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"Validation" simulation model

Cong Xu, Vernon M Chinchilli, Ming Wang
In longitudinal studies, matched designs are often employed to control the potential confounding effects in the field of biomedical research and public health. Because of clinical interest, recurrent time-to-event data are captured during the follow-up. Meanwhile, the terminal event of death is always encountered, which should be taken into account for valid inference because of informative censoring. In some scenarios, a certain large portion of subjects may not have any recurrent events during the study period due to nonsusceptibility to events or censoring; thus, the zero-inflated nature of data should be considered in analysis...
April 22, 2018: Statistics in Medicine
Wei Zhao, Songbai Ji
Advanced neuroimaging provides new opportunities to enhance head injury models, including the incorporation of white matter (WM) structural anisotropy. However, information from high-resolution neuroimaging has to be "down-sampled" to match typically coarse brain mesh. To understand how this mesh-image resolution mismatch affects impact simulation and subsequent response sampling, we compared three competing anisotropy implementations (using either voxels, tractography, or a multiscale submodeling), two response sampling strategies (element-wise or tractography-based), and two region segmentation methods (brain mesh vs...
April 21, 2018: Journal of Neurotrauma
Robert Brett McQueen, Marc D Breton, Joyce Craig, Hayden Holmes, Melanie D Whittington, Markus A Ott, Jonathan D Campbell
OBJECTIVE: The objective was to model clinical and economic outcomes of self-monitoring blood glucose (SMBG) devices with varying error ranges and strip prices for type 1 and insulin-treated type 2 diabetes patients in England. METHODS: We programmed a simulation model that included separate risk and complication estimates by type of diabetes and evidence from in silico modeling validated by the Food and Drug Administration. Changes in SMBG error were associated with changes in hemoglobin A1c (HbA1c) and separately, changes in hypoglycemia...
April 1, 2018: Journal of Diabetes Science and Technology
Todd J Zurlinden, Brad Reisfeld
BACKGROUND: Organophosphorus (OP) compounds are the most widely used group of insecticides in the world. Risk assessments for these chemicals have focused primarily on 10% inhibition of acetylcholinesterase in the brain as the critical metric of effect. Aside from cholinergic effects resulting from acute exposure, many studies suggest a linkage between cognitive deficits and long-term OP exposure. OBJECTIVE: In this proof-of-concept study, we focused on one of the most widely used OP insecticides in the world, chlorpyrifos (CPF), and utilized an existing physiologically based pharmacokinetic (PBPK) model and a novel pharmacodynamic (PD) dose-response model to develop a point of departure benchmark dose estimate for cognitive deficits following long-term, low-dose exposure to this chemical in rodents...
April 20, 2018: Environmental Health Perspectives
Yan Zhang, Jan Awrejcewicz, Olga Szymanowska, Siqin Shen, Xiaoxue Zhao, Julien S Baker, Yaodong Gu
The internal stress of the human foot enables efficient parametric evaluation of structural and functional impairments associated with foot deformities, such as hallux valgus (HV). However, the status of the internal stress of such a deformed foot remains insufficiently addressed due to the difficulties and limitations of experimental approaches. This study, using finite element (FE) methodology, investigated the influence of severe HV deformity on the metatarsal stress and the metatarsophalangeal (MTP) joint loading during balanced standing...
April 16, 2018: Computers in Biology and Medicine
Feng Pan, Odette Reifsnider, Ying Zheng, Irina Proskorovsky, Tracy Li, Jianming He, Sonja V Sorensen
OBJECTIVES: Treatment landscape in prostate cancer has changed dramatically with the emergence of new medicines in the past few years. The traditional survival partition model (SPM) cannot accurately predict long-term clinical outcomes because it is limited by its ability to capture the key consequences associated with this changing treatment paradigm. The objective of this study was to introduce and validate a discrete-event simulation (DES) model for prostate cancer. METHODS: A DES model was developed to simulate overall survival (OS) and other clinical outcomes based on patient characteristics, treatment received, and disease progression history...
April 2018: Value in Health: the Journal of the International Society for Pharmacoeconomics and Outcomes Research
Stefan H G Rietsch, Stephan Orzada, Stefan Maderwald, Sascha Brunheim, Bart W J Philips, Tom W J Scheenen, Mark E Ladd, Harald H Quick
PURPOSE: In this work a combined body coil array with 8 transmit/receive (Tx/Rx) meander elements and with 24 receive-only (Rx) loops (8Tx/32Rx) was developed and evaluated in comparison to an 8-channel transmit/receive body array (8Tx/Rx) based on meander elements serving as the reference standard. METHODS: Systematic evaluation of the RF array was performed on a body-sized phantom. Body imaging at 7T was performed in 6 volunteers in the body regions pelvis, abdomen, and heart...
