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Search Results: 1 - 10 of 6031 matches for " Timothy Hanson "
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SAS Macro BDM for Fitting the Dale Regression Model to Bivariate Ordinal Response Data
Garnett McMillan,Timothy Hanson
Journal of Statistical Software , 2005,
DPpackage: Bayesian Semi- and Nonparametric Modeling in R
Alejandro Jara,Timothy Hanson,Fernando A. Quintana,Peter Müller
Journal of Statistical Software , 2011,
Abstract: Data analysis sometimes requires the relaxation of parametric assumptions in order to gain modeling flexibility and robustness against mis-specification of the probability model. In the Bayesian context, this is accomplished by placing a prior distribution on a function space, such as the space of all probability distributions or the space of all regression functions. Unfortunately, posterior distributions ranging over function spaces are highly complex and hence sampling methods play a key role. This paper provides an introduction to a simple, yet comprehensive, set of programs for the implementation of some Bayesian nonparametric and semiparametric models in R, DPpackage. Currently, DPpackage includes models for marginal and conditional density estimation, receiver operating characteristic curve analysis, interval-censored data, binary regression data, item response data, longitudinal and clustered data using generalized linear mixed models, and regression data using generalized additive models. The package also contains functions to compute pseudo-Bayes factors for model comparison and for eliciting the precision parameter of the Dirichlet process prior, and a general purpose Metropolis sampling algorithm. To maximize computational efficiency, the actual sampling for each model is carried out using compiled C, C++ or Fortran code.
Modeling county level breast cancer survival data using a covariate-adjusted frailty proportional hazards model
Haiming Zhou,Timothy Hanson,Alejandro Jara,Jiajia Zhang
Statistics , 2015, DOI: 10.1214/14-AOAS793
Abstract: Understanding the factors that explain differences in survival times is an important issue for establishing policies to improve national health systems. Motivated by breast cancer data arising from the Surveillance Epidemiology and End Results program, we propose a covariate-adjusted proportional hazards frailty model for the analysis of clustered right-censored data. Rather than incorporating exchangeable frailties in the linear predictor of commonly-used survival models, we allow the frailty distribution to flexibly change with both continuous and categorical cluster-level covariates and model them using a dependent Bayesian nonparametric model. The resulting process is flexible and easy to fit using an existing R package. The application of the model to our motivating example showed that, contrary to intuition, those diagnosed during a period of time in the 1990s in more rural and less affluent Iowan counties survived breast cancer better. Additional analyses showed the opposite trend for earlier time windows. We conjecture that this anomaly has to be due to increased hormone replacement therapy treatments prescribed to more urban and affluent subpopulations.
Learning about Vegetarian Diets in School: Curricular Representations of Food and Nutrients in Elementary Health Education  [PDF]
Clara Hanson
Advances in Applied Sociology (AASoci) , 2012, DOI: 10.4236/aasoci.2012.21010
Abstract: This paper examines the way non-meat and plant based diets are discussed in four elementary curricula. The author used an open coding technique of grounded theory to understand the way food, nutrition and vegetarianism was discussed. The curricula relied heavily upon the USDA Food Pyramid and a related concept of “balance” for nutritional information. The curricula also discussed nutrition in terms of food and food groups, rather than in terms of nutrients. Although some of the curricula included information about the benefits of vegetarian diets, the high level of use of the Food Pyramid often overwhelmed the low level of information about vegetarianism.
Trends in U.S. Voting Attitudes with a Consideration of Variation by Gender and Race/Ethnicity  [PDF]
Sandra L. Hanson
Open Journal of Political Science (OJPS) , 2016, DOI: 10.4236/ojps.2016.64038
Abstract: Low turnout rates and discussions of disaffected voters are receiving considerable attention as we approach the 2016 U.S. presidential elections. Do trends in American’s attitudes about voting and correlates of these attitudes (political involvement, efficacy, and social connectedness) confirm the pessimistic assessments and do voters across gender and race/ethnic groups think similarly? Data from the American National Election Studies (ANES) provide some reason for optimism. Trends over the past few presidential election periods show a majority of Americans intend to vote and this majority is increasing. Trends show increases or stability on numerous correlates of voting attitudes including political involvement and social connectedness. Trends in voting attitudes by gender and race/ethnicity show considerable variation. Women and race/ethnic minorities (especially African Americans) are an important element of the positive trends shown here. Findings on external efficacy are an exception to the generally optimistic trends with data showing a majority of respondents don’t believe public officials care what people like the respondent think. However, trends do not show an increase in negative attitudes about public officials. Implications of the findings are considered.
