Obtain Fluorescence Spectra Research Articles

Effect of AlF3 and KF addition on the structure and luminescent properties of P2O5 – K2O – Nb2O5 – Bi2O3 glasses doped with Eu3+

Based on the developed phosphate glasses P2O5–K2O–Bi2O3–Nb2O5 doped with Eu3+, the influence of AlF3 and KF on the structural and luminescent properties was investigated. For this purpose, three series of glasses containing from 5 to 15 mol% fluorides were synthesized. Two of the series included the KF additive, which was introduced in two ways - proportionally and disproportionately at the expense of the K2O share. The structural characterization (XRD, FTIR) allowed us to determine the evolution of the internal structure of the glasses caused by changes in the type and content of the introduced additives and the presence of the Eu dopant. Similarly, using DSC/DTA, the thermal properties of undoped matrices were defined. The luminescence enhancement caused by the addition of ≥10 mol% fluorides was confirmed by the obtained fluorescence spectra. The presented studies not only expand the state of knowledge about the effects of fluorides on phosphate glasses but also demonstrate the ease of obtaining materials with improved properties suitable for use as phosphor in LEDs.

Research on fault diagnosis of transformer based on laser induced fluorescence technology

Transformer fault diagnosis is an indispensable part of normal operation of power equipment. Aiming at the problem that traditional gas chromatography and other methods take a long time to detect fault types, this paper proposes a laser-induced fluorescence spectroscopy (LIF) technology, combined with differential mutation brainstorm optimization algorithm (DBSO) to optimize the ELM model to identify transformer fault diagnosis types. Four different transformer oils were selected as experimental samples, including thermal fault oil, electrical fault oil, local damp oil and crude oil. LIF technology was used to obtain different spectral images of four oil samples. Firstly, the obtained fluorescence spectra were pre-treated by MSC and Normalize, and the dimensionality was reduced by PLS. Then, the data after dimension reduction are input into the ELM model for training, and the BSO algorithm and DBSO algorithm are used to optimize the parameters of ELM. Finally, the experiments show that the DBSO-ELM model pre-processed by MSC has the highest recognition accuracy, the goodness of fit (R2) is 1, and the mean square error (MSE) reaches 3.205e-31, which is higher than that of ELM model and BSO-ELM model. In the case of the same pre-processing, the fitness values based on the mean square error rate of the training set are lower than those of the other types of recognition algorithm models. Therefore, the MSC-PLS-DBSO-ELM model has the best recognition effect, which can be extended to transformer fault diagnosis and improve the accuracy and safety of power equipment detection.

Re-absorption and scattering of chlorophyll fluorescence in canopies: A revised approach

The measurement of chlorophyll fluorescence in remote way represents a tool that is becoming increasingly important in relation to the diagnosis of plant health and carbon budget on the planet. However, the detection of this emission is severely affected by distortions, due to processes of light re-absorption both in the leaf and in the canopy. Even though some advances have been made to correct the signal in the far-red, the whole spectral range needs to be addressed, in order to accurately assess plant physiological state. In 2018, we introduced a model to obtain fluorescence spectra at leaf level, from what was observed at canopy level. In this present work, we publish a revision of that physical model, with a more rigorous and exact mathematical treatment. In addition, multiple scattering between the soil and the canopy, and the fraction of land covered by vegetation have also been taken into consideration. We validate this model upon experimental measures, in three types of crops of agronomic interest (Pea, Rye grass and Maize) with different architecture. Our model accurately predicts both the shape of fluorescence spectra at leaf level from that measured at canopy level and the fluorescence ratio. Furthermore, not only do we eliminate artifacts affecting the spectral shape, but we are also able to calculate the quantum yield of fluorescence corrected for re-absorption, from the experimental quantum yield at canopy level. This represents an advance in the study of these systems because it offers the opportunity to make corrections for both the fluorescence ratio and the intensity of the observed fluorescence.

