MULTI-SCALE MECHANICAL BEHAVIOR ANALYSIS ON FLUID–SOLID COUPLING FOR OSTEONS IN VARIOUS GRAVITATIONAL FIELDS

2021 ◽  
Author(s):  
HAO ZHANG ◽  
HAI-YING LIU ◽  
CHUN-QIU ZHANG ◽  
ZHEN-ZHONG LIU ◽  
WEI WANG
Keyword(s):  
Gravitational Field ◽  
Fluid Shear Stress ◽  
Bone Matrix ◽  
Fluid Pressure ◽  
Gravity Gradient ◽  
Static Compression ◽  
Gravitational Fields ◽  
Multi Scale ◽  
Earth’S Gravitational Field ◽  
Mechanical Microenvironment

Background: Compact bone mainly consists of cylindrical osteon structures. In microgravity, the change in the mechanical microenvironment of osteocytes might be the root cause of astronauts’ bone loss during space flights. Methods: A multi-scale three-dimensional (3D) fluid–solid coupling finite element model of osteons with a two-stage pore structure was developed using COMSOL software based on the natural structure of osteocytes. Gradients in gravitational fields of [Formula: see text]1, 0, 1, 2.5, and 3.7[Formula: see text]g were used to investigate the changes in the mechanical microenvironment on osteocyte structure. The difference in arteriole pulsating pressure and static compression stress caused by each gravity gradient was investigated. Results: The mechanical response of osteocytes increased with the value of g, compared with the Earth’s gravitational field. For instance, the fluid pressure of osteocytes and the von Mises stress of bone matrix near lacunae decreased by 31.3% and 99.9%, respectively, in microgravity. Under static loading, only about 16.7% of osteocytes in microgravity and 58.3% of osteocytes in the Earth’s gravitational field could reach the fluid shear stress threshold of biological reactions in cell culture experiments. Compared with the Earth’s gravitational field, the pressure gradient inside osteocytes severely decreased in microgravity. Conclusion: The mechanical microenvironment of osteocytes in microgravity might cause significant changes in the mechanical microenvironment of osteocytes, which may lead to disuse osteoporosis in astronauts.

Oscillatory Bone Fluid Flow and its Role in Initiating Remodeling in the Absence of Matrix Strain

2001 ◽  
Author(s):  
Yixian Qin ◽  
Anita Saldanha ◽  
Tamara Kaplan
Keyword(s):  
Fluid Flow ◽  
Cellular Response ◽  
Fluid Shear Stress ◽  
Bone Matrix ◽  
Fluid Pressure ◽  
Streaming Potential ◽  
Bone Adaptation ◽  
Interstitial Fluid Flow ◽  
Bone Fluid Flow ◽  
Matrix Deformation

Abstract Load-generated intracortical fluid flow is proposed to be an important mediator for regulating bone mass and morphology [1]. Although the mechanism of cellular response to induced flow parameters, i.e., fluid pressure, pressure gradient, velocity, and fluid shear stress, are not yet clear, interstitial fluid flow driven by loading may be necessary to explain the adaptive response of bone, which is either coupled with load-induced strain magnitude or independent with matrix strain per se [2]. It has been demonstrated that load-induced intracortical fluid flow is contributed by both bone matrix deformation and induced intramedullary (IM) pressure [3]. To examine the hypothesis of fluid flow generated adaptation, it is necessary to test the mechanism under the circumstances of solely fluid induced bone adaptation in the absence of matrix deformation. While our previous data has demonstrated that bone fluid flow and its associated streaming potential product can be influenced by the dynamic IM pressure quantitatively [4], the objective of this study was to evaluate fluid induced bone adaptation in an avian ulna model using oscillatory IM fluid pressure loading in the absence of bone matrix strain. The potential fluid pathway was measured in the model.

scholarly journals Possible Alterations of Local Gravitational Field Inside a Superconductor

Entropy ◽  
2021 ◽  
Vol 23 (2) ◽  
pp. 193 ◽  
Author(s):  
Giovanni Alberto Ummarino ◽  
Antonio Gallerati
Keyword(s):  
Gravitational Field ◽  
Landau Theory ◽  
Time Dependent ◽  
Qualitative Comparison ◽  
Ginzburg Landau ◽  
High Tc ◽  
Gravitational Fields ◽  
Favorable Conditions

