Search Results (714)

It is found that the speckle structure of the photoinduced light scattering indicatrix of the LiNbO₃:Y³⁺(0.46 wt%) crystal and its behavior with the time of crystal irradiation with a laser undergo an atypical behavior caused by the features of the dissipation processes of laser-induced defects in the crystal. In the frequency range of 100–4000 cm⁻¹, the Raman spectra of the LiNbO₃:Y³⁺(0.46 wt%) single crystal were recorded upon excitation by visible (532 nm) and near-IR (785 nm) laser radiation. Five second-order Raman scattering lines were detected in the frequency range of 1000–2100 cm⁻¹, with the frequencies of two of them (of about 1790 and 1940 cm⁻¹) somewhat exceeding the doubled value of the frequencies of fundamental vibrations of the 4A₁(z)LO (longitudinal optical) and 9E(x,y) symmetry types, which allows us to attribute these lines to the overtones of the fundamental vibrations of 4A₁(z)LO and 9E(x,y). It is found that only one Raman scattering line is observed in the region of stretching vibrations of OH-groups (3200–3800 cm⁻¹). The frequency of this line is found to depend on the scattering geometry, varied within 3431–3438 cm⁻¹, and to be shifted to the low-frequency region by about 30–50 cm⁻¹ relative to the frequencies in the IR absorption spectrum. This finding may be due to the alternative prohibition rule due to the presence of the center of symmetry of the oxygen octahedra O₆ of the crystal structure. Full article

Distributed fiber optic sensing (DFOS) has emerged as a critical technology for structural health monitoring of large-scale infrastructure, offering unique advantages in terms of coverage and environmental adaptability. This review presents a comprehensive analysis of the two dominant technical routes: fully distributed sensing based on intrinsic backscattering and massive-capacity sensing based on ultra-weak fiber Bragg grating (UWFBG) networks. For backscattering-based systems—encompassing Raman, Brillouin, and Rayleigh scattering—the inherent trade-offs among signal-to-noise ratio (SNR), spatial resolution, and sensing range constitute major performance bottlenecks. This review systematically summarizes advanced demodulation and signal processing strategies designed to overcome these physical barriers, including pulse coding sequences, chaotic laser compressed correlation, and deep learning-enhanced noise reduction algorithms. In parallel, for UWFBG-based technologies, the evolution from traditional multiple-point fiber Bragg grating (FBG) array to quasi-distributed and fully distributed UWFBG network is discussed. This review highlights key breakthroughs in achieving high spatial resolution and high-speed interrogation through hybrid multiplexing, aliased spectrum reconstruction, and dispersion-based demodulation techniques. By synthesizing recent advances in modulation schemes, detection hardware, and algorithmic processing, this paper outlines the trajectory of DFOS technologies toward high-precision, long-distance, and real-time sensing networking. Full article

The influence of a non-resonant intense laser field on the optical absorption and Raman scattering processes in ZnO/Mg_0.2Zn_0.8O quantum wells is theoretically investigated. It is shown that the dressing field significantly modifies the confinement potential and reshapes the electronic wave functions, leading to tunable shifts in intersubband transition energies and changes in the dipole matrix elements. These laser-induced effects produce notable variations in the absorption spectrum and strongly modulate the Raman differential cross section and Raman gain. Under the application of a non-resonant laser field, the Raman gain is enhanced by almost a factor of four, whereas off-resonant pumping results in much weaker, yet still field-dependent, responses. The results demonstrate that intense laser fields provide an effective tool to dynamically control the optical and Raman properties of ZnO-based quantum well structures. Full article

