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The gonadotropin‐releasing hormone (GnRH) stimulation test is used to investigate testicular production of testosterone (T) when performing a breeding soundness examination. In male dogs with fertility problems, the prostate should also be investigated as prostatic conditions may frequently lower semen quality. Serum concentrations of canine prostatic‐specific esterase (CPSE) increase in dogs with benign prostatic hyperplasia (BPH). When performing a breeding soundness examination in a male dog, GnRH administration is frequently done at the beginning of the process and then both T and CPSE are assayed on the same serum sample collected 1 h following the GnRH injection. The aim of this study was to assess whether or not the administration of GnRH may alter CPSE concentrations in dogs with a healthy prostate. Twenty‐eight client‐owned intact adult male dogs were included in the study. Following a 7‐day sexual rest all male dogs underwent a clinical examination and an ultrasonographic examination of the prostatic gland. Prostatic size and parenchyma of every tested dog were evaluated by ultrasonography to assess prostatic conditions. Two different GnRH stimulation protocols were used, A = gonadorelin 50μg/dog SC (n = 15) and B = buserelin 0.12 μg/kg IV (n = 13). T and CPSE concentrations were measured before and 1 h after GnRH administration by a laser‐induced fluorescence analysis. Buserelin and gonadorelin were equally effective in causing a significant increase in serum T concentrations in the post GnRH sample. When considering the 28 dogs together, CPSE concentrations did not change following the stimulation test with either GnRH compound; however, in 4/28 cases, the post GnRH value was markedly increased to values compatible with a diagnosis of BPH. There was no difference in the action of buserelin or gonadorelin in causing an increase in serum T concentrations. CPSE secretion was increased in approximately 15% of dogs treated with either buserelin or gonadorelin. Therefore, whenever performing diagnostic testing in intact male dogs, CPSE should not be assayed on a post‐GnRH serum sample. [ABSTRACT FROM AUTHOR]

Aerogels were listed among the top ten emerging technologies in chemistry by IUPAC in 2022. Their record‐breaking properties sparked the emergence of a thriving insulation market, but solutions are sought to promote additional applications. A 3D assembly process based on direct ink writing of "aerogel‐in‐aerogel" nanocomposites is presented. The printed polyimide‐silica aerogels are non‐brittle (E = 6.7 MPa) with a super‐insulating thermal conductivity (20.3 mW m−1 K−1) and high thermal stability (T5wt% 447 °C). In addition, they display excellent low‐loss dielectric properties and microwave transmission over all relevant communication bands and can be functionalized for electromagnetic interference (EMI) shielding. The high shape‐fidelity printing, combined with laser‐induced etching of thermally conductive graphene layers, enable precise thermal management for portable electronics or maintain an extreme temperature gradient (−40 to +50°C) across a millimeter‐scale partition. [ABSTRACT FROM AUTHOR]

Incorporating additives to fuel into a piston engine is one strategy used to reduce wear on critical engine parts. The present study aims to experimentally characterize the presence of these additives on a wall after a fuel spray impact under representative Diesel and spark ignition engine conditions. For this purpose, a laser-induced fluorescence technique was implemented on a high pressure, high-temperature vessel. Spectroscopic characterizations of fuels and additives were carried out to design an optical strategy for both engine conditions. Fuel surrogates were chosen to allow the additives to be monitored and to mimic the behavior of commercial fuels. The results obtained for gasoline fuels show that at level of incorporation above 100 ppm the additives reach the surface, demonstrating the effectiveness of the additive use strategy. The results obtained for Diesel cases show that even for a high level of additive incorporation, the thermodynamic conditions lead to a complete evaporation of the additives before impact on the wall, which minimizes the expected effect of these additives on friction reduction. [ABSTRACT FROM AUTHOR]

Noncovalent fluorescence switching materials with specific molecular packing motifs for desired performance are difficult to design accurately due to the complexity of intermolecular interactions. Herein, a noncovalent interaction competition strategy to design fluorescence‐switching materials by fine‐modulating hydrogen‐bond and π–π interactions is proposed. Hydrogen bonds are generated by nitrogen/oxygen‐containing units while π–π interactions are generated between polycyclic aromatic hydrocarbons. After these two interactions are balanced in strength, they attempt to induce the formation of respective molecule assemblies stably under controllable conditions. Through thermal stimulus produced by a laser, a reversible assembly transition with high‐contrast monomer‐to‐excimer fluorescence switching is achieved, which demonstrates promising applications in rewritable optical recording and time‐dependent anti‐counterfeiting. This strategy provides a crucial step toward the controllable switching of supramolecular assembly for information handling. [ABSTRACT FROM AUTHOR]

The effect of reactant injection and mixing on detonation wave propagation is studied in a self-excited, optically-accessible linear detonation combustor operated with natural gas and oxygen. Fuel injection and mixing processes are captured with 100 kHz planar laser induced fluorescence (PLIF) measurements of acetone tracer injected into the fuel stream. Measurements are acquired at multiple orthogonal planes downstream of the reactant injection site to investigate the three-dimensional mixing field in the chamber. The fuel distribution field is correlated with simultaneously acquired OH * chemiluminescence measurements that provide a qualitative indication of heat release in the combustor. These measurements are used to provide quantitative information of the fuel injector recovery process and its impact on detonation wave structure across a range of equivalence ratios. While significant differences in the detonation wavefront are observed with change in equivalence ratio, the characterization of the fuel refill process into the chamber after the passage of the detonation wave highlights some key generalizable features. The time available for fuel recovery is consistently between 12 – 19% of the detonation wave period across an equivalence ratio range of 0.83 – 1.48. A linear correlation between injector recovery times and the ratio of the average detonation wave pressure amplitude relative to the pressure drop across the fuel injector is observed. Instantaneous and phase-averaged measurements of acetone-PLIF with the time-coincident OH * chemiluminescence images provide qualitative information of wave structure and injection dynamics along with quantification of fuel injector recovery, a key metric that drives combustor operation and performance. These measurements significantly enhance the ability to obtain detailed information on the intra- and inter-cycle spatiotemporal evolution of the reactant refill process and its coupled effects on the detonation wave structure and propagation. [ABSTRACT FROM AUTHOR]

The highly dynamic response of a continuously injected liquid fuel jet to rotating detonation waves is a critical parameter in the design, performance optimization, and modeling of a rotating detonation engine (RDE). In this work, this response is spatio-temporally resolved from the fuel injection point to the detonation channel using planar laser-induced fluorescence (PLIF) at imaging rates up to 1 MHz. A rotating detonation combustor (RDC) is operated on hydrogen and air to sustain stable detonation waves that interact in a one-way coupled manner with a single liquid fuel jet that propagates into the combustion chamber with cycle periods of ∼ 250 µs. Diesel is utilized as a realistic fuel surrogate with higher aromatic compounds to enable fluorescence excitation using the 355 nm third-harmonic output of a burst-mode Nd:YAG laser. By optimizing the technique to accommodate orders of magnitude variations in the fuel density throughout the injection process, the PLIF data enable measurements of (i) the overall refill dynamics after the arrival of the detonation wave, (ii) changes in the liquid spray trajectory with microsecond temporal resolution, and (iii) the time required to reestablish the quasi-steady axial refilling process as a function of peak chamber pressure relative to the air- and liquid-injector pressure drops. As the passage of the detonation wave imparts significant changes in the momentum flux ratio, the qualitative liquid break-up process and spatial distribution of the spray also vary significantly in time. Only as the injection system recovers late in the cycle does the fuel spray eventually return to a quasi-steady position and allow comparisons with theoretical jet trajectories. These data, enabled by ultra-high-speed PLIF imaging, represent some of the first detailed measurements for quantifying the dynamic response and recovery of liquid jets exposed to periodic detonations in an operating RDC. [ABSTRACT FROM AUTHOR]

