Rappresentazioni cortesi nella tarda letteratura norrena. Il caso della Saga di Hrolfr il palo

L'elaborato finale mira all'analisi delle figure monarchiche all'interno della Hrólfs saga kraka, una delle più celebri fornaldarsögur. Il lavoro si articola in tre capitoli, preceduti da un paragrafo introduttivo che descrive le finalità del lavoro. La prima parte della tesi verte sullo studio del genere della fornaldarsaga, analizzandola dal punto di vista storico e letterario (fornendo informazioni sulla datazione dei primi manoscritti e della comparsa del genere). La seconda parte riguarda i manoscritti della saga in esame, dai più importanti, impiegati di solito nella stesura di una nuova edizione, fino ai secondari, di solito frammenti o varianti del testo di partenza. Il terzo capitolo rappresenta il cuore del lavoro, analizzando non solo ogni singola figura monarchica all'interno della Hrólfs saga kraka, ma anche i loro doppi presenti all'interno di quelle fonti che raccontano la leggenda di Hrólfr 'il palo' (es. Beowulf, Grottasöngr, Gesta Danorum, Chronicon Lethrense latino e danese etc.), al fine di delinearne un'identità completa ed esaustiva

mtDNA and mitochondrial stress signaling in human diseases: A special issue

: The completion of the Special Issue dedicated to "mtDNA and mitochondrial stress signaling in human diseases" requests a final overall look to highlight the most valuable findings among the many presented data [...]

Improved critical current densities in B4C doped MgB2 based wires

An improvement of the transport critical current density, Jc, of MgB2 wires was obtained after addition of 10 wt.% B4C powders, after reaction at 800 C: Jc values of 1.10^4 A/cm2 at 4.2 K and 9T were obtained for wires of 1.11 mm diameter in a Fe matrix. The starting mixture of Mg and B was doped with sub-micrometric B4C, the ratio being Mg : B : B4C = 1: 2 : 0.08, corresponding to 10 wt.% B4C. For T > 800 C, a decrease of Jc was found, due to the reaction with the Fe sheath. In order to investigate the origin of the improvement of the transport properties for heat treatments up to 800 C, X-ray diffraction measurements were performed. A decrease of the lattice constant a from 0.30854 nm to 0.30797 nm was found, thus suggesting an effect of the substitution of Carbon on the properties of the wires. A comparison with the literature data shows that the addition of B4C powders leads to the second highest improvement of Jc reported so far after SiC, thus constituting an alternative for future applications.Comment: 18 pages, 8 figures, 1 tabl

La Gestione degli Accordi di Cooperazione nel progetto OpenSPCoop

Dalla analisi delle specifiche CNIPA alla realizzazione del componente Accordo di Cooperazione nel progetto OpenSPCoop con relativi casi d'uso per mostrarne le qualità e le applicazioni

Transport Properties and Exponential n-values of Fe/MgB2 Tapes With Various MgB2 Particle Sizes

Fe/MgB2 tapes have been prepared starting with pre-reacted binary MgB2 powders. As shown by resistive and inductive measurements, the reduction of particle size to a few microns by ball milling has little influence on Bc2, while the superconducting properties of the individual MgB2 grains are essentially unchanged. Reducing the particle size causes an enhancement of Birr from 14 to 16 T, while Jc has considerably increased at high fields, its slope Jc(B) being reduced. At 4.2K, values of 5.3*10^4 and 1.2*10^3 A/cm^2 were measured at 3.5 and 10 T, respectively, suggesting a dominant role of the conditions at the grain interfaces. A systematic variation of these conditions at the interfaces is undertaken in order to determine the limit of transport properties for Fe/MgB2 tapes. The addition of 5% Mg to MgB2 powder was found to affect neither Jc nor Bc2. For the tapes with the highest Jc values, very high exponential n factors were measured: n = 148, 89 and 17 at 3.5, 5 and 10T, respectively and measurements of critical current versus applied strain have been performed. The mechanism leading to high transport critical current densities of filamentary Fe/MgB2 tapes based on MgB2 particles is discussed.Comment: Presented at ICMC 2003, 25-28 May 200

Adiabatic normal zone development in MgB2 superconductors

A-priori knowledge of the normal zone development in MgB/sub 2/ conductors is essential for quench protection of applications. Therefore the normal zone propagation in a monofilament MgB/sub 2//Fe conductor under near-adiabatic conditions at 4.2 K has been measured and simulated. The results show normal zone propagation velocities up to several meters per second. In addition, by including the voltage-current relation into the computational model, the influence of the n-value on the normal zone propagation is determined. The simulations show that lower n-values suppress the normal zone propagation velocity due to lower heat generation in the MgB/sub 2/ filaments

Consequences of the peculiar intrinsic properties of MgB2 on its macroscopic current flow

The influence of two important features of magnesium diboride on the macroscopic transport properties of polycrystalline MgB2 is discussed in the framework of a percolation model. While two band superconductivity does not have significant consequences in the field and temperature range of possible power applications, the opposite is true for the anisotropy of the upper critical field. The field dependence of the critical current densities strongly increases and the macroscopic supercurrents disappear well below the apparent upper critical field. The common scaling laws for the field dependence of the volume pinning force are altered and Kramer's plot is no longer linear, although grain boundary pinning dominates in nearly all polycrystalline MgB2 conductors. In contrast to the conventional superconductors NbTi and Nb3Sn, a significant critical current anisotropy can be induced by the preparation technique of MgB2 tapes