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Finite growth models

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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
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
#7
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
#8
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
#9
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
#10
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
https://www.readbyqxmd.com/read/28293138/effective-equations-governing-an-active-poroelastic-medium
#11
J Collis, D L Brown, M E Hubbard, R D O'Dea
In this work, we consider the spatial homogenization of a coupled transport and fluid-structure interaction model, to the end of deriving a system of effective equations describing the flow, elastic deformation and transport in an active poroelastic medium. The 'active' nature of the material results from a morphoelastic response to a chemical stimulant, in which the growth time scale is strongly separated from other elastic time scales. The resulting effective model is broadly relevant to the study of biological tissue growth, geophysical flows (e...
February 2017: Proceedings. Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28276475/growth-mechanism-for-low-temperature-pvd-graphene-synthesis-on-copper-using-amorphous-carbon
#12
Udit Narula, Cher Ming Tan, Chao Sung Lai
Growth mechanism for synthesizing PVD based Graphene using Amorphous Carbon, catalyzed by Copper is investigated in this work. Different experiments with respect to Amorphous Carbon film thickness, annealing time and temperature are performed for the investigation. Copper film stress and its effect on hydrogen diffusion through the film grain boundaries are found to be the key factors for the growth mechanism, and supported by our Finite Element Modeling. Low temperature growth of Graphene is achieved and the proposed growth mechanism is found to remain valid at low temperatures...
March 9, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28275592/model-of-human-fetal-growth-in-hypoplastic-left-heart-syndrome-reduced-ventricular-growth-due-to-decreased-ventricular-filling-and-altered-shape
#13
Sukriti Dewan, Adarsh Krishnamurthy, Devleena Kole, Giulia Conca, Roy Kerckhoffs, Michael D Puchalski, Jeffrey H Omens, Heather Sun, Vishal Nigam, Andrew D McCulloch
INTRODUCTION: Hypoplastic left heart syndrome (HLHS) is a congenital condition with an underdeveloped left ventricle (LV) that provides inadequate systemic blood flow postnatally. The development of HLHS is postulated to be due to altered biomechanical stimuli during gestation. Predicting LV size at birth using mid-gestation fetal echocardiography is a clinical challenge critical to prognostic counseling. HYPOTHESIS: We hypothesized that decreased ventricular filling in utero due to mitral stenosis may reduce LV growth in the fetal heart via mechanical growth signaling...
2017: Frontiers in Pediatrics
https://www.readbyqxmd.com/read/28267878/quantification-of-substrate-and-cellular-strains-in-stretchable-3d-cell-cultures-an-experimental-and-computational-framework
#14
P González-Avalos, M Mürnseer, J Deeg, A Bachmann, J Spatz, S Dooley, R Eils, E Gladilin
The mechanical cell environment is a key regulator of biological processes . In living tissues, cells are embedded into the 3D extracellular matrix and permanently exposed to mechanical forces. Quantification of the cellular strain state in a 3D matrix is therefore the first step towards understanding how physical cues determine single cell and multicellular behaviour. The majority of cell assays are, however, based on 2D cell cultures that lack many essential features of the in vivo cellular environment. Furthermore, nondestructive measurement of substrate and cellular mechanics requires appropriate computational tools for microscopic image analysis and interpretation...
March 7, 2017: Journal of Microscopy
https://www.readbyqxmd.com/read/28264155/x-ray-bragg-ptychography-on-a-single-ingan-gan-core-shell-nanowire
#15
Dmitry Dzhigaev, Tomaš Stankevič, Zhaoxia Bi, Sergey Lazarev, Max Rose, Anatoly Shabalin, Juliane Reinhardt, Anders Mikkelsen, Lars Samuelson, Gerald Falkenberg, Robert Feidenhans'l, Ivan A Vartanyants
The future of solid-state lighting can be potentially driven by applications of InGaN/GaN core-shell nanowires. These heterostructures provide the possibility for fine-tuning of functional properties by controlling a strain state between mismatched layers. We present a nondestructive study of a single 400 nm-thick InGaN/GaN core-shell nanowire using two-dimensional (2D) X-ray Bragg ptychography (XBP) with a nanofocused X-ray beam. The XBP reconstruction enabled the determination of a detailed three-dimensional (3D) distribution of the strain in the particular nanowire using a model based on finite element method...