Unscented Kalman Filter for Brain-Machine Interfaces
Zheng Li, Joseph E. O'Doherty, Timothy L. Hanson, Mikhail A. Lebedev, Craig S. Henriquez, Miguel A. L. Nicolelis
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006243
Abstract: Brain machine interfaces (BMIs) are devices that convert neural signals into commands to directly control artificial actuators, such as limb prostheses. Previous real-time methods applied to decoding behavioral commands from the activity of populations of neurons have generally relied upon linear models of neural tuning and were limited in the way they used the abundant statistical information contained in the movement profiles of motor tasks. Here, we propose an n-th order unscented Kalman filter which implements two key features: (1) use of a non-linear (quadratic) model of neural tuning which describes neural activity significantly better than commonly-used linear tuning models, and (2) augmentation of the movement state variables with a history of n-1 recent states, which improves prediction of the desired command even before incorporating neural activity information and allows the tuning model to capture relationships between neural activity and movement at multiple time offsets simultaneously. This new filter was tested in BMI experiments in which rhesus monkeys used their cortical activity, recorded through chronically implanted multielectrode arrays, to directly control computer cursors. The 10th order unscented Kalman filter outperformed the standard Kalman filter and the Wiener filter in both off-line reconstruction of movement trajectories and real-time, closed-loop BMI operation.
Fifty years of entomological publications in the Revista de Biología Tropical
Revista de Biología Tropical , 2002,
Abstract: over its fifty year history nearly twenty percent of the papers published in the revista de biología tropical have been about inseets and arachnids. in the 1950's papers on arthropods of medical importance were dominant, in the 1960's there was a poliferation of papers on bees, and in more recent years the subjects have become incresingly diverse. in terms of nationality of contributing authors, the journal appears to have become increasingly international in later years.
Toxicants and physicochemical characteristics of the seeds of African black pear (Dacryodes edulis).
I Hanson
African Journal of Food, Agriculture, Nutrition and Development , 2009,
Abstract: This experiment investigated the antinutrients content and functional properties of the seeds of African black pear (Dacryodes edulis). The study derived its importance from the environmental problem posed by the seeds of this highly cherished fruit. The aim of the project was to determine through empirical means the possible recycling potential that might be inherent in the seeds of the African black pear. Three seed varieties of the same sample categorized as Small (S), Medium (M) and Large (L) were used for this study. Standard experimental protocols were employed in the estimation of all indices. Data obtained indicate that the seed samples contained phytic acid: 12.13 + 1.14; 12.37 + 1.82 and 13.37 + 0.65g/100g sample on dry matter basis (DMB), respectively for Small, Medium and Large. Trypsin inhibitory activities (TIA) were determined as 546.67 + 30.55; 520.00 + 20.00; and 473.33 + 23.10g/100g sample on DMB in the same order, respectively. High amounts of oxalate 0.24 + 0.02 g-1100g for Small; 0.35 + 0.03 g-1100g for Medium and 0.37 + 0.03 g-1100g for Large while tannins were also found to be (5.07 + 0.14; 5.16 + 0.08; 5.02 + 0.16)g- 1100g for Small; Medium; and Large, respectively in the seeds. Water and oil absorption capacity as well as foam capacity and bulk density for all the samples did not differ significantly (P>0.05). The Medium seed flour, however, showed significantly (P<0.05) higher values in emulsion activity (40.82 + 1.52)% and foam stability (6.20 + 0.33)% as compared to foam stability of the Large seed (5.80 + 0.08)% variety. It may, therefore, be concluded from the strength of this novel results, that the seeds of Dacryodes edulis contained high amounts of phytic acid, oxalate, TIA and tannins. Physicochemical data on the other hand suggest the seeds of Dacryodes edulis to have valuable functional attributes of industrial interest.
Encyclopedia of Psychology and Religion
Mark Hanson
Theological Librarianship , 2010,
Fifty years of entomological publications in the Revista de Biología Tropical
Paul Hanson
Revista de Biología Tropical , 2002,
Abstract: Over its fifty year history nearly twenty percent of the papers published in the Revista de Biología Tropical have been about inseets and arachnids. In the 1950's papers on arthropods of medical importance were dominant, in the 1960's there was a poliferation of papers on bees, and in more recent years the subjects have become incresingly diverse. In terms of nationality of contributing authors, the journal appears to have become increasingly international in later years. A través de su historia de cincuenta a os, casi veinte porciento de los artículos publicados en la Revista de Biología Tropical trataron de insectos y arácnidos. En los aiíos cincuenta dominaron los artículos sobre artrópodos de importancia médica, en los a os sesenta hubo una proliferación de artículos sobre abejas, y en los últimos a os los temas incluidos se hicieron más diversos. En términos de la nacionalidad de los autores contribuyentes, parece que la revista se ha vuelto más internacional en los últimos a os.
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