Abstract: A highly sensitive trace gas sensor based on Cavity Ring-down Spectroscopy (CRDS) makes use of a high power, multi-mode Fabry-Perot (FP) semiconductor laser with a broad wavelength range to excite a large number of cavity modes and multiple molecular transitions, thereby reducing the detector's susceptibility to vibration and making it well suited for field deployment. The laser beam is aligned on-axis to the cavity, improving the signal-noise-ratio while maintaining its vibration insensitivity. The use of a FP semiconductor laser has the added advantages of being inexpensive, compact and insensitive to vibration. The technique is demonstrated using a laser with an output power of at least 200 mW, preferably over 1.0 Watt, (?=400 nm) to measure low concentrations of Nitrogen Dioxide (NO2) in zero air. For single-shot detection, 530 ppt sensitivity is demonstrated with a measurement time of 60 ?s which allows for sensitive measurements with high temporal resolution.

Abstract: A highly sensitive trace gas sensor based on a Fabry-Perot semiconductor laser and cavity enhanced absorption spectroscopy is designed to be capable of measuring sub-ppb concentrations of trace gases in real time. The broad frequency range of the multi-mode Fabry-Perot semiconductor laser spans a large number of absorption lines of the species of interest enabling multiple line integrated absorption spectroscopy which improves the sensitivity of detection. Additionally, the broad wavelength range of the laser excites a large number of cavity modes simultaneously, thereby reducing the sensor's susceptibility to vibration and thermal fluctuations making it suitable for field based monitoring applications. Using a high finesse optical cavity also enhances the sensitivity of the sensor by providing large path lengths, on the order of kilometers, in a small volume. Relatively high laser power is used to compensate for the low coupling efficiency of a broad linewidth laser to the optical cavity.

Abstract: A safety cabinet has a plurality of walls defining a front open side and a pair of doors pivotal about respective horizontally spaced axes on the walls between a closed and an open position. Guides in the cabinet are each associated with a respective one of the doors, and respective links each have a front end connected to a respective one of the doors and a rear end shiftable front-to-back in a respective one of the guides. A connector extends between the rear ends of the links and shifts front-to-back with them. A closer is operatively engageable with the connector, and a spring applies bears on the closer to urge it against the connector for pushing same into the rear end position and closing the doors. An actuator normally holds the closer out of engagement with the connector during movement of same between the front and rear end positions.

Abstract: The invention relates to a method for treating vapours and condensates which arise during the production of polycondensates from bisphenols or high-value phenols by esterification and/or transesterification with alkyl or aryl esters of at least bivalent organic or inorganic acids. According to the invention, the treatment is carried out in a plurality of condensates and/or distillation columns which are connected in a step-by-step manner behind each other, each distillation column comprising a connected condensate. The dew point and the pressure in each condensate are adjusted such that in each step, monomers, oligomers or decomposition and transformation products are removed.