Changes In Dynamic Behavior Research Articles

Diffusion of Behavior in Network Games Orchestrated by Social Learning

The novelty of our model is to combine models of collective action on networks with models of social learning. Agents are connected according to an undirected graph, the social network, and have the choice between two actions: either to adopt a new behavior or technology or stay with the default behavior. The individual believed return depends on how many neighbors an agent has, how many of those neighbors already adopted the new behavior and some agent-specific cost-benefit parameter. There are four main insights of our model: (1) A variety of collective adoption behaviors is determined by the network. (2) Average inclination governs collective adoption behavior. (3) Initial inclinations determine the critical mass of adoption which ensures the new behavior to prevail. (4) Equilibria and dynamic behavior changes as we change the underlying network and other parameters. Given the complexity of the system we use a standard technique for estimating the solution.

Response Inhibition Induced in the Stop-signal Task by Transcranial Direct Current Stimulation of the Pre-supplementary Motor Area and Primary Sensoriomotor Cortex

[Purpose] This study examined whether transcranial direct current stimulation (tDCS) of both the pre-supplementary motor area (pre-SMA) and primary sensoriomotor cortex (M1) alters the response time in response inhibition using the stop-signal task (SST). [Methods] Forty healthy subjects were enrolled in this study. The subjects were randomly tested under the three: the pre-SMA tDCS, M1 tDCS, and Sham tDCS conditions. All subjects performed a SST in two consecutive phases: without or after the delivery of anodal tDCS over one of the target sites (pre-SMA or the M1) and under the Sham tDCS condition. [Results] Our findings demonstrated significant reductions in the stop processing times after the anodal tDCS over pre-SMA, and change response times were significantly greater under the pre-SMA tDCS condition compared to both the M1 tDCS condition and the Sham tDCS condition. There was no significant major effect after delivery of the tDCS for the go processing times observed among the three conditions. [Conclusion] Anodal tDCS of the pre-SMA or M1 during performance of the SST resulted in enhancement of the volitional stop movement in inhibitory control. Our results suggest that when concurrently applied with the SST, tDCS might be a useful adjuvant therapeutic modality for modulation of the response inhibition and its related dynamic behavioral changes between motor execution and suppression.

Analysis of Anterior Segment Dynamics Using Anterior Segment Optical Coherence Tomography Before and After Laser Peripheral Iridotomy

To evaluate changes in the speed of pupil constriction and in anterior segment parameters after laser peripheral iridotomy (LPI) in patients with angle closure using anterior segment optical coherence tomography. In this prospective observational study, videos of pupil and anterior segment changes in response to illumination were captured with real-time video recording using anterior segment optical coherence tomography and were analyzed frame by frame before and after LPI. Customized software was used to measure the speed of pupil constriction and changes in anterior chamber depth and anterior chamber area, as well as iris thickness at 750 μm from the scleral spur, at the sphincter muscle region (0.75 mm from the pupillary margin), and at the mid-iris location (half the distance between the scleral spur and the pupillary margin). Pupil diameter, angle opening distance, and trabecular-iris space area at 500 μm from the scleral spur were determined. The speed of pupil constriction was defined as the rate of pupil diameter change in response to illumination. Twenty-nine patients were included. Most were Chinese (26 of 29 [90%]) and female (18 of 29 [62%]). The anterior chamber area, angle opening distance at 500 μm from the scleral spur, and trabecular-iris space area at 500 μm from the scleral spur were significantly higher after LPI (P < .001). A significant increase was observed in the speed of pupil constriction after LPI (P < .005). In response to illumination, the rate of change in iris thickness at the sphincter muscle region and at 750 μm from the scleral spur was faster after LPI (P < .05). Similarly, an increase was observed in the speed of change of angle-opening distance at 500 μm from the scleral spur in response to illumination after LPI (P < .05). In patients with angle closure, changes in dynamic iridopupillary behavior are observed after LPI. The speed of pupillary constriction is faster after LPI.

