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https://www.readbyqxmd.com/read/28534799/expectation-maximization-algorithm-for-box-cox-transformation-cure-rate-model-and-assessment-of-model-mis-specication-under-weibull-lifetimes
#1
Suvra Pal, N Balakrishnan
In this paper, we develop likelihood inference based on the expectation maximization (EM) algorithm for the Box- Cox transformation cure rate model assuming the lifetimes to follow a Weibull distribution. A simulation study is carried out to demonstrate the performance of the proposed estimation method. Through Monte Carlo simulations, we also study the effect of model mis-specification on the estimate of cure rate. Finally, we analyze a well-known data on melanoma with the model and the inferential method developed here...
May 16, 2017: IEEE Journal of Biomedical and Health Informatics
https://www.readbyqxmd.com/read/28511730/simulation-in-canadian-postgraduate-emergency-medicine-training-a-national-survey
#2
Evan Russell, Andrew Koch Hall, Carly Hagel, Andrew Petrosoniak, Jeffrey Damon Dagnone, Daniel Howes
OBJECTIVES: Simulation-based education (SBE) is an important training strategy in emergency medicine (EM) postgraduate programs. This study sought to characterize the use of simulation in FRCPC-EM residency programs across Canada. METHODS: A national survey was administered to residents and knowledgeable program representatives (PRs) at all Canadian FRCPC-EM programs. Survey question themes included simulation program characteristics, the frequency of resident participation, the location and administration of SBE, institutional barriers, interprofessional involvement, content, assessment strategies, and attitudes about SBE...
May 17, 2017: CJEM
https://www.readbyqxmd.com/read/28508476/magnetic-resonance-electrical-properties-tomography-for-small-anomalies-using-boundary-conditions-a-simulation-study
#3
Joonsung Lee, Narae Choi, Jin Keun Seo, Dong-Hyun Kim
PURPOSE: Magnetic Resonance Electrical Property Tomography (MREPT) is an emerging imaging modality using measured B1 maps from Magnetic Resonance Imaging (MRI) to measure a distribution of electric conductivity and permittivity of the subject at the Larmor frequency. Conventional MREPT approachesat single transmit channel system using the Helmholtz equation rely on an assumption that conductivity and permittivity of the subject are locally homogeneous. For small tissue structures and tissue boundaries, in which the assumption of locally homogeneous conductivity and permittivity does not hold, the reconstructed conductivity values deviated from the actual values, so called "Boundary Artifacts"...
May 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28489173/new-technique-for-obesity-surgery-internal-gastric-plication-technique-using-intragastric-single-port-igs-igp-in-experimental-model
#4
Verena Müller, Panagiotis Fikatas, Safak Gül, Maximilian Noesser, Kirs Ten Fuehrer, Igor Sauer, Johann Pratschke, Ricardo Zorron
Background: Bariatric surgery is currently the most effective method to ameliorate co-morbidities as consequence of morbidly obese patients with BMI over 35 kg/m2. Endoscopic techniques have been developed to treat patients with mild obesity and ameliorate comorbidities, but endoscopic skills are needed, beside the costs of the devices. Aim: To report a new technique for internal gastric plication using an intragastric single port device in an experimental swine model...
January 2017: Arquivos Brasileiros de Cirurgia Digestiva: ABCD, Brazilian Archives of Digestive Surgery
https://www.readbyqxmd.com/read/28486872/model-validation-and-selection-for-personalized-medicine-using-dynamic-weighted-ordinary-least-squares
#5
Michael P Wallace, Erica Em Moodie, David A Stephens
Model assessment is a standard component of statistical analysis, but it has received relatively little attention within the dynamic treatment regime literature. In this paper, we focus on the dynamic-weighted ordinary least squares approach to optimal dynamic treatment regime estimation, introducing how its double-robustness property may be leveraged for model assessment, and how quasilikelihood may be used for model selection. These ideas are demonstrated through simulation studies, as well as through application to data from the sequenced treatment alternatives to relieve depression study...
January 1, 2017: Statistical Methods in Medical Research
https://www.readbyqxmd.com/read/28482110/functional-multiple-indicators-multiple-causes-measurement-error-models
#6
Carmen D Tekwe, Roger S Zoh, Fuller W Bazer, Guoyao Wu, Raymond J Carroll
Objective measures of oxygen consumption and carbon dioxide production by mammals are used to predict their energy expenditure. Since energy expenditure is not directly observable, it can be viewed as a latent construct with multiple physical indirect measures such as respiratory quotient, volumetric oxygen consumption, and volumetric carbon dioxide production. Metabolic rate is defined as the rate at which metabolism occurs in the body. Metabolic rate is also not directly observable. However, heat is produced as a result of metabolic processes within the body...
