Boost radiosurgery as a strategy after failure of initial management of pediatric primitive neuroectodermal tumors Clinical article

The aim in this study was to determine the outcomes of boost stereotactic radiosurgery, specifically Gamma Knife surgery (GKS), for recurrent primitive neuroectodermal tumors (PNETs) in children in whom initial multimodality management had failed.

Collective decoherence of cold atoms coupled to a Bose-Einstein condensate

We examine the time evolution of cold atoms (impurities) interacting with an environment consisting of a degenerate bosonic quantum gas. The impurity atoms differ from the environment atoms, being of a different species. This allows one to superimpose two independent trapping potentials, each being effective only on one atomic kind, while transparent to the other. When the environment is homogeneous and the impurities are confined in a potential consisting of a set of double wells, the system can be described in terms of an effective spin-boson model, where the occupation of the left or right well of each site represents the two (pseudo)-spin states. The irreversible dynamics of such system is here studied exactly, i.e. not in terms of a Markovian master equation. The dynamics of one and two impurities is remarkably different in respect of the standard decoherence of the spin-boson system. In particular, we show: (i) the appearance of coherence oscillations, (ii) the presence of super and subdecoherent states that differ from the standard ones of the spin-boson model, and (iii) the persistence of coherence in the system at long times. We show that this behaviour is due to the fact that the pseudospins have an internal spatial structure. We argue that collective decoherence also prompts information about the correlation length of the environment. In a one-dimensional (1D) configuration, one can change even more strongly the qualitative behaviour of the dephasing just by tuning the interaction of the bath.

Towards a strategy for the conservation of the freshwater pearl mussel Margaritifera margaritifera in County Donegal, Ireland

This study attempts to identify the habitat requirements of the pearl mussel Margaritifea margaritifera in County Donegal, in north west Ireland, an area with little urban, industrial or intensive agricultural development. No mussels occur in rivers where calcium and conductivity levels are high or where the substratum is predominantly bedrock or fine sediment but it was not possible to distinguish clearly between mussel and non-mussel sites on the basis of ordination analysis. However, rivers which still support mussels and rivers with historical records of mussels are loosely grouped. Rivers which formerly supported mussels but lack living M. margaritifera appear to have suitable habitat for mussels; pearl fishing is the most likely reason for the extinction of these mussel populations. Where population densities are high, for example in locations on the rivers Eske, Clady and Owenea, conservation may necessitate the establishment of reserves. The prospect for the successful reintroduction of mussels into former mussel rivers such as the Finn and Eany Water, where suitable habitat exists and water quality is high, is very good.