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https://www.readbyqxmd.com/read/28943701/automatic-falx-cerebri-and-tentorium-cerebelli-segmentation-from-magnetic-resonance-images
#1
Jeffrey Glaister, Aaron Carass, Dzung L Pham, John A Butman, Jerry L Prince
The falx cerebri and tentorium cerebelli are dural structures found in the brain. Due to the roles both structures play in constraining brain motion, the falx and tentorium must be identified and included in finite element models of the head to accurately predict brain dynamics during injury events. To date there has been very little research work on automatically segmenting these two structures, which is understandable given that their 1) thin structure challenges the resolution limits of in vivo 3D imaging, and 2) contrast with respect to surrounding tissue is low in standard magnetic resonance imaging...
February 2017: Proceedings of SPIE
https://www.readbyqxmd.com/read/28943673/a-statistical-framework-for-pathway-and-gene-identification-from-integrative-analysis
#2
Quefeng Li, Menggang Yu, Sijian Wang
In the era of big data, integrative analyses that pool data from different sources are now extensively conducted in order to improve performance. Among many interesting applications, genomics research is an area where integrative methods become popular tools to identify prognostic biomarkers for various diseases. In this paper, we propose such a framework for pathway and gene identification. Our method employs a hierarchical decomposition on genes' effects followed by a proper regularization to identify important pathways and genes across multiple studies...
April 2017: Journal of Multivariate Analysis
https://www.readbyqxmd.com/read/28943655/tough-and-strong-porous-bioactive-glass-pla-composites-for-structural-bone-repair
#3
Wei Xiao, Mohsen Asle Zaeem, Guangda Li, B Sonny Bal, Mohamed N Rahaman
Bioactive glass scaffolds have been used to heal small contained bone defects but their application to repairing structural bone is limited by concerns about their mechanical reliability. In the present study, the addition of an adherent polymer layer to the external surface of strong porous bioactive glass (13-93) scaffolds was investigated to improve their toughness. Finite element modeling (FEM) of the flexural mechanical response of beams composed of a porous glass and an adherent polymer layer predicted a reduction in the tensile stress in the glass with increasing thickness and elastic modulus of the polymer layer...
August 2017: Journal of Materials Science
https://www.readbyqxmd.com/read/28943156/a-continuum-theoretical-model-and-finite-elements-simulation-of-bacterial-flagellar-filament-phase-transition
#4
REVIEW
Xiaoling Wang, Shuo Meng, Jingshi Han
The Bacterial flagellar filament can undergo a polymorphic phase transition in response to both mechanical and chemical variations in vitro and in vivo environments. Under mechanical stimuli, such as viscous flow or forces induced by motor rotation, the filament changes its phase from left-handed normal (N) to right-handed semi-coiled (SC) via phase nucleation and growth. Our detailed mechanical analysis of existing experiments shows that both torque and bending moment contribute to the filament phase transition...
September 14, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28943087/stomatal-opening-involves-polar-not-radial-stiffening-of-guard-cells
#5
Ross Carter, Hugh Woolfenden, Alice Baillie, Sam Amsbury, Sarah Carroll, Eleanor Healicon, Spyros Sovatzoglou, Sioban Braybrook, Julie E Gray, Jamie Hobbs, Richard J Morris, Andrew J Fleming
It has long been accepted that differential radial thickening of guard cells plays an important role in the turgor-driven shape changes required for stomatal pore opening to occur [1-4]. This textbook description derives from an original interpretation of structure rather than measurement of mechanical properties. Here we show, using atomic force microscopy, that although mature guard cells display a radial gradient of stiffness, this is not present in immature guard cells, yet young stomata show a normal opening response...
September 18, 2017: Current Biology: CB
https://www.readbyqxmd.com/read/28941397/semi-analytical-modeling-of-anchor-loss-in-plate-mounted-resonators
#6
Christoph Schaal, Robert M'Closkey, Ajit Mal
A semi-analytical technique for estimating the energy loss in a resonator mounted to an infinite plate substrate is proposed in this paper. In a plate, only Lamb waves have to be considered, leading to a simplified characterization of the energy carried away from a vibrating source on the plate surface. Instead of employing absorbing elements at the boundaries of the plate-resonator finite element model, it is shown how the semi-analytical approach of stitching together analytical Lamb wave expressions to the finite element model can be utilized...
September 14, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28941258/magnetic-quantum-dots-steer-and-detach-microtubules-from-kinesin-coated-surfaces
#7
Kalpesh D Mahajan, Yixiao Cui, C Jenny Dorcéna, Nathan F Bouxsien, George D Bachand, Jeffrey J Chalmers, Jessica O Winter
BACKGROUND: The microtubule (MT)-kinesin system has been extensively studied because of its role in cellular processes, as well as its potential use for controllably transporting objects at the nanoscale. Thus, there is substantial interest in methods to evaluate MT properties, including bending radius and the binding energy of kinesin motor proteins to MT tracks. Current methods to identify these properties include optical tweezers, microfluidic devices, and magnetic fields. METHODS: Here, the use of magnetic quantum dots (i...
