MgO Nanoparticles as a Recyclable Heterogeneous Catalyst for the Synthesis of Polyhydroquinoline Derivatives under Solvent Free Conditions

Magnesium oxide nanopartticels in average size between 35–120 nm were prepared by sonochemistry method. Synthesis of polyhydroquinoline derivatives using MgO nanoparticles from the reaction of dimedone, benzaldehyde, ethyl acetoacetate and ammonium acetate under solvent‐free conditions is reported. Easy handling, reusability, thermal stability and non‐toxicity of the catalyst make the present protocol as an eco‐friendly and economically acceptable method for synthesis of these heterocycles.     

Ambidentate coordination of dimethyl sulfoxide in rhodium(III) complexes

The two dimethyl sulfoxide solvated rhodium(III) compounds, [Rh(dmso-κO)(5)(dmso-κS)](CF(3)SO(3))(3) (1 & 1* at 298 K and 100 K, respectively) and [Rh(dmso-κO)(3)(dmso-κS)(2)Cl](CF(3)SO(3))(2) (2), crystallize with orthorhombic unit cells in the space group Pna2(1) (No. 33), Z = 4. In the [Rh(dmso)(6)](3+) complex with slightly distorted octahedral coordination geometry, the Rh-O bond distance is significantly longer with O trans to S, 2.143(6) ? (1) and 2.100(6) ? (1*), than the mean Rh-O bond distance with O trans to O, 2.019 ? (1) and 2.043 ? (1*). In the [RhCl(dmso)(5)](3+) complex, the mean Rh-O bond distance with O trans to S, 2.083 ?, is slightly longer than that for O trans to Cl, 2.067(4) ?, which is consistent with the trans influence DMSO-κS > Cl > DMSO-κO of the opposite ligands. Raman and IR absorption spectra were recorded and analyzed and a complete assignment of the vibrational bands was achieved with support by force field calculations. An increase in the Rh-O stretching vibrational frequency corresponded to a decreasing trans-influence from the opposite ligand. The Rh-O force constants obtained were correlated with the Rh-O bond lengths, also including previously obtained values for other M(dmso)(6)(3+) complexes with trivalent metal ions. An almost linear correlation was obtained for the MO stretching force constants vs. the reciprocal square of the MO bond lengths. The results show that the metal ion-oxygen bonding of dimethyl sulfoxide ligands is electrostatically dominated in those complexes and that the stretching force constants provide a useful measure of the relative trans-influence of the opposite ligands in hexa-coordinated Rh(III)-complexes.     

On the Solution of Generalized Multiplicative Extremum Problems

The paper addresses the problem of maximizing a sum of products of positive and concave real-valued functions over a convex feasible set. A reformulation based on the image of the feasible set through the vector-valued function which describes the problem, combined with an adequate application of convex analysis results, lead to an equivalent indefinite quadratic extremum problem with infinitely many linear constraints. Special properties of this later problem allow to solve it by an efficient relaxation algorithm. Some numerical tests illustrate the approach proposed.     

Application of Gaussian quadrature method to characterize heavy ends of hydrocarbon fluids for modeling wax precipitation

The hydrocarbon plus fractions that comprise a significant portion of naturally occurring hydrocarbon fluids create major problems when determining the thermodynamic properties and the volumetric behavior of these fluids by equations of state. These problems arise due to the difficulty of properly characterizing the plus fractions (heavy ends). Proper characterization of the heavier components is important when cubic equations of state and/or solid formation thermodynamic models are used to describe complex phase behavior of reservoir fluids. The effect of heavy fractions characterization on thermodynamic modeling of wax precipitation has been investigated using different models including Won, Pan and proposed models. In order to characterize the plus fraction (heavier part) as a series of pseudocomponents, a probability model that expresses the mole fraction as a continuous function of the molecular weight has been used. The study has been conducted using several mixtures. Two different SCN (single carbon number), C₇₊${\text{C}}_{7^{+}}$ and C₁₀₊${\text{C}}_{{10}^{+}}$ were chosen. The Chosen SCN were distributed to multi-components of five, six, and/or ten using continuous function and Gaussian quadrature method. The results showed that the fractioning is required to be able to predict wax precipitation. Distribution of C₁₀₊${\text{C}}_{{10}^{+}}$ using a proper distribution function has shown improvement in predictions of WAT and the amount of wax deposited in comparison with the characterization of C₇₊${\text{C}}_{7^{+}}$ using semi-continuous approach. In predicting of WAT and the amount of wax build up the developed model showed superiority over the others.     

A new element for analyzing large deformation of thin Naghdi shell model. Part II: Plastic

In this paper a new element is developed that is based on Cosserat theory. In the finite element implementation of Cosserat theory shear locking can occur, especially for very thin shells. In the present investigation the director vector is constrained to remain perpendicular to the mid surface during deformation. It will be shown that this constraint yields accurate results in very large deformation of thin shells also the rate of convergency is very good. For plastic formulation, the model introduced by Simo is used and it has been reduced for constrained director vector and the consistent elasto-plastic tangent moduli is extracted for finite element solution. This model includes both kinematic and isotropic hardening. For numerical investigations an isoparametric nine node element is employed then by linearization of the principle of virtual work, material and geometric stiffness matrices are extracted. The validity and the accuracy of the proposed element is illustrated by the numerical examples and the results are compared with those available in the literature.     

