含氟水性涂料中全氟辛烷磺酰基化合物(PFOS)的高效液相色谱-串联质谱法测定

建立了用高效液相色谱-串联质谱(HPLC-MS/MS)测定含氟水性涂料中全氟辛烷磺酰基化合物(PFOS)的方法.含氟水性涂料中的PFOS采用超声提取,上清液经固相萃取柱淋洗萃取,萃取液经0.2 μm有机滤膜过滤后,以80:20 (体积比)的乙腈-10 mmol/L乙酸铵溶液为流动相,经HPLC分离后用多级反应监测(MRM)模式测定.用2个子离子的相对丰度定性,外标法定量.PFOS在0.002 ～0.1 mg/L范围内线性良好(r=0.999 5),回收率为96% ～101%,相对标准偏差为0.54% ～2.92%,方法的定量下限(S/N≥10)为2 mg/L(0.0002%),满足欧盟法规对含氟水性涂料中PFOS的限量检测要求.     

玩具中苯酚和双酚A的高效液相色谱-荧光检测方法研究

采用高效液相色谱分离,荧光检测器检测,建立了三种不同类型的玩具中苯酚和双酚A的测定方法.用超声提取的方式处理样品,对提取溶剂和提取时间进行选择,确定以甲醇-水(65:35,V/V)作为提取溶液,超声提取20 min.苯酚和双酚A分别在0.012～1.0 mg/L、0.03～2.5 mg/L范围内线性良好,相关系数均达到0.9999,检出限分别为0.6 mg/kg和1.5 mg/kg,不同加标水平的回收率为90.5%～104.3%,其相对标准偏差为0.4%～3.8%.该方法操作简便,灵敏度高、重现性好,能有效提取和测定三类玩具中的苯酚和双酚A.     

Role of Oxygen Vacancy Arrangement on the Formation of a Conductive Filament in a ZnO Thin Film

We perform first-principles calculations for ZnO thin films with oxygen vacancy defects. The densities of states, partial atomic densities of states, charge density differences and atomic populations are presented. We show that the SET process, i.e., from a high resistive state to a low resistive state, is attributable to the aggregation and regular arrangement of the oxygen vacancies, which causes the formation of conductive filaments and leads to the low resistive state of the system.     

宽视场航空高光谱成像仪光学系统设计

宽视场大相对孔径航空高光谱成像仪已成为航空海洋水色遥感等领域的迫切需求,根据宽视场和大相对孔径的研究目标,采用离轴两镜消像散望远镜和改进型Offner光谱仪匹配的结构型式,设计了一个视场40°、相对孔径1/2.2、工作波段0.4~1.0μm的航空高光谱成像仪光学系统,在传统Offner光谱仪中插入同心弯月透镜来提高Offner光谱仪的相对孔径和成像质量.运用光学设计软件ZEMAX对高光谱成像仪光学系统进行了光线追迹和优化设计,并对设计结构进行了分析.结果表明:光学系统各个波长的光学传递函数在奈奎斯特频率28lp/mm处均达到0.67以上,谱线弯曲和谱带弯曲均小于6.5%像元,便于光谱和辐射定标,完全满足设计指标要求,且体积小、重量轻,适合航空遥感应用.     

Hierarchical nanowires for high-performance electrochemical energy storage

Nanowires are promising candidates for energy storage devices such as lithium-ion batteries, su- per（：apa.citors and lithium-air batteries. However, simple-structured nanowires have some limitations hence the strategies to make improvements need to be explored and investigated. Hierarchical nanowires with enhanced periormanee have been considered as an ideal candidate for energy storage due to the novel structures and/or synergistic properties. This review describes some of the recent progresses in the hierarchical nanowire merits, classification, synthesis and performance in energy storage applieat, ions. Herein we discuss the hierarchical nanowires based on their structural design from three major categories, including exterior design, interior design and aligned nanowire assembly. This review also briefly outlines the prospects of hierarchical nanowires in morphology control, property enhancement and application versatility.     

