Helium-containing Ti Glms are prepared using magnetron sputtering in the helium-argon atmosphere. Isochronal annealing at different temperatures for an hour is employed to reveal the behaviour of helium bubble growth....Helium-containing Ti Glms are prepared using magnetron sputtering in the helium-argon atmosphere. Isochronal annealing at different temperatures for an hour is employed to reveal the behaviour of helium bubble growth. Ion beam analysis is used to measure the retained helium content. Helium can release largely when annealing above 970K. A thermal helium desorption spectroscopy system is constructed for assessment of the evolution of helium bubbles in the annealed samples by linear heating （OAK/s） from room temperature to 1500K. Also, Doppler broadening measurements of positron annihilation radiation spectrum are performed by using changeable energy positron beam. Bubble coarsening evolves gradually below 680K, migration and coalescence of small bubbles dominates in the range of 68-970 K, and the Ostwald ripening mechanism enlarges the bubbles with a massive release above 970K.展开更多
The electrochemical growth of nanowires in nuclear track membranes has been studied and a strong plasma absorption of copper nanowires in the visible region of the electromagnetic spectrum is observed.The result of th...The electrochemical growth of nanowires in nuclear track membranes has been studied and a strong plasma absorption of copper nanowires in the visible region of the electromagnetic spectrum is observed.The result of the plasma absorption is qualitatively in agreement with the prediction of the appropriate formulation of effective medium theory.展开更多
We study the structural defects in the SiO, film prepared by electron cyclotron resonance plasma chemical vapour deposition and annealing recovery evolution. The photoluminescence property is observed in the as-deposi...We study the structural defects in the SiO, film prepared by electron cyclotron resonance plasma chemical vapour deposition and annealing recovery evolution. The photoluminescence property is observed in the as-deposited and annealed samples. [-SiO3]^2- defects are the luminescence centres of the ultraviolet photoluminescence （PL） from the Fourier transform infrared spectroscopy and PL measurements. [-SiO3]^2- is observed by positron annihilation spectroscopy, and this defect can make the S parameters increase. After 1000℃ annealing, [-SiO3]^2- defects still exist in the films.展开更多
X65 low carbon steel was exposed to Co-60 radiation source with 1.25 MeV gamma rays, and cumulatively absorbed gamma irradiation doses（1, 2, and 3 Mgy） were obtained after different exposure time（333, 667, and 100...X65 low carbon steel was exposed to Co-60 radiation source with 1.25 MeV gamma rays, and cumulatively absorbed gamma irradiation doses（1, 2, and 3 Mgy） were obtained after different exposure time（333, 667, and 1000 h）. The effect of cumulative gamma irradiation on microstructure and corrosion behaviour of the carbon steel in unirradiated aerobic Beishan groundwater at 25℃ was investigated by using positron annihilation, scanning vibrating electrode, and electrochemical techniques. Cumulative gamma irradiation increases vacancy intensity and decreases open circuit potential（OCP） of carbon steel. They indicate that the irradiated carbon steel is activated. Measured current density distribution above the irradiated carbon steel shows that cumulative gamma irradiation accelerates localized corrosion after 0.5 h of immersion. In contrast, the analysis of electrochemical impedance spectroscopy of the irradiated carbon steel indicates that localized corrosion is transformed into general corrosion after 12 h of immersion, which is also accelerated by cumulative gamma irradiation.展开更多
Salvia miltiorrhiza bunge(SMB) has been widely used as a traditional Chinese medicine for a long time,and today more and more attention has been paid to the effective components in Chinese traditional medicine,especia...Salvia miltiorrhiza bunge(SMB) has been widely used as a traditional Chinese medicine for a long time,and today more and more attention has been paid to the effective components in Chinese traditional medicine,especially to rare earth elements(REEs).14 kinds of REEs in SMB from different areas were analyzed by the methods of ICP-MS.The results showed that the total concentration of REEs(as REO,the same below) ranged from 8.43(as dry weight,the same below) to 37.30 mg/kg,and the concentrations of La,Ce and Nd were higher than 2 mg/kg except Nd in SMB from Beijing.So the total concentration of REEs in SMB was much higher than that in rice,corn and barley,which could be the mechanism of curative effect of SMB on cardiovascular cerebrovascular system,digestive system,respiratory system,countershock and antibiotic.The character of other elements and the content of REEs in soil from different areas should be responsible for the difference,but the allocation mechanism of REEs in SMB should be further studied.展开更多
