A new species of Monocondylaeinae from the Amazon basin, and some considerations on this subfamily in the hydrographic systems of South America

In this work Tamsiella amazonica nov. sp. a new species of Nayades of the genus Tamsiella HAAS, belonging to the Juruá River, an affluent of the Solimões River, between Taumaturgo and Fóz do Bréu, Brazil, is described. At the same time an analysis and new regrouping of the existing genera of Monocondylaeinae, is made, giving some considerations about the geographical distribution of its genera in South American waters and its probable phyletic relationship

Fluctuations relation and external thermostats: an application to granular materials

In this note we discuss a paradigmatic example of interacting particles subject to non conservative external forces and to the action of thermostats consisting of external (finite) reservoirs of particles. We then consider a model of granular materials of interest for experimental tests that had recently attracted lot of attentions. This model can be reduced to the previously discussed example under a number of assumptions, in particular that inelasticity due to internal collisions can be neglected for the purpose of measuring the large deviation functional for entropy production rate. We show that if the restitution coefficient in the granular material model is close to one, then the required assuptions are verified on a specific time scale and we predict a fluctuation relation for the entropy production rate measured on the same time scale.Comment: 7 pages; updated to take into account comments received on the first version; to appear on J.Stat.Mech.(2006

Controllability for chains of dynamical scatterers

In this paper, we consider a class of mechanical models which consists of a linear chain of identical chaotic cells, each of which has two small lateral holes and contains a rotating disk at its center. Particles are injected at characteristic temperatures and rates from stochastic heat baths located at both ends of the chain. Once in the system, the particles move freely within the cells and will experience elastic collisions with the outer boundary of the cells as well as with the disks. They do not interact with each other but can transfer energy from one to another through collisions with the disks. The state of the system is defined by the positions and velocities of the particles and by the angular positions and angular velocities of the disks. We show that each model in this class is controllable with respect to the baths, i.e. we prove that the action of the baths can drive the system from any state to any other state in a finite time. As a consequence, one obtains the existence of at most one regular invariant measure characterizing its states (out of equilibrium)

The Nora Virtual Tour: an immersive visit in the ancient city

The ancient city of Nora was a Phoenician, Punic and Roman settlement rising on a peninsula in the south-western coast of Sardinia. Since 1990, the University of Padova has been carrying on an interdisciplinary research project of excavation, architectural analysis, historical reconstruction and cultural promotion of tourism in this site. The excavations allow us to increase our knowledge of Middle Imperial Roman urban planning and to get a better understanding of the whole city and its history; the restoration of excavated monuments using gravels with different colours helps more than 60,000 tourists every year to recognize the function of different areas. In spite of this, visitors experience difficulty in understanding a landscape of ruins with barely visible evidence. Thus, a complete virtual reconstruction of the ancient city has become essential. 3D models of the Phoenician and Roman settlement have been developed, reshaping archaeological plans produced in 25 years by Universities that work in the site. The main monuments of the Roman city and the major crossroads have been rendered in greater detail, using sample-based textures that give a photorealistic effect and implementing the models with furniture and decorations selected through reliable sources of information. 3D reconstructions are now available for tourist groups led by a guide in the Nora Virtual Tour: stereoscopic images have been rendered and uploaded in an app for mobile headsets that provides immersive virtual reality for the users. The guide controls the devices with a tablet using a Bluetooth connection: at the beginning of the visit, the tourists can view equirectangular panoramas of the ruins taken from a helicopter, then they are accompanied to hot-spots where the ancient monuments are shown in an evocative Roman reconstruction

Normal Heat Conductivity in a strongly pinned chain of anharmonic oscillators

We consider a chain of coupled and strongly pinned anharmonic oscillators subject to a non-equilibrium random forcing. Assuming that the stationary state is approximately Gaussian, we first derive a stationary Boltzmann equation. By localizing the involved resonances, we next invert the linearized collision operator and compute the heat conductivity. In particular, we show that the Gaussian approximation yields a finite conductivity $\kappa\sim\frac{1}{\lambda^2T^2}$, for $\lambda$ the anharmonic coupling strength.Comment: Introduction and conclusion modifie

Propagation of Chaos for a Thermostated Kinetic Model

We consider a system of N point particles moving on a d-dimensional torus. Each particle is subject to a uniform field E and random speed conserving collisions. This model is a variant of the Drude-Lorentz model of electrical conduction. In order to avoid heating by the external field, the particles also interact with a Gaussian thermostat which keeps the total kinetic energy of the system constant. The thermostat induces a mean-field type of interaction between the particles. Here we prove that, starting from a product measure, in the large N limit, the one particle velocity distribution satisfies a self consistent Vlasov-Boltzmann equation.. This is a consequence of "propagation of chaos", which we also prove for this model.Comment: This version adds affiliation and grant information; otherwise it is unchange

Heat transport in stochastic energy exchange models of locally confined hard spheres

We study heat transport in a class of stochastic energy exchange systems that characterize the interactions of networks of locally trapped hard spheres under the assumption that neighbouring particles undergo rare binary collisions. Our results provide an extension to three-dimensional dynamics of previous ones applying to the dynamics of confined two-dimensional hard disks [Gaspard P & Gilbert T On the derivation of Fourier's law in stochastic energy exchange systems J Stat Mech (2008) P11021]. It is remarkable that the heat conductivity is here again given by the frequency of energy exchanges. Moreover the expression of the stochastic kernel which specifies the energy exchange dynamics is simpler in this case and therefore allows for faster and more extensive numerical computations.Comment: 21 pages, 5 figure

Intriguing Heat Conduction of a Polymer Chain

We study heat conduction in a one-dimensional chain of particles with longitudinal as well as transverse motions. The particles are connected by two-dimensional harmonic springs together with bending angle interactions. Using equilibrium and nonequilibrium molecular dynamics, three types of thermal conducting behaviors are found: a logarithmic divergence with system sizes for large transverse coupling, 1/3 power-law at intermediate coupling, and 2/5 power-law at low temperatures and weak coupling. The results are consistent with a simple mode-coupling analysis of the same model. The 1/3 power-law divergence should be a generic feature for models with transverse motions.Comment: 4 page

Analyticity of the SRB measure for a class of simple Anosov flows

We consider perturbations of the Hamiltonian flow associated with the geodesic flow on a surface of constant negative curvature. We prove that, under a small perturbation, not necessarely of Hamiltonian character, the SRB measure associated to the flow exists and is analytic in the strength of the perturbation. An explicit example of "thermostatted" dissipative dynamics is constructed.Comment: 23 pages, corrected typo