydroxyl and alkyl-oxy radicals were generated by illuminating a phosphate buffer solution containing hydrogen peroxide and 2,2'-azobis (2-amidinopropane) dihydrochloride with a Hg-Xe arc lamp. The ESR adduct signal was sensitive and very stable. We concluded that instant coffee has high hydroxyl radical and alkyl-oxy radical scavenging activity. 展开更多
关键词 Radical scavenging COFFEE spin trapping electron spin resonance.
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Study on the synthesis of spin labeled poly(styrene-co-maleic acid)s and their segmental motion 被引量:1
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作者 Kaleem-Ur-Rahman Naveed Li Wang +9 位作者 Haojie Yu Qian Zhang Wei Xiong Raja Summe Ullah Ahsan Nazir Muhammad Usman Shah Fahad Amin Khan Md Alim Uddin Di Shen 《Magnetic Resonance Letters》 2022年第2期80-90,I0002,共12页
Study of the segmental mobility of polymer chains is important when the polymer is used as drag reduction agents of crude oil.Electron spin resonance(ESR)spectroscopy can provide important information about segmental ... Study of the segmental mobility of polymer chains is important when the polymer is used as drag reduction agents of crude oil.Electron spin resonance(ESR)spectroscopy can provide important information about segmental dynamics of polymer chains,which is related to their microenvironment.In this article,we employed an amphiphilic polymer to study the effect of hydrophilic/hydrophobic balance of the polymers on the segmental motion of polymer chains.Poly(styrene-co-maleic acid)(PSMA)was spin labeled with 4-amino TEMPO radicals by increasing the concentration of radical moiety on the polymer chains.The PSMA and spin labeled-PSMAs(SL-PSMAs)were characterized by nuclear magnetic resonance(NMR),Fourier transform infrared(FT-IR)spectroscopy,Cyclic voltammetry(CV)and ESR techniques.Inter-polymer complexes(IPCs)of SL-PSMA-2 were prepared by employing polyethylene glycols(PEGs)of varying molecular weights.The results showed that the increased hydrophobic interactions of nitroxide radicals on the SLPSMAs’chains reduced the rotational mobility of spin labels and the random coil-toglobular transition of polymer chains occurred at higher pH value for SL-PSMAs,which showed a slow motion component in the ESR spectra of SL-PSMAs.Further,by increasing the molecular weight of PEGs in IPCs the complexation was increased,which also reduced the rotational motion of spin labels due to interpolymer hydrogen bonding causing a slow motion component in the ESR spectra.©2021 The Authors. 展开更多
关键词 electron spin resonance(ESR) spin labeling Nitroxide radicals poly(styrene-co-maleic acid)s Segmental motion
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Optical nuclear spin polarization in quantum dots
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作者 李爱仙 段素青 张伟 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第10期535-539,共5页
Hyperfine interaction between electron spin and randomly oriented nuclear spins is a key issue of electron coherence for quantum information/computation. We propose an efficient way to establish high polarization of n... Hyperfine interaction between electron spin and randomly oriented nuclear spins is a key issue of electron coherence for quantum information/computation. We propose an efficient way to establish high polarization of nuclear spins and reduce the intrinsic nuclear spin fluctuations. Here, we polarize the nuclear spins in semiconductor quantum dot(QD) by the coherent population trapping(CPT) and the electric dipole spin resonance(EDSR) induced by optical fields and ac electric fields. By tuning the optical fields, we can obtain a powerful cooling background based on CPT for nuclear spin polarization. The EDSR can enhance the spin flip–flop rate which may increase the cooling efficiency. With the help of CPT and EDSR, an enhancement of 1300 times of the electron coherence time can be obtained after a 10-ns preparation time. 展开更多
关键词 nuclear spin polarization coherent population trapping electron dipole spin resonance
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TR-ESR Investigation on Reaction of Vitamin C with Excited Triplet of 9,10-phenanthrenequinone in Reversed Micelle Solutions 被引量:1
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作者 许新胜 史蕾 +2 位作者 刘毅 季学韩 崔执凤 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2011年第2期150-154,I0003,共6页
