A diode-laser-based ultraviolet absorption sensor for elemental mercury was developed and applied for measurements in a high-temperature flow reactor and in the exhaust stream of a coal-fired combustor. The final version of the sensor incorporates a 375-nm single-mode laser and a 784-nm distributed feedback (DFB) laser. The output of these lasers is sum-frequency mixed in a non-linear beta-barium borate crystal to generate a 254-nm beam. By tuning the frequency of the DFB laser, the ultraviolet beam frequency is tuned across the transition frequency of mercury at 253.7-nm. The tuning range is large enough that an off-resonant baseline was clearly visible on both sides of the Hg transition. Because of this large tuning range, the effects of broadband absorption can be effectively eliminated during data analysis. Broadband absorption is a major concern for lamp-based mercury sensor, and the sample to be monitored must be chemically treated prior to analysis to remove species such as SO{sub 2} that absorb near 253.7 nm. No pretreatment is required when our diode-laser-based sensor is used for elemental mercury measurements. Our laser sensor measurements were compared to measurements from a commercial mercury analyzer (CMA), and were generally in good agreement except that the insitu diode-laser-based sensor …

The first half of this report looks at the background of U.S. travel restrictions to Cuba over the last 40 years. The second half of this report looks at several initiatives from the 110th Congress that would ease U.S. travel restrictions to Cuba.