Synthesis of iron-MFI zeolite and its photocatalytic application for hydroxylation of phenol

This work focuses on the preparation of Fe-MFI zeolites by a one-step method with different iron concentrations and their characterization by different methods such as X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), nitrogen sorption measurements at 77 K, scanning and transmission electron microscopy (SEM and TEM), and UV–Vis reflectance diffuse spectroscopy. The results show that the modification of the zeolites with high iron concentrations led to the formation of well-dispersed oxides within the framework, decreasing the specific surface area. The photocatalytic activity of the iron-modified zeolites was evaluated using hydroxylation of phenol with hydrogen peroxide at room temperature. High conversion (80%) of phenol was obtained by Fe–Al-MFI (0.5) containing lower iron concentration. Interesting selectivity towards catechol was achieved, confirming that the reaction is influenced by sites on the external surface.     

Catalytic dehydrogenation of natural terpenes via CuPd alloy nanoparticles generated on mesoporous graphitic carbon nitride

A facile wet-chemical protocol for the synthesis of bimetallic CuPd alloy nanoparticles (NPs) anchored on mesoporous graphitic carbon nitride (m-gCN), serving as both stabilizer and support material, was presented herein. The presented protocol allowed to synthesize nearly monodisperse CuPd alloy NPs with an average particle size of 3.9 ± 0.9 nm without use of any additional surfactants and to prepare CuPd/m-gCN nanocatalysts with different Cu/Pd compositions (Cu₂₅Pd₇₅/m-gCN, Cu₃₅Pd₆₅/m-gCN, Cu₁₆Pd₇₄/m-gCN, Cu₃₂Pd₆₈/m-gCN, Cu₁₀Pd₉₀/m-gCN, and Cu₅₀Pd₅₀/m-gCN). After the detailed characterization of CuPd/m-gCN nanocatalysts, they were utilized as catalysts in the dehydrogenation of terpenes. Among all tested nanocatalysts, Cu₅₀Pd₅₀/m-gCN showed the highest activity in terms of the product yields within the same reaction time. Various parameters influencing the catalytic activity of Cu₅₀Pd₅₀/m-gCN were studied using himachalene as a model substrate and the optimum conditions were determined. Under the optimized reaction conditions, the catalytic application of Cu₅₀Pd₅₀/m-gCN nanocatalysts was extended to nine different terpenes and the corresponding products were obtained in high conversion yields (>90%) under mild conditions. A reusability test showed that Cu₅₀Pd₅₀/m-gCN nanocatalysts can be re-used up to four cycles without significant loss in their initial activity.     

Biosynthesis and Characterization of Extracellular Silver Nanoparticles from Streptomyces aizuneusis: Antimicrobial,Anti Larval,and Anticancer Activities

The ability of microorganisms to reduce inorganic metals has launched an exciting eco-friendly approach towards developing green nanotechnology. Thus, the synthesis of metal nanoparticles through a biological approach is an important aspect of current nanotechnology. In this study, Streptomyces aizuneusis ATCC 14921 gave the small particle of silver nanoparticles (AgNPs) a size of 38.45 nm, with 1.342 optical density. AgNPs produced by Streptomyces aizuneusis were characterized by means of UV-VIS spectroscopy and transmission electron microscopy (TEM). The UV-Vis spectrum of the aqueous solution containing silver ion showed a peak between 410 to 430. Moreover, the majority of nanoparticles were found to be a spherical shape with variables between 11 to 42 nm, as seen under TEM. The purity of extracted AgNPs was investigated by energy dispersive X-ray analysis (EDXA), and the identification of the possible biomolecules responsible for the reduction of Ag⁺ ions by the cell filtrate was carried out by Fourier Transform Infrared spectrum (FTIR). High antimicrobial activities were observed by AgNPs at a low concentration of 0.01 ppm, however, no deleterious effect of AgNPs was observed on the development and occurrence of Drosophila melanogaster phenotype. The highest reduction in the viability of the human lung carcinoma and normal cells was attained at 0.2 AgNPs ppm.     

6-alkoxy-3,4-dihydro-2h-pyrans from substituted α,β-unsaturated esters

Cycloaddition reactions of substituted α,β-unsaturated esters with various electronich olefins lead to 6-alkoxy-3,4-dihydro-2H-pyrans.     

Application of lower bound direct method to engineering structures

Direct methods provide elegant and efficient approaches for the prediction of the long-term behaviour of engineering structures under arbitrary complex loading independent of the number of loading cycles. The lower bound direct method leads to a constrained non-linear convex problem in conjunction with finite element methods, which necessitates a very large number of optimization variables and a large amount of computer memory. To solve this large-scale optimization problem, we first reformulate it in a simpler equivalent convex program with easily exploitable sparsity structure. The interior point with DC regularization algorithm (IPDCA) using quasi definite matrix techniques is then used for its solution. The numerical results obtained by this algorithm will be compared with those obtained by general standard code Lancelot. They show the robustness, the efficiency of IPDCA and in particular its great superiority with respect to Lancelot.     

