Journal of Biological Physics最新文献

This study evaluates the unsteady laminar flow and heat and mass transfer of a nanofluid in the appearance of gyrotactic microorganisms. In this analysis, using the Darcy–Forchheimer flow inside the vicinity of a nonlinearly stretched surface with Brownian motion and thermophoresis impacts. Similarity conversion is familiar with reduced governing models into dimensionless variables, and “bvp4c,” a MATLAB solver, is employed to find the computational outputs of this analysis. This analysis reports that the use of nanofluids provides better thermal characteristics which are helpful to enhance the heat transfer coefficient. Graphs for this analysis are created for distinct values of non-dimensionless parameters, whereas the coefficient of surface drag, heat flux, mass flux, and rate of microorganism density are all interpreted numerically and graphically. The high level of resistance provided by velocity slip and Forchheimer parameters leads to a decrease in velocity curves while an increment is seen in the temperature profile. It is also remarked that bioconvection Peclet number induces a decrement in the density distribution of motile microorganisms. In addition, it has been observed that the Nusselt number for a nonlinear stretching sheet is better as compared to a linear stretching sheet.

Conventional kinesin protein is a prototypical biological molecular motor that can step processively on microtubules towards the plus end by hydrolyzing ATP molecules, performing the biological function of intracellular transports. An important characteristic of the kinesin is the load dependence of its velocity, which is usually measured by using the single molecule optical trapping method with a large-sized bead attached to the motor stalk. Puzzlingly, even for the same kinesin, some experiments showed that the velocity is nearly independent of the forward load whereas others showed that the velocity decreases evidently with the increase in the magnitude of the forward load. Here, a theoretical explanation is provided of why different experiments give different dependencies of the velocity on the forward load. It is shown that both the stalk orientation and bead size play a critical role in the different dependencies. Additionally, the reason why the optical trapping experiments with the movable trap usually gave a sigmoid form of the velocity versus backward load whereas with the fixed trap gave a nearly linear form is also explained theoretically. The study is not only critical to the understanding of the response of the motor to the load but also provides strong insights into the coupling mechanism of the motor.

Graphical Abstract

The present article focuses on the analysis of the two-phase flow of blood via a stenosed artery under the influence of a pulsatile pressure gradient. The core and plasma regions of flow are modeled using the constitutive relations of Herschel-Bulkley and the Newtonian fluids, respectively. The problem is modeled in a cylindrical coordinate system. A modest stenosis assumption is used to simplify the non-dimensional governing equations of the flow issue. An explicit finite difference approach is used to solve the resultant nonlinear system of differential equations while accounting for the provided boundary conditions. After the necessary adjustments have been made to the crucial non-dimensional parameters, an analysis of the data behind the huge image, such as axial velocity, temperature field, concentration wall shear stress, flow rate, and flow impedance, is conducted. The current study shows that the curvature of blood vessels plays a significant role in influencing blood velocity. Specifically, a unit increase in the curvature radius results in a 24% rise in blood velocity.

A underlying complex dynamical behavior of double Allee effects in predator-prey system is studied in this article to understand the predator-prey relation more intensely from different aspects. We first propose a system with the Caputo sense fractional-order predator-prey system incorporating the Allee effect in prey populations to explain how the memory effect can change the different emergent states. Local stability analysis is analyzed by applying Matignon’s condition for the FDE system. Further, we consider a discrete-time system to show the influence of double Allee effects in non-overlapping generations. For discrete-time system, different bifurcations like Neimark-Sacker, flip bifurcations, irregularity in periodic oscillations, are observed. Irregularity occurs through a period-doubling cascade which is a common route to chaos in a dynamical sense. Maximum Lyapunov exponent (MLE) is shown to illustrate the irregular behaviors of discrete-time systems. The Allee effect influences system stability where the strong Allee effect enhances system stability whereas the stability is lost for the weak Allee effect. The extinction risk of populations in the presence of the Allee effect is a concerning issue. We have insight into how all populations survive along with stable extinction equilibrium. Our proposed systems exhibit different alternative states. Multiple stable attractor basins are plotted to depict the different alternative states of the FDE system as well as the discrete-time system. Initial population densities play a key role in the coexistence of all the populations otherwise there is a risk of species extinction. Besides analytical results, numerical simulation is performed to valid our analytical findings of different dynamical states like bifurcation, stability, irregularity as well as multi-stability.

In this paper, the dynamic behaviors of tuberculosis in the context of indirect environmental transmission are discussed by establishing the SEIRB epidemic model. The basic reproduction number is computed by employing the next-generation matrix approach. The global stability of disease-free equilibrium and endemic equilibrium is proved by constructing the Lyapunov function and the application of LaSalle’s invariance principle. It shows that when the basic reproduction number is greater than 1, tuberculosis will spread among the population. When the basic reproduction number is less than 1, tuberculosis will disappear. Finally, an optimal control problem is constructed by using the extended model, which reveals the spread of tuberculosis can be effectively controlled by eliminating Mycobacterium tuberculosis in the environment and controlling tuberculosis patients at the same time. Numerical example results show the effectiveness of the optimization strategies.

