ISSN 0253-2778

CN 34-1054/N

2017 Vol. 47, No. 12

Display Method:
Original Paper
Synthesis and characterization of sodium and potassium iminopyrrol-1-ides and their catalysis toward the ring-opening polymerization of rac-lactide
TIAN Lulu, WANG Zhongxia
2017, 47(12): 978-987. doi: 10.3969/j.issn.0253-2778.2017.12.002
Reaction of 2-(R2N=CH)-5-R-C4H2NH (H
Toxicity of halloysite nanotubes in liver of mice after oral administration
WANG Xue, XU Xiaolong, GONG Jiachun, GUI Zongxiang, HU Tingting
2017, 47(12): 988-995. doi: 10.3969/j.issn.0253-2778.2017.12.003
Halloysite is widely used in many fields due to its natural hollow nanotubular structure. To assess the liver toxicity of the purified halloysite nanotubes (HNTs) in mice via oral route, purified HNTs were orally administered to mice at 4, 20 and 100 mg/kg BW body weight (BW) every day for 30 d. Oral administration of HNTs stimulates the growth of the mice at low dose (4 mg/kg BW) with no liver toxicity, but inhibits the growth of the mice and induces oxidative stress in the liver at high dose (≥20 mg/kg BW). In addition, oral administration of HNTs at high dose causes Al accumulation in liver, which induces hepatic dysfunction and histopathologic changes.
Thermodynamic properties of a DNA hairpin under a pulling force
ZHANG Donghua, WANG Jiajun, XIA Baicheng, YU Wancheng
2017, 47(12): 996-1001. doi: 10.3969/j.issn.0253-2778.2017.12.004
The phase transition of a DNA hairpin under a pulling force was investigated by using the two-dimensional (2D) Langevin dynamics simulations. It is found that the unfolded probability could be quantitatively expressed as a function of the pulling force, which is interpreted from the perspective of statistical mechanics. Then, by performing vast simulations with different parameter sets, the force-intensity of base pairing and the force-temperature phase diagram was plotted, respectively. It is shown that the increasing intensity of base pairing and the decreasing temperature are in favor of the folded states. The phase diagrams obtained in the present work are conductive to deepening understanding of the thermodynamic properties of a DNA hairpin under a pulling force.
Study on X-ray nondestructive testing of SOFC metal brazing
SHI Weiwei, XIE Bin
2017, 47(12): 1002-1005. doi: 10.3969/j.issn.0253-2778.2017.12.005
In order to solve the sealing problems of tube plate type (plate type) solid oxide fuel cell(SOFC), 95AgCu solder was used to seal single cell and interconnector by air brazing. The difference between 95AgCu solder and powder was analyzed by X-ray nondestructive testing and the welding quality was evaluated through life test of single cells. Results show that the use of X-ray nondestructive test can not only optimize the welding process, but also form high-quality and imporous weld utilizing a forming welding piece. Measured open circuit voltage and single cell power within 120 h at 750 ℃ show that brazing materials and the process are suitable for sealing the SOFC stack.
Cloud property differences between precipitating and non-precipitating warm clouds over global oceans derived from satellite remote sensing
2017, 47(12): 1006-1014. doi: 10.3969/j.issn.0253-2778.2017.12.006
Data collected from quasi-synchronous Aqua/MODIS and CloudSat/CPR measurements were used to compare cloud parameters between precipitating and non-precipitating warm clouds over global oceans. The characteristics of cloud water vertical structure near cloud top, which were implied by the contrasts among the three cloud droplet effective radii (R16, R21, R37) retrieved from distinct near-infrared channels of MODIS, were especially examined and their discrepancies between the two cloud categories were clarified. It is found that the global distribution of warm clouds has notable regional features. The valid range of most cloud properties are similar for precipitating and non-precipitating warm clouds, including cloud top temperature (CTT), optical thickness (COT), geometrical thickness, cloud droplet effective radius (Re), cloud water path (CWP). But there is still evident distinction between their averages, with the COT, Re, CWP of precipitating warm clouds significantly higher than non-precipitating ones. According to the statistics, the model of R37
Localized atmospheric density prediction method based on NARX neural network
CHANG Xinzhuo, YANG Kaizhong, LI Xin, SHEN Hongxin, LI Hengnian
2017, 47(12): 1015-1022. doi: 10.3969/j.issn.0253-2778.2017.12.007
