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Dynamic systems theory

Martin I Jones, Mark R Wilson
In their target article, Hardy and colleagues outline some psychosocial factors that were proposed to underpin the development of serial sporting champions. In this commentary, we suggest that the psychodynamic compensatory mechanisms model described by Hardy et al. is limited by its failure to consider the role of the broader developmental systems in which an individual exists (including funding structure, community, culture, and historical niche). We suggest that any workable talent development model needs to consider the bidirectional relationships between individuals and their contexts, and as such, should be guided by a more dynamic, developmental systems theory approach...
2017: Progress in Brain Research
G Spagnolli, G Semeghini, L Masi, G Ferioli, A Trenkwalder, S Coop, M Landini, L Pezzè, G Modugno, M Inguscio, A Smerzi, M Fattori
We explore the interplay between tunneling and interatomic interactions in the dynamics of a bosonic Josephson junction. We tune the scattering length of an atomic ^{39}K Bose-Einstein condensate confined in a double-well trap to investigate regimes inaccessible to other superconducting or superfluid systems. In the limit of small-amplitude oscillations, we study the transition from Rabi to plasma oscillations by crossing over from attractive to repulsive interatomic interactions. We observe a critical slowing down in the oscillation frequency by increasing the strength of an attractive interaction up to the point of a quantum phase transition...
June 9, 2017: Physical Review Letters
Vladimir U Nazarov
We find an exact analytical solution to the exchange-only time-dependent density-functional theory (TDDFT) problem for a significant class of quasi-low-dimensional (QLD) materials: QLD electron gas with only one band filled in the direction perpendicular to the layer or wire. The theory yields the TD exchange potential as an explicit nonlocal operator of the TD spin density. The dressed interband (image states) excitation spectra of quasi-two-dimensional electron gas are obtained, while the comparison with the Kohn-Sham transitions provides insights into the qualitative and quantitative role of the many-body interactions...
June 9, 2017: Physical Review Letters
Javier Monroy, Victor Hernandez-Bennets, Han Fan, Achim Lilienthal, Javier Gonzalez-Jimenez
This work presents a simulation framework developed under the widely used Robot Operating System (ROS) to enable the validation of robotics systems and gas sensing algorithms under realistic environments. The framework is rooted in the principles of computational fluid dynamics and filament dispersion theory, modeling wind flow and gas dispersion in 3D real-world scenarios (i.e., accounting for walls, furniture, etc.). Moreover, it integrates the simulation of different environmental sensors, such as metal oxide gas sensors, photo ionization detectors, or anemometers...
June 23, 2017: Sensors
C Darmedru, C Demily, N Franck
OBJECTIVES: The association between schizophrenia and violence represents an important issue in psychiatry. Often highly publicized, violent acts raise the question of their detection, prevention, management and treatment. There is no single, direct and exclusive link between aggressiveness and the underlying psychiatric disorder. On the contrary, the processes underlying this violence are multiple and interlinked. In addition to static and dynamic risk factors, cognitive deficits play an important role in the genesis and maintenance of violent and aggressive behavior...
June 19, 2017: L'Encéphale
Dongya Jia, Mohit Kumar Jolly, Prakash Kulkarni, Herbert Levine
Waddington's epigenetic landscape, a famous metaphor in developmental biology, depicts how a stem cell progresses from an undifferentiated phenotype to a differentiated one. The concept of "landscape" in the context of dynamical systems theory represents a high-dimensional space, in which each cell phenotype is considered as an "attractor" that is determined by interactions between multiple molecular players, and is buffered against environmental fluctuations. In addition, biological noise is thought to play an important role during these cell-fate decisions and in fact controls transitions between different phenotypes...
June 22, 2017: Cancers
Michael H Cortez, Swati Patel
This paper explores how predator evolution and the magnitude of predator genetic variation alter the population-level dynamics of predator-prey systems. We do this by analyzing a general eco-evolutionary predator-prey model using four methods: Method 1 identifies how eco-evolutionary feedbacks alter system stability in the fast and slow evolution limits; Method 2 identifies how the amount of standing predator genetic variation alters system stability; Method 3 identifies how the phase lags in predator-prey cycles depend on the amount of genetic variation; and Method 4 determines conditions for different cycle shapes in the fast and slow evolution limits using geometric singular perturbation theory...
