Reliability-based optimization of maintenance scheduling of mechanical components under fatigue.

This study presents the optimization of the maintenance scheduling of mechanical components under fatigue loading. The cracks of damaged structures may be detected during non-destructive inspection and subsequently repaired. Fatigue crack initiation and growth show inherent variability, and as well the outcome of inspection activities. The problem is addressed under the framework of reliability based optimization. The initiation and propagation of fatigue cracks are efficiently modeled using cohesive zone elements. The applicability of the method is demonstrated by a numerical example, which involves a plate with two holes subject to alternating stress.

Tratamiento endovascular del aneurisma de aorta torácica descendente / Endovascular treatment of descending thoracic aorta aneurysm

BACKGROUND: The natural history of aneurysms ends in rupture and death. In 1990 the first endovascular exclusion of an aneurysm, using an endoluminal graft implanted through the femoral arteries was performed. More recently, the same procedure has been used for aneurysms of the thoracic aorta. AIM: To report our experience with endovascular treatment of thoracic aorta aneurysms. MATERIAL AND METHODS: Analysis of 14 patients (nine male), aged 30 to 79 years, treated between May 2001 and August 2002. RESULTS: The mean diameter of the aneurysms was 6.9 cm. The etiology was atherosclerotic in nine patients. The Excluder device (Gore) was preferentially used. There was no operative mortality or paraplegia. One patient had a transient leg monoparesis that reverted completely. No patient had type I endoleaks. Two patients had type II endoleaks on discharge, that sealed spontaneously. In a follow up, ranging from 2 to 17 months, one patient died of a bronchopneumonia and no aneurysm rupture has been detected. CONCLUSIONS: The short term results of endoluminal treatment of thoracic aorta aneurysms are excellent. This treatment is less invasive and has less complications than conventional surgery.

Lack of effect of HPA axis hyperactivity on hormonal responses to d-fenfluramine in major depressed patients: implications for pathogenesis of suicidal behaviour.

There is evidence for inhibitory effects of adrenocorticosteroids on serotonergic (5-HT) activity. However, in depression the relationship between altered cortisol levels and brain 5-HT function remains to be clarified. The aim of this study was to investigate whether hypothalamic-pituitary-adrenal (HPA) axis hyperactivity is associated with 5-HT dysfunction in depressed patients, especially in those with suicidal behaviour. Cortisol levels following the dexamethasone suppression test (DST, 1 mg PO) and prolactin, corticotropin and cortisol responses to the d-fenfluramine test (d-FEN, 45 mg PO) - a specific 5-HT releaser/uptake inhibitor - were measured in 71 drug-free DSM-IV major depressed inpatients (40 with a history of suicide attempt, 31 without) and 34 hospitalized healthy control subjects. Depressed patients showed higher post-DST cortisol levels but similar responses to d-FEN compared with control subjects. Hormonal responses to d-FEN were not correlated with cortisol levels (basal or post-DST). Among the depressed patients, DST suppressors and DST nonsuppressors exhibited no significant difference in endocrine responses to d-FEN. However, patients with a history of suicide attempt, when compared with patients without such a history, showed lower hormonal responses to d-FEN but comparable basal and post-DST cortisol levels. Taken together these results suggest that, in depression, HPA axis hyperactivity is not responsible for the reduced 5-HT activity found in patients with a history of suicidal behavior.

Genotoxic evaluation of eugenol using the bone marrow micronucleus assay.

Eugenol, a widely used chemical in clinical dentistry, was evaluated for genotoxicity using the bone marrow micronucleus (Mn) assay in mice. Three doses (100, 400 or 600 mg/kg) were administered intraperitoneally (i.p.). The animals were killed 30 h post-treatment and the frequency of Mn in 1000 polychromatic erythrocytes (PCE) was determined. Corn oil and methyl methanesulfonate (MMS) were used as negative and positive controls, respectively. Only 400 and 600 mg/kg doses showed significant induction of Mn. We also studied the effect of eugenol at different recovery times (24, 30 or 48 h) with a dose of 400 mg/kg. A positive Mn response was seen at all three post-treatment times, but the differences between them were not significant. For treatment and control groups, the cytotoxicity was in the normal range, measured as the ratio of PCE/NCE (normochromatic erythrocytes).