315 research outputs found
Output from paper: The s process in massive stars, a benchmark for neutron capture reaction rates
No full text<p>Title: "The s process in massive stars, a benchmark for neutron capture reaction rates"; Authors: Marco Pignatari, Roberto Gallino, Rene Reifarth</p><p>------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------</p><p>Content: tar.gz package including a README file and two folders. The folders contain all the abundance plots associated to the work Pignatari, Gallino & Reifarth, 2023 The European Physical Journal A, Special Issue on: 'From reactors to stars' in honor of Franz Kaeppeler. </p>
Multimedia fiction: theory and practice of Décio Pignatari s literary narrative
No full textA tese tem por temas a teoria e a prática da prosa ficcional em Décio Pignatari.
Décadas de trabalho em diferentes pólos da comunicação publicou ensaios e deu aulas de teoria da informação, atuou como articulista na imprensa, foi o primeiro intelectual a escrever seriamente sobre a TV no Brasil, traduziu Marshall McLuhan, fez publicidade e cinema transformaram Pignatari num criador multimídia. É essa característica que marca sua obra voltada para a ficção.
Pautada pelo uso de múltiplos recursos, verbais e não-verbais, literários e de mídias diversas, as narrativas de Décio Pignatari representam extensões de sua prosética como ele chama o seu pensamento sobre a prosa ficcional e vice-versa
Enquanto a plataforma teórica pignatariana para a ficção estabeleceu-se especialmente por meio de cursos, ensaios e artigos, sua produção em termos de narrativa literária deu origem aos seguintes títulos, que serão aqui analisados: 1)O rosto da memória, contos; 2)Panteros, romance; 3) Cléris und Lotta , que integra a antologia 21 Histórias de amor, mas que já aparecera, sem título, no corpo do prefácio de Cultura pós-nacionalista, coletânea de textos de não-ficção; e 4)Céu de lona, peça teatral.
Para estudar prosa ficcional de Décio Pignatari, a tese vale-se sobretudo da própria prosética que tem por base a semiótica de Charles Sanders Peirce. De acordo com Pignatari, a ficção, notadamente a que surge a partir de Ulisses (1922), de James Joyce, se apóia na secundidade peirceana, que se projeta sobre a terceiridade como um presente suspenso , ponto de encontro dos demais tempos, do máximo de gêneros e de discursos de distintos meios de comunicação.
Esta é a proposta do autor para sua prosa ficcional, espelho da prosética , que dela também se alimenta, conforme pretendemos demonstrar.
Ressalte-se que Décio Pignatari alcança pela primeira vez essa condição acadêmicaThe dissertation subject is the theory and practice of Décio Pignatari s fictional prose.
Decades of work in various fields of communication he has published essays, has taught information theory, has written to the press and was the first intellectual to write in-depth pieces on TV in Brazil, he has translated Marshall McLuhan, has produced advertising pieces, and cinema have made of Pignatari a multimedia creator. This approach also defines his fictional production.
Characterized by the usage of multiple resources, both verbal and non-verbal, literary and of various media, Décio Pignatari s narratives represent extensions of his prosética as he calls his thinking on the fictional prose and vice versa.
While the pignatarian theoretical platform catering his fiction has been established especially through courses, articles, and essays, his narrative literary production has originated the following works: 1) O rosto da memória [The face of memory], stories; 2) Panteros [Pantheros], novel; 3) Cléris und Lotta [Cléris and Lotta], narrative that integrates the anthology 21 Histórias de Amor [21 Love Stories], which had already appeared, untitled, in the foreword to Cultura pós-nacionalista [Post-Nationalist Culture], collected non-fictional texts; and 4) Céu de lona [Tent sky], a play.
To survey Décio Pignatari s fictional prose, the dissertation counts mostly on the very prosética which is based on Charles Sanders Peirce s semiotic. According to Pignatari, fiction, notably the one produced since the release of Ulysses (1922), by James Joyce, is dominated by Peirce s Secondness, which projects itself on Thirdness as a suspended gift, a meeting point of the other tenses, the maximum of genders and of distinct discourses of the media.
This is the author s purpose for his fictional prose, a prosética mirror, that also feeds itself, as we intend to demonstrate.
