Mid-infrared images of beta Pictoris and the possible role of planetesimal collisions in the central disk

When viewed in optical starlight scattered by dust, the nearly edge-on debris disk surrounding the A5V star beta Pictoris (distance 19.3 pc; ref. 1) extends farther than 1,450 au from the star. Its large-scale complexity has been well characterized, but the detailed structure of the disk's central approximately 200-au region has remained elusive. This region is of special interest, because planets may have formed there during the star's 10-20-million-year lifetime, perhaps resulting in both the observed tilt of 4.6 degrees relative to the large-scale main disk and the partial clearing of the innermost dust. A peculiarity of the central disk (also possibly related to the presence of planets) is the asymmetry in the brightness of the 'wings', in which the southwestern wing is brighter and more extended at 12 microm than the northeastern wing. Here we present thermal infrared images of the central disk that imply that the brightness asymmetry results from the presence of a bright clump composed of particles that may differ in size from dust elsewhere in the disk. We suggest that this clump results from the collisional grinding of resonantly trapped planetesimals or the cataclysmic break-up of a planetesimal.     

Uptake of a metabolically inert amino acid by brain tissue during high pressure oxygen exposure

Résumé L'étude de l'absorption de l'acide -aminoisobutyric-C¹⁴, par les tissues du cerveau des rats exposés à des pressions variées d'oxygène, a suggéré que l'hyperpression d'oxygène n'influence pas la perméabilité de la barrière hémoencéphalique.     

2-amino-1,4-naphthoquinone-N4,2-naphtylimine. A photo-oxidation product of 2-aminonaphthalene

Zusammenfassung Es wurde gezeigt, dass das Chinonimin 2-Amino-1,4-naphtochinon-N⁴-2-naphtylamin die Farbe von gealtertem Ö1 in der 2-Aminonaphtalinlösung verursacht. Diese farbige Verbindung entsteht durch die Photooxydation des Amins und scheint eine wichtige Rolle für die erhöhte krebserzeugende Wirksamkeit des alten Öls zu spielen.