672 research outputs found
Different amplitude and time distribution of the sound of light and classical music
Several pieces of different musical kinds were studied measuring , the
output amplitude of a peak detector driven by the electric signal arriving to
the loudspeaker. Fixed a suitable threshold , we considered ,
the number of times that , each of them we named event and
, the distribution of times between two consecutive events. Some
and distributions are displayed in the reported logarithmic
plots, showing that jazz, pop, rock and other popular rhythms have
noise-distribution, while classical pieces of music are characterized by more
complex statistics. We pointed out the extraordinary case of the aria
``\textit{La calunnia \`{e} un venticello}'', where the words describe an
avalanche or seismic process, calumny, and the rossinian music shows and
distribution typical of earthquakes.Comment: 3 pages with 4 figures, to be published in The European Physical
Journal
LA RICOSTRUZIONE DIFFICILE: CONFLITTI SOCIALI E IMPRESE ARCHITETTONICHE NEL VAL DI NOTO DOPO IL TERREMOTO DEL 1693
La storiografia riferita alle vicende post sismiche del Val di Noto ha ricorrentemente interpretato lo straordinario patrimonio
architettonico realizzato dopo il terremoto del 1693 come il risultato di uno sforzo collettivo, che vide coinvolti in
modo sinergico tutti i livelli della società siciliana. Il terremoto è stato insomma visto spesso come un evento traumatico
capace di saldare – in una sorta di comune reazione della vita contro la morte – il governo spagnolo, la nobiltà feudale,
il clero e le comunità urbane, queste ultime in una posizione subalterna rispetto alle determinazioni delle tre tradizionali
sfere del potere Ancién Regime (Monarchia, Nobiltà e Chiesa).Il progredire degli studi negli ultimi anni sta in realtà conducendo a ragionamenti più articolati e problematici. Se è
indubbio infatti che lo sforzo dei tre organi del potere fu sostanzialmente sinergico e rivolto soprattutto a far fronte
all’immediata emergenza, ben più complessa ed estesa risulta invece la reazione delle comunità urbane che, come è
ormai noto, andò ben oltre gli intenti puramente ricostruttivi, attraversando tutto l’arco del XVIII secolo
Transport of quantum excitations coupled to spatially extended nonlinear many-body systems
The role of noise in the transport properties of quantum excitations is a
topic of great importance in many fields, from organic semiconductors for
technological applications to light-harvesting complexes in photosynthesis. In
this paper we study a semi-classical model where a tight-binding Hamiltonian is
fully coupled to an underlying spatially extended nonlinear chain of atoms. We
show that the transport properties of a quantum excitation are subtly modulated
by (i) the specific type (local vs non-local) of exciton-phonon coupling and by
(ii) nonlinear effects of the underlying lattice. We report a non-monotonic
dependence of the exciton diffusion coefficient on temperature, in agreement
with earlier predictions, as a direct consequence of the lattice-induced
fluctuations in the hopping rates due to long-wavelength vibrational modes. A
standard measure of transport efficiency confirms that both nonlinearity in the
underlying lattice and off-diagonal exciton-phonon coupling promote transport
efficiency at high temperatures, preventing the Zeno-like quench observed in
other models lacking an explicit noise-providing dynamical system
The Anti-FPU Problem
We present a detailed analysis of the modulational instability of the
zone-boundary mode for one and higher-dimensional Fermi-Pasta-Ulam (FPU)
lattices. Following this instability, a process of relaxation to equipartition
takes place, which we have called the Anti-FPU problem because the energy is
initially fed into the highest frequency part of the spectrum, at variance with
the original FPU problem (low frequency excitations of the lattice). This
process leads to the formation of chaotic breathers in both one and two
dimensions. Finally, the system relaxes to energy equipartition on time scales
which increase as the energy density is decreased. We show that breathers
formed when cooling the lattice at the edges, starting from a random initial
state, bear strong qualitative similarities with chaotic breathers
EDACs and test integration strategies for NAND flash memories
Mission-critical applications usually presents several critical issues: the required level of dependability of the whole mission always implies to address different and contrasting dimensions and to evaluate the tradeoffs among them. A mass-memory device is always needed in all mission-critical applications: NAND flash-memories could be used for this goal. Error Detection And Correction (EDAC) techniques are needed to improve dependability of flash-memory devices. However also testing strategies need to be explored in order to provide highly dependable systems. Integrating these two main aspects results in providing a fault-tolerant mass-memory device, but no systematic approach has so far been proposed to consider them as a whole. As a consequence a novel strategy integrating a particular code-based design environment with newly selected testing strategies is presented in this pape
Discrete Breathers in a Realistic Coarse-Grained Model of Proteins
We report the results of molecular dynamics simulations of an off-lattice
protein model featuring a physical force-field and amino-acid sequence. We show
that localized modes of nonlinear origin (discrete breathers) emerge naturally
as continuations of a subset of high-frequency normal modes residing at
specific sites dictated by the native fold. In the case of the small
-barrel structure that we consider, localization occurs on the turns
connecting the strands. At high energies, discrete breathers stabilize the
structure by concentrating energy on few sites, while their collapse marks the
onset of large-amplitude fluctuations of the protein. Furthermore, we show how
breathers develop as energy-accumulating centres following perturbations even
at distant locations, thus mediating efficient and irreversible energy
transfers. Remarkably, due to the presence of angular potentials, the breather
induces a local static distortion of the native fold. Altogether, the
combination of this two nonlinear effects may provide a ready means for
remotely controlling local conformational changes in proteins.Comment: Submitted to Physical Biolog
Heat wave propagation in a nonlinear chain
We investigate the propagation of temperature perturbations in an array of
coupled nonlinear oscillators at finite temperature. We evaluate the response
function at equilibrium and show how the memory effects affect the diffusion
properties. A comparison with nonequilibrium simulations reveals that the
telegraph equation provides a reliable interpretative paradigm for describing
quantitatively the propagation of a heat pulse at the macroscopic level. The
results could be of help in understanding and modeling energy transport in
individual nanotubes.Comment: Revised version, 1 fig. adde
Biopolymer gels with "physical" cross-links: gelation kinetics, aging, heterogeneous dynamics, and macroscopic mechanical properties
Alginate is a natural biopolymer that forms, in the presence of divalent cations, ionic-bound gels typifying a large class of biological gels stabilized by non-covalent cross-links, and displaying a consistent restructuring kinetics. We investigate the kinetics of formation and aging of alginate gels by slow permeation of a curing CaCl2 agent by means of photon correlation imaging, a novel optical technique that allows obtaining the microscopic dynamics of the sample, while retaining at the same time the spatial resolution of imaging techniques. Specifically, the gelling kinetics displays a peculiar non-diffusive behavior, and the subsequent restructuring of the gel structure shares several features in common with the aging of colloidal gels, in particular for what concerns the occurrence of heterogeneous dynamics effects. A comparative analysis of the gel macroscopic mechanical properties at different aging stages further highlights distinctive effects arising from the non-permanent nature of the bonds
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