Circle grid fractal plate as a turbulent generator for premixed flame: an overview

This review paper focuses to ascertain a new approach in turbulence generation on the structure of premixed flames and external combustion using a fractal grid pattern. This review paper discusses the relationship between fractal pattern and turbulence flow. Many researchers have explored the fractal pattern as a new concept of turbulence generators, but researchers rarely study fractal turbulence generators on the structure premixed flame. The turbulent flow field characteristics have been studied tand investigated in a premixed combustion application. In terms of turbulence intensity, most researchers used fractal grid that can be tailored so that they can design the characteristic needed in premixed flame. This approach makes it extremely difficult to determine the exact turbulent burning velocity on the velocity fluctuation of the flow. The decision to carry out additional research on the effect circle grid fractal plate as a turbulent generator for premixed flame should depends on the blockage ratio and fractal pattern of the grid. 1

Mechanistic studies on the pH-controllable hydrogenation of NAD<SUP>+</SUP> by H<SUB>2</SUB> and generation of H<SUB>2</SUB> from NADH by a water-soluble biomimetic iridium complex

Functional biomimicking of hydrogenases at ambient conditions is challenging. Recently an Ir(III)-cyclometalated complex (J. Am. Chem. Soc. 2012, 134, 367) has been shown to catalyze the pH-dependent reversible reduction of NAD<SUP>+</SUP> (nicotinamide adenine dinucleotide) by dihydrogen in water medium. Yet, the reaction mechanism for the catalysis has not been unravelled comprehensively. Hence in this work, mechanisms for catalytic hydrogenation of NAD<SUP>+</SUP> to the reduced form of NAD<SUP>+</SUP> (NADH) and the reverse reaction catalyzed by the Ir(III)-cyclometalated complex have been proposed using the results obtained from density functional theory based calculations. The mechanism suggests that the carboxylate group of the Ir(III) complex can act as a proton relay between hydrogen and water molecules. As a consequence, the direction of the reaction is controlled by the pH of the medium. Splitting of H<SUB>2</SUB> and generation of H<SUB>2</SUB> are the rate-determining steps in the two directions with the same activation barrier height of 34.6 kcal/mol. Also, the mechanism supports that the σ-bond metathesis is preferred over oxidative addition of hydrogen. Results show that NADH may act as an inhibitor of the substrate at high basic pH

Novel chemistry for the selective oxidation of benzyl alcohol by graphene oxide and N-doped graphene

A novel mechanism for the selective activation of benzyl alcohol by graphene oxide and N-doped graphene has been proposed using density functional theory based calculations. Interestingly, the proposed mechanism opens new avenues for graphene and its derivative-based catalysis

Novel Chemistry for the Selective Oxidation of Benzyl Alcohol by Graphene Oxide and N‑Doped Graphene

A novel mechanism for the selective activation of benzyl alcohol by graphene oxide and N-doped graphene has been proposed using density functional theory based calculations. Interestingly, the proposed mechanism opens new avenues for graphene and its derivative-based catalysis

Dioxin sensing properties of graphene and hexagonal boron nitride based van der Waals solids: a first-principles study

The changes in the electronic properties of single and bilayers of graphene (G) and hexagonal boron nitride (h-BN) two dimensional (2D) sheets have been investigated upon interaction with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) by employing density functional theory (DFT) based calculations. The calculated interaction energy, band gap and charge transfer reveal that bilayer h-BN (BLBN) may serve as a better potential candidate for sensing TCDD than the other systems. To gain further insight into the sensing properties of these materials, the transmission spectra and current–voltage (I–V) characteristics have been calculated by using Non-Equilibrium Green's Function (NEGF) combined with DFT approach. It is interesting to mention that a Negative Differential Resistance (NDR) effect has been observed in a single layer BN (SLBN) nanoribbon upon interaction with TCDD. The calculated I–V characteristics of the BLBN nanoribbon–TCDD complex reveal that the interaction between the two systems enhances the current flow through the BLBN nanoribbon, which is appreciably higher than that of pristine BLBN. These findings may open up new avenues for the application of bilayers as possible sensors for pollutants

Improving the hydrogen storage capacity of metal organic framework by chemical functionalization

