Phase equilibria of (water + levulinic acid + dibasic esters) ternary systems

Liquid–liquid equilibrium (LLE) data of the solubility (binodal) curves and tie-line end compositions were examined for mixtures of {(water (1) + levulinic acid (2) + dimethyl succinate or dimethyl glutarate or dimethyl adipate (3)} at 298.15 K and 101.3 ± 0.7 kPa. The reliability of the experimental tie-line data was confirmed by using the Othmer–Tobias correlation. The LLE data of the ternary systems were predicted by UNIFAC method. The LLE data were correlated fairly well with UNIQUAC and NRTL models, indicating the reliability of the UNIQUAC and NRTL equations for these ternary systems. The best results were achieved with the NRTL equation, using non-randomness parameter (α = 0.3) for the correlation. Distribution coefficients and separation factors were measured to evaluate the extracting capability of the solvents.     

Structural and aromatic aspects for tautomerism of (Z)-6-((4-bromophenylamino)methylene)-2,3-dihydroxycyclohexa-2,4-dienone

The molecular and crystal structure of (Z)-6-((4-bromophenylamino)methylene)-2,3-dihydroxycyclohexa-2,4-dienone were determined by single crystal X-ray diffraction and spectroscopic methods. Molecules of the compound can be regarded as a resonance hybrid of cis-keto tautomer and zwitterionic form. Pairs of molecules of the compound generate pseudocyclic centrosymmetric R₂² (10) R_{2}^{2} (10) supramolecular synthons with the aid of O–H···O type intermolecular H-bonds. Stacking of R₂² (10) R_{2}^{2} (10) synthons along b-axis is stabilized by π···π interactions. Changes in both covalent topology and molecular geometry of the compound accompanying proton transfer were monitored by a relaxed PES scan with respect to hydroxyl bond length used as redundant internal coordinate. Quantum chemical studies at 6-311 + G(d,p) level reveal that bond lengths which are indicative to tautomerization process cannot reach their expected values even if proton transfer occurs in gas phase and pseudo-aromatic chelate ring formation has primary effect on the stabilization of NH tautomer. Resonance-assisted intramolecular H-bond affects the electronic state of its neighboring aromatic fragments.     

Discrete exact solutions to some nonlinear differential-difference equations via the (G′/G)-expansion method

We extended the (G′/G)-expansion method to two well-known nonlinear differential-difference equations, the discrete nonlinear Schrödinger equation and the Toda lattice equation, for constructing traveling wave solutions. Discrete soliton and periodic wave solutions with more arbitrary parameters, as well as discrete rational wave solutions, are revealed. It seems that the utilized method can provide highly accurate discrete exact solutions to NDDEs arising in applied mathematical and physical sciences.     

Conductivity and band gap of oligo-2-[(4-fluorophenyl) imino methylene] phenol and some of its oligomer-metal complexes

Schiff base oligomer of 2-[(4-fluorophenyl) imino methylene] phenol (FPIMP) was synthesized via oxidative polycondensation reaction in an alkaline medium. Oligomer-metal complex compounds were synthesized from the reactions of oligo-2-[(4-fluorophenyl) imino methylene] phenol (OFPIMP) with Co⁺², Ni⁺² and Cu⁺² ions. The synthesis was achieved by oxidative coupling based on air oxygen as an oxidant. While synthesized Schiff base oligomer was soluble in most common organic solvents, its metal complexes were only soluble in dimethylsulfoxide. Electrochemical HOMO and LUMO band gap (E_g) of monomer, oligomer and its metal complexes were calculated from oxidation and reduction onset values. According to cyclic voltammetry (CV) and UV-vis measurements, electrochemical energy gaps and optical band gap (E_g) values of monomer and oligomer were found to be 3.26 and 3.10; 3.15 and 2.96 eV, respectively. Conductivity measurements of doped and undoped Schiff base oligomer and its metal complexes were carried out by electrometer at a room temperature and atmospheric pressure and were calculated from four-point probe technique. When iodine was used as doping agent, conductivity of this oligomer and its metal complexes were observed to be increased.     

