Initial Bifurcation Research Articles (Page 1)

INTRODUCTION: One of the main factors limiting the effectiveness of percutaneous coronary intervention (PCI) in the long-term follow-up period is in-stent restenosis (ISR). One predictor of its development is the initial bifurcation lesion (BL) of the coronary arteries (CA). Such patients present a particularly complicated group for endovascular treatment. AIM: To compare the results of different treatment methods for patients with coronary heart disease and ISR in the area of CA bifurcation. MATERIALS AND METHODS: A single-center, non-randomized, retrospective study included 105 patients with coronary heart disease with ISR in the area of CA bifurcation, who underwent PCI from 2012 to 2023. Group 1 (n = 40) included patients who underwent repeat revascularization using a one-stent coronary stenting technique, group 2 (n = 32) included patients who underwent revascularization using a two-stent technique, group 3 (n = 33) included patients in whom a non-stent treatment technology was used — application of an antiproliferative drug using drug-eluting balloon catheters. The median follow-up period was 380 [264; 411] days. RESULTS: There were no statistically significant differences in the ISR recurrence rate in all groups, however, there was a tendency for it to increase in groups 2 and 3: 8 (25.0%) in group 2 and 8 (24.2%) in group 3 versus 4 (10.0%) in group 1, p = 0.18. The frequency of myocardial infarction did not differ significantly in patients of the analyzed groups: 2 (5.0%) in group 1, 2 (6.3%) in group 2 and 1 (3.0%) in group 3, p = 0,828. There were also no differences in the proportion of adverse cardiovascular vents between the groups: 6 (15.0%) in group 1, 11 (34.3%) in group 2, and 9 (27.3%) in group 3, p = 0.154. When using a one-stent coronary stenting technique, there was a tendency to reduction of the number of adverse cardiovascular events in the late postoperative period compared to other methods, but it did not reach a statistically significant level: 6 (15.0%) versus 20 (30.7%), p = 0.07. CONCLUSION: Endovascular revascularization in binary ISR of the CA bifurcation zone using a one-stent, two-stent techniques and drug-eluting balloon catheters ensures satisfactory immediate and long-term outcomes with no statistical difference.

The middle cerebral artery (MCA) shows significant morphological variability in its branching pattern. While bifurcation is the most common configuration, several other branching variants have been described. In this report, the authors present a new morphological variant-called asymmetrical pseudotetrafurcation-discovered during magnetic resonance angiography (MRA) in a 25-year-old woman. Imaging revealed an initial bifurcation of the MCA trunk, followed by trifurcation of one of the main branches at a distance of 1.55mm from the primary bifurcation point, resulting in a 4-branch pattern. Unlike previously reported cases of symmetrical pseudotetrafurcation, where both branches undergo bifurcation, this asymmetrical variant involves secondary branching in only one limb, leading to spatial asymmetry. The frequency and clinical significance of this anatomical pattern are not yet fully understood. However, recognizing such MCA branching variants is essential for accurate cerebrovascular imaging interpretation and can greatly influence the planning and performance of neurosurgical or endovascular procedures.

Abstract This study presents a novel approximation approach for the Fractional Rössler System using the Variational Iteration Method (VIM). The Fractional Rössler System, an extension of the classical Rössler System, incorporates fractional-order derivatives to capture more intricate dynamical behaviors. VIM is employed due to its efficiency in handling nonlinear fractional differential equations (FDEs) and its novel application to this system. A comparative analysis with the Adams-Bashforth-Moulton method has been conducted, and numerical values are presented to validate the effectiveness of VIM. The graphical results reveal significant chaotic dynamics, including the presence of strange attractors and sensitivity to initial conditions and bifurcation phenomena, indicating transitions between periodic and chaotic regimes. This work provides a new perspective on approximating fractional chaotic systems, demonstrating the potential of VIM in advancing the study of complex dynamical systems.

