380 research outputs found
The influence of transition metal solutes on dislocation core structure and values of Peierls stress and barrier in tungsten
Several transition metals were examined to evaluate their potential for
improving the ductility of tungsten. The dislocation core structure and Peierls
stress and barrier of screw dislocations in binary
tungsten-transition metal alloys (WTM) were investigated using
first principles electronic structure calculations. The periodic quadrupole
approach was applied to model the structure of dislocation. Alloying
with transition metals was modeled using the virtual crystal approximation and
the applicability of this approach was assessed by calculating the equilibrium
lattice parameter and elastic constants of the tungsten alloys. Reasonable
agreement was obtained with experimental data and with results obtained from
the conventional supercell approach. Increasing the concentration of a
transition metal from the VIIIA group, i.e. the elements in columns headed by
Fe, Co and Ni, leads to reduction of the elastic constant and
increase of elastic anisotropy A=. Alloying W with a group
VIIIA transition metal changes the structure of the dislocation core from
symmetric to asymmetric, similar to results obtained for WRe
alloys in the earlier work of Romaner {\it et al} (Phys. Rev. Lett. 104, 195503
(2010))\comments{\cite{WRECORE}}. In addition to a change in the core symmetry,
the values of the Peierls stress and barrier are reduced. The latter effect
could lead to increased ductility in a tungsten-based
alloy\comments{\cite{WRECORE}}. Our results demonstrate that alloying with any
of the transition metals from the VIIIA group should have similar effect as
alloying with Re.Comment: 12 pages, 8 figures, 3 table
Torpor in dark times : patterns of heterothermy are associated with the lunar cycle in a nocturnal bird
Many studies have shown that endotherms become more heterothermic when the costs of thermoregulation are high and /or when limited energy availability constrains thermoregulatory capacity. However, the roles of many ecological variables, including constraints on foraging opportunities and/ or success, remain largely unknown. To test the prediction that thermoregulatory patterns should be related to foraging opportunities in a heterothermic endotherm, we examined the relationship between the lunar cycle and heterothermy in Freckled Nightjars (Caprimulgus tristigma), which are visually orienting, nocturnal insectivores that are dependent on ambient light to forage. This model system provides an opportunity to assess whether variation in foraging opportunities influences the expression of heterothermy. The nightjars were active and foraged for insects when moonlight was available but become inactive and heterothermic in the absence of moonlight. Lunar illumination was a much stronger predictor of the magnitude of heterothermic responses than was air temperature (Ta). Our data suggest that heterothermy was strongly related to variation in foraging opportunities associated with the lunar cycle, even though food abundance appeared to remain relatively high throughout the study period. Patterns of thermoregulation in this population of Freckled Nightjars provide novel insights into the environmental and ecological determinants of heterothermy, with the lunar cycle, and not Ta, being the strongest predictor of torpor use.The University of Pretoria; the Natural Sciences and Engineering Research Council, Canada; and the
DST/NRF Centre of Excellence at the Percy FitzPatrick
Institute.http://www.uk.sagepub.com/journals/Journal200933ab201
Saartjie Baartman, Nelisiwe Xaba, and me: the politics of looking at South African bodies
Dance Artist/Choreographer Nelisiwe Xaba’s They Look at Me and That Is All They Think (2006) ‘refers to the story of Sara[tjie] Baartman […] the “Hottentot Venus”’ (2006. 9th Jomba! Contemporary dance experience 2006 programme, p. 7) who was taken from her homeland South Africa, and exhibited in Europe in the nineteenth century. After Baartman died in 1815, her remains were displayed in a museum in Paris until 1982. Xaba parallels the story of Baartman to her own experience of performing in Europe as a black South African woman. This article considers how They Look at Me and That Is All They Think exposes the politics surrounding the act of looking at a particular racial and gendered body in both the historical and contemporary context, and how the concept and articulation of the ‘superior’ European subject was dependent on the classification of Baartman, and other black Africans, as exotic others. In my practice-based research project How I Chased a Rainbow And Bruised My Knee (2007), which was a choreographic response to Xaba’s work, I theatricalize my identity as a white South African woman to make visible whiteness, its associated privilege, and how it is dependent on the representation of a particular type of blackness
Immunological crossreactivity between a cloned antigen of Onchocerca volvulus and a component of the retinal pigment epithelium.
