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Transfer entropy

F S Borges, E L Lameu, K C Iarosz, P R Protachevicz, I L Caldas, R L Viana, E E N Macau, A M Batista, M S Baptista
The characterization of neuronal connectivity is one of the most important matters in neuroscience. In this work, we show that a recently proposed informational quantity, the causal mutual information, employed with an appropriate methodology, can be used not only to correctly infer the direction of the underlying physical synapses, but also to identify their excitatory or inhibitory nature, considering easy to handle and measure bivariate time series. The success of our approach relies on a surprising property found in neuronal networks by which nonadjacent neurons do "understand" each other (positive mutual information), however, this exchange of information is not capable of causing effect (zero transfer entropy)...
February 2018: Physical Review. E
Julian Gonzalez-Ayala, A Medina, J M M Roco, A Calvo Hernández
The connection between Carnot-like and low-dissipation refrigerators is proposed by means of their entropy generation and the optimization of two unified, compromise-based figures of merit. Their optimization shows that only a limited set of heat transfer laws in the Carnot-like model are compatible with the results stemming from the low-dissipation approximation, even though there is an agreement of the related physical spaces of variables. A comparison between two operation regimes and relations among entropy generation, efficiency, cooling power...
February 2018: Physical Review. E
Jian Zhang
Transfer entropy from non-uniform embedding is a popular tool for the inference of causal relationships among dynamical subsystems. In this study we present an approach that makes use of low-dimensional conditional mutual information quantities to decompose the original high-dimensional conditional mutual information in the searching procedure of non-uniform embedding for significant variables at different lags. We perform a series of simulation experiments to assess the sensitivity and specificity of our proposed method to demonstrate its advantage compared to previous algorithms...
2018: PloS One
Sezen Cekic, Didier Grandjean, Olivier Renaud
This article proposes a systematic methodological review and an objective criticism of existing methods enabling the derivation of time, frequency, and time-varying Granger-causality statistics in neuroscience. The capacity to describe the causal links between signals recorded at different brain locations during a neuroscience experiment is indeed of primary interest for neuroscientists, who often have very precise prior hypotheses about the relationships between recorded brain signals. The increasing interest and the huge number of publications related to this topic calls for this systematic review, which describes the very complex methodological aspects underlying the derivation of these statistics...
March 15, 2018: Statistics in Medicine
Irina I Ignatova, Andrew S French, Roman V Frolov
Natural visual scenes are rarely random. Instead, intensity and wavelength change slowly in time and space over many regions of the scene, so that neighboring temporal and spatial visual inputs are more correlated, and contain less information than truly random signals. It has been suggested that sensory optimization to match these higher order correlations (HOC) occurs at the earliest visual stages, and that photoreceptors can process temporal natural signals more efficiently than random signals. We tested this early stage hypothesis by comparing the information content of Calliphora vicina photoreceptor responses to naturalistic inputs before and after removing HOC by randomizing phase...
March 14, 2018: Journal of Neurophysiology
Hua-Xin Zhang, Dan Zhou, Qing-Hua Xia
In this work, the interaction of an anti-HIV drug lamivudine and human serum albumin (HSA) was studied by multispectroscopic and molecular modeling methods. The fluorescence emission spectra showed that the fluorescence of HSA was quenched by lamivudine through static mechanism with HSA-lamivudine complex produced at ground state. According to the binding equilibriums observed at 4 different temperatures, the number of binding site, binding constant, enthalpy change, entropy change, and Gibbs free energy change of the interaction were calculated...
March 7, 2018: Journal of Molecular Recognition: JMR
Yaming Yan, Linze Song, Qiang Shi
By employing several lattice model systems, we investigate the free energy barrier and real-time dynamics of charge separation in organic photovoltaic (OPV) cells. It is found that the combined effects of the external electric field, entropy, and charge delocalization reduce the free energy barrier significantly. The dynamic disorder reduces charge carrier delocalization and results in the increased charge separation barrier, while the effect of static disorder is more complicated. Simulation of the real-time dynamics indicates that the free charge generation process involves multiple time scales, including an ultrafast component within hundreds of femtoseconds, an intermediate component related to the relaxation of the hot charge transfer (CT) state, and a slow component on the time scale of tens of picoseconds from the thermally equilibrated CT state...