Bioconvective flows over a thin needle hold significant importance in various fields, particularly in biomedical engineering, microfluidics, and environmental science. This paper examines the bioconvective flow properties of a copper and blood-based Casson nanofluid over a thin needle, accounting for gyrotactic microorganisms in the presence of a magnetic field. The two-phase nanofluid model is applied to formulate the flow problem. The system of non-dimensional ordinary differential equations is obtained by reducing the governing partial differential equations with the help of similarity variables. Further, the ODEs are numerically solved using the 4th-order Runge–Kutta method based Shooting technique. The similar solutions of the non-dimensional ODEs are represented graphically and the blood-based nanofluid’s velocity, temperature, concentration, and presence of microorganisms are examined with reference to the accompanying diagrams. A detailed analysis is provided for skin friction, Nusselt number, and microorganism density number. The primary outcomes reveal that the augmentation of the mixed convection parameter and buoyancy ratio parameter enhance the rate of heat transfer.

Cell fate decision is crucial in biological development and plays fundamental roles in normal development and functional maintenance of organisms. By identifying key regulatory interactions and molecules involved in these fate decisions, we can shed light on the intricate mechanisms underlying the cell fates. This understanding ultimately reveals the fundamental principles driving biological development and the origins of various diseases. In this study, we present an overarching framework which integrates pseudo-trajectory inference and differential analysis to determine critical regulatory interactions and molecules during cell fate transitions. To demonstrate feasibility and reliability of the approach, we employ the differentiation networks of hepatobiliary system and embryonic stem cells as representative model systems. By applying pseudo-trajectory inference to biological data, we aim to identify critical regulatory interactions and molecules during the cell fate transition processes. Consistent with experimental observations, the approach can allow us to infer dynamical cell fate decision processes and gain insights into the underlying mechanisms which govern cell state decisions.

This study presents a stochastic model of seed dispersal based on a branching random walk (BRW) framework, incorporating both homogeneous and non-homogeneous Poisson point processes (PPP). Building on the model introduced by Coletti et al. (2023), we examine the effects of habitat reduction on seed dispersal dynamics. We analyze the phase transition behavior of the BRW model under varying conditions of habitat fragmentation, focusing on how these conditions influence the critical dispersal rate. Specifically, we study a BRW on the real line with a non-homogeneous PPP driven by a log-normal density, constrained between spatial barriers. Our simulations localize the critical dispersal rate with respect to barrier positions and compare this dependence between homogeneous and non-homogeneous models.

The exploration of microgravity has garnered substantial scholarly attention due to its potential to offer unique insights into the behavior of biological systems. This study presents a preliminary investigation into the effects of simulated microgravity on esophageal cancer cells, examining various aspects such as morphology, growth behavior, adhesion, inhibition rate, and DNA damage. To achieve this, a novel microgravity simulator named “Gravity Challenge” was utilized for its effectiveness in minimizing external influences that could compromise microgravity conditions. The international cell line SK-GT-4 was utilized as the focal point of this investigation. Results revealed noticeable alterations in the growth behavior of cancer cells following exposure to simulated microgravity for 24 h, characterized by a loss of adhesion properties compared to control cells. Concurrently, cell viability exhibited a decline, as evidenced by cytotoxicity testing. Furthermore, the comet assay test demonstrated that cells subjected to microgravity simulation experienced a higher incidence of DNA damage compared to their control counterparts. In conclusion, this comprehensive examination of the impact of simulated microgravity on esophageal cancer cells extends beyond morphological changes, delving into genetic implications through observed DNA damage. The diminished vitality of cells under microgravity conditions underscores the multifaceted effects on cellular behavior in response to environmental variations. These findings represent a significant step towards understanding the dynamics of cancer cells, laying the groundwork for future research aimed at identifying potential therapeutic strategies for this disease.

The evolutionary origin of the inverted retina in the vertebrate eye is unknown. This paper explores a hypothetical evolutionary scenario that explains the unique orientation of the photoreceptors in the vertebrate retina. The proposed scenario follows the scientific accepted scenario for eye evolution and gradually builds up towards an eye prototype by considering light direction detection and increase in achievable spatial resolution as the driving forces. It suggests that eye retinas developed along two different morphological processes, an evagination process that results in the inverted retina in vertebrate eyes and an invagination process that results in a verted retina in cephalopod eyes. The development of the inverted vertebrate retina and eye prototype morphology is strongly substantiated by physics of vision. The proposed evolutionary sequence for vertebrate eye development is simple and has the full potential to explain the origin of the inverted retina and leads to an eye prototype enabling visual detection and orientation. It allows the emergence of eye structures like, extraocular muscles, tapetum lucidum, biconvex lens, cornea, and pupil. This study supports the suggestion that a primitive inverted retina in the predecessor of vertebrates is of ectodermal origin and available before neurulation occurred.