Search

Turquoise is one of the key ingredients in some magical Tibetan medicines, and its quality and content directly affect the medicine's effectiveness. In this paper, laser-induced breakdown spectroscopy (LIBS) technology was first applied to detect the raw materials of Tibetan medicine. The traditional data analysis methods could not meet the practical requirements of modern Tibetan medicine factories due to matrix effects. The concept of correlation coefficient (ρ) in pattern recognition technique was introduced as an evaluation index, and the model was established based on the intensities of the four characteristic Al and Cu spectral lines of the samples for different contents of turquoise, which was applied to estimate the contents of turquoise in the samples to be tested. We detected the LIBS on 126 samples of raw ore from 42 areas in China and evaluated the turquoise content using self-developed software with an error of <10%. This paper's technical testing process and methods can also be applied to test other mineral compositions and provide technical support for modernizing and standardizing Tibetan medicines. Graphical Abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

Femtosecond (fs) and nanosecond (ns) laser pulses have their own advantages and disadvantages in laser-induced breakdown spectroscopy (LIBS). This paper investigated fs + ns (FN) dual-pulse (DP) LIBS, utilizing the respective advantages of two laser pulses in LIBS. Compared to traditional single ns LIBS, applying a smaller energy fs pulse could effectively improve the LIBS emission. Firstly, this study discussed the spectra of FN DP LIBS with overlapping pulse time—that is, the FN DP inter-pulse delay (DID) was 0 μs. The results showed that the spectra were increased to three times that of a single ns LIBS. Subsequently, the DID between the two pulses was optimized. The results showed that as the DID between the two pulses increased, the spectral emission first increased and then decreased, ultimately remaining unchanged. The optimized DID was approximately 2 μs. Finally, using this optimized DID, the variation of spectral intensity with ns laser energy was discussed in DP LIBS. The spectral enhancement ratio increased from 3 with 0 μs DID to 6 with 2 μs DID. The investigation provides a reference in the application of FN DP LIBS element analysis. [ABSTRACT FROM AUTHOR]

The present paper reports the multi-analytical approach for the removal of thick layers of metallic overpaints from a Brancovan iconostasis of the "Holy Trinity" church in Măgureni, România, which was built in 1694. After a restoration procedure at the beginning of the 20th century, the polychrome sculpture of the frame, which was initially gilded with a thin silver foil, was covered with a thick metallic overpaint layer imitating silver and gold. Currently, the conservation project of the church is focused on restoring the original aspect; thus, the overpainting that presented strong oxidation and soiling was removed. The adopted conservation methodology involved physicochemical characterization of the pictorial layers via optical microscopy, laser-induced breakdown spectroscopy, and Fourier-transform infrared spectroscopy, followed by the removal of the overpaints. The cleaning tests were performed by evaluating several methods in order to find the proper regime that would help preserve as much of the underlying polychrome layers as possible. Based on the tests, it was decided that the best solution was to use laser cleaning for the rough removal of the metallic paint overlayers and finalizing with chemical cleaning. [ABSTRACT FROM AUTHOR]

Modeling the quantitative relationship between target components and measured spectral information is an essential part of laser-induced breakdown spectroscopy (LIBS) analysis. However, many traditional multivariate analysis algorithms must reduce the spectral dimension or extract the characteristic spectral lines in advance, which may result in information loss and reduced accuracy. Indeed, improving the precision and interpretability of LIBS quantitative analysis is a critical challenge in Mars exploration. To solve this problem, this paper proposes an end-to-end lightweight quantitative modeling framework based on ensemble convolutional neural networks (ECNNs). This method eliminates the need for dimensionality reduction of the raw spectrum along with other pre-processing operations. We used the ChemCam calibration dataset as an example to verify the effectiveness of the proposed approach. Compared with partial least squares regression (a linear method) and extreme learning machine (a nonlinear method), our proposed method resulted in a lower root-mean-square error for major element prediction (54% and 73% lower, respectively) and was more stable. We also delved into the internal learning mechanism of the deep CNN model to understand how it hierarchically extracts spectral information features. The experimental results demonstrate that the easy-to-use ECNN-based regression model achieves excellent prediction performance while maintaining interpretability. [ABSTRACT FROM AUTHOR]

The stream sediment (SS) records evolution information of the water system structure and sedimentary environment in specific regions during different geological periods, which is of great significance for studying the ancient planetary environment and the law of water system changes. Based on the SS of different geographical environments on Earth, remote laser-induced breakdown spectroscopy (remote-LIBS) technology combined with the multidimensional scaling-back propagation neural network (MDS-BPNN) algorithm was used to conduct an in-depth analysis of remote qualitative and quantitative detection of the elemental composition and content of SS. The results show that the detection system based on remote LIBS combined with an artificial neural network algorithm can achieve an ideal quantitative analysis of major and trace elements. The coefficients of determination (R2) of the test set for major elements is greater than 0.9996, and the root mean square error (RMSE) is less than 0.7325. The coefficients of determination (R2) of the test set for trace elements is greater than 0.9837, and the root mean square error is less than 42.21. In addition, for the application scenario of exploring extraterrestrial life, biominerals represented by stromatolite phosphorite (SP) are easy to form sand and enter into SS under weathering. Therefore, this paper discusses the feasibility of using remote-LIBS technology to detect and identify such minerals under the disappearance of SPs' macro- and micro-characteristics. From our research, we can find that remote-LIBS technology is the preferred candidate for discovering dust-covered biominerals. In geological environments rich in water system sedimentary rocks, such as Mars' ancient riverbeds, LIBS technology is crucial for deciphering the "life signals" hidden in the Martian sand. [ABSTRACT FROM AUTHOR]

