89 research outputs found
Energy-momentum and angular momentum of Goedel universes
We discuss the Einstein energy-momentum complex and the Bergmann-Thomson
angular momentum complex in general relativity and calculate them for
space-time homogeneous Goedel universes. The calculations are performed for a
dust acausal model and for a scalar-field causal model. It is shown that the
Einstein pseudotensor is traceless, not symmetric, the gravitational energy is
"density" is negative and the gravitational Poynting vector vanishes.
Significantly, the total (gravitational and matter) energy "density" fro the
acausal model is zero while for the casual model it is negative.The
Bergmann-Thomson angular momentum complex does not vanish for both G\"odel
models.Comment: an amended version, 24 pages, accepted to PR
Towards a Criminology of the Domestic
Criminology has paid insufficient attention to the âdomesticâ arena, as a locale that is being reconfigured through technological and social developments in ways that require us to reconsider offending and victimisation. This article addresses this lacuna. We take up Campbell's (2016) challenge that criminology needs to develop more sophisticated models of place and space, particularly in relation to changing patterns of consumption and leisure activity and the opportunities to offend in relation to these from within the domestic arena
Quantitative importance of staminodes for female reproductive success in Parnassia palustris under contrasting environmental conditions.
The five sterile stamens, or staminodes, in Parnassia palustris act both as false and as true nectaries. They attract pollinators with their conspicuous, but non-rewarding tips, and also produce nectar at the base. We removed staminodes experimentally and compared pollinator visitation rate and duration and seed set in flowers with and without staminodes in two different populations. We also examined the relative importance of the staminode size to other plant traits. Finally, we bagged, emasculated, and supplementary cross-pollinated flowers to determine the pollination strategy and whether reproduction was limited by pollen availability. Flowers in both populations were highly dependent on pollinator visitation for maximum seed set. In one population pollinators primarily cross-pollinated flowers, whereas in the other the pollinators facilitated self-pollination. The staminodes caused increased pollinator visitation rate and duration to flowers in both populations. The staminodes increased female reproductive success, but only when pollen availability constrained female reproduction. Simple linear regression indicated a strong selection on staminode size, multiple regression suggested that selection on staminode size was mainly caused by correlation with other traits that affected female fitness. [ABSTRACT FROM AUTHOR
Poleward bound: adapting to climate-driven species redistribution
One of the most pronounced effects of climate change on the worldâs oceans is the (generally) poleward movement of species and fishery stocks in response to increasing water temperatures. In some regions, such redistributions are already causing dramatic shifts in marine socioecological systems, profoundly altering ecosystem structure and function, challenging domestic and international fisheries, and impacting on human communities. Such effects are expected to become increasingly widespread as waters continue to warm and species ranges continue to shift. Actions taken over the coming decade (2021â2030) can help us adapt to species redistributions and minimise negative impacts on ecosystems and human communities, achieving a more sustainable future in the face of ecosystem change. We describe key drivers related to climate-driven species redistributions that are likely to have a high impact and influence on whether a sustainable future is achievable by 2030. We posit two different futuresâa âbusiness as usualâ future and a technically achievable and more sustainable future, aligned with the Sustainable Development Goals. We then identify concrete actions that provide a pathway towards the more sustainable 2030 and that acknowledge and include Indigenous perspectives. Achieving this sustainable future will depend on improved monitoring and detection, and on adaptive, cooperative management to proactively respond to the challenge of species redistribution. We synthesise examples of such actions as the basis of a strategic approach to tackle this global-scale challenge for the benefit of humanity and ecosystems
Running the club for love: Challenges for identity, accountability and governance relationships
The current context of State sport governance and funding structures in the United Kingdom continue to challenge national, regional and local bodies and community clubsâ abilities to fulfil ambitions to support participation and competition at all levels. Notwithstanding sport clubsâ laudable intentions to support involvement and encourage participation (often with limited resources, guidance and communication from National Governing Bodies (NGB)), clubs face considerable practical, political and ideological constraints that adversely affect their day-to-day operations and ability to translate sport policy in âactionâ in meaningful ways. Drawing on data from 21 athletic clubs in England, this paper examines how athletic clubsâ relations with the NGB, UK Athletics (UKA), raise questions about the clubsâ individual and collective identities, agendas, ideals and overall value to its members
Large-scale discovery of novel genetic causes of developmental disorders
Despite three decades of successful, predominantly phenotype-driven discovery of the genetic causes of monogenic disorders1, up to half of children with severe developmental disorders of probable genetic origin remain without a genetic diagnosis. Particularly challenging are those disorders rare enough to have eluded recognition as a discrete clinical entity, those with highly variable clinical manifestations, and those that are difficult to distinguish from other, very similar, disorders. Here we demonstrate the power of using an unbiased genotype-driven approach2 to identify subsets of patients with similar disorders. By studying 1,133 children with severe, undiagnosed developmental disorders, and their parents, using a combination of exome sequencing3,4,5,6,7,8,9,10,11 and array-based detection of chromosomal rearrangements, we discovered 12 novel genes associated with developmental disorders. These newly implicated genes increase by 10% (from 28% to 31%) the proportion of children that could be diagnosed. Clustering of missense mutations in six of these newly implicated genes suggests that normal development is being perturbed by an activating or dominant-negative mechanism. Our findings demonstrate the value of adopting a comprehensive strategy, both genome-wide and nationwide, to elucidate the underlying causes of rare genetic disorders
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Time in captivity, individual differences and foraging behaviour in wild-caught chaffinches
Wild-caught animals are often given a settling in period before experimental trials are initiated. We used wild-caught chaffinches (Fringilla coelebs) to investigate (a) the effect of settling in period duration on the likelihood that chaffinches foraged during experimental trials and (b) whether settling in period duration influenced measures of foraging and vigilance behaviour recorded from those experiments. The probability of collecting foraging data from an individual's first trial fell below 50% if it had been in captivity for more than 12 days prior to that trial, whereas the probability was >75% if trials were completed within two days of capture. The successful collection of foraging data from subsequent trials was also dependent on the number of days an individual spent in captivity prior to its first trial and on whether that individual foraged in its first trial, suggesting that some individuals were more inclined to forage in captivity. Individuals that foraged in their first trial had a 94% higher success rate in subsequent trials than those that did not. However, settling in period duration did not significantly influence the peck rate, mean search period or mean vigilance period of individuals that did forage. Our results show that allowing a settling in period actually reduced the likelihood of collecting foraging data from chaffinches and that commencing experiments shortly after capture increased data collection efficiency. We discuss the possibility that the inability to collect data from certain birds following a settling in period could lead to potentially important biases in results, particularly if propensity to forage is linked to an individual's coping strategy or personality. We conclude that it may not always be beneficial to allow wild-caught animals to habituate to captivity before commencing experiments. In some cases, testing animals soon after capture may increase the likelihood of data collection, reducing both the number of study animals required and the length of time they spend in captivity
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