Including Memory Effects Research Articles

Overall judgment of loudness of time-varying sounds.

Listeners can judge the overall loudness of time-varying sounds quite easily, i.e., assign a single value that represents the loudness of the entire sound. This holds even if the duration is long and the judgment includes memory effects. Different metrics for calculating overall loudness have been developed. They agree that overall loudness is higher than the mean of loudness over time. Percentiles like the N5, the loudness being exceeded 5% of the time, are adopted by ISO 532-1. In the present study the concept of an energy mean known from level measurements (ISO 1996-1) was applied to the loudness domain. This equivalent continuous loudness level, LLP, was compared to the N5 using a set of real-world sounds that was orthogonal between the two metrics over a wide dynamic range of 30 phon. Cross-modality matching with line length was used in three experiments with a focus on either the overall judgment of loudness, continuous judgment while a sound was played, or both. The LLP showed considerably higher correlations with overall judgments than N5. Comparing continuous instantaneous judgment with calculated instantaneous loudness suggests that the participants might have focused on the sounds' prominent portions.

Multinucleon transfer in central collisions of U238+U238

Quantal diffusion mechanism of nucleon exchange is studied in the central collisions of $^{238}$U + $^{238}$U in the framework of the stochastic mean-field (SMF) approach. For bombarding energies considered in this work, the di-nuclear structure is maintained during the collision. Hence, it is possible to describe nucleon exchange as a diffusion process for mass and charge asymmetry. Quantal neutron and proton diffusion coefficients, including memory effects, are extracted from the SMF approach and the primary fragment distributions are calculated.

Memory effects on epidemic evolution: The susceptible-infected-recovered epidemic model.

Memory has a great impact on the evolution of every process related to human societies. Among them, the evolution of an epidemic is directly related to the individuals' experiences. Indeed, any real epidemic process is clearly sustained by a non-Markovian dynamics: memory effects play an essential role in the spreading of diseases. Including memory effects in the susceptible-infected-recovered (SIR) epidemic model seems very appropriate for such an investigation. Thus, the memory prone SIR model dynamics is investigated using fractional derivatives. The decay of long-range memory, taken as a power-law function, is directly controlled by the order of the fractional derivatives in the corresponding nonlinear fractional differential evolution equations. Here we assume “fully mixed” approximation and show that the epidemic threshold is shifted to higher values than those for the memoryless system, depending on this memory “length” decay exponent. We also consider the SIR model on structured networks and study the effect of topology on threshold points in a non-Markovian dynamics. Furthermore, the lack of access to the precise information about the initial conditions or the past events plays a very relevant role in the correct estimation or prediction of the epidemic evolution. Such a “constraint” is analyzed and discussed.

Neurons in Primate Visual Cortex Alternate between Responses to Multiple Stimuli in Their Receptive Field.

A fundamental question concerning representation of the visual world in our brain is how a cortical cell responds when presented with more than a single stimulus. We find supportive evidence that most cells presented with a pair of stimuli respond predominantly to one stimulus at a time, rather than a weighted average response. Traditionally, the firing rate is assumed to be a weighted average of the firing rates to the individual stimuli (response-averaging model) (Bundesen et al., 2005). Here, we also evaluate a probability-mixing model (Bundesen et al., 2005), where neurons temporally multiplex the responses to the individual stimuli. This provides a mechanism by which the representational identity of multiple stimuli in complex visual scenes can be maintained despite the large receptive fields in higher extrastriate visual cortex in primates. We compare the two models through analysis of data from single cells in the middle temporal visual area (MT) of rhesus monkeys when presented with two separate stimuli inside their receptive field with attention directed to one of the two stimuli or outside the receptive field. The spike trains were modeled by stochastic point processes, including memory effects of past spikes and attentional effects, and statistical model selection between the two models was performed by information theoretic measures as well as the predictive accuracy of the models. As an auxiliary measure, we also tested for uni- or multimodality in interspike interval distributions, and performed a correlation analysis of simultaneously recorded pairs of neurons, to evaluate population behavior.

