The string model of the Cooper pair in the anisotropic superconductor

The analogy between the Cooper pair in high temperature superconductor and the quark-antiquark pair in quantum chromodynamics (QCD) is proposed. In QCD the nonlinear chromodynamical field between a quark and an antiquark is confined to a tube. So we assume that there is the strong interaction between phonons which can confine them to some tube too. This tube is described using the nonlinear Schr\"odinger equation. We show that it has an infinite spectrum of axially symmetric (string) solutions with negative finite linear energy density. The one-dimensional nonlinear Schr\"odinger equation has a finite spectrum (hence, it has a steady-state) which describes the Cooper pair squezeed between anisotropy planes in the superconductor. It is shown that in this model the transition temperature is approximately 45 K.Comment: final version, Latex, 9p, to be published in Phys. Rev.

Vertex-corrected perturbation theory for the electron-phonon problem with non-constant density of states

A series of weak-coupling perturbation theories which include the lowest-order vertex corrections are applied to the attractive Holstein model in infinite dimensions. The approximations are chosen to reproduce the iterated perturbation theory in the limit of half-filling and large phonon frequency (where the Holstein model maps onto the Hubbard model). Comparison is made with quantum Monte Carlo solutions to test the accuracy of different approximation schemes.Comment: 31 pages, 15 figures, typeset in ReVTe

Inter-cluster reactivity of Metallo-aromatic and anti-aromatic Compounds and Their Applications in Molecular Electronics: A Theoretical Investigation

Local reactivity descriptors such as the condensed local softness and Fukui function have been employed to investigate the inter-cluster reactivity of the metallo-aromatic (Al4Li- and Al4Na-) and anti-aromatic (Al4Li4 and Al4Na4) compounds. We use the concept of group softness and group Fukui function to study the strength of the nucleophilicity of the Al4 unit in these compounds. Our analysis shows that the trend of nucleophilicity of the Al4 unit in the above clusters is as follows; Al4Li- > Al4Na- > Al4Li4 > Al4Na 4 For the first time we have used the reactivity descriptors to show that these clusters can act as electron donating systems and thus can be used as a molecular cathode.Comment: 23 pages, 1 figure and 1 table of conten

Evolution in the split-peak structure across the Peak Effect region in single crystals of 2H2H-NbSe2_2

We have explored the presence of a two-peak feature spanning the peak effect (PE) region in the ac susceptibility data and the magnetization hysteresis measurements over a wide field-temperature regime in few weakly pinned single crystals of $2H$-NbSe$_2$, which display reentrant characteristic in the PE curve near $T_c$(0). We believe that the two-peak feature evolves into distinct second magnetization peak anomaly well separated from the PE with gradual enhancement in the quenched random pinning.Comment: 9 figure

Exact solution of the Falicov-Kimball model with dynamical mean-field theory

The Falicov-Kimball model was introduced in 1969 as a statistical model for metal-insulator transitions; it includes itinerant and localized electrons that mutually interact with a local Coulomb interaction and is the simplest model of electron correlations. It can be solved exactly with dynamical mean-field theory in the limit of large spatial dimensions which provides an interesting benchmark for the physics of locally correlated systems. In this review, we develop the formalism for solving the Falicov-Kimball model from a path-integral perspective, and provide a number of expressions for single and two-particle properties. We examine many important theoretical results that show the absence of fermi-liquid features and provide a detailed description of the static and dynamic correlation functions and of transport properties. The parameter space is rich and one finds a variety of many-body features like metal-insulator transitions, classical valence fluctuating transitions, metamagnetic transitions, charge density wave order-disorder transitions, and phase separation. At the same time, a number of experimental systems have been discovered that show anomalies related to Falicov-Kimball physics [including YbInCu4, EuNi2(Si[1-x]Gex)2, NiI2 and TaxN].Comment: 51 pages, 40 figures, submitted to Reviews of Modern Physic

Application of hexakisacetonitrile iron (III) perchlorate in organic synthesis

865-866<span style="font-size:12.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-in;mso-fareast-language:en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">Iron (III) perchlorate-CH3CN functions as an acid catalyst and promotes Ritter reaction. The reagent is not suitable to bring about oxidative decarboxylation and cleavage of glycols.</span

β,β -Dimethylacrylophenones : BF₃.Et₂O-POCl₃ catalysed acylation of phenols using β, β -dimethylacrylic acid

1237-1241Boron trifluoride etherate-phosphoryl chloride reagent is a useful reagent for the condensation between phenols and β, β -dimethylacrylic acid. The main products are acrylophenones. But surprisingly hydroquinone gives mono and diacrylates

An expedient synthesis of racemic combretastatin and isocombretastatin

817-821The stilbenoid constituents of Combretum caffrum possess pronounced antineoplastic and antimitotic activities. The most potent agents are R (-) combretastatin 1, and combretastatins A-1 to A-4. A novel and simple method for the synthesis of ±1 and isocombretastatin 5 in which an appropriately substituted 1, 3-diarylpropanoid is transformed into a stilbenoid is described. The key step involves the alkali induced rearrangement of chalcone epoxide 9 to α-hydroxy acid 10 and that is followed by oxidative decarboxylation and reduction

BIOCHEMICAL CHANGES OCCURRING DURING SPORULATION OF BACILLUS CEREUS: Inhibition of Sporulation by α-Picolinic Acid

The effects of nutritional and environmental conditions on sporulation and the properties of the spore have been extensively studied with the hope that these may provide a clue to the mecha-nism of dormancy and resistance of the bacterial endospore. However, there is no general agree-ment and our knowledge of these is still limited. The extensive literature dealing with the various aspects of sporogenesis has been reviewed b