Extrahepatic portal vein obstruction (EHPVO) is an important cause of noncirrhotic portal hypertension, especially in Third World countries. The etiology and clinical presentation are different in children and adults. The portal vein is transformed into a cavernoma, resulting in portal hypertension and oesophagogastic varices. In addition, extensive collateral circulation develops, involving paracholecystic, paracholedochal and pancreaticoduodenal veins resulting in formation of ectopic varices, and portal biliopathy. Besides variceal bleeding, which is the commonest presentation, patients may have symptomatic portal biliopathy, hypersplenism, and growth retardation. Although the liver may appear normal, functional compromise develops in the long term. Variceal bleeding in EHPVO can be successfully managed by endoscopic obliteration of varices, which has low morbidity but requires repeated visits, or by portosystemic shunt surgery, which provides good control of bleeding, possibly helps growth retardation, hypersplenism, and protects against future development of portal biliopathy but is associated with surgical mortality and is sometimes not feasible due to nonavailability of a satisfactory vessel.

Aberration-corrected transmission electron microscopy and high-angle annular dark field imaging was used to investigate the surface structures and internal defects of CeO2 nanoparticles (octahedra, rods, and cubes). Further, their catalytic reactivity in the water-gas shift (WGS) reaction and the exposed surface sites by using FTIR spectroscopy were tested. Rods and octahedra expose stable (111) surfaces whereas cubes have primarily (100) facets. Rods also had internal voids and surface steps. The exposed planes are consistent with observed reactivity patterns, and the normalized WGS reactivity of octahedra and rods were similar, but the cubes were more reactive. In situ FTIR spectroscopy showed that rods and octahedra exhibit similar spectra for -OH groups and that carbonates and formates formed upon exposure to CO whereas for cubes clear differences were observed. These results provide definitive information on the nature of the exposed surfaces in these CeO2 nanostructures and their influence on the WGS reactivity.

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Ceria nanorods were investigated using in situ Raman and FTIR spectroscopies for CO adsorption and subsequent reaction with water at 200 and 350 °C. The involvement of defects in ceria nanorods during CO adsorption and reaction with H 2 O is dependent on the temperature. At 200 °C, most of the carbonate and formate species formed in CO do not involve the formation of defects, while at 350 °C all of the carbonates and formates formed can be correlated to the formation of defects (15% by formates and 85% by mono/bidentate carbonates). Finally, at 350 °C very stable polydentate carbonates are formed that do not induce defects and cannot be regenerated with water.

Ceria nanoshapes (octahedra, wires, and cubes) were investigated for CO adsorption and subsequent reaction with water. Surprisingly, the reactivity of specific OH groups was explicitly determined by the ceria nanoshape. The nanoshapes showed different levels of carbonates and formates after exposure to CO, the amount of carbonates increasing from octahedral≪wires<cubes. Subsequent reaction with water at 200 °C was also found to be shape dependent, resulting in different amounts of recovered OH groups and removed carbonates and formates on the different ceria nanoshapes.