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Finite growth models

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https://www.readbyqxmd.com/read/28819754/development-of-the-hybrid-cells-in-series-model-to-simulate-ammonia-nutrient-pollutant-transport-along-the-umgeni-river
#1
Kayode O Olowe, Muthukrishnavellaisamy Kumarasamy
Discharge of organic waste results in high nutrient pollution of the water bodies which is a major menace to the environment. A high quantity of nutrients such as ammonia causes a reduction in the dissolved oxygen level and induces algal growth in the water bodies. Water quality models have been the tools to evaluate the rate at which streams can disperse the pollutants they receive. Many water quality models are flawed either because of their inadequacy to completely simulate the advection component of the pollutant transport, or because of the limited application of the models, due to inaccurate estimation of model parameters...
August 17, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28799362/on-the-time-required-to-freeze-water
#2
J R Espinosa, C Navarro, E Sanz, C Valeriani, C Vega
By using the seeding technique the nucleation rate for the formation of ice at room pressure will be estimated for the TIP4P/ICE model using longer runs and a smaller grid of temperatures than in the previous work. The growth rate of ice will be determined for TIP4P/ICE and for the mW model of water. Although TIP4P/ICE and mW have a similar melting point and melting enthalpy, they differ significantly in the dynamics of freezing. The nucleation rate of mW is lower than that of TIP4P/ICE due to its higher interfacial free energy...
December 7, 2016: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28797066/computationally-designed-lattices-with-tuned-properties-for-tissue-engineering-using-3d-printing
#3
Paul F Egan, Veronica C Gonella, Max Engensperger, Stephen J Ferguson, Kristina Shea
Tissue scaffolds provide structural support while facilitating tissue growth, but are challenging to design due to diverse property trade-offs. Here, a computational approach was developed for modeling scaffolds with lattice structures of eight different topologies and assessing properties relevant to bone tissue engineering applications. Evaluated properties include porosity, pore size, surface-volume ratio, elastic modulus, shear modulus, and permeability. Lattice topologies were generated by patterning beam-based unit cells, with design parameters for beam diameter and unit cell length...
2017: PloS One
https://www.readbyqxmd.com/read/28792412/evolutionary-public-health-introducing-the-concept
#4
REVIEW
Jonathan C K Wells, Randolph M Nesse, Rebecca Sear, Rufus A Johnstone, Stephen C Stearns
The emerging discipline of evolutionary medicine is breaking new ground in understanding why people become ill. However, the value of evolutionary analyses of human physiology and behaviour is only beginning to be recognised in the field of public health. Core principles come from life history theory, which analyses the allocation of finite amounts of energy between four competing functions-maintenance, growth, reproduction, and defence. A central tenet of evolutionary theory is that organisms are selected to allocate energy and time to maximise reproductive success, rather than health or longevity...
July 29, 2017: Lancet
https://www.readbyqxmd.com/read/28774060/numerical-approach-to-modeling-and-characterization-of-refractive-index-changes-for-a-long-period-fiber-grating-fabricated-by-femtosecond-laser
#5
Akram Saad, Yonghyun Cho, Farid Ahmed, Martin Byung-Guk Jun
A 3D finite element model constructed to predict the intensity-dependent refractive index profile induced by femtosecond laser radiation is presented. A fiber core irradiated by a pulsed laser is modeled as a cylinder subject to predefined boundary conditions using COMSOL5.2 Multiphysics commercial package. The numerically obtained refractive index change is used to numerically design and experimentally fabricate long-period fiber grating (LPFG) in pure silica core single-mode fiber employing identical laser conditions...
