Concentrations of dichlorodiphenyltrichloroethane (DDT) and its metabolites (designated as DDTs, the sum of o,p'- and p,p'-DDT, o,p'- and p,p'-DDE, and o,p'- and p,p'-DDD) in air and precipitation from the Pearl River Delta (PRD) of China were determined. Total concentrations of DDTs in air (gas + particle) and precipitation (dissolved + particle) were 170 +/- 120 pg m(-3) and 940 +/- 180 pg L(-1) for Dongguan (rural) and 240 +/- 120 pg m(-3) and 790 +/- 140 pg L(-1) for Shunde (rural), respectively, while they were 1550 +/- 640 pg L(-1) in precipitation from Guangzhou (urban). Log-transformed partition coefficients between air and particulate organic matter (log K'(oa)) of p,p'-DDT, p,p'-DDE, p,p'-DDD, o,p'-DDT, o,p'-DDE, and o,p'-DDD were 9.64 +/- 0.58, 10.07 +/- 0.56, 9.90 +/- 0.76, 10.06 +/- 0.66, 10.02 +/- 0.72, and 10.13 +/- 0.57, respectively: while those between water and particulate organic matter (log K'(om)) were 6.58 +/- 0.66, 6.36 +/- 0.53, 6.01 +/- 0.62, 6.41 +/- 0.42, 5.98 +/- 0.76, and 5.95 +/- 0.66, respectively. Total washout ratios by bulk rainfalls ranged from 4600 for o,p'-DDT to 54,000 for p,p'-DDT. Estimated average dry particle and wet depositional intensities in the PRD were 2.1 x 10(-6) and 1.6 x 10(-6) g m(-2) y(-1). (C) 2011 Elsevier Ltd. All rights reserved.
A series of conjugated oligo(p-phenylene-ethynylene) (OPE) molecules with backbone conformations (that is, the relative orientations of the contained phenylene units) controlled by competitive intramolecular hydrogen bonds to be either co-planar or random were synthesised and studied. In these oligomers, carboxylate and amido substituents were attached to alternate phenylene units in the OPE backbone. These functional groups were able to form intramolecular hydrogen bonds between neighbouring phenylene units. Thereby, all phenylene units in the backbone were confined in a co-planar conformation. This planarised structure featured a more extended effective conjugation length than that of regular OPEs with phenylene units adopting random orientation due to a low rotational-energy barrier. However, if a tri(ethylene glycol) (Tg) side chain was appended to the amido group, it enabled another type of intramolecular hydrogen bond, formed by the Tg chain folding back and the contained ether oxygen atom competing with the ester carbonyl group as the hydrogen-bond acceptor. The outcome of this competition was proven to depend on the length of the alkylene linker joining the ether oxygen atom to the amido group. Specifically, if the Tg chain folded back to form a five-membered cyclic structure, this hydrogen-bonding motif was sufficiently robust to overrule the hydrogen bonds between adjacent phenylene units. Consequently, the oligomers assumed non-planar conformations. However, if the side chain formed a six-membered ring by hydrogen bonding with the amido NH group, such a motif was much less stable and yielded in the competition with the ester carbonyl group from the adjacent phenylene unit. Thus, the hydrogen bonds between the phenylene units remained, and the co-planar conformation was manifested. In our system, the hydrogen bonds formed by the back-folded Tg chain and amido NH group relied on a single oxygen atom as the hydrogen-bond acceptor. The additional oxygen atoms in the Tg chain made a negligible contribution. A bifurcated hydrogen-bond motif was unimportant. From our results, in combination with the results from an independent study by Meijer et al.,([13]) it is evident that intramolecular hydrogen bonds involving back-folded oligo(ethylene glycol) moieties may differ in their structural details. Absorption spectroscopy served as a convenient yet sensitive technique for analysing hydrogen-bonding motifs in our study.
Gao Y, Yu H, Liu Y, Liu Y, Liu M, Zhao Y. Optimization for viewshed analysis on GPU, in Proceedings - 2011 19th International Conference on Geoinformatics, Geoinformatics 2011.; 2011. 访问链接
The interface between an electrode and the organic active layer is an important factor in organic solar cells (OSCs) that influences the power conversion efficiency (PCE). In this report, a buffer layer of 2-thenylmercaptan/Au self-assembly film is introduced into OSCs as a substitute for the poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT: PSS) layer. The electrode/active layer interface is meliorated by Au-S coordinate bond of self assembly after applying this buffer layer. The series resistance reduces from 20 Omega cm(2) in a device based on PEDOT:PSS to 10.2 Omega cm(2). Correspondingly, the fill factor (FF) increases from 0.50 to 0.64. Moreover, due to the dipole of this self-assembled layer, the open circuit voltage (V-oc) also increases slightly from 0.54 V to 0.56 V and the PCE reaches 2.5%. (C) 2010 Elsevier B.V. All rights reserved.
Investigation on PAHs in agricultural soils in Dongguan, South China were conducted. A total of 59 agricultural soil samples were collected from sites representative of the region for analysis of contents of 16 PAHs. Results show that 13 PAHs were detected with detectable ratios above 90%, Fie, Phe, Chr and Bbf were detected in all 59 samples, the detectable ratio of Ant was the lowest (13.56%). Sigma PAHs in soil samples is ranged from 29 to 2184 mug/kg, and 44.07%, 8.47% and 3.39% soil samples were slightly, moderately and heavily polluted by PAHs, respectively. Compared with other regions, Dongguan city is higher in soil PAHs contents, which can be confirmed that the increase of PAHs in agricultural soils is connected with human activities closely. Principal component analvsis demonstrate that the above-said 16 PAHs in agricultural soils may have three major contributors, corresponding to biomass burning, volatilization of oil production, and coal burning respectively. It is found that environmental factors (temperature, humidity), soil characters (pH, organic materials) and other pollutants (heavy metals) can affect environmental behaviors of PAHs. By means of ordinary Kriging interpolation, spatial distribution of 16 PAHs were studied. The results indicate that 16 PAHs vary greatly in spatial distribution between types, PAHs contents in west-north soils are much higher than that in south-east soils, and the highest PAHs contents area is in Wangniudun town, which hint that there are some pollutant sources connected with poisonous wastes combustion.
Chemical mechanisms for the production of secondary organic material (SOM) are developed in focused laboratory studies but widely used in the complex modeling context of the atmosphere. Given this extrapolation, a stringent testing of the mechanisms is important. In addition to particle mass yield as a typical standard for model-measurement comparison, particle composition expressed as O:C and H:C elemental ratios can serve as a higher dimensional constraint. A paradigm for doing so is developed herein for SOM production from a C(5)-C(10)-C(15) terpene sequence, namely isoprene, a-pinene, and beta-caryopyhllene. The model MCM-SIMPOL is introduced based on the Master Chemical Mechanism (MCM v3.2) and a group contribution method for vapor pressures (SIMPOL). The O:C and H:C ratios of the SOM are measured using an Aerosol Mass Spectrometer (AMS). Detailed SOM-specific AMS calibrations for the organic contribution to the H(2)O(+) and CO(+) ions indicate that published O:C and H:C ratios for SOM are systematically too low. Overall, the measurement-model gap was small for particle mass yield but significant for particle-average elemental composition. The implication is that a key chemical pathway is missing from the chemical mechanism. The data can be explained by the particle-phase homolytic decomposition of organic hydroperoxides and subsequent alkyl-radical-promoted oligomerization.