A parametric study for thick plates resting on elastic foundation with variable soil depth

The soil depth is generally considered to be constant for the analysis of plates resting on elastic foundation in the literature. However, it is most reasonable to have a variable subsoil depth as the plate dimensions get larger. In present study, linearly varying subsoil depth is considered as well as constant, linear and quadratic variation of modulus of elasticity with subsoil depth. Also, a parametric study is performed to demonstrate the behavior of thick plates on elastic foundations with variable soil depth. Modified Vlasov Model is used for the analysis of the plate foundation system, and 8-noded Mindlin plate element incorporating shear strain throughout plate thickness is used for the finite element model. Numerical examples are obtained from the literature to compare results and to show the influence of variable soil stratum depth on the behavior of plates. Displacements, bending moments, and shear forces are presented in tabular and graphical formats. As far as results are compared, it can be concluded that variable soil depth significantly affects the variation of the displacements and therefore the internal forces of the plate while keeping it constant ends up with unrealistic results.     

Hot-air drying of purslane (Portulaca oleracea L.)

Drying characteristics of purslane was experimentally studied in a cabinet dryer. The experimental drying data were fitted best to Modified Henderson and Pabis and Midilli et al. models apart from other models to predict the drying kinetics. The effective moisture diffusivity varied from 1.12 × 10^?9 to 3.60 × 10^?9 m²/s over the temperature range studied and activation energy was 53.65 kJ/mol.     

Some Remarks on Exp-Function Method and Its Applications-A Supplement

Recently, the authors of [Commun. Theor. Phys. 56 (2011) 397] made a number of useful observations on Exp-function method. In this study, we focus on another vital issue, namely, the misleading results of double Exp-function method.     

Traveling Wave Solutions for Nonlinear Differential-Difference Equations of Rational Types

Differential-difference equations are considered to be hybrid systems because the spatial variable n is discrete while the time t is usually kept continuous.Although a considerable amount of research has been carried out in the field of nonlinear differential-difference equations,the majority of the results deal with polynomial types.Limited research has been reported regarding such equations of rational type.In this paper we present an adaptation of the(G /G)-expansion method to solve nonlinear rational differential-difference equations.The procedure is demonstrated using two distinct equations.Our approach allows one to construct three types of exact traveling wave solutions(hyperbolic,trigonometric,and rational) by means of the simplified form of the auxiliary equation method with reduced parameters.Our analysis leads to analytic solutions in terms of topological solitons and singular periodic functions as well.     

Quantum Chemical,Spectroscopic, and X-Ray Diffraction Studies of N-diphenylphosphino-4-methylpiperidine Selenide (1)

The title molecule, N-diphenylphosphino-4-methylpiperidine selenide(1), was prepared and characterized by elemental analysis, ¹H-NMR, ³¹P-{¹H} NMR, IR, and X-ray single-crystal determination. The compound crystallizes in the monoclinic space group P 2₁/c. In addition to the molecular geometry from X-ray determination, vibrational frequencies and gauge, including atomic orbital (GIAO) ¹H- and ³¹P-{¹H} NMR chemical shift values of the title compound (1) in the ground state, were calculated using the Hartree–Fock and density functional methods with the 6-31G(d, p) basis set. The calculated results show that the optimized geometries can well reproduce the crystal structures. Besides, the theoretical vibrational frequencies and chemical shift values show good agreement with experimental values. The predicted nonlinear optical (NLO) properties of the title compound are greater than those of urea. In addition, density functional theory (DFT) calculations of the molecular electrostatic potentials (MEPs), frontier molecular orbitals (FMOs) of the title compound were carried out at the B3LYP/6-31G(d) level of theory.     

Radiostability of Allantoin by Using Electron Spin Resonance Spectroscopy

The radiosterilization potential and dosimetric feature of allantoin were investigated through the molecular degradations produced after ultraviolet and gamma irradiation using electron spin resonance, infrared, and ultraviolet spectroscopies and thermal measurement techniques (differential thermal analysis and the glass transition temperature). Although ultraviolet-irradiated allantoin presents no electron spin resonance signal, gamma irradiation exhibited an electron spin resonance signal of triplet appearance. Room temperature and high-temperature line intensity and spectrum area data and their variations with applied microwave power, storage time, annealing time, annealing temperature, and applied radiation dose were analyzed by assuming the production of two different types of radicals having different spectroscopic and decay characteristics. Based on its relatively stable nature toward gamma and ultraviolet radiations, it was concluded that allantoin itself and the products containing it can be sterilized by gamma and/or ultraviolet radiations without creating a great loss in its beneficial effects in the allowed radiosterilization dose limits.