Greedy Graph Colouring is a Misleading Heuristic

State of the art maximum clique algorithms use a greedy graph colouring as a bound. We show that greedy graph colouring can be misleading, which has implications for parallel branch and bound

Finding maximum k-cliques faster using lazy global domination

No abstract available

Multi-threading a state-of-the-art maximum clique algorithm

We present a threaded parallel adaptation of a state-of-the-art maximum clique algorithm for dense, computationally challenging graphs. We show that near-linear speedups are achievable in practice and that superlinear speedups are common. We include results for several previously unsolved benchmark problems

A Partitioning Algorithm for Maximum Common Subgraph Problems

We introduce a new branch and bound algorithm for the maximum common subgraph and maximum common connected subgraph problems which is based around vertex labelling and partitioning. Our method in some ways resembles a traditional constraint programming approach, but uses a novel compact domain store and supporting inference algorithms which dramatically reduce the memory and computation requirements during search, and allow better dual viewpoint ordering heuristics to be calculated cheaply. Experiments show a speedup of more than an order of magnitude over the state of the art, and demonstrate that we can operate on much larger graphs without running out of memory

Between Subgraph Isomorphism and Maximum Common Subgraph

When a small pattern graph does not occur inside a larger target graph, we can ask how to find "as much of the pattern as possible" inside the target graph. In general, this is known as the maximum common subgraph problem, which is much more computationally challenging in practice than subgraph isomorphism. We introduce a restricted alternative, where we ask if all but k vertices from the pattern can be found in the target graph. This allows for the development of slightly weakened forms of certain invariants from subgraph isomorphism which are based upon degree and number of paths. We show that when k is small, weakening the invariants still retains much of their effectiveness. We are then able to solve this problem on the standard problem instances used to benchmark subgraph isomorphism algorithms, despite these instances being too large for current maximum common subgraph algorithms to handle. Finally, by iteratively increasing k, we obtain an algorithm which is also competitive for the maximum common subgraph

Vogue’s attack on style bloggers shows how much the newcomers have the fashion mags rattled

For years, style bibles such as Vogue and Elle have found their exclusivity undermined by bloggers, who – with huge numbers of Facebook, Twitter and Instagram followers – have won over the designer brands that would normally only deal with major publications. Inevitably, this tension occasionally breaks the surface, as when Vogue editors recently lashed out at fashion bloggers in their Milan fashion week round-up column

NREM sleep spindles and slow wave sleep in younger and elderly women: an investigation of their influence on declarative memory consolidation

Previous research shows that slow wave sleep (SWS) and sleep spindles play an essential role in declarative memory consolidation. However, this role is not well understood in the ageing women. With advancing age, SWS and sleep spindles undergo significant decreases in duration and density, while there is a simultaneous decline in declarative memory. The primary aim of this research was to investigate the relationship between sleep architecture, sleep spindle activity, and declarative memory retention in two groups of women: 14 younger (M = 20.5±1.28 years) and 14 older females (M = 63.14±2.03 years). Participants underwent polysomnography on a baseline and experimental night and encoded a list of word-pairs of graded difficulty on the experimental night. Word-pair type included integrative, concrete and low concrete measures. Memory retention was then assessed pre- and post-sleep. Our results confirm the characteristic age-related decrease in SWS and sleep spindle activity in older adults. In the older group, SWS positively correlated with concrete word-pair retention, while spindle density and the number of spindles positively correlated with overall retention. In addition, the percentage change in spindle density, slow and fast density, and fast intensity from baseline to experimental night positively correlated with low concrete word-pairs. Finally, in the younger group, the number of spindles positively correlated with low concrete word-pairs and the percentage change in fast and slow spindle intensity correlated with concrete word-pair retention. Although younger women recalled more word-pairs than older women in both conditions, memory retention was largely preserved in both groups after sleep

Reintroduced beavers rapidly influence sediment storage and biogeochemistry in headwater streams of the Methow River, WA

To understand how rapidly beaver bioengineering impacts sediment organic material accumulation, we characterized the short-term, temporal dynamics of how reintroduced beavers have influenced sediment and organic material accumulation on 1st and 2nd order streams over the past decade. Sources of beaver related organics include coarse woody debris, fecal matter, and allochthonous material. We measured sediment physical properties, and analyzed samples for weight percent carbon and nitrogen. Our temporally constrained results provide insight into the rapidity at which beavers can influence biogeochemical systems in headwater streams

Modelling the effects of temperature changes on Schistosoma mansoni transmission

Schistosomiasis is a chronic parasitic disease, estimated to affect 237 million people worldwide. It is caused by infection with Schistosoma helminths, which spend part of their lifecycles in aquatic snails. The mortality, development and fecundity rates of the parasites and their intermediate host snails are very sensitive to water temperature. The distribution and prevalence of schistosome parasites are therefore likely to be affected by climate change, however the potential effects of this have been largely neglected. Only two mathematical models of temperature and schistosome transmission in Africa have previously been developed, and neither explicitly simulated all temperature-dependent stages of the parasite and snail lifecycles. The aim of this thesis is to advance understanding of the potential effects of climate change on S. mansoni transmission, using an agent-based modelling approach. A mathematical model of water temperature, snail population dynamics and S. mansoni transmission was developed. The model was parameterised using data from Biomphalaria pfeifferi, the most widespread intermediate host species in Africa, and the dynamics of the model were explored. Infection risk was shown to be highest (above 90% of the maximum) at a constant temperature of 15-19°C. Simulating diurnal variation in temperature and/or higher cercaria and miracidium removal rates increased the optimum temperature for transmission to 16-26°C. The effect of simulating different species of intermediate host snail was also investigated. Simulating Bi. alexandrina and Bi. glabrata increased the temperature at which infection risk was highest to 19-21°C and 20-26°C respectively. The model was run using climate projections for eastern Africa. Comparisons of model output at baseline with empirical data showed that suitable temperatures are necessary but not sufficient for both schistosome transmission, and for high prevalences of schistosomiasis. All else being equal, infection risk may increase by up to 20% over most of the area over the next 20 and 50 years. Increases may be higher in Rwanda, Burundi, south-west Kenya and eastern Zambia, and schistosomiasis may become newly endemic in parts of these areas. The results for 20 years’ time are robust to changes in simulated snail habitats. There is greater uncertainty about the effects of different habitats on changes in risk in 50 years’ time