November 21, 2016: Materials
https://www.readbyqxmd.com/read/28773915/comparative-study-on-crack-initiation-and-propagation-of-glass-under-thermal-loading
#6
Yu Wang, Qingsong Wang, Haodong Chen, Jinhua Sun, Linghui He
This paper explores the fracture process based on finite element simulation. Both probabilistic and deterministic methods are employed to model crack initiation, and several commonly used criteria are utilized to predict crack growth. It is concluded that the criteria of maximum tensile stress, maximum normal stress, and maximum Mises stress, as well as the Coulomb-Mohr criterion are able to predict the initiation of the first crack. The mixed-mode criteria based on the stress intensity factor (SIF), energy release rate, and the maximum principal stress, as well as the SIF-based maximum circumferential stress criterion are suitable to predict the crack propagation...
September 22, 2016: Materials
https://www.readbyqxmd.com/read/28772798/corrosion-fatigue-crack-growth-in-plates-a-model-based-on-the-paris-law
#7
Jesús Toribio, Juan-Carlos Matos, Beatriz González
In this paper, a Paris law-based model is presented whereby crack propagation occurs under cyclic loading in air (fatigue) and in an aggressive environment (corrosion-fatigue) for the case of corner cracks (with a wide range of aspect ratios in the matter of the initial cracks) in finite-thickness plates of 316L austenitic stainless steel subjected to tension, bending, or combined (tension + bending) loading. Results show that the cracks tend during their growth towards a preferential propagation path, exhibiting aspect ratios slightly lower than unity only for the case of very shallow cracks, and diminishing as the crack grows (increasing the relative crack depth)-more intensely in the case of bending than in the case of tension (the mixed loading tension/bending representing an intermediate case)...
April 22, 2017: Materials
https://www.readbyqxmd.com/read/28765601/enhanced-robustness-of-evolving-open-systems-by-the-bidirectionality-of-interactions-between-elements
#8
Fumiko Ogushi, János Kertész, Kimmo Kaski, Takashi Shimada
Living organisms, ecosystems, and social systems are examples of complex systems in which robustness against inclusion of new elements is an essential feature. A recently proposed simple model has revealed a general mechanism by which such systems can become robust against inclusion of elements with totally random interactions when the elements have a moderate number of links. The interaction is, however, in many systems often intrinsically bidirectional like for mutual symbiosis and competition in ecology...
August 1, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28759838/finite-element-analysis-of-mechanical-behavior-permeability-and-fluid-induced-wall-shear-stress-of-high-porosity-scaffolds-with-gyroid-and-lattice-based-architectures
#9
Davar Ali, Sadri Sen
Scaffold design necessitates the consideration of mechanical properties and fluid flow dynamics as the main factors in the development of such materials. The mechanical behavior of bone scaffolds is characterized by properties such as elastic modulus and compressive strength. In terms of fluid flow dynamics, within bone scaffolds, permeability is an important parameter that affects cells' biological activities, and flow-induced shear stress is used as a mechanical stimulant of cell growth. In this study, two scaffold architectures with gyroid and lattice-based rectangular unit cells were designed to analysis the effective elastic moduli, compressive strength, permeability and fluid flow-induced wall shear stress as functions of porosity...
July 25, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28757358/strontium-release-from-sr-2-loaded-bone-cements-and-dispersion-in-healthy-and-osteoporotic-rat-bone
#10
Marcus Rohnke, Stefanie Pfitzenreuter, Boris Mogwitz, Anja Henß, Jürgen Thomas, Dina Bieberstein, Thomas Gemming, Svenja K Otto, Seemun Ray, Matthias Schumacher, Michael Gelinsky, Volker Alt
Drug functionalization of biomaterials is a modern and popular approach in biomaterials research. Amongst others this concept is used for the functionalization of bone implants to locally stimulate the bone healing process. For example strontium ions (Sr(2+)) are administered in osteoporosis therapy to stimulate bone growth and have recently been integrated into bone cements. Based on results of different analytical experiments we developed a two-phase model for the transport of therapeutically active Sr(2+)-ions in bone in combination with Korsmeyer-Peppas kinetics for the Sr(2+) release from bone cement...
