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Shear stress

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https://www.readbyqxmd.com/read/29150346/aerodynamic-study-of-time-trial-helmets-in-cycling-racing-using-cfd-analysis
#1
F Beaumont, R Taiar, G Polidori, H Trenchard, F Grappe
The aerodynamic drag of three different time-trial cycling helmets was analyzed numerically for two different cyclist head positions. Computational Fluid Dynamics (CFD) methods were used to investigate the detailed airflow patterns around the cyclist for a constant velocity of 15 m/s without wind. The CFD simulations have focused on the aerodynamic drag effects in terms of wall shear stress maps and pressure coefficient distributions on the cyclist/helmet system. For a given head position, the helmet shape, by itself, obtained a weak effect on a cyclist's aerodynamic performance (<1...
November 8, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/29150280/nk-cell-recruitment-and-exercise-potential-immunotherapeutic-role-of-shear-stress-and-endothelial-health
#2
William Evans
Positive cancer patient outcomes, including increased time to recurrent events, have been associated with increased counts and function of natural killer (NK) cells. NK cell counts and function are elevated following acute exercise, and the generally accepted mechanism of increased recruitment suggests that binding of epinephrine releases NK cells from endothelial tissue via decreases in adhesion molecules following. I propose that blood flow-induced shear stress may also play a role in NK cell recruitment from the endothelium...
November 2017: Medical Hypotheses
https://www.readbyqxmd.com/read/29148433/a-flow-bioreactor-system-compatible-with-real-time-two-photon-fluorescence-lifetime-imaging-microscopy
#3
Nian Shen, Julia A Riedl, Daniel A Carvajal-Berrio, Zackary Davis, Michael G Monaghan, Shannon Lee Layland, Svenja Hinderer, Katja Schenke-Layland
Bioreactors are essential cell and tissue culture tools that allow the introduction of biophysical signals into in vitro cultures. One major limitation is the need to interrupt experiments and sacrifice samples at certain time points for analyses. To address this issue, we designed a bioreactor that combines high-resolution contact-free imaging and continuous flow in a closed system that is compatible with various types of microscopes. The high-throughput fluid flow bioreactor was combined with two-photon fluorescence lifetime imaging microscopy (2P-FLIM) and validated...
November 17, 2017: Biomedical Materials
https://www.readbyqxmd.com/read/29145514/why-patients-with-thbd-c-1611c-a-p-cys537x-nonsense-mutation-have-high-levels-of-soluble-thrombomodulin
#4
Yohann Jourdy, Nathalie Enjolras, Sandra Le Quellec, Jean Claude Bordet, Claude Négrier, Christine Vinciguerra, Yesim Dargaud
BACKGROUND: Recently our group has described a new autosomal dominant bleeding disorder characterized by very high plasma levels of soluble thrombomodulin (TM). The THBD c.1611C>A (p.Cys537X) mutation in heterozygous state was found in the propositus. This mutation leads to the synthesis of a truncated TM which has lost the last three amino-acids of the transmembrane domain and the cytoplasmic tail. OBJECTIVE: We investigated the mechanism responsible for TM shedding in endothelial cells with THBD c...
2017: PloS One
https://www.readbyqxmd.com/read/29145408/effect-of-pulse-pressure-on-borehole-stability-during-shear-swirling-flow-vibration-cementing
#5
Zhihua Cui, Chi Ai, Lei Lv, Fangxian Yin
The shear swirling flow vibration cementing (SSFVC) technique rotates the downhole eccentric cascade by circulating cementing fluid. It makes the casing eccentrically revolve at high speed around the borehole axis. It produces strong agitation action to the annulus fluid, makes it in the state of shear turbulent flow, and results in the formation of pulse pressure which affects the surrounding rock stress. This study was focused on 1) the calculation of the pulse pressure in an annular turbulent flow field based on the finite volume method, and 2) the analysis of the effect of pulse pressure on borehole stability...
