Study Of Dynamics Research Articles

Dynamics of a rank-one multiplicative perturbation of a unitary matrix

We provide a dynamical study of a model of multiplicative perturbation of a unitary matrix introduced by Fyodorov. In particular, we identify a flow of deterministic domains that bound the spectrum with high probability, separating the outlier from the typical eigenvalues at all sub-critical timescales. These results are obtained under generic assumptions on [Formula: see text] that hold for a variety of unitary random matrix models.

Synthesis, Characterization, Antimicrobial and In Silico Studies of isatin Schiff base linked 1,2,3-triazole hybrids.

A new series of isatin-Schiff base linked 1,2,3-triazole hybrids has been synthesized using CuAAC approach from (E)-3-(phenylimino)-1-(prop-2-yn-1-yl)indolin-2-one derivatives in high yield (73-91 %). These synthesized derivatives were characterized using FT-IR, 1H NMR, 13C NMR, 2D-NMR and HRMS spectral techniques. The in vitro antimicrobial activity assay proposed that most of the tested hybrids exhibited promising activity. Compound 5j displayed good significant antibacterial efficacy against P. aeruginosa and B. subtilis with MIC value of 0.0062 µmol/mL. While, 5j showed better antifungal potency against A. niger with MIC value of 0.0123 µmol/mL. The docking studies of most promising compounds were also performed with the well-known antibacterial and antifungal targets i.e. 1KZ1, 5TZ1. Molecular modelling investigations demonstrated that hybrids 5h and 5l exhibited good interactions with 1KZN and 5TZ1, with binding energies of -9.6 and -11.0 kcal/mol, respectively. Further, molecular dynamics studies of the compounds showing promising binding interactions were also carried out to study the stability of complexes of these hybrids with both the targets.

A Mean Field to Capture Asynchronous Irregular Dynamics of Conductance-Based Networks of Adaptive Quadratic Integrate-and-Fire Neuron Models.

Mean-field models are a class of models used in computational neuroscience to study the behavior of large populations of neurons. These models are based on the idea of representing the activity of a large number of neurons as the average behavior of mean-field variables. This abstraction allows the study of large-scale neural dynamics in a computationally efficient and mathematically tractable manner. One of these methods, based on a semianalytical approach, has previously been applied to different types of singleneuron models, but never to models based on a quadratic form. In this work, we adapted this method to quadratic integrate-and-fire neuron models with adaptation and conductance-based synaptic interactions. We validated the mean-field model by comparing it to the spiking network model. This mean-field model should be useful to model large-scale activity based on quadratic neurons interacting with conductance-based synapses.

How Irregular Geometry and Complex Feed Waveform Affect Pulsating Arterial Mass Transfer.

Alzheimer's disease is a progressive degenerative condition that has various levels of effect on one's memory. It is thought to be caused by a buildup of protein in small fluid-filled spaces in the brain called perivascular spaces (PVS). The PVS often takes on the form of an annular region around arteries and is used as a protein-clearing system for the brain. To analyze the modes of mass transfer in the PVS, a digitized scan of a mouse brain PVS segment was meshed and used for computational fluid dynamics (CFD) studies. Tandem analyses were then carried out and compared between the mouse PVS section and a cylinder with commensurate dimensionless parameters and hydraulic resistance. The geometry pair was used to first validate the CFD model and then assess mass transfer in various advection states: no flow, constant flow, sinusoidal flow, sinusoidal flow with zero net solvent flux, and an anatomically correct asymmetrical periodic flow. Two mass transfer situations were considered, one being a protein build-up and the other being a protein blend-down. The results showed that, for all the flows in question and both protein scenarios, there was nearly no protein clearance benefit by the anatomically correct PVS geometry. Surprisingly, solute blend-down was diffusion-dominated even for high Peclet numbers. Findings herein lead to the conclusion that minimal risk would be incurred by incorporating PVS geometry into existing reduce-order modeling arterial networks.

Synergistic Improvement of Antibacterial and Osteogenic Differentiation of Thermomechanically Processed Mg-Zr-Sr-Ce Alloy: Insights into the Role of Precipitate Evolution Supported by AIMD Simulation Study.

