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Dynamic systems theory

Michael B Liu, Christopher Y Ko, Zhen Song, Alan Garfinkel, James N Weiss, Zhilin Qu
Ventricular myocytes are excitable cells whose voltage threshold for action potential (AP) excitation is ∼-60 mV at which INa is activated to give rise to a fast upstroke. Therefore, for a short stimulus pulse to elicit an AP, a stronger stimulus is needed if the resting potential lies further away from the INa threshold, such as in hypokalemia. However, for an AP elicited by a long duration stimulus or a diastolic spontaneous calcium release, we observed that the stimulus needed was lower in hypokalemia than in normokalemia in both computer simulations and experiments of rabbit ventricular myocytes...
December 6, 2016: Biophysical Journal
N B Kroemer, C Burrasch, L Hellrung
By definition, instrumental actions are performed in order to obtain certain goals. Nevertheless, the attainment of goals typically implies obstacles, and response vigor is known to reflect an integration of subjective benefit and cost. Whereas several brain regions have been associated with cost/benefit ratio decision-making, trial-by-trial fluctuations in motivation are not well understood. We review recent evidence supporting the motivational implications of signal fluctuations in the mesocorticolimbic system...
2016: Progress in Brain Research
Lorenzo Zino, Alessandro Rizzo, Maurizio Porfiri
Activity-driven networks are a powerful paradigm to study epidemic spreading over time-varying networks. Despite significant advances, most of the current understanding relies on discrete-time computer simulations, in which each node is assigned an activity potential from a continuous distribution. Here, we establish a continuous-time discrete-distribution framework toward an analytical treatment of the epidemic spreading, from its onset to the endemic equilibrium. In the thermodynamic limit, we derive a nonlinear dynamical system to accurately model the epidemic spreading and leverage techniques from the fields of differential inclusions and adaptive estimation to inform short- and long-term predictions...
November 25, 2016: Physical Review Letters
John S Butler, Sophie Molholm, Gizely N Andrade, John J Foxe
An emerging neuropathological theory of Autism, referred to here as "the neural unreliability thesis," proposes greater variability in moment-to-moment cortical representation of environmental events, such that the system shows general instability in its impulse response function. Leading evidence for this thesis derives from functional neuroimaging, a methodology ill-suited for detailed assessment of sensory transmission dynamics occurring at the millisecond scale. Electrophysiological assessments of this thesis, however, are sparse and unconvincing...
December 6, 2016: Cerebral Cortex
Kendra S Heatwole Shank, Malcolm P Cutchin
OBJECTIVE: 'Community livability' is a widely used term that is still under-conceptualized. The purpose of the project was to theorize key dynamics of livability for older adults who are aging in place in their homes and communities. METHODS: Twelve community-dwelling adults (70+) were recruited in a multiple-case study design. Interviews and naturalistic observations were used over the course of 6months. Global positioning system (GPS) devices were used to generate maps (routines, routes, type and duration of activities) to elicit additional insights through interviews...
December 2016: Journal of Aging Studies
Laura B Hoch, Paul Szymanski, Kulbir Kaur Ghuman, Le He, Kristine Liao, Qiao Qiao, Laura M Reyes, Yimei Zhu, Mostafa A El-Sayed, Chandra Veer Singh, Geoffrey A Ozin
In2O3-x(OH)y nanoparticles have been shown to function as an effective gas-phase photocatalyst for the reduction of CO2 to CO via the reverse water-gas shift reaction. Their photocatalytic activity is strongly correlated to the number of oxygen vacancy and hydroxide defects present in the system. To better understand how such defects interact with photogenerated electrons and holes in these materials, we have studied the relaxation dynamics of In2O3-x(OH)y nanoparticles with varying concentration of defects using two different excitation energies corresponding to above-band-gap (318-nm) and near-band-gap (405-nm) excitations...
November 28, 2016: Proceedings of the National Academy of Sciences of the United States of America
A V Slunyaev, E N Pelinovsky
The role of multiple soliton and breather interactions in the formation of very high waves is disclosed within the framework of the integrable modified Korteweg-de Vries (MKdV) equation. Optimal conditions for the focusing of many solitons are formulated explicitly. Namely, trains of ordered solitons with alternate polarities evolve to huge strongly localized transient waves. The focused wave amplitude is exactly the sum of the focusing soliton heights; the maximum wave inherits the polarity of the fastest soliton in the train...
