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Viscoelastic

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https://www.readbyqxmd.com/read/28222498/creep-compliance-rheology-with-a-probe-like-cylindrical-geometry
#1
Kelly Connelly, Pooria Sharif-Kashani, Matt Farajzadeh, Jean-Pierre Hubschman, H Pirouz Kavehpour
BACKGROUND: Rheology experiments have been performed on the vitreous humor, a soft gel that rests inside of the eye, to study its viscoelastic behavior and underlying macromolecular structure. A significant challenge for experimentalists is preserving the macromolecular structure when removing vitreous from in vivo conditions. OBJECTIVE: We have developed a novel probe-like rheometer geometry that allows us to perform shear rheology experiments on the vitreous humor in situ...
February 10, 2017: Biorheology
https://www.readbyqxmd.com/read/28222100/development-of-topical-ophthalmic-in-situ-gel-forming-estradiol-delivery-system-intended-for-the-prevention-of-age-related-cataracts
#2
Udaya K Kotreka, Vicki L Davis, Moji C Adeyeye
The goal of this study was to develop and characterize an ion-activated in situ gel-forming estradiol (E2) solution eye drops intended for the prevention of age-related cataracts. Accordingly, in situ gelling eye drops were made using gellan gum as an ion-activated gel-forming polymer, polysorbate-80 as drug solubilizing agent, mannitol as tonicity agent, and combination of potassium sorbate and edetate disodium dihydrate (EDTA) as preservatives. The formulations were tested for the following characteristics: pH, clarity, osmolality, antimicrobial efficacy, rheological behavior, and in vitro drug release...
2017: PloS One
https://www.readbyqxmd.com/read/28221812/intermicellar-interactions-and-the-viscoelasticity-of-surfactant-solutions-complementary-use-of-sans-and-saxs
#3
Viviane Lutz-Bueno, Marianne Liebi, Joachim Kohlbrecher, Peter Fischer
In ionic surfactant micelles, basic interactions among distinct parts of surfactant monomers, their counterion, and additives are fundamental to tune molecular self-assembly and enhance viscoelasticity. Here, we investigate the addition of sodium salicylate (NaSal) to hexa-decyltrimethyl ammonium chloride and bromide (CTAC and CTAB) and 1-hexa-decyl pyridinium chloride and bromide (CPyCl and CPyBr), which have distinct counterions and headgroup structures, but the same hydrophobic tail. Different contrasts are obtained from small-angle neutron scattering SANS, which probes differences between the nucleus of atoms, and X-rays SAXS, which probes differences in electron density...
February 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28221707/dynamic-covalent-polymer-networks-from-old-chemistry-to-modern-day-innovations
#4
REVIEW
Weike Zou, Jiante Dong, Yingwu Luo, Qian Zhao, Tao Xie
Dynamic covalent polymer networks have long been recognized. With the initial focus on the unintended impact of dynamic covalent linkages on the viscoelasticity of commercial rubbers, efforts in modern times have transitioned into designing dynamic covalent polymer networks with unique adaptive properties. Whereas self-healing and thermoset reprocessing have been the primary motivations for studying dynamic covalent polymer networks, the recent discovery of the vitrimeric rheological behavior and solid-state plasticity for this type of material have opened up new opportunities in material innovations...
February 21, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28221703/multiblock-copolymer-based-dual-dynamic-disulfide-and-supramolecular-crosslinked-self-healing-networks
#5
So Young An, Seung Man Noh, Jung Kwon Oh
A new multiblock copolymer self-healing strategy is reported that centers on the synthesis of block copolymers designed with different self-healing motifs incorporated into individual blocks. As a proof of concept, a novel pentablock copolymer (ABCBA) consisting of a poly(ethylene glycol) middle block and self-healable symmetric blocks of a polymethacrylate with pendant disulfide linkages and carboxylic acids is synthesized by a combination of consecutive controlled radical polymerization with hydrolytic cleavage...
