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Viscoelastic

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https://www.readbyqxmd.com/read/28345866/biocompatible-hydroxylated-boron-nitride-nanosheets-polyvinyl-alcohol-interpenetrating-hydrogels-with-enhanced-mechanical-and-thermal-responses
#1
Lin Jing, Hongling Li, Roland Yingjie Tay, Bo Sun, Siu Hon Tsang, Olivier Cometto, Jinjun Lin, Edwin Hang Tong Teo, Alfred Iing Yoong Tok
Polyvinyl alcohol (PVA) hydrogels with tissue-like viscoelasticity, excellent biocompatibility and high hydrophilicity have been considered as promising cartilage replacement materials. However, lack of sufficient mechanical properties is a critical barrier to their usage as load-bearing cartilage substitutes. Herein, we report hydroxylated boron nitride nanosheets (OH-BNNS)/PVA interpenetrating hydrogels by cyclically freezing/thawing the aqueous mixture of PVA and highly hydrophilic OH-BNNS (up to 0.6 mg/mL, two times the highest reported so far)...
March 27, 2017: ACS Nano
https://www.readbyqxmd.com/read/28343118/real-time-formation-of-salivary-films-onto-polymeric-materials-for-dental-applications-differences-between-unstimulated-and-stimulated-saliva
#2
Florian Weber, Alejandro Barrantes
The formation of salivary films onto oral prostheses materials is of central importance for understanding their performance and interaction with oral tissue and flora. The aim of this work was to study and compare the salivary films formed from unstimulated and stimulated whole saliva on two common polymeric materials, polycarbonate and poly(methyl methacrylate). Irradiating these materials with UV light is a simple way to modify their wettability, roughness and ζ-potential. Therefore, the effect of UV exposure of polycarbonate and poly(methyl methacrylate) on saliva adsorption was also investigated...
March 9, 2017: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/28342325/development-of-a-rapid-matrix-digestion-technique-for-ultrastructural-analysis-of-elastic-fibers-in-the-intervertebral-disc
#3
Javad Tavakoli, John J Costi
Collagen and elastic fibers are two major fibrous constituents of the annulus fibrosus (AF) in the disc that contribute to its mechanical and viscoelastic properties. It was thought that elastic fibers play no substantial role in the function and properties of the disc as these fibers were irregularly distributed. Studies that have revealed highly organized elastic fibers with different regional orientation and distribution, while being strongly crosslinked with matrix, suggesting their contribution to disc structure-function properties...
March 21, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28336857/linear-and-nonlinear-rheology-combined-with-dielectric-spectroscopy-of-hybrid-polymer-nanocomposites-for-semiconductive-applications
#4
Roland Kádár, Mahdi Abbasi, Roxana Figuli, Mikael Rigdahl, Manfred Wilhelm
The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate) (EBA) nanocomposite hybrids containing graphite nanoplatelets (GnP) and carbon black (CB). The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix...
January 24, 2017: Nanomaterials
https://www.readbyqxmd.com/read/28336026/viscoelastic-studies-effective-tools-for-trauma-and-surgical-resuscitation-efforts
#5
Dagoberto Salinas
Trauma-induced coagulopathy (TIC) is an abrupt disruption of all hemostatic components of coagulation resulting from severe tissue injury and hypoperfusion. The effective management of TIC has remained elusive to clinicians using traditional laboratory methods, challenging efforts to improve outcomes related to uncontrolled bleeding. Recent initiatives have aimed to reduce TIC-associated morbidity and mortality, further invoking trauma experts to explore innovative modalities in the field of viscoelastic studies, such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM)...
