Superhalogens as Building Blocks of Super Lewis Acids

Lewis acids play an important role in synthetic chemistry. Using first-principle calculations on some newly designed molecules containing boron and organic heterocyclic superhalogen ligands, we show that the acid strength depends on the charge of the central atom as well as on the ligands attached to it. In particular, the strength of the Lewis acid increases with increasing electron withdrawing power of the ligand. With this insight, we highlight the importance of superhalogen-based ligands in the design of strong Lewis acids. Calculated fluoride ion affinity (FIA) values of B[C₂BNO(CN)₃]₃ and B[C₂BNS(CN)₃]₃ show that these are super Lewis acids.     

A new ferroelectric oxide Li2Pb2Pr2W2Ti4Nb4O30: Synthesis and characterization

A new ferroelectric oxide (Li₂Pb₂Pr₂W₂Ti₄Nb₄O₃₀) of tungsten bronze structural family has been synthesized by a solid-state reaction (mixed-oxide) route at high temperature (～1100 °C). X-ray structural analysis with room temperature diffraction data confirms the formation of a single phase compound. The scanning electron microscopic (SEM) texture of the surface of material sample exhibits a uniform grain distribution with a few small voids suggesting the formation of high-density pellet sample. Detailed studies of dielectric constant, tangent loss and polarization with temperature and frequency confirmed the existence of ferroelectric properties in the material with transition temperature much above room temperature. Study of electrical properties (impedance, modulus, conductivity, etc.) of the material exhibits a strong correlation between its micro-structure (i.e., bulk, grain boundary, etc.) and electrical parameters. The nature of variation of dc conductivity with temperature confirms the Arrhenius behavior of the material. The presence of ionic conductivity in the material was observed in its ac conductivity spectrum. Study of frequency dependence of ac conductivity suggests that the material obeys Jonscher's universal power law. The experimental electrical transport properties of the material clearly exhibit the existence of non-exponential-type of conductivity relaxation.     

Sequential double Auger decay in atoms: A quantum informatic analysis

We theoretically show that the process of inner-shell photoionization in an atom A, followed by the spontaneous sequential emission of two Auger electrons, produces various kinds of spin-entangled states of three flying electronic qubits. All properties of these states are completely pre-determined by the total spin quantum numbers of the electronic states of four atomic species (i.e., A, A^+∗, A2^+∗, A3+) participating in this process in the Russell-Saunders coupling. These tripartite states are readily characterized experimentally by measuring only energies of the three emitted electrons, without requiring any entanglement witness or other such protocols.     

Solidification of a semitransparent planar layer subjected to radiative and convective cooling

This work deals with the analysis of solidification of a semi-transparent planar layer subjected to radiative and convective cooling. Isothermal mushy-zone model is considered. Enthalpy formulation of the energy equation is solved using the lattice Boltzmann method. To compare the results, the same equation is also solved using the fully implicit finite volume method. Discrete ordinate method is used to compute the radiative information in both the approaches. Effects of radiative properties such as the extinction coefficient, the scattering albedo and refractive index on the solid fraction and temperature are analyzed. Results are validated with those available in the literature. Lattice Boltzmann method and the discrete ordinate method were found to work satisfactorily.     

General relations among observables in a large class of neutral-current processes mediated by one,two, or threeZ bosons

Without assuming any symmetry amongμ, e andτ leptons, we consider several neutral current processes involving 73 physical parameters and deduce general relations among them implied by different classes of gauge models with one, two and three neutralZ bosons. In the single-Z boson model there are 60 general relations while the two (three)-boson model leads to 48 (36) relations. If onlyμ-e universality is imposed, the physical parameters reduce to 41 and the single (two)-Z boson model yields 31 (22) relations, while only 13 relations exist for the threeZ boson model. Imposingμ-e-τ universality decreases the number of physical parameters to 18, while the number of relations in the single- and two-Z boson models reduces to 11 and 5, respectively. In these relations are contained those obtained by Hung and Sakurai and Parida and Rajasekaran in the corresponding cases. In addition we obtain some new inequalities among the observable parameters which are to be satisfied by all gauge models.     

三种特殊的双固定步网络环的生成树的数目

令Ｔ（Ｃ＾－（ｎ，ｌ，ｐ）是双固定步网络环Ｃ＾－（ｎ，ｌ，ｐ）的生成树的数目，在本文中给出了关于Ｔ（Ｃ＾－（ｎ，１，２）），Ｔ（Ｃ＾－（ｎ，１，３）和Ｔ（Ｃ＾－（ｎ，１，４））的三种递推式，且一般情况，Ｔ（Ｃ＾－（ｎ，１，ｐ）也可以按此思想考虑。     

Volume change during the formation of nanoporous gold by dealloying

We report a macroscopic shrinkage by up to 30 vol % during electrochemical dealloying of Ag-Au. Since the original crystal lattice is maintained during the process, we suggest that the formation of nanoporous gold in our experiments is accompanied by the creation of a large number of lattice defects and by local plastic deformation.     

Regularized numerical integration of multibody dynamics with the generalized method

This paper discusses the consistent regularization property of the generalized α method when applied as an integrator to an initial value high index and singular differential-algebraic equation model of a multibody system. The regularization comes from within the discretization itself and the discretization remains consistent over the range of values the regularization parameter may take. The regularization involves increase of the smallest singular values of the ill-conditioned Jacobian of the discretization and is different from Baumgarte and similar techniques which tend to be inconsistent for poor choice of regularization parameter. This regularization also helps where pre-conditioning the Jacobian by scaling is of limited effect, for example, when the scleronomic constraints contain multiple closed loops or singular configuration or when high index path constraints are present. The feed-forward control in Kane’s equation models is additionally considered in the numerical examples to illustrate the effect of regularization. The discretization presented in this work is adopted to the first order DAE system (unlike the original method which is intended for second order systems) for its A-stability and same order of accuracy for positions and velocities.     

Importance of specific surface area and basic sites of the catalyst in oxidative coupling of CH4 over LiO/MgO catalysts prepared by precipitation methods

A low specific surface area was found to be the key factor for catalytic conversion of CH₄ into C₂H₆ and C₂H₄. C₂-hydrocarbon selectivity increases with increase in basicity of the catalyst.

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CH₄ C₂H₆ C₂H₄. C₂- .