Liver cancer continues to be a predominant cause of cancer-related mortality globally, primarily attributable to late diagnosis and a scarcity of dependable biomarkers for early identification. Raman spectroscopy has emerged as a valuable analytical instrument for liver cancer detection, providing rapid, label-free, and non-destructive molecular profiling of biological specimens. Raman-based methodologies can discern malignant from non-malignant conditions by analyzing small biochemical alterations in biofluids, including blood, urine, and exosomes, as well as in liver tissue, yielding unique spectrum fingerprints. Progress in chemometric analysis, including machine learning models and multivariate statistical methods, has significantly improved the diagnostic precision of Raman spectroscopy, attaining elevated sensitivity and specificity across numerous studies. Furthermore, the integration of complementary techniques, such as surface-enhanced Raman spectroscopy (SERS) and Raman optical activity (ROA) has broadened its prospects for clinical application. This review article elucidates the contemporary applications of Raman spectroscopy in the diagnosis of liver cancer, presents pivotal findings across various sample types, and examines the challenges and future prospects of building Raman-based platforms as dependable diagnostic instruments in oncology. Full article

A simple and highly sensitive surface-enhanced Raman spectroscopy (SERS) method has been developed for the detection of thiram residues in fruit juices. Carboxymethyl cellulose (CMC) @ gold nanoparticles (Au NPs) hydrogel beads as SERS substrates were prepared through ionic crosslinking. The obtained porous CMC @ Au NPs hydrogel bead substrates showed excellent sensitivity for the detection of thiram in apple, grape, and orange juices, with detection limits of 0.001, 0.002, and 0.002 mg/L, respectively. The impact of primary non-target components in juices on SERS detection of thiram was investigated, revealing that the presence of sugars and acids caused varying degrees of interference in SERS measurements. This innovative, practical, and affordable CMC @ Au NPs porous hydrogel bead for thiram detection might be readily expanded to analyze a broad spectrum of other compounds found in food goods at trace amounts. Full article

Shagamite, KFe₁₁O₁₇ (IMA 2020-091) was discovered in the ferrite zone of gehlenite hornfels from the Hatrurim Complex exposed near Mt. Ye’elim, Hatrurim Basin, Israel. The mineral occurs in outer zones of gehlenite rock blocks that were heterogeneously altered by high-temperature (>1200 °C) ferritization. Ferritization was induced by K-bearing fluids or melts, generated as a by-product of late combustion processes. Shagamite crystallized from a thin melt that formed on the rock surface during cooling to approximately 800–900 °C. It is mainly associated with minerals of the magnetoplumbite group like barioferrite, Sr-analog of barioferrite, and gorerite but also with magnetite, maghemite, harmunite, devilliersite and K(Sr,Ca)Fe₂₃O₃₆ hexaferrite. Shagamite is a modular compound with a β-alumina-type structure (P6₃/mmc, a = 5.9327 (5), c = 23.782 (3) Å, γ = 120°, V = 724.91 (13) ų, Z = 2), and it is isostructural with diaoyudaoite, NaAl₁₁O₁₇, and kahlenbergite, KAl₁₁O₁₇. Its structure is also closely related, though non-isotypic, to those of the magnetoplumbite-group minerals. Shagamite is dark brown with a semi-metallic luster and forms platy crystals flattened on (001). Its mean empirical formula is: (K_1.00Ca_0.15Mn²⁺_0.05Na_0.04Rb_0.01)_Σ1.25(Fe_10.36Mn²⁺_0.15Al_0.14Mg_0.12Zn_0.10Ni_0.07Cu_0.03Cr³⁺_0.02Ti⁴⁺_0.01)_Σ11.00O₁₇. The Vickers microhardness VHN₂₅ = 507 kg/mm² corresponds to a Mohs hardness of ~5. The calculated density, based on the empirical formula and unit-cell parameters, is 4.12 g·cm⁻³. The main bands in the Raman spectrum of shagamite occur at 685 and 715 cm⁻¹ and are assigned to ν₁(FeO₄)⁵⁻ tetrahedral vibrations. Full article