June 21, 2017: Bulletin of Mathematical Biology
C-Z Gao, P M Dinh, P-G Reinhard, E Suraud
We study from a theoretical perspective the ionization of molecules and clusters induced by irradiation of a combined two-color laser field consisting of a train of attosecond XUV pulses in the presence of an IR field. We use time-dependent density-functional theory (TDDFT) in real time and real space as a theoretical tool. The calculated results are compared to experimental data when available. We also compare TDDFT with results obtained using a time-dependent Schrödinger equation (TDSE), which is well suited to simple systems while TDDFT allows dealing with more complex molecules and clusters...
June 21, 2017: Physical Chemistry Chemical Physics: PCCP
Luke J Eberhart-Phillips, Clemens Küpper, Tom E X Miller, Medardo Cruz-López, Kathryn H Maher, Natalie Dos Remedios, Martin A Stoffel, Joseph I Hoffman, Oliver Krüger, Tamás Székely
Adult sex ratio (ASR) is a central concept in population biology and a key factor in sexual selection, but why do most demographic models ignore sex biases? Vital rates often vary between the sexes and across life history, but their relative contributions to ASR variation remain poorly understood-an essential step to evaluate sex ratio theories in the wild and inform conservation. Here, we combine structured two-sex population models with individual-based mark-recapture data from an intensively monitored polygamous population of snowy plovers...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
E J Müller, S J van Albada, J W Kim, P A Robinson
The mechanisms underlying pathologically synchronized neural oscillations in Parkinson's disease (PD) and generalized epilepsies are explored in parallel via a physiologically-based neural field model of the corticothalamic-basal ganglia (CTBG) system. The basal ganglia (BG) are approximated as a single effective population and their roles in the modulation of oscillatory dynamics of the corticothalamic (CT) system and vice versa are analyzed. In addition to normal EEG rhythms, enhanced activity around 4 Hz and 20 Hz exists in the model, consistent with the characteristic frequencies observed in PD...
June 17, 2017: Journal of Theoretical Biology
Frédéric Barraquand, Stilianos Louca, Karen C Abbott, Christina A Cobbold, Flora Cordoleani, Donald L DeAngelis, Bret D Elderd, Jeremy W Fox, Priscilla Greenwood, Frank M Hilker, Dennis L Murray, Christopher R Stieha, Rachel A Taylor, Kelsey Vitense, Gail S K Wolkowicz, Rebecca C Tyson
Population cycling is a widespread phenomenon, observed across a multitude of taxa in both laboratory and natural conditions. Historically, the theory associated with population cycles was tightly linked to pairwise consumer-resource interactions and studied via deterministic models, but current empirical and theoretical research reveals a much richer basis for ecological cycles. Stochasticity and seasonality can modulate or create cyclic behaviour in non-intuitive ways, the high-dimensionality in ecological systems can profoundly influence cycling, and so can demographic structure and eco-evolutionary dynamics...
June 20, 2017: Ecology Letters
David Ayuso, Alicia Palacios, Piero Decleva, Fernando Martín
The combination of attosecond pump-probe techniques with mass spectrometry methods has recently led to the first experimental demonstration of ultrafast charge dynamics in a biomolecule, the amino acid phenylalanine [Calegari et al., Science, 2014, 346, 336]. Using an extension of the static-exchange density functional theory (DFT) method, the observed dynamics was explained as resulting from the coherent superposition of ionic states produced by the broadband attosecond pulse. Here, we have used the static-exchange DFT method to investigate charge migration induced by attosecond pulses in the glycine molecule...
June 20, 2017: Physical Chemistry Chemical Physics: PCCP
Christian Riesch, Günter Radons, Robert Magerle
We investigate the non-equilibrium dynamics of an ordered stripe-forming system free of topological defects. In particular, we study the ageing and the coarsening of orientation fluctuations parallel and perpendicular to the stripes via computer simulations based on a minimal phase-field model (model B with Coulomb interactions). Under the influence of noise, the stripe orientation field develops fluctuations parallel to the stripes, with the dominant modulation length λ*∥ increasing with time t as λ*∥ ∼ t(1/4) and the correlation length perpendicular to the stripes ξ(⊥)θ increasing as ξ(⊥)θ ∼ t(1/2)...