High-Lard and High-Fish Oil Diets Differ in Their Effects on Insulin Resistance Development, Mitochondrial Morphology and Dynamic Behaviour in Rat Skeletal Muscle

Fish oil (mainly omega 3 polyunsaturated fatty acids), differently from lard (mainly saturated fatty acids) has been suggested to have anti-inflammatory effects associated with amelioration of insulin sensibility. An important role in skeletal muscle insulin resistance development has been recently attributed to mitochondrial dynamic behavior. Mitochondria are dynamic organelles that frequently undergo fission/fusion processes and a shift toward fission process has been associated with skeletal muscle mitochondrial dysfunction and insulin resistance development. The present work aimed to evaluate if the replacement of lard with fish oil in high-fat diet positively affect skeletal muscle mitochondrial dynamic behavior in association with the improvement of insulin-resistance. Body weight gain, systemic insulin-resistance (glucose/insulin ratio), serum TNFα levels and skeletal muscle lipid content were assessed in rats fed a high-lard or high-fish-oil diet for 6 weeks. In skeletal muscle sections, immunohistochemical analysis were performed to detect the presence of insulin receptor substrate 1 (IRS1) and tyrosine phosphorylated IRS1 (key factor in insulin signalling pathway) as well as to detect the main proteins involved in mitochondrial fusion (MFN2 and OPA1) and fission (DRP1 and Fis1) processes. Skeletal muscle mitochondrial ultrastructural features were assessed by electron microscopy. High-fish oil feeding induced lower body weight gain, systemic inflammation and insulin-resistance development as well as skeletal muscle lipid accumulation compared to high-lard feeding. Skeletal muscle sections from high-fish oil fed rats exhibited a greater number of immunoreactive fibers for MFN2 and OPA1 proteins as well as weaker immunostaining for DRP1 and Fis1 compared to sections from high-lard fed rats. Electron microscopy observations suggested a prominent presence of fission events in L rats and fusion events in F rats. The positive effect of the replacement of lard with fish oil in high-fat diet on systemic and skeletal muscle insulin sensibility was associated to changes in mitochondrial dynamic behavior.

Fretting behavior in three different model support configurations

Fretting damage to fuel rods reduces the service lives of the fuel assemblies and therefore increases reactor operating costs. The future development of fretting-resistant spacer grids necessitates the investigation of fretting behavior by means of model tests. This paper presents the results of such tests carried out to investigate fretting in three different fuel rod support configurations. The tests were performed in water at room temperature in a fretting test stand (referred to below simply as “autoclave”) using test rods with zirconium-alloy cladding tubes. The test rod was excited by means of electromagnet to induce vibration. The depth of the fretting marks and their volume increased as testing progressed. The resulting increase in the grid-to-rod gap caused changes in rod dynamic behavior and in the intensity of rod motion. Fretting rate is affected by rod motion, and the presence of edges at the point of contact between rod and support accelerates fretting wear. Spring design affects not only the degree of fretting but also the time history of the fretting process. Steady-state fretting was identified in the case of rods supported by convex springs without edges at the point of rod-to-support contact. The results of the model tests should provide a better understanding of fretting processes inside the reactor. They should not, however, be used to describe real conditions inside a reactor.

Analytic treatment of tipping points for social consensus in large random networks

We introduce a homogeneous pair approximation to the naming game (NG) model by deriving a six-dimensional Open Dynamics Engine (ODE) for the two-word naming game. Our ODE reveals the change in dynamical behavior of the naming game as a function of the average degree {k} of an uncorrelated network. This result is in good agreement with the numerical results. We also analyze the extended NG model that allows for presence of committed nodes and show that there is a shift of the tipping point for social consensus in sparse networks.

Analysis of “reservoir–well” system conditions using functional diagnostic methods

This paper presents a functional diagnostic method based on the fractal dimension of time series fluctuations. The fluctuations are conditionally subdivided into two categories: straightening and non-straightening on the fractal plane. A simplified method of fractal dimension calculation of time series is presented. The sensitivity of the method to the data availability is assessed. A criterion for the estimation of process conditions with close fractal dimensions is offered. A non-parametric criterion is given for the fluctuations that do not straighten on the fractal plane. The criterion is shown to be capable of picking up the changes in dynamic system behavior. The suggested method is tested on a model and practical examples. A retrospective analysis of a well performance is presented as an example for practical applications. The calculation algorithm of the suggested criteria is straightforward, accurate, and significant in practical reservoir engineering.

