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Mechanical compression

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https://www.readbyqxmd.com/read/28318948/comparative-assessment-of-intrinsic-mechanical-stimuli-on-knee-cartilage-and-compressed-agarose-constructs
#1
A Completo, C Bandeiras, F Fonseca
A well-established cue for improving the properties of tissue-engineered cartilage is mechanical stimulation. However, the explicit ranges of mechanical stimuli that correspond to favorable metabolic outcomes are elusive. Usually, these outcomes have only been associated with the applied strain and frequency, an oversimplification that can hide the fundamental relationship between the intrinsic mechanical stimuli and the metabolic outcomes. This highlights two important key issues: the firstly is related to the evaluation of the intrinsic mechanical stimuli of native cartilage; the second, assuming that the intrinsic mechanical stimuli will be important, deals with the ability to replicate them on the tissue-engineered constructs...
March 17, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28317935/a-facile-template-route-to-periodic-mesoporous-organosilicas-nanospheres-with-tubular-structure-by-using-compressed-co2
#2
Xin Huang, Wei Li, Meijin Wang, Xiuniang Tan, Qian Wang, Cheng Wang, Mengnan Zhang, Jing Yuan
Periodic mesoporous organosilicas (PMOs) nanospheres with tubular structure were prepared with compressed CO2 using cationic and anionic mixed surfactant (CTAB/SDS) and triblock copolymer Pluronic P123 as bi-templates. TEM, N2 adsorption-desorption, solid NMR, and FTIR were employed to characterize the obtained materials. Compressed CO2 severed as acidic reagent to promote the hydrolysis of organosilicas, and could tune the morphology and structure of the obtained PMOs nanomaterials simple by adjusting the CO2 pressure during the synthesis process...
March 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28316947/analysis-of-the-mechanical-behavior-and-surface-rugosity-of-different-dental-die-materials
#3
Ciro T Niekawa, Simone Kreve, Gisseli Bertozzi A'vila, Gilmar Gil Godoy, J R Eduardo Vieira da Silva, Sergio Candido Dias
AIM: This work evaluated the mechanical and surface behavior of different die materials. The studied materials are polyurethane resin Exakto-Form (Bredent), Gypsum type IV, Fuji Rock EP (Gc), and Durone (Dentsply). MATERIALS AND METHODS: Two metallic matrices molded in polyvinyl siloxane provided 30 cylindrical test specimens for the diametral compression test and 30 hemispherical test specimens for the surface rugosity test. The cylindrical test specimens were submitted to tests of diametral compression strength using a DL2000 universal assay machine, with a load cell of 2000 Kgf and constant speed of 1 mm/min connected to the software...
January 2017: Journal of International Society of Preventive & Community Dentistry
https://www.readbyqxmd.com/read/28315970/a-root-penetration-model-of-arabidopsis-thaliana-in-phytagel-medium-with-different-strength
#4
Jie Yan, Bochu Wang, Yong Zhou
Phytagel media were evaluated as systems to mechanically impede roots of A. thaliana. Studying mechanical properties of Phytagel and exploring the root response to mechanical stimulation can facilitate plant culture and plant development. Breaking strengths of 0.5-2.0% phytagel media were tested by uniaxial compression test. Different phytagel concentrations were set to alter the strength of layers in growth medium. Negative correlations were observed between root length, straightness and medium strength. When roots elongated through soft upper-layer (0...
March 18, 2017: Journal of Plant Research
https://www.readbyqxmd.com/read/28314562/intermittent-vibration-protects-aged-muscle-from-mechanical-and-oxidative-damage-under-prolonged-compression
#5
Sing Wan Wong, Brian Chun Ho Cheung, Bruce Tak Keung Pang, Ateline Kwong, Anna Chung, Kenneth Ka Ho Lee, Arthur Fut Tak Mak
Deep tissue pressure ulcers, a serious clinical challenge originating in the muscle layer, are hardly detectable at the beginning. The challenge apparently occurs in aged subjects more frequently. As the ulcer propagates to the skin surface, it becomes very difficult to manage and can lead to fatal complications. Preventive measures are thus highly desirable. Although the complex pathological mechanisms have not been fully understood, prolonged and excessive physical challenges and oxidative stress are believed to be involved in the ulcer development...
