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Viscoelastic

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https://www.readbyqxmd.com/read/28535348/coarse-grained-modeling-of-polyethylene-melts-effect-on-dynamics
#1
Brandon L Peters, K Michael Salerno, Anupriya Agrawal, Dvora Perahia, Gary S Grest
The distinctive viscoelastic behavior of polymers results from a coupled interplay of motion on multiple length and time scales. Capturing the broad time and length scales of polymer motion remains a challenge. Using polyethylene (PE) as a model macromolecule, we construct coarse-grained (CG) models of PE with 3-6 methyl groups per CG bead and probe two critical aspects of the technique: pressure corrections required after iterative Boltzmann inversion (IBI) to generate CG potentials that match the pressure of reference fully-atomistic melt simulations and the transferability of CG potentials across temperatures...
May 23, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28534049/bio-inspired-metal-coordinate-hydrogels-with-programmable-viscoelastic-material-functions-controlled-by-longwave-uv-light
#2
Scott C Grindy, Niels Holten-Andersen
Control over the viscoelastic mechanical properties of hydrogels intended for use as biomedical materials has long been a goal of soft matter scientists. Recent research has shown that materials made from polymers with reversibly associating transient crosslinks are a promising strategy for controlling viscoelasticity in hydrogels, for example leading to systems with precisely tunable mechanical energy-dissipation. We and others have shown that bio-inspired histidine:transition metal ion complexes allow highly precise and tunable control over the viscoelastic properties of transient network hydrogels...
May 23, 2017: Soft Matter
https://www.readbyqxmd.com/read/28532876/treatment-of-the-scar-after-arthroscopic-surgery-on-a-knee
#3
Jacobo Alvira-Lechuz, Mercedes Roca Espiau, Elena Alvira-Lechuz
The aim of this paper is to present a treatment for scars based on percutaneous traction. This is a structural technique in which movements are performed against the barriers detected in different planes. The stages of this technique are described in detail along with the results after applying it to a postarthroscopic scar on a knee. The active and passive mobility of femoro-tibial and femoro-patellar articulations improved substantially after the treatment, as verified by signs such as pain relief, greater flexibility, disappearance of inflammation and a major recovery of tissue elasticity...
April 2017: Journal of Bodywork and Movement Therapies
https://www.readbyqxmd.com/read/28531978/quasi-static-and-ratcheting-properties-of-trabecular-bone-under-uniaxial-and-cyclic-compression
#4
Li-Lan Gao, Chao-Lei Wei, Chun-Qiu Zhang, Hong Gao, Nan Yang, Li-Min Dong
The quasi-static and ratcheting properties of trabecular bone were investigated by experiments and theoretical predictions. The creep tests with different stress levels were completed and it is found that both the creep strain and creep compliance increase rapidly at first and then increase slowly as the creep time goes by. With increase of compressive stress the creep strain increases and the creep compliance decreases. The uniaxial compressive tests show that the applied stress rate makes remarkable influence on the compressive behaviors of trabecular bone...
August 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28523375/a-model-for-one-dimensional-morphoelasticity-and-its-application-to-fibroblast-populated-collagen-lattices
#5
Shakti N Menon, Cameron L Hall, Scott W McCue, D L Sean McElwain
The mechanical behaviour of solid biological tissues has long been described using models based on classical continuum mechanics. However, the classical continuum theories of elasticity and viscoelasticity cannot easily capture the continual remodelling and associated structural changes in biological tissues. Furthermore, models drawn from plasticity theory are difficult to apply and interpret in this context, where there is no equivalent of a yield stress or flow rule. In this work, we describe a novel one-dimensional mathematical model of tissue remodelling based on the multiplicative decomposition of the deformation gradient...
May 18, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28522144/viscoelastic-tissue-plasminogen-activator-challenge-predicts-massive-transfusion-in-15-minutes
#6
Hunter B Moore, Ernest E Moore, Michael P Chapman, Benjamin R Huebner, Peter M Einersen, Solimon Oushy, Christopher C Silliman, Anirban Banerjee, Angela Sauaia
BACKGROUND: Coagulopathy is associated with massive transfusion in trauma, yet most clinical scores to predict this end point do not incorporate coagulation assays. Previous work has identified that shock increases circulating tissue plasminogen activator (tPA). When tPA levels saturate endogenous inhibitors, systemic hyperfibrinolysis can occur. Therefore, the addition of tPA to a patient's blood sample could stratify a patients underlying degree of shock and early coagulation changes to predict progression to massive transfusion...
April 17, 2017: Journal of the American College of Surgeons
https://www.readbyqxmd.com/read/28521987/coffee-grounds-as-filler-for-pectin-green-composites-with-competitive-performances-dependent-on-the-uv-irradiation
#7
Vincenzo Alessandro Cataldo, Giuseppe Cavallaro, Giuseppe Lazzara, Stefana Milioto, Filippo Parisi
Novel composite bioplastics were successfully prepared by filling pectin matrix with treated coffee grounds. The amount of coffee dispersed into the pectin was changed within a wide filler range. The morphology of the pectin/coffee hybrid films was studied by microscopic techniques in order to investigate their mesoscopic structure as well as the sizes distribution of the particles dispersed into the matrix. The micrographs showed that the coffee grounds are uniformly dispersed within the polymeric matrix. The morphological characteristics of the biocomposite films were correlated to their properties, such as wettability, water uptake, thermal behavior and mechanical performances...