Measurements were performed of K-shell ionization cross sections of Ti element by 10～30 keV positron impact using the thick-target method. The effects of multiple scattering of incident positron and from bremsstrahlu...Measurements were performed of K-shell ionization cross sections of Ti element by 10～30 keV positron impact using the thick-target method. The effects of multiple scattering of incident positron and from bremsstrahlung photons and annihilation photons with the thick-target method are discussed with the Monte Carlo code PENELOPE. Meanwhile, the Monte Carlo method is also applied to determine the detection efficiencies of X- and γ-ray detectors. Our experimental K-shell ionization cross sections for Ti element are compared with the distorted-wave Born approximation （DWBA） theoretical predictions, and it is found that the agreement of the experimental data and theoretical values is good and this indicates that the experimental method adopted in this study is applicable.展开更多
A method and system for automatically and simultaneously measuring the light output of multiple scintillators,or each scintillating unit of an array,were developed.Using a large area flat panel PSPMT H8500,the light o...A method and system for automatically and simultaneously measuring the light output of multiple scintillators,or each scintillating unit of an array,were developed.Using a large area flat panel PSPMT H8500,the light output and energy resolution were obtained automatically by comparing with reference scintillators or array using an Energy Table,Look-up Table and energy spectrum data.The aim of developing an efficient performance evaluation of scintillators was achieved.Using the method,a scintillator performance testing system was set up and six LYSO crystals and a 3×3 LYSO array were measured.The results showed that the light output and energy resolution were accurately measured automatically.The deviation of repeat measurements for the same sample was not more than 2%,and the nonlinear deviation of the system was not more than 3%.The system is suitable for measuring the performance of crystals,especially where the mass measurement of crystals and arrays is required.展开更多
Direct nitridation of Si(100)surface by low energy N^(+)_(2)ion beam implantation at room temperature for differention doses and angles of incidence has been investigated by in-situ Auger electron spectroscopy and gla...Direct nitridation of Si(100)surface by low energy N^(+)_(2)ion beam implantation at room temperature for differention doses and angles of incidence has been investigated by in-situ Auger electron spectroscopy and glancing Rutherford backscattering-channeling(RBS-C)measurements.The results show that with increase of N^(+)_(2)ion dose the N concentration in the Si surface increases and reaches to a surface stoichiometry close to that of Si3N4.The saturation dose and the thickness of the silicon nitride layer are related to the N^(+)_(2)ion energy.Complete nitride layer can be formed at incident angles of 0°-30°.At larger angles the degree of nitridation decreases and no nitride layer could be found at incident angles larger than 54°.The RBS-C results also suggest that a heavy damaged layer beneath the surface nitride layer can be formed due to ion beam implantation.展开更多
Yttria-stabilized zirconia （YSZ） is irradiated with 2.0-MeV Au2＋ ions and 30-keV He＋ ions. Three types of He, Au, Au ＋ He （successively） ion irradiation are performed. The maximum damage level of a sequential d...Yttria-stabilized zirconia （YSZ） is irradiated with 2.0-MeV Au2＋ ions and 30-keV He＋ ions. Three types of He, Au, Au ＋ He （successively） ion irradiation are performed. The maximum damage level of a sequential dual ion beam implanted sample is smaller than single Au ion implanted sample. A comparable volume swelling is found in a sequential dual ion beam irradiated sample and it is also found in a single Au ion implanted sample. Both effects can be explained by the partial reorganization of the dislocation network into weakly damaged regions in the dual ion beam implanted YSZ. A vacancy-assisted helium trapping/diffusion mechanism in the dual ion beam irradiated condition is discussed. No phase transformation or amorphization behavior happens in all types of ion irradiated YSZ.展开更多
Helium-containing titanium films were prepared on Si substrates with various biases applied by magnetron sputtering under stable He/Ar ambiance.Rutherford backscattering and elastic recoil detection analyses are used ...Helium-containing titanium films were prepared on Si substrates with various biases applied by magnetron sputtering under stable He/Ar ambiance.Rutherford backscattering and elastic recoil detection analyses are used to measure the thickness of the He-Ti films and the helium depth profile,respectively.Experiments of x-ray diffraction and variable energy positron annihilation spectroscopy are carried out to investigate the microstructures of titanium films and the corresponding helium-related defects developed.The behavior of the implanted He,the microstructure of the He-Ti film and the formation of He-related defects all are affected by the substrate biases applied.展开更多