Development of a Steady-State Fluorescence Spectroscopy System and a Time-Resolved Fluorescence Spectroscopy System

This document describes thoroughly the construction of two spectroscopic systems: One system for obtaining fluorescence spectra and another system for obtaining the fluorescence lifetime. The first system consists of obtaining the fluorescence spectrum and is constituted by a Czerny-Turner type monochromator, a photomultiplier tube (PMT), a system for modulating the excitation signal and a system for treating and filtering the fluorescent signal constituted by an electromechanical chopper, a lock-in amplifier and a fast response PMT; plus a set of lenses and a samples holder. The fluorescein dissolved in ethanol was used as a calibration standard, and an Nd:YAG laser source was used as a source of excitation, which emits in 532 nm, of continuous wave and stable power in time adjustable by current. On the other hand, a fluorescence time-resolved system was developed. This system consists of obtaining the fluorescence lifetime of different samples under study from a Voltage curve Vs Time obtained from the system and showing the decay behavior of the phenomenon. This has a pulsed laser unit as a source of excitation, emitting at 532 nm, 80 mJ of energy and with a pulse width of 4 ns. For this system, two semiconductor photodiode detectors with fast response have been built; both with a response of temporary uptake above 1 ns, thus providing obtaining fluorescence lifetime up to this value. Fluorescein was also used in this system as a standard sample, but in this case dissolved in a buffer-like solution; accompanied also by a brief study of the change in the average lifespan of fluorescence in function of the pH of the solution. The results obtained show that two automated systems, reproducible, accurate and of very low cost compared to the current ones, have been successfully implemented for the study of steady-state and time-resolved fluorescence spectroscopy.

Fiber-Optic System for Intraoperative Study of Abdominal Organs during Minimally Invasive Surgical Interventions

The paper presents the results of experimental measurements of endogenous fluorescence and blood perfusion in patients with pathology of the organs of hepatopancreatoduodenal area in vivo. A custom setup combining channels for fluorescence spectroscopy (excitation wavelengths of 365 nm and 450 nm) and laser Doppler flowmetry (1064 nm) with fibre optical probe for nondestructive laparoscopic measurements has been developed and applied during minimally invasive operation procedure. Preliminary measurements with two aforementioned channels have been performed at specified excitation wavelengths. The possibility of obtaining fluorescence spectra and laser Doppler flowmetry signals in vivo during minimally invasive interventions was shown. Obtained data show perspectives of further research on technical and methodological development of optical diagnostic methods for minimally invasive surgery. The obtained results can be used to provide a deeper understanding of pathological processes influence on optical properties of abdominal organs tissues, which will ultimately help surgeons to determine the state of vitality in tissues and mucous membranes directly during the process of surgical intervention.

Photoemission Spectra of Sound Tooth and Those of Different Carious Stages

Fluorescence, absorption, and excitation spectroscopy have been widely utilised as probes to collect basic information about physical, chemical, and biological processes. In this study nitrogen laser (N2) was used to induce emission in human teeth to distinguish between dental caries and sound teeth. Three samples of dental caries and one sample of sound teeth have been used to obtain fluorescence spectra illuminated with wavelengths of 337.1 nm, pulse energy 0.04 mJ and pulse time 100 nsec. The absorbance of dental caries and sound teeth was determined using UV-Vis spectrophotometer. The result showed an emission of broadband in the visible region from 363 nm to 627 nm; it provided an amount of information related to intrinsic fluorophores and allowed an accurate diagnosis by the use of the fluorescence intensity changes, it was observed significant decrease of the fluorescence signal intensity related to the carious stage in dental caries, while it was higher in the sound tooth spectrum indicates that the intensity is depending on the amount of decay. A definite diagnosis could be established based on the fluorescence intensity ratio. The future for laser induced fluorescence in diagnostic dentistry has been indicated as accurate and potentially applicable in a wide range in restorative dentistry, periodontology and endodontics.

Ensemble empirical mode decomposition based fluorescence spectral noise reduction for low concentration PAHs

A new noise reduction method based on ensemble empirical mode decomposition (EEMD) is proposed to improve the detection effect for fluorescence spectra. Polycyclic aromatic hydrocarbons (PAHs) pollutants, as a kind of important current environmental pollution source, are highly oncogenic. Using the fluorescence spectroscopy method, the PAHs pollutants can be detected. However, instrument will produce noise in the experiment. Weak fluorescent signals can be affected by noise, so we propose a way to denoise and improve the detection effect. Firstly, we use fluorescence spectrometer to detect PAHs to obtain fluorescence spectra. Subsequently, noises are reduced by EEMD algorithm. Finally, the experiment results show the proposed method is feasible.

