Facile synthesis of Nickel-iron based electrocatalyst anodes for efficient oxygen evolution reaction
OJC-Vol. 3 (2020), Issue 1, pp. 6 – 12 Open Access Full-Text PDF
Aisha Batool, Farah Kanwal, Shahzad Ahmad, Sumreen Asim, Murtaza Saleem
Abstract: In this research, we reported facile synthesis of efficient \(Ni_3Fe\) electrocatalyst nanostructures deposited on conducting carbon fibers surface by a simple chemical bath deposition method at moderate temperature. The composition, phase and electrocatalytic property of as-prepared binder-free electrocatalyst was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and electrochemical measurements. The as-synthesized \(Ni_3Fe@t-CF\) presented excellent performance and durability as water oxidation electrocatalyst in alkaline electrolyte owing to non-segregated deposition of \(Ni_3Fe\) nanostructures on conducting surface of carbon, high electrochemical surface area, and the fast absorption and desorption of water molecules during oxygen evolution reaction due to the \(3D\) architecture of conducting interlaced carbon fibers template.
Chemical composition and Antioxidant activity of essential oil from flowers of Couroupita guianensis Aubl. from El Salvador
OJC-Vol. 3 (2020), Issue 1, pp. 1 – 6 Open Access Full-Text PDF
Francesco Saverio Robustelli della Cuna, Ilaria Bruni, Morena L. Martínez, Marvin J. Núnez
Abstract: Couroupita guianensis Aubl. (Lecythidaceae) “Cannonball tree” is a tropical plant with ethnobotanical uses. The present study is focused on analyzing the essential oil composition of Couroupita guianensis (C. guianensi) fresh flowers collected in El Salvador. Steam distillation, coupled with GC/FID and GC/MS analysis were employed to characterize the chemical composition and in vitro antioxidant activity study were carried out using DPPH assay. Eugenol was identified to be the most abundant constituent and quantified as \(46.20\)% of the total volatiles. Other constituents were found to be \(2\)-phenylethanol \((34.82\)%), \((E)-(E)\)-farnesol \((5.53\)%), nerol \((3.95\)%), geraniol \((3.20\)%), benzyl alcohol \((1.77\)%). \(DPPH\) assay showed a dose-dependent antioxidant activity. The study demonstrated that C. guianensis essential oil from El Salvador is a rich source of eugenol, which may be responsible for its antioxidant properties. Based on these results, further studies on the antibacterial and antifungal activity of C. guianensis essential oil are of fundamental importance.
Truncating the series expansion for unsteady velocity-dependent Eyring-Powell fluid
EASL-Vol. 3 (2020), Issue 4, pp. 28 – 34 Open Access Full-Text PDF
Emran Khoshrouye Ghiasi, Samad Noeiaghdam
Abstract: The main difficulty in dealing with the basic differential equations of fluid momentum is in choosing an appropriate problem-solving methodology. In addition, it is necessary to correct minor errors incurred by neglecting some losses. However, in many cases, such methodologies suffer from long processing time (P-time). Therefore, this article focuses on the truncation technique involving an unsteady Eyring-Powell fluid towards a shrinking wall. The governing differential equations are converted to the non-dimensional from through similarity variables. It is seen that the present system is totally convergent in 8th-order approximate solution together with \(\hbar=-0.875\).
The forgotten index of complement graph operations and its applications of molecular graph
ODAM-Vol. 3 (2020), Issue 3, pp. 53 – 61 Open Access Full-Text PDF
Mohammed Saad Alsharafi, Mahioub Mohammed Shubatah, Abdu Qaid Alameri
Abstract: A topological index of graph \(G\) is a numerical parameter related to graph which characterizes its molecular topology and is usually graph invariant. Topological indices are widely used to determine the correlation between the specific properties of molecules and the biological activity with their configuration in the study of quantitative structure-activity relationships (QSARs). In this paper some basic mathematical operations for the forgotten index of complement graph operations such as join \(\overline {G_1+G_2}\), tensor product \(\overline {G_1 \otimes G_2}\), Cartesian product \(\overline {G_1\times G_2}\), composition \(\overline {G_1\circ G_2}\), strong product \(\overline {G_1\ast G_2}\), disjunction \(\overline {G_1\vee G_2}\) and symmetric difference \(\overline {G_1\oplus G_2}\) will be explained. The results are applied to molecular graph of nanotorus and titania nanotubes.
The rank of Pseudo walk matrices: controllable and recalcitrant pairs
ODAM-Vol. 3 (2020), Issue 3, pp. 41 – 52 Open Access Full-Text PDF
Alexander Farrugia
Abstract: A pseudo walk matrix \(\bf{W}_\bf{v}\) of a graph \(G\) having adjacency matrix \(\bf{A}\) is an \(n\times n\) matrix with columns \(\bf{v},\bf{A}\bf{v},\bf{A}^2\bf{v},\ldots,\bf{A}^{n-1}\bf{v}\) whose Gram matrix has constant skew diagonals, each containing walk enumerations in \(G\). We consider the factorization over \(\mathbb{Q}\) of the minimal polynomial \(m(G,x)\) of \(\bf{A}\). We prove that the rank of \(\bf{W}_\bf{v}\), for any walk vector \(\bf{v}\), is equal to the sum of the degrees of some, or all, of the polynomial factors of \(m(G,x)\). For some adjacency matrix \(\bf{A}\) and a walk vector \(\bf{v}\), the pair \((\bf{A},\bf{v})\) is controllable if \(\bf{W}_\bf{v}\) has full rank. We show that for graphs having an irreducible characteristic polynomial over \(\mathbb{Q}\), the pair \((\bf{A},\bf{v})\) is controllable for any walk vector \(\bf{v}\). We obtain the number of such graphs on up to ten vertices, revealing that they appear to be commonplace. It is also shown that, for all walk vectors \(\bf{v}\), the degree of the minimal polynomial of the largest eigenvalue of \(\bf{A}\) is a lower bound for the rank of \(\bf{W}_\bf{v}\). If the rank of \(\bf{W}_\bf{v}\) attains this lower bound, then \((\bf{A},\bf{v})\) is called a recalcitrant pair. We reveal results on recalcitrant pairs and present a graph having the property that \((\bf{A},\bf{v})\) is neither controllable nor recalcitrant for any walk vector \(\bf{v}\).
Uniformity of dynamic inequalities constituted on time Scales
EASL-Vol. 3 (2020), Issue 4, pp. 19 – 27 Open Access Full-Text PDF
Muhammad Jibril Shahab Sahir
Abstract: In this article, we present extensions of some well-known inequalities such as Young’s inequality and Qi’s inequality on fractional calculus of time scales. To find generalizations of such types of dynamic inequalities, we apply the time scale Riemann-Liouville type fractional integrals. We investigate dynamic inequalities on delta calculus and their symmetric nabla results. The theory of time scales is utilized to combine versions in one comprehensive form. The calculus of time scales unifies and extends some continuous forms and their discrete and quantum inequalities. By applying the calculus of time scales, results can be generated in more general form. This hybrid theory is also extensively practiced on dynamic inequalities.
