Theoretical study using DFT calculations on inhibitory action of four pyridazines on corrosion of copper in nitric acid

In this part 3, The inhibitive effect of four substituted pyridazines, 5-[hydroxy(phenyl)methyl]-6-methylpyridazin-3(2H)-one (P1), 4-(2-chlorobenzyl)-6-hydrazino-3-methyl-1,6-dihydro pyridazine (P2), 5-(2,6-dichlorobenzyl)-6-methylpyridazin-3(2H)-one (P3) and 5-[(2-chlorophenyl) (hydroxy)methyl]-6-methyl pyridazin-3(2H)-one (P4) against the copper corrosion in nitric acid solution is investigated using density functional approach B3LYP/6-31G* calculations. Results obtained by weight loss and polarization measurements in part 1 show that P1, P3, and P4 are the best inhibitors. The kinetic and adsorption parameters obtained in part 2 indicated that pyridazine acted preferentially by physical adsorption. The calculated quantum chemical parameters are the highest occupied molecular orbital, the lowest unoccupied molecular orbital, the separation energy, dipole moment, electronegativity, electron affinity, global hardness, softness, ionization potential, the fraction of electrons transferred, and the total energy. The obtained data are discussed according to the inhibition efficiencies obtained.     

Investigation on the effect of cellulosic nanoparticles’ morphology on the properties of natural rubber based nanocomposites

Cellulose whiskers and microfibrillated cellulose (MFC) were extracted from the rachis of date palm tree and characterized. These cellulosic nanoparticles were used as reinforcing phase to prepare nanocomposite films using latex of natural rubber as matrix. These films were obtained by the casting/evaporation method. The properties of the ensuing nanocomposite films were investigated using differential scanning calorimetry, toluene and water uptake experiments, dynamic mechanical analysis and tensile tests. The stiffness of the natural rubber was significantly increased above its glass-rubber transition temperature upon nanoparticles addition. The reinforcing effect was shown to be higher for nanocomposites with MFC compared to whiskers. It was ascribed to the higher aspect ratio and possibility of entanglements of the former. The presence of residual lignin, extractive substances and fatty acids at the surface of MFC was also suggested to promote higher adhesion level with the polymeric matrix.     

Off-lattice pattern recognition scheme for kinetic Monte Carlo simulations

We report the development of a pattern-recognition scheme for the off-lattice self-learning kinetic Monte Carlo (KMC) method, one that is simple and flexible enough that it can be applied to all types of surfaces. In this scheme, to uniquely identify the local environment and associated processes involving three-dimensional (3D) motion of an atom or atoms, space around a central atom is divided into 3D rectangular boxes. The dimensions and the number of 3D boxes are determined by the accuracy with which a process needs to be identified and a process is described as the central atom moving to a neighboring vacant box accompanied by the motion of any other atom or atoms in its surrounding boxes. As a test of this method to we apply it to examine the decay of 3D Cu islands on the Cu(100) and to the surface diffusion of a Cu monomer and a dimer on Cu(111) and compare the results and computational efficiency to those available in the literature.     

A review on silicene — New candidate for electronics

Silicene-the silicon-based counterpart of graphene-has a two dimensional structure that is responsible for the variety of potentially useful chemical and physical properties. The existence of silicene has been achieved recently owing to experiments involving epitaxial growth of silicon as stripes on Ag(001), ribbons on Ag(110), and sheets on Ag(111). The nano-ribbons observed on Ag(110) were found-by both high definition experimental scanning tunneling microscopy images and density functional theory calculations-to consist of an arched honeycomb structure. Angle resolved photo-emission experiments on these silicene nano-ribbons on Ag(110), along the direction of the ribbons, showed a band structure which is analogous to the Dirac cones of graphene. Unlike silicon surfaces, which are highly reactive to oxygen, the silicene nano-ribbons were found to be resistant to oxygen reactivity.On the theoretical side, recent extensive efforts have been deployed to understand the properties of standalone silicene sheets and nano-ribbons using both tight-binding and density functional theory calculations. Unlike graphene it is demonstrated that silicene sheets are stable only if a small buckling (0.44 Å) is present. The electronic properties of silicene nano-ribbons and silicene sheets were found to resemble those of graphene.Although this is a fairly new avenue, the already obtained outcome from these important first steps in understanding silicene showed promising features that could give a new future to silicon in the electronics industry, thus opening a promising route toward wide-range applications. In this review, we plan to introduce silicene by presenting the available experimental and theoretical studies performed to date, and suggest future directions to be explored to make the synthesis of silicene a viable one.     

