Dynamic Behavior Research Articles

Combined Impact of Multidelay Feedback Number and Interval: A Novel Mechanism for Controlling the Stability of Stochastic Duffing Systems

In this paper, we study a class of nonlinear stochastic Duffing oscillators with multidelay feedback. We propose an effective reduction approach with the help of center manifold theory and stochastic averaging method. Taking the initial time-delay [Formula: see text] as the parameter, we reduce the original system to a one-dimensional averaged Itô equation. Our analysis reveals that the original system exhibits stochastic bifurcations, including stochastic D and P bifurcations. Once we have a clear understanding of the bifurcation structure, we can use this knowledge to choose appropriate system parameters and place the system in the desired state. For instance, by adjusting the initial time-delay [Formula: see text] of the control system, we can stabilize the system and achieve the desired outcome. Numerical simulations also verify the theoretical results. With appropriate parameter choices, multiple time delays can destabilize the equilibrium and promote chaotic behaviors, and can also lead to more stable dynamical behavior. Remarkably, we discovered that increasing the interval of time delays and feedback numbers can enhance system stability. It may potentially serve as a novel mechanism for stabilizing stochastic systems. The study provides a solid theoretical foundation for exploring stochastic systems subject to complex time-delay feedback control, and offers a valuable framework for related fields.

The dynamic behavior of chromatophores marks the transition from bands to spots in leopard geckos

Reptilian skin coloration is spectacular and diverse, yet little is known about the ontogenetic processes that govern its establishment and the molecular signaling pathways that determine it. Here, we focus on the development of the banded pattern of leopard gecko hatchlings and the transition to black spots in the adult. With our histological analyses, we show that iridophores are present in the white and yellow bands of the hatchling and they gradually perish in the adult skin. Furthermore, we demonstrate that melanophores can autonomously form spots in the absence of the other chromatophores both on the regenerated skin of the tail and on the dorsal skin of the Mack Super Snow (MSS) leopard geckos. This color morph is characterized by uniform black coloration in hatchlings and black spots in adulthood; we establish that their skin is devoid of xanthophores and iridophores at both stages. Our genetic analyses identified a 13-nucleotide deletion in the PAX7 transcription factor of MSS geckos, affecting its protein coding sequence. With our single-cell transcriptomics analysis of embryonic skin, we confirm that PAX7 is expressed in iridophores and xanthophores, suggesting that it plays a key role in the differentiation of both chromatophores. Our in situ hybridizations on whole-mount embryos document the dynamics of the skin pattern formation and how it is impacted in the PAX7 mutants. We hypothesize that the melanophores-iridophores interactions give rise to the banded pattern of the hatchlings and black spot formation is an intrinsic capacity of melanophores in the postembryonic skin.

Magnetotransport of fluxoids in intermediate-phase type-II superconducting NbN thin films around Tc

The mixed state transport properties of type-II superconductors are strongly influenced by the dynamic behavior of quantized magnetic fluxoids around the critical temperature (Tc), where a combination of normal and superconducting properties is exhibited. To understand the mixed state transport properties of type-II superconducting NbN ultrathin films (2D) we measured sheet resistance (RxxM) and Hall resistance (RxyM) of a 5-nm-thick NbN film around Tc (10.75 K) at temperatures 10.40, 10.68, and 10.77 K. Hall resistance (HR) was measured in external out-of-plane and in-plane magnetic fields up to 6 T, using 100 µA and 1 mA driving current in Van der Pauw geometry. The electric field of applied bias and Lorentz force of applied external magnetic field causes a movement of the normal conducting electrons within each fluxoid. The moving fluxoids cause dissipation and generation of Hall voltage. We developed a macroscopic analysis of the Hall resistance arising from fluxoids, to advance the differentiation between dissipating current and superconducting currents in type-II superconductors at Tc. We have extracted the number of normal conducting carriers per fluxoid and areal density and mobility of the fluxoids in dependence on the external magnetic field. This differentiation provides valuable insights into the dissipation mechanisms observed during transport measurements, e.g., after localized heating due to single photon absorption in nanostructured type-II superconductors. Furthermore, the developed macroscopic analysis of Hall resistance of fluxoids shows promising potential for investigating the fundamental aspects of fluxoid-defect interactions in type-II superconductors. Published by the American Physical Society 2024

