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Pauline Videcoq, Adelin Barbacci, Carole Assor, Vincent Magnenet, Olivier Arnould, Sophie Le Gall, Marc Lahaye
The viscoelastic mechanical properties of water-rich plant tissues are fundamental for many aspects of organ physiology and plant functioning. These properties are determined partly by the water in cellular vacuole and partly by the mechanical properties of the cell wall, the latter varying according to the composition and organization of its polysaccharides. In this study, relationships between the viscoelastic properties of apple cortex parenchyma tissue and cell wall pectin, hemicelluloses, and cellulose structures were studied by infusing the tissue with selected sets of purified enzymes in a controlled osmoticum...
September 23, 2017: Journal of Experimental Botany
Owain Thomas, Emanuel Lybeck, Per Flisberg, Ulf Schött
BACKGROUND: Epidural anaesthesia and analgesia are indicated for oesophageal surgery. A rare but serious complication is spinal haematoma, which can occur on insertion, manipulation or withdrawal of catheters. Evidence and guidelines are vague regarding which tests are appropriate and how to interpret their results. We aimed to describe how routine coagulation test results change during oesophagectomy's perioperative course. METHODS: Following ethical approval, we retrospectively identified patients who had undergone oesophagectomy between 2002 and 2012...
2017: Perioperative Medicine
Lihua Lin, Mingyue Shen, Suchen Liu, Wei Tang, Zhijun Wang, Mingyong Xie, Jianhua Xie
Polysaccharide from Mesona chinensis is becoming increasingly attractive focus because of its gelling property and biological activities. In this study, the rheological properties of an acidic heteropolysaccharide from Mesona chinensis (MCP) were investigated in dilute and semidilute solutions. Dynamic rheology was systematically conducted to investigate the effects of concentration, temperature, pH values, salts and freeze-thaw variations on the rheological properties of MCP. Results showed that the rheological properties of MCP exhibited pseudoplastic characteristic and "gel-like" behaviour by the flow behavior detection...
October 12, 2017: International Journal of Biological Macromolecules
Sami Saadi, Nazamid Saari, Abdulkarim Sabo Mohammed, Hasanah Mohd Ghazali, Farooq Anwar
Cell impurities are an emerging nucleating molecular barriers having the capability in disordering the metabolic chain reactions of proteolysis, glycolysis and lipolysis. Their massive effects induced by copolymer crystal growth in compaction with metal and mineral transients are extended as well as in damaging DNA and mRNA structure motif and other molecular assembly e.g. histones structure unites. Their polycrystalline packing modes, polydispersity and their tendency to surface and interface adhesion prompted us in structuring scaffold biomaterials enriched with biopeptides, layered by phospho-glycerides ester-forms...
October 11, 2017: Journal of Controlled Release: Official Journal of the Controlled Release Society
Hamed Helisaz, Mohammad Hassan Saidi, Arman Sadeghi
The viscoelasticity effects on the reaction-diffusion rates in a Y-shaped microreactor are studied utilizing the PTT rheological model. The flow is assumed to be fully developed and considered to be created under a combined action of electroosmotic and pressure forces. In general, finite-volume-based numerical simulations are conducted to handle the problem; however, analytical solutions based on the depthwise averaging approach are also obtained for the case for which there is no reaction between the inlet components...
October 16, 2017: Analytica Chimica Acta
Sachi Koitani, Sonja Dieterich, Natalie Preisig, Kenji Aramaki, Cosima Stubenrauch
Does the presence of a gel network influence the properties of a lyotropic liquid crystal? Does the replacement of oil by a lyotropic liquid crystal influence the properties of an organogel? To answer these questions we study gelled lyotropic liquid crystals (LLC). In the present study we show that it is possible to gel the lamellar phase of the binary system water-didodecyl dimethylammonium bromide (2C12DAB) with the organogelator 12-hydroxyoctadecanoic acid (12-HOA). We compare various properties of the gelled LLC phases with the "parent systems", i...
October 13, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Fuat H Saner, Lasitha Abeysundara, Matthias Hartmann, Susan V Mallett
For over 50 years patients with liver cirrhosis were considered to be at markedly increased risk of bleeding. This dogma was seemingly supported by abnormalities in standard laboratory tests (SLTs), such as the prothrombin time, that were interpreted as indicating a bleeding diathesis. However, publications from the last decade have revealed SLTs to be poor predictors of bleeding and it is now understood that stable patients with cirrhosis have a rebalanced haemostatic system and preserved thrombin generation...
