Learning from graphs with structural variation

We study the effect of structural variation in graph data on the predictive performance of graph kernels. To this end, we introduce a novel, noise-robust adaptation of the GraphHopper kernel and validate it on benchmark data, obtaining modestly improved predictive performance on a range of datasets. Next, we investigate the performance of the state-of-the-art Weisfeiler-Lehman graph kernel under increasing synthetic structural errors and find that the effect of introducing errors depends strongly on the dataset.Comment: Presented at the NIPS 2017 workshop "Learning on Distributions, Functions, Graphs and Groups

Heavy metals in Greenland seabirds

From six Greenland districts we report the concentration of Zn, Cd, Hg and Se in muscle (pectoral), liver and kidney for 320 seabirds of the following species: Cepphus grylle, Uria lomvia, Clangula hyemalis, Mergus serrator, Larus glaucoides, L. hyperboreus, Rissa tridactyla, Pagophila eburnea, Fulmarus glacialis, Phalacrocorax carbo and Stercorarius pomarinus. Concentrations vary widely within species. Yearlings are low in Cd and Hg. Concentrations tend to increase with age. No significant differences between sexes were found. On a wet weight basis, the Zn concentration in liver and kidney is c. three times that of muscle. Gulls and the fulmar possess significantly more Zn in muscle than do other seabirds. The Cd concentration in liver and kidney is c. 20 and 80 times higher than in muscle, whereas the Hg concentration in liver and kidney is three to five times higher than that of muscle. The Se concentration in liver and kidney is c. five times the muscle concentration. Muscle, liver and kidney concentrations tend to correlate positively for Cd, Hg and Se. For Zn only liver and kidney concentrations correlate mutually. On a molar basis, the three organs of all species have a large excess of Se over Hg. The intra-organ association of elements is strongest for Zn and Cd in liver and kidney, and for Hg and Se generally. All four elements show consistently higher concentrations in birds from NW and NE Greenland than in those from S Greenland. For C. grylle from Avanersuaq, NW Greenland, the Cd concentration is twice that of birds from S Greenland, the difference being highly significant. Hg concentrations are not significantly different