Boosting Classifiers for Drifting Concepts

This paper proposes a boosting-like method to train a classifier ensemble from data streams. It naturally adapts to concept drift and allows to quantify the drift in terms of its base learners. The algorithm is empirically shown to outperform learning algorithms that ignore concept drift. It performs no worse than advanced adaptive time window and example selection strategies that store all the data and are thus not suited for mining massive streams. --

Within- and between-pen transmission of Classical Swine Fever Virus: a new method to estimate the basic reproduction ratio from transmission experiments

We present a method to estimate basic reproduction ratio R0 from transmission experiments. By using previously published data of experiments with Classical Swine Fever Virus more extensively, we obtained smaller confidence intervals than the martingale method used in the original papers. Moreover, our method allows simultaneous estimation of a reproduction ratio within pens R0w and a modified reproduction ratio between pens R'0b. Resulting estimates of R0w and R'0b for weaner pigs were 100 (95% CI 54.4-186) and 7.77 (4.68-12.9), respectively. For slaughter pigs they were 15.5 (6.20-38.7) and 3.39 (1.54-7.45), respectively. We believe, because of the smaller confidence intervals we were able to obtain, that the method presented here is better suited for use in future experiments

À quoi servent les schémas ? Tabularité et dynamisme linéaire

Cet article s’interroge sur la source de l’efficacité des schémas dans les exposés scientifiques. Il part du constat que la plupart des schémas utilisés en science associent des données orientées linéairement et une représentation spatiale ; cette conjonction du linéaire et du spatial peut être appelée « tabularité ». L’article démontre que la puissance explicative de ces schémas provient du fait qu’ils associent, dans une perception globale (voire immédiate) qu’il doit à sa tabularité, le général du paradigme avec la totalité des particuliers exprimée par sa structure syntagmatique.This papers examines the origin of the effectiveness of diagrams in scientific presentations. It recognizes that most diagrams used in science combine linearly oriented data and spatial representation ; this combination of linearity and spatiality can be called “tabularity”. The paper demonstrates that the explanatory power of these diagrams lies in the fact that they combine, in a global (even immediate) perception which they owe to their tabularity, the generality of the paradigm with all individuals expressed by their syntagmatic structure

An instability mechanism for particulate pipe flow

We present linear stability analysis for a simple model of particle-laden pipe flow. The model consists of a continuum approximation for the particles two-way coupled to the fluid velocity field via Stokes drag (Saffman 1962). We extend previous analysis in a channel (Klinkenberg et al. 2011) to allow for the initial distribution of particles to be inhomogeneous and in particular consider the effect of allowing the particles to be preferentially located around one radius in accordance with experimental observations. This simple modification of the problem is enough to alter the stability properties of the flow, and in particular can lead to a linear instability at experimentally realistic parameters. The results are compared to the experimental work of Matas et al. (2004a) and are shown to be consistent with the reported flow regimes.Comment: 15 pages, 11 figure

Malaria and land use: a spatial and temporal risk analysis in Southern Sri Lanka

Malaria / Waterborne diseases / Disease vectors / Land use / Water use / GIS / Statistical analysis / Risks / Mapping / Public health / Sri Lanka / Uda Walawe / Thanamalvila / Embilipitiya

Enhancing Bayesian risk prediction for epidemics using contact tracing

Contact tracing data collected from disease outbreaks has received relatively little attention in the epidemic modelling literature because it is thought to be unreliable: infection sources might be wrongly attributed, or data might be missing due to resource contraints in the questionnaire exercise. Nevertheless, these data might provide a rich source of information on disease transmission rate. This paper presents novel methodology for combining contact tracing data with rate-based contact network data to improve posterior precision, and therefore predictive accuracy. We present an advancement in Bayesian inference for epidemics that assimilates these data, and is robust to partial contact tracing. Using a simulation study based on the British poultry industry, we show how the presence of contact tracing data improves posterior predictive accuracy, and can directly inform a more effective control strategy.Comment: 40 pages, 9 figures. Submitted to Biostatistic

A Practical Procedure for the Construction and Reliability Analysis of Fixed Length Tests with Random Drawn Test Items

A procedure to construct valid and fair fixed-length tests with randomly drawn items from an item bank is described. The procedure provides guidelines for the set-up of a typical achievement test with regard to the number of items in the bank and the number of items for each position in a test. Further, a procedure is proposed to calculate the relative difficulty for individual tests and to correct the obtained score for each student based on the mean difficulty for all students and the particular test of a student. Also, two procedures are proposed for the problem to calculate the reliability of tests with randomly drawn items. The procedures use specific interpretations of regularly used methods to calculate Cronbach’s alpha and KR20 and the Spearman-Brown prediction formula. A simulation with R is presented to illustrate the accuracy of the calculation procedures and the effects on pass-fail decisions

Late-life depressive symptoms, religiousness, and mood in the last week of life

Aim of the current study is to examine whether previous depressive symptoms modify possible effects of religiousness on mood in the last week of life. After-death interviews with proxy respondents of deceased sample members of the Longitudinal Aging Study Amsterdam provided information on depressed mood in the last week of life, as well as on the presence of a sense of peace with the approaching end of life. Other characteristics were derived from interviews with the sample members when still alive. Significant interactions were identified between measures of religiousness and previous depressive symptoms (CES-D scores) in their associations with mood in the last week of life. Among those with previous depressive symptoms, church-membership, church-attendance and salience of religion were associated with a greater likelihood of depressed mood in the last week of life. Among those without previous depressive symptoms, church-attendance and salience of religion were associated with a higher likelihood of a sense of peace. For older adults in the last phase of life, supportive effects of religiousness were more or less expected. Fore those with recent depressive symptoms, however, religiousness might involve a component of existential doubt