In the present study, we have discussed the influence of forging temperature (623 K (FT623), 723 K (FT723) and 823 K (FT823)) on microstructure and texture evolution and its implication on mechanical behavior, in vitro-in vivo biocorrosion, antibacterial response, and cytocompatibility of microalloyed Mg-Zr-Sr-Ce alloy. Phase analysis, SEM, and TEM characterization confirm the presence of Mg12Ce precipitate, and its stability was further validated by performing ab initio molecular dynamic simulation study. FT723 exhibits strengthened basal texture, higher fraction of second phases, and particle-stimulated nucleation-assisted DRX grains compared to other two specimens, resulting in superior strength with comparable ductility. FT723 also exhibits superior corrosion resistance mainly due to the strengthened basal texture and lower dislocation density. All the specimens exhibit excellent antibacterial behavior with Gram-negative E. coli, Gram-positive Staphylococcus aureus, and Pseudomonas aeruginosa bacteria. 100% reduction of bacterial growth is observed within 24 h of culture of the specimens. Cytocompatibility was determined by challenging specimen extracts with the MC3T3-E1 cell lines. FT723 specimen exhibits the highest cell proliferation and alkaline phosphatase activity (ALP) because of its superior corrosion resistance. The ability of the specimens to be used in orthopedic implant application was evaluated by in vivo study in rabbit femur. Neither tissue-related infection nor the detrimental effect surrounding the implant was confirmed from histological analysis. Significant higher bone regeneration surrounding the FT723 specimen was observed in SEM analysis and fluorochrome labeling. After 60 days, the FT723 specimen exhibits the highest bone formation, suggesting it is a suitable candidate for orthopedic implant application.

Exploring the inhibitory action of betulinic acid on key digestive enzymes linked to diabetes via in vitro and computational models: approaches to anti-diabetic mechanisms

ABSTRACT Phytochemicals are now increasingly exploited as remedial agents for the management of diabetes due to side effects attributable to commercial antidiabetic agents. This study investigated the structural and molecular mechanisms by which betulinic acid exhibits its antidiabetic effect via in vitro and computational techniques. In vitro antidiabetic potential was analysed via on α-amylase, α-glucosidase, pancreatic lipase and α-chymotrypsin inhibitory assays. Its structural and molecular inhibitory mechanisms were investigated using Density Functional Theory (DFT) analysis, molecular docking and molecular dynamics (MD) simulation. Betulinic acid significantly (p < 0.05) inhibited α-amylase, α-glucosidase, pancreatic lipase and α-chymotrypsin enzymes with IC50 of 70.02 μg/mL, 0.27 μg/mL, 1.70 μg/mL and 8.44 μg/mL, respectively. According to DFT studies, betulinic acid possesses similar reaction in gaseous phase and water due to close values observed for highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO) and the chemical descriptors. The dipole moment indicates that betulinic acid has high polarity. Molecular electrostatic potential surface revealed the electrophilic and nucleophilic attack-prone atoms of the molecule. Molecular dynamic studies revealed a stable complex between betulinic acid and α-amylase, α-glucosidase, pancreatic lipase and α-chymotrypsin. The study elucidated the potent antidiabetic properties of betulinic acid by revealing its conformational inhibitory mode of action on enzymes involved in the onset of diabetes.

Multi-objective optimisation of a 2D backward-sfacing step channel with porous baffles