April 2017: AORN Journal
https://www.readbyqxmd.com/read/28332667/arrested-coalescence-of-viscoelastic-droplets-triplet-shape-and-restructuring
#6
Prerna Dahiya, Andrew DeBenedictis, Timothy J Atherton, Marco Caggioni, Stuart W Prescott, Richard W Hartel, Patrick T Spicer
The stability of shapes formed by three viscoelastic droplets during their arrested coalescence has been investigated using micromanipulation experiments. Addition of a third droplet to arrested droplet doublets is shown to be controlled by the balance between interfacial pressures driving coalescence and internal elasticity that resists total consolidation. The free fluid available within the droplets controls the transmission of stress during droplet combination and allows connections to occur via formation of a neck between the droplets...
March 23, 2017: Soft Matter
https://www.readbyqxmd.com/read/28330137/biotechnological-production-of-hyaluronic-acid-a-mini-review
#7
REVIEW
Jun Hui Sze, Jeremy C Brownlie, Christopher A Love
Hyaluronic acid (HA) is a polysaccharide found in the extracellular matrix of vertebrate epithelial, neural and connective tissues. Due to the high moisture retention, biocompatibility and viscoelasticity properties of this polymer, HA has become an important component of major pharmaceutical, biomedical and cosmetic products with high commercial value worldwide. Currently, large scale production of HA involves extraction from animal tissues as well as the use of bacterial expression systems in Streptococci...
June 2016: 3 Biotech
https://www.readbyqxmd.com/read/28326563/early-structural-and-functional-signature-of-3-day-human-skeletal-muscle-disuse-using-the-dry-immersion-model
#8
Rémi Demangel, Loïc Treffel, Guillaume Py, Thomas Brioche, Allan F Pagano, Marie-Pierre Bareille, Arnaud Beck, Laurence Pessemesse, Robin Candau, Claude Gharib, Angèle Chopard, Catherine Millet
Microgravity and hypoactivity are associated with skeletal muscle deconditioning. The decrease of muscle mass is an exponential decay with major changes in the first days. The purpose of the study was to dissect out the effects of a short-term 3-day dry immersion (DI) on human quadriceps muscle function and structure. The DI model, by suppressing all support zones, accurately reproduces the effects of microgravity. Twelve healthy volunteers (32 ± 5 yrs) completed 3 days of DI. Muscle function was investigated through maximal voluntary contraction (MVC) tests and muscle viscoelasticity...
March 22, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28324974/altered-viscoelastic-properties-of-stroke-affected-muscles-estimated-using-ultrasound-shear-waves-preliminary-data
#9
Ghulam Rasool, Allison B Wang, William Z Rymer, Sabrina S M Lee
As a result of a brain injury such as stroke, the skeletal muscles may undergo numerous structural and functional alterations. These abnormal changes are linked to muscle weakness, joint contracture, and abnormal muscle tone and eventually, result in motor impairment. A subset of these alterations affects passive muscle stiffness, i.e., viscoelastic properties. However, in vivo estimation of changes in viscoelastic properties is a challenging task. Here, we used the shear wave velocity, estimated through ultrasound SuperSonic imaging (SSI), as a surrogate for viscoelastic properties...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28323357/characterisation-of-clotting-factors-anticoagulant-protein-activities-and-viscoelastic-analysis-in-healthy-donkeys
#10
A Perez-Ecija, F J Mendoza
BACKGROUND: Studies have demonstrated differences in commonly measured hemostatic parameters between donkeys and horses. Whether clotting factors, anticoagulant protein activities and thromboelastography parameters also differ between species is still unknown. OBJECTIVES: To characterize hemostatic parameters in healthy donkeys and compare them to those of horses. STUDY DESIGN: Cross-sectional study. METHODS: Clotting Factors (V, VII, VIII, IX, X, XI and XII), and antithrombin III, Protein C and Protein S activities were measured in 80 healthy Andalusian and crossbred donkeys and 40 healthy Andalusian crossbred horses with assays based on human deficient plasmas...
