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Shear stress

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https://www.readbyqxmd.com/read/28527299/role-of-pickering-stabilization-and-bulk-gelation-for-the-preparation-and-properties-of-solid-silica-foams
#1
I Lesov, S Tcholakova, M Kovadjieva, T Saison, M Lamblet, N Denkov
Foaming of particulate suspensions, followed by foam drying, is developed as an efficient method for production of highly porous materials with various applications. A key factor for success is the appropriate choice of surfactants which both modify the particle surface and stabilize the foam. Here we compare the efficiency of this method for silica suspensions containing two surfactants which lead to very different types of foam stabilization. Cationic TTAB leads to particle-stabilized foams (Pickering stabilization) whereas zwitterionic CAPB - to surfactant-stabilized foams...
May 12, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28527189/patient-specific-3-d-modeling-of-blood-flow-in-a-multi-stenosed-left-coronary-artery
#2
Sarfaraz Kamangar, Irfan Anjum Badruddin, N Ameer Ahamad, Manzoor Elahi M Soudagar, Kalimuthu Govindaraju, N Nik-Ghazali, N J Salman Ahmed, T M Yunus Khan
The current study investigates the effect of multi stenosis on the hemodynamic parameters such as wall pressure, velocity and wall shear stress in the realistic left coronary artery. Patients CT scan image data of normal and diseased left coronary artery was chosen for the reconstruction of 3D coronary artery models. The diseased 3D model of left coronary artery shows a narrowing of more than 70% and 80% of area stenosis (AS) at the left main stem (LMS) and left circumflex (LCX) respectively. The results show that the decrease in pressure was found downstream to the stenosis as compared to the coronary artery without stenosis...
2017: Bio-medical Materials and Engineering
https://www.readbyqxmd.com/read/28527110/a-review-of-the-hemodynamic-factors-believed-to-contribute-to-vascular-access-dysfunction
#3
Connor V Cunnane, Eoghan M Cunnane, Michael T Walsh
A vascular access (VA) is used to facilitate hemodialysis in patients that suffer from end-stage renal disease. However, they suffer from high failure rates due to non-maturation and venous stenosis, with intimal hyperplasia (IH) the underlying cause of both conditions. Abnormal hemodynamic profiles, which arise following VA creation, are believed to lead to the development of IH. However, the exact physiological response that initiates this process is unknown. This review evaluates the different hemodynamic parameters that are hypothesised to correlate with the development of IH...
May 19, 2017: Cardiovascular Engineering and Technology
https://www.readbyqxmd.com/read/28526627/dynamic-fatigue-measurement-of-human-erythrocytes-using-dielectrophoresis
#4
Yuhao Qiang, Jia Liu, E Du
Erythrocytes must undergo severe deformation to pass through narrow capillaries and submicronic splenic slits for several hundred thousand times in their normal lifespan. Studies of erythrocyte biomechanics have been mainly focused on cell deformability and rheology measured from a single application of stress and mostly under a static or quasi-static state using classical biomechanical techniques, such as optical tweezers and micropipette aspiration. Dynamic behavior of erythrocytes in response to cyclic stresses that contributes to the membrane failure in blood circulation is not fully understood...
May 16, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28525819/combination-of-flow-and-micropattern-alignment-affecting-flow-resistant-endothelial-cell-adhesion
#5
Xianghui Gong, Jie Yao, Hongping He, Xixi Zhao, Xiaoyi Liu, Feng Zhao, Yan Sun, Yubo Fan
Assuring cell adhesion to an underlying biomaterial surface under blood flow is vital to functional vascular grafts design. In vivo endothelial cells (ECs) are located under the microenvironment of both surface topography of the basement membrane and the mechanical loading resulting from blood flow. Both topographical and mechanical factors should thus be considered when designing vascular grafts to enhance the flow-resistant EC adhesion. This study aims to investigate effects of integrating biomaterial surface topography and flow on EC adhesion, which was a deficit in previous studies...
May 2, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28525548/computational-fluid-dynamics-characterization-of-pulsatile-flow-in-central-and-sano-shunts-connected-to-the-pulmonary-arteries-importance-of-graft-angulation-on-shear-stress-induced-platelet-mediated-thrombosis
#6
Robert Ascuitto, Nancy Ross-Ascuitto, Martin Guillot, Carey Celestin
OBJECTIVES: Central (aorta) and Sano (right ventricle)-to-pulmonary artery (PA) shunts, palliative operations for infants with complex heart defects, can develop life-threatening thrombosis. We employed computational fluid dynamics (CFD) to study pulsatile flow in these shunts, with the goal to identify haemodynamic characteristics conducive to thrombus formation. METHODS: CFD, using the finite volume method with cardiac catheterization data, and computer simulations, based on angiography, were employed to determine flow-velocity field, wall shear stress (WSS) profile and oscillatory shear index (OSI)...
