Background 5-dihydroxyanthraquinone-2-carboxylic acid (rhein) inhibits oxidoreduction induced by reducing nicotingamide adenine dinucleotide in the mitochondria and reducing reactive oxygen species, it also suppresses...Background 5-dihydroxyanthraquinone-2-carboxylic acid (rhein) inhibits oxidoreduction induced by reducing nicotingamide adenine dinucleotide in the mitochondria and reducing reactive oxygen species, it also suppresses lipid peroxidation in rat brain homogenates. This study was to assess the effects of anthraquinone derivatives, rhein on synaptic transmission in the rat hippocampal CA_1 pyramidal cell layer by intracellular recording.Methods The excitatory postsynaptic potential (EPSP) evoked by stimulation of the Schaffer collaterals in the presence of bicuculline (15 μmol/L) was depressed by application of rhein (0.3-30 μmol/L). The amplitude of the EPSP was restored within 20 minutes after removal of rhein from the supernatant. At a concentration of 30 μmol/L, rhein reduced the amplitude of the EPSP to 42%±3.7% (n=24) of the control. Subsequently, wavelet spectral entropy was used to analyze the EPSP. Results A strong positive correlation was observed between the wavelet spectral entropy and other parameters such as amplitude, slope of rising phase and slope of descending phase of the EPSP. The paired-pulse facilitation (PPF) of the EPSP was significantly increased by rhein (30 μmol/L). The inhibitory postsynaptic potential (IPSP) recorded in the presence of CNQX (20 μmol/L) and APV (40 μmol/L) is not altered by rhein (30 μmol/L). Conclusions Rhein (30 μmol/L) can decrease the frequency but not the amplitude of the miniature EPSP (mEPSP). It is suggested that rhein inhibits excitatory synaptic transmission by decreasing the release of glutamate in rat hippocampal CA_1 pyramidal neurons.展开更多
In this work,the impact of the doping process on the photoluminescence emission of CaWO_(4) as a function of the concentration of Eu^(3+) cation(0.01 mol%,0.02 mol%,0.04 mol%,0.06 mol%,0.08 mol%,and 0.10 mol%) is disc...In this work,the impact of the doping process on the photoluminescence emission of CaWO_(4) as a function of the concentration of Eu^(3+) cation(0.01 mol%,0.02 mol%,0.04 mol%,0.06 mol%,0.08 mol%,and 0.10 mol%) is discussed in detail.Ca_(1-x)WO~4:xEu^(3+) samples were successfully synthesized by a simple coprecipitation method followed by microwave irradiation.The blue shift in the absorption edge confirms the quantum confinement effect and the band gap energy covers the range from 3.91 to 4.18 eV,as the amount of Eu^(3+) cations increases.The experimental results are sustained by first-principles calculations,at the density functional theory level,to decipher the geometry and electronic properties,thereby enabling a more accurate and direct comparison between theory and experiment for the Ca_(1-x)WO_(4):xEu^(3+) structure.展开更多
The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitatio...The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitation method with metal-nitrates as starting materials and mixed alkali (NaOH and Na2CO3) as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, and the crystal structure and particles morphology of the precursors which were calcined at 600, 800, 1000 ℃ for 3 h were characterized using XRD, SEM technologies. Compared with the solid state reaction of constituent oxides, when the pH value of the precipitating solution was in the range of 9.1～9.5, the LSCCF powders from the precursors caclined at 800 ℃ for 3 h had high purity, homogeneous and single perovskite phase. The electrical conductivity of the LSCCF samples sintered at 1200 ℃ for 3 h, which was measured as a function of temperatures from 100 to 800 ℃ by DC four-probe method in air, decreased with x from 0.05 to 0.20. The value of electrical conductivity was almost equal because of Ca2+, Sr2+ co-dopant resulting in the 'mix effect' while x=0.10 or 0.15. The electrical conductivity of all doped samples was higher than 100 S·cm-1 at intermediate temperatures from 500 to 800 ℃, and there was good compatibility between the LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.展开更多
