Cohesion and detachment in biofilm systems for different electron acceptor and donors

2007 ◽  
Vol 55 (8-9) ◽  
pp. 421-428 ◽  
Author(s):  
C. Coufort ◽  
N. Derlon ◽  
J. Ochoa-Chaves ◽  
A. Liné ◽  
E. Paul
Keyword(s):  
Basal Layer ◽  
Middle Layer ◽  
Electron Donors ◽  
Shear Stresses ◽  
Average Thickness ◽  
Low Shear Stress ◽  
Erosion Test ◽  
Biofilm Structure ◽  
Initial Biofilm ◽  
Low Shear

This work deals with the cohesion and detachment in biofilm systems for two electron acceptors and for two electron donors. Biofilms were developed on plates, under very low shear stress for one month and then subjected to an erosion test for two hours in a Couette-Taylor reactor. Biofilm was characterised in terms of average thickness and residual TOC mass. It was found that the biofilm structure is very heterogeneous and stratified. The top layer, which represents 60% of the biofilm mass, is very fragile and can be easily detached; the basal layer, which represents 20% of the biofilm mass, is very cohesive and can resist shear stresses up to 13 Pa. Between these two layers, a middle layer of intermediary cohesion represents 20% of the initial biofilm mass.

Analysis of Particle Trajectories in Aortic Artery Bifurcations With Stenosis

1989 ◽  
Vol 111 (4) ◽  
pp. 311-315 ◽  
Author(s):  
M. Nazemi ◽  
C. Kleinstreuer
Keyword(s):  
Shear Stress ◽  
Element Model ◽  
Spherical Particles ◽  
Shear Stresses ◽  
Atherosclerotic Lesions ◽  
Aortic Artery ◽  
Diseased Segment ◽  
Low Shear Stress ◽  
Accelerated Growth ◽  
Low Shear

The fluid-particle dynamics in a two-dimensonal symmetric branching channel with local occlusions representing a diseased segment of an aortic artery bifurcation has been analyzed. The validated finite element model simulates the trajectories and landing or impact sites of spherical particles for laminar flow in bifurcation channels with generalized wall conditions. Two hypotheses relating critical wall shear stress levels and plaque formation, previously postulated by Kleinstreuer et al. (1988) and Nazemi et al. (1989), have been confirmed. Low shear stress may contribute to the onset of atherosclerotic lesions and areas of critically low and high shear stresses are susceptible to accelerated growth of plaque.

On the Shear Bands and Shear Localizations in EHL Films

2004 ◽  
Author(s):  
L. Chang
Keyword(s):  
High Pressures ◽  
Glassy State ◽  
Shear Bands ◽  
Elastohydrodynamic Lubrication ◽  
Elastic Behavior ◽  
Plastic Behavior ◽  
Shear Stresses ◽  
Low Shear Stress ◽  
Recent Laboratory ◽  
Low Shear

Liquid lubricants in elastohydrodynamic lubrication (EHL) are subjected to high pressures of the magnitude of 109 N/m2 (GPa). Under these high pressures, the lubricants in room temperatures are usually in the glassy state behaving as amorphous solids. Similar to the polymers, the lubricants exhibit elastic or visco-elastic behavior under low-shear-stress loading and plastic or visco-plastic behavior with high shear stresses. Recent laboratory experiments have revealed two types of localized shear responses that can take place in the lubricant bulk. The localized shear may be active in the EHL film and may play a significant role in the responses exhibited by the contact conjunction. A typical example is the EHL traction. This paper summarizes the up-to-date research related to the shear localizations.

scholarly journals Computing of Low Shear Stress-Driven Endothelial Gene Network Involved in Early Stages of Atherosclerotic Process

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Federico Vozzi ◽  
Jonica Campolo ◽  
Lorena Cozzi ◽  
Gianfranco Politano ◽  
Stefano Di Carlo ◽  
...  
Keyword(s):  
Gene Expression ◽  
Shear Stress ◽  
Transcription Factors ◽  
Gene Network ◽  
Bioinformatics Analysis ◽  
Atherosclerotic Disease ◽  
Cell Phenotype ◽  
Shear Stresses ◽  
Low Shear Stress ◽  
Low Shear

Background. In the pathogenesis of atherosclerosis, a central role is represented by endothelial inflammation with influx of chemokine-mediated leukocytes in the vascular wall. Aim of this study was to analyze the effect of different shear stresses on endothelial gene expression and compute gene network involved in atherosclerotic disease, in particular to homeostasis, inflammatory cell migration, and apoptotic processes.Methods. HUVECs were subjected to shear stress of 1, 5, and 10 dyne/cm2in a Flow Bioreactor for 24 hours to compare gene expression modulation. Total RNA was analyzed by Affymetrix technology and the expression of two specific genes (CXCR4 and ICAM-1) was validated by RT-PCR. To highlight possible regulations between genes and as further validation, a bioinformatics analysis was performed.Results. At low shear stress (1 dyne/cm2) we observed the following: (a) strong upregulation of CXCR4; (b) mild upregulation of Caspase-8; (c) mild downregulation of ICAM-1; (d) marked downexpression of TNFAIP3. Bioinformatics analysis showed the presence of network composed by 59 new interactors (14 transcription factors and 45 microRNAs) appearing strongly related to shear stress.Conclusions. The significant modulation of these genes at low shear stress and their close relationships through transcription factors and microRNAs suggest that all may promote an initial inflamed endothelial cell phenotype, favoring the atherosclerotic disease.

