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Finite growth models

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https://www.readbyqxmd.com/read/28621284/comparison-of-platform-switched-and-sloping-shoulder-implants-on-stress-reduction-in-various-bone-densities-finite-element-analysis
#1
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/28618602/finite-thickness-effects-on-the-rayleigh-taylor-instability-in-accelerated-elastic-solids
#2
S A Piriz, A R Piriz, N A Tahir
A physical model has been developed for the linear Rayleigh-Taylor instability of a finite-thickness elastic slab laying on top of a semi-infinite ideal fluid. The model includes the nonideal effects of elasticity as boundary conditions at the top and bottom interfaces of the slab and also takes into account the finite transit time of the elastic waves across the slab thickness. For Atwood number A_{T}=1, the asymptotic growth rate is found to be in excellent agreement with the exact solution [Plohr and Sharp, Z...
May 2017: Physical Review. E
https://www.readbyqxmd.com/read/28614573/finite-element-modeling-of-avascular-tumor-growth-using-a-stress-driven-model
#3
Faezeh Iranmanesh, Mohammad Ali Nazari
Tumor growth being a multi-stage process has been investigated from different aspects. In the present study, an attempt is made to represent a constitutive-structure based model of avascular tumor growth in which the effects of tensile stresses caused by collagen fibers are considered. Collagen fibers as a source of anisotropy in the structure of tissue, is taken into account using a continuous fiber distribution formulation. To this end, a finite element modeling is implemented in which a neo-Hookean hyperelastic material is assigned to the tumor and its surrounding host...
June 14, 2017: Journal of Biomechanical Engineering
https://www.readbyqxmd.com/read/28614278/patient-specific-distraction-regimen-to-avoid-growth-rod-failure
#4
Aakash Agarwal, Arvind Jayaswal, Anand K Agarwal, Vijay K Goel
STUDY DESIGN: A finite element study to establish the relationship between patient's curve flexibility (determined using curve correction under gravity) in juvenile idiopathic scoliosis and the required distraction frequency to avoid growth rod fracture, as a function of time. OBJECTIVE: To perform a parametric analysis using a juvenile scoliotic spine model (single mid-thoracic curve with the apex at the eighth thoracic vertebra) and establish the relationship between curve flexibility (determined using curve correction under gravity) and the distraction interval that allows a higher factor of safety for the growth rods...
June 13, 2017: Spine
https://www.readbyqxmd.com/read/28604803/impact-of-tumor-position-conductivity-distribution-and-tissue-homogeneity-on-the-distribution-of-tumor-treating-fields-in-a-human-brain-a-computer-modeling-study
#5
Anders Rosendal Korshoej, Frederik Lundgaard Hansen, Axel Thielscher, Gorm Burckhardt von Oettingen, Jens Christian Hedemann Sørensen
BACKGROUND: Tumor treating fields (TTFields) are increasingly used in the treatment of glioblastoma. TTFields inhibit cancer growth through induction of alternating electrical fields. To optimize TTFields efficacy, it is necessary to understand the factors determining the strength and distribution of TTFields. In this study, we provide simple guiding principles for clinicians to assess the distribution and the local efficacy of TTFields in various clinical scenarios. METHODS: We calculated the TTFields distribution using finite element methods applied to a realistic head model...
2017: PloS One
https://www.readbyqxmd.com/read/28566701/mathematical-analysis-of-glioma-growth-in-a-murine-model
#6
Erica M Rutter, Tracy L Stepien, Barrett J Anderies, Jonathan D Plasencia, Eric C Woolf, Adrienne C Scheck, Gregory H Turner, Qingwei Liu, David Frakes, Vikram Kodibagkar, Yang Kuang, Mark C Preul, Eric J Kostelich
Five immunocompetent C57BL/6-cBrd/cBrd/Cr (albino C57BL/6) mice were injected with GL261-luc2 cells, a cell line sharing characteristics of human glioblastoma multiforme (GBM). The mice were imaged using magnetic resonance (MR) at five separate time points to characterize growth and development of the tumor. After 25 days, the final tumor volumes of the mice varied from 12 mm(3) to 62 mm(3), even though mice were inoculated from the same tumor cell line under carefully controlled conditions. We generated hypotheses to explore large variances in final tumor size and tested them with our simple reaction-diffusion model in both a 3-dimensional (3D) finite difference method and a 2-dimensional (2D) level set method...
May 31, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28566514/modelling-human-skull-growth-a-validated-computational-model
#7
Joseph Libby, Arsalan Marghoub, David Johnson, Roman H Khonsari, Michael J Fagan, Mehran Moazen
During the first year of life, the brain grows rapidly and the neurocranium increases to about 65% of its adult size. Our understanding of the relationship between the biomechanical forces, especially from the growing brain, the craniofacial soft tissue structures and the individual bone plates of the skull vault is still limited. This basic knowledge could help in the future planning of craniofacial surgical operations. The aim of this study was to develop a validated computational model of skull growth, based on the finite-element (FE) method, to help understand the biomechanics of skull growth...
