Modelling of microstructural evolution in multi-layered overlay coatings.

Functionally graded, multi-layered coatings are designed to provide corrosion protection over a range of operating conditions typically found in industrial gas turbines. A model incorporating diffusion, equilibrium thermodynamics and oxidation has been developed to simulate the microstructural evolution within a multi-layered coating system. The phase and concentration profiles predicted by the model have been compared with an experimental multi-layered system containing an Al-rich outer layer, a Cr-enriched middle layer and an MCrAlY-type inner layer deposited on a superalloy substrate. The concentration distribution and many microstructural features observed experimentally can be predicted by the model. The model is expected to be useful for assessing the microstructural evolution of multilayer coated systems which can be potentially used on industrial gas turbine aerofoils.

Impaired secretion of rat mannose-binding protein resulting from mutations in the collagen-like domain.

Serum mannose-binding protein (MBP) or mannose-binding lectin initiates the lectin branch of the innate immune response by binding to the surface of potentially pathogenic microorganisms and initiating complement fixation through an N-terminal collagen-like domain. Mutations in this region of human MBP are associated with immunodeficiency resulting from a reduction in the ability of the mutant MBPs to fix complement as well as from reduced serum concentrations. Inefficient secretion of the mutant proteins, which is one possible cause of the reduced serum levels, has been investigated using a mammalian expression system in which each of the naturally occurring human mutations has been recreated in rat serum MBP. The mutations Gly25-->Asp and Gly28-->Glu disrupt the disulfide-bonding arrangement of the protein and cause at least a 5-fold increase in the half-time of secretion of MBP compared with wild-type rat serum MBP. A similar phenotype, including a 3-fold increase in the half-time of secretion, disruption of the disulfide bonding arrangement, and inefficient complement fixation, is observed when nearby glucosylgalactosyl hydroxylysine residues at positions 27 and 30 are replaced with arginine residues. The results suggest that defective secretion resulting from structural changes in the collagen-like domain is likely to be a contributory factor for MBP immunodeficiency.

Patterns of distribution of endoscopic and histological changes in the ileal reservoir after restorative proctocolectomy for ulcerative colitis. A long-term follow-up study.

OBJECTIVE: This study was undertaken to assess the long-term macroscopic appearance of the ileal reservoir after restorative proctocolectomy for ulcerative colitis, to determine whether there is any correlation between macroscopic and histological changes and whether the distribution of these is homogeneous, focal or patchy. BACKGROUND: No study has examined the macroscopic appearance of the ileal reservoir over a long period and it is still unknown to what degree histological changes are diffuse or patchy. Moreover, the relationship between macroscopic and histological changes is poorly understood. METHOD: Fifty-nine patients were examined by one clinician (PSC) 5.3-14.5 years (median 8.2 years) postoperatively. A rigid sigmoidoscopy of the reservoir was performed. Four zones in the posterior midline at 5-cm intervals from the ileoanal anastomosis were inspected. At each level a macroscopic score of severity of inflammation was given and a biopsy taken. The degree of acute and chronic inflammation was assessed using a histopathological scoring system. RESULTS: All reservoirs showed macroscopic abnormalities, which were more marked distally in 14 (24%). There was no case in which severity of inflammation was greater in proximal than in distal zones. Endoscopy overall correlated with both acute and chronic histological changes. On histological examination the patients could be divided into three groups as follows: (1) all four biopsies were normal (group 1, n = 8, 14%), (2) the score of acute and chronic inflammation decreased from distal to proximal zones (group 2, n = 25, 42%) and (3) all four biopsies were abnormal with the same score (group 3, n = 26, 44%). The latter group significantly correlated with a present or past history of pouchitis. CONCLUSION: The study has shown that when there is a gradation of inflammation within the ileal reservoir this is more severe in distal than in proximal zones.

Endosonography of the anal sphincters: normal anatomy and comparison with manometry.

To determine the normal and anatomy in vivo, and endosonography and manometry were performed in 93 nulliparous females, and endosonography alone in 21 healthy males. Endosonography did not reveal any plane of cleavage between the components of the external and sphincter, though a changing pattern at different levels conforming to a trilaminar arrangement was apparent. The deep (proximal) aspect of the external sphincter was annular in 72% of females and 76% of males. The superficial external sphincter was elliptical in 76% and 86%, the subcutaneous part conical in 56% and 57%, respectively. The external sphincter was shorter anteriorly in females. Aberrant insertions from the external sphincter anteriorly were identified in 14%. The longitudinal muscle layer could be distinguished sonographically in all males, as the external sphincter was relatively hypoechoic, but in 60% of the females the longitudinal muscle and external sphincter were of similar echogenicity and sonographically indistinguishable. The subepithelial tissues and internal sphincter were identified in each subject. The external sphincter was thicker bilaterally (P = 0.001) in males (8.6 +/- 1 mm, mean +/- S.D.) compared to females (7.7 +/- 1.1), which related to the higher weight of the males (73 +/- 7 vs 65 +/- 11 kg, P < 0.0001). The mean maximum lateral thickness of the internal sphincter (1.8 +/- 0.5 vs 1.9 +/- 0.6) and the longitudinal muscle (2.5 +/- 0.6 vs 2.9) in females and males were not significantly different. There was no relationship between the manometric resting or squeeze pressures in the anal canal, and the internal or external sphincter thickness.

[Restorative proctocolectomy: which kind of reservoir?]. / La proctocolectomie restauratrice: quel type de réservoir?

Functional results after ileoanal anastomosis are better when a reservoir is used than when a straight reconstruction is carried out. Designs include the three loop (S) with and without a distal ileal segment, two loop (J), four loop (W) and lateral isoperistaltic (H). The evidence available indicates that frequency of defecation is inversely related to the size of the reservoir. It has also shown that a distal ileal segment may relate to failure of spontaneous evacuation. Non randomised studies suggest that larger reservoirs (eg S or W) give better results than a J reservoir. There is no apparent difference in the mobility of the reservoir to descend to the anal level whatever construction is used. Te particular design probably does not matter greatly provided: a) the reservoir is of sufficient capacity (three or four loop, or long double loop), and b) evacuation is facilitated by joining the pouch directly to the anus, thereby avoiding a distal ileal segment.

Chronic obstructive pulmonary disease anatomical cardiac studies.

An abattoir survey on horses diagnosed as suffering from chronic obstructive pulmonary disease (COPD) on clinical grounds showed that the right ventricular wall thickness was not significantly different from that of normal horses. However, the weight ratio between the left and right ventricles was found to be significantly (P less than 0.001) different in COPD affected, compared with control, horses in a study of 17 physiologically and pathologically confirmed COPD cases, using ventricular weight measurements. No clinical evidence of right heart failure nor post mortem evidence of right heart dilatation was observed in any COPD affected animals. It is suggested that the low incidence and degree of cor pulmonale in equine COPD may be related to the reversibility of the pulmonary hypertension associated with this disease.