This is the first "critical study" of Décio Pignatari s fictional prose and his prosétic
The Complex Behaviour of s-Process Element Abundances at Young Ages
No full textOpen clusters appear as simple objects in many respects, with a high degree of homogeneity in their (initial) chemical composition, and the typical solar-scaled abundance pattern that they exhibit for the majority of the chemical species. The striking singularity is represented by heavy elements produced from the slow process of the neutron-capture reactions. In particular, young open clusters (ages less than a few hundred Myr) give rise to the so-called barium puzzle: that is an extreme enhancement in their [Be/Fe] ratios, up to a factor of four of the solar value, which is not followed by other nearby s-process elements (e.g., lanthanum and cerium). The definite explanation for such a peculiar trend is still wanting, as many different solutions have been envisaged. We review the status of this field and present our new results on young open clusters and the pre-main sequence star RZ Piscium
Shades
No full textNeutron capture reactions are the main contributors to the synthesis of the heavy elements through the s-process. Together with 13C(α, n)16O, which has recently been measured by the LUNA collaboration in an energy region inside the Gamow peak, 22Ne(α, n)25Mg is the other main neutron source in stars. Its cross section is mostly unknown in the relevant stellar energy (450 keV < Ecm < 750 keV), where only upper limits from direct experiments and highly uncertain estimates from indirect sources exist. The ERC project SHADES (UniNa/INFN) aims to provide for the first time direct cross section data in this region and to reduce the uncertainties of higher energy resonance parameters. High sensitivity measurements will be performed with the new LUNA-MV accelerator at the INFN-LNGS laboratory in Italy: the energy sensitivity of the SHADES hybrid neutron detector, together with the low background environment of the LNGS and the high beam current of the new accelerator promises to improve the sensitivity by over 2 orders of magnitude over the state of the art, allowing to finally probe the unexplored low-energy cross section. Here we present an overview of the project and first results on the setup characterization
Convective–reactive nucleosynthesis of K, Sc, Cl and p-process isotopes in O–C shell mergers
No full text© 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. We address the deficiency of odd-Z elements P, Cl, K and Sc in Galactic chemical evolution models through an investigation of the nucleosynthesis of interacting convective O and C shells in massive stars. 3D hydrodynamic simulations of O-shell convection with moderate C-ingestion rates show no dramatic deviation from spherical symmetry. We derive a spherically averaged diffusion coefficient for 1D nucleosynthesis simulations, which show that such convective-reactive ingestion events can be a production site for P, Cl, K and Sc. An entrainment rate of 10-3M⊙s-1features overproduction factors OPs≈ 7. Full O-C shell mergers in our 1D stellar evolution massive star models have overproduction factors OPm> 1 dex but for such cases 3D hydrodynamic simulations suggest deviations from spherical symmetry. γ - process species can be produced with overproduction factors of OPm> 1 dex, for example, for130, 132Ba. Using the uncertain prediction of the 15M⊙, Z = 0.02 massive star model (OPm≈ 15) as representative for merger or entrainment convective-reactive events involving O- and C-burning shells, and assume that such events occur in more than 50 per cent of all stars, our chemical evolution models reproduce the observed Galactic trends of the odd-Z elements
Nucleosynthesis in Type Ia Supernovae
No full textThis thesis presents the post-processed isotopic yields from 39 SNIa models with masses of 1.4, 1.0 and 0.8 M⊙ and metallicities ranging from a 22Ne mass fraction of 0 to 0.1. In chapter 3 the full yields are presented, along with a description of the major production sites of relevent isotopes and a discussion of the metallicity dependency of the yields. We discuss, in detail, the production site of each isotope and its significance in relation to GCE. In chapter 4 we compare our post processed reults with source models and with the literature to varify our yields.In chapter 5, potential isotopic diagnostics of progenitor WD masses are identified from the post-processed results. We find that there are isotopictracerswhich distinguish the Chandresakar and sub-Chandresakarmassmodels, and that if these ratios are able to be investigated, either in the bulk solar material or through isotopic grain data, then the progenitors of SNIa, or the relative ratios of sub- to Chandresakar mass WD progenitors, may be determined through this method with further galactic chemical evolution modeling
Nucleosynthesis in Type Ia Supernovae
No full textThis thesis presents the post-processed isotopic yields from 39 SNIa models with masses of 1.4, 1.0 and 0.8 M⊙ and metallicities ranging from a 22Ne mass fraction of 0 to 0.1. In chapter 3 the full yields are presented, along with a description of the major production sites of relevent isotopes and a discussion of the metallicity dependency of the yields. We discuss, in detail, the production site of each isotope and its significance in relation to GCE. In chapter 4 we compare our post processed reults with source models and with the literature to varify our yields.In chapter 5, potential isotopic diagnostics of progenitor WD masses are identified from the post-processed results. We find that there are isotopictracerswhich distinguish the Chandresakar and sub-Chandresakarmassmodels, and that if these ratios are able to be investigated, either in the bulk solar material or through isotopic grain data, then the progenitors of SNIa, or the relative ratios of sub- to Chandresakar mass WD progenitors, may be determined through this method with further galactic chemical evolution modeling
Signatures of i-process nucleosynthesis
No full textNeutron capture nucleosynthesis is responsible for the production of heavy elements. Three neutron capture processes are currently known, each occurring at their own characteristic neutron density and operating in different ways. The slow neutron capture process operates at neutron densities of n ≈ 10⁷ 10¹⁰ cm⁻³, the rapid at neutron densities of = & 10²⁰ cm⁻³ and the intermediate at neutron densities of n ≥ 10¹² - 10¹⁵ cm⁻³. The intermediate neutron capture process (i process) is the focus of this work.The i process is now widely accepted to be the process that produces the unusual abundances of carbon-enhanced metal-poor (CEMP) -r/s stars. A challenge in recent years has been constraining a site for the i process. Given the large range in potential neutron densities, many astrophysical sites have the potential to host i-process conditions. Two of the most promising sites for the i process are: the intershell regions of low-mass, low-metallicity asymptotic giant branch stars and on rapidly accreting white dwarfs. This work provides abundance analyses of models of the two different scenarios.I first look at comparing both models to a sample of CEMP-r/s stars using j2 fitting. From this I was able to determine the abundance signatures that can make one model fit an i-process pattern more closely than another. I used this fitting technique to fit i-process models to other objects in the literature, including to phosphorus-rich stars. j2 fitting is also used to show that stellar models can be used to make predictions of the Th and U we would expect to see from the i process.I move on to investigating elemental abundance ratios that may help us distinguish an s process from an i process by using three-element plots. From this, I came up with four abundance ratios that have the potential to be useful as an i-process signature
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