February 21, 2017: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/28220602/mexametric-and-cutometric-assessment-of-the-signs-of-aging-of-the-skin-area-around-the-eyes-after-the-use-of-non-ablative-fractional-laser-non-ablative-radiofrequency-and-intense-pulsed-light
#6
Anna Maria Kołodziejczak, Helena Rotsztejn
The assessment of the signs of aging within eyes area in cutometric (skin elasticity) and mexametric (discoloration and severity of erythema) examination after the treatment with: non-ablative fractional laser, non-ablative radiofrequency (RF) and intense light source (IPL). This study included 71 patients, aged 33-63 years (the average age was 45.81) with Fitzpatrick skin type II and III. 24 patients received 5 successive treatment sessions with a 1,410-nm non-ablative fractional laser in two-week intervals, 23 patients received 5 successive treatment sessions with a non-ablative RF in one-week intervals and 24 patients received 5 successive treatment sessions with an IPL in two-week intervals...
February 21, 2017: Dermatologic Therapy
https://www.readbyqxmd.com/read/28219806/structural-characterization-and-viscoelastic-constitutive-modeling-of-skin
#7
Vincent R Sherman, Yizhe Tang, Shiteng Zhao, Wen Yang, Marc A Meyers
: A fascinating material, skin has a tensile response which exhibits an extended toe region of minimal stress up to nominal strains that, in some species, exceed 1, followed by significant stiffening until a roughly linear region. The large toe region has been attributed to its unique structure, consisting of a network of curved collagen fibers. Investigation of the structure of rabbit skin reveals that it consists of layers of wavy fibers, each one with a characteristic orientation. Additionally, the existence of two preferred layer orientations is suggested based on the results of small angle x-ray scattering...
February 17, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28219085/fibrinolysis-in-trauma-myth-reality-or-something-in-between
#8
Mark Walsh, Jacob Shreve, Scott Thomas, Ernest Moore, Hunter Moore, Daniel Hake, Tim Pohlman, Patrick Davis, Victoria Ploplis, Andres Piscoya, Julie Wegner, John Bryant, Anton Crepinsek, James Lantry, Forest Sheppard, Francis Castellino
The emphasis on fibrinolysis as an important contributor to trauma-induced coagulopathy (TIC) has led to a debate regarding the relative clinical significance of fibrinolysis in the setting of trauma. The debate has centered on two camps. The one camp defines fibrinolysis in trauma by standard coagulation tests as well as fibrin split products, D-dimers, and plasmin/antiplasmin levels. This camp favors a more liberal use of tranexamic acid and attributes more significance to hyperfibrinolysis in TIC. The other camp favors a definition of fibrinolysis based on the viscoelastic tests (VET), rotational thromboelastometry (ROTEM), and thromboelastography (TEG)...
February 20, 2017: Seminars in Thrombosis and Hemostasis
https://www.readbyqxmd.com/read/28219084/diagnosis-and-treatment-of-hyperfibrinolysis-in-trauma-a-european-perspective
#9
Lewis S Gall, Karim Brohi, Ross A Davenport
Fibrinolysis activation occurs almost universally after severe trauma. Systemic hyperfibrinolysis is a key component of acute traumatic coagulopathy and associated with poor clinical outcomes, although controversy exists over optimal treatment strategies. The mechanistic drivers and dynamics of fibrinolytic activation in response to injury and trauma resuscitation are currently unclear. Furthermore, therapeutic triggers are compounded by the lack of a sensitive and rapid diagnostic tool, with discrepancy between hyperfibrinolysis diagnosed by viscoelastic hemostatic assays versus biomarkers for fibrinolysis...
February 20, 2017: Seminars in Thrombosis and Hemostasis
https://www.readbyqxmd.com/read/28215336/micropipette-aspiration-a%C3%A2-unique-tool-for-exploring-cell-and-tissue-mechanics-in-vivo
#10
K Guevorkian, J-L Maître
Cell and tissue mechanical properties are paramount in controlling morphogenesis. Microaspiration techniques allow measuring the absolute values of mechanical properties in space and time in vivo. Here, we explain how to build a microaspiration setup that can be used for both cellular and tissue scale measurements. At the cellular scale, microaspiration allows the mapping in space and time of surface tensions of individual interfaces within a tissue to understand the forces shaping it. At the tissue scale, microaspiration can be used to measure macroscopic mechanical properties such as the viscoelasticity and tissue surface tension that regulate the dynamics of tissue deformation...