September 23, 2017: Biotechnology Journal
https://www.readbyqxmd.com/read/28940776/influence-of-collars-on-the-primary-stability-of-cementless-femoral-stems-a-finite-element-study-using-a-diverse-patient-cohort
#8
Rami M A Al-Dirini
For cementless femoral stems, there is debate as to whether a collar enhances primary stability and load transfer compared to collarless designs. Finite Element (FE) analysis has the potential to compare stem designs within the same cohort, allowing for subtle performance differences to be identified, if present. Subject-specific FE models of intact and implanted femora were run for a diverse cohort (21 males, 20 females; BMI 16.4-41.2 kg.m(-2) , age 50-80yrs). Collared and collarless versions of Corail® (DePuy Synthes) were sized and positioned using an automated algorithm that aligns the femoral/stem axes, preserves the head-centre location and maximises metaphyseal fit...
September 21, 2017: Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society
https://www.readbyqxmd.com/read/28940110/are-dxa-abmd-and-qct-fea-stiffness-and-strength-estimates-sensitive-to-sex-and-age
#9
Asghar Rezaei, Hugo Giambini, Timothy Rossman, Kent D Carlson, Michael J Yaszemski, Lichun Lu, Dan Dragomir-Daescu
Dual X-ray absorptiometry (DXA) measures areal bone mineral density (aBMD) by simplifying a complex 3D bone structure to a 2D projection and is not equally effective for explaining fracture strength in women and men. Unlike DXA, subject-specific quantitative computed tomography-based finite element analysis (QCT/FEA) estimates fracture strength using 3D bone mineral distribution and geometry. By using experimentally-measured femoral stiffness and strength from a one hundred sample cadaveric cohort that included variations in sex and age, we wanted to determine if QCT/FEA estimates were able to better predict the experimental variations than DXA/aBMD...
September 22, 2017: Annals of Biomedical Engineering
https://www.readbyqxmd.com/read/28938162/characterization-of-wedge-waves-propagating-along-wedge-tips-with-defects
#10
Ming-I Chen, Seng-Po Tesng, Pei-Yuan Lo, Che-Hua Yang
Wedge waves are guided acoustic waves propagating along the tip of a wedge with the energy tightly confined near the wedge. Anti-symmetric flexural (ASF) modes are wedge waves with their particle motion anti-symmetric with the apex mid-plane. This study investigates the behaviors of ASF modes propagation along wedge tips with perfect and imperfect rectangular defects. Numerical finite element simulations and experimental measurements using a laser ultrasound technique are employed to explore the behaviors of ASF modes interacting with defects...
September 14, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28938157/adsorption-combined-with-superconducting-high-gradient-magnetic-separation-technique-used-for-removal-of-arsenic-and-antimony
#11
Zenglu Qi, Tista Prasai Joshi, Ruiping Liu, Yiran Li, Huijuan Liu, Jiuhui Qu
Manganese iron oxide (MnFe2O4), an excellent arsenic(As)/antimony(Sb) removal adsorbent, is greatly restricted for the solid-liquid separation. Through the application of superconducting high gradient magnetic separation (HGMS) technique, we herein constructed a facility for the in situ solid-liquid separation of micro-sized MnFe2O4 adsorbent in As/Sb removal process. To the relative low initial concentration 50.0μgL(-1), MnFe2O4 material sorbent can still decrease As or Sb below US EPA's drinking water standard limit...
September 7, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28938147/development-of-an-experimental-model-of-burst-fracture-with-damage-characterization-of-the-vertebral-bodies-under-dynamic-conditions
#12
A Germaneau, T Vendeuvre, M Saget, P Doumalin, J C Dupré, F Brémand, F Hesser, C Brèque, P Maxy, M Roulaud, O Monlezun, P Rigoard
BACKGROUND: Burst fractures represent a significant proportion of fractures of the thoracolumbar junction. The recent advent of minimally invasive techniques has revolutionized the surgical treatment of this type of fracture. However mechanical behaviour and primary stability offered by these solutions have to be proved from experimental validation tests on cadaveric specimens. Therefore, the aim of this study was to develop an original and reproducible model of burst fracture under dynamic impact...
September 13, 2017: Clinical Biomechanics
https://www.readbyqxmd.com/read/28937328/biomechanical-effects-of-hybrid-stabilization-on-the-risk-of-proximal-adjacent-segment-degeneration-following-lumbar-spinal-fusion-using-an-interspinous-device-or-a-pedicle-screw-based-dynamic-fixator
#13
Chang-Hyun Lee, Young Eun Kim, Hak Joong Lee, Dong Gyu Kim, Chi Heon Kim
OBJECTIVE Pedicle screw-rod-based hybrid stabilization (PH) and interspinous device-based hybrid stabilization (IH) have been proposed to prevent adjacent-segment degeneration (ASD) and their effectiveness has been reported. However, a comparative study based on sound biomechanical proof has not yet been reported. The aim of this study was to compare the biomechanical effects of IH and PH on the transition and adjacent segments. METHODS A validated finite element model of the normal lumbosacral spine was used...
