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Spectral signatures of fluorescence and light absorption to identify crude oils found in the marine environment
摘要： To protect the natural marine ecosystem, it is necessary to continuously enhance knowledge of environmental contamination, including oil pollution. Therefore, to properly track the qualitative and quantitative changes in the natural components of seawater, a description of the essential spectral features describing petroleum products is necessary. This study characterises two optically-different types of crude oils (Petrobaltic and Romashkino) – substances belonging to multi-fluorophoric systems. To obtain the spectral features of crude oils, the excitation-emission spectroscopy technique was applied. The fluorescence and light absorption properties for various concentrations of oils at a stabilised temperature are described. Both excitation-emission spectra (EEMs) and absorption spectra of crude oils are discussed. Based on the EEM spectra, both excitation end emission peaks for the wavelength-independent fluorescence maximum (Exmax/Emmax) – characteristic points for each type of oil – were identified and compared with the literature data concerning typical marine chemical structures.
关键词： seawater,Excitation-emission spectra,fluorescence spectroscopy,oil pollution,absorption spectra
更新于2025-09-09 09:28:46
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Early Detection of Alzheimer’s Disease Using Non-invasive Near-Infrared Spectroscopy
摘要： Mild cognitive impairment (MCI) is a cognitive disorder characterized by memory impairment, wherein patients have an increased likelihood of developing Alzheimer’s disease (AD). The classification of MCI and different AD stages is therefore fundamental for understanding and treating the disease. This study aimed to comprehensively investigate the hemodynamic response patterns among various subject groups. Functional near-infrared spectroscopy (fNIRS) was employed to measure signals from the frontal and bilateral parietal cortices of healthy controls (n = 8), patients with MCI (n = 9), mild (n = 6), and moderate/severe AD (n = 7) during a digit verbal span task (DVST). The concentration changes of oxygenated hemoglobin (HbO) in various subject groups were thoroughly explored and tested. Result revealed that abnormal patterns of hemodynamic response were observed across all subject groups. Greater and steeper reductions in HbO concentration were consistently observed across all regions of interest (ROIs) as disease severity developed from MCI to moderate/severe AD. Furthermore, all the fNIRS-derived indexes were found to be significantly and positively correlated to the clinical scores in all ROIs (R ≥ 0.4, P < 0.05). These findings demonstrate the feasibility of utilizing fNIRS for the early detection of AD, suggesting that fNIRS-based approaches hold great promise for exploring the mechanisms underlying the progression of AD.
关键词： oxygenated hemoglobin,functional near-infrared spectroscopy,Alzheimer’s disease,hemodynamic response,mild cognitive impairment
更新于2025-09-09 09:28:46
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Potential of Near Infrared Spectroscopy for Classification of Different Delignificant Pre-Treatments on Banana Rachis
摘要： Delignificant pretreatments are fundamental in lignocellulosic materials preprocessing to remove lignin from biomass. Current wet chemical methods are time-consuming, labor-intensive and use hazardous reagents. Near Infrared Spectroscopy (NIRS) provides rapid and non-destructive analysis, and has shown promising results. Spectra collection (8000-4000 cm-1), combined with chemometric analysis based on Cluster Analysis and Principal Component Analysis, has allowed to perform qualitative study of banana rachis, a lignocellulosic residue of agricultural production.
关键词： Near infrared spectroscopy,Cluster analysis,Delignification,Pre-treatments,Banana rachis
更新于2025-09-09 09:28:46
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Binding Study of the Fluorescent Carbazole Derivative with Human Telomeric G-Quadruplexes
摘要： The carbazole ligand 3 was synthesized, characterized and its binding interactions with human telomeric (22HT) G-quadruplex DNA in Na+ and K+-containing buffer were investigated by ultraviolet-visible (UV-Vis) spectrophotometry, fluorescence, circular dichroism (CD) spectroscopy, and DNA melting. The results showed that the studied carbazole ligand interacted and stabilized the intramolecular G-quadruplexes formed by the telomeric sequence in the presence of sodium and potassium ions. In the UV-Vis titration experiments a two-step complex formation between ligand and G-quadruplex was observed. Very low fluorescence intensity of the carbazole derivative in Tris HCl buffer in the presence of the NaCl or KCl increased significantly after addition of the 22HT G4 DNA. Binding stoichiometry of the ligand/G-quadruplex was investigated with absorbance-based Job plots. Carbazole ligand binds 22HT with about 2:1 stoichiometry in the presence of sodium and potassium ions. The binding mode appeared to be end-stacking with comparable binding constants of ~105 M?1 as determined from UV-Vis and fluorescence titrations data. The carbazole ligand is able to induce formation of G4 structure of 22HT in the absence of salt, which was proved by CD spectroscopy and melting studies. The derivative of carbazole 3 shows significantly higher cytotoxicity against breast cancer cells then for non-tumorigenic breast epithelial cells. The cytotoxic activity of ligand seems to be not associated with telomerase inhibition.