We calculate the possible interaction between a superconductor and the static Earth’s gravitational fields, making use of the gravito-Maxwell formalism combined with the time-dependent Ginzburg–Landau theory. We try to estimate which are the most favorable conditions to enhance the effect, optimizing the superconductor parameters characterizing the chosen sample. We also give a qualitative comparison of the behavior of high–Tc and classical low–Tc superconductors with respect to the gravity/superfluid interplay.

scholarly journals Comment on “Measurement of quantum states of neutrons in the Earth’s gravitational field”

2003 ◽  
Vol 68 (10) ◽  
Author(s):  
Johan Hansson ◽  
David Olevik ◽  
Christian Türk ◽  
Hanna Wiklund
Keyword(s):  
Gravitational Field ◽  
Quantum States ◽  
Earth’S Gravitational Field

On the stability of the Earth's gravitational field

1983 ◽  
Vol 26 (2) ◽  
pp. 187-188
Author(s):  
Yu D Bulanzhe ◽  
Yu E Nesterikhin ◽  
N P Pariĭskiĭ
Keyword(s):  
Gravitational Field ◽  
Earth’S Gravitational Field ◽  
The Stability

scholarly journals TESLA GPUs versus MPI with OpenMP for the Forward Modeling of Gravity and Gravity Gradient of Large Prisms Ensemble

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Carlos Couder-Castañeda ◽  
Carlos Ortiz-Alemán ◽  
Mauricio Gabriel Orozco-del-Castillo ◽  
Mauricio Nava-Flores
Keyword(s):  
Parallel Computing ◽  
Graphics Processing Units ◽  
Forward Modeling ◽  
Gravity Gradient ◽  
Constant Density ◽  
Gravitational Fields ◽  
Design And Implementation ◽  
Cuda Technology ◽  
Performance Results ◽  
Graphics Processing

An implementation with the CUDA technology in a single and in several graphics processing units (GPUs) is presented for the calculation of the forward modeling of gravitational fields from a tridimensional volumetric ensemble composed by unitary prisms of constant density. We compared the performance results obtained with the GPUs against a previous version coded in OpenMP with MPI, and we analyzed the results on both platforms. Today, the use of GPUs represents a breakthrough in parallel computing, which has led to the development of several applications with various applications. Nevertheless, in some applications the decomposition of the tasks is not trivial, as can be appreciated in this paper. Unlike a trivial decomposition of the domain, we proposed to decompose the problem by sets of prisms and use different memory spaces per processing CUDA core, avoiding the performance decay as a result of the constant calls to kernels functions which would be needed in a parallelization by observations points. The design and implementation created are the main contributions of this work, because the parallelization scheme implemented is not trivial. The performance results obtained are comparable to those of a small processing cluster.

A discussion on orbital analysis - Determination of the Earth’s gravitational field from satellite orbits: methods and results

1967 ◽  
Vol 262 (1124) ◽  
pp. 119-134 ◽  
Keyword(s):  
Gravitational Field ◽  
Artificial Satellites ◽  
Satellite Orbits ◽  
Estimation Of Parameters ◽  
Earth’S Gravitational Field ◽  
Keplerian Ellipse ◽  
Orbital Data ◽  
Analysis Determination ◽  
Orbital Analysis

The structure of theories used in determining the gravitational field from the perturbations of orbits of artificial satellites is discussed and it is shown how it corresponds to the fact that small departures from a Keplerian ellipse are readily observed. Some current problems are mentioned. Statistical problems in the estimation of parameters of the field from orbital data are considered and recent estimates are summarized

scholarly journals PARAMETRIC INSTABILITY IN SCALAR GRAVITATIONAL FIELDS

2012 ◽  
Vol 27 (24) ◽  
pp. 1230023 ◽  
Author(s):  
TREVOR B. DAVIES ◽  
CHARLES H.-T. WANG ◽  
ROBERT BINGHAM ◽  
J. TITO MENDONÇA
Keyword(s):  
Gravitational Field ◽  
Field Effect ◽  
Strong Field ◽  
Parametric Instability ◽  
Spherically Symmetric ◽  
Scalar Tensor Theory ◽  
Subsequent Work ◽  
Dynamical Mechanism ◽  
Gravitational Fields ◽  
Tensor Theory

We present a brief review on a new dynamical mechanism for a strong field effect in scalar–tensor theory. Starting with a summary of the essential features of the theory and subsequent work by several authors, we analytically investigate the parametric excitation of a scalar gravitational field in a spherically symmetric radially pulsating neutron star.

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