Non-equilibrium and information: the role of cross-correlations

We discuss the relevance of information contained in cross-correlations among different degrees of freedom, which is crucial in non-equilibrium systems. In particular we consider a stochastic system where two degrees of freedom $X_1$ and $X_2$ - in contact with two different thermostats - are coupled together. The production of entropy and the violation of equilibrium fluctuation-dissipation theorem (FDT) are both related to the cross-correlation between $X_1$ and $X_2$. Information about such cross-correlation may be lost when single-variable reduced models, for $X_1$, are considered. Two different procedures are typically applied: (a) one totally ignores the coupling with $X_2$; (b) one models the effect of $X_2$ as an average memory effect, obtaining a generalized Langevin equation. In case (a) discrepancies between the system and the model appear both in entropy production and linear response; the latter can be exploited to define effective temperatures, but those are meaningful only when time-scales are well separated. In case (b) linear response of the model well reproduces that of the system; however the loss of information is reflected in a loss of entropy production. When only linear forces are present, such a reduction is dramatic and makes the average entropy production vanish, posing problems in interpreting FDT violations.Comment: 30 pages, 4 figures, 4 appendixe

Dynamic Response of Cantilever Retaining Walls Considering Soil Non-Linearity

For many decades the analysis of earth retaining structures under dynamic or seismic conditions has been carried out by means of standard limit equilibrium (Coulomb, M-O) or elastic methods (Wood, Veletsos and Younan). These approaches are simplified, as they make use of considerable approximations which are often applicable only under particular conditions. A different and perhaps more realistic approach is possible using established computer codes, which integrate numerically the governing equations of the soil and wall media. Since these problems may involve significant levels of strain in the backfill, material non-linearity should be taken into account to realistically simulate the response of the system. In the herein-reported study, a parametric analysis is carried out through the finite-difference code FLAC 5.0. Starting from simple cases involving elastic response, and moving gradually towards more realistic conditions, salient features of the dynamic wall-soil interaction problem are addressed. The case of non-linear hysteretic behaviour of soil and flexibility of wall is considered at a second stage. Results indicate that with increasing levels of acceleration, there is a clear transition from elastic behaviour (in which the aforementioned V-Y type methods are applicable), to plastic behaviour in which M-O methods are thought to be more suitable under pseudo-static conditions. The results of the parametric analyses are reported in terms of pertinent normalized parameters, to provide a general framework for the assessment of wall-soil dynamic interaction under strong seismic excitation

Approaches, Strategies and Theoretical and Practice-Based Research Methods to investigate and archive video art:Some reflections from the REWIND projects

This paper will discuss methodologies, approaches and issues, emerging out of three major research projects that have investigated early histories of video art in Europe: REWIND (2004 ongoing), REWINDItalia (2011-2014) and EWVA (2015-2018). The paper will discuss how the projects have engaged with the history of the apparatus, the identity and status of the artworks, preservation methods, and the legacy of these video artworks today. A particular focus will be on semi-structured questionnaires for interviews structured to capture oral histories, memories and recollections, that in some cases would have been otherwise lost to future knowledge and the uncovering of lost artworks and their available documentation. The speakers directly involved in the projects - will discuss solutions, risks and experiences encountered in the projects and future research perspectives for re-covering, collecting, archiving and narrating the histories of early video art in Europe. The paper will discuss also different practice-based research methods, platforms and engagement strategies, including re-installation and re-enactment

Transient Overload Characteristics of PM-Assisted Synchronous Reluctance Machines, Including Sensorless Control Feasibility

Synchronous reluctance machines are a highefficiency alternative to induction motors for variable-speed applications. To mitigate the well-known downside of their lower power factor, permanent-magnet-assisted topologies, in which either rare-earth or ferrite magnets are inserted into the rotor in suitable quantities, are often adopted. The design and optimization procedures for PM-assisted topologies have been thoroughly discussed in the related literature. This paper compares synchronous reluctance machines assisted with NdFeB and ferrite magnets, focusing on torque overload capability and feasibility of saliency-based position estimation algorithms. Three prototypes were realized and tested. They all have the stator of a commercial induction motor and the same customdesigned synchronous reluctance rotor laminations. Of the three prototypes, one is a pure synchronous reluctance motor, and the other two have NdFeB and ferrite magnets, respectively; both are designed to give the same torque at rated current. Results from simulations and experiments are presented comparing the transient overload capability of the three machines, in terms of torque capability and de-magnetization limit. A dynamic thermal model of the machines was developed within this scope. Moreover, the feasibility of saliency-based sensorless methods was investigated and is presented here for the three machines, both at high- and low-current loads. The results of the paper suggest that the ferrite-assisted solution is the best candidate for replacing induction motors in variable-speed applications, for its optimal tradeoff between performance and cost

Vaccination against Clostridium difficile using toxin fragments: Observations and analysis in animal models

