Quantitative Hydrogen Chloride Detection in Combustion Environments Using Tunable Diode Laser Absorption Spectroscopy with Comprehensive Investigation of Hot Water Interference

Hydrogen chloride (HCl) monitoring during combustion/gasification of biomass fuels and municipal solid waste, such as polyvinyl chloride (PVC) and food residues, is demanded to avoid the adverse effect of HCl to furnace operation and to improve the quality of the gas products. Infrared tunable diode laser absorption spectroscopy (IR-TDLAS) is a feasible nonintrusive in-situ method for HCl measurements in harsh environments. In the present work, the measurement was performed using the R(3) line of the ν2 vibrational band of HCl at 5739.25 cm–1 (1742.4 nm). Water vapor is ubiquitous in combustion/gasification environments, and its spectral interference is one of the most common challenges for IR-TDLAS. Spectral analysis based on the current well-known databases was found to be insufficient to achieve an accurate measurement. The lack of accurate temperature-dependent water spectra can introduce thousands parts per million (ppm) HCl overestimation. For the first time, accurate spectroscopic data of temperature-dependent water spectra near 5739.3 cm–1 were obtained based on a systematic experimental investigation of the hot water lines in a well-controlled, hot flue gas with a temperature varying from 1100 to 1950 K. With the accurate knowledge of hot water interference, the HCl TDLAS system can achieve a detection limit of about 100 ppm⋅m at around 1500 K, and simultaneously the gas temperature can be derived. The technique was applied to measure the temporally resolved HCl release and local temperature over burning PVC particles in hot flue gas at 1790 K.

Clinical Comparison of Diode Laser Assisted “v-Shape Frenectomy” and Conventional Surgical Method as Treatment of Ankyloglossia

(1) Background: Ankyloglossia, or tongue-tie is a condition, in which the tip of tongue cannot protrude beyond the lower incisor teeth because of short frenulum linguae, often containing scar tissue. Limitations of movement are the most important clinical symptoms of this condition, together with feeding, speech, and mechanical problems. (2) Methods: the present study included two groups of patients (group A and group B) including, respectively, 29 and 32 patients (61 patients total), aged from 8 to 12 and presenting ankyloglossia classified according to the Kotlow’s classification. The patients in group A underwent a common surgical procedure. For the patients of group B, a diode laser device (K2 mobile laser, Dentium, Korea) with a micro-pulsed wavelength of 980 ± 10 nm and power of 1.2 watts was used. The post-surgical discomfort of the patients (recording the pain perceived immediately after the end of the anesthesia and during the following week, using the Numeric Rating Scale (NRS) system) and healing characteristics (recorded using the Early Wound Healing Score or EHS) were evaluated. (3) Results: The results shows that the pain in the patients who underwent laser-assisted frenectomy is significantly reduced (p < 0.001) when compared to those who underwent conventional surgical frenectomy, both immediately after surgery (with a reduction in the average NRS of 80.6%) and after the first week (with a reduction in the average NRS of 86.58%). Additionally, in the same patients, an augmentation in the average value of the EHS of 45% was recorded, highlighting significantly (p < 0.001) better quality in the healing of the wound within the 24 h after surgery. Moreover, other advantages observed in the use of laser assisted-frenectomy are the absence of bleeding and, consequently, a clear operative field; no need to use sutures; no need to take painkillers or antibiotics after surgery; and having a faster recovery and less time needed to perform the operation. (4) Conclusions: within the limits of the present study, it seems possible to assert that the laser frenectomy performed using the v-shape technique presents a series of advantages if compared to the conventional surgical method.

Comb coherence-transfer and cavity ring-down saturation spectroscopy around 1.65μm: kHz-accurate frequencies of transitions in the 2ν3 band of 12CH4

Comb Coherence Transfer (CCT) uses a feed-forward frequency correction to transfer the optical phase of a frequency comb to the beam of a free-running diode laser. This allows to amplify...