May 8, 2017: Biometrics
https://www.readbyqxmd.com/read/28472220/the-spike-and-slab-lasso-cox-model-for-survival-prediction-and-associated-genes-detection
#7
Zaixiang Tang, Yueping Shen, Xinyan Zhang, Nengjun Yi
Motivation: Large-scale molecular profiling data have offered extraordinary opportunities to improve survival prediction of cancers and other diseases and to detect disease associated genes. However, there are considerable challenges in analyzing large-scale molecular data. Results: We propose new Bayesian hierarchical Cox proportional hazards models, called the spike-and-slab lasso Cox, for predicting survival outcomes and detecting associated genes. We also develop an efficient algorithm to fit the proposed models by incorporating EM steps (Expectation-Maximization) into the extremely fast cyclic coordinate descent algorithm...
May 4, 2017: Bioinformatics
https://www.readbyqxmd.com/read/28467302/single-protein-detection-in-crowded-molecular-environments-in-cryo-em-images
#8
J Peter Rickgauer, Nikolaus Grigorieff, Winfried Denk
We present an approach to study macromolecular assemblies by detecting component proteins' characteristic high-resolution projection patterns, calculated from their known 3D structures, in single electron cryo-micrographs. Our method detects single apoferritin molecules in vitreous ice with high specificity and determines their orientation and location precisely. Simulations show that high spatial-frequency information and-in the presence of protein background-a whitening filter are essential for optimal detection, in particular for images taken far from focus...
May 3, 2017: ELife
https://www.readbyqxmd.com/read/28437479/conformational-dynamics-of-bacterial-trigger-factor-in-apo-and-ribosome-bound-states
#9
Mehmet Tarik Can, Zeynep Kurkcuoglu, Gokce Ezeroglu, Arzu Uyar, Ozge Kurkcuoglu, Pemra Doruker
The chaperone trigger factor (TF) binds to the ribosome exit tunnel and helps cotranslational folding of nascent chains (NC) in bacterial cells and chloroplasts. In this study, we aim to investigate the functional dynamics of fully-atomistic apo TF and its complex with 50S. As TF accomodates a high percentage of charged residues on its surface, the effect of ionic strength on TF dynamics is assessed here by performing five independent molecular dynamics (MD) simulations (total of 1.3 micro-second duration) at 29 mM and 150 mM ionic strengths...
2017: PloS One
https://www.readbyqxmd.com/read/28435505/inter-rater-agreement-of-end-of-shift-evaluations-based-on-a-single-encounter
#10
Steven Warrington, Michael Beeson, Amber Bradford
INTRODUCTION: End-of-shift evaluation (ESE) forms, also known as daily encounter cards, represent a subset of encounter-based assessment forms. Encounter cards have become prevalent for formative evaluation, with some suggesting a potential for summative evaluation. Our objective was to evaluate the inter-rater agreement of ESE forms using a single scripted encounter at a conference of emergency medicine (EM) educators. METHODS: Following institutional review board exemption, we created a scripted video simulating an encounter between an intern and a patient with an ankle injury...
April 2017: Western Journal of Emergency Medicine
https://www.readbyqxmd.com/read/28432786/the-comprehensive-connectome-of-a-neural-substrate-for-on-motion-detection-in-drosophila
#11
Shin-Ya Takemura, Aljoscha Nern, Dmitri B Chklovskii, Louis K Scheffer, Gerald M Rubin, Ian A Meinertzhagen
Analysing computations in neural circuits often uses simplified models because the actual neuronal implementation is not known. For example, a problem in vision, how the eye detects image motion, has long been analysed using Hassenstein-Reichardt (HR) detector or Barlow-Levick (BL) models. These both simulate motion detection well, but the exact neuronal circuits undertaking these tasks remain elusive. We reconstructed a comprehensive connectome of the circuits of Drosophila's motion-sensing T4 cells using a novel EM technique...
April 22, 2017: ELife
https://www.readbyqxmd.com/read/28431087/a-method-for-learning-a-sparse-classifier-in-the-presence-of-missing-data-for-high-dimensional-biological-datasets
#12
Kristen Severson, Brinda Monian, J Christopher Love, Richard D Braatz
Motivation: This work addresses two common issues in building classification models for biological or medical studies: learning a sparse model, where only a subset of a large number of possible predictors is used, and training in the presence of missing data. This work focuses on supervised generative binary classification models, specifically linear discriminant analysis (LDA). The parameters are determined using an expectation maximization algorithm to both address missing data and introduce priors to promote sparsity...
April 18, 2017: Bioinformatics
https://www.readbyqxmd.com/read/28407218/incorporating-covariates-into-integrated-factor-analysis-of-multi-view-data
#13
Gen Li, Sungkyu Jung
In modern biomedical research, it is ubiquitous to have multiple data sets measured on the same set of samples from different views (i.e., multi-view data). For example, in genetic studies, multiple genomic data sets at different molecular levels or from different cell types are measured for a common set of individuals to investigate genetic regulation. Integration and reduction of multi-view data have the potential to leverage information in different data sets, and to reduce the magnitude and complexity of data for further statistical analysis and interpretation...
