scholarly journals Internal friction controls active ciliary oscillations near the instability threshold

2020 ◽  
Vol 6 (33) ◽  
pp. eabb0503 ◽  
Author(s):  
Debasmita Mondal ◽  
Ronojoy Adhikari ◽  
Prerna Sharma
Keyword(s):  
Internal Friction ◽  
Molecular Motors ◽  
Energy Input ◽  
Strain Softening ◽  
Elastic Stress ◽  
Fluid Motion ◽  
Sole Source ◽  
Instability Threshold ◽  
Ciliary Beating ◽  
External Fluid

Ciliary oscillations driven by molecular motors cause fluid motion at micron scale. Stable oscillations require a substantial source of dissipation to balance the energy input of motors. Conventionally, it stems from external fluid. We show, in contrast, that external fluid friction is negligible compared to internal elastic stress through a simultaneous measurement of motion and flow field of an isolated and active Chlamydomonas cilium beating near the instability threshold. Consequently, internal friction emerges as the sole source of dissipation for ciliary oscillations. We combine these experimental insights with theoretical modeling of active filaments to show that an instability to oscillations takes place when active stresses are strain softening and shear thinning. Together, our results reveal a counterintuitive mechanism of ciliary beating and provide a general experimental and theoretical methodology to analyze other active filaments, both biological and synthetic ones.

scholarly journals A New Unified Solution for Circular Tunnels Based on Generalized SMP Criterion considering the Strain Softening and Dilatancy

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Qifeng Guo ◽  
Jiliang Pan ◽  
Xinghui Wu ◽  
Xun Xi ◽  
Meifeng Cai
Keyword(s):  
Internal Friction ◽  
Plastic Zone ◽  
Strain Softening ◽  
Friction Angle ◽  
Surrounding Rock ◽  
Internal Friction Angle ◽  
Plastic State ◽  
Circular Tunnel ◽  
Dilatancy Angle ◽  
Elastic Plastic

According to the strain-softening characteristics of rock mass, an ideal elastic strain-softening model is developed, and the surrounding rock of tunnels is subdivided into the plastic broken zone, plastic strain-softening zone, and elastic zone. Based on the generalized spatially mobilized plane criterion, an elastic-plastic analytical solution of a circular tunnel is derived. The effects of intermediate principal stress, strain softening, and dilatancy are considered in the unified solution. The stress, displacement, and plastic zone radius of surrounding rock based on the SMP criterion are compared with those based on the Mohr–Coulomb criterion. Furthermore, the effects of parameters such as the softening modulus, dilatancy angle, and internal friction angle on the deformation and stress of tunnels are discussed. It has been found that the larger the dilatancy angle is, the larger the plastic zone displacement and the radius of the broken zone are. The larger the internal friction angle, the smaller the sizes of the plastic zone, the strain-softening zone, and the broken zone are. The deformation of surrounding rock in the broken zone is more sensitive to the internal friction angle than that in the strain-softening zone. The unified solution based on the SMP criterion provides a well understanding for the elastic-plastic state of tunnels, which can be the guidance for tunnel excavations and support designs.

An Experimental Study on the Mechanical Properties of Soils of the Landslide Induced by Rainfall

2011 ◽  
Vol 90-93 ◽  
pp. 1303-1306
Author(s):  
Dong Heng Hao ◽  
Jian Feng Qi ◽  
Bin Wang ◽  
Shu Qin Zhao
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Internal Friction ◽  
Water Content ◽  
Strain Softening ◽  
Friction Angle ◽  
Mechanical Parameters ◽  
Strain Stress ◽  
Geotechnical Tests ◽  
Sliding Zone

Geotechnical tests are performed to study the strain-stress behavior and mechanical parameters by using the automatic KTG triaxial shear apparatus. This study shows that the strain softening phenomenon emerges after the peak values of strain-stress relations appear for the sliding-body soils, and that the strain-stress relations are in the sate of strain hardening all the time for the sliding-zone soils although the water content keeps sameness. The variation laws of cohesion and internal friction angle with water content are respectively consistent with an exponential function and linear relation.

Effect of magnetic field and elastic stress on restoration of the internal friction of aluminum

1969 ◽  
Vol 12 (7) ◽  
pp. 970-972
Author(s):  
A. A. Rodionov ◽  
V. M. Gzogyan ◽  
I. V. Antonov
Keyword(s):  
Magnetic Field ◽  
Internal Friction ◽  
Elastic Stress

Hydraulic Fracturing Mechanical Mechanism Analyses for Soft Seams Considering Strain Softening Character

2013 ◽  
Vol 868 ◽  
pp. 319-325 ◽  
Author(s):  
Yi Lei ◽  
Wen Bin Wu
Keyword(s):  
Plastic Deformation ◽  
Elastic Modulus ◽  
Internal Friction ◽  
Hydraulic Fracturing ◽  
Poisson’S Ratio ◽  
Strain Softening ◽  
Fracture Initiation ◽  
Poisson's Ratio ◽  
Angle Of Internal Friction ◽  
Initiation Pressure

Mathematical model based on elasticity is not suitable for soft seam hydraulic fracturing mechanism study because its intensity is small, Poisson's ratio is relatively large, and its prone to plastic deformation. Based on plastic mechanics, the theory of large deformation and fracture mechanics theory, hydraulic fracturing of soft coal seam is divided into three phases, namely, coal bed compaction, fracture initiation and crack propagation from the view of the deformation mechanism, the occurring and developing mechanism. The initiation pressure of soft seams considered strain softening character after plastic deformation is obtained on the basis of above. The result shows that the initiation pressure is related to elastic modulus, Poisson's ratio, the angle of internal friction and residual strength. Elastic modulus is inversely proportional to the initiation pressure, the greater its value, the smaller the initiation pressure; but Poisson's ratio, the angle of internal friction and the residual strength and fracture initiation pressure is directly proportional relationship, the greater its value, since the smaller the crack pressure.