February 28, 2018: Journal of Chemical Physics
Tanmoy Sanyal, M Scott Shell
Bottom-up coarse grained (CG) models are now regularly pursued to enable large length and time scale molecular simulations of complex, often macromolecular systems. However, predicting fluid phase equilibria using such models remain fundamentally challenging. A major problem stems from the typically low transferability of CG models beyond the densities and/or compositions at which they are parameterized, which is necessary if they are to describe distinct structural and thermodynamic properties unique to each phase...
February 21, 2018: Journal of Physical Chemistry. B
Justin Faber, Dolores Bozovic
Experimental records of active bundle motility are used to demonstrate the presence of a low-dimensional chaotic attractor in hair cell dynamics. Dimensionality tests from dynamic systems theory are applied to estimate the number of independent variables sufficient for modelling the hair cell response. Poincaré maps are constructed to observe a quasiperiodic transition from chaos to order with increasing amplitudes of mechanical forcing. The onset of this transition is accompanied by a reduction of Kolmogorov entropy in the system and an increase in transfer entropy between the stimulus and the hair bundle, indicative of signal detection...
February 20, 2018: Scientific Reports
Krzysztof Ptaszyński
I study an autonomous quantum Maxwell's demon based on two exchange-coupled quantum dots attached to the spin-polarized leads. The principle of operation of the demon is based on the coherent oscillations between the spin states of the system which act as a quantum iSWAP gate. Due to the operation of the iSWAP gate, one of the dots acts as a feedback controller which blocks the transport with the bias in the other dot, thus inducing the electron pumping against the bias; this leads to the locally negative entropy production...
January 2018: Physical Review. E
Michael A Maloney, Ian Renshaw, Jonathon Headrick, David T Martin, Damian Farrow
Enhancing practice design is critical to facilitate transfer of learning. Considerable research has focused on the role of perceptual information in practice simulation, yet has neglected how affect and cognition are shaped by practice environments and whether this influences the fidelity of behavior (Headrick et al., 2015). This study filled this gap by examining the fidelity of individual (cognition, affect, and actions) and interpersonal behavior of 10 highly skilled Australian Taekwondo athletes fighting in training compared to competition...
2018: Frontiers in Psychology
Raju Kalaivani, Raju Reema, Narayanaswamy Srinivasan
The conserved function of protein phosphorylation, catalysed by members of protein kinase superfamily, is regulated in different ways in different kinase families. Further, differences in activating triggers, cellular localisation, domain architecture and substrate specificity between kinase families are also well known. While the transfer of γ-phosphate from ATP to the hydroxyl group of Ser/Thr/Tyr is mediated by a conserved Asp, the characteristic functional and regulatory sites are specialized at the level of families or sub-families...
February 13, 2018: PLoS Computational Biology
Bin Shi, Jiping Jiang, Bellie Sivakumar, Yi Zheng, Peng Wang
Field monitoring strategy is critical for disaster preparedness and watershed emergency environmental management. However, development of such is also highly challenging. Despite the efforts and progress thus far, no definitive guidelines or solutions are available worldwide for quantitatively designing a monitoring network in response to river chemical spill incidents, except general rules based on administrative divisions or arbitrary interpolation on routine monitoring sections. To address this gap, a novel framework for spatial-temporal network design was proposed in this study...
February 3, 2018: Water Research
Joseph L Servadio, Matteo Convertino
Development of composite indicators for integrated health in populations typically relies on a priori assumptions rather than model-free, data-driven evidence. Traditional variable selection processes tend not to consider relatedness and redundancy among variables, instead considering only individual correlations. In addition, a unified method for assessing integrated health statuses of populations is lacking, making systematic comparison among populations impossible. We propose the use of maximum entropy networks (MENets) that use transfer entropy to assess interrelatedness among selected variables considered for inclusion in a composite indicator...
