Fracture of thermally activated NiTi shape memory alloy wires

This paper presents a study on the fracture of NiTi SMA wire undergoing thermal cycling, activated through resistive heating, under a constant load referred to as thermo-mechanical cycling (TMC). In general, TMC results in initiation of a large number of surface cracks on the SMA wire perpendicular to the wire axis. After initiation, these cracks propagate simultaneously inside the material under cyclic strain. But, the important observation in this study is the generation of cracks in the bulk of the material during TMC, preferentially at the core region of the wire. It has been shown that generation of cracks at the core region is due to strain inhomogeneity during TMC as a consequence of variation in the volume fraction of austenite and martensite phases across the wire cross section. This strain inhomogeneity is attributed to temperature and stress gradients that can exist across the cross section of the wire during thermal cycling. Study shows that nucleation of cracks and their growth at the core region of the wire plays an important role in the fracture of thermally activated SMA wire

Endovascular treatment of active splenic bleeding after colonoscopy: a systematic review of the literature.

PURPOSE: Colonoscopy is reported to be a safe procedure that is routinely performed for the diagnosis and treatment of colorectal diseases. Splenic rupture is considered to be a rare complication with high mortality and morbidity that requires immediate diagnosis and management. Nonoperative management (NOM), surgical treatment (ST), and, more recently, proximal splenic artery embolization (PSAE) have been proposed as treatment options. The goal of this study was to assess whether PSAE is safe even in high-grade ruptures. METHODS: We report two rare cases of post colonoscopy splenic rupture. A systematic review of the literature from 2002 to 2010 (first reported case of PSAE) was performed and the three types of treatment compared. RESULTS: All patients reviewed (77 of 77) presented with intraperitoneal hemorrhage due to isolated splenic trauma. Splenic rupture was high-grade in most patients when grading was possible. Six of 77 patients (7.8 %) were treated with PSAE, including the 2 cases reported herein. Fifty-seven patients (74 %) underwent ST. NOM was attempted first in 25 patients with a high failure rate (11 of 25 [44 %]) and requiring a salvage procedure, such as PSAE or ST. Previous surgery (31 of 59 patients), adhesions (10 of 13), diagnostic colonoscopies (49 of 71), previous biopsies or polypectomies (31 of 57) and female sex (56 of 77) were identified as risk factors. In contrast, splenomegaly (0 of 77 patients), medications that increase the risk of bleeding (13 of 30) and difficult colonoscopies (16 of 51) were not identified as risk factors. PSAE was safe and effective even in elderly patients with comorbidities and those taking medications that increase the risk of bleeding, and the length of the hospital stay was similar to that after ST. CONCLUSION: We propose a treatment algorithm based on clinical and radiological criteria. Because of the high failure rate after NOM, PSAE should be the treatment of choice to manage grade I through IV splenic ruptures after colonoscopy in hemodynamically stabilized patients