The transport properties were studied for rare earth manganese oxide La_(0.67)Ca_(0.33)Mn_(1-x)Fe_xO_3 (x=0～0.3) systems. It is found that with increasing Fe^(3+)-doping content x, the resistance increases and the in...The transport properties were studied for rare earth manganese oxide La_(0.67)Ca_(0.33)Mn_(1-x)Fe_xO_3 (x=0～0.3) systems. It is found that with increasing Fe^(3+)-doping content x, the resistance increases and the insulator-metal transition temperature (T_(IM)) shifts to lower temperature. If the doping content is small, the transport properties manifest metallic characteristics in the temperature range of T<T_(IM), while they will obey a thermal activation model in the temperature range of T>T_(IM). Such a behavior may be attributed to the Fe^(3+)-doping and possible Mn ions scattering to electrons. The Fe^(3+) doping may lead to the formation of Fe^(3+)-O^(2-)-Mn^(4+) channels, which could terminate the double exchange Mn^(3+)-O^(2-)-Mn^(4+) channels. The antiferromagnetic clusters of Fe ions may induce the Mn ions to scetter to the electrons.展开更多
SINCE the discovery of high-T<sub>c</sub> superconductors, experiments have revealed that the phase diagrams of La<sub>2-x</sub>Sr<sub>x</sub>CuO<sub>4</sub> and YBa<...SINCE the discovery of high-T<sub>c</sub> superconductors, experiments have revealed that the phase diagrams of La<sub>2-x</sub>Sr<sub>x</sub>CuO<sub>4</sub> and YBa<sub>2</sub>Cu<sub>3</sub>O<sub>6+x</sub> resemble each other. The antiferromagnetic phase is commonly situated in the vicinity of the superconductive phase. In Bi-2212 sys-展开更多
The effect of Y substitution for Ca on the crystal structure and electronic states of Bi_2Sr_2CaCu_2O_(8+y) was studied. It is found that the modulation period of the incommensurate superlattice along b axis decreases...The effect of Y substitution for Ca on the crystal structure and electronic states of Bi_2Sr_2CaCu_2O_(8+y) was studied. It is found that the modulation period of the incommensurate superlattice along b axis decreases from 4.7b to about 4.0b gradually, which implies the change of the extra oxygen atoms residing within double Bi-O layers. Two kinds of modulation structures with periods of 4b and 8b exist in the same compound as Ca is completely substituted by Y. XPS was employed to study the change in the electronic structure. The results suggest that the variation of superconductivity is not caused by the slight change in crystal structure, but rather by the hole filling in O2p orbitals in CuO_2 layers. For this substituted system, it is still the case where one hole in Cu3d orbital (3d^9) is corresponding to the strong correlation antiferromaguetic insulator, and an extra hole in O2p orbital in CuO_2 layer (3d^9L) to the superconductor.展开更多
Magnetoresistanoe in the temperature region from 300 K to liquid helium temperature has been measured on good (100) oriented La2/3Ca1/3MnO2 thin films prepared by d.c. magnetron sputtering on ZrO2 (100) substrates. It...Magnetoresistanoe in the temperature region from 300 K to liquid helium temperature has been measured on good (100) oriented La2/3Ca1/3MnO2 thin films prepared by d.c. magnetron sputtering on ZrO2 (100) substrates. It is found that there appears a resistance peak at about TP = 72K at zero magnetic field, and this peak moves to higher temperature with increasing field H, and R decreases simultaneously. However, the magnetoresistance ratio MR = 5R /R (H) = (Ro~ RH) /RH has a different temperature dependence. There are also MR peaks, but the temperature of maximum MR is at about 25 K which does not change with changing external magnetic field. The heat treatment (annealed at 700C in 105’Pa O2 for 30min) will make R reduce dramatically and has an effect on the temperature dependence of R and its MR.展开更多
Epitaxial La2/3Ca1/3 MnO3 thin films were prepared on NdGaO3(110) substrates by d. c. magnetron sputtering method. The measurements of magnetoresistance ρ(H) upon magnetic field at different temperatures were carried...Epitaxial La2/3Ca1/3 MnO3 thin films were prepared on NdGaO3(110) substrates by d. c. magnetron sputtering method. The measurements of magnetoresistance ρ(H) upon magnetic field at different temperatures were carried out in the field range of 0 - 8 T. It is found that p(H) obeys the following relations: when the temperature(T) is higher than the Curie temperature Tc, ρ ( H ) =1/α(T)+β(T)H2; below Tc, ρ ( H ) = ρ0 ( T ) 1/A(T)+B(T)exp(H/C(Y)),and ρ(H) =1/κa(T)+γ(T)H when T is far below TC. It is Suggested that the negative magnetoresistive effect is mainly due to enhancement of the magnetoconductance.展开更多
