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Shear stress

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https://www.readbyqxmd.com/read/28222499/prediction-of-the-level-and-duration-of-shear-stress-exposure-that-induces-subhemolytic-damage-to-erythrocytes
#1
Michael J Simmonds, Herbert J Meiselman
BACKGROUND: Current generation mechanical circulatory assist devices are designed to minimize high shears to blood for prolonged durations to avoid hemolysis. However, red blood cells (RBC) demonstrate impaired capacity to deform when exposed to shear stress (SS) well below the "hemolytic threshold". OBJECTIVE: We endeavored to identify how changes in the magnitude and duration of SS exposure alter RBC deformability and subsequently develop a model to predict erythrocyte subhemolytic damage...
February 9, 2017: Biorheology
https://www.readbyqxmd.com/read/28220319/cfd-assessment-of-the-effect-of-convective-mass-transport-on-the-intracellular-clearance-of-intracellular-triglycerides-in-macrosteatotic-hepatocytes
#2
Gabriel Yarmush, Lucas Santos, Joshua Yarmush, Srivathsan Koundinyan, Mubasher Saleem, Nir I Nativ, Martin L Yarmush, Francois Berthiaume, Timothy J Maguire, Chris Guaghan
Donor livers available to transplant for patients with end-stage liver disease are in severe shortage. One possible avenue to expand the donor pool is to recondition livers that would be otherwise discarded due to excessive fat content. Severely steatotic livers (also known as fatty livers) are highly susceptible to ischemia-reperfusion injury and as a result, primary liver non-function post-transplantation. Prior studies in isolated perfused rat livers suggest that "defatting" may be possible in a timeframe of a few hours; thus, it is conceivable that fatty liver grafts could be recovered by machine perfusion to clear stored fat from the organ prior to transplantation...
February 20, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28217790/nanotribological-properties-of-nanostructured-poly-cysteine-methacrylate-brushes
#3
Omed Al-Jaf, Abdullah Alswieleh, Steven P Armes, Graham J Leggett
The nanomechanical properties of zwitterionic poly(cysteine methacrylate) (PCysMA) brushes grown from planar surfaces by atom transfer radical polymerisation have been characterised by friction force microscopy (FFM). FFM provides quantitative insights into polymer structure-property relationships and in particular illuminates the dependence of brush swelling on chain packing in nanostructured materials. In ethanol, which is a poor solvent for PCysMA, a linear friction-load relationship is observed, indicating that energy dissipation occurs primarily through ploughing...
February 20, 2017: Soft Matter
https://www.readbyqxmd.com/read/28214750/propagation-of-thickness-shear-waves-in-a-periodically-corrugated-quartz-crystal-plate-and-its-application-exploration-in-acoustic-wave-filters
#4
Peng Li, Li Cheng
The propagation of thickness shear waves in a periodically corrugated quartz crystal plate is investigated in the present paper using a power series expansion technique. In the proposed simulation model, an equivalent continuity of shear stress moment is introduced as an approximation to handle sectional interfaces with abrupt thickness changes. The Bloch theory is applied to simulate the band structures for three different thickness variation patterns. It is shown that the power series expansion method exhibits good convergence and accuracy, in agreement with results by finite element method (FEM)...
February 7, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28213494/plc%C3%AE%C2%B51-regulates-sdf-1%C3%AE-induced-lymphocyte-adhesion-and-migration-to-sites-of-inflammation
#5
Marianne Strazza, Inbar Azoulay-Alfaguter, Michael Peled, Alan V Smrcka, Edward Y Skolnik, Shekhar Srivastava, Adam Mor
Regulation of integrins is critical for lymphocyte adhesion to endothelium and migration throughout the body. Inside-out signaling to integrins is mediated by the small GTPase Ras-proximate-1 (Rap1). Using an RNA-mediated interference screen, we identified phospholipase Cε 1 (PLCε1) as a crucial regulator of stromal cell-derived factor 1 alpha (SDF-1α)-induced Rap1 activation. We have shown that SDF-1α-induced activation of Rap1 is transient in comparison with the sustained level following cross-linking of the antigen receptor...