May 19, 2017: Interactive Cardiovascular and Thoracic Surgery
https://www.readbyqxmd.com/read/28523446/in-vitro-quantification-of-luminal-denudation-after-crimping-and-balloon-dilatation-of-endothelialized-covered-stents
#7
Shigeo Ichihashi, Frederic Wolf, Thomas Schmitz-Rode, Kimihiko Kichikawa, Stefan Jockenhoevel, Petra Mela
PURPOSE: Covered stents have been demonstrated to reduce restenosis; however, the membrane's limited biocompatibility can still lead to thrombus formation. To obtain optimal surface hemocompatibility, endothelialization of the luminal surface has been proposed. However, the effect of delivery procedures, such as crimping and balloon dilatation, on the endothelial layer has not been quantified. This study investigated the impact of such procedures on endothelialized covered stents in vitro...
May 18, 2017: Cardiovascular and Interventional Radiology
https://www.readbyqxmd.com/read/28522896/shear-stress-counteracts-endothelial-cx3cl1-induction-and-monocytic-cell-adhesion
#8
Aaron Babendreyer, Lisa Molls, Daniela Dreymueller, Stefan Uhlig, Andreas Ludwig
Flow conditions critically regulate endothelial cell functions in the vasculature. Reduced shear stress resulting from disturbed blood flow can drive the development of vascular inflammatory lesions. On endothelial cells, the transmembrane chemokine CX3CL1/fractalkine promotes vascular inflammation by functioning as a surface-expressed adhesion molecule and by becoming released as soluble chemoattractant for monocytic cells expressing the receptor CX3CR1. Here, we report that endothelial cells from human artery, vein, or microvasculature constitutively express CX3CL1 when cultured under static conditions...
2017: Mediators of Inflammation
https://www.readbyqxmd.com/read/28518223/low-shear-stress-induces-endothelial-reactive-oxygen-species-via-the-at1r-enos-no-pathway
#9
Yuelin Chao, Peng Ye, Linlin Zhu, Xiangquan Kong, Xinliang Qu, Junxia Zhang, Jie Luo, Hongfeng Yang, Shaoliang Chen
Reactive oxygen species (ROS) contribute to many aspects of physiological and pathological cardiovascular processes. However, the underlying mechanism of ROS induction by low shear stress (LSS) remains unclear. Accumulating evidence has shown that the angiotensin II type 1 receptor (AT1R) is involved in inflammation, apoptosis, and ROS production. Our aim was to explore the role of AT1R in LSS-mediated ROS induction. We exposed human umbilical vein endothelial cells (HUVECs) to LSS (3 dyne/cm(2) ) for different periods of time...
May 18, 2017: Journal of Cellular Physiology
https://www.readbyqxmd.com/read/28517937/cellular-shuttles-monocytes-macrophages-exhibit-transendothelial-transport-of-nanoparticles-under-physiological-flow
#10
Thomas Moore, Daniel Hauser, Thomas Gruber, Barbara Rothen-Rutishauser, Marco Lattuada, Alke Petri-Fink, Ruth Lyck
A major hurdle in the development of biomedical nanoparticles (NP) is understanding how they interact with complex biological systems and navigate biological barriers to arrive at pathological targets. It is becoming increasingly evident that merely controlling particle physico-chemical properties may not be sufficient to mediate particle biodistribution in dynamic environments. Thus, researchers are increasingly turning towards more complex but likewise more physiological in vitro systems to study particle-cell/particle-system interactions...
May 18, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28515439/the-biomechanics-behind-extreme-osteophagy-in-tyrannosaurus-rex
#11
Paul M Gignac, Gregory M Erickson
Most carnivorous mammals can pulverize skeletal elements by generating tooth pressures between occluding teeth that exceed cortical bone shear strength, thereby permitting access to marrow and phosphatic salts. Conversely, carnivorous reptiles have non-occluding dentitions that engender negligible bone damage during feeding. As a result, most reptilian predators can only consume bones in their entirety. Nevertheless, North American tyrannosaurids, including the giant (13 metres [m]) theropod dinosaur Tyrannosaurus rex stand out for habitually biting deeply into bones, pulverizing and digesting them...