2017: Methods in Cell Biology
https://www.readbyqxmd.com/read/28214623/rheology-and-microstructure-of-aqueous-suspensions-of-nanocrystalline-cellulose-rods
#11
Yuan Xu, Aleks D Atrens, Jason R Stokes
HYPOTHESIS: Nanocrystalline cellulose (NCC) is a negatively charged rod-like colloid obtained from the hydrolysis of plant material. It is thus expected that NCC suspensions display a rich set of phase behaviour with salt and pH because of its anisotropic shape and electrical double layer that gives rise to liquid crystallinity and self-assembly respectively. It should thus be possible to tune the rheological properties of NCC suspensions for a wide variety of end-use applications. EXPERIMENTS: Rheology and structural analysis techniques are used to characterise surface-sulphated NCC suspensions as a function of pH, salinity (NaCl) and NCC concentration...
February 12, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28214621/interaction-of-non-aqueous-dispersions-of-silver-nanoparticles-with-cellular-membrane-models
#12
Gustavo Bonomi Soriano, Roselaine da Silva Oliveira, Fernanda Ferraz Camilo, Luciano Caseli
In this work, silver nanoparticles (AgNPs) dispersed in non-aqueous media and stabilized with polyether block polymers amide (PEBA) were incorporated in Langmuir monolayers of dipalmitoylphosphatidylcholine (DPPC), which served as a cell membrane model. The AgNPs presented surface activity, disturbing the viscoelastic properties of the floating film. They expanded the monolayers decreasing their surface elasticity as observed with surface pressure-area isotherms. Polarization modulation reflection-absorption spectroscopy showed that the permanence of AgNPs at the air-water interface is favored by PEBA, affecting both the hydrophilic and the hydrophobic groups of the phospholipid...
February 13, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28213338/a-uniaxial-cyclic-compression-method-for-characterizing-the-rheological-and-textural-behaviors-of-mechanically-dewatered-sewage-sludge
#13
Fenglin Liang, Martial Sauceau, Gilles Dusserre, Patricia Arlabosse
The mechanically dewatered sewage sludge with total solid content around 20% on a weight basis is very similar to yield stress fluid, its complex transition between solid and fluid states is not perfectly reversible and especially challenging in terms of pumping, land spreading and drying. To characterize the rheological and textural properties of highly concentrated sludge, a specific methodology based on uniaxial single and cyclic compression tests is developed. Three types of sludge samples (fresh original, fresh premixed and aged original ones) are extruded into cylinders and pressed between two parallel plates using a material testing machine...
February 7, 2017: Water Research
https://www.readbyqxmd.com/read/28213222/development-of-a-qcm-d-biosensor-for-ochratoxin-a-detection-in-red-wine
#14
Aleksandra Karczmarczyk, Karsten Haupt, Karl-Heinz Feller
Ochratoxin A (OTA), a highly toxic compound, is one of the most widely spread mycotoxins that contaminates a large variety of agricultural commodities. Due to its presence in the food chain, it imposes a hazard on both human and animal health. Therefore, there is a need for precise, fast and simple methods for toxin quantification. Herein, a novel sensor based on a quartz crystal microbalance with dissipation monitoring (QCM-D) and antibodies for specific analyte recognition was developed for rapid and sensitive detection of OTA in red wine...
