A biostratigraphical framework for geological correlation of the Middle Devonian strata in the Moray-Ness Basin Project area

This report presents an up dated biostratigraphical framework for correlation of the Middle Devonian strata exposed in onshore areas on the western margin of the Orcadian Basin. It focuses on the fossil fish faunas from Caithness and Orkney. The research has involved taxonomical and stratigraphical revision of key fossil fish specimens and whole assemblages held in museums and in private collections , together with targeted new field collecting in Caithness and on Orkney. This has enabled a robust pattern of distribution to be established for indicator species, based on faunas identified from large collections of individual species, so that presence/absence data are of significance in determining a more fully representative stratigraphical range for each species than was available hitherto. This approach has enabled detailed biostratigraphical correlations to be made within the Middle Devonian of the Reay area and on adjacent ground. It also provides new constraints on the regional biostratigraphical correlation between the flagstone sequences in Caithness and on Orkney. The importance of fossil fish assemblages that have been examined in collections from the Middle Devonian on the southern margin of the Moray Firth are currently being re-evaluated in terms of their ability to constrain new and existing regional and local stratigraphical correlations. The eventual aim of this work is to provide a consistent means of correlating all of the onshore Middle Devonian strata in the Moray-Ness Project area

Visual Mining of Epidemic Networks

We show how an interactive graph visualization method based on maximal modularity clustering can be used to explore a large epidemic network. The visual representation is used to display statistical tests results that expose the relations between the propagation of HIV in a sexual contact network and the sexual orientation of the patients.Comment: 8 page

Line graphs as social networks

The line graphs are clustered and assortative. They share these topological features with some social networks. We argue that this similarity reveals the cliquey character of the social networks. In the model proposed here, a social network is the line graph of an initial network of families, communities, interest groups, school classes and small companies. These groups play the role of nodes, and individuals are represented by links between these nodes. The picture is supported by the data on the LiveJournal network of about 8 x 10^6 people. In particular, sharp maxima of the observed data of the degree dependence of the clustering coefficient C(k) are associated with cliques in the social network.Comment: 11 pages, 4 figure

Shift of percolation thresholds for epidemic spread between static and dynamic small-world networks

The aim of the study was to compare the epidemic spread on static and dynamic small-world networks. The network was constructed as a 2-dimensional Watts-Strogatz model (500x500 square lattice with additional shortcuts), and the dynamics involved rewiring shortcuts in every time step of the epidemic spread. The model of the epidemic is SIR with latency time of 3 time steps. The behaviour of the epidemic was checked over the range of shortcut probability per underlying bond 0-0.5. The quantity of interest was percolation threshold for the epidemic spread, for which numerical results were checked against an approximate analytical model. We find a significant lowering of percolation thresholds for the dynamic network in the parameter range given. The result shows that the behaviour of the epidemic on dynamic network is that of a static small world with the number of shortcuts increased by 20.7 +/- 1.4%, while the overall qualitative behaviour stays the same. We derive corrections to the analytical model which account for the effect. For both dynamic and static small-world we observe suppression of the average epidemic size dependence on network size in comparison with finite-size scaling known for regular lattice. We also study the effect of dynamics for several rewiring rates relative to latency time of the disease.Comment: 13 pages, 6 figure

A motif-based approach to network epidemics

Networks have become an indispensable tool in modelling infectious diseases, with the structure of epidemiologically relevant contacts known to affect both the dynamics of the infection process and the efficacy of intervention strategies. One of the key reasons for this is the presence of clustering in contact networks, which is typically analysed in terms of prevalence of triangles in the network. We present a more general approach, based on the prevalence of different four-motifs, in the context of ODE approximations to network dynamics. This is shown to outperform existing models for a range of small world networks

