Making Graphene Nanoribbons Photoluminescent.

We demonstrate the alignment-preserving transfer of parallel graphene nanoribbons (GNRs) onto insulating substrates. The photophysics of such samples is characterized by polarized Raman and photoluminescence (PL) spectroscopies. The Raman scattered light and the PL are polarized along the GNR axis. The Raman cross section as a function of excitation energy has distinct excitonic peaks associated with transitions between the one-dimensional parabolic subbands. We find that the PL of GNRs is intrinsically low but can be strongly enhanced by blue laser irradiation in ambient conditions or hydrogenation in ultrahigh vacuum. These functionalization routes cause the formation of sp3 defects in GNRs. We demonstrate the laser writing of luminescent patterns in GNR films for maskless lithography by the controlled generation of defects. Our findings set the stage for further exploration of the optical properties of GNRs on insulating substrates and in device geometries.

[Long-term results following hepatico-jejunostomy with antireflux valve construction in congenital bile duct dilatation caused by abnormal junction of the choledochus]. / Langzeitresultate nach Hepatiko-Jejunostomie mit antirefluxiver Klappenbildung bei kongenitaler Gallengangsdilatation infolge Choledochusfehlmündung.

Cystic-cylindrical dilatation of the intrahepatic and extrahepatic bile ducts occurs rarely in childhood. Aetiologically, congenital pancreaticobiliary junction anomalies play a decisive part. Accurate preoperative diagnosis is by no means an easy matter. The best possible diagnostic approach to clarify the pathologico-anatomic conditions consists in sonography coupled with on-target partial intraoperative cholangiography presenting the preduodenal section of choledochus and pancreatic duct. Between 1979 and 1987 surgery was performed at the Paediatric Surgical Department of the Municipal Paediatric Hospital of Cologne on 18 patients suffering from intrahepatic and extrahepatic cysticocylindrical dilatation of the bile ducts due to confirmed ectopic pancreaticobiliary junction anomaly. This study does not include all other types of choledochus cysts or biliary duct dilatations without proven pancreaticobiliary junction anomaly. The treatment of choice is the resection of the dilated extrahepatic biliary ducts followed by hepatico-jejunostomy using the Roux-en-Y technique. To avoid cholangitis due to reflux of intestinal contents via the shunted jejunum loop, we are constructing a two-stage anti-refluxive muscular mucosa valve in the shunted loop; this practice has been followed by us since 1983. Permanent postoperative freedom from cholangitis in 10 children after construction of the valve prompts us to recommend this procedure also in other types of bile duct surgery, especially in the treatment of atresias.