February 2018: Science Advances
Cen Zhang, Rui Wang, Guowen Zhang, Deming Gong
Quercetin, one of the most abundant flavonoid in the daily diet, was found to reversibly inhibit the generation of uric acid and superoxide radicals (O2-)catalyzed by xanthine oxidase (XOD) in a mixed-type manner with IC50 values of (2.74±0.04)×10-6 and (2.90±0.03)×10-6molL-1, respectively, and the inhibition of quercetin on O2- generation may be ascribed to the reduced form of XOD by a ping-pong mechanism. XOD had one high affinity binding site for quercetin with a binding constant of 4.28×104Lmol-1 at 298K, and the binding process was predominately driven by van der Waals forces and hydrogen bonds on account of the negative enthalpy and entropy changes...
January 31, 2018: International Journal of Biological Macromolecules
Ludovic Troian-Gautier, Brian N DiMarco, Renato N Sampaio, Seth L Marquard, Gerald J Meyer
Recombination of electrons injected into TiO2 with molecular acceptors present at the interface represent an important loss mechanism in dye-sensitized water oxidation and photochemical electrical power generation. Herein, the kinetics for this interfacial electron transfer reaction to oxidized triphenylamine (TPA) acceptors was quantified over a 70° temperature range for para-methyl-TPA (Me-TPA) dissolved in acetonitrile solution, 4-[N,N-di(p-tolyl)amino]benzylphosphonic acid (a-TPA) anchored to the TiO2 interface, and a TPA covalently bound to a ruthenium sensitizer, [Ru(tpy-C6H4-PO3H2)(tpy-TPA)]2+ "RuTPA", where tpy is 2,2':6',2''-terpyridine...
February 5, 2018: Journal of the American Chemical Society
Junwen Chen, Yi Deng, Jingfeng Wang, Wenshi Lin
The recently developed maximum entropy production (MEP) model, an alternative parameterization of surface heat fluxes, is incorporated into the Weather Research and Forecasting (WRF) model. A pair of WRF cloud-resolving experiments (5 km grids) using the bulk transfer model (WRF default) and the MEP model of surface heat fluxes are performed to hindcast the October Madden-Julian oscillation (MJO) event observed during the 2011 Dynamics of the MJO (DYNAMO) field campaign. The simulated surface latent and sensible heat fluxes in the MEP and bulk transfer model runs are in general consistent with in situ observations from two research vessels...
November 2017: Journal of Advances in Modeling Earth Systems
Hiroshi Ashikaga, Ameneh Asgari-Targhi
To prevent sudden cardiac death, predicting where in the cardiac system an order-disorder phase transition into ventricular fibrillation begins is as important as when it begins. We present a computationally efficient, information-theoretic approach to predicting the locations of the wavebreaks. Such wavebreaks initiate fibrillation in a cardiac system where the order-disorder behavior is controlled by a single driving component, mimicking electrical misfiring from the pulmonary veins or from the Purkinje fibers...
January 31, 2018: Scientific Reports
Yang Zhou, Dong Zhou, Xi Jin, Lu Zhang, Xingyu Du, Bangsheng Li
High-entropy alloys have attracted much attention due to their unique microstructures and excellent properties. Since their invention more than ten years ago, research attention has been mainly focused on the study of multicomponent alloys with equiatomic or near-equiatomic compositions. Here we propose a novel design of non-equiatomic medium-entropy alloys that contain one matrix element and several equiatomic alloying elements. To verify the utility of this new design, a series of Co-free Fex(CrNiAl)100-x (at...
January 19, 2018: Scientific Reports
J Javier Brey, M I García de Soria, P Maynar
A Boltzmann-like kinetic equation for a quasi-two-dimensional gas of hard spheres is derived. The system is confined between two parallel hard plates separated a distance between one and two particle diameters. An entropy Lyapunov function for the equation is identified. In addition to the usual Boltzmann expression, it contains a contribution associated to the confinement of the particles. The steady properties of the system agree with equilibrium statistical mechanics results. Equations describing the energy transfer between the degrees of freedom parallel and perpendicular to the confining plates are obtained for some simple initial configurations...
October 2017: Physical Review. E
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