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Shear force

Lucas Brely, Federico Bosia, Nicola M Pugno
Contact unit size reduction is a widely studied mechanism as a means to improve adhesion in natural fibrillar systems, such as those observed in beetles or geckos. However, these animals also display complex structural features in the way the contact is subdivided in a hierarchical manner. Here, we study the influence of hierarchical fibrillar architectures on the load distribution over the contact elements of the adhesive system, and the corresponding delamination behaviour. We present an analytical model to derive the load distribution in a fibrillar system loaded in shear, including hierarchical splitting of contacts, i...
June 20, 2018: Soft Matter
Ashley B Hodge, Matthew A Deitemyer, Victoria L Duffy, Dmitry Tumin, Dorothy A Garbin, Kathleen K Nicol, Don Hayes, Mary J Cismowski, Andrew R Yates
Hemolysis is a known consequence of extracorporeal membrane oxygenation (ECMO) resulting from shear force within the different components of the extracorporeal circuit. The primary aim of this study was to evaluate the EOS PMP™ oxygenator for generation of plasma free hemoglobin (PfHg) over 24 hours at nominal operating range flow rates. The EOS ECMO™ (LivaNova, Inc.; formerly Sorin, Arvada, CO) is equipped with a plasma tight polymethylpentene (PMP) hollow fiber oxygenator. We hypothesized that PfHg generation would be elevated in circuits with higher flow rates, because of the significant pressure drop across the oxygenator according to manufacturer provided flow charts...
June 2018: Journal of Extra-corporeal Technology
Stacey M Chin, Christopher V Synatschke, Shuangping Liu, Rikkert J Nap, Nicholas A Sather, Qifeng Wang, Zaida Álvarez, Alexandra N Edelbrock, Timmy Fyrner, Liam C Palmer, Igal Szleifer, Monica Olvera de la Cruz, Samuel I Stupp
Skeletal muscle provides inspiration on how to achieve reversible, macroscopic, anisotropic motion in soft materials. Here we report on the bottom-up design of macroscopic tubes that exhibit anisotropic actuation driven by a thermal stimulus. The tube is built from a hydrogel in which extremely long supramolecular nanofibers are aligned using weak shear forces, followed by radial growth of thermoresponsive polymers from their surfaces. The hierarchically ordered tube exhibits reversible anisotropic actuation with changes in temperature, with much greater contraction perpendicular to the direction of nanofiber alignment...
June 19, 2018: Nature Communications
Bryan L Benson, Lucy Li, Jay T Myers, R Dixon Dorand, Umut A Gurkan, Alex Y Huang, Richard M Ransohoff
Leukocyte adhesion and extravasation are maximal near the transition from capillary to post-capillary venule, and are strongly influenced by a confluence of scale-dependent physical effects. Mimicking the scale of physiological vessels using in vitro microfluidic systems allows the capture of these effects on leukocyte adhesion assays, but imposes practical limits on reproducibility and reliable quantification. Here we present a microfluidic platform that provides multiple (54-512) technical replicates within a 15-minute sample collection time, coupled with an automated computer vision analysis pipeline that captures leukocyte adhesion probabilities as a function of shear and extensional stresses...
June 19, 2018: Scientific Reports
Ming Liu, Anqiang Sun, Xiaoyan Deng
BACKGROUND AND AIMS: The crossed limbs stent graft technique is regularly employed to treat abdominal aortic aneurysm patients with unfavorable aneurysm necks or widely splayed common iliac arteries. This article numerically evaluates the hemodynamic performance of the crossed limbs strategy by analyzing numerical simulations and conducting experiments using two series of idealized bifurcated stent grafts with different cross angles and cross positions. RESULTS: Results demonstrated that the absolute helicity at outlets decreased with increased cross angles and increased with decreased cross positions...
June 19, 2018: Biomedical Engineering Online
Jeong-Min Lee, Jae-Yeon Hwang, Jihyun Bae, Mae Ran Kim, Yong-Woo Kim, Su Eun Park, Jeong A Yeom, Jieun Roh
Purpose: This study evaluated the feasibility of acoustic radiation force impulse (ARFI) elastography and characterized the sonographic features of lymph nodes (LNs) with Kikuchi disease in pediatric patients. Methods: Seventy-six cervical LN biopsies were performed for the diagnosis of cervical lymphadenopathy. ARFI imaging was performed, and the characteristic ultrasound features of the biopsied LNs and the contralateral LNs were analyzed. We also reviewed clinical and conventional ultrasonographic findings...
