Beyond the demonstration of single-molecule (or singleatom) and organic-thin-film transistors, [1±4] a reliable electrode contact remains one of the most critical challenges in the development of molecular and organic electronics. Except for the tip of a scanning tunneling microscope, [5±7] more practical connections often involve a metal/ insulator(semiconductor)/metal thin-film structure, either through a gate thin-film dielectric assembly below the source±drain, [1±4] or a insulating thin-film separator which runs parallel to the molecular path. [8,9] To achieve practical applications, not only does one need ohmic contacts so that any nonlinearity can be correctly attributed, but also a much more insulating medium to minimize the influence from the surroundings.[10] However, one often encounters unexpected current±voltage characteristics which do not arise from the given atoms or molecules. For example, negative differential resistance (NDR) [11±15] and the memory effect (hysteresis) [16±21] were found not only in singlemolecule devices, but also in organic thin-film transistors, organic light-emitting devices, and metal/inorganic insulator/ metal systems.[22±26] Despite many years of effort, the precise origin of the phenomena remains unknown, which has become a major obstacle in the research and development of new electronic devices. In this report, we try to reveal the origin of such phenomena, based on new experiment results from various metals and both organic and polymeric thin films. The answer is surprisingly found to be two-dimensional (2D) single-electron tunneling due to nanometer-sized metal islands, which were manifested unexpectedly through a wellknown process where some nuclei were blocked from further growth by the sealing of electrode outside crevices. The results not only provide a satisfactory explanation of the anomalous phenomena, but also open a new door to the construction and fabrication of molecular electronic and memory devices.The widespread nature of the phenomena is shown by its easy duplication, using any metal electrode and any organic or inorganic thin-film insulator, or even semiconductors, since the anomalous current is usually several orders of magnitude higher than that of the nominal conductance. The typical current±voltage (I±V) curve showing NDR and a memory effect has two distinctive features. One is a local current maximum (when V = V max ), followed by a region of NDR. The other feature is the dual states for V < V max , where the ªonº state is obtained by reaching the V max first, and the ªoffº state is recovered by visiting a voltage beyond NDR before rapidly setting back to zero.[21] In addition, there are intermediate states available, [21,22] and the phenomena could be removed by exposure to oxygen gas. [13] Many models have been proposed, but so far none offers a satisfactory explanation. The arbitrary choice of metals and insulators of various energies immediately rejects any speculation related to, for example, a particular type of insulating or semiconduc...

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We compared patterns of soil bacterial community diversity and structure in six secondary forests (JM, Juglans mandshurica; QM, Quercus mongolica; MB, mixed Broadleaf forest; BE, Betula ermanii; CB, conifer-broadleaf forest; PT, Pinus tabuliformis) and two plantation forests (LG, Larix gmelinii; PK, Pinus koraiensis) of the Baishilazi Nature Reserve, China, based on the 16S rRNA high-throughput Illumina sequencing data. The correlations between the bacterial community and soil environmental factors were also examined. The results showed that the broadleaf forests (JM, QM, MB) had higher levels of total C (TC), total N (TN), available N (AN), and available K (AK) compared to the coniferous forests (PT, LG, PK) and conifer-broadleaf forest (CB). Different revegetation pathways had different effects on the soil bacterial community diversity and structure. For the α-diversity, the highest Shannon index and Simpson index were found in JM. The Simpson index was significantly positively correlated with the available P (AP) (P < 0.05), and the Shannon index was significantly positively correlated with AK (P < 0.05). Compared with others, the increased ACE index and Chao1 index were observed in the CB and MB, and both of these α-diversity were significantly negative with AK (P < 0.05). The relative abundances of bacterial phyla and genera differed among different revegetation types. At the phylum level, the dominant phylum groups in all soils were Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia, Chloroflexi, Bacteroidetes, Gemmatimonadetes, and Planctomycetes. Significant differences in relative abundance of bacteria phyla were found for Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, and Proteobacteria. Correlation analysis showed that Soil pH, TC, TN, AP, and AK were the main abiotic factors structuring the bacterial communities. As revealed by the clear differentiation of bacterial communities and the clustering in the heatmap and in the PCA plots, broadleaf forests and coniferous forests harbored distinct bacterial communities, indicating a significant impact of the respective reforestation pathway on soil bacterial communities in the Baishilazi Nature Reserve.

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The structure and magnetic properties of Y2Al3Fe14−xMnx (x=0–12) compounds have been investigated by means of x-ray diffraction and magnetization measurements. The Y2Al3Fe14−xMnx compounds have a hexagonal Th2Ni17-type structure. Their unit-cell volumes increase slowly with increasing x first, then increases rapidly with the further increase of x. This implies that there exists a positive spontaneous volume magnetostriction in the magnetic state of Y2Al3Fe14−xMnx compounds. X-ray diffraction of the Y2Al3Fe11Mn3 compound from 150 to 300 K shows that there appears a negative coefficient of thermal expansion, ᾱ≈−7.5×10−5/K, from 185 to 200 K. The Curie temperature and the saturation magnetization of these compounds show a rapid drop with increasing x.

Soil microorganisms play an important role in biogeochemical cycling. The bacterial community functional community profiles across different land use types in the mountainous region of eastern Liaoning Province, China, such as natural secondary forest (Quercus mongolica (QM)), shrub wood (SW), coniferous planation (Larix gmelini (LG), and Pinus koraiensis (PK)), and agricultural land (Zea mays (ZM)) were evaluated using high-throughput sequencing of the bacterial 16S rDNA gene, and predicted based on the FaProTax database. Bacterial functional groups varied across samples under different land use patterns. A total of 53 functional groups were acquired using FaProTaxin accordance with the classification annotation results of 16S rDNA sequences. These functional groups contained 5809 OTUs, accounting for 66.25% of all OTUs. The dominant functions were chemoheterotrophs and aerobicchemoheterotrophy with average relative abundance of 21.69% and 21.01%, respectively. In addition, we detected 15 and 12 ecological function groups related to the carbon and nitrogen cycles, respectively. The bacterial functional groups of ZM were clearly separated from those of PK, LG, QM, and SW, indicating that functional groups of agriculture soil differed from those of forest soils. Furthermore, the bacterial functional groups of LG and PK were obviously separated from those of QM and SW, suggesting that functional groups of broad leaf forest differed from those of coniferous forests. Also, we analyzed the main factors that influence soil bacterial community functional groups under different land use patterns. It was found that soil environmental conditions, especially soil pH, NH 4

Flexible organic field-effect transistors (OFETs) using solution-processable functionalized graphene for all the electrodes (source, drain, and gate) have been fabricated for the first time. These OFETs show performance comparable to corresponding devices using Au electrodes as the source/drain electrodes on SiO 2 /Si substrates with Si as the gate electrode. Also, these devices demonstrate excellent flexibility without performance degradation over severe bending cycles. Furthermore, inverter circuits have been designed and fabricated using these all-graphene-electrode OFETs. Our results demonstrate that the long-sought dream for all-carbon and flexible electronics is now much closer to reality.