Shear stresses in magnetorheological fluids: Role of magnetic saturation

1994 ◽  
Vol 65 (26) ◽  
pp. 3410-3412 ◽  
Author(s):  
J. M. Ginder ◽  
L. C. Davis
Keyword(s):  
Magnetorheological Fluids ◽  
Magnetic Saturation ◽  
Shear Stresses

Stiffness of the pleural surface of the chest wall is similar to that of the lung

2003 ◽  
Vol 95 (6) ◽  
pp. 2345-2349 ◽  
Author(s):  
Andrew Gouldstone ◽  
Richard E. Brown ◽  
James P. Butler ◽  
Stephen H. Loring
Keyword(s):  
Chest Wall ◽  
Elastohydrodynamic Lubrication ◽  
Geometric Standard Deviation ◽  
Parietal Pleura ◽  
Shear Stresses ◽  
Membrane Tension ◽  
Similar Extent ◽  
Spatial Uniformity ◽  
Pleural Surface

To address the role of the parietal pleura in reduction of mesothelial shear stresses during breathing, we measured the stiffness of the parietal pleural surface of mammalian chest walls using microindentation. The pleural surface was indented over ribs and intercostal spaces with rigid flat punches (tip radii of 0.01, 0.02, and 0.1 cm) to probe stiffness at length scales comparable with those of surface asperities. We found a tissue shear modulus of 6,700 dyn/cm2 and pleural membrane tension of 4,900 dyn/cm, with a geometric standard deviation of 0.42. These values are similar to those measured for the lung by Hajji et al., using indentation (Hajji MA, Wilson TA, and Lai-Fook SJ. J Appl Physiol Respirat Environ Exerc Physiol 47: 175–181, 1979). Surprisingly, the pleural surface over ribs and intercostal spaces exhibited similar stiffness. In addition, caudal regions exhibited lower stiffness than cranial regions. In the context of elastohydrodynamic lubrication, these results suggest that shear-induced pressures during breathing deform the chest wall and lung surfaces to a similar extent, promoting spatial uniformity of pleural fluid thickness and reducing shear stresses.

Recent developments in modeling ice sheet deformation

2020 ◽  
Author(s):  
Felicity McCormack ◽  
Roland Warner ◽  
Adam Treverrow ◽  
Helene Seroussi
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Vertical Shear ◽  
Shear Stresses ◽  
Polar Ice ◽  
Ice Flow ◽  
Polar Ice Sheets ◽  
Basal Shear ◽  
The Impact

<p>Viscous deformation is the main process controlling ice flow in ice shelves and in slow-moving regions of polar ice sheets where ice is frozen to the bed. However, the role of deformation in flow in ice streams and fast-flowing regions is typically poorly represented in ice sheet models due to a major limitation in the current standard flow relation used in most large-scale ice sheet models – the Glen flow relation – which does not capture the steady-state flow of anisotropic ice that prevails in polar ice sheets. Here, we highlight recent advances in modeling deformation in the Ice Sheet System Model using the ESTAR (empirical, scalar, tertiary, anisotropic regime) flow relation – a new description of deformation that takes into account the impact of different types of stresses on the deformation rate. We contrast the influence of the ESTAR and Glen flow relations on the role of deformation in the dynamics of Thwaites Glacier, West Antarctica, using diagnostic simulations. We find key differences in: (1) the slow-flowing interior of the catchment where the unenhanced Glen flow relation simulates unphysical basal sliding; (2) over the floating Thwaites Glacier Tongue where the ESTAR flow relation outperforms the Glen flow relation in accounting for tertiary creep and the spatial differences in deformation rates inherent to ice anisotropy; and (3) in the grounded region within 80km of the grounding line where the ESTAR flow relation locally predicts up to three times more vertical shear deformation than the unenhanced Glen flow relation, from a combination of enhanced vertical shear flow and differences in the distribution of basal shear stresses. More broadly on grounded ice, the membrane stresses are found to play a key role in the patterns in basal shear stresses and the balance between basal shear stresses and gravitational forces simulated by each of the ESTAR and Glen flow relations. Our results have implications for the suitability of ice flow relations used to constrain uncertainty in reconstructions and projections of global sea levels, warranting further investigation into using the ESTAR flow relation in transient simulations of glacier and ice sheet dynamics. We conclude by discussing how geophysical data might be used to provide insight into the relationship between ice flow processes as captured by the ESTAR flow relation and ice fabric anisotropy.</p>

New Interpretation of the Influence of Various Parameters on Texture Evolution in Damascene Cu Interconnect Lines

2005 ◽  
Vol 495-497 ◽  
pp. 1449-1454 ◽  
Author(s):  
Kabir Kumar Mirpuri ◽  
Jerzy A. Szpunar
Keyword(s):  
Dislocation Density ◽  
Texture Evolution ◽  
Shear Stresses ◽  
Principal Stresses ◽  
Line Spacing ◽  
Role Of Principal ◽  
New Interpretation ◽  
Cu Interconnect ◽  
Interconnect Lines

The article takes into account various factors which effect the texture evolution in the Cu lines. We propose here an explanation for the formation of {111}<110> and {111}<112> texture in the Cu lines. The explicit role of principal stresses, shear stresses and dislocations is discussed. The influence of line spacing on strength of the {111}<110> and {111}<112> texture components is also demonstrated in relation to the dislocation density.

