Estimating the orientation of Stage I crack paths through the direction of maximum variance of the resolved shear stress

2014 ◽  
Vol 58 ◽  
pp. 94-101 ◽  
Author(s):  
Luca Susmel ◽  
Roberto Tovo ◽  
Darrell F. Socie
2007 ◽  
Vol 293 (4) ◽  
pp. H2320-H2327 ◽  
Author(s):  
Joon-Young Park ◽  
Iain K. G. Farrance ◽  
Nicola M. Fenty ◽  
James M. Hagberg ◽  
Stephen M. Roth ◽  
...  

In endothelial cells, NF-κB is an important intracellular signaling molecule by which changes in wall shear stress are transduced into the nucleus to initiate downstream endothelial nitric oxide synthase ( NOS3) gene expression. We investigated whether NF-κ light-chain gene enhancer in B cells 1 (NFKB1) promoter polymorphism (−94 NFKB1 I/D, where I is the insertion allele and D is the deletion allele) was associated with 1) NOS3 gene expression in endothelial cells under physiological levels of unidirectional laminar shear stress (LSS) and 2) endothelial function in prehypertensive and stage I hypertensive individuals before and after a 6-mo supervised endurance exercise intervention. Competitive EMSAs revealed that proteins present in the nuclei of endothelial cells preferentially bound to the I allele NFKB1 promoter compared with the D allele. Reporter gene assays showed that the I allele promoter had significantly higher activity than the D allele. In agreement with these observations, homozygous II genotype cells had higher p50 expression levels than homozygous DD genotype cells. Cells with the homozygous II genotype showed a greater increase in NOS3 protein expression than did homozygous DD genotype cells under LSS. Functional experiments on volunteers confirmed higher baseline reactive hyperemic forearm blood flow, and, furthermore, the subgroup analysis revealed that DD homozygotes were significantly less prevalent in the exercise responder group compared with II and ID genotypes. We conclude that the −94 NFKB1 I/D promoter variation contributes to the modulation of vascular function and adaptability to exercise-induced flow shear stress, most likely due to differences in NFKB1 gene transactivity.


2011 ◽  
Vol 488-489 ◽  
pp. 747-750 ◽  
Author(s):  
Luca Susmel ◽  
David Taylor

The present paper is concerned with the use of the Modified Wöhler Curve Method (MWCM), applied in terms of nominal stresses, to estimate lifetime of notched components subjected to variable amplitude multiaxial fatigue loading. The MWCM is applied by defining the critical plane through that direction experiencing the maximum variance of the resolved shear stress: since the shear stress resolved along the above direction is a monodimensional quantity, fatigue cycles are directly counted by the classical Rain-Flow method. The performed validation exercise, based on an extensive experimental investigation, seems to strongly support the idea that the MWCM applied along with the classical nominal stress based approach is capable of accurately estimating fatigue damage also in notched components subjected to variable amplitude multiaxial load histories.


2020 ◽  
Vol 134 (17) ◽  
pp. 2399-2418
Author(s):  
Yoshito Yamashiro ◽  
Hiromi Yanagisawa

Abstract Blood vessels are constantly exposed to mechanical stimuli such as shear stress due to flow and pulsatile stretch. The extracellular matrix maintains the structural integrity of the vessel wall and coordinates with a dynamic mechanical environment to provide cues to initiate intracellular signaling pathway(s), thereby changing cellular behaviors and functions. However, the precise role of matrix–cell interactions involved in mechanotransduction during vascular homeostasis and disease development remains to be fully determined. In this review, we introduce hemodynamics forces in blood vessels and the initial sensors of mechanical stimuli, including cell–cell junctional molecules, G-protein-coupled receptors (GPCRs), multiple ion channels, and a variety of small GTPases. We then highlight the molecular mechanotransduction events in the vessel wall triggered by laminar shear stress (LSS) and disturbed shear stress (DSS) on vascular endothelial cells (ECs), and cyclic stretch in ECs and vascular smooth muscle cells (SMCs)—both of which activate several key transcription factors. Finally, we provide a recent overview of matrix–cell interactions and mechanotransduction centered on fibronectin in ECs and thrombospondin-1 in SMCs. The results of this review suggest that abnormal mechanical cues or altered responses to mechanical stimuli in EC and SMCs serve as the molecular basis of vascular diseases such as atherosclerosis, hypertension and aortic aneurysms. Collecting evidence and advancing knowledge on the mechanotransduction in the vessel wall can lead to a new direction of therapeutic interventions for vascular diseases.


2007 ◽  
Vol 177 (4S) ◽  
pp. 169-169
Author(s):  
Quoc-Dien Trinh ◽  
Pierre I. Karakiewicz ◽  
Thierry Lebeau ◽  
Dan Lewinshtein ◽  
Elie Antebi ◽  
...  

2005 ◽  
Vol 173 (4S) ◽  
pp. 116-117
Author(s):  
Hannes Steiner ◽  
Reinhard Peschel ◽  
Tilko Müller ◽  
Christian Gozzi ◽  
Georg C. Bartsch ◽  
...  

2001 ◽  
Vol 40 (4) ◽  
pp. 536-540 ◽  
Author(s):  
Finn Edler von Eyben ◽  
Ebbe Lindegaard Madsen ◽  
Ole Blaabjerg ◽  
Per Hyltoft Petersen ◽  
Hans von der Maase ◽  
...  

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