RESUMO
Ultrafast transient absorption spectroscopy is used to investigate the exciton dynamics of Type II ZnTe-ZnSe core-shell colloidal quantum dots. Surface-trapping is shown to occur within a few picosecond for hot electrons and with a few 10s of picoseconds for electrons cooled to the band-edge, and is the dominant process in the decay of the band-edge bleach for well-stirred samples pumped at moderate powers. The surface-trapped electrons produce a broad photo-induced absorption that spectrally overlaps with the band-edge, distorting and partially cancelling out the bleach feature. At high pump powers and for unstirred samples, these surface-trapped electrons can survive sufficiently long within the pumped volume to accumulate under repeated excitation of the sample, resulting in the formation of an additional exciton decay channel.
RESUMO
We report two cases of ileo-ileal intussusception due to a lymphoma in a 25-year-old and a leiomyoma in a 35-year-old woman. Both were diagnosed by laparotomy. Intussusception is a rare condition in adults and is usually difficult to diagnose. In contrast to childhood, idiopathic intussusception is quite rare in adults. The etiology is usually an intestinal tumor. In adults treatment is always surgical.