April 24, 2018: Ultrasonography
Janneke M Dickhout, J Mieke Kleijn, Rob G H Lammertink, Wiebe M de Vos
Adhesion of emulsified oil droplets to a surface plays an important role in processes such as crossflow membrane filtration, where the oil causes fouling. We present a novel technique, in which we study oil droplets on a model surface in a flow cell under shear force to determine the adhesive force between droplets and surface. We prepared an emulsion of hexadecane and used hydrophilic and hydrophobic glass slides as model surfaces. Different surfactants were used as emulsifiers: negatively charged sodium dodecyl sulphate (SDS), positively charged hexadecyltrimethylammonium bromide (CTAB) and nonionic Triton X-100...
June 18, 2018: Soft Matter
Vishal Metri, Ameur Louhichi, Jiajun Yan, Guilhem P Baeza, Krzysztof Matyjaszewski, Dimitris Vlassopoulos, Wim J Briels
The equilibrium mechanical properties of a cross-linked gel of telechelic star polymers are studied by rheology and Brownian dynamics simulations. The Brownian dynamics model consists of cores to which Rouse arms are attached. Forces between the cores are obtained from a potential of mean force model developed by Likos and co-workers. Both experimentally and in the simulations, networks were created by attaching sticker groups to the ends of the arms of the polymers, which were next allowed to form bonds among them in a one to one fashion...
April 24, 2018: Macromolecules
Jorien Claes, Bartosz Ditkowski, Laurens Liesenborghs, Tiago Rafael Veloso, Jose M Entenza, Philippe Moreillon, Thomas Vanassche, Peter Verhamme, Marc F Hoylaerts, Ruth Heying
Adhesion of Staphylococcus aureus to endothelial cells (ECs) is paramount in infective endocarditis. Bacterial proteins such as clumping factor A (ClfA) and fibronectin binding protein A (FnbpA) mediate adhesion to EC surface molecules and (sub)endothelial matrix proteins including fibrinogen (Fg), fibrin, fibronectin (Fn) and von Willebrand factor (vWF). We studied the influence of shear flow and plasma on the binding of ClfA and FnbpA (including its sub-domains A, A16+ , ABC, CD) to coverslip-coated vWF, Fg/fibrin, Fn or confluent ECs, making use of Lactococcus lactis , expressing these adhesins heterologously...
June 17, 2018: Thrombosis and Haemostasis
C C Santos, J Zhao, X Dong, S M Lonergan, E Huff-Lonergan, A Outhouse, K B Carlson, K J Prusa, C A Fedler, C Yu, S D Shackelford, D A King, T L Wheeler
The utility of Raman spectroscopic signatures of fresh pork loin (1 d & 15 d postmortem) in predicting fresh pork tenderness and slice shear force (SSF) was determined. Partial least square models showed that sensory tenderness and SSF are weakly correlated (R2  = 0.2). Raman spectral data were collected in 6 s using a portable Raman spectrometer (RS). A PLS regression model was developed to predict quantitatively the tenderness scores and SSF values from Raman spectral data, with very limited success...
May 29, 2018: Meat Science
Brendon Wahlberg, Harmanvir Ghuman, Jessie R Liu, Michel Modo
Intracerebral implantation of cell suspensions is finding its clinical translation with encouraging results in patients with stroke. However, the survival of cells in the brain remains poor. Although the biological potential of neural stem cells (NSCs) is widely documented, the biomechanical effects of delivering cells through a syringe-needle remain poorly understood. We here detailed the biomechanical forces (pressure, shear stress) that cells are exposed to during ejection through different sized needles (20G, 26G, 32G) and syringes (10, 50, 250 µL) at relevant flow rates (1, 5, 10 µL/min)...
June 15, 2018: Scientific Reports
A Tiwari, N Miyashita, N Espallargas, B N J Persson
There are two contributions to the friction force when a rubber block is sliding on a hard and rough substrate surface, namely, a contribution Fad = τf A from the area of real contact A and a viscoelastic contribution Fvisc from the pulsating forces exerted by the substrate asperities on the rubber block. Here we present experimental results obtained at different sliding speeds and temperatures, and we show that the temperature dependency of the shear stress τf , for temperatures above the rubber glass transition temperature Tg , is weaker than that of the bulk viscoelastic modulus...
June 14, 2018: Journal of Chemical Physics
Rijan Maharjan, Shomeek Mukhopadhyay, Benjamin Allen, Tobias Storz, Eric Brown
We experimentally characterize the impact response of concentrated suspensions consisting of cornstarch and water. We observe that the suspensions support a large normal stress-on the order of MPa-with a delay after the impactor hits the suspension surface. We show that neither the delay nor the magnitude of the stress can yet be explained by either standard rheological models of shear thickening in terms of steady-state viscosities, or impact models based on added mass or other inertial effects. The stress increase occurs when a dynamically jammed region of the suspension in front of the impactor propagates to the opposite boundary of the container, which can support large stresses when it spans between solid boundaries...
