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The aim of the present study was to examine how different types of tracking—
between-school streaming, within-school streaming, and course-by-course
tracking—shape students’ mathematics self-concept. This was done in an
internationally comparative framework using data from the Programme for
International Student Assessment (PISA). After controlling for individual
and track mean achievement, results indicated that generally for students
in course-by-course tracking, high-track students had higher mathematics
self-concepts and low-track students had lower mathematics self-concepts.
For students in between-school and within-school streaming, the reverse pat-
tern was found. These findings suggest a solution to the ongoing debate about
the effects of tracking on students’ academic self-concept and suggest that the
reference groups to which students compare themselves differ according to the
type of tracking.
The strong adhesion of sub-micron sized particles to surfaces is a nuisance, both for removing contaminating colloids from surfaces and for conscious manipulation of particles to create and test novel micro/nano-scale assemblies. The obvious idea of using detergents to ease these processes suffers from a lack of control: the action of any conventional surface-modifying agent is immediate and global. With photosensitive azobenzene containing surfactants we overcome these limitations. Such photo-soaps contain optical switches (azobenzene molecules), which upon illumination with light of appropriate wavelength undergo reversible trans-cis photo-isomerization resulting in a subsequent change of the physico-chemical molecular properties. In this work we show that when a spatial gradient in the composition of trans- and cis- isomers is created near a solid-liquid interface, a substantial hydrodynamic flow can be initiated, the spatial extent of which can be set, e.g., by the shape of a laser spot. We propose the concept of light induced diffusioosmosis driving the flow, which can remove, gather or pattern a particle assembly at a solid-liquid interface. In other words, in addition to providing a soap we implement selectivity: particles are mobilized and moved at the time of illumination, and only across the illuminated area.