2,312 research outputs found

    The Influence of Recreational Activity on Upland Ecosystems in the UK: A Review of Evidence

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    The uplands are an important destination for people wishing to experience the outdoors. These areas are also of great importance for biodiversity, landscape and understanding the effects of recreational activity in upland areas is important to ensuring that their use is environmentally sustainable. This work was commissioned so that the findings could be used by all those with an interest in or responsibility for, upland areas and to help make informed decisions about a range of activities and how they relate to the upland environment. Natural England commission a range of reports from external contractors to provide evidence and advice to assist us in delivering our duties. The views in this report are those of the authors and do not necessarily represent those of Natural England

    Non-Volatile Memory Characteristics of Submicrometre Hall Structures Fabricated in Epitaxial Ferromagnetic MnAl Films on GaAs

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    Hall-effect structures with submicrometre linewidths (<0.3pm) have been fabricated in ferromagnetic thin films of Mn[sub 0.60]Al[sub 0.40] which are epitaxially grown on a GaAs substrate. The MnAl thin films exhibit a perpendicular remanent magnetisation and an extraordinary Hall effect with square hysteretic behaviour. The presence of two distinct stable readout states demonstrates the potential of using ultrasmall ferromagnetic volumes for electrically addressable, nonvolatile storage of digital information

    The extraordinary Hall effect in coherent epitaxial tau (Mn,Ni)Al thin films on GaAs

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    Ultrathin coherent epitaxial films of ferromagnetic tau(Mn,Ni)0.60Al0.40 have been grown by molecular beam epitaxy on GaAs substrates. X-ray scattering and cross-sectional transmission electron microscopy measurements confirm that the c axis of the tetragonal tau unit cell is aligned normal to the (001) GaAs substrate. Measurements of the extraordinary Hall effect (EHE) show that the films are perpendicularly magnetized, exhibiting EHE resistivities saturating in the range of 3.3-7.1 muOMEGA-cm at room temperature. These values of EHE resistivity correspond to signals as large as +7 and -7 mV for the two magnetic states of the film with a measurement current of 1 mA. Switching between the two magnetic states is found to occur at distinct field values that depend on the previously applied maximum field. These observations suggest that the films are magnetically uniform. As such, tau(Mn,Ni)Al films may be an excellent medium for high-density storage of binary information

    DWYL? YOLO

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    Molting, Staging, and Wintering Locations of Common Eiders Breeding in the Gyrfalcon Archipelago, Ungava Bay

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    The northern common eider (Somateria mollissima borealis) has become a source of concern because of recent declines and possible overharvest. Birds that breed in the Canadian mid-Arctic winter in both Greenland and Canada, but the wintering grounds of birds that breed farther south are unknown. Our objectives were thus to identify the molting and wintering areas of birds breeding in Ungava Bay and to compare their home-range sizes during the pre-molt, molt, post-molt, and winter periods. Using satellite telemetry, we determined that common eiders breeding in the lower Arctic winter in Greenland (67%) and Canada (33%). These proportions are consistent with the split established for common eiders that breed farther north. Females spent their pre-molt period close to their breeding islands and had the smallest home ranges during the molt period. Winter home ranges were larger in Canada than in Greenland, probably because they contained more ice. Once settled, birds wintered in a relatively small area and did not undertake long movements. Distance between molt and winter sites ranged between 1054 and 2173 km. Duration of migration to or from wintering areas varied among individuals from rapid movement in a few days to slow progress over a month. Fall migration occurred in late October or early November, and spring migration, in early to mid-May. This study highlights the importance of Ungava Bay for northern common eiders and the need for international collaboration to ensure sustainable use of the resource.L’eider Ă  duvet du nord (Somateria mollissima borealis) reprĂ©sente une source de prĂ©occupation en raison de dĂ©clins rĂ©cents et de rĂ©coltes susceptibles d’ĂȘtre excessives. Les oiseaux nichant dans la zone arctique moyenne canadienne hivernent au Groenland et au Canada, mais l’aire d’hivernage des oiseaux nichant plus au sud n’est pas connue. Nos objectifs consistaient donc Ă  identifier les aires de mue et d’hivernage des oiseaux nichant dans la baie d’Ungava et de comparer leur aire d’activitĂ© lors des pĂ©riodes de prĂ©-mue, de mue, d’aprĂšs-mue et d’hiver. Au moyen de la tĂ©lĂ©mĂ©trie satellitaire, nous avons dĂ©terminĂ© que l’eider Ă  duvet nichant dans la zone arctique infĂ©rieure hiverne au Groenland (67 %) et au Canada (33 %). Ces proportions sont similaires Ă  celles trouvĂ©es dans les colonies d’eider Ă  duvet plus nordiques. Les femelles passent la pĂ©riode de la prĂ©-mue prĂšs de leurs Ăźles de nidification et sont les plus restreintes en termes d’aire utilisĂ©e lors de la pĂ©riode de mue. Les aires d’activitĂ© hivernale Ă©taient plus grandes au Canada qu’au Groenland, probablement en raison de la plus grande prĂ©sence de glaces au Canada. Une fois sur leur site d’hivernage, les oiseaux Ă©voluaient dans une aire relativement petite et n’entreprenaient pas de longs dĂ©placements. La distance entre les sites de mue et d’hivernage variait entre 1 054 et 2 173 kilomĂštres. La durĂ©e de la migration variait d’un individu Ă  l’autre, allant de dĂ©placements rapides sur quelques jours Ă  des dĂ©placements plus lents sur prĂšs d’un mois. La migration automnale a dĂ©butĂ© Ă  la fin octobre, dĂ©but novembre et celle du printemps vers le dĂ©but et la mi-mai. Cette Ă©tude met en Ă©vidence la grande importance de la baie d’Ungava pour l’eider Ă  duvet du nord de mĂȘme que le besoin de collaboration internationale pour assurer l’utilisation soutenue de cette ressource

