scholarly journals The human sperm beats anisotropically and asymmetrically in 3D

2019 ◽  
Author(s):  
Hermes Gadêlha ◽  
Paul Hernández-Herrera ◽  
Fernando Montoya ◽  
Alberto Darszon ◽  
Gabriel Corkidi
Keyword(s):  
Ion Channels ◽  
Mathematical Analysis ◽  
Molecular Motors ◽  
High Speed ◽  
3D Imaging ◽  
Human Sperm ◽  
Travelling Wave ◽  
Fundamental Question ◽  
Sperm Flagellum ◽  
Straight Line

The canonical beating of the human sperm flagellum is postulated to be symmetric. This is despite the reported asymmetries inherent to the flagellar axonemal structure, from distribution and activation of molecular motors to, even, the localisation of regulatory ion channels. This raises a fundamental question: how symmetric beating is possible within such intrinsically asymmetric flagellar complex? Here, we employ high-speed 3D imaging with mathematical analysis capable of resolving the flagellar movement in 4D (3D+time). This reveals that the human sperm beating is both anisotropic and asymmetric, and composed by a superposition of two transversal waves: an asymmetric travelling wave and a symmetric standing wave. This novel anisotropic travelling-pulsation mechanism induces sperm rolling self-organisation and causes a flagellar kinematic illusion, so that the beat appears to be symmetric if observed with 2D microscopy. The 3D beating anisotropy thus regularises the intrinsic flagellar asymmetry to achieve symmetric side-to-side movement and straight-line swimming.

scholarly journals A New Rotor Position Measurement Method for Permanent Magnet Spherical Motors

2018 ◽  
Vol 8 (12) ◽  
pp. 2415 ◽  
Author(s):  
Yin Lu ◽  
Cungang Hu ◽  
Qunjing Wang ◽  
Yi Hong ◽  
Weixiang Shen ◽  
...  
Keyword(s):  
Permanent Magnet ◽  
High Speed ◽  
Measurement Method ◽  
Coordinate Frame ◽  
Feature Points ◽  
Position Measurement ◽  
Experimental Platform ◽  
Rotor Position ◽  
Straight Line ◽  
The World

This paper proposes a new high-precision rotor position measurement (RPM) method for permanent magnet spherical motors (PMSMs). In the proposed method, a LED light spot generation module (LSGM) was installed at the top of the rotor shaft. In the LSGM, three LEDs were arranged in a straight line with different distances between them, which were formed as three optical feature points (OFPs). The images of the three OFPs acquired by a high-speed camera were used to calculate the rotor position of PMSMs in the world coordinate frame. An experimental platform was built to verify the effectiveness of the proposed RPM method.

scholarly journals Three-Dimensional (3-D) Immersed-Boundary (IB) Based Tornado Model for Computational Analysis of Disastrous Wind Load on Buildings

2021 ◽  
Author(s):  
Xixiong Guo ◽  
Jun Cao
Keyword(s):  
Wind Field ◽  
High Speed ◽  
Outer Boundary ◽  
Three Dimensional ◽  
Influence Factors ◽  
Research Direction ◽  
Wind Loading ◽  
Immersed Boundary ◽  
Design Strategies ◽  
Straight Line

This study is aimed at developing a novel computational framework that can essentially simulate a tornadic wind field and investigate the wind loadings on ground constructions. It is well known that tornado is a highly turbulent airflow that simultaneously translates, rotates and updrafts with a high speed. Tornadoes induce a significantly elevated level of wind forces if compared to a straight-line wind. A suitably designed building for a straight-line wind would fail to survive when exposed to a tornadic-like wind of the same wind speed. It is necessary to design buildings that are more resistant to tornadoes. Since the study of tornado dynamics relying on field observations and laboratory experiments is usually expensive, restrictive, and time-consuming, computer simulation mainly via the large eddy simulation (LES) method has become a more attractive research direction in shedding light on the intricate characteristics of a tornadic wind field. For numerical simulation of a tornado-building interaction scenario, it looks quite challenging to seek a set of physically-rational and meanwhile computationally-practical boundary conditions to accompany traditional CFD approaches; however, little literature can be found, as of today, in three-dimensional (3D) computational tornado dynamics study. Inspired by the development of the immersed boundary (IB) method, this study employed a re-tailored Rankine-combined vortex model (RCVM) that applies the “relative motion” principle to the translational component of tornado, such that the building is viewed as “virtually” translating towards a “pinned” rotational flow that remains time-invariant at the far field region. This revision renders a steady-state kinematic condition applicable to the outer boundary of a large tornado simulation domain, successfully circumventing the boundary condition updating process that the original RCVM would have to suffer, and tremendously accelerating the computation. Wind loading and its influence factors are comprehensively investigated and analyzed both on a single building and on a multiple-building configuration. The relation between the wind loadings and the height and shape of the building is also examined in detail. Knowledge of these loadings may lead to design strategies that can enable ground construction to be more resistant to tornadoes, reducing the losses caused by this type of disastrous weather.