Ghost Red Blood Cells For Enhanced Particle Detection With Defocusing PTV In Microcirculation Experiments

Particle tracking of rigid fluorescent particles in microcirculation environments is often found to be difficult, since the presence of red blood cells (RBCs) at physiologically relevant conditions (i.e., hematocrit) masks the particle images. In turn, making particle detection challenging. To overcome this difficulty, we propose to use ghost RBCs for enhanced particle detection. These are quasi-transparent RBCs obtained by removing the hemoglobin from normal RBCs. To understand whether the ghost RBCs can improve the particle detection, we performed defocusing particle tracking measurements with the general defocusing particle tracking (GDPT) method of the rigid fluorescent particles in normal and ghost RBC flows. The measurements were performed at physiological relevant hematocrit and for three different flow rates. From the three-dimensional particle trajectories, we evaluated the correlation coefficient from the GDPT evaluations and compared the fluid dynamic behavior of the two types of cells. Overall, the results show that ghost RBCs are an attractive solution for this type of experiments, since they improve the correlation coefficients up to values similar to cell-free experiments, while exhibiting a fluid dynamic behavior similar to normal RBCs i.e., in terms of velocity and relative viscosity data.

Systemic Inflammation Disrupts Circadian Rhythms and Diurnal Neuroimmune Dynamics

Circadian rhythms regulate physiological processes in approximately 24 h cycles, and their disruption is associated with various diseases. Inflammation may perturb circadian rhythms, though these interactions remain unclear. This study examined whether systemic inflammation induced by an intraperitoneal injection of lipopolysaccharide (LPS) could alter central and peripheral circadian rhythms and diurnal neuroimmune dynamics. Mice were randomly assigned to two groups: the saline control group and the LPS group. The diurnal expression of circadian clock genes and inflammatory cytokines were measured in the hypothalamus, hippocampus, and liver. Diurnal dynamic behaviors of microglia were also assessed. Our results revealed that the LPS perturbed circadian gene oscillations in the hypothalamus, hippocampus, and liver. Furthermore, systemic inflammation induced by the LPS could trigger neuroinflammation and perturb the diurnal dynamic behavior of microglia in the hippocampus. These findings shed light on the intricate link between inflammation and circadian disruption, underscoring their significance in relation to neurodegenerative diseases.

Dynamic Adhesive Behavior and Biofilm Formation of Staphylococcus aureus on Polylactic Acid Surfaces in Diabetic Environments

Interest in biodegradable implants has focused attention on the resorbable polymer polylactic acid. However, the risk of these materials promoting infection, especially in patients with existing pathologies, needs to be monitored. The enrichment of a bacterial adhesion medium with compounds that are associated with human pathologies can help in understanding how these components affect the development of infectious processes. Specifically, this work evaluates the influence of glucose and ketone bodies (in a diabetic context) on the adhesion dynamics of S. aureus to the biomaterial polylactic acid, employing different approaches and discussing the results based on the physical properties of the bacterial surface and its metabolic activity. The combination of ketoacidosis and hyperglycemia (GK2) appears to be the worst scenario: this system promotes a state of continuous bacterial colonization over time, suppressing the stationary phase of adhesion and strengthening the attachment of bacteria to the surface. In addition, these supplements cause a significant increase in the metabolic activity of the bacteria. Compared to non-enriched media, biofilm formation doubles under ketoacidosis conditions, while in the planktonic state, it is glucose that triggers metabolic activity, which is practically suppressed when only ketone components are present. Both information must be complementary to understand what can happen in a real system, where planktonic bacteria are the ones that initially colonize a surface, and, subsequently, these attached bacteria end up forming a biofilm. This information highlights the need for good monitoring of diabetic patients, especially if they use an implanted device made of PLA.

