Undulatory Propulsion

1953 ◽  
Vol s3-94 (28) ◽  
pp. 551-578
Author(s):  
J. GRAY
Keyword(s):  
Three Dimensional ◽  
Longitudinal Axis ◽  
Point Of View ◽  
The Body ◽  
Lateral Curvature ◽  
Tangential Forces ◽  
External Forces ◽  
Undulatory Swimming ◽  
Inclined Planes ◽  
The Waves

1. Typical undulatory progression over a rigid environment depends on three fundamental factors : (i) Internal bending couples change the lateral curvature of each region of the body to that previously characteristic of the region lying immediately anterior to itself. (ii) The phase of lateral bending varies along the length of the animal's body. (iii) The presence of external restraints prevents all regions of the body from moving along any path other than one tangential to their own circumference of curvature. 2. The magnitude of the forward tangential thrust imparted to the body depends on (a) the magnitude of the internally generated bending couples, and (b) the form of the waves. If friction operates on the surfaces of external restraint the thrust also depends on the coefficient of lateral friction and on the position of the restraints. 3. From a mechanical point of view, an undulating organism (irrespective of its size and internal structure) can be regarded either as a series of curved levers or as a series of inclined planes. 4. The general principles of undulatory swimming are the same as for a terrestrial glide, except for the fact that each element of the body must possess a component of motion normal to its surface if it is to contribute towards the propulsion of the animal; this type of motion can only occur when the waves move backwards relative to the ground. The animal cannot move forward as fast as the waves are propagated over the body. 5. The propulsive powers of three-dimensional waves are limited to the extent to which the organism is restrained by external forces from spinning about its own longitudinal axis. Otherwise the principles of progression are the same as for two-dimensional waves: the resultant of all the forces acting normally to the body is equal but opposite to that of all tangential forces.

scholarly journals Optimization-Based Biomechanical Evaluation of Isometric Exertions on a Brake Wheel

1993 ◽  
Vol 37 (10) ◽  
pp. 693-696 ◽  
Author(s):  
Christian A. Johnson ◽  
Jeffrey C. Woldstad
Keyword(s):  
Repeated Measures ◽  
Three Dimensional ◽  
Compressive Force ◽  
Biomechanical Model ◽  
The Body ◽  
Body Posture ◽  
Muscle Forces ◽  
Left Hand ◽  
Lumbar Muscle ◽  
External Forces

A static three-dimensional low-back biomechanical model was developed to estimate the levels of compressive force on the L3/L4 spinal joint during an experiment that simulated wheel turning. We recorded three-dimensional body posture and the resultant forces at the hands for analysis by the model. The model employed a standard link analysis procedure to resolve the external forces acting on the body to a resultant moment about L3/L4. The model then implemented an optimization algorithm to estimate the internal lumbar muscle forces generated to resist the external forces. The muscle forces and external forces were added to arrive at a prediction of compressive force at L3/L4. The experiment investigated the effects of general body posture, left hand grip, gender, and hand brake torque level upon predicted compressive force at L3/L4. A repeated measures analysis of variance (ANOVA) revealed all but one main effect and some interaction effects to be significant at p<0.05. Average predicted L3/L4 compressive forces at maximum wheel torque levels ranged from 1644N for females to 6926N for large males.

scholarly journals EFFECTS OF THE SCHROTH METHOD IN CHILDREN WITH IDIOPATHIC SCOLIOSIS

2019 ◽  
Vol 16 (2) ◽  
pp. 749
Author(s):  
Bojan Jorgić ◽  
Petra Mančić ◽  
Saša Milenković ◽  
Nikola Jevtić ◽  
Mladen Živković
Keyword(s):  
Idiopathic Scoliosis ◽  
Sagittal Plane ◽  
Three Dimensional ◽  
Exercise Program ◽  
Frontal Plane ◽  
Axial Rotation ◽  
The Body ◽  
Scoliosis Correction ◽  
Lateral Curvature ◽  
Positive Effect

