Photonic band gap effect in one-dimensional plasma dielectric photonic crystals

Propagation of electromagnetic waves in one-dimensional plasma dielectric photonic crystals, the superlattice structure consisting of alternating plasma and dielectric materials, is studied theoretically using transfer matrix method. Numerical calculation is presented for plasma-air finite and infinite periodic structures. The results of photonic band gap characteristics are discussed in terms of plasma density, plasma width, and number of unit cells (N).     

Electrochemical oxidation of aldehyde-N-arylhydrazones into symmetrical-2,5-disubstituted-1,3,4-oxadiazoles

A convenient, efficient and one-pot synthesis of chemically and pharmaceutically interesting symmetrical-2,5-disubstituted-1,3,4-oxadiazoles is reported. The protocol involves anodic oxidation of aldehyde-N-arylhydrazones in anhyd. MeCN–LiClO₄. Constant potential electrolysis carried out in an undivided cell and platinum electrodes leads to the formation of the corresponding oxadiazoles under ambient condition and the mechanism was deduced from voltammetry studies. The reaction proceeded smoothly with high atom economy.     

A Facile Synthesis of Ethyl 3-Aryl-2,2-dimethyl-cyclopropanecarboxylates,Intermediates for Pyrethroid Acaricides

A facile three step synthesis of 3-aryl-2,2-dimethyl-cyclopropanecarboxylates, intermediates for pyrethroid acaricides, involving formation of arylidene phenylsulfonylacetate, MIRC reaction of the latter with potassium 2-nitropropane and desulfonylation of the cyclopropane intermediate with sodium amalgam in fair overall yield is described.     

4‐Ethynyl‐4‐hydroxycyclohexan‐1‐one and 4‐ethynyl‐4‐hydroxy‐2,3,5,6‐tetramethylcyclohexa‐2,5‐dien‐1‐one

The title compounds, C₈H₁₀O₂, (I), and C₁₂H₁₄O₂, (II), occurred as by‐products in the controlled synthesis of a series of bis­(gem‐alkynols), prepared as part of an extensive study of synthon formation in simple gem‐alkynol derivatives. The two 4‐(gem‐alkynol)‐1‐ones crystallize in space group P2₁/c, (I) with Z′ = 1 and (II) with Z′ = 2. Both structures are dominated by O—H?O=C hydrogen bonds, which form simple chains in the cyclo­hexane derivative, (I), and centrosymmetric dimers, of both symmetry‐independent mol­ecules, in the cyclo­hexa‐2,5‐diene, (II). These strong synthons are further stabilized by C[triple‐bond]C—H?O=C, C_methylene—H?O(H) and C_methyl—H?O(H) interactions. The direct intermolecular interactions between donors and acceptors in the gem‐alkynol group, which characterize the bis­(gem‐alkynol) analogues of (I) and (II), are not present in the ketone derivatives studied here.     

Ternary Cu(II) complexes involving N-(1-naphthyl)ethylenediamine, ethylenediamine (N-N donors) and a series of amino acids (N-O? donors)

The dissociation constants for N-(l-naphthyl)ethylenediamine (NEN) and the formation constants for binary (ML) and ternary metal complexes (MLA), where M = Cu(II), L = alanine, phenylalanine, tryptophan, lysine, arginine, serine, threonine, aspartic acid or histidine and A = NEN or ethylenediamine (EN) have been determined by pH titrations and are reported at 35°C (gm = 0.2 M KNO₃). The relative stability of the ternary complexes are discussed in terms of statistical effects and the nature of ligands in the coordination sphere of the metal ion.     

Analyzing a multiserver bulk-service finite-buffer queue

This paper analyzes a finite-buffer multiserver bulk-service queueing system in which the interarrival and service times are, respectively, arbitrarily and exponentially distributed. Using the supplementary variable and the imbedded Markov chain techniques, we obtain the queue-length distributions at prearrival and arbitrary epochs. We also present Laplace–Stiltjes transform of the actual waiting-time distribution in the queue. Finally, several performance measures and a variety of numerical results in the form of tables and graphs are discussed.     

Buckling analysis of nanobeams with exponentially varying stiffness by differential quadrature method

We present the application of differential quadrature(DQ) method for the buckling analysis of nanobeams with exponentially varying stiffness based on four different beam theories of Euler-Bernoulli, Timoshenko, Reddy, and Levison.The formulation is based on the nonlocal elasticity theory of Eringen. New results are presented for the guided and simply supported guided boundary conditions. Numerical results are obtained to investigate the effects of the nonlocal parameter,length-to-height ratio, boundary condition, and nonuniform parameter on the critical buckling load parameter. It is observed that the critical buckling load decreases with increase in the nonlocal parameter while the critical buckling load parameter increases with increase in the length-to-height ratio.     

Nonlinear Evolution of a Gaussian Wave Perturbation in the Presence of a High Power Electromagnetic Plane Wave in the F Region Ionosphere

The interaction of a high power electromagnetic plane wave of uniform intensity with a weak electromagnetic Gaussian wave has been studies analytically. The two waves propagate vertically with almost the same frequency in the F region ionosphre. It is seen that the Gaussian wave acquires an oscillatory structure due to the nonlinear coupling of the strong plane wave and the weak Gaussian wave and the amplitude of these fluctuations grows with height. The growth, however, occurs only above a certain altitude z₀, which is determined by the plasma and wave parameters.     

Mutual Focusing of Electromagnetic Waves in the Ionospheric Plasma

A one dimensional analysis has been carried out to study the interaction of two co-axial electromagnetic waves propagating vertically at close frequencies in the F-region ionosphere. Coupled equations for the beam width parameters of the two interacting waves have been set up to determine the intensities in the axial direction. Two cases have been examined, i one of the em beams is assumed to be weak so that its influence on the medium as well as on the other beam is neglected, ii) the two beams are of comparable intensities so that they mutually influence each other. In the first case the axial intensity of the weak beam grows at the expense of the other one which is strong. Whereas in the other situation mutual influence results in the focusing of both the beams.