Low shear stress-induced endothelial mesenchymal transformation via the down-regulation of TET2

2021 ◽  
Vol 545 ◽  
pp. 20-26
Author(s):  
AFang Li ◽  
LiLan Tan ◽  
ShuLei Zhang ◽  
Jun Tao ◽  
Zuo Wang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Down Regulation ◽  
Low Shear Stress ◽  
Mesenchymal Transformation ◽  
Low Shear

Plaque and Shear Stress Distribution in Human Coronary Bifurcations: a Multi-Slice Computed Tomography Study

2007 ◽  
Author(s):  
Alina G. van der Giessen ◽  
Jolanda J. Wentzel ◽  
Frans N. van de Vosse ◽  
Antonius F. van der Steen ◽  
Pim J. de Feyter ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Shear Stress ◽  
Outer Wall ◽  
Atherosclerotic Plaques ◽  
Advanced Stage ◽  
Flow Divider ◽  
Low Shear Stress ◽  
Curved Vessels ◽  
Early Atherosclerosis ◽  
Low Shear

It is generally accepted that early atherosclerosis develops in low shear-stress (SS) regions such as the outer wall of arterial bifurcations and the inner bend of curved vessels (1). However, in clinical practice, it is common to observe atherosclerotic plaques at the flow-divider, or carina, of coronary bifurcations (2). Plaques at the carina are more frequently found in symptomatic patients, and may represent a more advanced stage of atherosclerosis. The carina is located in a region which is exposed to high SS. We hypothesize that if plaques are located in atheroprotective high SS regions, they have grown circumferentially from the atherogenic low SS regions.

CXCR4 expression in atherosclerotic lesions induced by low shear stress

2008 ◽  
Vol 32 (3) ◽  
pp. S18-S19
Author(s):  
Dang Heng Wei ◽  
Gui Xue Wang ◽  
Yi Ping Xia ◽  
Jian Jun Lei ◽  
Lu Shang Liu ◽  
...  
Keyword(s):  
Shear Stress ◽  
Cxcr4 Expression ◽  
Atherosclerotic Lesions ◽  
Low Shear Stress ◽  
Low Shear

Susceptibility of density-fractionated erythrocytes to subhaemolytic mechanical shear stress

2018 ◽  
Vol 42 (3) ◽  
pp. 151-157 ◽  
Author(s):  
Antony P McNamee ◽  
Kieran Richardson ◽  
Jarod Horobin ◽  
Lennart Kuck ◽  
Michael J Simmonds
Keyword(s):  
Blood Cell ◽  
Red Blood Cells ◽  
Red Blood Cell ◽  
Blood Cells ◽  
Shear Stresses ◽  
Mechanical Stimuli ◽  
Cell Deformability ◽  
Red Blood Cell Deformability ◽  
Cell Age ◽  
Low Shear

Introduction: Accumulating evidence demonstrates that subhaemolytic mechanical stresses, typical of circulatory support, induce physical and biochemical changes to red blood cells. It remains unclear, however, whether cell age affects susceptibility to these mechanical forces. This study thus examined the sensitivity of density-fractionated red blood cells to sublethal mechanical stresses. Methods: Red blood cells were isolated and washed twice, with the least and most dense fractions being obtained following centrifugation (1500 g × 5 min). Red blood cell deformability was determined across an osmotic gradient and a range of shear stresses (0.3–50 Pa). Cell deformability was also quantified before and after 300 s exposure to shear stresses known to decrease (64 Pa) or increase (10 Pa) red blood cell deformability. The time course of accumulated sublethal damage that occurred during exposure to 64 Pa was also examined. Results: Dense red blood cells exhibited decreased capacity to deform when compared with less dense cells. Cellular response to mechanical stimuli was similar in trend for all red blood cells, independent of density; however, the magnitude of impairment in cell deformability was exacerbated in dense cells. Moreover, the rate of impairment in cellular deformability, induced by 64 Pa, was more rapid for dense cells. Relative improvement in red blood cell deformability, due to low-shear conditioning (10 Pa), was consistent for both cell populations. Conclusion: Red blood cell populations respond differently to mechanical stimuli: older (more dense) cells are highly susceptible to sublethal mechanical trauma, while cell age (density) does not appear to alter the magnitude of improved cell deformability following low-shear conditioning.

scholarly journals Low Shear Stress Induced HMGB1 Translocation and Release via PECAM-1/PARP-1 Pathway to Induce Inflammation Response

PLoS ONE ◽  
2015 ◽  
Vol 10 (3) ◽  
pp. e0120586 ◽  
Author(s):  
Wei-dong Qin ◽  
Shao-hua Mi ◽  
Chen Li ◽  
Gui-xia Wang ◽  
Jian-ning Zhang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Inflammation Response ◽  
Low Shear Stress ◽  
Parp 1 ◽  
Low Shear
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