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#mechanics

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Philo Sophies

Contribution to the “#Quantum #Year #2025”

Foreword

To mark the 100th anniversary of the birth of “#quantum #mechanics” in #1925, #UNESCO has proclaimed 2025 as the “International Year of Quantum #Science and #Technology”. But as is often the case with such “UNESCO jubilee years”, they get lost in the “media mainstream”, especially when it comes to such “hard-to-digest fare” as quantum mechanics.

More at: cbuphilblog.wordpress.com/

or: philosophies.de/index.php/2025

Rxiv mechanobio

📰 "Spatiotemporal mapping of the contractile and adhesive forces sculpting early C. elegans embryos"
doi.org/doi:10.1101/2023.03.07
pubmed.ncbi.nlm.nih.gov/406311
#Mechanics #Cell

bioRxiv · Spatiotemporal mapping of the contractile and adhesive forces sculpting early C. elegans embryosEmbryo shape is determined by individual cell mechanics, intercellular interaction strength, and geometrical constraints. Models based on surface tensions at cell interfaces can predict 3D static cellular arrangements within aggregates. However, predicting the dynamics of such arrangements is challenging due to difficulties in measuring temporal changes in tensions. Here, we characterise the spatiotemporal changes in cellular tensions shaping the early nematode embryo using AFM, live microscopy, and tension inference. Using excoriated embryos, we validate a hybrid inference pipeline that calibrates relative inferred tensions temporally using cortical myosin enrichment and absolute tensions using AFM measurements. Applied to embryos within their native shell, we infer a spatiotemporal map of absolute tensions, revealing that ABa, ABp, and EMS compaction is driven by increased tension at free surfaces, while P2’s initial exclusion is due to high tension at intercellular contacts. We uncover a direct and non-affine contribution of cadherins to cell-cell contact tension, comparable to cadherins’ indirect contribution via actomyosin regulation. Highlights Open Access For the purpose of Open Access, the author has applied a CC BY public copyright license to any Author Accepted Manuscript version arising from this submission. ### Competing Interest Statement The authors have declared no competing interest. Grant-in-Aid for JSPS Fellows, 16J09469 Uehara Memorial Foundation, https://ror.org/00gc20a07 European Research Council, CoG-647186 Cancer Research UK, FC001086 Medical Research Council, FC001086 Wellcome Trust, FC001086 European Research Council, Grant agreement No. 949267 NIH Office of Research Infrastructure Programs, P40 OD010440
Orange Menace

Vintage tool people, any idea what this is? There are 3 slots which open & close with the handle, one edge of each is angled like it’s meant to cut. It’s like some sort of triple wire cutter, with lots of leverage.

My Dad had it in a box of old stuff brought from his parents’ house. There were old vehicle mechanics in the family.

#tools#vintage#vehicle
Rxiv mechanobio

📰 "Protein Drift-Diffusion in Membranes with Non-equilibrium Fluctuations arising from Gradients in Concentration or Temperature"
arxiv.org/abs/2506.22695 #Physics.Comp-Ph #Physics.Bio-Ph #Cond-Mat.Soft #Mechanics #Q-Bio.Sc #Nlin.Ao #Cell

arXiv.orgProtein Drift-Diffusion in Membranes with Non-equilibrium Fluctuations arising from Gradients in Concentration or TemperatureWe investigate proteins within heterogeneous cell membranes where non-equilibrium phenomena arises from spatial variations in concentration and temperature. We develop simulation methods building on non-equilibrium statistical mechanics to obtain stochastic hybrid continuum-discrete descriptions which track individual protein dynamics, spatially varying concentration fluctuations, and thermal exchanges. We investigate biological mechanisms for protein positioning and patterning within membranes and factors in thermal gradient sensing. We also study the kinetics of Brownian motion of particles with temperature variations within energy landscapes arising from heterogeneous microstructures within membranes. The introduced approaches provide self-consistent models for studying biophysical mechanisms involving the drift-diffusion dynamics of individual proteins and energy exchanges and fluctuations between the thermal and mechanical parts of the system. The methods also can be used for studying related non-equilibrium effects in other biological systems and soft materials.
Rxiv mechanobio

