Corcoran, C & Ryan, LM 2002, 'Exact dose-response inference' in Topics in Modelling of Clustered Data, pp. 195-205.
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Methods for analyzing correlated binary data have been well established in recent decades.P endergast et al. (1992) offer a review of methods for correlated binary data, with a focus on cluster-correlated observations.Some of these methods, including marginal, random effects, and Markovian or conditional models, have been introduced in Chapter 4 and studied in subsequent chapters.Ho wever, the justification of inferences thatrely on such methods usually rests upon the approximate normality of the statistics of interest. Such a distributional assumption may be untenablewhen samples are small or sparse.If a normal approximation is not accurate, the result might be tests that do not preserve the a priori testing level established by the investigator. Likewise, actual coverage probabilities for confidence intervals may be much lower or higher than the nominalconfidence level.Moreo ver, where likelihood or quasi-likelihood methods are applied, inference can be further complicated when parameter estimates lie at or near the boundary of the parameter space. The following two examples illustrate these perils of approximate unconditional inference for cluster-correlated binary data. In this chapter, we will use the examples introduced in Sections 2.7 and 2.8.
Cucchiara, R, Grana, C, Neri, G, Piccardi, M & Prati, A 2002, 'The Sakbot System for Moving Object Detection and Tracking' in Remagnino, P, Jones, G, Paragios, N & Regazzoni, C (eds), Video-Based Surveillance Systems, Springer US, New York, pp. 145-157.
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Geys, H, Molenberghs, G & Ryan, LM 2002, 'Generalized estimating equations' in Topics in Modelling of Clustered Data, pp. 77-87.
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Generalized estimating equations play an important role in the analysis of repeated or clustered outcomes of a non-normally distributed type. In this work, it will be used, together with pseudo-likelihood methodology, as nonlikelihood based method for the analysis of clustered binary data. A comparison between both will be made in Chapter 6. Also, the use of generalized estimating equations will be illustrated in the contexts of individual-level covariates and combined continuous and discrete outcomes, in Chapters 13 and 14, respectively. Further applications of the GEE technology can be found in Section 9.2.6 and Chapter 11. When we are mainly interested in first order marginal mean parameters and pairwise interactions, a full likelihood procedure can be replaced by quasilikelihood methods (McCullagh and Nelder 1989). In quasi-likelihood, the mean response is expressed as a parametric function of covariates; the variance is assumed to be a function of the mean up to possibly unknown scale parameters. Wedderburn (1974) first noted that likelihood and quasi-likelihood theories coincide for exponential families and that the quasi-likelihood “estimating equations” provide consistent estimates of the regression parameters β in any generalized linear model, even for choices of link and variance functions that do not correspond to exponential families.
Geys, H, Molenberghs, G & Ryan, LM 2002, 'Pseudo-likelihood estimation' in Topics in Modelling of Clustered Data, pp. 89-114.
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It is well known that full maximum likelihood estimation can become prohibitive for many models. For example, in the framework of a marginally specified odds ratio model (Lipsitz, Laird and Harrington 1991, Dale 1986, Molenberghs and Lesaffre 1994, Glonek and McCullagh 1995, Lang and Agresti 1994) for multivariate, clustered binary data, full maximum likelihood estimation is prohibitive, especially with large within-unit representation. Conditional models such as the Molenberghs and Ryan (1999) models, introduced in Section 4.2, are based on an exponential family model for multivariate binary data and exhibit a high flexibility to capture different patterns of non-linear dependencies of the marginal probabilities on the cluster size. Like most exponential family models, the Molenberghs and Ryan (1999) model enjoys well known properties, such as linearity of the log-likelihood in the minimal sufficient statistics, unimodality, etc. This implies a high numerical stability of iterative procedures to determine maximum likelihood estimators. In multivariate settings (with 3 or more outcomes), however, where the normalizing constant takes a complicated form, all of these advantages can be lost as this leads to excessive computational requirements. This is especially true for clusters of variable length, because the normalizing constant depends on the cluster size. Hence, alternative estimation methods, which do not require the explicit calculation of the normalizing constant, are in demand.
Ryan, LM 2002, 'Issues in modeling clustered data' in Topics in Modelling of Clustered Data, pp. 37-45.
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In Figure 1.4, the complexity of developmental toxicity studies is clearly illustrated. This, of course, implies there are a number of non-trivial challenges for model development (Molenberghs et al. 1998, Zhu and Fung 1996). Let us list the most important ones.
Stoianoff, NP 2002, 'Environmental Expenditure and the Natural Resources Industry in Australia' in Kreiser, L (ed), Critical Issues in International Environmental Taxation, CCH Incorporated, Chicago, USA, pp. 127-148.
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2001 marks the l0th anniversary since the Australian Federal Government made a marked effort to use taxation policy as a means of encouraging environmental responsibility. To the natural resources industry this translated into the provision of a special deduction for current or capital expenditure incurred on rehabilitation-related activities on or after 1 July 1991. More generally, a regime for the deductibility of environmental expenditure, such as environmental impact studies, and a regime for environmental protection expenditure were also introduced during this period.
Betensky, RA, Lindsey, JC, Ryan, LM & Wand, MP 2002, 'A local likelihood proportional hazards model for interval censored data', STATISTICS IN MEDICINE, vol. 21, no. 2, pp. 263-275.
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We discuss the use of local likelihood methods to fit proportional hazards regression models to right and interval censored data. The assumed model allows for an arbitrary, smoothed baseline hazard on which a vector of covariates operates in a proportional manner, and thus produces an interpretable baseline hazard function along with estimates of global covariate effects. For estimation, we extend the modified EM algorithm suggested by Betensky, Lindsey, Ryan and Wand. We illustrate the method with data on times to deterioration of breast cosmeses and HIV-1 infection rates among haemophiliacs
Cao, L & Dai, R 2002, 'Agent-oriented approach for dealing with open giant intelligent systems', Moshi Shibie yu Rengong Zhineng/Pattern Recognition and Artificial Intelligence, vol. 15, no. 3, p. 257.
