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Coil migration is a known complication of endovascular coiling of cerebral aneurysms. We report an acute coil migration occurring during coiling of an unruptured anterior choroidal aneurysm, while a separate coil was retrieved into the microcatheter concomitantly without direct contact between the coils. The “pulling” of a previously deployed stable coil is presented as an adverse effect that should be noted. This case exemplifies that not only direct entanglement or erroneous malposition can generate acute migration, but possibly, also alteration of physical forces during coil retrieval. A potential mechanism, similar to a venturi effect, caused by a quick suction within the microcatheter at its distal end, is suggested, and the clinical relevance of the case is discussed.

Accurate predictions from models based on physical principles are the ultimate metric of our biophysical understanding. Although there has been stunning progress toward structure prediction, quantitative prediction of enzyme function has remained challenging. Realizing this goal will require large numbers of quantitative measurements of rate and binding constants and the use of these ground-truth data sets to guide the development and testing of these quantitative models. Ground truth data more closely linked to the underlying physical forces are also desired. Here, we describe technological advances that enable both types of ground truth measurements. These advances allow classic models to be tested, provide novel mechanistic insights, and place us on the path toward a predictive understanding of enzyme structure and function.

Macroalgae are ecologically important organisms that often inhabit locations with physically challenging water motion. The biomechanical traits that permit their survival in these conditions have been of interest to biologists and engineers alike, but logistical and technical challenges of conducting investigations in macroalgal habitats have often prevented optimal study of these traits. Here, we review field methods for quantifying three major components of macroalgal biomechanics in moving water: fluid flow, macroalgal form, and hydrodynamic force. The implementation of some methodologies is limited due to the current state and accessibility of technology, but many of these limitations can be remedied by custom-built devices, borrowing techniques from other systems, or shifting lab-based approaches to the field. We also describe several frameworks for integrating flow, form, and force data that can facilitate comparisons of macroalgal biomechanics in field settings with predictions from theory and lab-based experiments, or comparisons between flow conditions, habitats, and species. These methods and frameworks, when used on scales that are relevant to the examined processes, can reveal mechanistic information about the functional traits that permit macroalgae to withstand physically challenging water motion in their habitats, using the actual fluid flows, macroalgal forms, and physical forces that occur in nature.

Soil physical quality is largely determined by interphase interactions at variable moisture content. This phenomenon allows us to consider the water retention curves as functions of the water content and its thermodynamic potentials as indicators of the soil physical quality and its dynamics. Diagrams of the physical quality of soils represented by water retention curves with areas of dominance of certain physical mechanisms and forces responsible for the interaction of physical phases were obtained for Eurasian soils included in the database (more than 400 samples) and grouped by five FAO/USDA textural classes. Original instrumental methods using centrifugal, gravitational, and temperature physical fields for water removal made it possible for the first time to obtain the thermodynamic characteristics of water retention in the entire range of soil water potential from 0 to 1 million J/kg. The main fundamental result is a physically based methodology for diagnosing the limiting (critical) values of the soil water content and its thermodynamic potentials, which divide the areas of dominance of various forms of soil moisture, physical forces, and mechanisms of interphase interactions on the diagrams of the physical quality of soils. The significance of non-capillary surface forces and mechanisms controlling water retention and physical quality of soils is shown. The results of determination of the optimal ranges of water content for Eurasian soils of different textures and geneses in connection with their soil-ecological and technological functions and services specify practical significance of this study.