Flax (Linum usitatissimum L.) is a crop widely cultivated for fiber and oil production. The screening method for flax breeding must effectively address the biochemical characteristics of flaxseeds. In this study, to characterize flax cultivars, we extracted oil, defatted kernel, hull, and mucilage from whole seeds for the ATR-FT-MIR and FT-Raman spectroscopic measurements. In addition, for ATR-FT-MIR analysis, oil samples were obtained by pressing the flaxseed directly onto the crystal surface. After removing any seed residues, a grease stain was used for the measurement, allowing for the acquisition of the oil spectrum from a single seed. This method also enabled the detection of free fatty acids, serving as evidence of seed damage. Both methods effectively estimated the degree of unsaturation as a cultivar marker. The vibrational spectra of defatted kernels showed strong protein features; polysaccharide bands dominated in hull and mucilage spectra. Discrimination of flax cultivars using principal component analysis of vibrational spectra in specific regions was the most promising for flaxseed oil and mucilage. Multivariate analysis of a set of selected variables sensitive to the flaxseed oil composition successfully distinguished all flax cultivars of this study. The strong correlation observed between ATR-FT-MIR and FT-Raman results confirmed that these methods are comparable for characterizing different grades of flaxseed oil. Full article

This study evaluates the swelling potential in clayey soils of the Paleogene Brebi, Mera, and Moigrad formations in the Transylvanian Basin (Romania) by integrating direct free-swelling tests (FS; STAS 1913/12-88) with indirect index-property diagrams and semi-quantitative X-ray diffraction (XRD; RIR method). The indirect analysis combines three swelling-susceptibility classification charts—Seed et al. (AI–clay), Van der Merwe (PI–clay), and Dakshanamurthy and Raman (LL–PI)—with mineralogical trends from the Casagrande plasticity chart, complemented by Holtz and Kovacs’s clay-mineral reference fields and Skempton’s activity concept (AI = PI/% < 2 µm). The geotechnical dataset comprises 88 Brebi, 46 Mera, and 263 Moigrad specimens (with parameter counts varying by test), an XRD was performed on a representative subset. The free swell (FS) results indicate that Brebi soils range from low to active behavior (50–135%) without reaching the very active class; most Brebi specimens fall in the medium-activity range. Moigrad spans the full FS spectrum (20–190%) but is predominantly in the medium-to-active range. In contrast, Mera soils exhibit predominantly active behavior, covering the full range of activity classes (30–170%). The empirical classification charts diverge systematically: clay-sensitive schemes tend to assign higher swell susceptibility than the LL–PI approach, especially in carbonate-influenced soils. XRD results corroborate these patterns: Brebi is calcite-rich (mean ≈ 53.5 wt% CaCO₃) with minor expandable minerals (mean ≈ 3.1 wt%); Mera is feldspathic (orthoclase mean ≈ 55.3 wt%) with variable expandable phases; and Moigrad has a higher clay-mineral content (mean ≈ 38.8 wt%). Overall, swelling is controlled by the combined effects of clay-fraction reactivity, clay volume continuity, and carbonate-related microstructural constraints. Full article

The degradation of mercapto organic contaminants is highly important for safety and environmental protection since the specific chemical properties and the strong nature of S-containing bonds can make them less susceptible to traditional degradation mechanisms compared to other types of organic bonds. Thus, degradation of mercapto organic contaminants often requires catalysts with specific bandgap properties to ensure efficient generation of reactive species and appropriate redox potential alignment. Hence, in this work, we prepared bandgap-engineered semiconductor photocatalysts based on nanoparticles of different silica-doped spinel cobalt ferrite [SiO₂/CoFe₂O₄] (abbreviated as SiMCoF) [SiMCoF-1, SiMCoF-2, and SiMCoF-3] and characterized them by different analytical techniques. Since the dopant composition in a heterogeneous semiconductor material has important effects on its photocatalytic efficiency because adjusting the dopant profile can modulate impurity bands and enhance optical properties, which is crucial for the oxidative degradation of organic pollutants. Results from TEM, SEM, and their EDS analysis revealed that increased SiO₂ content showed improved surface area in the matrix, facilitating the increased absorption of oxygen impurities. This is further observed by the higher R_max values presented in AFM of SiMCoF-3 (139 nm) compared to SiMCoF-2 (116 nm) and SiMCoF-1 (8.78 nm), depicting its larger effective surface area (100 µm²), which in turn increases the active binding sites in the matrix. The Raman spectrum and XRD pattern of SiMCoF-3 showed various crystal planes with different atomic arrangements and a smaller crystallite size, leading to varying affinities for oxygen impurities. As a result, the optical bandgap decreased from 3.42 eV to 2.89 eV for SiMCoF-3, which is attributed to the quantum confinement effects caused by the smaller particle size and the dispersion of silica particles in the cobalt ferrite matrix. Thus, SiMCoF-3 showed elevated degradation performance without using any potential oxidants over the degradation of mercapto organic contaminants such as 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, and thiophenol under sunlight irradiation compared to other ferrites, and showed better results than Fenton’s reagent. Full article

