scholarly journals Control of helical navigation by three-dimensional flagellar beating

2020 ◽  
Author(s):  
Dario Cortese ◽  
Kirsty Y. Wan
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Rotation ◽  
Live Cells ◽  
High Speed Imaging ◽  
Flagellar Beat ◽  
Motile Cells ◽  
Beat Pattern ◽  
Swimming Trajectories ◽  
Realistic Geometries

Helical swimming is a ubiquitous strategy for motile cells to generate self-gradients for environmental sensing. The model biflagellate Chlamydomonas reinhardtii rotates at a constant 1 – 2 Hz as it swims, but the mechanism is unclear. Here, we show unequivocally that the rolling motion derives from a persistent, non-planar flagellar beat pattern. This is revealed by high-speed imaging and micromanipulation of live cells. We construct a fully-3D model to relate flagellar beating directly to the free-swimming trajectories. For realistic geometries, the model reproduces both the sense and magnitude of the axial rotation of live cells. We show that helical swimming requires further symmetry-breaking between the two flagella. These functional differences underlie all tactic responses, particularly phototaxis. We propose a control strategy by which cells steer towards or away from light by modulating the sign of biflagellar dominance.

scholarly journals Reconstruction of the three-dimensional beat pattern underlying swimming behaviors of sperm

2021 ◽  
Vol 44 (7) ◽  
Author(s):  
A. Gong ◽  
S. Rode ◽  
G. Gompper ◽  
U. B. Kaupp ◽  
J. Elgeti ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Intrinsic Property ◽  
Human Sperm ◽  
Bending Waves ◽  
Flagellar Beat ◽  
Beat Pattern ◽  
Glass Interface ◽  
Two Space Dimensions ◽  
Swimming Trajectories ◽  
Physical And Chemical

Abstract  The eukaryotic flagellum propels sperm cells and simultaneously detects physical and chemical cues that modulate the waveform of the flagellar beat. Most previous studies have characterized the flagellar beat and swimming trajectories in two space dimensions (2D) at a water/glass interface. Here, using refined holographic imaging methods, we report high-quality recordings of three-dimensional (3D) flagellar bending waves. As predicted by theory, we observed that an asymmetric and planar flagellar beat results in a circular swimming path, whereas a symmetric and non-planar flagellar beat results in a twisted-ribbon swimming path. During swimming in 3D, human sperm flagella exhibit torsion waves characterized by maxima at the low curvature regions of the flagellar wave. We suggest that these torsion waves are common in nature and that they are an intrinsic property of beating axonemes. We discuss how 3D beat patterns result in twisted-ribbon swimming paths. This study provides new insight into the axoneme dynamics, the 3D flagellar beat, and the resulting swimming behavior. Graphic abstract

Analysis of the Flagellar Beat Pattern of Male Ectocarpus Siliculosus Gametes (Phaeophyta) in Relation to Chemotactic Stimulation by Female Cells

1981 ◽  
Vol 92 (1) ◽  
pp. 53-66
Author(s):  
ANNETTE GELLER ◽  
DIETER G. MÜLLER
Keyword(s):  
Linear Correlation ◽  
Mode Of Action ◽  
High Speed ◽  
Sex Attractant ◽  
Cell Axis ◽  
Ectocarpus Siliculosus ◽  
Bending Waves ◽  
Flagellar Beat ◽  
Beat Pattern ◽  
Negative Linear Correlation

Heterocontic male Ectocarpus siliculosus gametes respond to the sex-attractant ectocarpen by changing their locomotive behaviour. However, the mode of action of the flagella is not changed by the presence of ectocarpen. High-speed cinemicrography shows that gametes moving close to a coverglass perform planar bending waves with their front flagellum. Straight or slightly curved swimming paths are generated by enhanced upward bends of the front flagellum to compensate for the asymmetrical insertion of both flagella. Narrower curves are connected with increasing downward bends of the front flagellum. There is a negative linear correlation between the average deflexion of the front flagellum (μm) from the cell axis and the radius of track (correlation coefficient 0.94). Additionally, freely swimming gametes exhibit elliptical and rotary wave motions, suggesting a relationship between thigmotaxis and mode of action of the front flagellum. The rigid hind flagellum performs one rapid sideward beat when the gametes swim in narrow curves. This appears to provide a steering function.

