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Modeling and Simulation

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https://www.readbyqxmd.com/read/29150953/new-algorithm-for-simulation-of-proteoglycan-loss-and-collagen-degeneration-in-the-knee-joint-data-from-the-osteoarthritis-initiative
#1
Mika E Mononen, Petri Tanska, Hanna Isaksson, Rami K Korhonen
Osteoarthritis is a harmful joint disease but prediction of disease progression is problematic. Currently, there is only one modeling framework which can be applied to predict the progression of knee osteoarthritis but it only considers degenerative changes in the collagen fibril network. Here, we have developed the framework further by considering all of the major tissue changes (proteoglycan content, fluid flow and collagen fibril network) occurring in osteoarthritis. While excessive levels of tissue stresses controlled degeneration of the collagen fibril network, excessive levels of tissue strains controlled the decrease in proteoglycan content and the increase in permeability...
November 18, 2017: Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society
https://www.readbyqxmd.com/read/29150933/design-of-a-novel-continuous-flow-reactor-for-low-ph-viral-inactivation
#2
Stephanie A Parker, Linus Amarikwa, Kevin Vehar, Raquel Orozco, Scott Godfrey, Jon Coffman, Parviz Shamlou, Cameron L Bardliving
Insufficient mixing in laminar flow reactors due to diffusion-dominated flow limits their use in applications where narrow residence time distribution (RTD) is required. The aim of this study was to design and characterize a laminar flow (Re 187.7-375.5) tubular reactor for low pH viral inactivation with enhanced radial mixing via the incorporation of curvature and flow inversions. Towards this aim, the reactor described here, Jig in a Box (JIB), was designed with a flow path consisting of alternating 270° degree turns...
November 18, 2017: Biotechnology and Bioengineering
https://www.readbyqxmd.com/read/29150827/implications-of-tourist-macaque-interactions-for-disease-transmission
#3
Charlotte Carne, Stuart Semple, Ann MacLarnon, Bonaventura Majolo, Laëtitia Maréchal
During wildlife tourism, proximity or actual contact between people and animals may lead to a significant risk of anthropozoonotic disease transmission. In this paper, we use social network analysis, disease simulation modelling and data on animal health and behaviour to investigate such risks at a site in Morocco, where tourists come to see wild Barbary macaques (Macaca sylvanus). Measures of individual macaques' network centrality-an index of the strength and distribution of their social relationships and thus potentially their ability to spread disease-did not show clear and consistent relationships with their time spent in close proximity to, or rate of interacting with, tourists...
November 17, 2017: EcoHealth
https://www.readbyqxmd.com/read/29150817/two-step-estimation-of-models-between-latent-classes-and-external-variables
#4
Zsuzsa Bakk, Jouni Kuha
We consider models which combine latent class measurement models for categorical latent variables with structural regression models for the relationships between the latent classes and observed explanatory and response variables. We propose a two-step method of estimating such models. In its first step, the measurement model is estimated alone, and in the second step the parameters of this measurement model are held fixed when the structural model is estimated. Simulation studies and applied examples suggest that the two-step method is an attractive alternative to existing one-step and three-step methods...
November 17, 2017: Psychometrika
https://www.readbyqxmd.com/read/29150816/cognitive-diagnosis-for-small-educational-programs-the-general-nonparametric-classification-method
#5
Chia-Yi Chiu, Yan Sun, Yanhong Bian
The focus of cognitive diagnosis (CD) is on evaluating an examinee's strengths and weaknesses in terms of cognitive skills learned and skills that need study. Current methods for fitting CD models (CDMs) work well for large-scale assessments, where the data of hundreds or thousands of examinees are available. However, the development of CD-based assessment tools that can be used in small-scale test settings, say, for monitoring the instruction and learning process at the classroom level has not kept up with the rapid pace at which research and development proceeded for large-scale assessments...