The role of thermal gradients in inducing a succession of flow bifurcations resulting in a chaotic flow, a precursor to turbulence, is studied through a non-classical heat wave theory. Natural convective flow in an enclosure caused by thermal gradients that exist between a heater mounted inside and cold vertical walls is considered. Two-dimensional unsteady incompressible flow is considered with the Boussinesq approximation. The Cattaneo–Christov heat flux that incorporates thermal relaxation and can reduce to the classical Fourier model is assumed. Finite-volume based computational results are obtained. Long-term solutions after initial transients were focused, and the flow and heat transfer characteristics are obtained for moderately high Rayleigh numbers and different aspect ratios A of the enclosure. The oscillating flows are studied through a phase path, the overall Nusselt number, and power spectral density. In the Fourier model, the resulting symmetric thermal plume directly undergoes Hopf bifurcation for A = 1 and 1.5, whereas it undergoes pitchfork bifurcation followed by Hopf bifurcation for A = 2 and 2.5. The Cattaneo model is also found to introduce the initial symmetry-breaking pitchfork bifurcation for A = 2 and 2.5. The Ruelle–Takens–Newhouse scenario through an interval of quasiperiodic motions admitting frequency-locked periodic cycles is preferred for the onset of turbulence in both the Fourier and Cattaneo models. Thermal relaxation makes frequency locking stronger even after the appearance of a weakly chaotic motion in tall enclosures. The Cattaneo–Christov heat flux suppresses the appearance of bifurcations and delays the onset of turbulence in square enclosures, whereas an opposite effect is seen in tall enclosures.

In this paper, a global amplitude-controlled discrete hyperchaotic memristive map is designed utilizing the hyperbolic tangent function. This map exhibits fixed points arranged in a line along the y-axis, and the stability distributions of these fixed points are delineated based on variations in both the initial conditions of the map and the parameter plane. The dynamic characteristics of the map were examined through the analysis of its 2D dynamics and the largest Lyapunov exponent (LE) distribution. The existence of multistability was robustly confirmed through a comprehensive analysis of the basin of attraction, the spectra of LE that depend on initial values, bifurcation diagrams, and trajectory plots. Additionally, the amplitude of the map can be adjusted both globally and locally through manipulation of the non-bifurcation parameter. Subsequently, a digital circuit powered by a microcontroller was designed to embody the map. In comparison to recent maps, the newly devised map exhibits superior efficacy in the realm of image encryption applications.

ABSTRACTCurrent research on frost heave‐induced cracking in fractures of rock masses in cold regions typically assumes that fractures are fully saturated. However, in actual engineering practice, rock mass fractures are often in an unsaturated state. Upon freezing, the fracture surfaces are subjected to a complex combination of gas pressure, freezing pressure, and ice friction forces. This study investigates the crack initiation mechanisms of unsaturated rock fractures with asymmetric edge cracks under gas‐ice pressure conditions. Assuming a small yield range, we derive the calculation formulas for gas pressure after freezing, stress intensity factor, crack initiation angle, and crack initiation stress based on the complex variable function and elastic‐plastic crack mechanics theory. Additionally, an improved phase‐field model is proposed for calculating dynamic crack propagation in mixed‐mode I‐II fractures, with key parameters analyzed and discussed. The results demonstrate that: By comparing the analytical solutions with numerical calculations, the validity of the proposed model is verified. During the freezing process, dynamic crack propagation in unsaturated fractures will exhibit bifurcation. At higher water saturation levels, crack propagation shows a pattern of initial bifurcation followed by subsequent merging.

As a key component of lightweight impact-protection devices, thin-walled structures with marvelous specific energy absorption (SEA) have attracted wide attention. Inspired by leaf venation in royal water lily, a hybrid multi-cell thin-walled structure with fractal and hierarchy architectures is proposed. Its crashworthiness is compared with traditional cylinder by combining finite element simulation and experiment, and corresponding mechanism is revealed. The results show that due to more folds and smaller folded wavelength, the venation-like structure exhibits better crashworthiness than the cylinder. Increasing the initial bifurcation number and hierarchy level of venation-like structure will introduce massive corner constraints, especially the hierarchy level, which benefits folding deformation and improving effectively crashworthiness. Further, a fully hybrid venation-like structure is designed by introducing gradient architecture. With the increase of length-gradient or thickness-gradient, the SEA first linearly increases and then slightly decreases. Under the optimal length-gradient, majority of area exhibits high internal energy. By taking the gradient length and thickness simultaneously, a kind of hybrid deformation mode with quasi-uniform small folding and overall large folding appears, where multiple small folds interacts strongly, achieving good load-bearing capacity. The optimal SEA of venation-like structure is 81.5% higher than that of the cylinder.

