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Abstract Fabricating flexible vanadium dioxide (VO2) films is a serious challenge towards commercial applications. In this work, we proposed a new strategy to directly deposit VO2 thermochromic films on flexible substrates by using Cr2O3 structural template layer, which can serve as growth template for low temperature (~300 °C) deposition of VO2 films. The obtained crystalline VO2 films on flexible substrates show significant phase transition properties with narrow hysteresis loops. Optical and electrical characterizations have indicated phase transition features of the flexible VO2 films, with an excellent solar modulation ability (~60% at 2500 nm) and a resistivity change over 2 orders of magnitude. Meanwhile, the flexible VO2 film exhibits narrow hysteresis loops during the phase transition process, and the hysteresis loop widths are less than 1 °C. Flexibility and stability of VO2 film in this work has been demonstrated by a designed bending test, which can maintain stable thermochromic performance after over 5000 bending cycles. This work provided a facile strategy to fabricate VO2 films on flexible substrates as flexible electronic devices.

AbstractSilicon (Si) is generally considered a beneficial element for the growth of higher plants, especially under stress conditions, but the mechanisms remain unclear. Here, we tested the hypothesis that Si improves salt tolerance through mediating important metabolism processes rather than acting as a mere mechanical barrier. Seedlings of sorghum (Sorghum bicolor L.) growing in hydroponic culture were treated with NaCl (100 mm) combined with or without Si (0.83 mm). The result showed that supplemental Si enhanced sorghum salt tolerance by decreasing Na+ accumulation. Simultaneously, polyamine (PA) levels were increased and ethylene precursor (1‐aminocyclopropane‐1‐carboxylic acid: ACC) concentrations were decreased. Several key PA synthesis genes were up‐regulated by Si under salt stress. To further confirm the role of PA in Si‐mediated salt tolerance, seedlings were exposed to spermidine (Spd) or a PA synthesis inhibitor (dicyclohexylammonium sulphate, DCHA) combined with salt and Si. Exogenous Spd showed similar effects as Si under salt stress whereas exogenous DCHA eliminated Si‐enhanced salt tolerance and the beneficial effect of Si in decreasing Na+ accumulation. These results indicate that PAs and ACC are involved in Si‐induced salt tolerance in sorghum and provide evidence that Si plays an active role in mediating salt tolerance.

Abstract Methane hydrate (MH) is regarded as one of the potential and substantial energy resources. The permeability of hydrate-bearing layer (HBL) can potentially influence heat and mass transfer during hydrate dissociation by depressurization. In this study, a reservoir-scale MH model was constructed to investigate the effect of permeability anisotropy on gas production behaviors by depressurization with a horizontal well. The numerical results indicate that permeability anisotropy can initially negatively influence the hydrate dissociation and gas production, but later promote the process. Meanwhile, permeability anisotropy can lead to an increase of ratio of gas phase to total production and gas-to-water ratio during long-term gas production. Moreover, permeability anisotropy can enhance the horizontal flow and the dissociation reaction in the top part of the HBL for a long period, but also leads to an increase of accumulated free gas in the reservoir. Furthermore, the comparison of horizontal well production and vertical well production indicates that the horizontal well can increase the gas production by one order of magnitude than that of vertical well during a production period of 360 days, and permeability anisotropy appears to have less effect on gas production in the initial short stage when using the vertical well.

Biomass burning (BB) is one of the largest sources of carbonaceous aerosols with adverse impacts on air quality, visibility, health and climate. BB emits a few specific aromatic acids (p-hydroxybenzoic, vanillic, syringic and dehydroabietic acids) which have been widely used as key indicators for source identification of BB-derived carbonaceous aerosols in various environmental matrices. In addition, measurement of p-hydroxybenzoic and vanillic acids in snow and ice cores have revealed the historical records of the fire emissions. Despite their uniqueness and importance as tracers, our current understanding of analytical methods, concentrations, diagnostic ratios and degradation processes are rather limited and scattered in literature. In this review paper, firstly we have summarized the most established methods and protocols for the measurement of these aromatic acids in aerosols and ice cores. Secondly, we have highlighted the geographical variability in the abundances of these acids, their diagnostic ratios and degradation processes in the environments. The review of the existing data indicates that the concentrations of aromatic acids in aerosols vary greatly with locations worldwide, typically more abundant in urban atmosphere where biomass fuels are commonly used for residential heating and/or cooking purposes. In contrast, their concentrations are lowest in the polar regions which are avoid of localized emissions and largely influenced by long-range transport. The diagnostic ratios among aromatic acids can be used as good indicators for the relative amounts and types of biomass (e.g. hardwood, softwood and herbaceous plants) as well as photochemical oxidation processes. Although studies suggest that the degradation processes of the aromatic acids may be controlled by light, pH and hygroscopicity, a more careful investigation, including closed chamber studies, is highly appreciated.

