Maria Blettner

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Motivated by the properties of spreading activation and conceptual distance, the authors propose a metric, called Distance, on the power set of nodes in a semantic net. Distance is the average minimum path length over all painvise combinations of nodes between two subsets of nodes. Distance can be successfully used to assess the conceptual distance between(More)
Simulation studies present an important statistical tool to investigate the performance, properties and adequacy of statistical models in pre-specified situations. One of the most important statistical models in medical research is the proportional hazards model of Cox. In this paper, techniques to generate survival times for simulation studies regarding(More)
The widespread use of cellular telephones has generated concern about possible adverse health effects, particularly brain tumors. In this population-based case-control study carried out in three regions of Germany, all incident cases of glioma and meningioma among patients aged 30-69 years were ascertained during 2000-2003. Controls matched on age, gender,(More)
A case control study was conducted where cases were children younger than 5 years (diseased between 1980 and 2003) registered at the german childhood cancer registry (GCCR). Population-based matched controls (1:3) were selected from the corresponding registrar's office. Residential proximity to the nearest nuclear power plant was determined for each subject(More)
BACKGROUND Vascular leakage and shock are the major causes of death in patients with dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Thirty years ago, complement activation was proposed to be a key underlying event, but the cause of complement activation has remained unknown. METHODS The major nonstructural dengue virus (DV) protein NS1(More)
BACKGROUND The use of review articles and meta-analysis has become an important part of epidemiological research, mainly for reconciling previously conducted studies that have inconsistent results. Numerous methodologic issues particularly with respect to biases and the use of meta-analysis are still controversial. METHODS Four methods summarizing data(More)
INTRODUCTION The causes of leukemia are largely unclear. The question whether leukemia rates are increased near nuclear power plants is controversial. The German Childhood Cancer Registry has published an epidemiological case-control study on childhood cancer and nuclear power plants. METHOD The study was based on the distance of children's residences(More)
The very rapid worldwide increase in mobile phone use in the last decade has generated considerable interest in the possible health effects of exposure to radio frequency (RF) fields. A multinational case–control study, INTERPHONE, was set-up to investigate whether mobile phone use increases the risk of cancer and, more specifically, whether the RF fields(More)
OBJECTIVES To provide direct estimates of risk of cancer after protracted low doses of ionising radiation and to strengthen the scientific basis of radiation protection standards for environmental, occupational, and medical diagnostic exposures. DESIGN Multinational retrospective cohort study of cancer mortality. SETTING Cohorts of workers in the(More)
A 15-Country collaborative cohort study was conducted to provide direct estimates of cancer risk following protracted low doses of ionizing radiation. Analyses included 407,391 nuclear industry workers monitored individually for external radiation and 5.2 million person-years of follow-up. A significant association was seen between radiation dose and(More)