Our data show that lucid dreaming constitutes a hybrid state of consciousness with definable and measurable differences from waking and from REM sleep, particularly in frontal areas.

The three-body breakup 6 He→ 4 Heϩnϩn is studied experimentally, using a secondary 6 He ion beam of 240 MeV/nucleon incident on carbon and lead targets. Integrated cross sections for one-and two-neutron knockout and differential cross sections d/dE* and d/d for inelastic nuclear or electromagnetic excitations into the 6 He continuum are presented. The E1-strength distribution is deduced from electromagnetic cross sections and is found to exhaust (10Ϯ2)% of the energy-weighted Thomas-Reiche-Kuhn sum rule or (40Ϯ8)% of the cluster sum rule for excitation energies below 5 MeV. Both the energy-weighted and non-energy-weighted dipole cluster sum rules are almost exhausted integrating the strength up to 10 MeV, a fact from which the root-mean-square distance between the ␣ core and the two valence neutrons of r ␣Ϫ2n ϭ(3.36Ϯ0.39) fm is derived. The known I ϭ2 ϩ ͑1.80 MeV͒ resonance in 6 He is observed in nuclear inelastic scattering; model-dependent values of the quadrupole deformation parameter ␦ 2 ϭ(1.7Ϯ0.3) fm or B(E2,0 ϩ →2 ϩ )ϭ(3.2Ϯ0.6)e 2 fm 4 are derived. No clear signature could be obtained for predicted higherlying 2 ϩ resonances, but low-lying continuum strength of multipolarity other than dipole, likely of monopole and quadrupole multipolarity, is indicated by the data. Two-body correlations in the decaying 4 Heϩnϩn system are investigated. The astrophysical relevance of the data with regard to the two-neutron capture process 4 He(2n,␥) 6 He is briefly discussed.

Recent findings link fronto-temporal gamma electroencephalographic (EEG) activity to conscious awareness in dreams, but a causal relationship has not yet been established. We found that current stimulation in the lower gamma band during REM sleep influences ongoing brain activity and induces self-reflective awareness in dreams. Other stimulation frequencies were not effective, suggesting that higher order consciousness is indeed related to synchronous oscillations around 25 and 40 Hz.

HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion induced collisions. Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and dense hadronic matter. The detector system is characterized by an 85 % azimuthal coverage over a polar angle interval from 18• to 85• , a single electron efficiency of 50 % and a vector meson mass resolution of 2.5 %. Identification of pions, kaons and protons is achieved combining time-of-flight and energy loss measurements over a large momentum range. This paper describes the main features and the performance of the detector system.

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