ICP-MS法测定不同采收时间宽叶荨麻中微量元素含量

采用微波消解,ICP-MS法分析不同采收时间宽叶荨麻中18种微量元素Al,Ba,Ca,Co,Cr,Cu,Fe,K,Li,Mg,Mn,Mo,Na,Ni,P,Pb,S和Zn的含量。该方法的相对标准偏差在1.2%～5.3%之间,加标回收率在95.4%～101.2%之间。结果表明宽叶荨麻中K,P,S,Ca,Na含量较高;Fe,Mg,Mn,Zn含量次之;有潜在生理毒性的元素Al,Cr,Pb的含量较低,并且在宽叶荨麻中微量元素呈现明显的季节性动态变化,此结果为进一步研究宽叶荨麻药理药效与微量元素的关系以及更好的开发这一资源提供理论数据。     

Precise measurement of the line width of the photoassociation spectra of ultracold molecules by using a frequency shifter

We propose a technique to precisely measure the line width of the photoassociation spectra of the excited cesium molecule by using a frequency shifter to generate two laser beams with a precise frequency difference. A series of photoassociation (PA) spectra are recorded with two laser beam induced molecular lines, whose peak separation serves as an accurate frequency ruler to measure the line width of the PA spectra. The full width half maximum line width was studied as a function of PA laser intensity. The extrapolated value at zero laser intensity is (34.84 ± 0.22) MHz. By analyzing other broadening mechanisms, a value of (32.02 ± 0.70) MHz was deduced. It is shown that this scheme is inexpensive, simple, robust, and is promising for applications in a variety of other atomic species.     

Model study on steady heat capacity in driven stochastic systems

We explore two- and three-state Markov models driven out of thermal equilibrium by non-potential forces, to demonstrate basic properties of the steady heat capacity based on the concept of quasistatic excess heat. It is shown that large enough driving forces can make the steady heat capacity negative. For both the low- and high-temperature regimes we propose an approximative thermodynamic scheme in terms of “dynamically renormalized” effective energy levels.     

High-bandwidth and low-loss photonic crystal power-splitter with parallel output based on the integration of Y-junction and waveguide bends

A 1×2 power-splitter with parallel output that exhibits high-bandwidth and low-loss splitting for TE-polarized light is designed based on a photonic crystal slab in a silicon-on-insulator (SOI) material. The high performance is achieved by the integration of a Y-junction and 60° waveguide bends, which is designed to ensure single-mode operation, and keep the output channels of the power-splitter be parallel to the input channel. With a three-dimensional finite-difference time-domain (3D-FDTD) technique, ultralow-loss output of the optimized power-splitter with normalized transmission above 45% (in the range 3.216±0.18 dB) is obtained in the high-bandwidth range 1472–1634 nm, which covers the entire C-band of optical communication. In addition, the simulation results demonstrate that when the manufacture error of the lattice shift (dx) is in the range of ±10 nm, the disturbance of the transmission and the bandwidth are 1.52% and 6.79%, respectively. Both the specific result and the general idea of integration design are promising in the optical integrated circuit (OIC) and integrated optical devices in the future.     

点缺陷对硼掺杂直拉硅单晶p/p~+外延片中铜沉淀的影响

系统研究了点缺陷对晶体硅中氧沉淀生成的影响,及点缺陷和氧沉淀对重掺硼直拉硅单晶p/p⁺外延片中铜沉淀的影响.样品先在不同的气氛下进行1250℃/60 s快速热处理,随后在750℃/8 h+1050℃/16 h常规热处理过程中引入铜沾污.通过腐蚀结合光学显微镜研究发现,以O₂作为保护气氛时,p⁺衬底中的沉淀密度较小,以Ar和N₂作为保护气氛时,重掺硼p⁺衬底中生成了高密度的沉淀,且在上述所有样品的外延层中均无缺陷生成.研究认为,以O₂作为保护气时引入的自间隙硅原子（Si_I）可以抑制沉淀的形成,而以Ar和N₂作为保护气氛时引入的空位则会促进沉淀的生成,这是导致此差异的主要原因.另外,研究还发现,p/p⁺外延结构能很好地吸除硅片中的铜杂质,从而保持了外延层的洁净.     