Scoliosis is a multifactorial three-dimensional (3D) spinal deformation which always includes elementary deformations on three planes: a lateral curvature on the frontal plane, loss of natural physiological curvature on the sagittal plane and, in most cases, increase of lordosis in the lumbosacral joint (hyperlordosis), and a (very typical) vertebral axial rotation on the horizontal plane. One of the best methods in scoliosis correction is the Schroth method. In view of the above, the objective of this study is to identify the effects of the Schroth method on correcting functional-motor status in children with adolescent idiopathic scoliosis (IS). The participant sample comprised 20 children, of an average age of 14.5, who took part in the 10-day Schroth Camp. The following measure instruments were used for the assessment of the effect of the Schroth method: the Sorensen test, the Sit-and-reach test, and height assessment. Statistically significant improvements were identified across the results of all three tests, for the Sorensen test: 45.6±19.29 s, the Sit-and-reach test: 4.05±2.25 cm, and height 1.4±0.66 cm. It can be concluded that the conducted Schroth method exercise program exerted a positive effect on improving motor functionality, as well as enhancing flexibility and isometric endurance of the lumbar extensors of the spine. Additionally, there was an increase in height, which indicates a positive effect in terms of the functionality and symmetry of the left and right sides of the body, and in terms of improved posture on the frontal and sagittal planes.

Canal-Otolith Interactions After Off-Vertical Axis Rotations I. Spatial Reorientation of Horizontal Vestibuloocular Reflex

2000 ◽  
Vol 83 (3) ◽  
pp. 1522-1535 ◽  
Author(s):  
Karin Jaggi-Schwarz ◽  
Hubert Misslisch ◽  
Bernhard J. M. Hess
Keyword(s):  
Semicircular Canal ◽  
Three Dimensional ◽  
Head Tilt ◽  
Vertical Axis ◽  
Longitudinal Axis ◽  
The Body ◽  
Spatial Transformation ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Spatial Reorientation

We examined the three-dimensional (3-D) spatial orientation of postrotatory eye velocity after horizontal off-vertical axis rotations by varying the final body orientation with respect to gravity. Three rhesus monkeys were oriented in one of two positions before the onset of rotation: pitched 24° nose-up or 90° nose-up (supine) relative to the earth-horizontal plane and rotated at ±60°/s around the body-longitudinal axis. After 10 turns, the animals were stopped in 1 of 12 final positions separated by 30°. An empirical analysis of the postrotatory responses showed that the resultant response plane remained space-invariant, i.e., accurately represented the actual head tilt plane at rotation stop. The alignment of the response vector with the spatial vertical was less complete. A complementary analysis, based on a 3-D model that implemented the spatial transformation and dynamic interaction of otolith and lateral semicircular canal signals, confirmed the empirical description of the spatial response. In addition, it allowed an estimation of the low-pass filter time constants in central otolith and semicircular canal pathways as well as the weighting ratio between direct and inertially transformed canal signals in the output. Our results support the hypothesis that the central vestibular system represents head velocity in gravity-centered coordinates by sensory integration of otolith and semicircular canal signals.

Simple mechanisms organise orientation of escape swimming in embryos and hatchling tadpoles of Xenopus laevis

2000 ◽  
Vol 203 (12) ◽  
pp. 1869-1885 ◽  
Author(s):  
A. Roberts ◽  
N.A. Hill ◽  
R. Hicks
Keyword(s):  
Mathematical Model ◽  
Xenopus Laevis ◽  
High Speed ◽  
Three Dimensional ◽  
Longitudinal Axis ◽  
The Body ◽  
Video Recordings ◽  
Stage Of Development ◽  
Physical Features ◽  
Neutrally Buoyant

