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Maximum likelihood estimate

Selvakkadunko Selvaratnam, Yanqing Yi, Alwell Oyet
Due to increasing discoveries of biomarkers and observed diversity among patients, there is growing interest in personalized medicine for the purpose of increasing the well-being of patients (ethics) and extending human life. In fact, these biomarkers and observed heterogeneity among patients are useful covariates that can be used to achieve the ethical goals of clinical trials and improving the efficiency of statistical inference. Covariate-adjusted response-adaptive (CARA) design was developed to use information in such covariates in randomization to maximize the well-being of participating patients as well as increase the efficiency of statistical inference at the end of a clinical trial...
December 10, 2018: Biometrical Journal. Biometrische Zeitschrift
Lauren M Hill, Carol E Golin, Nisha C Gottfredson, Brian W Pence, Bethany DiPrete, Jessica Carda-Auten, Jennifer S Groves, Sonia Napravnik, David Wohl, Kevin Knight, Patrick M Flynn
Depression is a known risk factor for antiretroviral therapy (ART) non-adherence, but little is known about the mechanisms explaining this relationship. Identifying these mechanisms among people living with HIV (PLHIV) after release from prison is particularly important, as individuals during this critical period are at high risk for both depression and poor ART adherence. 347 PLHIV recently released from prison in North Carolina and Texas were included in analyses to assess mediation of the relationship between depressive symptoms at 2 weeks post-release and ART adherence (assessed by unannounced telephone pill counts) at weeks 9-21 post-release by the hypothesized explanatory mechanisms of alcohol use, drug use, adherence self-efficacy, and adherence motivation (measured at weeks 6 and 14 post-release)...
December 7, 2018: AIDS and Behavior
Rodrigo Carvajal, Rafael Orellana, Dimitrios Katselis, Pedro Escárate, Juan Carlos Agüero
We present an algorithm for a class of statistical inference problems. The main idea is to reformulate the inference problem as an optimization procedure, based on the generation of surrogate (auxiliary) functions. This approach is motivated by the MM algorithm, combined with the systematic and iterative structure of the Expectation-Maximization algorithm. The resulting algorithm can deal with hidden variables in Maximum Likelihood and Maximum a Posteriori estimation problems, Instrumental Variables, Regularized Optimization and Constrained Optimization problems...
2018: PloS One
Lisa Jean Taylor-Swanson, Kenneth Pike, Ellen Sullivan Mitchell, Jerald R Herting, Nancy Fugate Woods
OBJECTIVE: The purpose of this study was to test the association of two dimensions of self-awareness with hot flash (HF) severity. METHODS: A subset of women from the Seattle Midlife Women's Health Study (N = 232) provided data for these analyses. Structural equation modeling was used to evaluate two dimensions of self-awareness (Internal States Awareness [ISA] and Self-Reflectiveness [SR]), and secondary factors of perceived stress, anxiety, and attitudes toward menopause as continuous with earlier life, health perceptions, and menopausal stage with respect to HF severity...
December 10, 2018: Menopause: the Journal of the North American Menopause Society
Ippei Yoshida, Kazuki Hirao, Ryuji Kobayashi
INTRODUCTION: Occupational therapy (OT) is defined as the promotion of client health and well-being through a client-centred practice. However, there is a tendency to rely on the therapist's experiences and values, and there is a difference between the client's and therapist's perceptions regarding the current activity that the client is engaged in. In previous studies that have applied 'flow', activities supported by OT in elderly people were analysed, indicating a difference in recognition...
December 9, 2018: BMJ Open
S Vanini, P Calvini, P Checchia, A Rigoni Garola, J Klinger, G Zumerle, G Bonomi, A Donzella, A Zenoni
In recent decades, muon imaging has found a plethora of applications in many fields. This technique succeeds to infer the density distribution of big inaccessible structures where conventional techniques cannot be used. The requirements of different applications demand specific implementations of image reconstruction algorithms for either multiple scattering or absorption-transmission data analysis, as well as noise-suppression filters and muon momentum estimators. This paper presents successful results of image reconstruction techniques applied to simulated data of some representative applications...
December 10, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Mohammod Mostazir, Rod S Taylor, William Henley, Ed Watkins
OBJECTIVE: To undertake a methodological review of statistical methods used in randomised controlled trials (RCTs) for handling intervention non-adherence. STUDY DESIGN: Bibliographic databases were searched using predefined search terms. RESULTS: A substantive number of identified studies (56%) were excluded as they only used naive per-protocol (PP) analysis for handling non-adherence. Our review included 58 articles published between 1991 to 2015...