关键词： carbazole derivative,telomerase,biological activity,G-quadruplex,telomere,spectroscopy
更新于2025-09-09 09:28:46
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Dense restructuring of amorphous silicon network induced by non-bonded hydrogen
摘要： We con?rmed the presence of non-bonded hydrogens (NBHs) in hydrogenated amorphous silicon (a-Si:H) ?lms, using a combination of multiple techniques (Rutherford backscattering spectrometry/hydrogen forward scattering, Fourier-transform infrared spectroscopy-attenuated total re?ection, and thermal desorption spectrometry). The hydrogen e?usion pro?le of an a-Si:H ?lm with large amounts of NBHs was analyzed in detail. We report the e?ect of NBHs on band structure and electrical conductivity, and we present additional considerations for previous data on number density of silicon, optical bandgap, and vacancy size distribution [J. Non-Cryst. Solids 447, 207 (2016)]. The e?ect of NBHs on the a-Si network is explained by the “dense restructuring model”.
关键词： thermal desorption spectrometry,Rutherford backscattering spectrometry,hydrogenated amorphous silicon,non-bonded hydrogens,dense restructuring model,Fourier-transform infrared spectroscopy
更新于2025-09-09 09:28:46
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Optical properties and electronic structures of Cu <sub/>2</sub> ZnSnS <sub/>4</sub> , Cu <sub/>2</sub> ZnGeS <sub/>4</sub> , and Cu <sub/>2</sub> Zn(Ge,Sn)S <sub/>4</sub> and Cu <sub/>2</sub> Zn(Ge,Sn)Se <sub/>4</sub> solid solutions
摘要： Cu2Zn(GexSn1%x)S4 (CZGTS) samples were synthesized by a mechanochemical process and sequential heating. The phases in the obtained powders were analyzed by X-ray di?raction. The band-gap energies of the CZGTS samples were determined by the di?use re?ectance spectra of UV–vis–NIR spectroscopy. The band gap energy of the CZGTS system linearly increased from 1.49 eV for Cu2ZnSnS4 (x = 0.0) to 2.25 eV for Cu2ZnGeS4 (x = 1.0). Their energy levels of valence band maximum (VBM) from the vacuum level were estimated from the ionization energies measured by photoemission yield spectroscopy (PYS). The energy levels of conduction band minimum (CBM) were determined by addition of the band-gap energies to the VBM levels. The energy level of VBM of the CZGTS solid solution was almost constant. On the other hand, the CBM level of the CZGTS solid solution linearly increased from %3.96 eV for Cu2ZnSnS4 (x = 0.0) to %3.28 eV for Cu2ZnGeS4 (x = 1.0) with the increasing Ge content. For CZGTS solar cells with CdS bu?er layer, unfavorable cli?-type conduction band o?set was expected. We also synthesized Cu2ZnSnSe4, Cu2ZnGeSe4, and Cu2Zn(Ge,Sn)Se4 (CZGTSe) solid solution samples and determined their energy levels of VBM and CBM. For Cu2Zn(GexSn1%x)Se4 system with 0.3 3 x 3 1.0, similar cli?-type conduction band o?set was is expected. However, desirable positive spike-type conduction band o?set was expected for the Cu2Zn(GexSn1%x)Se4 solar cells with 0.0 3 x 3 0.2 and CdS bu?er layer.
关键词： photoemission yield spectroscopy,Cu2Zn(GexSn1%x)S4,conduction band minimum,valence band maximum,band-gap energies,solar cells
更新于2025-09-09 09:28:46
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Individual optimal attentional strategy during implicit motor learning boosts frontoparietal neural processing efficiency: A functional near-infrared spectroscopy study
摘要： Introduction: Optimal focus of attention is a crucial factor for improving motor learning. Most previous studies have shown that directing attention to movement outcome (external focus; EF) is more effective than directing attention to body movement itself (internal focus; IF). However, our recent studies demonstrated that the optimal attentional strategy in healthy and clinical populations varies depending on individual motor imagery ability. To explore the neurological basis underlying individual optimal attentional strategy during motor learning tasks, in the present study, we measured frontoparietal activities using functional near‐infrared spectroscopy (fNIRS). Methods: Twenty‐eight participants performed a visuomotor learning task requiring circular tracking. During the task, the participants were required to direct their attention internally or externally. The individual optimal attentional strategy was determined by comparing the after‐effect sizes between the IF and EF conditions. Results: Fifteen participants showed larger after‐effects under the EF condition (External‐dominant), whereas the others showed larger after‐effects under the IF condition (Internal‐dominant). Based on the differences in neural activities between Internal‐ and External‐dominant groups, we identified the right dorsolateral prefrontal cortex (Brodmann area 46) and right somatosensory association cortex (Brodmann area 7) as the neural bases associated with individual optimal attentional strategy during motor learning. Furthermore, we observed a significant negative correlation, that is, lower activity in these areas was associated with a larger after‐effect size under the optimal attentional strategy. Conclusion: Our findings demonstrated that more efficient neural processing in the frontoparietal area under the individual optimal attentional strategy can accelerate motor learning.
