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Weisi Li, Barry Belmont, Joan M Greve, Adam B Manders, Brian C Downey, Xi Zhang, Zhen Xu, Dongming Guo, Albert Shih
PURPOSE: The mechanical and imaging properties of polyvinyl chloride (PVC) can be adjusted to meet the needs of researchers as a tissue-mimicking material. For instance, the hardness can be adjusted by changing the ratio of softener to PVC polymer, mineral oil can be added for lubrication in needle insertion, and glass beads can be added to scatter acoustic energy similar to biological tissue. Through this research, the authors sought to develop a regression model to design formulations of PVC with targeted mechanical and multimodal medical imaging properties...
October 2016: Medical Physics
Gary S Grest
The coupled dynamics of entangled polymers, which span broad time and length scales, govern their unique viscoelastic properties. To follow chain mobility by numerical simulations from the intermediate Rouse and reptation regimes to the late time diffusive regime, highly coarse grained models with purely repulsive interactions between monomers are widely used since they are computationally the most efficient. Here using large scale molecular dynamics simulations, the effect of including the attractive interaction between monomers on the dynamics of entangled polymer melts is explored for the first time over a wide temperature range...
October 14, 2016: Journal of Chemical Physics
Nayeon Lee, M F Horstemeyer, R Prabhu, Jun Liao, Hongjoo Rhee, Youssef Hammi, Robert D Moser, Lakiesha N Williams
In this study a woodpecker's hyoid apparatus was characterized to determine its impact mitigation mechanism using finite element (FE) analysis. The woodpecker's hyoid apparatus, comprising bone and muscle, has a unique geometry compared to those of other birds. The hyoid starts at the beak tip, surrounds the woodpecker's skull, and ends at the upper beak/front head intersection while being surrounded by muscle along the whole length. A FE model of the hyoid apparatus was created based on the geometry, microstructure, and mechanical properties garnered from our experimental measurements...
October 25, 2016: Bioinspiration & Biomimetics
Harriet Lea-Banks, Boon Teo, Eleanor Stride, Constantin C Coussios
A significant barrier to successful drug delivery is the limited penetration of nanoscale therapeutics beyond the vasculature. Building on recent in vivo findings in the context of cancer drug delivery, the current study investigates whether modification of nanoparticle drug-carriers to increase their density can be used to enhance their penetration into viscoelastic materials under ultrasound exposure. A computational model is first presented to predict the transport of identically sized nanoparticles of different densities in an ultrasonic field in the presence of an oscillating microbubble, by a combination of primary and secondary acoustic radiation forces, acoustic streaming and microstreaming...
November 21, 2016: Physics in Medicine and Biology
Maria Giovanna Sabbieti, Alessandra Dubbini, Fulvio Laus, Emanuele Paggi, Andrea Marchegiani, Melania Capitani, Luigi Marchetti, Fabrizio Dini, Tina Vermonden, Piera Di Martino, Dimitrios Agas, Roberta Censi
The present study reports on the biocompatibility in vivo after intramuscular and subcutaneous administration in Balb/c mice of vinyl sulphone bearing p(HPMAm-lac1-2)-PEG-p(HPMAm-lac1-2)/thiolated hyaluronic acid hydrogels, designed as novel injectable biomaterials for potential application in the fields of tissue engineering and regenerative medicine. Ultrasonography, used as a method to study hydrogel gelation and residence time in vivo, showed that, upon injection, the biomaterial efficiently formed a hydrogel by simultaneous thermal gelation and Michael Addition cross-linking forming a viscoelastic spherical depot at the injection site...
October 24, 2016: Journal of Tissue Engineering and Regenerative Medicine
Rushad Shroff, Mathew Francis, Natasha Pahuja, Leio Veeboy, Rohit Shetty, Abhijit Sinha Roy
PURPOSE: To quantitatively evaluate microdistortions in Bowman's layer and change in corneal stiffness after small incision lenticule extraction (SMILE). METHODS: This was a prospective, longitudinal, and interventional study. Thirty eyes of 30 patients were screened preoperatively and underwent SMILE for treatment of myopia with astigmatism. Visual acuity, refraction, optical coherence tomography (OCT; Bioptigen, Inc., Morrisville, NC) imaging of the layer and air-puff applanation (Corvis-ST, OCULUS Optikgeräte Gmbh, Germany) was performed before and after surgery (1 day, 1 week, and 1 month)...