Time-resolved electron spin resonance has been used to study quenching reactions between the antioxidant Vitamin C (VC) and the triplet excited states of 9,10-phenanthrenequinone (PAQ) in ethylene glycol-water (E... Time-resolved electron spin resonance has been used to study quenching reactions between the antioxidant Vitamin C (VC) and the triplet excited states of 9,10-phenanthrenequinone (PAQ) in ethylene glycol-water (EG-H2O) homogeneous and inhomogeneous reversed micelle solutions. Reversed micelle solutions were used to be the models of physiological environment of biological cell and tissue. In PAQ/EG-H2O homogeneous solution, the excited triplet of PAQ (3PAQ*) abstracts hydrogen atom from solvent EG. In PAQ/VC/EG-H2O solution, 3pAQ* abstracts hydrogen atom not only from solvent EG but also from VC. The quenching rate constant of 3pAQ* by VC is close to the diffusion-controlled value of 1.41 × 108 L/(mol.s). In hexadecyltrimethylammonium bromide (CTAB)/EG-H2O and aerosol OT (AOT)/EG- H2O reversed micelle solutions, 3pAQ* and VC react around the water-oil interface of the reversed micelle. Exit of 3pAQ* from the lipid phase slows down the quenching reaction. For Triton X-100 (TX-100)/EG-H2O reversed micelle solution, PAQ and VC coexist inside the hydrophilic polyethylene glycol core, and the quenching rate constant of 3pAQ* by VC is larger than those in AOT/EG-H2O and CTAB/EG-H2O reversed micelle solutions, even a little larger than that in EG-H2O homogeneous solution. The strong emissive chemically induced dynamic electron polarization of As'- resulted from the effective TM spin polarization transfer in hydrogen abstraction of 3pAQ* from VC. 展开更多
关键词 9 10-phenanthrenequinone Vitamin C Time-resolved electron spin resonance Reversed micelle
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PSⅡ Photoinhibition and O_2~ Production 被引量:1
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作者 靳月华 陶大立 《Acta Botanica Sinica》 CSCD 2000年第1期10-14,共5页
To know more about the site of O -· 2 production in thylakoids, the F v/F m ratio was measured in parallel with the oxygen free_radical production detected by electron spin resonance (ESR) using Tiron... To know more about the site of O -· 2 production in thylakoids, the F v/F m ratio was measured in parallel with the oxygen free_radical production detected by electron spin resonance (ESR) using Tiron as a probe in the isolated thylakoids of Scots pine ( Pinus sylvestris L.). As the light intensity was strong enough to induce photoinhibition leading to reduction in the F v/F m ratio, the intensity of the TH · signal representing the superoxide production was enhanced. The TH · signal was also stimulated by 3_(3,4_dichloropheneyl)_1,1_dimethylurea but was suppressed by exogenous scavengers or by 2,6_dichlorophenol indophenol. Therefore, the superoxide production is closely related to photoinhibition in PSⅡ. The novel results may further promote research on the mechanism of photoinhibition and on the structure and function of PSⅡ as well. 展开更多
关键词 PHOTOINHIBITION superoxide F v/F m Scots pine PSⅡ electron spin resonance
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Probing hydroxyl radical generation from H2O2 upon plasmon excitation of gold nanorods using electron spin resonance: Molecular oxygen-mediated activation 被引量:3
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作者 Tao wen Hui Zhang +3 位作者 Yu Chong Wayne G. Wamer Jun-Jie Yin Xiaochun Wu 《Nano Research》 SCIE EI CAS CSCD 2016年第6期1663-1673,共11页
Gold nanostructures are among the noble metal nanomaterials being intensely studied due to their good biocompatibility, tunable localized surface plasmon resonance (SPR), and ease of modification. These properties g... Gold nanostructures are among the noble metal nanomaterials being intensely studied due to their good biocompatibility, tunable localized surface plasmon resonance (SPR), and ease of modification. These properties give gold nano- structures many potential chemical and biomedical applications. Herein, we demonstrate the critical role of oxygen activation during the decomposition of hydrogen peroxide (H202) in the presence of photoexcited gold nanorods (AuNRs) by using electron spin resonance (ESR) techniques. Upon SPR excitation, 02 is activated first, and the resulting reactive intermediates further activate H202 to produce ,OH. The reactive intermediates exhibit singlet oxygen-like (102-1ike) reactivity, indicated by 102-specific oxidation reaction, quenching behaviors, and the lack of the typical 102 ESR signal. In addition, by using the antioxidant sodium ascorbate (NaA) as an example, we show that hydroxyl radicals from H202 activation can induce much stronger NaA oxidation than that in the absence of H202. These results may have significant biomedical implications. For example, as oxidative stress levels are known to influence tumorigenesis and cancer progression, the ability to control redox status inside tumor microenvironments using noble metal nanostructures may provide new strategies for regulating the metabolism of reactive oxygen species and new approaches for cancer treatment. 展开更多
