纳米技术的标准化进程和伦理问题

纳米技术的快速发展和纳米技术产品的逐步进入市场, 引起了人们就使用纳米产品对人类健康、安全和环境产生影响的特别关注, 这也是目前伦理学所关心的问题. 标准化不仅在消除贸易障碍、促进国际技术交流和贸易发展、提高产品在国际市场上的竞争能力方面具有重大作用, 对于保障身体健康、生命和环境的安全同样具有重要作用. 本文介绍了纳米技术的健康、安全和环境的标准化进程. 认为上述工作将促进社会科学和自然科学在纳米伦理问题上的交流与沟通, 以期共同解决纳米伦理问题.     

Field trial of an HTS filter system on a CDMA base station

This paper presents the field trial results of a high temperature superconductor filter system (HTSFS) in a code division multiple access (CDMA) mobile communication base station (BTS) in Tangshan, China. The center frequency of the HTSFS is 830 MHz with 1.4% fractional bandwidth. The noise figure (NF) of the HTSFS, including connectors and cables, is 0.8 dB. The field trial results show that after the HTSFS was installed in the receiver front-end of a CDMA base station, the transmitting power of handset was decreased by 3.1 dB on average. Up to now, the HTSFS has been running steadily in the base station for more than 22 months, demonstrating the reliability and stability of the system.     

Concentration level and distribution of polycyclic aromatic hydrocarbons in soil and grass around Mt. Qomolangma, China

High mountains may serve as a condenser for persistent organic pollutants. In the present study, soil and grass samples from Mt. Qomolangma region, China were collected from 4600 to 5620 m a.s.I and were analyzed for polycyclic aromatic hydrocarbons （PAHs） to determine if they are concentrated at colder, more elevated sites and to evaluate their possible resources and fractionation. The total PAHs concentration in soil samples was 〈 600 ng g^-1, the critical value to differentiate PAHs levels in remote and urban regions. This implied the PAHs levels at Mt. Qomolangma are relatively low and what one might expect in such a remote region of the world. These low values may represent a soil background for mid-latitude Northern Hemisphere soils away from the direct influence of an anthropogenic source. As for the distribution pattern, the low molecular weight PAHs were prone to accumulate at higher altitude, while the high molecular weight PAHs inversely related or unrelated with elevation. Based on high concentration of phenanthrene at elevated sample site and the ratios of individual PAHs, we deduced that home-heating combustion and vehicle emission may result in the constitution trait of PAHs in this mountain region. Monsoon traveling over India, Pakistan and other countries with dense population may carry contaminant to Mt. Qomolangma region.     

一种学生管理信息系统的设计与实现

给出了一种学生管理信息系统的设计与实现，详细地论述了系统中的学生信息表示，给出了系统组成，系统功能，并已在湘潭大学基本上实现了该系统。     

Genetic analysis and gene mapping of a dominant presenescing leaf gene <Emphasis Type="Italic">PSL3</Emphasis> in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Leaf senescence as an active process is essential for plant survival and reproduction. However, premature senility is harmful to agricultural production. In this study, a rice mutant, named as psl3 (presescing leaf 3) isolated from EMS-treated Jinhui 10, displays obvious premature senility features both in morphological and physiological level. Genetic analysis showed that mutant trait was controlled by a single dominant gene (PSL3), which was located on rice chromosome 7 between SSR marker c7sr1 and InDel marker ID10 with an interval of 53.5 kb. The result may be useful for the isolation of the PSL3 gene.     

Water solubility in orthopyroxene: Dependence on temperature and Al content

The water solubility in Al-Fe-Mg orthopyroxene [(Mg,Fe,Al)(Si,Al)O₃: X _Fe = 0.1] was investigated as a function of temperature and Al contents. Experiments were performed at 10 kbar with temperatures ranging from 800 to 1200°C under water-saturated conditions. Water contents in the (Mg,Fe)SiO₃-H₂O-Al₂O₃ system were determined using unpolarized Fourier transform infrared spectroscopy. The present results show that water solubility in Al-bearing orthopyroxene decreases systematically with temperature from approximately 1 weight % at 800°C to 568 ± 58 ppm at 1200°C and increase significantly with increasing Al₂O₃ contents under the same annealing temperature and pressure. Combined with published results on the dependence of hydroxyl solubility on water fugacity and pressure, the present results can be described by the relation $C_{OH} = A(T)f_{H_2 O}^{n = 0.5} \exp \left( { - \frac{{\Delta H^{1bar} + \Delta V^{solid} P}} {{RT}}} \right)$ where A = 0.0024 ± 0.0015 ppm/bar^0.5, ΔH ^1bar = ?103.348 ± 9.768 kJ/mol, and solid ΔV ^solid = 9.2 ± 1.1 cm³/mol. This equation implies that the incorporation mechanism of water in aluminous orthopyroxene involves the isolated OH groups. Based on the experimentally established solubility model used in this study, it is suggested that water solubility decreases with increasing temperature under typical upper mantle pressure. The predicted temperature dependence of water solubility is in good agreement with the previous experimental observations in Al-bearing orthopyroxene, but the opposite dependence is observed in Al-free systems. Moreover, our estimation of the water solubility in upper-mantle minerals as a function of depth for a typical oceanic geotherm might be of potential importance in interpreting the geophysical observations.     