April 21, 2018: Medical Physics
Muhammad Hanif Ramlee, Mohd Ayub Sulong, Evelyn Garcia-Nieto, Daniel Angure Penaranda, Antonio Ros Felip, Mohammed Rafiq Abdul Kadir
Pilon fractures can be caused by high-energy vertical forces which may result in long-term patient immobilization. Many experts in orthopedic surgery recommend the use of a Delta external fixator for type III Pilon fracture treatment. This device can promote immediate healing of fractured bone, minimizing the rate of complications as well as allowing early mobilization. The characteristics of different types of the Delta frame have not been demonstrated yet. By using the finite element method, this study was conducted to determine the biomechanical characteristics of six different configurations (Model 1 until Model 6)...
April 21, 2018: Medical & Biological Engineering & Computing
Shiping Wen, Xudong Xie, Zheng Yan, Tingwen Huang, Zhigang Zeng
Memristor describes the relationship between charge and flux. Although several window functions for memristors based on the HP linear and nonlinear dopant drift models have been studied, most of them are inadequate to capture the full characteristics of memristors. To address this issue, this paper proposes a unified window function to describe a general memristor with restrictions of its parameters given. Compared with other window functions, the proposed function demonstrates high validity and accuracy. In order to make the simulation results have high consistency with the results of actual circuit, we apply the new window function to the simulation of a memristor-based multilayer neural network (MNN) circuit...
April 3, 2018: Neural Networks: the Official Journal of the International Neural Network Society
M Azari, A V Le, M Lübken, M Denecke
A mathematical model for a granular biofilm reactor for leachate treatment was validated by long-term measured data to investigate the mechanisms and drivers influencing biological nitrogen removal and microbial consortia dynamics. The proposed model, based on Activated Sludge Model (ASM1), included anaerobic ammonium oxidation (anammox), nitrifying and heterotrophic denitrifying bacteria which can attach and grow on granular activated carbon (GAC) particles. Two kinetic descriptions for the model were proposed: with and without soluble microbial products (SMP) and extracellular polymeric substance (EPS)...
April 2018: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Muhammad Arba, Andry Nur-Hidayat, Ruslin, Muhammad Yusuf, Sumarlin, Rukman Hertadi, Setyanto Tri Wahyudi, Slamet Ibrahim Surantaadmaja, Daryono H Tjahjono
The ubiquitin-proteasome system plays an important role in protein quality control. Currently, inhibition of the proteasome has been validated as a promising approach in anticancer therapy. The 20S core particle of the proteasome harbors β5 subunit which is a crucial active site in proteolysis. Targeting proteasome β5 subunit which is responsible for the chymotrypsin-like activity of small molecules has been regarded as an important way for achieving therapeutics target. In the present study, a series of porphyrin derivatives bearing either pyridine or pyrazole rings as meso-substituents were designed and evaluated as an inhibitor for the β5 subunit of the proteasome by employing molecular docking and dynamics simulations...
April 16, 2018: Computational Biology and Chemistry
Marine Menut, Loïc Boussel, Xavier Escriva, Benyebka Bou-Saïd, Hélène Walter-Le Berre, Yann Marchesse, Antoine Millon, Nellie Della Schiava, Patrick Lermusiaux, John Tichy
Blood is a complex fluid in which the presence of the various constituents leads to significant changes in its rheological properties. Thus, an appropriate non-Newtonian model is advisable; and we choose a Modified version of the rheological model of Phan-Thien and Tanner (MPTT). The different parameters of this model, derived from the rheology of polymers, allow characterization of the non-Newtonian nature of blood, taking into account the behavior of red blood cells in plasma. Using the MPTT model that we implemented in the open access software OpenFOAM, numerical simulations have been performed on blood flow in the thoracic aorta for a healthy patient...
March 29, 2018: Journal of Biomechanics
Benjamin D Duval, Rajan Ghimire, Melannie D Hartman, Mark A Marsalis
External inputs to agricultural systems can overcome latent soil and climate constraints on production, while contributing to greenhouse gas emissions from fertilizer and water management inefficiencies. Proper crop selection for a given region can lessen the need for irrigation and timing of N fertilizer application with crop N demand can potentially reduce N2O emissions and increase N use efficiency while reducing residual soil N and N leaching. However, increased variability in precipitation is an expectation of climate change and makes predicting biomass and gas flux responses to management more challenging...