November 17, 2017: Psychometrika
https://www.readbyqxmd.com/read/29150815/score-based-tests-of-differential-item-functioning-via-pairwise-maximum-likelihood-estimation
#6
Ting Wang, Carolin Strobl, Achim Zeileis, Edgar C Merkle
Measurement invariance is a fundamental assumption in item response theory models, where the relationship between a latent construct (ability) and observed item responses is of interest. Violation of this assumption would render the scale misinterpreted or cause systematic bias against certain groups of persons. While a number of methods have been proposed to detect measurement invariance violations, they typically require advance definition of problematic item parameters and respondent grouping information...
November 17, 2017: Psychometrika
https://www.readbyqxmd.com/read/29150814/detecting-multiple-random-changepoints-in-bayesian-piecewise-growth-mixture-models
#7
Eric F Lock, Nidhi Kohli, Maitreyee Bose
Piecewise growth mixture models are a flexible and useful class of methods for analyzing segmented trends in individual growth trajectory over time, where the individuals come from a mixture of two or more latent classes. These models allow each segment of the overall developmental process within each class to have a different functional form; examples include two linear phases of growth, or a quadratic phase followed by a linear phase. The changepoint (knot) is the time of transition from one developmental phase (segment) to another...
November 17, 2017: Psychometrika
https://www.readbyqxmd.com/read/29150802/ion-imprinted-electrospun-nanofibers-of-chitosan-1-butyl-3-methylimidazolium-tetrafluoroborate-for-the-dynamic-expulsion-of-thorium-iv-ions-from-mimicked-effluents
#8
Prakash Macchindra Gore, Latika Khurana, Suhail Siddique, Anjana Panicker, Balasubramanian Kandasubramanian
The present study explores the innocuous, biocompatible, and extremely competent molecularly imprinted chitosan/RTIL electrospun nanofibers having average diameter of 30 nm for the expulsion of thorium (IV) ions from the mimicked effluent waste. The extended Flory-Huggins theory and three-dimensional molecular modeling have been effectively premeditated via Materials Studio software for enumerating the inter-miscibility and compatibility (Chi parameter (χ) = 1.019, mixing energy (Emix) = 0.603 kcal/mol) of the chitosan/RTIL (1-butyl-3-methylimidazolium tetrafluoroborate)...
November 17, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/29150767/cell-migration-in-1d-and-2d-nanofiber-microenvironments
#9
Horacio M Estabridis, Aniket Jana, Amrinder Nain, David J Odde
Understanding how cells migrate in fibrous environments is important in wound healing, immune function, and cancer progression. A key question is how fiber orientation and network geometry influence cell movement. Here we describe a quantitative, modeling-based approach toward identifying the mechanisms by which cells migrate in fibrous geometries having well controlled orientation. Specifically, U251 glioblastoma cells were seeded onto non-electrospinning Spinneret based tunable engineering parameters fiber substrates that consist of networks of suspended 400 nm diameter nanofibers...
November 17, 2017: Annals of Biomedical Engineering
https://www.readbyqxmd.com/read/29150764/projections-for-the-changes-in-growing-season-length-of-tree-ring-formation-on-the-tibetan-plateau-based-on-cmip5-model-simulations
#10
Minhui He, Bao Yang, Vladimir Shishov, Sergio Rossi, Achim Bräuning, Fredrik Charpentier Ljungqvist, Jussi Grießinger
The response of the growing season to the ongoing global warming has gained considerable attention. In particular, how and to which extent the growing season will change during this century is essential information for the Tibetan Plateau, where the observed warming trend has exceeded the global mean. In this study, the 1960-2014 mean length of the tree-ring growing season (LOS) on the Tibetan Plateau was derived from results of the Vaganov-Shashkin oscilloscope tree growth model, based on 20 composite study sites and more than 3000 trees...
November 17, 2017: International Journal of Biometeorology
https://www.readbyqxmd.com/read/29150722/cross-lagged-analysis-of-interplay-between-differential-traits-in-sibling-pairs-validation-and-application-to-parenting-behavior-and-adhd-symptomatology
#11
Arden Moscati, Brad Verhulst, Kevin McKee, Judy Silberg, Lindon Eaves
Understanding the factors that contribute to behavioral traits is a complex task, and partitioning variance into latent genetic and environmental components is a useful beginning, but it should not also be the end. Many constructs are influenced by their contextual milieu, and accounting for background effects (such as gene-environment correlation) is necessary to avoid bias. This study introduces a method for examining the interplay between traits, in a longitudinal design using differential items in sibling pairs...