Cao, L, Nan, J & Dai, R 2002, 'Intelligent Mobile Agents for Distributed Information Integration', Xitong Fangzhen Xuebao - Journal of System Simulation, vol. 14, no. 11, pp. 1517-1520.
Cao, LB & Dai, RW 2002, 'Software architecture of the hall for workshop of metasynthetic engineering', Ruan Jian Xue Bao/Journal of Software, vol. 13, no. 8, pp. 1430-1435.
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This paper focuse on the software architecture of the network-based Hall for Workshop of Metasynthetic Engineering. A nested client/Agent/server computing scheme-incorporated Requester-Mediator-Provider model is deployed. The framework and its working mechanism of an HWME (hall for workshop of metasynthetic engineering) for macroeconomic decision-making through Java-based intelligent information agents on the basis of above scheme are discussed. Combinations of mobility of agents and message-passing mechanism, algorithm and interaction, multiple types of agent technology and multiple design patterns are flexibly used in this system. Compared with the other client/server and the browser/server computing schemes, this system is more flexible, and has less response time and lower requirement for network performance.
Celedon, JC, Litonjua, AA, Ryan, L, Platts-Mills, T, Weiss, ST & Gold, DR 2002, 'Exposure to cat allergen, maternal history of asthma, and wheezing in first 5 years of life', LANCET, vol. 360, no. 9335, pp. 781-782.
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We looked for an association between early exposure to pets and asthma and wheezing in children whose mothers or fathers did or did not have a history of asthma. We followed up 448 children, who had at least one parent with a history of atopy, from birth to 5 years. Among children whose mothers had no history of asthma, exposure to a cat or a Fel d 1 concentration of at least 8 μg/g at the age of 2-3 months was associated with a reduced risk of wheezing between the ages of 1 and 5 years. However, among children whose mothers did have a history of asthma, such exposures were associated with an increased risk of wheezing at or after the age of 3 years. There was no association between wheezing and exposure to dog or dog allergen, and the father's allergy status had no effect on the relation between childhood wheezing and cat exposure.
Celedon, JC, Litonjua, AA, Ryan, L, Weiss, ST & Gold, DR 2002, 'Bottle feeding in the bed or crib before sleep time and wheezing in early childhood', PEDIATRICS, vol. 110, no. 6, p. e77.
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OBJECTIVE: Bottle feeding in the bed or crib before sleep time has been associated with an increased risk of wheezing in the first year of life. We examined whether bottle feeding in the bed or crib before sleep time in the first year of life is associated with wheezing in the first 5 years of life. METHODS: In a prospective cohort study of 448 children with parental history of atopy followed from birth, we examined the relation between the number of bimonthly parental reports of bottle feeding in the bed or crib before sleep time in the first year of life (range: 0-6 reports) and parental report of wheezing in the first 5 years of life. Additional outcome measures included recurrent wheezing (> or =2 episodes of wheezing in the previous year) and asthma (physician-diagnosed asthma and > or =1 episode of wheezing in the previous year) at the age of 5 years. RESULTS: The risk of recurrent wheezing and asthma at 5 years of age increased significantly with each additional report of bottle feeding in the bed or crib before sleep time in the first year of life. The risk of wheezing between the ages of 1 and 5 years increased with each additional report of bottle feeding in the bed or crib before sleep time in the first year of life. As an example, a child whose parents reported bottle feeding in the bed or crib before sleep time on 3 occasions in the first year of life had 1.5 times higher risk of wheezing between the ages of 1 and 5 years than a child whose parents did not report bottle feeding in the bed or crib before sleep time in the first year of life (95% confidence interval for relative risk: 1.12-2.12). CONCLUSIONS: Among children with parental history of atopy, bottle feeding in the bed or crib before sleep time in the first year of life is a risk factor for recurrent wheezing and asthma at 5 years of age and a risk factor for wheezing between the ages of 1 and 5 years.
Celedon, JC, Litonjua, AA, Ryan, L, Weiss, ST & Gold, DR 2002, 'Day care attendance, respiratory tract illnesses, wheezing, asthma, and total serum IgE level in early childhood', ARCHIVES OF PEDIATRICS & ADOLESCENT MEDICINE, vol. 156, no. 3, pp. 241-245.
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Background: It has been hypothesized that day care-related infections may explain the inverse relation between day care attendance in early life and asthma in childhood. Objective: To examine the relation between day care attendance or respiratory tract illnesses in the first year of life and wheezing and asthma in the first 4 years of life among children with a parental history of atopy who were followed up from birth. Results: Day care attendance in the first year of life was inversely associated with geometric mean total serum IgE level (12.9 [+/- 1 SD = 3.3, 51.4] IU/mL for day care vs 18.5 [+/- 1 SD = 5.3, 64.7] IU/mL for no day cared P=.03) at 2 years of age but not significantly associated with wheezing at or after 2 years of age. Having at least 1 physician-diagnosed lower respiratory tract illness in the first year of life was significantly associated with recurrent wheezing (odds ratio [OR], 2.0; 95% confidence interval [CI], 1.0-4.1) and asthma (OR, 2.5; 95% CI, 1.1-5.5) at 4 years of age, but not with any wheezing (infrequent and frequent) at 3 years or older. Illnesses of the upper respiratory tract (greater than or equal to1 physician-diagnosed upper respiratory tract illness or greater than or equal to3 episodes of nasal catarrh) in the first year of life were associated with any wheezing (frequent and infrequent) between the ages of 1 and 4 years, but not with recurrent wheezing or asthma at 4 years of age. Conclusions: Our results suggest that among children with a parental history of atopy the protective effect of day care attendance in early life against the development of atopy has begun by 2 years of age, and that a protective effect of day care attendance in early life against wheezing may not be observed until after 4 years of age.
