1,079 research outputs found
Letter of recommendation from W. J. Lauritzen, Assoc. Construction Supt. at Tule Lake Project for Mr. Lawrence Asoo, September 10, 1943
No full textLetter from W. J. Lauritzen, Associate Construction Superintendent at Tule Lake to Whom It May Concern introducing Mr. Lawrence Asoo and praising his work as a landscape gardener foreman at Tule Lake in the Maintenance Unit.Bunzo Asoo was born in 1897 in Hiroshima, Japan. Haruye Asoo was born in 1982 in Okinawa, Japan. He immigrated to the U.S. in 1914 and helped his father on a farm in Vorden, California. In 1915, Bunzo went to an English language school in San Francisco. In 1920, he returned to Japan for an arranged marriage with Haruye. They had seven children. They farmed in the Sacramento area during the 1920s and 30. In May 1942, the family was forced to evacuate to Arboga Assembly Center, then to Tule Lake and Topaz Relocation Centers. The Asoo's returned to Sacramento in 1945, where Bunzo became a landscape gardener
Inference in Graphical Gaussian Models with Edge and Vertex Symmetries with the gRc Package for R
No full textIn this paper we present the R package gRc for statistical inference in graphical Gaussian models in which symmetry restrictions have been imposed on the concentration or partial correlation matrix. The models are represented by coloured graphs where parameters associated with edges or vertices of same colour are restricted to being identical. We describe algorithms for maximum likelihood estimation and discuss model selection issues. The paper illustrates the practical use of the gRc package.
Comparison of Lauritzen-Spiegelhalter and successive restrictions algorithms for computing probability distributions in Bayesian networks
No full text© 2016 Author(s). The basic task of any probabilistic inference system in Bayesian networks is computing the posterior probability distribution for a subset or subsets of random variables, given values or evidence for some other variables from the same Bayesian network. Many methods and algorithms have been developed to exact and approximate inference in Bayesian networks. This work compares two exact inference methods in Bayesian networks-Lauritzen-Spiegelhalter and the successive restrictions algorithm-from the perspective of computational efficiency. The two methods were applied for comparison to a Chest Clinic Bayesian Network. Results indicate that the successive restrictions algorithm shows more computational efficiency than the Lauritzen-Spiegelhalter algorithm
AN USER-OPTIMAL ROUTE CHOICE MODEL WITH ASYMMETRIC COST FUNCTIONS INCORPORATING INTERSECTION-RELATED TRAVEL TIMES.
No full textThis report describes a traffic assignment model which is innovative in two respects as compared with models conventionally used in practice. First, each turning movement in the street intersections of the network is represented by a travel time-flow relationship; conventional models represent only approach travel times and flows, although turning movements may be accounted for. Second, the travel times for each turning movement are determined as a function of all flows in the intersection as well as the appropriate cycle time and green splits for those flows. Such cost functions are termed asymmetric because of their mathematical properties. In conventional models, each link's travel time depends only on that link's flow. This model is implemented and solved for a small street network for St. Charles, Illinois. To the authors' knowledge, it is the first implementation of such a model with realistic link functions and a real network. The report describes how the link travel time-flow functions were estimated statistically from simulated intersection operations. Then, the experience with the solving model computationally is documented. A lengthy discussion of future research directions concludes the report
Analysis of forensic DNA mixtures with artefacts
No full textDNA is now routinely used in criminal investigations and court cases, although DNA samples taken at crime scenes are of varying quality and therefore present challenging problems for their interpretation. We present a statistical model for the quantitative peak information obtained from an electropherogram of a forensic DNA sample and illustrate its potential use for the analysis of criminal cases. In contrast with most previously used methods, we directly model the peak height information and incorporate important artefacts that are associated with the production of the electropherogram. Our model has a number of unknown parameters, and we show that these can be estimated by the method of maximum likelihood in the presence of multiple unknown individuals contributing to the sample, and their approximate standard errors calculated; the computations exploit a Bayesian network representation of the model. A case example from a UK trial, as reported in the literature, is used to illustrate the efficacy and use of the model, both in finding likelihood ratios to quantify the strength of evidence, and in the deconvolution of mixtures for finding likely profiles of the individuals contributing to the sample. Our model is readily extended to simultaneous analysis of more than one mixture as illustrated in a case example. We show that the combination of evidence from several samples may give an evidential strength which is close to that of a single-source trace and thus modelling of peak height information provides a potentially very efficient mixture analysis
Applications of differential geometry to statistics
No full textChapters 1 and 2 are both surveys of the current work in applying
geometry to statistics. Chapter 1 is a broad outline of all the work done so far,
while Chapter 2 studies, in particular, the work of Amari and that of Lauritzen.
