Effect of synthesis duration on the morphological and structural modification of the sea urchin-nanostructured γ-MnO2 and study of its electrochemical reactivity in alkaline medium

Single-crystalline nanorods and sea urchin-like morphology of the γ-MnO₂ nanostructures were successfully synthesized by hydrothermal method at different synthesis durations. The as-synthesized products were characterized by the techniques X-ray powder diffraction (XRD), field emission gun-scanning electron microscope (FEG-SEM) coupled with energy-dispersive X-ray elemental analysis (EDX), transmission electron microscope (TEM), isotherms of N₂ adsorption/desorption and BET-BJH models. The effect of synthesis duration on the morphology, porous structure, and crystallographic form of MnO₂ powders was studied. The electrochemical reactivity of as-prepared powders was investigated in 1 mol L^?1 KOH by both cyclic voltammetry and impedance spectroscopy by using a micro-cavity electrode. The results show that the best electrochemical reactivity of the MnO₂ powder was obtained with synthesis duration of 24 h.     

The Use of Modified Clay as an Efficient Heterogeneous and Ecofriendly Catalyst for the Synthesis of Chalcones via Claisen-Schmidt Condensation

Russian Journal of Applied Chemistry - Clay modified by potassium fluoride (KF-modified clay) was used as an ecological alternative and heterogeneous catalyst for the preparation of chalcones via...     

Lobularia libyca: Phytochemical Profiling,Antioxidant and Antimicrobial Activity Using In Vitro and In Silico Studies

Lobularia libyca (L. libyca) is a traditional plant that is popular for its richness in phenolic compounds and flavonoids. The aim of this study was to comprehensively investigate the phytochemical profile by liquid chromatography, electrospray ionization and tandem mass spectrometry (LC-ESI-MS), the mineral contents and the biological properties of L. libyca methanol extract. L. libyca contains significant amounts of phenolic compounds and flavonoids. Thirteen compounds classified as flavonoids were identified. L. libyca is rich in nutrients such as Na, Fe and Ca. Moreover, the methanol extract of L. libyca showed significant antioxidant activity without cytotoxic activity on HCT116 cells (human colon cancer cell line) and HepG2 cells (human hepatoma), showing an inhibition zone of 13 mm in diameter. In silico studies showed that decanoic acid ethyl ester exhibited the best fit in β-lactamase and DNA gyrase active sites; meanwhile, oleic acid showed the best fit in reductase binding sites. Thus, it can be concluded that L. libyca can serve as a beneficial nutraceutical agent, owing to its significant antioxidant and antibacterial potential and due to its richness in iron, calcium and potassium, which are essential for maintaining a healthy lifestyle.     

On convexity for energy decay rates of a viscoelastic equation with boundary feedback

In this paper we consider a viscoelastic equation with a nonlinear feedback localized on a part of the boundary. We establish an explicit and general decay rate result, using some properties of the convex functions. Our result is obtained without imposing any restrictive growth assumption on the damping term and strongly weakening the usual assumptions on the relaxation function.     

A blow-up result in a nonlinear abstract evolution system with delay

In this paper we consider a second-order abstract evolution system with delay. We show that, under suitable conditions on the initial data and the involved functionals, the energy of solutions blows up in finite-time. We also give some concrete examples to illustrate our main result.     

On formation of singularities in one-dimensional nonlinear thermoelasticity

Dedicated to Bernard D. Coleman on the occasion of his 60^th birthday     

Blow Up in a Semilinear Wave Equation

We consider a semilinear wave equation of the form u_tt(x, t) - Δu(x, t) = - m(x, t)u_t(x, t) + ∇Φ(x) ⋅ ∇u(x, t ) + b(x)|u(x, t)|^{p-2}u(x, t) where p > 2. We show, under suitable conditions on m, Φ, b, that weak solutions break down in finite time if the initial energy is negative. This result improves an earlier one by the author [1].