Celedon, JC, Litonjua, AA, Ryan, L, Weiss, ST & Gold, DR 2002, 'Lack of association between antibiotic use in the first year of life and asthma, allergic rhinitis, or eczema at age 5 years', AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE, vol. 166, no. 1, pp. 72-75.
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Five retrospective studies have reported an association between antibiotic use in early life and asthma in childhood. We studied the relationship between the use of oral antibiotics in the first year of life and asthma, allergic rhinitis, and eczema at age 5 years among 448 children with a parental history of atopy monitored from birth. After adjustment for potential confounders, we found no significant association between antibiotic use in the first year of life and asthma (odds ratio [OR] for one versus no courses of antibiotics, 0.5; 95% confidence interval [CI] for OR, 0.2 to 1.5; OR for two or more versus no courses of antibiotics, 1.0; 95% CI for OR, 0.5 to 2.2), recurrent wheezing, allergic rhinitis, or eczema at age 5 years. There was no significant association between antibiotic use in the first year of life and having at least one of three atopic diseases (asthma, allergic rhinitis, or eczema) at age 5 years (OR for one versus no courses of antibiotics, 0.7; 95% CI, 0.4 to 1.4, OR for two or more versus no courses of antibiotics, 0.9; 95% Cl, 0.5 to 1.4). Our findings do not support the hypothesis that antibiotic use in early life is associated with the subsequent development of asthma and atopy in childhood.
Chen, YC, Su, HJJ, Guo, YLL, Hsueh, YM, Smith, TJ, Ryan, LM, Lee, MS & Christani, DC 2002, 'Arsenic methylation and bladder cancer risk', EPIDEMIOLOGY, vol. 13, no. 4, pp. S164-S164.
Cho, SI, Goldman, MB, Ryan, LM, Chen, C, Damokosh, AI, Christiani, DC, Lasley, BL, O'Connor, JF, Wilcox, AJ & Xu, X 2002, 'Reliability of serial urine HCG as a biomarker to detect early pregnancy loss', HUMAN REPRODUCTION, vol. 17, no. 4, pp. 1060-1066.
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Background: To examine the reliability of HCG as a biomarker for early pregnancy loss, five experienced researchers independently assessed data from 153 menstrual cycles, determining whether each cycle represented,no conception,' a 'continuing conception' or a 'conception lost.' Methods: Urine samples were analysed by immunoradiometric assay using a combination of capture antibodies for the intact heterodimer (B109) and for an epitope common to the beta subunit and the beta core fragment (B204). For each cycle, HCG data were presented as graphs of daily assay results. Summary statistics for HCG assays from 46 women who had undergone bilateral tubal ligation represented baseline values. Results: Pairwise agreement among the assessors for any of the three options ranged from 78-89%. At least three experts agreed for 147 cycles (96%), accounting for 28 conception losses and 19 continuing conceptions. The multi-rater kappa was 0.62 for the conception lost category and 0.68 for continuing conceptions, indicating substantial agreement. Conclusion: The main sources of disagreement involved deciding whether there was sufficient information for assessment, interpreting cycle parameters such as cycle length or bleeding event, and interpreting a distinct HCG rise pattern that does not exceed the baseline value obtained from the sterilized women.
Claeskens, G, Aerts, M, Molenberghs, G & Ryan, L 2002, 'Robust benchmark dose determination based on profile score methods', ENVIRONMENTAL AND ECOLOGICAL STATISTICS, vol. 9, no. 4, pp. 357-377.
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Clark, C, Berkman, L, Kawachi, I & Ryan, L 2002, 'Perceptions of neighborhood safety and consequences for mobility in elderly populations.', AMERICAN JOURNAL OF EPIDEMIOLOGY, vol. 155, no. 11, pp. s74-s74.
Clark, DE & Ryan, LM 2002, 'Concurrent prediction of hospital mortality and length of stay from risk factors on admission', HEALTH SERVICES RESEARCH, vol. 37, no. 3, pp. 631-645.
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Objective. To develop a method for predicting concurrently both hospital survival and length of stay (LOS) for seriously ill or injured patients, with particular attention to the competing risks of death or discharge alive as determinants of LOS. Data Sources. Previously collected 1995-1996 registry data on 2,646 cases of injured patients from three trauma centers in Maine. Study Design. Time intervals were determined for which the rates of discharge or death were relatively constant. Poisson regression was used to develop a model for each type of terminal event, with risk factors on admission contributing proportionately to the subsequent rates for each outcome in each interval. Mean LOS and cumulative survival were calculated from a combination of the resulting piecewise exponential models. Principal Findings. Age, Glasgow Coma Scale, Abbreviated Injury Scores, and specific mechanisms of injury were significant predictors of the rates of death and discharge, with effects that were variable in different time intervals. Predicted probability of survival and mean LOS from the model were similar to actual values for categorized patient groups. Conclusions. Piecewise exponential models may be useful in predicting LOS, especially if determinants of mortality are separated from determinants of discharge alive.
Duty, SM, Silva, MJ, Barr, DB, Brock, JW, Ryan, L, Chen, Z, Herrick, RF, Christiani, D & Hauser, R 2002, 'Urinary phthalate monoesters at general population exposure levels are associated with altered semen quality.', EPIDEMIOLOGY, vol. 13, no. 4, pp. S197-S197.
Duty, SM, Singh, NP, Ryan, L, Chen, Z, Lewis, C, Huang, T & Hauser, R 2002, 'Reliability of the comet assay in cryopreserved human sperm', HUMAN REPRODUCTION, vol. 17, no. 5, pp. 1274-1280.
