Why Use Multiple Representations in the Mathematics Classroom? Views of English and German Preservice Teachers

Dealing with multiple representations and their connections plays a key role for learners to build up conceptual knowledge in the mathematics classroom. Hence, professional knowledge and views of mathematics teachers regarding the use of multiple representations certainly merit attention. In particular, investigating such views of preservice teachers affords identifying corresponding needs for teacher education. However, specific empirical research is scarce. Taking into account the possible role of culture, this study consequently focuses on views about using multiple representations held by more than 100 English and more than 200 German preservice teachers. The results indicate that there are culture-dependent aspects of preservice teachers’ views, but also that there are common needs for professional development.

     

Effect of foster care on young children's language learning

This report examines 174 young children's language outcomes in the Bucharest Early Intervention Project, the first randomized trial of foster placement after institutional care. Age of foster placement was highly correlated with language outcomes. Placement by 15 months led to similar expressive and receptive language test scores as typical age peers at 30 and 42 months. Placement from 15 to 24 months also led to dramatic language improvement. In contrast, children placed after 24 months had the same severe language delays as children in institutional care. Language samples at 42 months confirmed that placement after 24 months led to lower expressive skill.     

Knots and links

Knots appear in a variety of contexts in physics, chemistry and biology. This article is an introduction to the science of knots and links for the uninitiated and it outlines why scientists find them fascinating.     

Formation of embryoid bodies using dielectrophoresis

Embryoid body (EB) formation forms an important step in embryonic stem cell differentiation invivo. In murine embryonic stem cell (mESC) cultures EB formation is inhibited by the inclusion of leukaemic inhibitory factor (LIF) in the medium. Assembly of mESCs into aggregates by positive dielectrophoresis (DEP) in high field regions between interdigitated oppositely castellated electrodes was found to initiate EB formation. Embryoid body formation in aggregates formed with DEP occurred at a more rapid rate-in fact faster compared to conventional methods-in medium without LIF. However, EB formation also occurred in medium in which LIF was present when the cells were aggregated with DEP. The optimum characteristic size for the electrodes for EB formation with DEP was found to be 75-100 microns; aggregates smaller than this tended to merge, whilst aggregates larger than this tended to split to form multiple EBs. Experiments with ESCs in which green fluorescent protein (GFP) production was targeted to the mesodermal gene brachyury indicated that differentiation within embryoid bodies of this size may preferentially occur along the mesoderm lineage. As hematopoietic lineages during normal development derive from mesoderm, the finding points to a possible application of DEP formed EBs in the production of blood-based products from ESCs.     

A high resolution laser scanning model of the Roman theater in Pinara,Turkey – comparison to previous measurements and search for the causes of damage

The archaeological site Pinara, southwest Turkey, which includes several remarkable objects of cultural heritage, has been the focus of several previous archaeoseismic studies. One of these examined the setting of the Roman theater in the east of Pinara by a lidar survey. A gross inclination of the stone rows of the auditorium of 0.81° towards N 314°E was interpreted as a consequence of recent coseismic tectonic movements. A new survey of the theater with a terrestrial phase laser scanner is the basis for a model with 15 times higher resolution and 28 times more data points. Parallel to the fieldwork in this study, the process and accuracy of the leveling of the 3D point clouds produced by the scanner was tested in a series of experiments. Based on the orientation of the blocks forming the seats of the theater, we suggest six sections with changing average inclination of the seats and a fault line separating a northern and a southern section. While the previously found overall inclination of the auditorium is confirmed by the new model and the dip direction agrees, the inclination is 0.58° compared to previously determined 0.81°. The almost perfect increase of inclination with the height of the first 10 entire seating rows and the nearly constant inclination from row 11 onward, makes systematic measurement errors during the construction a possible cause. This is an alternative scenario to the interpretation of a coseismic displacement of the conglomerate block on which the theater was built.     

Soviet military maps and archaeological survey in the Samarkand region

In Central Asia, the introduction of mechanised farming and the transformation of the landscape caused by agricultural intensification over the last 50 years have resulted in the massive destruction of archaeological remains. In this paper, we focus on an underestimated and unexploited type of remote sensing for the study of landscape change and anthropic impact on cultural heritage: 1:10,000 Soviet military maps of the 1950s. We present their use in the case study of the Archaeological Map of the Samarkand region. We argue that their precision and the early date at which they were produced make it possible to employ them as a reference tool for systematic survey and archaeological heritage management in Central Asia and throughout the former Soviet Union. We discuss the results of an archaeological survey based on these maps and show how they can be used to evaluate the destruction of archaeological mounds during the last 50 years, by contrasting them with modern satellite imagery.