📰 "Multicontinuum Homogenization for Poroelasticity Model"
arxiv.org/abs/2506.20890 #Physics.Comp-Ph #Mechanics #Math.Na #Cs.Na #Cs.Ce #Cell

arXiv.orgMulticontinuum Homogenization for Poroelasticity ModelIn this paper, we derive multicontinuum poroelasticity models using the multicontinuum homogenization method. Poroelasticity models are widely used in many areas of science and engineering to describe coupled flow and mechanics processes in porous media. However, in many applications, the properties of poroelastic media possess high contrast, presenting serious computational challenges. It is well known that standard homogenization approaches often fail to give an accurate solution due to the lack of macroscopic parameters. Multicontinuum approaches allow us to consider such cases by defining several average states known as continua. In the field of poroelasticity, multiple-network models arising from the multiple porous media theory are representatives of these approaches. In this work, we extend previous findings by deriving the generalized multicontinuum poroelasticity model. We apply the recently developed multicontinuum homogenization method and provide a rigorous derivation of multicontinuum equations. For this purpose, we formulate coupled constraint cell problems in oversampled regions to consider different homogenized effects. Then, we obtain a multicontinuum expansion of the fine-scale fields and derive the multicontinuum model supposing the smoothness of macroscopic variables. We present the most general version of equations and the simplified ones based on our numerical experiments. Numerical results are presented for different heterogeneous media cases and demonstrate the high accuracy of our proposed multicontinuum models.
*
Alex@rtnVFRmedia Suffolk UK

I keep seeing this #pictogram (top right hand corner, stick man holding a #spanner and wearing a #rosette ) on parts of #VW cars (it was also on the #DSG gearbox of my Polo). I know it means "qualified/trained #mechanic only should work on this assembly and the one in my picture is a specification of oil and refrigerant for the airco),

I've not found any sources that #mechanics in Germany get #rosettes on completing their training, and in UK a rosette is either associated with political party membership or you might get one if you won some kind of #sports event (or a beauty contest) so I'm curious as to why its used..

Rxiv mechanobio

📰 "Prediction of the aqueous redox properties of functionalized quinones using a new QM/MM variational formulation"
arxiv.org/abs/2506.12448 #Physics.Chem-Ph #Cond-Mat.Soft #Mechanics #Matrix

arXiv.orgPrediction of the aqueous redox properties of functionalized quinones using a new QM/MM variational formulationWe recently proposed a method coupling quantum mechanics (QM) methods and molecular density functional theory (MDFT) to describe mixed quantum-classical systems [J. Chem. Phys. 161, 014113 (2024)]. This approach is particularly appropriate to account for solvent effect into QM calculations. We introduce a new variational formulation for the grand potential of a mixed quantum-classical system. Within the Born-Oppenheimer approximation and neglecting electronic entropy, the quantum solute is described by a product of electronic and nuclear density matrices, both depending parametrically on coordinates of the classical solvent. It can then be shown that a functional of the total density matrix satisfies a variational principle for the grand potential. Using a mean-field approximation, we express the grand potential of the mixed quantum-classical system as a variational problem which depends only on the nuclear density matrix, which experiences an external field generated by the electronic and classical one-particle densities. In practice, the grand potential is computed by a series of coupled classical and quantum DFT calculations, together with geometry optimization.
Rxiv mechanobio

📰 "Dynamic and Geometric Shifts in Wave Scattering"
arxiv.org/abs/2506.07144 #Physics.Optics #Mechanics #Quant-Ph #Matrix

arXiv.orgDynamic and Geometric Shifts in Wave ScatteringSince Berry's pioneering 1984 work, the separation of geometric and dynamic contributions in the phase of an evolving wave has become fundamental in wave physics, underpinning diverse phenomena in quantum mechanics, optics, and condensed matter. Here we extend this geometric-dynamic decomposition from the wave-evolution phase to a distinct class of wave scattering problems, where observables (such as frequency, momentum, or position) experience shifts in their expectation values between the input and output wave sates. We describe this class of problems using a unitary scattering matrix and the associated generalized Wigner-Smith operator (GWSO), which involves gradients of the scattering matrix with respect to conjugate variables (time, position, or momentum, respectively). We show that both the GWSO and the resulting expectation-values shifts admit gauge-invariant decompositions into dynamic and geometric parts, related respectively to gradients of the eigenvalues and eigenvectors of the scattering matrix. We illustrate this general theory through a series of examples, including frequency shifts in polarized-light transmission through a time-varying waveplate (linked to the Pancharatnam-Berry phase), momentum shifts at spatially varying metasurfaces, optical forces, beam shifts upon reflection at a dielectric interface, and Wigner time delays in 1D scattering. This unifying framework illuminates the interplay between geometry and dynamics in wave scattering and can be readily applied to a broad range of physical systems.
Rxiv mechanobio