Sequences of nonlinear differential equations with related solutions

Summary A second-order nonlinear differential equation which occurs (together with variants of it) in many problems of applied mathematics, physics and engineering is here reduced to a first-order equation. This equation contains a parameter which is a quadratic rational function of two parameters appearing in the original equation. By applying a certain identity for a quadratic rational function, two (finite or infinite) sequences of nonlinear differential equations are generated whose solutions are determinable whenever the solution of any equation belonging to a sequence is known. The cases amenable to exact solution by quadrature are given. Entrata in Redazione il 16 luglio 1968.     

A new five-unknown refined theory based on neutral surface position for bending analysis of exponential graded plates

In the present paper, a new sinusoidal higher-order plate theory is developed for bending of exponential graded plates. The effects due to transverse shear and normal deformations are both included. The number of unknown functions involved in the present theory is only five as against six or more in case of other shear and normal deformation theories. The theory accounts for sinusoidal distribution of the transverse shear strains, and satisfies the zero traction boundary conditions on the surfaces of the plate without using shear correction factor. Based on the sinusoidal shear and normal deformation theory, the position of neutral surface is determined and the governing equilibrium equations based on neutral surface are derived. There is no stretching–bending coupling effect in the neutral surface-based formulation, and consequently, the governing equations of functionally graded plates based on neutral surface have the simple forms as those of isotropic plates. Numerical results of present theory are compared with three-dimensional elasticity solutions and other higher-order theories reported in the literature. It can be concluded that the proposed theory is accurate and efficient in predicting the bending response of exponential graded plates.     

Films thickness effect on structural and optoelectronic properties of hydrogenated amorphous germanium (a-Ge:H)

Thin films of hydrogenated amorphous germanium (a-Ge:H) deposited at high growth rate by radiofrequency (RF) glow discharge with 1 sccm GeH₄ diluted in 40 sccm H₂ have been studied. The effect of the films thicknesses on the defect density and on the structural parameters was carefully investigated by means of infrared spectroscopy, optical transmission measurements, and the photothermal deflection spectroscopy (PDS) technique. The results of this investigation show that when the films thicknesses increase, the total hydrogen content (C_H) decreases and the hydrogen-bonding configuration changes. The results of these changes appear clearly on the defects density and on the microstructure parameter of the films, while the disorder parameter E_OV and the optical gap E_T remain practically constant (E_OV ≈ 45 ± 2 meV, E_T = 1.08 ± 0.02 eV). The improvement of these parameters is mainly due to the incorporation of the hydrogen in the bulk of the material as the monohydride groups (Ge-H) rather than the polyhydride groups (Ge-H₂ and Ge-H_2n) when the films thicknesses increase.     

Diffusion processes of trimers on missing row surfaces: \mathrm{Cu }_{3}/\mathrm{Ag }(110) and \mathrm{Ag }_{3}/\mathrm{Cu }(110)

A semi-empirical potential according to the embedded atom, has been applied to investigate the diffusion of trimers by computing the energy barriers for different mechanisms. Our attention was more focused on the leapfrog process which is likely to occur on missing row surfaces. The activation barriers of this mechanism are calculated using drag method at 0K. These barriers are found to be 0.64 and 0.68 eV for hopping out the channel for $\mathrm{Cu }_{3}/\mathrm{Ag }(110) \mathrm{and Ag }_{3}/\mathrm{Cu }$ (110) respectively. While for hopping down at the other side they are about 0.42 and 0.32 eV. Moreover, a deep metastable position is observed during leapfrog diffusion leading to some spectacular trimer motion. At high temperature and essentially for $\mathrm{Cu }_{3}/\mathrm{Ag }$ (110), we also observed a competition between leapfrog process and concerted jump mechanism with a deformation of trimer geometry. Implications of these findings are briefly discussed.     

Spectrophotometric Determination of Metformin via Charge-Transfer Complex with Iodine

Abstract

A spectroscopic method is described for the determination of Metformin based on its formation of molecular complex with iodine in dichloroethane. Quantitative measurements are made at the maximum absorption of 295nm. The molar ratio of the formed metformin-iodine complex is 1:1 as revealed by Job's method. Beers' law is obeyed in the range 2–12 ug.ml^?1 base solution. The proposed method is statistically comparable with the official B. P. method. When applied to pharmaceutical preparation, tablets, average percentage recovery of 99.97 ± 0.81 was obtained.