Search

[Display omitted] • A novel approach for quantifying HSAD's mass transfer was proposed. • In the mixing process, feedstock tended to accumulate around the 1st stage impeller. • HSAD's mixing homogeneity remained unachieved after 4 h. • Prolonging the mixing time could not significantly improve the mass transfer. • The novel measuring approach visualized the mass transfer in HSAD. High solid anaerobic digestion (HSAD) is a promising technology for the treatment of organic waste. Mixing process in HSAD is quite difficult with long mixing time, poor homogenization, significant short-circuiting and stagnant zones. However, the mass transfer in mixing process in HSAD has not been visualized due to the lack of a proper method. In this study, a novel approach for experimentally quantifying the mass transfer in HSAD's mixing process was proposed in a mixing tank equipped with multistage impellers by means of the Laser Induced Fluorescence (LIF) technique. Flow field was investigated for better illustrating the mass transfer, thus Particle Image Velocimetry (PIV) and Computational Fluid Dynamics (CFD) technique were conducted for flow field measurement. The obtained results revealed that the feedstock tended to accumulate around the impeller in the HSAD system, especially near the 1st stage. The tracer diffused rapidly around the 1st impeller in t = 10 s, but the diffusion around the 2nd impeller was quite tough even after 4 h 08 min 23 s. And prolonging mixing time could not significantly improve the flow pattern along with the mixing. In this study, new insight was thrown into the visualization of the mass transfer in mixing process within a HSAD reactor. The visualization of mass transfer in the mixing process in HSAD could offer reference information to the study of the mixing process of HSAD even in full-scale. [ABSTRACT FROM AUTHOR]

Nowadays scientific study of Cultural Heritage accompanies most of the time historical artistic evaluation and an assessment of the conservation state by humanistic experts and restorers. Several laboratory methods with high sensitivity are well established (ICP-MS, FTIR,...), and many methods for in situ rough characterization of large surface are widely diffused (thermovision, UV photography,...), in addition to instrumentation for punctual analysis to be applied also in field (XRF, colorimetry,...). However, the request for systems that can provide rapid detailed characterization on large surface in any storage conditions is still a hot topic. This is combined with the ever-increasing demand for digital material for documentation, fruition and study. Laser-based systems, and in particular Laser Induced Fluorescence (LIF), Laser Induced Breakdown Spectroscopy and Raman spectroscopy, due to the characteristics of these sources and the detectors to which they can be coupled, respond well to these needs. The TECFIS-DIM (Diagnostic and Metrology) Laboratory of the ENEA center of Frascati (Rome, Italy) in the last decade has put an effort to develop more and more compact and efficient laser systems for in situ material characterization on cultural heritage surfaces. Here two prototypal LIF systems have been used to characterize marble surfaces treated with ancient and modern materials and a rapid recognition and mapping method has been developed and tested thanks to the individuation of discriminant spectral features. Results are reported on test samples created in lab with known substances and in situ on real artworks. [ABSTRACT FROM AUTHOR]

Abstract A multiwavelength laser induced fluorescence (LIF) LIDAR system, which can be employed around the clock for detecting oil spills in a marine environment, has been developed. The system incorporates a pulsed Nd: YAG laser, Nd: YAG laser amplifier and two KD*P crystals for generating 266 nm, 355 nm and 532 nm. Additionally, the LIF LIDAR system incorporates a nitrogen laser pumped dye laser system operating at 428 nm (Stilbene 420 dye), a Newtonian telescope, motorized monochromator, a photomultiplier detection system and a data acquisition system. Fluorescence intensity measurements collected from fresh and weathered oil samples using the LIF LIDAR system are presented. Strong fluorescence spectra were detected from refined and crude oils when excited with 266 nm. Finally, a brief description for the principle components algorithm used for identifying and classifying unknown oil samples is provided. [ABSTRACT FROM AUTHOR]

Oxygen present in the ambient gas medium may affect both laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) emission through a reduction of emission intensity and persistence. In this study, an evaluation is made on the role of oxygen in the ambient environment under atmospheric pressure conditions in LIBS and laser ablation (LA)-LIF emission. To generate plasmas, 1064 nm, 10 ns pulses were focused on an aluminum alloy sample. LIF was performed by frequency scanning a CW laser over the 396.15 nm (3s 2 4s 2 S 1/2 → 3s 2 3p 2 P° 3/2 ) Al I transition. Time-resolved emission and fluorescence signals were recorded to evaluate the variation in emission intensity caused by the presence of oxygen. The oxygen partial pressure ( p o ) in the atmospheric pressure environment using N 2 as the makeup gas was varied from 0 to 400 Torr O 2 . 2D–fluorescence spectroscopy images were obtained for various oxygen concentrations for simultaneous evaluation of the emission and excitation spectral features. Results showed that the presence of oxygen in the ambient environment reduces the persistence of the LIBS and LIF emission through an oxidation process that depletes the density of atomic species within the resulting laser-produced plasma (LPP) plume. [ABSTRACT FROM AUTHOR]