October 12, 2017: Minerva Anestesiologica
Hanifeh Khayyeri, Parmis Blomgran, Malin Hammerman, Mikael J Turunen, Annika Löwgren, Manuel Guizar-Sicairos, Per Aspenberg, Hanna Isaksson
Tendon function and homeostasis rely on external loading. This study investigates the biological mechanisms behind tendon biomechanical function and how the mechanical performance is affected by reduced daily loading. The Achilles tendons of 16 weeks old female Sprague Dawley rats (n = 40) were unloaded for 5 weeks by inducing muscle paralysis with botulinum toxin injections in the right gastrocnemius and soleus muscles. The contralateral side was used as control. After harvest, the tendons underwent biomechanical testing to assess viscoelasticity (n = 30 rats) and small angle X-ray scattering to determine the structural properties of the collagen fibrils (n = 10 rats)...
October 12, 2017: Scientific Reports
Chae Bin Kim, Ki-Beom Jeong, Beom Joo Yang, Jong-Won Song, Bon Cheol Ku, Seunghyun Lee, Seung Ki Lee, Chiyoung Park
We herein report a facile, cost-competitive, and scalable method for producing viscoelastic conductors via one-pot melt-blending using polymers and supramolecular gels composed of carbon nanotubes (CNTs), diphenylamine (DP), and benzophenone (BP). When mixed, a non-volatile eutectic liquid (EL) produced by simply blending DP with BP (1:1 molar ratio) enabled not only the gelation of CNTs (EL-CNTs) but also the dissolution of a number of commodity polymers. In order to take these advantages, viscoelastic conductors were produced via one-pot melt-blending the EL and CNTs with a model thermoplastic elastomer, poly(styrene-b-butadiene-b-styrene) (SBS, styrene 30 wt%)...
October 10, 2017: Angewandte Chemie
Michel E Safar
In patients with uncomplicated essential hypertension, cardiac output remains within normal ranges and intravascular volume is normal or low, assuming the presence of a sufficient Windkessel effect and usual resistance and compliance calculations. However, mean circulatory pressure is elevated in these patients. In addition, vascular resistance is augmented, and most importantly, the viscoelasticity of the cardiovascular system is substantially impaired. Such considerations are essential to understanding the mechanisms behind carotid-femoral arterial stiffness, a major risk factor in individuals with hypertension...
October 12, 2017: Nature Reviews. Cardiology
Bram Schroyen, James W Swan, Peter Van Puyvelde, Jan Vermant
An important parameter for the performance of nanomaterials is the degree by which the nanoparticles are dispersed in a matrix. Optical microscopy or scattering methods are useful to characterise the state of dispersion, but are not generally applicable to all materials. Electron microscopy methods are laborious in preparation and typically offer only quantitative information on a very local scale. In the present work we investigate how high frequency rheological measurements can be used for partially dispersed suspensions at intermediate to higher particle loadings, even for high viscous matrices...
October 12, 2017: Soft Matter
V H Giang Phan, Thavasyappan Thambi, Bong Sup Kim, Dai Phu Huynh, Doo Sung Lee
Stimuli-responsive hydrogels, known as smart hydrogels, are three-dimensional amphiphilic or hydrophilic polymer networks that are able to change their volume or phase, and other properties, including viscosity, structure, and dimension, in response to changes in pH, temperature, and magnetic or electric field. Highly swellable, dual-responsive bovine serum albumin (BSA)-based injectable hydrogels are prepared here by the chemical conjugation of pH- and temperature-responsive oligo(sulfamethazine acrylate-co-N-isopropylacrylamide) (oligo(SMA-co-NIPAM)) copolymers on the surface of BSA through carbodiimide-mediated chemistry...
October 11, 2017: Biomaterials Science
Veena T Kelleppan, Jackson E Moore, Thomas M McCoy, Anna V Sokolova, Liliana de Campo, Brendan Luke Wilkinson, Rico F Tabor
Long-chain amidopropyl betaines are known for their ability to self-assemble into viscoelastic wormlike micellar structures. Here, we explore the effect of tail-group molecular architecture on this process, comparing five molecules, each with C18 chains but different levels of unsaturation and branching. The surfactants are synthesised from stearic, oleic, linoleic, linolenic and isostearic acids. The self-assembly of these molecules in aqueous solutions is explored using small- and ultra-small-angle neutron scattering (SANS and USANS)...
