782 research outputs found
Recommended from our members
Chris Cannings: A Life in Games
Chris Cannings was one of the pioneers of evolutionary game theory. His early work was inspired by the formulations of John Maynard Smith, Geoff Parker and Geoff Price; Chris recognized the need for a strong mathematical foundation both to validate stated results and to give a basis for extensions of the models. He was responsible for fundamental results on matrix games, as well as much of the theory of the important war of attrition game, patterns of evolutionarily stable strategies, multiplayer games and games on networks. In this paper we describe his work, key insights and their influence on research by others in this increasingly important field. Chris made substantial contributions to other areas such as population genetics and segregation analysis, but it was to games that he always returned. This review is written by three of his students from different stages of his career
A review of data on abundance, trends in abundance, habitat use and diet of ice-breeding seals in the Southern Ocean
The development of models of marine ecosystems in the Southern Ocean is becoming increasingly important as a means of understanding and managing impacts such as exploitation and climate change. Collating data from disparate sources, and understanding biases or uncertainties inherent in those data, are important first steps for improving ecosystem models. This review focuses on seals that breed in ice habitats of the Southern Ocean (i.e. crabeater seal, Lobodon carcinophaga; Ross seal, Ommatophoca rossii; leopard seal, Hydrurga leptonyx; and Weddell seal, Leptonychotes weddellii). Data on populations (abundance and trends in abundance), distribution and habitat use (movement, key habitat and environmental features) and foraging (diet) are summarised, and potential biases and uncertainties inherent in those data are identified and discussed. Spatial and temporal gaps in knowledge of the populations, habitats and diet of each species are also identified
Inclusion of seasonal variation in river system microbial communities and phototroph activity increases environmental relevance of laboratory chemical persistence tests
Regulatory tests assess crop protection product environmental fate and toxicity before approval for commercial use. Although globally applied laboratory tests can assess biodegradation, they lack environmental complexity. Microbial communities are subject to temporal and spatial variation, but there is little consideration of these microbial dynamics in the laboratory. Here, we investigated seasonal variation in the microbial composition of water and sediment from a UK river across a two-year time course and determined its effect on the outcome of water-sediment (OECD 308) and water-only (OECD 309) biodegradation tests, using the fungicide isopyrazam. These OECD tests are performed under dark conditions, so test systems incubated under non-UV light:dark cycles were also included to determine the impact on both inoculum characteristics and biodegradation. Isopyrazam degradation was faster when incubated under non-UV light at all collection times in water-sediment microcosms, suggesting that phototrophic communities can metabolise isopyrazam throughout the year. Degradation rate varied seasonally between inoculum collection times only in microcosms incubated in the light, but isopyrazam mineralisation to 14CO2 varied seasonally under both light and dark conditions, suggesting that heterotrophic communities may also play a role in degradation. Bacterial and phototroph communities varied across time, but there was no clear link between water or sediment microbial composition and variation in degradation rate. During the test period, inoculum microbial community composition changed, particularly in non-UV light incubated microcosms. Overall, we show that regulatory test outcome is not influenced by temporal variation in microbial community structure; however, biodegradation rates from higher tier studies with improved environmental realism, e.g. through addition of non-UV light, may be more variable. These data suggest that standardised OECD tests can provide a conservative estimate of pesticide persistence end points and that additional tests including non-UV light could help bridge the gap between standard tests and field studies
Sprinkling with random regular graphs
We conjecture that the distribution of the edge-disjoint union of two random
regular graphs on the same vertex set is asymptotically equivalent to a random
regular graph of the combined degree, provided that the combined degree and the
complementary degrees are growing. We verify this conjecture for the cases when
the graphs are sufficiently dense or sparse. We also prove an asymptotic
formula for the expected number of spanning regular subgraphs in a random
regular graph
A bioenergetics model for estimating prey consumption by an Adélie penguin population in East Antarctica
Assisted stellar suicide in V617 Sgr
V617 Sgr is a V Sagittae star - a group of binaries thought to be the
galactic counterparts of the Compact Binary Supersoft X-ray Sources - CBSS. To
check this hypothesis, we measured the time derivative of its orbital period.
Observed timings of eclipse minima spanning over 30,000 orbital cycles are
presented. We found that the orbital period evolves quite rapidly: P/Pdot = 1.1
x 10^{6} years. This is consistent with the idea that V617 Sgr is a wind driven
accretion supersoft source. As the binary system evolves with a time-scale of
about one million years, which is extremely short for a low mass evolved
binary, it is likely that the system will soon end either by having its
secondary completely evaporated or by the primary exploding as a supernova of
type Ia.Comment: 4 pages, accepted for publication in A&A Letter
Entangled Mechanical Oscillators
Hallmarks of quantum mechanics include superposition and entanglement. In the
context of large complex systems, these features should lead to situations like
Schrodinger's cat, which exists in a superposition of alive and dead states
entangled with a radioactive nucleus. Such situations are not observed in
nature. This may simply be due to our inability to sufficiently isolate the
system of interest from the surrounding environment -- a technical limitation.
Another possibility is some as-of-yet undiscovered mechanism that prevents the
formation of macroscopic entangled states. Such a limitation might depend on
the number of elementary constituents in the system or on the types of degrees
of freedom that are entangled. One system ubiquitous to nature where
entanglement has not been previously demonstrated is distinct mechanical
oscillators. Here we demonstrate deterministic entanglement of separated
mechanical oscillators, consisting of the vibrational states of two pairs of
atomic ions held in different locations. We also demonstrate entanglement of
the internal states of an atomic ion with a distant mechanical oscillator.Comment: 7 pages, 2 figure
Transfer of training in an academic leadership development program for program coordinators
The higher education sector has increasingly begun to pay more attention to academic leadership. This qualitative study explores how such an investment in a 20-week leadership development program influenced the behaviour of 10 academic staff in the role of program coordinator 6 to 12 months following participation in the program. Otherwise known as program directors or department chairs, academic staff in this role are responsible for coordinating and leading degree courses or programs. Leadership learning and changes in the behaviour of program coordinators was evident, particularly in regard to building influence, communicating more effectively and managing upwards. Improved confidence in their ability to perform the role was a lasting outcome and the use of peer learning and coaching was an important part of the success of the intervention. However, workload factors, succession planning and orientation were seen to be factors that impact on leadership development in this role. The findings suggest that participation in well designed academic leadership programs can result in a lasting transfer of training for program coordinators
- …