Although transpiration-driven transport of xylem sap is well known to operate under absolute negative pressure, many terrestrial, vascular plants show positive xylem pressure above atmospheric pressure on a seasonal or daily basis, or during early developmental stages. The actual location and mechanisms behind positive xylem pressure remain largely unknown, both in plants that show seasonal xylem pressure before leaf flushing, and those that show a diurnal periodicity of bleeding and guttation. Available evidence shows that positive xylem pressure can be driven based on purely physical forces, osmotic exudation into xylem conduits, or hydraulic pressure in parenchyma cells associated with conduits. The latter two mechanisms may not be mutually exclusive and can be understood based on a similar modelling scenario. Given the renewed interest in positive xylem pressure, this review aims to provide a constructive way forward by discussing similarities and differences of mechanistic models, evaluating available evidence for hydraulic functions, such as rehydration of tissues, refilling of water stores, and embolism repair under positive pressure, and providing recommendations for future research, including methods that avoid or minimise cutting artefacts.

The application of phagotrophic algae in waste activate sludge (WAS) treatment can largely accelerate WAS organics reclamation rate, because the phagotrophic capability of phagotrophic algae on intact microbial cells provides an efficient and fast way to digest microbial cells, which eliminate the need of the time-consuming hydrolysis of WAS solid organics. In this research work, different pretreatment methods of anoxia, alkali, and ultrasound were compared in terms of efficiency in releasing microbial cells from WAS flocs and subsequent growth of phagotrophic algae. Results show that ultrasonic pretreatment was the most efficient method since it yielded the highest microbial cell release and subsequent algae growth, while requiring the shortest pretreatment time. Mathematical modelling shows that the release of microbial cells in anoxic and ultrasonic pretreatment was achieved mainly through breaking physical forces of attraction, while the release of microbial cells in alkali pretreatment was achieved through breaking ionic bonds. Re-floc of released microbial cells was observed during algae growth, and the microbial cells released through breaking ionic bonds were less liable to reform floc. The electricity consumption of ultrasonic pretreatment was the highest, which was 6.9 times and 17.9 times of that of alkali and anoxic pretreatment. The electricity consumption of ultrasonic pretreatment can be reduced by performing alkali pretreatment prior to ultrasonic pretreatment.

Body size, arguably the most important attribute of all organisms in the living world, is a reliable predictor of their physiological rates and life-history attributes. Metabolic rates of all organisms (MR) are related directly to their body mass (M) as an allometric function $$MR = \alpha M{\textstyle{3 \over 4}}$$ (Kleiber’s rule). The high, mass-specific metabolic rates of small animals can be accounted for by their high surface area/volume ratios. The much-discussed ‘metabolic theory of ecology’ is essentially an expansion of Kleiber’s rule equation to include two additional metabolism-influencing factors—temperature and resource availability—with a more generalized quarter-power exponent. According to this theory, many physiological rates, life-history traits and ecological processes follow quarter-power scaling laws. Living organisms must also obey the laws of physics. The relative importance of different physical forces to the organisms living on land or in water is also dependent on their body size.

The last decade has witnessed a rapid growth in understanding of the pivotal roles of mechanical stresses and physical forces in cell biology. As a result an integrated view of cell biology is evolving, where genetic and molecular features are scrutinized hand in hand with physical and mechanical characteristics of cells. Physics of liquid crystals has emerged as a burgeoning new frontier in cell biology over the past few years, fueled by an increasing identification of orientational order and topological defects in cell biology, spanning scales from subcellular filaments to individual cells and multicellular tissues. Here, we provide an account of most recent findings and developments together with future promises and challenges in this rapidly evolving interdisciplinary research direction., Invited review to appear in "Trends in Cell Biology"

Physical forces, such as dielectric, magnetic, electric, optical, and acoustic force, provide useful principles for the manipulation of particles, which are impossible or difficult with other approaches. Microparticles, including polymer particles, liquid droplets, and biological cells, can be trapped at a particular position and are also transported to arbitrary locations in an appropriate external physical field. Since the force can be externally controlled by the field strength, we can evaluate physicochemical properties of particles from the shift of the particle location. Most of the manipulation studies are conducted for particles of sub-micrometer or larger dimensions, because the force exerted on nanomaterials or molecules is so weak that their direct manipulation is generally difficult. However, the behavior, interactions, and reactions of such small substances can be indirectly evaluated by observing microparticles, on which the targets are tethered, in a physical field. We review the recent advancements in the manipulation of particles using a physical force and discuss its potentials, advantages, and limitations from fundamental and practical perspectives.