2017: PloS One
https://www.readbyqxmd.com/read/29143545/taz-responds-to-fluid-shear-stress-to-regulate-the-cell-cycle
#6
Hyun Jung Lee, Adesuwa Ewere, Miguel F Diaz, Pamela L Wenzel
Physical forces associated with tumor growth and drainage alter cancer cell invasiveness and metastatic potential. We previously showed that fluid frictional force, or shear stress, typical of lymphatic flow induces YAP1/TAZ activation in prostate cancer cells to promote motility dependent upon YAP1 but not TAZ. Here, we show that shear stress elevates TAZ protein levels and promotes TAZ nuclear localization. Increased TAZ activity drives increased DNA synthesis and induces AMOTL2, ANKRD1, and CTGF gene transcription independently of YAP1...
November 16, 2017: Cell Cycle
https://www.readbyqxmd.com/read/29141415/contribution-to-viscosity-from-the-structural-relaxation-via-the-atomic-scale-green-kubo-stress-correlation-function
#7
V A Levashov
We studied the connection between the structural relaxation and viscosity for a binary model of repulsive particles in the supercooled liquid regime. The used approach is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the correlation functions between the atomic level stresses. Previously we used the approach to study an iron-like single component system of particles. The role of vibrational motion has been addressed through the demonstration of the relationship between viscosity and the shear waves propagating over large distances...
November 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29139052/a-validated-patient-specific-fsi-model-for-vascular-access-in-haemodialysis
#8
A M de Villiers, A T McBride, B D Reddy, T Franz, B S Spottiswoode
The flow rate inside arteriovenous fistulas is many times higher than physiological flow and is accompanied by high wall shear stress resulting in low patency rates. A fluid-structure interaction finite element model is developed to analyse the blood flow and vessel mechanics to elucidate the mechanisms that can lead to failure. The simulations are validated against flow measurements obtained from magnetic resonance imaging data.
November 14, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/29138312/correlating-cell-shape-and-cellular-stress-in-motile-confluent-tissues
#9
Xingbo Yang, Dapeng Bi, Michael Czajkowski, Matthias Merkel, M Lisa Manning, M Cristina Marchetti
Collective cell migration is a highly regulated process involved in wound healing, cancer metastasis, and morphogenesis. Mechanical interactions among cells provide an important regulatory mechanism to coordinate such collective motion. Using a self-propelled Voronoi (SPV) model that links cell mechanics to cell shape and cell motility, we formulate a generalized mechanical inference method to obtain the spatiotemporal distribution of cellular stresses from measured traction forces in motile tissues and show that such traction-based stresses match those calculated from instantaneous cell shapes...
November 14, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29137778/the-use-of-ultrasound-to-reduce-internal-concentration-polarization-in-forward-osmosis
#10
Yongjun Choi, Tae-Mun Hwang, Sanghyun Jeong, Sangho Lee
Unlike reverse osmosis (RO) that is dominated by the hydraulic pressure differential, forward osmosis (FO) uses the osmotic pressure gradient as the driving force between a dilute feed solution and a concentrated draw solution across a membrane. High pressure is not required in FO, which means that FO can be used as an alternative to RO as an energy-saving separation process in desalination technology. However, a major limiting factor of the FO process is the internal concentration polarization (ICP). Because of the stagnant environment inside the porous supporting layer of a FO membrane, it is difficult to mitigate the ICP by simply increasing the shear stress or promoting turbulence...
March 2018: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/29137742/ultrasound-coupled-with-supercritical-carbon-dioxide-for-exfoliation-of-graphene-simulation-and-experiment
#11
Yanzhe Gai, Wucong Wang, Ding Xiao, Yaping Zhao
Ultrasound coupled with supercritical CO2 has become an important method for exfoliation of graphene, but behind which a peeling mechanism is unclear. In this work, CFD simulation and experiment were both investigated to elucidate the mechanism and the effects of the process parameters on the exfoliation yield. The experiments and the CFD simulation were conducted under pressure ranging from 8MPa to 16MPa, the ultrasonic power ranging from 12W to 240W and the frequency of 20kHz. The numerical analysis of fluid flow patterns and pressure distributions revealed that the fluid shear stress and the periodical pressure fluctuation generated by ultrasound were primary factors in exfoliating graphene...