In this paper, the double-pulse laser-induced breakdown spectroscopy (DP-LIBS) technique was used to analyze the heavy metal samples collected in the atmosphere using an air sampler. The enhancement characteristics of the plasma spectra were studied by using different laser wavelength combinations with 1064, 532, and 355 nm Nd:YAG lasers. The plasma spectrum of the sample was greatly enhanced when the combined laser wavelengths were 355 and 1064 nm. On this basis, the optimal inter-pulse delay time is obtained to get the maximum plasma spectrum. The relationship of the signal to background ratio, electron temperature, and electron density of the plasma spectrum with inter-pulse delay and acquisition delay is also discussed. Finally, the optimal pulse delay and acquisition time were obtained. DP-LIBS technology can effectively improve the detection effect of heavy metals in the atmosphere, which is a very promising tool in the field of environmental monitoring. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS), as a promising analytical technique for coal analysis, is greatly affected by the matrix effect. Existing studies have a fundamental understanding of the matrix effect in coal pellets, but the matrix effect in coal particle flow has never been studied previously. This paper aims to characterize the matrix effect in the coal particle flow and compares it with that in the coal pellets. Using seven coal samples with similar carbon content but different matrices, we investigate the spectral analytical response of C I 247.86 nm to the carbon content. Additionally, the ablation crater profiling method and the fast-imaging approach have been applied to characterize the ablation mass and the laser thermal effect, followed by the in-depth analysis of the matrix effect in coal particle flow. The experimental results show that particle flow analysis can ensure stable ablation mass and alleviate the laser thermal effect. Based on these improvements, LIBS analysis of particle flow reveals a milder matrix effect compared with pellets, reducing the inconsistency of spectral analytical response from 21.64% to 12.87%. [ABSTRACT FROM AUTHOR]

Dielectric response and charge decay test are widely used for evaluating the electric properties of the insulation pressboards in the converter transformer. In this paper, Frequency Domain Spectroscopy (FDS) test, breakdown test, and charge decay characteristics experiments are carried out on the cellulose pressboards modified by TiO 2 with different mass fractions and diameters. The FDS of the modified cellulose pressboards at ambient temperature is measured from 0.0001 to 1000 Hz by IDAX 300. The process is conducted at the laboratory to study the characteristics parameters of the dielectric response behaviors, such as complex relative permittivity. The results show that the values of the relative permittivity for the insulation pressboards modified by TiO 2 (5 wt%, 10 nm) are reduced. To verify the accurate results, the microstructures of the pressboards modified by 5 wt% with 10 nm diameter are observed by a Scanning Electron Microscope (SEM). The breakdown strength tests are carried on the samples modified by 1 wt%, 3 wt%, 5 wt%, 7 wt% with 10 nm TiO 2 under the intensity electric and high-temperature field, respectively. The values of the breakdown strength are increased by 38% and 11.5% for single layer samples and oil/pressboard composite insulation models modified by 5 wt% nano-TiO 2 filler. In addition, the charge decay characteristics are tested on the samples. The proper proportion additions can reduce the trap density. [ABSTRACT FROM AUTHOR]

Medicinal plants play a vital role in herbal medical field and allopathic medicine field industry. Chemical and spectroscopic studies of Taraxacum officinale, Hyoscyamus niger, Ajuga bracteosa, Elaeagnus angustifolia, Camellia sinensis, and Berberis lyceum are conducted in this paper by using a 532-nm Nd:YAG laser in an open air environment. These medicinal plant's leaves, roots, seed, and flowers are used to treat a range of diseases by the locals. It is crucial to be able to distinguish between beneficial and detrimental metal elements in these plants. We demonstrated how various elements are categorized and how roots, leaves, seeds and flowers of same plants differ from each other on the basis of elemental analysis. Furthermore, for classification purpose, different classification models, partial least square discriminant analysis (PLS-DA), k-nearest neighbors (kNN), and principal component analysis (PCA) are used. We found silicon (Si), aluminum (Al), iron (Fe), copper (Cu), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), manganese (Mn), phosphorous (P), and vanadium (V) in all of the medicinal plant samples with a molecular form of carbon and nitrogen band. We detected Ca, Mg, Si, and P as primary components in all of the plant samples, as well as V, Fe, Mn, Al, and Ti as essential medicinal metals, and additional trace elements like Si, Sr, and Al. The result's findings show that the PLS-DA classification model with single normal variate (SNV) preprocessing method is the most effective classification model for different types of plant samples. The average correct classification rate obtained for PLS-DA with SNV is 95%. Moreover, laser-induced breakdown spectroscopy (LIBS) was successfully employed to perform rapid, sensitive, and quantitative trace element analysis on medicinal herbs and plant samples. [ABSTRACT FROM AUTHOR]

This paper gives an insight to formation of ablation craters on float glass samples due to irradiation by high energetic nanosecond laser pulses and its optimisation for laser-induced breakdown spectroscopy (LIBS) analysis. Use of such lasers is less common for material processing, therefore ablation and eventual degradation of the samples has not been in the focus technical studies. Meanwhile high energy pulses can be optimal for certain applications, such as LIBS. Here the properties of ablation craters on common float glass samples after high energetic laser pulse irradiation were investigated. LIBS spectra were obtained and their quality was compared against the irradiation parameters such as wavelength and focusing conditions. It was found that these have a significant effect on crater formation, but parameters can be set to allow ablation without major degradation of the sample. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Energy-dispersive X-ray fluorescence (EDXRF) analysis is one of the standard techniques for the evaluation of mineral deposits. The advantage of EDXRF is the fast delivery of information about the bulk elemental composition as well as the elemental composition of each mineral class. With micro energy-dispersive X-ray fluorescence (µ-EDXRF) analysis, information can be obtained with a micrometer resolution. However, it has some limitations. With EDXRF, light elements (e.g., lithium) cannot be detected, and the count rates for carbon, fluorine and sodium are very low. This might lead to a misinterpretation of the mineral classes and the worth of the deposit. Furthermore, the identification of the alteration phases of primary minerals is ambiguous. Here, we will present an approach to overcome the limitations of µ-EDXRF by complementing it with combined laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy. In contrast to EDXRF, LIBS is able to detect all elements, including light elements. Raman spectroscopy can identify mineral phases and eventually provide additional information on their alterations and modifications. In the present paper, we show results for two different samples covering a certain chemical and mineralogical range that demonstrate the potential of the proposed combination of methods for the chemical and mineralogical analysis of geological samples. [ABSTRACT FROM AUTHOR]