关键词 gold nanorod oxygen activation hydroxyl radicalplasmon catalysis electron spin resonance
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Free radical scavenging abilities of polypeptide from Chlamys farreri 被引量:2
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作者 韩志武 初晓 +3 位作者 刘成娟 王跃军 孙谧 王春波 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2006年第3期325-328,共4页
We investigated the radical scavenging effect and antioxidation property of polypeptide ex- tracted from Chlamys farreri (PCF) in vitro using chemiluminescence and electron spin resonance (ESR) methods. We examined th... We investigated the radical scavenging effect and antioxidation property of polypeptide ex- tracted from Chlamys farreri (PCF) in vitro using chemiluminescence and electron spin resonance (ESR) methods. We examined the scavenging effects of PCF on superoxide anions ( O?2 ), hydroxyl radicals (OH·), peroxynitrite (ONOO-) and the inhibiting capacity of PCF on peroxidation of linoleic acid. Our experiment suggested that PCF could scavenge oxygen free radicals including superoxide anions ( O2? ) (IC50 =0.3 mg/ml), hydroxyl radicals (OH·) (IC50 = 0.2 μg/ml) generated from the reaction systems and effectively inhibit the oxidative activity of ONOO- (IC50 = 0.2 mg/ml). At 1.25 mg/ml of PCF, the inhibi- tion ratio on lipid peroxidation of linoleic acid was 43 %. The scavenging effect of PCF on O?2 , OH· and ONOO- free radicals were stronger than those of vitamin C but less on lipid peroxidation of linoleic acid. Thus PCF could scavenge free radicals and inhibit the peroxidation of linoleic acid in vitro. It is an anti- oxidant from marine products and potential for industrial production in future. 展开更多
关键词 POLYPEPTIDE Chlamys farreri free radical ANTIOXIDANT CHEMILUMINESCENCE electron spin resonance (ESR)
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Buyang Huanwu decoction enhances cell membrane fluidity in rats with cerebral ischemia/reperfusion 被引量:2
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作者 Chenxu Li 《Neural Regeneration Research》 SCIE CAS CSCD 2012年第21期1605-1610,共6页
After bilateral carotid artery occlusion for 30 minutes and reperfusion for 2 hours, distinct pathological changes presented in the cerebral cortex and cerebellum of rats. Compared with normal rats, nerve cell membran... After bilateral carotid artery occlusion for 30 minutes and reperfusion for 2 hours, distinct pathological changes presented in the cerebral cortex and cerebellum of rats. Compared with normal rats, nerve cell membrane fluidity significantly decreased in ischemia/reperfusion rats as detected by spin-labeling electron spin resonance, consistent with order parameter S and rotational correlation time TC measurements. Brain nerve cells from rats with ischemia/reperfusion injury were cultured with 1-100 mg/mL Buyang Huanwu decoction. Results showed that Buyang Huanwu decoction gradually increased membrane fluidity dose-dependently to normal levels, and eliminated hydroxide (OH') and superoxide (O2') free radicals dose-dependenUy. These findings suggest that Buyang Huanwu decoction can protect against cell membrane fluidity changes in rats with ischemia/ reperfusion injury by scavenging free radicals. 展开更多
关键词 Buyang Huanwu decoction ISCHEMIA/REPERFUSION electron spin resonance cell membrane fluidity free radical BRAIN neural regeneration
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Dating of the topmost terrace in the Jingxian Basin,Anhui Province:an indication of the establishment of the Qingyijiang River 被引量:2
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作者 HU Chun-sheng HU Chen-qi +3 位作者 LIU Shao-chen XU Guang-lai WU Li YANG Li-hui 《Journal of Mountain Science》 SCIE CSCD 2017年第3期549-557,共9页
