The European Physical Journal E最新文献

We present a simple and inexpensive method for measuring weak cohesive interactions. This technique is applied to the specific case of oil droplets with a depletion interaction, dispersed in an aqueous solution. The experimental setup involves creating a short string of droplets while immobilizing a single droplet. The droplets are held together via depletion interactions, and a single cohesive bond holds together nearest neighbours. Initially, the buoyant droplets are held in a flat horizontal chamber. The droplets float to the top of the chamber and are in contact with a flat glass interface. In the horizontal configuration, there is no component of the effective buoyant force acting in the plane of the chamber. The angle of the chamber is gradually increased, and the effective buoyant force acting on the string of droplets slowly increases. At a critical point, when the combination of gravity and buoyancy is equal to the cohesive force, the droplet string will detach from the immobile droplet. Our method allows for a simple direct measurement of cohesive forces on the tens of pico-Newton scale. To illustrate the validity of this technique, the droplet radii and concentration of depletant are varied, and their impact on the cohesive force is measured. This method offers a simple, accessible, and reproducible means of exploring cohesive interactions beyond the specific case of oil droplets and a depletion interaction.

(Top) Side and top-down view schematic of the experimental chamber. (Bottom) Stable and unstable dangling chain of droplets. The chain detaches from the stationary droplet once the effective buoyant force is greater than the cohesive force

The creep behavior of an amorphous poly(etherimide) polymer is investigated in the vicinity of its glass transition in a weakly non linear regime where the acceleration of the creep response is driven by local configurational rearrangements. From the time shifts of the creep compliance curves under stresses from 1 to 15 MPa and in the temperature range between (T_g -10K) and (T_g), where (T_g) is the glass transition temperature, we determine a macroscopic acceleration factor. The macroscopic acceleration is shown to vary as (e^{-(Sigma /Y)}) temperature with (n=2 pm 0.2), where (Sigma ) is the macroscopic stress and Y is a decreasing function of compliance. Because at the beginning of creep, the stress is homogeneous, the macroscopic acceleration is thus similar to the local one, in agreement with the recent theory of Long et al. (Phys Rev Mat 2:105601, 2018) which predicts (n=2). For larger compliances, the decrease of Y is interpreted as a signature of the development of stress disorder during creep.

Left: The acceleration of creep kinetics in a weakly non-linear regime in the vicinity of the glass transition is described through an acceleration function F which depends on both the applied stress and the compliance J(t) as a result of the stress induced shift of the relaxation time of nanometric domains (from top to bottom: increasing applied creep stresses). Right : Description of an amorphous polymer glass as a disordered medium made up of nanometric domains with widely distributed relaxation times.

Understanding the values and origin of fundamental physical constants, one of the grandest challenges in modern science, has been discussed in particle physics, astronomy and cosmology. More recently, it was realized that fundamental constants have a biofriendly window set by life processes involving motion and flow. This window is related to intrinsic fluid properties such as energy and length scales in condensed matter set by fundamental constants. Here, we discuss important extrinsic factors governing the viscosity of complex fluids operating in life processes due to collective effects. We show that both extrinsic and intrinsic factors affecting viscosity need to be taken into account when estimating the biofriendly range of fundamental constants from life processes, and our discussion provides a straightforward recipe for doing this. Remarkably, the viscosity of a complex fluid such as blood with significant extrinsic effects is not far from the intrinsic viscosity calculated using the fundamental constants only, and we discuss the reason for this in terms of dynamics of contact points between cells.

Intelligent decisions in response to external informative input can allow organisms to achieve their biological goals while spending very little of their own resources. In this paper, we develop and study a minimal model for a navigational task, performed by an otherwise completely motorless particle that possesses the ability of hitchhiking in a bath of active Brownian particles (ABPs). Hitchhiking refers to identifying and attaching to suitable surrounding bath particles. Using a reinforcement learning algorithm, such an agent, which we refer to as intelligent hitchhiking particle (IHP), is enabled to persistently navigate in the desired direction. This relatively simple IHP can also anticipate and react to characteristic motion patterns of their hosts, which we exemplify for a bath of chiral ABPs (cABPs). To demonstrate that the persistent motion of the IHP will outperform that of the bath particles in view of long-time ballistic motion, we calculate the mean-squared displacement and discuss its dependence on the density and persistence time of the bath ABPs by means of an analytic model.

Illustration of an intelligent hitchhiking particle (IHP) in a bath of active Brownian particles (ABPs). The IHP fulfills a navigational task by holding on to an ABP only if its orientation points upwards, enabling persistent motion.

Scaling arguments are presented for end-to-wall reaction and end-to-end reactions of grafted chains for non-self-avoiding and self-avoiding chains with and without hydrodynamic interaction. The most realistic minimal model for the experiments of Kim and Lee (J Phys Chem Lett 12:4576, 2021. https://doi.org/10.1021/acs.jpclett.1c00962) is a chain tethered to a plane, the chain having excluded volume and hydrodynamic interaction with end-to-end reactions. From our scaling argument, such a chain obeys a law of mass action where the macroscopic reaction rate is proportional to the microscopic reaction rate multiplied by the probability that the chain ends are close together. More precisely, this means for long chains there is no diffusion controlled limit. In addition, a polymer attached to a plane where the end reacts with the entire plane, end-to-wall reactions, was also investigated. For sufficiently long polymers, this system is always diffusion controlled, even with excluded volume and hydrodynamic interaction. We test the scaling arguments for the simplest case of a non-self-avoiding chains obeying Rouse dynamics. The numerical results agree with the scaling analysis for both end-to-wall and end-to-end reactions of the grafted chain. In particular, our numerical simulations support the end-to-end reaction of a tethered non-self-avoiding is the marginal case in the scaling sense.

The idea of linear Diophantine fuzzy sets (LDFs) is a novel tool for analysis, soft computing, and optimization. Recently, the concept of a linear Diophantine fuzzy graph has been proposed in 2022. The aim of this research is to extend topological numbers to LDFSs. A real value assigned to a particular graph is known as a topological graph theoretic parameter. We extend the bound of the crisp graph toward the linear Diophantine fuzzy graph (LDFG), including the edge and vertex deletion operations via LDFG theoretic parameters. We also investigate the interesting bound of the LDFGs via LDFG theoretic parameters. Finally, for decision-making problems, we developed an algorithm by exploiting the relationship between LDFG theoretic parameters and LDFSs. Based on the established approach, we discussed a numerical example of an application of a medical diagnosis using the linear Diophantine fuzzy Sombor graph parameter and the first, fifth, and sixth versions of the linear Diophantine fuzzy Sombor graph parameters.

A way to the extension of fuzzy topological numbers.

We propose a simple numerical model for the motion of microswimmers based on the immersed boundary method. The swimmer, either pusher or puller, is represented by a distribution of point forces corresponding to the body and the flagellum. We study in particular the minimal model consisting of only three beads (two for the body and one for the flagellum) connected by rigid, inextensible links. When the beads are collinear, standard straight swimming is realized and, in the absence of propulsion, we demonstrate that the model recovers Jeffery’s equation for a thin rod. Conversely, by imposing an angle between body and flagellum the swimmer moves on circular orbits. We discuss how two swimmers, in collinear or non-collinear geometry, scatter upon encounter. Finally, we explore the dynamics of a large number of swimmers reacting to one another only via hydrodynamic interactions, and exemplify their complex collective dynamics in both straight and circular swimmers.