Scaling in Small-World Resistor Networks

We study the effective resistance of small-world resistor networks. Utilizing recent analytic results for the propagator of the Edwards-Wilkinson process on small-world networks, we obtain the asymptotic behavior of the disorder-averaged two-point resistance in the large system-size limit. We find that the small-world structure suppresses large network resistances: both the average resistance and its standard deviation approaches a finite value in the large system-size limit for any non-zero density of random links. We also consider a scenario where the link conductance decays as a power of the length of the random links, $l^{-\alpha}$. In this case we find that the average effective system resistance diverges for any non-zero value of $\alpha$.Comment: 15 pages, 6 figure

Color Dynamics in External Fields

We investigate the vacuum dynamics of U(1), SU(2), and SU(3) lattice gauge theories in presence of external (chromo)magnetic fields, both in (3+1) and (2+1) dimensions. We find that the critical coupling for the phase transition in compact U(1) gauge theory is independent of the strength of an external magnetic field. On the other hand we find that, both in (3+1) and (2+1) dimensions, the deconfinement temperature for SU(2) and SU(3) gauge systems in a constant abelian chromomagnetic field decreases when the strength of the applied field increases. We conclude that the dependence of the deconfinement temperature on the strength of an external constant chromomagnetic field is a peculiar feature of non abelian gauge theories and could be useful to get insight into color confinement.Comment: 26 pages, 14 figure

The association of osteoarthritis risk factors with localized, regional and diffuse knee pain

SummaryObjectiveTo identify determinants of different patterns of knee pain with a focus on risk factors for knee osteoarthritis (OA).DesignThe Knee Pain Map is an interviewer-administered assessment that asks subjects to characterize their knee pain as localized, regional, or diffuse. A total of 2677 participants from the Osteoarthritis Initiative were studied.We used multinomial logistic regression to examine the relationship between risk factors for OA and knee pain patterns. We examined the bivariate and multivariate relationships of knee pain pattern with age, body mass index (BMI), sex, race, family history of total joint replacement, knee injury, knee surgery, and hand OA.ResultsWe compared 2462 knees with pain to 1805 knees without pain. In the bivariate analysis, age, sex, BMI, injury, surgery, and hand OA were associated with at least one pain pattern. In the multivariate model, all of these variables remained significantly associated with at least one pattern. When compared to knees without pain, higher BMI, injury, and surgery were associated with all patterns. BMI had its strongest association with diffuse pain. Older age was less likely to be associated with localized pain while female sex was associated with regional pain.ConclusionsWe have shown that specific OA risk factors are associated with different knee pain patterns. Better understanding of the relationship between OA risk factors and knee pain patterns may help to characterize the heterogeneous subsets of knee OA

Signatures of small-world and scale-free properties in large computer programs

A large computer program is typically divided into many hundreds or even thousands of smaller units, whose logical connections define a network in a natural way. This network reflects the internal structure of the program, and defines the ``information flow'' within the program. We show that, (1) due to its growth in time this network displays a scale-free feature in that the probability of the number of links at a node obeys a power-law distribution, and (2) as a result of performance optimization of the program the network has a small-world structure. We believe that these features are generic for large computer programs. Our work extends the previous studies on growing networks, which have mostly been for physical networks, to the domain of computer software.Comment: 4 pages, 1 figure, to appear in Phys. Rev.

Convergence of the critical attractor of dissipative maps: Log-periodic oscillations, fractality and nonextensivity

For a family of logistic-like maps, we investigate the rate of convergence to the critical attractor when an ensemble of initial conditions is uniformly spread over the entire phase space. We found that the phase space volume occupied by the ensemble W(t) depicts a power-law decay with log-periodic oscillations reflecting the multifractal character of the critical attractor. We explore the parametric dependence of the power-law exponent and the amplitude of the log-periodic oscillations with the attractor's fractal dimension governed by the inflexion of the map near its extremal point. Further, we investigate the temporal evolution of W(t) for the circle map whose critical attractor is dense. In this case, we found W(t) to exhibit a rich pattern with a slow logarithmic decay of the lower bounds. These results are discussed in the context of nonextensive Tsallis entropies.Comment: 8 pages and 8 fig