36 research outputs found

    An individual-based model to explore the impacts of lesser-known social dynamics on wolf populations

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    The occurrence of wolf populations in human-dominated landscapes is challenging worldwide because of conflicts with human activities. Modeling is an important tool to project wolf dynamics and expansion, and help in decision making concerning management and conservation. However, some individual behaviors and pack dynamics of the wolf life cycle are still unclear to ecologists. Here we present an individual-based model (IBM) to project wolf populations while exploring the lesser-known processes of the wolf life cycle. IBMs are bottom-up models that simulate the fate of individuals interacting with each other, with population-level properties emerging from the individual-level simulations. IBMs are particularly adapted to represent social species such as the wolf that exhibits complex individual interactions. Our IBM projects wolf demography including fine-scale individual behavior and pack dynamics based on up-to-date scientific literature. We explore four processes of the wolf life cycle whose consequences on population dynamics are still poorly understood: the pack dissolution following the loss of a breeder, the adoption of young dispersers by packs, the establishment of new packs through budding, and the different breeder replacement strategies. While running different versions of the IBM to explore these processes, we also illustrate the modularity and flexibility of our model, an asset to model wolf populations experiencing different ecological and demographic conditions. The different parameterization of pack dissolution, territory establishment by budding, and breeder replacement processes influence the projections of wolf populations. As such, these processes require further field investigation to be better understood. The adoption process has a lesser impact on model projections. Being coded in R to facilitate its understanding, we expect that our model will be used and further adapted by ecologists for their own specific applications

    Shape evolution in the neutron-rich osmium isotopes:Prompt γ-ray spectroscopy of Os 196

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    The shape transition in the neutron-rich Os isotopes is studied by investigating the neutron-rich 196Os nucleus through in-beam γ-ray spectroscopy using a two-proton transfer reaction from a 198Pt target to a 82Se beam. The beam-like recoils were detected and identified with the large-acceptance magnetic spectrometer PRISMA, and the coincident γ rays were measured with the advanced gamma tracking array (AGATA) demonstrator. The de-excitation of the low-lying levels of the yrast-band of 196Os were identified for the first time. The results are compared with state-of-the-art beyond-mean-field calculations, performed for the even-even 188-198Os isotopes. The new results suggest a smooth transition in the Os isotopes from a more axial rotational behavior towards predominately vibrational nuclei through triaxial configurations. An almost perfect γ-unstable/triaxial rotor yrast band is predicted for 196Os which is in agreement with the experimentally measured excited state

    Nuclear Fission: : A Review of Experimental Advances and Phenomenology

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    In the last two decades, through technological, experimental and theoretical advances, the situation in experimental fission studies has changed dramatically. With the use of advanced production and detection techniques both much more detailed and precise information can now be obtained for the traditional regions of fission research and, crucially, new regions of nuclei have become routinely accessible for fission studies.
 This work first of all reviews the recent developments in experimental fission techniques, in particular the resurgence of transfer-induced fission reactions with light and heavy ions, the emerging use of inverse-kinematic approaches, both at Coulomb and relativistic energies, and of fission studies with radioactive beams.
 The emphasis on the fission-fragment mass and charge distributions will be made in this work, though some of the other fission observables, such as prompt neutron and γ-ray emission will also be reviewed.
 A particular attention will be given to the low-energy fission in the so far scarcely explored nuclei in the very neutron-deficient lead region. They recently became the focus for several complementary experimental studies, such as β-delayed fission with radioactive beams at ISOLDE(CERN), Coulex-induced fission of relativistic secondary beams at FRS(GSI), and several prompt fusion-fission studies. The synergy of these approaches allows a unique insight in the new region of asymmetric fission around <sup>180</sup>Hg, recently discovered at ISOLDE. Recent extensive theoretical efforts in this region will also be outlined.
 The unprecedented high-quality data for fission fragments, completely identified in <i>Z</i> and <i>A</i>, by means of reactions in inverse kinematics at FRS(GSI) and VAMOS(GANIL) will be also reviewed. These experiments explored an extended range of mercury-to-californium elements, spanning from the neutron-deficient to neutron-rich nuclides, and covering both asymmetric, symmetric and transitional fission regions.
 Some aspects of heavy-ion induced fusion-fission and quasifission reactions will be also discussed, which reveal their dynamical features, such as the fission time scale. The crucial role of the multi-chance fission, probed by means of multinucleon-transfer induced fission reactions, will be highlighted.
 The review will conclude with the discussion of the new experimental fission facilities which are presently being brought into operation, along with promising 'next-generation' fission approaches, which might become available within the next decade

    Understanding attitudes towards native wildlife and biodiversity in the UK: the role of zoos

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    The present paper draws from a study of the role of zoos in forming attitudes towards biodiversity and native wild carnivores that are considered for reintroduction. The project is being developed by an interdisciplinary team (wildlife conservation, psychology, education) working towards the development of a questionnaire to investigate this topic in the UK. Research suggests that experiences with live animals in zoos may encourage empathy, through personal connection, which in turn facilitates greater concern towards biodiversity. Concomitantly, the reintroduction of wild carnivores to their native habitats may contribute to biodiversity by helping regulate ecosystem dynamics. Carnivores also carry a rich cultural and historical heritage. IUCN guidelines state the need for public support to establish a reintroduced population in the wild, therefore, carnivore restoration efforts benefit from the understanding of the human dimensions. A pilot study was carried out in Kent (spring 2015) using focus groups and interviews to investigate attitudes towards biodiversity, with particular focus on two species of carnivores native to the British Isles and currently considered for reintroduction (the European lynx Lynx lynx and the pine marten Martes martes) and the role of zoos in promoting support towards biodiversity conservation. Results suggest an association between seeing native wild carnivore species in the zoo and emotional responses such as ‘breaking down fears’, but also concerns about a disconnect between people and nature, and misunderstanding about the role of zoos in ‘protecting’ species. Below we offer a discussion of the themes that emerged from the analysis of focus groups and interviews in relation to biodiversity

    Lifetimes of excited states in triaxially deformed

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    Lifetimes of excited states in 107Tc, 109Rh, 111Rh, and 113Rh were measured at GANIL using the Recoil-Distance Doppler Shift method. The neutron-rich nuclei were produced in fission reactions in inverse kinematics with a 238U beam impinging on a 9Be target. Fission fragments were identified event-by-event in the ray-tracing spectrometer VAMOS++ and correlated with prompt γ\gamma rays observed around the target position with the EXOGAM Ge detector array. Several lifetimes were obtained for states in the positive-parity yrast bands in the four nuclei and compared to triaxial particle-rotor calculations. The results clarify the configuration for the strongest positive-parity band in 107Tc and suggest a gradual increase of triaxial deformation with atomic number Z, reaching almost maximum triaxiality for the neutron-rich Rh nuclei

    Lifetime measurments of excited states in neutron-rich fission fragments

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    Expérience GANIL/VAMOS/EXOGAMInternational audienceLifetimes of short-lived excited states in a wide range of neutron-richfission fragments were measured using the recoil distance Doppler shift(RDDS) technique, which was applied to fusion-fission reactions in inversekinematics for the first time. The fission fragments were identified eventby-event in mass, charge, and atomic number using the VAMOS magneticspectrometer at GANIL. Gamma rays originating from the fission fragmentswere measured with the EXOGAM array of Ge Clover detectors aroundthe target position. Using a degrader, the change in the Doppler shiftof the γ\gamma ray allows the application of the RDDS method. Details of theexperimental technique will be discussed and the status for the ongoinganalysis for odd-mass yttrium isotopes will be presented
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