Diversity-oriented synthetic approach to naturally abundant S-amino acid based benzannulated enantiomerically pure medium ring heterocyclic scaffolds employing inter- and intramolecular mitsunobu reactions

The diversity-oriented organic synthesis of enantiomerically pure benzannulated oxazepine, diazepine, thiazepine, oxazocine, and diazocine scaffolds is described from easily accessible naturally occurring S-amino acids as chiral synthons. Inter- and intramolecular Mitsunobu reactions for the formation of carbon-nitrogen, carbon-oxygen, and carbon-sulfur bonds have been used as key transformations to construct these biologically important privileged heterocycles. This is the first example where the Mitsunobu approach has been utilized for the construction of S-amino acid based seven- and eight-membered ring systems.     

A novel photoadditive for polyolefin photostabilization: hindered amine light stabilizer

Hindered‐amine light stabilizers were surface anchored to polyethylene and polypropylene thin films by: i) direct photo‐grafting of 1,2,2,6,6‐pentamethyl piperidinyl‐4‐acrylate onto the surface and ii) by reacting of 1,2,2,6,6‐pentamethyl‐4‐piperidinol with succinic anhydride functionalized polyolefin surface. The samples were exposed to UV irradiation in air and the oxidative‐degradation of the polymers was studied with FT‐IR spectroscopy. The photo‐stability of surface anchored Hindered‐amine stabilizers (HAS) was compared with films stabilized with commercial HAS by melt blending. The results of the study evince superiority of surface anchored HAS over that of melt blended polyolefins.     

Experimental study of heat transfer characteristics in oscillating fluid flow in tube

In the present work, an experimental investigation of heat transfer enhancement parameters of the oscillating flow heat exchanger under different frequencies, tidal displacement, and heat fluxes is carried out. The effect of different parameters on experimental effective thermal conductivity and convective heat transfer coefficient in cooling region is studied using correlations given by different researchers. A correlation for experimental effective thermal conductivity in terms of S²√ω is derived based on experimental data. This correlation is useful for predicting the optimum value of S²√ω before onset of turbulence.     

Multiresolution analysis of fluctuations in non-stationary time series through discrete wavelets

We illustrate the efficacy of a discrete wavelet based approach to characterize fluctuations in non-stationary time series. The present approach complements the multifractal detrended fluctuation analysis (MF-DFA) method and is quite accurate for small size data sets. As compared to polynomial fits in the MF-DFA, a single Daubechies wavelet is used here for detrending purposes. The natural, built-in variable window size in wavelet transforms makes this procedure well suited for non-stationary data. We illustrate the working of this method through the analysis of binomial multifractal model. For this model, our results compare well with those calculated analytically and obtained numerically through MF-DFA. To show the efficacy of this approach for finite data sets, we also do the above comparison for Gaussian white noise time series of different sizes. In addition, we analyze time series of three experimental data sets of tokamak plasma and also spin density fluctuations in 2D Ising model.     

Mach-Zehnder interferometer-based tree architecture for all-optical logic and arithmetic operations

Interferometric devices for optical processing have been of great interest in recent years. Semiconductor optical amplifier (SOA)-based Mach-Zehnder interferometer (MZI) has already taken a significant role in the field of ultra-fast all-optical signal processing. Optical tree architecture (OTA) provides important contributions in optical interconnecting networks. In this communication, we have tried to exploit the advantages of both OTA and SOA-based MZI switches. We have proposed SOA-MZI-based tree architecture, a new and alternative scheme, for integrated all-optical logic and arithmetic operations. This architecture can enable one to perform all-optical processing of signals, including two input logic operations, half-adder, full-adder, full-subtractor, one-bit data comparator, etc.     

A phenol-induced structural transition in aqueous cetyltrimethylammonium bromide solution

The effect of phenol on the structure of micellar solution of a cationic surfactant, cetyltrimethylammonium bromide (CTAB) was investigated using viscosity, dynamic light scattering (DLS), small angle neutron scattering (SANS) and nuclear magnetic resonance (NMR) techniques. The relative viscosity and apparent hydrodynamic diameters of the micelles in CTAB solution increase initially and then decrease with addition of phenol. SANS studies indicate a prolate ellipsoidal structure of the micelles. The axial ratio of the prolate ellipsoidal micelles increases and then decreases with addition of phenol, consistently with DLS and viscosity measurements. NMR studies confirm the solubilization of phenol to the palisade layer and growth of the micelles at high concentration of phenol as revealed from the broadening of peaks.     

Correlation of mesogenic properties with intermolecular interaction energy for homologous series of HnCBP

Intermolecular interaction energy between a pair of molecules of homologous series 4, 4′-disubstituted biphenyl of the general formula HO?(CH₂)_n?O?C₆H₄?C₆H₄?CN(n = 3 ? 11) (H_nCBP) has been evaluated under various interacting conditions viz. stacking, in-plane and terminal interaction. Molecular geometry of the studied molecules was fully optimized without any constraint and checked for imaginary frequencies using hybrid density functional B3LYP combined with 6–31 g^** basis set. Electronic structure of the molecules obtained through these calculations has been utilized to calculate electrostatic and polarization energies under Rayleigh-Schrodinger perturbation theory modified with multi-centered multi-pole expansion method. Dispersion and repulsion energies have been evaluated using Kitaigorodskii formula. The identified minimum energy complexes have been further utilized to evaluate interaction energy under super molecular approach by employing M06 and DFT-D methods. A comparative analysis of the results has been reported with a view to examine suitability of different methods to study molecular aggregations in moderately large organic systems.     

Dual catalysis with an Ir(III)-Au(I) heterodimetallic complex: reduction of nitroarenes by transfer hydrogenation using primary alcohols

A triazolyl-di-ylidene ligand has been used for the preparation of a homodimetallic complex of gold, and a heterodimetallic compound of gold and iridium. Both complexes have been fully characterized and their molecular structures have been determined by means of X-ray diffraction. The catalytic properties of these two complexes have been evaluated in the reduction of nitroarenes by transfer hydrogenation using primary alcohols. The two complexes afford different reaction products; whereas the Au(I)-Au(I) catalyst yields a hydroxylamine, the Ir(III)-Au(I) complex facilitates the formation of an imine.