Influence of membrane properties on physically reversible and irreversible fouling in membrane bioreactors.

This study aimed to examine the impact of membrane properties on membrane fouling in membrane bioreactor (MBR). Membrane fouling was divided into two categories: physically reversible and irreversible fouling. Membrane properties related to each type of membrane fouling were investigated separately. Five microfiltration (MF) and one ultrafiltration (UF) membranes with different properties (pore size, contact angle, roughness, zeta potential, and pure water permeability) were examined with a laboratory-scale MBR, fed with synthetic wastewater. Two separate experiments were conducted: the first to examine physically reversible fouling, and the second to examine physically irreversible fouling. The correlation between the degree of each type of fouling and membrane properties was studied. High correlation was observed between the degree of physically reversible fouling and roughness (R(2)=0.96). In contrast, with regard to physically irreversible fouling, strong correlation between roughness and degree of membrane fouling can only be found in the case of MF membranes. Except for the membrane with the highest roughness, the degree of physically irreversible fouling can be well correlated with pure water permeability (lower pure water permeability results in higher degree of physically irreversible fouling) including UF membrane. On the basis of the results obtained in this study, it can be concluded that roughness is an important factor in determination of physically reversible fouling regardless of the types of membrane (i.e. MF or UF membranes) and evolutions of physically irreversible fouling can be mitigated when an MBR is operated with membranes with smooth surface and high pure water permeability.

Xanthogranulomatous cholecystitis mimicking gallbladder cancer: report of a case.

A 61-year-old woman was admitted to our hospital with abnormal findings of abdominal computed tomography. Whereas she had neither fever nor abdominal pain, a cholecystitis was suspected. Ultrasonography showed a mass in the gallbladder with several stones, and an unclear border between the gallbladder and liver. Computed tomography showed a large-mass in the gallbladder with findings that seemed to indicate hepatic invasion and para-aortic lymph node metastasis. On the basis of these findings, we made a diagnosis of gallbladder cancer associated with hepatic invasion and lymph node metastasis. We treated this gallbladder tumor by hepatic arterial infusion chemotherapy via catheter with cisplatin and 5-fluorouracil. Four weeks after administration of the anti-cancer drugs, the tumorous lesion of the gallbladder could not be detected by abdominal imagings, and the gallbladder wall revealed no irregular findings. During laparotomy, the gallbladder showed signs of chronic cholecystitis, and a cholecystectomy was performed. Findings of the resected specimens showed severe inflammation, fibrosis, and bleeding in the gallbladder wall with infiltration by many foamy cells. Histopathological diagnosis was xanthogranulomatous cholecystitis. We report here a case of xanthogranulomatous cholecystitis mimicking gallbladder cancer and review the literature.

[Aortic arch surgery in the elderly].

A consecutive series of 16 patients over 75 years old who underwent aortic arch operations with hypothermic selective cerebral perfusion from 1994 to 1997 was analyzed. These patients (group O) was compared with 18 patients aged from 70 to 74-year-old (group M) and 38 patients under the age of 69 (group Y) who underwent aortic arch operation during the same period. There were 5 males and 11 females with a mean age of 77.8 years (range 75 to 86) in group O. Twelve patients were in aortic dissection and 4 patients were in atherosclerotic aneurysms. There were 5 hospital deaths (31.2%) in group O, 2 (11.1%) in group M and 2 (5.3%) in group Y. There was significant difference in hospital mortality rate between group O and group Y. Cerebral complication occurred in 2 patients (12.5%) and postoperative respiratory failure occurred in 7 (47%) in group O. Aortic arch operations for the elderly patients can be performed with increased but operative mortality in the elderly patients remains high. In this study, we discussed that influence of risk factors on the operative result and operative indication in the elderly patients.

Surgical treatment of aneurysms of the aortic arch using a simplified selective cerebral perfusion technique.

Between April 1989 and October 1993, 35 patients underwent aortic arch reconstruction for aneurysms using cardiopulmonary bypass (CPB) with selective cerebral perfusion (SCP). Of the 35 patients, the initial 19 (Group P) consecutively received simplified SCP (partial brachiocephalic perfusion; PBP), and the next 16 (Group S) were consecutively treated with standard SCP. For cerebral protection, blood was supplied to the right axillary artery in Group P, and to the right axillary and the left common carotid arteries in Group S. The aneurysms was aortic dissection in 24 patients, and was secondary to arteriosclerosis in the remaining 11. Partial replacement of the aortic arch together with the ascending aorta was the most commonly performed procedure in both groups. The cardiopulmonary bypass time and the cardiac arrest time were not significantly different between the two groups. The overall cerebral perfusion time was significantly longer in Group S (100 min) than in Group P (65 min); however, when 2 patients with an accidental prolongation of the cerebral perfusion time in Group S were excluded, there was no significant difference in the cerebral perfusion time between the two groups. Early death occurred in 3 patients (15.8%) in Group P, and 2 patients (12.5%) in Group S, however, there were no deaths related to the selective cerebral perfusion technique, and there were no late deaths in either group. Cerebral complications were seen in 1 patient in each group (6.3% vs. 6.7%, not significant). These results suggest that the simplified SCP (PBP) under hypothermic CPB provides as satisfactory cerebral protection as standard SCP, so long as the patency of the circle of Willis is confirmed.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical treatment for acute aortic dissection and coexistent degenerative aortic aneurysm. Report of three cases.

Acute aortic dissection occurring in an aorta previously afflicted with degenerative, atherosclerotic is unusual. We report three cases with acute aortic dissection (DeBakey type III-b) occurring in an aorta which had a preexistent degenerative aortic aneurysm. Two of the three patients had acute aortic dissection originating from the distal end of the degenerative aneurysm, and the remaining one had the acute aortic dissection and degenerative aneurysm at different segments of the aorta. Since the risk of rupture is likely to be much higher in the patients with coexistence of acute aortic dissection and degenerative aortic aneurysm, compared with patients with DeBakey type III acute aortic dissection alone, we believe that a prompt and aggressive surgical approach is essential to prevent rupture, and that digital subtraction angiography (DSA) is more helpful in making a correct diagnosis and in helping to decide surgical procedures and supportive methods than other noninvasive diagnostic procedures.