July 27, 2017: Journal of Controlled Release: Official Journal of the Controlled Release Society
https://www.readbyqxmd.com/read/28753828/risk-of-testosterone-flare-in-the-era-of-the-saturation-model-one-more-historical-myth
#11
REVIEW
Yonah Krakowsky, Abraham Morgentaler
CONTEXT: When luteinizing hormone-releasing hormone (LHRH) agonists were introduced in the 1980s, it was universally believed that the initial transient rise in serum testosterone (T), termed T flare, caused rapid prostate cancer (PCa) growth and led to disease progression, complications, and death. It became routine to offer antiandrogens (AAs) to prevent these risks. However, over the last decade, it has become recognized that androgens have a finite ability to stimulate PCa growth (the saturation model), providing a theoretical challenge to the risks of T flare...
July 1, 2017: European Urology Focus
https://www.readbyqxmd.com/read/28735563/a-gaussian-approximation-approach-for-value-of-information-analysis
#12
Hawre Jalal, Fernando Alarid-Escudero
Most decisions are associated with uncertainty. Value of information (VOI) analysis quantifies the opportunity loss associated with choosing a suboptimal intervention based on current imperfect information. VOI can inform the value of collecting additional information, resource allocation, research prioritization, and future research designs. However, in practice, VOI remains underused due to many conceptual and computational challenges associated with its application. Expected value of sample information (EVSI) is rooted in Bayesian statistical decision theory and measures the value of information from a finite sample...
July 1, 2017: Medical Decision Making: An International Journal of the Society for Medical Decision Making
https://www.readbyqxmd.com/read/28735548/strain-driven-shape-evolution-of-stacked-in-ga-n-quantum-disks-embedded-in-gan-nanowires
#13
Javier Bartolomé, Michael Hanke, David van Treeck, Achim Trampert
The fabrication of nanowires with axial multiquantum wells or disks presenting a homogeneous size and shape distribution along the whole stack is still an unresolved challenge, despite being essential for narrowing their light emission bandwidth. In this work we demonstrate that the commonly observed change in the shape of the disks along the stacking direction proceeds in a systematic, predictable way. High- resolution transmission electron microscopy of stacked (In,Ga)N quantum discs embedded in GaN nanowires with diameters of ∼40 nm and lengths of ∼700 nm and finite element method calculations show that, contrary to what is normally assumed, this change is not related to the radial growth of the nanowires, which is shown to be negligible, but to the strain relaxation of the whole active region...
July 27, 2017: Nano Letters
https://www.readbyqxmd.com/read/28724145/tense-marking-in-the-english-narrative-retells-of-dual-language-preschoolers
#14
Svenja Gusewski, Raúl Rojas
Purpose: This longitudinal study investigated the emergence of English tense marking in young (Spanish-English) dual language learners (DLLs) over 4 consecutive academic semesters, addressing the need for longitudinal data on typical acquisition trajectories of English in DLL preschoolers. Method: Language sample analysis was conducted on 139 English narrative retells elicited from 39 preschool-age (Spanish-English) DLLs (range = 39-65 months). Growth curve models captured within- and between-individual change in tense-marking accuracy over time...
July 26, 2017: Language, Speech, and Hearing Services in Schools
https://www.readbyqxmd.com/read/28718989/formation-of-stone-wales-edge-multistep-reconstruction-and-growth-mechanisms-of-zigzag-nanographene
#15
Jing-Shuang Dang, Wei-Wei Wang, Jia-Jia Zheng, Shigeru Nagase, Xiang Zhao
Although the existence of Stone-Wales (5-7) defect at graphene edge has been clarified experimentally, theoretical study on the formation mechanism is still imperfect. In particular, the regioselectivity of multistep reactions at edge (self-reconstruction and growth with foreign carbon feedstock) is essential to understand the kinetic behavior of reactive boundaries but investigations are still lacking. Herein, by using finite-sized models, multistep reconstructions and carbon dimer additions of a bared zigzag edge are introduced using density functional theory calculations...