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Background: Although the comet assay has potential value for measuring DNA damage in large epidemiological human sperm studies, it is impractical to perform the assay daily on fresh semen samples. Therefore, before its use in epidemiological studies, the reliability of the comet assay in measuring DNA damage in cryopreserved sperm should be compared with that in fresh human sperm. Methods: Semen samples from 16 men were cryopreserved in liquid nitrogen (LN) using four methods: flash freezing with and without cryopreservative, and programmable freezing with and without cryopreservative. Neutral microgel electrophoresis was performed and comets were stained with YOYO-1. Comet length was measured using an eyepiece micrometer at × 400 magnification. Results: The highest correlation was between comet assay results obtained from fresh human semen compared with semen flash frozen without cryopreservative (R = 0.88). However, the method of cryopreservation, as compared with other sources of variability, accounted for only 6% of the variability. Inter-individual variability accounted for 20%, and individual sperm-to-sperm variability within an ejaculate accounted for 65%. Conclusions: Flash-freezing in LN without cryopreservative most closely reproduced the results obtained using fresh human semen samples, and thereby represents the most appropriate cryopreservation method for human semen in epidemiological studies utilizing the neutral comet assay.
Gabrys, B 2002, 'Neuro-fuzzy approach to processing inputs with missing values in pattern recognition problems', International Journal of Approximate Reasoning, vol. 30, no. 3, pp. 149-179.
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Ha, E, Cho, SI, Chen, DF, Chen, CZ, Ryan, L, Smith, TJ, Xu, XP & Christiani, DC 2002, 'Parental exposure to organic solvents and reduced birth weight', ARCHIVES OF ENVIRONMENTAL HEALTH, vol. 57, no. 3, pp. 207-214.
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The authors investigated the association of birth weight with maternal and paternal exposure to organic solvents in 1,222 couples employed in a large petrochemical corporation in Beijing, China, during the period between 1994 and 1998. A trained interviewer assessed parental exposures to organic solvents. The authors used generalized additive models to examine the association between birth weight and parental exposure to organic solvents. After the authors adjusted for potential confounders, maternal exposure to solvents was significantly associated with reduced birth weight (-81.7 gm, 95% confidence interval = −106.3, −3.1), and reduced birth weights of female babies and of younger mothers' babies were statistically significant. Maternal exposure to organic solvents was associated with reduced birth weight in this population, but paternal exposure to organic solvents was not similarly associated. © 2002 Taylor and Francis Group, LLC.
Hauser, R, Altshul, L, Chen, ZY, Ryan, L, Overstreet, J, Schiff, I & Christiani, DC 2002, 'Environmental organochlorines and semen quality: Results of a pilot study', ENVIRONMENTAL HEALTH PERSPECTIVES, vol. 110, no. 3, pp. 229-233.
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There have been numerous studies that suggest that sperm concentrations (sperm counts) are declining in men. However, other studies suggest that sperm counts are not declining or may be increasing in some areas. Although there is disagreement on whether there is a downward temporal trend in sperm counts, the studies provide evidence that sperm counts vary by geographic location. It has been hypothesized that the geographic variation in sperm concentrations may be due to environmental exposures, lifestyle factors, or some unknown causes. To determine whether contemporary ambient levels of polychlorinated biphenyls (PCBs) and p,p′-DDE are associated with altered semen quantity and quality, we selected a study population without specific exposure to PCBs or p,p′-DDE. The present study presents the results from a pilot study on the relationship between serum PCBs and p,p′-DDE and semen quality in 29 subjects recruited from the Massachusetts General Hospital Andrology Laboratory. Of the 29 subjects, 3 had sperm concentrations < 20 million/mL, 7 had < 50% motile sperm, 9 had < 4% normal morphology, and 6 were below normal in more than one semen parameter. The 18 subjects with normal spermatozoa concentration, motility, and morphology were used as comparison subjects. The mean (SE) concentration of the sum of PCBs and p,p′-DDE was 242 ng/g lipids (34.0) and 354 ng/g lipids (120), respectively, for men with below normal motility as compared to 202 ng/g lipids (16.6) and 240 ng/g lipids (31.1), respectively, for the comparison subjects. The data showed general trends that were suggestive of an association between PCBs and p,p′-DDE and abnormal motility, as well as with sperm concentration and morphology. A full-scale study is currently in progress.
Houseman, EA, Ryan, L, Levy, JI & Spengler, JD 2002, 'Autocorrelation in real-time continuous monitoring of microenvironments', JOURNAL OF APPLIED STATISTICS, vol. 29, no. 6, pp. 855-872.
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Interpretation of continuous measurements in microenvironmental studies and exposure assessments can be complicated by autocorrelation, the implications of which are often not fully addressed. We discuss some statistical issues that arose in the analysis of microenvironmental particulate matter concentration data collected in 1998 by the Harvard School of Public Health. We present a simulation study that suggests that Generalized Estimating Equations, a technique often used to adjust for autocorrelation, may produce inflated Type I errors when applied to microenvironmental studies of small or moderate sample size, and that Linear Mixed Effects models may be more appropriate in small-sample settings. Environmental scientists often appeal to longer averaging times to reduce autocorrelation. We explore the functional relationship between averaging time, autocorrelation, and standard errors of both mean and variance, showing that longer averaging times impair statistical inferences about main effects. We conclude that, given widely available techniques that adjust for autocorrelation, longer averaging times may be inappropriate in microenvironmental studies.
Li, J & Wong, L 2002, 'Identifying good diagnostic gene groups from gene expression profiles using the concept of emerging patterns', Bioinformatics, vol. 18, no. 5, pp. 725-734.