To discern how mechanical forces coordinate biological outcomes, methods that map cell-generated forces in a spatiotemporal manner, and at cellular length scales, are critical. In their native environment, whether it be within compact multicellular three-dimensional structures or sparsely populated fibrillar networks of the extracellular matrix, cells are constantly exposed to a slew of physical forces acting on them from all directions. At the same time, cells exert highly localized forces of their own on their surroundings and on neighboring cells. Together, the generation and transmission of these forces can control diverse cellular activities and behavior as well as influence cell fate decisions. To thoroughly understand these processes, we must first be able to characterize and measure such forces. However, our experimental needs and technical capabilities are in discord-while it is apparent that we should study cell-generated forces within more biologically relevant 3D environments, this goal remains challenging because of caveats associated with complex "sensing-transduction-readout" modalities. In this Review, we will discuss the latest techniques for measuring cell-generated forces. We will highlight recent advances in traction force microscopy and examine new alternative approaches for quantifying cell-generated forces, both of individual cells and within 3D tissues. Finally, we will explore the future direction of novel cellular force-sensing tools in the context of mechanobiology and next-generation biomaterials design.

How does STEM knowledge learned in school change students’ brains? Using fMRI, we presented photographs of real-world structures to engineering students with classroom-based knowledge and hands-on lab experience, examining how their brain activity differentiated them from their “novice” peers not pursuing engineering degrees. A data-driven MVPA and machine-learning approach revealed that neural response patterns of engineering students were convergent with each other and distinct from novices’ when considering physical forces acting on the structures. Furthermore, informational network analysis demonstrated that the distinct neural response patterns of engineering students reflected relevant concept knowledge: learned categories of mechanical structures. Information about mechanical categories was predominantly represented in bilateral anterior ventral occipitotemporal regions. Importantly, mechanical categories were not explicitly referenced in the experiment, nor does visual similarity between stimuli account for mechanical category distinctions. The results demonstrate how learning abstract STEM concepts in the classroom influences neural representations of objects in the world.

Here, we study the evolution of specialization using realistic computer simulations of bacteria that secrete two public goods in a dynamic fluid. Through this first principles approach, we find physical factors such as diffusion, flow patterns, and decay rates are as influential as fitness economics in governing the evolution of community structure, to the extent that when mechanical factors are taken into account, (1) Generalist communities can resist becoming specialists, despite the invasion fitness of specialization, (2) Generalist and specialists can both resist cheaters despite the invasion fitness of free-riding, (3) Multiple community structures can coexist despite the opposing force of competitive exclusion. Our results emphasize the role of spatial assortment and physical forces on niche partitioning and the evolution of diverse community structures., 15 pages, 6 figures

The importance of knowing the processes of choice, decision-making is determined by the objective role that they play in the organization of human activity. An important feature of man is his unique ability to make decisions in the most difficult conditions of activity, which are characterized by high uncertainty, the presence of many inconsistent criteria, lack of time, high responsibility and more. The target effectiveness of the decision can be assessed only after its implementation, but the prediction of potential decisions is possible only if the study of its neuropsychological mechanisms. Cost-effectiveness is characterized by intellectual, physical, neuropsychological and material costs of decision-making. The non-standard situation, as a rule, seeks to reduce cost-effectiveness, because in this case the solutions are achieved by the exertion of intellectual, emotional and physical forces and is determined by the ability of the individual to act in such an environment. The neuropsychological mechanisms of such decisions are of interest to science in terms of ensuring the adequacy and timing of such decisions, which is hypothetically related to the morphological and psychoneurological characteristics of the subjects of action. In the context of our study, it is important to conduct a thorough psychological analysis of different types of unusual situations in the coach and find ways to improve the effectiveness of decisions, which primarily depends on the level of psychological readiness of the individual to perform its.