Effectiveness of Suspended Lead Dampers in Steel Building Structural Model Subjected to Impact Load

This paper delves into an in-depth experimental investigation focusing on the dynamic behavior of steel frame buildings employing passive damping through suspended lead dampers. The primary objective revolves around scrutinizing a three-story steel frame building model to elucidate the effects of integrating lead dampers into the outer tubular square-section columns. By strategically embedding these dampers, the study aims to showcase the resultant reductions in both acceleration and displacement. To execute this analysis, an impact load is precisely applied to the mid-center of the middle column along the x-axis of the first story of the steel frame. The experimental setup employs six wireless accelerometers strategically positioned across the frame to capture comprehensive data on its response at diverse locations. Various quantities of lead dampers are systematically incorporated into each testing scenario to gauge the extent of passive damping’s influence on the structural response of steel buildings to impact loads. Throughout the experiments, acceleration-time relations are meticulously recorded at each story, facilitating a comparative assessment of outcomes with and without the presence of lead dampers. The findings of the study underscore a marked decrease in vibration levels at higher floors of the steel model subsequent to the installation of lead dampers within the structure. Furthermore, a noteworthy trend emerges indicating that an augmented number of lead dampers within the building yields a commensurate decrease in vibration amplitude. This detailed investigation offers valuable insights into the efficacy of passive damping mechanisms, thereby contributing to the advancement of seismic-resistant structural design practices.

Transient Dynamic Response of Generally Shaped Arches under Interval Uncertainties

This paper endeavors to investigate the characteristics of the transient dynamic response of a generally shaped arch when influenced by uncertain parameters while being subjected to specific external excitation. The equations of motion of the generally shaped arches are derived by the differential quadrature (DQ) method, and the deterministic dynamic responses are calculated using the Newmark-β method. By employing the Chebyshev inclusive function, an interval method based on a non-intrusive polynomial surrogate model is developed, and the uncertain dynamic responses are reckoned by enabling numerical simulations. The results of the proposed interval method are compared with those obtained from the scanning method for validation. The effects of various shapes and rise span ratios on the dynamic responses are investigated through a parametric study. The results suggest that the degree of fluctuation in the uncertain dynamic behavior is influenced by the type of parameter. Additionally, the responses of each shaped arch decrease with the increase in the rise span ratios, and with the same rise span ratio, the deterministic responses and corresponding uncertain responses are also affected by the shape of the arch, and they are considered to be at a minimum when the arch shape is parabolic. This study will enhance understanding of the dynamic properties of arches with uncertainties and provide some basis for the assessment and health monitoring of arch structures.

Advanced Analytical and Numerical Studies on Coupled Schrödinger Equations with Fractional Order Damping

This paper embarks on a thorough analytical and numerical exploration of coupled Schrödinger equations under the influence of fractional order damping mechanisms. By integrating fractional damping, which introduces memory effects and non-local dissipative interactions, into the coupled Schrödinger framework, we aim to dissect and understand the nuanced dynamics that govern these complex quantum systems. The research delves into the mathematical underpinnings, stability characteristics, and the dynamical behaviors that emerge from the intricate balance between quantum coupling and fractional damping effects. Through a blend of analytical rigor and sophisticated numerical simulations, this study unveils new insights into the complex interplay among quantum entanglement, dissipation, and non-linear dynamics, offering potential implications for quantum computing, optical systems, and beyond.

Kinetically Controlled and Nonequilibrium Assembly of Block Copolymers in Solution.

Covalent polymers are versatile macromolecules that have found widespread use in society. Contemporary methods of polymerization have made it possible to construct sequence polymers, including block copolymers, with high precision. Such copolymers assemble in solution when the blocks have differing solubilities. This produces nano- and microparticles of various shapes and sizes. While it is straightforward to draw an analogy between such amphiphilic block copolymers and phospholipids, these two classes of molecules show quite different assembly characteristics. In particular, block copolymers often assemble under kinetic control, thus producing nonequilibrium structures. This leads to a rich variety of behaviors being observed in block copolymer assembly, such as pathway dependence (e.g., thermal history), nonergodicity and responsiveness. The dynamics of polymer assemblies can be readily controlled using changes in environmental conditions and/or integrating functional groups situated on polymers with external chemical reactions. This perspective highlights that kinetic control is both pervasive and a useful attribute in the mechanics of block copolymer assembly. Recent examples are highlighted in order to show that toggling between static and dynamic behavior can be used to generate, manipulate and dismantle nonequilibrium states. New methods to control the kinetics of block copolymer assembly will provide endless unanticipated applications in materials science, biomimicry and medicine.