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Abstract Motivations and Results: Gene groups that are significantly related to a disease can be detected by conducting a series of gene expression experiments. This work is aimed at discovering special types of gene groups that satisfy the following property. In each group, its member genes are found to be one-to-one contained in pre-determined intervals of gene expression level with a large frequency in one class of cells but are never found unanimously in these intervals in the other class of cells. We call these gene groups emerging patterns, to emphasize the patterns' frequency changes between two classes of cells. We use effective discretization and gene selection methods to obtain the most discriminatory genes. We also use efficient algorithms to derive the patterns from these genes. According to our studies on the ALL/AML dataset and the colon tumor dataset, some patterns, which consist of one or more genes, can reach a high frequency of 90%, or even 100%. In other words, they nearly or fully dominate one class of cells, even though they rarely occur in the other class. The discovered patterns are used to classify new cells with a higher accuracy than other reported methods. Based on these patterns, we also conjecture the possibility of a personalized treatment plan which converts colon tumor cells into normal cells by modulating the expression levels of a few genes. Contact: jinyan@krdl.org.sg; limsoon@krdl.org.sg * To whom correspondence should be addressed.
Li, Y & Ryan, L 2002, 'Modeling spatial survival data using semiparametric frailty models', BIOMETRICS, vol. 58, no. 2, pp. 287-297.
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We propose a new class of semiparametric frailty models for spatially correlated survival data. Specifically, we extend the ordinary frailty models by allowing random effects accommodating spatial correlations to enter into the baseline hazard function multiplicatively. We prove identifiability of the models and give sufficient regularity conditions. We propose drawing inference based on a marginal rank likelihood. No parametric forms of the baseline hazard need to be assumed in this semiparametric approach. Monte Carlo simulations and the Laplace approach are used to tackle the intractable integral in the likelihood function. Different spatial covariance structures are explored in simulations and the proposed methods are applied to the East Boston Asthma Study to detect prognostic factors leading to childhood asthma.
Litonjua, AA, Milton, DK, Celedon, JC, Ryan, L, Weiss, ST & Gold, DR 2002, 'A longitudinal analysis of wheezing in young children: The independent effects of early life exposure to house dust endotoxin, allergens, and pets', JOURNAL OF ALLERGY AND CLINICAL IMMUNOLOGY, vol. 110, no. 5, pp. 736-742.
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Background: It has been postulated that exposure to bacterial endotoxins and animals early in life might confer protection against the development of asthma and allergies. Objective: We investigated the longitudinal effects of exposure to house dust endotoxin (HDE), allergen levels, and the presence of a dog in the home on wheezing in young children over a 4-year period. Methods: Two hundred twenty-six children younger than 5 years were followed for 4 years. Endotoxin and allergen levels were measured from house dust collected at baseline. Longitudinal associations were investigated by using a proportional hazards technique that allowed for multiple outcomes per subject. Results: Exposure to high concentrations of HDE of greater than the median level was associated with an increased risk for wheezing over the period of observation (multivariate relative risk, 1.52; 95% CI, 1.07-2.14), but this risk rapidly decreased over time (P for trend = .005). Exposure to cockroach allergen was associated with increased risk for wheezing, whereas exposure to cat allergen and the presence of a dog in the home were both associated with decreased risk for wheezing. The risks associated with cockroach allergen, cat allergen, and dog did not change over the period of observation. Conclusion: The negative associations between exposures to dogs and cat allergen and wheeze appear to be independent of the effects of endotoxin and suggest that separate mechanisms might mediate the effects of HDE exposure and pet exposure on the developing immune system.
Liu, H, Li, J & Wong, L 2002, 'A comparative study on feature selection and classification methods using gene expression profiles and proteomic patterns.', Genome Inform, vol. 13, pp. 51-60.
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Feature selection plays an important role in classification. We present a comparative study on six feature selection heuristics by applying them to two sets of data. The first set of data are gene expression profiles from Acute Lymphoblastic Leukemia (ALL) patients. The second set of data are proteomic patterns from ovarian cancer patients. Based on features chosen by these methods, error rates of several classification algorithms were obtained for analysis. Our results demonstrate the importance of feature selection in accurately classifying new samples.
LUO, X, ZHANG, C & JENNINGS, NR 2002, 'A HYBRID MODEL FOR SHARING INFORMATION BETWEEN FUZZY, UNCERTAIN AND DEFAULT REASONING MODELS IN MULTI-AGENT SYSTEMS', International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems, vol. 10, no. 04, pp. 401-450.
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This paper develops a hybrid model which provides a unified framework for the following four kinds of reasoning: 1) Zadeh's fuzzy approximate reasoning; 2) truth-qualification uncertain reasoning with respect to fuzzy propositions; 3) fuzzy default reasoning (proposed, in this paper, as an extension of Reiter's default reasoning); and 4) truth-qualification uncertain default reasoning associated with fuzzy statements (developed in this paper to enrich fuzzy default reasoning with uncertain information). Our hybrid model has the following characteristics: 1) basic uncertainty is estimated in terms of words or phrases in natural language and basic propositions are fuzzy; 2) uncertainty, linguistically expressed, can be handled in default reasoning; and 3) the four kinds of reasoning models mentioned above and their combination models will be the special cases of our hybrid model. Moreover, our model allows the reasoning to be performed in the case in which the information is fuzzy, uncertain and partial. More importantly, the problems of sharing the information among heterogeneous fuzzy, uncertain and default reasoning models can be solved efficiently by using our model. Given this, our framework can be used as a basis for information sharing and exchange in knowledge-based multi-agent systems for practical applications such as automated group negotiations. Actually, to build such a foundation is the motivation of this paper.
Ruta, D & Gabrys, B 2002, 'A Theoretical Analysis of the Limits of Majority Voting Errors for Multiple Classifier Systems', Pattern Analysis and Applications, vol. 5, no. 4, pp. 333-350.
