scholarly journals 3D Microstructure of Tendon Collagen Fibrils using Serial Block-Face SEM and a Mechanical Model for Load Transfer

2019 ◽  
Author(s):  
Babak N. Safa ◽  
John M. Peloquin ◽  
Jessica R. Natriello ◽  
Jeffrey L. Caplan ◽  
Dawn M. Elliott
Keyword(s):  
Load Transfer ◽  
Three Dimensional ◽  
Collagen Fibrils ◽  
Helical Structures ◽  
Multiple Length Scales ◽  
Tendon Biomechanics ◽  
Block Face ◽  
Tail Tendon ◽  
Matrix Shear ◽  
Complex Architecture

AbstractTendon’s hierarchical structure allows for load transfer between its fibrillar elements at multiple length scales. Tendon microstructure is particularly important, because it includes the cells and their surrounding collagen fibrils, where mechanical interactions can have potentially important physiological and pathological contributions. However, the three-dimensional microstructure and the mechanisms of load transfer in that length scale are not known. It has been postulated that interfibrillar matrix shear or direct load transfer via the fusion/branching of small fibrils are responsible for load transfer, but the significance of these mechanisms is still unclear. Alternatively, the helical fibrils that occur at the microstructural scale in tendon may also mediate load transfer, however, these structures are not well studied due to the lack of a three-dimensional visualization of tendon microstructure. In this study, we used serial block-face scanning electron microscopy (SBF-SEM) to investigate the threedimensional microstructure of fibrils in rat tail tendon. We found that tendon fibrils have a complex architecture with many helically wrapped fibrils. We studied the mechanical implications of these helical structures using finite element modeling and found that frictional contact between helical fibrils can induce load transfer even in the absence of matrix bonding or fibril fusion/branching. This study is significant in that it provides a three-dimensional view of the tendon microstructure and suggests friction between helically wrapped fibrils as a mechanism for load transfer, which is an important aspect of tendon biomechanics.

scholarly journals Helical fibrillar microstructure of tendon using serial block-face scanning electron microscopy and a mechanical model for interfibrillar load transfer

2019 ◽  
Vol 16 (160) ◽  
pp. 20190547 ◽  
Author(s):  
Babak N. Safa ◽  
John M. Peloquin ◽  
Jessica R. Natriello ◽  
Jeffrey L. Caplan ◽  
Dawn M. Elliott
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Load Transfer ◽  
Three Dimensional ◽  
Helical Structures ◽  
3D Microstructure ◽  
Face Scanning ◽  
Block Face ◽  
Matrix Shear ◽  
Scanning Electron

Tendon's hierarchical structure allows for load transfer between its fibrillar elements at multiple length scales. Tendon microstructure is particularly important, because it includes the cells and their surrounding collagen fibrils, where mechanical interactions can have potentially important physiological and pathological contributions. However, the three-dimensional (3D) microstructure and the mechanisms of load transfer in that length scale are not known. It has been postulated that interfibrillar matrix shear or direct load transfer via the fusion/branching of small fibrils are responsible for load transfer, but the significance of these mechanisms is still unclear. Alternatively, the helical fibrils that occur at the microstructural scale in tendon may also mediate load transfer; however, these structures are not well studied due to the lack of a three-dimensional visualization of tendon microstructure. In this study, we used serial block-face scanning electron microscopy to investigate the 3D microstructure of fibrils in rat tail tendon. We found that tendon fibrils have a complex architecture with many helically wrapped fibrils. We studied the mechanical implications of these helical structures using finite-element modelling and found that frictional contact between helical fibrils can induce load transfer even in the absence of matrix bonding or fibril fusion/branching. This study is significant in that it provides a three-dimensional view of the tendon microstructure and suggests friction between helically wrapped fibrils as a mechanism for load transfer, which is an important aspect of tendon biomechanics.

