Diquark structure in heavy quark baryons in a geometric model

Using a geometric model to study the structure of hadrons, baryons having one, two and three heavy quarks have been studied here. The study reveals diquark structure in baryons with one and two heavy quarks but not with three heavy identical quarks.     

Coupling of elastic and thermal deformations I

Flow, Turbulence and Combustion - The general solution for the stress and temperature distribution in an isotropic thermoelastic solid occupying the half space has been given when the classical...     

Lignin as a Natural Carrier for the Efficient Delivery of Bioactive Compounds: From Waste to Health

Lignin is a fascinating aromatic biopolymer with high valorization potentiality. Besides its extensive value in the biorefinery context, as a renewable source of aromatics lignin is currently under evaluation for its huge potential in biomedical applications. Besides the specific antioxidant and antimicrobial activities of lignin, that depend on its source and isolation procedure, remarkable progress has been made, over the last five years, in the isolation, functionalization and modification of lignin and lignin-derived compounds to use as carriers for biologically active substances. The aim of this review is to summarize the current state of the art in the field of lignin-based carrier systems, highlighting the most important results. Furthermore, the possibilities and constraints related to the physico–chemical properties of the lignin source will be reviewed herein as well as the modifications and processing required to make lignin suitable for the loading and release of active compounds.     

Theoretical calculation of the pKa values of some drugs in aqueous solution

In this work, calculations of pK_a values have been performed on benzoic acid and its para‐substituted derivatives and some drugs by using Gaussian 98 software package. Gas‐phase energies were calculated with HF/6‐31 G** and B3LYP/6‐31 G** levels of theory. Free energies of solvation have been computed using the polarizable continuum model (PCM), conductor‐like PCM (CPCM), and the integral equation formalism‐PCM at the same levels which have been used for geometry determination in the gas‐phase. The results that show the calculated pK_a values using the B3LYP are better than those using the corresponding HF. In comparison to the other models, the results obtained indicate that the PCM model is a suitable solvation model for calculating pK_a values. For the investigated compounds, a good agreement between the experimental and the calculated pK_a values was also observed. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Modification of Co/Al2O3 Fischer–Tropsch Nanocatalysts by Adding Ni: A Kinetic Approach

In this article, the effects of Ni (Co:Ni ratio = 4:1) on the performances and kinetic parameters of Co/Al₂O₃ nanocatalysts are explored in Fischer–Tropsch synthesis. As a result, the probability of chain growth increases and the deactivation rate decreases with addition of Ni. The properties of catalysts are characterized at different stages using Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and the vibrating sample magnetometer technique. The Co/Ni/Al₂O₃ catalyst with higher surface area and pore size exhibits higher activity and C₅₊ selectivity. The different results obtained for room‐temperature ferromagnetism have been attributed to the different metal oxides in the catalysts. The Fischer Tropsch kinetic study is done on the basis of the Langmuir–Hinshelwood–Hougen–Watson adsorption theory. Seven kinetic expressions based on the carbide and enolic mechanisms are selected. All experimental data are theoretically examined with these kinetic expressions to derive the best kinetic according to the linear and nonlinear approaches. The kinetic parameters of the fitted model, including the rate constant (k) and activation energy (E_a), are calculated with the Levenberg–Marquardt and genetic algorithm. The results show that by adding Ni the activation energy (E_a) decreases, the reaction rate (–R_CO) increases, and the CO adsorption on the Co/Ni/Al₂O₃ catalyst is faster as well.     

Hadronic modes in the quark plasma with an internal symmetry

We show that requiring the quark partition function to be color singlet in the SU(3) color gauge group leads to reordering of the thermodynamic potential in terms of the colorless multiquark modes (, qqq, , ) at any given temperature. These color-singlet structures are not bound states in a real sense, rather they are a combination of constituent quarks only. In accord with the “preconfinement” property of QCD, under a suitable confining mechanism, these could evolve into color-singlet hadrons/baryons at low temperatures. At fairly high temperatures, these multiquark color-singlet structures exist in the plasma as hadronic modes, just as in the more familiar low-temperature phase. This suggests that there exists a strong color correlation in the plasma at all temperatures. Received: 25 May 1999 / Published online: 2 November 1999     

Characterization and Reactivity of a Tetrahedral Copper(II) Alkylperoxido Complex

A tetrahedral Cu^II alkylperoxido complex [Cu^II(TMG₃tach)(OOCm)]⁺ ( 1^OOCm ) (TMG₃tach={2,2′,2′′-[(1s,3s,5s)-cyclohexane-1,3,5-triyl]tris-(1,1,3,3-tetramethyl guanidine)}, OOCm=cumyl peroxide) is prepared and characterized by UV/Vis, cold-spray ionization mass spectroscopy (CSI-MS), resonance Raman, and EPR spectroscopic methods. Product analysis of the self-decomposition reaction of 1^OOCm in acetonitrile (MeCN) indicates that the reaction involves O−O bond homolytic cleavage of the peroxide moiety with concomitant C−H bond activation of the solvent molecule. When an external substrate such as 1,4-cyclohexadiene (CHD) is added, the O−O bond homolysis leads to C−H activation of the substrate. Furthermore, the reaction of 1^OOCm with 2,6-di-tert-butylphenol derivatives produces the corresponding phenoxyl radical species (ArO^.) together with a Cu^I complex through a concerted proton-electron transfer (CPET) mechanism. Details of the reaction mechanisms are explored by DFT calculations.