Subjects -> PHYSICS (Total: 857 journals)     - ELECTRICITY AND MAGNETISM (10 journals)    - MECHANICS (22 journals)    - NUCLEAR PHYSICS (53 journals)    - OPTICS (92 journals)    - PHYSICS (625 journals)    - SOUND (25 journals)    - THERMODYNAMICS (30 journals) PHYSICS (625 journals)            First | 1 2 3 4 | Last
 Showing 201 - 400 of 741 Journals sorted alphabetically International Journal of Astronomy and Astrophysics       (Followers: 36) International Journal of Biological, Physical and Chemical Studies International Journal of Computational Materials Science and Surface Engineering       (Followers: 7) International Journal of Damage Mechanics       (Followers: 5) International Journal of Engineering and Applied Physics International Journal of Fatigue       (Followers: 41) International Journal of Fracture       (Followers: 14) International Journal of Geometric Methods in Modern Physics       (Followers: 2) International Journal of Geophysics       (Followers: 5) International Journal of Heat and Fluid Flow       (Followers: 41) International Journal of Low Radiation International Journal of Low-Carbon Technologies       (Followers: 1) International Journal of Mass Spectrometry       (Followers: 17) International Journal of Material Forming       (Followers: 1) International Journal of 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Similar Journals
 Journal of Applied SpectroscopyJournal Prestige (SJR): 0.179 Number of Followers: 9      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1573-8647 - ISSN (Online) 0021-9037 Published by Springer-Verlag  [2469 journals]
• Characteristics of the Analytical Resonator of a Weak Absorption
Spectrometer

Abstract: The characteristics of a weak absorption spectrometer consisting of a frequency-tunable diode laser and an external analytical resonator are considered. It is shown how the resonator parameters and the frequency tuning rate affect the sensitivity of the spectrometer and the reproduction of the shape and width of the recorded line.
PubDate: 2022-03-28

• Radiative Characteristics of Shock-Heated Oxygen

Abstract: The emission spectra of oxygen behind the front of a strong shock wave were studied in the range of shock wave speeds of 5.7–7.4 and 8.1–10.0 km/s at pressures of 1.0 and 0.25 Torr in front of the wave front. Time-integrated sweeps of radiation over a wide spectral range of 200–675 nm and time oscillograms of oxygen radiation were obtained. Analysis of the obtained panoramic spectra shows that at low shock wave speeds the radiation spectrum is dominated by a system of Schumann–Runge molecular bands. Increase of the shock wave speed leads to the appearance of strong atomic lines in the emission spectrum. Features of the time oscillograms for the most typical lines of the spectrum (the radiation of molecular oxygen at a wavelength of 213 nm (Schumann–Runge system) and atomic oxygen at wavelengths of 394 and 645 nm) are identified.
PubDate: 2022-03-25

• Ultra-High-Resolution Fluorescence Spectroscopy Upon Excitation of Atoms
by Pulsed Radiation in Thin Gas Cells

Abstract: The method of sub-Doppler fluorescence spectroscopy is proposed and is based on the narrowing behavior with time of the velocity distribution of optically excited atoms (molecules) of a rarefied gas medium in a thin cell after exposure to a sufficiently short light pulse. Changes in the established sub-Doppler resonances with time and the essential dependence of these resonances on the gas-cell dimensions are analyzed.
PubDate: 2022-03-25

• Flight Parameter Setting of Unmanned Aerial Vehicle Hyperspectral Load

Abstract: Correct flight parameters are critical for obtaining high-quality unmanned aerial vehicle (UAV) remote sensing images. For the UAV, the Rikola hyperspectral load needs to set the instrument's exposure time, UAV flight mode, flight altitude, and other issues when acquiring data. Using the control variable method, UAV Rikola hyperspectral images were collected under different parameters, and the gray-scale target and image's quantitative evaluation index was used to obtain the spectral curves of gray-scale targets, ground features, signal-to-noise ratio (SNR), information entropy, and sharpness of imagery. The results of the comparative analysis show: the vegetation hyperspectral data quality was better when determining the Rikola hyperspectral exposure time using the 64% diffuse plate; UAV hover mode and cruise mode had little impact on data quality; when the flight altitude was within 100 m above ground level, the higher the flying height, the better the data quality. This study therefore provides evidence for obtaining high-quality data using UAV hyperspectral load.
PubDate: 2022-03-25