Many amphibian tadpoles hatch and swim before their inner ears and sense of spatial orientation differentiate. We describe upward and downward swimming responses in hatchling Xenopus laevis tadpoles from stages 32 to 37/38 in which the body rotates about its longitudinal axis. Tadpoles are heavier than water and, if touched while lying on the substratum, they reliably swim upwards, often in a tight spiral. This response has been observed using stroboscopic photography and high-speed video recordings. The sense of the spiral is not fixed for individual tadpoles. In ‘more horizontal swimming’ (i.e. in directions within +/−30 degrees of the horizontal), the tadpoles usually swim belly-down, but this position is not a prerequisite for subsequent upward spiral swimming. Newly hatched tadpoles spend 99 % of their time hanging tail-down from mucus secreted by a cement gland on the head. When suspended in mid-water by a mucus strand, tadpoles from stage 31 to 37/38 tend to swim spirally down when touched on the head and up when touched on the tail. The three-dimensional swimming paths of stage 33/34 tadpoles were plotted using simultaneous video images recorded from the side and from above. Tadpoles spiralled for 70 % of the swimming time, and the probability of spiralling increased to 1 as swim path angles became more vertical. Tadpoles were neutrally buoyant in Percoll/water mixtures at 1.05 g cm(−)(3), in which anaesthetised tadpoles floated belly-down and head-up at 30 degrees. In water, their centre of mass was ventral to the muscles in the yolk mass. A simple mathematical model suggests that the orientation of tadpoles during swimming is governed by the action of two torques, one of which raises the head (i.e. increases the pitch) and the other rotates (rolls) the body. Consequently, tadpoles (i) swim belly-down when the body is approximately horizontal because the body is ballasted by dense yolk, and (ii) swim spirally at more vertical orientations when the ballasting no longer stabilises orientation. Measurements in tethered tadpoles show that dorsal body flexion, which could produce a dorsal pitch torque, is present during swimming and increases with tailbeat frequency. We discuss how much of the tadpole's behaviour can be explained by our mathematical model and suggest that, at this stage of development, oriented swimming responses may depend on simple touch reflexes, the organisation of the muscles and physical features of the body, rather than on vestibular reflexes.

scholarly journals On the dilatational stability of the Earth

1906 ◽  
Vol 77 (519) ◽  
pp. 486-499 ◽  
Keyword(s):  
Hydrostatic Pressure ◽  
Equilibrium Configuration ◽  
Three Dimensional ◽  
Point Of View ◽  
The Body ◽  
Elastic Solids ◽  
Ordinary Experience ◽  
One Dimensional ◽  
The Earth ◽  
Interesting Paper

The theory of elastic solids usually proceeds upon the assumption that the body is initially in a state of ease, free from stress and strain. Displacements from this condition, due to given forces, or vibrations about it, are then investigated, and they are subject to the limitation that Hooke’s law shall be applicable throughout and that the strain shall everywhere be small. When we come to the case of the earth, supposed to be displaced from a state of ease by the mutual gravitation of its parts, these limits are transgressed; and several writers who have adopted this point of view have indicated the obstacles which inevitably present themselves. In his interesting paper Professor Jeans, in order to attain mathematical definiteness, goes the length of introducing forces to counteract the self-gravitation: “That is to say, we must artificially annul gravitation in the equilibrium configuration, so that this equilibrium configuration may be completely unstressed, and each element of matter be in its normal state.” How wide a departure from actuality is here implied will be understood if we reflect that under such forces the interior of the earth would probably be as mobile as water. It appears to me that a satisfactory treatment of these problems must start from the condition of the earth as actually stressed by its self-gravitation, and that the difficulties to be faced in following such a course may not be so great as has been supposed. The stress, which is so enormous as to transcend all ordinary experience, is of the nature of a purely hydrostatic pressure, and as to this surely there can be no serious difficulty. After great compression the response to further compressing stress is admittedly less than at first, but there is no reason to doubt that the reaction is purely elastic and that the material preserves its integrity. At this point it may be well to remark, in passing, upon the confusion often met with in geological and engineering writings arising from the failure to distinguish between a one-dimensional and a three-dimensional, or hydrostatic, pressure. When rock or cast iron is said to be crushed by such and such a pressure, it is the former kind of pressure which is, or ought to be, meant. meant. There is no evidence of crushing under purely hydrostatic pressure, however great.

