Arylene ethynylene macrocycles containing 9,10-anthrylene or 1,4-naphthylene units were synthesized. In chloroform, significant resonance upfield shifting was observed with beta-protons of anthrylene and naphthylene in NMR spectra. This was considered to result from partial stacking of these aromatic units intramolecularly, driven by attractive pi-pi interactions. DFT calculations supported the proposed intramolecular stacking motif. Moreover, a liquid-crystal phase was exhibited by the anthrylene-containing macrocycle, by virtue of the unique discotic shape.
Total atmospheric OH reactivities (k(OH)) have been measured as reciprocal OH lifetimes by a newly developed instrument at a rural site in the densely populated Pearl River Delta (PRD) in Southern China in summer 2006. The deployed technique, LP-LIF, uses laser flash photolysis (LP) for artificial OH generation and laser-induced fluorescence (LIF) to measure the time-dependent OH decay in samples of ambient air. The reactivities observed at PRD covered a range from 10 s(-1) to 120 s(-1), indicating a large load of chemical reactants. On average, k(OH) exhibited a pronounced diurnal profile with a mean maximum value of 50 s(-1) at daybreak and a mean minimum value of 20 s(-1) at noon. The comparison of reactivities calculated from measured trace gases with measured k(OH) reveals a missing reactivity of about a factor of 2 at day and night. The reactivity explained by measured trace gases was dominated by anthropogenic pollutants (e. g., CO, NOx, light alkenes and aromatic hydrocarbons) at night, while it was strongly influenced by local, biogenic emissions of isoprene during the day. Box model calculations initialized by measured parameters reproduce the observed OH reactivity well and suggest that the missing reactivity is contributed by unmeasured, secondary chemistry products (mainly aldehydes and ketones) that were photochemically formed by hydrocarbon oxidation. Overall, k(OH) was dominated by organic compounds, which had a maximum contribution of 85% in the afternoon. The paper demonstrates the usefulness of direct reactivity measurements, emphasizes the need for direct measurements of oxygenated organic compounds in atmospheric chemistry studies, and discusses uncertainties of the modelling of OVOC reactivities.
Gao W, Ma S, Zhang L, Su L, Zhao D. AVS Video Coding Standard. In: Intelligent Multimedia Communication: Techniques and Applications. ; 2010. pp. 125–166. 访问链接
Based on full 3D finite element method simulations, the transmission of a dielectric-loaded surface plasmon polariton waveguide (DLSPPW) based 1/4 circle is calculated for a 90 degrees bend model and a 270 degrees bend model, respectively. It is found that the 270 degrees bend model gives almost pure bending loss while the 90 degrees bend model contains additional coupling loss. The models are applied to deduce the loss and unloaded quality factor of DLSPPW based waveguide ring resonators (WRRs) and the results of the 270 degrees bend model agree well with direct simulating results of the WRRs. Thus the 270 degrees bend model gives a fast and simple way to calculate bending loss and it is helpful for WRR design because no wavelength scan is needed.