163,302 research outputs found
Chemical evolution of dwarf irregular and blue compact galaxies
No full textAims: Dwarf irregular and blue compact galaxies are very interesting objects since they are relatively simple and unevolved. We aim at deriving the formation and chemical evolution history of late-type dwarf galaxies and at comparing it with DLA systems.
Methods: We present new models for the chemical evolution of these galaxies by assuming different regimes of star formation (bursting and continuous) and different kinds of galactic winds (normal and metal-enhanced). The dark-to-baryonic mass ratio is assumed to be ten in these models. The chemical evolution model follows the evolution of He, C, N, O, S, Si, and Fe in detail. We have collected the most recent data on these galaxies and compared them with our model's results. We also collected data for damped-Lyman α-systems.
Results: Our results show that in order to reproduce all the properties of these galaxies, including the spread in the chemical abundances, the star formation should have proceeded in bursts and the number of bursts should be not more than ten in each galaxy, and that metal-enhanced galactic winds are required. The presence of metal-enhanced galactic winds can by itself reproduce the observed mass-metallicity relation, although an increasing efficiency of star formation and/or number and/or duration of bursts can also reproduce such a relation equally well.
Conclusions: Metal-enhanced winds, together with an increasing amount of star formation with galactic mass, are required to explain most of the properties of these galaxies. Normal galactic winds, where all the gas is lost at the same rate, do not reproduce the features of these galaxies. On the other hand, a global increase in the amount of star formation (increasing efficiency, number of bursts, or burst duration) with galactic mass is able by itself to reproduce the mass-metallicity relation even without winds, but without metal-enhanced winds is not able to explain many other constraints. We suggest that these galaxies should have suffered a different number of bursts varying from two to ten and that the efficiency of metal-enhanced winds should not have been too high (λmw ~ 1). We predict for these galaxies present-time type Ia SN rates from 0.00084 and 0.0023 per century. Finally, by comparing the abundance patterns of damped Lyman-α objects with our models, we conclude that they are very likely the progenitors of the current dwarf irregulars
Dewey: intelligenza e percezione
No full textProfilo critico del pensiero di Dewey in rapporto agli odierni sviluppi della riflessione pragmatista, con particolare attenzione ai temi della definizione della mente e della percezione
Fattori estetici nella costituzione della simbolicità
No full textAnalisi comparativa delle teorie della percezione di Cassirer e Gehlen, volta a mostrare come l'approccio antropologico consenta di evidenziare che la funzione simbolica è immanente alla stessa sensorialità
Application of Matteucci Voltage Pulses of Amorphous Wires in Sensing Both Direction and Magnitude of Twist
No full textIn this work the effect of torsion on the Matteucci voltage pulses in amorphous wires has been studied. It has been shown that: Amplitude of the pulses decreases to zero at a twist angle that depends on the chemical composition of the wire. From zero torsion, the amplitude of the Matteucci voltage increases when the wires are twisted counter-clockwise. However, when the wires are twisted clockwise, the amplitude of the Matteucci voltage pulses decreases up to a minimum point (zero) before, finally, starting to increase. This is a clear distinction (in behaviour) between clockwise and counter-clockwise torsion, which can be employed to determine the direction of initial twist. Also, the low torsion region of the torsion-Matteucci voltage characteristic shows a clear possibility of employing the stress sensitive Matteucci voltage to determine the magnitude of torsion. The Matteucci voltage is quite sensitive to the torsion. It is thus expected to provide high sensitivity for measurement of torsion in the “low and very low torsion region”. It has also been established that when the positioning of the amorphous wire in the magnetizing coil is reversed (wire ends are interchanged), the torsion-Matteucci voltage characteristic obtained is virtually a mirror image of the previous direction. For instance, if the zero amplitude Matteucci voltage was being obtained at a twist angle of 45° clockwise, it will now be obtained at an angle of the same magnitude, but for a counter-clockwise twist. The physics of this latter phenomenon too would be of interest to researchers of physics of magnetism.
J. agric. Sci. technol. Vol.5(1) 2003: 116-12
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
The aesthetic field: Arnold Berleant's philosophy as a new understanding of experience
No full textThe essay aims to identify the original matrix of Berleant’s aesthetic thought by deepening his initial research on the notion of “field”. Berleant analyzes the “aesthetic field” by considering it as a dynamic texture that stands outside the dualisms that have characterized modern philosophy. At the core of this analysis is the fruitful convergence between different traditions from which Berleant draws for laying out his philosophical program. In particular, if phenomenology leads him to thematize the connection between experience and judgment, pragmatism leads him to establish the cornerstone of the experiential (and above all perceptual) character of the aesthetic as such. Thanks to this, the perspective developed by Berleant since the seventies of the twentieth century still proves to be largely vital, as it is capable of delineating an anthropological horizon centered on the analysis of the “environmental” practices of the so-called “aesthetic engagement”
School Psychology in Italy: Current status and challenges for future development.
No full textAs ISPA President Jimerson noted in his President’s Letter in the March 2017 edition of World-go-Round: “services provided by school psychologists vary within and between countries in response to a country’s history and needs” (Jimerson, 2017, p.1). The current development of school psychology in Italy continues to respond to the country’s history and needs; however, we are finding that almost 10 years after the publication of the Handbook of International School Psychology (Jimerson et al., 2006), where Italy was identified as a country where school psychology was at the initial stages of self-identity, Italian school psychologists still struggle to be recognized as “uniquely qualified members of school teams that support students' ability to learn and teachers' ability to teach, as defined by the National Association of School Psychologists (NASP)”. Such a lack of professional identity is mainly due to the non-existence of a definitive national regulation governing the general practice of psychology in schools, as well as the absence of a licence for “school psychologist” in order to work within the school context. This contribution reviews school psychology in the Italian context, aiming at both updating and promoting the understanding and advancement of school psychology around the world
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