February 27, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28314143/a-hybrid-molecular-dynamics-study-on-the-non-newtonian-rheological-behaviors-of-shear-thickening-fluid
#6
Kaihui Chen, Yu Wang, Shouhu Xuan, Xinglong Gong
To investigate the microstructural evolution dependency on the apparent viscosity in shear-thickening fluids (STFs), a hybrid mesoscale model combined with stochastic rotation dynamics (SRD) and molecular dynamics (MD) is used. Muller-Plathe reverse perturbation method is adopted to analyze the viscosities of STFs in a two-dimensional model. The characteristic of microstructural evolution of the colloidal suspensions under different shear rate is studied. The effect of diameter of colloidal particles and the phase volume fraction on the shear thickening behavior is investigated...
March 8, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28306642/damage-identification-on-vertebral-bodies-during-compressive-loading-using-digital-image-correlation
#7
Hannah M Gustafson, Angela D Melnyk, Gunter P Siegmund, Peter A Cripton
STUDY DESIGN: Ex vivo compression experiments on isolated cadaveric vertebrae OBJECTIVE.: To qualitatively compare the fracture locations identified in video analysis with the locations of high compressive strain measured with DIC on vertebral bodies and to evaluate the timing of local damage to the cortical shell relative to the global yield force SUMMARY OF BACKGROUND DATA.: In previous ex vivo experiments, cortical bone fracture has been identified using various methods including acoustic emission sensors, strain gages, video analysis, or force signals...
March 16, 2017: Spine
https://www.readbyqxmd.com/read/28306309/thermal-fluctuations-of-ferroelectric-nanodomains-in-a-ferroelectric-dielectric-pbtio_-3-srtio_-3-superlattice
#8
Qingteng Zhang, Eric M Dufresne, Pice Chen, Joonkyu Park, Margaret P Cosgriff, Mohammed Yusuf, Yongqi Dong, Dillon D Fong, Hua Zhou, Zhonghou Cai, Ross J Harder, Sara J Callori, Matthew Dawber, Paul G Evans, Alec R Sandy
Ferroelectric-dielectric superlattices consisting of alternating layers of ferroelectric PbTiO_{3} and dielectric SrTiO_{3} exhibit a disordered striped nanodomain pattern, with characteristic length scales of 6 nm for the domain periodicity and 30 nm for the in-plane coherence of the domain pattern. Spatial disorder in the domain pattern gives rise to coherent hard x-ray scattering patterns exhibiting intensity speckles. We show here using variable-temperature Bragg-geometry x-ray photon correlation spectroscopy that x-ray scattering patterns from the disordered domains exhibit a continuous temporal decorrelation due to spontaneous domain fluctuations...
March 3, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28303236/treating-the-critically-ill-with-radiotherapy-lessons-learned-from-a-young-woman-with-cardiac-angiosarcoma
#9
Emma C Fields, Bryan Squires, Harry Lomas
BACKGROUND: Treating patients who are critically ill with radiotherapy (RT) brings a unique set of challenges as it involves treating patients who require mechanical life support, unconventional positioning, and a multidisciplinary team approach to ensure safety. However, when the benefits of such treatment outweigh the risks, the challenges can be overcome, as demonstrated in this unique case of cardiac angiosarcoma. CASE DESCRIPTION: This is a case of a 42-year-old female with a right sided cardiac angiosarcoma who quickly developed cardiac tamponade and respiratory failure related to compression of her right heart by the tumor...
2017: Frontiers in Oncology
https://www.readbyqxmd.com/read/28302485/novel-calcified-gum-arabic-porous-nano-composite-scaffold-for-bone-tissue-regeneration
#10
M Hadavi, S Hasannia, Sh Faghihi, F Mashayekhi, H H Zadeh, S B Mostofi
The aim of this study was to investigate the biomechanical and biological properties of a nanocomposite scaffold containing both mineral and polysaccharide constituents. Hydroxyapatite nanoparticles (n-HA) was synthesized from dead abra ovata shells using wet chemical methods and was used in different ratios in concert with gum Arabic, a branched plant polysaccharide. N-HA/gum nanocomposite was fabricated with freeze-drying process and characterized by FTIR and SEM for chemical structure and morphology. Porosity was estimated using liquid substitution method...
