The growth of thin PbO layers on lead films: II. Theory

The lead oxidation data obtained in the experimental part of this paper were analyzed statistically and found to fit a rate law of the form, $\text{d}\text{X}\text{d}\text{t}\text{= α}\text{exp}\text{(}\text{X}{}_1\text{X}\text{)}$. Using this dependence and certain known characteristics of orthorhombic PbO crystals, an oxidation mechanism is proposed which invokes the generation of oxygen vacancies at the Pb/PbO interface and their attentdant electric-field assisted transport across the oxide layer. This model seems to be consistent with the defect structure of PbO, and provides an explanation for the effects of temperature, oxygen pressure, lead microstructure and indium doping on the oxidation rate parameters, α and X. When combined with the observed thickness dependence of the oxide strain, the results suggests that the field required for the growth law arises from a piezoelectric potential present across the PbO layer. The α and X₁ parameters show an expected interactive dependence upon one another, and the piezoelec-trically-coupled electric and mechanical forces control the oxidation rate.     

高通量天然产物化学和毛细管核磁共振探头技术的应用

介绍了近几年为高通量药物筛选构建大型天然产物样品库的高通量天然产物化学,即多通道平行高效液相制备和平行液质联用分析技术;详细介绍了核磁共振新技术即体积小和质量灵敏度高的毛细管核磁共振探头技术,该探头技术的成功应用使得天然产物样品库中活性化合物的结构鉴定所需样品量降低到前所未有的微克级水平;展望了源于中药的天然产物作为小分子探针开展脑功能方面的化学基因组学研究。     

Synthesis and metalation of novel fluorescent conjugated macrocycles

[reaction: see text] Large shape-persistent conjugated macrocycles with tunable pore diameters in the nanometer regime were prepared by a simple, one-pot procedure. These new self-assembled macrocycles contain rings of 48-66 covalently bonded atoms and can bind multiple metal ions, forming soluble luminescent complexes.     

Electron cyclotron wave propagation, absorption, and backscattermeasurements in a laboratory plasma

Broadband microwave propagation and absorption processes and backscatter from objects immersed in a magnetized, finite, warm plasma column is addressed. In particular, the propagation, absorption, and backscatter of electron cyclotron waves are measured and compared with bounded vacuum hot plasma wave propagation, absorption, and ray tracing theory. The nonreciprocal nature of the transmission and absorption in an anisotropic plasma is measured. A homodyne technique which isolates the scattering from a single object in the plasma from the scattering from all other objects in the plasma and the walls of the containment device is developed and utilized. The range of absorption frequencies and nonreciprocity of the transmission signal are shown to be well correlated with wave trajectories in the associated regions of the Clemmow-Mullaly-Allis (CMA) diagram. It is shown that quasi-parallel propagation of electron cyclotron waves near resonance is present and that the transverse effects of wavenumber on propagation in the cylindrical plasma are small