The Amazon Basin provides an excellent environment for studying the sources, transformations, and properties of natural aerosol particles and the resulting links between biological processes and climate. With this framework in mind, the Amazonian Aerosol Characterization Experiment (AMAZE-08), carried out from 7 February to 14 March 2008 during the wet season in the central Amazon Basin, sought to understand the formation, transformations, and cloud-forming properties of fine-and coarse-mode biogenic aerosol particles, especially as related to their effects on cloud activation and regional climate. Special foci included (1) the production mechanisms of secondary organic components at a pristine continental site, including the factors regulating their temporal variability, and (2) predicting and understanding the cloud-forming properties of biogenic particles at such a site. In this overview paper, the field site and the instrumentation employed during the campaign are introduced. Observations and findings are reported, including the large-scale context for the campaign, especially as provided by satellite observations. New findings presented include: (i) a particle number-diameter distribution from 10 nm to 10 mu m that is representative of the pristine tropical rain forest and recommended for model use; (ii) the absence of substantial quantities of primary biological particles in the submicron mode as evidenced by mass spectral characterization; (iii) the large-scale production of secondary organic material; (iv) insights into the chemical and physical properties of the particles as revealed by thermodenuder-induced changes in the particle number-diameter distributions and mass spectra; and (v) comparisons of ground-based predictions and satellite-based observations of hydrometeor phase in clouds. A main finding of AMAZE-08 is the dominance of secondary organic material as particle components. The results presented here provide mechanistic insight and quantitative parameters that can serve to increase the accuracy of models of the formation, transformations, and cloud-forming properties of biogenic natural aerosol particles, especially as related to their effects on cloud activation and regional climate.
For CareBeijing-2006, two sites were established in urban and suburban regions of Beijing in summer 2006. Observations of O(3) and its precursors together with meteorological parameters at both sites are presented. Gross ozone production rate P(O(3)) and sensitivity to nitric oxides (NO(x)) and volatile organic compounds (VOCs) were investigated using an observation-based photochemical box model (OBM). P(O(3)) varied from nearly zero to 120 and 50 ppb h(-1) for urban and suburban sites, respectively. These rates were greater than the accumulation rates of the observed oxidant (O(3) + NO(2)) concentrations. The O(3) episodes typically appeared under southerly wind conditions with high P(O(3)), especially at the urban site. Sensitivity studies with and without measured nitrous acid (HONO) as a model constraint suggested that the estimated P(O(3)) at both sites was strongly enhanced by radical production from HONO photolysis. Both NO(x)- and VOC-sensitive chemistries existed over time scales from hours to days at the two sites. The variation in O(3)-sensitive chemistry was relatively well explained by the ratio of the average daytime total VOC reactivity (k(TVOC)) to NO, with the transition chemistry corresponding to a k(TVOC)/NO value of 2-4 s(-1) ppb(-1). Pronounced diurnal variations in the O(3) production regime were found. In the morning, conditions were always strongly VOC-limited, while in the afternoon, conditions were variable for different days and different sites. The model-calculated results were tested by measurements of H(2)O(2), HNO(3), total OH reactivity, and HO(x) radicals. The OBM was generally capable of correctly simulating the levels of P(O(3)), although it might tend to overpredict the VOC-sensitive chemistry.
Poly(3-hexylthiophene) (P3HT):1-(3-methoxycarbonyl)-propyl-1-Phenyl-(6,6)C-61 (PCBM) photovoltaic devices based on ordinary paper as substrate were fabricated. Au layer deposited on paper by RF magnetron sputtering was used as anode. The hybrid layer of LiF co-evaporated with Al was used for transparent cathode, and the light transmittance could reach to similar to 70%. By optimizing the mass proportion of LiF and Al, we could get the best papery solar cells with the short current density and open circuit voltage 0.1 mA/cm(2) and 0.39 V. respectively. The corresponding power conversion efficiency was measured to be 0.13 parts per thousand illuminated with 100 mW/cm(2) air mass 1.5 global (AM 1.5 G) simulated sunlight. (C) 2010 Elsevier B.V. All rights reserved.
Ultrafine particle (UFP) number and size distributions were simultaneously measured at five urban and rural sites during the summer of 2007 in Ontario, Canada as part of the Border Air Quality and Meteorology Study (BAQS-Met 2007). Particle formation and growth events at these five sites were classified based on their strength and persistence as well as the variation in geometric mean diameter. Regional nucleation and growth events and local short-lived strong nucleation events were frequently observed at the near-border rural sites, upwind of industrial sources. Surprisingly, the particle number concentrations at one of these sites were higher than the concentrations at a downtown site in a major city, despite its high traffic density. Regional nucleation and growth events were favored during intense solar irradiance and in less polluted cooler drier air. The most distinctive regional particle nucleation and growth event during the campaign was observed simultaneously at all five sites, which were up to 350 km apart. Although the ultrafine particle concentrations and size distributions generally were spatially heterogeneous across the region, a more uniform spatial distribution of UFP across the five areas was observed during this regional nucleation event. Thus, nucleation events can cover large regions, contributing to the burden of UFP in cities and potentially to the associated health impacts on urban populations. Local short-lived nucleation events at the three near-border sites during this summer three-week campaign were associated with high SO2, which likely originated from US and Canadian industrial sources. Hence, particle formation in southwestern Ontario appears to often be related to anthropogenic gaseous emissions but biogenic emissions at times also contribute. Longer-term studies are needed to help resolve the relative contributions of anthropogenic and biogenic emissions to nucleation and growth in this region.
Crystalline microwires of a phenyleneethynylene (PE) macrocycle self-assembled from solution exhibited superior photoconductive properties. Photoswitches fabricated with single wires afforded nA-scale photocurrents with on/off ratios of ca. 10(3). At a bias of 30 volts highest gain value achieved was up to 4.5. The stable and rapid responses to light qualify these microwire-based devices for excellent photoswitches or photodetectors.