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#mechanics

7 posts6 participants1 post today
Public
Rxiv mechanobio

📰 "Ovarian Mechanobiology: Understanding the Interplay Between Mechanics and Follicular Development"
doi.org/doi:10.3390/cells14050
pubmed.ncbi.nlm.nih.gov/400720
#Extracellular #Mechanical #Mechanics

MDPIOvarian Mechanobiology: Understanding the Interplay Between Mechanics and Follicular DevelopmentThe ovary is a dynamic organ where mechanical forces profoundly regulate follicular development, oocyte maturation, and overall reproductive function. These forces, originating from the extracellular matrix (ECM), granulosa and theca cells, and ovarian stroma, influence cellular behavior through mechanotransduction, translating mechanical stimuli into biochemical responses. This review explores the intricate interplay between mechanical cues and ovarian biology, focusing on key mechanosensitive pathways such as Hippo signaling, the PI3K/AKT pathway, and cytoskeletal remodeling, which govern follicular dormancy, activation, and growth. Additionally, it examines how ovarian aging disrupts the mechanical microenvironment, with ECM stiffening and altered mechanotransduction contributing to a decline in ovarian reserve and reproductive potential. Emerging technologies, including 3D culture systems and organ-on-chip platforms, are highlighted for their ability to replicate the ovarian microenvironment and advance drug discovery and therapeutic interventions. By integrating mechanobiological principles, this review aims to enhance our understanding of ovarian function and provide new strategies for preserving fertility and combating infertility.
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Alex@rtnVFRmedia Suffolk UK

Interesting story of a owned in in the 1980s (and the ladies who ran it were also ). Whilst society has got marginally better for people in the meantime, its still a shame that even today such a business remains unusual (whilst there are slightly more female , they are still relatively rare or dependent on men as employers, and other women tend to just end up in admin roles)

bbc.co.uk/news/articles/cm2dz0

Three women sit in, or perch on, an old-fashioned green car outside a garage. They are all smiling at the camera. The fashion, haircuts and quality of the photograph indicate it is the 1980s.
BBC NewsFilm screening about 1980s women mechanics in Sheffield sells outThree friends set up their own garage because they could not find jobs in male-dominated industry.
Public
Y⃒̸̷̝̜̙ͥͥͥngmar

Giving @davepolaschek's suggestion a try. The T-40 wheel I found in the garage is getting some use as uh, round lever? What do you even call this.

It kinda worked. Well, it didn't budge as I was pulling, but when it fell over while under tension it levered the beam out of the ground sideways and a little forward.

Still refuses to go further, but I'm having a strong coffee and sweets and shall stubbornly continue.

The pesky concrete beam in our garden is now attached with a very beefy chain to a very beefy piece of wire rope. A big tractor steel wheel (sans tyre) is rolled in front of it, with the wire rope leading over the wheel and off to a tractor not depicted here. The ground is churned up from pulling many other concrete beams out of the garden already.
Same arrangement, excep the wheel has fallen over sideways. The wire rope still leads through what used to be its top. The beam however has shifted in the direction of the fallen wheel and left its deep groove for the first time.
The rear end of the beam with a gap that is now about a metric foot longer (we only have metric feet here, sorry, they're about one foot long though). The standard reference foot including boot is next to it. It's a size 44, in case you need to calibrate.
#Farm#Mechanics#Concrete
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Pustam | पुस्तम | পুস্তম🇳🇵

An Article in the Annual Review of Condensed Matter Physics on Turbulence by KR Sreenivasan and J Schumacher
annualreviews.org/content/jour

What is the turbulence problem, and when can we say it’s solved? 🌪️ This deep dive by Sreenivasan & Schumacher explores the math, physics, and engineering challenges of turbulence—from Navier-Stokes equations to intermittency and beyond. A must-read for anyone fascinated by chaos, complexity, and the unsolved mysteries of fluid dynamics! 🌀

A summary of the talk presented by KR Sreenivasan in December 2023 at the International Center for Theoretical Sciences (ICTS-TIFR) in Bengaluru, as part of a program on field theory and turbulence.
youtube.com/watch?v=fwVSBYh-KC

"Field Theory and Turbulence" program link: icts.res.in/discussion-meeting

#FluidDynamics #Physics #NavierStokes #UnsolvedMystery #Mechanics #Dynamics #FluidMechanics #Science #Chaos #TurbulentMotion #Randomness #Chaotic #Fluid #ClassicalMechanics
#Turbulence

