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Photofragmentation laser-induced fluorescence of ozone: an in situ tool for precise mapping of ozone concentration in non-thermal plasmas
摘要： The absolute spatially resolved concentration of ozone has been determined in the near afterglow of a novel type of atmospheric multi-hollow barrier discharge using photofragmentation laser-induced fluorescence. The method consists of two steps: (i) photodissociation of O3 to O(3P) and O2(X3Σg?) with considerable vibrational excitation; (ii) predissociation laser-induced fluorescence of the molecular fragment via the O2(B 3Σu?, v′ = 0 ← X 3Σg?, v″ = 6) transition. Both processes happen during the same laser pulse, requiring the same excitation wavelength (≈248 nm). The fluorescence signal has been calibrated by infrared absorption. The method allows in situ observation before the afterglow chemistry significantly affects the O3 concentration, and is capable of revealing inhomogeneous ozone distributions in the reactor.
关键词： ozone,spatial resolution,non-thermal plasmas,photofragmentation laser-induced fluorescence
更新于2025-09-11 14:15:04
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Laser-induced fluorescence (LIF) as a smart method for fast environmental virological analyses: validation on Picornaviruses
摘要： Virological analysis is time-consuming and expensive. The aim of this work is to demonstrate the applicability of laser-induced fluorescence (LIF) to the classification of viruses, reducing the time for this analysis and its costs. Experimental tests were performed in which different viruses were irradiated with a UV laser emitting at 266 nm and the emitted spectra were recorded by a spectrometer. The classification techniques show the possibility of discriminating viruses. Although the application of the LIF technique to biological agents has been thoroughly studied by many researchers over the years, this work aims at validating for the first time its applicability to virological analyses. The development of a fast virological analysis may revolutionize this field, allowing fast responses to epidemiologic events, reducing their risks and improving the efficiency of monitoring environments. Moreover, a cost reduction may lead to an increase in the monitoring frequency, with an obvious enhancement of safety and prevention.
关键词： Laser-induced fluorescence,environmental monitoring,virological analyses,virus classification
更新于2025-09-11 14:15:04
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OH planar laser-induced fluorescence measurement for H<sub>2</sub>/O<sub>2</sub> jet diffusion flames in rocket combustion condition up to 7.0 MPa
摘要： This study focuses on the application of OH planar laser-induced fluorescence (OH-PLIF) in high-pressure rocket combustion conditions, up to 7.0 MPa. The signal to noise ratio of PLIF degrades in high-pressure combustion owing to effects such as line broadening and interference from intense chemiluminescence. The OH(2,0) band excitation method was applied to obtain the OH(2,1) fluorescence emitted near 290 nm and filter out the intense OH(0,0) band chemiluminescence emitted near 308 nm. The gaseous H2/O2 (GH2/GO2) jet diffusion flame was formed using a recessed coaxial shear injector. The GH2/GO2 injection Reynolds number, Re (ReH2/ReO2 ≈ 2320/22800–4660/45600), was varied to examine the variation of the flame structure and reaction zone thickness under each pressure condition Pc, and Re injection condition. In addition, the variation of the experimentally derived full width at half maximum (FWHM) of the radial OH distribution, ?OH, with the Damk?ehler number, Da, was compared with that of the simulated FWHM of the OH mole fraction, ?OH-SIM. The OH distribution was clearly observed in the instantaneous PLIF image while eliminating the intense OH chemiluminescence even in the highest pressure condition of 7.0 MPa, which is a pressure higher than any of the previous OH-PLIF studies conducted on rocket combustion. The flame structure showed the typical characteristics of a turbulent jet diffusion flame and depended on Re rather than on the chamber pressure Pc. The variation of ?OH with Da corresponded qualitatively with ?OH-SIM and showed the characteristics of flame stretch in the vicinity of the injector.
关键词： Jet diffusion flame,High-pressure combustion,Laser-induced fluorescence,Chemiluminescence,OH(2,0) band excitation
更新于2025-09-11 14:15:04
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AIP Conference Proceedings [AIP Publishing HIGH-ENERGY PROCESSES IN CONDENSED MATTER (HEPCM 2019): Proceedings of the XXVI Conference on High-Energy Processes in Condensed Matter, dedicated to the 150th anniversary of the birth of S.A. Chaplygin - Novosibirsk, Russia (3–5 April 2019)] HIGH-ENERGY PROCESSES IN CONDENSED MATTER (HEPCM 2019): Proceedings of the XXVI Conference on High-Energy Processes in Condensed Matter, dedicated to the 150th anniversary of the birth of S.A. Chaplygin - Investigation of the photobleaching effect on the measurement of laser-induced fluorescence excitation-emission matrices of biological tissues
摘要： Photobleaching effect on laser-induced fluorescence excitation-emission matrices of biological tissues was investigated. Rat brain tissues were used as an object of study. Tunable laser was used as an excitation source with wavelength in 210-290 nm range with 10 nm steps. The fluorescence spectra were measured depending on irradiation dose and wavelength. The photobleaching rate was estimated as an absorbed radiation dose when peak fluorescence intensity decreases 2.7 times. The above level of intensity decrease is achieved at absorbed dose of 58 mJ/cm2 for the 210 nm wavelength, and at 2550 mJ/cm2 for 290 nm. The highest absorbed dose (4333 mJ/cm2) and respectively the lowest bleaching rate falls on 250 nm. It had been shown that higher photobleaching rate at shorter wavelengths in general has negligible effect on the excitation-emission matrices measurements.
关键词： excitation-emission matrices,laser-induced fluorescence,photobleaching,biological tissues
更新于2025-09-11 14:15:04
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Laser-Induced Fluorescence Emission (L.I.F.E.) as Novel Non-Invasive Tool for In-Situ Measurements of Biomarkers in Cryospheric Habitats
摘要： Global warming affects microbial communities in a variety of ecosystems, especially cryospheric habitats. However, little is known about microbial-mediated carbon fluxes in extreme environments. Hence, the methodology of sample acquisition described in the very few studies available implies two major problems: A) high resolution data require a large number of samples, which is difficult to obtain in remote areas; B) unavoidable sample manipulation such as cutting, sawing, and melting of ice cores that leads to a misunderstanding of in situ conditions. In this study, a prototype device that requires neither sample preparation nor sample destruction is presented. The device can be used for in situ measurements with a high spectral and spatial resolution in terrestrial and ice ecosystems and is based on the Laser-Induced Fluorescence Emission (L.I.F.E.) technique. Photoautotrophic supraglacial communities can be identified by the detection of L.I.F.E. signatures in photopigments. The L.I.F.E. instrument calibration for the porphyrin derivates chlorophylla (chla) (405 nm laser excitation) and B-phycoerythrin (B-PE) (532 nm laser excitation) is demonstrated. For the validation of this methodology, L.I.F.E. data were ratified by a conventional method for chla quantification that involved pigment extraction and subsequent absorption spectroscopy. The prototype applicability in the field was proven in extreme polar environments. Further testing on terrestrial habitats took place during Mars analog simulations in the Moroccan dessert and on an Austrian rock glacier. The L.I.F.E. instrument enables high resolution scans of large areas with acceptable operation logistics and contributes to a better understanding of the ecological potential of supraglacial communities in the context of global change.
关键词： chlorophyll,glacial melt,laser-induced fluorescence emission (L.I.F.E.),ice,cryospheric habitats,phycoerythrin,non-invasive
更新于2025-09-11 14:15:04