November 18, 2016: Physical Review Letters
Jin-Jin Ding, Hou-Dao Zhang, Yao Wang, Rui-Xue Xu, Xiao Zheng, YiJing Yan
A unified theory for minimum exponential-term ansatzes on bath correlation functions is proposed for numerically efficient and physically insightful treatments of non-Markovian environment influence on quantum systems. For a general Brownian oscillator bath of frequency Ω and friction ζ, the minimum ansatz results in the correlation function a bi-exponential form, with the effective Ω¯ and friction ζ¯ being temperature dependent and satisfying Ω¯/Ω=(ζ¯/ζ)(1/2)=r¯BO/rBO≤ 1, where r¯BO=ζ¯/(2Ω¯) and rBO=ζ/(2Ω)...
November 28, 2016: Journal of Chemical Physics
Christopher C Ballard, C Clark Esty, David A Egolf
Equilibrium statistical mechanics allows the prediction of collective behaviors of large numbers of interacting objects from just a few system-wide properties; however, a similar theory does not exist for far-from-equilibrium systems exhibiting complex spatial and temporal behavior. We propose a method for predicting behaviors in a broad class of such systems and apply these ideas to an archetypal example, the spatiotemporal chaotic 1D complex Ginzburg-Landau equation in the defect chaos regime. Building on the ideas of Ruelle and of Cross and Hohenberg that a spatiotemporal chaotic system can be considered a collection of weakly interacting dynamical units of a characteristic size, the chaotic length scale, we identify underlying, mesoscale, chaotic units and effective interaction potentials between them...
November 2016: Chaos
Robert Lickliter
Biologists and psychologists are re-thinking the long-standing premise of genes as the primary cause of development, a view widely embraced in 20th-century biology. This shift in thinking is based in large part on: (1) the growing appreciation of the complex, distributed regulatory dynamics of gene expression; and (2) the growing appreciation of the probabilistic, contingent, and situated nature of development. We now appreciate that what actually unfolds during individual development represents only one of many possibilities...
December 1, 2016: Wiley Interdisciplinary Reviews. Cognitive Science
Lei Zhao, Jin Wang
Recent studies on Caenorhabditis elegans reveal that gene manipulations can extend its lifespan several fold. However, how the genes work together to determine longevity is still an open question. Here we construct a gene regulatory network for worm ageing and quantify its underlying potential and flux landscape. We found ageing and rejuvenation states can emerge as basins of attraction at certain gene expression levels. The system state can switch from one attractor to another driven by the intrinsic or external perturbations through genetics or the environment...
November 2016: Journal of the Royal Society, Interface
Adam Santoro, Paul W Frankland, Blake A Richards
: Over the course of systems consolidation, there is a switch from a reliance on detailed episodic memories to generalized schematic memories. This switch is sometimes referred to as "memory transformation." Here we demonstrate a previously unappreciated benefit of memory transformation, namely, its ability to enhance reinforcement learning in a dynamic environment. We developed a neural network that is trained to find rewards in a foraging task where reward locations are continuously changing...
November 30, 2016: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Adrian Klein, Martin Bock, Wolfgang Alt
The development of first cellular structures played an important role in the early evolution of life. Early evolution of life probably took place on a molecular level in a reactive environment. The iron-sulfur theory postulates the formation of cell-like structures on catalytic surfaces. Experiments show that H2S together with FeS and other metallic centers drive auto-catalytic surface reactions, in which organic molecules such as pyruvic and amino acids occur. It is questionable which mechanisms are needed to form cell-like structures under these conditions...
November 27, 2016: Bio Systems
Reza Assaran Darban, Behzad Shareghi, Ahmad Asoodeh, Jamshidkhan Chamani
The present study was carried out to characterize ACE inhibitory peptides which are release from the trypsin hydrolysate of wheat gluten protein. The binding of two inhibitory peptide (P4 and P6) to human serum albumin (HSA) under physiological conditions has been investigated by multi- spectroscopic in combination with molecular modeling techniques. Time-resolved and quenching fluorescence spectroscopies results revealed that the quenching of HSA fluorescence by P4 and P6 in the binary and ternary systems caused HSA-peptides complexes formation...