The results of a study of the degradation of the cyclotrimethylenetrinitramine (RDX) traces carried in fingerprints depending on the fingerprint number are presented. The surface concentration of the trace was assessed using macrophotography in polarized light and by the method of laser fragmentation/laser-induced fluorescence. A technique for estimating the surface concentration of RDX traces in sweat-fat fingerprints based on pixel-by-pixel scanning of macrophotographs is described. The data of parallel experiments on remote laser detection of RDX particles in fingerprints are presented. A comparison shows that the results of the direct measurements of the total trace area are in good agreement with the LF/LIF response data. [ABSTRACT FROM AUTHOR]

Determination of the iron oxide nanoparticles (IONPs) local temperature during laser heating is important in the aspect of laser phototherapy. We have carried out theoretical modeling of IONPs local electromagnetic (EM) field enhancement and heating under the laser action near individual IONPs and ensembles of IONPs with different sizes, shapes and chemical phases. For experimental determination of IONPs temperature, we used fluorescence thermometry with rhodamine B (RhB) based on its lifetime. Depending on the IONPs shape and their location in space, a significant change in the spatial distribution of the EM field near the IONPs surface is observed. The local heating of IONPs in an ensemble reaches sufficiently high values; the relative change is about 35 °C for Fe2O3 NPs. Nevertheless, all the studied IONPs water colloids showed heating by no more than 10 °C. The heating temperature of the ensemble depends on the thermal conductivity of the medium, on which the heat dissipation depends. During laser scanning of a cell culture incubated with different types of IONPs, the temperature increase, estimated from the shortening of the RhB fluorescence lifetime, reaches more than 100 °C. Such "hot spots" within lysosomes, where IONPs predominantly reside, lead to severe cellular stress and can be used for cell therapy. [ABSTRACT FROM AUTHOR]

The experimental investigation of the effects of O2 injection on the magnetized Ar plasma flow in the linear plasma device was conducted by using the measurement of laser induced fluorescence (LIF) with electric probes. The LIF measurement was based on the Ar ion transition from the 3d4F7/2 metastable level to the 4p4D5/2 level at a wavelength of 668.61 nm. In addition, the analysis of ion velocity distribution functions (IVDFs) involved the detection of fluorescence light emitted from the 4p4D5/2 level to the 4s4P3/2 level, which had a wavelength of 442.72 nm. For a comprehensive analysis of the intricate interaction between O2 injection and the behavior of the Ar plasma flow, the oxygen was injected into the Ar plasma, and the O2/Ar ratio ranged from 0% to 14% while maintaining a constant pressure of 2 mTorr. The Zeeman splitting in the IVDFs was clearly observable for pure Ar plasma due to 800 G as the high magnetic field strength. The split form disappeared due to a small amount of oxygen injected as the O2/Ar ratio of 3.5%. The LIF intensity is in agreement with the tendency of plasma density due to the reduction of Ar ions by charge transfer, quenching, and neutralization as O2 is injected into the Ar plasma. The experimental results show that the effects on temperature and flow velocity for the Ar ions are insignificant when O2 is injected into the Ar plasma at the O2/Ar ratio of 0%–14%, in contrast to the large change in the electron temperature. [ABSTRACT FROM AUTHOR]

Background: Pig‐derived tissues could overcome the shortage of human donor organs in transplantation. However, the glycans with terminal α‐Gal and Neu5Gc, which are synthesized by enzymes, encoded by the genes GGTA1 and CMAH, are known to play a major role in immunogenicity of porcine tissue, ultimately leading to xenograft rejection. Methods: The N‐glycome and glycosphingolipidome of native and decellularized porcine pericardia from wildtype (WT), GGTA1‐KO and GGTA1/CMAH‐KO pigs were analyzed by multiplexed capillary gel electrophoresis coupled to laser‐induced fluorescence detection. Results: We identified biantennary and core‐fucosylated N‐glycans terminating with immunogenic α‐Gal‐ and α‐Gal‐/Neu5Gc‐epitopes on pericardium of WT pigs that were absent in GGTA1 and GGTA1/CMAH‐KO pigs, respectively. Levels of N‐glycans terminating with galactose bound in β(1‐4)‐linkage to N‐acetylglucosamine and their derivatives elongated by Neu5Ac were increased in both KO groups. N‐glycans capped with Neu5Gc were increased in GGTA1‐KO pigs compared to WT, but were not detected in GGTA1/CMAH‐KO pigs. Similarly, the ganglioside Neu5Gc‐GM3 was found in WT and GGTA1‐KO but not in GGTA1/CMAH‐KO pigs. The applied detergent based decellularization efficiently removed GSL glycans. Conclusion: Genetic deletion of GGTA1 or GGTA1/CMAH removes specific epitopes providing a more human‐like glycosylation pattern, but at the same time changes distribution and levels of other porcine glycans that are potentially immunogenic. [ABSTRACT FROM AUTHOR]

This paper reports the findings from a three-dimensional direct numerical simulation conducted to investigate the turbulent flame behaviors of premixed high-hydrogen content syngas (with 50% hydrogen on a per mole basis) and air mixtures. To accomplish this, a laminar flame front is placed in a homogeneous isotropic decaying turbulence field composed of a syngas–air mixture at an equivalence ratio of 0.7 and allowed to evolve for 1.4 eddy turnover times. Homogeneous isotropic turbulence is generated using a helical forcing function in a cubic domain with a grid size of 256 × 256 × 256. The Reynolds number based on the Taylor microscale, Reλ, is 57 for the generated turbulence field. The laminar flame front is placed at the center of the domain. The premixture enters the domain at a velocity of 8 m/s and at an initial temperature of 800 K. The pressure remains constant at 1 atm. In addition to quantifying the spatial and temporal evolution of turbulent characteristics and flame structure, the study also focuses on identifying turbulence/flame interactions, specifically, the impact of these interactions on flame thickness. Energy transfer from small to large scales, i.e., a reverse cascade is observed as a result of energy release due to chemical reactions at the small scales that is transferred to larger scales. The increase in turbulent intensities due to chemical reactions correlates with flame thickening. [ABSTRACT FROM AUTHOR]