August 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28521984/rheological-properties-of-gels-formed-by-physical-interactions-between-hyaluronan-and-cationic-surfactants
#8
Tereza Venerová, Miloslav Pekař
The aim of this paper is the rheological characterization of the concentrated, gel-like phase, which arises from mixed solutions of sodium hyaluronate and oppositely charged surfactant above its critical micellar concentration. The effects of hyaluronan molecular weight (from 300 to 2kDa) and the concentration of initial solutions (0.5 and 2% for hyaluronan, 50 or 200mM for surfactant) were investigated. All systems demonstrated viscoelastic properties which can be modified over a broad range of several decades of both storage and loss moduli by the hyaluronan molecular weight and initial concentrations...
August 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28521803/physical-interface-dynamics-alter-how-robotic-exosuits-augment-human-movement-implications-for-optimizing-wearable-assistive-devices
#9
Matthew B Yandell, Brendan T Quinlivan, Dmitry Popov, Conor Walsh, Karl E Zelik
BACKGROUND: Wearable assistive devices have demonstrated the potential to improve mobility outcomes for individuals with disabilities, and to augment healthy human performance; however, these benefits depend on how effectively power is transmitted from the device to the human user. Quantifying and understanding this power transmission is challenging due to complex human-device interface dynamics that occur as biological tissues and physical interface materials deform and displace under load, absorbing and returning power...
May 18, 2017: Journal of Neuroengineering and Rehabilitation
https://www.readbyqxmd.com/read/28520734/interfacial-mechanisms-for-stability-of-surfactant-laden-films
#10
M Saad Bhamla, Chew Chai, Marco A Àlvarez-Valenzuela, Javier Tajuelo, Gerald G Fuller
Thin liquid films are central to everyday life. They are ubiquitous in modern technology (pharmaceuticals, coatings), consumer products (foams, emulsions) and also serve vital biological functions (tear film of the eye, pulmonary surfactants in the lung). A common feature in all these examples is the presence of surface-active molecules at the air-liquid interface. Though they form only molecular-thin layers, these surfactants produce complex surface stresses on the free surface, which have important consequences for the dynamics and stability of the underlying thin liquid film...
2017: PloS One
https://www.readbyqxmd.com/read/28520431/anomalous-behavior-of-ultra-low-amplitude-capillary-waves-a-glimpse-of-the-viscoelastic-properties-of-interfacial-water
#11
Antonio Raudino, Domenica Raciti, Mario Corti
We investigate, both theoretically and by a differential interferometric technique, the behavior of large-wavelength capillary waves (of order of 10^-4 m) selectively excited at the surface of drops and bubbles with typical eigenfrequencies of order of 10^2 Hz. The resonance peaks of gas bubbles or hydrocarbon drops in water (radius less than 1 mm) highlight anomalously small dissipation in the region of ultra-low (sub-nanometric) oscillation amplitudes, reaching a plateau at higher amplitudes. This is in sharp contrast to the usual oscillating systems, where an anomalous behavior holds at large amplitudes alone...
May 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28520166/operator-based-variability-of-equine-thromboelastography
#12
Kristen Thane, Daniela Bedenice, Ana Pacheco
OBJECTIVE: To determine the extent of intraoperator (between duplicate samples) and interoperator (between different operators) variability in equine thromboelastography (TEG). DESIGN: Kaolin-activated TEG was performed in duplicate by operator-pair A/B or A/C (2 groups of 10 horses) using discrete setups, within 30-45 minutes of vacuum-assisted blood collection. Recorded TEG variables included clot initiation time (R), clot formation time (K), rate of clot formation (α), clot strength (MA), and viscoelastic/shear strength (G)...
May 18, 2017: Journal of Veterinary Emergency and Critical Care
https://www.readbyqxmd.com/read/28515328/mechanotransmission-in-endothelial-cells-subjected-to-oscillatory-and-multi-directional-shear-flow
#13
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/28511122/robotic-assessment-of-neuromuscular-characteristics-using-musculoskeletal-models-a-pilot-study
#14
V R Jayaneththi, J Viloria, L G Wiedemann, C Jarrett, A J McDaid
OBJECTIVE: Non-invasive neuromuscular characterization aims to provide greater insight into the effectiveness of existing and emerging rehabilitation therapies by quantifying neuromuscular characteristics relating to force production, muscle viscoelasticity and voluntary neural activation. In this paper, we propose a novel approach to evaluate neuromuscular characteristics, such as muscle fiber stiffness and viscosity, by combining robotic and HD-sEMG measurements with computational musculoskeletal modeling...
