Agricultural soils are considered to have great potential for carbon sequestration through land-use change. In this paper, we compiled data from the literatures and studied the change in soil organic carbon (SOC) following the 'Grain-for-Green' Programme (GGP, i.e., conversion from farmland to plantation, secondary forests and grasslands) in China. The results showed that SOC stocks accumulated at an average rate of 36Á67 g m À2 y À1 in the top 20 cm with large variation. The current SOC storage could be estimated using the initial SOC stock and year since land use transformation (Adjusted R 2 ¼ 0Á805, p ¼ 0Á000). After land use change, SOC stocks decreased during the initial 4-5 years, followed by an increase after above ground vegetation restoration. Annual average precipitation and initial SOC stocks had a significant effect ( p < 0Á05) on the rate of change in SOC, while no significant effects were observed between plantation and natural regeneration ( p > 0Á05). The ongoing 'Grain-for-Green' project might make significant contribution to China's carbon sequestration.
Porosity-free nanocrystalline ͑nc͒ element Se samples with mean grain sizes ranging from 13 to 70 nm were synthesized by crystallizing a melt-quenched amorphous Se solid. Microstructures of the nc-Se ͑with a hcp structure͒ samples were characterized by means of quantitative x-ray-diffraction measurements. The Bragg reflection and the background intensities, as well as the reflection shape of the x-ray-diffraction patterns for the nc Se were analyzed according to data fitting of the measurement results. The grain-size dependencies of the microstrain, lattice parameters, unit-cell volume, and the mean Debye-Waller parameter were determined. With a reduction of grain size, the microstrain increases significantly along ͗100͘ direction but decreases along ͗104͘ direction, and exhibits an increasing anisotropic microstrain behavior. The lattice parameter a was found to increase evidently while c decreased slightly with a decreasing grain size, resulting in a significant lattice distortion with a dilated unit-cell volume. It agrees with the observation that the mean Debye-Waller parameter increases with a reduction of grain size, suggesting larger displacements of atoms from their ideal lattice sites in the nc-Se samples with smaller grains. The similarity of the grain-size dependencies of these structural parameters as that of the grain-boundary volume fraction implies that the intrinsic microstructure feature of nc materials is closely related to the crystallite dimension and the amount of grain boundaries.
Chalcogenide Ge2Sb2Te5 thin films have been widely exploited as binary bit recording materials in optical and non-volatile electronic information storage, where the crystalline and amorphous states are marked as the information bits “0” and “1”, respectively. In this work, we demonstrate the use of Ge2Sb2Te5 thin films as multi-level grayscale image recording materials. High-resolution grayscale images are recorded on Ge2Sb2Te5 thin films through taking advantage of laser-induced structural evolution characteristic. Experimental results indicate that the change of laser energy results in the structural evolution of Ge2Sb2Te5 thin films. The structural evolution induces the difference of electronic polarizability and reflectivity, and high-resolution grayscale images are recorded on Ge2Sb2Te5 thin films through direct laser writing method, accordingly.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.