This study investigates auto-ignition and heat release characteristics of pilot hydrogen chemical energy in a scramjet combustor equipped with a single cavity. Experiments are conducted in a direct-connected facility simulating Mach 6.0 flight conditions with a total temperature of 1350 K and total pressure of 1.75 MPa. Data are obtained from schlieren imaging, hydroxyl planar laser-induced fluorescence, flame emission, and 10-kHz static pressure transducers. The present investigation extends the pilot hydrogen ignition delay experimental dataset and clarifies the instabilities present in the ignition process. The results show that the supersonic internal flow of a confined cavity exhibits self-oscillating behavior with a dominant frequency of approximately 141.3 Hz. The primary chemical reaction occurs at mid-cavity, where the chemical energy of the pilot hydrogen begins to be converted into heat energy, then approaches the cavity ramp before finally being distributed across the whole cavity. The combustion mode is the cavity-stabilized scramjet mode. The distribution of hydroxyl radicals varies significantly because the combustion in the cavity is unsteady. The ignition delay time increases as the injection pressure rises. However, an injection pressure of 4.0 MPa produces an ignition delay of 24.7 ms, which is apparently shorter than the delay under an injection pressure of 3.5 MPa and similar to that under an injection pressure of 3.0 MPa. The injection of pilot hydrogen under high pressures induces greater heat release and more intense blockage effects, thus enhancing the probability of successful ignition and stable combustion. [ABSTRACT FROM AUTHOR]

This paper presents the flow and flame characteristics of a highly turbulent reactive flow over a backward-facing step inside a windowed combustor. Flow and combustion experiments were performed at Re = 15,000 and Re = 30,000 using high-resolution 10 kHz PIV and 10 kHz PLIF diagnostic techniques. Grid turbulators (Grid) with two different hole diameters (HD of 1.5 mm and 3 mm) and blockage ratios (BR of 46%, 48%, 62%, and 63%) were considered for the turbulence study. Grids introduced different turbulent length scales (LT) in the flow, causing the small eddies and turbulence intensity to increase downstream. The backward-facing step increased the turbulence level in the recirculation zone. This helped to anchor the flame in that zone. The small HD grids (Grids 1 and 3) produced continuous fluid structures (small-scale), whereas the larger HD grids (Grids 2 and 4) produced large-scale fluid structures. Consequently, the velocity fluctuation was lower (~25.6 m/s) under small HD grids and higher (~27.7 m/s) under large HD grids. The flame study was performed at Φ = 0.8, 1.0, and 1.2 using C-X CH PLIF. An Adaptive MATLAB-based flame imaging scheme has been developed for turbulent reacting flows. Grids 1 and 3 induced more wrinkles in the flame due to higher thermal instabilities, pressure fluctuation, and diffusion under those grids. The flamelet breakdown and burnout events were higher under Grids 2 and 4 due to higher thermal diffusivity and a slower diffusion rate. It was observed that the flame wrinkling and flame stretching are higher at Re = 30,000 compared to Re = 15,000. The Borghi–Peters diagram showed that the flames were within the thin reaction zone except for Grid 1 at Re = 15,000, where flames fell in the corrugated zone. It was observed from PIV and PLIF analyses that Re and LT mostly controlled the flame and flow characteristics. [ABSTRACT FROM AUTHOR]

Significant information on the dynamics of the plasma constituents in Hall effect thrusters can be obtained using minimally intrusive techniques, such as laser-induced fluorescence (LIF) diagnostics. Indeed, LIF provides an excellent tool to determine the ion velocity distribution function with high spatial resolution. Even in a steady-state operation, recording time-resolved maps of the velocity distribution is relevant due to persisting time-dependent features of the thruster discharge. One of the preeminent phenomena that render the ion velocity distribution to be time dependent is commonly attributed to the breathing mode, characterized by pronounced oscillations in the discharge current. The goal of this work is to propose a new technique for plasma dynamic studies based on LIF spectroscopy with phase-resolution during the breathing period. For this purpose, the Hilbert transform is used to define the instantaneous phase of oscillation of the thruster current. Ion velocity distribution modification over assigned phases of oscillation is measured simultaneously and in real-time thanks to a fully numerical analysis of the data. [ABSTRACT FROM AUTHOR]

In this work, we report an annular beam confocal laser-induced fluorescence (LIF) configuration, which allows for high spatial resolution measurements of plasma properties in plasma setups and sources with limited optical access. The proposed LIF configuration utilizes the annular laser beam generated by a pair of diffractive axicons. The LIF signal is collected along the main optical axis within the ring region. It is shown experimentally that at a focal distance of 300 mm, a spatial resolution of ∼5.3 mm can be achieved. Using geometric optics estimations, we showed that ∼1 mm resolution at the same focal distance could potentially be achieved by modifying laser beam parameters. This approaches the localization accuracy of conventional LIF collection methods (with crossing laser beam injection and fluorescence collection optical paths). Measurements of the ion velocity distribution function in an argon plasma using both the confocal LIF with an annular laser beam and conventional LIF demonstrate a satisfactory agreement. The proposed LIF setup has potential applications for diagnostics in various plasma processing equipment and plasma sources, such as hollow cathodes, microplasmas, electric propulsion, etc. [ABSTRACT FROM AUTHOR]

Lab-based experimental and computational methods were used to study the atmospheric degradation of two promising "green" solvents: pinacolone, (CH3)3 CC(O)CH3 , and methyl pivalate, (CH3)3 CC(O)OCH3. Pulsed laser photolysis coupled to pulsed laser-induced fluorescence was used to determine absolute rate coefficients (in 10 -12 cm 3 molec. -1 s -1) of k1 (297 K) = (1.2 ± 0.2) for OH + (CH3)3 CC(O)CH3 (Reaction R1) and k2 (297 K) = (1.3 ± 0.2) for OH + (CH3)3 CC(O)OCH3 (Reaction R2), in good agreement with one previous experimental study. Rate coefficients for both reactions were found to increase at elevated temperature, with k1(T) adequately described by k1 (297–485 K) = 2.1 × 10 -12 exp(-200/T) cm 3 molec. -1 s -1. k2(T) exhibited more complex behaviour, with a local minimum at around 300 K. In the course of this work, k3 (295–450 K) was obtained for the well-characterised reaction OH + C2H5OH (ethanol; Reaction R3), in satisfactory agreement with the evaluated literature. UV–Vis spectroscopy experiments and computational calculations were used to explore cross-sections for (CH3)3 CC(O)CH3 photolysis (Reaction R4), while (CH3)3 CC(O)OCH3 showed no sign of absorption over the wavelengths of interest. Absorption cross-sections for (CH3)3 CC(O)CH3 , σ4(λ) , in the actinic region were larger, and the maximum was red-shifted compared to estimates (methyl ethyl ketone (MEK) values) used in current state-of-science models. As a consequence, we note that photolysis (Reaction R4) is likely the dominant pathway for removal of (CH3)3 CC(O)CH3 from the troposphere. Nonetheless, large uncertainties remain as quantum yields φ4(λ) remain unmeasured. Lifetime estimates based upon Reactions (R1) and (R4) span the range 2–9 d and are consequently associated with a poorly constrained estimated photochemical ozone creation potential (POCP E). In accord with previous studies, (CH3)3 CC(O)OCH3 did not absorb in the actinic region, allowing for straightforward calculation of an atmospheric lifetime of ≈ 9 d and a small POCP E≈ 11. [ABSTRACT FROM AUTHOR]