AbstractPorous baffles can be used to enhance heat transfer in various engineering applications, including electronic cooling, gas turbine blades, and chemical reactors. Also, the backward-facing step is a widely used configuration in fluid dynamics studies due to its simplicity and relevance to real-world geometries. This study examines heat transfer and flow characteristics in a backward-facing step channel featuring a heated bottom wall and two porous baffles. A computational fluid dynamics model, validated against prior research, is used to investigate flow and temperature fields. The innovation of this work lies in the application of multi-objective optimisation to search for a set of solutions that establish a trade-off between the average Nusselt number and the pressure drop. The optimisation specifically considers various parameters of the porous baffles, including height, width, distance from the step, and Darcy number, to identify optimal design configurations. Results show that porous baffles significantly improve heat transfer compared to a backward-facing step channel without them, despite an increase in pressure drop due to their presence. This work offers valuable insights into the trade-off between heat transfer performance and pressure drop, crucial for designing efficient heat transfer systems. By exploring the Pareto-Frontier, which represents various optimal design solutions, the study provides practical guidance when seeking to optimise heat transfer in backward-facing step channels with porous baffles. The findings contribute to advancing the understanding of heat transfer enhancement, highlighting the potential of porous baffles as a viable solution for improving thermal management in engineering systems.

A Molecular Dynamics Study of Mechanical and Conformational Properties of Conjugated Polymer Thin Films

A Molecular Dynamics Study of Mechanical and Conformational Properties of Conjugated Polymer Thin Films

The Effects of Edge Dislocations on The Corrosion Behavior of Pure Iron in Liquid Lead-Bismuth Eutectic: A Molecular Dynamics Study

The effect of liquid lead–bismuth eutectic (LBE) on the corrosion evolution of iron-based materials with varying densities of edge dislocation defects was studied. Molecular dynamics simulations were conducted at temperatures ranging from 823 K to 1173 K, and the process of penetration of Pb and Bi atoms at the dislocation core was analyzed. The results indicated that Fe atoms near the dislocation core have the lowest substitution energy (−4.79 eV/atom), making them more likely to be replaced by Pb and Bi atoms. Moreover, it was found that the increase in dislocation density did not result in a high penetration depth of LBE atoms, attributed to the interaction of dislocations. These findings provide crucial insights into the LBE corrosion mechanism in iron-based materials with dislocation defects.

Ab initio molecular dynamics study on the local structures and solid/liquid interface in liquid Al-Ti and Al-B-Ti alloys

High-purity aluminum, owing to its excellent physical and chemical properties, finds extensive applications across various fields. A comprehensive understanding of the local structure of liquid Al-based alloys and the characteristics of solute atoms at the forefront of the solid-liquid interface is highly advantageous for the purification of aluminum. Ab initio molecular dynamics (AIMD) simulations were employed to study the local structures, element interactions and electronic structures in Al-Ti and Al-B-Ti melts, together with the behaviors of Ti atom and B-Ti atom pair at the solid/liquid interface forefront of Al. In the Al-B-Ti ternary melt, there are stronger interactions between B and Ti atoms than those between Al and B atoms as well as between Al and Ti atoms. The introduction of B atoms leads to the disruption of Al-Ti bonds and the formation of B-Ti bonds, thereby altering the state of Ti atoms in the melt and then influencing their diffusion properties. The dynamic process of B-Ti bond formation in the melt has been elucidated. The bond angle distribution function shows that the geometric configuration around Ti atoms in the Al melt undergoes significant changes with the addition of B atoms. A strong hybridization occurs between the 3d orbital of Ti atom and the 2p orbital of B atom. Moreover, a notable charge accumulation between B and Ti atoms, indicates the strong interaction between them. The addition of Ti atom can promote the migration of the Al solid/liquid interface. The B-Ti bond is very stable at the forefront of the Al solid/liquid interface, and the formation of B-Ti bond significantly drag the migration of the Al solid/liquid interface.

GeC/SnSe2 van der waals heterostructure: A promising direct Z-scheme photocatalyst for overall water splitting with strong optical absorption, high solar-to-hydrogen energy conversion efficiency and superior catalytic activity

