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https://www.readbyqxmd.com/read/28641249/eit-imaging-regularization-based-on-spectral-graph-wavelets
#1
Bo Gong, Benjamin Schullcke, Sabine Krueger-Ziolek, Marko Vauhkonen, Gerhard Wolf, Ullrich Mueller-Lisse, Knut Moeller
The objective of Electrical Impedance Tomographic reconstruction is to identify the distribution of tissue conductivity from electrical boundary conditions. This is an ill-posed inverse problem usually solved under the finite element method framework. In previous studies, standard sparse regularization was used for difference EIT to achieve a sparse solution. However, regarding element-wise sparsity, standard sparse regularization interferes with the smoothness of conductivity distribution between neighboring elements and is sensitive to noise...
June 16, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28640923/how-much-detail-is-needed-in-modeling-a-transcranial-magnetic-stimulation-figure-8-coil-measurements-and-brain-simulations
#2
Petar I Petrov, Stefano Mandija, Iris E C Sommer, Cornelis A T van den Berg, Sebastiaan F W Neggers
BACKGROUND: Despite TMS wide adoption, its spatial and temporal patterns of neuronal effects are not well understood. Although progress has been made in predicting induced currents in the brain using realistic finite element models (FEM), there is little consensus on how a magnetic field of a typical TMS coil should be modeled. Empirical validation of such models is limited and subject to several limitations. METHODS: We evaluate and empirically validate models of a figure-of-eight TMS coil that are commonly used in published modeling studies, of increasing complexity: simple circular coil model; coil with in-plane spiral winding turns; and finally one with stacked spiral winding turns...
2017: PloS One
https://www.readbyqxmd.com/read/28634733/dynamic-properties-of-human-tympanic-membrane-after-exposure-to-blast-waves
#3
Warren G Engles, Xuelin Wang, Rong Z Gan
Blast overpressure causes dynamic damage to middle ear components, and tympanic membrane (TM) rupture is the most frequent middle ear injury. However, it is unclear how the blast waves change mechanical properties of the TM and affect sound transmission through the ear. This paper reports the current study on dynamic properties of the TM after exposure to blast waves by using acoustic loading and laser Doppler vibrometry (LDV). The TM specimens were prepared from human temporal bones following exposures to blast overpressure...
June 20, 2017: Annals of Biomedical Engineering
https://www.readbyqxmd.com/read/28633565/febio-history-and-advances
#4
Steve A Maas, Gerard A Ateshian, Jeffrey A Weiss
The principal goal of the FEBio project is to provide an advanced finite element tool for the biomechanics and biophysics communities that allows researchers to model mechanics, transport, and electrokinetic phenomena for biological systems accurately and efficiently. In addition, because FEBio is geared toward the research community, the code is designed such that new features can be added easily, thus making it an ideal tool for testing novel computational methods. Finally, because the success of a code is determined by its user base, integral goals of the FEBio project have been to offer support and outreach to our community; to provide mechanisms for dissemination of results, models, and data; and to encourage interaction between users...
June 21, 2017: Annual Review of Biomedical Engineering
https://www.readbyqxmd.com/read/28632407/prediction-of-the-structural-response-of-the-femoral-shaft-under-dynamic-loading-using-subject-specific-finite-element-models
#5
Gwansik Park, Taewung Kim, Jason Forman, Matthew B Panzer, Jeff R Crandall
The goal of this study was to predict the structural response of the femoral shaft under dynamic loading conditions using subject-specific finite element (SS-FE) models and to evaluate the prediction accuracy of the models in relation to the model complexity. In total, SS-FE models of 31 femur specimens were developed. Using those models, dynamic three-point bending and combined loading tests (bending with four different levels of axial compression) of bare femurs were simulated, and the prediction capabilities of five different levels of model complexity were evaluated based on the impact force time histories: baseline, mass-based scaled, structure-based scaled, geometric SS-FE, and heterogenized SS-FE models...