The design, circuit realization and applications of chaotic system with offset-boosting and multistability

Based on the foundation of a three-dimensional Jerk chaotic system, a novel four-dimensional chaotic system based on a memristor with cosine magneto-memristor is proposed. The system’s dynamical behavior is analyzed using bifurcation diagrams, Lyapunov exponents, multiple bifurcation diagrams, two-parameter Lyapunov exponents, complexity, and attractor basins. It is found that this new chaotic system exhibits characteristics such as multistability, transient chaos, intermittent chaos, spike discharge, controllable multi-vortex, and offset-boosting. The chaotic system is designed and simulated in analog circuit and realized in a digital circuit using a Field-Programmable Gate Array (FPGA). The consistency between simulation results and implementation results demonstrates the existence and feasibility of the system. Finally, the significance and superiority of the control scheme are verified based on the adaptive anti-synchronization control strategy, and the synchronization strategy is applied to image encryption, and the results show that the encryption effect is excellent and the anti-jamming ability is strong.

Extreme dependence of dynamics on concentration in highly crowded polyelectrolyte solutions.

Charge-carrying species, such as polyelectrolytes, are vital to natural and synthetic processes that rely on their dynamic behavior. Through single-particle tracking techniques, the diffusivity of individual polyelectrolyte chains and overall system viscosity are determined for concentrated polylysine solutions. These studies show scaling dependences of D ~ c-6.1 and η ~ c7.2, much stronger than theoretical predictions, drawing the applicability of power law fits into question. Similar trends are observed in concentrated solutions prepared at various pH and counterion conditions. These hindered system dynamics appear universal to polyelectrolyte systems and are attributed to the large effective excluded volumes of polyelectrolyte chains inducing glassy dynamics. The framework of the Vrentas-Duda free-volume theory is used to compare polyelectrolyte and neutral systems. Supported by this theory, excluding counterion mass from total polymer mass results in all environmental conditions collapsing onto a common trendline. These results are applicable to crowded biological systems, such as intracellular environments where protein mobility is strongly inhibited.

Nonlinear Static and Dynamic Responses of a Floating Rod Pendulum

Abstract A novel nonlinear dynamics model is developed in this paper to describe the static and dynamic nonlinear behaviors of a rod pendulum partially immersed in still water. The pendulum is hinged above the water level and subject to nonlinear gravity, hydrostatic, and hydrodynamic loads, all of which are incorporated into the system dynamics. The nonlinear static behavior and stability of the pendulum have been characterized by analyzing the fixed points. It is found that Pitchfork bifurcation governs the relationship between the rod density (the control parameter) and the static equilibrium angle. The pendulum's nonlinear response to external harmonic torque is obtained using Harmonic Balance Method (HBM). The influence of system parameters, including hinge height, rod diameter, and rod density, on the nonlinear frequency response is examined. Upon altering the system parameters, particularly the rod density, it is found that the system exhibits either a softening or a hardening effect.

Well-defined tricobalt tetraoxide's critical morphology effect on the structure-reactivity relationship.

