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Monitoring Applications (monitoring + application)
Selected AbstractsGaN-based Schottky diodes for hydrogen sensing in transformer oilPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006Peter Sandvik Abstract We report the demonstration of robust, GaN-based hydrogen sensors for use directly in transformer oil. These 1 mm2 Schottky diodes were immersed in a closed loop with Voltesso insulating oil for 21 months of continuous testing. They showed good reproducibility in response to hydrogen gases, while exposed to varying temperatures. We will briefly discuss the transformer monitoring application, the device design and fabrication process, and the sensor performance from 21-months of testing. Transfer functions from oil temperature and dissolved gas concentration have been quantified, and those will be briefly discussed. These new sensors offer a novel alternative to electrochemical cell-based sensors for various applications. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High-sensitivity detection of biological amines using fast Hadamard transform CE coupled with photolytic optical gatingELECTROPHORESIS, Issue 17 2007Kevin L. Braun Abstract Here, we report the first utilization of Hadamard transform CE (HTCE), a high-sensitivity, multiplexed CE technique, with photolytic optical gating sample injection of caged fluorescent labels for the detection of biologically important amines. Previous implementations of HTCE have relied upon photobleaching optical gating sample injection of fluorescent dyes. Photolysis of caged fluorescent labels reduces the fluorescence background, providing marked enhancements in sensitivity compared to photobleaching. Application of fast Hadamard transform CE (fHTCE) for fluorescein-based dyes yields a ten-fold higher sensitivity for photolytic injections compared to photobleaching injections, due primarily to the reduced fluorescent background provided by caged fluorescent dyes. Detection limits as low as 5,pM (ca. 18,molecules per injection event) were obtained with on-column LIF detection using fHTCE in less than 25,s, with the capacity for continuous, online separations. Detection limits for glutamate and aspartate below 150,pM (1,2,amol/injection event) were obtained using photolytic sample injection, with separation efficiencies exceeding 1×106,plates/m and total multiplexed separation times as low as 8,s. These results strongly support the feasibility of this approach for high-sensitivity dynamic chemical monitoring applications. [source] Real-time quadrupole mass spectrometer analysis of gas in borehole fluid samples acquired using the U-tube sampling methodologyGEOFLUIDS (ELECTRONIC), Issue 3 2006B. M. FREIFELD Abstract Sampling of fluids in deep boreholes is challenging because of the necessity of minimizing external contamination and maintaining sample integrity during recovery. The U-tube sampling methodology was developed to collect large volume, multiphase samples at in situ pressures. As a permanent or semi-permanent installation, the U-tube can be used for rapidly acquiring multiple samples or it may be installed for long-term monitoring applications. The U-tube was first deployed in Liberty County, TX to monitor crosswell CO2 injection as part of the Frio CO2 sequestration experiment. Analysis of gases (dissolved or separate phase) was performed in the field using a quadrupole mass spectrometer, which served as the basis for determining the arrival of the CO2 plume. The presence of oxygen and argon in elevated concentrations, along with reduced methane concentration, indicates sample alteration caused by the introduction of surface fluids during borehole completion. Despite producing the well to eliminate non-native fluids, measurements demonstrate that contamination persists until the immiscible CO2 injection swept formation fluid into the observation wellbore. [source] Applications of electronic noses and tongues in food analysisINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2004Anil K. Deisingh Summary This review examines the applications of electronic noses and tongues in food analysis. A brief history of the development of sensors is included and this is illustrated by descriptions of the different types of sensors utilized in these devices. As pattern recognition techniques are widely used to analyse the data obtained from these multisensor arrays, a discussion of principal components analysis and artificial neural networks is essential. An introduction to the integration of electronic tongues and noses is also incorporated and the strengths and weaknesses of both are described. Applications described include identification and classification of flavour and aroma and other measurements of quality using the electronic nose. The uses of the electronic tongue in model analyses and other food, beverage and water monitoring applications are discussed. [source] Spatial refractive index measurement of porcine artery using differential phase optical coherence microscopyLASERS IN SURGERY AND MEDICINE, Issue 10 2006Jeehyun Kim PhD Abstract Background and Objectives We describe a methodology to record spatial variation of refractive index of porcine renal artery using differential phase optical coherence microscopy (DP-OCM). Study Design/Materials and Methods The DP-OCM provides quantitative