The Impact of the Spectral Band Number and Width on the Oil Pollution Diagnostics on Earth Surface by Laser Fluorescence Method

Using the remote sensing methods is the most promising for day-to-day control of oil pollution. The laser-induced fluorescence method provides efficient detection and classification of oil pollutions. To monitor oil pollutions on the earth surface is more complicated than on the water one because of lower fluorescence intensity and interfering fluorescence of natural objects available on the earth surface. Properties of oil pollution classifiers depend largely on the number and positions of spectral bands of fluorescence registration. Reducing the number of spectral bands allows us to diminish computation complexity and cost of equipment. In some cases the reduction increases classification accuracy. The number of spectral bands can be reduced through increasing their width. The paper presents mathematical modeling of oil pollution detection and classification. The experimentally obtained fluorescence spectra of oil pollutions on different substrates were used as input data. The k-nearest neighbors algorithm was used to detect and classify oil pollutions. Cross validation was applied in mathematical modeling. The mathematical modeling results have shown that for oil pollutions detection using over 8 spectral bands (band width less than 50 nm) a classification error rate does not depend on the further increasing number of the spectral bands. As to the type classification of oil pollutions (4 classes), an increasing width of the spectral bands up to 60 nm (the number of spectral bands reduced up 7) does not lead to a significantly decreasing overall classification accuracy. In the case of the sort classification of oil pollutions (8 classes) a local maximum of the overall accuracy has been observed at 25-30 nm width of the spectral band (14-16 spectral bands). The spectral resolution improvement (increasing the number of bands) does give an essentially increasing accuracy. The paper has shown that to detect and classify oil pollutions on the earth surface there is no need to acquire fluorescence with high spectral resolution and numerous spectral bands.

Potential of fluorescence spectroscopy in detection of low-levels of gluten in flour: A preliminary study

Celiac disease is caused due to the ingestion of gluten containing food products. Eating gluten free diet is only way to avoid its occurrence. Gluten free products may get contaminated during the handling and processing operation which leads to the adverse impact on the gluten intolerant patients. Three different gluten free mixes were adulterated with two different types of wheat flours to get the gluten concentration in the range of 0–5 % by making 94 sample combinations. The obtained fluorescence spectra from these samples were transformed using multiplicative scatter correction (MSC) pre-processing to develop partial least square regression (PLSR) model for the prediction of low-levels of gluten. The obtained results showed a high value of 0.90 correlation coefficient (R2) with 0.46 % root mean square error of cross-validation (RMSECV). The calibration and prediction models also showed the same R2 with root mean square error of calibration (RMSEC) and prediction (RMSEP) of 0.41 % and 0.46 % respectively. Hence fluorescence spectroscopy can be used to estimate the level of adulteration which is helpful for developing a sensor for determination of low-levels of gluten as a rapid and non-invasive method in food applications.

Exploring the capabilities of fluorometric online monitoring on chinese hamster ovary cell cultivations producing a monoclonal antibody.

Online monitoring of Chinese hamster ovary fed-batch cell cultures via two-dimensional fluorescence spectroscopy (2DFS) was evaluated in this work. Particular attention was directed toward different process strategies regarding the use of nutrient-rich feed media and temperature shifts. These intentionally performed process manipulations broadened the variances in the obtained fluorescence spectra and this was suspected to hamper the generation of reliable soft sensors. Principal component analysis of the obtained fluorescence data showed that temperature shift and feeding strategy had a considerable impact on the fluorescence signals. Partial least square regression models were calculated for the prediction of glucose, lactate, monoclonal antibody (mAb), and viable cell concentrations (VCC). It was aimed to integrate all 2DFS datasets in the respective calibration models regardless of the process-strategy-dependent diversity. Contrary to the expectations, it was feasible to calibrate soft sensors for the online prediction of glucose (7 latent variables (LVs), Rcal2 = 0.97, rout mean squared error of prediction (RMSEP) = 1.1 g L-1 ), lactate (5 LV; Rcal2 = 0.96; RMSEP = 0.5 g L-1 ) and mAb concentrations (4 LV; Rcal2 = 0.99; RMSEP = 11.4 mg L-1 ). Feeding and temperature shifts had the highest impact on the VCC model (3 LV; Rcal2 = 0.94; RMSEP 3.8 × 105 mL-1 ), nevertheless the prediction of VCC from the fed-batch 2DFS data was feasible. The results strongly indicate that variances in the datasets due to the process strategy can be tolerated to some extent by the respective soft sensors. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1592-1600, 2016.

Fluorescence of iodine-127 and iodine-129 isotopes excited by radiation of copper vapor lasers (578.2 nm): I. Fluorescence of 127I2

This two-part paper reports the results of the first theoretical and experimental studies of the fluorescence of molecular iodine-127 and iodine-129 isotopes excited by copper vapor laser radiation (578.2 nm). This first part deals with the study of iodine-127 fluorescence. Excited transitions were identified, and obtained fluorescence spectra were investigated in detail.

