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https://www.readbyqxmd.com/read/28433790/a-strain-mediated-corrosion-model-for-bioabsorbable-metallic-stents
#1
E Galvin, D O'Brien, C Cummins, B J Mac Donald, C Lally
This paper presents a strain-mediated phenomenological corrosion model, based on the discrete finite element modelling method which was developed for use with the ANSYS Implicit finite element code. The corrosion model was calibrated from experimental data and used to simulate the corrosion performance of a WE43 magnesium alloy stent. The model was found to be capable of predicting the experimentally observed plastic strain-mediated mass loss profile. The non-linear plastic strain model, extrapolated from the experimental data, was also found to adequately capture the corrosion-induced reduction in the radial stiffness of the stent over time...
April 19, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28427653/thermolysis-synthesis-of-pure-phase-nio-from-novel-sonochemical-synthesized-ni-ii-nano-metal-organic-supramolecular-architecture
#2
Younes Hanifehpour, Ali Morsali, Babak Mirtamizdoust, Sang Woo Joo, Behzad Soltani
Nano-structures of a new supramolecular coordination compound of divalent nickel with the pyrazol (pzH) containing the terminal azide anions, [Ni(pzH)2(N3)2] (1), with discrete molecular architecture (DMA) in solid state was synthesized via sonochemical method. The new nanostructure was characterized by scanning electron microscopy, X-ray powder diffraction, IR, and elemental analysis. Compound 1 was structurally characterized by single crystal X-ray diffraction and the single-crystal X-ray data shows that the coordination number of Ni (II) ions is six, (NiN6), with four N-donor atoms from neutral "pzH" ligands and two N-donors from two terminal azide anions...
July 2017: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/28425900/mobiliser-des-repr%C3%A3-sentations-ethnoculturelles-pour-expliquer-les-disparit%C3%A3-s-d%C3%A2-acc%C3%A3-s-aux-soins-de-sant%C3%A3-au-burkina-faso
#3
Loubna Belaid, Patrick Cloos, Valéry Ridde
OBJECTIFS: Cette étude vise à décrire la mobilisation des représentations ethnoculturelles par des agents et des gestionnaires de santé pour expliquer l'échec partiel d'une politique de santé maternelle et discuter des conséquences potentielles de ces représentations sur l'accès aux soins de santé des populations.MÉTHODES : Il s'agit d'une recherche qualitative de type socio-anthropologique mobilisant des entretiens approfondis, des discussions informelles, des observations non participantes menées dans les centres de santé et une analyse documentaire...
April 20, 2017: Canadian Journal of Public Health. Revue Canadienne de Santé Publique
https://www.readbyqxmd.com/read/28425587/hybrid-finite-difference-finite-element-immersed-boundary-method
#4
Boyce E Griffith, Xiaoyu Luo
The immersed boundary method is an approach to fluid-structure interaction that uses a Lagrangian description of the structural deformations, stresses, and forces along with an Eulerian description of the momentum, viscosity, and incompressibility of the fluid-structure system. The original immersed boundary methods described immersed elastic structures using systems of flexible fibers, and even now, most immersed boundary methods still require Lagrangian meshes that are finer than the Eulerian grid. This work introduces a coupling scheme for the immersed boundary method to link the Lagrangian and Eulerian variables that facilitates independent spatial discretizations for the structure and background grid...
April 20, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28380864/transient-polarized-radiative-transfer-analysis-in-a-scattering-medium-by-a-discontinuous-finite-element-method
#5
Cun-Hai Wang, Hong-Liang Yi, He-Ping Tan
Transient (time-dependent) polarized radiative transfer in a scattering medium exposed to an external collimated beam illumination is conducted based on the time-dependent polarized radiative transfer theory. The transient term, which persists the nanosecond order time and cannot be ignored for the time-dependent radiative transfer problems induced by a short-pulsed beam, is considered as well as the polarization effect of the radiation. A discontinuous finite element method (DFEM) is developed for the transient vector radiative transfer problem and the derivation of the discrete form of the governing equation is presented...
April 3, 2017: Optics Express
https://www.readbyqxmd.com/read/28365300/comparison-of-video-analysis-and-simulations-of-a-drum-coating-process
#6
P Boehling, G Toschkoff, R Dreu, S Just, P Kleinebudde, A Funke, H Rehbaum, J G Khinast
Tablet coating is a common unit operation in the pharmaceutical industry. To improve currently established processes, it is important to understand the influence of the process parameters on the coating quality. One of the critical parameters is the tablet velocity. In this work, numerical results are compared to results obtained experimentally. Tablet movement in the drums was simulated using the Discrete Element Method (DEM). The simulation parameters were adapted to fit the simulation to the experimental data...