To alleviate the energy crisis and achieve green energy conversion, the heterojunctions that can be applied to the photocatalytic decomposition of water have attracted attention. In this paper, we design a novel two-dimensional GeC/SnSe2 heterostructure and investigate in detail the structural stability, electronic characteristics, photocatalytic activity and optical behavior as well as the effects due to the applied strain based on the first-principles. Firstly, the most stable γ-stacking mode is determined by combining energy comparison, thermodynamic and dynamic studies. Second, the analysis of electronic properties demonstrates that the GeC/SnSe2 heterostructure exhibits a type-II energy band arrangement and a direct Z-scheme photocatalytic mechanism. This pivotal aspect enhances the separation of photogenerated carriers at the interface and facilitates the active participation of the most proficient materials in oxidation-reduction processes during photocatalytic hydrolysis reactions. The hydrolysis reaction's Gibbs free energy shift demonstrates the GeC/SnSe2 heterostructure's superior photocatalytic activity in neutral and alkaline environments and can spontaneously carry out the overall hydrolysis reaction, and this outstanding ability is not affected by the −4% to 4% strain range. In addition, the GeC/SnSe2 heterostructure has outstanding solar-to-hydrogen efficiency (58.18%) and excellent light absorption capability (up to 4×105cm−1) within visible light. The implications of these discoveries point towards the direct Z-scheme GeC/SnSe2 heterostructure holds promise as an excellent candidate for photocatalytic water splitting applications.

Experimental Study of Condensation Heat Transfer and Droplet Dynamics on Multiple Horizontal Copper Tubes with Superhydrophobic Characteristics

We conducted an experimental study on the condensation heat transfer and droplet dynamics on multiple horizontal copper tubes with superhydrophobic characteristics. Condensation heat transfer has various industrial applications such as power plants and air-conditioning systems. Because condensers are typically designed in multiple-tube configurations, studying the phenomenon of multiple tubes is important. We investigated the effect of a superhydrophobic surface modification, which induces dropwise condensation, on the heat transfer performance of multiple-tube condensers. The purpose of this research is to evaluate the extent to which heat transfer performance is improved by comparing superhydrophobic tubes with bare tubes and to analyze the impact of droplet dynamics on heat transfer performance. The results show that the heat transfer coefficient of the superhydrophobic tubes is improved by approximately 9.5%–44.9% compared to that of bare tubes. Droplet dynamic analysis revealed differences in droplet behavior between the superhydrophobic tubes and bare tubes, including the formation of droplets by condensation, the process of droplets falling on the tube surface, and the impact of droplets falling on other tubes in a multiple-tube configuration. Based on these results and observations, it can be concluded that the heat transfer performance of the superhydrophobic tube is superior to that of the bare tube. The droplet dynamic analysis demonstrated that the droplets formed on the superhydrophobic surface could be easily removed by the flow, leading to more efficient heat transfer. These findings highlight the potential for more efficient heat transfer in multiple tubes through superhydrophobic modifications.

Visualizing Dynamic Single Atom Catalysis.

Many industrial chemical processes, including for producing fuels, foods, pharmaceuticals, chemicals and environmental controls, employ heterogeneous solid state catalysts at elevated temperatures in gas or liquid environments. Dynamic reactions at the atomic level play a critical role in catalyst stability and functionality. In-situ visualization and analysis of atomic-scale processes in real time under controlled reaction environments can provide important insights into practical frameworks to improve catalytic processes and materials. This review focuses on innovative real time in-situ EM methods, including recent progress in analytical in-situ environmental (scanning) transmission EM (ESTEM and ETEM) with single atom resolution for visualizing dynamic single atom catalysis under controlled flowing gas reaction environments. ESTEM studies of single atom dynamics of reactions, and of sintering deactivation, contribute to a better-informed understanding of the yield and stability of catalyst operations. Advances in in-situ technologies, including gas and liquid sample holders, nano-tomography and higher voltages, as well as challenges and opportunities in tracking reacting atoms, are highlighted. The findings show that the understanding and application of fundamental processes in catalysis can be improved, with valuable economic, environmental, and societal benefits. This article is protected by copyright. All rights reserved.

Six-dimensional quantum dynamics of an Eley-Rideal reaction between gaseous and adsorbed hydrogen atoms on Cu(111).