It is shown that the four fundamental physical forces, i.e. weak interaction, strong interaction, electromagnetism and gravity, all have their origin in the quark as the single true elementary particle.This requires conceiving the quark as a Dirac particle in a pseudo-tachyon mode, which possesses two real dipole moments: the common one associated with its angular momentum and a second one that is polarisable in a scalar field. This Dirac particle carries a regular charge magnetic monopole without Dirac’s string, theorized by Comay. The boson carrier of its field of energy is the gluon showing an exponential decay of its spatial range because of the influence of an omni-present energetic background field, known as the Higgs field, in this article interpreted as the Lambda in Einstein’s Field Equation.

BACKGROUND Freestyle skiers must optimize their aerial performance by maintaining the strength and coordination to propel themselves in the air and adapt to landings and take-offs on uneven surfaces. The purpose of this study is to investigate the differences in areal bone mineral density (aBMD) and body composition in freestyle skiers and nonfreestyle skiing controls. HYPOTHESIS We hypothesized that the unique demands and summation of forces experienced by freestyle athletes would manifest as greater femoral neck aBMD, lower percent body fat, and lower BMI than nonfreestyle skiing controls. LEVEL OF EVIDENCE Level 3, Retrospective Cohort Study. METHODS 18 freestyle skiers (14M 4F, [27.56 ± 5.22 years]) and 15 controls (7M 8F, [26.93 ± 3.54 years]) were measured with dual energy X-ray absorptiometry (DXA) to determine total body composition, hip and lumbar spine aBMD, and bone mineral composition (BMC). Height and weight were measured with an in-office stadiometer and scale. Questionnaires were used to determine physical activity and pertinent medical history. Between-group variations were analyzed with an analysis of variance (ANOVA) and stratified by sex. RESULTS Percent body fat, hip and lumbar spine aBMD, BMC, and area were all similar between freeski and nonfreeski athletes (p

Chalcogen‐bonding cascade switching was introduced recently to produce the chemistry tools needed to image physical forces in biological systems. In the original flipper probe, one methyl group appeared to possibly interfere with the cascade switch. In this report, this questionable methyl group is replaced by a hydrogen. The deletion of this methyl group in planarizable push‐pull probes was not trivial because it required the synthesis of dithienothiophenes with four different substituents on the four available carbons. The mechanosensitivity of the resulting demethylated flipper probe was nearly identical to that of the original. Thus methyl groups in the switching region are irrelevant for function, whereas those in the twisting region are essential. This result supports the chalcogen‐bonding cascade switching concept and, most importantly, removes significant synthetic demands from future probe development., Not every atom matters: Chemistry tools made for the fluorescent imaging of physical forces in biological systems subjected to single methyl group deletions: Whereas methyl groups in the twisting region are essential, the pink methyl in the switching region does not interfere with function, a result that required significant multistep organic synthesis to obtain and will therefore be thoroughly appreciated in future probe design.

Physical forces and mechanical properties have critical roles in cellular function, physiology and disease. Over the past decade, atomic force microscopy (AFM) techniques have enabled substantial advances in our understanding of the tight relationship between force, mechanics and function in living cells and contributed to the growth of mechanobiology. In this Primer, we provide a comprehensive overview of the use of AFM-based force spectroscopy (AFM-FS) to study the strength and dynamics of cell adhesion from the cellular to the single-molecule level, spatially map cell surface receptors and quantify how cells dynamically regulate their mechanical and adhesive properties. We first introduce the importance of force and mechanics in cell biology and the general principles of AFM-FS methods. We describe procedures for sample and AFM probe preparations, the various AFM-FS modalities currently available and their respective advantages and limitations. We also provide details and recommendations for best usage practices, and discuss data analysis, statistics and reproducibility. We then exemplify the potential of AFM-FS in cellular and molecular biology with a series of recent successful applications focusing on viruses, bacteria, yeasts and mammalian cells. Finally, we speculate on the grand challenges in the area for the next decade. Atomic force microscopy-based force spectroscopy can probe the strength and dynamics of cell adhesion to understand how physical forces influence cellular function, physiology and disease. Here, Dufrene and colleagues discuss the ability of this technology to work as an ultra-sensitive force sensor to study the adhesion and elasticity of complex biological systems including viruses, bacteria, yeasts and mammalian cells.