September 22, 2017: Journal of Neurosurgery. Spine
https://www.readbyqxmd.com/read/28937224/thermocapillary-droplet-actuation-effect-of-solid-structure-and-wettability
#14
George Karapetsas, Nikolaos T Chamakos, Athanasios G Papathanasiou
We examine the thermocapillary-driven flow of a droplet on a non-uniformly heated patterned surface. Using a sharp-interface scheme, capable of efficiently modelling the flow over complex surfaces, we perform 2D and 3D finite element simulations for a wide range of substrate wettabilities, i.e. from hydrophilic to super-hydrophobic surfaces. Our results demonstrate that the contact angle hysteresis, due to the presence of the solid structures, is responsible for the appearance of a critical thermal gradient beyond which droplet migration is possible that has been reported by experimental observations...
September 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28936526/modeling-the-impedance-spectra-of-mixed-conducting-thin-films-with-exposed-and-embedded-current-collectors
#15
Jiapeng Liu, Francesco Ciucci
In this article, we develop a new finite-element-based model for the simulation of the electrochemical impedance spectroscopy (EIS) response of mixed ionic electronic conducting (MIEC) thin films. We first validated the model against experimental data for Sm-doped CeO2 (SDC) symmetrical films deposited on an yittria-stabilized ZrO2 (YSZ) substrate, a pure ionic conductor. We first studied the configuration where the patterned electrodes are placed on top of the MIEC ("exposed" configuration). Our model is capable of correctly reproducing the EIS response and the total capacitance, together with their dependence on the oxygen partial pressure...
September 22, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28936039/comparative-three-dimensional-finite-element-analysis-of-implant-supported-fixed-complete-arch-mandibular-prostheses-in-two-materials
#16
João Paulo Mendes Tribst, Dayana Campanelli de Morais, Alexandre Abhdala Alonso, Amanda Maria de Oliveira Dal Piva, Alexandre Luis Souto Borges
BACKGROUND: The increase of requests for implant-supported prosthesis (ISP) with zirconia as infrastructure has attracted a lot of attention due to its esthetics, biocompatibility, and survival rate similar to metallic infrastructure. The aim of this study was to evaluate the influence of two different framework materials on stress distribution over a bone tissue-simulating material. MATERIALS AND METHODS: Two ISP were modeled and divided into two infrastructure materials: titanium (Ti) and zirconia...
July 2017: Journal of Indian Prosthodontic Society
https://www.readbyqxmd.com/read/28935483/force-and-deformation-stresses-in-customized-and-non-customized-plates-during-simulation-of-advancement-genioplasty
#17
V F Ramos, L A P F Pinto, R T Basting
PURPOSE: The aim of this study was to evaluate the distribution of deformation stresses in customized and non-customized plates during simulated advancement genioplasty, using the finite element method. METHODS: A customized plate (Traumec) was developed with 4.75 mm advancement, in ASTM F67 Grade 2 titanium, with four screws. Non-customized (standard) plates with 6 mm advancement (Stryker with six screws and Osteomed with four screws) were used for comparison...
August 31, 2017: Journal of Cranio-maxillo-facial Surgery
https://www.readbyqxmd.com/read/28934689/dynamical-modeling-of-tissue-electroporation
#18
Damien Voyer, Aude Silve, Lluis M Mir, Riccardo Scorretti, Clair Poignard
In this paper, we propose a new dynamical model of tissue electroporation. The model is based on equivalent circuit approach at the tissue. Considering two current densities from cells and extracellular matrix, we identify the macroscopic homogenised contribution of the cell membranes. Our approach makes it possible to define a macroscopic homogenised electric field and a macroscopic homogenised transmembrane potential. This provides a direct link between the cell scale electroporation models and the tissue models...
September 5, 2017: Bioelectrochemistry
https://www.readbyqxmd.com/read/28934616/a-model-based-bayesian-solution-for-characterization-of-complex-damage-scenarios-in-aerospace-composite-structures
#19
H Reed, Cara A C Leckey, A Dick, G Harvey, J Dobson
Ultrasonic damage detection and characterization is commonly used in nondestructive evaluation (NDE) of aerospace composite components. In recent years there has been an increased development of guided wave based methods. In real materials and structures, these dispersive waves result in complicated behavior in the presence of complex damage scenarios. Model-based characterization methods utilize accurate three dimensional finite element models (FEMs) of guided wave interaction with realistic damage scenarios to aid in defect identification and classification...
September 5, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28934161/improving-the-process-of-adjusting-the-parameters-of-finite-element-models-of-healthy-human-intervertebral-discs-by-the-multi-response-surface-method
#20
Fátima Somovilla Gómez, Rubén Lostado Lorza, Marina Corral Bobadilla, Rubén Escribano García
The kinematic behavior of models that are based on the finite element method (FEM) for modeling the human body depends greatly on an accurate estimate of the parameters that define such models. This task is complex, and any small difference between the actual biomaterial model and the simulation model based on FEM can be amplified enormously in the presence of nonlinearities. The current paper attempts to demonstrate how a combination of the FEM and the MRS methods with desirability functions can be used to obtain the material parameters that are most appropriate for use in defining the behavior of Finite Element (FE) models of the healthy human lumbar intervertebral disc (IVD)...
September 21, 2017: Materials
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