No abstract

The transformation of iron compounds (R-FeOOH, γ-FeOOH, ferrihydrite, limonite, and pyrite) into pyrrhotite (Fe 1-x S) was systematically investigated through the sulfidation tests with elemental sulfur in the absence of feed coal under liquefaction conditions. The order of transformation temperature into pyrrhotite was as follows: ferrihydrite, FeOOH (250 °C) < limonite ore (300 °C) < pyrite ore (350 °C). The crystal growth of pyrrhotite proceeded in the following order: γ-FeOOH < limonite, R-FeOOH, ferrihydrite < pyrite (FeS 2 ). Both transmission electron microscopy observations and corresponding X-ray diffraction data indicated that the ultrafine crystallites of Fe 1-x S could be initially formed into the framework of iron oxyhydroxide particles at lower temperatures, followed by growing up to the large hexagonal crystal at higher temperatures through the disappearance of its framework. The presence of H 2 S is effective not only to maintain the sulfur-rich stoichiometry of Fe 1-x S but also to suppress the crystal growth of pyrrhotite. A good correlation between the oil yield and the crystallite size of pyrrhotite was obtained for the fresh and the used catalysts, indicating the higher oil yield with smaller crystallite size. γ-FeOOH exhibited an excellent catalytic activity for the coal liquefaction due to the transformation into pyrrhotite with smaller crystallite size under the liquefaction conditions. The used catalyst, pyrrhotite in CLB-THFI, demonstrated a sufficient catalytic activity, although the oil yield decreased slightly as compared to that of the fresh catalyst. Catalyst deactivation through the deposition of coal mineral matters or organic residues appears to be considerably small.

A 77-year-old man with severe chronic obstructive pulmonary disease was admitted to our hospital for surgical treatment of a proximal descending thoracic aortic aneurysm (dTAA) and an infrarenal abdominal aortic aneurysm (AAA). The patient had poor respiratory function; however, a simultaneous abdominal aortic replacement and thoracic stent-graft placement were successfully performed without any complications. This case report demonstrates that simultaneous abdominal aortic replacement and thoracic stent-graft placement for multiple aneurysms may be feasible and can safely be performed in selected high-risk patients, despite the many problems associated with the treatment of aortic aneurysms using stent grafts.

It is suggested that the preoperative measurement of evoked spinal potential during temporary balloon occlusion is clinically useful for the assessment of the risk to paraplegia occurring in transluminally placed endoluminal prosthetic grafts.

Whereas the operative results for thoracic aortic aneurysms (TAA) have improved in recent years, the results for distal arch aneurysms (DAA) remain unsatisfactory. We report herein the initial results of open stent grafting (OSG) applied using an improved endotracheal tube for surgical treatment of high-risk DAA. OSG was used to treat DAA in five men aged 69-80 years (mean, 77 years). Four cases involved chronic obstructive pulmonary disease, and the remaining case involved both ischemic heart disease and chronic renal failure. Previous surgical repairs of an abdominal aortic aneurysm had been performed in four patients, and thoracoplasty and reconstruction of the lower extremities had been performed in the remaining patient. Under selective cerebral perfusion, OSG with revascularization of two cerebral branches was performed in two patients, whereas OSG with total arch replacement was performed in three patients. The procedure was successful in all cases. There were no complications related to cerebrospinal disorders, and complete thrombosis of the aneurismal sac was achieved in all cases. The new deployment method using an endotracheal tube offers numerous advantages, including reduced aortic wall injury and accurate placement of the stent graft in the operative field. These initial results suggest that this specific approach makes OSG a useful surgical procedure in the treatment of high-risk DAA.