November 29, 2016: Journal of Biomolecular Structure & Dynamics
Matt R Cross, Matt Brughelli, Pierre Samozino, Jean-Benoit Morin
The ability of the human body to generate maximal power is linked to a host of performance outcomes and sporting success. Power-force-velocity relationships characterize limits of the neuromuscular system to produce power, and their measurement has been a common topic in research for the past century. Unfortunately, the narrative of the available literature is complex, with development occurring across a variety of methods and technology. This review focuses on the different equipment and methods used to determine mechanical characteristics of maximal exertion human sprinting...
November 28, 2016: Sports Medicine
Michael D Collins, Chris J Jackson, Benjamin R Walker, Peter J O'Connor, Elliroma Gardiner
Over the last 40 years or more the personality literature has been dominated by trait models based on the Big Five (B5). Trait-based models describe personality at the between-person level but cannot explain the within-person mental mechanisms responsible for personality. Nor can they adequately account for variations in emotion and behavior experienced by individuals across different situations and over time. An alternative, yet understated, approach to personality architecture can be found in neurobiological theories of personality, most notably reinforcement sensitivity theory (RST)...
November 28, 2016: Psychological Bulletin
Toon Haer, W J Wouter Botzen, Hans de Moel, Jeroen C J H Aerts
Recent studies showed that climate change and socioeconomic trends are expected to increase flood risks in many regions. However, in these studies, human behavior is commonly assumed to be constant, which neglects interaction and feedback loops between human and environmental systems. This neglect of human adaptation leads to a misrepresentation of flood risk. This article presents an agent-based model that incorporates human decision making in flood risk analysis. In particular, household investments in loss-reducing measures are examined under three economic decision models: (1) expected utility theory, which is the traditional economic model of rational agents; (2) prospect theory, which takes account of bounded rationality; and (3) a prospect theory model, which accounts for changing risk perceptions and social interactions through a process of Bayesian updating...
November 28, 2016: Risk Analysis: An Official Publication of the Society for Risk Analysis
Robert Kozma
Walter J. Freeman was a giant of the field of neuroscience whose visionary work contributed various experimental and theoretical breakthroughs to brain research in the past 60 years. He has pioneered a number of Electroencephalogram and Electrocorticogram tools and approaches that shaped the field, while "Freeman Neurodynamics" is a theoretical concept that is widely known, used, and respected among neuroscientists all over the world. His recent death is a profound loss to neuroscience and biomedical engineering...
December 2016: Cognitive Neurodynamics
Andrew J Holmes, Yi Vee Chew, Feyza Colakoglu, John B Cliff, Eline Klaassens, Mark N Read, Samantha M Solon-Biet, Aisling C McMahon, Victoria C Cogger, Kari Ruohonen, David Raubenheimer, David G Le Couteur, Stephen J Simpson
Diet influences health and patterns of disease in populations. How different diets do this and why outcomes of diets vary between individuals are complex and involve interaction with the gut microbiome. A major challenge for predicting health outcomes of the host-microbiome dynamic is reconciling the effects of different aspects of diet (food composition or intake rate) on the system. Here we show that microbial community assembly is fundamentally shaped by a dichotomy in bacterial strategies to access nitrogen in the gut environment...
November 15, 2016: Cell Metabolism
R Christopher Sheldrick, Dominic J Breuer, Razan Hassan, Kee Chan, Deborah E Polk, James Benneyan
BACKGROUND: Clinical decision-making has been conceptualized as a sequence of two separate processes: assessment of patients' functioning and application of a decision threshold to determine whether the evidence is sufficient to justify a given decision. A range of factors, including use of evidence-based screening instruments, has the potential to influence either or both processes. However, implementation studies seldom specify or assess the mechanism by which screening is hypothesized to influence clinical decision-making, thus limiting their ability to address unexpected findings regarding clinicians' behavior...
November 25, 2016: Implementation Science: IS
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