Fast 3D imaging algorithm for high-speed spinning targets based on GRT-CLEAN

2018 ◽  
Vol 33 (3) ◽  
pp. 228-238
Author(s):  
王 会 WANG Hui ◽  
巨 欢 JU Huan ◽  
方 阳 FANG Yang ◽  
李荣旭 LI Rong-xu ◽  
王保平 WANG Bao-ping
Keyword(s):  
High Speed ◽  
3D Imaging ◽  
Imaging Algorithm ◽  
Spinning Targets

High-speed 3D imaging of the beating heart using temporal estimation

1987 ◽  
Vol 39 (3) ◽  
pp. 279-290 ◽  
Author(s):  
R.S. Acharya ◽  
P.B. Heffernan ◽  
R.A. Robb ◽  
H. Wechsler
Keyword(s):  
High Speed ◽  
3D Imaging ◽  
Beating Heart ◽  
Temporal Estimation

scholarly journals High-speed Imaging at 3 Tesla: A Technical and Clinical Review with an Emphasis on Whole-brain 3D Imaging

2004 ◽  
Vol 3 (4) ◽  
pp. 177-187 ◽  
Author(s):  
Shinji NAGANAWA ◽  
Hisashi KAWAI ◽  
Hiroshi FUKATSU ◽  
Takeo ISHIGAKI ◽  
Tomomi KOMADA ◽  
...  
Keyword(s):  
Clinical Review ◽  
High Speed ◽  
3D Imaging ◽  
3 Tesla ◽  
High Speed Imaging ◽  
Whole Brain

scholarly journals Uniform Distribution and Densification of Jets in Needleless Electrospinning Using Annular Tip Nozzle

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1301 ◽  
Author(s):  
Hongbo Chen ◽  
Chuansheng Wang ◽  
Imdad Ali ◽  
Haoyi Li ◽  
Xiaoqing Chen ◽  
...  
Keyword(s):  
Free Surface ◽  
High Speed ◽  
Repulsive Force ◽  
Closed Curve ◽  
Environmental Friendliness ◽  
Ultrafine Fibers ◽  
Needleless Electrospinning ◽  
Straight Line ◽  
Distribution Process ◽  
Practical Guidance

Numerous jets can be generated simultaneously on a nozzle by needleless melt electrospinning technology which has the advantages of solvent-free residues and environmental friendliness; and potential industrial application prospects. In this paper, the linear annular tip nozzle was taken as the research object, and the high-speed image acquisition of the jets generation and distribution process of annular tip nozzle was carried out and compared with that of straight-line tip nozzle. The results showed that the repulsive force between the jets caused a slight adjustment in the position of the jets on the free surface, the force between the jets on the annular closed curve canceled each other and eventually reached the equilibrium state, making the position of the jets stable and the distance between the jets the same, and the distance between the jets was related to the intensity of the induced electric field at the tip of the nozzle. Relevant conclusions can provide scientific and practical guidance for the design of needleless electrospinning nozzles on free surface in order to achieve uniform and efficient preparation of ultrafine fibers.

scholarly journals Human sperm uses asymmetric and anisotropic flagellar controls to regulate swimming symmetry and cell steering

2020 ◽  
Vol 6 (31) ◽  
pp. eaba5168 ◽  
Author(s):  
Hermes Gadêlha ◽  
Paul Hernández-Herrera ◽  
Fernando Montoya ◽  
Alberto Darszon ◽  
Gabriel Corkidi
Keyword(s):  
High Speed ◽  
Reproductive Tract ◽  
Three Dimensional ◽  
Human Sperm ◽  
Bilateral Symmetry ◽  
Female Reproductive Tract ◽  
Optical Illusion ◽  
3D Microscopy ◽  
Molecular Components ◽  
Molecular Asymmetries

Flagellar beating drives sperm through the female reproductive tract and is vital for reproduction. Flagellar waves are generated by thousands of asymmetric molecular components; yet, paradoxically, forward swimming arises via symmetric side-to-side flagellar movement. This led to the preponderance of symmetric flagellar control hypotheses. However, molecular asymmetries must still dictate the flagellum and be manifested in the beat. Here, we reconcile molecular and microscopic observations, reconnecting structure to function, by showing that human sperm uses asymmetric and anisotropic controls to swim. High-speed three-dimensional (3D) microscopy revealed two coactive transversal controls: An asymmetric traveling wave creates a one-sided stroke, and a pulsating standing wave rotates the sperm to move equally on all sides. Symmetry is thus achieved through asymmetry, creating the optical illusion of bilateral symmetry in 2D microscopy. This shows that the sperm flagellum is asymmetrically controlled and anisotropically regularized by fast-signal transduction. This enables the sperm to swim forward.

Compressibility Effects in High Speed Air Flow

1931 ◽  
Vol 35 (247) ◽  
pp. 665-674
Author(s):  
S. G. Hooker
Keyword(s):  
Angular Velocity ◽  
Perfect Fluid ◽  
Mathematical Analysis ◽  
High Speed ◽  
Equations Of Motion ◽  
Centre Of Gravity ◽  
High Speeds ◽  
Real Fluid ◽  
Special Cases ◽  
Compressibility Effects

Any theoretical attempt to evaluate the forces and couples experienced by an aircraft when in flight by a mathematical analysis of the pressures exerted by the air when in motion about the various parts, leads to what have, so far, proved insuperable difficulties. It involves the integration of the equations of motion of a real fluid, and, except in a few very special cases, these have been insoluble. The actual motion of a fluid is affected by a number of its properties, and, in general, accounts would have to be taken of its density, viscosity, and at high speeds its compressibility. In certain circumstances the effect of these last two can be neglected and the classical theory of hydrodynamics dealing with the motion of a non-viscous, incompressible or perfect fluid can be applied. A further simplification consists in supposing that the motion is irrotational, that is, any small portion of the fluid at a point has no angular velocity about its centre of gravity.

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