June 20, 2017: Computer Methods in Biomechanics and Biomedical Engineering
https://www.readbyqxmd.com/read/28632058/assessment-of-model-based-image-matching-for-future-reconstruction-of-unhelmeted-sport-head-impact-kinematics
#6
Gregory J Tierney, Hamed Joodaki, Tron Krosshaug, Jason L Forman, Jeff R Crandall, Ciaran K Simms
Player-to-player contact inherent in many unhelmeted sports means that head impacts are a frequent occurrence. Model-Based Image-Matching (MBIM) provides a technique for the assessment of three-dimensional linear and rotational motion patterns from multiple camera views of a head impact event, but the accuracy is unknown for this application. The goal of this study is to assess the accuracy of the MBIM method relative to reflective marker-based motion analysis data for estimating six degree of freedom head displacements and velocities in a staged pedestrian impact scenario at 40 km/h...
February 28, 2017: Sports Biomechanics
https://www.readbyqxmd.com/read/28631937/the-effect-of-the-sagittal-ridge-angle-on-cartilage-stress-in-the-equine-metacarpo-phalangeal-fetlock-joint
#7
Helen Liley, Helen Davies, Elwyn Firth, Thor Besier, Justin Fernandez
Fatigue failure of bones of the metacarpo-phalangeal (fetlock, MCP) joint is common in thoroughbred racehorses. Stresses within the fetlock joint cartilages are affected by the morphology of the third metacarpal bone (MC3) and proximal phalangeal bone, and the steepness of the median sagittal ridge of MC3 is believed to be associated with fracture. This study investigated the influence of the steepness of the sagittal ridge on cartilage stress distribution using a finite element model of the joint. Changes to the steepness of the sagittal ridge were made by applying a parabolic function to the mesh, creating four different models with sagittal ridge angles ranging from 95° to 105°...
June 15, 2017: Computer Methods in Biomechanics and Biomedical Engineering
https://www.readbyqxmd.com/read/28631619/modeling-trans-spinal-direct-current-stimulation-for-the-modulation-of-the-lumbar-spinal-motor-pathways
#8
Alexander Kuck, Dick Stegeman, Edwin van Asseldonk
OBJECTIVE: Trans-spinal direct current stimulation (tsDCS) is a potential new technique for the treatment of spinal cord injury (SCI). TsDCS aims to facilitate plastic changes in the neural pathways of the spinal cord with a positive effect on SCI recovery. To establish tsDCS as a possible treatment option for SCI, it is essential to gain a better understanding of its cause and effects. We seek to understand the acute effect of tsDCS, including the generated electric field (EF) and its polarization effect on the spinal circuits, to determine a cellular target...
June 20, 2017: Journal of Neural Engineering
https://www.readbyqxmd.com/read/28630862/influence-of-deformation-and-stress-between-bone-and-implant-from-various-bite-forces-by-numerical-simulation-analysis
#9
Hsin-Chung Cheng, Boe-Yu Peng, May-Show Chen, Chiung-Fang Huang, Yi Lin, Yung-Kang Shen
Endosseous oral implant is applied for orthodontic anchorage in subjects with multiple tooth agenesis. Its effectiveness under orthodontic loading has been demonstrated clinically and experimentally. This study investigates the deformation and stress on the bone and implant for different bite forces by three-dimensional (3D) finite element (FE) methods. A numerical simulation of deformation and stress distributions around implants was used to estimate the survival life for implants. The model was applied to determine the pattern and distribution of deformations and stresses within the endosseous implant and on supporting tissues when the endosseous implant is used for orthodontic anchorage...
2017: BioMed Research International
https://www.readbyqxmd.com/read/28629601/a-custom-made-temporomandibular-joint-prosthesis-for-fabrication-by-selective-laser-melting-finite-element-analysis
#10
Xiangliang Xu, Danmei Luo, Chuanbin Guo, Qiguo Rong
A novel and custom-made selective laser melting (SLM) 3D-printed alloplastic temporomandibular joint (TMJ) prosthesis is proposed. The titanium-6aluminium-4vanadium (Ti-6Al-4V) condyle component and ultra-high molecular weight polyethylene (UHMWPE) fossa component comprised the total alloplastic TMJ replacement prosthesis. For the condyle component, an optimized tetrahedral open-porous scaffold with combined connection structures, i.e. an inlay rod and an onlay plate, between the prosthesis and remaining mandible was designed...