Influence of Geometric Features of the Peripheral Part of the Thin-Walled Spherical Segment on the Explosive Throwing Process

2020 ◽  
pp. 76-87
Author(s):  
M.A. Baburin ◽  
V.D. Baskakov ◽  
S.V. Eliseev ◽  
K.A. Karnaukhov ◽  
V.A. Tarasov
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Rotation ◽  
Aerodynamic Coefficients ◽  
Peripheral Part ◽  
High Speed Impact ◽  
Wide Range ◽  
Main Factors ◽  
Thin Walled ◽  
Axisymmetric Shape

The main factors controlling the formation of the stern of explosively formed projectiles are investigated using numerical calculations in a three-dimensional formulation of a problem. To form folds in the stern, it is proposed to use thin-walled spherical segments with a peripheral thickness deviation in terms of decreasing or increasing with respect to the thickness in the central part. The configurations of explosively formed projectiles with inclined folds in the stern are shown, and it is proposed to describe the fold inclination by two angles of its position. The effect of folds in the stern on the change in aerodynamic coefficients for a wide range of angle of attack is numerically studied. The angular velocity of the axial rotation of explosively formed projectiles with inclined folds in the stern is estimated based on the Newton method and considering the angles of its position. The results obtained are of interest to specialists working in the field of physics of explosion and high-speed impact, as well as those dealing with aerodynamics of aircrafts, mainly of axisymmetric shape

Three-dimensional flow structure and string cavitation in a fuel injector and their effects on discharged liquid jet

2019 ◽  
Vol 22 (1) ◽  
pp. 243-256 ◽  
Author(s):  
Rubby Prasetya ◽  
Akira Sou ◽  
Junichi Oki ◽  
Akira Nakashima ◽  
Keiya Nishida ◽  
...  
Keyword(s):  
Vortex Ring ◽  
Flow Structure ◽  
High Speed ◽  
Three Dimensional ◽  
Liquid Jet ◽  
Fuel Injector ◽  
High Speed Imaging ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Stereo Particle Image Velocimetry

Two kinds of cavitation may occur in mini-sac type diesel injectors. The first is geometrical cavitation, which can usually be seen as a film-like structure in the nozzle. The second is the filament-like string cavitation. Both types of cavitation are known to affect fuel spray characteristics, although the effects of geometrical cavitation and that of string cavitation have not been individually clarified. Moreover, the mechanism behind string cavitation occurrence is still unclear. String cavitation usually occurs at low needle lift, which might indicate the existence of a vortex ring flow in the sac. However, because of the difficulty in precise flow measurement of the three-dimensional flow structure in the sac, the link between vortex ring flow and string cavitation occurrence in the sac has not been proven. In this study, high-speed imaging of string cavitation, geometrical cavitation, and discharged liquid jet of an enlarged three-hole mini-sac diesel fuel injector was conducted to individually clarify the effects of string cavitation and geometrical cavitation on the discharged liquid jet angle. Furthermore, tomographic–stereo particle image velocimetry was carried out on the sac. The experiments were conducted at two different needle lifts, to clarify the link between needle lifts and flow structure in the sac, as well as how it affects string cavitation occurrence and liquid jet angle. The results confirmed that at low needle lift, vortex ring flow forms in the sac, which may induce helical flow in the nozzle, resulting in a large jet angle. Vortex strength varies with time, and string cavitation occurs when the vortex is particularly strong. As a result, the magnitude of the jet angle increase at low needle lift is enhanced when string cavitation occurs. At high needle lift, flow pattern in the sac becomes relatively uniform, which makes it harder for string cavitation to form.