Rapid sea-level change in the Late Guadalupian (Permian) on the Tethyan side of South China: litho- and biostratigraphy of the Chaotian section in Sichuan

The Capitanian (Late Guadalupian) Maokou Formation at Chaotian in northern Sichuan, South China, is composed mainly of shallow marine shelf carbonates deposited on the Tethyan side of South China. By detailed field mapping and scientific drilling, we newly found out unique fossil assemblages and a sharp lithologic change in the upper part of the Maokou Formation. The main part of the Maokou Formation (over 130 m thick) is composed of algal packstone with Wordian-Capitanian large-tested fusulines, rugose corals and other sessile benthos, whereas the Uppermost Member (13 m thick) is composed of black limy mudstone/chert with Capitanian offshore biota (ammonoids, radiolarians, and conodonts). The topmost Capitanian conodont zones are missing; however, the Maokou Formation is disconformably overlain by 260+/-4 Ma volcanic ash (Wangpo bed) and the Early Lopingian Wujiaping Formation with plant-bearing coaly mudstone and shallow marine carbonates (packstone). The newly identified facies change indicates that northern Sichuan has experienced rapid sea-level changes in the late Guadalupian, i.e., first a transgression in the mid-Capitanian and then a regression across the Guadalupian-Lopingian boundary. As the end-Guadalupian is characterized by a global regression, such a volatile sea-level fluctuation, in particular the sea-level rise, is unique to the Tethyan side of South China. The newly recognized relatively deep-water late Guadalupian sequence adds new paleo-environmental information and further provides a paleotectonic interpretation of the low-latitude eastern Tethyan margin immediately before the end-Guadalupian mass extinction.     

Transmission phase of a quantum dot with Kondo correlation near the unitary limit

The complex transmission amplitude of a quantum dot (QD) with Kondo correlation was measured near the unitary limit. The transmission phase was observed to evolve almost linearly over a range of about 1.5 pi when the Fermi energy was scanned through a spin degenerate energy level of the QD. Surprisingly, the phase in the Coulomb Blockade regime, with one more electron entering the dot, was strongly affected by a preexistence of Kondo correlation. These results suggest that a full explanation of the Kondo effect may go beyond the framework of the Anderson model.     

Ultrasound promoted synthesis of thioesters from 2-mercaptobenzoxa(thia)zoles

An ultrasound-enhanced method has been developed for the synthesis of a variety of thioesters from benzoyl chlorides and 2-mercaptobenzoxa(thia)zoles. Applying this methodology, 14 compounds were synthesized in excellent yields.     

5,10,15-三(五氟苯基)Corrole及其相似卟啉化合物的光物理特性

采用稳态和时间分辨的瞬态光谱技术对比研究了一种Corrole化合物5,10,15-三(五氟苯基)Corrole(FtsTPC)和一种卟啉化合物5,10,15,20-四(五氟苯基)卟啉(F20TPP)的光物理特性.结果表明:F15TPC的B带吸收峰较宽而F20TPP的强而窄,F15TPC的Q带有两个吸收峰而F20TPP有四个.F15TPC的荧光量子产率为0.15,荧光寿命为4.8 ns,F20TPP的荧光量子产率为0.05,荧光寿命为11.1 ns;与F20TPP相比F15TPC具有发光效率高、荧光寿命短的特点.F15TPC具有较大的发光速率常数和无辐射跃迁速率常数,这可能是由于F15TPC少了一个氟代苯基,致使其发色团本身的电子结构发生变化所致.另外空间结构的不对称性和非共面性也对其光物理性质有影响.