Two-color laser field-induced plasma filaments are efficient broadband terahertz (THz) sources with intense THz waves emitted mainly in the forward direction, and they have been investigated intensively. However, investigations on the backward emission from such THz sources are rather rare. In this paper, we theoretically and experimentally investigate the backward THz wave radiation from a two-color laser field-induced plasma filament. In theory, a linear dipole array model predicts that the proportion of the backward emitted THz wave decreases with the length of the plasma filament. In our experiment, we obtain the typical waveform and spectrum of the backward THz radiation from a plasma with a length of about 5 mm. The dependence of the peak THz electric field on the pump laser pulse energy indicates that the THz generation processes of the forward and backward THz waves are essentially the same. As the laser pulse energy changes, there is a peak timing shift in the THz waveform, implying a plasma position change caused by the nonlinear-focusing effect. Our demonstration may find applications in THz imaging and remote sensing. This work also contributes to a better understanding of the THz emission process from two-color laser-induced plasma filaments. [ABSTRACT FROM AUTHOR]

The burning of incense produces toxic and harmful gases and particulate matters, posing a tremendous threat to both human health and the atmospheric environment. As a consequence, online in situ detection, classification, and traceability of burnt incense are of vital importance. In this paper, taking ambergris, musk, and Tibetan incense as examples, laser-induced breakdown spectroscopy (LIBS) is applied to the online detection of smoke and ash from the burning of three common types of incenses. It is found that metallic elements such as K, Mg, and Ca are present in the smoke. In contrast, more complex metallic elements, such as Fe, Al, Mn, Sr, etc., are present in the incense ash. By comparing the smoke and ash spectra of three different incenses, the feature spectra with large differences are selected, and the data are dimensionality reduced using the principal component analysis. Combined with error back propagation training artificial neural networks, the classification and traceability models of the smoke and ash from different incenses are performed, and the final recognition accuracies are 93.24% and 96.33%, respectively. All the results indicate that the combination of LIBS and machine learning has good application prospects for detecting and online tracing different incense smoke and ash and is also beneficial for human health and the natural environment. [ABSTRACT FROM AUTHOR]

This paper presents the results of an analysis of carbon (in the form of graphene oxide) deposited on the surface of threads made from stainless steel 316 and titanium alloy Ti6Al4V used in orthopedics using Laser Induced Breakdown Spectroscopy (LIBS). The aim of the article is to indicate the possibility of using the LIBS spectra for the study of thin layers, including graphene derivatives and other elements. Stratigraphic measurements allowed the detection of differences in the spectra peaks of individual elements, not only in the surface layer itself and in the native material, but also in the intermediate layer connecting the two layers. Due to the clear difference in the outline of the spectrum of graphene oxide and the spectrum of the native material of the samples analyzed, a clear incorporation of carbon atoms into the surface layer was observed. A factor analysis was performed, which confirmed the incorporation of graphene oxide into the surface layer of the native material of the elements examined. [ABSTRACT FROM AUTHOR]

This paper aims toward the successful detection of harmful materials in a substance by integrating machine learning (ML) into laser-induced breakdown spectroscopy (LIBS). LIBS is used to distinguish five different synthetic polymers where eight different heavy material contents are also detected by LIBS. Each material intensity-wavelength graph is obtained and the dataset is constructed for classification by a machine learning (ML) algorithm. Seven popular machine learning algorithms are applied to the dataset which include eight different substances with their wavelength-intensity value. Machine learning algorithms are used to train the dataset, results are discussed and which classification algorithm is appropriate for this dataset is determined. [ABSTRACT FROM AUTHOR]

IEC 60156 and IEC 60897 were standardized with the purpose of evaluating the breakdown voltage of liquid dielectrics both under AC and impulse voltages. AC breakdown voltage determination is a simple method but only able to provide information on the presence of contaminants. The limit of this test is the large scatter in the results and, for this reason, this IEC standard has been recently revised. Impulse breakdown voltage determination allows discrimination of different dielectric liquids, also in terms of their chemical composition. This test has only limited application because of the dimensions of the high voltage generator. The present paper shows a comparison among breakdown voltages of various mineral oils and natural esters under both AC and impulse voltages. The paper presents also an effort to describe how these two tests may reveal the electrical performance of the dielectric liquid under test. [ABSTRACT FROM AUTHOR]

The laser-induced breakdown spectroscopy (LIBS) analysis method displays significant matrix effects which greatly hinder the application of this technology. Even if the concentration of a certain element is constant, the physical properties and composition of the sample will affect the element signal. In order to further deepen the understanding of matrix effects, in this paper, the effect of matrix effects (Al matrix and Fe matrix) on the quantitative analysis of Si, Mn, Cr and Cu under different laser defocusing amounts and spectrometer delays is researched. This study found that the matrix effects have different degrees of effect on the analysis line under different experimental parameters. Moreover, the effect of the matrix effects can be reduced by adjusting the laser defocus amount and spectrometer delay. In addition, taking the spectrum generated by the pure sample as the matrix background and subtracting the intensity value of the matrix background at the analysis line can reduce the interference of the matrix effects. After deducting the matrix background, the determination coefficient of mixed quantitative analysis of the three elements Si, Cu, and Cr in Al and Fe matrixes can reach more than 0.99. Besides, for the Mn 257.6 nm, which is severely interfered by the spectrum of the Al matrix and Fe matrix, respectively, the determination coefficient of the mixed quantitative analysis can reach 0.9855. [ABSTRACT FROM AUTHOR]

JAAS Journal of Analytical Atomic Spectrometryrsc. li/ jaas Volume 39 Number 5 May 2024 Pages 1179– 1430 ISSN 0267- 9477 PAPER Jian Wu et al. Synergy enhancement and signal uncertainty of magnetic- spatial confi nement in fi ber- optic laser- induced breakdown spectroscopy [Extracted from the article]