2018: PloS One
H Gong, R Pishgar, J H Tay
Aerobic granulation is a recent technology with high level of complexity and sensitivity to environmental and operational conditions. Artificial neural networks (ANN), computational tools capable of describing complex nonlinear systems, are the best fit to simulate aerobic granular bioreactors. In this study, two feedforward backpropagation ANN models were developed to predict chemical oxygen demand (COD) (Model I) and total nitrogen (TN) removal efficiencies (Model II) of aerobic granulation technology under steady-state condition...
April 19, 2018: Environmental Technology
João-Paulo-Mendes Tribst, Vinicius-Aneas Rodrigues, Amanda-Maria-de Oliveira Dal Piva, Alexandre-Luiz-Souto Borges, Renato-Sussumu Nishioka
Background: Through the biomechanical study of dental implants, it is possible to understand the dissipation effects of masticatory loads in different situations and prevent the longevity of osseointegration. Aims: To evaluate the microstrains generated around external hexagon implants, using axial and non-axial loads in a fixed four-element prosthesis with straight implants and implants inclined at 17°. Material and Methods: Three implants were modeled using CAD software following the manufacturer's measurements...
January 2018: Journal of Clinical and Experimental Dentistry
Vijay Govindarajan, John Mousel, H S Udaykumar, Sarah C Vigmostad, David D McPherson, Hyunggun Kim, Krishnan B Chandran
Highly resolved three-dimensional (3D) fluid structure interaction (FSI) simulation using patient-specific echocardiographic data can be a powerful tool for accurately and thoroughly elucidating the biomechanics of mitral valve (MV) function and left ventricular (LV) fluid dynamics. We developed and validated a strongly coupled FSI algorithm to fully characterize the LV flow field during diastolic MV opening under physiologic conditions. Our model revealed that distinct MV deformation and LV flow patterns developed during different diastolic stages...
April 18, 2018: Scientific Reports
Kati Blomberg, Pascal Kosse, Anna Mikola, Anna Kuokkanen, Tommi Fred, Mari Heinonen, Michela Mulas, Manfred Luebken, Marc Wichern, Riku Vahala
An Activated Sludge Model #3 (ASM3)-based, pseudo-mechanistic model describing nitrous oxide (N2O) production was created in this study to provide more insight into the dynamics of N2O production, consumption, and emissions at a full-scale wastewater treatment plant (WWTP). N2O emissions at the studied WWTP are monitored throughout the plant with an FT-IR analyzer, while the developed model encountered N2O production in the biological reactors via both ammonia oxidizing bacteria (AOB) nitrification and heterotrophic denitrifiers...
April 18, 2018: Environmental Science & Technology
Jakob P Ulmschneider, Martin B Ulmschneider
Ever since the first molecular mechanics computer simulations of biological molecules became possible, there has been the dream to study all complex biological phenomena in silico, simply bypassing the enormous experimental challenges and their associated costs. For this, two inherent requirements need to be met: First, the time scales achievable in simulations must reach up to the millisecond range and even longer. Second, the computational model must accurately reproduce what is measured experimentally. Despite some recent successes, the general consensus in the field to date has been that neither of these conditions have yet been met and that the dream will be realized, if at all, only in the distant future...
April 18, 2018: Accounts of Chemical Research
Haochen Zhao, Linai Kuang, Lei Wang, Pengyao Ping, Zhanwei Xuan, Tingrui Pei, Zhelun Wu
BACKGROUND: Recently, numerous laboratory studies have indicated that many microRNAs (miRNAs) are involved in and associated with human diseases and can serve as potential biomarkers and drug targets. Therefore, developing effective computational models for the prediction of novel associations between diseases and miRNAs could be beneficial for achieving an understanding of disease mechanisms at the miRNA level and the interactions between diseases and miRNAs at the disease level. Thus far, only a few miRNA-disease association pairs are known, and models analyzing miRNA-disease associations based on lncRNA are limited...
April 17, 2018: BMC Bioinformatics
Yin Sheng, Zhigang Zeng
This paper discusses impulsive synchronization of stochastic reaction-diffusion neural networks with Dirichlet boundary conditions and hybrid time delays. By virtue of inequality techniques, theories of stochastic analysis, linear matrix inequalities, and the contradiction method, sufficient criteria are proposed to ensure exponential synchronization of the addressed stochastic reaction-diffusion neural networks with mixed time delays via a designed impulsive controller. Compared with some recent studies, the neural network models herein are more general, some restrictions are relaxed, and the obtained conditions enhance and generalize some published ones...
March 29, 2018: Neural Networks: the Official Journal of the International Neural Network Society
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