A pressure-shear plate impact experiment for investigating transient friction

A pressure-shear plate impact experiment is introduced to study time-resolved friction at interfaces subjected to high sliding speeds under relatively high normal pressures. The conditions of slip at the interface are varied by changing the surface roughness of the impacting plates and by varying the applied normal to shear stress ratio. The configuration offers the simplicity of allowing the interpretation of the experimental data by using the frame-work of one-dimensional plane wave analysis. The interfacial material pairs investigated in the present study are comprised of a wear-resistant grade of tungsten carbide and either an AISI 4340 steel or a Ti-6AI-4V alloy. The experimental results indicate that the coefficient of friction increases with the increase in surface roughness of the tungsten-carbide plates and with cumulative slip at the interface.     

X-ray K-absorption fine structure study of CuxZn1-xFe2O4 (x = 0.2, 0.4, 0.6 and 0.8)

For Cu_xZn_1-xFe₂O₄ spinel ferrites (x = 0.2, 0.4, 0.6 and 0.8), EXAFS of Cu and Fe K-absorption edges have been studied employing LSS theory. With change in copper content, in the spinel system, the basic dependence of cation distribution on degree of inversion has been reported by plotting variation of bond distance “d” with EXAFS parameter ‘α’. This is further substantiated by plotting chemical shifts (ΔE) with EXAFS parameter ‘α’. The necessity of the determination of final state wavefunction for the knowledge of distribution of charge is stressed.     

LiBr-catalyzed one-pot three-component domino strategy toward the construction of β-phosphonomalonates scaffolds in aqueous conditions

Abstract

LiBr-mediated domino Knoevenagel-phospha-Michael strategy has been established for the synthesis of β-phosphonomalonates under aqueous conditions. It is noteworthy that the developed protocol is effective with a wide range of aldehydes to deliver a diverse range of β-phosphonomalonates in good to excellent yields. The mild reaction conditions, easier procedure, use of aqueous media, inexpensive and water tolerant property of LiBr are important advantages of this protocol.     

Template-engineered metal macrocyclic complexes: Synthesis and biological activity

Three new azamacrocylic complexes of divalent transition-metal ions were synthesized by taking Co(II), Ni(II), and Cu(II) metal ions as templates. The macrocyclic ligand (1²Z,5²Z,5⁴E)-1¹,1²,1³,1⁴,1⁵,1⁶,5¹,5²,5³,5⁴,5⁵,5⁶-dodecahydro-2,4,6,8-tetraaza-1 (2,4),5(4,2)-pyrimidine-3,7(1,2)-dibenzenacyclooctaphane-1⁶,5⁶-dione was derived from o-phenylenediamine (OPD) and 2-thiobarbituric acid (TBA). All the complexes were fully characterized through spectroscopic techniques and elemental analyses. The structures of the macrocyclic complexes were determined by IR, UV–vis, ESI-MS, TGA, molar conductance, magnetic moment, and electron spin resonance data. On the basis of the above studies, the complexes may be formulated as [MLX₂], in which L is a macrocyclic ligand and X = CH₃COO⁻. All the macrocyclic complexes were biologically screened to evaluate their antimicrobial efficacy. DNA binding study of two representative complexes was performed by UV–vis titrations.     

Low‐noise,vibrational phase‐sensitive chemical imaging by balanced detection RIKE

We perform a back‐to‐back comparison between two nonlinear vibrational imaging techniques: stimulated Raman scattering (SRS) and balanced detection Raman‐induced Kerr effect (BD‐RIKE). Using a compact fiber‐based laser system for generation of pump and Stokes signals, we image polymer beads as well as human hepatocytes under the same experimental conditions. We show that BD‐RIKE, despite the slightly lower signal levels, consistently offers an improved signal‐to‐noise ratio with respect to SRS, resulting in significantly higher image quality. Importantly, we observe that such quality is not affected by the static birefringence of the sample, which makes BD‐RIKE a robust and attractive alternative to SRS. We also highlight a unique advantage of the technique, which is its capability to easily access both the real and imaginary parts of the nonlinear susceptibility, thus allowing for vibrational phase imaging. The phase information can be readily obtained from BD‐RIKE with minimal experimental effort and provides an additional chemical selectivity channel for coherent Raman microscopy. Copyright © 2014 John Wiley & Sons, Ltd.     