Metallization of the β-SiC(100) 3 × 2 surface: A DFT investigation

Using density functional theory (DFT) we report results for the electronic structure and vibrational dynamics of hydrogenated silicon carbide (001) (3 × 2) surfaces with various levels of hydrogenation. These results were obtained using density functional theory with a generalized gradient exchange correlation function. The calculations reveal that metallization can be achieved via hydrogen atoms occupying the second silicon layer. Further increase of hydrogen occupation on the second silicon layer sites results in a loss of this metallization. For the former scenario, where metallization occurs, we found a new vibrational mode at 1870 cm^? 1, which is distinct from the mode associated with hydrogen atoms on the first layer. Furthermore, we found the diffusion barrier for a hydrogen atom to move from the second to the third silicon layer to be 258 meV.     

Adjustment of the moments of the project completion times when activity times are exponentially distributed

The problem of determining the moment of the project completion time (MPCT) with stochastic activity durations is addressed. In the direct approach the MPCT is obtained after analyzing all possible network paths which is NP-hard problem. A recursive method for determining MPCT by proceeding iteratively over the nodes is the computationally least demanding and therefore the most efficient approach. Unfortunately, the moment methods which are available in literature ignore some aspects. In this paper, an adjustment of the moment completion time is discussed. Two illustrative examples are presented.     

Generalized n-tuple colorings of a graph: A counterexample to a conjecture of Brigham and Dutton

In their papers (Technical Report CS-TR 50, University of Central Florida, 1980; J. Combin. Theory Ser. B32 (1982), 90–94) Brigham and Dutton introduce the notion of (n : i)-chromatic numbers of a graph, a generalization of Stahl's nth chromatic numbers (J. Combin. Theory Ser. B20, (1976), 185–203). The (n : i)-chromatic number of a graph G, denoted by χ_nⁱ(G), is the smallest integer m such that each vertex of G can be colored with a set of n colors in {1, 2,…, m} in such a way that any two adjacent vertices have exactly i colors in common. Brigham and Dutton conjecture at the end of loc cit that for all integers n and i with 0 ≤ i ≤ n ? 1, and for every graph G, χ_nⁱ⁺¹(G) ≤ χ_nⁱ(G). We prove this conjecture in some special cases and disprove it in the general case.     

PROTOCHLOROPHYLL(IDE)630 PHOTOSENSITIZES ACTIVE Ca2+ ACCUMULATION IN MICROSOMAL AND MITOCHONDRIAL FRACTIONS ISOLATED FROM PLANTS

Abstract— White light irradiation of a microsomal fraction from etiolated plants affects their ATP-dependent Ca²⁺ accumulation by inhibiting active uptake and enhancing passive efflux. The succinate-dependent mitochondrial Ca²⁺ accumulation as well is decreased by light. The wavelength dependence of these light effects as well as their low quantum yield suggest non-phototransformable protochloro-phyll(ide) [PChl(ide)] to be the photoreceptor. PChlide has been isolated from corn leaves pretreated with 5-amino levulinic acid. Addition of Pchlide causes photosensitization of an otherwise light insensitive microsomal Ca²⁺ accumulation. The observed light effect may be due to contamination of the mitochondrial as well as the microsomal fractions with PChl(ide)‡ containing particles. Irradiation of the intact tissue leads to the almost complete disappearance of the light effect on the in vitro Ca²⁺ accumulation.     

Nonlinear three-point third-order boundary value problems

In this paper we consider three-point boundary value problems for third-order differential equations. We provide simple sufficient conditions in order to obtain a priori bounds on solutions. We then rely on the topological transversality theorem of Granas or on Schaefer’s theorem to prove existence of solutions.