March 14, 2017: Biochemical and Biophysical Research Communications
https://www.readbyqxmd.com/read/28302458/the-effects-of-dexmedetomidine-pretreatment-on-the-pro-and-anti-inflammation-systems-after-spinal-cord-injury-in-rats
#11
Hui Rong, Zhibin Zhao, Jiying Feng, Yishan Lei, Hao Wu, Rao Sun, Zuoxia Zhang, Bailing Hou, Wei Zhang, YuE Sun, Xiaoping Gu, Zhengliang Ma, Yue Liu
Excessive inflammatory responses play important roles in the aggravation of secondary damage to an injured spinal cord. Dexmedetomidine (DEX), a selective α2-adrenoceptor agonist, has recently been implied to be neuroprotective in clinical anesthesia, but the underlying mechanism is elusive. As signaling through Toll-like receptor 4 (TLR4) and nicotinic receptors (nAChRs, notably α7nAChR) play important roles in the pro- and anti-inflammation systems in the central nervous system, respectively, this study investigated whether and how they were modulated by DEX pretreatment in a rat model of spinal cord compression...
March 14, 2017: Brain, Behavior, and Immunity
https://www.readbyqxmd.com/read/28302412/mechanical-behavior-of-idealized-stingray-skeleton-inspired-tiled-composites-as-a-function-of-geometry-and-material-properties
#12
A K Jayasankar, R Seidel, J Naumann, L Guiducci, A Hosny, P Fratzl, J C Weaver, J W C Dunlop, M N Dean
Tilings are constructs of repeated shapes covering a surface, common in both manmade and natural structures, but in particular are a defining characteristic of shark and ray skeletons. In these fishes, cartilaginous skeletal elements are wrapped in a surface tessellation, comprised of polygonal mineralized tiles linked by flexible joints, an arrangement believed to provide both stiffness and flexibility. The aim of this research is to use two-dimensional analytical models to evaluate the mechanical performance of stingray skeleton-inspired tessellations, as a function of their material and structural parameters...
February 28, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28302318/regional-differences-of-tibial-and-femoral-cartilage-in-the-chondrocyte-gene-expression-immunhistochemistry-and-composite-in-different-stages-of-osteoarthritis
#13
A Lahm, D Dabravolski, H Spank, H Merk, J Esser, R Kasch
The function of articular cartilage as an avascular tissue is mainly served by collagen type II and proteoglycan molecules. Within this matrix homeostasis between production and breakdown of the matrix is exceptionally sensitive. The current study was conducted to identify regional differences in specific alterations in cartilage composition during the osteoarthritic process of the human knee joint. Therefor the changes in the expression of the key molecules of the extracellular matrix were measured in dependence of the anatomical side (femoral vs tibial) and associated with immunohistochemistry and quantitative measurement...
February 24, 2017: Tissue & Cell
https://www.readbyqxmd.com/read/28298943/hepatic-vein-transit-time-of-second-generation-ultrasound-contrast-agent-new-tool-in-the-assessment-of-portal-hypertension
#14
Siciliani Luisa, Giovanna Vitale, Anna Rita Sorbo, Pompili Maurizio, Rapaccini Gian Lodovico
PURPOSE: It has been demonstrated that Doppler waveform of the hepatic vein (normally triphasic) is transformed into a biphasic or monophasic waveform in cirrhotic patients. The compressive mechanism of liver tissue has been considered up till now the cause of this change. Moreover, cirrhotics show, after USCA injection, a much earlier HVTT due to intrahepatic shunts. Our aim was to prospectively evaluate the correlation between Doppler pattern of hepatic vein and HVTT of a second-generation USCA; we also correlated HVTT with the most common indexes of portal hypertension...
