Catalano, PJ, Chang, LY, Harkema, JR, Kaden, DA, Last, JA, Mellick, PW, Parks, WC, Pinkerton, KE, Radhakrishnamurthy, B & Ryan, LM 1995, 'Consequences of prolonged inhalation of ozone on F344/N rats: collaborative studies. Part XI: Integrative Summary.', Res Rep Health Eff Inst, no. 65 Pt 11, pp. 1-54.
Catalano, PJ, Rogus, J & Ryan, LM 1995, 'Consequences of prolonged inhalation of ozone on F344/N rats: collaborative studies. Part X: Robust composite scores based on median polish analysis.', Res Rep Health Eff Inst, no. 65 Pt 10, pp. 1-57.
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This report describes some of the statistical methods used to analyze data from the National Toxicology Program/Health Effects Institute Collaborative Ozone Project. The purpose of the collaborative study was to assess the health effects of chronic ozone inhalation. Data were obtained from a subset of 164 F344/N rats dedicated to use by the Health Effects Institute from a standard ozone inhalation study conducted by Battelle Pacific Northwest Laboratories for the National Toxicology Program. The study involved eight groups of investigators, each assessing different types of ozone-related health effects. These included studies of respiratory function and of structural, cellular, and biochemical changes in the lungs and airways. Designing and analyzing a study with several groups of investigators raises many statistical challenges. The highest design priority for this study was that each investigation be individually interpretable as an independent study. This meant that each investigator had to receive an adequate number of animals, balanced with respect to level of ozone exposure and other factors such as the gender of the rats and the time they were killed. Another feature of the collaborative study was the opportunity it provided to assess and quantify the effect of ozone exposure on a broad spectrum of endpoints, and to explore the relations between the different types of effect. Maximizing the potential to assess these correlations required that the individual animals studied by the different groups of investigators overlap as much as possible. This aspect of the statistical design required careful consideration of the compatibility between various investigations. Fortunately, the degree of compatibility was substantial. In many cases, for example, it was possible to assess respiratory function in the animals before they were killed, and then to divide the tissue among several different investigators. This report concentrates on the methods that wer...
Cucchiara, R, Distefano, L & Piccardi, M 1995, 'Detection of Circular Objects by Wave Propagation on a Mesh-Connected Computer', Journal of Parallel and Distributed Computing, vol. 31, no. 1, pp. 77-87.
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Circular objects can be detected in low-contrast and/or blurred images by propagating intensity values according to a two-dimensional wave equation and then finding peaks generated by constructive interference. The paper proposes a parallel algorithm for
Godambe, VP 1995, '[Inference Based on Estimating Functions in the Presence of Nuisance Parameters]: Comment', Statistical Science, vol. 10, no. 2, pp. 158-173.
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GOETGHEBEUR, ELS & RYAN, L 1995, 'Analysis of competing risks survival data when some failure types are missing', Biometrika, vol. 82, no. 4, pp. 821-833.
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We propose a method to analyse competing risks survival data when failure types are missing for some individuals. Our approach is based on a standard proportional hazards structure for each of the failure types, and involves the solution to estimating equations. We present consistent and asymptotically normal estimators of the regression coefficients and related score tests. An appealing feature is that individuals with known failure types make the same contributions as they would to a standard proportional hazards analysis. Contributions of individuals with unknown failure types are weighted according to the probability that they failed from the cause of interest. Efficiency and robustness are discussed. Results are illustrated with data from a breast cancer trial. © 1995 Biometrika Trust.
LEGLER, JM, LEFKOPOULOU, M & RYAN, LM 1995, 'EFFICIENCY AND POWER OF TESTS FOR MULTIPLE BINARY OUTCOMES', JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION, vol. 90, no. 430, pp. 680-693.
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Global tests provide a useful tool for comparing two or more groups with respect to multiple correlated outcomes. We adapt and compare the performance of tests that have been suggested for use with multiple continuous outcomes to the case of multiple binary outcomes. Comparisons and guidelines are based on asymptotic relative efficiencies (ARE’s) and simulations. These results are illustrated using an application from teratology. We extend the work of Lefkopoulou and Ryan to include general M-group comparisons alternatives where group effects may differ for each outcome. A concise form for this general class of score tests is derived. To compute the ARE’s for this class of tests, we devise a useful characterization of the alternative space based on multivariate polar coordinates. Our findings indicate that the common outcome effect tests are efficient for a remarkably large range of circumstances. A simple formula applies to compute the maximum number of unaffected outcomes that can be included in a set of outcomes for which the common outcome effect tests remain more efficient than those derived under multidimensional alternatives. For comparison, other global tests are also considered in the simulations: two tests based on resampling (maximal and minimal z tests), a rank-sum test, a generalized least squares test, and a test based on collapsing multiple endpoints to a single binary outcome. Besides the common outcome effect tests, the resampling tests and the rank-sum test are found to perform very well for the cases under consideration. © 1995 Taylor & Francis Group, LLC.
Piccardi, M, Cinotti, TS & Zuffi, S 1995, 'A preliminary performance evaluation of the Quadrics architecture with the DARPA image understanding benchmark', Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), vol. 919, pp. 124-129.
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This work presents a preliminary performance evaluation of the Quadrics SIMD massively parallel computer in the execution of a suite of image processing algorithms. The suite is extracted from the low-level and intermediate-level processing sections of the widely-used DARPA Image Understanding benchmark for parallel computers. Implementation issues are briefly described and data partitioning and mapping is addressed. Measurements carried out on two different machine configurations are reported and compared with the performance of other well-known parallel systems.
Ryan, LM 1995, '[Inference Based on Estimating Functions in the Presence of Nuisance Parameters]: Comment', Statistical Science, vol. 10, no. 2, pp. 189-193.
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Whyte, MP, Landt, M, Ryan, LM, Mulivor, RA, Henthorn, PS, Fedde, KN, Mahuren, JD & Coburn, SP 1995, 'Alkaline phosphatase: placental and tissue-nonspecific isoenzymes hydrolyze phosphoethanolamine, inorganic pyrophosphate, and pyridoxal 5'-phosphate. Substrate accumulation in carriers of hypophosphatasia corrects during pregnancy.', Journal of Clinical Investigation, vol. 95, no. 4, pp. 1440-1445.
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Hypophosphatasia features selective deficiency of activity of the tissue-nonspecific (liver/bone/kidney) alkaline phosphatase (ALP) isoenzyme (TNSALP); placental and intestinal ALP isoenzyme (PALP and IALP, respectively) activity is not reduced. Three phosphocompounds (phosphoethanolamine [PEA], inorganic pyrophosphate [PPi], and pyridoxal 5'-phosphate [PLP]) accumulate endogenously and appear, therefore, to be natural substrates for TNSALP. Carriers for hypophosphatasia may have decreased serum ALP activity and elevated substrate levels. To test whether human PALP and TNSALP are physiologically active toward the same substrates, we studied PEA, PPi, and PLP levels during and after pregnancy in three women who are carriers for hypophosphatasia. Hypophosphatasemia corrected during the third trimester because of PALP in maternal blood. Blood or urine concentrations of PEA, PPi, and PLP diminished substantially during that time. After childbirth, maternal circulating levels of PALP decreased, and PEA, PPi, and PLP levels abruptly increased. In serum, unremarkable concentrations of IALP and low levels of TNSALP did not change during the study period. We conclude that PALP, like TNSALP, is physiologically active toward PEA, PPi, and PLP in humans. We speculate from molecular/crystallographic information, indicating significant similarity of structure of the substrate-binding site of ALPs throughout nature, that all ALP isoenzymes recognize these same three phosphocompound substrates.
