2,074 research outputs found
Fluctuations in the Ensemble of Reaction Pathways
The dominant reaction pathway (DRP) is a rigorous framework to
microscopically compute the most probable trajectories, in non-equilibrium
transitions. In the low-temperature regime, such dominant pathways encode the
information about the reaction mechanism and can be used to estimate
non-equilibrium averages of arbitrary observables. On the other hand, at
sufficiently high temperatures, the stochastic fluctuations around the dominant
paths become important and have to be taken into account. In this work, we
develop a technique to systematically include the effects of such stochastic
fluctuations, to order k_B T. This method is used to compute the probability
for a transition to take place through a specific reaction channel and to
evaluate the reaction rate
Global Quantum Correlation in the Ising model
We study quantum correlations in an isotropic Ising ring under the effects of
a transverse magnetic field. After characterizing the behavior of two-spin
quantum correlations, we extend our analysis to global properties of the ring,
using a figure of merit for quantum correlations that shows enough sensitivity
to reveal the drastic changes in the properties of the system at criticality.
This opens up the possibility to relate statistical properties of quantum
many-body systems to suitably tailored measures of quantum correlations that
capture features going far beyond standard quantum entanglement.Comment: Published in the International Journal of Quantum Information as part
of the special issue devoted to "Quantum Correlations: entanglement and
beyond
Noise Induced Phenomena in the Dynamics of Two Competing Species
Noise through its interaction with the nonlinearity of the living systems can
give rise to counter-intuitive phenomena. In this paper we shortly review noise
induced effects in different ecosystems, in which two populations compete for
the same resources. We also present new results on spatial patterns of two
populations, while modeling real distributions of anchovies and sardines. The
transient dynamics of these ecosystems are analyzed through generalized
Lotka-Volterra equations in the presence of multiplicative noise, which models
the interaction between the species and the environment. We find noise induced
phenomena such as quasi-deterministic oscillations, stochastic resonance, noise
delayed extinction, and noise induced pattern formation. In addition, our
theoretical results are validated with experimental findings. Specifically the
results, obtained by a coupled map lattice model, well reproduce the spatial
distributions of anchovies and sardines, observed in a marine ecosystem.
Moreover, the experimental dynamical behavior of two competing bacterial
populations in a meat product and the probability distribution at long times of
one of them are well reproduced by a stochastic microbial predictive model.Comment: 23 pages, 8 figures; to be published in Math. Model. Nat. Phenom.
(2016
A knowledge based architecture for the virtual restoration of ancient photos
Historical images are essential documents of the recent past. Nevertheless, time and bad preservation
corrupt their physical supports. Digitization can be the solution to extend their \u201clives\u201d, and digital techniques
can be used to recover lost information. This task is often difficult and time-consuming, if commercial
restoration tools are used for the purpose. A new solution is proposed to help non-expert users
in restoring their damaged photos. First, we defined a dual taxonomy for the defects in printed and digitized
photos. We represented our restoration domain with an ontology and we created some rules to
suggest actions to perform in case of some specific events. Classes and properties of the ontology are
included into a knowledge base, that grows dynamically with its use. A prototypal tool and a web application
version have been implemented as an interface to the database, and to support non-expert users
in the restoration process
The status of Orobanche crenata in Sicily and preliminary observations on Orobanche crenata susceptibility in Vicia faba
Since more than 10 years we are recording Orobanche crenata populations variations and testing traditional remedies to assess their applicability in a low impact agriculture that may be applied also in developing countries. Starting from the observation that often in C Sicily dense fields of Broadbean show lower Broomrape infestation, we did some preliminary observations on Orobanche crenata susceptibility in Vicia faba var. faba and Vicia faba var. equina with different agricultural techniques. First results show a higher resistance of the latter sowed at higher densities
Upstream and downstream of recombinants biomolecules to health care industry
sem informação201
characterization and manufacturing of a paraffin wax as fuel for hybrid rockets
The hybrid propulsion performed with paraffin waxes exhibits most attractive capabilities compared to solid or liquid engines, e.g., throttleability and re-ignition, alongside higher regression rates compared to the conventional hydroxyl terminated polybutadiene (HTPB) hybrid fuel. This is because the paraffin wax forms a thin and hydro-dynamically unstable liquid layer, and then enhances the regression rate with the entrainment of droplets from the liquid-gas interface. Nevertheless, some critical open points on the manufacturing of the paraffin fuel grains still persist, because the paraffin wax exhibits high shrinkage during the solidification phase, leading to the formation of cavities, cracks and internal rips, which may be detrimental to the mechanical properties and the structural integrity of the fuel grain. In this context, this paper deals with a wide calorimetric, thermo-mechanical and physical characterization of the paraffin wax selected to manufacture the hybrid rocket engines (HRE) fuel grain, in order to gain a thorough knowledge of the material necessary to avoid the formation of critical defects. Several manufacturing methods were investigated, and it was found that only laboratory scale processes, based on the use of a heated circular mould-piston apparatus, are able to avoid the formation of critical defects, with the application of both high temperature and pressure. Keywords: Paraffin wax, Hybrid rockets, Manufacturing, SASOL® 0907, Regression rat
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