Observation Of Continuous Fracturing In Crosshole Seismic Experiments In Crystalline Rock

Crosshole seismic data were gathered in a metamorphic section. These data exhibited anomalous events that were ultimately attributed to the interaction of tube waves and converted tube waves with a continuous fracture connecting the transmitter and receiver boreholes. The pattern of the anomaly is distinctive and easily recognized in a crosshole seismic section and might prove to be useful in the evaluation of high volume inter-borehole fluid communication, or in the assessment of hydrofracture effectiveness

Design of an Automated Rapid Vapor Concentrator and Its Application in Nitroaromatic Vapor Sampling

An automated, rapid-cycling vapor concentrator and sample introduction device was designed and evaluated. The device consists of an inert deactivated fused silica capillary sampling loop. The temperature of the loop was manipulated through contact with a cold plate or a hot plate, maintained at pre-selected temperatures with a thermoelectric cooler and heating cartridge, respectively. The position of the loop was controlled with a stepper motor under microprocessor control. The low mass of the loop permit its rapid cooling and heating. This permits efficient trapping of adsorptive vapors such as the nitroaromatics from the air stream and also allows rapid and quantitative transfer of the trapped analytes to the detection system. The use of at thermoelectric cooler permits variable trapping temperatures and increased sampling selectivity without the use of cumbersome cryogenic fluids. Chemically inert sampling train surfaces prevent analyte loss due to irreversible adsorption and cross contamination between samples. The device was evaluated for rapid analysis of nitroaromatic and chlorinated aromatic vapors from air stream at trace concentrations with a selective electron capture detection system. Trapping efficiencies of \u3e 95 percent can be readily obtained with the device for nitroaromatics at ppb and sub ppb concentrations

A Rapid Vapor Concentrator and Detection System for Nitroaromatics

An automated, rapid-cycling vapor concentrator and sensor was designed and evaluated for detection of nitroaromatic compounds. The concentrator consists of an inert deactivated fused silica capillary loop. The temperature of the loop was manipulated through contact with a cold plate or a hot plate. Plates were maintained at pre-selected temperatures with a thermoelectric cooler and a cartridge heater. The low thermal mass of the loop permitted rapid trapping and desorption cycles. The chemical inertness of the fused silica tubing not only led to efficient transfer of nitroaromatics from the air stream to the detection system but also minimized cross contamination between samples. The detection system consisted of a tandem arrangement of electron attachment detectors and an electron attachment reactor. These devices were operated with compact custom electronics. The use of the electron attachment reactor and thermoelectric cooler permitted enhanced selectivity. The device was evaluated for rapid determination of nitroaromatic from air streams at trace concentrations. Detection limits down to sub parts per billion (ppb) were obtained