Download or read book Synchronous Detection of Laser induced Fluorescence written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Many toxic or carcinogenic organic molecules have large absorption and fluorescence emission cross sections and can thus be detected by laser-induced fluorescence (LIF) in liquid samples at parts-per-billion levels or better. The technique of synchronous detection of laser-induced fluorescence (SDLIF) provides a way to distinguish between the fluorescence from a toxic molecule and the fluorescence from a background substance. This is done by synchronously scanning the laser excitation and fluorescence detection wavelengths at a fixed wavelength separation. What is measured in the overlap integral of the excitation and emission spectra that is considerably narrower than the entire fluorescence spectrum. The discussion of these techniques is centered on the point and remote detection of polynuclear aromatic hydrocarbons, aromatic amines, and organophosphates having applications in certain manufacturing processes as well as in coal liquefaction and gasification plants.

Download or read book Laser based Instrumentation for the Detection of Chemical Agents written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Several laser-based techniques are being evaluated for the remote, point, and surface detection of chemical agents. Among the methods under investigation are optoacoustic spectroscopy, laser-induced breakdown spectroscopy (LIBS), and synchronous detection of laser-induced fluorescence (SDLIF). Optoacoustic detection has already been shown to be capable of extremely sensitive point detection. Its application to remote sensing of chemical agents is currently being evaluated. Atomic emission from the region of a laser-generated plasma has been used to identify the characteristic elements contained in nerve (P and F) and blister (S and Cl) agents. Employing this LIBS approach, detection of chemical agent simulants dispersed in air and adsorbed on a variety of surfaces has been achieved. Synchronous detection of laser-induced fluorescence provides an attractive alternative to conventional LIF, in that an artificial narrowing of the fluorescence emission is obtained. The application of this technique to chemical agent simulants has been successfully demonstrated. 19 figures.

Download or read book Laser Detection of Toxic Molecules and Carcinogens written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluorescence from large organic molecules is broadband and relatively structureless. Thus, the detection of hazardous molecules in various environments using laser-induced fluorescence is difficult because of obscuration from other fluorescing sources (paints, other impurities, etc.). Laser-optical techniques that can be used to avoid this problem are discussed. The techniques of Synchronous Detection of Laser-Induced Fluorescence (SDLIF), and Resonant Raman Scattering are discussed. It is concluded that resonance Raman scattering processes and SDLIF are possible techniques for detecting large organic molecules in the environment. Because of sensitivity problems, it is doubtful that any of the Raman techniques will be useful for remote sensing of trace quantities in the atmosphere. For strongly fluorescing molecules (fluorescence quantum yields> 1%) the SDLIF technique is expected to prove useful for remote sensing of trace quantities (ppM) of these molecules in the vicinity of pollution sources such as synfuel plants.

