Simulation of emission spectra from nonuniform reactive laser-induced plasmas

Indole clubbed 2,4-thiazolidinedione linked 1,2,3-triazole as a potent antimalarial and antibacterial agent against drug-resistant strain and molecular modeling studies

In the face of escalating challenges of microbial resistance strains, this study describes the design and synthesis of 5-({1-[(1H-1,2,3-triazol-4-yl)methyl]-1H-indol-3-yl}methylene)thiazolidine-2,4-dione derivatives, which have demonstrated significant antimicrobial properties. Compared with the minimum inhibitory concentrations (MIC) values of ciprofloxacin on the respective strains, compounds 5a, 5d, 5g, 5l, and 5m exhibited potent antibacterial activity with MIC values ranging from 16 to 25 µM. Almost all the synthesized compounds showed lower MIC compared to standards against vancomycin-resistant enterococcus and methicillin-resistant Staphylococcus aureus strains. Additionally, the majority of the synthesized compounds demonstrated remarkable antifungal activity, against Candida albicans and Aspergillus niger, as compared to nystatin, griseofulvin, and fluconazole. Furthermore, the majority of compounds exhibited notable inhibitory effects against the Plasmodium falciparum strain, having IC50 values ranging from 1.31 to 2.79 μM as compared to standard quinine (2.71 μM). Cytotoxicity evaluation of compounds 5a-q on SHSY-5Y cells at up to 100 μg/mL showed no adverse effects. Comparison with control groups highlights their noncytotoxic characteristics. Molecular docking confirmed compound binding to target active sites, with stable protein-ligand complexes displaying drug-like molecules. Molecular dynamics simulations revealed dynamic stability and interactions. Rigorous tests and molecular modeling unveil the effectiveness of the compounds against drug-resistant microbes, providing hope for new antimicrobial compounds with potential safety.

Laser Ablation Plasmas and Spectroscopy for Nuclear Applications

The development of measurement methodologies to detect and monitor nuclear-relevant materials remains a consistent and significant interest across the nuclear energy, nonproliferation, safeguards, and forensics communities. Optical spectroscopy of laser-produced plasmas is becoming an increasingly popular diagnostic technique to measure radiological and nuclear materials in the field without sample preparation, where current capabilities encompass the standoff, isotopically resolved and phase-identifiable (e.g., UO and UO2 ) detection of elements across the periodic table. These methods rely on the process of laser ablation (LA), where a high-powered pulsed laser is used to excite a sample (solid, liquid, or gas) into a luminous microplasma that rapidly undergoes de-excitation through the emission of electromagnetic radiation, which serves as a spectroscopic fingerprint for that sample. This review focuses on LA plasmas and spectroscopy for nuclear applications, covering topics from the wide-area environmental sampling and atmospheric sensing of radionuclides to recent implementations of multivariate machine learning methods that work to enable the real-time analysis of spectrochemical measurements with an emphasis on fundamental research and development activities over the past two decades. Background on the physical breakdown mechanisms and interactions of matter with nanosecond and ultrafast laser pulses that lead to the generation of laser-produced microplasmas is provided, followed by a description of the transient spatiotemporal plasma conditions that control the behavior of spectroscopic signatures recorded by analytical methods in atomic and molecular spectroscopy. High-temperature chemical and thermodynamic processes governing reactive LA plasmas are also examined alongside investigations into the condensation pathways of the plasma, which are believed to serve as chemical surrogates for fallout particles formed in nuclear fireballs. Laser-supported absorption waves and laser-induced shockwaves that accompany LA plasmas are also discussed, which could provide insights into atmospheric ionization phenomena from strong shocks following nuclear detonations. Furthermore, the standoff detection of trace radioactive aerosols and fission gases is reviewed in the context of monitoring atmospheric radiation plumes and off-gas streams of molten salt reactors. Finally, concluding remarks will present future outlooks on the role of LA plasma spectroscopy in the nuclear community.

A Laser-Based Method for the Detection of Honey Adulteration

In the present work, laser-induced breakdown spectroscopy, aided by some machine learning algorithms (i.e., linear discriminant analysis (LDA) and extremely randomized trees (ERT)), is used for the detection of honey adulteration with glucose syrup. In addition, it is shown that instead of the entire LIBS spectrum, the spectral lines of inorganic ingredients of honey (i.e., calcium, sodium, and potassium) can be also used for the detection of adulteration providing efficient discrimination. The constructed predictive models attained high classification accuracies exceeding 90% correct classification.