Within this work, the causes of collapses and damages occurred in masonry artefacts have been evaluated to properly identify suitable monitoring and restoration methods. In this regard, a comprehensive literature review has been performed. Based on the results, moisture has been found to be a critical parameter, that affects the structural health of masonry artefacts. Various non-destructive methods were employed to measure moisture and monitor the materials involved, including Infrared Thermography, Electrical Resistivity Tomography, Ground Penetrating Radar, Laser Scanning and Digital Terrestrial Photogrammetry, Global Navigation Satellite Systems, Unilateral Nuclear Magnetic Resonance, Laser-Induced Fluorescence technique, Acoustic Imaging and Acoustic Tomography, Geographic Information System, on-site survey process and computer modeling of the structure with specific FEM software. Finally, the implementation of tie-beams, Fiber Reinforced Polymers layers, ventilation, draining systems, and high-quality materials are proposed as solutions for controlling the moisture effect and retrofitting. [ABSTRACT FROM AUTHOR]

Olive oils are more expensive compared with other vegetable oils. Therefore, adulterating such expensive oil is prevalent. The traditional methods for olive oil adulteration detection are complex and require pre-analysis sample preparation. Therefore, simple and precise alternative techniques are required. In the present study, the Laser-induced fluorescence (LIF) technique was implemented for detecting alteration and adulteration of olive oil mixed with sunflower or corn oil based on the post-heating emission characteristics. Diode-pumped solid-state laser (DPSS, λ = 405 nm) was employed for excitation and the fluorescence emission was detected via an optical fiber connected to a compact spectrometer. The obtained results revealed alterations in the recorded chlorophyll peak intensity due to olive oil heating and adulteration. The correlation of the experimental measurements was evaluated via partial least-squares regression (PLSR) with an R-squared value of 0.95. Moreover, the system performance was evaluated using receiver operating characteristics (ROC) with a maximum sensitivity of 93%. [ABSTRACT FROM AUTHOR]

The complex formation of Eu(III) and Cm(III) was studied via tetradentate, hexadentate, and octadentate coordinating ligands of the aminopolycarboxylate family, viz., nitrilotriacetate (NTA3−), ethylenediaminetetraacetate (EDTA4−), and ethylene glycol-bis(2-aminoethyl ether)-N,N,N′,N′-tetraacetate (EGTA4−), respectively. Based on the complexones' pKa values obtained from 1H nuclear magnetic resonance (NMR) spectroscopic pH titration, complex formation constants were determined by means of the parallel-factor-analysis-assisted evaluation of Eu(III) and Cm(III) time-resolved laser-induced fluorescence spectroscopy (TRLFS). This was complemented by isothermal titration calorimetry (ITC), providing the enthalpy and entropy of the complex formation. This allowed us to obtain genuine species along with their molecular structures and corresponding reliable thermodynamic data. The three investigated complexones formed 1:1 complexes with both Eu(III) and Cm(III). Besides the established Eu(III)–NTA 1:1 and 1:2 complexes, we observed, for the first time, the existence of a Eu(III)–NTA 2:2 complex of millimolar metal and ligand concentrations. Demonstrated for thermodynamic studies on Eu(III) and Cm(III) interaction with complexones, the utilized approach is commonly applicable to many other metal–ligand systems, even to high-affinity ligands. [ABSTRACT FROM AUTHOR]

Laser Induced Fluorescence (LIF) spectroscopy has been widely applied to fieldwork measurements of OH radicals, and of HO2, following conversion to OH, over a wide variety of conditions, on different platforms, and in simulation chambers. Conventional calibration of HOx (OH + HO2) instruments has mainly relied on a single method, generating known concentrations of HOx from H2O vapour photolysis in a flow of zero air impinging just outside the sample inlet (SHOx = CHOx.[HOx], where SHOx is the observed signal and CHOx is the calibration factor). The FAGE (Fluorescence Assay by Gaseous Expansion) apparatus designed for HOx measurements in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) at the University of Leeds has been used to examine the sensitivity of FAGE to external gas temperatures (266 -- 348 K). The conventional calibration methods give the temperature dependence of COH (relative to the value at 293 K) of (0.0059 ± 0.0015) K-1 and CHO2 of (0.014 ± 0.013) K-1. Errors are 2σ. COH was also determined by observing the decay of hydrocarbons (typically cyclohexane) caused by OH reactions giving COH (again, relative to the value at 293 K) of (0.0038 ± 0.0007) K-1. Additionally, CHO2 was determined based on the second order kinetics of HO2 recombination with the temperature dependence of CHO2, relative to 293 K being (0.0064 ± 0.0034) K-1. The temperature dependence of CHOx depends on HOx number density, quenching, relative population of the probed OH rotational level and HOx transmission from inlet to detection axis. The first three terms can be calculated and, in combination with the measured values of CHOx, show that HOx transmission increases with temperature. Comparisons with other instruments and the implications of this work are discussed. [ABSTRACT FROM AUTHOR]

Background: Oxides of lanthanide rare-earth elements show great potential in the fields of imaging and therapeutics due to their unique electrical, optical and magnetic properties. Oxides of lanthanide-based nanoparticles enable high-resolution imaging of biological tissues by magnetic resonance imaging (MRI), computed tomography (CT) imaging, and fluorescence imaging. In addition, they can be used to detect, treat, and regulate diseases by fine-tuning their structure and function. It remains challenging to achieve safer, efficient, and more sensitive nanoparticles for clinical applications through the structural design of functional and nanostructured rare-earth materials. Result: In this study, we designed a mesoporous silica-coated core–shell structure of europium oxide ions to obtain near-infrared two-photon excitation fluorescence while maintaining high contrast and resolution in MRI. We designed enhanced 800 nm photoexcitation nanostructures, which were simulated by the finite-difference method (FDM) and finite-difference time-domain method (FDTD). The nanoparticle structure, two-photon absorption, up-conversion fluorescence, magnetic properties, cytotoxicity, and MRI were investigated in vivo and in vitro. The nanoparticle has an extremely strong optical fluorescence response and multiple excitation peaks in the visible light band under the 405 nm continuous-wave laser excitation. The nanoparticle was found to possess typical optical nonlinearity induced by two-photon absorption by ultrafast laser Z-scan technique. Two-photon excited fluorescence of visible red light at wavelengths of 615 nm and 701 nm, respectively, under excitation of the more biocompatible near-infrared (pulsed laser at 800 nm). In an in vitro MRI study, a T1 relaxation rate of 6.24 mM−1 s−1 was observed. MRI in vivo showed that the nanoparticles could significantly enhance the signal intensity in liver tissue. Conclusions: These results suggest that this sample has applied potential in visible light fluorescence imaging and MRI. [ABSTRACT FROM AUTHOR]

A novel frictional drag reducing self-polishing copolymer (FDR-SPC) was first developed by the authors. The FDR-SPC is a special derivative of an SPC that was designed to achieve skin frictional drag reduction in turbulent water flow by releasing polyethylene glycol (PEG) into water through a hydrolysis reaction. Thus, the FDR-SPC coating acts as a continuous medium accommodating countless, molecular-level polymer injectors. However, direct evidence of such PEG release has not yet been demonstrated. Here, we report the results of in situ PEG concentration measurement based on the planar laser-induced fluorescence (PLIF) method. Polyethylene glycol methacrylate (PEGMA) was probed by the fluorescent functional material dansyl, and the fluorescence intensity from dansyl-PEG was then measured to quantify the concentration in the flow. The near-wall concentration of dansyl-PEG is observed to range from 1 to 2 ppm depending on the flow speed, which corroborates the existence of a drag reducing function for the FDR-SPC. In the concurrent measurement of skin friction, the present FDR-SPC specimen exhibited a skin friction reduction ratio of 9.49% at the freestream flow speed U = 5 m / s . In the comparative experiment of dansyl-PEGMA solution injection, the skin friction was found to decrease by 11.9%, which is in reasonable accordance with that for the FDR-SPC. [ABSTRACT FROM AUTHOR]