April 13, 2017: Biometrics
https://www.readbyqxmd.com/read/28403371/development-of-a-theoretical-practical-script-for-clinical-simulation
#14
Renata Paula Fabri, Alessandra Mazzo, José Carlos Amado Martins, Ariadne da Silva Fonseca, César Eduardo Pedersoli, Fernanda Berchelli Girão Miranda, Laís Fumincelli, Rui Carlos Negrão Baptista
OBJECTIVE: To develop a theoretical-practical script based on the opinion of experts to be used in simulated clinical activities. METHOD: Qualitative study through analysis of content of interviews with experts on the theme in order to develop the proposed script. Of the 24 invited experts, 12 specialists from educational institutions in Brazil and abroad participated in the study in compliance with the ethical precepts. The experts responded to questions on the characterization of their study attributes and described the items required for the development of a simulated scenario...
April 10, 2017: Revista da Escola de Enfermagem da U S P
https://www.readbyqxmd.com/read/28380783/vectorial-eigenvector-method-for-simulating-the-polarization-dependent-resonator
#15
Youyou Hu, Xiaofeng He, Sisi Liu, Xiahui Tang, Bo Li
Derived from the eigenvector method (EM), a vectorial eigenvector method (VEM) for the mode calculation of polarization dependent resonator is presented. New transfer matrices of laser resonant cavities with polarization-selective devices are built by using Jones matrix representation. The eigenvectors computed by solving the matrix eigenequation manifest the mode characteristics of resonators, including cylindrical vector (CV) modes. Comparing with EM, the VEM inherits EM's superiorities and extends scalar models to vector models...
March 6, 2017: Optics Express
https://www.readbyqxmd.com/read/28370077/flexible-fitting-to-cryo-em-density-map-using-ensemble-molecular-dynamics-simulations
#16
Osamu Miyashita, Chigusa Kobayashi, Takaharu Mori, Yuji Sugita, Florence Tama
Flexible fitting is a computational algorithm to derive a new conformational model that conforms to low-resolution experimental data by transforming a known structure. A common application is against data from cryo-electron microscopy to obtain conformational models in new functional states. The conventional flexible fitting algorithms cannot derive correct structures in some cases due to the complexity of conformational transitions. In this study, we show the importance of conformational ensemble in the refinement process by performing multiple fittings trials using a variety of different force constants...
April 1, 2017: Journal of Computational Chemistry
https://www.readbyqxmd.com/read/28367256/investigating-differences-in-brain-functional-networks-using-hierarchical-covariate-adjusted-independent-component-analysis
#17
Ran Shi, Ying Guo
Human brains perform tasks via complex functional networks consisting of separated brain regions. A popular approach to characterize brain functional networks in fMRI studies is independent component analysis (ICA), which is a powerful method to reconstruct latent source signals from their linear mixtures. In many fMRI studies, an important goal is to investigate how brain functional networks change according to specific clinical and demographic variabilities. Existing ICA methods, however, cannot directly incorporate covariate effects in ICA decomposition...
December 2016: Annals of Applied Statistics
https://www.readbyqxmd.com/read/28344722/assessment-of-emergency-medicine-residents-a-systematic-review
#18
REVIEW
Isabelle N Colmers-Gray, Kieran Walsh, Teresa M Chan
BACKGROUND: Competency-based medical education is becoming the new standard for residency programs, including Emergency Medicine (EM). To inform programmatic restructuring, guide resources and identify gaps in publication, we reviewed the published literature on types and frequency of resident assessment. METHODS: We searched MEDLINE, EMBASE, PsycInfo and ERIC from Jan 2005 - June 2014. MeSH terms included "assessment," "residency," and "emergency medicine." We included studies on EM residents reporting either of two primary outcomes: 1) assessment type and 2) assessment frequency per resident...
February 2017: Canadian Medical Education Journal
https://www.readbyqxmd.com/read/28336911/2d-hybrid-analysis-approach-for-building-three-dimensional-atomic-model-by-electron-microscopy-image-matching
#19
Atsushi Matsumoto, Naoyuki Miyazaki, Junichi Takagi, Kenji Iwasaki
In this study, we develop an approach termed "2D hybrid analysis" for building atomic models by image matching from electron microscopy (EM) images of biological molecules. The key advantage is that it is applicable to flexible molecules, which are difficult to analyze by 3DEM approach. In the proposed approach, first, a lot of atomic models with different conformations are built by computer simulation. Then, simulated EM images are built from each atomic model. Finally, they are compared with the experimental EM image...
March 23, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28334132/maximum-likelihood-estimation-and-em-algorithm-of-copas-like-selection-model-for-publication-bias-correction
#20
Jing Ning, Yong Chen, Jin Piao
Publication bias occurs when the published research results are systematically unrepresentative of the population of studies that have been conducted, and is a potential threat to meaningful meta-analysis. The Copas selection model provides a flexible framework for correcting estimates and offers considerable insight into the publication bias. However, maximizing the observed likelihood under the Copas selection model is challenging because the observed data contain very little information on the latent variable...
February 25, 2017: Biostatistics
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