Various helium-containing titanium films were deposited on Si substrates by magnetron sputtering under different helium/argon (He/Ar) ambiances.Helium concentrations and corresponding depth profiles in the Ti films ar...Various helium-containing titanium films were deposited on Si substrates by magnetron sputtering under different helium/argon (He/Ar) ambiances.Helium concentrations and corresponding depth profiles in the Ti films are obtained by elastic recoil detection analysis (ERDA).X-ray diffraction (XRD) measurements are carried out to evaluate the crystallization of the titanium films.Vacancy-type defects and their depth profiles were revealed by slow positron beam analysis (SPBA).It is found that the defect-characteristic parameter S rises with the increment of the He/Ar flow ratios.The variation of S indicates the formation and evolution of various Herelated defects,with uniform distribution into the depth around 400nm.展开更多
OBJECTIVE The antioxidative system in human hepatocellular carcinoma was investigated. METHODS The activities of cytosolic catalase (CAT), superoxide dismu-tase, glutathione peroxidase (GSH-Px), glutathione S-tranfera...OBJECTIVE The antioxidative system in human hepatocellular carcinoma was investigated. METHODS The activities of cytosolic catalase (CAT), superoxide dismu-tase, glutathione peroxidase (GSH-Px), glutathione S-tranferase and levels of reduced glutathione, total protein thiols and malondialdehyde were assayed in 10 cases of hepatocellular carcinoma and adjacent normal liver. RESULTS Hepatoma tissues showed higher activities of CAT, GSH -Px and lower content of total antioxidative capacity compared to adjacent normal liver tissue (P<0.05). CONCLUSION These findings suggest that the antioxidative defense-related enzymes and antioxidants are largely regulated in hepatoma cells. However, the mechanism which is not clear requires further investigation.展开更多
The mineralization ages reported in the past in the Tuwu-Yandong copper district not only are different,but also fall into the Hercynian epoch.This study has achieved 9 zircon and 7 apatite fission track analysis resu...The mineralization ages reported in the past in the Tuwu-Yandong copper district not only are different,but also fall into the Hercynian epoch.This study has achieved 9 zircon and 7 apatite fission track analysis results.The zircon fission track ages range from 158 Ma to 289 Ma and the apatite ages are between 64 Ma and 140 Ma.The mineralization accords with the regional tectonics in the copper district.We consider that the zircon fission track age could reveal the mineralization age based on annealing zone temperature of 140―300℃and retention temperature of~250℃for zircon fission track,and metallogenetic temperature of 120―350℃in this ore district.Total three mineralization epochs have been identified,i.e.,289―276 Ma,232―200 Ma and 165―158 Ma,and indicate occurrence of the min-eralization in the Indosinian and Yanshan epochs.Corresponding to apatite fission track ages,the three tectonic-mineralizing epochs are 140―132 Ma,109―97 Ma and 64 Ma,which means age at about 100℃after the mineralization.The three epochs lasted 146 Ma,108 Ma and about 100 Ma from~250℃to~100℃and trend decrease from early to late.It is shown by the fission track modeling that this district underwent three stages of geological thermal histories,stable in Cretaceous and cooling both before Cretaceous and after 20 Ma.展开更多
In this study, iron speciation in five standard clay samples was characterized. Iron mobilization from these clays was then measured in acidic media. For comparison, a commercially available Arizona test dust （ATD） ...In this study, iron speciation in five standard clay samples was characterized. Iron mobilization from these clays was then measured in acidic media. For comparison, a commercially available Arizona test dust （ATD） was also observed. The results showed that the free-Fe contents of clays were commonly lower than that of dust aerosols. The components of clays were dominant by the structural Fe held in the aluminosilicate lattice. The iron solubility of the clays were in the order of KGa-2 〉 SWy-2 〉 CCa-2 〉 IMt-2 〉 NAu- 2. Based upon the M6ssbauer spectrum and transmission electron microscopy （TEM） analysis, the Fe（Ⅱ） fraction and the Fe/Si ratio of clay particles changed after dissolution, suggesting the total Fe solubility depended on the Fe atom states existing within the aluminosilicate lattice. The Fe in KGa-2 and SWy-2 was most likely substituted for alkaline elements as the interlayer ions held by ionic bonds in the aluminosilicate, which are more liable to dissolution. However, the Fe in NAu-2 was more likely to be bound by strong covalent bonds in aluminosilicate mineral, which is less soluble. The much highly soluble Fe in ATD was not only linked to the dissolution of an appreciable fraction of Fe（Ⅱ）, but also could be attributed to the fact that the Fe bonds in the clay fraction of ATD were mainly present as ionic bonds. The TEM images showed that reacted clay particles displayed less aggregate particles, with nanoparticle aggregates and the Fe/S-rich tiny particles attached to the remains.展开更多
Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge struct...Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy,Ti^3＋-V O defect complexes（or clusters） have been identified in annealed crystals at a high vacuum.We elucidate that the unpaired 3d electrons in Ti^3＋ ions provide the observed room-temperature ferromagnetism.In addition,excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.展开更多
The magnetic properties and defect types of virgin and N-doped TiO2 single crystals are probed by superconducting quantum interference device （SQUID）, X-ray photoelectron spectroscopy （XPS）, and positron annihilat...The magnetic properties and defect types of virgin and N-doped TiO2 single crystals are probed by superconducting quantum interference device （SQUID）, X-ray photoelectron spectroscopy （XPS）, and positron annihilation analysis （PAS）. Upon N doping, a twofold enhancement of the saturation magnetization is observed. Apparently, this enhancement is not related to an increase in oxygen vacancy, rather to unpaired 3d electrons in Ti3＋, arising from titanium vacancies and the replacement of O with N atoms in the futile structure. The production of titanium vacancies can enhance the room temperature ferromagnetism （RTFM）, and substitution of O with N is the onset of ferromagnetism by inducing relatively strong ferromagnetic ordering.展开更多
In this paper, the impact of the viaduct on flow and traffic exhausting particles dispersion within urban street canyons was numerically simulated using a computational fluid dynamics （CFD） model. Two-dimensional fl...In this paper, the impact of the viaduct on flow and traffic exhausting particles dispersion within urban street canyons was numerically simulated using a computational fluid dynamics （CFD） model. Two-dimensional flow and dispersion of particles from traffic exhausts were modeled using the standard k-e turbulence model. The street canyons with a viaduct at different widths and different heights above the ground are simulated. The results show that the airflow in street canyon is evidently in- fluenced by the viaduct： The position of the main vortex center is changed, especially there are two strong vortexes when the viaduct is placed at 10 m height above the ground. It is found based on the study of the particles number concentrations （PNCs） that the viaduct may mitigate the pollution level in the street canyon sometimes. The impact of the viaduct width on PNCs is stronger than that of the height. The study of PNDs reveals that the mean PNCs at the wall of upwind building increase when a viaduct is placed in street canyon. In addition, it is found based on the study of mean particles residence time （PRT） that the removal of the particles strongly correlates to the mean PNCs. The results indicate that the viaduct is an important factor to influence the flow patterns and particles dispersion in street canyons.展开更多
By thermal neutron irradiation particle tracking autoradiography(PTA)technique,the development of boron segregation at grain boundaries in ultra-low carbon micro-alloy steels was investigated during cooling from 1150&...By thermal neutron irradiation particle tracking autoradiography(PTA)technique,the development of boron segregation at grain boundaries in ultra-low carbon micro-alloy steels was investigated during cooling from 1150°C to 850°C,and the effect of Cu on boron segregation at grain boundaries was discussed.By positron annihilation lifetime(PAL)technique,the changes of vacancy-type defects with temperatures and the effect of Cu on vacancy-type defects in the cooling process were discussed.Results show that,the concentration of boron at grain boundaries increases rapidly at the beginning of the cooling;after that,it begins to decrease;and then,it increases gradually again.The addition of Cu not only increases the concentration of boron at grain boundaries but also speeds up the development process of boron segregation at grain boundaries.During the continuous cooling process,the addition of Cu significantly affects the change of vacancy-type defects with temperatures in ultra-low carbon micro-alloy steels.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 10176008, 50131050 and 10475016.