Quantal nucleon diffusion: Central collisions of symmetric nuclei

Quantal diffusion mechanism of nucleon exchange is studied in the central collisions of several symmetric heavy-ion collisions in the framework of the Stochastic Mean-Field (SMF) approach. Since at bombarding energies below the fusion barrier, di-nuclear structure is maintained, it is possible to describe nucleon exchange as a diffusion process familiar from deep-inelastic collisions. Quantal diffusion coefficients, including memory effects, for proton and neutron exchanges are extracted microscopically employing the SMF approach. The quantal calculations of neutron and proton variances are compared with the semi-classical results.

Les effets du contact par le regard : un enjeu thérapeutique ?

IntroductionThe perception of a direct gaze – that is, of another individual's gaze directed at the observer that leads to eye contact – is known to influence a wide range of cognitive processes and behaviors. We stress that these effects mainly reflect positive impacts on human cognition and may thus be used as relevant tools for therapeutic purposes. ObjectivesIn this review, we aim (1) to provide an exhaustive review of eye contact effects while discussing the limits of the dominant models used to explain these effects, (2) to illustrate the therapeutic potential of eye contact by targeting those pathologies that show both preserved gaze processing and deficits in one or several functions that are targeted by the eye contact effects, and (3) to propose concrete ways in which eye contact could be employed as a therapeutic tool. Discussion(1) We regroup the variety of eye contact effects into four categories, including memory effects, activation of prosocial behavior, positive appraisals of self and others and the enhancement of self-awareness. We emphasize that the models proposed to account for these effects have a poor predictive value and that further descriptions of these effects is needed. (2) We then emphasize that people with pathologies that affect memory, social behavior, and self and/or other appraisal, and self-awareness could benefit from eye contact effects. We focus on depression, autism and Alzheimer's disease to illustrate our proposal. To our knowledge, no anomaly of eye contact has been reported in depression. Patients suffering from Alzheimer disease, at the early and moderate stage, have been shown to maintain a normal amount of eye contact with their interlocutor. We take into account that autism is controversial regarding whether gaze processing is preserved or altered. In the first view, individuals are thought to elude or omit gazing at another's eyes while in the second, individuals are considered to not be able to process the gaze of others. We adopt the first stance following the view that people with autism are not interested in processing social signals such as gaze but could do so efficiently if properly motivated. For each pathology we emphasize that eye contact could be used, for example, to enhance sensitivity to bodily states, thus improving emotional decision making (in autism); to lead to more positive appraisal of the self and others (in depression); to improve memory performances (in Alzheimer disease) and, more generally, to motivate the recipient to engage in the therapeutic process. (3) Finally we propose two concrete ways to employ eye contact effects as a therapeutic tool. The first is to develop cognitive-behavioral tools to learn and/or motivate the recipient to create frequent and prolonged eye contact periods. The second is to raise awareness among caregivers of the beneficial effects of eye contact and to teach them the way to use eye contact to reach its optimum effects. Future investigations are however needed to explore the ways in which eye contact effects can be efficiently integrated in therapeutic strategies, as well as to identify the clinical populations that can benefit from such therapeutic interventions.

Functional Mode Hot Electron Transfer Theory

Charge carriers that have been driven out of thermal equilibrium by their excessive vibrational energies are termed hot carriers. A theory has been developed to model the injection of these vibrationally excited electrons by explicitly accounting for the time-dependent thermal relaxation of the electron-transfer driving vibrational mode, as ascertained using functional mode analysis. Specifically, the thermal relaxation rate of the driving mode is first determined through the so-called frozen-phonon approach after which the energy-dependent line shape function is revisited to include memory effects for the vibrational quanta within the framework of Fermi’s golden rule. As shown by the numerical simulations of a 6-methyl-azulene-2-carboxylic acid dye molecule bound to an anatase TiO2[101] surface, our new theory not only yields persistently faster electron injection rates with higher incident photon energy but also exhibits a sharp increase when the vibrational quanta of the photoexcited dye molecule chang...

