The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied ...The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries（pores） of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.展开更多
The 2-（hydroxymethyl）pyridine modified C60 （PY-C60） and methoxydiglycol modified C60 （MDG-C60） are synthesized using Bingel-Hirsch reaction and characterized by nuclear magnetic resonance （NMR） and mass spectr...The 2-（hydroxymethyl）pyridine modified C60 （PY-C60） and methoxydiglycol modified C60 （MDG-C60） are synthesized using Bingel-Hirsch reaction and characterized by nuclear magnetic resonance （NMR） and mass spectra. PY-C60 and MDG-C60 can bind to glucose oxidase （GOx） and quench the fluorescence of tryptophan （Trp） residue in GOx through static mechanism. The conformation of GOx is disturbed after formation of complex with these fullerene derivatives. Kinetic analysis indicates that PY-C60 and MDG-C60 may affect the catalytic activity of GOx with a partial mixed-type inhibition mechanism. In the plasma glucose concentration range （3.6--5.2 mmol·L-1）, PY-C60 may significantly accelerate the catalytic velocity of GOx, however, MDG-C60 exerts almost no obvious change to the initial velocity of GOx, suggesting that elaborate design of molecular structure of fullerene derivative is very important for regulating the biological activity of fullerene-enzyme complex.展开更多
Non-relativistic phase shifts for a generalized Yukawa potential V(r) =-V_0( e^(-αr)/r)-V_1( e^(-2αr)/r^2) are studied by the amplitude-phase method and by a frequently used analytic method based on a Pekeris-type a...Non-relativistic phase shifts for a generalized Yukawa potential V(r) =-V_0( e^(-αr)/r)-V_1( e^(-2αr)/r^2) are studied by the amplitude-phase method and by a frequently used analytic method based on a Pekeris-type approximation of power-law potential terms.Small variations of V_1 seem to have marginal effects on the effective potential and on exact phase shifts.However,as pointed out in this study,a Pekeris-type approximation in scattering applications often implies serious distortions of both effective potentials and phase shifts.The Pekeris-type based analytic approximation in this study seems to give low-quality scattering results for this model potential at low energies.展开更多
基金funded by the National Natural Science Foundation of China(51372193)the Natural Science Basic Research Plan in the Shaanxi Province of China(2014JM6224)
文摘The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries（pores） of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.
基金This work was supported by National Natural Science Foundation of China （No. 21073143）, the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry （Nos. N9YK0003, N9YK0005）, Northwestern Ploytechnical University Foundation for Fundamental Research （Nos. JC200822, JC20100239）.
文摘The 2-（hydroxymethyl）pyridine modified C60 （PY-C60） and methoxydiglycol modified C60 （MDG-C60） are synthesized using Bingel-Hirsch reaction and characterized by nuclear magnetic resonance （NMR） and mass spectra. PY-C60 and MDG-C60 can bind to glucose oxidase （GOx） and quench the fluorescence of tryptophan （Trp） residue in GOx through static mechanism. The conformation of GOx is disturbed after formation of complex with these fullerene derivatives. Kinetic analysis indicates that PY-C60 and MDG-C60 may affect the catalytic activity of GOx with a partial mixed-type inhibition mechanism. In the plasma glucose concentration range （3.6--5.2 mmol·L-1）, PY-C60 may significantly accelerate the catalytic velocity of GOx, however, MDG-C60 exerts almost no obvious change to the initial velocity of GOx, suggesting that elaborate design of molecular structure of fullerene derivative is very important for regulating the biological activity of fullerene-enzyme complex.
文摘Non-relativistic phase shifts for a generalized Yukawa potential V(r) =-V_0( e^(-αr)/r)-V_1( e^(-2αr)/r^2) are studied by the amplitude-phase method and by a frequently used analytic method based on a Pekeris-type approximation of power-law potential terms.Small variations of V_1 seem to have marginal effects on the effective potential and on exact phase shifts.However,as pointed out in this study,a Pekeris-type approximation in scattering applications often implies serious distortions of both effective potentials and phase shifts.The Pekeris-type based analytic approximation in this study seems to give low-quality scattering results for this model potential at low energies.