March 21, 2017: Equine Veterinary Journal
https://www.readbyqxmd.com/read/28321914/a-compact-0-5%C3%A2-t-mr-elastography-device-and-its-application-for-studying-viscoelasticity-changes-in-biological-tissues-during-progressive-formalin-fixation
#11
Jürgen Braun, Heiko Tzschätzsch, Clara Körting, Angela Ariza de Schellenberger, Marika Jenderka, Toni Drießle, Michael Ledwig, Ingolf Sack
PURPOSE: To develop a method of compact tabletop magnetic resonance elastography (MRE) for rheological tests of tissue samples and to measure changes in viscoelastic powerlaw constants of liver and brain tissue during progressive fixation. METHODS: A 10-mm bore, 0.5-T permanent-magnet-based MRI system was equipped with a gradient-amplifier-controlled piezo-actuator and motion-sensitive spin echo sequence for inducing and measuring harmonic shear vibrations in cylindrical samples...
March 20, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28321450/ultrafast-pressure-sensing-with-transient-tunnelling-currents
#12
Ashok S Chauhan, Isaac Taylor-Harrod, Samuel D Littlejohn, Alain Nogaret
We report and systematically study large amplitude piezoresistance spikes in thin composite films under stress. These spikes are characterized by a unique double exponential decay which we demonstrate to be the signature of transient tunnelling currents. We establish an expression that predicts the dynamic conductivity of the composite with only three material parameters and use it to infer the magnitude of applied stress from resistance spikes, thus achieving quasi-instantaneous readout unhindered by viscoelastic relaxation...
March 21, 2017: Nanoscale
https://www.readbyqxmd.com/read/28317970/rheological-and-dynamic-insights-into-an-in-situ-reactive-interphase-with-graft-copolymers-in-multilayered-polymer-systems
#13
Bo Lu, Khalid Lamnawar, Abderrahim Maazouz
We provide rheological and dynamic insights into the role of an in situ reactive interphase with graft copolymers in multilayered polymer systems, using a polyamide-6 (PA6)/maleic anhydride grafted poly(vinylidene fluoride) (PVDF-g-MAH) bilayer as a model. Firstly, the influence of the reactive interphase on macroscopic melt flow behavior was studied. The in situ generated interphase from coupling reactions in bilayers significantly contributed to overall viscoelastic responses in both linear and nonlinear regimes...
March 20, 2017: Soft Matter
https://www.readbyqxmd.com/read/28317893/chemical-control-of-the-viscoelastic-properties-of-vinylogous-urethane-vitrimers
#14
Wim Denissen, Martijn Droesbeke, Renaud Nicolaÿ, Ludwik Leibler, Johan M Winne, Filip E Du Prez
Vinylogous urethane based vitrimers are polymer networks that have the intrinsic property to undergo network rearrangements, stress relaxation and viscoelastic flow, mediated by rapid addition/elimination reactions of free chain end amines. Here we show that the covalent exchange kinetics significantly can be influenced by combination with various simple additives. As anticipated, the exchange reactions on network level can be further accelerated using either Brønsted or Lewis acid additives. Remarkably, however, a strong inhibitory effect is observed when a base is added to the polymer matrix...
March 20, 2017: Nature Communications
https://www.readbyqxmd.com/read/28317718/effect-of-coacervation-conditions-on-the-viscoelastic-properties-of-n-o-carboxymethyl-chitosan-gum-arabic-coacervates
#15
Guo-Qing Huang, Yan-Li Du, Jun-Xia Xiao, Guan-Yun Wang
The effects of coacervation acidity, phase separation temperature, ionic strength, and biopolymer ratio on the viscoelasticity of the N,O-carboxymethyl chitosan (NOCC) - gum Arabic (GA) coacervate were investigated by using coacervate yield as the indicator of electrostatic interaction strength. The strongest interaction between NOCC and GA occurred at pH 3.0, whereas the highest modulus values were found in the coacervate separated at pH 6.0. The coacervate yield did not vary with phase separation temperature in the range 4-55°C, but the coacervate viscoelasticity declined as the temperature increased from 25°C to 45°C and then peaked at 55°C...