Public
Rxiv mechanobio

📰 "Cell mechanics, environmental geometry, and cell polarity control cell-cell collision outcomes"
arxiv.org/abs/2503.06239 #Physics.Bio-Ph #Cond-Mat.Soft #Mechanics #Cell

arXiv logo
arXiv.orgCell mechanics, environmental geometry, and cell polarity control cell-cell collision outcomesInteractions between crawling cells, which are essential for many biological processes, can be quantified by measuring cell-cell collisions. Conventionally, experiments of cell-cell collisions are conducted on two-dimensional flat substrates, where colliding cells repolarize and move away upon contact with one another in "contact inhibition of locomotion" (CIL). Inspired by recent experiments that show cells on suspended nanofibers have qualitatively different CIL behaviors than those on flat substrates, we develop a phase field model of cell motility and two-cell collisions in fiber geometries. Our model includes cell-cell and cell-fiber adhesion, and a simple positive feedback mechanism of cell polarity. We focus on cell collisions on two parallel fibers, finding that larger cell deformability (lower membrane tension), larger positive feedback of polarization, and larger fiber spacing promote more occurrences of cells walking past one another. We can capture this behavior using a simple linear stability analysis on the cell-cell interface upon collision.
Public
Rxiv mechanobio

📰 "Machine Learning Enhanced Calculation of Quantum-Classical Binding Free Energies"
arxiv.org/abs/2503.03955 #Cond-Mat.Dis-Nn #Physics.Comp-Ph #Physics.Chem-Ph #Physics.Bio-Ph #Mechanics #Cell

arXiv.orgMachine Learning Enhanced Calculation of Quantum-Classical Binding Free EnergiesBinding free energies are a key element in understanding and predicting the strength of protein--drug interactions. While classical free energy simulations yield good results for many purely organic ligands, drugs including transition metal atoms often require quantum chemical methods for an accurate description. We propose a general and automated workflow that samples the potential energy surface with hybrid quantum mechanics/molecular mechanics (QM/MM) calculations and trains a machine learning (ML) potential on the QM energies and forces to enable efficient alchemical free energy simulations. To represent systems including many different chemical elements efficiently and to account for the different description of QM and MM atoms, we propose an extension of element-embracing atom-centered symmetry functions for QM/MM data as an ML descriptor. The ML potential approach takes electrostatic embedding and long-range electrostatics into account. We demonstrate the applicability of the workflow on the well-studied protein--ligand complex of myeloid cell leukemia 1 and the inhibitor 19G and on the anti-cancer drug NKP1339 acting on the glucose-regulated protein 78.
Public
Rxiv mechanobio

📰 "A linearly-implicit energy preserving scheme for geometrically nonlinear mechanics based on non-canonical Hamiltonian formulations"
arxiv.org/abs/2503.04695 #Physics.Comp-Ph #Mechanics #Dynamics #Math.Na #Matrix #Cs.Na

arXiv.orgA linearly-implicit energy preserving scheme for geometrically nonlinear mechanics based on non-canonical Hamiltonian formulationsThis work presents a novel formulation and numerical strategy for the simulation of geometrically nonlinear structures. First, a non-canonical Hamiltonian (Poisson) formulation is introduced by including the dynamics of the stress tensor. This framework is developed for von-Kármán nonlinearities in beams and plates, as well as finite strain elasticity with Saint-Venant material behavior. In the case of plates, both negligible and non-negligible membrane inertia are considered. For the former case the two-dimensional elasticity complex is leveraged to express the dynamics in terms of the Airy stress function. The finite element discretization employs a mixed approach, combining a conforming approximation for displacement and velocity fields with a discontinuous stress tensor representation. A staggered, linear implicit time integration scheme is proposed, establishing connections with existing explicit-implicit energy-preserving methods. The stress degrees of freedom are statically condensed, reducing the computational complexity to solving a system with a positive definite matrix. The methodology is validated through numerical experiments on the Duffing oscillator, a von-Kármán beam, and a column undergoing finite strain elasticity. Comparisons with fully implicit energy-preserving method and the explicit Newmark scheme demonstrate that the proposed approach achieves superior accuracy while maintaining energy stability. Additionally, it enables larger time steps compared to explicit schemes and exhibits computational efficiency comparable to the leapfrog method.
Public
Rxiv mechanobio

