9 research outputs found
Microstructure and Porosity of Laser Welds in Cast Ti-6Al-4V with Addition of Boron
Addition of small amounts of boron to cast Ti-6Al-4V alloy has shown to render a finer microstructure and improved mechanical properties. For such an improved alloy to be widely applicable for large aerospace structural components, successful welding of such castings is essential. In the present work, the microstructure and porosity of laser welds in a standard grade cast Ti-6Al-4V alloy as well as two modified alloy versions with different boron concentrations have been investigated. Prior-β grain reconstruction revealed the prior-β grain structure in the weld zones. In fusion zones of the welds, boron was found to refine the grain size significantly and rendered narrow elongated grains. TiB particles in the prior-β grain boundaries in the cast base material restricted grain growth in the heat-affected zone. The TiB particles that existed in the as cast alloys decreased in size in the fusion zones of welds. The hardness in the weld zones was higher than in the base material and boron did not have a significant effect on hardness of the weld zones. The fusion zones were smaller in the boron-modified alloys as compared with Ti-6Al-4V without boron. Computed tomography X-ray investigations of the laser welds showed that pores in the FZ of the boron modified alloys were confined to the lower part of the welds, suggesting that boron addition influences melt pool flow
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A Study to Compare Oral Sumatriptan with Oral Aspirin plus Oral Metoclopramide in the Acute Treatment of Migraine
In a double-blind, placebo-controlled study, the efficacy, safety and tolerability of 100 mg oral sumatriptan, given as a dispersible tablet, was compared with that of 900 mg oral aspirin plus 10 mg oral metoclopramide in the acute treatment of migraine. A total of 358 patients treated up to three migraine attacks within 3 months, recording clinical information on a diary card. In attack 1, headache relief after 2 h, defined as a reduction in severity from severe or moderate pain to mild or no pain, was recorded in 56% (74/133) of patients who took sumatriptan and 45 % (62/138) of patients who took aspirin plus metoclopramide (p = 0.078). This analysis of the primary efficacy end point was not statistically significant. However, for attacks 2 and 3 (secondary end points), headache relief was achieved in 58 versus 36% of patients (p = 0.001) and 65 versus 34% of patients (p < 0.001), respectively. Relief from nausea, vomiting, photophobia and phonophobia was similar in both treatment groups. Rescue medication was required by fewer patients treated with sumatriptan than by those who received aspirin plus metoclopramide (attack 1, 34 versus 56%, p < 0.001; attack 2, 32 versus 51 %, p = 0.001, and attack 3, 35 versus 54%, p = 0.001). Sumatriptan also produced a faster improvement and resolution of migraine attacks. Comparing the sumatriptan and aspirin plus metoclopramide treatment groups, complete resolution of the attack occurred within 6 h in 32 versus 19% (attack 1), 35 versus 23% (attack 2) and 32 versus 20% of patients (attack 3). There was, however, a lower incidence of headache recurrence within 48 h in patients who received aspirin plus metoclopramide: attack 1, 42 % on sumatriptan versus 33% on aspirin plus metoclopramide (NS); attack 2, 37 versus 27% (NS), and attack 3, 42 versus 30% (p = 0.038). Adverse events were reported by 42 % of patients on sumatriptan and 29% of patients on aspirin plus metoclopramide (p = 0.009), but these were generally mild or moderate. Treatment was rated as reasonable, good or excellent by 66 % of patients in the sumatriptan group, compared with 45% of those in the aspirin plus metoclopramide group (p < 0.001). Moreover, 70% of sumatriptan-treated patients said they would be prepared to take the treatment again, compared with 46% of patients who received aspirin plus metoclopramide (p < 0.001). Overall, oral sumatriptan produced faster and greater relief of migraine headache and was more highly rated by patients than oral aspirin plus oral metoclopramide