A newly developed analytical strategy was applied to profile the total serum N-glycome of 64 colorectal cancer (CRC) patients before and after surgical intervention. In this cohort, it was previously found that serum N-glycome alterations in CRC were associated with patient survival. Here, fluorescent labeling of serum N-glycans was applied using procainamide and followed by sialic acid derivatization specific for α2,6- and α2,3-linkage types via ethyl esterification and amidation, respectively. This strategy allowed efficient separation of specific positional isomers on reversed-phase liquid chromatography–fluorescence detection–mass spectrometry (RPLC-FD-MS) and complemented the previous glycomics data based on matrix-assisted laser desorption/ionization (MALDI)-MS that did not include such separations. The results from comparing pre-operative CRC to post-operative samples were in agreement with studies that identified a decrease in di-antennary structures with core fucosylation and an increase in sialylated tri- and tetra-antennary N-glycans in CRC patient sera. Pre-operative abundances of N-glycans showed good performance for the classification of adenocarcinoma and led to the revisit of the previous MALDI-MS dataset with regard to histological and clinical data. This strategy has the potential to monitor patient profiles before, during, and after clinical events such as treatment, therapy, or surgery and should also be further explored. [ABSTRACT FROM AUTHOR]

Laser ablation multi‐collector mass spectrometry (LA‐MC‐ICP‐MS) has emerged as the technique of choice for in situ measurements of Sr isotopes in geological minerals. However, the method poses analytical challenges and there is no widely adopted standardised approach to collecting these data or correcting the numerous potential isobaric inferences. Here, we outline practical analytical procedures and data reduction strategies to help establish a consistent framework for collecting and correcting Sr isotope measurements in geological materials by LA‐MC‐ICP‐MS. We characterise a new set of plagioclase reference materials, which are available for distribution to the community, and present a new data reduction scheme for the Iolite software package to correct isobaric interferences for different materials and analytical conditions. Our tests show that a combination of Kr‐baseline subtraction, Rb‐peak‐stripping using βRb derived from a bracketing glass reference material, and a CaCa or CaAr correction for plagioclase and CaCa or CaAr + REE2+ correction for rock glasses, yields the most accurate and precise 87Sr/86Sr measurements for these materials. Using the analytical and correction procedures outlined herein, spot analyses using a beam diameter of 100 μm or rastering with a 50–65 μm diameter beam can readily achieve < 100 ppm 2SE repeatability ("internal") precision for 87Sr/86Sr measurements for materials with < 1000 μg g‐1 Sr. [ABSTRACT FROM AUTHOR]

The plasma in contact with liquids has led to various novel applications such as plasma biomedicine, material synthesis, and so on. However, the phenomenon of evaporation under plasma treatment and its impact on plasma–liquid interactions has a limited understanding. In this study, the spatially and temporally resolved behavior of water vapor production and its induced influences on plasma properties and gaseous chemistry were studied in detail in an atmospheric pressure pin‐to‐water pulsed He discharge. Diagnostic methods such as laser‐induced fluorescence (LIF) and high‐resolution optical emission spectroscopy (OES) were applied to determine the water vapor and OH radical densities, as well as key plasma parameters such as the gas temperature and electron density. It shows that the physicochemical properties of plasma vary among different discharge regions due to evaporation behavior stimulated during the pulsed discharge‐on phase. In addition, using simulation based on the experimental data, the mechanisms of how water vapor affects the observed spatiotemporal behaviors of OH radicals in different discharge regions are understood. Compared to the pin‐anode and liquid‐cathode sheath regions, proper electron parameters such as density and temperature, as well as water vapor density in the plasma‐positive column, significantly enhance the production of reactive OH radical through the dominant path of electron‐stimulated H2O dissociation. However, higher levels of electron parameters in the intense discharge region near the positive‐pin boundary enhance OH dissociation and finally result in the hollow distribution of OH density. From the global kinetic plasma simulation, the production of reactive hydroxide species playing key roles in plasma medicine treatments, such as O, H, HO2, H2O2, and hydrated ions including H+(H2O)4 and H+(H2O)5, are promoted noticeably as a result of the enhanced water evaporation process. [ABSTRACT FROM AUTHOR]

The development of laser-induced incandescence (LII) approach for characterizing the production of high-purity non-carbonaceous metal oxides produced in flame synthesis systems is in progress. This work aims to prove the feasibility of LII measurement for titanium dioxide (TiO 2 ). In previous works, laser-induced emission (LIE) was investigated for flame-synthetized TiO 2 particles. However, the presence of carbon materials was detected. As this calls into question the nature of the signal, we consider in this work LIE of high-purity engineered TiO 2 nanoparticles to circumvent the carbon issue. Specifically, we investigate the spectral and temporal laser-induced emissions of pure TiO 2 nanoparticles dispersed in a non-reactive environment. In parallel, LIE from carbon black is examined to validate the strategy and highlight differences between carbon black and TiO 2 . The TiO 2 results indicate that depending on the laser fluence, different prompt interferences appear. The literature suggests that these non-thermal emissions are likely to be from fluorescence or phase-selective laser-induced breakdown spectroscopy, both characterized by a short lifetime. To avoid these parasitic signals, measurement acquisition time is delayed. A spectral red-shift is observed with time as a result of decreasing particle temperature. This proves the LII nature of delayed emission from pure TiO 2 , which is confirmed by the LII-like nature of the temporal signals. [ABSTRACT FROM AUTHOR]

Incomplete evaporation of liquid fuel films inside the combustion chamber is a major source of soot and particulate emissions in internal combustion engines. In this study, quantitative imaging of liquid fuel films on the cylinder wall is performed by laser-induced fluorescence (LIF) in a single cylinder engine with optical access to the cylinder liner. A four-component surrogate fuel mixed with 0.5% anisole as the fluorescent tracer was directly injected in a single injection into the motored engine. Fuel impinging on the cylinder wall is excited at 266 nm at kHz repetition rates and imaged by a high-speed camera coupled with an image intensifier. Simultaneously, lubricating oil doped with 0.01 mmol/l pyrromethene 567 is excited at 532 nm and imaged with a second camera. The fuel film thickness on the cylinder wall is compared for two different injections timings, 285 and 240°CA before top-dead center. The initial fuel film thickness is similar for both, but evaporation occurs faster for the later injection, such that the film thickness is similar at the time the piston rings reach the fuel films. When the rings scrape the fuel off the wall, it accumulates on top of the first piston ring and is partly transported downwards to the second and third ring. In the simultaneous oil image, washout of lubricating oil is seen. [ABSTRACT FROM AUTHOR]

