@article{EmmertKneisel2017,
  author    = {Emmert, Adrian and Kneisel, Christof},
  title     = {Internal structure of two alpine rock glaciers investigated by quasi-3-D electrical resistivity imaging},
  series = {The Cryosphere},
  volume    = {11},
  journal   = {The Cryosphere},
  doi       = {10.5194/tc-11-841-2017},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-157569},
  pages     = {841-855},
  year      = {2017},
  abstract  = {Interactions between different formative processes are reflected in the internal structure of rock glaciers. Therefore, the detection of subsurface conditions can help to enhance our understanding of landform development. For an assessment of subsurface conditions, we present an analysis of the spatial variability of active layer thickness, ground ice content and frost table topography for two different rock glaciers in the Eastern Swiss Alps by means of quasi-3-D electrical resistivity imaging (ERI). This approach enables an extensive mapping of subsurface structures and a spatial overlay between site-specific surface and subsurface characteristics. At Nair rock glacier, we discovered a gradual descent of the frost table in a downslope direction and a constant decrease of ice content which follows the observed surface topography. This is attributed to ice formation by refreezing meltwater from an embedded snow bank or from a subsurface ice patch which reshapes the permafrost layer. The heterogeneous ground ice distribution at Uertsch rock glacier indicates that multiple processes on different time domains were involved in the development. Resistivity values which represent frozen conditions vary within a wide range and indicate a successive formation which includes several advances, past glacial overrides and creep processes on the rock glacier surface. In combination with the observed topography, quasi-3-D ERI enables us to delimit areas of extensive and compressive flow in close proximity. Excellent data quality was provided by a good coupling of electrodes to the ground in the pebbly material of the investigated rock glaciers. Results show the value of the quasi-3-D ERI approach but advise the application of complementary geophysical methods for interpreting the results.},
  language  = {en}
}
@article{GreefrathOldenburgSilleretal.2023,
  author    = {Greefrath, Gilbert and Oldenburg, Reinhard and Siller, Hans-Stefan and Ulm, Volker and Weigand, Hans-Georg},
  title     = {Mathematics students' characteristics of basic mental models of the derivative},
  series = {Journal f{\"u}r Mathematik-Didaktik},
  volume    = {44},
  journal   = {Journal f{\"u}r Mathematik-Didaktik},
  number    = {1},
  issn      = {0173-5322},
  doi       = {10.1007/s13138-022-00207-9},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-324317},
  pages     = {143-169},
  year      = {2023},
  abstract  = {The concept of derivative is characterised with reference to four basic mental models. These are described as theoretical constructs based on theoretical considerations. The four basic mental models—local rate of change, tangent slope, local linearity and amplification factor—are not only quantified empirically but are also validated. To this end, a test instrument for measuring students' characteristics of basic mental models is presented and analysed regarding quality criteria. Mathematics students (n = 266) were tested with this instrument. The test results show that the four basic mental models of the derivative can be reconstructed among the students with different characteristics. The tangent slope has the highest agreement values across all tasks. The agreement on explanations based on the basic mental model of rate of change is not as strongly established among students as one would expect due to framework settings in the school system by means of curricula and educational standards. The basic mental model of local linearity plays a rather subordinate role. The amplification factor achieves the lowest agreement values. In addition, cluster analysis was conducted to identify different subgroups of the student population. Moreover, the test results can be attributed to characteristics of the task types as well as to the students' previous experiences from mathematics classes by means of qualitative interpretation. These and other results of students' basic mental models of the derivative are presented and discussed in detail.},
  language  = {en}
}