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Sammel, MD & Ryan, LM 2002, 'Effects of covariance misspecification in a latent variable model for multiple outcomes', STATISTICA SINICA, vol. 12, no. 4, pp. 1207-1222.
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Sammel and Ryan (1996) developed a latent variable model that allows for covariate effects on multiple continuous outcomes. While the approach provides an effective tool for data reduction and global test for covariate effects, it makes strong assumptions about the covariance among the outcomes. In addition, some parameters axe common to both the mean and variance suggesting that robustness could be a problem. This manuscript evaluates model misspecification on tests of exposure effects derived from the latent variable model. We develop a robust score test which is valid under misspecified variance assumptions and compare it to one based on Generalized Estimating Equations (GEE) (Liang and Zeger (1986)), under varying assumptions on the true model. Both models have similar loss in power under variance misspecification while the estimated global effect of the covariate is more biased towards the null for the GEE model than the LV model. As the variance/scale of the outcomes increases, the performance of the LV model improves. As for asymptotic comparisons, test performance depends upon the amount of variability and correlation among the outcomes. The LV model test is superior when the data are highly correlated, p > 0.3, and with large variance. When uncorrelated outcomes are incorporated, the GEE model is superior, except when only the correlated outcomes axe impacted by the exposure.
Shichao Zhang & Chengqi Zhang 2002, 'Anytime mining for multiuser applications', IEEE Transactions on Systems, Man, and Cybernetics - Part A: Systems and Humans, vol. 32, no. 4, pp. 515-521.
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Shichao Zhang & Chengqi Zhang 2002, 'Encoding probability propagation in belief networks', IEEE Transactions on Systems, Man, and Cybernetics - Part A: Systems and Humans, vol. 32, no. 4, pp. 526-531.
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Complexity reduction is an important task in Bayesian networks. Recently, an approach known as the linear potential function (LPF) model has been proposed for approximating Bayesian computations. The LPF model can effectively compress a conditional probability table into a linear function. This correspondence extends the LPF model to approximate propagation in Bayesian networks. The extension focuses on encoding probability propagation as a polynomial function for a class of tractable problems.
Stoler, JM, Ryan, LM & Holmes, LB 2002, 'Alcohol dehydrogenase 2 genotypes, maternal alcohol use, and infant outcome', JOURNAL OF PEDIATRICS, vol. 141, no. 6, pp. 780-785.
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Objective: To determine whether different alleles of the ADH2 gene (ADH2-1, ADH2-2 and ADH2-3) with differing levels of enzymatic activity can alter the risk of fetal alcohol effects. Study design: ADH2 genotypes were performed on 404 pregnant high-risk women and 139 infants as part of a larger study of alcohol use in pregnancy. Mothers were interviewed about alcohol use during pregnancy, and their infants were examined for alcohol-related features without knowledge of the exposure status. Results: The ADH2-1/3 genotype was more prevalent among black women (46%) than expected (33%); the rate among white women was low as expected (2%). More black women who reported high alcohol use during the pregnancy had the ADH2-1/3 genotype compared with those who reported no alcohol use (70% vs 44%). Sixty percent of the affected black infants had the ADH2-1/3 genotype compared with 29% of the unaffected infants (P <.045). The maternal genotype correlated with her chance of having an infant with alcohol-related physical features (odds ratio = 2.49). This association remained significant after accounting for confounders, such as smoking and maternal weight gain. Alcohol exposure was not significantly associated with infant outcome in black infants after accounting for genotype, smoking, and maternal weight gain, but this association could only be tested in 10 infants of mothers with high exposure. Conclusion: Women with the ADH2-1/3 genotype may be at greater risk for having an affected infant, which may be the result of greater ingestion of alcohol.
Yeoh, E-J, Ross, ME, Shurtleff, SA, Williams, WK, Patel, D, Mahfouz, R, Behm, FG, Raimondi, SC, Relling, MV, Patel, A, Cheng, C, Campana, D, Wilkins, D, Zhou, X, Li, J, Liu, H, Pui, C-H, Evans, WE, Naeve, C, Wong, L & Downing, JR 2002, 'Classification, subtype discovery, and prediction of outcome in pediatric acute lymphoblastic leukemia by gene expression profiling', Cancer Cell, vol. 1, no. 2, pp. 133-143.
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Treatment of pediatric acute lymphoblastic leukemia (ALL) is based on the concept of tailoring the intensity of therapy to a patient's risk of relapse. To determine whether gene expression profiling could enhance risk assignment, we used oligonucleotide
Zhang, S & Zhang, C 2002, 'Discovering causality in large databases', Applied Artificial Intelligence, vol. 16, no. 5, pp. 333-358.
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Cavalli, F, Cucchiara, R, Piccardi, M & Prati, A 1970, 'Performance analysis of MPEG-4 decoder and encoder', International Symposium on VIPromCom Video/Image Processing and Multimedia Communications, 4th EURASIP - IEEE Region 8 International Symposium on Video/Image Processing and Multimedia Communications, Croatian Soc. Electron. Marine, Zadar, Croatia, pp. 227-231.
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Chen, Y, Lin, M, Krewski, D, Burnett, RT, Villeneuve, PJ, McGrail, K & Hertzmann, C 1970, 'Socioeconomic status, thoracic particulate matter and asthma hospitalization in Vancouver', EPIDEMIOLOGY, LIPPINCOTT WILLIAMS & WILKINS, pp. S154-S155.
Chengqi Zhang & Shichao Zhang 1970, 'Database clustering for mining multi-databases', 2002 IEEE World Congress on Computational Intelligence. 2002 IEEE International Conference on Fuzzy Systems. FUZZ-IEEE'02. Proceedings (Cat. No.02CH37291), 2002 IEEE World Congress on Computational Intelligence. 2002 IEEE International Conference on Fuzzy Systems. FUZZ-IEEE'02, IEEE, Hawaii, USA, pp. 974-980.