Determination of Boron Isotope Ratios in Tooth Enamel by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) After Matrix Separation by Ion Exchange Chromatography

Boron isotopes in teeth has been a new proxy for dietary reconstructions and its resistance to diagenetic alteration. In this study a method using inductively coupled plasma source mass spectrometry (ICP-MS) for the measurement of boron isotope ratio in human dental enamel has been developed. Human dental enamel were digested with HNO3-H2O2 in a microwave system. Boron in solution was separated from the matrix components using Amberlite IRA-743 resin. The factors that may affect precision and accuracy in isotope ratio determination by ICP-MS, including memory effects, mass bias drift, and concentration effects, were investigated to obtain optimum conditions. Then, the 10B/11B ratios in teeth were measured. The results showed that 2% of HNO3 + 2% of NH3•H2O, selected as the diluent/rinse solution could be effective in the elimination of boron memory effect. There was no concentration effect on boron isotope ratios when the ratio of samples B concentration to standard B concentration (refers to Csample/Cstd) varied from 0.5 to 2. The result of 10B/11B ratios in tooth enamel by sex and age fluctuated over a broad range, ranged from 0.2007 to 0.2574. This method is expected to be used for boron isotope ratio analyses in archeometry, forensic identification, paleoecology, and other disciplines in the future.

Lagrangian quantum turbulence model based on alternating superfluid/normal fluid stochastic dynamics

Inspired by recent measurements of the velocity and acceleration statistics of Lagrangian tracer particles embedded in a turbulent quantum liquid we propose a new superstatistical model for the dynamics of tracer particles in quantum turbulence. Our model consists of random sequences S/N/S/… where the particle spends some time being trapped on vortex lines of the superfluid (S) and some time in the normal liquid (N). This model leads to a superposition of power law distributions generated in the superfluid and Gaussian distributions in the normal liquid, in excellent agreement with experimental measurements. We include memory effects into our analysis and present analytic predictions for probability densities and correlation functions.

The Influence of Human Heterogeneity to Information Spreading

Humans are an integral part of the wide world and material areas, and morphological difference is widespread. In this paper, we propose a model to emphasize the influence of human heterogeneity to information spreading on social networks, and the properties including memory effects, social reinforcement, non-redundancy and human heterogeneity are taken into account. Simulation results indicate that the small-world networks generate the most effective spreading for the stronger human heterogeneity; however, for the weaker human heterogeneity, the regular networks will be more effective. In addition, for a given BA scale-free network, the stronger human heterogeneity will be more conducive to information spreading.

Analytical modelling of an U-Oscillating Water Column and performance in random waves

The oscillating water column (OWC) technology is recognized as one of the most effective solutions for exploiting sea wave energy in a scenario including hundreds of promising devices. In this context, the novel U-OWC device has been recently introduced as a further development of the OWC. This device differs from the conventional OWC as it utilizes a small vertical U-duct for connecting the air pocket to the open wave field. The objective of this paper is to propose a consistent representation of the wave field interacting with the U-OWC in the context of a linearized theory of water waves and, then, an analytical description of the U-OWC dynamics. Such a representation overcomes the drawbacks of the analytical models proposed, at the present time, in the open literature. Moreover, it allows including memory effects previously neglected.Next, the performance of the U-OWC is investigated by Monte Carlo simulations. In this regard, several simulations are produced for testing the efficiency of the device in sea waves compatible with power spectral density of wind-generated waves and of swells. The efficiency is evaluated according to a number of parameters, that allow highlighting the remarkable amount of energy absorbed by the system. The influence of the turbine is investigated, as well, by comparing the performance of monoplane (with and without guide vanes), biplane and contra-rotating turbines.

Memory effects in spontaneous emission processes

We consider a quantum-mechanical analysis of spontaneous emission in terms of an effective two-level system with a vacuum decay rate ${\ensuremath{\Gamma}}_{0}$ and transition angular frequency ${\ensuremath{\omega}}_{A}$. Our analysis is in principle exact, even though presented as a numerical solution of the time evolution including memory effects. The results so obtained are confronted with previous discussions in the literature. In terms of the dimensionless lifetime $\ensuremath{\tau}=t{\ensuremath{\Gamma}}_{0}$ of spontaneous emission, we obtain deviations from exponential decay of the form $O(1/\ensuremath{\tau})$ for the decay amplitude as well as the previously obtained asymptotic behaviors of the form $O(1/{\ensuremath{\tau}}^{2})$ or $O(1/\ensuremath{\tau}{\mathrm{ln}}^{2}\ensuremath{\tau})$ for $\ensuremath{\tau}\ensuremath{\gg}1$. The actual asymptotic behavior depends on the adopted regularization procedure as well as on the physical parameters at hand. We show that for any reasonable range of $\ensuremath{\tau}$ and for a sufficiently large value of the required angular frequency cutoff ${\ensuremath{\omega}}_{c}$ of the electromagnetic fluctuations, i.e., ${\ensuremath{\omega}}_{c}\ensuremath{\gg}{\ensuremath{\omega}}_{A}$, one obtains either a $O(1/\ensuremath{\tau})$ or a $O(1/{\ensuremath{\tau}}^{2})$ dependence. In the presence of physical boundaries, which can change the decay rate with many orders of magnitude, the conclusions remains the same after a suitable rescaling of parameters.

