RHCO: A Relation-aware Heterogeneous Graph Neural Network with Contrastive Learning for Large-scale Graphs

Heterogeneous graph neural networks (HGNNs) have been widely applied in heterogeneous information network tasks, while most HGNNs suffer from poor scalability or weak representation when they are applied to large-scale heterogeneous graphs. To address these problems, we propose a novel Relation-aware Heterogeneous Graph Neural Network with Contrastive Learning (RHCO) for large-scale heterogeneous graph representation learning. Unlike traditional heterogeneous graph neural networks, we adopt the contrastive learning mechanism to deal with the complex heterogeneity of large-scale heterogeneous graphs. We first learn relation-aware node embeddings under the network schema view. Then we propose a novel positive sample selection strategy to choose meaningful positive samples. After learning node embeddings under the positive sample graph view, we perform a cross-view contrastive learning to obtain the final node representations. Moreover, we adopt the label smoothing technique to boost the performance of RHCO. Extensive experiments on three large-scale academic heterogeneous graph datasets show that RHCO achieves best performance over the state-of-the-art models

Modeling Dynamic Heterogeneous Graph and Node Importance for Future Citation Prediction

Accurate citation count prediction of newly published papers could help editors and readers rapidly figure out the influential papers in the future. Though many approaches are proposed to predict a paper's future citation, most ignore the dynamic heterogeneous graph structure or node importance in academic networks. To cope with this problem, we propose a Dynamic heterogeneous Graph and Node Importance network (DGNI) learning framework, which fully leverages the dynamic heterogeneous graph and node importance information to predict future citation trends of newly published papers. First, a dynamic heterogeneous network embedding module is provided to capture the dynamic evolutionary trends of the whole academic network. Then, a node importance embedding module is proposed to capture the global consistency relationship to figure out each paper's node importance. Finally, the dynamic evolutionary trend embeddings and node importance embeddings calculated above are combined to jointly predict the future citation counts of each paper, by a log-normal distribution model according to multi-faced paper node representations. Extensive experiments on two large-scale datasets demonstrate that our model significantly improves all indicators compared to the SOTA models.Comment: Accepted by CIKM'202

Calculated phase diagrams, iron tolerance limits, and corrosion of Mg-Al alloys

The factors determining corrosion are reviewed in this paper, with an emphasis on iron tolerance limit and the production of high-purity castings. To understand the iron impurity tolerance limit, magnesium phase diagrams were calculated using the Pandat software package. Calculated phase diagrams can explain the iron tolerance limit and the production of high-purity castings by means of control of melt conditions; this is significant for the production of quality castings from recycled magnesium. Based on the new insight, the influence of the microstructure on corrosion of magnesium alloys is reviewed

Leaf and root nutrient concentrations and stoichiometry along aridity and soil fertility gradients

Questions: Leaf nitrogen (N), phosphorus (P) concentrations and N : P ratio have been extensively studied along environmental gradients, but whether and how leaves and roots show similar responses to climatic and fertility gradients is little studied. Also, the responses of leaf and root N and P in different plant functional types (PFT; legumes, grasses, forbs and shrubs) to environmental gradients are poorly known. We examined the following two hypotheses: (a) P concentration and N : P ratios in leaves or fine roots would not be modulated by soil N for legumes while they would be for non-legume PFTs; (b) Species turnover would have stronger influence on the responses of N and P concentrations and N : P ratios of plant tissues along aridity and soil fertility gradients than intraspecific variation. Study site: Ordos Plateau, China. Methods: We collected samples of leaf and fine roots covering 95 species of 28 families across 17 sites affiliated to four vegetation types on the dry Ordos Plateau of North China and compared variations in N and P concentrations and N : P ratios in both leaves and fine roots among PFTs. Results: We found that legumes had higher N concentrations in leaves and fine roots than the non-legume PFTs. Leaf and fine root P and N : P ratios increased with increasing soil N for most non-legume PFTs, but the relationships were decoupled for legumes. Species turnover had a stronger contribution to these relationships of N and P in leaves and fine roots along aridity and soil N gradients than intraspecific variation. Conclusions: When modeling vegetation nutrient stocks and cycling, the predictive power could be improved by taking into account not only influences of soil fertility but also of climate on leaf and root tissue N and soil N on tissue P and N : P ratio, especially for non-legume functional types

Plant Interactions with Changes in Coverage of Biological Soil Crusts and Water Regime in Mu Us Sandland, China

Plant interactions greatly affect plant community structure. Dryland ecosystems are characterized by low amounts of unpredictable precipitation as well as by often having biological soil crusts (BSCs) on the soil surface. In dryland plant communities, plants interact mostly as they compete for water resources, and the direction and intensity of plant interaction varies as a function of the temporal fluctuation in water availability. Since BSCs influence water redistribution to some extent, a greenhouse experiment was conducted to test the hypothesis that the intensity and direction of plant interactions in a dryland plant community can be modified by BSCs. In the experiment, 14 combinations of four plant species (Artemisia ordosica, Artemisia sphaerocephala, Chloris virgata and Setaria viridis) were subjected to three levels of coverage of BSCs and three levels of water supply. The results show that: 1) BSCs affected plant interaction intensity for the four plant species: a 100% coverage of BSCs significantly reduced the intensity of competition between neighboring plants, while it was highest with a 50% coverage of BSCs in combination with the target species of A. sphaerocephala and C. virgata; 2) effects of the coverage of BSCs on plant interactions were modified by water regime when the target species were C. virgata and S. viridis; 3) plant interactions were species-specific. In conclusion, the percent coverage of BSCs affected plant interactions, and the effects were species-specific and could be modified by water regimes. Further studies should focus on effects of the coverage of BSCs on plant-soil hydrological processes