Partially Folded Aggregation Intermediates of Human γD-, γC-, and γS-Crystallin Are Recognized and Bound by Human αB-Crystallin Chaperone

Human γ-crystallins are long-lived, unusually stable proteins of the eye lens exhibiting duplicated, double Greek key domains. The lens also contains high concentrations of the small heat shock chaperone α-crystallin, which suppresses aggregation of model substrates in vitro. Mature-onset cataract is believed to represent an aggregated state of partially unfolded and covalently damaged crystallins. Nonetheless, the lack of cell or tissue culture for anucleate lens fibers and the insoluble state of cataract proteins have made it difficult to identify the conformation of the human γ-crystallin substrate species recognized by human α-crystallin. The three major human lens monomeric γ-crystallins, γD, γC, and γS, all refold in vitro in the absence of chaperones, on dilution from denaturant into buffer. However, off-pathway aggregation of the partially folded intermediates competes with productive refolding. Incubation with human αB-crystallin chaperone during refolding suppressed the aggregation pathways of the three human γ-crystallin proteins. The chaperone did not dissociate or refold the aggregated chains under these conditions. The αB-crystallin oligomers formed long-lived stable complexes with their γD-crystallin substrates. Using α-crystallin chaperone variants lacking tryptophans, we obtained fluorescence spectra of the chaperone–substrate complex. Binding of substrate γ-crystallins with two or three of the four buried tryptophans replaced by phenylalanines showed that the bound substrate remained in a partially folded state with neither domain native-like. These in vitro results provide support for protein unfolding/protein aggregation models for cataract, with α-crystallin suppressing aggregation of damaged or unfolded proteins through early adulthood but becoming saturated with advancing age.

Effects of diaphragm discharge in water solutions containing humic substances

Preliminary results of research focused on the applications of DC diaphragm discharge in water solutions containing humic substances are presented in this paper. Diaphragm discharge investigated by this work was created in the reactor using constant DC high voltage up to 2 kV that gave the total input power from 100 to 200 W. Presented work investigated decomposition of humic substances by the electric discharge in the dependence of discharge conditions (electrode polarity) as well as solution properties (electrolyte kind, pH). Especially substantial effect of pH on humic acid decomposition has been observed when acidic conditions stimulated the degradation process. Absorption spectroscopy in UV-VIS region together with fluorescence spectroscopy has been used for the detection of changes in humic solutions. Index of humification was calculated from obtained fluorescence spectra and a significant decrease of aromatic components in the humic mixture was determined during the discharge treatment.

Tungsten carbide revisited: New anion photoelectron spectrum and density functional theory calculations

A new anion photoelectron (PE) spectrum of WC(-) is presented and analyzed using existing and new calculations. This spectrum is different from the PE spectrum previously published [X. Li et al., J. Chem. Phys. 111, 2464 (1999)], which we suggest was actually the PE spectrum of W(-). The ground anion state is determined by calculations and comparison with spectral features to be the (2)Delta(32) state. The (3)Delta(1)-(2)Delta(32) transition is observed at an electron binding energy of 2.155 eV, which corresponds to the adiabatic electron affinity of WC. The bond length of the anion is determined to be 1.771(5) A. A number of spectral assignments corresponding to both excited anion and neutral states are made based on previously obtained fluorescence spectra [S. M. Sickafoose et al., J. Chem. Phys. 116, 993 (2002)] and density functional theory calculations.

Resolution of the excitation–emission spectra of FMN in rigid poly(vinyl alcohol) matrices

The excitation–emission spectra of flavin mononucleotide (FMN) were measured in rigid PVA films for concentrations ranging from 6.92 × 10 −4 M to 1.03 M. The theoretical three-linear decomposition of the excitation–emission spectra indicated the presence of two absorption and emission centers corresponding to FMN monomer and dimer, respectively. The component of the fluorescence profile corresponding to the FMN monomer has a large negative part which is the mirror image of the emission band profile of the dimer. The elimination of this part by taking a linear combination of the emission components of the monomer and of the dimer resulted in emission spectrum, which is in a very good agreement with the monomer spectrum measured directly. The appearance of a negative part of the monomer emission profile obtained by trilinear decomposition of the emission–absorption spectra of FMN can be explained in terms of the non-radiative reverse energy transfer from the FMN dimers to the FMN monomers. The presented results confirm that the FMN molecules in rigid PVA form dimers but not higher order aggregates. Moreover, they enable to obtain fluorescence spectra of dimers and suggest that FMN dimers may take part in the process of non-radiative energy transfer occurring in photoreception phenomena.