June 16, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28628834/functional-niti-grids-for-in-situ-straining-in-the-tem
#11
U Schürmann, C Chluba, N Wolff, D Smazna, R Lima de Miranda, P Junker, R Adelung, E Quandt, L Kienle
In situ measurements are a pivotal extension of conventional transmission electron microscopy (TEM). By means of the shape memory alloy NiTi thin film Functional Grids were produced for in situ straining as alternative or at least complement of expensive commercial holders. Due to the martensite-austenite transition temperature straining effects can be observed by use of customary heating holders in the range of 50 to 100°C. The grids can be produced in diversified designs to fit for different strain situations...
June 9, 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/28625344/confined-photonic-mode-propagation-observed-in-photoemission-electron-microscopy
#12
Theodore Stenmark, R C Word, R Könenkamp
Using photoemission electron microscopy (PEEM) we present a comparative analysis of the wavelength dependence of propagating fields in a simple optical slab waveguide and a thin film photonic crystal W1-type waveguide. We utilize an interferometric imaging approach for light in the near-ultraviolet regime where a 2-photon process is required to produce photoelectron emission. The typical spatial resolution in these experiments is < 30nm. Electromagnetic theory and finite element simulations are shown to be in good agreement with the experimental observations...
June 13, 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/28624880/wing-cross-veins-an-efficient-biomechanical-strategy-to-mitigate-fatigue-failure-of-insect-cuticle
#13
H Rajabi, P Bazargan, A Pourbabaei, Sh Eshghi, A Darvizeh, S N Gorb, D Taylor, J-H Dirks
Locust wings are able to sustain millions of cycles of mechanical loading during the lifetime of the insect. Previous studies have shown that cross veins play an important role in delaying crack propagation in the wings. Do cross veins thus also influence the fatigue behaviour of the wings? Since many important fatigue parameters are not experimentally accessible in a small biological sample, here we use the finite element (FE) method to address this question numerically. Our FE model combines a linear elastic material model, a direct cyclic approach and the Paris law and shows results which are in very good agreement with previously reported experimental data...
June 17, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28623683/the-effects-of-unilateral-alloplastic-temporomandibular-joint-replacement-on-the-opposite-side-natural-joint-a-finite-element-analysis
#14
Burak Bekcioglu, Emel Bulut, Burcu Baş
PURPOSE: The purpose of this study was to evaluate the stress distribution on the temporomandibular joint (TMJ) prosthesis and contralateral natural TMJ with finite-element analysis. MATERIALS AND METHODS: A TMJ implant was used to create a 3-dimensional model with a computer. This model was integrated with a mandible model created with a computer by use of computed tomography images, similar to a real TMJ replacement procedure. Masticatory loads were applied to the model...
May 24, 2017: Journal of Oral and Maxillofacial Surgery
https://www.readbyqxmd.com/read/28623521/exploring-for-the-optimal-structural-design-for-the-3d-printing-technology-for-cranial-reconstruction-a-biomechanical-and-histological-study-comparison-of-solid-vs-porous-structure
#15
Jun Young Lim, Namhyun Kim, Jong-Chul Park, Sun K Yoo, Dong Ah Shin, Kyu-Won Shim
PURPOSE: Cranioplasty for recovering skull defects carries the risk for a number of complications. Various materials are used, including autologous bone graft, metallic materials, and non-metallic materials, each of which has advantages and disadvantages. If the use of autologous bone is not feasible, those artificial materials also have constraints in the case of complex anatomy and/or irregular defects. MATERIAL AND METHODS: This study used metal 3D-printing technology to overcome these existing drawbacks and analyze the clinical and mechanical performance requirements...
June 16, 2017: Child's Nervous System: ChNS: Official Journal of the International Society for Pediatric Neurosurgery
https://www.readbyqxmd.com/read/28623061/comparison-of-extraosseous-talotarsal-stabilization-implants-in-a-stage-ii-adult-acquired-flatfoot-model-a-finite-element-analysis
#16
Jian Xu, Xin Ma, Daping Wang, Wei Lu, Weimin Zhu, Kan Ouyang, Haifeng Liu, Hao Li, Luoyong Jiang
Subtalar arthroereisis has been proved to be an efficient method for correcting flexible adult flatfoot. However, the optimal sinus tarsi implant is still debated and yet to be determined. In the present study, we compared the biomechanical effects of type I and II sinus tarsi implants in stage II adult-acquired flatfoot deformity (AAFD). First, a finite element model of stage II AAFD was established in which virtual surgery of subtalar arthroereisis was simulated. The indexes of plantar stress distribution, peak von Mises of the medial and lateral columns, strain of the medial ligaments and plantar fascia, arch height, talo-first metatarsal angle, calcaneus pitch angle, talonavicular coverage angle, and hindfoot valgus angle were all compared and analyzed...