Short-Pulse Lasers: A Versatile Tool in Creating Novel Nano-/Micro-Structures and Compositional Analysis for Healthcare and Wellbeing Challenges

Driven by flexibility, precision, repeatability and eco-friendliness, laser-based technologies have attracted great interest to engineer or to analyze materials in various fields including energy, environment, biology and medicine. A major advantage of laser processing relies on the ability to directly structure matter at different scales and to prepare novel materials with unique physical and chemical properties. It is also a contact-free approach that makes it possible to work in inert or reactive liquid or gaseous environment. This leads today to a unique opportunity for designing, fabricating and even analyzing novel complex bio-systems. To illustrate this potential, in this paper, we gather our recent research on four types of laser-based methods relevant for nano-/micro-scale applications. First, we present and discuss pulsed laser ablation in liquid, exploited today for synthetizing ultraclean "bare" nanoparticles attractive for medicine and tissue engineering applications. Second, we discuss robust methods for rapid surface and bulk machining (subtractive manufacturing) at different scales by laser ablation. Among them, the microsphere-assisted laser surface engineering is detailed for its appropriateness to design structured substrates with hierarchically periodic patterns at nano-/micro-scale without chemical treatments. Third, we address the laser-induced forward transfer, a technology based on direct laser printing, to transfer and assemble a multitude of materials (additive structuring), including biological moiety without alteration of functionality. Finally, the fourth method is about chemical analysis: we present the potential of laser-induced breakdown spectroscopy, providing a unique tool for contact-free and space-resolved elemental analysis of organic materials. Overall, we present and discuss the prospect and complementarity of emerging reliable laser technologies, to address challenges in materials' preparation relevant for the development of innovative multi-scale and multi-material platforms for bio-applications.

Quantitative laser-induced breakdown spectroscopy for discriminating neoplastic tissues from non-neoplastic ones

In this paper, we present a method to distinguish neoplastic tissues from non-neoplastic ones using calibration-free laser-induced breakdown spectroscopy (CF-LIBS). For this propose, plasma emission was collected from neoplastic and non-neoplastic tissues taken from the ovarian cancer mice models. Results were obtained by utilizing the characteristic plasma emission lines of different elements that have been confirmed in the investigated samples. From the temporal evolution of plasma emission, the optimum temporal-observation-windows are identified for LIBS investigation. The concentrations of the detected elements in tissues were measured by a calibration-free approach based on data process of plasma parameters at the local thermodynamic equilibrium. The neoplastic specimens provided more energetic plasma than non-neoplastic ones that resulting in higher peaks intensities, electron density and electron temperature especially in the early windows (between 0.1 µs to 0.8 µs). Results demonstrated higher concentrations of major and trace elements such as Mg, Fe, Ca, Na, and K in the neoplastic tissues. Finally, the results using CF-LIBS method were found to be in good agreement with that of Inductive coupled plasma-optical emission spectroscopy (ICP-OES).

Laser-Induced Breakdown Spectroscopy Assisted by Machine Learning for Plastics/Polymers Identification

In the present work, Laser-Induced Breakdown Spectroscopy (LIBS) is used for the discrimination/identification of different plastic/polymeric samples having the same polymeric matrix but containing different additives (as e.g., fillers, flame retardants, etc.). For the classification of the different plastic samples, some machine learning algorithms were employed for the analysis of the LIBS spectroscopic data, such as the Principal Component Analysis (PCA) and the Linear Discriminant Analysis (LDA). The combination of LIBS technique with these machine learning algorithmic approaches, in particular the latter, provided excellent classification results, achieving identification accuracies as high as 100%. It seems that machine learning paves the way towards the application of LIBS technique for identification/discrimination issues of plastics and polymers and eventually of other classes of organic materials. Machine learning assisted LIBS can be a simple to use, efficient and powerful tool for sorting and recycling purposes.

Transition Rates for 3s3p2 4P–3s3p4s 4Po Transitions in Al i

Fully relativistic calculations have been performed for two multiplets, 3 s 3 p 2 4 P and 3 s 3 p 4 s 4 P o , in Al i. Wave functions were obtained for all levels of these multiplets using the grasp programs. Reported are the E1 transitions rates for all transitions between levels of these multiplets. Transition energies and transition rates are compared with observed values and other theory. Our calculated transition rates are smaller by about 10% than observed rates, reducing a large discrepancy between earlier calculations and experiments.

Ideal radiation source for plasma spectroscopy generated by laser ablation

Laboratory plasmas inherently exhibit temperature and density gradients leading to complex investigations. We show that plasmas generated by laser ablation can constitute a robust exception to this. Supported by emission features not observed with other sources, we achieve plasmas of various compositions which are both uniform and in local thermodynamic equilibrium. These properties characterize an ideal radiation source opening multiple perspectives in plasma spectroscopy. The finding also constitutes a breakthrough in the analytical field as fast analyses of complex materials become possible.

Compositional Analysis of Aerosols Using Calibration-Free Laser-Induced Breakdown Spectroscopy

We demonstrate that the elemental composition of aerosols can be measured using laser-induced breakdown spectroscopy (LIBS) without any preliminary calibration with standard samples. Therefore, a nanosecond Nd:YAG laser beam was focused into a flux of helium charged with alumina aerosols of a few micrometers diameter. The emission spectrum of the laser-generated breakdown plasma was recorded with an echelle spectrometer coupled to a gated detector. The spectral features including emission from both the helium carrier gas and the Al2O3 aerosols were analyzed on the base of a partial local thermodynamic equilibrium. Thus, Boltzmann equilibrium distributions of population number densities were assumed for all plasma species except of helium atoms and ions. By analyzing spectra recorded for different delays between the laser pulse and the detector gate, it is shown that accurate composition measurements are only possible for delays ≤1 μs, when the electron density is large enough to ensure collisional equilibrium for the aerosol vapor species. The results are consistent with previous studies of calibration-free LIBS measurements of solid alumina and glass and promote compositional analysis of aerosols via laser-induced breakdown in helium.