Characterizing Dynamic Transitions Associated With Snap-Through: A Discrete System

Geometrically nonlinear structures often possess multiple equilibrium configurations. Under extreme conditions of excitation, it is possible for these structures to exhibit oscillations about and between these co-existing configurations. This behavior may have serious implications for fatigue in the context of aircraft surface panels. Snap-through is a name often given to sudden changes in dynamic behavior associated with mechanical instability (buckling). This is an often encountered problem in hypersonic vehicles in which severe thermal loading and acoustic excitation conspire to create an especially hostile environment for structural elements. In this paper, a simple link model is used, experimentally and numerically, to investigate the mechanisms of snap-through buckling from a phenomenological standpoint.

Differences in White Matter Fiber Tract Development Present From 6 to 24 Months in Infants With Autism

Evidence from prospective studies of high-risk infants suggests that early symptoms of autism usually emerge late in the first or early in the second year of life after a period of relatively typical development. The authors prospectively examined white matter fiber tract organization from 6 to 24 months in high-risk infants who developed autism spectrum disorders (ASDs) by 24 months. The participants were 92 high-risk infant siblings from an ongoing imaging study of autism. All participants had diffusion tensor imaging at 6 months and behavioral assessments at 24 months; a majority contributed additional imaging data at 12 and/or 24 months. At 24 months, 28 infants met criteria for ASDs and 64 infants did not. Microstructural properties of white matter fiber tracts reported to be associated with ASDs or related behaviors were characterized by fractional anisotropy and radial and axial diffusivity. The fractional anisotropy trajectories for 12 of 15 fiber tracts differed significantly between the infants who developed ASDs and those who did not. Development for most fiber tracts in the infants with ASDs was characterized by higher fractional anisotropy values at 6 months followed by slower change over time relative to infants without ASDs. Thus, by 24 months of age, those with ASDs had lower values. These results suggest that aberrant development of white matter pathways may precede the manifestation of autistic symptoms in the first year of life. Longitudinal data are critical to characterizing the dynamic age-related brain and behavior changes underlying this neurodevelopmental disorder.

Detection of changes in cracked aluminium plate determinism by recurrence analysis

The paper investigates changes in determinism of undamaged and cracked aluminium plates with respect to excitation frequencies. Harmonic excitation of frequencies corresponding to structural resonances has been used to vibrate the plates. Vibration responses have been analysed using recurrence plots and recurrence quantification analysis. The smallest sufficient embedding dimension has been estimated using the false nearest neighbour’s algorithm. Mutual information analysis has been applied to determine the relevant time delays. The results demonstrate that performed analysis indicates changes in dynamic behaviour of the plates with respect to various excitation frequencies and crack modes.

Identification of a nonlinear joint in an elastic structure using optimum equivalent linear frequency response function

As the main source of local nonlinearities, joints can lead to drastic changes in dynamic behavior of structures in a global scale. Finite element (FE) models often lack these nonlinearities and are incapable of representing nonlinear behavior. Therefore, the identification of nonlinear dynamic mechanical properties of the joint is necessary, in order to develop a faithful FE model of the structure. In the present work, dynamic parameters of a nonlinear joint are identified using an optimum equivalent linear frequency response function of the structure. A test rig, which includes a beam that can produce cubic stiffness spring characteristic as a nonlinear joint, is built, and nonlinear dynamic characteristics of the beam are identified. In addition to hardening behavior related to cubic stiffness, softening effects were also observed in some measured modes in which further investigation attributed that behavior to the presence of a bolt in the test rig.

Dynamic behavioral, neurochemical and molecular changes induced by antidepressant drugs

Dynamic behavioral, neurochemical and molecular changes induced by antidepressant drugs