文摘Helium-containing Ti Glms are prepared using magnetron sputtering in the helium-argon atmosphere. Isochronal annealing at different temperatures for an hour is employed to reveal the behaviour of helium bubble growth. Ion beam analysis is used to measure the retained helium content. Helium can release largely when annealing above 970K. A thermal helium desorption spectroscopy system is constructed for assessment of the evolution of helium bubbles in the annealed samples by linear heating （OAK/s） from room temperature to 1500K. Also, Doppler broadening measurements of positron annihilation radiation spectrum are performed by using changeable energy positron beam. Bubble coarsening evolves gradually below 680K, migration and coalescence of small bubbles dominates in the range of 68-970 K, and the Ostwald ripening mechanism enlarges the bubbles with a massive release above 970K.
基金Supported by the open laboratory of nuclear analysis technique of Chinese Academy of Sciencesin part by the 95 key project of Chinese Academy of Sciences.
文摘The electrochemical growth of nanowires in nuclear track membranes has been studied and a strong plasma absorption of copper nanowires in the visible region of the electromagnetic spectrum is observed.The result of the plasma absorption is qualitatively in agreement with the prediction of the appropriate formulation of effective medium theory.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10475096 and 10575112, the Institute of Heavy Ion Physics of Peking University, and Beijing Free Electron Laser Laboratory.
文摘We study the structural defects in the SiO, film prepared by electron cyclotron resonance plasma chemical vapour deposition and annealing recovery evolution. The photoluminescence property is observed in the as-deposited and annealed samples. [-SiO3]^2- defects are the luminescence centres of the ultraviolet photoluminescence （PL） from the Fourier transform infrared spectroscopy and PL measurements. [-SiO3]^2- is observed by positron annihilation spectroscopy, and this defect can make the S parameters increase. After 1000℃ annealing, [-SiO3]^2- defects still exist in the films.
基金supported by Key Research Program of Frontier Sciences,Chinese Academy of Sciences[QYZDY-SSWJSC012]National Natural Science Foundation[No.51771211]+1 种基金the National Key Research and Development Program of China[2017YFB0702100,2016YFE0105200]Key Program of the Chinese Academy of Sciences[ZDRW-CN-2017-1]
文摘X65 low carbon steel was exposed to Co-60 radiation source with 1.25 MeV gamma rays, and cumulatively absorbed gamma irradiation doses（1, 2, and 3 Mgy） were obtained after different exposure time（333, 667, and 1000 h）. The effect of cumulative gamma irradiation on microstructure and corrosion behaviour of the carbon steel in unirradiated aerobic Beishan groundwater at 25℃ was investigated by using positron annihilation, scanning vibrating electrode, and electrochemical techniques. Cumulative gamma irradiation increases vacancy intensity and decreases open circuit potential（OCP） of carbon steel. They indicate that the irradiated carbon steel is activated. Measured current density distribution above the irradiated carbon steel shows that cumulative gamma irradiation accelerates localized corrosion after 0.5 h of immersion. In contrast, the analysis of electrochemical impedance spectroscopy of the irradiated carbon steel indicates that localized corrosion is transformed into general corrosion after 12 h of immersion, which is also accelerated by cumulative gamma irradiation.
基金Project supported by Foundation of Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,Chinese Academy of Sciences (K139)Youth Foundation of General Research Institutes for Nonferrous Metals (83218)
文摘Salvia miltiorrhiza bunge(SMB) has been widely used as a traditional Chinese medicine for a long time,and today more and more attention has been paid to the effective components in Chinese traditional medicine,especially to rare earth elements(REEs).14 kinds of REEs in SMB from different areas were analyzed by the methods of ICP-MS.The results showed that the total concentration of REEs(as REO,the same below) ranged from 8.43(as dry weight,the same below) to 37.30 mg/kg,and the concentrations of La,Ce and Nd were higher than 2 mg/kg except Nd in SMB from Beijing.So the total concentration of REEs in SMB was much higher than that in rice,corn and barley,which could be the mechanism of curative effect of SMB on cardiovascular cerebrovascular system,digestive system,respiratory system,countershock and antibiotic.The character of other elements and the content of REEs in soil from different areas should be responsible for the difference,but the allocation mechanism of REEs in SMB should be further studied.