November 17, 2017: Behavior Genetics
https://www.readbyqxmd.com/read/29150721/adaptive-snp-set-association-testing-in-generalized-linear-mixed-models-with-application-to-family-studies
#12
Jun Young Park, Chong Wu, Saonli Basu, Matt McGue, Wei Pan
In genome-wide association studies (GWAS), it has been increasingly recognized that, as a complementary approach to standard single SNP analyses, it may be beneficial to analyze a group of functionally related SNPs together. Among the existent population-based SNP-set association tests, two adaptive tests, the aSPU test and the aSPUpath test, offer a powerful and general approach at the gene- and pathway-levels by data-adaptively combining the results across multiple SNPs (and genes) such that high statistical power can be maintained across a wide range of scenarios...
November 17, 2017: Behavior Genetics
https://www.readbyqxmd.com/read/29150691/mechanical-regulation-of-organ-asymmetry-in-leaves
#13
Jiyan Qi, Binbin Wu, Shiliang Feng, Shouqin Lü, Chunmei Guan, Xiao Zhang, Dengli Qiu, Yingchun Hu, Yihua Zhou, Chuanyou Li, Mian Long, Yuling Jiao
How appendages, such as plant leaves or animal limbs, develop asymmetric shapes remains a fundamental question in biology. Although ongoing research has revealed the genetic regulation of organ pattern formation, how gene activity ultimately directs organ shape remains unclear. Here, we show that leaf dorsoventral (adaxial-abaxial) polarity signals lead to mechanical heterogeneity of the cell wall, related to the methyl-esterification of cell-wall pectins in tomato and Arabidopsis. Numerical simulations predicate that mechanical heterogeneity is sufficient to produce the asymmetry seen in planar leaves...
September 2017: Nature Plants
https://www.readbyqxmd.com/read/29150680/potential-landscape-of-high-dimensional-nonlinear-stochastic-dynamics-with-large-noise
#14
Ying Tang, Ruoshi Yuan, Gaowei Wang, Xiaomei Zhu, Ping Ao
Quantifying stochastic processes is essential to understand many natural phenomena, particularly in biology, including the cell-fate decision in developmental processes as well as the genesis and progression of cancers. While various attempts have been made to construct potential landscape in high dimensional systems and to estimate transition rates, they are practically limited to the cases where either noise is small or detailed balance condition holds. A general and practical approach to investigate real-world nonequilibrium systems, which are typically high-dimensional and subject to large multiplicative noise and the breakdown of detailed balance, remains elusive...
November 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29150649/non-empirical-atomistic-dipole-interaction-model-for-quantum-plasmon-simulation-of-nanoparticles
#15
Jaechang Lim, Sungwoo Kang, Jaewook Kim, Woo Youn Kim, Seol Ryu
Plasmonic nanoparticles in the quantum regime exhibit characteristic optical properties that cannot be described by classical theories. Time-dependent density functional theory (TDDFT) is rising as a versatile tool for study on such systems, but its application has been limited to very small clusters due to rapidly growing computational costs. We propose an atomistic dipole-interaction-model for quantum plasmon simulations as a practical alternative. Namely the atomic dipole approximation represents induced dipoles with atomic polarizabilities obtained from TDDFT without empirical parameters...