The hydrogen storage capacity of transition metal decorated terphenyl linkers was investigated using density functional theory based M05-2X, M06 and wB97XD methods. The –OH and –SH groups are used as anchors to bind various transition metals such as Sc, Ti, V, and Cr on terphenyl linker. It has been found that each transition metal can bind four hydrogen molecules through Kubas interaction. The correlation between electron density at the bond critical point corresponding to H–H bond and concomitant intermolecular distances between transition metal and hydrogen molecules has been used to illustrate the Kubas mechanism. Further, to estimate the bulk storage capacity, 42 hydrogen molecules are allowed to interact with the new metal organic framework fragment in all possible binding sites. The calculated interaction energy per hydrogen molecule is found to be −3.38 kcal/mol. Comparison of this value with previous reports shows that this energy is suitable for room temperature hydrogen storage applications

Interaction of collagen like peptides with gold nanosurfaces: a molecular dynamics investigation

In this study, an attempt has been made to understand the interaction between collagen like peptides (CPs) with a gold nanosurface (AuNS) using a classical molecular dynamics simulation. Results reveal that the adsorption of CPs onto the gold surface depends on the amino acid composition of the collagen like peptides. It is evident from the findings that the Hyp residue of collagen interacts favorably with the AuNS. It is interesting to note that the model CP without a Hyp residue does not adsorb well on the surface. Results indicate that gold nanosurfaces or gold nanoparticles can be exploited to detect breast cancer due to the increased content of Hyp residues in the Gly–XAA–YAA triplet of collagen in breast cancer tissues. These results provide useful information for designing collagen based scaffolds for tissues engineering applications

A new class of MPV type reduction in group 4 alkoxide complexes of salicylaldiminato ligands: Efficient catalysts for the ROP of lactides, epoxides and polymerization of ethylene

New titanium (IV), zirconium (IV) and hafnium (IV) alkoxide complexes supported by the tridentate [O,N,N] salicylaldiminato ligands were synthesized in high yields and characterized by conventional spectroscopic techniques and single crystal X-ray analysis. The structural composition for some of these complexes was as a result of in situ intramolecular Meerwein–Ponndorf–Verley (MPV) type reduction of the imine moiety from the ligand, resulting in the formation of unexpected amido compounds. Theoretical calculations were performed at the DFT level to calculate the energy barrier for this reduction and rationalize the reactivity pattern. These complexes were found to be active towards the bulk ring opening polymerization (ROP) of rac-lactide (rac-LA), l-lactide (l-LA) and ε-caprolactone (CL), resulting in polymers with good number average molecular weight (Mn) and controlled molecular weight distributions (MWDs). The poly(lactic acid) (PLA) resulting from rac-LA were predominately heterotactic. Interestingly, these compounds were found to catalyze the ROP of epoxides such as rac-cyclohexene oxide (rac-CHO), rac-styrene oxide (rac-SO) and rac-propylene oxide (rac-PO) under solvent free condition. The kinetic and mechanistic studies associated with the polymerization have been included. In addition, these compounds were found to be useful as precatalysts for the polymerization of ethylene

Unraveling the reaction mechanism, enantio and diastereoselectivities of selenium ylide promoted epoxidation

1001-1009The reaction between chiral selenium ylide and benzaldehyde leads to the formation of (2S,3S)-trans-epoxide with high enantio- and diastereoselectivity. Density functional theory and Hartree-Fock calculations using 6-31G(d) basis set have been performed to understand the reaction mechanism and factors associated with enantio- and diastereoselectivities. Conformation of chiral selenium ylide has been found to have a strong influence on the stability of the initial addition transition state between ylide and benzaldehyde. Calculated enantio- and diastereoselectivities from the energy differences between B3LYP/6-31G(d) addition TSs are in good agreement with the experimental data. The rate and diastereoselectivity are controlled by the <i style="mso-bidi-font-style: normal">cisoid-transoid rotational transition state. Analysis of transition state geometries clearly reveals that unfavorable eclipsing interaction between phenyl groups of the benzaldehyde and ylidic substituents mainly governs the energy differences between the enantio and diastereomeric transition states. The favourable reactivity is also explained through Fukui function calculations