March 2018: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/29137378/trastuzumab-distribution-in-an-in-vivo-and-in-vitro-model-of-brain-metastases-of-breast-cancer
#12
Tori B Terrell-Hall, Mohamed Ismail Nounou, Fatema El-Amrawy, Jessica I G Griffith, Paul R Lockman
Background: Drug and antibody delivery to brain metastases has been highly debated in the literature. The blood-tumor barrier (BTB) is more permeable than the blood-brain barrier (BBB), and has shown to have highly functioning efflux transporters and barrier properties, which limits delivery of targeted therapies. Methods: We characterized the permeability of (125)I-trastuzumab in an in-vivo, and fluorescent trastuzumab-Rhodamine123 (t-Rho123) in a novel microfluidic in-vitro, BBB and BTB brain metastases of breast cancer model...
October 13, 2017: Oncotarget
https://www.readbyqxmd.com/read/29133350/extracellular-histones-induce-erythrocyte-fragility-and-anemia
#13
Farzaneh Kordbacheh, Connor H O'Meara, Lucy A Coupland, Patrick M Lelliott, Christopher R Parish
Extracellular histones have been shown to play an important pathogenic role in many diseases, primarily through their cytotoxicity towards nucleated cells and their ability to promote platelet activation with resultant thrombosis and thrombocytopenia. In contrast, little is known about the effect of extracellular histones on erythrocyte function. We demonstrate here that histones promote erythrocyte aggregation, sedimentation and, using a novel in vitro shear stress model, induce erythrocyte fragility and lysis in a concentration dependent manner...
November 13, 2017: Blood
https://www.readbyqxmd.com/read/29131889/poisson-contraction-and-fiber-kinematics-in-tissue-insight-from-collagen-network-simulations
#14
Catalin Picu, Sai Deogekar, Mohammad Islam
Connective tissue mechanics is highly non-linear, exhibits a strong Poisson effect and is associated with significant collagen fiber re-arrangement. Although the general features of the stress-strain behavior in tension and compression and under uniaxial, biaxial and shear loading have been discussed extensively, especially from the macroscopic perspective, the Poisson effect and the kinematics of filaments have received less attention. In general, the relationship between the microscopic fiber network mechanics and the macroscopic experimental observations remains poorly defined...
November 13, 2017: Journal of Biomechanical Engineering
https://www.readbyqxmd.com/read/29128350/biomechanical-behavior-of-adhesive-cement-layer-and-periodontal-tissues-on-the-restored-teeth-with-zirconia-rbfdps-using-three-kinds-of-framework-design-3d-fea-study
#15
Ayana Uraba, Reina Nemoto, Kosuke Nozaki, Tasuku Inagaki, Satoshi Omori, Hiroyuki Miura
PURPOSE: To investigate stress and strain concentrations on resin-bonded fixed dental prostheses (RBFDPs) frameworks of different design using finite element analysis. METHODS: A human dry skull was scanned and models were produced using three-dimensional printer. After abutment preparation, three frameworks, including a three-unit RBFDP, and two-unit cantilevered RBFDPs using #21 and #23 for the abutment tooth, were fabricated. Scanned data were subtracted to define boundary of each structure...