The ability to sense and respond to physical forces is critical for the proper function of cells, tissues, and organisms across the evolutionary tree. Plants sense gravity, osmotic conditions, pathogen invasion, wind, and the presence of barriers in the soil, and dynamically integrate internal and external stimuli during every stage of growth and development. While the field of plant mechanobiology is growing, much is still poorly understood—including the interplay between mechanical and biochemical information at the single-cell level. In this review, we provide an overview of the mechanical properties of three main components of the plant cell and the mechanoperceptive pathways that link them, with an emphasis on areas of complexity and interaction. We discuss the concept of mechanical homeostasis, or “mechanostasis,” and examine the ways in which cellular structures and pathways serve to maintain it. We argue that viewing mechanics and mechanotransduction as emergent properties of the plant cell can be a useful conceptual framework for synthesizing current knowledge and driving future research.

In this publication, novel bio-based composites made of epoxidized natural rubber with 50 mol% of epoxidation (ENR-50) are presented. The obtained materials, partially cured with a totally environmentally friendly crosslinking system consisting of natural ingredients, including quercetin and silica, exhibit a self-healing ability resulting from the self-adhesion of ENR-50 and reversible physical forces between the curing agent and the matrix. The impact of natural components on the crosslinking effect in uncured ENR-50 matrix was analyzed based on rheometric measurements, mechanical tests and crosslinking density. The partially crosslinked samples were next cut into two separate pieces, which were instantly contacted together under a small manual press, left at room temperature for a few days for the healing process to occur and finally retested. The healing efficiency was estimated by measuring mechanical properties before and after the healing process and was also confirmed by photos taken using optical and scanning electron microscope (SEM). According to the results, a combination of silica and quercetin is a totally safe, natural and effective crosslinking system dedicated to epoxidized natural rubber. The novel composites containing ingredients safe for human beings exhibit promising self-healing properties with a healing efficiency of up to 45% without any external stimuli and stand a chance of becoming innovative biomedical materials.

Nearly all structures in our body experience mechanical forces. At a molecular scale, these forces are detected by ion channels that function as mechanotransducers converting physical forces into electrochemical responses. Here we focus on PIEZOs, a family of mechanically activated ion channels comprising PIEZO1 and PIEZO2. The significance of these channels is highlighted by their roles in touch and pain sensation as well as in cardiovascular and respiratory physiology, among others. Moreover, mutations in PIEZOs cause somatosensory, proprioceptive, and blood disorders. The goal here is to present the diverse physiology and pathophysiology of these unique channels, discuss ongoing research and critical gaps in the field, and explore the pharmaceutical interest in targeting PIEZOs for therapeutic development.

Cells coexist together in colonies or as tissues. Their behaviour is controlled by an interplay between intercellular forces and biochemical regulation. We develop a simple model of the cell cycle, the fundamental regulatory network controlling growth and division, and couple this to the physical forces arising within the cell collective. We analyse this model using both particle-based computer simulations and a continuum theory. We focus on 2D colonies confined in a channel. These develop moving growth fronts of dividing cells with quiescent cells in the interior. The profile and speed of these fronts are non-trivially related to the substrate friction and the cell cycle parameters, providing a possible approach to measure such parameters in experiments., Comment: Revised version, as accepted to appear in PRX

