The high-intensity reflectometer of the Jülich Centre for Neutron Science: MARIA.

MARIA (magnetism reflectometer with high incident angle) is a world class vertical sample reflectometer dedicated to the investigation of thin films in the fields of magnetism, soft matter and biology. The elliptical vertically focusing guide allows one to measure small samples with a typical size of 1 × 1 cm very efficiently. The double-bounce polarizer and the in situ pumped 3He SEOP (spin-exchange optical pumping) neutron spin filter cell for analysing the polarization of the reflected neutron beam can be moved into the beam in seconds. The polarized flux of MARIA amounts to 5 × 107 n (s cm2)-1 at the sample position with a horizontally collimated beam of 3 mrad, a wavelength of λ = 4.5 Šand a wavelength resolution of Δλ/λ = 10%. In the non-polarized mode a flux of 1.2 × 108 n (s cm2)-1 is achieved in this configuration. MARIA is also capable of grazing-incidence small-angle neutron scattering measurements, using a pinhole collimation with two four-segment slits and an absorber that prevents the focusing of the elliptical guide in the vertical direction.

Cognitive and emotional processing at high altitude.

INTRODUCTION: Exposure to altitude reduces oxygen supply to the central nervous system and may cause a variety of neuropsychological impairments. We investigated the relationship between certain cognitive functions and cardiovascular and respiratory variables during acute hypobaric hypoxia. METHODS: There were three groups of seven men who were each exposed to a 2-h altitude profile (AP) involving 30 min at each of the following simulated altitudes (m): AP1, 450-1500-3000; AP2, 450-1500-4500; Control 450-650-650. The neuropsychological tests included word fluency and three word-association tasks tapping processes of cognitive flexibility and emotion regulation. A lateralized tachistoscopic lexical decision task with high and low emotional target words was also administered to assess possible shifts in hemispheric superiorities for positive and negative affect. RESULTS: No significant differences in word fluency, word association, or lateralized lexical decision performances were found, despite a significant oxygen desaturation and a drop in diastolic BP at 4500 m, indicating the beginning of central hypoxia in terms of a functional impairment of the vasomotor center. CONCLUSION: During acute exposure to hypobaric hypoxia, selected cognitive and affective functions mediated by the frontal lobe were preserved. Functional hemispheric asymmetries for emotional processes remained unchanged.