    Optimal discrete stopping times for reliability growth tests

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    Often, the duration of a reliability growth development test is specified in advance and the decision to terminate or continue testing is conducted at discrete time intervals. These features are normally not captured by reliability growth models. This paper adapts a standard reliability growth model to determine the optimal time for which to plan to terminate testing. The underlying stochastic process is developed from an Order Statistic argument with Bayesian inference used to estimate the number of faults within the design and classical inference procedures used to assess the rate of fault detection. Inference procedures within this framework are explored where it is shown the Maximum Likelihood Estimators possess a small bias and converges to the Minimum Variance Unbiased Estimator after few tests for designs with moderate number of faults. It is shown that the Likelihood function can be bimodal when there is conflict between the observed rate of fault detection and the prior distribution describing the number of faults in the design. An illustrative example is provided

    Miniaturized data loggers and computer programming improve seabird risk and damage assessments for marine oil spills in Atlantic Canada

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    Obtaining useful information on marine birds that can aid in oil spill (and other hydrocarbon release) risk and damage assessments in offshore environments is challenging. Technological innovations in miniaturization have allowed archival data loggers to be deployed successfully on marine birds vulnerable to hydrocarbons on water. A number of species, including murres (both Common, Uria aalge, and Thick-billed, U. lomvia) have been tracked using geolocation devices in eastern Canada, increasing our knowledge of the seasonality and colony-specific nature of their susceptibility to oil on water in offshore hydrocarbon production areas and major shipping lanes. Archival data tags are starting to resolve questions around behaviour of vulnerable seabirds at small spatial scales relevant to oil spill impact modelling, specifically to determine the duration and frequency at which birds fly at sea. Advances in data capture methods using voice activated software have eased the burden on seabird observers who are collecting increasingly more detailed information on seabirds during ship-board and aerial transects. Computer programs that integrate seabird density and bird behaviour have been constructed, all with a goal of creating more credible seabird oil spill risk and damage assessments. In this paper, we discuss how each of these technological and computing innovations can help define critical inputs into seabird risk and damage assessments, and when combined, can provide a more realistic understanding of the impacts to seabirds from any hydrocarbon release

    The oxidative costs of territory quality and offspring provisioning

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    The costs of reproduction are an important constraint that shapes the evolution of life histories, yet our understanding of the proximate mechanism(s) leading to such life-history trade-offs is not well understood. Oxidative stress is a strong candidate measure thought to mediate the costs of reproduction, yet empirical evidence supporting that increased reproductive investment leads to oxidative stress is equivocal. We investigated whether territory quality and offspring provisioning increase oxidative stress in male snow buntings (Plectrophenax nivalis) using a repeated sampling design. We show that arrival oxidative stress is not a constraint on territory quality or the number of offspring fledged. Nevertheless, owners of higher-quality territories experienced an oxidative cost, with this cost increasing more rapidly in younger males. Males that provisioned offspring at a high rate also experienced increased oxidative stress. Together, these findings support the potential role of oxidative stress in mediating life-history trade-offs. Future work should consider that reproductive workload is not limited to offspring care, and other activities - including territory defence - may contribute significantly to the costs of reproduction. © 2013 European Society For Evolutionary Biology
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