Lepton distribution in top decay: A probe of new physics and top-polarization

We investigate the possibilities of studying new physics in various processes of t-quark production using kinematical distributions of the secondary lepton coming from decay of t quarks. We show that the angular distributions of the secondary lepton are insensitive to the anomalous tbW vertex and hence are pure probes of new physics in a generic process of t-quark production. The effects of t polarization on the distributions of the decay lepton are demonstrated for top-pair production process at a γγ-collider mediated by a heavy Higgs boson.      

B and collider physics: Working group report

This report summarises the work done during WHEPP-6 (Institute of Mathematical Sciences, Chennai, India, Jan 3–15, 2000) in Working group on ‘B and collider physics’.     

Fourier Multipliers and Littlewood‐Paley for modulation spaces

In this paper we have studied Fourier multipliers and Littlewood‐Paley square functions in the context of modulation spaces. We have also proved that any bounded linear operator from modulation space into itself possesses an l₂‐valued extension. This is an analogue of a well known result due to Marcinkiewicz and Zygmund on classical ‐spaces.     

Understanding the Role of Parallel Pathways via In‐Situ Switching of Quantum Interference in Molecular Tunneling Junctions

This study describes the modulation of tunneling probabilities in molecular junctions by switching one of two parallel intramolecular pathways. A linearly conjugated molecular wire provides a rigid framework that allows a second, cross‐conjugated pathway to be effectively switched on and off by protonation, affecting the total conductance of the junction. This approach works because a traversing electron interacts with the entire quantum‐mechanical circuit simultaneously; Kirchhoff's rules do not apply. We confirm this concept by comparing the conductances of a series of compounds with single or parallel pathways in large‐area junctions using EGaIn contacts and single‐molecule break junctions using gold contacts. We affect switching selectively in one of two parallel pathways by converting a cross‐conjugated carbonyl carbon into a trivalent carbocation, which replaces destructive quantum interference with a symmetrical resonance, causing an increase in transmission in the bias window.     

Crystal structure of Alanine‐Copper(II) complex to understand the mechanism of salt induced prebiotic oligomerization of amino acids

Oligomerization of amino acid monomers is the vital step in the formation of longer peptides and functional proteins. In spite of continuing efforts towards solving the puzzle of origin of life, the mystery of chemical evolution remains unsolved. Out of various pathways proposed for the formation of peptides under prebiotic conditions, salt induced peptides synthesis presents the most plausible scenario. In attempts to study mechanism of prebiotic oligomerization of amino acid on primitive earth the current study was aimed to determine the crystal structure of intermediate copper amino acid complex and its supra‐molecular assembly. The Structure of the copper alanine complex obtained from SIPF was studied by x‐ray crystallography. The self‐assembling properties of complex into supra‐molecular nanostructures were studied using Field‐emission electron microscopy (FE‐SEM). Results showed the occurrence of racemization of amino acids. This is the first structural study for copper alanine complex formed from prebiotic peptide synthesis pathway. The aggregational properties of intermediate complex showed the formation of rod like crystals and nanospheres. The findings from our study showed the possible mechanism of prebiotic oligomerization of amino acids on the primitive earth towards formation of longer peptides and functional proteins.     

Spin‐1 Bose Hubbard Model with Nearest Neighbour Extended Interaction

A spinor () Bose gas is studied in presence of a density‐density interaction through a mean field approach and a perturbation theory for either sign of the spin dependent interaction, namely the antiferromagnetic (AF) and the ferromagnetic cases. In the AF case, the charge density wave (CDW) phase appears to be sandwiched between the Mott insulating (MI) and the supersolid phases for small values of the extended interaction strength. But the CDW phase completely occupies the MI lobe when the extended interaction strength is larger than a certain critical value related to the width of the MI lobes and hence opens up the possibilities of spin singlet and nematic CDW insulating phases. In the ferromagnetic case, the phase diagram shows similar features as that of the AF case and are in complete agreement with a spin‐0 Bose gas. The perturbation expansion calculations nicely corroborate the mean field phase results in both these cases. Further, we extend our calculations in presence of a harmonic confinement and obtained the momentum distribution profile that is related to the absorption spectra in order to distinguish between different phases.     

Time-varied synthesis of hierarchical ZnO microspheres and their applications in dye-sensitized solar cells

Journal of Solid State Electrochemistry - Hierarchically nano-structured ZnO microspheres have been synthesized solvothermally at variable reaction times (6, 12, 36, and 48 h) by using...     

A lattice Boltzmann model for adsorption breakthrough

A lattice Boltzmann model is developed to simulate the one-dimensional (1D) unsteady state concentration profiles, including breakthrough curves, in a fixed tubular bed of non-porous adsorbent particles. The lattice model solves the 1D time dependent convection–diffusion–reaction equation for an ideal binary gaseous mixture, with solute concentrations at parts per million levels. The model developed in this study is also able to explain the experimental adsortption/desorption data of organic vapours (toluene) on silica gel under varying conditions of temperature, concentrations and flowrates. Additionally, the programming code written for simulating the adsorption breakthrough is modified with minimum changes to successfully simulate a few flow problems, such as Poiseuille flow, Couette flow, and axial dispersion in a tube. The present study provides an alternative numerical approach to solving such types of mass transfer related problems.