1,026 research outputs found

    Dynamics of Multifragmentation in Heavy Ion Collisions

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    We review multifragmentation data obtained at the SIS/GSI accelerator using heavy ion beams with (0.1-1)A GeV together with the ALADIN and FOPI experimental setups.Comment: 25 pages, with 38 included figures; invited talk at the Nishinomiya-Yukawa Symposium on Frontiers of Nuclear Collision Dynamics, Japan (nov.18-19); to be published in Progress of Theoretical Physic

    Transverse flow of nuclear matter in collisions of heavy nuclei at intermediate energies

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    The Quantum Molecular Dynamics Model (IQMD) is used to investigate the origin of the collective transverse velocity observed in heavy ion experiments. We find that there are three contributions to this effect: initial-final state correlations, potential interactions and collisions. For a given nuclear equation of state (eos) the increase of the transverse velocity with increasing beam energy is caused by the potential part. For a given beam energy the collective transverse velocity is independent of the nuclear eos but the relative contributions of potential and collisions differ. In view of the importance of the potential interactions between the nucleons it is not evident that the similarity of the radial velocities measured for fragments at beam energies below 1 AGeV and that for mesons at beam energies above 2 AGeV is more than accidental.Comment: 5 pages, 5 figures, revtex, OASIS ref PLB1700

    Stratigraphy, bathymetry and synsedimentary tectonics of the Early Jurassic of NW Switzerland

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    The Early Jurassic full-marine sediments in NW Switzerland accumulated in the slowly subsiding area between the southwestern part of the Swabian Basin and the eastern Paris Basin. These deposits are dominated by fine-grained siliciclastics, but calcarenitic and phosphorite-rich strata are intercalated. Unlike in the adjacent regions of SW Germany and E France, they are arranged in a quite complex stratigraphic architecture characterised by rather abrupt facies changes, erosive truncations and gaps. Despite many common features in NW Switzerland, the sediments are considerably different with deposits of a similar age in SW Germany and E France that the definition of regional lithostratigraphic units is justified constituting the “Staffelegg Formation”. The Staffelegg Formation comprises 11 members and 9 beds. Several of these beds represent distinct correlation horizons. Some of them correspond to strata or erosional unconformities encountered in the Swabian realm, some of them can be correlated with strata in the Paris Basin. The thickness of the Early Jurassic strata varies between 25 and 70 m. In the eastern and central parts of NW Switzerland, sediments Sinemurian in age constitute about 90% of the thickness. To the West, however, in the Mont Terri area, Pliensbachian and Toarcian deposits form 70% of the thickness. The accommodation space of the Early Jurassic strata was controlled mainly by eustatic sea-level changes. While eustatic sea-level rise was low, isopach maps having a chronostratigraphic resolution of one sub-stage provide clear evidence of differential subsidence as pre-existing faults in the basement that formed during the late Palaeozoic became reactivated. Orientation of relative thickness anomalies follow the fault trends either those of the Rhenish Lineament or those of the North Swiss Permocarboniferous Trough. Isopach anomalies are superimposed on a general trend of decreasing thickness to the South. Their small areal extension suggests that strike-slip movements occurred locally with a mosaic of basement blocks. Reactivation of faults in the basement during the Early Jurassic is also evidenced by temporally enhanced hydrothermal activity as documented by chronometric age of veins and mineral alterations

    Modelling incomplete fusion dynamics of weakly-bound nuclei at near-barrier energies

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    The classical dynamical model for reactions induced by weakly-bound nuclei at near-barrier energies is developed further. It allows a quantitative study of the role and importance of incomplete fusion dynamics in asymptotic observables, such as the population of high-spin states in reaction products as well as the angular distribution of direct alpha-production. Model calculations indicate that incomplete fusion is an effective mechanism for populating high-spin states, and its contribution to the direct alpha production yield diminishes with decreasing energy towards the Coulomb barrier. It also becomes notably separated in angles from the contribution of no-capture breakup events. This should facilitate the experimental disentanglement of these competing reaction processes.Comment: 12 pages, 7 figures (for better resolution figures please contact the author), Accepted in Journal of Physics

    Medium mass fragments production due to momentum dependent interactions

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    The role of system size and momentum dependent effects are analyzed in multifragmenation by simulating symmetric reactions of Ca+Ca, Ni+Ni, Nb+Nb, Xe+Xe, Er+Er, Au+Au, and U+U at incident energies between 50 MeV/nucleon and 1000 MeV/nucleon and over full impact parameter zones. Our detailed study reveals that there exist a system size dependence when reaction is simulated with momentum dependent interactions. This dependence exhibits a mass power law behavior.Comment: 5 figure

    Digital Inclusion as a Core Component of Social Inclusion

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    There is a large body of research that has examined digital inequities, inequalities, and divides—i.e., those countries, communities, and individuals digitally left behind or disadvantaged. Whereas we know quite a lot about what is lacking and for whom, there is less focus on what works to alleviate these inequalities and divides in a variety of cultural contexts. This thematic issue brings together scholarship on digital inclusion initiatives and research from over 20 countries and in the context of numerous aspects, including different types of initiatives as well as different types of target audiences for these initiatives. Each article provides unique insights into what does and does not work in various communities, making recommendations on what could be done to improve the examined initiatives. We hope that the breadth and depth of articles presented here will be useful not just for academic audiences seeking to broaden their understanding of digital inclusion and ‘what can be done’ rather than focusing on ‘what is amiss,’ but also for policymakers and digital inclusion initiatives who are eager to expand and advance their digital inclusion work within their communities

    Re-evaluating Moodie's Opisthotonic-Posture Hypothesis in Fossil Vertebrates Part I: Reptiles—the taphonomy of the bipedal dinosaurs Compsognathus longipes and Juravenator starki from the Solnhofen Archipelago (Jurassic, Germany)

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    More or less complete and articulated skeletons of fossil air-breathing vertebrates with a long neck and tail often exhibit a body posture in which the head and neck are recurved over the back of the animal. Additionally, the tail is typically drawn over the body, while the limbs have a rigid appearance. In palaeontological literature, this "opisthotonic posture” of such fossils still requires a causal interpretation in an etiological context. According to this hypothesis, there is a presumption of a cerebral disorder generating perimortem muscle spasms that are preserved by rapid burial or other sequestration of a skeleton in the fossil record. We re-evaluate this "opisthotonic posture hypothesis” by analysing the non-avian theropods Compsognathus longipes and Juravenator starki from the famous South Franconian plattenkalks of the Upper Jurassic Solnhofen Archipelago. Decay experiments with the extant domestic fowl Gallus gallus L. and analysis of the theropods' constructional morphological constraints reveal that the opisthotonic posture is not a peri- but a postmortem phenomenon. By analysing the timeline of decomposition, it is possible to recognise different stages of decay, depending on the varying decay resistance of soft tissues. Adipocere formation must have blocked further decay until embedding was completed by minimal sedimentation. Analyses of the palaeoenvironment of the basins of the Solnhofen Archipelago show that the conditions of deposition of individual basins cannot be considered to be similar, even inside the same time frame. Therefore, a generalised approach of looking at the depositional setting must be excluded. Assumptions by Faux and Padian (2007) that the accepted palaeoenvironmental reconstruction of the Solnhofen FossillagerstĂ€tte has to be questioned in the light of the opisthotonic posture hypothesis enforce the need for a review of palaeoecological factors of the Franconian Plattenkalks from a taphonomic perspectiv
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