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Search Results: 1 - 10 of 240871 matches for " James R. Gattiker "
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Calibration of Computational Models with Categorical Parameters and Correlated Outputs via Bayesian Smoothing Spline ANOVA
Curtis B. Storlie,William A. Lane,Emily M. Ryan,James R. Gattiker,David M. Higdon
Statistics , 2014,
Abstract: It has become commonplace to use complex computer models to predict outcomes in regions where data does not exist. Typically these models need to be calibrated and validated using some experimental data, which often consists of multiple correlated outcomes. In addition, some of the model parameters may be categorical in nature, such as a pointer variable to alternate models (or submodels) for some of the physics of the system. Here we present a general approach for calibration in such situations where an emulator of the computationally demanding models and a discrepancy term from the model to reality are represented within a Bayesian Smoothing Spline (BSS) ANOVA framework. The BSS-ANOVA framework has several advantages over the traditional Gaussian Process, including ease of handling categorical inputs and correlated outputs, and improved computational efficiency. Finally this framework is then applied to the problem that motivated its design; a calibration of a computational fluid dynamics model of a bubbling fluidized which is used as an absorber in a CO2 capture system.
Parallel Bayesian Additive Regression Trees
Matthew T. Pratola,Hugh A. Chipman,James R. Gattiker,David M. Higdon,Robert McCulloch,William N. Rust
Statistics , 2013,
Abstract: Bayesian Additive Regression Trees (BART) is a Bayesian approach to flexible non-linear regression which has been shown to be competitive with the best modern predictive methods such as those based on bagging and boosting. BART offers some advantages. For example, the stochastic search Markov Chain Monte Carlo (MCMC) algorithm can provide a more complete search of the model space and variation across MCMC draws can capture the level of uncertainty in the usual Bayesian way. The BART prior is robust in that reasonable results are typically obtained with a default prior specification. However, the publicly available implementation of the BART algorithm in the R package BayesTree is not fast enough to be considered interactive with over a thousand observations, and is unlikely to even run with 50,000 to 100,000 observations. In this paper we show how the BART algorithm may be modified and then computed using single program, multiple data (SPMD) parallel computation implemented using the Message Passing Interface (MPI) library. The approach scales nearly linearly in the number of processor cores, enabling the practitioner to perform statistical inference on massive datasets. Our approach can also handle datasets too massive to fit on any single data repository.
Computer Model Calibration using the Ensemble Kalman Filter
Dave Higdon,Matt Pratola,James Gattiker,Earl Lawrence,Salman Habib,Katrin Heitmann,Steve Price,Charles Jackson,Michael Tobis
Statistics , 2012,
Abstract: The ensemble Kalman filter (EnKF) (Evensen, 2009) has proven effective in quantifying uncertainty in a number of challenging dynamic, state estimation, or data assimilation, problems such as weather forecasting and ocean modeling. In these problems a high-dimensional state parameter is successively updated based on recurring physical observations, with the aid of a computationally demanding forward model that prop- agates the state from one time step to the next. More recently, the EnKF has proven effective in history matching in the petroleum engineering community (Evensen, 2009; Oliver and Chen, 2010). Such applications typically involve estimating large numbers of parameters, describing an oil reservoir, using data from production history that accumulate over time. Such history matching problems are especially challenging examples of computer model calibration since they involve a large number of model parameters as well as a computationally demanding forward model. More generally, computer model calibration combines physical observations with a computational model - a computer model - to estimate unknown parameters in the computer model. This paper explores how the EnKF can be used in computer model calibration problems, comparing it to other more common approaches, considering applications in climate and cosmology.
Calyculin A induces prematurely condensed chromosomes without histone H1 phosphorylation in mammalian G1-phase cells  [PDF]
James R. Paulson, Erica R. Vander Mause
Advances in Biological Chemistry (ABC) , 2013, DOI: 10.4236/abc.2013.33A005

It is shown here that one can induce prematurely condensed chromosomes (PCCs) in G1-phase human (HeLa) and mouse (FT210) cells by treating them with the protein phosphatase inhibitor calyculin A. However, histone H1 is not phosphorylated in these G1-PCCs. It has previously been proposed that histone H1 phosphorylation is responsible for mitotic chromosome condensation, but our results suggest that this is not the case. They indicate instead that phosphorylation of histone H1 is not required for chromosome condensation. It is known that the Cdk1 protein kinase, which triggers mitosis and also phosphorylates histone H1, cannot be activated in G1-phase because mitotic cyclins are not present. Since calyculin A induces PCCs in G1-phase in the absence of active Cdk1, our results suggest that inactivation of protein phosphatases may be just as important for the onset of chromosome condensation and other mitotic events as the activation of protein kinases.

