Bose-Einstein condensation in random directed networks

We consider the phenomenon of Bose-Einstein condensation in a random growing directed net- work. The network grows by the addition of vertices and edges. At each time step the network gains a vertex with probabilty p and an edge with probability 1 − p. The new vertex has a fitness (a, b) with probability f(a, b). A vertex with fitness (a, b), in-degree i and out-degree j gains a new incoming edge with rate a(i + 1) and an outgoing edge with rate b(j + 1). The Bose-Einstein condensation occurs as a function of fitness distribution f(a, b)

Tsallis entropy approach to radiotherapy treatments

The biological effect of one single radiation dose on a living tissue has been described by several radiobiological models. However, the fractionated radiotherapy requires to account for a new magnitude: time. In this paper we explore the biological consequences posed by the mathematical prolongation of a model to fractionated treatment. Nonextensive composition rules are introduced to obtain the survival fraction and equivalent physical dose in terms of a time dependent factor describing the tissue trend towards recovering its radioresistance (a kind of repair coefficient). Interesting (known and new) behaviors are described regarding the effectiveness of the treatment which is shown to be fundamentally bound to this factor. The continuous limit, applicable to brachytherapy, is also analyzed in the framework of nonextensive calculus. Also here a coefficient arises that rules the time behavior. All the results are discussed in terms of the clinical evidence and their major implications are highlighted.Comment: 6 figures, accepted for publication to Physica