X-ray peak profiling,optical parameters and catalytic properties of pure and CdS doped ZnO–NiO nanocomposites

Russian Journal of Applied Chemistry - In the current study, XRD peak profile analysis, optical and catalytic properties of pure ZnO–NiO and CdS doped ZnO-NiO nanocomposites were...     

Determination of rain attenuation parameters for free space optical link in tropical rain

Free space optics (FSO) is a promising communication technique for various types of services in the optical access network. Single beam FSO system in tropical rainy weather is vulnerable to atmospheric rain attenuation, so it is necessary to have precise power law parameters of rain attenuation in tropical regions. In this study, the power law parameters k, and α are estimated as 2.03 and 0.74, respectively for the FSO applications in tropical South-East Asian weather. These parameters were evaluated by using least square mean equation (LSME) method with Levenberg–Marquardt optimization based on the one year collected heavy rain data. The obtained parameter values for tropical weather are contributed to improve link performance for high-speed networks.     

Study of H-bonded assemblies of the solvates of anthracene derivatives: guest effect on the crystal symmetry and spectroscopic properties

Two solvates of title compound 1-acetyl-3-naphthyl-5-(9-anthryl)-2-pyrazoline solvate(ANNP) (1a) with chloroform (1b) and acetic acid (1c) and a single crystal of another title compound 1-acetyl-3-(4-chloro)phenyl-5-(9-anthryl)-2-pyrazoline (ACAP) (2a) and its adduct with phenol (2b) were afforded via solution growth technique. The structure of these solids were confirmed and verified by multiple techniques such as single crystal X-ray diffraction (SCXRD) analysis, PXRD, DSC/TGA and Infrared spectroscopy. Structural analysis indicates that guest inclusion results not only in stronger hydrogen bonds, but also in a larger number of favourable C–H?π interactions between ANNP/ACAP molecules. The solvates show symmetry reduction guest effect comparing with the guest free molecules of ANNP and ACAP. Moreover, characteristic changes have been observed in the Infrared bands of the solvates owing to the formation of hydrogen bonds between host–guest.     

Velocity selection for ultracold atoms using bimodal mazer action: Effects of detuning

In this paper, we discuss the effects of detuning on the velocity selection for ultracold three-level atoms in Λ configuration using mazer action. We find sharp resonances in the transmission probability with respect to the detuning. Our results show that the velocity selection of ultracold atoms can easily be tuned and enhanced using off-resonant field in a bimodal cavity.     

MEMS accelerometer embedded in a self-mixing displacement sensor for parasitic vibration compensation

A self-mixing (SM) laser displacement sensor coupled with a microelectromechanical system (MEMS) accelerometer is presented that enables reliable displacement measurements even in the case of a nonstationary laser head. The proposed technique allows the use of SM-based sensors for embedded applications. The system resolution is currently limited to approximately 300?nm due to the noise characteristics of the currently used accelerometer. It is shown that this resolution can be greatly improved by the use of a low noise accelerometer.     

Optimization and Characterization of Mesoporous Sulfonated Carbon Catalyst and Its Application in Modeling and Optimization of Acetin Production

In this study, an optimized mesoporous sulfonated carbon (OMSC) catalyst derived from palm kernel shell biomass was developed using template carbonization and subsequent sulfonation under different temperatures and time conditions. The OMSC catalyst was characterized using acid-base titration, elemental analysis, XRD, Raman, FTIR, XPS, TPD-NH₃, TGA-DTA, SEM, and N₂ adsorption–desorption analysis to reveal its properties. Results proved that the OMSC catalyst is mesoporous and amorphous in structure with improved textural, acidic, and thermal properties. Both FTIR and XPS confirmed the presence of -SO₃H, -OH, and -COOH functional groups on the surface of the catalyst. The OMSC catalyst was found to be efficient in catalyzing glycerol conversion to acetin via an acetylation reaction with acetic acid within a short period of 3 h. Response surface methodology (RSM), based on a two-level, three-factor, face-centered central composite design, was used to optimize the reaction conditions. The results showed that the optimized temperature, glycerol-to-acetic acid mole ratio, and catalyst load were 126 °C, 1:10.4, and 0.45 g, respectively. Under these optimum conditions, 97% glycerol conversion (GC) and selectivities of 4.9, 27.8, and 66.5% monoacetin (MA), diacetin (DA), and triacetin (TA), respectively, were achieved and found to be close to the predicted values. Statistical analysis showed that the regression model, as well as the model terms, were significant with the predicted R² in reasonable agreement with the adjusted R² (<0.2). The OMSC catalyst maintained excellent performance in GC for the five reaction cycles. The selectivity to TA, the most valuable product, was not stable until the fourth cycle, attributable to the leaching of the acid sites.     

