Assessing pre-service history teachers’ pedagogical content knowledge with a video survey using open-ended writing assignments and standardized rating items

This paper explores pre-service history teachers’ ability to recognize and reflect on typical situations occurring in the history classroom and to link these to students’ historical learning. Therefore, we draw on the concept of professional vision (Goodwin, 1994), which assumes that teachers need a professional knowledge base to monitor and to reason about teaching and student learning. Based on theoretical notions of teachers’ pedagogical content knowledge (PCK), we investigated history teachers’ professional vision by means of a video survey with integrated video clips, open-ended writing assignments and standardized item ratings. We collected data from 303 and 220 pre-service teachers at the beginning and at the end, respectively, of their subject-specific teacher training. The collected data open up the possibility of ‘simultaneous triangulation’ (Morse, 1991), which was used for test validation. First, we tested the reliability of the closed-ended test instrument using item response theory, in order to develop a feasible test model. Second, we investigated the validity of the test instrument by comparing test results with the findings of the open-ended writing task. In general, student teachers reached rather low test scores. They experienced difficulties in assessing classroom events in terms of their potential to support historical competencies and to evaluate the consequences for students’ learning. Findings from the open writing assignment show that student teachers commented largely on generic teaching strategies while hardly noticing student learning. In sum, the chosen methodological approaches seem to contribute to a more distinct picture of preservice teachers’ abilities to reason about history teaching and learning

Arrays of High Tilt-Angle Micromirrors for Multiobject Spectroscopy

Micromirror arrays are promising components for generating reflective slit masks in future multiobject spectrographs. The micromirrors, 100 μm times200 μm in size, are etched in bulk single crystal silicon, whereas a hidden suspension is realized by surface micromachining. The micromirrors are actuated electrostatically by electrodes located on a second chip. The use of silicon on insulator (SOI) wafers for both mirror and electrode chip ensures thermal compatibility for cryogenic operation. A system of multiple landing beams has been developed, which latches the mirror at a well-defined tilt angle when actuated. Arrays of 5times5 micromirrors have been realized. The tilt angle obtained is 20deg at a pull-in voltage of 90 V. Measurements with an optical profiler showed that the tilt angle of the actuated and locked mirror is stable with a precision of 1 arcmin over a range of 15 V. This locking system makes the tilt angle independent from process variations across the wafer and, thus, provides uniform tilt angle over the whole array. The surface quality of the mirrors in actuated state is better than 10-nm peak to valley and the local roughness is about 1-nm root mean square

Hat die Geometrie am lumbosacralen Übergang Einfluss auf die Ausbildung einer isolierten Osteochondrose L5/S1?

Men and women with isolated osteochondrosis L5/S1 (excluding transitional anomalies) were compared against a corresponding group of healthy volunteers to see whether there is any geometric or statistical evidence that might constitute predisposing factors for isolated osteochondrosis L5/S1. Arithmetic means, variances, standard deviations, and correlation coefficients were calculated for all the characteristics determined for the two groups. Multiple linear discriminant analysis was used to try to reproduce any classifications our groupings of the characteristic bearers on the basis of their characteristics. It was found that the position of the sacrum in the pelvis and the extent of lumbar lordosis play a major role. To detect a predisposition for isolated osteochondrosis L5/S1, it is thus necessary to evaluate: the position of the sacrum with regard to the pelvis and the degree of lumbar lordosis-excluding that of the fifth lumbar vertebra-in the angle system. This evaluation can be performed by measuring the dorsal inclination of the sacrum (the delta angle) and the Albrecht inclination