Treatment of humic acids solutions by DC diaphragm discharge

This paper presents results obtained from a preliminary investigation of humic acids solutions treated by the DC non-pulsed diaphragm discharge. The first attempts at the removal of humic acids from water by the diaphragm discharge were carried out in a batch discharge reactor. The UV-VIS absorption spectroscopy and the fluorescence spectroscopy were used as fast analytical methods for the determination of changes in humic acids chemical structure. From the obtained fluorescence spectra of the treated solutions, the index of humification was calculated as a ratio of the emission intensities at 470 and 400 nm. The index value points to the ratio of aromatic and aliphatic components in the humic acids mixture. The decrease of the index indicates the increasing aliphatic character of the mixture. Results obtained from the discharge treatment of humic acids solutions are compared to those obtained from experiments with organic dyes dissolved in water and their decomposition by the diaphragm discharge.

Spectroscopy of 142NdO: New results

142NdO molecules have been produced by heating 142Nd 2O 3 to about 2100 K in a vacuum furnace in the presence of argon gas. A ring dye laser operating with DCM dye has been used to excite 142NdO transitions in the 636–666 nm spectral region, and induced fluorescence has been spectroscopically analysed at high resolution with a Fourier transform spectrometer. Contributions from thermal emission have been simultaneously observed. Two new low-lying electronic states have been detected, at energies of about 2708 and 4139 cm −1, designated as [2.7], most probably observed at ν = 1, and [4.1], likely to be (2)6 (observed at ν = 0). The ν = 1 level of the (1)6 state, already known at ν = 0, has been observed for the first time. Most levels pumped by the laser, between 14 000 and 17 400 cm −1, could be identified from earlier work. In addition, by studying in more detail recently obtained fluorescence spectra [J. Mol. Spectrosc. 225 (2004) 132] spectroscopic constants have been improved for a number of states. Finally, from thermal emission spectra, rotational analyses of the 0–0 bands of two new systems, [16.4] − (2)5 and [14.1] − X4, and reanalyses at higher resolution of the 0–0 bands of the systems V, VII, VIII, and X have been carried out. A consistent set of spectroscopic constants of the levels of 142NdO characterized as yet is presented.

FLUORESCENT-SPECTROSCOPIC RESEARCH OF IN VIVO TISSUES PATHOLOGICAL CONDITIONS

The steady-state spectra of autofluorescence and the reflection coefficient on the excitation wavelength of some stomach tissues in vivo with various pathological conditions (surface gastritis, displasia, cancer) are measured under excitation by the nitrogen laser irradiation (λ ex =337.1 nm ). The contour expansion of obtained fluorescence spectra into contributions of components is conducted by the Gaussian–Lorentzian curves method. It is shown that at least 7 groups of fluorophores forming a total luminescence spectrum can be distinguished during the development of displasia and tumor processes. The correlation of intensities of flavins and NAD(P)·H fluorescence is determined and the degree of respiratory activity of cells for the functional condition considered is estimated. The evaluations of the fluorescence quantum yield of the tissue's researched are given.

Early Diagnostics and Control of the Degree of Seriousness of Gestosis by the Concentration of Endogenous Porphyrins

Using the spectral‐fluorescent method, we have studied the dynamics of the presence of protoporphyrin and copropoporphyrin in the erythrocytes of the blood of women patients in the course of normal pregnancy and that complicated by gestosis of different degrees of seriousness. Considerable attention is paid to the processing of the obtained fluorescence spectra of an extracted mixture, because it is necessary for direct application of this method in medicine and biology. The results show that the fluorescent method makes it possible to determine the seriousness of gestosis and also to carry out its diagnostics at the preclinical stage.

Temperature and localization of atoms in three-dimensional optical lattices

We report temperature measurements of atoms trapped in a three-dimensional ~3D! optical lattice, a welldefined laser-cooling situation that can be treated with currently available theoretical tools. We also obtain fluorescence spectra from a 3D optical lattice, from which we obtain quantitative information about the trapping atoms, including the oscillation frequencies, spatial localization, and a temperature, which is in good agreement with our direct measurements. For comparison we study a 1D lattice using the same atom ~cesium!.