A Computer Simulation of the Blood Flow at the Aortic Bifurcation With Flexible Walls

1993 ◽  
Vol 115 (3) ◽  
pp. 306-315 ◽  
Author(s):  
Zheng Lou ◽  
Wen-Jei Yang
Keyword(s):  
Blood Flow ◽  
Moving Boundary ◽  
Shear Stresses ◽  
Arbitrary Lagrangian Eulerian ◽  
Aortic Bifurcation ◽  
Arbitrary Lagrangian Eulerian Method ◽  
Flexible Walls ◽  
Linear Viscoelastic ◽  
Flow Reversals

To understand the role of fluid dynamics in atherogenesis, especially the effect of the flexibility of arteries, a two-dimensional numerical model for blood flow at the aortic bifurcation with linear viscoelastic walls is developed. The arbitrary Lagrangian-Eulerian method is adopted to deal with the moving boundary problem. The wall expansion induces flow reversals or eddies during the decelerating systole while the wall contraction restricts them during the diastole. A flexible bifurcation experiences the shear stresses about 10 percent lower than those of a rigid one.

Molecular Analysis of Type 1 VWD Mutations: Effects of Mutant:Wild-Type Transfection Ratio and Protein Degradation

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1210-1210
Author(s):  
Tara C White-Adams ◽  
Paula M Jacobi ◽  
Sandra L Haberichter ◽  
Jorge A Di Paola
Keyword(s):  
Conflicts Of Interest ◽  
Phenotypic Variability ◽  
Statistical Significance ◽  
Von Willebrand Disease ◽  
Incomplete Penetrance ◽  
Shear Stresses ◽  
Dependent Manner ◽  
Von Willebrand

Abstract Abstract 1210 Background: Von Willebrand disease (VWD), the most frequently diagnosed bleeding disorder, is characterized by variable expressivity and incomplete penetrance. Bleeding severity in type 1 VWD does not always correlate with plasma VWF levels, except in cases of severe deficiency. It is possible that the phenotypic variability observed in type 1 VWD is related to the final ratio of mutant vs. wild-type (WT) subunits in the mature VWF multimeric structure. The aim of this study was to determine the role of mutant:WT transfection ratio on von Willebrand factor (VWF) expression, secretion and degradation in VWD type 1 mutations. Methods: Type 1 VWD mutations with reported normal multimer distribution were chosen from the D'-D3 region of VWF. Mutations of cysteine residues were eliminated to avoid interference with inter- and intra-chain disulfide linkages. Mutations were generated by performing site-directed mutagenesis on full-length human VWF cDNA within the pcDNA3.1(-)A vector, which appends VWF with a Myc-His tag (denoted mH). The following mutations were generated: M771I, R782Q, R924W, I1094T and T1156M. Mutant VWF was co-transfected with WT VWF contained within the pCIneo vector (mutant mH:WT pCIneo ratios investigated were 1:3, 2:2, 3:1, 4:0). Recombinant (r)VWF expression was measured using ELISA and concentrations were determined by comparison to a standard curve generated with pooled normal plasma. Multimer composition was analyzed using SDS-agarose gel electrophoresis followed by Western blot. Statistical significance was determined using one-way ANOVA with post-hoc Tukey test. Results: Homozygous expression of R924W or I1094T had no effect on rVWF expression or secretion compared to WT, while M771I, R782Q and T1156M significantly increased intracellular protein retention. Co-expression of M771I or R782Q at varying ratios with WT was able to partially correct rVWF secretion, although intracellular retention remained significantly higher than WT at all ratios (n=3, * p<0.05, Figure 1). Co-expression with WT cDNA was also able to correct T1156M retention in a dose-dependent manner (n=3, Figure 1), as described previously [Lethagen, Thromb and Haemost, 2002]. Multimer analysis of co-transfection supernatants exhibited normal and full distribution of multimers, as expected for type 1 VWD mutations. Others have shown previously that heterodimers of WT and C1149R VWF, a type 1 VWD mutation, are degraded by the proteasome [Bodo et al, Blood, 2001], presumably via recognition of a folding defect within the mutant subunit. In order to determine the role of proteasomal degradation in the decreased secretion levels of our mutants, we performed experiments in the presence of the proteasome inhibitor MG-132. Treatment of co-transfected cells (mutant:WT 2:2) with 1 mM MG-132 for 16 hours prior to harvesting did not significantly affect secretion or overall expression of rVWF, suggesting that this pathway is not involved in the regulation of the expression of our mutants. Discussion: Our data demonstrate that M771I, T1156M and R782Q induce a significant increase in intracellular retention compared to WT protein, which could contribute to a quantitative deficiency in type 1 VWD, while R924W and I1094T do not appear to interfere with VWF production or secretion. Variable levels of intracellular retention have been observed in a previous study of VWF mutations identified in type 1 VWD patients [Eikenboom, et al, J Thromb Haemost, 2009]. While one interpretation of these results is that R924W or I1094T may not be causative mutations in type 1 VWD, other mechanisms including protein clearance and function remain to be explored. Although type 1 VWD mutations variably affect expression and secretion levels in vitro, studying platelet rolling on these mutants at a range of physiological shear stresses will provide valuable information regarding whether the degree of incorporation of mutant subunits into VWF multimers can affect supramolecular structure, and ultimately, hemostatic function. Disclosures: No relevant conflicts of interest to declare.

The role of shear stresses in mineral transformations

2010 ◽  
Vol 46 (5) ◽  
pp. 446-450
Author(s):  
Yu. S. Genshaft ◽  
G. N. Bazhenova
Keyword(s):  
Shear Stresses ◽  
Mineral Transformations

Role of organic coating on carbonyl iron suspended particles in magnetorheological fluids

2005 ◽  
Vol 97 (10) ◽  
pp. 10Q912 ◽  
Author(s):  
I. B. Jang ◽  
H. B. Kim ◽  
J. Y. Lee ◽  
J. L. You ◽  
H. J. Choi ◽  
...  
Keyword(s):  
Carbonyl Iron ◽  
Suspended Particles ◽  
Organic Coating ◽  
Magnetorheological Fluids
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