March 2017: Journal of Ultrasound
https://www.readbyqxmd.com/read/28298299/time-compression-of-visual-perception-around-microsaccades
#15
Gongchen Yu, Mingpo Yang, Peng Yu, Michael C Dorris
Even during fixation, our eyes are in constant motion. For example, microsaccades are small (typically<1°) eye movements that occur 1~3 times/second. Despite their tiny and transient nature, our percept of visual space is compressed prior to microsaccades (Hafed 2013). As visual space and time are interconnected at both the physical and physiological levels, we asked whether microsaccades also affect the temporal aspects of visual perception. Here we demonstrate that the perceived interval between transient visual stimuli was compressed if accompanied by microsaccades...
March 15, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28298005/cation-induced-monolayer-collapse-at-lower-surface-pressure-follows-specific-headgroup-percolation
#16
Kaushik Das, Bijay Kumar Sah, Sarathi Kundu
A Langmuir monolayer can be considered as a two-dimensional (2D) sheet at higher surface pressure which structurally deform with mechanical compression depending upon the elastic nature of the monolayer. The deformed structures formed after a certain elastic limit are called collapsed structures. To explore monolayer collapses at lower surface pressure and to see the effect of ions on such monolayer collapses, out-of-plane structures and in-plane morphologies of stearic acid Langmuir monolayers have been studied both at lower (≈6...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28297957/macroscopic-momentum-and-mechanical-energy-equations-for-incompressible-single-phase-flow-in-porous-media
#17
Catherine Teresa Paéz-García, Francisco J Valdés-Parada, Didier Lasseux
Modeling flow in porous media is usually focused on the governing equations for mass and momentum transport, which yield the velocity and pressure at the pore or Darcy scales. However, in many applications, it is important to determine the work (or power) needed to induce flow in porous media, and this can be achieved when the mechanical energy equation is taken into account. At the macroscopic scale, this equation may be postulated to be the result of the inner product of Darcy's law and the seepage velocity...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28297643/effects-of-polymer-length-and-salt-concentration-on-the-transport-of-ssdna-in-nanofluidic-channels
#18
Weixin Qian, Kentaro Doi, Satoyuki Kawano
Electrokinetic phenomena in micro/nanofluidic channels have attracted considerable attention because precise control of molecular transport in liquids is required to optically and electrically capture the behavior of single molecules. However, the detailed mechanisms of polymer transport influenced by electroosmotic flows and electric fields in micro/nanofluidic channels have not yet been elucidated. In this study, a Langevin dynamics simulation was used to investigate the electrokinetic transport of single-stranded DNA (ssDNA) in a cylindrical nanochannel, employing a coarse-grained bead-spring model that quantitatively reproduced the radius of gyration, diffusion coefficient, and electrophoretic mobility of the polymer...
March 14, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28297335/on-the-accuracy-of-dose-prediction-near-metal-fixation-devices-for-spine-sbrt
#19
Zhangkai J Cheng, Regina M Bromley, Brad Oborn, Martin Carolan, Jeremy T Booth
The metallic fixations used in surgical procedures to support the spine mechanically usually consist of high-density materials. Radiation therapy to palliate spinal cord compression can include prophylactic inclusion of potential tumor around the site of such fixation devices. Determination of the correct density and shape of the spine fixation device has a direct effect on the dose calculation of the radiation field. Even with the application of modern computed tomography (CT), under- or overestimation of dose, both immediately next to the device and in the surrounding tissues, can occur due to inaccuracies in the dose prediction algorithm...
May 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28296412/negative-linear-compressibility-due-to-layer-sliding-in-a-layered-mof
#20
Qingxin Zeng, Kai Wang, Yuancun Qiao, Xiaodong Li, Bo Zou
Negative linear compressibility (NLC) is a rare and counterintuitive phenomenon because materials with this property would expand along one specific direction when uniformly compressed. NLC materials have a broad range of potential applications in designing pressure sensors, artificial muscles and so on. Designing and searching for systems with NLC is desired and crucial for material and compression science. Herein, with the help of high-pressure X-ray diffraction measurements and density functional theory calculations, we find that the 2D layered Co(SCN)2(pyrazine)2 exhibits NLC with a new mechanism-layer sliding...
March 15, 2017: Journal of Physical Chemistry Letters
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