• Purely Electronic Optical Transition and Direct Band Gap of a
Semiconductor

Abstract: The possibility of using the method of determining the frequency of a purely electronic transition based on the diffuse molecular vibrational spectrum to determine the width of the direct forbidden band gap of semiconductors is tested with a positive result. This method is used to determine width of the direct band gap between the valence band and the photoconductivity band from the photoconductivity spectrum.
PubDate: 2022-03-25

• Dual-Channel More Flexible Salamo-Like Chemosensor for Fluorogenic Sensing
of Copper Ion in Semi-Aqueous Medium

Abstract: The optical properties of the symmetric salamo-like chemical probe (H2CS) of Cu2+ were studied in EtOH/H2O (1:1, v/v) solution by UV-Vis and fluorescence spectroscopy. In the fluorescence spectrum, the coordination of Cu2+ with H2CS results in fluorescence quenching owing to the paramagnetic nature of Cu2+ ions. The binding constant of Cu2+ to the H2CS sensor was calculated as 1.17 × 1011 M–1 and LOD was obtained as 5.3 × 10–8 M. When Cu2+ ions were added, the UV-Vis spectra changed, obviously due to the electron transfer from sensor to metal bond, and a new absorption band appeared at 372 nm. When the ethylenediaminetetraacetic acid (EDTA) solution was added to the H2CS–Cu2+ solution, causing a large binding constant, with EDTA releasing the free sensor molecule and finally achieving a fluorescence shutdown phenomenon.
PubDate: 2022-03-25

• Formation of Narrow-Band N-Type Optical Resonance in Vapors of Potassium
Atoms

Abstract: An N-type optical resonance that formed in the Λ-system of potassium atoms (D1 lines) using two CW narrow-band lasers and a spectroscopic cell with a length of 1.5 cm that contained vapors of potassium atoms and buffer neon gas with a partial pressure of 20 Torr was investigated. The N-type resonance was shown to be split into three equidistant components in a longitudinal magnetic field. The N-type resonance parameters formed in vapors of cesium and rubidium atoms were compared. It was found that the initial and final levels were the lower ground levels Fg = 1, 2 when the N-type resonance was formed.
PubDate: 2022-03-25

• Microstructural Analysis of a Glass Dedicated to the Radioactive Waste
Confinement by Raman and FTIR Spectroscopy

Abstract: This study deals with the structural changes occurring in a Mo-reach glass dedicated to the confi nement of Moreach radioactive waste that contains different contents of Cs2O oxide, ranging from 0.3 to 0.6 wt.%. The glass synthesis was carried out by the double melting method at 1380°C, followed by a stage of 2 h at 600°C. Neodymium was an actinide simulator. The glasses were characterized by their physical and microstructural properties using different spectroscopic techniques. As the experiment shows, the glass geometrical density varies between 1.96 and 2.75 g/cm3. X-ray diffraction (XRD) analysis shows amorphous features, with traces of crystalline germs, identified as the CaMoO4 powellite phase, which probably formed during glass cooling. Fourier transform infra-red (FTIR) analysis reveals the main chemical bounds in the glasses: Si–O–Si and O–Si–O in SiO4, B–O–B in BO3, and Al–O– Al in AlO4. The addition of Cs2O raises the rate of polymerization in the glass network and then decreases the number of no-bridged oxygens (NBO). Raman spectroscopic analysis reveals the absorption bands of $$\mathrm{Mo}{\mathrm{O}}_4^{2-}$$ in CaMoO4. It shows that the Mo environment is altered by the addition of increasing contents of Cs2O in the glass. This is evidenced by the absorption bands shifts at 319, 792, and 844 cm–1. The absorption band located at 700 cm–1, ascribed to the elongation of SiO4 and AlO4, is attenuated for 0.4 and 0.6% of the Cs2O content. It shifts to 680–900 cm–1 due to the glass high Mo content but increases in intensity with the Cs2O content, thus disturbing the alkali positions of Ca and Na, with Cs remaining soluble in the glass. One can conclude that a little rise in the Cs2O content inhibits the phase separation of both Na and Ca molybdates. The glasses analyses do not show particular changes in the lanthanide valences, which are probably in a +III oxidation state. The addition of Cs2O in this kind of glass network remains an issue with respect to the coherence of its microstructure. However, about 0.6 wt.% of Cs2O has been incorporated in the glass network, with no Cs2O phases segregation.
PubDate: 2022-03-25