May 2017: Journal of the Royal Society, Interface
https://www.readbyqxmd.com/read/28536534/a-bio-realistic-finite-element-model-to-evaluate-the-effect-of-masticatory-loadings-on-mouse-mandible-related-tissues
#8
Alexander Tsouknidas, Lucia Jimenez-Rojo, Evangelos Karatsis, Nikolaos Michailidis, Thimios A Mitsiadis
Mice are arguably the dominant model organisms for studies investigating the effect of genetic traits on the pathways to mammalian skull and teeth development, thus being integral in exploring craniofacial and dental evolution. The aim of this study is to analyse the functional significance of masticatory loads on the mouse mandible and identify critical stress accumulations that could trigger phenotypic and/or growth alterations in mandible-related structures. To achieve this, a 3D model of mouse skulls was reconstructed based on Micro Computed Tomography measurements...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28534795/choroid-neovascularization-growth-prediction-with-treatment-based-on-reaction-diffusion-model-in-3d-oct-images
#9
Shuxia Zhu, Fei Shi, Dehui Xiang, Weifang Zhu, Haoyu Chen, Xinjian Chen
Choroid neovascularization (CNV) is caused by new blood vessels growing in the choroid and penetrating the Bruch membrane. It is the major cause of vision disability in many retinal diseases. Though anti-vascular endothelial growth factor (VEGF) injection has proved to be effective for treating CNV, treatment planning is essential to ensure the efficacy while reducing the risk. For this purpose, we propose a CNV growth model based on longitudinal Optical Coherence Tomography (OCT) images. The reaction-diffusion model is applied to simulate the growth and shrinkage of CNV volumes, and is solved by using finite element method (FEM)...
May 16, 2017: IEEE Journal of Biomedical and Health Informatics
https://www.readbyqxmd.com/read/28531983/development-of-haptic-based-piezoresistive-artificial-fingertip-toward-efficient-tactile-sensing-systems-for-humanoids
#10
Amin TermehYousefi, Saman Azhari, Amin Khajeh, Mohd Nizar Hamidon, Hirofumi Tanaka
Haptic sensors are essential devices that facilitate human-like sensing systems such as implantable medical devices and humanoid robots. The availability of conducting thin films with haptic properties could lead to the development of tactile sensing systems that stretch reversibly, sense pressure (not just touch), and integrate with collapsible. In this study, a nanocomposite based hemispherical artificial fingertip fabricated to enhance the tactile sensing systems of humanoid robots. To validate the hypothesis, proposed method was used in the robot-like finger system to classify the ripe and unripe tomato by recording the metabolic growth of the tomato as a function of resistivity change during a controlled indention force...
August 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28469383/a-numerical-handling-of-the-boundary-conditions-imposed-by-the-skull-on-an-inhomogeneous-diffusion-reaction-model-of-glioblastoma-invasion-into-the-brain-clinical-validation-aspects
#11
Georgios S Stamatakos, Stavroula G Giatili
A novel explicit triscale reaction-diffusion numerical model of glioblastoma multiforme tumor growth is presented. The model incorporates the handling of Neumann boundary conditions imposed by the cranium and takes into account both the inhomogeneous nature of human brain and the complexity of the skull geometry. The finite-difference time-domain method is adopted. To demonstrate the workflow of a possible clinical validation procedure, a clinical case/scenario is addressed. A good agreement of the in silico calculated value of the doubling time (ie, the time for tumor volume to double) with the value of the same quantity based on tomographic imaging data has been observed...
2017: Cancer Informatics
https://www.readbyqxmd.com/read/28428446/the-finite-state-projection-approach-to-analyze-dynamics-of-heterogeneous-populations
#12
Rob Johnson, Brian Munsky
Population modeling aims to capture and predict the dynamics of cell populations in constant or fluctuating environments. At the elementary level, population growth proceeds through sequential divisions of individual cells. Due to stochastic effects, populations of cells are inherently heterogeneous in phenotype, and some phenotypic variables have an effect on division or survival rates, as can be seen in partial drug resistance. Therefore, when modeling population dynamics where the control of growth and division is phenotype dependent, the corresponding model must take account of the underlying cellular heterogeneity...
May 11, 2017: Physical Biology
https://www.readbyqxmd.com/read/28415271/mean-cluster-approach-indicates-cell-sorting-time-scales-are-determined-by-collective-dynamics
#13
Carine P Beatrici, Rita M C de Almeida, Leonardo G Brunnet
Cell migration is essential to cell segregation, playing a central role in tissue formation, wound healing, and tumor evolution. Considering random mixtures of two cell types, it is still not clear which cell characteristics define clustering time scales. The mass of diffusing clusters merging with one another is expected to grow as t^{d/d+2} when the diffusion constant scales with the inverse of the cluster mass. Cell segregation experiments deviate from that behavior. Explanations for that could arise from specific microscopic mechanisms or from collective effects, typical of active matter...