📰 "A structure-preserving and thermodynamically compatible cell-centered Lagrangian finite volume scheme for continuum mechanics"
arxiv.org/abs/2506.03081 #Physics.Comp-Ph #Mechanics #Math.Na #Cs.Na #Cell

arXiv.orgA structure-preserving and thermodynamically compatible cell-centered Lagrangian finite volume scheme for continuum mechanicsIn this work we present a novel structure-preserving scheme for the discretization of the Godunov-Peshkov-Romenski (GPR) model of continuum mechanics written in Lagrangian form. This model admits an extra conservation law for the total energy (first principle of thermodynamics) and satisfies the entropy inequality (second principle of thermodynamics). Furthermore, in the absence of algebraic source terms, the distortion field of the continuum and the specific thermal impulse satisfy a curl-free condition, provided the initial data are curl-free. Last but not least, the determinant of the distortion field is related to the density of the medium, i.e. the system is also endowed with a nonlinear algebraic constraint. The objective of this work is to construct and analyze a new semi-discrete thermodynamically compatible cell-centered Lagrangian finite volume scheme on moving unstructured meshes that satisfies the following structural properties of the governing PDE exactly at the discrete level: i) compatibility with the first law of thermodynamics, i.e. discrete total energy conservation; ii) compatibility with the second law of thermodynamics, i.e. discrete entropy inequality; iii) exact discrete compatibility between the density and the determinant of the distortion field; iv) exact preservation of the curl-free property of the distortion field and of the specific thermal impulse in the absence of algebraic source terms. We show that it is possible to achieve all above properties simultaneously. Unlike in existing schemes, we choose to directly discretize the entropy inequality, hence obtaining total energy conservation as a consequence of an appropriate and thermodynamically compatible discretization of all the other equations.
Rxiv mechanobio

📰 "Weighted Point Configurations with Hyperuniformity: An Ecological Example and Models"
arxiv.org/abs/2501.12807 #Cond-Mat.Stat-Mech #Physics.Bio-Ph #Mechanics #Q-Bio.Pe #Nlin.Ao #Matrix

arXiv.orgWeighted Point Configurations with Hyperuniformity: An Ecological Example and ModelsRandom point configurations are said to be in hyperuniform states, if density fluctuations are anomalously suppressed in large-scale. Typical examples are found in Coulomb gas systems in two dimensions especially called log-gases in random matrix theory, in which points are repulsively correlated by long-range potentials. In infertile lands like deserts continuous survival competitions for water and nutrition will cause long-ranged repulsive interactions among plants. We have prepared digital data of spatial configurations of center-of-masses for bushes weighted by bush sizes which we call masses. Data analysis shows that such ecological point configurations do not show hyperuniformity as unmarked point processes, but are in hyperuniform states as marked point processes in which mass distributions are taken into account. We propose the non-equilibrium statistical-mechanics models to generate marked point processes having hyperuniformity, in which iterations of random thinning of points and coalescing of masses transform initial uncorrelated point processes into non-trivial point processes with hyperuniformity. Combination of data analysis and computer simulations shows the importance of strong correlations in probability law between spatial point configurations and mass distributions of individual points to realize hyperuniform marked point processes.
jexner 🏳️‍🌈

Mechanically gifted people of Mastodon, I have a question: would it be possible to build something that looks like a snake, rolled up but with it's head 30 - 50cm above ground, that I could put into the basket on my bike and that would slowly sway while I'm riding, like purposefully, from side to side?

Please say yes! And please tell me how!

#BikeTooter#Mechanics#DIY
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