Evidence for Interfibrillar Shear Load Transfer Between Sliding Fibrils in Tendon

2013 ◽  
Author(s):  
Spencer E. Szczesny ◽  
Dawn M. Elliott
Keyword(s):  
Load Transfer ◽  
Tensile Load ◽  
Tissue Level ◽  
Collagen Fibrils ◽  
Shear Stresses ◽  
Shear Lag ◽  
Shear Lag Model ◽  
Lag Model ◽  
Tail Tendon ◽  
The Impact

While collagen fibrils are understood to be the primary tensile load bearing components in tendon, how loads applied at the tissue level are transmitted across each element within the tissue hierarchical structure is unclear. A central unresolved question is whether collagen fibrils bear load independently or if the applied load is transferred across the fibrils through interfibrillar shear forces. Relative sliding between fibrils is suggested by findings that fibril strains within rat tail tendon fascicles do not agree with the applied tissue tensile strains [1]. Other studies using confocal microscopy have directly measured sliding behavior [2,3]; however, the impact that interfibrillar sliding has on tendon macroscale mechanics and whether sliding is associated with interfibrillar shear stresses are unknown. Therefore, the objective of this work is to quantify the contribution of interfibrillar sliding on tendon macroscale mechanics by simultaneously measuring the tissue behavior at both length-scales and interpreting the results with a micro-structural shear lag model directly incorporating interfibrillar shear stresses. We hypothesize that the reduced stiffness and increased viscosity observed in the tissue macroscale properties at higher strains are due to increases in interfibrillar sliding and that this behavior is consistent with a shear lag model involving interfibrillar shear stress.

scholarly journals Serial Block-Face Scanning Electron Microscopy Reveals That Intercellular Nuclear Migration Occurs in Most Normal Tobacco Male Meiocytes

2021 ◽  
Vol 12 ◽  
Author(s):  
Sergey Mursalimov ◽  
Nobuhiko Ohno ◽  
Mami Matsumoto ◽  
Sergey Bayborodin ◽  
Elena Deineko
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cell Wall ◽  
Three Dimensional ◽  
Nuclear Migration ◽  
Male Meiosis ◽  
Face Scanning ◽  
Block Face ◽  
Plant Meiosis ◽  
Scanning Electron

Serial block-face scanning electron microscopy (SBF-SEM) was used here to study tobacco male meiosis. Three-dimensional ultrastructural analyses revealed that intercellular nuclear migration (INM) occurs in 90–100% of tobacco meiocytes. At the very beginning of meiosis, every meiocyte connected with neighboring cells by more than 100 channels was capable of INM. At leptotene and zygotene, the nucleus in most tobacco meiocytes approached the cell wall and formed nuclear protuberances (NPs) that crossed the cell wall through the channels and extended into the cytoplasm of a neighboring cell. The separation of NPs from the migrating nuclei and micronuclei formation were not observed. In some cases, the NPs and nuclei of neighboring cells appeared apposed to each other, and the gap between their nuclear membranes became invisible. At pachytene, NPs retracted into their own cells. After that, the INM stopped. We consider INM a normal part of tobacco meiosis, but the reason for such behavior of nuclei is unclear. The results obtained by SBF-SEM suggest that there are still many unexplored features of plant meiosis hidden by limitations of common types of microscopy and that SBF-SEM can turn over a new leaf in plant meiosis research.

A new three-dimensional model of the organization of proteoglycans and collagen fibrils in the human corneal stroma

2004 ◽  
Vol 78 (3) ◽  
pp. 493-501 ◽  
Author(s):  
Linda J. Müller ◽  
Elizabeth Pels ◽  
Lucas R.H.M. Schurmans ◽  
Gijs F.J.M. Vrensen
Keyword(s):  
Three Dimensional ◽  
Corneal Stroma ◽  
Collagen Fibrils ◽  
Dimensional Model ◽  
Three Dimensional Model

scholarly journals A damage model for collagen fibres with an application to collagenous soft tissues