June 13, 2017: Journal of Foot and Ankle Surgery: Official Publication of the American College of Foot and Ankle Surgeons
https://www.readbyqxmd.com/read/28622909/biomechanical-evaluation-of-a-novel-pedicle-screw-based-interspinous-spacer-a-finite-element-analysis
#17
Hsin-Chang Chen, Jia-Lin Wu, Shou-Chieh Huang, Zheng-Cheng Zhong, Shiu-Ling Chiu, Yu-Shu Lai, Cheng-Kung Cheng
Interspinous spacers have been designed to provide a minimally invasive surgical technique for patients with lumbar spinal stenosis or foraminal stenosis. A novel pedicle screw-based interspinous spacer has been developed in this study, and the aim of this finite element experiment was to investigate the biomechanical differences between the pedicle screw-based interspinous spacer (M-rod system) and the typical interspinous spacer (Coflex-F™). A validated finite element model of an intact lumbar spine was used to analyze the insertions of the Coflex-F™, titanium alloy M-rod (M-Ti), and polyetheretherketone M-rod (M-PEEK), independently...
June 13, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28622020/the-effect-of-direct-and-indirect-force-transmission-on-peri-implant-bone-stress-a-contact-finite-element-analysis
#18
Annike Rand, Meike Stiesch, Michael Eisenburger, Andreas Greuling
In almost all finite element (FE) studies in dentistry, virtual forces are applied directly to dentures. The purpose of this study was to develop a FE model with non-linear contact simulation using an antagonist as force transmitter and to compare this with a similar model that uses direct force transmission. Furthermore, five contact situations were created in order to examine their influence on the peri-implant bone stresses, which are relevant to the survival rate of implants. It was found that the peri-implant bone stresses were strongly influenced by the kind of force transmission and contact number...
August 2017: Computer Methods in Biomechanics and Biomedical Engineering
https://www.readbyqxmd.com/read/28621284/comparison-of-platform-switched-and-sloping-shoulder-implants-on-stress-reduction-in-various-bone-densities-finite-element-analysis
#19
Joji Markose, S Suresh, Shruthi Eshwar, K Rekha, Vipin Jain, Supriya Manvi
INTRODUCTION: Comparison of platform switched (PS), sloping shoulder, and regular implants on stress reduction in various bone densities with finite element analysis. MATERIALS AND METHODS: A total of 12 three-dimensional finite element models were built to analyze the stress distribution model. Nobel Biocare 4.3 × 8 mm regular platform replace select implant with matching diameter easy abutment, Nobel Biocare 4.3 × 8 mm replace select implant PS with 3.5 mm diameter easy abutment, Bicon 4 × 8 mm implant with 4 mm diameter sloping shoulder abutments were created virtually in compact bone density using software...
June 1, 2017: Journal of Contemporary Dental Practice
https://www.readbyqxmd.com/read/28621279/comparative-evaluation-of-stress-developed-on-rotary-retreatment-instruments-during-retrieval-of-gutta-percha
#20
Dhanasekaran Sihivahanan, T Vinay Kumar Reddy, Anchu Rachel Thomas, Natarajan Senthilnathan, Murali Sivakumar, Sushmita Shivanna
AIM: The aim of the study is to compare the maximum stress distribution on the rotary retreatment instruments within the root canal at cervical, middle, and the apical one-third during retreatment of gutta-percha. MATERIALS AND METHODS: A human mandibular premolar was scanned, and three-dimensional geometry of the root was reconstructed using finite element analysis (FEA) software package (ANSYS). The basic model was kept unchanged; tooth models were created using the same dimensions and divided into two groups as follows: Group I: ProTaper Universal retreatment system and group II: Mtwo rotary retreatment system...
June 1, 2017: Journal of Contemporary Dental Practice
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