Link Prediction Based on Local Random Walk

The problem of missing link prediction in complex networks has attracted much attention recently. Two difficulties in link prediction are the sparsity and huge size of the target networks. Therefore, the design of an efficient and effective method is of both theoretical interests and practical significance. In this Letter, we proposed a method based on local random walk, which can give competitively good prediction or even better prediction than other random-walk-based methods while has a lower computational complexity.Comment: 6 pages, 2 figure

Effective and Efficient Similarity Index for Link Prediction of Complex Networks

Predictions of missing links of incomplete networks like protein-protein interaction networks or very likely but not yet existent links in evolutionary networks like friendship networks in web society can be considered as a guideline for further experiments or valuable information for web users. In this paper, we introduce a local path index to estimate the likelihood of the existence of a link between two nodes. We propose a network model with controllable density and noise strength in generating links, as well as collect data of six real networks. Extensive numerical simulations on both modeled networks and real networks demonstrated the high effectiveness and efficiency of the local path index compared with two well-known and widely used indices, the common neighbors and the Katz index. Indeed, the local path index provides competitively accurate predictions as the Katz index while requires much less CPU time and memory space, which is therefore a strong candidate for potential practical applications in data mining of huge-size networks.Comment: 8 pages, 5 figures, 3 table

Predicting Missing Links via Local Information

Missing link prediction of networks is of both theoretical interest and practical significance in modern science. In this paper, we empirically investigate a simple framework of link prediction on the basis of node similarity. We compare nine well-known local similarity measures on six real networks. The results indicate that the simplest measure, namely common neighbors, has the best overall performance, and the Adamic-Adar index performs the second best. A new similarity measure, motivated by the resource allocation process taking place on networks, is proposed and shown to have higher prediction accuracy than common neighbors. It is found that many links are assigned same scores if only the information of the nearest neighbors is used. We therefore design another new measure exploited information of the next nearest neighbors, which can remarkably enhance the prediction accuracy.Comment: For International Workshop: "The Physics Approach To Risk: Agent-Based Models and Networks", http://intern.sg.ethz.ch/cost-p10

Conformational Equilibria of β-Alanine and Related Compounds as Studied by NMR Spectroscopy

The vicinal proton−proton couplings of the dipolar form of β-alanine in water, alcohol−water, and dimethyl sulfoxide−water solutions indicate little conformational preference and are consistent with an essentially statistical equilibrium of the gauche or trans conformations. The position of the equilibrium is only slightly affected, over a temperature range of about 130°, by changes in dielectric constants ranging from 30 to 80 or by massive changes in ionic strength. Quantum-mechanical calculations at the HF/6-31G^(**) and LMP2/cc-pVTZ levels were found to give rather good parallels with experiment, although suggesting the gauche conformation to be 2−3 kcal/mol more stable in water or methanol than actually observed. A number of related compounds, such as N,N,N-trimethyl-β-alanine and N,N-diethyl-β-alanine, as well as the conjugate acid and conjugate base of β-alanine, also show no significant conformational preference in water solution. In conformity with these results, the zwitterionic form of piperidine-3-carboxylic acid (nipecotic acid) has about the same preference for equatorial carboxylate as cyclohexanecarboxylic acid itself. Taurine shows no significant conformational preference except in basic solution, where the couplings indicate about 53% of the gauche conformation. In contrast, N,N,N-trimethyltaurine is predominantly trans in acidic or neutral solution. The conformational equilibria of the N,N,N-trimethyltaurine species are most likely governed by steric hindrance, because there are rather large tetrahedral groups at each end of the ethano chains. Yet, even here the energy difference between gauche and trans is only about 1.2 kcal

An NMR and Quantum-Mechanical Investigation of Tetrahydrofuran Solvent Effects on the Conformational Equilibria of 1,4-Butanedioic Acid and Its Salts

Vicinal proton−proton NMR couplings have been used to compare the influences of water and tetrahydrofuran (THF) as solvents on the conformational equilibria of 1,4-butanedioic (succinic) acid and its mono- and dianionic salts. An earlier NMR investigation (Lit, E. S.; Mallon, F. K.; Tsai, H. Y.; Roberts, J. D. J. Am Chem. Soc. 1993, 115, 9563−9567) showed that, in water, the conformational preferences for the gauche conformations for butanedioic acid and its monoanion and dianion were, respectively, ∼84%, 66%, and 43%, essentially independent of the nature of the cation or concentration. We now report the corresponding gauche percentages calculated in the same way for 0.05 M solutions in THF to be 66%, 90−100%, and 46−64%. Substantial evidence was adduced for the rotational angle between the substituents in the monoanion being ∼70°. The positions of conformational equilibria of the salts in THF, particularly of the dianion, were found to be rather insensitive to concentration and temperature, but more sensitive to the amount of water present. Ab initio quantum-mechanical calculations for 1,4-butanedioate dianion indicate that, as expected for the gas phase, the trans conformation of the dianion should be heavily favored over the gauche, but, in both THF and water, the gauche conformation is calculated to predominate with rotational angles substantially less than 60°. This conclusion is, in fact, generally consistent with the experimental vicinal proton couplings, which are wholly inconsistent with the trans conformation

From one pandemic to another: emerging lessons from COVID-19 for tackling physical inactivity in cities

Physical inactivity is a global pandemic. The COVID-19 crisis has altered global patterns of physical activity in ways that were unimaginable before the outbreak. Enforced restrictions on mobility and the mass closure of indoor fitness centres has highlighted the limitations of many urban areas for enabling physical activity and reinforced inequalities in physical activity opportunities across cities. However, unprecedented reductions in mobility and increases in localised physical activity provide unique insight on opportunities for urban health promotion. COVID-19 responses can, therefore, encourage new perspectives in urban planning and inspire novel future strategies to design more sustainable, healthier and equitable cities