50 research outputs found

    Late normal tissue response in the rat spinal cord after carbon ion irradiation

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    Background: The present work summarizes the research activities on radiation-induced late effects in the rat spinal cord carried out within the “clinical research group ion beam therapy” funded by the German Research Foundation (DFG, KFO 214). Methods and materials: Dose–response curves for the endpoint radiation-induced myelopathy were determined at 6 different positions (LET 16–99 keV/μm) within a 6 cm spread-out Bragg peak using either 1, 2 or 6 fractions of carbon ions. Based on the tolerance dose TD50 of carbon ions and photons, the relative biological effectiveness (RBE) was determined and compared with predictions of the local effect model (LEM I and IV). Within a longitudinal magnetic resonance imaging (MRI)-based study the temporal development of radiation-induced changes in the spinal cord was characterized. To test the protective potential of the ACE (angiotensin converting enzyme)-inhibitor ramipril™, an additional dose–response experiment was performed. Results: The RBE-values increased with LET and the increase was found to be larger for smaller fractional doses. Benchmarking the RBE-values as predicted by LEM I and LEM IV with the measured data revealed that LEM IV is more accurate in the high-LET, while LEM I is more accurate in the low-LET region. Characterization of the temporal development of radiation-induced changes with MRI demonstrated a shorter latency time for carbon ions, reflected on the histological level by an increased vessel perforation after carbon ion as compared to photon irradiations. For the ACE-inhibitor ramipril™, a mitigative rather than protective effect was found. Conclusions: This comprehensive study established a large and consistent RBE data base for late effects in the rat spinal cord after carbon ion irradiation which will be further extended in ongoing studies. Using MRI, an extensive characterization of the temporal development of radiation-induced alterations was obtained. The reduced latency time for carbon ions is expected to originate from a dynamic interaction of various complex pathological processes. A dominant observation after carbon ion irradiation was an increase in vessel perforation preferentially in the white matter. To enable a targeted pharmacological intervention more details of the molecular pathways, responsible for the development of radiation-induced myelopathy are required

    Society, security, sovereignty and the state in Somalia : from statelessness to statelessness?

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    Is the state in modern circumstances a necessary and inevitable form of social organization, one, which once it emerges in a given society, is a permanent fixture? This is the question that will be critically considered in this book. What is meant by the state in this context is a political entity comprising a variety of institutions, which exercise control over violence within particular territorial boundaries. See: introduction.

    Deaf Education in Brazil: Contexts, Challenges, and Perspectives

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    Changes in the past two decades have improved the position of the deaf in Brazil: Brazilian Sign Language (Libras) is an officially recognized language, deaf children can go to school, and bilingual education is available to deaf students. However, many deaf children do not attend school, and enrollment rates in high school and higher education are low. Moreover, the language policy views of the Brazilian deaf movement and the Brazilian Ministry of Education do not align. The deaf movement pleads for bilingual deaf schools, whereas the Brazilian government follows an inclusion policy. This chapter presents an overview of the position of the deaf in Brazil and their participation in education, considering national deaf policy and its implications for and impact on deaf education. Teaching practices in bilingual education are discussed, and recommendations and challenges for Brazilian deaf education are considered
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