This study reports the sustainable synthesis and thermal, morphological, and structural characterization of multifunctional silver/hydroxyapatite nanocomposite prepared from recycled caprine bone. The organic extract from caprine bone was characterized using Fourier Transform Infrared (FTIR) and Ultraviolet–Visible Spectroscopy (UV-Vis). The biogenic hydroxyapatite (CHAP) and its silver composite (Ag@CHAP) were characterized using thermal gravimetric analysis (TGA), Raman spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscope (TEM). The photocatalytic activity of Ag@CHAP was quantitatively confirmed through the degradation of Crystal Violet (5 ppm) under sunlight, achieving a high removal efficiency of 99.8% under optimum conditions, demonstrating significant potential for wastewater remediation. Ag@CHAP also demonstrated enhanced antimicrobial activity compared with CHAP and showed broad-spectrum efficacy against clinical human isolates P. aeruginosa ATCC 10145, E. coli ATCC 35218, S. aureus ATCC 25923, and C. albicans (human isolate). The in vitro hemolytic-activity assays revealed that both CHAP and Ag@CHAP had no hemolytic activity after 24 h of red blood cells incubation and effectively reduced lead-induced hemolysis from 86.73% to 39.35% and 49.13%, respectively. These findings confirm CHAP and Ag@CHAP as stable, biocompatible, and high-performance materials with promising applications in the sustainable water-treatment and biomedical fields. Full article

The iron-oxide-copper-gold (IOCG) skarns of the Tatatila-Las Minas mining district in central Mexico represent a structurally-controlled, exhumed fossil geothermal system located in the eastern sector of the Trans-Mexican Volcanic Belt (TMVB). The district was historically exploited for gold and copper mineralization. The emplacement of the ore bodies was controlled by regional Neogene–Quaternary NE- and NW-striking fault systems formed during the extensional evolution of the TMVB. These faults acted as conduits for high-temperature hydrothermal fluids circulating during the cooling of the Neogene magmatic intrusions. By integrating detailed field study with available exploration borehole data, the spatial distribution of the skarn bodies was reconstructed. Three main emplacement geometries were identified: (a) at contacts between magmatic bodies and host rocks, (b) as lenticular or irregular bodies parallel to the host rock foliation, and (c) at the intersections of near-orthogonal faults. Although structural controls on skarn formation represent a key factor in ore emplacement, their analysis remains scarcely explored. This paper therefore contributes to filling this gap by providing a detailed characterization of the structural framework governing IOCG skarn development at Tatatila–Las Minas. The results improve understanding of IOCG systems formation and provide predictive criteria for mineral exploration in similar geological settings, potentially reducing exploration and mining risks. Full article

This study investigates the effect of laser power, focal length, and number of passes on the fabrication of graphene-based strain sensors using a 450 nm diode laser at the upper limit of the UV spectrum. Polyimide substrates were irradiated to produce laser-induced graphene, and the resulting sensors were evaluated under three-point bending tests. The main requirements for deformation sensors—adequate conductivity, mechanical stability under bending, and high sensitivity (gauge factor)—were assessed through morphological analysis by SEM, Raman spectroscopy, and electrical characterization using the Van der Pauw method. The results indicate that laser power is the critical factor influencing graphene quality and sensor performance, while focal length has a negligible effect and additional passes reduce material quality and sensitivity. Overall, this work demonstrates the feasibility of producing functional, low-cost graphene strain sensors with a commercial diode laser, offering a scalable and affordable alternative for sensor fabrication. Full article