March 20, 2017: ACS Nano
https://www.readbyqxmd.com/read/28262769/finite-size-effects-on-bacterial-population-expansion-under-controlled-flow-conditions
#16
Francesca Tesser, Jos C H Zeegers, Herman J H Clercx, Luc Brunsveld, Federico Toschi
The expansion of biological species in natural environments is usually described as the combined effect of individual spatial dispersal and growth. In the case of aquatic ecosystems flow transport can also be extremely relevant as an extra, advection induced, dispersal factor. We designed and assembled a dedicated microfluidic device to control and quantify the expansion of populations of E. coli bacteria under both co-flowing and counter-flowing conditions, measuring the front speed at varying intensity of the imposed flow...
March 6, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28258413/viscosity-and-haemodynamics-in-a-late-gestation-rat-feto-placental-arterial-network
#17
Nikhilesh Bappoo, Lachlan J Kelsey, Louis Parker, Tim Crough, Carmel M Moran, Adrian Thomson, Megan C Holmes, Caitlin S Wyrwoll, Barry J Doyle
The placenta is a transient organ which develops during pregnancy to provide haemotrophic support for healthy fetal growth and development. Fundamental to its function is the healthy development of vascular trees in the feto-placental arterial network. Despite the strong association of haemodynamics with vascular remodelling mechanisms, there is a lack of computational haemodynamic data that may improve our understanding of feto-placental physiology. The aim of this work was to create a comprehensive 3D computational fluid dynamics model of a substructure of the rat feto-placental arterial network and investigate the influence of viscosity on wall shear stress (WSS)...
March 3, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28256235/cell-contractility-facilitates-alignment-of-cells-and-tissues-to-static-uniaxial-stretch
#18
Elisabeth G Rens, Roeland M H Merks
During animal development and homeostasis, the structure of tissues, including muscles, blood vessels, and connective tissues, adapts to mechanical strains in the extracellular matrix (ECM). These strains originate from the differential growth of tissues or forces due to muscle contraction or gravity. Here we show using a computational model that by amplifying local strain cues, active cell contractility can facilitate and accelerate the reorientation of single cells to static strains. At the collective cell level, the model simulations show that active cell contractility can facilitate the formation of strings along the orientation of stretch...
February 28, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28242899/investigation-on-temperature-fields-in-industrial-chilling-of-pork-legs-for-pdo-parma-ham-production-and-coupled-temperature-microbial-growth-simulation
#19
Massimiliano Rinaldi, Matteo Cordioli, Davide Barbanti
In the present work, temperature distribution within an industrial blast chiller with pork leg for Protected Designation of Origin Parma ham production was studied and the slowest cooling zone and the fastest cooling zone were recognized. Moreover, apparent heat transfer coefficients in both positions were calculated and resulted equal to 27.1 and 15.6 W m(-2) °C(-1), respectively. A finite element method model by distinguishing the three main components (skin, lean meat and bone) of the leg for the unsteady heat transfer during cooling was developed and validated against industrial chiller data...
January 2017: Journal of Food Science and Technology
https://www.readbyqxmd.com/read/28224240/simulation-of-cell-substrate-traction-force-dynamics-in-response-to-soluble-factors
#20
Tao Liu
Finite element (FE) simulations of contractile responses of vascular muscular thin films (vMTFs) and endothelial cells resting on an array of microposts under stimulation of soluble factors were conducted in comparison with experimental measurements reported in the literature. Two types of constitutive models were employed in the simulations, i.e. smooth muscle cell type and non-smooth muscle cell type. The time histories of the effects of soluble factors were obtained via calibration against experimental measurements of contractile responses of tissues or cells...
February 21, 2017: Biomechanics and Modeling in Mechanobiology
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