October 2016: Translational Vision Science & Technology
Owain Thomas, Hampus Rein, Karin Strandberg, Ulf Schött
BACKGROUND: The risk of spinal haematoma in patients receiving epidural catheters is estimated using routine coagulation tests, but guidelines are inconsistent in their recommendations on what to do when results indicate slight hypocoagulation. Postoperative patients are prone to thrombosis, and thromboelastometry has previously shown hypercoagulation in this setting. We aimed to better understand perioperative haemostasis by comparing results from routine and advanced tests, hypothesizing that patients undergoing major upper gastrointestinal surgery would be deficient in vitamin K-dependent coagulation factors because of malnutrition, or hypocoagulative because of accumulation of low molecular weight heparin (LMWH)...
2016: Perioperative Medicine
David B MacManus, Baptiste Pierrat, Jeremiah G Murphy, Michael D Gilchrist
The brain is a complex organ made up of many different functional and structural regions consisting of different types of cells such as neurons and glia, as well as complex anatomical geometries. It is hypothesized that the different regions of the brain exhibit significantly different mechanical properties which may be attributed to the diversity of cells within individual brain regions. The regional viscoelastic properties of P56 mouse brain tissue, up to 70 μm displacement, are presented and discussed in the context of traumatic brain injury, particularly how the different regions of the brain respond to mechanical loads...
October 21, 2016: Acta Biomaterialia
Miriam Rothdiener, Miriam Hegemann, Tatiana Uynuk-Ool, Brandan Walters, Piruntha Papugy, Phong Nguyen, Valentin Claus, Tanja Seeger, Ulrich Stoeckle, Karen A Boehme, Wilhelm K Aicher, Jan P Stegemann, Melanie L Hart, Bodo Kurz, Gerd Klein, Bernd Rolauffs
Using matrix elasticity and cyclic stretch have been investigated for inducing mesenchymal stromal cell (MSC) differentiation towards the smooth muscle cell (SMC) lineage but not in combination. We hypothesized that combining lineage-specific stiffness with cyclic stretch would result in a significantly increased expression of SMC markers, compared to non-stretched controls. First, we generated dense collagen type I sheets by mechanically compressing collagen hydrogels. Atomic force microscopy revealed a nanoscale stiffness range known to support myogenic differentiation...
October 24, 2016: Scientific Reports
Kai Chen, Jiacheng Li, Yuhong Feng, Furui He, Qingfeng Zhou, Dunchao Xiao, Yiyuan Tang
Amphiphilic polymers that form self-assembled structures in aqueous media have been investigated and used for the diagnosis and therapy of various diseases, including cancer. In our work, a series of environment-sensitive hydrophobic alginates (Ugi-Alg) with various weight-average molecular mass values (Mw~6.7×10(5)-6.7×10(4)g/mol) were synthesized via Ugi reaction. The structure of Ugi-Alg was characterized by (1)HNMR spectrometer. The electrostatic self-assembly of different molecular weight (Mw) and composition (M/G ratio) of Ugi-Alg chain under various Na(+) concentrations, was investigated by dynamic light scattering, electron spin resonance experiments, and transmission electron microscopy...
January 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
D Papadogiannis, A Iliadi, T G Bradley, N Silikas, G Eliades, T Eliades
OBJECTIVE: To evaluate the viscoelastic properties of two experimental BPA-free and one BisGMA-based orthodontic resin composite adhesives for bonding fixed retainers. METHODS: A commercially available BisGMA-based (TXA: Transbond LR) and two bisphenol A-free experimental adhesives (EXA and EXB) were included in the study. The viscoelastic behavior of the adhesives was evaluated under static and dynamic conditions at dry and wet states and at various temperatures (21, 37, 50°C)...
October 18, 2016: Dental Materials: Official Publication of the Academy of Dental Materials
Bavand Keshavarz, Eric C Houze, John R Moore, Michael R Koerner, Gareth H McKinley
The breakup and atomization of complex fluids can be markedly different than the analogous processes in a simple Newtonian fluid. Atomization of paint, combustion of fuels containing antimisting agents, as well as physiological processes such as sneezing are common examples in which the atomized liquid contains synthetic or biological macromolecules that result in viscoelastic fluid characteristics. Here, we investigate the ligament-mediated fragmentation dynamics of viscoelastic fluids in three different canonical flows...
October 7, 2016: Physical Review Letters
Anwar Madkhali, Michael Chernos, Dana Grecov, Ezra Kwok
BACKGROUND: Osteoarthritis is a common, localized joint disease that causes pain, stiffness and reduced mobility. Osteoarthritis is particularly common in the knees. The effects of osteoarthritis on the rheology of synovial fluid in the knees are not fully understood and consequently require further study. OBJECTIVE: The purpose of this study is to investigate the effects of protein content on synovial fluid shear rheology. A secondary study outcome will include study of the temperature dependence of synovial fluid behaviour...