February 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28213338/a-uniaxial-cyclic-compression-method-for-characterizing-the-rheological-and-textural-behaviors-of-mechanically-dewatered-sewage-sludge
#6
Fenglin Liang, Martial Sauceau, Gilles Dusserre, Patricia Arlabosse
The mechanically dewatered sewage sludge with total solid content around 20% on a weight basis is very similar to yield stress fluid, its complex transition between solid and fluid states is not perfectly reversible and especially challenging in terms of pumping, land spreading and drying. To characterize the rheological and textural properties of highly concentrated sludge, a specific methodology based on uniaxial single and cyclic compression tests is developed. Three types of sludge samples (fresh original, fresh premixed and aged original ones) are extruded into cylinders and pressed between two parallel plates using a material testing machine...
February 7, 2017: Water Research
https://www.readbyqxmd.com/read/28213332/shear-stress-enhances-ca-2-sparks-through-nox2-dependent-mitochondrial-reactive-oxygen-species-generation-in-rat-ventricular-myocytes
#7
Joon-Chul Kim, Jun Wang, Min-Jeong Son, Sun-Hee Woo
Shear stress enhances diastolic and systolic Ca(2+) concentration in ventricular myocytes. Here, using confocal Ca(2+) imaging in rat ventricular myocytes, we assessed the effects of shear stress (~16dyn/cm(2)) on the frequency of spontaneous Ca(2+) sparks and explored the mechanism underlying shear-mediated Ca(2+) spark regulation. The frequency of Ca(2+) sparks was immediately increased by shear stress (by ~80%), and increased further (by ~150%) during prolonged exposure (20s). The 2-D size and duration of individual sparks were increased by shear stimulation...
February 14, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28212934/effects-of-basil-seed-gum-cress-seed-gum-and-quince-seed-gum-on-the-physical-textural-and-rheological-properties-of-whipped-cream
#8
Reza Farahmandfar, Maryam Asnaashari, Reza Salahi, Tandis Khosravi Rad
This study focuses on the physical, textural and rheological properties of low fat (LF) whipped cream with 30% fat content developed with Basil seed gum (BSG), Cress seed gum (CSG) and Quince seed gum (QSG) at the concentration of 0.1 and 0.3% (wt/wt) and comparison with high fat (HF) whipped cream sample (55%) as control. Flow curves were analyzed using Herschel bulkey and Carreau models through a fitting procedure. The rheological investigations confirmed that all samples were shear thinning fluid exhibiting a yield stress and thixotropy properties...
February 14, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28211801/effect-of-shear-induced-platelet-activation-on-red-blood-cell-aggregation
#9
Hoyoon Lee, Kisung Lee, Byoung-Kwon Lee, Alexander V Priezzhev, Sehyun Shin
Mechanical shear stress is one of the important factors for platelet activation. Although shear stress has been frequently utilized in many applications of diagnostic bio-equipment, there has been little consideration as to whether shear stress induces platelet activation and consequently alters hemorheological characteristics. Therefore, we investigated the effect of shear-induced platelet activation on red blood cell (RBC) aggregation. The hypothesis of the present research is as follows: Platelets activated by high shear stress secrete substances, which can affect hemorheological characteristics to promote RBC aggregation...
February 17, 2017: Clinical Hemorheology and Microcirculation
https://www.readbyqxmd.com/read/28211170/endothelial-glycocalyx-as-a-critical-signalling-platform-integrating-the-extracellular-haemodynamic-forces-and-chemical-signalling
#10
REVIEW
Ye Zeng
The glycocalyx covers the human mammalian cells and plays important roles in stroke, inflammation and atherosclerosis. It has also been shown to be involved in endothelial mechanotransduction of shear stress. Shear stress induces the remodelling of the major component of the glycocalyx including glypican-1, a cell membrane heparan sulphate proteoglycan. Other factors, such as sphingosine-1-phosphate (S1P), protect the glycocalyx against syndecan-1 ectodomain shedding and induce the synthesis of heparan sulphate...
