A taxonomy for wavelet neural networks applied to nonlinear modelling

This article presents a novel classification of wavelet neural networks based on the orthogonality/non-orthogonality of neurons and the type of nonlinearity employed. On the basis of this classification different network types are studied and their characteristics illustrated by means of simple one-dimensional nonlinear examples. For multidimensional problems, which are affected by the curse of dimensionality, the idea of spherical wavelet functions is considered. The behaviour of these networks is also studied for modelling of a low-dimension map.

Bystander Signalling: Exploring Clinical Relevance Through New Approaches and New Models

Classical radiation biology research has centred on nuclear DNA as the main target of radiation-induced damage. Over the past two decades, this has been challenged by a significant amount of scientific evidence clearly showing radiation-induced cell signalling effects to have important roles in mediating overall radiobiological response. These effects, generally termed radiation-induced bystander effects (RIBEs) have challenged the traditional DNA targeted theory in radiation biology and highlighted an important role for cells not directly traversed by radiation. The multiplicity of experimental systems and exposure conditions in which RIBEs have been observed has hindered precise definitions of these effects. However, RIBEs have recently been classified for different relevant human radiation exposure scenarios in an attempt to clarify their role in vivo. Despite significant research efforts in this area, there is little direct evidence for their role in clinically relevant exposure scenarios. In this review, we explore the clinical relevance of RIBEs from classical experimental approaches through to novel models that have been used to further determine their potential implications in the clinic. 

Time and Cell Type Dependency of Survival Responses in Co-cultured Tumor and Fibroblast Cells after Exposure to Modulated Radiation Fields

Advanced radiotherapy techniques such as intensity-modulated radiation therapy (IMRT) achieve high levels of conformity to the target volume through the sequential delivery of highly spatially and temporally modulated radiation fields, which have been shown to impact radiobiological response. This study aimed to characterize the time and cell type dependency of survival responses to modulated fields using single cell type (SCT) and mixed cell type (MCT) co-culture models of transformed fibroblast (AG0-1522b) cells, and prostate (DU-145) and lung (H460) cancer cells. In SCT cultures, in-field responses showed no significant time dependency while out-of-field responses occurred early, and plateaued 6 h after irradiation in both DU-145 and H460 cells. Under modulated beam configurations MCT co-cultures showed cell-specific, differential out-of-field responses depending on the irradiated in-field and responding out-of-field cell type. The observed differential out-of-field responses may be due to the genetic background of the cells, in particular p53 status, which has been shown to mediate radiation-induced bystander effects (RIBEs). These data provide further insight into the radiobiological parameters that influence out-of-field responses, which have potential implications for advanced radiotherapy modalities and may provide opportunities for biophysical optimization in radiotherapy treatment planning.