In the form of direct abstraction of a surface adsorbate by a gaseous projectile, the Eley-Rideal (ER) reaction at the gas-surface interface manifests interesting dynamics. Unfortunately, high-dimensional quantum dynamical (QD) studies for ER reactions remain very challenging, which demands a large configuration space and the coordinate transformation of wavefunctions. Here, we report the first six-dimensional (6D) fully coupled quantum scattering method for studying the ER reaction between gas phase H(D) atoms and adsorbed D(H) atoms on a rigid Cu(111) surface. Reaction probabilities and product rovibrational state distributions obtained by this 6D model are found to be quite different from those obtained by reduced-dimensional QD models, demonstrating the high-dimensional nature of the ER reaction. Using two distinct potential energy surfaces (PESs), we further discuss the influence of the PES on the calculated product vibrational and rotational state distributions, in comparison with experimental results. The lateral corrugation and the exothermicity of the PES are found to play a critical role in controlling the energy disposal in the ER reaction.

Comparative Retention Analysis of Intercalated Cations Inside the Interlayer Gallery of Lamellar and Nonlamellar Graphene Oxide Membranes in Reverse Osmosis Process: A Molecular Dynamics Study.

Over the past decade, multilayered graphene oxide (GO) membranes have emerged as promising candidates for desalination applications. Despite their potential, a comprehensive understanding of separation mechanisms remains elusive due to the intricate morphology and structural arrangement of interlayer galleries. Moreover, a critical concern of multilayered GO membranes is their susceptibility to swelling within aqueous environments, which hinders their practical implementation. Therefore, this study introduces cation intercalation within GO laminates to elucidate the underlying factors governing swelling behavior and subsequently mitigate it. Moreover, this study performed nonequilibrium molecular dynamics simulations on the cation (Mg2+ or K+)-intercalated lamellar and nonlamellar GO membranes to understand the effect of the arrangement of GO sheets on the retention time of intercalated cations within GO layers, water permeance, and salt rejection mechanism in the reverse osmosis process using cation-intercalated GO membranes. Our results highlight that lamellar GO membranes exhibit higher water permeance, attributed to their well-defined interlayer gallery structure. On the other hand, nonlamellar GO membranes display superior salt rejection due to their complex interlayer gallery structure that impedes salt permeation. Moreover, the structural complexity of nonlamellar GO membranes contributes to greater stability by retention of the more intercalated cations for a longer time within the layers. Furthermore, it is observed that a higher percentage of Mg2+ cations remained inside the GO laminates as compared to K+ cations, hence resulting in the greater stability of the Mg2+-intercalated GO membrane in the aqueous environment.

A Study of Problems Faced by Engineering Students in Mathematical Subjects using Fuzzy Cognitive Mappings

Introduction: One of the main concerns and issues for educators, particularly for engineering students, has been the caliber of mathematics instruction and learning. There are many different concepts and skills that make up mathematics. The improvement of problem-solving skills is one of mathematics' key functions. Numerous colleges struggle with the issue of students quitting because of mathematics because it is frequently thought of as a topic that students find difficult to master. Objectives: The study's goal is to examine the reasons why engineering students struggle with math. In this research, using fuzzy cognitive map techniques (FCM), we analyze the challenges engineering students encounter when trying to earn grades in math-related courses. FCM is a blend of some fuzzy logic and neural network ideas. FCM is made up of collections of concepts and all the different causal relationships that connect them. Methods: We created a model of the issues and causal relationships that engineering students faced when trying to succeed in mathematics classes. Both statically and dynamically, utilizing concepts from graph theory and simulations, the model is examined. Also we applied DEMATEL one of the Multi Criteria Decision Making method. Results: The analysis reveals that the main issue is not just the students' lack of mathematical background knowledge, but also their attitude toward learning, psychological response to the first failure, and lack of effort to complete additional tasks or attend tutorials. Conclusions: Using the FCM method, a model was created for the case of problems faced by engineering college students in scoring marks in mathematical related subjects based on the opinion of a domain expert. The model was first examined statically. The model was then simulated in a dynamic and it was predicted that there should be an attitude change in teachers and as well as students. Through the above static and dynamic studies of the FCM model was identified as important and useful decision support system, since it capable to provide support to decision makers, by making predictions on various scenarios that are imposed on the FCM model.