Through this work, an experimental setup and pre-processing method for obtaining fluorescence and quasi-noise-free Raman spectra of minerals for in situ mineral identification in an underground environment is proposed. It uses a combination of methodologies like dual excitation wavelengths, Shifted Excitation Raman Difference Spectroscopy (SERDS), and deep learning-based U-Net model for background and noise correction. The dual excitation wavelengths technique employs a near-infrared SERDS laser for the fingerprint and a red laser for the large Raman shift region. The SERDS laser operates at two excitation wavelengths and is tuneable in the vicinity of 785 nm. The red laser uses 671 nm excitation wavelength. The obtained fingerprint and large Raman shift Raman spectra are then fed to a pre-processing method containing the trained U-Net model for obtaining a background-corrected and quasi-noise-free Raman spectrum. The proposed method addresses issues of existing handheld Raman systems in terms of spectrometer sensitivity, spectrum acquisition speed, pre-processing time, fluorescence effects, and other interferences due to surrounding light or vibration. The obtained final processed Raman spectrum is then deconstructed into pseudo-Voigt peaks. The identification of the minerals can be based on the number and the positions of the pseudo-Voigt peaks. Samples of gypsum (CaSO₄·2H₂O) and anhydrite (CaSO₄) were used for evaluating the performance of the proposed method. The influence of measurement time on the reproducibility and precision of the peak identification and, thus, mineral identification is also analyzed. Full article

A review of studies has shown that aromatic azo and hydrazo derivatives are used in a wide spectrum of fields, including food, pharmaceutical, and cosmetic products, as well as in technical and electronic technologies, which has contributed to the development of new such compounds. In this work, the structures of newly obtained 4-methyl-3,5-dinitro-2-(2-phenylhydrazinyl)pyridine (4MDNPHP) and its azo derivative, 4-methyl-3,5-dinitro-2-[(E)-phenyldiazenyl]pyridine (4MDNPAP), were established by spectroscopic (NMR, IR, Raman, and UV-Vis) and emission studies. Single-crystal X-ray diffraction analysis was used to determine the molecular structure of the studied compounds, and the results were compared with DFT calculations (B3LYP/6-311G(2d,2p)). The collected X-ray data revealed that the crystal of the hydrazo compound (4MDNPHP) belongs to the triclinic space group P$\overline{1}$ (Z = 2), whereas the crystal of the azo compound (4MDNPAP) follows the symmetry of the monoclinic space group P2₁/n (Z = 4). Both presented derivatives crystallized with one molecule in the asymmetric unit. Specific properties of the hydrazo bridge C_ϕ-NH-NH-C_θ moiety and its azo counterpart C_ϕ-N=N-C_θ were considered in detail. Full article

A promising approach to alleviate the emerging capacity limitations in backbone optical networks is to employ the Super C+L-band, which provides an available spectrum of roughly 12 THz. Network throughput is a key metric for analyzing the performance of such networks; however, evaluating this metric is a complex task due to the interplay between physical and network layer aspects. Physical modeling, which accounts for signal impairments, is particularly complex in these scenarios due to the presence of Stimulated Raman Scattering (SRS), which transfers energy from the C to the L band. On the other hand, network layer modeling is also challenging due to the influence of numerous factors, including physical topology, routing, and traffic characteristics. For the networks considered here, we propose a machine learning approach to predict both the network throughput and the average channel capacity for the Shannon and real cases, and to investigate how these metrics depend on various physical topology parameters. The approach relies on an Artificial Neural Network (ANN) model, whose predictions are interpreted using the SHapley Additive exPlanations (SHAP) method to identify the importance of various topological parameters. Furthermore, the ANN is trained using data obtained from a previously developed simulator that takes into account both physical and network aspects. The analysis provides valuable insights for designing future ultra-high-capacity optical backbone networks. Full article