Particle number size distributions between 3 nm and 10 mm were measured in Beijing, China. New particle formation events were observed on around 40% of the measurement days from March 2004 to February 2005 and were generally observed under low relative humidity and sunny conditions. Though occurring during all seasons, new particle formation events had highest frequency in spring and lowest frequency in summer. Events were classified as "clean'' or "polluted'' groups mainly according to the condensational sink and the local wind. The formation rate range was from 3.3 to 81.4 cm(-3) s(-1). The growth rate varied from 0.1 to 11.2 nm h(-1). The seasonal variation of condensable vapor concentration showed the highest values during summer months due to enhanced photochemical and biological activities as well as stagnant air masses preventing exchange with cleaner air.
The optical upconversion of infrared light to visible light has been achieved in photosensitizer-doped organic light-emitting diodes, where poly(N-vinylcarbazole) doped with infrared photosensitizer of 2,4,7-trinitro-9-fluorenylidene malonitrile was used as hole-transporting layer, and tris(8-hydroxyquinoline) aluminum acted as both emitting and electron-transporting layers. Both electroluminescent intensity and current were enhanced under infrared illumination. The enhancement ratio was obtained as 2.45 times for electroluminescent emission and 1.45 times for current. This work brought forth a prototype design for novel flexible organic optical upconversion device used in near infrared field. (c) 2007 American Institute of Physics.