Mutual dependencies : ‘change’ and ‘discourse’

status: publishe

Exploring differential effects of an intervention on historical inquiry tasks: a qualitative analysis of 12th-grade students’ progress

Multiple-documents-based (inquiry) tasks are often used to examine historical thinking, as they require students to apply discipline-specific ways of reasoning and writing. Intervention studies using such tasks have often relied on principles from cognitive apprenticeship to make these discipline-specific heuristics explicit to students. While several studies have found positive results, they offer little insight into how and where exactly students’ progress on historical thinking manifests itself, nor into the differential effects of the intervention. Building on essay data gathered during an intervention study on students’ historical inquiry skills, this study explores differential effects of the intervention according to students’ initial historical inquiry ability. To this end, a purposeful sample of students was selected for whom the intervention was particularly effective. The qualitative analysis of students’ essay tasks (pretest and posttest) revealed remarkable differences between students with high and low pretest scores. Although both groups made progress on all aspects of the essay task, they differed in terms of where and how this progress manifested itself: at posttest, students with a high initial score outperformed others in evaluating sources and rebuttals. This study offers insight into patterns of progress in students’ historical inquiry skills which can inform differentiation in instructional practices

Constraint methods for determining pathways and free energy of activated processes

Activated processes from chemical reactions up to conformational transitions of large biomolecules are hampered by barriers which are overcome only by the input of some free energy of activation. Hence, the characteristic and rate-determining barrier regions are not sufficiently sampled by usual simulation techniques. Constraints on a reaction coordinate r have turned out to be a suitable means to explore difficult pathways without changing potential function, energy or temperature. For a dense sequence of values of r, the corresponding sequence of simulations provides a pathway for the process. As only one coordinate among thousands is fixed during each simulation, the pathway essentially reflects the system's internal dynamics. From mean forces the free energy profile can be calculated to obtain reaction rates and insight in the reaction mechanism. In the last decade, theoretical tools and computing capacity have been developed to a degree where simulations give impressive qualitative insight in the processes at quantitative agreement with experiments. Here, we give an introduction to reaction pathways and coordinates, and develop the theory of free energy as the potential of mean force. We clarify the connection between mean force and constraint force which is the central quantity evaluated, and discuss the mass metric tensor correction. Well-behaved coordinates without tensor correction are considered. We discuss the theoretical background and practical implementation on the example of the reaction coordinate of targeted molecular dynamics simulation. Finally, we compare applications of constraint methods and other techniques developed for the same purpose, and discuss the limits of the approach

Educationalization of Social Problems and the Educationalization of the Modern World

The catchword ‘educationalization,’ which enjoyed some popularity around 1920, has been used increasingly since the 1980s, first in the German and then in the Belgian and English discussions. Although the uses of and intentions behind the term are far from identical, they all express a perceived intersection between distinct social practices, one of which is education. As a rule, this intersection is interpreted as assigning education the task of coping with perceived social problems. Accordingly, the most popular expression of this mode of thought has been labeled, in an abstracting way, the educationalization of social problems. This entry builds on that but suggests a more comprehensive view, less reactive in character, by claiming that since the 18th century, the construction of modernity, progress, and open future depends on an idea of education that promises to be the engine of modernity by means of (new) and broadly disseminated knowledge and technologies and, at the same time, an instance of moral reassurance empowering the individual exposed to these modern conditions and their moral hazards to act morally or virtuously. Educationalization of the modern world, in this more comprehensive way, is a key concept for understanding and deciphering the grand narratives of modernity and the modern self

Detecting a stochastic gravitational wave background with the Laser Interferometer Space Antenna

The random superposition of many weak sources will produce a stochastic background of gravitational waves that may dominate the response of the LISA (Laser Interferometer Space Antenna) gravitational wave observatory. Unless something can be done to distinguish between a stochastic background and detector noise, the two will combine to form an effective noise floor for the detector. Two methods have been proposed to solve this problem. The first is to cross-correlate the output of two independent interferometers. The second is an ingenious scheme for monitoring the instrument noise by operating LISA as a Sagnac interferometer. Here we derive the optimal orbital alignment for cross-correlating a pair of LISA detectors, and provide the first analytic derivation of the Sagnac sensitivity curve.Comment: 9 pages, 11 figures. Significant changes to the noise estimate

Calibration and Characterization of the IceCube Photomultiplier Tube

Over 5,000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-inch diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts.Comment: 40 pages, 12 figure