• Luminescence in the LiF–MgF2 System Activated by Rare Earths

Abstract: In recent years, several reports have appeared on luminescence in LiMgF3. Important applications have also been claimed. There is no record of LiMgF3 in the ICDD database. In light of the crystallographic studies on ABF3 compounds and especially the finding that LiMgF3 is not formed, the reports on the LiMgF3 based phosphors appear interesting. Our reinvestigation confirmed that LiMgF3 does not exist. It is quite likely that the interesting properties described in the literature for LiMgF3, in fact, belong to the frozen eutectic or two-phase system. All the same, the existence of eutectic was exploited to melt MgF2 at much lower temperature (735°C) than the melting point of MgF2 (1263°C). We prepared LiF–MgF2:Eu2+ and LiF–MgF2:Ce3+ by melting at 735°C. These materials exhibited properties similar to those of MgF2:Eu2+ and MgF2:Ce3+ phosphors, respectively. Thus, using the lower melting point of eutectic, it might be possible to prepare various MgF2 based phosphors at temperatures as low as 735°C, against the high melting point of 1263°C for MgF2.
PubDate: 2022-03-25

• Some Methods for Determining Pre-Explosive Concentrations of Gas Mixtures

Abstract: A theoretical study of infrared and interferometric methods of gas analysis has been carried out. Circuit implementations of devices have been developed, and an experimental solution of the problem of obtaining approximately the same sensitivity of the combustible gas detector to the gas components of the mixture has also been described. For both considered gas analyzers, the problem of controlling the selectivity of the analysis of gas components in an air mixture with an error of ~10% has been solved.
PubDate: 2022-03-25

• Digital Colorimetry of Indicator Test-Systems Using a Smartphone and
Chemometric Analysis in Determination of Quinolones in Pharmaceuticals

Abstract: A combined approach was developed for the identification and determination of quinolone antibiotics in pharmaceuticals using solid-state fluorescence digital colorimetry and chemometric analysis. The eigen fluorescence of quinolones and quinolone-sensitized fluorescence of europium(III) were studied in various matrices. A test system consisting of four indicator zones was proposed. Irradiation by UV light (365 nm) of quinolone solutions applied to the indicator zones of test systems produced blue fluorescence on cellulose paper (CP) and plates for high-performance thin layer chromatography (HPTLC) and pink fluorescence (CP–Eu, HPTLC–Eu). The fluorescence intensity on the surface of the matrices was measured using a smartphone. It was shown that chemometric analysis, which enabled the analysis time to be reduced and research data to be visualized, could be used. The data were processed by principal component analysis (PCA), hierarchical cluster analysis, and the k-means method using XLSTAT software. Quinolone antibiotics in tablet forms were identified and quantified using chemometric analysis. Calibration curves in the PCA and k-means methods had a logarithmic form in the determined concentration range of 0.5–250 μg/mL (R2 ≥ 0.98). A technique for determination of fluoroquinolones in pharmaceuticals was proposed. The relative standard deviation did not exceed 0.09.
PubDate: 2022-03-25

• Influence of Temperature on the Fluorescence Duration and Electronic
Spectra of Metal-Free Tetrapyrroles in an Organic Polymer