📰 "Controlling tissue size by active fracture"
arxiv.org/abs/2503.03126 #Physics.Bio-Ph #Mechanics #Q-Bio.Qm #Q-Bio.To #Q-Bio.Cb #Cell

arXiv.orgControlling tissue size by active fractureGroups of cells, including clusters of cancerous cells, multicellular organisms, and developing organs, may both grow and break apart. What physical factors control these fractures? In these processes, what sets the eventual size of clusters? We develop a framework for understanding cell clusters that can fragment due to cell motility using an active particle model. We compute analytically how the break rate of cell-cell junctions depends on cell speed, cell persistence, and cell-cell junction properties. Next, we find the cluster size distributions, which differ depending on whether all cells can divide or only the cells on the edge of the cluster divide. Cluster size distributions depend solely on the ratio of the break rate to the growth rate - allowing us to predict how cluster size and variability depend on cell motility and cell-cell mechanics. Our results suggest that organisms can achieve better size control when cell division is restricted to the cluster boundaries or when fracture can be localized to the cluster center. Our results link the general physics problem of a collective active escape over a barrier to size control, providing a quantitative measure of how motility can regulate organ or organism size.
Public
Rxiv mechanobio

📰 "Surface tension-driven boundary growth in tumour spheroids"
arxiv.org/abs/2410.03344 #Physics.Bio-Ph #Cond-Mat.Soft #Mechanics #Cell

arXiv.orgSurface tension-driven boundary growth in tumour spheroidsGrowing experimental evidence highlights the relevant role of mechanics in the physiology of solid tumours, even in their early stages. While most of the mathematical models describe tumour growth as a volumetric increase of mass in the bulk, in vitro experiments on tumour spheroids have demonstrated that cell proliferation occurs in a thin layer at the boundary of the cellular aggregate. In this work, we investigate how elasticity and surface tension interact during the development of tumour spheroids. We model the spheroid as a hyperelastic material undergoing boundary accretion, where the newly created cells are deformed by the action of surface tension. This growth leads to a frustrated reference configuration, resulting in the appearance of residual stress. Our theoretical framework is validated using experimental results from the literature. Like fully developed tumours, spheroids open when subjected to radial cuts. Remarkably, this behaviour is observed even in newly formed spheroids, which lack residual stress. Through both analytical solutions and numerical simulations, we show that this phenomenon is driven by elastocapillary interactions, where the residual stress developed in grown spheroids amplifies the tumour opening. Our model's outcomes align with experimental observations and allow us to estimate the surface tension acting on tumour spheroids.
Public
Rxiv mechanobio

📰 "Theoretical Analysis of Power-Law Stress Relaxation and Calcium-Dependent Passive Mechanics in Cardiac Muscle"
biorxiv.org/content/10.1101/20 #Mechanical #Mechanics #Myosin

bioRxiv · Theoretical Analysis of Power-Law Stress Relaxation and Calcium-Dependent Passive Mechanics in Cardiac MuscleThis study investigates the passive viscoelastic mechanical properties of cardiac muscle by introducing a theoretical model that explains the power-law kinetics of passive stress decay. The model accounts for two parallel processes contributing to passive mechanics: an elastic component and a viscoelastic component designed to simulate stress/strain-mediated unfolding of serial domains in the titin molecule. Under stress, serial globular domains within the elastic region of the titin molecule reversibly unfold. This unfolding phenomenon contributes to both hysteresis (a lag in stress between loading and unloading) and preconditioning effects in simulated striated muscle mechanics. Moreover, experimental evidence indicates that stress relaxation in cardiac muscle follows a power law, and that the muscle’s nonlinear stress-strain relationship and hysteresis behavior are calcium-dependent. To analyze these mechanical phenomena, we simulate the apparent viscous element as a mesoscopic-scale ensemble of chains, each composed of serial globular domains that unfold in a stress-dependent manner. Although the model was developed to represent the behavior of titin, it equivalently represents any contributing process involving a linked series of domains that undergo stress-mediated unfolding. By providing a unified basis for the observed viscoelastic and preconditioning effects, calcium dependency, and power-law stress relaxation phenomena, this study offers a novel theoretical basis for understanding and simulating the role of titin in striated muscle mechanics. Key points 1. Passive stress relaxation of cardiac muscle follows a power-law decay, a phenomenon that is explained using a theoretical model of dynamic unfolding of globular domains along polymer chain. 2. The theoretical model simulates the behavior of titin, a giant sarcomere protein linking myosin thick filaments to the Z disk and providing passive restoring force during muscle stretch. 3. The theoretical model is able to account the observed effects of calcium on the effective viscoelastic passive mechanics of cardiac muscle. 4. This model provides a theoretical basis for understanding passive visocelastic properties and titin’s role in striated muscle mechanics. ### Competing Interest Statement The authors have declared no competing interest.
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