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Finite growth models

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
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
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
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
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
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
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
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
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
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
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
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
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
M Cóndor, J M García-Aznar
Cell adhesion is crucial for cells to not only physically interact with each other but also sense their microenvironment and respond accordingly. In fact, adherent cells can generate physical forces that are transmitted to the surrounding matrix, regulating the formation of cell-matrix adhesions. The main purpose of this work is to develop a computational model to simulate the dynamics of cell-matrix adhesions through a cohesive formulation within the framework of the finite element method and based on the principles of continuum damage mechanics...
February 17, 2017: Biomechanics and Modeling in Mechanobiology
Genís Torrents, Xavier Illa, Eduard Vives, Antoni Planes
A simple model for the growth of elongated domains (needle-like) during a martensitic phase transition is presented. The model is purely geometric and the only interactions are due to the sequentiality of the kinetic problem and to the excluded volume, since domains cannot retransform back to the original phase. Despite this very simple interaction, numerical simulations show that the final observed microstructure can be described as being a consequence of dipolar-like interactions. The model is analytically solved in 2D for the case in which two symmetry related domains can grow in the horizontal and vertical directions...
January 2017: Physical Review. E
Hossein Azizi, Sebastian Gurevich, Nikolas Provatas
We explore numerically the morphological patterns of thermodiffusive instabilities in combustion fronts with a continuum fuel source, within a range of Lewis numbers and ignition temperatures, focusing on the cellular regime. For this purpose, we generalize the recent model of Brailovsky et al. to include distinct process kinetics and reactant heterogeneity. The generalized model is derived analytically and validated with other established models in the limit of infinite Lewis number for zero-order and first-order kinetics...
January 2017: Physical Review. E
Naftali R Smith, Baruch Meerson, Pavel V Sasorov
Height fluctuations of growing surfaces can be characterized by the probability distribution of height in a spatial point at a finite time. Recently there has been spectacular progress in the studies of this quantity for the Kardar-Parisi-Zhang (KPZ) equation in 1+1 dimensions. Here we notice that, at or above a critical dimension, the finite-time one-point height distribution is ill defined in a broad class of linear surface growth models unless the model is regularized at small scales. The regularization via a system-dependent small-scale cutoff leads to a partial loss of universality...
January 2017: Physical Review. E
Santiago Orrego, Huakun Xu, Dwayne Arola
The oral cavity frequently undergoes localized changes in chemistry and level of acidity, which threatens the integrity of the restorative material and supporting hard tissue. The focus of this study was to evaluate the changes in fatigue crack growth resistance of dentin and toughening mechanisms caused by lactic acid exposure. Compact tension specimens of human dentin were prepared from unrestored molars and subjected to Mode I opening mode cyclic loads. Fatigue crack growth was achieved in samples from mid- and outer-coronal dentin immersed in either a lactic acid solution or neutral conditions...
April 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Wansun Kim, Soo Hyun Lee, Sang Hun Kim, Jae-Chul Lee, Sang Woong Moon, Jae Su Yu, Samjin Choi
Gold-decorated, vertically grown ZnO nanorods (NRs) on a flexible graphite sheet (Au/ZnONRs/G) were developed for surface-enhanced Raman scattering (SERS)-based biosensing to identify trace amounts of human aqueous humors. This Au/ZnONRs/G SERS-functionalized sensor was fabricated via two steps: hydrothermal synthesis-induced growth of ZnO NRs on graphite sheets for nanostructure fabrication, followed by e-beam evaporator-induced gold metallization on ZnONRs/G for SERS functionalization. The thickness of the Au layer and the height of the ZnO NRs for enhancing SERS performance were adjusted to maximize Raman intensity, and the optimized Au/ZnONRs/G nanostructures were verified by the electric finite element computational models to maximize the electric fields...
February 22, 2017: ACS Applied Materials & Interfaces
Hongping Ma, Xinbin Cheng, Jinlong Zhang, Hongfei Jiao, Bin Ma, Yongjian Tang, Zhouling Wu, Zhanshan Wang
Two types of engineered nodules in Ta<sub>2</sub>O<sub>5</sub>/SiO<sub>2</sub> high-reflection coatings were prepared using electron beam evaporation and an ion-assisted deposition processes to facilitate poor and good boundary continuity, respectively. The influence of nodular boundary continuity on their nanosecond laser damage characteristics was investigated through experimental studies, combined with 3D finite-difference time domain simulations and photo-thermal micro-characterizations...
February 1, 2017: Optics Letters
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