In Chapters 3 and 4 we study some open problems which have been raised
by Lauritzen's work. In particular we look in detail at some of the differential
geometric theory behind Lauritzen's defmition of a Statistical manifold.
The following chapters follow a different line of research. We look at a new
non symmetric differential geometric structure which we call a preferred point
manifold. We show how this structure encompasses the work of Amari and
Lauritzen, and how it points the way to many generalizations of their results. In
Chapter 5 we define this new structure, and compare it to the Statistical manifold
theory. Chapter 6 develops some examples of the new geometry in a statistical
context. Chapter 7 starts the development of the pure theory of these preferred
point manifolds.
In Chapter 8 we outline possible paths of research in which the new
geometry may be applied to statistical theory.
We include, in an appendix, a copy of a joint paper which looks at some
direct applications of differential geometry to a statistical problem, in this case it is
the problem of the behaviour of the Wald test with nonlinear restriction functions
Whole-blood culture is a valid low-cost method to measure monocytic cytokines - a comparison of cytokine production in cultures of human whole-blood, mononuclear cells and monocytes
No full textWhole-blood and peripheral blood mononuclear cell (PBMC) cultures are used as non-validated surrogate measures of monocytic cytokine production. The aim of this investigation was to compare ex vivo cytokine production from human whole-blood and PBMC with that from isolated monocytes. We also assessed the intra- and inter-individual variation in cytokine production. In 64 healthy men (age 19–40 years) IL-6, TNF and IL-10 were measured by enzyme-linked immunosorbent assay in supernatants from whole-blood, PBMC and monocytes cultured 24 h with lipopolysaccharide (LPS) or UV-killed L. acidophilus. Cytokines produced from whole-blood was found to be more strongly correlated with monocytic cytokines than cytokines from PBMC, particularly after LPS-stimulation: r = 0.57, P < 0.001 versus r = 0.33, P = 0.01 for IL-6 and r = 0.43, P < 0.001 versus r = 0.30, P = 0.02 for TNF-?. Adjustment for a preceding 8-week dietary fatty acid-intervention did not change any of the associations. Based on measurements at three time-points 8 weeks apart the intra-individual variation was ? 50% smaller than the inter-individual variation (P < 0.05) in most whole-blood cytokine responses and LPS-stimulated IL-6 from PBMC. We conclude that whole-blood cultures are well-suited low-cost proxy-measures of monocytic cytokine production. Moreover, large inter-individual variation in cytokine production was demonstrated whereas the individual responses in whole-blood were reproducible even over long time-periods
The TM algorithm for maximising a conditional likelihood function
No full textThis paper describes an algorithm for maximising a conditional likelihood function when the corresponding unconditional likelihood function is more easily maximised. The algorithm is similar to the EM algorithm but different as the parameters rather than the data are augmented and the conditional rather than the marginal likelihood function is maximised. In exponential families the algorithm takes a particular simple form which is computationally very close to the EM algorithm. The algorithm alternates between a T-step which calculates a tilted version of the unconditional likelihood function and an M-step which maximises it. The algorithm applies to mixed graphical chain models (Lauritzen and Wermuth, 1989) and their generalisations (Edwards, 1990), and was developed with these in mind, but it may have applications beyond these. The algorithm has been implemented in the most recent version of the MINI software (Edwards, 2000), where it was named the ME algorithm. The name has been changed to avoid confusion with the algorithm described by Marschner (2001). © 2001 Biometrika Trust
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