Shadow radiation and Fresnel diffraction of acoustic waves.

Fresnel diffraction is a fundamental wave phenomenon. This article explains its physical nature using the examples of the diffraction of acoustic waves at soft and hard half-planes and at large apertures on a black screen. It is shown that the shadow radiation by opaque screens plays a central role in these diffraction phenomena. Fresnel-Kirchhoff diffraction at large apertures is presented as an asymptotic form of the shadow radiation. Fresnel and Grimaldi-type diffraction at the soft and hard half-planes is revealed as interference of the shadow radiation and the incident wave.

Diffraction of acoustic waves at two-dimensional hard trilateral cylinders with rounded edges: First-order physical theory of diffraction approximation.

The paper explores diffraction of acoustic waves at a two-dimensional hard trilateral cylinder with rounded edges. It represents the extension of the physical theory of diffraction (PTD) for finite objects with rounded edges. A first-order PTD approximation is developed. Integral equations are formulated for acoustic fringe waves and solved by method of moments (MoM). Good agreement is observed with the exact solution found by MoM when the object size exceeds a few wavelengths.

The Kß/Kα X-ray intensity ratios of Cu and Ag in Cu-Ag thin alloy films.

Kß/Kα X-ray intensity ratio values of Cu and Ag in CuxAg1-x (x = 53.5, 67.6, 76.9, 85.4, 89.6) thin alloy films produced from two different sources by the physical vapour deposition method have been determined by the Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) method. The changes in the crystal structures of CuxAg1-x thin alloy films caused by the changes in the Cu and Ag concentrations, which affect the valence electronic structure have been investigated by the X-ray Diffraction (XRD) techniques. The obtained values were compared with the theoretical and fitted values for pure Cu and Ag elements.

Evaluation of ecological risk, source, and spatial distribution of some heavy metals in marine sediments in the Middle and Eastern Black Sea region, Turkey.

In the present study, the concentration levels of heavy metals such as Mn, Fe, Ni, Cu, Zn, Cr, and Pb in sediment samples collected from 16 sampling locations in the Middle and Eastern Black Sea regions, Turkey, were measured using energy dispersive X-ray fluorescence spectroscopy (EDXRF). Various pollution parameters and methods, such as the enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), pollution load index (PLI), ecological risk index (RI), and geo-spatial distribution patterns, were used to assess the pollution status, ecological risks, and sources of metals in sediment in detail. The mean concentrations of Mn, Fe, Ni, Cu, Zn, Cr, and Pb were found to be 565.38, 46,000, 34.38, 104.06, 109.88, 87.31, and 32.31 mg/kg, respectively. Results showed that the mean concentrations of Cu, Zn, and Pb exceeded the crustal shale value, with the exception of Mn, Fe, Ni, and Cr. According to the calculated pollution parameters, although minimal or moderate pollution was detected in the area investigated, it was determined that there was a very low ecological risk. Multivariate statistical analysis results showed that Cu, Zn, and Pb levels in the investigated region were slightly influenced by anthropogenic inputs such as mining and agricultural practices. In addition, the geo-spatial distributions of Cu, Zn, Fe, and Pb were found to be higher in this region due to the mining activities carried out in the Eastern Black Sea region.

Determination of valence electronic structure of Ni in Ni-B alloy coatings using Kß-to-Kα X-ray intensity ratios.

In this study, Kß-to-Kα X-ray intensity ratios of Ni in Ni-B alloy coatings were investigated. These samples were excited by 59.5 keV gamma-rays from a 241Am annular radioactive source. K X-rays emitted by the samples were counted using an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. The Kß-to-Kα X-ray intensity ratios of Ni-B alloys are compared with pure Ni and each other. Deviations between the results were explained by the change in valence electronic structures of Ni in Ni-B alloy coatings.

Crystal structure, DFT and HF calculations and radical scavenging activities of (E)-4,6-dibromo-3-methoxy-2-[(3-methoxyphenylimino)methyl]phenol.

