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

Chasing the Robert E. Lee: Boat Races on the Mississippi River

Perhaps the most famous steamboat race on the Mississippi River came when the Robert E. Lee beat the Natchez from New Orleans to St. Louis in 1870. The record stood for some six decades, when a wave of races up the river started

Tests Of A Fractal Model Of Topography

This thesis tested a fractal model of topography using a variety of measurement techniques (including the variogram method, the cell counting method, and the dividers method) applied to a range of surface types. The methods were first tested for reliability and accuracy by applying them to simulated surfaces of known fractal dimensions. Then, the methods were applied to 58 datasets obtained from U.S.G.S. Digital Elevation Models which covered 9 physiographic provinces in the United States.;The fractal model was found to be a valid model. It fit some topographic datasets well but did not consistently fit all datasets. The fractal dimension was found to vary depending on elevation, direction, and sample size. Those methods which were applied to individual contours were found to consistently produce different dimensions than those methods which were applied to the surfaces. However, it was found that the physiographic provinces could be statistically distinguished using the fractal dimension (D). In addition, it was discovered that the intercepts obtained from the variogram analyses could also be used to separate landform types.;An interesting result of this thesis research was that the fractal model analyses brought to light differences within physiographic provinces that were otherwise not visible using traditional morphometric parameters.;New avenues of research have been identified as a result of the findings of this research

Exploration of the ‘Mean World Syndrome’ in Dutch Older Persons

It was hypothesized that persons aged 57 and over who use more types of mass media, such as internet, television and newspapers, are more anxious and afraid. Also the effects of the different types of media as well as the different contents are explored. The sample originates from the Longitudinal Aging Study Amsterdam (LASA) and consists of 1536 respondents, who were assessed in 2005/2006. It was found that reading newspapers as well as internet use decreases anxiety and fear, whereas television viewing increases these. Mixed findings were found if the content of the programmes was taken into account

Investigation of DNA-free genome editing in Arabidopsis thaliana with pre-assembled CRISPR-Cas9 ribonucleoproteins and transcripts.

Master's thesis in Biological chemistryProgrammable sequence-specific nucleases (SSNs) produces double stranded breaks (DSBs) in the genome in a site-specific manner. The following repair through endogenous repair systems allows targeted genome editing, which among others can be used to genetically improve crops. The superior SSN is the RNA-guided engineered nucleases (RGENs) derived from the adaptive immune system -clustered regulatory interspaced short palindromic repeats (CRISPR) and its associated protein 9 (Cas9) of Streptococcus pyogenes. Only three components are required to generate site specific cleavage; Cas9 endonuclease, a single guide RNA (sgRNA) containing spacer, and a genomic target site upstream of a protospacer adjacent motif (PAM). Upon binding of spacer to genomic target site, it directs cleavage of the site by Cas9 endonuclease. DNA-free genome edited plants are more likely to be labelled as non-gene modified organisms (non-GMOs), which will have a great impact and value for agriculture, and resulting in a more efficient breeding of crops and production of food. The main object of this thesis is to investigate DNA-free genome editing in Arabidopsis thaliana (A. thaliana) using RGENs, and further on investigate the ability to produce a DNA-free gene modified whole plant. To achieve this, we shall directly deliver the RGEN components as both pre-assembled ribonucleoprotein (RNP) complex and in vitro transcribed transcripts, to protoplasts of A. thaliana. The components to set up DNA-free RGENs genetic editing in protoplasts were successfully generated. Two sgRNA encoding gens, containing spacers targeting Phytoene desaturase 3 (PDS3) marker gene of A. thaliana was generated through sub cloning of spacers into a sgRNA expression vector, and success was confirmed by sequencing. Transcripts of the two sgRNA and Cas9 mRNA were generated by vitro transcription. To confirm transcripts functionality containing the predicted spacers, the sgRNAs and commercial Cas9 nuclease were combined to in vitro digest PDS3 target sites. This proved the functionality for one of the designed sgRNA. To be able to do in vivo editing, we needed to optimize the isolation of healthy protoplasts, which proved to be a challenge. High numbers of healthy protoplasts were isolated, but during transformation, they died. However, after substantial trials, and by changing several parameters we were able to optimize the protocol and achieved high number of healthy protoplasts both before and after transformation. Subsequently, isolated protoplasts were transfected with both pre-assembled ribonucleoprotein (RNP) complex and in vitro transcribed transcripts of Cas9 and sgRNA. Genetic modifications were analysed using T7 Endonuclease I assay, but without success. In order to be able to experimentally optimize our plans, we also successfully expressed the Cas9 protein, which can be purified and used for the pre-assembled RNP complex. Successful in vivo studies would help us comparing the editing efficiency of the pre-assembled RNP complex to Cas9 transcripts.submittedVersio

A psychometric perspective on personalized assessment in education

Education has long grappled with the intricacies of providing truly personalized assessment. This dissertation addresses the limitations of conventional assessment methods, especially the widely employed linear tests. A variety of models and methods are introduced to enhance the efficiency, validity, and reliability of assessments. A robust procedure to create fair fixed-length tests, utilizing randomly selected items from an item bank, is delineated, emphasizing guidelines on item setup and procedures to adjust scores based on mean test difficulty. This approach incorporates traditional statistical measures, such as Cronbach’s alpha and the Spearman-Brown prediction formula, to ensure the reliability of tests using random item selections. Secondly, a model for computerized adaptive practice, inspired by the Elo rating system, is introduced. This model, exemplified by the Maths Garden system, updates ability and item difficulty estimations in real-time. It factors in both response time and accuracy in its scoring rule, with children's performance data substantiating its reliability, validity, and user satisfaction. Furthermore, this newly proposed scoring rule, is investigated for its performance across various domains. Findings revealed its strong reliability and validity without discernible individual performance biases. Lastly, in the realm of Elo-based adaptive systems, the importance of item quality is highlighted. Through simulations, methods to determine item discrimination were compared, with the logistic model inclusive of the intercept emerging as the most effective. This method's effectiveness was further affirmed using real-world data from the aforementioned Maths Garden system