A novel analysis technique of elements at ambient conditions has been developed. The technique is based on microwave-assisted laser-induced breakdown spectroscopy (MW-LIBS) applied to acoustically levitated samples. The technique has been demonstrated using three solid samples with different properties and compositions. These are ore containing multiple elements (OREAS 520), aluminium oxide (Al3O2) and gypsum (CaSO4·2H2O). The mass of samples was 21 mg, 23 mg, and 55 mg for gypsum, mineral ore, and Al3O2, respectively. Significant signal enhancements were recorded for a variety of elements, using microwave-assisted laser-induced breakdown spectroscopy and levitation (MW-LIBS–Levitation). The signal enhancement for Mn I (403.07 nm), Al I (396.13 nm) and Ca II (393.85 nm) was determined as 123, 46, and 63 times, respectively. Moreover, it was found that MW-LIBS–Levitation minimises the self-absorption of the Ca I (422.67 nm) and Na I (588.99 nm and 589.59 nm) spectral lines. In addition to the signal enhancements, the levitation process produces a spinning motion in the solids with an angular frequency of 7 Hz. This feature benefits laser-based analysis as a fresh sample is introduced at each laser pulse, eliminating the need for the usual mechanical devices. Based on the single-shot analysis, it was found that ∼80% of the laser pulses produced successful MW-LIBS–Levitation detection, confirming an impressive repeatability of the process. This contactless analytical technique can be applied in ambient pressure and temperature conditions with high sensitivity, which can benefit disciplines such as forensics science, isotope analysis, and medical analysis, where the sample availability is often diminutive. [ABSTRACT FROM AUTHOR]

For in situ detection via laser-induced breakdown spectroscopy (LIBS), the effect of the sample surface morphology matrix exacerbates spectral variations, leading to inaccurate and unstable analysis results, even under ideal laboratory conditions. Thus, it is essential to consider the influence of sample surface morphology on LIBS to obtain optimal detection results. Therefore, to reduce this influence, herein, we proposed spectral correction methods to correct LIBS spectra based on our previous research results on the relationship between LIBS characteristic spectral intensity and physical parameter of the sample surface morphology, where the parameter was the angle θ between the tangent of the sample surface and the horizontal direction. The results showed that the fluctuations in the corrected spectra were reduced and the relative standard deviation (RSD) was less than 10%, and the spectral intensities were close to that of the samples with a flat surface morphology. To assess the effectiveness of the proposed methods in improving the quantitative analysis accuracy, Cr, Ni, and Mn elements in standard stainless-steel samples were analyzed by partial least squares regression (PLSR). We established the model using the spectra of standard samples with a flat surface morphology as the training set, and the results showed that the accuracy was very low when the test set was the spectra of samples without a flat surface morphology, with R² of 0.781, 0.779, and 0.695 for Cr, Ni, and Mn elements, respectively. In contrast, when the test set was the corrected spectra, R2 increased to 0.950, 0.925, and 0.825 for Cr, Ni, and Mn elements, respectively, and the RMSE and MRE were reduced. When the corrected spectra of standard samples without a flat surface morphology were added to the training set, the accuracy was improved, with R² of 0.978, 0.939, and 0.929 for the three elements and their RMSE and MRE were minimum. [ABSTRACT FROM AUTHOR]

As there are distinct variations in economic value for greenish-white to white nephrites based on their geographical origin, it is crucial to develop a robust origin discrimination method for them. The reported correlation between the intensity of spectra and material properties gives us a clue that such a correlation may exist in nephrites worldwide. In this study, 364 pieces of greenish-white to white nephrite jades from different locations, including Qiemo, Qinghai, Xiuyan and Yecheng in China, South Korea, and Russia, were analyzed using laser-induced breakdown spectroscopy (LIBS). Four machine learning methods, including linear discriminant analysis (LDA), support vector machine (SVM), partial least squares discriminant analysis (PLS-DA), random forest (RF), and an ensemble learning approach known as a voting classifier for origin discrimination were then employed. The results show a higher training accuracy of 99.81% (LDA), 94.01% (SVM), 100% (PLS-DA), 98.08% (RF), and 99.93% (voting classifier), with corresponding testing accuracies of 96.13%, 93.04%, 94.99%, 95.90%, and 99.93%, respectively. By appropriately selecting voting weights, the voting classifier effectively mitigates misclassification, achieving balanced accuracy for each origin. Therefore, the LIBS analyses could be utilized in the origin discrimination of greenish-white to white nephrite jades, offering valuable insights for accurately evaluating these gemstones, based on the successful application of various machine learning methods in the origin discrimination of nephrite jades. An integrated voting ensemble method was further introduced, providing new possibilities for rapid discrimination in diverse industries, including gemstone trading, manufacturing, archaeology, and more. [ABSTRACT FROM AUTHOR]

This article reports on an advanced level physical laboratory experiment designed for college level undergraduate education and for scholars who need specialized training on using and interpreting Laser-Induced Breakdown Spectroscopy. The technical principle, experimental operation and sample preparation of Laser-Induced Breakdown Spectroscopy are introduced in detail. A presentation and discussion of the use of Laser-Induced Breakdown Spectroscopy in the traceability of four common samples is emphasized. Combining Laser-Induced Breakdown Spectroscopy with Machine Learning, two distinct datasets are constructed through the extraction of spectral features. Dimensionality reduction of spectral data is performed using Linear Discriminant Analysis, while the Random Forest model is employed for provenance classification. Finally, the interpretability of the Random Forest model is leveraged to explore the contributions of different spectral elements to provenance tracing. Results demonstrated the system's effectiveness in not only accurately identifying ash types but also in elucidating the influential chemical components, offering significant implications for material analysis and environmental monitoring. On an educational standpoint, this paper will allow any reader, in particular, undergraduate and graduate students, to gain a better understanding of the theory and practice of Laser-Induced Breakdown Spectroscopy and machine learning. [ABSTRACT FROM AUTHOR]

Femtosecond laser-ablation spark-induced breakdown spectroscopy (fs-LA-SIBS) and out-of-bag random forest regression (OOB-RFR) were developed for accurate quantitative analysis of the elements manganese (Mn), chromium (Cr), and nickel (Ni) in steel alloys. A femtosecond laser operating at 1 kHZ was used as the laser ablation source and a spark discharge unit was utilized to enhance the peak intensity of atomic emission. The characteristic lines of Mn, Cr, and Ni elements in steel alloys were determined using the NIST database. The two hyperparameters ntree and mtry of RFR were optimized through OOB error, and the OOB-RFR model was obtained. In the experiment, the predictive performance of OOB-RFR, support vector machine (SVM) regression, and partial least squares regression (PLS) on steel alloy spectral data was compared and analyzed. The results indicate that the OOB-RFR model exhibits lower computational iterations and higher performance than other models in regression prediction of Mn, Cr, and Ni elements. In the OOB-RFR model, the root mean square error (RMSE), the average relative error (MRE) and the coefficient of determination (R2) of Mn, Cr, and Ni elements in the training samples were 0.0051, 0.0018 and 0.9976, respectively, and the RMSE, MRE and R2 of the three elements in testing samples were 0.0018, 0.0009 and 0.9369, respectively. Therefore, the combination of the fs-LA-SIBS technique and OOB-RFR has great potential in the rapid determination of elements in steel and even in the metallurgical field. [ABSTRACT FROM AUTHOR]