Topological superconductivity in Janus monolayer transition metal dichalcogenides

The Janus monolayer transition metal dichalcogenides (TMDs) $MXY$ ($M={\rm Mo}$, W, $etc$. and $X, Y={\rm S}$, Se, $etc$.) have been successfully synthesized in recent years. The Rashba spin splitting in these compounds arises due to the breaking of out-of-plane mirror symmetry. Here we study the pairing symmetry of superconducting Janus monolayer TMDs within the weak-coupling framework near critical temperature $T_{\rm c}$, of which the Fermi surface (FS) sheets centered around both $ărGamma$ and $K (K')$ points. We find that the strong Rashba splitting produces two kinds of topological superconducting states which differ from that in its parent compounds. More specifically, at relatively high chemical potentials, we obtain a time-reversal invariant $s + f + p$-wave mixed superconducting state, which is fully gapped and topologically nontrivial, $i.e.$, a $\mathbb{Z}_2$ topological state. On the other hand, a time-reversal symmetry breaking $d + p + f$-wave superconducting state appears at lower chemical potentials. This state possess a large Chern number $|C|=6$ at appropriate pairing strength, demonstrating its nontrivial band topology. Our results suggest the Janus monolayer TMDs to be a promising candidate for the intrinsic helical and chiral topological superconductors.     

Rotational Deformation of Neutron Stars

The rotational deformations of two kinds of neutron stars are calculated by using Hartle‘s slow-rotation formulism. The results show that only the faster rotating neutron star gives an obvious deformation. For the slow rotating neutron star with a period larger than hundreds of millisecond, the rotating deformation is very weak.     

Origin of the Downturn in Inverse Susceptibility Observed above the Curie Temperature in Perovskite Manganites

The measurement of low-field susceptibility X as a function of temperature T for La2/3Ca1/3MnO3 shows a significant downturn in 1/X(T) above the Curie temperature Tc, a behaviour generally observed in perovskite manganites. Such a downturn is argued to be due to the segregation of ferromagnetic clusters with larger spins in the paramagnetic matrix. Based on this consideration, a phenomenological expression for X(T) is proposed,in which the total susceptibility is assumed to be a sum of two susceptibilities arising from magnetic entities in the PM background and the FM clusters with T-dependent effective spins, respectively. The result is in good agreement with the experimental data obtained in La2/3Ca1/3MnO3.     

Unusual Transport Properties near the Insulator-Metal Transition in Colossal Magnetoresistive Manganites

It is argued that a combination of the Griffiths theory and the double-exchange mechanism predicts the random distribution of ferromagnetic metallic clusters above the Curie temperature TC in colossal magnetoresistive manganites. Along this line, we propose a model for the temperature dependence of resistivity that yields a quantitative agreement with experimental data obtained in a typical manganite La2/3Ca1/3MnO3. Our result indicates that the formation and growth of ferromagnetic metallic clusters are responsible for the observation of unusual transport properties near the insulator-metal transition.     

质子中子星物质的热力学性质

在相对论σ-ω-ρ模型的平均场近似下, 研究了质子中子星物质在均熵状态下的组成、温度和物态方程. 如给定每一个重子的熵, 一些热力学量的值将随重子密度的增加而增加, 当考虑超子时, 这些值会减小. 给定重子密度, 中子在S=2时的组分比S=1时的小, 而质子、电子、μ子在S=2时的组分比S=1时的大, 特别是在低密度区域. S是每个重子的熵. 保持重子密度不变, 在低密度区域, 超子在S=2时的组分比S=1时的大, 在高密度区域则相反. 同样, 在同一重子密度处, S=2时的温度、能量密度及压强分别比S=1时的大. 另外, 有限熵对粒子组分和温度的影响比对质子中子星物质的物态方程的影响大. 还研究了反粒子的贡献, 他们确实很小.