2020 ◽  
Vol 476 (2236) ◽  
pp. 20190821
Author(s):  
Gerhard A. Holzapfel ◽  
Ray W. Ogden
Keyword(s):  
Soft Tissues ◽  
Damage Model ◽  
Three Dimensional ◽  
Collagen Fibres ◽  
Physiological Loading ◽  
Cross Links ◽  
Complex Boundary ◽  
Tail Tendon ◽  
Similar Basis ◽  
Rat Tail

We propose a mechanical model to account for progressive damage in collagen fibres within fibrous soft tissues. The model has a similar basis to the pseudoelastic model that describes the Mullins effect in rubber but it also accounts for the effect of cross-links between collagen fibres. We show that the model is able to capture experimental data obtained from rat tail tendon fibres, and the combined effect of damage and collagen cross-links is illustrated for a simple shear test. The proposed three-dimensional framework allows a straightforward implementation in finite-element codes, which are needed to analyse more complex boundary-value problems for soft tissues under supra-physiological loading or tissues weakened by disease.

scholarly journals The morphological classification of distant radio galaxies explored with three-dimensional simulations

2019 ◽  
Vol 490 (1) ◽  
pp. 1363-1382 ◽  
Author(s):  
Michael D Smith ◽  
Justin Donohoe
Keyword(s):  
Radio Galaxy ◽  
Three Dimensional ◽  
Radio Galaxies ◽  
Morphological Classification ◽  
Helical Structures ◽  
Radio Jets ◽  
Source Type ◽  
Radio Lobe ◽  
Three Dimensional Simulations

ABSTRACT We explore the observational implications of a large systematic study of high-resolution three-dimensional simulations of radio galaxies driven by supersonic jets. For this fiducial study, we employ non-relativistic hydrodynamic adiabatic flows from nozzles into a constant pressure-matched environment. Synchrotron emissivity is approximated via the thermal pressure of injected material. We find that the morphological classification of a simulated radio galaxy depends significantly on several factors with increasing distance (i.e. decreasing observed resolution) and decreasing orientation often causing reclassification from FR II (limb-brightened) to FR I (limb-darkened) type. We introduce the Lobe or Limb Brightening Index (LBI) to measure the radio lobe type more precisely. The jet density also has an influence as expected with lower density leading to broader and bridged lobe morphologies as well as brighter radio jets. Hence, relating observed source type to the intrinsic jet dynamics is not straightforward. Precession of the jet direction may also be responsible for wide relaxed sources with lower LBI and FR class as well as for X-shaped and double–double structures. Helical structures are not generated because the precession is usually too slow. We conclude that distant radio galaxies could appear systematically more limb darkened due to merger-related redirection and precession as well as due to the resolution limitation.

Precision Diagnosis of Electric Multiple Units for Performance Evaluation

2007 ◽  
Vol 353-358 ◽  
pp. 2585-2588 ◽  
Author(s):  
Jeong Guk Kim ◽  
Kyung Taek Park ◽  
Sung Cheol Yoon ◽  
Sung Tae Kwon
Keyword(s):  
Load Transfer ◽  
Three Dimensional ◽  
Engineering Analysis ◽  
Actual Performance ◽  
Analysis Techniques ◽  
Electrical Systems ◽  
Dimensional Measurements ◽  
Wear Evaluation ◽  
And Performance ◽  
Multiple Units

The precision diagnosis of subway electric multiple units (EMUs) was conducted with various types of engineering analysis techniques for the current performance and wear evaluation. The evaluation was conducted on detailed parts of EMUs, such as car bodies, bogies, braking systems, and electrical systems of EMUs. Several characterization means including nondestructive evaluation techniques, corrosion testing, and three-dimensional measurements, were employed for the evaluation of car bodies and bogies. For braking system, degradation and performance tests were conducted, while the functional and degradation tests were performed on electrical system in order to identify the actual performance of the system. Moreover, stress and structural analyses using commercial finite element method (FEM) software provided important information on stress distribution and load transfer mechanisms. In this investigation, various advanced engineering analysis techniques for the safety analysis of subway EMUs have been introduced and the analysis results have been used to provide the critical information for the criteria of safety assessment.

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