关键词： individual differences,dorsolateral prefrontal cortex,somatosensory association cortex,visuomotor learning,functional near‐infrared spectroscopy,focus of attention
更新于2025-09-09 09:28:46
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Quantitative analysis of stibnite content in raw ore by Raman spectroscopy and chemometric tools
摘要： This paper presents a non‐destructive and fast methodology to quantify the stibnite content in raw ore samples using Raman spectroscopy. A total of 120 raw ore reference samples were obtained from a froth flotation process, and multipoint collection and averaging were used to obtain Raman spectra from the raw ore samples. Our aim was to create the best multivariate calibration model for the quantitative analysis of stibnite contents in the raw ore samples. Several strategies were evaluated to generate a robust model; these strategies included preprocessing methods (de‐nosing, baseline correction, and vector normalization), selecting the key wavenumbers for the quantitative analysis of stibnite, and building a multivariate calibration model. Synergy interval partial least squares (PLS), backward interval PLS, stability competitive adaptive reweighted sampling, and PLS with a genetic algorithm (GA) were investigated to build the linear multivariable models, whereas artificial neural network (ANN) and support vector regression (SVR) preceded by GAs (GA‐ANN and GA‐SVR) were implemented to build the non‐linear multivariable models. Experimental results showed that the best multivariable calibration model for stibnite was obtained by a combination of an ANN and GA (GA‐ANN). In contrast to the PLS model based on the full spectrum, the root mean square error of calibration and root mean square error of prediction of the GA‐ANN method for the calibration and validation sets were reduced to 0.2038 from 0.3552 and to 0.2196 from 0.3927, respectively, and the squares of the correlation coefficients of the calibration and validation sets were increased to 0.9369 from 0.8053 and 0.9219 from 0.7561, respectively. The above results indicate that the multivariable calibration model for stibnite is stable. Furthermore, this method could be used in the froth flotation process to precisely determine the stibnite content in raw ore samples.
关键词： Raman spectroscopy,stibnite content,multivariate regression,chemometric tools,wavenumber selection
更新于2025-09-09 09:28:46
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Lewis Acid Modulation of meso-Pyridyl BODIPY Chromophores
摘要： Two pyridyl-substituted BODIPY compounds are shown to interact with the strong Lewis acid B(C6F5)3. The borane adducts are characterized by multinuclear NMR and in one case by X-ray crystallography. The titration of pyridyl-substituted BODIPYs with B(C6F5)3 results in a bathochromic shift of the UV-vis absorption and emission spectra, with the magnitude of the shift depending on the distance of the bound borane from the BODIPY core. In meso-4-pyridyl-BODIPY, binding of B(C6F5)3 induces a small ca. 230 cm?1 red shift in the UV-vis absorption maximum, with a much larger 1950 cm?1 shift in the photoluminescence maximum. In meso-4-pyridylphenyl-BODIPY, where the pyridine Lewis base is separated from the BODIPY core by a phenyl spacer, smaller shifts of ca. 120 cm?1 in UV-vis absorption and 330 cm?1 in photoluminescence are observed. This work shows that these organic chromophores can interact with Lewis acids as a means of systematically perturbing the electronic structure and excited-state properties.
关键词： Boron,UV/Vis Spectroscopy,Lewis acids,Fluorescence,BODIPY
更新于2025-09-09 09:28:46
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Molecular structure of PANI and its homologue PANI–PEO2000 catalyzed by Maghnite-H+ (Algerian MMT): synthesis, characterization and physical and chemical properties
摘要： The homopolymer (PANI) and its homologue PANI–PEO2000 copolymer have been prepared under effect of Maghnite-H+ (Algerian MMT) in different weight percentages (wt%) by cationic polymerization method. The formation of the hydrogen bonding between PANI and PEO2000 and structure of PANI are predicted by the FT-IR and 1HNMR spectra. Glass transition temperature of pure PANI and pure PEO2000 are, respectively, Tg = 74 °C and Tg = 65 °C, but DSC analysis for the copolymer (PANI–PEO2000) showed only one (Tg = 16.79 °C) implying compatibility of PANI and PEO2000. Here we can suggest that under suitable condition (the amount of catalyst, molecular weight and functionality of the reactive stabilizer (PEO2000) and molar ratio of (PANI/PEO2000), our catalyst can improve the morphology, structure and chemical properties of PANI and its homologue PANI–PEO2000.
关键词： Maghnite-H+,1HNMR spectroscopy,DSC,PEO,GPC,Conducting polymer,Green catalyst,Polyaniline
更新于2025-09-09 09:28:46