文摘Background 5-dihydroxyanthraquinone-2-carboxylic acid (rhein) inhibits oxidoreduction induced by reducing nicotingamide adenine dinucleotide in the mitochondria and reducing reactive oxygen species, it also suppresses lipid peroxidation in rat brain homogenates. This study was to assess the effects of anthraquinone derivatives, rhein on synaptic transmission in the rat hippocampal CA_1 pyramidal cell layer by intracellular recording.Methods The excitatory postsynaptic potential (EPSP) evoked by stimulation of the Schaffer collaterals in the presence of bicuculline (15 μmol/L) was depressed by application of rhein (0.3-30 μmol/L). The amplitude of the EPSP was restored within 20 minutes after removal of rhein from the supernatant. At a concentration of 30 μmol/L, rhein reduced the amplitude of the EPSP to 42%±3.7% (n=24) of the control. Subsequently, wavelet spectral entropy was used to analyze the EPSP. Results A strong positive correlation was observed between the wavelet spectral entropy and other parameters such as amplitude, slope of rising phase and slope of descending phase of the EPSP. The paired-pulse facilitation (PPF) of the EPSP was significantly increased by rhein (30 μmol/L). The inhibitory postsynaptic potential (IPSP) recorded in the presence of CNQX (20 μmol/L) and APV (40 μmol/L) is not altered by rhein (30 μmol/L). Conclusions Rhein (30 μmol/L) can decrease the frequency but not the amplitude of the miniature EPSP (mEPSP). It is suggested that rhein inhibits excitatory synaptic transmission by decreasing the release of glutamate in rat hippocampal CA_1 pyramidal neurons.
基金Project supported in part by Fundacao de AmparoàPesquisa do Estado de Sao Paulo-FAPESP(2013/07296-2,2016/23891-6,2017/26105-4,2019/01732-1)Financiadora de Estudos e Projetos-FINEP,Conselho Nacional de Desenvolvimento Científico e Tecnológico-CNPQ(166281/2017-4,305792/2020-2)CAPES。
文摘In this work,the impact of the doping process on the photoluminescence emission of CaWO_(4) as a function of the concentration of Eu^(3+) cation(0.01 mol%,0.02 mol%,0.04 mol%,0.06 mol%,0.08 mol%,and 0.10 mol%) is discussed in detail.Ca_(1-x)WO~4:xEu^(3+) samples were successfully synthesized by a simple coprecipitation method followed by microwave irradiation.The blue shift in the absorption edge confirms the quantum confinement effect and the band gap energy covers the range from 3.91 to 4.18 eV,as the amount of Eu^(3+) cations increases.The experimental results are sustained by first-principles calculations,at the density functional theory level,to decipher the geometry and electronic properties,thereby enabling a more accurate and direct comparison between theory and experiment for the Ca_(1-x)WO_(4):xEu^(3+) structure.
基金the National High-Tech Development Plan (2006AA05Z417)the Natural Science Foundation of Lia-oning Province (20062145)the Education department of Liaoning Province (05L073)
文摘The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitation method with metal-nitrates as starting materials and mixed alkali (NaOH and Na2CO3) as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, and the crystal structure and particles morphology of the precursors which were calcined at 600, 800, 1000 ℃ for 3 h were characterized using XRD, SEM technologies. Compared with the solid state reaction of constituent oxides, when the pH value of the precipitating solution was in the range of 9.1～9.5, the LSCCF powders from the precursors caclined at 800 ℃ for 3 h had high purity, homogeneous and single perovskite phase. The electrical conductivity of the LSCCF samples sintered at 1200 ℃ for 3 h, which was measured as a function of temperatures from 100 to 800 ℃ by DC four-probe method in air, decreased with x from 0.05 to 0.20. The value of electrical conductivity was almost equal because of Ca2+, Sr2+ co-dopant resulting in the 'mix effect' while x=0.10 or 0.15. The electrical conductivity of all doped samples was higher than 100 S·cm-1 at intermediate temperatures from 500 to 800 ℃, and there was good compatibility between the LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.
