1,721,049 research outputs found
Research and technological development of beta-emitting radiopharmaceuticals produced with radioactive ion beams
No full textAn innovative method is proposed for the production of carrier-free - radiopharmaceuticals, based on the Isotope Separation On-Line (ISOL) technique in the framework of the SPES (Selective Production of the Exotic Species) project. SPES is a nuclear physics project under advanced construction at Legnaro National Laboratories of INFN (Istituto Nazionale di Fisica Nucleare).
The innovation of the method relies not only on the new physical technique but mainly on the final product. The class of radiopharmaceutical obtainable, indeed, can be considered completely new, since they have a high purity in terms of specific activity (5 orders of magnitude bigger than traditional ones); specific activity is the ratio between radioactivity and mass of the element
Electrical-thermal-structural finite element simulation and experimental study of a plasma ion source for the production of radioactive ion beams
No full textThe production target and the ion source constitute the core of the selective production of exotic
species (SPES) facility. In this complex experimental apparatus for the production of radioactive
ion beams, a 40 MeV, 200 μA proton beam directly impinges a uranium carbide target, generating
approximately 1013 fissions per second. The transfer line enables the unstable isotopes generated by
the 238U fissions in the target to reach the ion source, where they can be ionized and finally accelerated
to the subsequent areas of the facility. In this work, the plasma ion source currently adopted for
the SPES facility is analyzed in detail by means of electrical, thermal, and structural numerical
models. Next, theoretical results are compared with the electric potential difference, temperature,
and displacement measurements. Experimental tests with stable ion beams are also presented and
discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Thermal-electric coupled-field finite element modeling and experimental testing of high-temperature ion sources for the production of radioactive ion beams
No full textIn isotope separation on line facilities the target system and the related ion source are two of
the most critical components. In the context of the selective production of exotic species (SPES)
project, a 40 MeV 200 μA proton beam directly impinges a uranium carbide target, generating
approximately 1013 fissions per second. The radioactive isotopes produced in this way are then
directed to the ion source, where they can be ionized and finally accelerated to the subsequent areas of
the facility. In this work both the surface ion source and the plasma ion source adopted for the SPES
facility are presented and studied by means of numerical thermal-electric models. Then, numerical
results are compared with temperature and electric potential difference measurements, and finally
the main advantages of the proposed simulation approach are discussed. C 2015 AIP Publishing
LLC
Thermal and Structural Characterization of a Titanium Carbide/Carbon Composite for Nuclear Applications
Full text linkIn the framework of ISOL (isotope separation on-line) facilities, porous carbides are among the most employed target materials for the production of radioactive ion beams for research. As foreseen by the ISOL technique, a production target is impinged by an energetic particle beam, inducing nuclear reactions from such an interaction. The resulting radionuclides are subsequently released, thanks to the high target working temperature (1600–2000 °C); ionized; and extracted into a beam. Since the target microstructure and porosity play a fundamental role in the radionuclide release efficiency, custom-made target materials are often specifically produced, resulting in unknown thermal and structural properties. Considering that such targets might undergo intense thermal stresses during operation, a thermal and structural characterization is necessary to avoid target failure under irradiation. In the presented work, a custom-made porous titanium carbide that was specifically designed for application as an ISOL target was produced and characterized. The thermal characterization was focused on the evaluation of the material emissivity and thermal conductivity in the 600–1400 °C temperature range. For the estimation of a reference material tensile stress limit, the virtual thermoelastic parameter approach was adopted. In particular, for the aforementioned temperature range, an emissivity between 0.7 and 0.8 was measured, whereas a thermal conductivity between 8 and 10 W/mK was estimated
Neutron irradiation effects on standard and oxygenated silicon diodes
No full textSilicon diodes processed on standard and oxygenated silicon substrates by two different manufacturers have been irradiated by neutrons in a nuclear reactor and by the 9Be(d,n)10B nuclear reaction. The leakage current density (JD) increase is linear with the neutron fluence. JD and its annealing curve at 80°C do not present any sizeable dependence on substrate oxygenation and/or manufacturing process. On the contrary, standard devices from one manufacturer present the lowest acceptor introduction rate (β) for the effective substrate doping concentration (Neff), showing that the β dependence on the particular process can be important, overtaking the small substrate oxygenation effect. Finally, the average saturation value of the Neff reverse annealing is slightly lower for the oxygenated samples, pointing out a positive effect of the substrate oxygenation even for devices irradiated by neutrons
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