Analysis and Design of Low Phase-Noise Oscillators With Nonlinear Resonators

It is known that the dynamics and phase noise of resonator-based self-sustained nonlinear oscillators is affected by the presence of a nonlinear resonator. In fact, it has been shown that resonator nonlinearity can enhance the oscillator phase noise under certain conditions. This paper offers a new formulation and analytical approach to describe the effect of resonator nonlinearity on the phase noise of self-sustained oscillators. The analysis applies properties of stochastic Ito integrals to oscillator's averaged stochastic nonlinear differential equations with periodic steady state solutions. The results offer insight into designing low phase-noise oscillators with nonlinear resonators. We show that for a given nonlinear oscillator topology, there is an optimum power incident on the resonator that minimizes the phase noise. As a proof of concept, the analysis is applied to a 1.5-GHz CMOS oscillator that uses a nonlinear film bulk acoustic resonator (FBAR). A nonlinear model including memory effects for the FBAR is proposed and used in the formulation. At the optimum design point, the oscillator shows measured phase noise of -110 dBc/Hz at 1 kHz, -125 dBc/Hz at 10 kHz, -145 dBc/Hz at 100 kHz, and -160 dBc/Hz at 10-MHz offset frequencies while consuming 40 mW of dc power. This results in 10 fs of timing jitter.

Time Analysis of the Three Characteristic Behaviours of Dual-Porosity Media. I: Fluid Flow and Solute Transport

Homogenisation of consolidation and compressible fluid flow in dual-porosity media has highlighted the existence of three characteristic macroscopic behaviours. These three behaviours are, namely, a dual-porosity description which includes memory effects, a single-porosity description with which the microporosity is simply ignored and an intermediate behaviour which we refer as behaviour with reservoir effect. With this latter, the whole dual-porosity medium is represented by an equivalent single-porosity medium. In contrast with a single-porosity behaviour, the porosity of the entire dual-porosity medium is accounted for. During solute transport in dual-porosity media, while memory effects are most often experimentally observed, the homogenised model obtained for the most general values of the involved parameters leads to a model with reservoir effect. Therefore, the observed memory effects are not reproduced by this model and a clear interpretation of the origins of these effects remains an unresolved issue. The study is presented in two complementary articles. The objective of this article is, first, to determine a physical interpretation of the existence of the three characteristic behaviours of dual-porosity media. This is performed by exploring the homogenised models and their domains of validity for the analogy of heat conduction in a dual-conductivity composite. This leads to the original result that consists to relate each type of behaviour to a specific relationship between two characteristic times. This is then used for interpreting the results obtained for compressible flow in dual-porosity media. Finally, it allows to elucidate the conditions under which memory effects may occur during solute transport in dual-porosity media.

Relaxation of excited molecules in a medium with memory at short and long times

Two qualitatively different approaches to the dynamics of vibrational wave packets in the presence of medium-induced relaxation, with taking into account relaxation memory effects and without taking them into account (Makovian approximation) were compared for a molecular system with one vibrational degree of freedom (the Morse oscillator) in a medium. The time evolution of the populations of levels, mean system energy, and response of “pumping-probing” experiments were calculated. It was found that, as distinct from the Markovian approximation, the approach including memory effects can predict the evolution of a molecular system satisfying the detailed equilibrium principle. The two approaches specified also predict the existence of a qualitative difference of phase characteristics in the behavior of the system at short times.

Robustness Analysis of a Boolean Model of Gene Regulatory Network with Memory

The response to different kinds of perturbations of a discrete model of gene regulatory network, which is a generalization of the random Boolean network (RBN) model, is discussed. The model includes memory effects, and the analysis pays particular attention to the influence on the system stability of a parameter (i.e., the decay time of the gene products) that determines the duration of the memory effects. It is shown that this parameter deeply affects the overall behavior of the system, with special regard to the dynamical regimes and the sensitivity. Furthermore, a noteworthy divergence in the response of systems characterized by different memory lengths in the presence of either temporary or permanent damages is highlighted, as is the substantial difference, with respect to classical RBNs, between the specific dynamical regime and the landscape of the attractors.