December 7, 2018: Journal of Clinical Epidemiology
Tao Feng, Jizhe Wang, Hongdi Li
Maximum likelihood reconstruction of activity and attenuation (MLAA) for PET data with time-of-flight (TOF) information can determine the activity distribution up to a scale, and the attenuation map Radon transform up to a related constant. Prior knowledge is widely used for the determination of the constant. However, prior knowledge could be inaccurate due to patient variation and may result in quantitation errors. Our goal is to develop a method that can determine the scale and the related constant in the TOF-MLAA algorithm to obtain quantitatively accurate activity and attenuation maps...
November 14, 2018: Physics in Medicine and Biology
Johan Gustafsson, Gustav Brolin, Michael Ljungberg
This paper presents the development and validation of a Monte Carlo-based singe photon emission computed tomography reconstruction program for parallel-hole collimation contained within the SIMIND Monte Carlo framework. The Monte Carlo code is used as an accurate forward-projector and is combined with a simplified back-projector to perform iterative tomographic reconstruction using the Maximum Likelihood Expectation Maximization and Ordered Subsets Expectation Maximization algorithms, together forming a program called SIMREC...
November 14, 2018: Physics in Medicine and Biology
Joe Alexander, Roger A Edwards, Marina Brodsky, Luigi Manca, Roberto Grugni, Alberto Savoldelli, Gianluca Bonfanti, Birol Emir, Ed Whalen, Steve Watt, Bruce Parsons
Prior work applied hierarchical clustering, coarsened exact matching (CEM), time series regressions with lagged variables as inputs, and microsimulation to data from three randomized clinical trials (RCTs) and a large German observational study (OS) to predict pregabalin pain reduction outcomes for patients with painful diabetic peripheral neuropathy. Here, data were added from six RCTs to reduce covariate bias of the same OS and improve accuracy and/or increase the variety of patients for pain response prediction...
2018: PloS One
Frank Konietschke, Tim Friede, Markus Pauly
Count data are common endpoints in clinical trials, for example magnetic resonance imaging lesion counts in multiple sclerosis. They often exhibit high levels of overdispersion, that is variances are larger than the means. Inference is regularly based on negative binomial regression along with maximum-likelihood estimators. Although this approach can account for heterogeneity it postulates a common overdispersion parameter across groups. Such parametric assumptions are usually difficult to verify, especially in small trials...
December 5, 2018: Biometrical Journal. Biometrische Zeitschrift
Laura Pérez García, Jaime Donlucas Pérez, Giorgio Volpe, Alejandro V Arzola, Giovanni Volpe
The accurate measurement of microscopic force fields is crucial in many branches of science and technology, from biophotonics and mechanobiology to microscopy and optomechanics. These forces are often probed by analysing their influence on the motion of Brownian particles. Here we introduce a powerful algorithm for microscopic force reconstruction via maximum-likelihood-estimator analysis (FORMA) to retrieve the force field acting on a Brownian particle from the analysis of its displacements. FORMA estimates accurately the conservative and non-conservative components of the force field with important advantages over established techniques, being parameter-free, requiring ten-fold less data and executing orders-of-magnitude faster...
December 4, 2018: Nature Communications
Iveren Winifred Nyinoh
Hit, Lead & Candidate Discovery Mycobacteria populations can undergo mutations in their DNA sequence during replication, which if not repaired would be transferred to future generations. Earlier studies have tackled the estimation of mutation rate in mycobacteria at fixed concentrations. However, in this study, in vitro spontaneous mutations in Mycobacterium smegmatis (Msm) mc2 155 (Msm) that confers resistance to some of the most important antitubercular drugs; isoniazid (INHr ), rifampicin (RIFr ), kanamycin (KANr ) and streptomycin (STRr ) were first determined at several highly lethal concentrations, a few of which have not been previously investigated, in a fluctuation assay...
December 3, 2018: Drug Development Research
Yun Li, Sijian Wang, Peter X-K Song, Naisyin Wang, Ling Zhou, Ji Zhu
The linear mixed-effects model (LMM) is widely used in the analysis of clustered or longitudinal data. This paper aims to address analytic challenges arising from estimation and selection in the application of the LMM to high-dimensional longitudinal data. We develop a doubly regularized approach in the LMM to simultaneously select fixed and random effects. On the theoretical front, we establish large sample properties for the proposed method under the high-dimensional setting, allowing both numbers of fixed effects and random effects to be much larger than the sample size...