May 1, 2017: Talanta
https://www.readbyqxmd.com/read/28210001/visualization-of-au-nanoparticles-buried-in-a-polymer-matrix-by-scanning-thermal-noise-microscopy
#15
Atsushi Yao, Kei Kobayashi, Shunta Nosaka, Kuniko Kimura, Hirofumi Yamada
Several researchers have recently demonstrated visualization of subsurface features with a nanometer-scale resolution using various imaging schemes based on atomic force microscopy. Since all these subsurface imaging techniques require excitation of the oscillation of the cantilever and/or sample surface, it has been difficult to identify a key imaging mechanism. Here we demonstrate visualization of Au nanoparticles buried 300 nm into a polymer matrix by measurement of the thermal noise spectrum of a microcantilever with a tip in contact to the polymer surface...
February 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28209923/novel-involvement-of-rhebl1-in-sphingosylphosphorylcholine-induced-keratin-phosphorylation-and-reorganization-binding-to-and-activation-of-akt1
#16
Hyun Ji Kim, Hyun Jung Byun, Mi Kyung Park, Eun Ji Kim, Gyeoung Jin Kang, Chang Hoon Lee
Sphingosylphosphorylcholine induces keratin phosphorylation and reorganization, and increases viscoelasticity of metastatic cancer cells such as PANC-1 cells. However, the mechanism involved in sphingosylphosphorylcholine-induced keratin phosphorylation and reorganization is largely unknown. Sphingosylphosphorylcholine dose- and time-dependently induces the expression of RhebL1. The involvement of RhebL1 in sphingosylphosphorylcholine-induced events including keratin 8 (K8) phosphorylation, reorganization, migration and invasion was examined...
February 15, 2017: Oncotarget
https://www.readbyqxmd.com/read/28208996/stress-distribution-under-commercial-denture-liners-a-finite-element-and-clinical-analysis
#17
Rahul Shrivastava, Saurabh Chaturvedi, Ashok Kumar Verma, Mariyum Ali, Amrita Nagendra, Mudita Chaturvedi
INTRODUCTION: Previous studies have shown that 20-30% of denture users have been dissatisfied with their dentures. AIM: To evaluate the stress pattern under elastic and viscoelastic denture liners using 3-Dimensional Finite Element Analysis (FEA) and its clinical correlation using a questionnaire. MATERIALS AND METHODS: The study had both in-vitro and in-vivo phases. In in-vitro phase fabrication of a virtual parametric model of edentulous maxilla and dentures with overlying mucosa was made...
December 2016: Journal of Clinical and Diagnostic Research: JCDR
https://www.readbyqxmd.com/read/28208801/atomic-force-microscopy-a-powerful-tool-to-address-scaffold-design-in-tissue-engineering
#18
Marica Marrese, Vincenzo Guarino, Luigi Ambrosio
Functional polymers currently represent a basic component of a large range of biological and biomedical applications including molecular release, tissue engineering, bio-sensing and medical imaging. Advancements in these fields are driven by the use of a wide set of biodegradable polymers with controlled physical and bio-interactive properties. In this context, microscopy techniques such as Atomic Force Microscopy (AFM) are emerging as fundamental tools to deeply investigate morphology and structural properties at micro and sub-micrometric scale, in order to evaluate the in time relationship between physicochemical properties of biomaterials and biological response...
February 13, 2017: Journal of Functional Biomaterials
https://www.readbyqxmd.com/read/28208480/transverse-vibration-of-nematic-elastomer-timoshenko-beams
#19
Dong Zhao, Ying Liu, Chuang Liu
Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28207656/biomechanical-evaluation-of-transpedicular-nucleotomy-with-intact-annulus-fibrosus
#20
Fabrizio Russo, Robert A Hartman, Kevin M Bell, Nam Vo, Gwendolyn A Sowa, James D Kang, Gianluca Vadalà, Vincenzo Denaro
STUDY DESIGN: Biomechanical testing of partially nucleotomized ovine cadaveric spines. OBJECTIVE: To explore how the nucleus pulposus (NP) affects the biomechanical behavior of the intervertebral disc (IVD) by performing a partial nucleotomy via the transpedicular approach. SUMMARY OF BACKGROUND DATA: Mechanical loading represents a crucial part of IVD homeostasis. However, traditional regenerative strategies require violation of the annulus fibrosus (AF) resulting in significant alteration of joint mechanics...
February 15, 2017: Spine
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