Clostridium difficile is a major cause of antibiotic associated diarrhea. Recently, we have shown that effective protection can be mediated in hamsters through the inclusion of specific recombinant fragments from toxin A and B in a systemically delivered vaccine. Interestingly while neutralizing antibodies to the binding domains of both toxin A and B are moderately protective, enhanced survival is observed when fragments from the glucosyltransferase region of toxin B replace those from the binding domain of this toxin. In this addendum, we discuss additional information that has been derived from such vaccination studies. This includes observations on efficacy and cross-protection against different ribotypes mediated by these vaccines and the challenges that remain for a vaccine which prevents clinical symptoms but not colonization. The use and value of vaccination both in the prevention of infection and for treatment of disease relapse will be discussed

Non-equilibrium thermodynamics. IV: Generalization of Maxwell, Claussius-Clapeyron and Response Functions Relations, and the Prigogine-Defay Ratio for Systems in Internal Equilibrium

We follow the consequences of internal equilibrium in non-equilibrium systems that has been introduced recently [Phys. Rev. E 81, 051130 (2010)] to obtain the generalization of Maxwell's relation and the Clausius-Clapeyron relation that are normally given for equilibrium systems. The use of Jacobians allow for a more compact way to address the generalized Maxwell relations; the latter are available for any number of internal variables. The Clausius-Clapeyron relation in the subspace of observables show not only the non-equilibrium modification but also the modification due to internal variables that play a dominant role in glasses. Real systems do not directly turn into glasses (GL) that are frozen structures from the supercooled liquid state L; there is an intermediate state (gL) where the internal variables are not frozen. Thus, there is no single glass transition. A system possess several kinds of glass transitions, some conventional (L \rightarrow gL; gL\rightarrow GL) in which the state change continuously and the transition mimics a continuous or second order transition, and some apparent (L\rightarrow gL; L\rightarrow GL) in which the free energies are discontinuous so that the transition appears as a zeroth order transition, as discussed in the text. We evaluate the Prigogine-Defay ratio {\Pi} in the subspace of the observables at these transitions. We find that it is normally different from 1, except at the conventional transition L\rightarrow gL, where {\Pi}=1 regardless of the number of internal variables.Comment: 42 pages, 3 figures, citations correcte

Monte Carlo studies of the ordering of the one-dimensional Heisenberg spin glass with long-range power-law interactions

The nature of the ordering of the one-dimensional Heisenberg spin-glass model with a long-range power-law interaction is studied by extensive Monte Carlo simulations, with particular attention to the issue of the spin-chirality decoupling/coupling. Large system sizes up to $L=4096$ are studied. With varying the exponent $\sigma$ describing the power-law interaction, we observe three distinct types of ordering regimes. For smaller $\sigma$, the spin and the chirality order at a common finite temperature with a common correlation-length exponent, exhibiting the standard spin-chirality coupling behavior. For intermediate $\sigma$, the chirality orders at a temperature higher than the spin, exhibiting the spin-chirality decoupling behavior. For larger $\sigma$, both the spin and the chirality order at zero temperature. We construct a phase diagram in the $\sigma$ versus the temperature plane, and discuss implications of the results. Critical properties associated with both the chiral-glass and the spin-glass transitions are also determined.Comment: 28 pages, 26 figures, to appear in J. Phys. Soc. Jp

Analysis of overload and sensorless control capability of PM-assisted synchronous reluctance machines

Synchronous reluctance machines are a valid alternative to induction motors for industrial applications requiring variable speed regulation. To mitigate the well-known downside of their lower power factor, permanent-magnetassisted topologies are adopted. Both high-strength rare-earth magnets and low cost ferrite magnets can be used in such machines. Their design and optimization procedures have been discussed in related literature. This paper compares synchronous reluctance machines assisted with NdFeB and ferrite magnets, focusing on torque overload capability and feasibility of saliencybased position estimation algorithms. Three prototypes were realized and tested. They all have the stator of a commercial induction motor, and three custom synchronous reluctance rotors with same laminations: one has no magnets, the other two have NdFeB and ferrite magnets respectively, designed to give the same torque at rated current. Results from simulations and experiments are presented, focusing on torque and demagnetization limits in the over-current loading range. Moreover, the feasibility of saliency-based sensorless methods is investigated, both at high and low current loads. The results of the paper suggest that the ferrite-assisted solution is the candidate solution for replacing induction motors in variable speed applications

Identification of the critical temperature from non-equilibrium time-dependent quantities

We present a new procedure able to identify and measure the critical temperature. This method is based on the divergence of the relaxation time approaching the critical point in quenches from infinite temperature. We introduce a dimensionless quantity that turns out to be time-independent at the critical temperature. The procedure does not need equilibration and allows for a relatively fast identification of the critical temperature. The method is first tested in the ferromagnetic Ising model and then applied to the one-dimensional Ising spin glass with power-law interactions. Here we always find a finite critical temperature also in presence of a uniform external field, in agreement with the mean-field picture for the low temperature phase of spin glasses.Comment: 6 pages, 10 figure

Replica analysis of a preferential urn model

We analyse a preferential urn model with randomness using the replica method. The preferential urn model is a stochastic model based on the concept "the rich get richer." The replica analysis clarifies that the preferential urn model with randomness shows a fat-tailed occupation distribution. The analytical treatments and results would be useful for various research fields such as complex networks, stochastic models, and econophysics.Comment: 6 pages, 2 figure