November 8, 2017: Journal of Prosthodontic Research
https://www.readbyqxmd.com/read/29128216/strain-hardening-and-anisotropy-in-tensile-fracture-properties-of-sheared-model-mozzarella-cheeses
#16
Prateek Sharma, Peter A Munro, Tzvetelin T Dessev, Peter G Wiles, E Allen Foegeding
We studied the tensile fracture properties of model Mozzarella cheeses with varying amounts of shear work input (3.3-73.7 kJ/kg). After manufacture, cheeses were elongated by manual rolling at 65°C followed by tensile testing at 21°C on dumbbell-shaped samples cut both parallel and perpendicular to the rolling direction. Strain hardening parameters were estimated from stress-strain curves using 3 different methods. Fracture stress and strain for longitudinal samples did not vary significantly with shear work input up to 26...
November 8, 2017: Journal of Dairy Science
https://www.readbyqxmd.com/read/29126223/atheroprone-flow-activates-inflammation-via-endothelial-atp-dependent-p2x7-p38-signalling
#17
Jack P Green, Celine Souilhol, Ioannis Xanthis, Laura Martinez-Campesino, Neil P Bowden, Paul C Evans, Heather L Wilson
Objective: Atherosclerosis is a focal disease occurring at arterial sites of disturbed blood flow that generates low oscillating shear stress. Endothelial inflammatory signalling is enhanced at sites of disturbed flow via mechanisms that are incompletely understood. The influence of disturbed flow on endothelial ATP receptors and downstream signalling was assessed. Methods and Results: Cultured human endothelial cells were exposed to atheroprotective (high uniform) or atheroprone (low oscillatory) shear stress for 72 hours prior to assessment of ATP responses...
November 6, 2017: Cardiovascular Research
https://www.readbyqxmd.com/read/29125824/intraluminal-valves-development-function-and-disease
#18
REVIEW
Xin Geng, Boksik Cha, Md Riaj Mahamud, R Sathish Srinivasan
The circulatory system consists of the heart, blood vessels and lymphatic vessels, which function in parallel to provide nutrients and remove waste from the body. Vascular function depends on valves, which regulate unidirectional fluid flow against gravitational and pressure gradients. Severe valve disorders can cause mortality and some are associated with severe morbidity. Although cardiac valve defects can be treated by valve replacement surgery, no treatment is currently available for valve disorders of the veins and lymphatics...
November 1, 2017: Disease Models & Mechanisms
https://www.readbyqxmd.com/read/29125641/assessing-the-impact-of-germination-and-sporulation-conditions-on-the-adhesion-of-bacillus-spores-to-glass-and-stainless-steel-by-fluid-dynamic-gauging
#19
Ke Xu Zhou, Nan Li, Graham Christie, D Ian Wilson
The adhesion of spores of 3 Bacillus species with distinctive morphologies to stainless steel and borosilicate glass was studied using the fluid dynamic gauging technique. Marked differences were observed between different species of spores, and also between spores of the same species prepared under different sporulation conditions. Spores of the food-borne pathogen B. cereus were demonstrated to be capable of withstanding shear stresses greater than 1500 Pa when adhered to stainless steel, in contrast to spores of Bacillus subtilis and Bacillus megaterium, which detached in response to lower shear stress...
November 2017: Journal of Food Science
https://www.readbyqxmd.com/read/29125372/matched-increases-in-cerebral-artery-shear-stress-irrespective-of-stimulus-induce-similar-changes-in-extra-cranial-arterial-diameter-in-humans
#20
Kurt J Smith, Ryan L Hoiland, Ryan Grove, Hamish McKirdy, Louise Naylor, Philip N Ainslie, Daniel J Green
The mechanistic role of arterial shear stress in the regulation of cerebrovascular responses to physiological stimuli (exercise and hypercapnia) is poorly understood. We hypothesised that, if shear stress is a key regulator of arterial dilation, then matched increases in shear, induced by distinct physiological stimuli, would trigger similar dilation of the large extra-cranial arteries. Participants ( n = 10) participated in three 30-min experimental interventions, each separated by ≥48 h: (1) mild-hypercapnia (FICO2:∼0...
January 1, 2017: Journal of Cerebral Blood Flow and Metabolism
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