Download or read book Tracer based Planar Laser induced Fluorescence Diagnostics written by Brian Ho-yin Cheung and published by Stanford University. This book was released on 2011 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two advances to tracer-based planar laser-induced fluorescence (PLIF) diagnostics are presented in this work. The first improvement is the development of a 3-pentanone fluorescence quantum yield (FQY) database and model for a wide range of conditions in support of quantitative PLIF diagnostics. In addition, this work presents a sensitive, time-resolved tracer-based PLIF diagnostic, accomplished by using a continuous-wave (CW) laser with the high-FQY tracer toluene. Because of its ease of use and desirable photophysical properties, PLIF diagnostics using 3-pentanone as a tracer are common, particularly for internal combustion engine (ICE) diagnostics. Thus, there is a need for 3-pentanone FQY measurements and modeling over a wide range of temperatures, pressures, and excitation wavelengths. For insight into the collisionless process in the FQY model, measurements were made in 3-pentanone vapor at low-pressures across a range of temperatures using a flowing cell. Laser excitation with 248, 266, 277, 308 nm wavelengths were utilized, and Rayleigh scattering of the laser beam was used to calibrate the optical efficiency of the collection optics and detector. This low-pressure data allows calculation of the 3-pentanone fluorescence rate and non-radiative de-excitation rate in the fluorescence model. The vibrational relaxation cascade parameter for 3-pentanone collisions was also determined. Measurements of 3-pentanone FQY were also made over a range of temperatures and pressures relevant to diagnostic applications, and, in particular, combined high-temperature and high-pressure conditions applicable to internal combustion engines (ICE). These data were collected in a custom-built optical cell capable of simultaneous high-pressure and high-temperature conditions. The behavior of the FQY in nitrogen for temperatures up to 745 K and in air up to 570 K was examined for pressures from 1 to 25 bar. These data were used to further optimize the parameters in the FQY model representing collisional processes. The large quantity of data with 308 nm excitation allowed optimization of the nitrogen quenching rate, and data in air were used to optimize the oxygen quenching rate. These data were also used to optimize the vibrational relaxation parameters for nitrogen and oxygen. The model with the updated parameters is consistent with the data collected in the current work, as well as with fluorescence measurements made in optical ICEs up to 1100 K and 28 bar. Another area of tracer-based PLIF diagnostics development is time-resolved imaging. Because PLIF diagnostics are often performed using pulsed lasers, the time resolution of measurements is limited to the pulse rate of laser. Use of a high-powered visible laser with an off-the-shelf cavity frequency doubler is shown to produce a moderate-power CW beam in the ultraviolet wavelength regime. Application of this CW source to excite toluene, a high-FQY tracer, yields a sensitive, time-resolved tracer-based PLIF diagnostic. Fluctuation detection limits for tracer mole fraction were investigated by applying the diagnostic to an atmospheric temperature and pressure nitrogen jet seeded with 4% toluene, and detection limits of better than 1% of the maximum toluene mole fraction were achieved for detection of fluorescence signal at a point, along a line, and over a plane. The diagnostic was also demonstrated on a turbulent jet for line and planar detection and demonstrated the potential for toluene time-resolved PLIF diagnostics with CW lasers.

Download or read book Laser based Instrumentation for Detection of Chemical warfare Agents written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Several laser-based techniques are being developed for remote, point, and surface contamination detection of chemical warfare agents. These techniques include optoacoustic spectroscopy, laser-induced breakdown spectroscopy, and synchronous detection of laser-induced fluorescence. Detection limits in the part-per-million to part-per-billion regime have been demonstrated.

Download or read book Fossil Energy Update written by and published by . This book was released on 1982 with total page 780 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optical Instrumentation for On line Analysis of Chemical Processes written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Optical diagnostics provide the capability for nonintrusive, on-line, real time analysis of chemical process streams. Several laser-based methods for monitoring fossil energy processes have been evaluated. Among the instrumentation techniques which appear quite promising are coherent anti-Stokes Raman spectroscopy (CARS), laser-induced breakdown spectroscopy (LIBS), and synchronous detection of laser-induced fluorescence (SDLIF). A CARS diagnostic was implemented on a coal gasifier and was successfully employed to measure species concentrations and temperatures within the process stream. The LIBS approach has been used to identify total trace impurities (e.g., Na, K, and S) within a gasifier. Recently, individual components in mixtures of aromatics hydrocarbons have been resolved via the synchronous detection of laser-induced fluorescence. 9 figures.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1983 with total page 976 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.

Download or read book Applications of Laser Induced Fluorescence Detection in Biomedical Analysis written by John Emerson Kuo and published by . This book was released on 1985 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Integrated Laser Induced Fluorescence Detection for Parallelizable Microfluidic Single Cell Analysis written by Debbie Lo and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microfluidic devices employing on-chip capillary electrophoresis (ÂľCE) have the potential to analyze single cells at high throughput while demanding less sample volume. However, to date, detecting the lower limit of the biological dynamic range involves coupling the fluorescence into confocal set-ups using externally cooled photomultiplier tubes (PMTs) which inhibit parallelization of the analysis. The integration of photodetector elements directly on-chip is desirable, but thus far, demonstrated systems are unable to detect targets without increasing target concentration by chemical techniques such as polyermase chain reaction (PCR). To address these demands, this work will investigate a laser-induced fluorescence (LIF) detection scheme using a high-index micro-ball lens embedded in a carbon-blackened polydimethylsiloxane (PDMS) panchromatic filter. The lens-filter layer enables simultaneous excitation rejection and fluorescence enhancement to couple fluorescence from a microfluidic channel to a surface detector. Furthermore, a method is proposed to optimize signal-to-noise ratio (SNR) in these higher dark current environments towards the goal of multiplexable and parallelizable integrated LIF detection.