February 17, 2017: Journal of Cellular and Molecular Medicine
https://www.readbyqxmd.com/read/28209993/suppression-of-tak1-pathway-by-shear-stress-counteracts-the-inflammatory-endothelial-cell-phenotype-induced-by-oxidative-stress-and-tgf-%C3%AE-1
#11
Ee Soo Lee, Llorenç Solé Boldo, Bernadette O Fernandez, Martin Feelisch, Martin C Harmsen
Endothelial dysfunction is characterised by aberrant redox signalling and an inflammatory phenotype. Shear stress antagonises endothelial dysfunction by increasing nitric oxide formation, activating anti-inflammatory pathways and suppressing inflammatory pathways. The TAK1 (MAP3K7) is a key mediator of inflammation and non-canonical TGF-β signalling. While the individual roles of TAK1, ERK5 (MAPK7) and TGF-β pathways in endothelial cell regulation are well characterised, an integrative understanding of the orchestration of these pathways and their crosstalk with the redox system under shear stress is lacking...
February 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28209576/differences-in-hemodynamics-and-rupture-rate-of-aneurysms-at-the-bifurcation-of-the-basilar-and-internal-carotid-arteries
#12
R Doddasomayajula, B Chung, F Hamzei-Sichani, C M Putman, J R Cebral
BACKGROUND AND PURPOSE: Cerebral aneurysms in the posterior circulation are known to have a higher rupture risk than those in the anterior circulation. We sought to test the hypothesis that differences in hemodynamics can explain the difference in rupture rates. MATERIALS AND METHODS: A total of 117 aneurysms, 63 at the tip of the basilar artery (27 ruptured, 36 unruptured, rupture rate = 43%) and 54 at the bifurcation of the internal carotid artery (11 ruptured, 43 unruptured, rupture rate = 20%) were analyzed with image-based computational fluid dynamics...
February 16, 2017: AJNR. American Journal of Neuroradiology
https://www.readbyqxmd.com/read/28209345/multiobjective-optimization-of-cartilage-stress-for-non-invasive-patient-specific-recommendations-of-high-tibial-osteotomy-correction-angle-a-novel-method-to-investigate-alignment-correction
#13
Keke Zheng, Corey J Scholes, Junning Chen, David Parker, Qing Li
Medial opening wedge high tibial osteotomy (MOWHTO) is a surgical procedure to treat knee osteoarthritis associated with varus deformity. However, the ideal final alignment of the Hip-Knee-Ankle (HKA) angle in the frontal plane, that maximizes procedural success and post-operative knee function, remains controversial. Therefore, the purpose of this study was to introduce a subject-specific modeling procedure in determining the biomechanical effects of MOWHTO alignment on tibiofemoral cartilage stress distribution...
February 13, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28209171/integrated-strategy-for-in-vitro-characterization-of-a-bileaflet-mechanical-aortic-valve
#14
Francesca Maria Susin, Stefania Espa, Riccardo Toninato, Stefania Fortini, Giorgio Querzoli
BACKGROUND: Haemodynamic performance of heart valve prosthesis can be defined as its ability to fully open and completely close during the cardiac cycle, neither overloading heart work nor damaging blood particles when passing through the valve. In this perspective, global and local flow parameters, valve dynamics and blood damage safety of the prosthesis, as well as their mutual interactions, have all to be accounted for when assessing the device functionality. Even though all these issues have been and continue to be widely investigated, they are not usually studied through an integrated approach yet, i...