November 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29150543/toxicokinetics-and-physiologically-based-pharmacokinetic-modeling-of-the-shellfish-toxin-domoic-acid-in-nonhuman-primates
#16
Jing Jing, Rebekah Petroff, Sara Shum, Brenda Crouthamel, Ariel R Topletz, Kimberly S Grant, Thomas M Burbacher, Nina Isoherranen
Domoic acid (DA), a neurotoxin, is produced by marine algae and has caused toxications worldwide in animals and humans. However, the toxicokinetics of DA has not been fully evaluated, and information is missing on the disposition of DA following oral exposures at doses that are considered safe for human consumption. In this study, toxicokinetics of DA were investigated in cynomolgus monkeys, following single doses of 5 µg/kg DA iv, 0.075 mg/kg DA po and 0.15 mg/kg DA po. Following iv dosing, DA had a systemic clearance of 124 ± 71 ml/hr/kg, volume of distribution at steady state of 131±71 ml/kg and elimination half-life of 1...
November 17, 2017: Drug Metabolism and Disposition: the Biological Fate of Chemicals
https://www.readbyqxmd.com/read/29150480/effect-of-time-to-diagnostic-testing-for-breast-cervical-and-colorectal-cancer-screening-abnormalities-on-screening-efficacy-a-modeling-study
#17
Carolyn M Rutter, Jane J Kim, Reinier G S Meester, Brian L Sprague, Emily A Burger, Ann G Zauber, Mehmet Ali Ergun, Nicole G Campos, Chyke A Doubeni, Amy Trentham-Dietz, Stephen Sy, Oguz Alagoz, Natasha Stout, Iris Lansdorp-Vogelaar, Douglas A Corley, Anna Tosteson
BACKGROUND: Patients who receive an abnormal cancer screening result require follow-up for diagnostic testing, but the time to follow-up varies across patients and practices. METHODS: We used a simulation study to estimate the change in lifetime screening benefits when time to follow-up for breast, cervical, and colorectal cancers was increased. Estimates were based on four independently developed microsimulation models that each simulated the life course of adults eligible for breast (women aged 50-74 years), cervical (women aged 21-65 years), or colorectal (adults aged 50-75 years) cancer screening...
November 17, 2017: Cancer Epidemiology, Biomarkers & Prevention
https://www.readbyqxmd.com/read/29150299/a-new-analytical-model-for-the-changes-of-vascular-endothelial-growth-factor-in-ischemic-diseases
#18
Feng Qiu, Hui Cao, Yue Wu
Vascular endothelial growth factors (VEGFs) play an important role in ischemic diseases. However, few studies focused on the generation and decay process of VEGF and no model yet can quantify different VEGF behavior caused in different area, like heart or brain. We compare the results across different groups and quantify the effectiveness of the selected training protocols. By applying the model to experimental data, the analytical model has been proposed to simulate the changes of vascular endothelial growth factor as a function of time and training protocols in ischemic diseases...
November 2017: Medical Hypotheses
https://www.readbyqxmd.com/read/29150270/m-biceps-femoris-a-wolf-in-sheep-s-clothing-the-downside-of-a-lower-limb-injury-prevention-training
#19
Thomas Ertelt, Thomas Gronwald
Both, hamstring and ACL injuries are among the most typical injuries, particularly in change of direction and high speed running sports. They're also difficult to treat. Therefore, in the past few years, sports medicine practitioners and exercise scientists have mainly been focusing on the development and implementation of preventive programs in order to reduce the number of lower limb injuries, mainly by improving knee alignment. A number of studies have been able to prove the success of these training interventions, which are mainly addressing sensorimotor abilities and plyometric activities...
November 2017: Medical Hypotheses
https://www.readbyqxmd.com/read/29150134/stress-generation-in-mandibular-anterior-teeth-restored-with-different-types-of-post-and-core-at-various-levels-of-ferrule
#20
Anatolii Savychuk, Marianthi Manda, Christos Galanis, Christofer Provatidis, Petros Koidis
STATEMENT OF PROBLEM: Pertinent evidence regarding the mechanical integrity of mandibular anterior teeth restored with a post-and-core is limited. PURPOSE: The purpose of this finite element analysis study was to compare the impact of the post type (glass fiber post-and-resin core or cast post-and-core) along with the ferrule effect on the stress fields generated in endodontically treated mandibular lateral incisors and canines. MATERIAL AND METHODS: Three-dimensional models of the segmented mandible were developed...
November 15, 2017: Journal of Prosthetic Dentistry
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