Experimental study on spectral responses of offshore oil slick

Using the seawater taken from Liaodong Bay and crude oil taken from Liaohe Oilfield, a laboratory experiment was designed to study the change of reflectance spectrum of artificial offshore oil slick with its thickness and to identify the spectrum ranges suitable for quantifying the thickness of the oil slick. During the experiment, crude oil was continuously dropped into the seawater to generate artificial oil slick with different thicknesses. After every drop of crude oil was added, reflectance spectrum of the oil slick was measured with a high resolution spectroradiometer （ASD FieldSpec Pro FR）. The influence of oil slick thickness on its reflectance spectrum was explored through statistical analysis. The results show that the reflectance of oil slick changes marginally with oil slick thickness and higher than that of seawater in infrared band from 1150 to 2500 nm. This spectrum range can be practically used to distinguish oil slick from seawater. In the spectrum range from 400 to 1150 nm, the reflectance of oil slick decreases with its thickness. The negative power function is the best-fit function expressing the relationship between the reflectance and thickness. The spectral characteristics of oil slick are very distinct at 550 and 645 nm. They are the best wavelengths for monitoring the existence of offshore oil slick and estimating its thickness.     

左旋聚乳酸纳米纤维膜的热处理研究

研究了热牵伸和热定型处理对静电纺丝左旋聚乳酸平行纳米纤维膜力学性能和微观结构的影响。拉伸试验表明,在100 ℃热空气条件下,沿纤维排列方向上牵伸300%、热定型10 min的纤维膜力学性能最佳,其抗拉强度和模量分别达到103 MPa和1.83 GPa。扫描及透射电子显微镜观察显示,经热牵伸后,纤维的直径随牵伸率的增加而减小,其致密及平行程度相应提高,纤维内部转变为垂直于纤维轴且平行排列的片晶结构。差示扫描量热分析结果表明,纤维膜的结晶度随牵伸率的增加而增大,随热定型时间先增加后减小。广角X射线衍射和小角X射线散射分析可知,纤维膜经热处理后的结晶为α型,其微晶尺寸及晶面间距均随牵伸率的增加而减小,随热定型时间先增加后减小,而纤维内部的针状微缺陷随着牵伸率的增加而变得更加狭长有序,使得纤维膜的力学性能得以提高。     

Measurement of the Newtonian gravitational constant based on the principle of free fall

The Newtonian gravitational constant (G) is one of the fundamental physical constants. This paper introduces a method to determine the Newtonian gravitational constant based on the principle of free fall, through measuring the change of gravity from the disturbed mass with an FG5/112 absolute gravimeter. This method has good repeatability. The measurement precision can be improved by error control and a large number of experiments. The constant G is obtained by two experiments, and the measured value is (6.6665±0.0554)×10⁻¹¹ m³/(kg·s²). Supported by the National Basic Research Program of China (Grant No. 2003CB716300) and Key Project of the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-125)     

Magnetocrystalline anisotropy and spin-wave stiffness in tensile-strained La0.67Ba0.33MnO3 films: An investigation via ferromagnetic resonance

Tensile-strained epitaxial La_0.67Ba_0.33MnO₃ (LBMO) film has been prepared by magnetron sputtering technique on (001) oriented spinel MgAl₂O₄ substrate. The transport and magnetic measurements give an insulator-metal transition and paramagnetic-ferromagnetic transition occurring at ～150 K and 250 K respectively, which implies the phase separation in such a tensile-strained film. By analyzing the angular and temperature dependences of the ferromagnetic resonance (FMR), we determine the magnetocrystalline anisotropy of the film. It is found that the tensile-strained film is dominated by an easy-axis corresponding to the compressive out-of-plane direction, though the magnitudes of anisotropy constants are relatively small and their temperature dependences are some complex. Furthermore, the FMR spectra show additional spin wave resonance (SWR), and the field positions can be indexed to follow a linear dependence on the square of index n. The scaling gives a spin-wave exchange stiffness D of 20.7 meV Ų at low temperature, which is less than half of that in strain-free LBMO films, implying that the double exchange interaction is remarkably suppressed in the tensile-strained LBMO films.