Publications

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.', Research report (Health Effects Institute), no. 65 Pt 11, pp. 1-55.

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.', Research report (Health Effects Institute), no. 65 Pt 10.
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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 were speciall...

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

Geweke, J & Runkle, D 1995, 'A Fine Time for Monetary Policy?', Federal Reserve Bank of Minneapolis Quarterly Review, vol. 19, no. 1, pp. 18-31.
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Almost everyone would agree--even we in the Federal Reserve System--that monetary policy can be improved. But improving it requires accurate empirical descriptions of the current policy and the relationship between that policy and the economic variables policymakers care about. With those descriptions, we could, conceivably, predict how economic outcomes would change under alternative policies and hence find policies that lead to better economic outcomes. The first requirement of this policymaking problem is policy identification, and it is the focus of this study. Policy identification entails a specification of the instrument the Federal Reserve controls and a description of how that instrument is set based on information available when a policy decision is made. Because policy identification is a crucial step in the search for improved monetary policy, it has received much attention in the literature.

Goetghebeur, E & Ryan, LM 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.

Gopalsamy, K, He, X & Sun, D 1995, 'On The Oscillatory Convergence Of Solutions Of A Neutral Delay Diffusion Equation', International Journal Of Systems Science, vol. 26, no. 3, pp. 563-576.
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Sufficient conditions are obtained for the trivial solution of the initial-boundary value problem partial derivative/partial derivative t [u(t, X) - cu(t - sigma, x)] = D partial derivative(2)u(t, x)/partial derivative x(2) - au(t - tau, x) partial deriv

Gopalsamy, K, Li, J & He, XZ 1995, 'On the Construction of Periodic Solutions of Kaplan-Yorke Type for Some Differential Delay Equations', Applicable Analysis, vol. 59, no. 1-4, pp. 65-80.
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In this paper we point out the main idea to yield periodic solutions of Kaplan-Yorke type of differential delay equations. Some new sufficient conditions for the existence of Kaplan-Yorke type periodic solutions have been given. Many interesting examples are also disscused. © 1995, Taylor & Francis Group, LLC. All rights reserved.

He, X 1995, 'Global attractivity of linear non-autonomous neutral differential-difference equations', Acta Mathematicae Applicatae Sinica, vol. 11, no. 2, pp. 184-191.
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In this paper, by constructing Liapunov functionals, we study the global attractivity of linear non-autonomous neutral differential difference equation {Mathematical expression} and obtain some new easily-checked sufficient conditions for the global attractivity of the zero solution of equation (1). © 1995 Science Press, Beijing, China and Allerton Press, Inc., New York, U.S.A.

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.

Peppas, P & Williams, MA 1995, 'Constructive modelings for theory change', Notre Dame Journal of Formal Logic, vol. 36, no. 1, pp. 120-133.
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Alchourron, Gärdenfors and Makinson have developed and investigated a set of rationality postulates which appear to capture much of what is required of any rational system of theory revision. This set of postulates describes a class of revision functions, however it does not provide a constructive way of defining such a function. There are two principal constructions of revision functions, namely an epistemic entrenchment and a system of spheres. We refer to their approach as the AGM paradigm. We provide a new constructive modeling for a revision function based on a nice preorder on models, and furthermore we give explicit conditions under which a nice preorder on models, an epistemic entrenchment, and a system of spheres yield the same revision function. Moreover, we provide an identity which captures the relationship between revision functions and update operators (as defined by Katsuno and Mendelzon). © 1995, Duke University Press. All Rights Reserved.

Piccardi, M, Cinotti, T & Zuffi, S 1995, 'A Preliminary Performance Evaluation Of The Quadrics Architecture With The Darpa Image Understanding Benchmark', High-performance Computing And Networking, 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 t

Ryan, LM 1995, 'Comment', Statistical Science, vol. 10, no. 2, pp. 189-193.
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Ryan, LM 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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Wang, J, Xu, G & Wang, N 1995, 'Mathematical model for calculating the flux of laser scattering by single particle in arbitrary directions', Yingyong Jiguang/Applied Laser Technology, vol. 15, no. 2, pp. 79-78.
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A formula for calculating the scattered light intensity from a single particle by using the Mie's theory was derived here, and based on which, the scattered light-flux in a certain solid-angle in arbitrary direction was further obtained to correct the mistake occuring in the expression on the light-flux existed in one of the references listed.

Whyte, M, Landt, M, Mulivor, R, Henthorn, P, Fedde, K, Mahuren, J, Coburn, S & Ryan, LM 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-non-specific (liver/bone/kidney) alkaline phosphatase (ALP) isoenzyme (TNSALP); placental and intestinal ALP isoenzyme (PALP and IALP, respectively) activity is not reduced, Three p

Zhang, C 1995, 'The Design And Implementation Of A Knowledge-based Communication-system In A Framework For Distributed Expert-systems', IEEE Transactions On Communications, vol. 43, pp. 1926-1936.
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Williams, MA 1995, 'Conditionalizing expectations', ANZIIS 1995 - Proceedings of the 3rd Australian and New Zealand Conference on Intelligent Information Systems, pp. 111-116.
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© 1995 IEEE. All rights reserved. An information system characterizes a view of the world. Typically this view is incomplete and subject to change, as a consequence such systems use nonmonotonic reasoning to form expectations about the world, and they modify their expectations as new information is acquired. For instance, database systems use the closed world assumption a very naive variety of nonmonotonic reasoning, and their expectations are updated when new information becomes available in the form of transactions. Gardenfors and Makinson have shown that nonmontonic inferences can be constructed from a preference ordering of expectations. In this paper we adapt the process of conditionalization and techniques developed in the area of belief revision to handle changes in the nonmonotonic information encapsulated in an expectation ordering. Thereby providing a mechanism for modeling the removal of old expectations, the incorporation of new expectations, as well as the raising and lowering of existing expectations. Changes to the expectation ordering using conditionalization are based on a relative measure of minimal change.