May 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28515328/mechanotransmission-in-endothelial-cells-subjected-to-oscillatory-and-multi-directional-shear-flow
#12
Mahsa Dabagh, Payman Jalali, Peter J Butler, Amanda Randles, John M Tarbell
Local haemodynamics are linked to the non-uniform distribution of atherosclerosic lesions in arteries. Low and oscillatory (reversing in the axial flow direction) wall shear stress (WSS) induce inflammatory responses in endothelial cells (ECs) mediating disease localization. The objective of this study is to investigate computationally how the flow direction (reflected in WSS variation on the EC surface over time) influences the forces experienced by structural components of ECs that are believed to play important roles in mechanotransduction...
May 2017: Journal of the Royal Society, Interface
https://www.readbyqxmd.com/read/28515175/role-for-reactive-oxygen-species-in-flow-stimulated-inner-medullary-collecting-duct-endothelin-1-production
#13
Will Wheatley, Donald E Kohan
Inner medullary collecting duct (IMCD)-derived endothelin-1 (ET-1) is stimulated by volume expansion, in part through augmented luminal flow, whereupon it can elicit natriuresis and diuresis. Since flow can alter nitric oxide (NO) and reactive oxygen species (ROS), both of which can affect collecting duct salt transport, we asked whether NO and/or ROS mediate flow-stimulated IMCD ET-1. Mouse IMCD3 cells were exposed to flow and ET-1/GAPDH mRNA assessed. A shear stress of 10 dyne/cm2 for 1 hr increased ET-1 mRNA by 4-fold compared to no flow (ET-1 flow response)...
May 17, 2017: American Journal of Physiology. Renal Physiology
https://www.readbyqxmd.com/read/28514440/extreme-hydrothermal-conditions-at-an-active-plate-bounding-fault
#14
Rupert Sutherland, John Townend, Virginia Toy, Phaedra Upton, Jamie Coussens, Michael Allen, Laura-May Baratin, Nicolas Barth, Leeza Becroft, Carolin Boese, Austin Boles, Carolyn Boulton, Neil G R Broderick, Lucie Janku-Capova, Brett M Carpenter, Bernard Célérier, Calum Chamberlain, Alan Cooper, Ashley Coutts, Simon Cox, Lisa Craw, Mai-Linh Doan, Jennifer Eccles, Dan Faulkner, Jason Grieve, Julia Grochowski, Anton Gulley, Arthur Hartog, Jamie Howarth, Katrina Jacobs, Tamara Jeppson, Naoki Kato, Steven Keys, Martina Kirilova, Yusuke Kometani, Rob Langridge, Weiren Lin, Timothy Little, Adrienn Lukacs, Deirdre Mallyon, Elisabetta Mariani, Cécile Massiot, Loren Mathewson, Ben Melosh, Catriona Menzies, Jo Moore, Luiz Morales, Chance Morgan, Hiroshi Mori, Andre Niemeijer, Osamu Nishikawa, David Prior, Katrina Sauer, Martha Savage, Anja Schleicher, Douglas R Schmitt, Norio Shigematsu, Sam Taylor-Offord, Damon Teagle, Harold Tobin, Robert Valdez, Konrad Weaver, Thomas Wiersberg, Jack Williams, Nick Woodman, Martin Zimmer
Temperature and fluid pressure conditions control rock deformation and mineralization on geological faults, and hence the distribution of earthquakes. Typical intraplate continental crust has hydrostatic fluid pressure and a near-surface thermal gradient of 31 ± 15 degrees Celsius per kilometre. At temperatures above 300-450 degrees Celsius, usually found at depths greater than 10-15 kilometres, the intra-crystalline plasticity of quartz and feldspar relieves stress by aseismic creep and earthquakes are infrequent...
May 17, 2017: Nature
https://www.readbyqxmd.com/read/28513889/mechanically-induced-bone-formation-is-not-sensitive-to-local-osteocyte-density-in-rat-vertebral-cancellous-bone
#15
Erin N Cresswell, Thu M Nguyen, Michael W Horsfield, Adrian J Alepuz, Thomas A Metzger, Glen L Niebur, Christopher J Hernandez
Osteocytes play an integral role in bone by sensing mechanical stimuli and releasing signaling factors that direct bone formation. The importance of osteocytes in mechanotransduction suggests that regions of bone tissue with greater osteocyte populations are more responsive to mechanical stimuli. To determine the effects of osteocyte population on bone functional adaptation we applied mechanical loads to the 8(th) caudal vertebra of skeletally mature female Sprague Dawley rats (6 months of age, n = 8 loaded, n = 8 sham controls)...
