The attritional wear of human enamel and four different composite resins for the veneering of crowns was evaluated in a dual-axis chewing simulator over up to 1200000 loading cycles. Enamel showed less wear than the composite resins. However, an ultrafine compact-filled composite resin (Targis) showed a wear not statistically significantly different from that of enamel. The other composite resins showed a statistically significantly higher wear than enamel regardless whether microfine, ultrafine midway-filled or ultrafine compact-filled.

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Abstract. Measurements of ozone and its precursors conducted within the HaChi (Haze in China) project in summer 2009 were analyzed to characterize volatile organic compounds (VOCs) and their effects on ozone photochemical production at a suburban site in the North China Plain (NCP). Ozone episodes, during which running 8-h average ozone concentrations exceeding 80 ppbv lasted for more than 4 h, occurred on about two thirds of the observational days during the 5-week field campaign. This suggests continuous ozone exposure risks in this region in the summer. Average concentrations of nitrogen oxides (NO x ) and VOCs are about 20 ppbv and 650 ppbC, respectively. On average, total VOC reactivity is dominated by anthropogenic VOCs. The contribution of biogenic VOCs to total ozone-forming potential, however, is also considerable in the daytime. Key species associated with ozone photochemical production are 2-butenes (18 %), isoprene (15 %), trimethylbenzenes (11 %), xylenes (8.5 %), 3-methylhexane (6 %), n-hexane (5 %) and toluene (4.5 %). Formation of ozone is found to be NO xlimited as indicated by measured VOCs/NO x ratios and further confirmed by a sensitivity study using a photochemical box model NCAR MM. The Model simulation suggests that ozone production is also sensitive to changes in VOC reactivity under the NO x -limited regime, although this sensitivity depends strongly on how much NO x is present.

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For comprehensive development of organic solar cells (OSCs), some factors such as environmental stability, low cost, insensitive film thickness, component contents tolerance, and green preparation processes are equally crucial to achieve high power conversion efficiencies (PCEs). In this work, a small molecule 3-(diethylamino)-7-imino-7H-benzo[4,5]imidazo[1,2-a]chromeno[3,2-c]pyridine-6-carbonitrile (DIBC), which is commercially available at low cost, is utilized to realize high-performance ternary OSCs. Demonstrated via Fourier transform infrared and 2D-1 HNMR, DIBC can form hydrogen bond interactions with [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 71 BM) in solid films. Further electrostatic potential (ESP) calculations indicate that the hydrogen bond interaction enhances the ESP of PC 71 BM and accelerates charge transport between donor and acceptor. As a result, poly(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl) benzo[1,2-b;4,5-b0]dithiophene-2,6diylalt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl(PTB7-Th):DIBC:PC 71 BM-based ternary OSC achieves a maximum efficiency of 12.17%, which is the best result of green solvent processed fullerene OSCs at present. It is noteworthy that the ternary OSCs also show great tolerance to film thickness and blend ratios. These unique properties are attributed to the hydrogen-bond-linked DIBC and PC 71 BM, which modulates molecule distribution and improves film morphology with an interpenetrating network structure. Furthermore, the DIBC containing device also exhibits good thermal and light radiation stability. These results illustrate that intermolecular hydrogen bond interaction has great potential for realizing high-performance OSCs.

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