Epithelial, stem‐cell derived organoids are ideal building blocks for tissue engineering, however, scalable and shape‐controlled bio‐assembly of epithelial organoids into larger and anatomical structures is yet to be achieved. Here, a robust organoid engineering approach, Multi‐Organoid Patterning and Fusion (MOrPF), is presented to assemble individual airway organoids of different sizes into upscaled, scaffold‐free airway tubes with predefined shapes. Multi‐Organoid Aggregates (MOAs) undergo accelerated fusion in a matrix‐depleted, free‐floating environment, possess a continuous lumen, and maintain prescribed shapes without an exogenous scaffold interface. MOAs in the floating culture exhibit a well‐defined three‐stage process of inter‐organoid surface integration, luminal material clearance, and lumina connection. The observed shape stability of patterned MOAs is confirmed by theoretical modelling based on organoid morphology and the physical forces involved in organoid fusion. Immunofluorescent characterization shows that fused MOA tubes possess an unstratified epithelium consisting mainly of tracheal basal stem cells. By generating large, shape‐controllable organ tubes, MOrPF enables upscaled organoid engineering towards integrated organoid devices and structurally complex organ tubes., A robust organoid upscaling and engineering approach, Multi‐Organoid Patterning and Fusion (MOrPF), is presented to assemble individual airway organoids of different sizes into scaffold‐free airway tubes of anatomically relevant size and shape. Airway organoid fusion undergoes inter‐organoid surface integration, luminal material clearance, and lumina connection. MOrPF enables shape‐defined organoid engineering toward integrated organoid devices and structurally complex organ tubes.

The size of a cell is determined by a combination of synthesis, self-assembly, incoming matter and the balance of mechanical forces. Such processes operate at the single-cell level, but they are deeply interconnected with cell-cycle progression, resulting in a stable average cell size at the population level. Here, we examine this phenomenon by reviewing the physics of growth processes that operate at vastly different timescales, but result in the controlled production of daughter cells that are close copies of their mothers. We first review the regulatory mechanisms of size at short timescales, focusing on the contribution of fundamental physical forces. We then discuss the multiple relevant regulation processes operating on the timescale of the cell cycle. Finally, we look at how these processes interact: one of the most important challenges to date involves bridging the gap between timescales, connecting the physics of cell growth and the biology of cell-cycle progression. Cell size is regulated by processes ranging from rapid fluctuations to slower growth and division. Limited dialogue between communities studying these disparate timescales has hindered our understanding of size control—a gap bridged by this Review.

The development of physiologically relevant intestinal models fueled by breakthroughs in primary cell-culture methods has enabled successful recapitulation of key features of intestinal physiology. These advances, paired with engineering methods, for example incorporating chemical gradients or physical forces across the tissues, have yielded ever more sophisticated systems that enhance our understanding of the impact of the host microbiome on human physiology as well as on the genesis of intestinal diseases such as inflammatory bowel disease and colon cancer. In this review we highlight recent advances in the development and usage of primary cell-derived intestinal models incorporating monolayers, organoids, microengineered platforms, and macrostructured systems, and discuss the expected directions of the field.

Mechanical signals affect many aspects of biological processes. Physical forces from the extracellular microenvironment are ultimately transmitted to the nucleus and elicit a response that result in the deformation and remodeling of the nucleus. Recent studies have shown that nuclear deformation has several consequences such as reorganization of chromatin, changes in gene expression, and nuclear envelope rupture. It is widely believed that a direct coupling between the cytoskeleton and nucleoskeleton is required for nuclear deformation; however, some studies have proposed alternative mechanisms for nuclear deformation and the transmission of mechanical signals and stresses from the cytoskeleton to the nucleus. Herein, we review the processes, in which the cell nucleus experiences stresses and discuss the evidence of involvement of a direct link between the cytoskeleton and nucleoskeleton in nuclear deformation.

Cell function was incessantly regulated by several microenvironments that were dependent on chemical and physical interactions. Physical forces, such as compressive stress, shear stress, an...