measurement of thin specimen phase retardation and refractive index by measuring optical path-length changes on the order of a few nanometers and with a lateral resolution of 3 µm. The DP-OCM instrumentation is an all-fiber, dual-channel Michelson interferometer constructed using a polarization maintaining (PM) fiber. Results Two-dimensional en face dual-channel phase images are taken over a 150,×,200 µm region on a microscopic slide, and the images are reconstructed by plotting a two-dimensional refractive index map as the OCM beam is moved across the sample. Conclusions Because the DP-OCM can record transient changes in the optical path-length, the system may be used to record quantitative optical path-length alterations of tissue in response to various stimuli. A fiber-based DP-OCM may have the potential to substantially improve in vivo imaging of individual cells for a variety of clinical diagnostics, and monitoring applications. Lasers Surg. Med. © 2006 Wiley-Liss, Inc. [source] Rate Responsive Pacing Using Transthoracic Impedance Minute Ventilation Sensors: A Multicenter Study on Calibration StabilityPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2002FIRAT DURU DURU, F., et al.: Rate Responsive Pacing Using Transthoracic Impedance Minute Ventilation Sensors: A Multicenter Study on Calibration Stability. Previous studies showed that transthoracic impedance. Previous studies showed that transthoracic impedance minute ventilation (IMV), as measured by a pacemaker sensor, is closely correlated to actual minute ventilation (VE·) determined by standard methods. The aim of this study was to analyze the changes in the calibration between IMV and VE· at rest and during exercise over time. Fifteen patients (age 60 ± 13 years) with Medtronic Kappa 400 pacemakers completed a baseline visit followed by two visits separated by 1 month and 1 week, respectively. In each patient, VE· (L/min) was monitored at rest in the supine and sitting positions and during graded bicycle ergometer exercise using a standard cardiopulmonary metabolic gas analysis system with simultaneous recording of IMV (,/min) using DR-180 extended telemetry monitors. Calibration at rest was defined as the ratio of IMV to VE·, calculated from 1-minute average values in the supine and sitting positions. Calibration during bicycle exercise was defined as intercept (IMV value at VE·= 10 L/min-typical VE· value at beginning of exercise), and slope of the IMV/VE· regression line. The calibration of IMV showed individual variability over time. The magnitude (absolute value) of observed fractional changes in calibration at 1 month was 0.23 ± 0.20 (rest-supine), 0.20 ± 0.15 (rest-sitting), 0.18 ± 0.19 (exercise-intercept), 0.28 ± 0.35 (exercise-slope), and 0.18 ± 0.15, 0.15 ± 0.09, 0.28 ± 0.39, and 0.27 ± 0.15, respectively, at 1 week. The magnitude of change at 1 month was not statistically different from the magnitude of change at 1 week. In conclusion, the calibration of IMV, as measured by a pacemaker sensor, versus actual VE· may demonstrate variability. However, this study also suggests that the observed changes are not cumulative over time. These results have implications for patient monitoring applications using these sensors and for development of future pacemaker rate response algorithms. [source] Philips QT Interval Measurement Algorithms for Diagnostic, Ambulatory, and Patient Monitoring ECG ApplicationsANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2009F.A.C.C., Sophia H. Zhou Ph.D. Background: Commonly used techniques for QT measurement that identify T wave end using amplitude thresholds or the tangent method are sensitive to baseline drift and to variations of terminal T wave shape. Such QT measurement techniques commonly underestimate or overestimate the "true" QT interval. Methods: To find the end of the T wave, the new Philips QT interval measurement algorithms use the distance from an ancillary line drawn from the peak of the T wave to a point beyond the expected inflection point at the end of the T wave. We have adapted and optimized modifications of this basic approach for use in three different ECG application areas: resting diagnostic, ambulatory Holter, and in-hospital patient monitoring. The Philips DXL resting diagnostic algorithm uses an alpha-trimming technique and a measure of central tendency to determine the median QT value of eight most reliable leads. In ambulatory Holter ECG analysis, generally only two or three channels are available. QT is measured on a root-mean-square vector magnitude signal. Finally, QT measurement in the real time in-hospital application is among the most challenging areas of QT measurement. The Philips real time QT interval measurement algorithm employs features from both Philips DXL 12-lead and ambulatory Holter QT algorithms with further enhancements. Results: The diagnostic 12-lead algorithm has been tested against the gold standard measurement database established by the CSE group with results surpassing the industrial ECG measurement accuracy standards. Holter and monitoring algorithm performance data on the PhysioNet QT database were shown to be similar to the manual measurements by two cardiologists. Conclusion: The three variations of the QT measurement algorithm we developed are suitable for diagnostic 12-lead, Holter, and patient monitoring applications. [source] | ||||||||||