In this study, (E)-4,6-dibromo-3-methoxy-2-[(3-methoxyphenylimino)methyl]phenol has been synthesized and characterized by using X-ray technique and FT-IR experimentally and using B3LYP/6-31G(d,p) and HF/6-31G(d,p) methods theoretically. The intermolecular and intramolecular interactions of the title compound have been determined according to X-ray results. The molecular geometry, vibrational frequencies of the title compound in the ground state have been calculated using the density functional B3LYP and HF method with the 6-31G(d,p) basis set and calculated bond parameters and vibrational frequencies values show good agreement with experimental values. Theoretical and experimental results show that tautomeric form of the structure is phenol-imine form. Besides HOMO-LUMO energy gap, molecular electrostatic potential map were performed at B3LYP/6-31G(d,p) level. It is worthy note of that, the free radical scavenging activities of the title compound were assessed using DPPH˙, DMPD˙(+), and ABTS˙(+) assays. The obtained results show that the title compound has effective DPPH˙ (SC50 2.61±0.09 µg/mL), DMPD˙(+) (SC50 2.82±0.14 µg/mL), and ABTS˙(+) (SC50 4.91±0.18 µg/mL) radical scavenging activities when compared with standard antioxidants (BHA, rutin, and trolox).

Molecular structure, quantum mechanical calculation and radical scavenging activities of (E)-4,6-dibromo-2-[(3,5-dimethylphenylimino)methyl]-3-methoxyphenol and (E)-4,6-dibromo-2-[(2,6-dimethylphenylimino)methyl]-3-methoxyphenol compounds.

In this study, (E)-4,6-dibromo-2-[(3,5-dimethylphenylimino)methyl]-3-methoxyphenol and (E)-4,6-dibromo-2-[(2,6-dimethylphenylimino)methyl]-3-methoxyphenol compounds have been synthesized and characterized by using X-ray crystallographic method, FT-IR and Density functional method. The molecular geometry, vibrational frequencies of the title compounds in the ground state have been calculated by using B3LYP with the 6-31G(d,p) basis set. The tautomeric form of the compounds has been demonstrated by using single crystal X-ray method, FT-IR spectrometer and DFT method. In addition, HOMO-LUMO energy gap, molecular electrostatic potential map and NBO analysis of the compounds are performed at B3LYP/6-31G(d,p) level. It may be remarked that the free radical scavenging activities of the title compounds were assessed using DPPH, DMPD+, and ABTS+ assays. The obtained results show that especially compound 2 has effective DPPH (SC50 1.52±0.14 µg/mL), DMPD+ (SC50 1.22±0.21 µg/mL), and ABTS+ (SC50 3.32±0.17 µg/mL) scavenging activities compared with standards (BHA, rutin, and trolox).

The trace element analysis in freshwater fish species, water and sediment in Iyidere stream (Rize-Turkey).

Many environmental problems like dam construction, agricultural debris, flooding and industrial establishments threaten Iyidere stream (Rize, Turkey) on the southeastern coast of the Black Sea (Turkey). The trace element concentrations in water, fish and sediments in lyidere stream (Rize, Turkey) were investigated in this study. The concentration of six different elements in ten freshwater fish species and sediment was determined using energy dispersive X-ray fluorescence method. A radioisotope excited X-ray fluorescence analysis using the method of multiple standard addition is applied for the elemental analysis of fish and sediments. Water samples for trace metals were analyzed using standard spectrophotometry methods. A qualitative analysis of spectral peaks showed that ten different freshwater fish samples (Chondrostoma colchicum, Chalcalburnus chalcoides, Salmo trutta labrax, Alburnoides bipunctatus, Leuciscus cephalus, Barbus taurus escherichia, Capoeta tinca, Neogobius kessleri, Rutilus frisii, Lampetra lanceolata) and sediment contained phosphorus (P), sulphur (S), chlorine (Cl), potassium (K), calcium (Ca) and titanium (Ti). Heavy metals as toxic elements for biota (Pb, Cd, Hg, Zn and Mn etc.) were not detected in fish, water and sediments. Thus, It can be declared that freshwater fish of Iyidere does not contains health risks for consumers in terms of metal pollution.