On the northern fringe of Mt. Huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang... On the northern fringe of Mt. Huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang River, one of the longest tributaries of the lower Yangtze River, developed three staircase terraces. The topmost terrace (i.e., the T3 terrace) tread is 38 - 39 m above fiver level, and the top of the gravels is generally covered by 3 - 10.9 m of red clay deposits. Systematic magnetostratigraphy and electron spin resonance dating are used to research the timing of the establishment of the Qingyijiang River. The main results show that the topmost terrace developed no later than 900 kyr ago and that the appearance of the Qingyijiang River occurred correspondingly at least before 900 kyr ago on the northern fringe of Mt. Huangshan. In view of the almost synchronous age,the establishment of the Qingyijiang River was seemingly a response to the Mid-Pleistocene Revolution when the 100 kyr cycle commenced, and the Kunlun-Huanghe movement during the early- middle Pleistocene transition. In addition, the establishment of the Qingyijiang River possibly reflected the birth of the modem Yangtze River to some degree. Therefore the timing of the formation of the Yangtze River is restricted to no later than 900 kyr ago based on the appearance of the Qingyijiang River . 展开更多
关键词 Qingyijiang River Topmost terrace MAGNETOSTRATIGRAPHY electron spin Resonance dating Establishment timing Jingxian Basin
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Magnetic transition behavior of perovskite manganites Nd0.5Sr0.3Ca0.2MnO3 polycrystalline 被引量:2
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作者 邢茹 万素磊 +5 位作者 王文清 郑琳 金香 周敏 鲁毅 赵建军 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第4期376-379,共4页
A polycrystalline sample Ndo.5Sro.3Cao.2MnO3 is prepared by the conventional solid state reaction method. The structure and magnetic properties are investigated with x-ray diffraction (XRD) patterns, a superconducti... A polycrystalline sample Ndo.5Sro.3Cao.2MnO3 is prepared by the conventional solid state reaction method. The structure and magnetic properties are investigated with x-ray diffraction (XRD) patterns, a superconducting quantum in- terference device (SQUID), and electron spin resonance (ESR). The sample is in single phase with the space group Pbnm symmetry. With the decrease of temperature, Ndo.sSro.3Cao.2MnO3 undergoes three magnetic transitions: ferromagnetic transition at Tc ≈ 210 K, charge-ordering at Tco ≈ 175 K, and antiferromagnetic transition at TN = 155 K. In addition, the activation energy Ea ≈ 52.78 meV can be extracted by curve fitting. 展开更多
关键词 MAGNETIC transition: electron spin resonance activation energy
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Kinetics and Mechanism of Catalytic Reduction of U(Ⅵ)with Hydrazine on Platinum Catalysts in Nitric Acid Media 被引量:1
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作者 Xiao-teng Zhang Shuai Hao +4 位作者 Fei-fei Tang Bin Li Xian-ming Zhou Li-sheng Liu Liang-shu Xia 《Chinese Journal of Chemical Physics》 SCIE EI CAS CSCD 2022年第5期813-822,I0012,共11页
The kinetics of U(IV)produced by hydrazine reduction of U(VI)with platinum as a catalyst in nitric acid media was studied to reveal the reaction mechanism and optimize the reaction process.Electron spin resonance(ESR)... The kinetics of U(IV)produced by hydrazine reduction of U(VI)with platinum as a catalyst in nitric acid media was studied to reveal the reaction mechanism and optimize the reaction process.Electron spin resonance(ESR)was used to determine the influence of nitric acid oxidation.The effects of nitric acid,hydrazine,U(VI)concentration,catalyst dosage and temperature on the reaction rate were also studied.In addition,the simulation of the reaction process was performed using density functional theory.The results show that the influence of oxidation on the main reaction is limited when the concentration of nitric acid is below 0.5 mol/L.The reaction kinetics equation below the concentration of 0.5 mol/L is found as:−dc(UO_(2)^(2+))/dt=kc^(0.5323)(UO_(2)^(2+))c^(0.2074)(N_(2)H_(5)^(+))c^(−0.2009)(H^(+)).When the temperature is 50℃,and the solid/liquid ratio r is 0.0667 g/mL,the reaction kinetics constant is k=0.00199(mol/L)^(0.4712)/min.Between 20℃ and 80℃,the reaction rate gradually increases with the increase of temperature,and changes from chemically controlled to diffusion-controlled.The simulations of density functional theory give further insight into the influence of various factors on the reaction process,with which the reaction mechanisms are determined according to the reaction kinetics and the simulation results. 展开更多
关键词 URANIUM Reaction kinetics electron spin resonance HYDRAZINE Density functional theory
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Luminescence and ESR Studies of CaS:Dy Phosphor
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作者 Vijay Singh 朱俊杰 +2 位作者 T. K. Gundu Rao Manoj Tiwari 潘宏程 《Chinese Physics Letters》 SCIE CAS CSCD 2005年第12期3182-3185,共4页