This study explores the application of laser-induced breakdown spectroscopy (LIBS) to classify steel samples, which gives a novel idea of utilizing the matrix effect. In engineering applications, carbon-steel, which has the same elemental composition, is usually processed into different microstructures through heat treatment processes. It results in the steel having different element distribution characteristics at the microscopic scale, and is considered to be one of the reasons for the matrix effect in the LIBS field. In this study, the matrix effect of LIBS spectra is used as the feature for microstructure classification of carbon-steel. According to this idea, our study introduces a rapid classification method of LIBS spectra using the random projection (RP) technique in convolutional neural networks (CNNs), which has achieved the accuracy of 99% in 25 seconds. The experimental results show that the dimensionality reduction without spectral preprocessing by the RP-CNN method enhances the impact of matrix effect. This study provides an efficient deep learning method for similar LIBS spectra obtained from steel samples with different microstructures, which has great potential in the LIBS application of engineering material evaluation. [ABSTRACT FROM AUTHOR]

The impact of oxidation chemistry on the emission characteristics and spatial structure of laser-produced Ce metal plasmas was investigated using laser-induced breakdown spectroscopy (LIBS) and time-resolved fast-gated imaging employing narrowband optical filters. Images of the plasma emission show that CeO coexists with atomic species in the periphery and vortex ring of the plasma plume. Image processing was also applied to combine independent monochromatic images of the plasma emission into a single merged image, culminating in a timelapse on the spatiotemporal evolution of atomic and molecular species within the plasma plume. The formation of CeO species was observed to proceed faster for plasmas generated in atmospheres containing larger concentrations of oxygen based on ratios of CeO-to-atomic emission intensities. These same ratios were shown to plateau and decrease at later times (≥25 μs), potentially indicating the depletion of CeO number densities in the plasma as the monoxide undergoes reactions to form higher polyatomic oxides. Altogether, these results provide fundamental insights into the chemical dynamics and intermixing between plasma-gas species in laser ablation cerium plasmas, advancing our understanding on optical signatures of nuclear-relevant materials to enable in-field measurement capabilities. [ABSTRACT FROM AUTHOR]

This article presents an innovative application of kHz regime μLIBS – Laser-Induced Breakdown Spectroscopy for generating detailed compositional maps of geological samples. The method effectively covers large areas (tens of cm2) rapidly while maintaining high lateral resolution (below 20 μm), producing some of the most extensive LIBS compositional images to date, with a size of 10 million pixels. Employing elemental-based images, we developed a direct methodology for mineral phase identification through mask-creation operations and logical relationships. This approach was successfully applied to reconstruct the mineralogical map of a Li-ore from the west-European Variscan belt, identifying 14 different mineral phases, including economically valuable ones like lepidolite, cassiterite, and columbite-group minerals. Furthermore, based on the reverse normative calculation, the chemical composition of the sample was calculated from the mineral phases previously obtained. The kHz μLIBS approach marks a significant advancement in elemental and phase imaging, especially pertinent to geological applications, providing comprehensive petro-geochemical insights, essential for a fast geological characterization. [ABSTRACT FROM AUTHOR]

Nonlinear interaction of two or three synchronized coplanar filaments was demonstrated to generate plasma gratings with high electron density capable of effectively exciting samples. This excitation was further enhanced by multi-photoionization and electron collision. Consequently, an increase in laser pulse energy led to a decrease in the full width at half maxima (FWHM) of spectral lines, primarily observed in breakdown spectroscopic lines due to electron signal enhancement. Moreover, by measuring the emission line intensity as a function of time delay and excitation laser pulse energy, the radiative lifetime and self-absorption correlation coefficient of neutral atomic and ionic lines were determined to exhibit longed plasma lifetimes in the presence of filament interaction. The enhancement was particularly notable when using three coplanar coupled filaments for excitation, as it resulted in a plasma lifetime increase of approximately 50–60 ns compared to that when using two filaments for atomic lines. These findings indicate that high-electron density in plasma gratings could improve the application of filament-induced breakdown spectroscopy by enhancing spectral resolution, radiative lifetime, and spectral reproducibility. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy was used to investigate the elemental structure and discrimination of bacteria growth phases. Two bacterial specimens including Gram-negative E. coli and Gram-positive S. aureus, are selected at four different times during the growth phases with recorded optical densities of 0.4, 0.8, 1.2 (exponential growth phase), and 2.2 (stationary growth phase). By comparing the intensities of C, Ca, Na, Mg, K, O, H, and CN bonds in the LIBS fingerprint spectrum in the growth phases, different patterns of elemental composition for both bacteria of interest, including their structure. Multivariate linear discriminant analysis is applied to the "principal lines" and the "mixture of principal lines and their ratios". Analysis results depict different growth phases of bacteria are discriminated against each other during various classification accuracies ranging from 90% to 100%. Based on the results of the combination of LIBS and LDA, it is concluded that these bacteria can be classified during the growth process with high accuracy and precision. [ABSTRACT FROM AUTHOR]

We explore the application of artificial neural networks (ANNs) for predicting plasma temperatures in Laser-Induced Breakdown Spectroscopy (LIBS) analysis. Estimating plasma temperature from emission spectra is often challenging due to spectral interference and matrix effects. Traditional methods like the Boltzmann plot technique have limitations, both in applicability due to various matrix effects and in accuracy owing to the uncertainty of the underlying spectroscopic constants. Consequently, ANNs have already been successfully demonstrated as a viable alternative for plasma temperature prediction. We leverage synthetic data to isolate temperature effects from other factors and study the relationship between the LIBS spectra and temperature learnt by the ANN. We employ various post-hoc model interpretation techniques, including gradient-based methods, to verify that ANNs learn meaningful spectroscopic features for temperature prediction. Our findings demonstrate the potential of ANNs to learn complex relationships in LIBS spectra, offering a promising avenue for improved plasma temperature estimation and enhancing the overall accuracy of LIBS analysis. [ABSTRACT FROM AUTHOR]