May 10, 2017: Computers in Biology and Medicine
https://www.readbyqxmd.com/read/28509781/correction-of-severe-coagulopathy-and-hyperfibrinolysis-by-tranexamic-acid-and-recombinant-factor-viia-in-a-cirrhotic-patient-after-trauma-a-case-report
#15
Jack Louro, Katherine Andersen, Roman Dudaryk
Coagulopathy induced by trauma or cirrhosis is a well-recognized entity. Viscoelastic testing has been used in either condition for goal-directed transfusion and detection of fibrinolysis since conventional coagulation tests do not correlate with clinical risk of bleeding. Hemostatic resuscitation may not be adequate for a trauma patient with liver disease due to complex alterations in coagulation systems and occasionally require adjuvant therapy. We report a case of trauma-induced coagulopathy presenting as severe hyperfibrinolysis in a cirrhotic patient who was refractory to hemostatic resuscitation but was rapidly corrected by the administration of tranexamic acid and recombinant Factor VIIa...
May 12, 2017: A & A Case Reports
https://www.readbyqxmd.com/read/28509684/histone-complexed-dna-fragments-levels-are-associated-with-coagulopathy-endothelial-cell-damage-and-increased-mortality-after-severe-pediatric-trauma
#16
Robert T Russell, Sarah C Christiaans, Tate Nice, Morgan Banks, Vincent Mortellaro, Charity Morgan, Amy Duhachek-Stapelman, Steven J Lisco, Jeffrey D Kerby, Brant M Wagener, Mike K Chen, Jean-François Pittet
BACKGROUND: The release of damage-associated molecular pattern molecules (DAMPs) in the extracellular space secondary to injury has been shown to cause systemic activation of the coagulation system and endothelial cell damage. We hypothesized that pediatric trauma patients with increased levels of histone-complexed DNA fragments (hcDNA) would have evidence of coagulopathy and endothelial damage that would be associated with poor outcomes. METHODS: We conducted a prospective observational study of 149 pediatric trauma patients and 62 control patients at two level 1 pediatric trauma centers from 2013-2016...
May 15, 2017: Shock
https://www.readbyqxmd.com/read/28505719/active-rotational-and-translational-microrheology-beyond-the-linear-spring-regime
#17
Lachlan J Gibson, Shu Zhang, Alexander B Stilgoe, Timo A Nieminen, Halina Rubinsztein-Dunlop
Active particle tracking microrheometers have the potential to perform accurate broadband measurements of viscoelasticity within microscopic systems. Generally, their largest possible precision is limited by Brownian motion and low frequency changes to the system. The signal to noise ratio is usually improved by increasing the size of the driven motion compared to the Brownian as well as averaging over repeated measurements. New theory is presented here whereby error in measurements of the complex shear modulus can be significantly reduced by analyzing the motion of a spherical particle driven by nonlinear forces...
April 2017: Physical Review. E
https://www.readbyqxmd.com/read/28505594/the-rheological-behavior-of-a-fast-setting-calcium-phosphate-bone-cement-and-its-dependence-on-deformation-conditions
#18
Erdem Şahin, Dilhan M Kalyon
Calcium phosphate cements are osteoconductive biomaterials that are widely used for bone repair and regeneration applications, including spinal fusion, vertebroplasty, khyphoplasty, cranioplasty and periodontal surgeries. The flow and deformation behavior (rheology) and injectability of the calcium phosphate bone cements to the treatment site are governed by the setting kinetics of the cement during which the initially flowable, viscous cement paste transforms into a rigid elastic solid. Here time-dependent development of the linear viscoelastic properties of a brushite-forming calcium phosphate cement are characterized and linked to the mechanism and kinetics of the setting reaction and to the injectability window available during the surgical applications of the cement...
May 10, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28504293/quantifying-the-sensitivity-of-the-network-structure-and-properties-from-simultaneous-measurements-during-photopolymerization
#19
Swarnavo Sarkar, Paula J Baker, Edwin P Chan, Sheng Lin-Gibson, Martin Y M Chiang
We present a method that combines experimental and computational approaches to assess a comprehensive set of structural and functional evolution during a network formation process via photopolymerization. Our work uses the simultaneous measurement of the degree of conversion, polymerization stress, the change in reaction temperature, and shrinkage strain in situ. These measurements are combined with the theory of viscoelastic materials to deduce the relaxation time and frequency-dependent modulus of the polymerizing network...
May 15, 2017: Soft Matter
https://www.readbyqxmd.com/read/28504278/high-frequency-linear-rheology-of-hydrogels-probed-by-ultrasound-driven-microbubble-dynamics
#20
Akaki Jamburidze, Marco De Corato, Axel Huerre, Angelo Pommella, Valeria Garbin
Ultrasound-driven microbubble dynamics are central to biomedical applications, from diagnostic imaging to drug delivery and therapy. In therapeutic applications, the bubbles are typically embedded in tissue, and their dynamics are strongly affected by the viscoelastic properties of the soft solid medium. While the behaviour of bubbles in Newtonian fluids is well characterised, a fundamental understanding of the effect on ultrasound-driven bubble dynamics of a soft viscoelastic medium is still being developed...
May 15, 2017: Soft Matter
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