AbstractBichromophoric compound 3β‐((2‐(methoxycarbonyl)bicyclo[2.2.1]hepta‐2,5‐diene‐3‐yl)carboxy)androst‐5‐en‐17β‐yl‐[2‐(N‐carbazolyl)acetate] (NBD‐S‐CZ) was synthesized and its photochemistry was examined by fluorescence quenching, flash photolysis, and chemically induced dynamic nuclear polarization (CIDNP) methods. Fluorescence quenching measurements show that intramolecular electron transfer from the singlet excited state of the carbazole to the norbornadiene group in NBD‐S‐CZ occurs with an efficiency (ΦSET) of about 14 % and rate constant (kSET) of about 1.6×107 s−1. Phosphorescence and flash photolysis studies reveal that intramolecular triplet energy transfer and electron transfer from the triplet carbazole to the norbornadiene group proceed with an efficiency (ΦTET + ΦTT) of about 52 % and rate constant (kTET + kTT) of about 3.3×105 s−1. Upon selective excitation of the carbazole chromophore, nuclear polarization is detected for protons of the norbornadiene group (emission) and its quadricyclane isomer (enhanced absorption); this suggests that the isomerization of the norbornadiene group to the quadricyclane proceeds by a radical‐ion pair recombination mechanism in addition to intramolecular triplet sensitization. The long‐distance intramolecular triplet energy transfer and electron transfers starting both from the singlet and triplet excited states are proposed to proceed by a through‐bond mechanism.

AbstractWe investigated the δ15N profile of N (extractable NH, NO, and organic N (EON)) in the soil of a N‐saturated subtropical forest. The order of δ15N in the soil was EON > NH > NO. Although the δ15N of EON had been expected to be similar to that of bulk soil N, it was higher than that of bulk soil N by 5‰. The difference in δ15N between bulk soil N and EON (Δ15Nbulk‐EON) was correlated significantly with the soil C/N ratio. This correlation implies that carbon availability, which determines the balance between N assimilation and dissimilation of soil microbes, is responsible for the high δ15N of EON, as in the case of soil microbial biomass δ15N. A thorough δ15N survey of available N (NH, NO, and EON) in the soil profiles from the organic layer to 100 cm depth revealed that the δ15N of the available N forms did not fully overlap with the δ15N of plants. This mismatch in δ15N between that of available N and that of plants reflects apparent isotopic fractionation during N uptake by plants, emphasizing the high N availability in this N‐saturated forest. Copyright © 2010 John Wiley & Sons, Ltd.

Wind power can help ensure regional energy security and also mitigate both global greenhouse gas and local air pollutant emissions, leading to co-benefits. With rapid installation of wind power equipment, it is critical to uncover the embodied emissions of greenhouse gas and air pollutants from wind power sector so that emission mitigation costs can be compared with a typical coal-fired power plant. In order to reach such a target, we conduct a life cycle analysis for wind power sector by using the Chinese inventory standards. Wind farms only release 1/40 of the total CO2 emissions that would be produced by the coal power system for the same amount of power generation, which is equal to 97.48% of CO2 emissions reduction. Comparing with coal power system, wind farms can also significantly reduce air pollutants (SO2, NOX and PM10), leading to 80.38%, 57.31% and 30.91% of SO2, NOX and PM10 emissions reduction, respectively. By considering both recycling and disposal, wind power system could reduce 2.74×104 t of CO2 emissions, 5.65×104 kg of NOX emissions, 2.95×105 kg of SO2 emissions and 7.97×104 kg of PM10 emissions throughout its life cycle. In terms of mitigation cost, a wind farm could benefit 37.14 US$ from mitigating 1ton of CO2 emissions. The mitigation cost rates of air pollutants were 7.94 US$/kg of SO2, 10.79 US$/kg of NOx, and 80.79 US$/kg of PM10.Our research results strongly support the development of wind power so that more environmental benefits can be gained. However, decentralized wind power developers should consider not only project locations close to the demand of electricity and wind resources, but also the convenient transportation for construction and recycling, while centralized wind power developers should focus on incorporating wind power into the grids in order to avoid wind power loss.

AbstractUrban land‐use change has the potential to affect local to global biogeochemical carbon (C) and nitrogen (N) cycles and associated greenhouse gas (GHG) fluxes. We conducted a meta‐analysis to (1) assess the effects of urbanization‐induced land‐use conversion on soil nitrous oxide (N2O) and methane (CH4) fluxes, (2) quantify direct N2O emission factors (EFd) of fertilized urban soils used, for example, as lawns or forests, and (3) identify the key drivers leading to flux changes associated with urbanization. On average, urbanization increases soil N2O emissions by 153%, to 3.0 kg N ha−1 year−1, while rates of soil CH4 uptake are reduced by 50%, to 2.0 kg C ha−1 year−1. The global mean annual N2O EFd of fertilized lawns and urban forests is 1.4%, suggesting that urban soils can be regional hotspots of N2O emissions. On a global basis, conversion of land to urban greenspaces has increased soil N2O emission by 0.46 Tg N2O‐N year−1 and decreased soil CH4 uptake by 0.58 Tg CH4‐C year−1. Urbanization driven changes in soil N2O emission and CH4 uptake are associated with changes in soil properties (bulk density, pH, total N content, and C/N ratio), increased temperature, and management practices, especially fertilizer use. Overall, our meta‐analysis shows that urbanization increases soil N2O emissions and reduces the role of soils as a sink for atmospheric CH4. These effects can be mitigated by avoiding soil compaction, reducing fertilization of lawns, and by restoring native ecosystems in urban landscapes.