The action of waving cylindrical tails in propelling microscopic organisms

1952 ◽  
Vol 211 (1105) ◽  
pp. 225-239 ◽  
Keyword(s):  
Lateral Displacement ◽  
Spiral Waves ◽  
Point Of View ◽  
The Body ◽  
Rubber Tube ◽  
Flexible Cylinder ◽  
Applied Torque ◽  
The Waves ◽  
Surrounding Fluid ◽  
Made In

The action of the tail of a spermatozoon is discussed from the hydrodynamical point of view. The tail is assumed to be a flexible cylinder which is distorted by waves of lateral displacement propagated along its length. The resulting stress and motion in the surrounding fluid is analyzed mathematically. Waves propagated backwards along the tail give rise to a forward motion with velocity proportional to the square of the ratio of the amplitude of the waves to their length. The rate at which energy must be supplied to maintain the waves against the reaction of the surrounding fluid is calculated. Similar calculations for the case when waves of lateral displacement are propagated as spirals show that the body is propelled at twice the speed given it by waves of the same amplitude when the motion is confined to an axial plane. An externally applied torque is necessary to prevent the reaction of the fluid due to spiral waves from causing the cylinder to rotate. This is remarkable because the cylinder itself does not rotate. A working model of a spermatozoon was made in which spiral waves could travel down a thin rubber tube without rotating it. The torque just referred to was observed and was balanced by an eccentric weight. The performance of the model while swimming freely in glycerine was compared with the calculations. The calculated speed of the model was higher than was observed, but this discrepancy could be accounted for by the fact that the model has a body containing its motive power while the calculations refer to a disembodied tail.

scholarly journals An Update on Virtopsy- A Modern Forensic Investigation Tool

KYAMC Journal ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 48-52
Author(s):  
Mushtaq Ahmad ◽  
Md Zubaidur Rahman ◽  
Farial Naima Rahman
Keyword(s):  
Imaging System ◽  
Three Dimensional ◽  
Developed Countries ◽  
Point Of View ◽  
The Body ◽  
New Era ◽  
Autopsy Examination ◽  
Resolution Imaging ◽  
Magnetic Resonance Imaging Mri

Virtopsy is a virtual alternative to a traditional autopsy, conducted with scanning and imaging technology. In developed countries Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) are now being evaluated as complementary means for determination of cause of death. This paper explores the latest development and implication of virtopsy from ethical, clinical and technical point of view. Published literature in different journals with strict inclusion and exclusion criteria were extensively reviewed through use of general and Meta search engines to elucidate the applications and implications of virtual autopsy. The modern high-resolution imaging has been used as a well described aid in the setting of post-mortem investigations. Virtopsy introduces a new era in autopsy examination. It utilizes the technological innovation of modern imaging system to obtain best results and three Dimensional (3D) images of the body in multiple plains without mutilation of the human body. Now a days virtopsy is very much acceptable procedure to the forensic society. In western worlds virtopsy is likely to replace conventional autopsies in future. We can also try to implement this modern system in our country. KYAMC Journal.2021;12(1): 48-52

scholarly journals A new penalty/stochastic approach to an application of the covering problem: the Gamma Knife treatment

2020 ◽  
Author(s):  
Marilis Bahr Karam Venceslau ◽  
Helder Manoel Venceslau ◽  
Renan Vicente Pinto ◽  
Gustavo Dias ◽  
Nelson Maculan
Keyword(s):  
Mathematical Programming ◽  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Three Dimensional ◽  
Stochastic Approach ◽  
Point Of View ◽  
The Body ◽  
Covering Problem ◽  
Mathematical Programming Problem ◽  
Stochastic Local Search

The covering problem of a three dimensional body using different radius spheres is considered. The motivating application - the treatment planning of Gamma Knife radiosurgery - is briefly discussed. We approach the problem only by the geometric covering point of view, that is, given a set of spheres and a body, the objective is to cover the body using the smallest possible number of spheres, regardless of the dosage issue. In order to solve this mathematical programming problem, we consider an approach based on the application of penalty and stochastic local search techniques. Finally, some illustrative results and comparisons are presented.