scholarly journals Active mechanical threading by a molecular motor

2021 ◽  
Author(s):  
Nicolai N. Bach ◽  
Verena Josef ◽  
Harald Maid ◽  
Henry Dube
Keyword(s):  
Molecular Motors ◽  
Energy Input ◽  
Molecular Motor ◽  
External Energy ◽  
Crucial Step ◽  
Molecular Events ◽  
Translation Motion ◽  
Motor Structure ◽  
Step Mechanism ◽  
A Current

Molecular motors transform external energy input into directional motions and offer exquisite precision for nano-scale manipulations. In order to make full use of molecular motor capacities, their directional motions need to be transmitted and used for powering downstream molecular events – a current great challenge for molecular engineers. Here we present a macrocyclic molecular motor structure able to perform repetitive molecular threading of a flexible polyethylene glycol chain through the macrocycle. This mechanical threading event is actively powered by the motor motions and leads to a direct translation of the unidirectional motor rotation into an unidirectional translation motion (chain versus ring). The step by step mechanism of the active mechanical threading is elucidated and also the actual threading step is identified as a combined helix inversion and threading event. The here established molecular machine function resembles the crucial step of macroscopic weaving or sewing processes and therefore offers a first entry point for realizing a “molecular knitting” counterpart.

Video-microscopic measurement of cell-substratum traction forces generated by locomoting keratocytes

1993 ◽  
Vol 51 ◽  
pp. 188-189
Author(s):  
Tim Oliver ◽  
Michelle Leonard ◽  
Juliet Lee ◽  
Akira Ishihara ◽  
Ken Jacobson
Keyword(s):  
Silicone Rubber ◽  
Molecular Motors ◽  
Video Frame ◽  
Traction Forces ◽  
Cell Traction Forces ◽  
Latex Beads ◽  
Cell Traction ◽  
Local Cell ◽  
Microscopic Measurement ◽  
Kinetics Of

We are using video-enhanced light microscopy to investigate the pattern and magnitude of forces that fish keratocytes exert on flexible silicone rubber substrata. Our goal is a clearer understanding of the way molecular motors acting through the cytoskeleton co-ordinate their efforts into locomotion at cell velocities up to 1 μm/sec. Cell traction forces were previously observed as wrinkles(Fig.l) in strong silicone rubber films by Harris.(l) These forces are now measureable by two independant means.In the first of these assays, weakly crosslinked films are made, into which latex beads have been embedded.(Fig.2) These films report local cell-mediated traction forces as bead displacements in the plane of the film(Fig.3), which recover when the applied force is released. Calibrated flexible glass microneedles are then used to reproduce the translation of individual beads. We estimate the force required to distort these films to be 0.5 mdyne/μm of bead movement. Video-frame analysis of bead trajectories is providing data on the relative localisation, dissipation and kinetics of traction forces.

Role of the Cilia Membrane in Control of Microtubule Sliding

1980 ◽  
Vol 38 ◽  
pp. 612-615
Author(s):  
Edna S. Kaneshiro
Keyword(s):  
Control Mechanism ◽  
Beat Frequency ◽  
Surface Membrane ◽  
Ciliary Membrane ◽  
Ciliary Beating ◽  
Ciliary Reversal ◽  
Voltage Dependent ◽  
Reversal Mechanism ◽  
And Function

It is currently believed that ciliary beating results from microtubule sliding which is restricted in regions to cause bending. Cilia beat can be modified to bring about changes in beat frequency, cessation of beat and reversal in beat direction. In ciliated protozoans these modifications which determine swimming behavior have been shown to be related to intracellular (intraciliary) Ca2+ concentrations. The Ca2+ levels are in turn governed by the surface ciliary membrane which exhibits increased Ca2+ conductance (permeability) in response to depolarization. Mutants with altered behaviors have been isolated. Pawn mutants fail to exhibit reversal of the effective stroke of ciliary beat and therefore cannot swim backward. They lack the increased inward Ca2+ current in response to depolarizing stimuli. Both normal and pawn Paramecium made leaky to Ca2+ by Triton extrac¬tion of the surface membrane exhibit backward swimming only in reactivating solutions containing greater than IO-6 M Ca2+ Thus in pawns the ciliary reversal mechanism itself is left operational and only the control mechanism at the membrane is affected. The topographic location of voltage-dependent Ca2+ channels has been identified as a component of the ciliary mem¬brane since the inward Ca2+ conductance response is eliminated by deciliation and the return of the response occurs during cilia regeneration. Since the ciliary membrane has been impli¬cated in the control of Ca2+ levels in the cilium and therefore is the site of at least one kind of control of microtubule sliding, we have focused our attention on understanding the structure and function of the membrane.

Internal friction in a martensitic high-carbon steel

2001 ◽  
Vol 81 (12) ◽  
pp. 2797-2808
Author(s):  
Rustem Bagramov, Daniele Mari, Willy Benoi
Keyword(s):  
Carbon Steel ◽  
Internal Friction ◽  
High Carbon Steel ◽  
High Carbon

A simple system to measure internal friction and creep

1992 ◽  
Vol 2 (9) ◽  
pp. 1779-1786
Author(s):  
A. M. Bastawros ◽  
M. Z. Said
Keyword(s):  
Internal Friction ◽  
Simple System
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