Abstract: Spectral and luminescent characteristics and the duration of fluorescence were measured for a series of metal-free tetrapyrroles in polyvinylbutyral solid films at 293 and 77 K. The results provided evidence for the lack of a viscosity factor in the case of the fluorescence enhancement under study, i.e., for the tetrapyrroles showing the enhancement effect in liquid solutions (tetraazaporphine and substituted tetraazachlorin). The fluorescence duration in the film increased insignificantly on lowering the temperature to 77 K. An analysis of the experimental data made it possible to estimate the quantum yields of internal conversion and intersystem crossing for tetraazaporphine and tetraazachlorin, which were the fundamental structures in the tetrapyrrole series.
PubDate: 2022-03-25

• Detection of Multiple-Heated Edible Oil Based on Fluorescence Spectroscopy

Abstract: This study analyzed the fluorescence intensity, integrated intensity of the spectral area, and fluorescence peak of vegetable oil samples subjected to different heating conditions. The photon lifetime of the vegetable oil was then calculated using the fluorescence lifetime method, which can determine whether the sample has been repeatedly heated at high temperatures. Combining these two methods improves the accuracy of detection and can help solve the problem of false and missed detection, providing a strong basis for the detection of high-temperature heated vegetable oil.
PubDate: 2022-03-25

• Analysis of Porous Nanosilicon by Raman Spectroscopy

Abstract: Technologies for the production of nanostructured silicon and porous nanosilicon are presented. A method for the synthesis of porous nanosilicon by electrochemical etching is described. The main parameters for the generation of porous silicon with given characteristics are presented. The results from investigations of samples of porous silicon obtained with a InVia Raman Renishaw spectrometer, with which it is possible to record and identify both amorphous and crystalline phase components in samples, are described. The crystal structure of the samples was determined from the results of granulometric investigations. The absence of amorphous silicon in the samples was confirmed by approximation of the Raman spectra. A shift of the lines toward smaller energies, characteristic of nanoparticles with nanoparticles with decreased size, is observed in the Raman spectra. A stable strong band in the region of 700–900 nm, which confirms the nanocrystalline nature of the samples, is observed in the photoluminescence spectra. The effectiveness and sensitivity of Raman spectroscopy, which make it possible to determine even insignificant changes in the crystalline and amorphous fraction of the silicon structures, were demonstrated.
PubDate: 2022-03-25

• Molecular Mobility of Crude Oils Via Electron Paramagnetic Resonance of

Abstract: This study aimed to investigate the molecular mobility of crude oils using the linewidth of the free radical electron paramagnetic resonance signal (EPR) as a molecular mobility probe. For this, aromatic and paraffinic crude oil samples were analyzed by X-band EPR spectroscopy, NMR experiments in time domain (TD-NMR), and rheometry. The variations on the half height linewidth with temperature presented a similar behavior for both samples, being related to different molecular mobility regimes. EPR results were compared to the variation of viscosity with temperature obtained by rheometry and TD-NMR. The results showed changes in the decrease trend of viscosity for the paraffinic sample at a temperature close to the range in which it is observed the transition from rigid to liquid regime in the EPR analysis. EPR technique showed more detailed information about the regime transition for the oil samples studied, which is in agreement with the results obtained by rheometry and TD-NMR.
PubDate: 2022-03-25

• Analysis of the Products from the Reaction of L-Cysteine with Fe(III)
Compounds in Acidic Medium

Abstract: The reaction of L-cysteine solution with the iron(III) compounds FeCl3, Fe2(SO4)3, and Fe(NO3)3 in an acidic medium (pH 2) was studied. The reaction was complete in 30 min and formed L-cystine (21–40%) as the main product. The reaction of L-cysteine with FeCl3 formed L-cysteine sulfonic acid in the solution as a by-product. The products from the reaction of L-cysteine with the Fe(III) compounds were interpreted by IR and NMR spectroscopy.
PubDate: 2022-03-25

• Spatial Distribution of Signals of Active-Pulse Vision Systems from a
Diffusely Reflecting Underlying Surface

