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STRUTTURA E MEMORIA NELL'OPERA DI MORTON FELDMAN
No full textIl ruolo della memoria nella musica di Morton Feldman è stato tematizzato da Feldman stesso fin dagli anni Ottanta e poi da molti contributi musicologici sulla sua opera. Tuttavia è mancata nella maggior parte dei casi una prospettiva più specificamente cognitivista, basata sul riconoscimento della relazione tra percezione, schemi strutturali e memoria.
Gli studi sulla memoria hanno dimostrato come essa dipenda fortemente dalla presenza di schemi strutturali tra gli elementi con i quali entriamo in relazione. La presenza di una struttura riconoscibile che metta in relazione i vari elementi di una certa sequenza permette cioè di ricordare quella sequenza più facilmente rispetto ad un’altra in cui non vi siano collegamenti strutturali riconoscibili. Questo vale per sequenze di numeri, come per lettere, parole o suoni.
Il modo in cui determinate caratteristiche sonore producono – a vari livelli – relazioni strutturali significative alla percezione è stato indagato tra gli altri in modo particolarmente approfondito da Albert Bregman che nei suoi studi su quella che viene definita Auditory Scene Analysis descrive i meccanismi che consentono al nostro sistema uditivo di rintracciare/riconoscere/costruire relazioni strutturali significative tra i suoni.
In questo lavoro vengono analizzate alcune opere di Feldman appartenenti ai diversi periodi compositivi che si possono delineare all’interno della sua produzione, contraddistinte da caratteristiche affatto diverse. I principi dell’ASA saranno alla base dell'analisi che in questa prospettiva metterà in evidenza come le scelte compositive operate da Feldman in alcuni casi tendano ad assecondare la formazione di strutture percettive significative ed in altri invece a contrastare la formazione di relazioni strutturali. Nella sua produzione più tarda Feldman sembra infine tentare una paradossale ossimorica sintesi tra questi estremi. I principi dell’ASA forniscono inoltre una cornice esplicativa all’interno della quale dare ragione delle conseguenze di queste scelte sulla percezione e sulla memoria
Novel polymers for biomedical and pharmaceutical applications: synthesis and characterization
No full textThe aim of this PhD thesis work has been the synthesis of novel antimicrobial amphiphilic polymers to prevent microbial biofilm related-infections and counteract microbial resistance onset. In fact, microbial biofilms are difficultly eradicable due to their high antibiotic resistance. To reach this purpose different strategies along this work were exploited
The role of dynamical friction in the formation of Compact Massive Objects
No full textIn this thesis it has been treated the physical process called dynamical friction, which
is responsible for the decay of massive objects traveling in systems composed by lighter
particles, such as a Globular Cluster traveling in a Galaxy or massive stars moving in
stellar systems. After a careful validation, the treatment it has been applied to real
astrophysical objects on different scales. On small scales, it has been provided a study
on the possible formation of Intermediate Mass Black Holes in Globular Clusters, as
results of the decaying and merging of massive stars within the center of the clusters.
Considering larger scales, it has been studied the evolution of the Globular Cluster
System belonging to the dwarf spheroidal galaxy known as Fornax, giving a possible
solution to the so-called ”Fornax timing problem” and providing a wide set of initial
condition for the clusters which allows to predict with good approximation their observed
positions. Moreover, it has been studied the formation in the center of galaxies of dense,
massive clusters, commonly referred as Nuclear Star Clusters. In particular, the work
made here is based on the so-called ”dry merger scenario”, in which this central super-
cluster has been formed by the merging of decaying Globular Clusters. Using statistical
and analytical arguments, it has been possible to provide scaling laws, which connects
the Nuclear Star Cluster mass with the host global properties, in excellent agreement
with observed scaling laws. In the last part of the thesis, it has been studied the problem
of the lacking of Nuclear Star Clusters in galaxies whose masses are above ten billion of
solar masses. Using a wide set of direct N-body simulations, it has been demonstrated
that the tidal effects induced by a central Super Massive Black Holes could leads to the
total disruption of the building blocks of the central super clusters, i.e. the Globular
Clusters, suppressing, or even preventing at all, the formation of a Nuclear Star Clusters
Static and Rotating Neutron Stars in a Relativistic Formulation of All Fundamental Interactions and Astrophysical Applications
No full textIn the first part of our work, we formulated the equilibrium equa-
tions for static neutron stars, taking into account strong, weak, elec-
tromagnetic, and gravitational interactions within the framework of
general relativity and relativistic nuclear mean field theory. We shown
that the Tolman-Oppenheimer-Volkoff (TOV) equations are super-
seded and the use of the Einstein-Maxwell-Thomas-Fermi (EMTF) sys-
tem of equations is mandatory. The key points are the constancy of the
general relativistic Fermi energies of particles, the “Klein potentials”,
throughout the configuration, and the use of the global charge neutral-
ity over the whole configuration as requested by the EMTF system of
equations. The local charge neutrality is replaced due to its inconsis-
tency with the equations of motions of the EMTF system of equations.
The solution of EMTF leads to a new structure of the neutron stars:
a positively charged core at supranuclear density, surrounded by an
electron layer of thickness of the order of the electron screening scale,
and at lower density, a neutral ordinary crust.
Then, we introduced rotation on the new neutron stars model, fol-
lowing the slow rotation approximation in the Hartle-Thorne formal-
ism. Integrating the equations of equilibrium for different central den-
sities and circular velocities, we have been able to compute mass M,
polar Rp and equatorial Req radii , angular momentum J, eccentric-
ity ǫ and quadrupole moment Q of the configurations. We accounted
for the Keplerian mass-shedding limit and the axisymmetric secular
instability. We computed the minimum mass for the globally neutral
neutron stars, under which them result gravitationally unbound. No
unbound configurations have been found for the locally neutral neutron
stars, meaning that no minimum mass limit exist for this case.
Afterward, we showed the inaccuracy of some analytic universal
formulas, generally used in the literature, for the Keplerian sequence
and for the moment of inertia of neutron stars. The values for the mo-
ment of inertia I and the Keplerian rotational frequency fK, obtained
through our model, have been compared and contrasted with such for-
mulas. We analyzed the effect on the magnetic field of pulsars on
respect to the case in which fiducial parameters are used. We showed
that the magnetic field inferred from the magnetic-dipole formula can
be overestimated up to one order of magnitude if fiducial parameters
are adopted. We analyzed in particular the case of the high-magnetic
field pulsar class. We found that the magnetic field of all the high-
magnetic field pulsars can turn to be under-critical for appropriate
values of the neutron star mass. We finally computed the range of
neutron star masses for which the X-ray luminosity of these pulsars
can be well explained via the loss of rotational energy and therefore
they fall into the family of ordinary rotation powered pulsars
ASSETTO COGNITIVO E LIVELLI DI NEOPTERINA NEL LIQUOR IN PAZIENTI HIV POSITIVI ASINTOMATICI: UNO STUDIO PILOTA
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