Engineering Porous Carbon with Precise Sizes to Promote Surface‐Dominated Storage in Sodium‐Ion Batteries

AbstractAs the sole commercially viable anode material for sodium‐ion batteries, hard carbon currently faces challenges such as slow diffusion kinetics in the low voltage range and low safety due to sodium deposition. In order to deepen the understanding of the pseudocapacitive processes of hard carbon in the high voltage range and enhance sodium storage capacity, this study systematically investigates the electrochemical performance and ion storage of ZIF‐8‐derived porous carbons (ZPCs) of different sizes. We propose a mathematical model based on a spherical particle core‐shell structure, which profoundly reveals the relationship between size and specific surface area, as well as the linear relationship between specific surface area and specific capacity. Moreover, simply by reducing the size of the porous carbon, the specific capacity increased by 86.5 mAh g−1. Dynamic studies reveal that in nano‐porous carbon materials, sodium‐ion storage primarily relies on defect adsorption. Size reduction enhances physical adsorption and surface capacitance response, with ZPC‐80 exhibiting lower resistance and higher diffusion coefficient, indicating that size reduction improves electronic conductivity and charge transfer efficiency, achieving excellent reversible capacity and cycling stability. This work yields a profound insight into the dynamic characteristics of hard carbon anode materials, presenting a new perspective for the design of efficient sodium‐ion batteries.

Outer billiards in the spaces of oriented geodesics of the three‐dimensional space forms

AbstractLet be the three‐dimensional space form of constant curvature , that is, Euclidean space , the sphere , or hyperbolic space . Let be a smooth, closed, strictly convex surface in . We define an outer billiard map on the four‐dimensional space of oriented complete geodesics of , for which the billiard table is the subset of consisting of all oriented geodesics not intersecting . We show that is a diffeomorphism when is quadratically convex. For , has a Kähler structure associated with the Killing form of . We prove that is a symplectomorphism with respect to its fundamental form and that can be obtained as an analogue to the construction of Tabachnikov of the outer billiard in defined in terms of the standard symplectic structure. We show that does not preserve the fundamental symplectic form on associated with the cross product on , for . We initiate the dynamical study of this outer billiard in the hyperbolic case by introducing and discussing a notion of holonomy for periodic points.

Multimorbid life expectancy across race, socio-economic status, and sex in South Africa

Multimorbidity is increasing globally as populations age. However, it is unclear how long individuals live with multimorbidity and how it varies by social and economic factors. We investigate this in South Africa, whose apartheid history further complicates race, socio-economic, and sex inequalities. We introduce the term ‘multimorbid life expectancy’ (MMLE) to describe the years lived with multimorbidity. Using data from the South African National Income Dynamics Study (2008–17) and incidence-based multistate Markov modelling, we find that females experience higher MMLE than males (17.3 vs 9.8 years), and this disparity is consistent across all race and education groups. MMLE is highest among Asian/Indian people and the post-secondary educated relative to other groups and lowest among African people. These findings suggest there are associations between structural inequalities and MMLE, highlighting the need for health-system and educational policies to be implemented in a way proportional to each group’s level of need.

Analytical study of soliton dynamics in the realm of fractional extended shallow water wave equations

In this study, we use the Khater Method (KM) as an efficient analytical tool to solve (3+1)-dimensional fractional extended shallow water wave equations (FESWWEs) with conformable derivatives. The KM transforms fractional partial differential equations to ordinary differential equations (ODEs) via strategic variable transformation. Then, series-form solutions to these ODEs are proposed, which turn them into nonlinear algebraic systems. The solution to this set of algebraic equations yields shock travelling wave solutions expressed in hyperbolic, trigonometric, exponential, and rational functions. The study’s findings are corroborated by 2D, 3D, and contour graphs that show the changing patterns of the detected shock travelling waves. These findings have important significance for the discipline, offering vital insights into the intricate dynamics of FESWWEs. The effectiveness of KM is demonstrated by its capacity to produce varied solutions and contribute to a thorough knowledge of such complex phenomena.