Multiple adaptations to light and nutrient heterogeneity in the clonal plant Leymus secalinus with a combined growth form

Essential resources for plant growth are always heterogeneously distributed in natural ecosystems. Clonal plants can selectively place ramets in resource-rich patches to efficiently use heterogeneously distributed resources by altering spacer performance. Leymus secalinus, with a combination of phalanx and guerilla growth forms, can produce both spreading and clumping ramets. Previous studies have shown that nutrient availability decreases the proportion of spreading ramets. It was hypothesized that L. secalinus could place more ramets in resource-rich patches by producing more clumping ramets. To test this hypothesis, L secalinus was grown under artificial conditions with heterogeneously distributed nutrients and light. Results showed that L. secalinus not only altered the spacer length and specific spacer biomass between spreading ramets, but also balanced the trade-off between phalanx and guerilla growth forms to place more ramets in resource-rich patches, even if the patches were very small. Such multiple adaptations by L. secalinus, together with a division of labor, may enable it to efficiently use heterogeneous resources in natural ecosystems and to subsequently change the localized environment. (C) 2015 Elsevier GmbH. All rights reserved

Multiple adaptations to light and nutrient heterogeneity in clonal plant Leymus secalinus with a combined growth form

Essential resources for plant growth are always heterogeneously distributed in natural ecosystems. Clonal plants can selectively place ramets in resource-rich patches to efficiently use heterogeneously distributed resources by altering spacer performance. Leymus secalinus, with a combination of phalanx and guerilla growth forms, can produce both spreading and clumping ramets. Previous studies have shown that nutrient availability decreases the proportion of spreading ramets. It was hypothesized that L. secalinus could place more ramets in resource-rich patches by producing more clumping ramets. To test this hypothesis, L secalinus was grown under artificial conditions with heterogeneously distributed nutrients and light. Results showed that L. secalinus not only altered the spacer length and specific spacer biomass between spreading ramets, but also balanced the trade-off between phalanx and guerilla growth forms to place more ramets in resource-rich patches, even if the patches were very small. Such multiple adaptations by L. secalinus, together with a division of labor, may enable it to efficiently use heterogeneous resources in natural ecosystems and to subsequently change the localized environment. (C) 2015 Elsevier GmbH. All rights reserved

Efficient photoinduced charge transfer in chemically-linked organic-metal Ag-P3HT nanocomposites

A novel nanocomposite of P3HT and Ag nanoparticles (Ag-P3HT) has been synthesized by laser ablation. The fluorescence wavelength of the nanocomposite can be tuned by varying the ablation duration. The steady-state emission maximum at 580 nm for pristine P3HT shows significant blueshift to wavelengths ranging from 520 to 550 nm for Ag-P3HT. NMR, FTIR and XPS spectroscopy confirm that chemical links are formed between P3HT and silver nanoparticles (NPs) in the nanocomposite. For the sample with an emission maximum at 530 nm, 1H NMR spectra indicate that 66% of the P3HT thiophene ring protons are replaced by Ag NPs. Time-resolved spectroscopy demonstrates that charge transfer efficiency increases for Ag-P3HT and this is attributed to the enhanced intimate interfacial contact between the chemically-bonded metal NPs and polymer chains. The synthetic route outlined provides a one-pot and green strategy for producing metal-organic polymeric materials, with controlled luminescence wavelengths and efficient photoinduced charge transfer that meet the requirement for developing high-performance organic light-emitting and photovoltaic devices

Impact of land-use on carbon storage as dependent on soil texture: Evidence from a desertified dryland using repeated paired sampling design

Desertification resulting from land-use affects large dryland areas around the world, accompanied by carbon loss. However it has been difficult to interpret different land-use contributions to carbon pools owing to confounding factors related to climate, topography, soil texture and other original soil properties. To avoid such confounding effects, a unique systematic and extensive repeated design of paired sampling plots of different land-use types was adopted on Ordos Plateau, N China. The sampling enabled to quantify the effects of the predominant land-use types on carbon storage as dependent on soil texture, and to define the most promising land-use choices for carbon storage, both in grassland on sandy soil and in desert grassland on brown calcareous soil. The results showed that (1) desertification control should be an effective measure to improve the carbon sequestration in sandy grassland, and shrub planting should be better than grass planting; (2) development of man-made grassland should be a good choice to solve the contradictions of ecology and economy in desert grassland; (3) grassland on sandy soil is more vulnerable to soil degradation than desert grassland on brown calcareous soil. The results may be useful for the selection of land-use types, aiming at desertification prevention in drylands. Follow-up studies should directly investigate the role of soil texture on the carbon storage dynamic caused by land-use change