基金supported by National Natural Science Foundation of China (Nos.10674097,10774106)
文摘Measurements were performed of K-shell ionization cross sections of Ti element by 10～30 keV positron impact using the thick-target method. The effects of multiple scattering of incident positron and from bremsstrahlung photons and annihilation photons with the thick-target method are discussed with the Monte Carlo code PENELOPE. Meanwhile, the Monte Carlo method is also applied to determine the detection efficiencies of X- and γ-ray detectors. Our experimental K-shell ionization cross sections for Ti element are compared with the distorted-wave Born approximation （DWBA） theoretical predictions, and it is found that the agreement of the experimental data and theoretical values is good and this indicates that the experimental method adopted in this study is applicable.
基金Supported by National Natural Science Foundation of China (10805049,11175200)Knowledge Innovation Program of the Chinese Academy of Sciences,Grant (KJCX2-EW-N06)Special-funded Programme on National Key Scientific Instruments and Equipment Development (2011YQ120096)
文摘A method and system for automatically and simultaneously measuring the light output of multiple scintillators,or each scintillating unit of an array,were developed.Using a large area flat panel PSPMT H8500,the light output and energy resolution were obtained automatically by comparing with reference scintillators or array using an Energy Table,Look-up Table and energy spectrum data.The aim of developing an efficient performance evaluation of scintillators was achieved.Using the method,a scintillator performance testing system was set up and six LYSO crystals and a 3×3 LYSO array were measured.The results showed that the light output and energy resolution were accurately measured automatically.The deviation of repeat measurements for the same sample was not more than 2%,and the nonlinear deviation of the system was not more than 3%.The system is suitable for measuring the performance of crystals,especially where the mass measurement of crystals and arrays is required.
基金Supported by the National Natural Science Foundation of China under Grant No.19275059the Chinese Academy of Sciences.
文摘Direct nitridation of Si(100)surface by low energy N^(+)_(2)ion beam implantation at room temperature for differention doses and angles of incidence has been investigated by in-situ Auger electron spectroscopy and glancing Rutherford backscattering-channeling(RBS-C)measurements.The results show that with increase of N^(+)_(2)ion dose the N concentration in the Si surface increases and reaches to a surface stoichiometry close to that of Si3N4.The saturation dose and the thickness of the silicon nitride layer are related to the N^(+)_(2)ion energy.Complete nitride layer can be formed at incident angles of 0°-30°.At larger angles the degree of nitridation decreases and no nitride layer could be found at incident angles larger than 54°.The RBS-C results also suggest that a heavy damaged layer beneath the surface nitride layer can be formed due to ion beam implantation.
基金supported by the National Basic Research and Development Program of China(Grant Nos.2010CB832904 and 2010CB832902)the National Natural Science Foundation of China(Grant No.91226202)
文摘Yttria-stabilized zirconia （YSZ） is irradiated with 2.0-MeV Au2＋ ions and 30-keV He＋ ions. Three types of He, Au, Au ＋ He （successively） ion irradiation are performed. The maximum damage level of a sequential dual ion beam implanted sample is smaller than single Au ion implanted sample. A comparable volume swelling is found in a sequential dual ion beam irradiated sample and it is also found in a single Au ion implanted sample. Both effects can be explained by the partial reorganization of the dislocation network into weakly damaged regions in the dual ion beam implanted YSZ. A vacancy-assisted helium trapping/diffusion mechanism in the dual ion beam irradiated condition is discussed. No phase transformation or amorphization behavior happens in all types of ion irradiated YSZ.
基金by the National Natural Science Foundation of China under Grant Nos 10775102 and 10775101.
文摘Helium-containing titanium films were prepared on Si substrates with various biases applied by magnetron sputtering under stable He/Ar ambiance.Rutherford backscattering and elastic recoil detection analyses are used to measure the thickness of the He-Ti films and the helium depth profile,respectively.Experiments of x-ray diffraction and variable energy positron annihilation spectroscopy are carried out to investigate the microstructures of titanium films and the corresponding helium-related defects developed.The behavior of the implanted He,the microstructure of the He-Ti film and the formation of He-related defects all are affected by the substrate biases applied.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10775102 and 10775101.