Redox Mechanism and Evaluation of Kinetic and Thermodynamic Parameters of 1,3‐Dioxolo[4,5‐g]pyrido[2,3‐b]quinoxaline Using Electrochemical Techniques

The electrochemical behavior of a biologically important heterocyclic compound, 1,3‐dioxolo[4,5‐g]pyrido[2,3‐b]quinoxaline was investigated by cyclic, square wave and differential pulse voltammetry in solutions of different pH. Kinetic and thermodynamic parameters like standard rate constant, diffusion coefficient, apparent energy of activation_, standard Gibbs free energy and enthalpy and entropy changes were evaluated. Limits of detection and quantification were determined by square wave voltammetry. The redox mechanism of the compound was proposed on the basis of experimental results. Computational chemistry was used as a tool for the verification of experimental outcomes and assessment of different theoretical parameters     

Some Novel Results Involving Prototypical Computation of Zagreb Polynomials and Indices for SiO4 Embedded in a Chain of Silicates

A topological index as a graph parameter was obtained mathematically from the graph’s topological structure. These indices are useful for measuring the various chemical characteristics of chemical compounds in the chemical graph theory. The number of atoms that surround an atom in the molecular structure of a chemical compound determines its valency. A significant number of valency-based molecular invariants have been proposed, which connect various physicochemical aspects of chemical compounds, such as vapour pressure, stability, elastic energy, and numerous others. Molecules are linked with numerical values in a molecular network, and topological indices are a term for these values. In theoretical chemistry, topological indices are frequently used to simulate the physicochemical characteristics of chemical molecules. Zagreb indices are commonly employed by mathematicians to determine the strain energy, melting point, boiling temperature, distortion, and stability of a chemical compound. The purpose of this study is to look at valency-based molecular invariants for SiO4 embedded in a silicate chain under various conditions. To obtain the outcomes, the approach of atom–bond partitioning according to atom valences was applied by using the application of spectral graph theory, and we obtained different tables of atom—bond partitions of SiO4. We obtained exact values of valency-based molecular invariants, notably the first Zagreb, the second Zagreb, the hyper-Zagreb, the modified Zagreb, the enhanced Zagreb, and the redefined Zagreb (first, second, and third). We also provide a graphical depiction of the results that explains the reliance of topological indices on the specified polynomial structure parameters.     

Integrated Hydrogeological,Hydrochemical, and Isotopic Assessment of Seawater Intrusion into Coastal Aquifers in Al-Qatif Area,Eastern Saudi Arabia

Seawater intrusion (SWI) is the main threat to fresh groundwater (GW) resources in coastal regions worldwide. Early identification and delineation of such threats can help decision-makers plan for suitable management measures to protect water resources for coastal communities. This study assesses seawater intrusion (SWI) and GW salinization of the shallow and deep coastal aquifers in the Al-Qatif area, in the eastern region of Saudi Arabia. Field hydrogeological and hydrochemical investigations coupled with laboratory-based hydrochemical and isotopic analyses (¹⁸O and ²H) were used in this integrated study. Hydrochemical facies diagrams, ionic ratio diagrams, and spatial distribution maps of GW physical and chemical parameters (EC, TDS, Cl⁻, Br⁻), and seawater fraction (f_sw) were generated to depict the lateral extent of SWI. Hydrochemical facies diagrams were mainly used for GW salinization source identification. The results show that the shallow GW is of brackish and saline types with EC, TDS, Cl⁻, Br⁻ concentration, and an increasing f_sw trend seaward, indicating more influence of SWI on shallow GW wells located close to the shoreline. On the contrary, deep GW shows low f_sw and EC, TDS, Cl⁻, and Br⁻, indicating less influence of SWI on GW chemistry. Moreover, the shallow GW is enriched in ¹⁸O and ²H isotopes compared with the deep GW, which reveals mixing with recent water. In conclusion, the reduction in GW abstraction in the central part of the study area raised the average GW level by three meters. Therefore, to protect the deep GW from SWI and salinity pollution, it is recommended to implement such management practices in the entire region. In addition, continuous monitoring of deep GW is recommended to provide decision-makers with sufficient data to plan for the protection of coastal freshwater resources.