CaS phosphor activated with Dy ions is prepared by the solid-state diffusion method. The phosphor is characterized by x-ray powder diffraction, thermogravimetric analysis and photoiuminescence. Defect centres formed i... CaS phosphor activated with Dy ions is prepared by the solid-state diffusion method. The phosphor is characterized by x-ray powder diffraction, thermogravimetric analysis and photoiuminescence. Defect centres formed in CaS:Dy are studied using the technique of electron spin resonance. The thermoluminescence glow curve shows peaks at around 117℃ and 345℃. Irradiated CaS:Dy exhibits ESR lines due to defect centres. The thermal annealing behaviour of one of the defect centres appears to correlate with the TL peaks at 117℃ and 345℃. This centre is characterized by an isotropic g-value of 2.0035 and is assigned to an F^+ centre. 展开更多
关键词 electron spin RESONANCE CALCIUM SULFIDE THIN-FILMS CATHODOLUMINESCENCE PARAMETERS EU
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Consumption of Mercury-contaminated Rice Induces Oxidative Stress and Free Radical Aggravation in Rats
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作者 XIU-LING JI GUI-WEN JIN +3 位作者 JIN-PING CHENG WEN-HUA WANG JING LU LI-YA QU 《Biomedical and Environmental Sciences》 SCIE CAS CSCD 2007年第1期84-89,共6页
Objective To study the oxidative stress induced by consumption of mercury-contaminated rice in rats, and to assess the possible public health risk of mercury contamination in Wanshan mining area. Methods Sprague Dawle... Objective To study the oxidative stress induced by consumption of mercury-contaminated rice in rats, and to assess the possible public health risk of mercury contamination in Wanshan mining area. Methods Sprague Dawley rats were fed the mercury-contaminated rice produced from Wanshan area for 90 days. The antioxidant status and the free radicals in rat serum were evaluated. Results High mercury accumulation in organs of rats fed the mercury-contaminated rice confirmed the server pollution of mercury in Wanshan mining area. The intensity of electron spin resonance (ESR) signal increased by 87.38% in rats fed the rice from Wanshan compared with that in the control rats fed the rice from Shanghai, suggesting that chronic dietary consumption of rice from mercury mining area could induce an aggravation of free radicals. Feeding the mercury-contaminated rice was associated with significant decreases in the antioxidant enzymatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and concentration of serum nitric oxide (NO), but it had no effect on serum nitric oxide synthase (NOS) activity. Feeding the mercury-contaminated rice raised the level of serum malonyldialdehyde (MDA), indicating the occurrence of oxidative stress. Conclusion The long-term dietary consumption of mercury-contaminated rice induces the aggravation of free radicals and exerts oxidative stress. 展开更多
关键词 electron spin resonance Free radicals MERCURY Oxidative stress RICE
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Relationship of annealing time and intrinsic defects of unintentionally doped 4H-SiC
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作者 程萍 张玉明 +1 位作者 张义门 郭辉 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第9期595-598,共4页
With annealing temperature kept at 1573 K, the effects of annealing time on stability of the intrinsic defects in epitaxial unintentionally doped 4H-SiC prepared by low pressure chemical vapour deposition have been st... With annealing temperature kept at 1573 K, the effects of annealing time on stability of the intrinsic defects in epitaxial unintentionally doped 4H-SiC prepared by low pressure chemical vapour deposition have been studied by electron spin resonance (ESR) and low temperature photoluminescence. This paper reports the results shown that annealing time has an important effect on the intrinsic defects in unintentionally doped 4H-SiC when annealing temperature kept at 1573 K. When the annealing time is less than 30 min, the intensity of ESR and photoluminescence is increasing with annealing time prolonged, and reaches the maximum when annealing time is 30 min. Then the intensity of ESR and photoluminescence is rapidly decreased with the longer annealing time, and much less than that of as-grown 4H-SiC when annealing time is 60 min, which should be related with the interaction among the intrinsic defects during the annealing process. 展开更多
关键词 intrinsic defects annealing time low temperature photoluminescence electron spin resonance
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