February 16, 2017: Biomedical Engineering Online
https://www.readbyqxmd.com/read/28208493/inertia-and-universality-of-avalanche-statistics-the-case-of-slowly-deformed-amorphous-solids
#15
Kamran Karimi, Ezequiel E Ferrero, Jean-Louis Barrat
By means of a finite elements technique we solve numerically the dynamics of an amorphous solid under deformation in the quasistatic driving limit. We study the noise statistics of the stress-strain signal in the steady-state plastic flow, focusing on systems with low internal dissipation. We analyze the distributions of avalanche sizes and durations and the density of shear transformations when varying the damping strength. In contrast to avalanches in the overdamped case, dominated by the yielding point universal exponents, inertial avalanches are controlled by a nonuniversal damping-dependent feedback mechanism, eventually turning negligible the role of correlations...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28208491/dynamic-shear-jamming-in-dense-granular-suspensions-under-extension
#16
Sayantan Majumdar, Ivo R Peters, Endao Han, Heinrich M Jaeger
Unlike dry granular materials, a dense granular suspension like cornstarch in water can strongly resist extensional flows. At low extension rates, such a suspension behaves like a viscous fluid, but rapid extension results in a response where stresses far exceed the predictions of lubrication hydrodynamics and capillarity. To understand this remarkable mechanical response, we experimentally measure the normal force imparted by a large bulk of the suspension on a plate moving vertically upward at a controlled velocity...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28208468/colloidal-polycrystalline-monolayers-under-oscillatory-shear
#17
Ivo Buttinoni, Mathias Steinacher, Hendrik Th Spanke, Juho Pokki, Severin Bahmann, Bradley Nelson, Giuseppe Foffi, Lucio Isa
In this paper we probe the structural response to oscillatory shear deformations of polycrystalline monolayers of soft repulsive colloids with varying area fraction over a broad range of frequencies and amplitudes. The particles are confined at a fluid interface, sheared using a magnetic microdisk, and imaged through optical microscopy. The structural and mechanical response of soft materials is highly dependent on their microstructure. If crystals are well understood and deform through the creation and mobilization of specific defects, the situation is much more complex for disordered jammed materials, where identifying structural motifs defining plastically rearranging regions remains an elusive task...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28208459/channelization-in-porous-media-driven-by-erosion-and-deposition
#18
R Jäger, M Mendoza, H J Herrmann
We develop and validate a new model to study simultaneous erosion and deposition in three-dimensional porous media. We study the changes of the porous structure induced by the deposition and erosion of matter on the solid surface and find that when both processes are active, channelization in the porous structure always occurs. The channels can be stable or only temporary depending mainly on the driving mechanism. Whereas a fluid driven by a constant pressure drop in general does not form steady channels, imposing a constant flux always produces stable channels within the porous structure...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28208450/thermal-effects-in-dislocation-theory-ii-shear-banding
#19
J S Langer
The thermodynamic dislocation theory presented in previous papers is used here to describe shear-banding instabilities. Central ingredients of the theory are a thermodynamically defined effective configurational temperature and a formula for the plastic strain rate determined by thermally activated depinning of entangled dislocations. This plastic strain rate is extremely sensitive to variations of the stress and the ordinary temperature. As a result of this sensitivity, the system undergoes rapid shear banding instabilities when ordinary thermal relaxation is slow...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28207961/muscle-stiffness-of-posterior-lower-leg-in-runners-with-a-history-of-medial-tibial-stress-syndrome
#20
Junya Saeki, Masatoshi Nakamura, Sayaka Nakao, Kosuke Fujita, Ko Yanase, Noriaki Ichihashi
Previous history of medial tibial stress syndrome (MTSS) is a risk factor for MTSS relapse, which suggests that there might be some physical factors that are related to MTSS development in runners with a history of MTSS. The relationship between MTSS and muscle stiffness can be assessed in a cross-sectional study that measures muscle stiffness in subjects with a history of MTSS, who do not have pain at the time of measurement, and in those without a history of MTSS. The purpose of this study was to compare the shear elastic modulus, which is an index of muscle stiffness, of all posterior lower leg muscles of subjects with a history of MTSS and those with no history and investigate which muscles could be related to MTSS...
February 16, 2017: Scandinavian Journal of Medicine & Science in Sports
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