Mullite–zirconia composites containing 20% zirconia（mass fraction） were prepared by reaction sintering route utilizing Indian coastal zircon flour and sillimanite beach sand. 4%-12% of CaO（mole fraction） with res...Mullite–zirconia composites containing 20% zirconia（mass fraction） were prepared by reaction sintering route utilizing Indian coastal zircon flour and sillimanite beach sand. 4%-12% of CaO（mole fraction） with respect to zirconia was used as additive. The effect of additive on densification, microstructure as well as various mechanical and thermo-mechanical properties was studied. Incorporation of CaO reduced the densification temperature of the composites to 1550 ℃ compared to 1600 ℃（for CaO free samples）. CaO formed small amount of liquid phase（calcium aluminosilicate）, which facilitated sintering. Average grain size of the composites decreased up to 4% CaO addition, afterwards grain size increased with further addition of CaO. Samples with 4% CaO exhibited ～225 MPa of flexural strength, ～6 MPa·m^1/2 of fracture toughness and significant improvement in thermal shock resistance. CaO stabilized the tetragonal zirconia phase and thus improved the mechanical properties.展开更多
AIM:To describe a modified technique for placement of a tracheobronchial self-expanding plastic stent(SEPS) in patients with benign refractory hypopharyngeal strictures in order to improve dysphagia and allow strictur...AIM:To describe a modified technique for placement of a tracheobronchial self-expanding plastic stent(SEPS) in patients with benign refractory hypopharyngeal strictures in order to improve dysphagia and allow stricture remodeling.METHODS:A case series of four consecutive patients with complex hypopharyngeal strictures after combinedtherapy for laryngeal cancer,previously submitted to multiple sessions of dilation without lasting improvement,is presented.All patients underwent placement of a small diameter and unflared tracheobronchial SEPS.Main outcome measurements were improvement of dysphagia and avoiding of repeated dilation.RESULTS:The modified introducer system allowed an easy and technically successful deployment of the tracheobronchial Polyflex stent through the stricture.All four patients developed complications related to stent placement.Two patients had stent migration(one proximal and one distal),two patients developed phanryngocutaneous fistulas and all patients with stents in situ for more than 8 wk had hyperplastic tissue growth at the upper end of the stent.Stricture recurrence was observed at 4 wk follow-up after stent removal in all patients CONCLUSION:Although technically feasible,placement of a tracheobronchial SEPS is associated with a high risk of complications.Small diameter stents must be kept in place for longer than 3 mo to allow adequate time for stricture remodeling.展开更多
基金the Council of Scientific and Industrial Research (CSIR), Govt. of India, for financial support under project No. ESC-0202
文摘Mullite–zirconia composites containing 20% zirconia（mass fraction） were prepared by reaction sintering route utilizing Indian coastal zircon flour and sillimanite beach sand. 4%-12% of CaO（mole fraction） with respect to zirconia was used as additive. The effect of additive on densification, microstructure as well as various mechanical and thermo-mechanical properties was studied. Incorporation of CaO reduced the densification temperature of the composites to 1550 ℃ compared to 1600 ℃（for CaO free samples）. CaO formed small amount of liquid phase（calcium aluminosilicate）, which facilitated sintering. Average grain size of the composites decreased up to 4% CaO addition, afterwards grain size increased with further addition of CaO. Samples with 4% CaO exhibited ～225 MPa of flexural strength, ～6 MPa·m^1/2 of fracture toughness and significant improvement in thermal shock resistance. CaO stabilized the tetragonal zirconia phase and thus improved the mechanical properties.
文摘AIM:To describe a modified technique for placement of a tracheobronchial self-expanding plastic stent(SEPS) in patients with benign refractory hypopharyngeal strictures in order to improve dysphagia and allow stricture remodeling.METHODS:A case series of four consecutive patients with complex hypopharyngeal strictures after combinedtherapy for laryngeal cancer,previously submitted to multiple sessions of dilation without lasting improvement,is presented.All patients underwent placement of a small diameter and unflared tracheobronchial SEPS.Main outcome measurements were improvement of dysphagia and avoiding of repeated dilation.RESULTS:The modified introducer system allowed an easy and technically successful deployment of the tracheobronchial Polyflex stent through the stricture.All four patients developed complications related to stent placement.Two patients had stent migration(one proximal and one distal),two patients developed phanryngocutaneous fistulas and all patients with stents in situ for more than 8 wk had hyperplastic tissue growth at the upper end of the stent.Stricture recurrence was observed at 4 wk follow-up after stent removal in all patients CONCLUSION:Although technically feasible,placement of a tracheobronchial SEPS is associated with a high risk of complications.Small diameter stents must be kept in place for longer than 3 mo to allow adequate time for stricture remodeling.