scholarly journals Laser-induced forward transfer of viscoplastic fluids

2019 ◽  
Vol 880 ◽  
pp. 497-513 ◽  
Author(s):  
Maziyar Jalaal ◽  
Martin Klein Schaarsberg ◽  
Claas-Willem Visser ◽  
Detlef Lohse
Keyword(s):  
High Speed ◽  
Laser Energy ◽  
Three Dimensional ◽  
Liquid Jet ◽  
Control Parameters ◽  
Optimal Conditions ◽  
High Speed Imaging ◽  
Three Dimensional Printing ◽  
Forward Transfer ◽  
Dimensional Printing

Laser-induced forward transfer (LIFT) is a nozzle-free printing technology that can be used for two- and three-dimensional printing. In LIFT, a laser pulse creates an impulse inside a thin film of material that results in the formation of a liquid jet. We experimentally study LIFT of viscoplastic materials by visualizing the process of jetting with high-speed imaging. The shape of the jet depends on the laser energy, focal height, surface tension and material rheology. We theoretically identify the characteristic jetting velocity and how it depends on the control parameters, and define non-dimensional groups to classify the regimes of jetting. Based on the results, we propose the optimal conditions for printing with LIFT technology.

Electrically tunable lenses – eliminating mechanical axial movements during high-speed 3D live imaging

2021 ◽  
Vol 134 (16) ◽  
Author(s):  
Christoforos Efstathiou ◽  
Viji M. Draviam
Keyword(s):  
Cell Biology ◽  
High Speed ◽  
Imaging Techniques ◽  
Three Dimensional ◽  
Cost Effective ◽  
High Speed Imaging ◽  
Liquid Lenses ◽  
Live Cell Microscopy ◽  
Tunable Lenses ◽  
Cell Microscopy

ABSTRACT The successful investigation of photosensitive and dynamic biological events, such as those in a proliferating tissue or a dividing cell, requires non-intervening high-speed imaging techniques. Electrically tunable lenses (ETLs) are liquid lenses possessing shape-changing capabilities that enable rapid axial shifts of the focal plane, in turn achieving acquisition speeds within the millisecond regime. These human-eye-inspired liquid lenses can enable fast focusing and have been applied in a variety of cell biology studies. Here, we review the history, opportunities and challenges underpinning the use of cost-effective high-speed ETLs. Although other, more expensive solutions for three-dimensional imaging in the millisecond regime are available, ETLs continue to be a powerful, yet inexpensive, contender for live-cell microscopy.

scholarly journals Three-dimensional flow and lift characteristics of a hovering ruby-throated hummingbird

2014 ◽  
Vol 11 (98) ◽  
pp. 20140541 ◽  
Author(s):  
Jialei Song ◽  
Haoxiang Luo ◽  
Tyson L. Hedrick
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Leading Edge ◽  
Dynamics Simulation ◽  
Vertical Force ◽  
Imaging Data ◽  
High Speed Imaging ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Wake Interaction

A three-dimensional computational fluid dynamics simulation is performed for a ruby-throated hummingbird ( Archilochus colubris ) in hovering flight. Realistic wing kinematics are adopted in the numerical model by reconstructing the wing motion from high-speed imaging data of the bird. Lift history and the three-dimensional flow pattern around the wing in full stroke cycles are captured in the simulation. Significant asymmetry is observed for lift production within a stroke cycle. In particular, the downstroke generates about 2.5 times as much vertical force as the upstroke, a result that confirms the estimate based on the measurement of the circulation in a previous experimental study. Associated with lift production is the similar power imbalance between the two half strokes. Further analysis shows that in addition to the angle of attack, wing velocity and surface area, drag-based force and wing–wake interaction also contribute significantly to the lift asymmetry. Though the wing–wake interaction could be beneficial for lift enhancement, the isolated stroke simulation shows that this benefit is buried by other opposing effects, e.g. presence of downwash. The leading-edge vortex is stable during the downstroke but may shed during the upstroke. Finally, the full-body simulation result shows that the effects of wing–wing interaction and wing–body interaction are small.

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