Chlorophyll fluorescence measurements have been widely applied as non-destructive methods to study the photosynthetic efficiency of plants, under control or stress conditions. Compared to most protocols of pulse amplitude modulation (PAM) fluorometry, laser induced chlorophyll fluorescence (LIF) has the advantages of not requiring pulses to be delivered at close range, allowing the remote analysis of a great number of individual plants in a short period of time. Such analyses are extremely useful, for instance, when doing large phenotyping screens of Arabidopsis thaliana mutants or ecotypes. Water deficit is a major abiotic stress compromising plant growth and productivity. Arabidopsis has been adopted as the main model organism in plant sciences and it has been widely used in plant stress studies. However, reports on the applications of LIF techniques to this model plant are scarce. Here we report the use of LIF to investigate changes in chlorophyll a (Chl a ) fluorescence signature under progressive drought of potted Arabidopsis plants (Slow Stress) and under fast dehydration of detached leaves (Fast Stress). Results show that the two dehydration methods cause distinct modifications on the red/far-red Chl a fluorescence ratio ( F 690 / F 730 ) and on the wavelengths of Chl a fluorescence maxima. These differences are likely related to distinct changes in water content, photosynthetic pigments, anthocyanins, fatty acid composition and other metabolic adaptations, which are differently regulated in Slow and Fast Stress. Of particular interest are Chl a emission fluorescence changes, which take place under progressive drought, before a substantial decrease in leaf water content. Additionally, no differences were found on LIF emission spectra between fully expanded and young leaves. However, the choice of leaf surface influenced fluorescence emission, with the abaxial surface displaying lower fluorescence and higher F 690 / F 730 ratios. Results suggest that LIF is a fast and non-destructive tool suitable for high-throughput phenotyping of Arabidopsis under water deficit. [ABSTRACT FROM AUTHOR]

Confined impinging jet reactors (CIJMs) are very efficient mixing devices. Due to the generation of high turbulent dissipation and, thus, intensive mixing of two colliding liquid flows CIJMs are widely used in laboratory applications. Besides low construction effort, these mixers enable a sensitive control of fast reactions, an efficient initial homogenization of educts and consequently a rapid build-up of supersaturation as the driving force for precipitation and crystallization. The understanding of fluid mechanics and mixing in those CIJMs is of fundamental interest for a proper description of parallel or consecutive processes. Therefore, this paper gives an insight into characteristic procedures, with the main focus on the turbulent flow regime in a T- and Y-CIJM. Experimental investigation on the local mixing behavior of liquid-phase impinging jets in static mixers is carried out by using an optical laser induced fluorescence (LIF) and particle image velocimetry (PIV) setup. In order to avoid optical measurement errors due to the cylindrical geometry, a refractive index correction of fluids with the ionic additive NH 4 SCN has been carried out. Due to poor information in literature, important properties of the corrected aqueous solution are listed. Another main focus of this work lies in the mathematical modeling of the flow field based on computational fluid dynamics (CFD) methods. The transient hybrid Detached Eddy-SST- k – ω turbulence approach is introduced as a computational cost-efficient highly accurate method to calculate flow conditions in turbulent CIJMs. LIF and PIV as well as pressure drop measurements provide a wide set of data that serve to validate CFD simulations. [ABSTRACT FROM AUTHOR]

Studies have been performed to evaluate a direct laser induced fluorescence (LIF) technique for measurements of atmospheric sulfur dioxide (SO2). The technique is novel in that it uses a nontunable laser source that is spectrally coincident with absorption of the SO2 molecule near 223 nm that allows sensitive measurements at environmentally relevant concentrations. In this report, the spectral characteristics and analytical capabilities of the nontunable LIF approach have been evaluated and preliminary measurements of ambient SO2 are reported. The current limit of detection is 0.5 ppb and compares well to other analytical spectroscopy methods used for atmospheric measurements of SO2. The results indicate strong feasibility for the nontunable LIF approach for SO2 measurements and suggest ways for method improvement. [ABSTRACT FROM PUBLISHER]

[Display omitted] • Efficient and sensitive FITC labeling process was optimized using DoE approach. • The optimized labeling process could be easily implemented for pharmaceuticals. • DoE combined with multivariate statistical modeling was used to optimize the process. • Variance component analysis was integrated to DoE to estimate process variability. Fluorescence, especially laser induced fluorescence (LIF), is a powerful detection technique thanks to its specificity and high sensitivity. The use of fluorescence detection hyphenated to separation technique often requires the labeling of analytes with suitable fluorescent dye, such as FITC for the labeling of molecules presenting amino groups. Nevertheless, the labeling of analytes could be a tedious, time consuming and a non-robust step of the analytical workflow. In this context, the objective of the present work was to propose a robust and reliable FITC labeling process. Primary and secondary amino compounds (i.e. synthetic cathinones) were selected as model compounds because they are representative of a large proportion of pharmaceutical small molecules. Based on prior knowledge, DoE combined with multivariate statistical modeling was performed to optimize the process. Reaction time and pH of reaction buffer were highlighted as the most critical parameters to control the process. The study showed also the benefit of short reaction time to maximize the labeling efficiency. Indeed, optimal condition was defined as reaction time of 32 min with ratio between FITC and analytes of 40.4 and the buffer reaction pH of 9.7. In addition, variance component analysis was integrated to the DoE to estimate the variability of process and to evaluate its applicability for quantitative purpose. These chemometric approaches helped to develop an efficient labeling process able to reach high sensitivity for CE-LIF analysis (i.e. 10 nM) with good precision (i.e. intermediate precision values lower or close to 5 %). [ABSTRACT FROM AUTHOR]