2018: Statistics and its Interface
Milena A Gianfrancesco, Laura Trupin, Stephen Shiboski, Mark van der Laan, Jonathan Graf, John Imboden, Jinoos Yazdany, Gabriela Schmajuk
OBJECTIVE: Prior studies around the relationship between smoking and rheumatoid arthritis (RA) disease activity have reported inconsistent findings, which may be ascribed to heterogeneous study designs or biases in statistical analyses. We examined the association between smoking and RA outcomes using statistical methods that account for time-varying confounding and loss to followup. METHODS: We included 282 individuals with an RA diagnosis using electronic health record data collected at a public hospital between 2013 and 2017...
December 1, 2018: Journal of Rheumatology
Eun-Hyun Lee, Seung Hei Moon, Myung Sun Cho, Eun Suk Park, Soon Young Kim, Jin Sil Han, Jung Hee Cheio
PURPOSE: This study aimed to evaluate the psychometric properties of the Depression Anxiety Stress Scales 21 and 12 in a Korean population. METHODS: The Depression Anxiety Stress Scales were translated into Korean using a translation and back-translation technique, and the content validity was assessed by an expert panel. Participants were recruited from 6 community health centers (n = 431) and 2 community mental health centers (n = 50). A field test of the psychometric properties of the instruments was conducted using confirmatory factor analysis with bootstrap maximum-likelihood estimation involving 1,000 samples, Pearson's analysis, t-test, and Cronbach's alpha coefficient...
November 29, 2018: Asian Nursing Research
Ben Kelcey
Structural equation modeling with full information maximum likelihood estimation is the predominant method to empirically assess complex theories involving multiple latent variables in addiction research. Although full information estimators have many desirable properties including consistency, a major limitation in structural equation models is that they often sustain significant bias when implemented in small to moderate size studies (e.g., fewer than 100 or 200). Recent literature has developed a limited information estimator designed to address this limitation-conceptually implemented through a bias-corrected factor score path analysis approach-that has been shown to produce unbiased and efficient estimates in small to moderate sample settings...
October 27, 2018: Addictive Behaviors
Jean P Boubli, Hazel Byrne, Maria N F da Silva, José Silva-Júnior, Rodrigo Costa Araújo, Fabrício Bertuol, Jonas Gonçalves, Fabiano Melo, Anthony B Rylands, Russell A Mittermeier, Felipe E Silva, Stephen D Nash, Gustavo Canale, Raony de M Alencar, Rogerio Rossi, Jeferson Carneiro, Iracilda Sampaio, Izeni P Farias, Horácio Schneider, Tomas Hrbek
The taxonomy of the titi monkeys (Callicebinae) has recently received considerable attention. It is now recognised that this subfamily is composed of three genera with 33 species, seven of them described since 2002. Here, we describe a new species of titi, Plecturocebus, from the municipality of Alta Floresta, Mato Grosso, Brazil. We adopt an integrative taxonomic approach that includes phylogenomic analyses, pelage characters, and locality records. A reduced representation genome-wide approach was employed to assess phylogenetic relationships among species of the eastern Amazonian clade of the Plecturocebus moloch group...
November 26, 2018: Molecular Phylogenetics and Evolution
Joan Guàrdia-Olmos, Esteve Gudayol-Ferré, Geisa B Gallardo-Moreno, Mar Martínez-Ricart, Maribel Peró-Cebollero, Andrés A González-Garrido
BACKGROUND: Type 1 diabetes mellitus (T1D) affects the entire cellular network of the organism. Some patients develop cognitive disturbances due to the disease, but several authors have suggested that the brain develops compensatory mechanisms to minimize or prevent neuropsychological decline. The present study aimed to assess the effective connectivity underlying visuospatial working memory performance in young adults diagnosed with T1D using neuroimaging techniques (fMRI). METHODS: Fifteen T1D right-handed, young adults with sustained metabolic clinical stability and a control group matched by age, sex, and educational level voluntarily participated...
2018: PloS One
Guangyu Zuo, Yinke Dou, Ruibo Lei
Snow depth and sea ice thickness in the Polar Regions are significant indicators of climate change and have been measured over several decades by ice-tethered buoys. However, sea ice temperature profiles measured by ice-tethered buoys are rarely used to infer snow depth and sea ice thickness owing to the lack of automatic discrimination algorithms, restricting the use of the data for sea ice thermodynamics studies. In this study, snow depth and sea ice thickness were retrieved through the measurements of sea ice temperature profiles using discrimination algorithms of the change point and the maximum likelihood detection methods...
November 27, 2018: Sensors
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