Exploring travelling wave solutions, bifurcation, chaos, and sensitivity analysis in the (3+1)-dimensional gKdV-ZK model: A comprehensive study using Lie symmetry methodology

Blood flow effects in a patient with a thoracic aortic endovascular prosthesis

Numerical investigation of combustion instability in a single-element liquid rocket engine: Intermittency routes before and after thermoacoustic instability

As a promising technique, the spatial information of an object can be acquired by employing active illumination of sinusoidal patterns in the Fourier single-pixel imaging. However, the major challenge in this field is that a large number of illumination patterns should be generated to record measurements in order to avoid the loss of object details. In this paper, an optical multiple-image authentication method is proposed based on sparse sampling and multiple logistic maps. To improve the measurement efficiency, object images to be authenticated are randomly sampled based on the spatial frequency distribution with smaller size, and the Fourier sinusoid patterns generated for each frequency are converted into binarized illumination patterns using the Floyd-Steinberg error diffusion dithering algorithm. In the generation process of the ciphertext, two chaotic sequences are used to randomly select spatial frequency for each object image and scramble all measurements, respectively. Considering initial values and bifurcation parameters of logistic maps as secret keys, the security of the cryptosystem can be greatly enhanced. For the first time to our knowledge, how to authenticate the reconstructed object image is implemented using a significantly low number of measurements (i.e., at a very low sampling ratio less than 5% of Nyquist limit) in the Fourier single-pixel imaging. The experimental results as well as simulations illustrate the feasibility of the proposed multiple-image authentication mechanism, which can provide an effective alternative for the related research.

Muscle denervation promotes functional interactions between glial and mesenchymal cells through NGFR and NGF

Seasonal effects powerfully shape the population dynamics with periodic climate changes because species naturally adjust their dynamics with seasonal variations. In response to these effects, sometimes population dynamics exhibit synchrony or generate chaos. However, synchronized dynamics enhance species' persistence in naturally unstable environments; thus, it is imperative to identify parameters that alter the dynamics of an ecosystem and bring it into synchrony. This study examines how ecological parameters enable species to adapt their dynamics to seasonal changes and achieve phase synchrony within ecosystems. For this, we incorporate seasonal effects as a periodic sinusoidal function into a tri-trophic food chain system where two crucial bio-controlling parameters, Allee and refugia effects, are already present. First, it is shown that the seasonal effects disrupt the limit cycle and bring chaos to the system. Further, we perform rigorous mathematical analysis to perform the dynamical and analytical properties of the nonautonomous version of the system. These properties include sensitive dependence on initial condition (SDIC), sensitivity analysis, bifurcation results, the positivity and boundedness of the solution, permanence, ultimate boundedness, and extinction scenarios of species. The SDIC characterizes the presence of chaotic oscillations in the system. Sensitivity analysis determines the parameters that significantly affect the outcome of numerical simulations. The bifurcation study concerning seasonal parameters shows a higher dependency of species on the frequency of seasonal changes than the severity of the season. The bifurcation study also examines the bio-controlling parameters and reveals various dynamic states within the system, such as fold, transcritical branch points, and Hopf points. Moreover, the mathematical analysis of our seasonally perturbed system reveals the periodic coexistence of all species and a globally attractive solution under certain parametric constraints. Finally, we examine the role of essential parameters that contribute to phase synchrony. For this, we numerically investigate the defining role of the coupling dimension coefficient, bio-controlling parameters, and other parameters associated with seasonality. This study infers that species can tune their dynamics to seasonal effects with low seasonal frequency, whereas the species' tolerance for the severity of seasonal effects is relatively high. The research also sheds light on the correlation between the degree of phase synchrony, prey biomass levels, and the severity of seasonal forcing. This study offers valuable insights into the dynamics of ecosystems affected by seasonal perturbations, with implications for conservation and management strategies.

The specialized cell types of the mucociliary epithelium (MCE) lining the respiratory tract enable continuous airway clearing, with its defects leading to chronic respiratory diseases. The molecular mechanisms driving cell fate acquisition and temporal specialization during mucociliary epithelial development remain largely unknown. Here, we profile the developing Xenopus MCE from pluripotent to mature stages by single-cell transcriptomics, identifying multipotent early epithelial progenitors that execute multilineage cues before specializing into late-stage ionocytes and goblet and basal cells. Combining in silico lineage inference, in situ hybridization, and single-cell multiplexed RNA imaging, we capture the initial bifurcation into early epithelial and multiciliated progenitors and chart cell type emergence and fate progression into specialized cell types. Comparative analysis of nine airway atlases reveals an evolutionary conserved transcriptional module in ciliated cells, whereas secretory and basal types execute distinct function-specific programs across vertebrates. We uncover a continuous nonhierarchical model of MCE development alongside a data resource for understanding respiratory biology.

