Dispersion of quasi-particles in high Tc cuprates

The interplay between superconductivity (SC) and antiferromagnetism (AFM) is studied in strongly correlated systems of high T _c Cuprate superconductors. It is assumed that superconductivity arises due to BCS pairing mechanism in presence of AFM in Cu lattices of Cu-O planes. The total Hamiltonian of the system is mean field one and has been solved exactly by writing the equations of motion for the single particle Green’s functions. Equations for the appropriate single particle co-relation functions are derived and the order parameters corresponding to SC and AFM are determined. It is assumed that the Fermi energy ∈ _F = 0 and the renormalized localized f energy level coincide with the Fermi level. All the quantities in the final equation for h and Δ are made dimensionless by dividing by 2t, where t is the hopping integral. The temperature dependent values of staggered magnetic field (h) and SC gap (Δ) were determined by solving self-consistent equations for h and Δ. The quasiparticle energy bands are function of AFM gap (h), SC gap (Δ) and hybridization (V). Then the dispersion of quasi-particles are studied at different temperatures by considering temperature dependent values of h and Δ and varying other different model parameters.      

3 + 2]-cycloaddition of nonstabilized azomethine ylides. 10. An efficient strategy for the construction of x-Azatricyclo[m.n.0. 0

Various new structural entities related to x-azatricyclo[m.n.0. 0(a)()(,)(b)()]alkanes are constructed by the intramolecular [3 + 2] dipolar cycloaddition of nonstabilized cyclic azomethine ylides. The ylide is generated by the sequential double desilylation of N-alkyl alpha,alpha'-bis(trimethylsilyl)cyclic amines using Ag(I)F as a one-electron oxidant.     

A homometallic tricapped cubane cluster: [(Cp*Mo)4B4H4(μ4-BH)3] (Cp* = η5-C5Me5)

The reaction of [Cp*MoCl(4)] with an excess of LiBH(4), followed by thermolysis with tellurium powder in toluene, afforded a tricapped cubane cluster, [(Cp*Mo)(4)B(4)H(4)(μ(4)-BH)(3)] (1), which represents an unprecedented metal-rich metallaborane cluster with a cubane core containing 58 cluster valence electrons (cve) and three metal-metal bonds.     

Tetrazolo[1,5‐a]quinoline‐4‐carbaldehyde and its Schiff base on mild steel as corrosion inhibitor in 1 M HCl solution: electrochemistry,theoretical and SEM surface analysis

The corrosion inhibition impact of two quinoline derivatives, viz tetrazolo [1,5‐a] quinoline‐4‐carbaldehyde ( TQC ) and (Z) ?5‐methyl‐N‐(tetrazolo [1,5‐a] quinolin‐4‐ylmethylene) thiazol‐2‐amine ( MTQT ), has been examined against mild steel in 1 M HCl solution using conventional weight loss, potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy, quantum chemical, and scanning electron microscopic studies. The experimental results have showed that TQC and MTQT revealed a good corrosion inhibition and that the inhibition efficiency increases with the increase of concentration of inhibitor to attain 94.54% for TQC and 99.25% for MTQT at 25 ppm. Polarization measurements suggest that TQC and MTQT act as a mixed‐type inhibitor. A synergism between inhibitors can be observed by polarization measurements. Electrochemical impedance spectroscopy measurements show an increase of the transfer resistance with the inhibitor concentration. Adsorption of TQC and MTQT on the mild steel surfaces in 1 N HCl solution follows the Langmuir adsorption isotherm model. Furthermore, quantum chemical calculations have been conducted using B3LYP functional and 6‐31G(d,p) basis set to complement the experimental evidences. Copyright © 2015 John Wiley & Sons, Ltd.     

Molecular conformation and liquid structure of 2-propanol through neutron diffraction

The neutron diffraction data analysis of deuterated liquid 2-propanol at room temperature to define its molecular conformation is presented. 2-Propanol being a large molecule with twelve atomic sites, the conformation analysis is tricky and an improved method of data analysis is given. The intermolecular structural correlations, i.e., hydrogen-bonded liquid structure, can be modelled accurately to extract the nature of the average hydrogen-bonded molecular association in liquid state at room temperature. Like other alcohols these are mostly hexamer ring chain (HRC) clusters. The cluster analysis of recent X-ray data available in the literature also support the same liquid structure.     

Second law analysis of a cyclic regenerator in presence of longitudinal heat conduction in matrix

The present analysis gives an account of exergy destruction in regenerative heat exchangers used in cryogenic applications from the view point of Second Law of Thermodynamics. Unlike the previous studies, the present work considers the solid storage matrix with temperature variation along both spatial and temporal co-ordinates. The present analysis also considers the effect of matrix longitudinal heat conduction on the Second Law behaviour. Finite longitudinal conductivity, which results from the distribution of temperature in the matrix, acts as a major non-ideality associated with the analyses done so far. The present analysis shows that the introduction of longitudinal conduction ensures the optimization of charging period for the regenerator. This makes it possible to optimize the regenerator performance globally to produce optimum combination of N _tu and charging time. It is also observed that a decrease in longitudinal conductivity reduces the optimum charging time. Thus the non-existence of thermodynamic optima at the absence of longitudinal conduction is explained adequately. Received on 12 May 1998     

Theory of nuclear quadrupole interactions in aluminum and copper metals in presence of muon

The electric field gradients at²⁷Al and⁶³Cu nuclei which are nearest neighbors to the muon in the face-centered cubic metals aluminum and copper, with muon at an octahedral interstitial site, are studied. The electron density fluctuations needed for the evaluation of the electronic, or valence, contributions to field gradients are taken from earlier investigations involving the spherical solid approximation. The enhancement factors a that have to be applied to the electric field-gradients obtained from these approximations, due to the departures of the electronic wave-functions from plane-wave character, and the incorporation of antishielding effects, have been obtained for both APW and OPW approaches to the conduction electron wave-functions and good agreement is found between the results by the two approaches. Size effects due to the lattice distortion associated with the presence of the muon are included through actual point ion summations using available calculated displacements of the ions surrounding the muon. The valence contributions are the dominant ones but the size effect contributions are also significant. The net field-gradient obtained for the²⁷Al site is significantly smaller than experiment while that for⁶³Cu is substantially larger than experiment. Possible sources that could lead to better agreement with experiment are discussed and it is concluded that major improvement is needed in the valence effect contributions in both metals.     

Characterization of polynomials and divided difference

For distinct points x₁,x₂,…,x_n in ℛ (the reals), letϕ[x₁, x₂,…,x_n] denote the divided difference ofϕ. In this paper, we determine the general solutionϕ,g: ℛ → ℛ of the functional equationϕ[x₁,x₂,…,x_n] =g(x₁,+ x₂ + … + x_n) for distinct x₁,x₂,…, x_n in ℛ without any regularity assumptions on the unknown functions.     

Modified complex method for constrained design and optimization of optical multilayer thin-film devices

A new computer design program based on the modified-complex method has been developed for constrained optimization and refinement of optical thin-film multilayer devices. This program is having a provision to include both limiting constraints as well as constraint equations. Constraints are suitably accommodated to generate designs which are practicable and withstand high laser power. Various rapid convergent processes like dynamic contraction and expansion of feasible vertices are incorporated for efficient scanning of the constraint parametric space. A broad band IR antireflection coating has been designed to test its relative efficiency with respect to other available methods. A wide varieties of highly useful multilayer devices have been successfully developed using this method.