Gamma Tubulin Phospho Regulation: Insights into Spindle Assembly

The mitotic spindle is composed of spindle poles, chromatin, and pole-to-pole and pole-kinetochore microtubules. Pole-kinetochore microtubules are anchored at the spindle poles, with the opposite end attached to centromeric chromatin. Pole-to-pole microtubules are represented by cross-linked microtubules from the opposite poles, and form the microtubule core bundle (CMB), that plays an important role in stability of pre-anaphase mitotic spindle. The mitotic spindle is a highly coupled mechanical system, whose dynamic behavior changes in response of Cdk1-dependent signaling.In cells, the majority of spindle microtubules are assembled from nucleation sites located at the spindle poles, centrosomes in animal cells and spindle pole bodies in yeast. γ-tubulin is an essential part of γ-TuRC (γ-Tubulin Ring Complex), a template for nucleating the majority of microtubules in the cell. Here, we show the coupling of Cdk1-phosphorylation state of γ-tubulin with microtubule organization during assembly of the mitotic spindle. We use confocal microscopy and high-resolution analysis of fluorescently labeled proteins to characterize in vivo the dynamic behavior of the spindle during its assembly in wild-type cells, phospho-mimicking and phosphor-inhibiting mutants. We reconstructed short (1-2.5 μm) spindles using EM tomography and could establish the relative stoichiometry of γ -TuRC : microtubules in phosphor-mutants of γ-tubulin. Our results suggest that γ−tubulin is a key regulator of number and organization of microtubules. Here, we propose a model, where the phosphorylation state of γ -tubulin contributes to determination of microtubule fate during spindle assembly and stabilizing the spindle prior and during anaphase.

Application of Chen's system to detecting weak harmonic signals

The detection of weak harmonic signals has important practical value. In this paper, the detection of weak harmonic signals in strong noise is realized with the controlled Chen's system. Dynamics can be divided into slowly varying dynamics and fast varying dynamics, so a slowly varying dynamics is obtained by an averaging method. The critical values of detection parameters are determined, which lead to a sudden change of system dynamical behavior from periodic orbit to stable equilibrium point. Weak harmonic signals can be detected by adjusting the detection parameters and observing the change of system variables. Simulation results show that weak harmonic signals in strong noise can be detected accurately with this system. Compared with existing detection methods with chaotic oscillator, this method is of stronger immunity to noise, and the accurate range of parameter threshold can be obtained through theoretical analysis, which enables its popularization and application in relevant fields.

Yielding and shear induced melting of 2D mixed crystals of spheres and dimers

We performed constant stress and constant shear rate non-equilibrium molecular dynamics simulations to study the effects on mechanical properties of introducing varying amounts of dimers (dumbbells) in two-dimensional mixed crystals of monomers (spheres) and dimers. We observe that dislocation cages formed by blocking orientations of dimer particles introduce two opposing effects on the mechanical strength and rheological properties of such systems. Upon increasing the dimer concentration, the number of dislocations and vacancies increases, ‘weakening’ the crystal, but also the size of dislocation cages reduces, reinforcing the crystal by an effect similar to ‘grain-boundary strengthening’. In our constant stress simulations, these competing effects lead to a non-monotonic dependence of yield stress on the dimer fraction wherein it first drops and then increases. In our constant shear simulations, the crystals exhibit a plateau region in the stress vs. strain rate curves right around the yield stress values, confirming a change in dynamical and structural behavior at these points. Further, we find evidence of an unusual transitional phase before the crystal melts as shear increases: for any composition of the crystal an intermediate state is reached where a dynamic balance occurs between the rate of crystal growth (driven by thermodynamics) and the rate of melting (driven by shear). Such an intermediate state (whose onset agrees with the plateau region in the stress vs. strain curves) exhibits a heterogeneous structure and shear banding at a local level, while exhibiting a hexatic-like behavior at the macroscopic level. We also find differences in the solid and hexatic-like phases with respect to their stress relaxation mechanism, with the latter exhibiting a phase lag between the instantaneous stress and the ‘micro-structural yielding’ event.

Dynamic psychological and behavioral changes in the adoption and maintenance of exercise.

Although health cognitions are regarded as key determinants for health behavior change, they are rarely studied from a dynamic perspective, evaluating the impact of changes in cognitions on changes in behavior. In the present study, we examine how changes in phase-specific and generic health cognitions influence first, the adoption of exercise and later, the maintenance of the newly acquired behavior. Participants were middle-aged, Finnish adults participating in a lifestyle intervention to prevent Type 2 diabetes (N = 389). Health cognitions and exercise were measured at baseline (preintervention) and twice after a lifestyle intervention took place (at 3 months and after 1 year). The results show that both phase-specific and generic health cognitions changed during the intervention. However, these changes were most pronounced within those participants who started at a lower level to begin with. Most important, evidence for the dynamic interplay between changes in health cognitions and health behavior was observed: Phase-specific health cognitions facilitated the adoption as well as the maintenance of behavior changes. Thus, health cognitions are amenable to change, and these changes are adaptive in terms of initiating and maintaining health behavior change. This has implications both for practical intervention research, as well as for theory development.

