Annealing Behaviour of Helium Bubbles in Titanium Films by Thermal Desorption Spectroscopy and Positron Beam Analysis

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.

Fabrication and Optical Property of Copper Nanowires in Nuclear Track Membranes

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.

Evolution of Structural Defects in SiOx Films Fabricated by Electron Cyclotron Resonance Plasma Chemical Vapour Deposition upon Annealing Treatment

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.

Preliminary Measurement of the K-Shell Ionization Cross Sections of Ti by Positron Impact in the Low Energy Region

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.

An efficient method and system for simultaneously measuring the performance of vast scintillating materials

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.

Auger Electron Spectroscopy and Rut herford Backscattering-Channeling Study of Silicon Nitride Formation by Low Energy N^(+)_(2)Ion Implantation

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.

Irradiation effect of yttria-stabilized zirconia by high dose dual ion beam irradiation

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.

Bias Effects on the Growth of Helium-Containing Titanium Films

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.

Helium-Related Defect Evolution in Titanium Films by Slow Positron Beam Analysis

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.

Preliminary Study of Oxidative Stress in Human Hepatocellular Carcinoma and Adjacent Normal Liver Tissues

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.

应用全脑逐像素形态学自动分析方法研究阿尔茨海默氏病的灰质缺失(英文)

目的采用计算机处理核磁共振图像(magnetic resonance imaging,MRI),研究阿尔茨海默氏病(Alzheime's disease,AD)患者的灰质萎缩区域。方法采用逐像素形态学(voxeI-based morphometry,VBM)方法。结果和正常老年人对照组相比,AD病人的海马、海马旁回、内嗅皮层、杏仁体、尾状核头部、颞中回、扣带回、顶下小叶、岛叶和前额叶背外侧区双侧萎缩；右侧丘脑枕、颞上回、顶上小叶不同程度萎缩,而感觉运动皮层、小脑和枕叶相对保持完好。结论 VBM方法克服了以往使用人工勾画感兴趣区(ROI)方法的可重复性差,费时等缺点,可以客观、自动和全面地分析AD的灰质减少,具有良好的临床应用前景。

Defect types and room-temperature ferromagnetism in undoped rutile TiO_2 single crystals

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.

Defect types and room temperature ferromagnetism in N-doped rutile TiO_2 single crystals

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.

Modeling the impact of the viaduct on particles dispersion from vehicle exhaust in street canyons

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.

Effect of Cu on the boron segregation at grain boundaries and vacancy-type defects in ultra-low carbon micro-alloy steels

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.

Investigation of scatter from out of the field of view and multiple scatter in PET using Monte Carlo simulations

In fully three-dimensional （3D） positron emission tomography （PET） imaging, the scatter fraction （SF） is about 40% 60%, which may degrade the imaging quality severely. Scatter correction is important for high quality image reconstruction. Model-based scatter correction has been proved to be accurate and available in clinical PET. However, it does not correct the scatter from out of the field of view （OFOV） and multiple scatters. In this study, we demonstrate the radial and axial distribution of scatters from OFOV when the source is located in different radial positions. In order to apply the above conclusions to different PET systems, we characterize the scatters from OFOV as a function of the ratio of the scanner diameter to the length of the axial field of view （AFOV） by modeling several typical whole-body and micro PET systems. The proportions of true events （S0-0）, single scatter of one photon （S1-0）, single scatter of both photons （S1-1）, double scatter of one photon （S2-0） and multiple scatter （Sm） are also calculated and compared. Here the 3D-PET Monte Carlo simulations are performed with the Geant4 Application for Tomography Emission （GATE）. In summary, the scatters from OFOV tend to be recorded on the lines of response （LOR） far away from the source. They have a much more serious impact on whole-body PET than micro PET depending on the ratio of scanner diameter to the length of AFOV. In whole-body PET, twice scatters including single scatter of both photons （S1-1） and double scatter of one photon （S2-0） add up to about 12% so that twice scatter correction must be taken into account to acquire a high quality reconstruction image.

Effect of cumulative gamma irradiation on microstructure and corrosion behaviour of X65 low carbon steel

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.

Content of rare earth elements in Salvia miltiorrhiza bunge from different areas

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.

Atomic force microscopy study of the rabbit skeletal muscle ryanodine receptors in different functional states

Atomic force microscope was applied to investigate the effect of extrinsic phospholipid on the structure of rabbit skeletal muscle ryanodine receptor/calcium release channel (RyR1). In addition, in the presence of extrinsic phospholipid, the height and elasticity of the RyR1s in different functional states were also measured. The results indicate: (i) most of the RyR1s showed a normal structure only in the presence of extrinsic phospholipid; (ii) treatment of the RyR1s with AMP and Ca2+ together could increase their Young's Modulus but not change their apparent height; (iii) no detectable change in either height or Young's Modulus of the RyR1s appeared, if the RyR1s were treated with other activators or inhibitors.