A simple and effective method to introduce precise amounts of doping in nanomaterials produced from the bottom-up assembly of colloidal nanoparticles (NPs) is described. The procedure takes advantage of a ligand displacement step to incorporate controlled concentrations of halide ions while removing carboxylic acids from the NP surface. Upon consolidation of the NPs into dense pellets, halide ions diffuse within the crystal structure, doping the anion sublattice and achieving n-type electrical doping. Through the characterization of the thermoelectric properties of nanocrystalline PbS, we demonstrate this strategy to be effective to control charge transport properties on thermoelectric nanomaterials assembled from NP building blocks. This approach is subsequently extended to PbTe(x)Se(1-x)@PbS core-shell NPs, where a significant enhancement of the thermoelectric figure of merit is achieved.

A subclavian central venous catheter wandered spontaneously between the superior caval and the internal jugular veins. The case supports the routine of regular X-ray checks for catheter position.

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A 65-year-old woman presented in July 198 1 with anorexia and abdominal discomfort. Two months later she experienced retching and lower abdominal pain shortly after eating so that she had to resort to a liquid diet; she lost about 7 kg.Her pulse was regular and the heart and chest sounds were normal; the blood pressure was 160/100. There was a 8 x 6 cm pulsating mass in the epigastrium with a loud bruit, transmitted down the iliac arteries.An arteriogram showed a dissecting aneurysm of the aorta arising in the descending thoracic aorta and extending to the abdominal aorta. There was no bloodflow into the thrombosed sac of dissection. The coeliac axis and superior mesenteric artery were occluded, the main blood supply to the gut coming from the inferior mesenteric artery. The liver and stomach were very poorly supplied from small branches of the aorta.A xylose absorption test was grossly abnormal indicating jejunal malabsorption. Because of the extent of the dissection it was decided that resection of the aorta with reimplantation of renal and mesenterial arteries would be unduly hazardous.The first attempt to relieve visceral ischaemia was performed in another country with reimplantation of the superior mesenteric artery to a point below the pancreas. The patient's condition was unchanged and a new arteriogram in February 1982 showed some flow but a stenosis at the origin of the reimplanted artery. A second operation in our hospital revealed a thrill in the reimplanted mesenteric artery, its origin being embedded in adhesions and fibrotic tissue. After mobilization the thrill vanished and a flow of 220 ml/min was measured in the artery.The patient's condition still did not improve. The postoperative course was complicated by pulmonary embolism, and increasing abdominal angina so that she had to be nourished parenterally. An arteriogram showed a functioning superior mesenteric artery but there was little or no flow to the liver and stomach.It was, therefore, decided to operate for the third time. After a few weeks of parenteral hyperalimentation the patient was operated on again. A 5 mm Gore-tex graft was placed retroperitoneally from the right external iliac artery to the hepatic artery. Before anastomosis the pressure in the hepatic artery was 69/47 mmHg (pressure in arm 160195). After the anastomosis the pressure in the hepatic artery rose to 100165 mmHg (pressure in arm 125/85). A substantial improvement of the bloodflow to the gallbladder and stomach was noticed.After this the patient's condition improved dramatically.The symptoms of indigestion and abdominal pain disappeared immediately. Aortography performed a month after operation showed good function in the graft with good filling of arteries to the liver and stomach ( Figure 1). Five months after operation the patient was in excellent condition, had gained 11 kg and was totally free of her previous symptoms. DiscussionBowel ischaemia due to occlusion of the mesenteric arteries is rare'. When the occlusion is due to an aortic aneurysm treatment usually i...