March 2017: Physical Review. E
https://www.readbyqxmd.com/read/28397797/general-characteristics-of-relative-dispersion-in-the-ocean
#14
Raffaele Corrado, Guglielmo Lacorata, Luigi Palatella, Rosalia Santoleri, Enrico Zambianchi
The multi-scale and nonlinear nature of the ocean dynamics dramatically affects the spreading of matter, like pollutants, marine litter, etc., of physical and chemical seawater properties, and the biological connectivity inside and among different basins. Based on the Finite-Scale Lyapunov Exponent analysis of the largest available near-surface Lagrangian data set from the Global Drifter Program, our results show that, despite the large variety of flow features, relative dispersion can ultimately be described by a few parameters common to all ocean sub-basins, at least in terms of order of magnitude...
April 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28393160/dielectric-spectroscopy-platform-to-measure-mcf10a-epithelial-cell-aggregation-as-a-model-for-spheroidal-cell-cluster-analysis
#15
K L Heileman, M Tabrizian
3-Dimensional cell cultures are more representative of the native environment than traditional cell cultures on flat substrates. As a result, 3-dimensional cell cultures have emerged as a very valuable model environment to study tumorigenesis, organogenesis and tissue regeneration. Many of these models encompass the formation of cell aggregates, which mimic the architecture of tumor and organ tissue. Dielectric impedance spectroscopy is a non-invasive, label free and real time technique, overcoming the drawbacks of established techniques to monitor cell aggregates...
May 2, 2017: Analyst
https://www.readbyqxmd.com/read/28364758/predictability-of-large-scale-atmospheric-motions-lyapunov-exponents-and-error-dynamics
#16
Stéphane Vannitsem
The deterministic equations describing the dynamics of the atmosphere (and of the climate system) are known to display the property of sensitivity to initial conditions. In the ergodic theory of chaos, this property is usually quantified by computing the Lyapunov exponents. In this review, these quantifiers computed in a hierarchy of atmospheric models (coupled or not to an ocean) are analyzed, together with their local counterparts known as the local or finite-time Lyapunov exponents. It is shown in particular that the variability of the local Lyapunov exponents (corresponding to the dominant Lyapunov exponent) decreases when the model resolution increases...
March 2017: Chaos
https://www.readbyqxmd.com/read/28340243/finite-time-parametric-identification-for-the-model-representing-the-metabolic-and-genetic-regulatory-effects-of-sequential-aerobic-respiration-and-anaerobic-fermentation-processes-in-escherichia-coli
#17
Alfonso Sepúlveda-Gálvez, Jesús Agustín Badillo-Corona, Isaac Chairez
Mathematical modelling applied to biological systems allows for the inferring of changes in the dynamic behaviour of organisms associated with variations in the environment. Models based on ordinary differential equations are most commonly used because of their ability to describe the mechanisms of biological systems such as transcription. The disadvantage of using this approach is that there is a large number of parameters involved and that it is difficult to obtain them experimentally. This study presents an algorithm to obtain a finite-time parameter characterization of the model used to describe changes in the metabolic behaviour of Escherichia coli associated with environmental changes...
March 17, 2017: Mathematical Medicine and Biology: a Journal of the IMA
https://www.readbyqxmd.com/read/28323481/the-emergence-of-life-as-a-first-order-phase-transition
#18
Cole Mathis, Tanmoy Bhattacharya, Sara Imari Walker
It is well known that life on Earth alters its environment over evolutionary and geological timescales. An important open question is whether this is a result of evolutionary optimization or a universal feature of life. In the latter case, the origin of life would be coincident with a shift in environmental conditions. Here we present a model for the emergence of life in which replicators are explicitly coupled to their environment through the recycling of a finite supply of resources. The model exhibits a dynamic, first-order phase transition from nonlife to life, where the life phase is distinguished by selection on replicators...
March 2017: Astrobiology
https://www.readbyqxmd.com/read/28317393/structural-analysis-of-two-different-stent-configurations
#19
M Simão, J M Ferreira, J Mora-Rodriguez, H M Ramos
Two different stent configurations (i.e. the well known Palmaz-Schatz (PS) and a new stent configuration) are mechanically investigated. A finite element model was used to study the two geometries under combining loads and a computational fluid dynamic model based on fluid structure interaction was developed investigating the plaque and the artery wall reactions in a stented arterial segment. These models determine the stress and displacement fields of the two stents under internal pressure conditions. Results suggested that stent designs cause alterations in vascular anatomy that adversely affect arterial stress distributions within the wall, which have impact in the vessel responses such as the restenosis...
March 20, 2017: Computer Methods in Biomechanics and Biomedical Engineering
https://www.readbyqxmd.com/read/28293628/numerical-method-for-the-design-of-healing-chamber-in-additive-manufactured-dental-implants
#20
Hsiao-Chien Lee, Pei-I Tsai, Chih-Chieh Huang, San-Yuan Chen, Chuen-Guang Chao, Nien-Ti Tsou
The inclusion of a healing chamber in dental implants has been shown to promote biological healing. In this paper, a novel numerical approach to the design of the healing chamber for additive-manufactured dental implants is proposed. This study developed an algorithm for the modeling of bone growth and employed finite element method in ANSYS to facilitate the design of healing chambers with a highly complex configuration. The model was then applied to the design of dental implants for insertion into the posterior maxillary bones...
2017: BioMed Research International
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