August 1, 2017: Food Chemistry
https://www.readbyqxmd.com/read/28303612/infant-skin-maturation-preliminary-outcomes-for-color-and-biomechanical-properties
#16
M O Visscher, S A Burkes, D M Adams, A M Hammill, R R Wickett
BACKGROUND: Newborn infant skin changes after birth but studies have focused on the epidermal barrier. Dermal properties are relevant for care, but literature on postnatal changes is sparse. We further characterized skin maturational changes in lightness, color and response to biomechanical stress. METHODS: Normal skin sites from subsets of participants in a trial on the progression and stage of infantile hemangiomas were retrospectively examined. Standardized photographs were analyzed as L*, a*, and b* images...
March 16, 2017: Skin Research and Technology
https://www.readbyqxmd.com/read/28302286/viscoelastic-hemostatic-assays-in-the-management-of-the-pediatric-trauma-patient
#17
Christine M Leeper, Barbara A Gaines
Viscoelastic hemostatic assays (VHA), such as TEG and ROTEM, are whole blood tests that depict functional coagulation both numerically and graphically. The development of rapid VHA technology, which allows for the first data points to result within minutes of test initiation, has increased the utility of these tests in the treatment of trauma patients. Both adult and pediatric centers have integrated VHAs into trauma resuscitation and transfusion protocols. Literature regarding the use of VHAs for injured children is limited...
February 2017: Seminars in Pediatric Surgery
https://www.readbyqxmd.com/read/28300744/a-modified-simple-technique-of-removing-the-lens-cortex-during-cataract-surgery
#18
Kyung Eun Han, Se Hoon Han, Dongkwon Lim, Min Chul Shin
We describe here a surgical technique of removing the remaining cortex after phacoemulsification without performing the conventional irrigation/aspiration (I/A) procedure. In this technique, the remaining cortex attached to the posterior capsule was separated and dissected into several pieces by continuous irrigation with balanced salt solution, which was supplied through a syringe attached to a bent, blunt-tip needle. Approximately, 10 s of manual irrigation separated most of the remaining cortex from the posterior capsule...
January 2017: Indian Journal of Ophthalmology
https://www.readbyqxmd.com/read/28299993/a-new-perspective-on-the-risk-of-hypercoagulopathy-in-ovarian-hyperstimulation-syndrome-using-thromboelastography
#19
Eyal Zohav, Benny Almog, Aviad Cohen, Ishai Levin, Varda Deutsch, Ariel Many, Ami Amit, Yoni Cohen
Thromboelastography (TEG) provides real-time assessment of hemostasis by measuring the viscoelastic properties, coagulation factor, and platelet activity in whole blood samples. In this prospective case-control study, we wanted to investigate whether blood clot formation assessment, using TEG, can identify a hypercoagulable state in women with severe ovarian hyperstimulation syndrome (OHSS). Thirty-six women who were hospitalized with severe OHSS were allocated to the OHSS group and 32 women undergoing controlled ovarian hyperstimulation but who did not develop OHSS were allocated to the control group...
January 1, 2017: Reproductive Sciences
https://www.readbyqxmd.com/read/28298678/effects-of-locust-bean-gum-on-the-structural-and-rheological-properties-of-resistant-corn-starch
#20
Raza Hussain, Ajaypal Singh, Hamed Vatankhah, Hosahalli S Ramaswamy
In this study, interactions between resistant corn starch (RS) (5% w/w) and locust bean gum (LBG) (0, 0.125, 0.25, 0.50 and 1.0% w/v) on the viscoelastic, pasting and morphological characteristics of aqueous dispersions were evaluated. Results showed that the storage modulus (G'), loss modulus (G''), and apparent viscosity values of starch/gum (RS/LBG) mixtures were enhanced with the addition of LBG, and the rheograms demonstrated a biphasic behavior. RS/LBG samples were predominantly either solid like (G' > G'') or viscous (G'' > G'), depending on the added concentration level of LBG...
March 2017: Journal of Food Science and Technology
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