Plant organs arise through complex interactions between biological and physical factors that control morphogenesis. While there has been tremendous progress in the understanding of the genetics behind development, we know much less about how mechanical forces control growth in plants. In recent years, new multidisciplinary research combining genetics, live-imaging, physics, and computational modeling has begun to fill this gap by revealing the crucial role of biomechanics in the establishment of plant organs. In this review, we provide an overview of our current understanding of growth during initiation, patterning, and expansion of shoot lateral organs. We discuss how growth is controlled by physical forces, and how mechanical stresses generated during growth can control morphogenesis at the level of both cells and tissues. Understanding the mechanical basis of growth and morphogenesis in plants is in its early days, and many puzzling facts are yet to be deciphered.

Pod dehiscence or pod shattering is one of the major factors leading to remarkable yield losses in soybean. The anatomical and morphological configuration of pod tissues is related to the dehiscence mechanism. Soybean pod forms abscission layers at the binding sites of its margins and accumulates the force to dehisce pod walls on drying during and after maturation. Pod opening is governed not only by a consequence of the weakening of the dorsal and ventral dehiscence zones but also by the tension in the cells of the inner sclerenchyma layer as a result of dehydration. The lignified fiber cap cells in the suture and the cell structure of the mesocarp play a role in preventing separation of the two halves. For separation to occur, physical forces have to trigger the detachment of cells at the separation layer, in an interplay that involves weakening of cell adhesion and tensions provided by the surrounding tissues or external agents. Pod dehiscence in soybean has a minimal relationship with the pod thickness-to-width ratio, while the thickness of the pod wall and extent of sclerenchymatous dorsal bundle caps might be appropriate indicators. There is also a critical pod moisture content for shattering. Moisture content of pods and environmental relative humidity are closely correlated with the degree of pod dehiscence. Intrinsic factors may modify the pod shattering response. Further analyses of pod tissues, particularly chemical structure and cell wall degrading enzymes of the pod wall will help to fully understand pod dehiscence in soybean.

During the summer, giant jellyfish (Nemopilema nomurai) are transported from their main seeding and nursery ground, Jiangsu Province and the coast of China, to Korean coastal waters by the currents of the Yellow Sea (YS) and the East China Sea, causing problems for swimmers and hampering fisheries. In this study, we derive new velocity fields based on satellite measurements and develop particle-tracking experiments to simulate and analyze the interannual change of N. nomurai abundance off the coast of Korea. The velocity fields are calculated by combining Ekman currents and geostrophic currents based on an analytical solution of an approximated momentum equation. For validation, we compare the particle-tracking experiment results with in situ observations obtained from the Korean National Institute of Fisheries Science. The combined velocity fields during the summer show that geostrophic currents are of the same order as Ekman currents over the YS, implying that the interannual changes in N. nomurai abundance off the coast of Korea are determined by combined Ekman and geostrophic currents. In addition, N. nomurai distribution off the coast of China in April is considered an important factor driving blooms around Korean coasts. To test this supposition, we conducted a sensitivity experiment that adjusted the position of particles off the coast of China in April. Results demonstrate that the appearance of N. nomurai can increase by a factor of three depending on the initial distribution of the jellyfish off the coast of China before eastward transport in April.

Many dynamic physiological processes, including embryo development and wound healing, involve collective cell migration. During this process, leader cells emerge in self-organization manner to guide other cells migration. The mechanisms of their formation, however, are not clear. We hypothesized that the physical forces among cells, and between cell and substrate influence the formation of leader cells. Here, we presented a computational model of cell monolayer migration based on the Glazier-Graner-Hogeweg (GGH) model. Our results indicated that the adhesion forces among cells and the cell-substrate adhesion forces regulate the formation of leader cells. Increasing cellular mobility also affected the characters of leader cells. In summary, our results provided evidence for that physical forces among cells and between cell and substrate, along with mobility of individual cells, affect the self-organization process of leader cell formation during collective cell migration.

Researchers are probing the subtle physical forces that sculpt cells and bodies. Listen to an audio version of a recent Nature feature.