文摘The transport properties were studied for rare earth manganese oxide La_(0.67)Ca_(0.33)Mn_(1-x)Fe_xO_3 (x=0～0.3) systems. It is found that with increasing Fe^(3+)-doping content x, the resistance increases and the insulator-metal transition temperature (T_(IM)) shifts to lower temperature. If the doping content is small, the transport properties manifest metallic characteristics in the temperature range of T<T_(IM), while they will obey a thermal activation model in the temperature range of T>T_(IM). Such a behavior may be attributed to the Fe^(3+)-doping and possible Mn ions scattering to electrons. The Fe^(3+) doping may lead to the formation of Fe^(3+)-O^(2-)-Mn^(4+) channels, which could terminate the double exchange Mn^(3+)-O^(2-)-Mn^(4+) channels. The antiferromagnetic clusters of Fe ions may induce the Mn ions to scetter to the electrons.
文摘SINCE the discovery of high-T<sub>c</sub> superconductors, experiments have revealed that the phase diagrams of La<sub>2-x</sub>Sr<sub>x</sub>CuO<sub>4</sub> and YBa<sub>2</sub>Cu<sub>3</sub>O<sub>6+x</sub> resemble each other. The antiferromagnetic phase is commonly situated in the vicinity of the superconductive phase. In Bi-2212 sys-
基金Project supported by the National Natural Science Foundation of China and by the Laboratory of Structure and Element Analysis, Academia Sinica
文摘The effect of Y substitution for Ca on the crystal structure and electronic states of Bi_2Sr_2CaCu_2O_(8+y) was studied. It is found that the modulation period of the incommensurate superlattice along b axis decreases from 4.7b to about 4.0b gradually, which implies the change of the extra oxygen atoms residing within double Bi-O layers. Two kinds of modulation structures with periods of 4b and 8b exist in the same compound as Ca is completely substituted by Y. XPS was employed to study the change in the electronic structure. The results suggest that the variation of superconductivity is not caused by the slight change in crystal structure, but rather by the hole filling in O2p orbitals in CuO_2 layers. For this substituted system, it is still the case where one hole in Cu3d orbital (3d^9) is corresponding to the strong correlation antiferromaguetic insulator, and an extra hole in O2p orbital in CuO_2 layer (3d^9L) to the superconductor.
基金supported by the National Natural Science Foundation of China.
文摘Magnetoresistanoe in the temperature region from 300 K to liquid helium temperature has been measured on good (100) oriented La2/3Ca1/3MnO2 thin films prepared by d.c. magnetron sputtering on ZrO2 (100) substrates. It is found that there appears a resistance peak at about TP = 72K at zero magnetic field, and this peak moves to higher temperature with increasing field H, and R decreases simultaneously. However, the magnetoresistance ratio MR = 5R /R (H) = (Ro~ RH) /RH has a different temperature dependence. There are also MR peaks, but the temperature of maximum MR is at about 25 K which does not change with changing external magnetic field. The heat treatment (annealed at 700C in 105’Pa O2 for 30min) will make R reduce dramatically and has an effect on the temperature dependence of R and its MR.
基金Project supported by the National Natural Science Foundation of China (Grant No. 19504012) the Chinese Academy of Sciences
文摘Epitaxial La2/3Ca1/3 MnO3 thin films were prepared on NdGaO3(110) substrates by d. c. magnetron sputtering method. The measurements of magnetoresistance ρ(H) upon magnetic field at different temperatures were carried out in the field range of 0 - 8 T. It is found that p(H) obeys the following relations: when the temperature(T) is higher than the Curie temperature Tc, ρ ( H ) =1/α(T)+β(T)H2; below Tc, ρ ( H ) = ρ0 ( T ) 1/A(T)+B(T)exp(H/C(Y)),and ρ(H) =1/κa(T)+γ(T)H when T is far below TC. It is Suggested that the negative magnetoresistive effect is mainly due to enhancement of the magnetoconductance.