October 19, 2016: Biorheology
Juan P Cattalini, Judith Roether, Alexander Hoppe, Fatemeh Pishbin, Luis Haro Durand, Alejandro Gorustovich, Aldo R Boccaccini, Silvia Lucangioli, Viviana Mouriño
Novel multifunctional nanocomposite scaffolds made of nanobioactive glass and alginate crosslinked with therapeutic ions such as calcium and copper were developed for delivering therapeutic agents, in a highly controlled and sustainable manner, for bone tissue engineering. Alendronate, a well-known antiresorptive agent, was formulated into microspheres under optimized conditions and effectively loaded within the novel multifunctional scaffolds with a high encapsulation percentage. The size of the cation used for the alginate crosslinking impacted directly on porosity and viscoelastic properties, and thus, on the degradation rate and the release profile of copper, calcium and alendronate...
October 21, 2016: Biomedical Materials
Belfor Antonio Galaz, Rodrigo Hernan Acevedo
Ultrasound poroelastography is an imaging modality used to characterize the temporal behavior of soft tissue that can be modeled as a solid permeated by interconnected pores filled with liquid (poroelastic medium). It could be useful in the stage classification of lymphedema. Generally, time-constant models are applied to strain images, and precision of the fitting process, computational cost and versatility in response to changes in tissues properties are crucial aspects of clinical applications. In the work described here, we performed creep experiments on poroelastic phantoms and used rheologic models to visualize the changes in viscoelastic response associated with fluid mobility...
October 17, 2016: Ultrasound in Medicine & Biology
Natalia Estévez, Pablo Fuciños, Verónica Bargiela, Guillermo Picó, Nadia Woitovich Valetti, Clara Asunción Tovar, M Luisa Rúa
A β-Lactoglobulin fraction (r-βLg) was isolated from whey hydrolysates produced with cardosins from Cynara cardunculus. The impact of the hydrolysis process on the r-βLg structure and the rheological properties of heat-induced gels obtained thereafter were studied at different pH values. Differences were observed between r-βLg and commercial β-Lg used as control. Higher values for the fluorescence emission intensity and red shifts of the emission wavelength of r-βLg suggested changes in its tertiary structure and more solvent-exposed tryptophan residues...
March 15, 2017: Food Chemistry
Soya Shinkai, Tadasu Nozaki, Kazuhiro Maeshima, Yuichi Togashi
The mammalian genome is organized into submegabase-sized chromatin domains (CDs) including topologically associating domains, which have been identified using chromosome conformation capture-based methods. Single-nucleosome imaging in living mammalian cells has revealed subdiffusively dynamic nucleosome movement. It is unclear how single nucleosomes within CDs fluctuate and how the CD structure reflects the nucleosome movement. Here, we present a polymer model wherein CDs are characterized by fractal dimensions and the nucleosome fibers fluctuate in a viscoelastic medium with memory...
October 2016: PLoS Computational Biology
Jun Qiu, Fang-Fang Li
Mechanical properties of a single cell and its mechanical response under stimulation play an important role in regulating interactions between cell and extracellular matrix and affecting mechanotransduction. Osteocytes exhibit solid-like viscoelastic behavior in response to the interstitial fluid shear resulting from tissue matrix deformation. This study intends to quantitatively describe the mechanical behavior of osteocytes combining in vitro experiment and fluid-structure interaction (FSI) finite element (FE) model...
October 17, 2016: Biomechanics and Modeling in Mechanobiology
O V Kim, R I Litvinov, J Chen, D Z Chen, J W Weisel, M S Alber
Fibrin and collagen as well as their combinations play an important biological role in tissue regeneration and are widely employed in surgery as fleeces or sealants and in bioengineering as tissue scaffolds. Earlier studies demonstrated that fibrin-collagen composite networks displayed improved tensile mechanical properties compared to the isolated protein matrices. Unlike previous studies, here unconfined compression was applied to a fibrin-collagen filamentous polymer composite matrix to study its structural and mechanical responses to compressive deformation...
October 14, 2016: Matrix Biology: Journal of the International Society for Matrix Biology
Yue Zhao, Conggui Chen, Sihua Yang, Da Xing
Photoacoustic viscoelasticity imaging (PAVEI) is a technique that directly provides the morphology of biological tissues with correlative mechanical information. In this Letter, we demonstrate the use of PAVEI to successfully characterize early-stage atherosclerotic plaques. Lipid, as the main material in early plaque lesions, embedded in gelatin was imaged to test the feasibility of PAVEI. Atherosclerosis of rabbits was studied ex vivo, and the rabbit arteries were imaged to show the intrinsic contrast of PAVEI...
October 1, 2016: Optics Letters
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