This article reviews the advances made during the past two decades in the application of Laser-Induced Breakdown Spectroscopy (LIBS) to biological samples, specifically soft tissues (both animal and human). The first sections include a historical overview and a summary of the biomedical relevance of analyzing metals in these tissues. Next, statistical methods employed in some works are presented, along with a detailed description of the innovations developed in experimental systems. The remainder of the review reports the approaches used in the experiments, focusing on a description of the advances that have enabled the successful application of LIBS to soft tissues. The results are evaluated, and the major challenges remaining for this type of sample are discussed. The aim of this review is to provide useful information that encourages future research on LIBS for biological samples. [ABSTRACT FROM AUTHOR]

The electrical demands in several countries around the world are increasing due to the huge energy requirements of prosperous economies and the human activities of modern life. Published Papers This special issue contains 10 highly qualified papers related to the latest advances and technologies in Power Systems Operation, Control, Protection, and Security. The study aims to evaluate the performance of the protection algorithm by implementing different mother wavelets for signal analysis and determines a suitable mother wavelet for power system protection applications. [Extracted from the article]

The objectives of this paper will be to discuss the issues related to the determination of the limits of detection (LOD) in laser-induced breakdown spectroscopy (LIBS) analytical applications. The derivation of the commonly used '3-sigma over slope' rule and its evolution towards the new official definition recently adopted by the International Union of Pure and Applied Chemistry (IUPAC) will be illustrated. Methods for extending the calculation of the LOD to LIBS multivariate analysis will also be discussed, using as an example the detection of Cu traces in cast iron samples by LIBS. [ABSTRACT FROM AUTHOR]

China's first Mars rover, Zhurong, landed on the southern region of Utopia Planitia, Mars, on 14 May 2021 (UTC). Zhurong is equipped with the Mars Surface Composition Detection Package (MarSCoDe), which analyzes the Martian surface's material composition. Composed of laser-induced breakdown spectroscopy (LIBS), short-wave infrared spectroscopy (SWIR), and a microimaging camera, MarsCoDe can work at a distance of 1.6–7 m to analyze element abundance and the mineralogy of targets on the Martian surface. Analysis shows that the wavelengths of MarSCoDe onboard LIBS spectra acquired within the same probe period will have different degrees of drift, leading to deviation in qualitative and quantitative elemental analysis. This paper finds that the spectrum drift follows a quadratic function relationship with the CCD temperature of the MarSCoDe spectrometer, based on which a wavelength calibration method is established. According to the function, the drift of a certain channel is calculated by the corresponding CCD temperature, and then the wavelength of the spectrum is calibrated by the drift. The accuracy of this calibration method for the position of peak wavelength in the LIBS spectrum can reach about 1/5 of the apparatus spectral width, and the cross-validation analysis using a norite standard sample shows that it is comparable to the wavelength calibration accuracy of the ChemCam onboard data product. [ABSTRACT FROM AUTHOR]

The paper considers the emission spectra and dependences of the emission intensity of a number of carbon lines in absolute units for laser plasma generated by laser pulse on CO2, CHF3, and CF4 gas jets on the gas pressure at the nozzle inlet. A pulsed Nd:YAG laser, λ = 1064 nm, τ = 5.2 ns, Eimp = 0.8 J was used. Gas-jet targets were formed by a supersonic conical nozzle, the pressure at the nozzle inlet varied in the range of 5–25 bar. The emission spectra of the investigated gases were compared and the reasons for the different dependences of the radiation intensity on the gas pressure at the nozzle inlet were analyzed. [ABSTRACT FROM AUTHOR]

To prevent air pollution and achieve air quality regulations, it is essential to develop analytical techniques that can determine the concentration of metals in aerosol particles, both in the gas phase and after collection onto filters. Total reflection X-ray fluorescence spectroscopy (TXRF) and laser-induced breakdown spectroscopy (LIBS) are emerging as complementary techniques for determining the elemental composition of aerosol particles. The accuracy of their results relies on calibration methods based on aerosol and multi-element filters representative of the on-line measurement conditions and particulate collection for off-line measurement, respectively. In this paper we propose a novel methodology for characterizing nebulization generated aerosol particles dispersion and deposition by means of TXRF to assess the use of an aerosol generator to produce calibration samples for LIBS and TXRF analysis. Particles concentration and size distribution of the aerosol produced by nebulizing a Cu salt aqueous solution are measured inside a glove box modifying the production parameters and collecting the corresponding particulate deposited on reflectors. The most stable conditions are observed at average flow rate and selected for studying the aerosol spatial distribution. The Cu mass collected on reflectors positioned at a fixed distance and radial geometry with respect to the nozzle exit is measured by TXRF and increases linearly with time. Results suggest that this experimental configuration could be used to realize calibration samples for TXRF analysis representative of particulate deposition. The use of these aerosols as LIBS calibration samples could lead to significant errors due to the observed flow asymmetry. Copyright © 2022 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Fiber lasers are characterized by high efficiency, good beam quality, and high reliability and are widely used in industries. In addition, the high repetition frequency of fiber lasers can increase the analytical efficiency greatly. In this paper, a nanosecond fiber laser was introduced to be the ablation source in laser-induced breakdown spectroscopy (LIBS) for determining copper, magnesium, and manganese in aluminum alloys. Because of the high repetition frequency of the fiber laser, the conventional delay-acquisition strategy was unavailable. Discrete wavelet transform (DWT) was used to mitigate the interference of the Bremsstrahlung background. Standard calibration and internal calibration methods were also compared for quantitative analyses. The results demonstrated that the combination of DWT and internal calibration effectively improved the analytical accuracy. After optimization, the R2s of the FL-LIBS system for Cu, Mg, and Mn were 0.9897, 0.9964, and 0.9979, respectively; the root mean squared error of cross validation was 0.0414, 0.0462, and 0.031 wt. %, respectively. This study provides a convenient method for the rapid elemental analysis of aluminum alloys. [ABSTRACT FROM AUTHOR]

