Graph Sampling-based Meta-Learning for Molecular Property Prediction

Molecular property is usually observed with a limited number of samples, and researchers have considered property prediction as a few-shot problem. One important fact that has been ignored by prior works is that each molecule can be recorded with several different properties simultaneously. To effectively utilize many-to-many correlations of molecules and properties, we propose a Graph Sampling-based Meta-learning (GS-Meta) framework for few-shot molecular property prediction. First, we construct a Molecule-Property relation Graph (MPG): molecule and properties are nodes, while property labels decide edges. Then, to utilize the topological information of MPG, we reformulate an episode in meta-learning as a subgraph of the MPG, containing a target property node, molecule nodes, and auxiliary property nodes. Third, as episodes in the form of subgraphs are no longer independent of each other, we propose to schedule the subgraph sampling process with a contrastive loss function, which considers the consistency and discrimination of subgraphs. Extensive experiments on 5 commonly-used benchmarks show GS-Meta consistently outperforms state-of-the-art methods by 5.71%-6.93% in ROC-AUC and verify the effectiveness of each proposed module. Our code is available at https://github.com/HICAI-ZJU/GS-Meta.Comment: Accepted by IJCAI 202

Synchronous multi-decadal climate variability of the whole Pacific areas revealed in tree rings since 1567

Oceanic and atmospheric patterns play a crucial role in modulating climate variability from interannual to multi-decadal timescales by causing large-scale co-varying climate changes. The brevity of the existing instrumental records hinders the ability to recognize climate patterns before the industrial era, which can be alleviated using proxies. Unfortunately, proxy based reconstructions of oceanic and atmospheric modes of the past millennia often have modest agreements with each other before the instrumental period, raising questions about the robustness of the reconstructions. To ensure the stability of climate signals in proxy data through time, we first identified tree-ring datasets from distant regions containing coherent variations in Asia and North America, and then interpreted their climate information. We found that the multi-decadal covarying climate patterns of the middle and high latitudinal regions around the northern Pacific Ocean agreed quite well with the climate reconstructions of the tropical and southern Pacific areas. This indicates a synchronous variability at the multi-decadal timescale of the past 430 years for the entire Pacific Ocean. This pattern is closely linked to the dominant mode of the Pacific sea surface temperature (SST) after removing the warming trend. This Pacific multi-decadal SST variability resembles the Interdecadal Pacific Oscillation

Tree ring pattern of roots exhumed by soil erosion

Mountains are subject to uplift and erosion. Human interference with the landscape by intensive agriculture, construction works, and tourism contributes to the removal of soil. We measured erosion rate by root exposure dating. Results of a pilot study of Shen Men Mt. at Tianshui and Kong Tong Mt. at Pingliang, Gansu province of China are reported here. New exhumation markers are introduced, separating aboveground features from mechanical stress-induced features. Change from root texture to stem texture, as defined by ring width and latewood width changes, reaction wood, distorted symmetry, simple and repeated wounds, open and closed wounds, abraded wound, onlap and offlap pattern of wound-affected growth increments, and simple and multiple discolouration by phenolic staining are illustrated and described here

Moisture stress of a hydrological year on tree growth in the Tibetan Plateau and surroundings

Investigations of climate-growth interactions can shed light on the response of forest growth to climate change and the dendroclimatic reconstructions. However, most existing studies in the climatically important Tibetan Plateau (TP) and surrouding regions focus on linear growth responses to environmental variation. Herein we investigated both the linear and the nonlinear climate-growth interactions for 152 tree-ring chronologies in the TP and vicinity. Weintroduced the boosted regression tree (BRT) technique to study the nonlinear climate-growth relationships by pooling several sites with similar climate-growth relationships to mitigate potential biases due to the shortness of the instrumental records. Across most of the TP and surroundings, tree growth is stressed by drought. The warming induced drought has been evidenced by the strong interactions between temperature and precipitation in the BRT analyses. The drought stress on forest growth is particularly conspicuous for a hydrological year over much of the Northern TP and surroundings. The BRT analyses indicate the compensation effect of moisture prior to the growing season for the moisture deficit in the early growing season in May to July, when most of the ring-width formation occurs.Peer reviewe

An Ensemble Weighting Approach for Dendroclimatology : Drought Reconstructions for the Northeastern Tibetan Plateau

Peer reviewe

An increase in the biogenic aerosol concentration as a contributing factor to the recent wetting trend in Tibetan Plateau

A significant wetting trend since the early 1980s in Tibetan Plateau (TP) is most conspicuous in central and eastern Asia as shown in the instrumental data and the long-term moisture sensitive tree rings. We found that anomalies in the large-scale oceanic and atmospheric circulations do not play a significant role on the wetting trend in TP. Meanwhile, the weak correlation between local temperature and precipitation suggests that the temperature-induced enhancement of the local water cycle cannot fully explain the wetting trend either. This may indicate the presence of nonlinear processes between local temperature and precipitation. We hypothesize that the current warming may enhance the emissions of the biogenic volatile organic compounds (BVOC) that can increase the secondary organic aerosols (SOA), contributing to the precipitation increase. The wetting trend can increase the vegetation cover and cause a positive feedback on the BVOC emissions. Our simulations indicate a significant contribution of increased BVOC emissions to the regional organic aerosol mass and the simulated increase in BVOC emissions is significantly correlated with the wetting trend in TP.Peer reviewe

Hydroclimate Variations in Central and Monsoonal Asia over the Past 700 Years

Peer reviewe

Improved spring temperature reconstruction using earlywood blue intensity in southeastern China

Because instrumental observations are too short to fully represent long-term natural variability, high-resolution temperature proxy records are essential to understanding past climate and assessing current climate variability in the context of long-term patterns. In the subtropics, progress in this field has been hampered by a relative lack of long and truly temperature-sensitive proxy records. In this study, we provide an assessment of the dendroclimatic potential of blue intensity (BI) and ring-width (RW) measurements from two hot/humid Pinus massoniana sites in China. Our results show that RW exhibits a significant (p < .05) response to precipitation over a hydrological year (previous November to October) and to temperature over the winter–spring season (January to March). We find the earlywood blue intensity parameter to be the most robust parameter for reconstruction purposes; over the 1916–2015 period, it explains 36% of regional-scale spring season (March–May) temperature variance. Strong agreements between the current reconstruction and observed temperature over a large area of southeastern China implied that our reconstruction exhibited high reliability and large spatial representation. As expected, our reconstructed temperature data are directly correlated with El Niño–Southern Oscillation. These results suggest that there is great potential to use BI to advance our understanding of temperature variability in regions hot and humid climate regimes. However, more studies are needed to understand (1) which subtropical tree species will be appropriate for use and (2) how to overcome biases from differential staining between sapwood and heartwood