External Representations in the Teaching and Learning of Introductory Chemistry  [PDF]
James R. Cox, Bethany W. Jones
Creative Education (CE) , 2011, DOI: 10.4236/ce.2011.25067
Abstract: This manuscript describes the role that external representations, such as diagrams and sketches, can play in organizing and learning concepts presented in a one-semester chemistry course (general, organic and biochemistry) designed for nursing students. Although external representations are typically found in chemistry textbooks and instructor-drawn notes, students are usually not taught or prompted to use various types of external representations to promote learning. Representations created by an instructor and a student are discussed to highlight effective ways to foster student participation in creating various diagrams. In addition, a student provides a perspective on the educational value of creating external representations and the roles of visual thinking and creativity in learning introductory chemistry. Although the model for this approach has been an introductory chemistry course, this approach can be widely applied across disciplines.
The Sociological Determination: A Reflexive Look at Conducting Local Disaster Research after Hurricane Katrina  [PDF]
Timothy J. Haney, James R. Elliott
Sociology Mind (SM) , 2013, DOI: 10.4236/sm.2013.31002

This paper examines the process of collecting data on New Orleanians affected by Hurricane Katrina. It does so by focusing upon the experiences of local researchers who were simultaneously conducting research on and within the disaster. It also documents one research team’s attempt to generate a random sample of residents from several New Orleans neighborhoods, stratified both by racial composition and level of damage. Further, it describes the challenges associated with navigating complex bureaucracies that are themselves affected by the disaster. Results demonstrate that our methods for drawing samples from six New Orleans neighborhoods yielded highly representative samples, even in heavily damaged neighborhoods where the long-term displacement required a multi-pronged strategy that involved contact by mail, telephone, and visits to local churches. The paper concludes by making recommendations for facilitating future research by locally affected researchers.


Active Management of Plant Canopy Temperature as a Tool for Modifying Plant Metabolic Activity  [PDF]
James R. Mahan, John J. Burke
American Journal of Plant Sciences (AJPS) , 2015, DOI: 10.4236/ajps.2015.61028
Abstract: The relationship between a plant and its thermal environment is a major determiner of its growth and development. Since plants grow and develop within continuously variable thermal environments, they are subjected to continuous thermal variation over their life cycle. Transpiration serves to uncouple the temperature of the plant from that of its environment in a manner that reduces the occurrence of high temperature stresses that can limit plant performance. In some agriculturally important plants, there are desirable metabolic outcomes that are associated with specific stress events (e.g. wine grapes). In these plants it is often desirable to induce temperature and water stresses of known magnitude and duration at specific points in the growing season. In this study we used a computer-controlled irrigation system that used cotton canopy temperature to control irrigation in greenhouse-grown plants over a 10-day period. The system was designed to irrigate in a manner that altered the canopy temperature relative to specific temperature thresholds (28°C, 30°C, 32°C and 34°C). The results demonstrate that automated irrigation management based on canopy temperature is capable of altering the temporal pattern of canopy temperature in a desired manner using a feed-back loop. Potential limitations on this action are related to the range of air temperatures, radiation and humidity within the environment.
Using Sports Wagering Markets to Evaluate and Compare Team Winning Streaks in Sports  [PDF]
R. Alan Bowman, Thomas Ashman, James Lambrinos
American Journal of Operations Research (AJOR) , 2015, DOI: 10.4236/ajor.2015.55029
Abstract: Point spreads and money lines from sports wagering markets are used to evaluate the impressiveness of team streaks. Sports wagering data have previously been useful in assessing competitive balance in sports. Our approach was motivated by the amount of media scrutiny that accompanied the winning streak of the NBA’s Miami Heat and the point streak of the NHL’s Chicago Blackhawks which occurred simultaneously for the most part in 2013. The topic came to the forefront again with the 2014-2015 winning streak of the Atlanta Hawks. Three streaks are highlighted in our paper. The length of the streaks, the quality of the competition, injuries, and a variety of other factors were mentioned in the media but the discussion was limited to subjective opinions as no way of properly weighing relative influence of the factors was identified. Wagering markets provide an excellent source of information for making these judgments. Several complementary measures are described and the most impressive team streaks within and across professional baseball, basketball, football, and ice hockey are identified.
Learning High School Biology in a Social Context  [PDF]
Amitabha Basu, Deborah Aglira, James R. Spotila
Creative Education (CE) , 2017, DOI: 10.4236/ce.2017.815165
Abstract: In this research, we developed a process that helped students connect cell and molecular biology concepts with problems in context of their lives. Specifically, we supplemented traditional teaching with problem, project and inquiry based laboratories, without changing the structure of the mandated biology curriculum. We ran the process twice, following the classroom based action research model. Our initial foray exhibited better student-developed projects and a modest improvement of test grades. Second time we compared changes in problem solving skills, attitude toward reading, writing and problem solving and improvement of traditional test grades from the beginning and end of the school year. This process made the biological concepts so interesting that by the end of the year nearly all students significantly (t(55) = -8.95, p ≤ 0.05) improved problem-solving skills and some students went further to develop and solve independent inquiries. They also exhibited improved attitude towards reading, writing and problem solving. However, we didn’t observe any causal relationship between improvement of problem solving skills and test grade, since its trend showed little difference between first and second trial.
Riesz bases and positive operators on Hilbert space
James R. Holub
International Journal of Mathematics and Mathematical Sciences , 2003, DOI: 10.1155/s0161171203202349
Abstract: It is shown that a normalized Riesz basis for a Hilbert space H (i.e., the isomorphic image of an orthonormal basis in H) induces in a natural way a new, but equivalent, inner product on H in which it is an orthonormal basis, thereby extending the sense in which Riesz bases and orthonormal bases are thought of as being the same. A consequence of the method of proof of this result yields a series representation for all positive isomorphisms on a Hilbert space.
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