This work characterizes the compressibility dynamics in turbulent fast flames for a range of turbulent flame speeds. These turbulent fast flames experience increased effects of compressibility through the formation of strong shocks and may develop a runaway acceleration combined with a pressure buildup that leads to turbulence induced deflagration-to-detonation transition (tDDT). Simultaneous high-speed particle image velocimetry, OH* chemiluminescence, schlieren, and pressure measurements are used to examine the reacting flow field and flame dynamics. We examine flames with turbulent flame speeds ranging from 100 to 600 m/s. At lower turbulent flame speeds, the flame is not able to produce favorable background conditions for deflagration-to-detonation transition (DDT) onset, and thus flame compressibility and turbulence amplification are less dominant, resulting in a weaker acoustic coupling between the flame and compressed region. As the turbulent burning velocities exceed the Chapman–Jouguet deflagration speed, favorable background conditions are produced, as we observe flame-generated shocks and flame-generated turbulence with higher turbulent velocities and larger turbulent scales. At this regime, the flame is categorized to be at the runaway transition regime that leads to tDDT. [ABSTRACT FROM AUTHOR]

In this article, the authors present an experimental investigation of the thermochemical relaxation regions downstream of symmetric Mach reflections generated in Mach 8.5 flows with stagnation enthalpies from 7 to 10 MJ/kg. The experiment was performed in the Hypervelocity Expansion Tunnel at the National Aerothermochemistry and Hypersonics Laboratory of Texas A&M University. The investigation focused on studying the nitric oxide morphology in the vicinity of a strong normal shock wave and shear layers. Experimental planar laser-induced fluorescence measurements at 250 kHz repetition rate with a quasi-simultaneous natural emission photography demonstrate a sufficient rejection of natural emission and reveal intricate flow structures in the shock vicinity. Steady computational fluid dynamics (CFD) flow solutions obtained with the US3D software were used to simulate laser-induced fluorescence signal levels for quantitative comparison against the experimentally acquired data. The investigation accomplished four objectives: complex flowfield visualization in the vicinity of the Mach stem with 4 μs temporal resolution, evaluation of the level of high-temperature chemistry effects introduced to the freestream by the expansion tunnel, both qualitative and quantitative CFD simulation validation, and cross-checking or introduction of fundamental properties of nitric oxide laser-induced fluorescence including absorption cross section for vibrationally excited states of nitric oxide and a collisional quenching cross section of nitric oxide by atomic nitrogen. [ABSTRACT FROM AUTHOR]

Fuel injection and distribution play an important role in the formation and migration of hot streaks in gas turbine combustors and determine the exit temperature uniformity especially for modern low emission combustors that have little or no primary and dilution air flows. To better understand the underlying mechanism of the formation and evolution of hot streak, both experimental and numerical investigations have been carried out in a centrally staged tri-sector model combustor. Flow, spray, and flame have been investigated by particle image velocimetry and planar laser-induced fluorescence. The exit temperature distributions are also measured and analyzed with both laser diagnostics and simulation results. The results show that increasing fuel-to-air ratio (FAR) or fuel staging ratio enhances the formation of high temperature hot streak and leads to high overall temperature distribution factor and radial temperature distribution factor at the combustor exit. It is found that the high temperature zone is formed through the non-premixed combustion of pilot stage and resides in the shear layer of pilot stage and primary circulation zone. Increasing FAR at low power conditions and increasing SR at high power conditions promote the formation of a large hot streak area through pilot stage combustion and thus deteriorate the uniformity of temperature distribution at the combustor exit. [ABSTRACT FROM AUTHOR]

Results are presented of the experimental study of the dynamic characteristics of the laser fragmentation/laser-induced fluorescence (LF/LIF) process in nitrobenzene and para-nitrotoluene vapors under synchronized two-pulse laser irradiation. The efficiency of the LF/LIF method can be increased by several times if the time delay between the pulses of fragmentation (248.4 nm) and excitation (247.87 nm) of NO fragments is in the range 20–40 ns. [ABSTRACT FROM AUTHOR]

Achieving full premixing and complete evaporation in lean prevaporized premixed combustors is challenging as it depends on the spray injector characteristics, prevaporisation strategy, and flow conditions. This article experimentally explores the stability and structure of a turbulent swirling n -heptane spray flame under various degrees of prevaporization. The results show that preheating the air to 343 K and 393 K has little effect on the lean blow-off velocity, while recessing the fuel injection significantly decreases the lean stability limit. To correlate these limits, various attempts to define a Damköhler number were made, but unlike previous studies with no prevaporisation, the difficulty in defining laminar flame speed in the present case does not allow a single correlation to work for all degrees of prevaporization. Four stable cases that differ in equivalence ratio, air preheat temperature, and fuel injection recess are investigated using one-dimensional PDA, OH* chemiluminescence and CH 2 O-planar laser-induced fluorescence (PLIF). Cases without fuel injection recess or air preheat exhibit a conical-shaped heat release zone near the shear layers. Preheating the air to 393 K reduced the Sauter mean diameter, increased prevaporization, and enabled a second heat release zone downstream of the fuel injection. Recessing the fuel injection by 25 mm reduced droplet velocities and led to a semi-spherical instead of a conical heat release zone. The CH 2 O-PLIF signal without injection recess was high along the central axis and its distribution resembled that observed for spray jet flames. In contrast, with recessed spray injection, CH 2 O was mainly found outside the central recirculation zone and only appeared inside during lean blow-off; similar to previous work with premixed flames. These findings show that different methods of prevaporization, which only differ by subtle changes in droplet characteristics, strongly impact flame stability. The present data can be used for turbulent flame modelling focusing on sprays and finite-rate kinetics. [ABSTRACT FROM AUTHOR]

In recent years, conditioned particle image velocimetry (CPIV) has attracted much attention for flame front extraction. It is an economical and straightforward technique because the flame front can be obtained simply from Mie-scattering images. In the current work, Mie-scattering and hydroxyl planar laser-induced fluorescence (OH-PLIF) measurements were taken simultaneously to study the applicability of CPIV under conditions with varying equivalence ratios, and the reliable working range of the CPIV method and the source of bias were clarified quantitatively. The premixed dimethyl ether (DME)/air flames stabilized on a two-dimensional bluff body were tested. It is found that the accuracy of the CPIV method worsens as the equivalence ratio decreases. The bias of CPIV is supposed to be related to the flame structure and aerodynamics. The extraction deviation in the upstream region for the stable flames is more significant than that in the downstream area due to the intensified interaction between the shear layer and flame near the bluff body. However, for the flames approaching the lean blow-off (LBO), the bias in the upstream part is smaller than that in the downstream area, which is related to the "back-support" of the hot recirculation zone (RZ). In addition, the difference between the results obtained by CPIV and OH-PLIF is usually the preheat layer of flame and concave-wrinkled location of OH-PLIF filled with CH2O radicals, especially under conditions close to the LBO, which can be used to estimate the spatial distribution of CH2O. [ABSTRACT FROM AUTHOR]