July 18, 2017: Journal of Computational Chemistry
https://www.readbyqxmd.com/read/28705446/a-novel-sax-stent-method-in-treatment-of-ascending-aorta-and-aortic-arch-aneurysms-evaluated-by-finite-element-simulations
#16
M C Arokiaraj, M De Beule, G De Santis
OBJECTIVES: A novel stent method to simplify treatment of proximal ascending aorta and aortic arch aneurysms was developed and investigated by finite element analysis. Therapy of ascending aortic and aortic arch aneurysms is difficult and challenging and is associated with various complications. METHODS: A 55mm wide×120mm long stent was designed without the stent graft and the stent was deployed by an endovascular method in a virtual patient-specific aneurysm model...
February 2017: J Med Vasc
https://www.readbyqxmd.com/read/28698087/computational-fluid-dynamics-simulation-of-hemodynamic-alterations-in-sigmoid-sinus-diverticulum-and-ipsilateral-upstream-sinus-stenosis-after-stent-implantation-in-patients-with-pulsatile-tinnitus
#17
Yanjing Han, Qingqing Yang, Zeran Yang, Jun Xia, Tianhao Su, Long Jin, Aike Qiao, Jianan Yu
OBJECTIVE: To investigate the relationships between upstream venous sinus stenosis and pulsatile tinnitus (PT), and to assess the correlation with diverticulum growth and the effectiveness of stent implantation METHODS: A patient-specific geometric models were constructed using computed tomography venography images from a patient with PT with sigmoid sinus diverticulum(SSD) and upstream transverse sinus stenosis, in whom stenting of the upstream sinus stenosis alone achieved complete remission of PT...
July 8, 2017: World Neurosurgery
https://www.readbyqxmd.com/read/28690042/the-impact-of-subchondral-bone-cysts-on-local-bone-stresses-in-the-medial-femoral-condyle-of-the-equine-stifle-joint
#18
Lance L Frazer, Elizabeth M Santschi, Kenneth J Fischer
Subchondral lucency (SCL), also referred to as subchondral bone cysts, can cause clinical problems in horses and humans. In humans, SCLs occur in youths and adolescents [1] due to mechanical factors (often related to athletics) and in skeletally mature individuals secondary to osteoarthritis (OA). In horses, SCL most commonly occurs in the medial femoral condyle (MFC) of growing horses (without OA), and causes lameness. The cause of equine SCL is debated, but bone trauma due to overload is the likely mechanism...
July 6, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28685857/biomechanical-simulations-of-costo-vertebral-and-anterior-vertebral-body-tethers-for-the-fusionless-treatment-of-pediatric-scoliosis
#19
Carl-Éric Aubin, Julien Clin, Jeremy Rawlinson
Compression-based fusionless tethers are an alternative to conventional surgical treatments of pediatric scoliosis. Anterior approaches place an anterior (ANT) tether on the anterolateral convexity of the deformed spine to modify growth. Posterior, or costo-vertebral (CV), approaches have not been assessed for biomechanical and corrective effectiveness. The objective was to biomechanically assess CV and ANT tethers using six patient-specific, finite element models of adolescent scoliotic patients (11.9 ± 0...
July 7, 2017: Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society
https://www.readbyqxmd.com/read/28685434/computational-simulation-of-tumor-hypoxia-based-on-in-vivo-microvasculature-assessed-in-a-dorsal-skin-window-chamber
#20
Lina Xu, Peter Vaupel, Siwei Bai, Bjoern Menze, Kuangyu Shi
Malignant growth usually leads to the depletion of oxygen (O2) supply in most solid tumors. Hypoxia can cause resistance to standard radiotherapy, some chemotherapy and immunotherapy. Furthermore, it can also trigger malignant progression by modulating gene expression and inducing genetic instability. The relationship between microvasculature, perfusion and tumor hypoxia has been intensively studied and many computational simulations have been developed to model tissue O2 transport. Usually simplified 2D phantoms are used to investigate tumor hypoxia and it is assumed that vessels are perpendicular to the region of interest and randomly distributed across the domain...
2017: Advances in Experimental Medicine and Biology
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