scholarly journals Structure of the Erdenet ore district according to gravimetric data

2021 ◽  
Vol 44 (4) ◽  
pp. 369-381
Author(s):  
E. K. Turutanov ◽  
V. S. Kanaykin
Keyword(s):  
Three Dimensional ◽  
Point Of View ◽  
The Body ◽  
Spatial Proximity ◽  
Geochemical Data ◽  
Tectonic Inheritance ◽  
Three Dimensional Mapping ◽  
Gravimetric Data ◽  
Granitoid Intrusions ◽  
Ore District

The purpose of the study is construction of a model of the upper crust structure of the ore region in Mongolia and the three-dimensional mapping of intrusive bodies with which copper-porphyry mineralization is associated. An areal gravity survey was carried out with an observation density of 1 point per 6 km2 with the measurement accuracy of ±0.8 mGal. As a result, it was found that copper-molybdenum ore occurrences of the area including the Erdenet ore district are confined to local gravitational minima, which are interpreted as thickening of the body of the Selenga granitoids. The latter are confined to local depressions of this body base. The spatial proximity of supply channels of small ore-bearing intrusions and large granitoid bodies of the Selenga complex has been established. Porphyry ore intrusions are confined to rather wide (about 10 km) zones located above the depressions of the base of all intrusions of the Selenga complex (both granitoid and diorite). Since the local base depressions of the granitoid intrusions correspond to the position of magma supply channels, ore-bearing small intrusions were introduced approximately in the same places where the supply channels of granitoid intrusions of the Selenga complex existed. Therefore, it can be assumed that this case is characterized by not only tectonic inheritance (confined to the same faults and their intersection points), but also by a genetic one, since residual melts of the same foci, in which intrusion magma of the Selenga complex was generated might be the sources of small intrusions. From this point of view, the expediency of distinguishing an independent Erdenet complex seems to be controversial. Geophysical data on the spatial proximity of specified intrusion supply channels permit only to raise the question of such expediency. The solution to this issue is possible on the basis of a comprehensive analysis of petrological and geochemical data.

Numerical Studies of Blood Flow in Left Coronary Model

2019 ◽  
Vol 13 ◽  
Author(s):  
Rupali Pandey ◽  
Manoj Kumar ◽  
Vivek Kumar Srivastav
Keyword(s):  
Blood Flow ◽  
Coronary Artery ◽  
Left Coronary Artery ◽  
Three Dimensional ◽  
Healthy Person ◽  
Point Of View ◽  
The Body ◽  
Numerical Studies ◽  
Artery Disease ◽  
Three Dimensional Models

In the present paper, the simulation of blood flow in the left coronary artery is performed using angiography images of a healthy person. Artery blockage is the most prevailing cause of coronary artery disease (CAD). The presence of blockage inside the artery breaks the continuity of blood supply to the other part of the body and therefore causes for heart attack. In the present study, two different three-dimensional models namely; normal and 50% plaque are used for the numerical studies. Five inlet velocities 0.10, 0.20, 0.50, 0.70 and 0.80 m/s are considered corresponding to different blood flow conditions to study the effect of velocity on the human heart. Finite Volume Method (FVM) based Computational fluid dynamics (CFD) technique is executed for the numerical simulation of blood flow. Hemodynamics factors are computed and compared for the two geometrical models (Normal Vs. Blockage model). Area Average Wall Shear Stress (AAWSS) ranges from 4.1-33.6 Pa at the façade of the Left Anterior Descending (LAD) part of the Left Coronary Artery (LCA) for the constricted artery. The predominantly low WSS index is analogous to the normal artery affirms the existence of plaque. From the medical point of view, this can prove as an excellent factor for early diagnosis of CAD. Therefore, a hindrance can be created in the increasing frequency of myocardial infarction (MI).

Sign in / Sign up

Export Citation Format

Share Document