1,721,021 research outputs found
Apprendimento e affetti: storie di luce e di ombre
No full textScopo di questo lavoro è quello di indagare il rapporto esistente tra apprendimento e affetti, per evidenziarne la stretta connessione. Si è scelto quindi l'ottica psicoanalitica ed in particolare la corrente kleiniana, come vertice teorico di riferimento che indaga come i fattori emotivi siano coinvolti nei processi di pensiero. In particolare si è fatto riferimento alla teoria di Bion sull'origine del pensiero, analizzata da Marcoli (1997). A tal fine si sono analizzati i materiali prodotti dai bambini di una prima elementare, durante lo svolgimento di un progetto, che aveva come fulcro l'esplorazione del legame esistente tra luce ed ombra, attraverso attività di tipo laboratoriale. In questo modo si è cercato di cogliere come i bambini hanno affrontato il processo di conoscenza: solo in pochi casi si è riscontrato un blocco di fronte all'ignoto, mentre per la maggior parte si è messo in atto un processo di cambiamento e di crescita, anche grazie all'aiuto dell'adulto. Questo lavoro ha quindi inteso sottolineare come sia possibile, nella pratica educativa, cogliere i vissuti emotivi implicati nel processo di apprendimento, attraverso una maggiore consapevolezza delle dinamiche affettive e una progettazione educativa atta a coinvolgere l'alunno nella sua globalità
Galactic fountains and outflows in star-forming dwarf galaxies: Interstellar medium expulsion and chemical enrichment
No full textWe investigate the impact of supernova (SN) feedback in gas-rich dwarf galaxies experiencing a low-to-moderate star formation rate, typical of relatively quiescent phases between starbursts. We calculate the long-term evolution of the interstellar medium (ISM) and the metal-rich SN ejecta using three-dimensional hydrodynamic simulations, in which the feedback energy is deposited by Type II SNe exploding in distinct OB associations. We find that a circulation flow similar to galactic fountains is generally established, with some ISM lifted at heights of one to a few kpc above the galactic plane. This gas forms an extraplanar layer, which falls back to the plane in ≈108 yr, once the star formation stops. Very little or no ISM is expelled outside the galaxy system for the star formation rates considered, even though in the most powerful model the SN energy is comparable to the gas binding energy. The metal-rich SN ejecta is instead more vulnerable to the feedback and we find that a significant fraction (25-80 per cent) is vented in the intergalactic medium, even for low SN rates (7 × 10-5 to 7 × 10-4 yr-1). About half of the metals retained by the galaxy are located far (z > 500 pc) from the galactic plane. Moreover, our models indicate that the circulation of the metal-rich gas out from and back to the galactic disc is not able to erase the chemical gradients imprinted by the (centrally concentrated) SN explosions.We investigate the impact of supernova (SN) feedback in gas-rich dwarf galaxies experiencing a low-to-moderate star formation rate, typical of relatively quiescent phases between starbursts. We calculate the long-term evolution of the interstellar medium (ISM) and the metal-rich SN ejecta using three-dimensional hydrodynamic simulations, in which the feedback energy is deposited by Type II SNe exploding in distinct OB associations. We find that a circulation flow similar to galactic fountains is generally established, with some ISM lifted at heights of one to a few kpc above the galactic plane. This gas forms an extraplanar layer, which falls back to the plane in ≈108 yr, once the star formation stops. Very little or no ISM is expelled outside the galaxy system for the star formation rates considered, even though in the most powerful model the SN energy is comparable to the gas binding energy. The metal-rich SN ejecta is instead more vulnerable to the feedback and we find that a significant fraction (25-80 per cent) is vented in the intergalactic medium, even for low SN rates (7 × 10-5 to 7 × 10-4 yr-1). About half of the metals retained by the galaxy are located far (z > 500 pc) from the galactic plane. Moreover, our models indicate that the circulation of the metal-rich gas out from and back to the galactic disc is not able to erase the chemical gradients imprinted by the (centrally concentrated) SN explosions
The dance of heating and cooling in galaxy clusters: three-dimensional simulations of self-regulated active galactic nuclei outflows
No full textIt is now widely accepted that heating processes play a fundamental role in galaxy clusters, struggling in an intricate but fascinating ‘dance' with its antagonist, radiative cooling. Last-generation observations, especially X-ray, are giving us tiny hints about the notes of this endless ballet. Cavities, shocks, turbulence and wide absorption lines indicate that the central active nucleus is injecting a huge amount of energy in the intracluster medium. However, which is the real dominant engine of self-regulated heating? One of the models we propose is massive subrelativistic outflows, probably generated by a wind disc or just the result of the entrainment on kpc scale by the fast radio jet. Using a modified version of the adaptive mesh refinement code FLASH 3.2, we have explored several feedback mechanisms that self-regulate the mechanical power. Two are the best schemes that answer our primary question, that is, quenching cooling flow and at the same time preserving a cool core appearance for a long-term evolution (7 Gyr): one is more explosive (with efficiencies ̃ 5 × 10-3-10-2), triggered by central cooled gas, and the other is gentler, ignited by hot gas Bondi accretion (with ɛ= 0.1). These three-dimensional simulations show that the total energy injected is not the key aspect, but the results strongly depend on how energy is given to the intracluster medium. We follow the dynamics of the best models (temperature, density, surface brightness maps and profiles) and produce many observable predictions: buoyant bubbles, ripples, turbulence, iron abundance maps and hydrostatic equilibrium deviation. We present an in-depth discussion of the merits and flaws of all our models, with a critical eye towards observational concordance
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
3D Numerical Simulations of AGN Outflows in Clusters and Groups
Full text linkWe compute 3D hydrodynamic models of jet outflows from the central AGN that carry mass as well as energy to the hot gas in galaxy clusters and groups. These flows have many attractive attributes for solving the cooling flow problem: why the hot gas temperature and density profiles resemble cooling flows but show no spectral evidence of cooling to low temperatures. Subrelativistic jets, described by a few parameters, are assumed to be activated when gas flows toward or cools near a central SMBH. As the jets proceed out from the center, they entrain more and more ambient gas. Using approximate models for a rich cluster (A1795), a poor cluster (2A 0336+096) and a group (NGC 5044), we show that mass-carrying jets with intermediate mechanical efficiencies (~10−3) can reduce for many Gyr the global cooling rate to or below the low values implied by X-ray spectra, while maintaining T and profiles similar to those observed, at least in clusters. Groups are much more sensitive to AGN heating and present extreme time variability in both profiles. Finally, the intermittency of the feedback generates multiple generations of X-ray cavities similar to those observed in Perseus cluster and elsewhere. Thus, we also study the formation of buoyant bubbles and weak shocks in the ICM, along with the injection of metals by SNIa and stellar winds
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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