Simulations of a non-Markovian description of nucleation

In most nucleation theories, the state of a nucleating system is described by a distribution of droplet masses and this distribution evolves as a memoryless stochastic process. This is incorrect for a large class of nucleating systems. In a recent paper [J. Kuipers and G. T. Barkema, Phys. Rev. E 79, 062101 (2009)], we presented a non-Markovian model for droplet growth that includes memory effects and this model was treated analytically in the absence of a free energy landscape. In this paper, the model is considered with a free energy barrier present. Nucleation rates are measured in the prototypical example of nucleation in the Ising model. Results of direct simulations and the non-Markovian theory agree within a factor of 2 for spin-flip dynamics, and within 20% for local spin-exchange dynamics, even though the measured nucleation rates vary over 27 orders of magnitude.

Interrogation of a dynamic multi-catalyst ensemble in asymmetric catalysis

The ‘Trost Standard Ligand’ (2) is a chiral diphosphine ligand that distinguishes itself by the high selectivity it induces in the Pd-catalysed reactions of allylic substrates that generate slim cyclic or small linear intermediates. However, a range of unusual features, including memory effects, inverse dependence of selectivity and rate on catalyst concentration, high sensitivity to counter-ion, particularly chloride, and decreasing enantioselectivities at lower temperatures, are often encountered, thus requiring considerable optimisation of reaction conditions to attain optimum selectivity. These features can be accounted for by a model involving a dynamic multi-catalyst ensemble. To gain evidence for this model, the manner in which diphosphine 2 interacts with Pd–allyl cations, and in particular the higher-order systems it generates, has been investigated by use of NMR, isotopic labelling, polarimetry, UV, neutron scattering, X-ray crystallography and molecular modeling. Ligand 2 coordinates to Pd–allyl cations to generate a mononuclear P,P-chelate. This is found to readily form non-chelate oligomers, present in a range of forms, including rings, for which high homochiral selectivity in oligomerisation is demonstrated by the technique of pseudoenantiomers. All of these species are in relatively rapid equilibrium, with half-lives for interconversion in the range 2–6 s. Higher-order aggregation is also detected, and thus at even moderate concentrations (>50 mM) large rod-like aggregates are formed.

Ultrafast electron dynamics in metals: Real-time analysis of a reflected light field using photoelectrons

We propose an approach to address ultrafast charge-carrier dynamics of metals by analyzing the momentum change in photoelectrons interacting with a transient optical grating at a metal surface. Photoelectrons are excited by an ultraviolet femtosecond laser pulse which precedes an infrared pulse setting up the transient grating. We measure the kinetic energy of the photoelectrons which are accelerated by the grating's ponderomotive potential and thus sample the respective electric field. The method is capable to access phase and amplitude differences between the incoming and the reflected light fields. The latter is determined by the response of the conduction-band electrons to the light field. We report on a demonstration of such an experimental scheme using a Gd(0001) surface and calculate the reflected field by a simplified transport equation. We derive a method to determine the average electron-scattering rate and study the time-dependent evolution of amplitude and phase of the reflected electric field including memory effects in the optically induced polarization dynamics. Finally, we discuss the required steps of this approach to probe ultrafast dynamics in metals experimentally.

Statistical mechanical theory for steady state systems. VIII. General theory for a Brownian particle driven by a time- and space-varying force

A Brownian particle subject to a time- and space-varying force is studied with the second entropy theory for nonequilibrium statistical mechanics. A fluctuation expression is obtained for the second entropy of the path, and this is maximized to obtain the most likely path of the particle. Two approaches are used, one based on the velocity correlation function and one based on the position correlation function. The approaches are a perturbation about the free particle result and are exact for weak external forces. They provide a particularly simple way of including memory effects in time-varying driven diffusion. The theories are tested against computer simulation data for a Brownian particle trapped in an oscillating parabolic well. They accurately predict the phase lag and amplitude as a function of drive frequency, and they account quantitatively for the memory effects that are important at high frequencies and that are missing in the simplest Langevin equation.