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Chengqi Zhang, Chunsheng Li & Zili Zhang 1970, 'An agent-based framework for petroleum information services from distributed heterogeneous data resources', Ninth Asia-Pacific Software Engineering Conference, 2002., Asia-Pacific Software Engineering Conference, IEEE Comput. Soc, Gold Coast, Australia, pp. 593-602.
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© 2002 IEEE. For making good decisions in the area of petroleum production, it is becoming a big problem how to timely gather sufficient and correct information, which may be stored in databases, data files, or on the World Wide Web. In this paper, Gaia methodology and Open Agent Architecture were employed to contribute a framework to solve above problem. The framework consists of three levels, namely, role mode, agent type, and agent instance. The model with five roles is analyzed. Four agent types are designed Six agent instances are developed for constructing the system of petroleum information services. The experimental results show that all agents in the system can work cooperatively to organize and retrieve relevant petroleum information. The successful implementation of the framework shows that agent-based technology can significantly facilitate the construction of complex systems in distributed heterogeneous data resource environment.
Chun-Sheng Li, Cheng-Qi Zhang & Zi-Li Zhang 1970, 'An agent-based intelligent system for information gathering from World Wide Web environment', Proceedings. International Conference on Machine Learning and Cybernetics, 2002 International Conference on Machine Learning and Cybernetics, IEEE, Beijing, China, pp. 1852-1857.
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To use the vast amount of information efficiently and effectively from websites is very important for making informed decisions. There are, however, still many problems that need to be overcome in the information gathering research arena to enable the delivery of relevant information required by users. In this paper, an information gathering system is develop by means of multiple agents to solve those problems. We employed some ideas of Gaia methodology and Open Agent Architecture to analyze and design the system. The system consists of query preprocessing agent, information retrieval agent, information filtering agent, and information management agent. The filtering agent is trained with categorized documents and can provide users with the necessary information. The experimental results show that all agents in the system can work cooperatively to retrieve relevant information from the World Wide Web environment.
Cucchiara, R, Prati, A & Piccardi, M 1970, 'Data-type dependent cache prefetching for MPEG applications', Conference Proceedings of the IEEE International Performance, Computing, and Communications Conference (Cat. No.02CH37326), 2002 IEEE International Performance, Computing, and Communications Conference, IEEE, Phoenix, USA, pp. 115-122.
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Data cache prefetching is an effective technique So improve performance of cache memories, whenever the pre fetching algorithm is able to correctly predict useful data to be prefetched. To this aim, adequate information on the program's data locality must be used by the prefetching algorithm. In particular, multimedia applications are characterized by a substantial amount of image and video processing, which exhibits spatial locality in both the dimensions of the 2D data structures used for images and frames. However, in multimedia programs many memory references are made also to non-image data, characterized by standard spatial locality. In this work, we explore the adoption of different prefetching techniques in dependence of the data type (i. e., image and non-image), thus making it possible to tune the prefetching algorithms to the different forms of locality, and achieving overall performance optimization. In order to prevent interference between the two different data types, a split cache with two separated caches for image and non-image data is also evaluated as an alternative So a standard unified cache. Results on a multimedia workload (MPEG-2 and MPEG-4 decoders) show that standard prefetching techniques such as One-block-lookahead and the Stride Prediction Table are effective for standard data, while novel 2D prefetching techniques perform best on image data. In addition, at a parity of size, unified caches offer in general better performance that split caches, thank to the more flexible allocation of a unified cache space.
Gabrys, B 1970, 'Agglomerative learning algorithms for general fuzzy min-max neural network', The Journal of VLSI Signal Processing, 10th IEEE Workshop on Neural Networks for Signal Processing (NNSP 2000), Springer Science and Business Media LLC, UNIV SYDNEY, SYDNEY, AUSTRALIA, pp. 67-82.
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Gabrys, B 1970, 'Combining neuro-fuzzy classifiers for improved generalisation and reliability', Proceedings of the 2002 International Joint Conference on Neural Networks. IJCNN'02 (Cat. No.02CH37290), 2002 International Joint Conference on Neural Networks (IJCNN), IEEE, HONOLULU, HI, pp. 2410-2415.
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Gunes, H, Piccardi, M & Jan, T 1970, 'Automated Classification of Female Facial Beauty Using Learning Algorithms', Proceedings of Image and Vision Computing New Zealand 2002, Image and Vision Computing Conference, 2002 Image and Vision Computing New Zealand, Auckland, New Zealand, pp. 169-173.
He, S, Hintz, TB & Wu, Q 1970, 'An Overview of Object Recognition on the Spiral Architecture', Proceedings of International Conference on Imaging Science, Systems, and Technology (CISST2002), International Conference Imaging Science, Systems and Technology, CSREA, Las Vegas, pp. 14-20.
He, S, Hintz, TB & Wu, Q 1970, 'Neural Network Based Image Edge Detection Within Spiral Architecture', Proceedings of the International Conference on Parallel and Distributed Processing Techniques and Applications, International Conference on Parallel and Distributed Processing Techniques and Applications, CSREA Press, Las Vegas, USA, pp. 21-27.
Jan, T, Krishna, A, Piccardi, M & Hintz, TB 1970, 'Effective Surveillance Image Analysis Using Combination of Linear Regression Model and Modified Probabilistic Neural Networks', Proceedings of Image and Vision Computing New Zealand 2002, Image and Vision Computing Conference, 2002 Image and Vision Computing New Zealand, Auckland, New Zealand, pp. 19-22.