Measurement of liquid temperature in single or multiphase systems is a topic of high interest for fluid mechanics in order to have a better understanding of heat exchange and phase changes in many physical problems as well as for improving industrial processes. Laser-induced fluorescence thermometry is a powerful tool to investigate liquid temperature in permanent or transient conditions due to the fast fluorescence response of the technique. By diluting a fluorescent dye sensible to temperature in a liquid and after laser excitation of this solution at a specific and known wavelength, fluorescence is emitted by the dye almost instantaneously and could be isolated as a function of the temperature of the dye thanks to a ratiometric method. In this work, two fluoresceins commonly used as fluorescent dyes were spectrally studied in water at excitation wavelengths of 473 and 532 nm. Fluorescein Disodium and Fluorescein 27 were chosen as they present positive and high-temperature sensitivities as well as low toxicity. Also, systematic calibrations between − 10 and 80 °C under liquid state are reported for aqueous solutions. Results are compared to available data from the literature, and temperature sensitivity is discussed in relation with pH, excitation wavelength and temperature range in order to extend the knowledge on the topic and for clarification regarding some confusion found in the literature. Finally, we proposed an improvement of a method analyzing the sensitivity as a function of the wavelength for a better approach in the process of selecting spectral bands for LIF-T applications. Following this method, two examples of practical application are given for dye and spectral band selection depending on the constraints of experimental measurement. [ABSTRACT FROM AUTHOR]

Diagnostics based on laser-induced quenching (LIQ) and laser-induced fluorescence (LIF) is planned to be used at the T-15MD tokamak for local measurements of the atomic hydrogen density na(HI) in divertor plasma. Both physical and technical aspects of the diagnostic system development are considered. For plasma diagnostic, it is proposed to use the time-modulated thulium fiber laser with the wavelength of 1875 nm and peak power of 5 W. Two light collection systems will be used for observing the signals. The intravacuum and "atmospheric" systems will be used for performing measurements in the region of the separatrix strike-point and in the rest of the divertor region, respectively. Using the modified collisional-radiative model, the applicability of the diagnostics was physically justified by the calculations of the expected quenching and fluorescence signals, as well as the background radiation at the wavelengths of hydrogen lines. In the calculations, the 2D-distributions of plasma parameters are used obtained by the SOLPS 4.3 code for tokamak operation scenarios with and without additional plasma heating. When using the LIQ method, the expected errors in measuring the na(HI) density are within 10% for most points and do not exceed 25% for all scenarios of tokamak operation considered, provided that the signals are averaged over 10 ms. The LIF method makes it possible to carry out measurements with relative errors up to 50%. [ABSTRACT FROM AUTHOR]

Underutilized fruits like kadam are bio-reserves of numerous biochemical and minerals and have the potential to be used as food alternatives and supplements to fulfill the needs of malnourished populations. The production of quality fruits needs monitoring throughout the growth and ripening in order to build consumer and industry confidence. The nondestructive optical spectroscopic techniques have immense potential to monitor the growth and ripening indices of the fruits. Hence, this study explores the potential of laser-induced fluorescence and confocal micro Raman spectroscopy for the reliable and cost effective monitoring of growth and ripening of kadam fruits. The analysis of the laser-induced fluorescence measurements reveals that the ripening of the kadam fruits may be monitored by analyzing the fluorescence emission of chlorophyll and carotenoids. The decrease in the intensity of chlorophyll fluorescence accompanied by the increase in the intensity of the carotenoid bands is the characteristic fluorescence signature associated with the ripening of the kadam fruits. Hence, upon the ripening of the fruits, the concentration of chlorophyll decreases considerably with the accumulation of carotenoids. This fact is further complimented by confocal micro Raman measurements, which show that as the fruit ripens, the intensity of carotenoid bands increases dramatically. The observed spectral features may be used by the horticulture scientists and nutritionists to monitor the growth, maturity, and ripening of underutilized fruits like kadam in order to maximize the quality and minimize postharvest losses. [ABSTRACT FROM AUTHOR]

IntroductionPathogenic fungi, such as Plasmopara viticola and Erysiphe necator, severely threaten the annual yield of grapes in both quantity and quality. In contrast to other crop production systems, fungicides are intensively applied in viticulture as a countermeasure. The goal of precision viticulture is to optimize vineyard performance as well as the environmental impact by reducing fungicides and applying different techniques and combined strategies. Therefore, new emerging technologies are required, including non-invasive detection, as well as monitoring and tools for the early and in-field detection of fungal development. MethodsIn this study, we investigated leaves of potted vines (Vitis vinifera cv. ‘Riesling’) and traced the development of the inoculated leaves using our new remote detection system vinoLAS®, which is based on laser-induced fluorescence spectroscopy. We ran a measurement campaign over a period of 17 days.ResultsWe were able to detect a leaf infection with P. viticola, the causal agent of downy mildew, between 5 and 7 days after inoculation. Our results provide evidence for a successful application of laser-based standoff detection in vineyard management in the future. Thus, the vinoLAS system can serve as a model technology for the detection of pathogenic disease symptoms and thus monitoring complete vineyard sites. This allows for early countermeasures with suitable crop protection approaches and selected hot-spot treatments.DiscussionAs P. viticola is considered one of the most damaging fungi in European viticulture, disease mapping via this monitoring tool will help to reduce fungicide applications, and will, therefore, support the implementation of the European Green Deal claims.

The ion velocities within the discharge channel of the 600 W magnetically shielded and unshielded Hall thrusters are measured by the laser-induced fluorescence technique to quantitatively evaluate the erosion of the channel walls. Visual inspection of the magnetically shielded Hall thruster has qualitatively indicated that the discharge channel has been successfully shielded from the bombarding of the plasma, while the erosion occurs in the unshielded counterpart. In addition, the ion velocities along the thruster centerline indicate that the voltage utilization efficiency of MSHT-600 is higher than that of USHT-600 and comparable to the state-of-the-art BHT-600 thruster. Furthermore, measurements performed inside the discharge channel show that the ions deep inside the channel impact the channel walls backward in the shielded thruster, while forward in the unshielded one. Moreover, the plasma potential along the channel walls remains as high as the anode potential in the shielded thruster, while it dramatically decreases in the unshielded one. When accounting for the sheath potential acceleration, the maximum erosion rate of the inner and outer walls of USHT-600 is 1.3 and 3.1 μm/h, respectively, based on the plasma parameters of SPT-100, while the maximum value of the weighted average erosion rate of MSHT-600 is 0.08 and 0.04 μm/h, respectively, for two cases of the ion number density. Compared to the erosion rate of SPT-100, it is qualitatively and quantitatively confirmed that strong shielding of the discharge channel is realized and high performance is maintained in the designed thruster with a magnetically shielded configuration. [ABSTRACT FROM AUTHOR]

Rotationally and fine-structure resolved B ̃ ← X ̃ laser-induced fluorescence (LIF) spectra of alkoxy radicals have been simulated with a "coupled two-states model" [J. Liu, J. Chem. Phys. 148, 124112 (2018)], in which the nearly degenerate X ̃ and à states are considered together. These two electronic states are separated by the "difference potential" and coupled by the spin–orbit (SO) interaction and the Coriolis interaction. Molecular constants determined in fitting the LIF spectra using the coupled two-states model provide quantitative insight into the SO and Coriolis interactions, as well as other intramolecular dynamics, including the pseudo-Jahn–Teller effect. The spectroscopic model also allows semi-quantitative prediction of effective spin-rotation constants using molecular geometry and SO constants, which can be calculated ab initio with considerable accuracy. The dependence of fit values of molecular constants on the size and conformation of alkoxy radicals is discussed. [ABSTRACT FROM AUTHOR]