Theoretical investigation into the mechanism of reductive elimination from bimetallic palladium complexes

Reductive elimination of C-Cl and C-C bonds from binuclear organopalladium complexes containing Pd-Pd bonds with overall formal oxidation state +III are explored by density functional theory for dichloromethane and acetonitrile solvent environments. An X-ray crystallographically authenticated neutral complex, [(L-C,N)ClPd(μ-O(2)CMe)](2) (L = benzo[h]quinolinyl) (I), is examined for C-Cl coupling, and the proposed cation, [(L-C,N)PhPd(1)(μ-O(2)CMe)(2)Pd(2)(L-C,N)](+) (II), examined for C-C coupling together with (L-C,N)PhPd(1)(μ-O(2)CMe)(2)Pd(2)Cl(L-C,N) (III) as a neutral analogue of II. In both polar and nonpolar solvents, reaction from III via chloride dissociation from Pd(2) to form II is predicted to be favored. Cation II undergoes Ph-C coupling at Pd(1) with concomitant Pd(1)-Pd(2) lengthening and shortening of the Pd(1)-O bond trans to the carbon atom of L; natural bond orbital analysis indicates that reductive coupling from II involves depopulation of the d(x(2)-y(2)) orbital of Pd(1) and population of the d(z(2)) orbitals of Pd(1) and Pd(2) as the Pd-Pd bond lengthens. Calculations for the symmetrical dichloro complex I indicate that a similar dissociative pathway for C-Cl coupling is competitive with a direct (nondissociative) pathway in acetonitrile, but the direct pathway is favored in dichloromethane. In contrast to the dissociative mechanism, direct coupling for I involves population of the d(x(2)-y(2)) orbital of Pd(1) with Pd(1)-O(1) lengthening, significantly less population occurs for the d(z(2)) orbital of Pd(1) than for the dissociative pathway, and d(z(2)) at Pd(2) is only marginally populated resulting in an intermediate that is formally a Pd(1)(I)-Pd(2)(III) species, (L-Cl-N,Cl)Pd(1)(μ-O(2)CMe)Pd(2)Cl(O(2)CMe)(L-C,N) that releases chloride from Pd(2) with loss of Pd(I)-Pd(III) bonding to form a Pd(II) species. A similar process is formulated for the less competitive direct pathway for C-C coupling from III, in this case involving decreased population of the d(z(2)) orbital of Pd(2) and strengthening of the Pd(I)-Pd(III) interaction in the analogous intermediate with η(2)-coordination at Pd(1) by L-Ph-N, C(1)-C(2).     

Selective mono- to perarylations of tetrabromothiophene by a cyclobutene-1,2-diylbisimidazolium preligand

(Cyclobut-1-ene-1,2-diyl)bis(1-methylimidazolium)tetrafluoroborate is applied as preligand in palladium-catalyzed cross-coupling reactions starting from tetrabromothiophene for the synthesis of mono-, bi-, tri-, and tetraaryl-substituted thiophenes bearing up to four different aryl rings. A synthetic kit for preparations of nine different substitution patterns of arylated thiophenes is presented by application of only one single catalyst system. In agreement with DFT calculations, which predict energetically low rotational barriers in triaryl-3-bromothiophenes and tetraarylthiophenes, no NOE effects between adjacent aryl rings are detectable. The regioselectivity of their syntheses has therefore been elucidated by reduction of triaryl-3-bromothiophene to 2,3,5-triarylthiophene followed by HMBC, HSQC, and NOESY NMR measurements. Additionally, results of an X-ray single structure analysis are presented.     

Specific adhesion of vesicles to compliant bio-adhesive substrates

Cell behavior is mediated by variety of physiochemical properties of the extracellular matrix (ECM). Mechanical stiffness of ECM, in particular, is found to be a major regulator for the multiple aspects of cellular function. Experiments show that cells generally exhibit an apparent adhesion preference for stiffer substrates. The effect of substrate elasticity is also found to be strongly coupled with adhesivity of the substrate. To understand the underlying physics of rigidity sensing mechanism in cells, in this study we use a vesicle-substrate system to model cell adhesion as a first order approximation. Within this framework, an equilibrium thermodynamic analysis is undertaken to elucidate the interplay between substrate compliance and equilibrium configuration of an adherent vesicle. The equilibrium adhesion is assumed to ensure minimization of the free energy contributed by substrate deformation and interfacial adhesive and repulsive interactions between the membrane and substrate. The predictions of this purely mechanistic model are found to be qualitatively analogous to some of the characteristic features of cell adhesion to compliant bio-adhesive substrates. This observation suggests that the physical aspects of the membrane–substrate interfacial interactions could passively contribute in regulation of the rigidity sensing by cells.     

Green's function of two-dimensional time-fractional diffusion equation using addition formula of Wright function

In this paper, using the Mellin transform of Wright function we derive an addition formula for the Wright function. In some special cases, addition formulas for the Hermite, Bessel and Mittag-Leffler functions are also given and the Green's function of two-dimensional time-fractional diffusion equation is presented in the whole plane.     

Quantum feedback control: how to use verification theorems and viscosity solutions to find optimal protocols

While feedback control has many applications in quantum systems, finding optimal control protocols for this task is generally challenging. So-called ‘verification theorems’ and ‘viscosity solutions’ provide two useful tools for this purpose: together they give a simple method to check whether any given protocol is optimal, and provide a numerical method for finding optimal protocols. While treatments of verification theorems usually use sophisticated mathematical language, this is not necessary. In this article we give a simple introduction to feedback control in quantum systems, and then describe verification theorems and viscosity solutions in simple language. We also illustrate their use with a concrete example of current interest.