March 30, 2017: European Journal of Pharmaceutical Sciences
https://www.readbyqxmd.com/read/28350406/power-free-digital-and-programmable-dispensing-of-picoliter-droplets-using-a-digit-chip
#7
A Mepham, J D Besant, A W Weinstein, I B Burgess, E H Sargent, S O Kelley
There is a growing need for power-free methods to manipulate small volumes of liquids and thereby enable use of diagnostic assays in resource-limited settings. Most existing self-powered devices provide analog manipulation of fluids using paper, capillary or pressure-driven pumps. These strategies are well-suited to manipulating larger micro- and milliliter-scale volumes at constant flow rates; however, they fail to enable the manipulation of nanoliter and picoliter volumes required in assays using droplets, capillary sampling (e...
April 11, 2017: Lab on a Chip
https://www.readbyqxmd.com/read/28297998/splash-detail-due-to-a-single-grain-incident-on-a-granular-bed
#8
Takahiro Tanabe, Takashi Shimada, Nobuyasu Ito, Hiraku Nishimori
Using the discrete element method, we study the splash processes induced by the impact of a grain on a randomly packed bed. Good correspondence is obtained between our numerical results and the findings of previous experiments for the movement of ejected grains. Furthermore, the distributions of the ejection angle and ejection speed for individual grains vary depending on the relative timing at which the grains are ejected after the initial impact. Obvious differences are observed between the distributions of grains ejected during the earlier and later splash periods: the form of the vertical ejection-speed distribution varies from a power-law form to a lognormal form with time; this difference may determine grain trajectory after ejection...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28294574/phase-field-boundary-conditions-for-the-voxel-finite-cell-method-surface-free-stress-analysis-of-ct-based-bone-structures
#9
L H Nguyen, S K F Stoter, T Baum, J S Kirschke, M Ruess, Z Yosibash, D Schillinger
The voxel finite cell method employs unfitted finite element meshes and voxel quadrature rules to seamlessly transfer CT data into patient-specific bone discretizations. The method, however, still requires the explicit parametrization of boundary surfaces to impose traction and displacement boundary conditions, which constitutes a potential roadblock to automation. We explore a phase-field based formulation for imposing traction and displacement constraints in a diffuse sense. Its essential component is a diffuse geometry model generated from metastable phase-field solutions of the Allen-Cahn problem that assumes the imaging data as initial condition...
March 11, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28289574/digital-morphing-wing-active-wing-shaping-concept-using-composite-lattice-based-cellular-structures
#10
Benjamin Jenett, Sam Calisch, Daniel Cellucci, Nick Cramer, Neil Gershenfeld, Sean Swei, Kenneth C Cheung
We describe an approach for the discrete and reversible assembly of tunable and actively deformable structures using modular building block parts for robotic applications. The primary technical challenge addressed by this work is the use of this method to design and fabricate low density, highly compliant robotic structures with spatially tuned stiffness. This approach offers a number of potential advantages over more conventional methods for constructing compliant robots. The discrete assembly reduces manufacturing complexity, as relatively simple parts can be batch-produced and joined to make complex structures...
March 1, 2017: Soft Robotics
https://www.readbyqxmd.com/read/28280517/mixed-total-variation-and-l-1-regularization-method-for-optical-tomography-based-on-radiative-transfer-equation
#11
Jinping Tang, Bo Han, Weimin Han, Bo Bi, Li Li
Optical tomography is an emerging and important molecular imaging modality. The aim of optical tomography is to reconstruct optical properties of human tissues. In this paper, we focus on reconstructing the absorption coefficient based on the radiative transfer equation (RTE). It is an ill-posed parameter identification problem. Regularization methods have been broadly applied to reconstruct the optical coefficients, such as the total variation (TV) regularization and the L(1) regularization. In order to better reconstruct the piecewise constant and sparse coefficient distributions, TV and L(1) norms are combined as the regularization...
2017: Computational and Mathematical Methods in Medicine
https://www.readbyqxmd.com/read/28269628/development-of-an-open-source-cosimulation-method-of-the-knee
#12
Anne Schmitz, Davide Piovesan
Rigid body dynamics and soft tissue loads are solved simultaneously in a cosimulation framework to couple musculoskeletal dynamics and tissue mechanics. The goal of this work was to implement a validated, open-source cosimulation framework of the knee to determine how this coupling affects computed cartilage loads. The kinematic knee joint of a generic whole body model in the open-source software OpenSim was replaced by a previously developed discrete element knee model that consisted of a six degree of freedom (dof) tibiofemoral joint and one dof patellofemoral joint...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28268867/fea-modeling-and-fluid-flow-simulation-of-human-rectum-with-inserted-bowel-catheters
#13
Yong Zhang, Tina VanRiper, Brian Rague, Drew Weidman
In this project, fluid flow and fluid-structure interaction are studied for the human lower gastrointestinal (GI) region. The study consists of two steps. First, we apply meshing methods to discretize both the human lower GI model and the catheter model at sufficient resolution suitable for importing into a Finite Element Analysis (FEA) tool. For model discretization, 3D models of the colon reconstructed from human MRI slices are used to obtain the valid inlet and outlet boundary surfaces. To resolve the viscous boundary layer in flow studies, a special structure of the near-wall volumetric mesh is built by triangular prisms that construct quasi-structured, multiple near-boundary sub-layers...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28249103/a-hybrid-computational-model-to-explore-the-topological-characteristics-of-epithelial-tissues
#14
Ismael González-Valverde, José Manuel García Aznar
Epithelial tissues show a particular topology where cells resemble a polygon-like shape, but some biological processes can alter this tissue topology. During cell proliferation, mitotic cell dilation deforms the tissue and modifies the tissue topology. Additionally, cells are reorganized in the epithelial layer and these rearrangements also alter the polygon distribution. We present here a computer-based hybrid framework focused on the simulation of epithelial layer dynamics that combines discrete and continuum numerical models...