October 10, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Matthew C Murphy, John Huston, Richard L Ehman
Magnetic resonance elastography (MRE) is an imaging technique for noninvasively and quantitatively assessing tissue stiffness, akin to palpation. MRE is further able assess the mechanical properties of tissues that cannot be reached by hand including the brain. The technique is a three-step process beginning with the introduction of shear waves into the tissue of interest by applying an external vibration. Next, the resulting motion is imaged using a phase-contrast MR pulse sequence with motion encoding gradients that are synchronized to the vibration...
October 6, 2017: NeuroImage
Hao Wu, Yupan Shang, Jiaqing Zhang, Lek Hang Cheang, Xiaoli Zeng, Mei Tu
Physical properties of extracellular matrix, including elasticity and microstructure, have been considered as important factors inducing stem cell differentiation. This study developed a novel type of liquid crystal-based matrix by combining the elastic property of polyurethane with viscoelastic liquid crystal to generate a soft elastic response resembling physical microenvironment of stem cell niche, and explored the mechano-driving cell behaviors. Addition of varying liquid crystal concentration (10 wt%, 30 wt% and 50 wt%) had great effects on surface morphology and elastic modulus of liquid crystal/ polyurethane composite substrates...
October 2017: Journal of Biomaterials Applications
Chantelle Venter, Hester Magdalena Oberholzer, Janette Bester, Mia-Jeanne van Rooy, Megan Jean Bester
BACKGROUND/AIMS: Heavy metal pollution is increasing in the environment, contaminating water, food and air supplies. This can be linked to many anthropogenic activities. Heavy metals are absorbed through the skin, inhalation and/or orally. Irrespective of the manner of heavy metal entry in the body, the blood circulatory system is potentially the first to be affected following exposure and adverse effects on blood coagulation can lead to associated thrombotic disease. Although the plasma levels and the effects of cadmium (Cd) and chromium (Cr) on erythrocytes and lymphocytes have been described, the environmental exposure to heavy metals are not limited to a single metal and often involves metal mixtures, with each metal having different rates of absorption, different cellular, tissue, and organ targets...
October 9, 2017: Cellular Physiology and Biochemistry
Sana Waheed, Annabel L Butcher, Michelle L Oyen
Native biological tissues are viscoelastic materials that undergo time-dependent loading in vivo. It is therefore crucial to ensure that biomedical materials have a suitable viscoelastic response for a given application. In this study, the viscoelastic properties of electrospun poly(vinyl alcohol) are investigated using tensile load relaxation testing. A five-parameter generalised Maxwell constitutive model is found to characterise the experimental response. The effect of polymer concentration and electrospinning voltage on model parameters is investigated in detail...
September 23, 2017: Journal of the Mechanical Behavior of Biomedical Materials
Bishnu P Khanal, Moritz Knoche
Cuticles envelope primary surfaces of the above-ground portion of plants. They function as barriers to water movement and to gas exchange, and in pathogen defense. To serve as a barrier on growing organs, cuticles must remain intact but at the same time must accommodate ongoing growth. Minimizing cuticle failure has stimulated significant research on the cuticle's mechanical properties. The objective here is to review the literature on the mechanical properties of isolated fruit and leaf cuticles. Cuticles are viscoelastic polymers...
September 13, 2017: Journal of Experimental Botany
Lynne E Bilston
Magnetic resonance elastography and related shear wave ultrasound elastography techniques can be used to estimate the mechanical properties of soft tissues in vivo by using the relationships between wave propagation and the elastic properties of materials. These techniques have found numerous clinical and research applications, tracking changes in tissue properties as a result of disease or other interventions. Most dynamic elastography approaches estimate tissue elastic (or viscoelastic) properties from a simplified version of the equations for the propagation of acoustic waves through a homogeneous linear (visco)elastic medium...
October 9, 2017: NMR in Biomedicine
Nan Xiang, Zhonghua Ni, Hong Yi
Herein, we proposed a strategy for controlling the particle focusing position in Dean-coupled elasto-inertial flows via adjusting the polymer concentration of viscoelastic fluids. The physics behind the control strategy was then explored and discussed. At high polymer concentrations, the flowing particles could be single-line focused exactly at the channel centerline under the dominated elastic force. The center-line focusing in our spiral channel may employed as a potential pretreatment scheme for microflow cytometry detection...
October 9, 2017: Electrophoresis
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