1,3-Dipolar cycloadditions of dimethyl 2-benzylidenecyclopropane-1,1-dicarboxylate and a number of C-aryl or C-amido nitrones proceed with high efficiency and selectivity with the formation of only one isomeric spiro[cyclopropane-1,4-isoxazolidine] cycloadduct. 相似文献
Biodiesel was synthesized from soybean oil by transesterification over Li2SiO3 catalyst.The Li2SiO3 can be used for biodiesel production directly without further drying or thermal pretreatment,no obvious difference in the FAME conversion(92.4-96.7%) between the air-exposed catalyst(24-72 h) and the fresh one(94.2%).This leads to important benefits when considering industrial applications of Li2SiO3 as a solid catalyst for storing and handling catalyst without taking special actions. 相似文献
In this paper we experimentally and numerically study the left-handed behavior in a biplanar metamaterial operating at microwave
frequency. The metamaterial consists of ϕ-shaped metallic patterns on both sides of a dielectric spacer. The origin of negative refractive index is elucidated by performing
the effective medium analysis. Additionally, the dependence of the left-handed transmission on geometric parameters, such
as the periodicities, the shapes of metallic slabs and continuous wires, and the impact of spacer separation, is examined. 相似文献
Novel luminescent electrospun (ES) fibers have been successfully prepared from a conjugated rod–coil block copolymer, poly[2,7‐(9,9‐dihexylfluorene)]‐block‐poly(methyl methacrylate) (PF‐b‐PMMA) using a single‐capillary spinneret. Experiment results indicate that PF‐b‐PMMA ES fibers prepared from THF, THF/DMF (50/50), and DMF contain PF block aggregated structures of dot‐like (5–10 nm), line‐like (10–20 nm), and ellipse‐like structure (25–50 nm), respectively. Such variation of aggregation size leads to a red‐shift of the absorption or luminescence spectra. In addition, the fiber diameters decrease upon enhancing the DMF content. The present study demonstrates that blue light‐emitting ES fibers are successfully prepared from conjugated rod–coil diblock copolymers and their aggregate morphology and photophysical properties could be tuned through use of selective solvent.