High-spin structures of 86,87,88,89Y isotopes

In the present paper nuclear structure properties of ^86,87,88,89Y isotopes have been investigated using large-scale shell-model calculations within the full f _5/2pg9/2 model space. The calculations have been performed with JUN45 and jj44b effective interactions that have been proposed for use in the f _5/2, p _3/2, p _1/2, g _9/2 model space for both protons and neutrons. Reasonable agreement between experimental and calculated values are obtained. This work will add more information to the previous study by the projected shell model [Eur. Phys. J. A 48, 138 (2012)], where full-fledged shell-model calculations were proposed for these nuclei.     

Role of electron correlation in the polydeprotonation of benzene to form trianions

Computations for anion, dianions, and trianions of benzene are carried out to study the role of electron correlation in the polydeprotonation of benzene leading to benzene trianions both in the singlet and triplet states. The computations, while assessing the use of polarization and diffuse functions, are performed with Møller–Plesset second‐order (MP2) perturbation theory and coupled‐cluster theory up to the level of CCSD(T)/6‐311++G(d,p)//MP2/6‐311++G(d,p), and with density functional theory (DFT) employing a hybrid, B3LYP, and a meta‐hybrid, M05‐2X, exchange‐correlation functionals with Gaussian basis set 6‐311++G(d,p) and correlation consistent basis set aug‐cc‐pVDZ. The deprotonation energies, including zero‐point energy correction, of benzene anion and dianions are found to be highly sensitive to the quantum mechanical method and the basis set used. The formation of dianions and trianions, where the anionic centers lie adjacent to each other, is observed with unusual behavior in the deprotonation energy and the geometrical parameters obtained from the different level of the theories. The two exchange‐correlation functionals compared show contrasting and unusual results for the trianionic species particularly for the triplet states, even if the diffuse functions are included in the basis set. Besides this, the ortho‐dianion and 1,3,5‐trianion are predicted to be ground‐state triplet at CCSD(T)/6‐311++G(d,p)//MP2/6‐311++G(d,p) and DFT/M05‐2X/6‐311++G(d,p) levels, whereas DFT/B3LYP/6‐311++G(d,p) predicts meta‐dianion and 1,2,3‐trianion to be ground‐state triplet where all the anionic centers lie adjacent to each other. Copyright © 2014 John Wiley & Sons, Ltd.     

Realizable high-order finite-volume schemes for quadrature-based moment methods

Dilute gas–particle flows can be described by a kinetic equation containing terms for spatial transport, gravity, fluid drag and particle–particle collisions. However, direct numerical solution of kinetic equations is often infeasible because of the large number of independent variables. An alternative is to reformulate the problem in terms of the moments of the velocity distribution. Recently, a quadrature-based moment method was derived for approximating solutions to kinetic equations. The success of the new method is based on a moment-inversion algorithm that is used to calculate non-negative weights and abscissas from the moments. The moment-inversion algorithm does not work if the moments are non-realizable, which might lead to negative weights. It has been recently shown [14] that realizability is guaranteed only with the 1st-order finite-volume scheme that has an inherent problem of excessive numerical diffusion. The use of high-order finite-volume schemes may lead to non-realizable moments. In the present work, realizability of the finite-volume schemes in both space and time is discussed for the 1st time. A generalized idea for developing realizable high-order finite-volume schemes for quadrature-based moment methods is presented. These finite-volume schemes give remarkable improvement in the solutions for a certain class of problems. It is also shown that the standard Runge–Kutta time-integration schemes do not guarantee realizability. However, realizability can be guaranteed if strong stability-preserving (SSP) Runge–Kutta schemes are used. Numerical results are presented on both Cartesian and triangular meshes.     

Asymmetric syn-selective direct aldol reaction of protected hydroxyacetone catalyzed by primary amino acid derived bifunctional organocatalyst in the presence of water

A new series of water compatible primary-tertiary diamine catalysts derived from natural primary amino acids bearing a hydrophobic side chain have been synthesized. These new primary-tertiary diamine-Br?nsted acid conjugates bifunctional organocatalysts efficiently catalyzes the asymmetric direct syn selective cross-aldol reaction of different protected hydroxyacetone with various aldehydes in high yield (94%) and high enantioselectivity (up to 97% ee of syn) and dr of 91 : 9 (syn/anti) under mild reaction conditions.