This review focuses on exploring the intricate relationship between the catalyst particle size and shape on a nanoscale level and how it affects the performance of reactions. Drawing from decades of research, valuable insights have been gained. Intentionally shaping catalyst particles makes exposing a more significant percentage of reactive facets possible, enabling the control of overactive sites. In this study, the effectiveness of Co3O4 nanoparticles (NPs) with nanometric size as a catalyst is examined, with a particular emphasis on the coordination patterns between oxygen and cobalt atoms on the surface of these NPs. Investigating the correlation between the structure and reactivity of the exposed NPs reveals that the form of Co3O4 with nanometric size can be modified to tune its catalytic capabilities finely. Morphology-dependent nanocatalysis is often attributed to the advantageous exposure of reactive crystal facets accumulating numerous active sites. However, experimental evidences highlight the importance of considering the reorganization of NPs throughout their actions and the potential synergistic effects between nearby reactive and less-active aspects. Despite the significant role played by the atomic structure of Co3O4 NPs with nanometric size, limited attention has been given to this aspect due to challenges in high-resolution characterizations. To bridge this gap, this review strongly advocates for a comprehensive understanding of the relationship between the structure and reactivity through real-time observation of individual NPs during the operation. Proposed techniques enable the assessment of dimensions, configuration, and interfacial arrangement, along with the monitoring of structural alterations caused by fluctuating temperature and gaseous conditions. Integrating this live data with spectroscopic methods commonly employed in studying inactive catalysts holds the potential for an enhanced understanding of the fundamental active sites and the dynamic behavior exhibited in catalytic settings.

Establishing the origin of Marcus-inverted-region behaviour in the excited-state dynamics of cobalt(III) polypyridyl complexes.

Growing interest in the use of first-row transition metal complexes in a number of applied contexts-including but not limited to photoredox catalysis and solar energy conversion-underscores the need for a detailed understanding of their photophysical properties. A recent focus on ligand-field photocatalysis using cobalt(III) polypyridyls in particular has unlocked unprecedented excited-state reactivities. Photophysical studies on Co(III) chromophores in general are relatively uncommon, and so here we carry out a systematic study of a series of Co(III) polypyridyl complexes in order to delineate their excited-state dynamics. Compounds with varying ligand-field strengths were prepared and studied using variable-temperature ultrafast transient absorption spectroscopy. Analysis of the data establishes that the ground-state recovery dynamics are operating in the Marcus inverted region, in stark contrast to what is typically observed in other first-row metal complexes. The analysis has further revealed the underlying reasons driving this excited-state behaviour, thereby enabling potential advancements in the targeted use of the Marcus inverted region for a variety of photolytic applications.

Dynamic mechanical behavior of CNT-reinforced epoxy under medium-strain rate: A comparative study

Carbon nanotubes (CNTs) are generally recognized as one of the most effective fillers to improve the properties of polymeric materials. Subjected to dynamic loading, polymer-based materials often exhibit high strain rate sensitivity. This research investigates the effectiveness of CNTs fillers on the mechanical properties of an epoxy resin at low to medium strain rates through conducting a comparative experimental study. Performing tensile and shear tests, the elastic modulus and strength properties of CNT/epoxy and pure epoxy resin are measured at different strain rates. By proposing an empirical logarithmic relationship, the prediction of dynamic elastic modulus and strength properties at any desired low to medium strain rate is facilitated. For measuring the dynamic fracture toughness of CNT/epoxy and pure epoxy resin at medium strain rate, the instrumented charpy impact test based on the Dynamic Key Curves (DKC) method is used. Experimental measurements still imply on significant enhancements in axial and shear properties and also dynamic fracture toughness up to medium strain rates of 150 s−1 by adding small portion of CNTs.

Effect of temperature and pre-stretch on the dynamic performance of dielectric elastomer minimum energy structure