May 2018: Physical Review. E
Eva Kormanikova, Kamila Kotrasova
This article provides the useful data information on multiscale modeling of liquid storage laminated composite cylindrical tank under seismic load. The investigation process is divided into three levels. Within the numerical homogenization, the hexagonal microstructure one-eighth and full RVE model is assumed on micro-scale level. Homogenization of unidirectional lamina is done in four steps. For effective material properties of the whole laminate, the laminated representative volume element is assumed on meso-scale level...
June 2018: Data in Brief
Melis Goktas, Chuanfu Luo, Ruby May A Sullan, Ana E Bergues-Pupo, Reinhard Lipowsky, Ana Vila Verde, Kerstin G Blank
Coiled coils are important nanomechanical building blocks in biological and biomimetic materials. A mechanistic molecular understanding of their structural response to mechanical load is essential for elucidating their role in tissues and for utilizing and tuning these building blocks in materials applications. Using a combination of single-molecule force spectroscopy (SMFS) and steered molecular dynamics (SMD) simulations, we have investigated the mechanics of synthetic heterodimeric coiled coils of different length (3-4 heptads) when loaded in shear geometry...
May 28, 2018: Chemical Science
Yijue Diao, Rosa M Espinosa-Marzal
The friction between two adjacent tectonic plates under shear loading may dictate seismic activities. To advance the understanding of mechanisms underlying fault strength, we investigate the frictional characteristics of calcite in an aqueous environment. By conducting single-asperity friction experiments using an atomic force microscope, here we show three pathways of energy dissipation with increasing contact stresses: viscous shear of a lubricious solution film at low normal stresses; shear-promoted thermally activated slip, similar to dry friction but influenced by the hydrated ions localized at the interface; and pressure-solution facilitated slip at sufficiently high stresses and slow sliding velocities, which leads to a prominent decrease in friction...
June 13, 2018: Nature Communications
Rong-Guang Xu, Yongsheng Leng
The fundamental questions of how lubricant molecules organize into a layered structure under nanometers confinement and what is the interplay between layering and friction are still not well answered in the field of nanotribology. While the phase transition of lubricants during a squeeze-out process under compression is a long-standing controversial debate (i.e., liquid-like to solid-like phase transition versus amorphous glass-like transition), recent different interpretations to the stick-slip friction of lubricants in boundary lubrication present new challenges in this field...
June 13, 2018: Proceedings of the National Academy of Sciences of the United States of America
Xinyu Zhang, Qingmin Wang, Zhen Lyu, Xuehua Gao, Pengpeng Zhang, Haoming Lin, Yanrong Guo, Tianfu Wang, Siping Chen, Xin Chen
BACKGROUND: The pathological or physiological changes of a crystalline lens directly affect the eye accommodation and transmittance, and then they increase the risk of presbyopia and cataracts for people in the middle and old age groups. There is no universally accepted quantitative method to measure the lens' mechanical properties in vivo so far. This study aims to investigate the possibility of assessing the age-related stiffness change of crystalline lens by acoustic-radiation-force-based ultrasound elastography (ARF-USE) in a rabbit model in vivo...
June 13, 2018: Biomedical Engineering Online
X Li, Y Wang, Y Y Sun, D D Pan, J X Cao
In order to figure out the effect of ultrasound treatments (UT) on the tenderizing pathway of goose meat, breast muscles of 32 Eastern Zhejiang White Geese were treated with different ultrasound powers (the control, 300 and 600 W) at 40 kHz for 30 min. Shear force, cooking loss, myofibrillar fraction index (MFI), particle size, morphological analysis of actin filaments and the levels of F-actin and G-actin were investigated during 168 h storage. Results showed that 600 W group had the lowest shear force and cooking loss at 24, 48, 96 and 168 h among treatments, while 300 W UT decreased shear force and cooking loss compared to the control...
April 20, 2018: Poultry Science
A Orkusz
The objective of the work was to investigate the effect of modified atmosphere (MA) packaging (high oxygen modified atmosphere and vacuum) on pH, water holding capacity and cooking loss of raw goose meat, and on the sensory assessment and shear force of roasted meat. Samples refrigerated at 1°C were tested within 24 h after slaughter (unpacked meat) and on d 4, 7, 11, and 14 of storage (modified atmosphere or vacuum packed meat).The type of atmosphere used in packaging determined the functional properties of goose meat such as: pH, WHC, cooking loss and shear force...
April 20, 2018: Poultry Science
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