Download or read book Laser Induced Fluorescence Spectroscopy for the Detection of the Biodistribution of Photosensitizers written by Marigo Stavridi and published by . This book was released on 1992 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Publications of Los Alamos Research written by Los Alamos National Laboratory and published by . This book was released on 1984 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Strategies for Planar Laser induced Fluorescence Thermometry in Shock Tube Flows written by Ji Hyung Yoo and published by Stanford University. This book was released on 2011 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis was motivated by the need to better understand the temperature distribution in shock tube flows, especially in the near-wall flow regions. Two main ideas in planar laser-induced fluorescence (PLIF) diagnostics are explored in this thesis. The first topic is the development of a single-shot PLIF diagnostic technique for quantitative temperature distribution measurement in shock tube flow fields. PLIF is a non-intrusive, laser-based diagnostic technique capable of instantaneously imaging key flow features, such as temperature, pressure, density, and species concentration, by measuring fluorescence signal intensity from laser-excited tracer species. This study performed a comprehensive comparison of florescence tracers and excitation wavelengths to determine the optimal combination for PLIF imaging in shock tube flow applications. Excitation of toluene at 248nm wavelength was determined to be the optimal strategy due to the resulting high temperature sensitivity and fluorescence signal level, compared to other ketone and aromatic tracers at other excitation wavelengths. Sub-atmospheric toluene fluorescence yield data was measured to augment the existing photophysical data necessary for this diagnostic technique. In addition, a new imaging test section was built to allow PLIF imaging in all regions of the shock tube test section, including immediately adjacent to the side and end walls. The signal-to-noise (SNR) and spatial resolution of the PLIF images were optimized using statistical analysis. Temperature field measurements were made with the PLIF diagnostic technique across normal incident and reflected shocks in the shock tube core flow. The resulting images show uniform spatial distribution, and good agreement with conditions calculated from the normal shock jump equations. Temperature measurement uncertainty is about 3.6% at 800K. The diagnostic was also applied to image flow over a wedge. The resulting images capture all the flow features predicted by numerical simulations. The second topic is the development of a quantitative near-wall diagnostic using tracer-based PLIF imaging. Side wall thermal boundary layers and end wall thermal layers are imaged to study the temperature distribution present under constant pressure conditions. The diagnostic technique validated in the shock tube core flow region was further optimized to improve near-wall image quality. The optimization process considered various wall materials, laser sheet orientations, camera collection angles, and optical components to find the configuration that provides the best images. The resulting images have increased resolution (15[Mu]m) and are able to resolve very thin non-uniform near-wall temperature layers (down to 60[Mu]m from the surface). The temperature field and thickness measurements of near-wall shock tube flows under various shock conditions and test gases showed good agreement with boundary layer theory. To conclude this thesis, new applications and future improvements to the developed PLIF diagnostic technique are discussed. These suggested refinements can provide an even more robust and versatile PLIF imaging technique capable of measuring a wider range of flow conditions near walls.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Excitation detection strategies for OH planar laser induced fluorescence measurements in the presence of interfering fuel signal and absorption effects written by and published by . This book was released on 2011 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser induced Fluorescence for Medical Diagnostics written by Stefan Andersson-Engels and published by . This book was released on 1989 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Lab on a Chip written by Edwin Oosterbroek and published by Elsevier. This book was released on 2003-10-02 with total page 403 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past ten years there has been a rapid growth of the research and application area known as Lab-on-a-Chip. After an initial focus on electrokinetic separation techniques on chip, the scope of the field has widened to include topics like microfluidics, DNA analysis, cell analysis, microreactors and mass spectrometer interfacing. As well as the analytical chemistry community, synthetic chemists, chemical engineers, biochemists and biomedical engineers are now also becoming more and more interested in using new micro- and nanotechnological techniques. This first Lab-on-a-Chip book contains a broad collection of papers on microtechnology, microfluidics, analytical methods and applications. All contributions are written by leading researchers in their respective fields, and provide new scientists with an overview of the field, to make him/her aware of the enormous opportunities offered by modern technology. The work presented in this book will definitely stimulate readers to new ideas and concepts, and lead to further innovations in this area. Provides a quick introduction into the different aspects of this field Describes technology that has already revolutionized the world of chemical and biochemical analysis and synthesis All contributions are written by leading researchers in their respective fields