Abstract: The characteristics of the spatial-energy profile of the pulse energy profile recorded from a diffusely scattering horizontal plane under inclined illumination are studied. The maximum signal, position of the maximum, and size of the region of best visibility are studied as functions of the delay distance for different relationships among the durations of the pulse and the signal registration times. Analytic results are obtained for rectangular pulses. Numerical methods are used to obtain results relating to real-form pulses.
PubDate: 2022-03-01

• Development and Validation of UV Spectrophotometric Method for
Determination of Chrysin and Its Solubility Studies

Abstract: The present work is based on the method development and validation of the UV-spectrophotometric method for the quantitative estimation of chrysin. We studied how the nature of the solvent affects chrysin solubility. The stock and diluted solutions were scanned using a UV visible spectrophotometer to obtain the λmax. The absorbance of the samples was recorded to obtain a calibration curve, which was followed by regression using MS Excel and Sigma stat software. The method developed by this process was further validated using parameters such as linearity, precision, limit of detection, limit of quantification, accuracy, and ruggedness. The solubility of chrysin was checked at 35°C in different oils, solvents, and co-solvents. The λmax of chrysin in methanol was found to be 367 nm. The calibration curve of the drug follows linearity (2–10 μg/mL) with a correlation coefficient of 0.991. At three different levels, i.e., 80, 100, and 120%, the method's accuracy was checked utilizing the percent recovery (97–99.5%). The precision studies were carried out in terms of intraday and interday variations. The ruggedness of the proposed method was studied by taking two. The solubility of chrysin was found to be the maximum in methanol (216.80 ± 0.0097 μg/mL) among the oils, solvents, and co-solvents used. Thus, based on the experiments done, the developed method was observed to be accurate, precise, and reproducible. The viscosity of the solvent and the possibility of hydrogen bonding are two crucial factors that affected the solubility of chrysin in the solvents.
PubDate: 2022-03-01

• Linewidths of Proton Nuclear Magnetic Resonance Peaks Obtained for Jaw
Cysts and Abscesses at 400 MHz

Abstract: We compare the nuclear magnetic resonance (NMR) linewidths of semi-heavy water (HOD) proton peaks in 29 nonhemorrhagic jaw cysts, 8 hemorrhagic cysts, and 19 abscesses. We also investigate the dependence of linewidths on fluid content and radio frequency (RF) application angles. The mixtures used for comparisons were prepared by adding 0.05 mL of each cyst or abscess to 0.95 mL of D2O. A series of mixtures containing varying amounts of the sample was also prepared. NMR measurements of all mixtures at 400 MHz were acquired using only a 90° RF pulse. The mean linewidths of the cystic groups were quite different (p = 0.004) from each other. However, there was a moderate difference between the mean linewidths of nonhemorrhagic cysts and abscesses (p = 0.048) and between those of hemorrhagic cysts and abscesses (p = 0.045). The linewidth increases linearly with increasing fluid content but decreases with increasing RF application angle. In conclusion, the data suggest that linewidth measurements can distinguish cysts from abscesses. The concentration dependence of the linewidth also suggests that the rapid chemical exchange of protons between free and bound HODs contributes to the broadening of the linewidth.
PubDate: 2022-03-01

• Spectral and Luminescent Properties of
21-Thia-5,10,15,20-Tetra-(4-Sulfonatophenyl)Porphyrin: Role of
Heterosubstitution and Halochroism

Abstract: The spectral and luminescent properties of hydrophilic 21-thia-5,10,15,20-tetra(4-sulfonatophenyl)porphyrin and 5,10,15,20-tetra(4-sulfonatophenyl)porphyrin in solutions at 293 K were compared. Peculiarities of halochromic effects due to the replacement of a pyrrole by a thiophene ring in the macrocycle were revealed for the first time. Multicenter interactions on the periphery and in the core of the macrocycle led to modulation of spin–orbit couplings, which became apparent in changes of the fluorescence quenching efficiency. Fluorescence of the doubly protonated heteroporphyrins was shown to be quenched as compared to the free bases whereas fluorescence enhancement was observed for the doubly protonated forms.
PubDate: 2022-03-01

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