Indigenous oyster fisheries persisted for millennia and should inform future management
Historical ecology has revolutionized our understanding of fisheries and cultural landscapes, demonstrating the value of historical data for evaluating the past, present, and future of Earth’s ecosystems. Despite several important studies, Indigenous fisheries generally receive less attention from scholars and managers than the 17th–20th century capitalist commercial fisheries that decimated many keystone species, including oysters. We investigate Indigenous oyster harvest through time in North America and Australia, placing these data in the context of sea level histories and historical catch records. Indigenous oyster fisheries were pervasive across space and through time, persisting for 5000–10,000 years or more. Oysters were likely managed and sometimes “farmed,” and are woven into broader cultural, ritual, and social traditions. Effective stewardship of oyster reefs and other marine fisheries around the world must center Indigenous histories and include Indigenous community members to co-develop more inclusive, just, and successful strategies for restoration, harvest, and management.Results - Indigenous fisheries of abundance. - Oysters in monuments and ritual landscapes. - Not all forgotten: Indigenous use of oysters. Indigenous - Capitalist commercial fisheries and ecological collapse. Discussion Method
Positive reinforcement targeting abstinence in substance misuse (PRAISe): Study protocol for a Cluster RCT & process evaluation of contingency management
There are approximately 256,000 heroin and other opiate users in England of whom 155,000 are in treatment for heroin (or opiate) addiction. The majority of people in treatment receive opiate substitution treatment (OST) (methadone and buprenorphine). However, OST suffers from high attrition and persistent heroin use even whilst in treatment. Contingency management (CM) is a psychological intervention based on the principles of operant conditioning. It is delivered as an adjunct to existing evidence based treatments to amplify patient benefit and involves the systematic application of positive reinforcement (financial or material incentives) to promote behaviours consistent with treatment goals. With an international evidence base for CM, NICE recommended that CM be implemented in UK drug treatment settings alongside OST to target attendance and the reduction of illicit drug use. While there was a growing evidence base for CM, there had been no examination of its delivery in UK NHS addiction services. The PRAISe trial evaluates the feasibility, acceptability, clinical and cost effectiveness of CM in UK addiction services. It is a cluster randomised controlled effectiveness trial of CM (praise and financial incentives) targeted at either abstinence from opiates or attendance at treatment sessions versus no CM among individuals receiving OST. The trial includes an economic evaluation which explores the relative costs and cost effectiveness of the two CM intervention strategies compared to TAU and an embedded process evaluation to identify contextual factors and causal mechanisms associated with variations in outcome. This study will inform UK drug treatment policy and practice.
Trial registration ISRCTN 01591254
A construção da União Europeia no decorrer de seus tratados instituidores
Resumo: Este estudo apresenta o percurso de construção da União Europeia ao longo dos sucessivos Tratados, demonstrando a formação de suas competências e de seu aparato institucional. Também indica de que maneira o constante conflito entre posição supranacionalista, de um lado, e intergovernamentalista, de outro, implicou num processo de integração nem sempre incontroverso, mas contínuo. Será possível verificar, assim, como a União Europeia tem progressivamente ampliado sua esfera de poder e exigido um número cada vez maior atribuições, em razão das contingências oriundas da vida no bloco. De tal constatação, tornar-se-á mais clara a conclusão de que, hoje, a solução de muitos problemas nacionais e europeus já não pode ser pensada sem uma atuação ao menos conjunta da União Europeia, tendo em vista a profundidade dos vínculos entre os Estados-membros e o grande número de ferramentas titularizadas pelo ente supraestata
Conceptualising household food insecurity in Northern Ireland: risk factors, implications for society and the economy, and recommendations for business and policy response
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