Structure des fragments de fission de masse A = 100 - 110 : mesures de temps de vie et analyses en champ moyen et au-delà

Neutron-rich nuclei of mass A=100-110 are of great interest for the study of nuclear structure far from stability. Previous experimental and theoretical studies suggest a complex evolution of deformation and collectivity in the isotopic chains of Zr, Mo, Ru and Pd.In order to extend information on the evolution of the collectivity towards higher spin states and more neutron-rich nuclei, lifetimes of excited states were measured in nuclei produced through a fusion-fission reaction in inverse kinematic at GANIL. Fission fragments were separated and identified in both A and Z with the high acceptance magnetic spectrometer VAMOS while the EXOGAM germanium detectors array was used for the coincident gamma-ray detection. Lifetimes of about twenty excited states were extracted using the plunger device of Cologne. This is the first RDDS measurement on fission fragments which are identified in A and Z on an event-by-event basis. The study of this mass region is completed by theoretical calculations using self consistent mean field and beyond mean field methods implemented with the Gogny force (D1S). The structure of the ground states and the excited states is described with Hartree-Fock-Bogoliubov calculations with constraints placed on the axial and triaxial deformations. Individual excitations are investigated through blocking calculations and the high spin states are studied through cranking calculations. Finally, an approximated generator coordinate method (GCM+GOA) using the 5DCH hamiltonian is used to describe the low energy collective states and to interpret the experimental evolution of the collectivity.Les noyaux riches en neutrons de masse A=100-110 constituent une région de grand intérêt pour l'étude de la structure nucléaire loin de la stabilité. De précédentes études de cette région de masse ont déjà révélé la complexité de l'évolution de la collectivité et de la déformation dans les chaînes isotopiques de Zr, Mo, Ru et Pd. Afin d'étendre les données expérimentales sur la collectivité à des états de plus haut spin et à des noyaux plus riches en neutrons, des temps de vie d'états excités ont été mesurés dans des noyaux produits par une réaction de fusion-fission en cinématique inverse au GANIL. Les fragments de fission étaient séparés et identifiés en A et Z grâce au spectromètre magnétique de grande acceptance VAMOS tandis que le rayonnement gamma était détecté dans l'ensemble de détecteurs germanium EXOGAM. Environ vingt temps de vie d'états 2+, 4+ et 6+ ont été extraits à l'aide du plunger de Cologne. Cette expérience représente la première mesure RDDS dans des fragments de fission identifiés évènement par évènement à la fois en A et Z.Cette étude des noyaux de masse A=100-110 est complétée par des calculs auto-cohérents de champ moyen et au-delà avec la force de Gogny (D1S). La structure des états fondamentaux et excités est décrite dans le cadre du modèle de Hartree-Fock-Bogoliubov avec des contraintes sur les déformations axiale et triaxiale. Les excitations individuelles sont étudiées par des calculs bloqués et les états de haut spin sont décrits dans l'approximation du champ tournant. Enfin, la méthode de la coordonnée génératrice approchée par un hamiltonien collectif en cinq dimensions (5DCH) est appliquée aux états collectifs de basse énergie. Les résultats sont comparés aux mesures de la collectivité

La trufficulture, un or noir pour la région méditerranéenne

Après le déclin de la trufficulture française, depuis le début du siècle, l'I.N.R.A. a consenti un effort pour améliorer la connaissance de la biologie et de l'écologie de la truffe. Un renouveau de cette culture est maintenant sérieusement envisagé

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

Fission in inverse kinematics

Fission is a unique tool to study nuclear properties. The SOFIA Collaboration takes advantage of the inverse kinematics technique to measure fission yields for a large range of systems, including exotic nuclei. Both fragments are fully identified in charge and mass, a unique feature. The use of Coulomb interaction as fission trigger results in a low excitation energy in the fissioning system, allowing to study the influence of nuclear structure on fission. Using samples of SOFIA results, this paper addresses some open questions about fission such as the evolution of elemental yields with mass and the transition between asymmetric and symmetric fission

Phosphorylation of phosducin-like protein BDM-1 by protein kinase 2 (CK2) is required for virulence and Gβ subunit stability in the fungal plant pathogen Cryphonectria parasitica

Phosducin-like proteins are conserved regulatory components of G-protein signalling pathways, which mediate many physiological processes. Identified throughout eukaryotic genomes, they are thought to serve as regulators of Gβγ assembly. Cryphonectria parasitica, a plant pathogen and causative agent of chestnut blight, contains three Gα, one Gβ, one Gγ subunits and phosducin-like protein BDM-1 that have important roles in pigmentation, sporulation and virulence. Deletion of either Gβ subunit or BDM-1 produces identical phenotypes. Additionally, we report that the Gβ subunit is not detectable in absence of BDM-1. Given that the regulatory role of phosducin-like proteins may be influenced by protein kinase 2 (CK2), we confirmed that BDM-1 is a phosphoprotein that can be targeted by CK2 in vitro. Mutagenesis of the five putative CK2 sites revealed that native phosphorylation likely occurs at two locations. Strains bearing a single or double serine to alanine substitutions at those sites were significantly less virulent with only minor phenotypic changes from vegetative colonies. Therefore, CK2 activity appears to mediate key signals that are required for virulence, but not for vegetative growth. Expression of selected CK2 mutants resulted in reduced accumulation of the Gβ subunit, suggesting that phosphorylation of BDM-1 influences Gβ stability

A horizontal ice core from Taylor Glacier, its implications for Antarctic climate history, and an improved Taylor Dome ice core time scale

Ice core records from Antarctica show mostly synchronous temperature variations during the last deglacial transition, an indication that the climate of the entire continent reacted as one unit to the global changes. However, a record from the Taylor Dome ice core in the Ross Sea sector of East Antarctica has been suggested to show a rapid warming, similar in style and synchronous with the Oldest Dryas—Bølling warming in Greenland. Since publication of the Taylor Dome record, a number of lines of evidence have suggested that this interpretation is incorrect and reflects errors in the underlying time scale. The issues raised regarding the dating of Taylor Dome currently linger unresolved, and the original time scale remains the de facto chronology. We present new water isotope and chemistry data from nearby Taylor Glacier to resolve the confusion surrounding the Taylor Dome time scale. We find that the Taylor Glacier record is incompatible with the original interpretation of the Taylor Dome ice core, showing that the warming in the area was gradual and started at ∼18 ka BP (before 1950) as seen in other East Antarctic ice cores. We build a consistent, up‐to‐date Taylor Dome chronology from 0 to 60 ka BP by combining new and old age markers based on synchronization to other ice core records. The most notable feature of the new TD2015 time scale is a gas age—ice age difference of up to 12,000 years during the Last Glacial Maximum, by far the largest ever observed

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