Jan, T, Piccardi, M & Hintz, TB 1970, 'Detection of Suspicious Pedestrian Behaviour Using Modified Probabilistic Neural Networks', Proceedings of Image and Vision Computing New Zealand 2002, Image and Vision Computing Conference, 2002 Image and Vision Computing New Zealand, Auckland, New Zealand, pp. 237-241.
Li, J & Wong, L 1970, 'Geography of Di.erences between Two Classes of Data', Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Springer Berlin Heidelberg, pp. 325-337.
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Easily comprehensible ways of capturing main differences between two classes of data are investigated in this paper. In addition to examining individual differences, we also consider their neighbourhood. The new concepts are applied to three gene expression datasets to discover diagnostic gene groups. Based on the idea of prediction by collective likelihoods (PCL), a new method is proposed to classify testing samples. Its performance is competitive to several state-of-the-art algorithms. © 2002 Springer-Verlag Berlin Heidelberg.
Qiang Wu, Xiangjian He & Hintz, T 1970, 'Distributed image processing on spiral architecture', Fifth International Conference on Algorithms and Architectures for Parallel Processing, 2002. Proceedings., Fifth International Conference on Algorithms and Architectures for Parallel Processing, IEEE Comput. Soc, Beijing, China, pp. 84-91.
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© 2002 IEEE. Improving computation efficiency is a key issue in image processing, especially in edge detection, which is very computationally intensive. With the development of real-time applications of image processing, fast processing response is becoming more critical. In this paper, a technique for distributed image processing on a spiral architecture is proposed, which provides a platform for speeding up image processing based on clusters.
Ruta, D & Gabrys, B 1970, 'New Measure of Classifier Dependency in Multiple Classifier Systems', MULTIPLE CLASSIFIER SYSTEMS, 3rd International Workshop on Multiple Classifier Systems, Springer Berlin Heidelberg, CAGLIARI, ITALY, pp. 127-136.
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Ruta, D & Gabrys, B 1970, 'Static Field Approach for Pattern Classification', SOFT-WARE 2002: COMPUTING IN AN IMPERFECT WORLD, 1st International Conference on Computing in an Imperfect World (SOFT-WARE 2002), Springer Berlin Heidelberg, BELFAST, NORTH IRELAND, pp. 232-246.
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Wu, Q, He, S & Hintz, TB 1970, 'Scaling Factor Computation in Image Partitioning on Spiral Architecture', Proc. International Conference on Parallel and Distributed Processing Techniques and Applications, International Conference on Parallel and Distributed Processing Techniques and Applications, CSREA Press, Las Vegas, US, pp. 28-33.
Yan, X, Zhang, C, Zhang, S & Debenham, JK 1970, 'Association Rule Mining by Agents', Proceedings of International Conference on Machine Learning and Applications, International Conference on Machine Learning and Applications, CSREA Press, Las Vegas, USA, pp. 77-83.
Zhang, C, Yan, X, Zhang, S & Kennedy, PJ 1970, 'Mining Very Large Databases Using Software Agents', Proceedings of the International Conference on Machine Learning and Application (ICMLA 02), International Conference on Machine Learning and Application (ICMLA 02), CSREA Press, Las Vegas, USA, pp. 84-90.
Zhang, Z & Zhang, C 1970, 'An Agent-Based Hybrid Intelligent System for Financial Investment Planning', Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Pacific Rim International Conference on Artificial Intelligence, Springer Berlin Heidelberg, Tokyo, Japan, pp. 355-364.
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© Springer-Verlag Berlin Heidelberg 2002. Many complex problems including financial investment planning require hybrid intelligent systems that integrate many intelligent techniques including expert systems, fuzzy logic, neural networks, and genetic algorithms. However, hybrid intelligent systems are difficult to develop due to complicated interactions and technique incompatibilities. This paper describes a hybrid intelligent system for financial investment planning that was built from agent points of view. This system currently consists of 13 different agents. The experimental results show that all agents in the system can work cooperatively to provide reasonable investment advice. The system is very flexible and robust. The success of the system indicates that agent technologies can significantly facilitate the construction of hybrid intelligent systems.
Zhang, Z & Zhang, C 1970, 'An improvement to matchmaking algorithms for middle agents', Proceedings of the first international joint conference on Autonomous agents and multiagent systems part 3 - AAMAS '02, the first international joint conference, ACM Press, Bologna, Italy, pp. 1340-1347.
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A question frequently asked in multi-agent systems (MASs) concerns the efficient search for suitable agents to solve a specific problem. To answer this question, different types of middle agents are usually employed. The performance of middle agents relies heavily on the matchmaking algorithms used. Matchmaking is the process of finding an appropriate provider for a requester through a middle agent. There has been substantial work on matchmaking in different kinds of middle agents. To our knowledge, almost all currently used matchmaking algorithms missed one point when doing matchmaking - the matchmaking is only based on the advertised capabilities of provider agents. The actual performance of provider agents in accomplishing delegated tasks is not considered at all. This results in the inaccuracy of the matchmaking outcomes as well as the random selection of provider agents with the same advertised capabilities. The quality of service of different service provider agents varies from one agent to another even though they claimed they have the same capabilities. To this end, it is argued that the practical performance of service provider agents has a significant impact on the matchmaking outcomes of middle agents. An improvement to matchmaking algorithms is proposed, which makes the algorithms have the ability to consider the track records of agents in accomplishing delegated tasks. How to represent, accumulate, and use track records as well as how to give initial values for track records in the algorithm are discussed. A prototype is also built to verify the algorithm. Based on the improved algorithm, the matchmaking outcomes are more accurate and reasonable.
Zhang, Z & Zhang, C 1970, 'An improvement to matchmaking algorithms for middle agents', Proceedings of the first international joint conference on Autonomous agents and multiagent systems part 3 - AAMAS '02, the first international joint conference, ACM Press.
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