Localized pattern formations and “two-phase” deformations are studied theoretically in soft compressible cylinders subject to surface tension and axial loading through several force-controlled loading scenarios. By drawing upon known results for separate yet mathematically similar elastic localization problems, a concise family of analytical bifurcation conditions for localized bulging or necking are derived in terms of a general compressible strain energy function. The effect of material compressibility and strain-stiffening behaviour on the bifurcation point is analysed, and comparisons between our theoretical bifurcation conditions and the corresponding numerical simulation results of Dortdivanlioglu and Javili (Extreme Mech. Lett. 55, 2022) are made. It is then explained how the fully developed “two-phase” (Maxwell) state which evolves from the initial localized bifurcation solution can be comprehensively understood using the simple analytical expressions for the force parameters corresponding to the primary axial tension deformation. The power of this simple analytical approach in validating numerical simulation results for elastic localization and phase-separation-like problems of this nature is highlighted.

This paper presents a speech encryption scheme by performing a combination of modified chaotic maps inspired by classic logistic and cubic maps. The main idea was to enhance the performance of classical chaotic maps by extending the range of the chaotic parameter. The resulted combining map was applied to a speech encryption scheme by using the confusion and diffusion architecture. The evaluation results showed a good performance regarding the chaotic behaviors such as initial value, control parameter, Lyapunov exponent, and bifurcation diagram. Simulations and computer evaluations with security analysis showed that the proposed chaotic system exhibits excellent performance in speech encryption against various attacks. The results obtained demonstrated the efficiency of the proposed scheme compared to an existing valuable method for static and differential cryptographic attacks.

Influence of rigid wall on the nonlinear pulsation of nearby bubble

Abstract This study investigates the effects of surface fluxes on ventilation pathways and the development of Hurricane Michael (2018), and is a real-case comparison to previous idealized modeling studies that investigate ventilation. Two modeling experiments are conducted by altering surface exchange coefficients to achieve a strong and weak experiment. Ventilation pathways are evaluated to understand how the vortex responds to dry-air infiltration. Pathways for dry-air infiltration are split into downdraft and radial ventilation. Results show that downdraft ventilation at low levels is maximized left of shear, exists between the surface and a height of 3 km, and is associated with rainband activity. Trajectories from downdraft ventilation demonstrate slower thermodynamic recovery for the weaker experiment. The slower recovery contributes to the initial intensity bifurcation between experiments. Radial ventilation has two pathways. At low levels, it is coupled with downdraft ventilation. Aloft, between heights of 5 and 10 km, it is maximized upshear and associated with storm-relative flow. This pathway is similar for each experiment initially, suggesting that the initial bifurcation of intensity is not a consequence of radial ventilation aloft. Trajectories from radial ventilation during a later time period show the destructive impact of lower-θe air in the near environment on convection upshear and right of shear for the weaker experiment. This study demonstrates how ventilation pathways at low levels and aloft are affected by surface fluxes, and how ventilation pathways operate, at different times, to affect tropical cyclone development.

Over the last decade, the chaotic behaviors of dynamical systems have been extensively explored. Recently, discovering or developing a 2D system of ordinary differential equations (ODEs) capable of exhibiting chaotic dynamical behaviors is an attractive research topic. In this study, a chaotic system with a 2D system of nonsmooth ODEs has been developed. This system is can exhibit chaotic dynamical behaviors. Its main dynamical behaviors, including time-series trajectories, phase portraits of attractors, and equilibria and their stability, have been investigated. The developed system has been verified by an excessive variety of fascinating chaotic behaviors, such as chaotic attractor, symmetry, sensitivity to initial conditions (ICs), fractal dimension, autocorrelation, power spectrum, Lyapunov exponent, and bifurcation diagram. Analytical and numerical simulations are used to study the dynamical behaviors of such a system. The developed system has extreme sensitivity to ICs, a fractal dimension of more than 1.8 and less than 2.05, an autocorrelation fluctuating randomly about an average of zero, a broadband power spectrum, and one positive Lyapunov exponent. The obtained numerical simulation results have proven the capability of the developed 2D system for exciting chaotic dynamical behaviors

Nonlinear size-dependent bending and forced vibration of internal flow-inducing pre- and post-buckled FG nanotubes