Premature bearing failures can be attributed to several factors such as improper selection of bearing, rise in temperature, corrosive media, dirt, abusive handling, improper installation, and servicing practices. In the present study, damage analysis made on the prematurely failed differential pinion tapered roller bearing is discussed. A detailed metallurgical analysis is carried out on the failed bearing and the probable root cause was traced to higher preload on the bearing resulting in temperature rise and degradation of lubrication. Excessive preload caused rubbing of rollers against the cone rib leading to temperature rise. This in turn degraded the lubricant and caused eventual seizure. The steep rise in temperature was confirmed by the presence of untempered martensitic structure in the raceway load zone of the cone.

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Parole chiave: RM, epidermoide, tumori intracranici RIASSUNTO -Gli epidermoidi intracranici hanno caratteristiche RM che sono utili ad una precoce identificazione e riconoscimento, favorendo le possibilita terapeutiche chirurgiche.In due anni abbiamo raccolto due casi di epidermoidi intradurali della fossa cranica posteriore, entrambi i pazienti sono stati studiati anche dopo iniezione di contrasto paramagnetico (Gd-DTPA, 0,2 ml/kg di peso corporeo ).In entrambi si e dimostrata la presenza di una massa extra-assiale, neutra al contrasto, insinuantesi negli spazi subaracnoidei senza significativi segni di massa, l'esame tomografico RM e estremamente informativo non solo per evidenziare la lesione, ma anche per chiarire i rapporti con le altre importanti strutture anatomiche cerebrali. SUMMARY-Intracranial epidermoids have quite characteristic appearances on MR imaging, which is useful in early diagnosis and delineation permitting curative surgery.We have encountered 2 cases of posterior fossa intradura!cepidermoids over a period of 2 years. MR contrast (Gac/opentetate dimeglumine 0.2 m! per kg body weight) was administered in both the patients.Nonenhancing, extra axial, soft tissue mass insinuating between the available sub-arachnoid spaces with lack of significant mass effect was ohserved in both the cases.Multiplanar MR imaging is extremely informative in bringing out not only the extent of the lesion but also its relationship with other important cerebral structures.

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The surgical management of adult coarctation of aorta is quite challenging. Endovascular intervention has limited role in adult calcified coarctation of aorta. Various surgical options are available for management. We are reporting a 58 year old intractable hypertensive male with calcified coarctation of aorta who underwent an Extra Anatomical Bypass using 20mm Integard Woven Dacron graft from left subclavian artery to descending thoracic aorta. He had an uneventful postoperative period with a small gradient across the conduit.