558 research outputs found

    Detection

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    This review on second- and third-generation multidetectors devoted to heavy-ion collisions aims to cover the last twenty years. The presented list of devices is not exhaustive but regroups most of the techniques used during this period for nuclear reactions at intermediate energy (≈ 10A MeV to 1A GeV), both for charged-particle and neutron detection. The main part will be devoted to 4π multidetectors, projectile decay fragmentation, high-resolution magnetic spectrometers, auxiliary detectors and neutron detection. The last part will present the progress in electronics and detection in view of the construction of future-generation detectors

    Exclusive Studies of Charged-Particle Emission in 1-H and 3-He-Induced Reactions on Heavy Nuclei

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    This research was sponsored by the National Science Foundation Grant NSF PHY-931478

    Emissioin of Intermediate Mass Fragments During Fission

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    This research was sponsored by the National Science Foundation Grant NSF PHY-931478

    IMF Emission in the 14-N + nat-Ag, Au Reactions at E/A = 60-100 MeV

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    This research was sponsored by the National Science Foundation Grant NSF PHY-931478

    Root dentinal microcracks: a post-extraction experimental phenomenon?

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    Aim To investigate the prevalence, location and pattern of pre‐existing microcracks in non‐endodontically treated teeth from fresh cadavers. Micro‐computed tomography (micro‐CT) technology was used as the analytical tool enabling full screening of the root dentine with the teeth retained in their original alveolar socket. Methodology As a pilot study and to validate the present method, a series of 4 high‐resolution scans were performed on one bone‐block specimen with teeth collected post‐mortem: (i) entire bone‐block including the teeth, (ii) second molar tooth extracted atraumatically from the bone‐block, (iii) extracted tooth dehydrated to induce dentinal defects and (iv) entire bone‐block following reinsertion of the extracted tooth into its matching alveolar socket. In the main study, forty‐two dentoalveolar maxillary and mandibular bone‐blocks each containing 3–5 adjacent teeth (a total of 178 teeth) were collected post‐mortem and scanned in a micro‐CT device. All cross‐section images of the 178 teeth (n = 65 530) were screened from the cementoenamel junction to the apex to identify the presence of dentinal defects. Results In the pilot study, the microcracks observable when the dehydrated tooth was outside the bone‐block remained detectable when the entire bone‐block plus reinserted tooth was scanned. This means that the screening process revealed the presence of the same microcracks in both experimental situations (the tooth outside and inside the maxillary bone‐block). From a total of 178 teeth in the bone‐blocks removed from cadavers, 65 530 cross‐sectional images were analysed and no dentinal microcracks were detected. Conclusions This in situ cadaveric model revealed the lack of pre‐existing dentinal microcracks in non‐endodontically treated teeth. Thus, the finding of dentinal microcracks observed in previous cross‐sectional images of stored extracted teeth is unsound and not valid. It should be assumed that microcracks observed in stored extracted teeth subjected to root canal procedures are a result of the extraction process and/or the post‐extraction storage conditions. Therefore, as a consequence, the presence of such dentinal microcracks in stored extracted teeth – observable in cross‐sectional images of the roots – should be referred to as experimental dentinal microcracks

    Fragment Isospin as a Probe of Heavy-Ion Collisions

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    Isotope ratios of fragments produced at mid-rapidity in peripheral and central collisions of 114Cd ions with 92Mo and 98Mo target nuclei at E/A = 50 MeV are compared. Neutron-rich isotopes are preferentially produced in central collisions as compared to peripheral collisions. The influence of the size (A), density, N/Z, E*/A, and Eflow/A of the emitting source on the measured isotope ratios was explored by comparison with a statistical model (SMM). The mid-rapidity region associated with peripheral collisions does not appear to be neutron-enriched relative to central collisions.Comment: 12 pages including figure

    Fragment Production in Non-central Collisions of Intermediate Energy Heavy Ions

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    The defining characteristics of fragment emission resulting from the non-central collision of 114Cd ions with 92Mo target nuclei at E/A = 50 MeV are presented. Charge correlations and average relative velocities for mid-velocity fragment emission exhibit significant differences when compared to standard statistical decay. These differences associated with similar velocity dissipation are indicative of the influence of the entrance channel dynamics on the fragment production process

    Excitation and decay of projectile-like fragments formed in dissipative peripheral collisions at intermediate energies

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    Projectile-like fragments (PLF:15<=Z<=46) formed in peripheral and mid-peripheral collisions of 114Cd projectiles with 92Mo nuclei at E/A=50 MeV have been detected at very forward angles, 2.1 deg.<=theta_lab<=4.2 deg. Calorimetric analysis of the charged particles observed in coincidence with the PLF reveals that the excitation of the primary PLF is strongly related to its velocity damping. Furthermore, for a given V_PLF*, its excitation is not related to its size, Z_PLF*. For the largest velocity damping, the excitation energy attained is large, approximately commensurate with a system at the limiting temperatureComment: 5 pages, 6 figure

    Local singlets, frustration, and unconventional superconductivity in the organic charge-transfer solids

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    We suggest that superconductivity (SC) in the organic charge transfer solids (CTS) is reached from a Bond-Charge Density Wave (BCDW). We discuss an effective model for the BCDW to SC transition, an attractive U extended Hubbard Hamiltonian with repulsive nearest neighbor interaction V. We discuss experimental consequences of the theory for different classes of CTS superconductors as well as related inorganic materials.Comment: 4 pages, 2 figures, ECRYS 200
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