May 17, 2017: Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society
https://www.readbyqxmd.com/read/28513477/microtube-array-membrane-bioreactor-promotes-neuronal-differentiation-and-orientation
#16
Sabrina Morelli, Antonella Piscioneri, Simona Salerno, Chien-Chung Chen, Chee Ho Chew, Lidietta Giorno, Enrico Drioli, Loredana De Bartolo
An important challenge in neuronal tissue engineering is to create innovative tools capable of promoting cellular response in terms of neuronal differentiation and neurite orientation that may be used as investigational platforms for studying neurobiological events and neurodegenerative disorders. A novel membrane bioreactor was created to provide a 3D well-controlled microenvironment for neuronal outgrowth. The bioreactor consisted of poly-L-lactic acid highly aligned microtube array (PLLA-MTA) membranes assembled in parallel within a chamber that establish an intraluminal and an extraluminal compartment whose communication occurs through the pores of the MTA membrane walls...
May 17, 2017: Biofabrication
https://www.readbyqxmd.com/read/28512791/peptide-functionalized-fluorescent-particles-for-in-situ-detection-of-nitric-oxide-via-peroxynitrite-mediated-nitration
#17
Jason Y H Chang, Lesley W Chow, W Michael Dismuke, C Ross Ethier, Molly M Stevens, W Daniel Stamer, Darryl R Overby
Nitric oxide (NO) is a free radical signaling molecule that plays a crucial role in modulating physiological homeostasis across multiple biological systems. NO dysregulation is linked to the pathogenesis of multiple diseases; therefore, its quantification is important for understanding pathophysiological processes. The detection of NO is challenging, typically limited by its reactive nature and short half-life. Additionally, the presence of interfering analytes and accessibility to biological fluids in the native tissues make the measurement technically challenging and often unreliable...
May 17, 2017: Advanced Healthcare Materials
https://www.readbyqxmd.com/read/28512313/a-rapid-capillary-pressure-driven-micro-channel-to-demonstrate-newtonian-fluid-behavior-of-zebrafish-blood-at-high-shear-rates
#18
Juhyun Lee, Tzu-Chieh Chou, Dongyang Kang, Hanul Kang, Junjie Chen, Kyung In Baek, Wei Wang, Yichen Ding, Dino Di Carlo, Yu-Chong Tai, Tzung K Hsiai
Blood viscosity provides the rheological basis to elucidate shear stress underlying developmental cardiac mechanics and physiology. Zebrafish is a high throughput model for developmental biology, forward-genetics, and drug discovery. The micro-scale posed an experimental challenge to measure blood viscosity. To address this challenge, a microfluidic viscometer driven by surface tension was developed to reduce the sample volume required (3μL) for rapid (<2 min) and continuous viscosity measurement. By fitting the power-law fluid model to the travel distance of blood through the micro-channel as a function of time and channel configuration, the experimentally acquired blood viscosity was compared with a vacuum-driven capillary viscometer at high shear rates (>500 s(-1)), at which the power law exponent (n) of zebrafish blood was nearly 1 behaving as a Newtonian fluid...
May 16, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28512221/shear-bands-as-manifestation-of-a-criticality-in-yielding-amorphous-solids
#19
Giorgio Parisi, Itamar Procaccia, Corrado Rainone, Murari Singh
Amorphous solids increase their stress as a function of an applied strain until a mechanical yield point whereupon the stress cannot increase anymore, afterward exhibiting a steady state with a constant mean stress. In stress-controlled experiments, the system simply breaks when pushed beyond this mean stress. The ubiquity of this phenomenon over a huge variety of amorphous solids calls for a generic theory that is free of microscopic details. Here, we offer such a theory: The mechanical yield is a thermodynamic phase transition, where yield occurs as a spinodal phenomenon...
May 16, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28508133/children-and-adolescents-macrovascular-reactivity-level-and-dynamics-but-not-the-microvascular-response-is-associated-with-body-mass-index-and-arterial-stiffness-levels
#20
Yanina Zócalo, Marco Marotta, Victoria García-Espinosa, Santiago Curcio, Pedro Chiesa, Gustavo Giachetto, Daniel Bia
INTRODUCTION: The existing evidence indicates that primary prevention of atherosclerotic disease should begin in childhood. Detection of children and adolescents at risk for atherosclerosis may allow early intervention to decrease the atherosclerotic process, thereby preventing or delaying cardiovascular disease. Vascular reactivity (VR) is altered even by early atherosclerosis. Obesity is a main cardiovascular risk factor (CVRF) observed in childhood. If childhood obesity associates impaired macro and/or micro VR is controversial...
May 15, 2017: High Blood Pressure & Cardiovascular Prevention: the Official Journal of the Italian Society of Hypertension
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