文摘Various helium-containing titanium films were deposited on Si substrates by magnetron sputtering under different helium/argon (He/Ar) ambiances.Helium concentrations and corresponding depth profiles in the Ti films are obtained by elastic recoil detection analysis (ERDA).X-ray diffraction (XRD) measurements are carried out to evaluate the crystallization of the titanium films.Vacancy-type defects and their depth profiles were revealed by slow positron beam analysis (SPBA).It is found that the defect-characteristic parameter S rises with the increment of the He/Ar flow ratios.The variation of S indicates the formation and evolution of various Herelated defects,with uniform distribution into the depth around 400nm.
基金This work was supported by the National Natural Science Foundation of China (Major Project No.10490180) Chinese Academy of Sciences (No. KJCX-N01).
文摘OBJECTIVE The antioxidative system in human hepatocellular carcinoma was investigated. METHODS The activities of cytosolic catalase (CAT), superoxide dismu-tase, glutathione peroxidase (GSH-Px), glutathione S-tranferase and levels of reduced glutathione, total protein thiols and malondialdehyde were assayed in 10 cases of hepatocellular carcinoma and adjacent normal liver. RESULTS Hepatoma tissues showed higher activities of CAT, GSH -Px and lower content of total antioxidative capacity compared to adjacent normal liver tissue (P<0.05). CONCLUSION These findings suggest that the antioxidative defense-related enzymes and antioxidants are largely regulated in hepatoma cells. However, the mechanism which is not clear requires further investigation.
基金Supported by the National Basic Research Priorities Program(Grant No 2001CB409804)the National Natural Science Foundation of China(Grant Nos 10475093,10175076 and 40072068)
文摘The mineralization ages reported in the past in the Tuwu-Yandong copper district not only are different,but also fall into the Hercynian epoch.This study has achieved 9 zircon and 7 apatite fission track analysis results.The zircon fission track ages range from 158 Ma to 289 Ma and the apatite ages are between 64 Ma and 140 Ma.The mineralization accords with the regional tectonics in the copper district.We consider that the zircon fission track age could reveal the mineralization age based on annealing zone temperature of 140―300℃and retention temperature of~250℃for zircon fission track,and metallogenetic temperature of 120―350℃in this ore district.Total three mineralization epochs have been identified,i.e.,289―276 Ma,232―200 Ma and 165―158 Ma,and indicate occurrence of the min-eralization in the Indosinian and Yanshan epochs.Corresponding to apatite fission track ages,the three tectonic-mineralizing epochs are 140―132 Ma,109―97 Ma and 64 Ma,which means age at about 100℃after the mineralization.The three epochs lasted 146 Ma,108 Ma and about 100 Ma from~250℃to~100℃and trend decrease from early to late.It is shown by the fission track modeling that this district underwent three stages of geological thermal histories,stable in Cretaceous and cooling both before Cretaceous and after 20 Ma.