Simple models for quorum sensing: Nonlinear dynamical analysis

Quorum sensing refers to the change in the cooperative behavior of a collection of elements in response to the change in their population size or density. This behavior can be observed in chemical and biological systems. These elements or cells are coupled via chemicals in the surrounding environment. Here we focus on the change of dynamical behavior, in particular from quiescent to oscillatory, as the cell population changes. For instance, the silent behavior of the elements can become oscillatory as the system concentration or population increases. In this work, two simple models are constructed that can produce the essential representative properties in quorum sensing. The first is an excitable or oscillatory phase model, which is probably the simplest model one can construct to describe quorum sensing. Using the mean-field approximation, the parameter regime for quorum sensing behavior can be identified, and analytical results for the detailed dynamical properties, including the phase diagrams, are obtained and verified numerically. The second model consists of FitzHugh-Nagumo elements coupled to the signaling chemicals in the environment. Nonlinear dynamical analysis of this mean-field model exhibits rich dynamical behaviors, such as infinite period bifurcation, supercritical Hopf, fold bifurcation, and subcritical Hopf bifurcations as the population parameter changes for different coupling strengths. Analytical result is obtained for the Hopf bifurcation phase boundary. Furthermore, two elements coupled via the environment and their synchronization behavior for these two models are also investigated. For both models, it is found that the onset of oscillations is accompanied by the synchronized dynamics of the two elements. Possible applications and extension of these models are also discussed.

Dynamic cycles of unsold new housing stocks, investment in housing, and housing supply–demand

Unsold new housing stocks may be closely related to housing market fluctuation, especially the difference between housing supply and demand, which is influenced by macroeconomic conditions. These factors simultaneously influence developers’ investment decisions and, thus, housing supply over time. However, previous research on the housing market has focused on explaining the statistical relationships among factors with reduced-form equations rather than analyzing dynamic behavioral changes. Thus, system dynamics should be introduced to analyze the dynamic cycles of unsold new housing stocks, housing investment, and housing supply–demand. This study develops Causal Loop Diagrams (CLDs), in which dynamic relationships are presented, and Stock–Flow Diagrams (SFD) for quantitative simulation by introducing normalized unit modeling by elementary relationship (NUMBER). The simulation results show that system dynamics can explain dynamic relationships in the housing market by focusing on unsold new housing stocks. In terms of the practical use of system dynamics models, governments can establish housing policies and developers can make decisions on investment in housing by considering unsold new housing stocks and their influence on the housing market. However, further consideration should be given to developing a method to reflect unpredictable economic events, such as the global financial crisis, in the system dynamics model.

Incorporating individual health-protective decisions into disease transmission models: a mathematical framework

It is anticipated that the next generation of computational epidemic models will simulate both infectious disease transmission and dynamic human behaviour change. Individual agents within a simulation will not only infect one another, but will also have situational awareness and a decision algorithm that enables them to modify their behaviour. This paper develops such a model of behavioural response, presenting a mathematical interpretation of a well-known psychological model of individual decision making, the health belief model, suitable for incorporation within an agent-based disease-transmission model. We formalize the health belief model and demonstrate its application in modelling the prevalence of facemask use observed over the course of the 2003 Hong Kong SARS epidemic, a well-documented example of behaviour change in response to a disease outbreak.

Structure and properties development in poly(phenylene sulfide) fibers, part I: Effect of material and melt spinning process variables

AbstractThe detailed research study of manufacturing PPS fibers using melt spinning and further enhancement of tensile properties by drawing and annealing experiments, a study lacking as of today in open scientific literature, was the focus of this research. This article discusses the effect of polymer molecular weight (MW) and melt spinning process variables on the structure and properties development in melt spun fibers manufactured from proprietary Fortron® linear PPS resins. Structure‐properties relationship was studied using several characterization tools like tensile testing, differential scanning calorimetry, polarized light optical microscopy, and wide‐angle x‐ray scattering. Changes in dynamic mechanical behavior of as‐spun fibers manufactured from resins of varying MW and different melt spinning take‐up speeds were also studied. The study showed that by a combination of higher MW of the polymer and spinning at higher take‐up speeds, tensile properties of as‐spun PPS fibers can be improved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011