This work concerns 2D SPECT imaging with uniform attenuation in the activity region. In this paper, it is shown that exact and stable reconstruction does not require the data to be known over 360• as has been previously assumed. An angular range of 180• is sufficient in parallel-beam geometry. A reconstruction formula which uses only data on a half-turn is provided with implementation details. Simulations are performed to support the mathematical result.

Abstract. This paper presents an innovative method to interpret the content of a video scene using a depth camera. Cameras that provide distance instead of color information are part of a promising young technology but they come with many difficulties: noisy signals, small resolution, and ambiguities, to cite a few.By taking advantage of the robustness to noise of a recent background subtraction algorithm, our method is able to extract useful information from the depth signals. We further enhance the robustness of the algorithm by combining this information with that of an RGB camera. In our experiments, we demonstrate this increased robustness and conclude by showing a practical example of an immersive application taking advantage of our algorithm.

This work presents new mathematical results on the inversion of the exponential x-ray transform. It is shown that a reconstruction formula can be obtained for any dataset whose projection directions consist of a union of half great circles on the unit sphere. A basic example of such a dataset is the semi-equatorial band. The discussion in the paper is mostly focused on this example. The reconstruction formula takes the form of a Neumann (geometric) series and is both exact and stable. The exponential x-ray transform has been mainly studied in SPECT imaging. In this context, our results demonstrate mathematically that fully 3D image reconstruction in SPECT with non-zero attenuation does not always require symmetric datasets (opposing views).

The school environment of the 21st century is shaped by rapidly changing social and societal conditions that teachers need to adapt to, increasing linguistic, cultural and ethnic diversity among other things. The development of attitudes to cope with these constant societal transformations is one of the main challenges of teacher professionalization today. In this chapter, we concentrate on the self-positioning and argumentation patterns of two Luxembourgish primary school teachers. We focus on the question how these teachers construct differences and homogeneity, what kind of categories and norms they rely on (e.g. performance, sociocultural background, and language) and in how far mechanisms of in- and exclusion become visible.With its trilingual tradition and school system (mainly Luxembourgish, French and German), and at the same time a highly diverse society with more than 170 nationalities, Luxembourg represents a particularly interesting case. As the recent PISA studies have repeatedly shown, the Luxembourgish school system (including its traditional trilingualism and strong orientation on language education) produces a high degree of inequality, and represents an important challenge especially for children of migration.With our study, which is based on in-depth interviews and which adopts an analytical approach combining elements of content and discourse analysis, we found a tendency towards a backward oriented idealized orientation of the past and a high degree of insecurity. We also show which ambivalences the teachers are confronted with and their efforts to deal with these ambivalences.We hope to contribute to a deeper understanding of how teachers position themselves vis a vis the existing diversity in schools, and which discourse and argumentation patterns they rely on. We see this study as part of research on teacher professionalization that will be useful for reflexive pre- and in-service teacher training.