基金provided by Ministry of Science and Technology of the People's Republic of China(2016YFC0202700)Ministry of Science and Technology of the People's Republic of China(2016YFE0112200)+3 种基金Ministry of Science and Technology of the People's Republic of China(2016YFC0203700)National Natural Science Foundation of China(Nos.21577022,21190053,and 40975074)International Cooperation Project of Shanghai Municipal Government(15520711200)Marie Sk?odowska-Curie Actions(690958-MARSU-RISE-2015)
文摘In this study, iron speciation in five standard clay samples was characterized. Iron mobilization from these clays was then measured in acidic media. For comparison, a commercially available Arizona test dust （ATD） was also observed. The results showed that the free-Fe contents of clays were commonly lower than that of dust aerosols. The components of clays were dominant by the structural Fe held in the aluminosilicate lattice. The iron solubility of the clays were in the order of KGa-2 〉 SWy-2 〉 CCa-2 〉 IMt-2 〉 NAu- 2. Based upon the M6ssbauer spectrum and transmission electron microscopy （TEM） analysis, the Fe（Ⅱ） fraction and the Fe/Si ratio of clay particles changed after dissolution, suggesting the total Fe solubility depended on the Fe atom states existing within the aluminosilicate lattice. The Fe in KGa-2 and SWy-2 was most likely substituted for alkaline elements as the interlayer ions held by ionic bonds in the aluminosilicate, which are more liable to dissolution. However, the Fe in NAu-2 was more likely to be bound by strong covalent bonds in aluminosilicate mineral, which is less soluble. The much highly soluble Fe in ATD was not only linked to the dissolution of an appreciable fraction of Fe（Ⅱ）, but also could be attributed to the fact that the Fe bonds in the clay fraction of ATD were mainly present as ionic bonds. The TEM images showed that reacted clay particles displayed less aggregate particles, with nanoparticle aggregates and the Fe/S-rich tiny particles attached to the remains.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61006066)the National Natural Science Foundation of China (Grant No. 11175191)
文摘Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy,Ti^3＋-V O defect complexes（or clusters） have been identified in annealed crystals at a high vacuum.We elucidate that the unpaired 3d electrons in Ti^3＋ ions provide the observed room-temperature ferromagnetism.In addition,excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.
基金supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.61006066)
文摘The magnetic properties and defect types of virgin and N-doped TiO2 single crystals are probed by superconducting quantum interference device （SQUID）, X-ray photoelectron spectroscopy （XPS）, and positron annihilation analysis （PAS）. Upon N doping, a twofold enhancement of the saturation magnetization is observed. Apparently, this enhancement is not related to an increase in oxygen vacancy, rather to unpaired 3d electrons in Ti3＋, arising from titanium vacancies and the replacement of O with N atoms in the futile structure. The production of titanium vacancies can enhance the room temperature ferromagnetism （RTFM）, and substitution of O with N is the onset of ferromagnetism by inducing relatively strong ferromagnetic ordering.
基金supported by the Major Project of Knowledge Innovation Program of Chinese Academy of Sciences (Grant No.KJCX3.SYW.N3)the National Natural Science Foundation of China (Grant No.10675159)the Shanghai Natural Science Foundation (Grant No.09ZR1438200)
文摘In this paper, the impact of the viaduct on flow and traffic exhausting particles dispersion within urban street canyons was numerically simulated using a computational fluid dynamics （CFD） model. Two-dimensional flow and dispersion of particles from traffic exhausts were modeled using the standard k-e turbulence model. The street canyons with a viaduct at different widths and different heights above the ground are simulated. The results show that the airflow in street canyon is evidently in- fluenced by the viaduct： The position of the main vortex center is changed, especially there are two strong vortexes when the viaduct is placed at 10 m height above the ground. It is found based on the study of the particles number concentrations （PNCs） that the viaduct may mitigate the pollution level in the street canyon sometimes. The impact of the viaduct width on PNCs is stronger than that of the height. The study of PNDs reveals that the mean PNCs at the wall of upwind building increase when a viaduct is placed in street canyon. In addition, it is found based on the study of mean particles residence time （PRT） that the removal of the particles strongly correlates to the mean PNCs. The results indicate that the viaduct is an important factor to influence the flow patterns and particles dispersion in street canyons.
基金supported by the National Natural Science Foundation of China(Grant No.51276016)the National Basic Research Program of China("973" Project)(Grant No.2012CB720406)
文摘By thermal neutron irradiation particle tracking autoradiography(PTA)technique,the development of boron segregation at grain boundaries in ultra-low carbon micro-alloy steels was investigated during cooling from 1150°C to 850°C,and the effect of Cu on boron segregation at grain boundaries was discussed.By positron annihilation lifetime(PAL)technique,the changes of vacancy-type defects with temperatures and the effect of Cu on vacancy-type defects in the cooling process were discussed.Results show that,the concentration of boron at grain boundaries increases rapidly at the beginning of the cooling;after that,it begins to decrease;and then,it increases gradually again.The addition of Cu not only increases the concentration of boron at grain boundaries but also speeds up the development process of boron segregation at grain boundaries.During the continuous cooling process,the addition of Cu significantly affects the change of vacancy-type defects with temperatures in ultra-low carbon micro-alloy steels.