Dielectric Elastomer Minimum Energy Structures (DEMES) have the ability of actively adjusting their shape to accommodate complex scenarios, understanding the actuation mechanism of DEMES is essential for their effective design and control, which has rendered them a focus of research in the field of soft robotics. The actuation ability of DEMES is usually influenced by external conditions, among which the electromechanical properties of DE materials are highly sensitive to temperature changes, and the pre-stretch ratio of DE materials has a significant impact on the dynamic performance of DEMES. Therefore, it is necessary to study the effects of temperature and pre-stretch ratio on the nonlinear dynamic behavior of DEMES. In this paper, in response to the lack of research on the influence of DE pre-stretch ratio on the actuation characteristics of DEMES, this paper proposes a systematic modeling and analysis framework that comprehensively considers pre-stretch factors, temperature factors, and viscoelastic factors, and establishes the motion control equation of DEMES affected by the coupling effect of DE pre-stretch ratio and temperature. The proposed analytical framework is used to analyze the evolution of the electromechanical response of DEMES under voltage excitation under the coupling of DE pre-stretch ratio and temperature. The results indicate that the bending angle, inelastic deformation, resonant frequency, and dynamic stability of DEMES can be jointly adjusted by the DE pre-stretch ratio and ambient temperature. A low pre-stretch ratio of DE can lead to dynamic instability of DEMES, while appropriate temperature conditions and higher pre-stretch ratios can significantly improve the actuation ability of DEMES. This can provide theoretical guidance for the design and deformation control of DEMES.

Towards accurate prediction of the dynamic behavior and failure mechanisms of three-dimensional braided composites: A multiscale analysis scheme

In this paper, a dynamic multiscale model is proposed for three-dimensional four-directional (3D4D) braided composites, considering the effects of strain rate and shear enhanced failure mechanism. The strain rate-dependent constitutive models are established for both resin and yarns. The accuracy of the yarn model is validated by comparing the simulated stress-strain curves with the experimental results obtained from the Split Hopkinson Pressure Bar (SHPB) tests with various strain rates. The shear enhancement coefficient of the yarn is determined from the failure envelopes with a discussion of crack propagation angles. The results show that, based on the calculated microscale properties, the mesoscale model accurately predicts both the longitudinal and transverse compressive strain-stress behavior of 3D4D braided composites at different strain rates. A comparative analysis reveals that the shear-enhanced failure model achieves a better prediction compared with other counterparts, such as Hashin-Rotem and Tsai-Wu Models. The proposed dynamic multiscale scheme for 3D braided composites is an efficient and accurate tool to characterize their multiscale features and strain rate-dependent behavior.

Exploring threshold dynamics of a behavioral epidemic model featuring two susceptible classes and second-order jump–diffusion

Understanding and modeling behavioral changes during epidemic outbreaks is crucial for devising effective public health interventions. In this paper, we introduce an enhanced behavioral epidemic model that integrates novel elements to better capture real-world phenomena. Our model incorporates logistic growth as a recruitment rate, reflecting the population’s intrinsic growth constraints. Additionally, we consider two incidence rates to account for varying transmission dynamics. To extend the model’s applicability, we introduce perturbations through second-order jump–diffusion processes, allowing for abrupt changes in population dynamics. We define a threshold parameter based on the properties of an auxiliary system, which distinguishes between the existence of a unique stationary distribution and stochastic extinction. Through numerical simulations, we validate our theoretical findings and demonstrate the impact of nonlinear noise on the model dynamical behavior.

Entanglement inside a black hole before the Page time

We investigate the evolution of entanglement within an open, strongly coupled system interacting with a heat bath as its environment, in the frameworks of both the doubly holographic model and the Sachdev-Ye-Kitaev (SYK) model. Generally, the entanglement within the system initially increases as due to internal interactions; however, it eventually dissipates into the environment. In the doubly holographic setup, we consider an end-of-the-world brane in the bulk to represent an eternal black hole coupled with its radiation and the evolution of the global thermofield double (TFD) state. For small black holes, the reflected entropy between the bipartition exhibits a ramp-plateau-slump behavior, where the plateau arises due to the phase transition of the entanglement wedge cross-section before the Page time. Similarly, the mutual information between the bipartition displays a ramp-slop-stabilizing behavior. In quantum mechanics, we consider a double copy of the SYK-plus-bath system in a global TFD state, resembling an eternal black hole interacting with an environment. The Rényi mutual information within the double-copied SYK clusters exhibits a ramp-plateau-slope-stabilizing behavior. The dynamic behaviors of the entanglement quantities observed in these two models are attributable to the competition between the internal interaction of the system and the external interaction with the baths. Our study provides a fine-grained picture of the entanglement dynamics inside black holes before their Page time.