With the development of modern industry, it can be said that from industrial production to the basic necessities of life, plastic products can be seen everywhere. What follows is the disposal of plastic waste. How to deal with plastic waste correctly is closely related to people's health and the earth's environment. In this paper, laser-induced breakdown spectroscopy is applied for the online in situ detection of plastic and its combustion smoke. According to the spectrum obtained, the main components of plastics are Ca, Mg, Na, K, C, H and O. In the spectrum of smoke, the characteristic peaks of the elements C, H, O and N are observed. In addition, the online detection of heavy metal pollution is simulated. Finally, principal component analysis and error back propagation artificial neural networks were applied for the identification of different plastics and their combustion smoke, and the identification accuracy reaches 92.73% and 77.42% respectively. All the results indicate that laser-induced breakdown spectroscopy technology has great potential in the identification of similar objects and the monitoring of air pollutants. [ABSTRACT FROM AUTHOR]

The removal of aged varnish on artistic paintings is a delicate intervention and the use of UV laser for this purpose is of special relevance. In particular, the use of nanosecond-pulsed lasers operating at 213 nm has been noted to produce good results in mock-up samples, but it has not been tested in real artworks. In this paper, we report on the application of this procedure for the first time on a contemporary oil easel painting with naturally aged varnish. The obtained results were compared with those achieved using traditional solvents, specifically a mixture of ligroin:acetone. Additionally, hot water was used to remove surface dirt. The performance of the different cleaning procedures was assessed with a range of techniques, including low-power microscopy, UV lamp illumination, laser-induced fluorescence (LIF), and laser-induced breakdown spectroscopy (LIBS). Of the tested treatments, the best performance is obtained by nanosecond laser irradiation at 213 nm using an adequate laser fluence (typically 0.14 J/cm2) that allows controlled and efficient removal of the outermost aged varnish layer without affecting the underlying non-aged varnish and paint layers. [ABSTRACT FROM AUTHOR]

Hyperfine structures of highly charged ions (HCIs) are favourable spectroscopic targets for exploring fundamental physics along with nuclear properties. Recent proposals of HCI atomic clocks highlight their importance, especially for many-electron HCIs, and they have been theoretically investigated by refining atomic-structure calculations. However, developments in hyperfine spectroscopy of many-electron HCIs have not proceeded due to experimental difficulty. Here, we demonstrate hyperfine-structure-resolved laser spectroscopy of HCIs in an electron beam ion trap plasma, employing the magnetic-dipole transition in the 4d95s state of 127I7+. Ion-state manipulation by controlled electron collisions in the well-defined laboratory plasma enables laser-induced fluorescence spectroscopy of trapped HCIs. The observed spectrum of evaporatively cooled ions under low magnetic fields shows characteristic features reflecting the hyperfine structures. The present demonstration using combined optical and plasma approaches provides a benchmark for state-of-the-art atomic calculations of hyperfine structures in many-electron HCIs, and offers possibilities for a variety of unexploited experiments. Highly charged ions (HCIs) have opened up various research frontiers in fundamental physics, such as recent proposals for atomic clocks based on heavy HCIs with many electrons. This paper demonstrates a laser spectroscopic method using an electron beam ion trap plasma with a quasi-Zeeman-free low magnetic field to deepen understanding of their hyperfine structure. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) is a powerful method for non-invasive elemental composition monitoring which can be applied for processing graded metal alloys, provided that challenges with reliable and rapid spectral data processing are overcome to enable composition analysis in real-time. In this study, we describe an integrated experimental-computational methodology for analyzing LIBS spectra data obtained from graded composition metal alloy surfaces with a mean rate of composition analysis up to 15.7 Hz. The accuracy and speed of this method was assessed via analysis of a graded Al Cu film prepared by magnetron sputtering representing a gradient alloy processed by additive manufacturing. Using a pulsed femtosecond laser and gated sCMOS detector, a series of LIBS measurements were taken across the composition gradient of an Al Cu sputtered alloy. Energy Dispersive Spectroscopy (EDS) was used both to calibrate composition measurements and quantify the error of the LIBS-based rapid analysis method demonstrated in this paper, which yielded a mean percent error relative to the EDS data in the composition measurement along the gradient as low as 1.4 % when optimized for the cumulative number of probe laser pulses on a single measurement spot. The femtosecond probe pulse method described in this paper allows for the alloy composition to be accurately measured in hundredths of a second, potentially allowing for real-time composition monitoring in gradient alloy processing, including thin film sputtering, additive manufacturing, and other rapid processing technologies for graded metal alloys. • Rapid quantitative spectroscopic analysis method for composition measurement of graded alloys • Integrated computational-experimental approach for real time, in situ LIBS analysis • Accuracy validation of composition measurements using graded, sputtered Al Cu thin film • Optimization of number of cumulative laser pulses for reduced error in composition data [ABSTRACT FROM AUTHOR]

In the realm of biological experimental research, bacterial deposition on scientific instruments' surfaces can compromise the integrity of experimental outcomes. Prolonged bacterial accumulation may even result in diminished instrument functionality, rendering them incapable of normal operation. Traditional chemical cleaning methods carry the risk of secondary contamination and are unsuitable for decontaminating precision optical or electronic instruments. Therefore, it is imperative to develop novel non-contact, waterless, contamination-free, and non-destructive decontamination methods. This paper introduces an innovative two-dimensional high-speed scanning sterilization technique based on high repetition rate laser-induced quasi-continuous plasmas. The experiment targeted Escherichia coli and Bacillus subtilis for decontamination, investigating the impact of laser energy, repetition rate, scanning rate, repetition scanning times, and focal distance on the inactivation rate. The results indicate that at a laser repetition rate of 15 kHz, an energy of 680 μJ/pulse, a repetition scanning of 10 times, and a focal distance of −50 mm, the decontamination efficiency reaches 26.7 mm2/min, with an inactivation rate exceeding 98 %, achieving rapid and efficient decontamination of bacteria adhering to the carrier. Furthermore, the paper explores the decontamination mechanism of laser-induced plasma, demonstrating that the primary mechanism of bacterial inactivation using this technique is the action of the plasma rather than the thermal ablation effect of laser irradiation. The proposed laser-based bacterial decontamination device is characterized by its compact design, integrability, ease of operation, and high inactivation effectiveness. This makes it a promising solution with broad applications in the fields of biological science, precision optoelectronics, medical devices, food processing, and more. Moreover, it integrates with LIBS technology to achieve the integrated development of identification and disinfection. [ABSTRACT FROM AUTHOR]

