67 research outputs found
An individual-based model to explore the impacts of lesser-known social dynamics on wolf populations
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
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
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
Etudes sur le Pommier (I). Compte rendu des travaux effectués de 1940 à 1953
- Autocompatibilité et intercompatibilité par B. Bidabe (p. 249-253)[br/]
- Caractères des variétés par B. Bidabe & R. Arnaud (p. 254-262)[br/]
- Dépérissement du pommier par J. Grente (p. 263-270
Tomorebuild : a new data reduction software package for scanning transmission ion microscopy tomography
A new data reduction software package has been developed at CENBG for scanning transmission ion microscopy tomography (STIM-T) data. This program, TomoRebuild, has been designed in Visual C++® in the Windows® environment. Fortran 77® routines from the Donner Library were translated to C++ for the reconstruction of 2D and 3D data using the filtered backprojection algorithm. Tomography images are stored as ASCII files to be displayed using a graphic interface. A graphic software based on the AMIRA® environment was developed to extract and display 3D structures according to their density. The whole program was designed to be interactive, simple to use and easily adjustable to different experimental conditions. 3D STIM-T was carried out on microcomposite materials, allowing determination of the density of a thin AlN layer deposited on a SiC microfibre
A new data reduction software package for scanning transmission ion microscopy tomography
A new data reduction software package has been developed at CENBG for scanning transmission ion microscopy tomography (STIM-T) data. This program, TomoRebuild, has been designed in Visual C++® in the Windows® environment. Fortran 77® routines from the Donner Library were translated to C++ for the reconstruction of 2D and 3D data using the filtered backprojection algorithm. Tomography images are stored as ASCII files to be displayed using a graphic interface. A graphic software based on the AMIRA® environment was developed to extract and display 3D structures according to their density. The whole program was designed to be interactive, simple to use and easily adjustable to different experimental conditions. 3D STIM-T was carried out on microcomposite materials, allowing determination of the density of a thin AlN layer deposited on a SiC microfibre
Development of Metal-Ceramic-Lubricant Composite Coatings Obtained by Cold Spray for Tribological Applications in the Automotive Industry
International audienceOne of the main levers to reduce CO2 emissions in cars and trucks is mass and friction reduction, which is often achieved through the use of special coatings. The aim of the present work was to develop metal-ceramic-lubricant composite coatings with the best combination of wear, seizure, fatigue, and thermal resistance. Metal-based coatings incorporating hard particles and solid lubricants were cold sprayed onto steel substrates and the relationship between coating microstructure and tribology was studied. To meet the demanding tribological requirements of heavily loaded engines, the interfaces between the different components were optimized by selecting appropriate feedstock powders and assessing a wide range of process parameters. Alumina-reinforced bronze composite coatings were made from powders with different morphologies. Aggregated ceramic powders were found to be more beneficial in terms of wear than massive powders, and graphite was found to be effective for reducing seizure
Growth and ultrastructural modifications to chestnut calli induced by culture filtrates of virulent and hypovirulent Cryphonectria parasitica strains
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