Variance Reduction in Analytical Chemistry : New Numerical Methods in Chemometrics and Molecular Simulation

This thesis is based on five papers addressing variance reduction in different ways. The papers have in common that they all present new numerical methods. Paper I investigates quantitative structure-retention relationships from an image processing perspective, using an artificial neural network to preprocess three-dimensional structural descriptions of the studied steroid molecules. Paper II presents a new method for computing free energies. Free energy is the quantity that determines chemical equilibria and partition coefficients. The proposed method may be used for estimating, e.g., chromatographic retention without performing experiments. Two papers (III and IV) deal with correcting deviations from bilinearity by so-called peak alignment. Bilinearity is a theoretical assumption about the distribution of instrumental data that is often violated by measured data. Deviations from bilinearity lead to increased variance, both in the data and in inferences from the data, unless invariance to the deviations is built into the model, e.g., by the use of the method proposed in paper III and extended in paper IV. Paper V addresses a generic problem in classification; namely, how to measure the goodness of different data representations, so that the best classifier may be constructed. Variance reduction is one of the pillars on which analytical chemistry rests. This thesis considers two aspects on variance reduction: before and after experiments are performed. Before experimenting, theoretical predictions of experimental outcomes may be used to direct which experiments to perform, and how to perform them (papers I and II). After experiments are performed, the variance of inferences from the measured data are affected by the method of data analysis (papers III-V).

Pedagogiken i tiden : Om framväxten av nya undervisningsformer under tidigt 2000-tal – exemplet Kunskapsskolan

The study concerns the new educational activities that emerge within the deregulated school system at the beginning of the 21st century. Which ideas guide the work? How is the activity formed? What does one hope to achieve? The aim of the thesis is to explore these educational practices in one of the larges independent schools in Sweden – Kunskapsskolan. The study was based upon a sociocultural perspective on learning and on twenty situated interviews with seven principals. Tools central for the activity in Kunskapsskolan were used as basis for the interviews. A qualitative analysis has been used; one of the methods for analysis applied is phenomenography. The study shows how the school, with the help of centrally developed tools, organised the teaching and the environments for learning that were implemented in all schools of the company. Individually organised teaching is the foundation for all teaching, where the students are expected to be self-regulated and self-correcting and use the tools provided for their learning. With regards to the students’ learning, the teachers’ role is mainly related to individual tutorial conversations. Thereby the tools intended to create freedom and control for the students, also create problems and obstacles. Students who do not learn to use the tools have difficulties in managing their studies. The new tools also affect the teachers’ work. In comparison with other schools, the teachers are expected to submit to the educational model and a centrally controlled planning. The teaching is centrally planned in subject specific stages or subject integrated courses. Teachers can influence the central planning by working collaboratively in teacher teams but not individually. The main commission of the teachers is to follow the educational model decided by the company. In comparison with the traditional school, both teachers and students are given new roles. When learning is individually organised for the students, the teachers are expected to develop their knowledge collectively. According to the results, both students and teachers have different approaches to the system – they can submit to the system or approach it in a more independent and reflective way.