When alloy composition information is sought across a single large artefact assemblage, how well do handheld methods solve the problem of museum environments which restrict the movement of artefacts and destructive sampling, and which have limited in‐house technical resources? The usefulness of relatively low‐cost handheld analytical instruments still needs evaluating in such arenas. The potential advantages which handheld laser‐induced breakdown spectrometry (HH‐LIBS), with its affordability, speed and micro‐destructive corrosion‐penetrating ability, might offer over handheld X‐ray fluorescence (HH‐XRF)/portable X‐ray fluorescence (pXRF) in large intra‐assemblage comparisons of broad copper alloy composition were examined and reported on by the present study (tin and lead being the elements of interest). The context was an archaeological study in a major Greek museum, aimed at exploring the social and economic significance of alloying choice at a single large representative site of the Bronze–Iron transition, c.1200 bc. Archaeological interpretations are presented in another paper, with the alloying patterns/choices identified only being outlined in the present paper. The results of the methods comparison described suggest that HH‐LIBS has potential, but that HH‐XRF, despite its variable limitations in relation to penetrating corrosion (discussed here), is still the most reliable method for work in such circumstances. [ABSTRACT FROM AUTHOR]

Material ablation driven by focused laser pulses is an important aspect of laser-induced breakdown spectroscopy (LIBS). It has frequently been used to ablate non-representative layers from the surface or to generate analytic depth profiles of samples. In this paper we discuss the crosstalk effects of the locally ablated surface on the LIBS measurement of the underlying bulk material. As a measuring object, a model artefact is chosen consisting of an iron-free brass bulk sample on which a steel plate with a thickness of 500 μm was brought in close contact. This steel sheet acts as a surrogate for a non-representative surface layer. It is shown by LIBS measurements and cross polish methods that an indirect interaction between the expanding plasma originating from the substrate and the surface layer at the crater walls as well as a recasting of the ablated material from the steel plate have a notable influence on LIBS measurements of the underlying bulk sample. By a two-step ablation sequence crosstalk effects can be reduced to levels equivalent to those persisting for the model artefact without the steel sheet. [ABSTRACT FROM AUTHOR]

This paper illustrates systematic development of a convenient analytical method for the determination of chromium and cadmium in tannery wastewater using laser-induced breakdown spectroscopy (LIBS). A new approach was developed by which liquid was converted into solid phase sample surface using absorption paper for subsequent LIBS analysis. The optimized values of LIBS parameters were 146.7mJ for chromium and 89.5mJ for cadmium (laser pulse energy), 4.5 µs (delay time), 70mm (lens to sample surface distance), and 7mm (light collection system to sample surface distance). Optimized values of LIBS parameters demonstrated strong spectrum lines for each metal keeping the background noise atminimum level. The new method of preparing metal standards on absorption papers exhibited calibration curves with good linearity with correlation coefficients, R2 in the range of 0.992 to 0.998. The developed method was tested on real tannery wastewater samples for determination of chromium and cadmium. [ABSTRACT FROM AUTHOR]

A fast and sensitive estimation of Cu and Cr in aqueous solution by laser induced breakdown spectroscopy (LIBS) was realized by using a simple pre-treatment methodology of aqueous solution. Sodium hydroxide (NaOH) is added to the sample to raise the pH (>12) of the solution to form hydroxides of metals which leads to formation of colloids. This colloidal solution is spread over a filter paper, dried in air and subsequently subjected to LIBS. The LIBS signal intensity was found to be two orders of magnitude higher than the solution without adding NaOH. Under optimized experimental conditions, linear calibration plots were obtained in the range of 0.05–0.8 μg/mL of Cu and Cr, with good correlation coefficients (R2 > 0.995) using Yb as an internal standard. The detection limits of Cu and Cr were found to be 0.020 and 0.025 μg/mL respectively. Tap and rain water samples spiked with Cu and Cr are analysed by the proposed method and recoveries are in the range of 93–117%. Unlabelled Image • Colloidal solution of Cu and Cr is prepared by adding concentrated NaOH. • LIBS signal of dried solution over filter paper is enhanced by nearly two orders. • The present method is simple and quick to improve the sensitivity of liquid sample. • The detection limits of Cu and Cr were found to be 0.025 μg/mL. • Recoveries of Cu and Cr ions in water samples are in the range of 93–117%. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) has been appreciated as a valuable analytical tool in the cultural heritage field owing to its unique technological superiority, particularly in combination with chemometric methods. Feature selection (FS) as an indispensable pre-processing step in data optimization, for eliminating the redundant or irrelevant features from high-dimensional data to enhance the predictive capacity and result comprehensibility of multivariate classification based on LIBS technology. In this paper, a novel hybrid filter/wrapper method based on the MI-DBS algorithm was proposed to enhance the qualitative analysis performance of the LIBS technique. The proposed method combines the advantages of the mutual information (MI) algorithm based filter method and bi-directional selection (DBS) algorithm based wrapper method. The MI algorithm is the first to remove the redundant or uncorrelated features so that a simplified input subset can be established. Then, the DBS algorithm is used to further select the retained features and hence to seek an optimal feature subset with good predictive performance. To benefit the above feature selection process, the wavelet transform denoising (WTD) method was used to reduce the noise from LIBS spectra. LIBS experiments were performed using 35 archaeological ceramic samples. Besides, the proposed hybrid filter/wrapper method was implemented through a random forest (RF) based nonlinear multivariate classification method. Through a comparison between several other feature selection methods and the proposed method, it has been seen that the proposed method is the best regarding the predictive performance and number of the selected features. Finally, the MI-DBS algorithm is used to seek the optimal features from the full spectrum (220–720 nm); the corresponding sensitivity, specificity and accuracy acquired through the RF classifier for the test set were 0.9722, 0.9956 and 0.9850. It is shown from the general results that the MI-DBS algorithm is more effective in terms of improving the model performance and decreasing the redundant or uncorrelated features and computational time and serves as a good alternative for FS in multivariate classification. [ABSTRACT FROM AUTHOR]