March 1, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28227886/development-of-an-open-source-cosimulation-method-of-the-knee
#15
Anne Schmitz, Davide Piovesan, Anne Schmitz, Davide Piovesan, Anne Schmitz, Davide Piovesan
Rigid body dynamics and soft tissue loads are solved simultaneously in a cosimulation framework to couple musculoskeletal dynamics and tissue mechanics. The goal of this work was to implement a validated, open-source cosimulation framework of the knee to determine how this coupling affects computed cartilage loads. The kinematic knee joint of a generic whole body model in the open-source software OpenSim was replaced by a previously developed discrete element knee model that consisted of a six degree of freedom (dof) tibiofemoral joint and one dof patellofemoral joint...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28227065/fea-modeling-and-fluid-flow-simulation-of-human-rectum-with-inserted-bowel-catheters
#16
Yong Zhang, Tina VanRiper, Brian Rague, Drew Weidman, Yong Zhang, Tina VanRiper, Brian Rague, Drew Weidman, Tina VanRiper, Drew Weidman, Brian Rague, Yong Zhang
In this project, fluid flow and fluid-structure interaction are studied for the human lower gastrointestinal (GI) region. The study consists of two steps. First, we apply meshing methods to discretize both the human lower GI model and the catheter model at sufficient resolution suitable for importing into a Finite Element Analysis (FEA) tool. For model discretization, 3D models of the colon reconstructed from human MRI slices are used to obtain the valid inlet and outlet boundary surfaces. To resolve the viscous boundary layer in flow studies, a special structure of the near-wall volumetric mesh is built by triangular prisms that construct quasi-structured, multiple near-boundary sub-layers...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28207956/application-of-network-methods-for-understanding-evolutionary-dynamics-in-discrete-habitats
#17
Gili Greenbaum, Nina H Fefferman
In populations occupying discrete habitat patches, gene flow between habitat patches may form an intricate population structure. In such structures, the evolutionary dynamics resulting from interaction of gene flow patterns with other evolutionary forces may be exceedingly complex. Several models describing gene flow between discrete habitat patches have been presented in the population genetics literature; however, these models have usually addressed relatively simple settings of habitable patches, and have stopped short of providing general methodologies for addressing non-trivial gene flow patterns...
February 16, 2017: Molecular Ecology
https://www.readbyqxmd.com/read/28183069/a-dynamic-model-of-the-piezoelectric-traveling-wave-rotary-ultrasonic-motor-stator-with-the-finite-volume-method
#18
I A Renteria Marquez, V Bolborici
This manuscript presents a method to model in detail the piezoelectric traveling wave rotary ultrasonic motor (PTRUSM) stator response under the action of DC and AC voltages. The stator is modeled with a discrete two dimensional system of equations using the finite volume method (FVM). In order to obtain accurate results, a model of the stator bridge is included into the stator model. The model of the stator under the action of DC voltage is presented first, and the results of the model are compared versus a similar model using the commercial finite element software COMSOL Multiphysics...
May 2017: Ultrasonics
https://www.readbyqxmd.com/read/28181798/shape-morphing-materials-from-stimuli-responsive-hydrogel-hybrids
#19
Seog-Jin Jeon, Adam W Hauser, Ryan C Hayward
The formation of well-defined and functional three-dimensional (3D) structures by buckling of thin sheets subjected to spatially nonuniform stresses is common in biological morphogenesis and has become a subject of great interest in synthetic systems, as such programmable shape-morphing materials hold promise in areas including drug delivery, biomedical devices, soft robotics, and biomimetic systems. Given their ability to undergo large changes in swelling in response to a wide variety of stimuli, hydrogels have naturally emerged as a key type of material in this field...
February 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28163785/efficient-estimation-of-the-maximum-metabolic-productivity-of-batch-systems
#20
Peter C St John, Michael F Crowley, Yannick J Bomble
BACKGROUND: Production of chemicals from engineered organisms in a batch culture involves an inherent trade-off between productivity, yield, and titer. Existing strategies for strain design typically focus on designing mutations that achieve the highest yield possible while maintaining growth viability. While these methods are computationally tractable, an optimum productivity could be achieved by a dynamic strategy in which the intracellular division of resources is permitted to change with time...
2017: Biotechnology for Biofuels
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