ABSTRACT
This paper presents the thermal behavior of non-resonant (quasi-static) piezoelectric biaxial MEMS scanners with Bragg reflectors. These scanners were developed for LIDAR (LIght Detection And Ranging) applications using a pulsed 1550 nm laser with an average power of 2 W. At this power, a standard metal (gold) reflector can overheat and be damaged. The Bragg reflector developed here has up to 24 times lower absorption than gold, which limits heating of the mirror. However, the use of such a reflector involves a technological process completely different from that used for gold and induces, for example, different final stresses on the mirror. In view of the high requirements for optical power, the behavior of this reflector in the event of an increase in temperature needs to be studied and compared with the results of previous studies using gold reflectors. This paper shows that the Bragg reflector remains functional as the temperature rises and undergoes no detrimental deformation even when heated to 200 °C. In addition, the 2D-projection model revealed a 5% variation in optical angle at temperatures up to 150 °C and stability of 2D scanning during one hour of continuous use at 150 °C. The results of this study demonstrate that a biaxial piezoelectric MEMS scanner equipped with Bragg reflector technology can reach a maximum temperature of 150 °C, which is of the same order of magnitude as can be reached by scanners with gold reflectors.
ABSTRACT
PURPOSE: The purpose of this study was to evaluate the LigaSure vessel sealing system as an alternative to closed hemorrhoidectomy. METHODS: Sixty-one patients with Grade 3 or 4 symptomatic hemorrhoids were prospectively randomly assigned to undergo hemorrhoidectomy with the LigaSure vessel sealing system or hemorrhoidectomy using the conventional Ferguson procedure. We determined the operation time, postoperative pain, amount of time taken off from work, and complications associated with both techniques. RESULTS: Mean operative time for the LigaSure hemorrhoidectomy was 15 +/- 5.4 minutes and for the Ferguson operation, 21.2 +/- 8.2 minutes. The difference was significant (P < 0.01). There was also a significant decrease in pain measurements reported on postoperative Days 1 and 2 (P < 0.05) in the LigaSure group. The incidence of postoperative wound swelling and complications were similar between two groups. There was no difference in the period of time off from work between patient groups. CONCLUSION: This study confirms that LigaSure system can achieve a radical ablation of hemorrhoids, reduce operative time, and result in less postoperative pain on postoperative Days 1 and 2.