Errors of orbit determination and prediction for low earth orbit (LEO) satellites mainly arise from the lack of accuracy in existing atmospheric density models. The lack of observation methods and insufficient understanding of physical mechanism of the upper atmosphere have brought difficulties to the modelling of atmospheric density. Two line element (TLE) was used to calibrate the MSIS atmospheric model, aiming at getting a localized density model along the orbit. Then a predictor was built based on the nonlinear autoregressive neural network with exogenous inputs (NARX). It uses calibrated MISIS model and a set of proxies of solar and geomagnetic activities to predict localized density values along the future orbit of a satellite. This model was applied for different types of satellite orbits and tested for different prediction windows. Comparison with the predictor based on the MSIS model shows a decrease in the mean error of the proposed model, which throws new light on improving the accuracy of LEO satellites’ short-time prediction.
A novel generator for the preparation of monodisperse femtoliter droplets at high frequency
WU Tao, LUO Zhaofeng, WU Ping, HE Liqun
2017, 47(12): 1023-1028. doi: 10.3969/j.issn.0253-2778.2018.12.008
It has been experimentally demonstrated that droplets, as tiny as 2 μm in diameter, can be generated at rates as high as 20 kHz, with much lower flow rates than needed in the case of conventional flow focusing. The configuration for generating such small droplets consists of a capillary cross, with an exit orifice inserted into the disperse phase channel. With such a structure, the interface of two immiscible fluids is deformed to a shape like Taylor cone. Upon its formation, tiny droplets are issued from the cone tip. This method is found to be highly stable across the flow rate ratios of external to internal fluids, 1~60. By manipulating capillary inner diameters, tip diameters and tip positions, as well as the flow ratio, one can effectively produce droplets in various sizes.
CFD analysis of flow distributions and pressure drops in the whole CFETR WCCB blanket module with different turbulence models
GAO Zhongping, ZHAO Pinghui, LI Yuanjie, DENG Weiping, GE Zhihao, NIE Xingchen
2017, 47(12): 1029-1036. doi: 10.3969/j.issn.0253-2778.2017.12.009
As a primary blanket candidate for CFETR(China Fusion Engineering Test Reactor), the water-cooled ceramic breeder (WCCB) blanket is now attracting enormous attention owing to the admirable thermal hydraulic performance and experienced industrial base of pressurized water. To analyze the flow distributions and pressure drops in the designed WCCB blanket, three dimensional numerical simulation of the coolant flow in the whole WCCB module was conducted based on the computational fluid dynamics (CFD) method. The results demonstrate that the flow distribution is uniform in cooling plates (CPs), stiffening plates (SPs) and side walls (SWs), but is non-uniform in the first wall (FW) with the unevenness of mass flow rate in FW being about 30%. The maximal pressure drop is in the CPs caused by the long coolant channel and the frequent change of flow direction. The effect of turbulence models needs to be comprehensively studied due to structural complexity of the designed manifold. Sensitivity analysis of turbulence models shows that different turbulence models have little effect on the mass flux distributions in all parts of the blanket module. However, the deviation of pressure drops is notable as a result of different turbulence models. In addition, the current design of the blanket module needs to be optimized further because of the non-uniform flow distribution in FW.
Effect of post-annealing on the structure and dielectric property of La2Ti2O7 thin film
SHAO Tao, WANG Yuyin, LI Yuanyuan, YANG Mei, HU Chuansheng, QI Zeming
2017, 47(12): 1037-1043. doi: 10.3969/j.issn.0253-2778.2017.12.010
La2Ti2O7 thin films were grown on Si (100) substrates by using pulsed laser deposition method. The effect of post-annealing on the structural and dielectric properties of the films at different temperatures was studied by using X-ray diffraction, atomic force microscopy and synchrotron infrared transmission spectroscopy. The results show that the as-deposited thin film is amorphous and annealing thin film is crystallized into monoclinic structure. The infrared spectrum reveals that the annealing can significantly increase the dielectric constant. The as-deposited thin film has a low dielectric constant attributed to the loss of some phonon modes, especially the low frequency mode. This indicates post-annealing has an important influence on the dielectric property of La2Ti2O7 thin film.