Fine particulate matter (PM2.5) is a significant health issue in Chinese megacities. However, little information is available regarding the PM2.5-bound toxic organics, especially their sources, atmospheric transformations, and health implications. In this study, we assessed the levels of polycyclic aromatic hydrocarbons (PAHs) and their nitrated, hydroxylated, and oxygenated derivatives (i.e., NPAHs, OHPAHs, and OPAHs, respectively) in PM2.5 collected in Beijing over a 1year period. The median concentration of 23 PAHs, 15 NPAHs, 16 OHPAHs, and 7 OPAHs in PM2.5 was 53.8, 1.14, 1.40, and 3.62ngm(-3), respectively. Much higher concentrations and mass percentages for all species were observed in the heating season, indicating a higher toxicity of PM2.5 during this period of time. Positive matrix factorization was applied to apportion the sources of PAHs and their derivatives. It was found that traffic emissions in the nonheating season, and coal combustion and biomass burning in the heating season, were the major primary sources of PAHs and their derivatives. Secondary formation, however, contributed significantly to the derivatives of PAHs (especially NPAHs and OPAHs) in the nonheating season, suggesting significant impacts of atmospheric transformation on the toxicity of PM2.5.
Much effort has been made for reducing nitrous oxide (N2O) emission in wastewater treatment processes. This paper presents an interesting way to minimize N2O in aerobic denitrification by strain Pseudomonas stutzeri PCN-1 with help of corn flour as cheaper additional carbon source. Experimental results showed that maximal N2O accumulation by strain PCN-1 was only 0.02% of removed nitrogen if corn flour was used as sole carbon source, which was significantly reduced by 52.07-99.81% comparing with others such as succinate, glucose, acetate and citrate. Sustained release of reducing sugar from starch and continuous expression of nosZ coding for N2O reductase contributed to the special role of corn flour as the ideal carbon source for strain PCN-1. Further experiments in sequencing batch reactors (SBRs) demonstrated similarly efficient nitrogen removal with much less N2O emission due to synergy of the novel strain and activated sludge, which was then confirmed by quantitative PCR analysis. (C) 2015 Elsevier Ltd. All rights reserved.
Following older debates in international relations literature concerning the relative importance of domestic versus systemic factors, newer debates emphasize interdependence among states and the complex interactions between systemic and domestic factors. As globalization and democratization advance, theories and empirical models of international politics have become more complicated. We present a systematic theoretical categorization of relationships between domestic and systemic variables. We use this categorization so that scholars can match their theory to the appropriate empirical model and assess the degree to which systemic factors affect their arguments. We also present two advances at the frontier of these empirical models. In one, we combine hierarchical models of moderating relationships with spatial models of interdependence among units within a system. In the other, we provide a model for analyzing spatial interdependence that varies over time. This enables us to examine how the level of interdependence among units has evolved. We illustrate our categorization and new models by revisiting the recent international political economy (IPE) debate over the relationship between trade policy and regime type in developing countries.
This paper presents an analysis for the impedance transformation ratio of microwave rectifier, implemented as an energy recycling unit suitable for RF outphasing transmitters. The experimental demonstration is realised by two single-ended microwave rectifiers with different impedance transformation ratios to separately replace the power-wasting resistive load of an isolating combiner in a multilevel LINC system. The measurement results show that the implemented rectifier can improve the overall efficiency of the multilevel LINC system from original 39.5 % to 46.7 % and 44.9 % respectively, without affecting linearity.
Real-time mass spectra of the non-refractory species in submicron aerosol particles were recorded in a tropical rainforest in the central Amazon Basin during the wet season from February to March 2008, as a part of the Amazonian Aerosol Characterization Experiment (AMAZE-08). Organic material accounted on average for more than 80% of the non-refractory submicron particle mass concentrations during the period of measurements. There was insufficient ammonium to neutralize sulfate. In this acidic, isoprene-rich, HO2-dominant environment, positive-matrix factorization of the time series of particle mass spectra identified four statistical factors to account for the 99% of the variance in the signal intensities of the organic constituents. The first factor was identified as associated with regional and local pollution and labeled "HOA" for its hydrocarbon-like characteristics. A second factor was associated with long-range transport and labeled "OOA-1" for its oxygenated characteristics. A third factor, labeled "OOA-2," was implicated as associated with the reactive uptake of isoprene oxidation products, especially of epoxydiols to acidic haze, fog, or cloud droplets. A fourth factor, labeled "OOA-3," was consistent with an association with the fresh production of secondary organic material (SOM) by the mechanism of gasphase oxidation of biogenic volatile organic precursors followed by gas-to-particle conversion of the oxidation products. The suffixes 1, 2, and 3 on the OOA labels signify ordinal ranking with respect to the extent of oxidation represented by the factor. The process of aqueous-phase oxidation of water-soluble products of gas-phase photochemistry might also have been associated to some extent with the OOA-2 factor. The campaign-average factor loadings had a ratio of 1.4 : 1 for OOA-2 : OOA-3, suggesting the comparable importance of particle-phase compared to gas-phase pathways for the production of SOM during the study period.
Colloidal CdS nanorods similar to 4.9 nm in diameter and similar to 60 nm long were positioned in gold bow-tie electrodes with a gap of similar to 50 nm by an AC dielectrophoresis process to construct optoelectronic devices. The fabricated devices exhibited an excellent photoresponse to white and blue light, but no response to green light. However, the response of the devices to white light could be degraded by green light. This is considered to be related to surface plasmon polaritons suppressing the generation of photo-carriers in the CdS nanorods. The results indicate that surface plasmons do not always benefit nano-optoeletronic devices. (C) 2015 The Japan Society of Applied Physics