Time-resolved spontaneous and laser-induced unimolecular fragmentation of perylene cations (C20H12+) has been measured on timescales up to 2 s in a cryogenic electrostatic ion beam storage ring. We elaborate a quantitative model, which includes fragmentation in competition with radiative cooling via both vibrational and electronic (recurrent fluorescence) de-excitation. Excellent agreement with experimental results is found when sequential fragmentation of daughter ions co-stored with the parent perylene ions is included in the model. Based on the comparison of the model to experiment, we constrain the oscillator strength of the D1 → D0 emissive electronic transition in perylene (fRF = 0.055 ± 0.011), as well as the absolute absorption cross section of the D5 ← D0 excitation transition (σabs > 670 Mb). The former transition is responsible for the laser-induced and recurrent fluorescence of perylene, and the latter is the most prominent in the absorption spectrum. The vibrational cooling rate is found to be consistent with the simple harmonic cascade approximation. Quantitative experimental benchmarks of unimolecular processes in polycyclic aromatic hydrocarbon ions like perylene are important for refining astrochemical models. [ABSTRACT FROM AUTHOR]

A semiempirical potential energy curve for the a3Σ+-state of the KRb molecule with only five parameters is reported. The potential is continuous over the entire range of internuclear distances and has the correct long-range attractive dispersion potential from established theory. The potential provides an equally good fit of the laser induced fluorescence Fourier transform spectroscopic data of Pashov et al. [Phys. Rev. A 76, 022511 (2007)] as their multi-parameter potential. The new potential is supported by the good agreement of the well parameters De, Re and the harmonic vibrational constant ωe with combining-rule estimates. The scattering lengths for all six isotopologues are also in excellent agreement with experiment with a 0.2% adjustment within theoretical uncertainty of the leading dispersion coefficient C6. An analysis of the harmonic vibrational constant ωe and the constant ωexe of the potential of Pashov et al. reveals a significant difference to the present potential which turned out to be due to an oscillatory deviation in their potential in the vicinity of the potential minimum. The new potential is, thus, the best available because its simplicity is ideal for further applications. [ABSTRACT FROM AUTHOR]

A new laser-induced fluorescence spectrum was observed in the region of 350 nm–360 nm. The spectrum was observed in the reaction between the CHBrCHBr and OH radicals and in the reaction of CHBrCHBr and CH2CHBr with atomic oxygen O(3P). The spectrum was assigned to the B ̃ − − X ̃ transition of the trans-CHBrCHO (trans-2-bromovinoxy) radical. The B ̃ − − X ̃ electronic transition energy (T0) was 28 542 cm−1, which was 242 cm−1 lower than that of the unsubstituted vinoxy radical (CH2CHO). From an analysis of the laser-induced single vibronic level fluorescence aided by ab initio calculations, some of the vibrational frequencies were assigned to the ground electronic state ν3 (C–O str.) = 1581 cm−1, ν6 (C–C str.) = 1130 cm−1, and ν8 (C–C–O bend.) = 409 cm−1. The fluorescence lifetimes of the excited B ̃ state were 35 ns–75 ns, depending on the excited vibrational modes, implying that predissociation had accelerated as the energy level (v′) increased. [ABSTRACT FROM AUTHOR]

Snapshot multispectral imaging of chemical species in the flame is essential for improved understanding of the combustion process. In this article, we investigate the different configurations of a structured laser sheet-based multispectral imaging approach called the Frequency Recognition Algorithm for Multiple Exposures (FRAME). Using FRAME, a snapshot of Laser-Induced Fluorescence (LIF) of Polycyclic Aromatic Hydrocarbons (PAH) excited by 283.5 nm laser and Laser-Induced Incandescence (LII) of soot particles excited by 532 nm laser are acquired simultaneously on a single FRAME image. A laminar diffusion flame of acetylene produced by a Gülder burner is used for the experiments. The standard FRAME approach is based on creating two spatially modulated laser sheets and arranging them in a cross-patterned configuration (X). However, the effect of using different configurations (angles) of the two laser sheets on the multispectral planar imaging of the flame has not yet been studied. Therefore, we have compared the FRAME approach in four different configurations while keeping the same flame conditions. First, we have compared the relation between laser fluence and LII signals with and without spatial modulation of the 532 nm laser sheet and found that both detections follow the same curve. When comparing the maps of flame species reconstructed from the standard FRAME configuration and other configurations, there are some dissimilarities. These differences are attributed to minor changes in the imaging plane, optical alignment, laser path length, different modulation frequencies of the laser sheet, laser extinction, laser fluence, etc.

Characterizing ionization wave propagation in low temperature plasma jets is critical to predicting production of reactive species and plasma–surface interactions for biomedical applications and surface functionalization. In this paper, results from optical emission and laser induced fluorescence measurements of the ionization wave in a He plasma jet operating in a controlled gas environment are discussed and used for comparison with numerical modeling. The ionization wave was observed using ICCD (Intensified Charge Coupled Device) imaging and characterized by time and spatially resolved electron density measurements using laser-collision-induced fluorescence. The plasma jet was initially characterized using pure He (nominally at 200 Torr), while varying pressure and voltage. When operating in pure He, the ionization wave broadly expands exiting the plasma tube. Increasing the operating pressure reduces the speed and isotropic expansion of the ionization wave. The jet operated with a humid He shroud was also studied. The humid He shroud results in the electron density increasing and having an annular profile due to the lower ionization potential of H2O compared to He and localized photoionization in the mixing region. Numerical modeling highlighted the importance of resonance radiation emitted by excited states of He, photoelectron emission from the quartz tube, and the kinetic behavior of the electrons produced by photoionization ahead of the ionization front. [ABSTRACT FROM AUTHOR]

Electronic spectra for the hypermetallic oxide MgOMg have been observed in the 21 100 cm−1–24 000 cm−1 spectral range using laser induced fluorescence and two-photon resonantly enhanced ionization techniques. Rotationally resolved data confirmed the prediction of a X ̃ 1 Σ g + ground state. The spectrum was highly congested due to the optical activity of a low-frequency bending mode and the presence of three isotopologues with significant natural abundances. Ab initio calculations predict a bent equilibrium structure for the à 1B2 upper state, consistent with the observation of a long progression of the bending vibration mode. However, the vibrational intervals were not reproduced by the theoretical calculations. In part, this discrepancy is attributed to strong vibronic coupling between multiple electronically excited states. Two-photon ionization measurements were used to determine an ionization energy of 6.5800(25) eV. [ABSTRACT FROM AUTHOR]

In this Tutorial, various methods of optical spectroscopy representing certain interest for magnetron discharge characterization are overviewed. The main principles, the implementation examples, and the selected results are given for each technique, accompanied by short discussions and suggestions for further reading. Both passive and active optical methods are covered, including optical absorption and laser-based techniques. The advantages and drawbacks of each diagnostic approach are critically analyzed. Special attention is devoted to the techniques extensively used by the authors in their own work, such as line ratio methods, absorption spectroscopy, interferometry, and laser-induced fluorescence. [ABSTRACT FROM AUTHOR]