August 6, 2017: Interface Focus
Linda Giacomozzi, Michael Gatchell, Nathalie de Ruette, Michael Wolf, Giovanna D'Angelo, Henning T Schmidt, Henrik Cederquist, Henning Zettergren
We have studied collisions between tetraphenylporphyrin cations and He or Ne at center-of-mass energies in the range 50-110 eV. The experimental results were interpreted in view of density functional theory calculations of dissociation energies and classical molecular dynamics simulations of how the molecules respond to the He/Ne impact. We demonstrate that prompt atom knockout strongly contributes to the total destruction cross sections. Such impulse driven processes typically yield highly reactive fragments and are expected to be important for collisions with any molecular system in this collision energy range, but have earlier been very difficult to isolate for biomolecules...
June 19, 2017: Physical Chemistry Chemical Physics: PCCP
Erik Bernitt, Hans-Günther Döbereiner, Nir S Gov, Arik Yochelis
During macropinocytosis, cells remodel their morphologies for the uptake of extracellular matter. This endocytotic mechanism relies on the collapse and closure of precursory structures, which are propagating actin-based, ring-shaped vertical undulations at the dorsal (top) cell membrane, a.k.a. circular dorsal ruffles (CDRs). As such, CDRs are essential to a range of vital and pathogenic processes alike. Here we show, based on both experimental data and theoretical analysis, that CDRs are propagating fronts of actin polymerization in a bistable system...
June 19, 2017: Nature Communications
Yuling Chen, Yang Lou, Jesse Yen
During conventional ultrasound imaging, the need for multiple transmissions for one image and the time of flight for a desired imaging depth limit the frame rate of the system. Using a single plane wave pulse during each transmission followed by parallel receive processing allows for high frame rate imaging. However, image quality is degraded because of the lack of transmit focusing. Beamforming by spatial matched filtering (SMF) is a promising method which focuses ultrasonic energy using spatial filters constructed from the transmit-receive impulse response of the system...
July 2017: Ultrasonic Imaging
Mette Birch Kristensen, Anders Bentien, Michele Tedesco, Jacopo Catalano
In this work we use the general space-charge (SC) theory for a combined transport model of fluid and ion through cylindrical nanopores to derive equations for the membrane potential and counter-ion transport numbers. We discuss this approach for ion exchange membranes assuming aqueous domains as interconnected network of cylindrical pores. The transport number calculations from the SC theory are compared with the corresponding ones from the uniform potential (UP) and Teorell-Meyer-Sievers (TMS) models in the case of both zero and non-zero concentration gradient across the membrane and with an applied current density...
June 8, 2017: Journal of Colloid and Interface Science
José Dávila Velderraín, Juan Carlos Martínez-García, Elena R Álvarez-Buylla
Mathematical models based on dynamical systems theory are well-suited tools for the integration of available molecular experimental data into coherent frameworks in order to propose hypotheses about the cooperative regulatory mechanisms driving developmental processes. Computational analysis of the proposed models using well-established methods enables testing the hypotheses by contrasting predictions with observations. Within such framework, Boolean gene regulatory network dynamical models have been extensively used in modeling plant development...
2017: Methods in Molecular Biology
Alexander B Boyd, Dibyendu Mandal, Paul M Riechers, James P Crutchfield
A central result that arose in applying information theory to the stochastic thermodynamics of nonlinear dynamical systems is the information-processing second law (IPSL): the physical entropy of the Universe can decrease if compensated by the Shannon-Kolmogorov-Sinai entropy change of appropriate information-carrying degrees of freedom. In particular, the asymptotic-rate IPSL precisely delineates the thermodynamic functioning of autonomous Maxwellian demons and information engines. How do these systems begin to function as engines, Landauer erasers, and error correctors? We identify a minimal, and thus inescapable, transient dissipation of physical information processing, which is not captured by asymptotic rates, but is critical to adaptive thermodynamic processes such as those found in biological systems...
June 2, 2017: Physical Review Letters
Jader P Santos, Gabriel T Landi, Mauro Paternostro
The characterization of irreversibility in general quantum processes is an open problem of increasing technological relevance. Yet, the tools currently available to this aim are mostly limited to the assessment of dynamics induced by equilibrium environments, a situation that often does not match the reality of experiments at the microscopic and mesoscopic scale. We propose a theory of irreversible entropy production that is suited for quantum systems exposed to general, nonequilibrium reservoirs. We illustrate our framework by addressing a set of physically relevant situations that clarify both the features and the potential of our proposal...
June 2, 2017: Physical Review Letters
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